@article{he_zhang_song_zhao_gao_2024, title={Modeling of yarn-shaped supercapacitors - Unraveling its length dependent output}, volume={595}, ISSN={["1873-2755"]}, DOI={10.1016/j.jpowsour.2024.234067}, abstractNote={Yarn-shaped energy-storage devices are promising power sources for electronic textiles, since they carry the possibility to be seamlessly integrated into various fabrics. The energy/power outputs of these devices are inevitably a function of their lengths, the dependence on which is yet to be thoroughly explored. Despite numerous research on yarn-shaped supercapacitors (YSCs) and batteries, the correlation between yarn length and their electrochemical output remains ambiguous, and sometimes even controversial. Herein, a dual transmission-line model for YSCs is created and used to fit the electrochemical impedance spectra (EIS) of YSCs ranging from 10 cm to 300 cm in length. The evolution of equivalent series resistances, electrolyte diffusion resistances and capacitances of YSCs as yarn length increases is investigated. Given the structure and components of YSCs used in this study, a favorable length range of 40–60 cm has been identified to achieve the best electrochemical performance, including the lowest internal resistance and the highest specific capacitance, where the highest energy and power densities sit. The mathematical model introduced in this work provides a reasonable description of the electrochemical behaviors of YSCs in different yarn lengths, offering a theoretical foundation to guide the design of these devices for specific application scenarios.}, journal={JOURNAL OF POWER SOURCES}, author={He, Nanfei and Zhang, Xi and Song, Junhua and Zhao, Feng and Gao, Wei}, year={2024}, month={Mar} }
 @article{he_king_xie_zhao_gao_2023, title={A Multidirectional Forearm Electromagnetic Generator Designed via Numerical Simulations}, volume={12}, ISSN={["2076-0825"]}, DOI={10.3390/act12060225}, abstractNote={Harvesting biomechanical energy from daily human body motions provides a promising and sustainable power solution for wearable electronics, whose current power supplies, i.e., batteries, have unsatisfactory capacity and durability due to volume, shape, and flexibility constraints. Electromagnetic generators (EMGs) are favorable energy transducers because of their high energy-conversion efficiency, low dependence on frequencies, and long-term stability. However, an EMG that can effectively harvest energy from multi-directional arm motions at aperiodic low frequencies are yet to be created. Here, we introduce a unique EMG configuration by combining a linear and a helix frame into a monolithic unit (EMG-LH), enabling the EMG to scavenge energy from all kinds of arm motions up to 6 degrees of freedom (DOFs) (movement along XYZ axes and forearm rotations). The EMG frame geometry is designed and optimized according to numerical simulations. To clarify the working mechanism and maximize the power output, the copper coils’ winding pattern, the magnets’ velocity profiles, and the resulting voltage output are numerically simulated and then experimentally verified. Our EMG-LH outperforms linear EMGs (EMG-Ls) and helix EMGs (EMG-Hs) in harvesting energy from all arm motions. This work explicitly presents a forearm-wearable energy harvester as a sustainable power source for wearable electronics.}, number={6}, journal={ACTUATORS}, author={He, Nanfei and King, Colton and Xie, Qizheng and Zhao, Feng and Gao, Wei}, year={2023}, month={Jun} }
 @article{chen_hua_ling_liu_chen_ju_gao_mills_tao_yin_2023, title={An airflow-driven system for scalable production of nano-microfiber wrapped triboelectric yarns for wearable applications}, volume={477}, ISSN={["1873-3212"]}, url={https://doi.org/10.1016/j.cej.2023.147026}, DOI={10.1016/j.cej.2023.147026}, journal={CHEMICAL ENGINEERING JOURNAL}, author={Chen, Yu and Hua, Jie and Ling, Yali and Liu, Yang and Chen, Mingtai and Ju, Beomjun and Gao, Wei and Mills, Amanda and Tao, Xiaoming and Yin, Rong}, year={2023}, month={Dec} }
 @article{subjalearndee_he_cheng_tesatchabut_eiamlamai_phothiphiphit_saensuk_limthongkul_intasanta_gao_et al._2023, title={Wet Spinning of Graphene Oxide Fibers with Different MnO2 Additives}, volume={15}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.3c02989}, abstractNote={We present the fabrication of graphene oxide (GO) and manganese dioxide (MnO2) composite fibers via wet spinning processes, which entails the effects of MnO2 micromorphology and mass loading on the extrudability of GO/MnO2 spinning dope and on the properties of resulted composite fibers. Various sizes of rod and sea-urchin shaped MnO2 microparticles have been synthesized via hydrothermal reactions with different oxidants and hydrothermal conditions. Both the microparticle morphology and mass loading significantly affect the extrudability of the GO/MnO2 mixture. In addition, the orientation of MnO2 microparticles within the fibers is largely affected by their microscopic surface areas. The composite fibers have been made electrically conductive via chemical or thermal treatments and then applied as fiber cathodes in Zn-ion battery prototypes. Thermal annealing under an argon atmosphere turns out to be an appropriate method to avoid MnO2 dissolution and leaching, which have been observed in the chemical treatments. These rGO/MnO2 fiber cathodes have been assembled into prototype Zn-ion batteries with Zn wire as the anode and xanthan-gum gel containing ZnSO4 and MnSO4 salts as the electrolyte. The resulted electrochemical output depends on the annealing temperature and MnO2 distribution within the fiber cathodes, while the best performer shows stable cycling stability at a maximum capacity of ca. 80 mA h/g.}, number={15}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Subjalearndee, Nakarin and He, Nanfei and Cheng, Hui and Tesatchabut, Panpanat and Eiamlamai, Priew and Phothiphiphit, Somruthai and Saensuk, Orapan and Limthongkul, Pimpa and Intasanta, Varol and Gao, Wei and et al.}, year={2023}, month={Apr}, pages={19514–19526} }
 @article{mainka_gao_he_dillet_lottin_2022, title={A General Equivalent Electrical Circuit Model for the characterization of MXene/graphene oxide hybrid-fiber supercapacitors by electrochemical impedance spectroscopy - Impact of fiber length}, volume={404}, ISSN={["1873-3859"]}, DOI={10.1016/j.electacta.2021.139740}, abstractNote={Performance engineering of electrochemical energy-storage devices such as Supercapacitors (SCs) requires updated modeling capable of characterizing their electrical output in unique device geometries. In this work, an Equivalent Electrical Circuit (EEC) is developed to fit the impedance data of pseudo-capacitive and electrostatic fiber-shaped supercapacitors (FSCs). The model is applied for the interpretation of impedance data measured on FSCs made of reduced Graphene Oxide (rGO) and MXene in the case of pseudo-capacitors and pure carbon in the case of Electrical Double-Layer Capacitors (EDLCs) as active electrode materials, and polyvinylalcohol (PVA) gel infiltrated with sulfuric acid as the electrolyte and separator. The FSC charge storage behavior is modeled using a Transmission Line Model (TLM) including a finite Warburg impedance for pseudo-capacitance, and a Constant-Phase Element (CPE) for the electrostatic contribution. The high frequency part of the Nyquist plots is characterized by a 45° straight line and the use of a TLM clearly improves the fit quality compared to a Randles circuit usually used for pseudo-capacitor modeling. The difference between the two ciruits becomes more visible as the length of the SC yarns increases, which is consistent with the observed increase in internal resistance with fiber length evidenced with the TLM. Furthermore, the fitting results indicate that the internal resistance of the TLM predominantly corresponds to the electrical resistance of the fiber, i.e. the electron conductive phase of the electrode, instead of the electrolyte ionic resistance in usual SCs. Finally, the low frequency part of the spectra is correctly modeled by a CPE without any leakage resistance, showing that self-discharge is not a significant issue for the electrostatic contribution, at least in the frequency range tested.}, journal={ELECTROCHIMICA ACTA}, author={Mainka, Julia and Gao, Wei and He, Nanfei and Dillet, Jerome and Lottin, Olivier}, year={2022}, month={Feb} }
 @article{chen_chen_wang_ling_fisher_li_hart_mu_gao_tao_et al._2022, title={Flexible, durable, and washable triboelectric yarn and embroidery for self-powered sensing and human-machine interaction}, volume={104}, ISSN={["2211-3282"]}, url={http://dx.doi.org/10.1016/j.nanoen.2022.107929}, DOI={10.1016/j.nanoen.2022.107929}, abstractNote={The novel combination of textiles and triboelectric nanogenerators (TENGs) successfully achieves self-powered wearable electronics and sensors. However, the fabrication of Textile-based TENGs remains a great challenge due to complex fabrication processes, low production speed, high cost, poor electromechanical properties, and limited design capacities. Here, we reported a new route to develop Textile-based TENGs with a facile, low-cost, and scalable embroidery technique. 5-ply ultrathin enameled copper wires, low-cost commercial materials, were utilized as embroidery materials with dual functions of triboelectric layers and electrodes in the Textile-based TENGs. A single enameled copper wire with a diameter of 0.1 mm and a length of 30 cm can produce over 60 V of open-circuit voltage and 0.45 µA of short circuit current when in contact with polytetrafluoroethylene (PTFE) fabric at the frequency of 1.2 Hz and the peak value of contact force of 70 N. Moreover, the triboelectric performance of enameled copper wire after plasma treatment can be better than that without plasma treatment, such as the maximum instantaneous power density can reach 245 μW/m which is ∼ 1.5 times as much as the untreated wire. These novel embroidery TENGs possess outstanding triboelectric performance and super design capacities. A 5 × 5 cm2 embroidery sample can generate an open-circuit voltage of 300 V and a short circuit current of 8 μA under similar contact conditions. The wearable triboelectric embroidery can be employed in different parts of the wear. A self-powered, fully fabric-based numeric keypad was designed based on triboelectric embroidery to serve as a human-machine interface, showing good energy harvesting and signal collection capabilities. Therefore, this study opens a new generic design paradigm for textile-based TENGs that are applicable for next-generation smart wearable devices.}, journal={NANO ENERGY}, publisher={Elsevier BV}, author={Chen, Yu and Chen, Erdong and Wang, Zihao and Ling, Yali and Fisher, Rosie and Li, Mengjiao and Hart, Jacob and Mu, Weilei and Gao, Wei and Tao, Xiaoming and et al.}, year={2022}, month={Dec} }
 @article{subjalearndee_he_cheng_tesatchabut_eiamlamai_limthongkul_intasanta_gao_zhang_2022, title={Gamma((sic))-MnO2/rGO Fibered Cathode Fabrication from Wet Spinning and Dip Coating Techniques for Cable-Shaped Zn-Ion Batteries}, volume={1}, ISSN={["2524-793X"]}, url={https://doi.org/10.1007/s42765-021-00118-3}, DOI={10.1007/s42765-021-00118-3}, journal={ADVANCED FIBER MATERIALS}, author={Subjalearndee, Nakarin and He, Nanfei and Cheng, Hui and Tesatchabut, Panpanat and Eiamlamai, Priew and Limthongkul, Pimpa and Intasanta, Varol and Gao, Wei and Zhang, Xiangwu}, year={2022}, month={Jan} }
 @article{ramesh_davis_roros_zhou_he_gao_menegatti_khan_genzer_2022, title={Nonwoven Membranes with Infrared Light-Controlled Permeability}, volume={9}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.2c13280}, abstractNote={This study presents the development of the first composite nonwoven fiber mats (NWFs) with infrared light-controlled permeability. The membranes were prepared by coating polypropylene NWFs with a photothermal layer of poly(N-isopropylacrylamide) (PNIPAm)-based microgels impregnated with graphene oxide nanoparticles (GONPs). This design enables "photothermal smart-gating" using light dosage as remote control of the membrane's permeability to electrolytes. Upon exposure to infrared light, the GONPs trigger a rapid local increase in temperature, which contracts the PNIPAm-based microgels lodged in the pore space of the NWFs. The contraction of the microgels can be reverted by cooling from the surrounding aqueous environment. The efficient conversion of infrared light into localized heat by GONPs coupled with the phase transition of the microgels above the lower critical solution temperature (LCST) of PNIPAm provide effective control over the effective porosity, and thus the permeability, of the membrane. The material design parameters, namely the monomer composition of the microgels and the GONP-to-microgel ratio, enable tuning the permeability shift in response to IR light; control NWFs coated with GONP-free microgels displayed thermal responsiveness only, whereas native NWFs showed no smart-gating behavior at all. This technology shows potential toward processing temperature-sensitive bioactive ingredients or remote-controlled bioreactors.}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Ramesh, Srivatsan and Davis, Jack and Roros, Alexandra and Zhou, Chuanzhen and He, Nanfei and Gao, Wei and Menegatti, Stefano and Khan, Saad and Genzer, Jan}, year={2022}, month={Sep} }
 @article{he_song_liao_zhao_gao_2022, title={Separator threads in yarn-shaped supercapacitors to avoid short-circuiting upon length}, volume={6}, ISSN={["2397-4621"]}, DOI={10.1038/s41528-022-00150-2}, abstractNote={Abstract Yarn-shaped supercapacitors (YSCs) are becoming promising energy-supply units with decent mechanical flexibility to be integrated into e-textiles in various shapes and locations. However, a robust YSC configuration that can provide long-term and reliable power output, especially after rigorous weaving and knitting processes, as well as all kinds of end uses, is yet to be established. Most YSCs today still suffer from short-circuiting upon length, primarily due to the structure failure of gel electrolyte that also works as the separator. Herein, we report the incorporation of separator threads in a twisted YSC, to withstand repetitive mechanical deformations. Separator threads are wrapped outside of yarn electrodes as a scaffold to accommodate gel electrolyte, while chemistry and wrapping density of these threads are investigated. With processing parameters optimized, we present an YSC configuration that can bear mechanical deformations along almost all directions, leading to reliable power units in woven or knit fabrics.}, number={1}, journal={NPJ FLEXIBLE ELECTRONICS}, author={He, Nanfei and Song, Junhua and Liao, Jinyun and Zhao, Feng and Gao, Wei}, year={2022}, month={Mar} }
 @article{wang_shim_he_pourdeyhimi_gao_2021, title={Modeling the Triboelectric Behaviors of Elastomeric Nonwoven Fabrics}, volume={11}, ISSN={["1521-4095"]}, url={https://doi.org/10.1002/adma.202106429}, DOI={10.1002/adma.202106429}, abstractNote={Theoretical modeling of triboelectric nanogenerators (TENGs) is fundamental to their performance optimization, since it can provide useful guidance on the material selection, structure design, and parameter control of relevant systems. Built on the theoretical model of film‐based TENGs, here, an analytical model is introduced for conductor‐to‐dielectric contact‐mode nonwoven‐based TENGs, which copes with the unique hierarchical structure of nonwovens and details the correlation between the triboelectric output (maximum transferred charge density) and nonwoven structural parameters (thickness, solidity, and average fiber diameter). A series of styrene–ethylene–butylene–styrene nonwoven samples are fabricated through a melt‐blowing process to map nonwoven structural features within certain ranges, while an ion‐injection protocol is adopted to quantify the triboelectric output with superior consistency and reproducibility. With a database containing structural features and triboelectric output of 43 nonwoven samples, a good model fitting is achieved via nonlinear regression analysis in Python, which also shows good predictive power and suggests the existing of tribo‐output maxima at a specific thickness, solidity, or average fiber diameter when other structural parameters are fixed. The model is also successfully applied to a group of polypropylene meltblown nonwovens, which verifies its universality on meltblown‐nonwoven‐based TENGs.}, journal={ADVANCED MATERIALS}, publisher={Wiley}, author={Wang, Yanan and Shim, Eunkyoung and He, Nanfei and Pourdeyhimi, Behnam and Gao, Wei}, year={2021}, month={Nov} }
 @article{kim_ramalingam_balakumar_zhang_gao_son_bradford_2020, title={Chemically interconnected ternary AgNP/polypyrrole/functionalized buckypaper composites as high-energy-density supercapacitor electrodes}, volume={739}, ISSN={["1873-4448"]}, DOI={10.1016/j.cplett.2019.136957}, abstractNote={In this study, a chemically interconnected composite, called EBP-PPY-AgNP, was fabricated to develop high-performance hybrid supercapacitor electrodes. The composite consists of epoxide-functionalized buckypaer (EBP), polypyrrole (PPY), and silver nanoparticles (AgNP). The structure was characterized using Raman spectroscopy, X-ray photon spectroscopy (XPS), and scanning electron microscopy (SEM). Also, cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) analyses were conducted to estimate the electrochemical performance. The results were more excellent than those of the other electrodes not chemically interconnected. Finally, the energy density was calculated, and the value was higher than in previous studies that examined electrodes with similar materials.}, journal={CHEMICAL PHYSICS LETTERS}, author={Kim, Hyungjoo and Ramalingam, Manivannan and Balakumar, Vellaichamy and Zhang, Xiangwu and Gao, Wei and Son, Young-A and Bradford, Philip D.}, year={2020}, month={Jan} }
 @article{he_liao_zhao_gao_2020, title={Dual-Core Supercapacitor Yarns: An Enhanced Performance Consistency and Linear Power Density}, volume={12}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.0c00182}, abstractNote={Pliable energy-storage devices are arousing great attention recently due to their important roles in rapid-growing wearable/implantable electronic systems, among which yarn-shaped supercapacitors (YSCs) are promising candidates since they carry great design versatility with tunable sizes and shapes. However, existing challenges of YSCs include inferior power output and poor performance consistency as compared to their planner counterparts, mainly due to their unique linear geometry and curved interfaces. Here an YSC comprised of wet-spun fibers of reduced graphene oxide (rGO) and MXene sheets is demonstrated, which exhibits prominent decreases in equivalent series resistance (ESR), and thus increases in power output upon increasing length, which is contradictory to the common expectations of a typical YSC, carrying revolutionary promises for practical applications. A much higher power density (2502.6 μW cm-2) can be achieved at an average energy density of 27.1μWh cm-2 (linearly, 510.9 μW cm-1 at 5.5 μWh cm-1) via our unique dual-core design. The YSCs also present good stability upon stretching and bending, compatible with further textile processing. This work provides new insights toward the fabrication of textile-based energy-storage devices for real-world applications.}, number={13}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={He, Nanfei and Liao, Jinyun and Zhao, Feng and Gao, Wei}, year={2020}, month={Apr}, pages={15211–15219} }
 @article{he_patil_qu_liao_zhao_gao_2020, title={Effects of Electrolyte Mediation and MXene Size in Fiber-Shaped Supercapacitors}, volume={3}, ISSN={["2574-0962"]}, DOI={10.1021/acsaem.0c00024}, abstractNote={Flexible and pliable fiber electrodes with decent electrical conductivity and high capacitance density are crucial to fiber-shaped supercapacitors (FSCs) whose real-world applications include elect...}, number={3}, journal={ACS APPLIED ENERGY MATERIALS}, author={He, Nanfei and Patil, Shradha and Qu, Jiangang and Liao, Jinyun and Zhao, Feng and Gao, Wei}, year={2020}, month={Mar}, pages={2949–2958} }
 @article{zhang_xiang_wang_xiong_gao_pan_2020, title={Image retrieval of wool fabric. Part II: based on low-level color features}, volume={90}, ISSN={["1746-7748"]}, DOI={10.1177/0040517519881819}, abstractNote={Color is difficult to distinguish by human vision and is described by keywords, resulting in low efficiency of wool fabric retrieval in factories at present. To obtain the process sheets of existing products and reduce the work of color measurement in sample analysis, this paper proposes an effective method based on dominant colors (DCs) and color moments (CMs) for wool fabric image retrieval. Firstly, the image was scaled to reduce computational time. Then, the hue, saturation, value color space was divided into 128 parts by the fast color quantization algorithm to extract the DCs of the image. Meanwhile, the CMs based on image partition were calculated in CIE L*a*b* color space to describe the spatial color information. Subsequently, different similarity measure methods were carried out based on the DC feature and CM feature. Finally, experiments were conducted on a wool fabric image database with 20,000 images for parameter optimization and verification. The average precision and recall were up to 87% and 44%, respectively. Experimental results show that the proposed scheme can retrieve images with the same or similar colors quickly and effectively and it outperformed other methods, providing referential assistance for the factory worker when retrieving wool fabrics.}, number={7-8}, journal={TEXTILE RESEARCH JOURNAL}, author={Zhang, Ning and Xiang, Jun and Wang, Lei and Xiong, Nian and Gao, Weidong and Pan, Ruru}, year={2020}, month={Apr}, pages={797–808} }
 @article{schneible_shi_young_ramesh_he_dowdey_dubnansky_libya_gao_santiso_et al._2020, title={Modified gaphene oxide (GO) particles in peptide hydrogels: a hybrid system enabling scheduled delivery of synergistic combinations of chemotherapeutics}, volume={8}, ISSN={["2050-7518"]}, DOI={10.1039/d0tb00064g}, abstractNote={The scheduled delivery of synergistic drug combinations is increasingly recognized as highly effective against advanced solid tumors. Of particular interest are composite systems that release a sequence of drugs with defined kinetics and molar ratios to enhance therapeutic effect, while minimizing the dose to patients. In this work, we developed a homogeneous composite comprising modified graphene oxide (GO) nanoparticles embedded in a Max8 peptide hydrogel, which provides controlled kinetics and molar ratios of release of doxorubicin (DOX) and gemcitabine (GEM). First, modified GO nanoparticles (tGO) were designed to afford high DOX loading and sustained release (18.9% over 72 h and 31.4% over 4 weeks). Molecular dynamics simulations were utilized to model the mechanism of DOX loading as a function of surface modification. In parallel, a Max8 hydrogel was developed to release GEM with faster kinetics and achieve a 10-fold molar ratio to DOX. The selected DOX/tGO nanoparticles were suspended in a GEM/Max8 hydrogel matrix, and the resulting composite was tested against a triple negative breast cancer cell line, MDA-MB-231. Notably, the composite formulation afforded a combination index of 0.093 ± 0.001, indicating a much stronger synergism compared to the DOX-GEM combination co-administered in solution (CI = 0.396 ± 0.034).}, number={17}, journal={JOURNAL OF MATERIALS CHEMISTRY B}, author={Schneible, John D. and Shi, Kaihang and Young, Ashlyn T. and Ramesh, Srivatsan and He, Nanfei and Dowdey, Clay E. and Dubnansky, Jean Marie and Libya, Radina L. and Gao, Wei and Santiso, Erik and et al.}, year={2020}, month={May}, pages={3852–3868} }
 @article{kim_ramalingam_balakumar_zhang_gao_son_bradford_2019, title={AgNP/crystalline PANI/EBP-composite-based supercapacitor electrode with internal chemical interactions}, volume={136}, ISSN={["1097-4628"]}, url={https://publons.com/publon/26924632/}, DOI={10.1002/app.48164}, abstractNote={ABSTRACT In this article, polyaniline (PANI) was conformally coated on epoxide‐functionalized buckypaper (EBP). Because of the presence of epoxide functional groups, chemical interactions occurred between oxygen in the epoxide groups and NH in the PANI. These chemical interactions were identified by peak shifts and intensity changes in Raman spectra. Additionally, crystalline peaks were clearly observed through X‐ray diffraction. However, Raman peak changes or crystalline peaks were not observed in nonfunctionalized buckypaper (purified pristine buckypaper [PPBP])‐based composites. Both hydrogen bonding and crystalline nature of EBP‐PANI enhanced its electrical conductivity, producing a specific capacitance better than that of PPBP‐PANI. Finally, Ag nanoparticles (AgNPs) were applied to EBP‐PANI to further enhance its electrical conductivity. Owing to the presence of AgNPs and their interactions with the N in PANI, the specific capacitance of EBP‐PANI‐AgNP reached 915.62 F/g. These results emphasize the positive effect of chemical interactions and crystalline nature of EBP‐based composites on their electrochemical performance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 48164.}, number={44}, journal={JOURNAL OF APPLIED POLYMER SCIENCE}, author={Kim, Hyungjoo and Ramalingam, Manivannan and Balakumar, Vellaichamy and Zhang, Xiangwu and Gao, Wei and Son, Young-A and Bradford, Philip D.}, year={2019}, month={Nov} }
 @article{shi_huang_wang_zhou_yang_wang_gao_xia_2019, title={Electronic Metal-Support Interaction To Modulate MoS2-Supported Pd Nanoparticles for the Degradation of Organic Dyes}, volume={2}, ISSN={["2574-0970"]}, DOI={10.1021/acsanm.9b00297}, abstractNote={Electronic modulation of heterogeneous metal catalysts has been considered as an effective means to optimize their catalytic performance. Two-dimensional nanomaterials, typically used as the supporting substrates for anchoring the active metal nanoparticles, are well-known to profoundly influence the electronic structure of metals through interfacial electronic metal–support interaction (EMSI). However, the detailed investigation of EMSI for catalytic enhancement still remains obscure at the microscopic level. Herein, we propose to utilize MoS2 nanosheets to modulate the electronic structure of Pd through EMSI and investigate the influence of “support effect” of MoS2 on the catalytic activity of Pd utilizing degradation of methylene blue (MB) with the electron donor NaBH4 as a simple model reaction. Mechanistic investigations reveal that the electron transfer from Pd to MoS2 makes a highly electron-deficient Pd surface. During the target catalysis, this interfacial electronic structure makes the surface o...}, number={6}, journal={ACS APPLIED NANO MATERIALS}, author={Shi, Yi and Huang, Xiao-Kun and Wang, Yang and Zhou, Yue and Yang, Dong-Rui and Wang, Feng-Bin and Gao, Wei and Xia, Xing-Hua}, year={2019}, month={Jun}, pages={3385–3393} }
 @article{qiao_liu_gao_huang_2019, title={Graphene oxide model with desirable structural and chemical properties}, volume={143}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2018.11.063}, abstractNote={Due to unique chemical, electrical and optical properties, graphene oxide has been widely used as a promising candidate for many applications. Theoretical GO models developed so far present a good description of its chemical structure. However, when it comes to the structural properties, such as the size and distribution of vacancy defects, the curvature (or roughness), there exist significant gaps between computational models and experimentally synthesized GO materials. In this work, we carry out reactive molecular dynamics simulations and use experimental characteristics to fine tune theoretical GO models. Attentions have been paid to the vacancy defects, the distribution and hybridization of carbon atoms, and the overall C/O ratio of GO. The GO models proposed in this work have been significantly improved to represent quantitative structural details of GO materials synthesized via the modified Hummers method. The temperature-programmed protocol and the computational post analyses of Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, vacancy size and curvature distribution, are of general interest to a broad audience working on GO structures from other synthesis methods and other two-dimensional materials and their composites.}, journal={CARBON}, author={Qiao, Qi and Liu, Chang and Gao, Wei and Huang, Liangliang}, year={2019}, month={Mar}, pages={566–577} }
 @article{he_shan_wang_pan_qu_wang_gao_2019, title={Mordant inspired wet-spinning of graphene fibers for high performance flexible supercapacitors}, volume={7}, ISSN={["2050-7496"]}, DOI={10.1039/c8ta12337c}, abstractNote={Al3+ coagulated wet-spun graphene fibers show a large surface area and high electrical conductivity, resulting in large capacitance.}, number={12}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={He, Nanfei and Shan, Weitao and Wang, Julia and Pan, Qin and Qu, Jiangang and Wang, Guofeng and Gao, Wei}, year={2019}, month={Mar}, pages={6869–6876} }
 @article{qu_he_patil_wang_banerjee_gao_2019, title={Screen Printing of Graphene Oxide Patterns onto Viscose Nonwovens with Tunable Penetration Depth and Electrical Conductivity}, volume={11}, ISSN={["1944-8252"]}, url={http://dx.doi.org/10.1021/acsami.9b00715}, DOI={10.1021/acsami.9b00715}, abstractNote={Graphene-based e-textiles have attracted great interest because of their promising applications in sensing, protection, and wearable electronics. Here, we report a scalable screen-printing process along with continuous pad-dry-cure treatment for the creation of durable graphene oxide (GO) patterns onto viscose nonwoven fabrics at controllable penetration depth. All the printed nonwovens show lower sheet resistances (1.2-6.8 kΩ/sq) at a comparable loading, as those reported in the literature, and good washfastness, which is attributed to the chemical cross-linking applied between reduced GO (rGO) flakes and viscose fibers. This is the first demonstration of tunable penetration depth of GO in textile matrices, wherein GO is also simultaneously converted to rGO and cross-linked with viscose fibers in our processes. We have further demonstrated the potential applications of these nonwoven fabrics as physical sensors for compression and bending.}, number={16}, journal={ACS APPLIED MATERIALS & INTERFACES}, publisher={American Chemical Society (ACS)}, author={Qu, Jiangang and He, Nanfei and Patil, Shradha V. and Wang, Yanan and Banerjee, Debjyoti and Gao, Wei}, year={2019}, month={Apr}, pages={14944–14951} }
 @article{li_xiong_liu_gao_shamey_2018, title={Determining the colorimetric attributes of multicolored materials based on a global correction and unsupervised image segmentation method}, volume={57}, ISSN={["2155-3165"]}, url={https://doi.org/10.1364/AO.57.007482}, DOI={10.1364/AO.57.007482}, abstractNote={Fast and accurate measurement of colors in multicolored prints using commercial instruments or existing computer vision systems remains a challenge due to limitations in image segmentation methods and the size and complexity of the colored patterns. To determine the colorimetric attributes (L*a*b*) of multicolored materials, an approach based on global color correction and an effective unsupervised image segmentation is presented. The colorimetric attributes of all patches in a ColorChecker chart were measured spectrophotometrically, and an image of the chart was also captured. Images were segmented using a modified Chan-Vese method, and the sRGB values of each patch were extracted and then transformed into L*a*b* values. In order to optimize the transformation process, the performance of 10 models was examined by minimizing the average color differences between measured and calculated colorimetric values. To assess the performance of the model, a set of printed samples was employed and the color differences between the predicted and measured L*a*b* values of samples were compared. The results show that the modified Chan-Vese method, with suitable settings, generates satisfactory segmentation of the printed images with mean and maximum ΔE00 values of 2.43 and 4.28 between measured and calculated values.}, number={26}, journal={APPLIED OPTICS}, author={Li, Zhongjian and Xiong, Nian and Liu, Jiajun and Gao, Weidong and Shamey, Renzo}, year={2018}, month={Sep}, pages={7482–7491} }
 @article{pan_tong_he_liu_shim_pourdeyhimi_gao_2018, title={Electrospun Mat of Poly(vinyl alcohol)/Graphene Oxide for Superior Electrolyte Performance}, volume={10}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.7b14498}, abstractNote={Here, we describe an electrospun mat of poly(vinyl alcohol) (PVA) and graphene oxide (GO) as a novel solid-state electrolyte matrix, which offers better performance retention upon drying after infiltrated with aqueous electrolyte. The PVA-GO mat overcomes the major issue of conventional PVA-based electrolytes, which is the ionic conductivity decay upon drying. After exposure to 45 ± 5% relative humidity at 25 °C for 1 month, its conductivity decay is limited to 38.4%, whereas that of pure PVA mat is as high as 84.0%. This mainly attributes to the hygroscopic nature of GO and the unique nanofiber structure within the mat. Monolithic supercapacitors have been derived directly on the mat via a well-developed laser scribing process. The as-prepared supercapacitor offers an areal capacitance of 9.9 mF cm-2 at 40 mV s-1 even after 1 month of aging under ambient conditions, with a high device-based volumetric energy density of 0.13 mWh cm-3 and a power density of 2.48 W cm-3, demonstrating great promises as a more stable power supply for wearable electronics.}, number={9}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Pan, Qin and Tong, Ningjun and He, Nanfei and Liu, Yixin and Shim, Eunkyoung and Pourdeyhimi, Behnam and Gao, Wei}, year={2018}, month={Mar}, pages={7927–7934} }
 @article{babaahmadi_montazer_gao_2018, title={Surface modification of PET fabric through in-situ reduction and cross-linking of graphene oxide: Towards developing durable conductive fabric coatings}, volume={545}, ISSN={["1873-4359"]}, DOI={10.1016/j.colsurfa.2018.02.018}, abstractNote={A durable electro-conductive polyethylene terephthalate (PET) fabric has been fabricated via reduction and cross-linking of graphene oxide (GO) with SnCl2. The stannous ions (Sn2+) reduce GO and generate multilayer cross-linked and reduced graphene oxide (XrGO) coatings on PET fabric surfaces. In addition to the chemical treatments, thermal annealing was also used to improve the electrical conductivity and durability of coatings on PET surface. The planner aromatic structure of PET promotes the adsorption of the XrGO sheets via π–π interactions, and the adsorbed XrGO sheets can be physically fused onto the surface of PET fibers below 200 °C, mainly due to the thermoplastic nature of PET. A good washing fastness and mechanical stability has been observed confirming the effectiveness of the chemical cross-linking and thermal anealing on the durability of the conductive coating onto the PET fabric surface.}, journal={COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS}, author={Babaahmadi, Vahid and Montazer, Majid and Gao, Wei}, year={2018}, month={May}, pages={16–25} }
 @article{he_yoo_meng_yildiz_bradford_park_gao_2017, title={Engineering biorefinery residues from loblolly pine for supercapacitor applications}, volume={120}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2017.05.056}, abstractNote={Recycling agricultural waste biomass into high-value-added products is of great importance to offset the cost of biofuel production. Here, we make biochar-based activated carbons (BACs) from loblolly pine chips via different carbonization recipes and chemical activations. BACs were then assembled into electrochemical double-layer capacitors (EDLCs) as electrode materials. Surprisingly, pyrolysis at lower temperatures (300 °C and 350 °C) rendered better electrochemical performance of BACs than those done at higher temperatures (500 °C and 700 °C). This is mainly due to the large surface area and high pore volume generated at the lower temperatures. Among all the pyrolysis recipes, flash pyrolysis at 300 °C produced the BAC with the highest specific capacitance (74 F g−1 at 20 mV s−1), exceeding the specific capacitance of commercial activated carbon (NORIT®) by 45%. This report demonstrates the great potential of our refinery recipe to engineer BACs from the sustainable, affordable, and abundant natural wastes for energy-storage applications, which opens the door for a group of biorefinery residues for value-added applications.}, journal={CARBON}, author={He, Nanfei and Yoo, Seunghyun and Meng, Jiajia and Yildiz, Ozkan and Bradford, Philip D. and Park, Sunkyu and Gao, Wei}, year={2017}, month={Aug}, pages={304–312} }
 @article{lu_lin_chen_hu_liu_yu_gao_dickey_gu_2017, title={Enhanced Endosomal Escape by Light-Fueled Liquid-Metal Transformer}, volume={17}, ISSN={["1530-6992"]}, DOI={10.1021/acs.nanolett.6b04346}, abstractNote={Effective endosomal escape remains as the "holy grail" for endocytosis-based intracellular drug delivery. To date, most of the endosomal escape strategies rely on small molecules, cationic polymers, or pore-forming proteins, which are often limited by the systemic toxicity and lack of specificity. We describe here a light-fueled liquid-metal transformer for effective endosomal escape-facilitated cargo delivery via a chemical-mechanical process. The nanoscale transformer can be prepared by a simple approach of sonicating a low-toxicity liquid-metal. When coated with graphene quantum dots (GQDs), the resulting nanospheres demonstrate the ability to absorb and convert photoenergy to drive the simultaneous phase separation and morphological transformation of the inner liquid-metal core. The morphological transformation from nanospheres to hollow nanorods with a remarkable change of aspect ratio can physically disrupt the endosomal membrane to promote endosomal escape of payloads. This metal-based nanotransformer equipped with GQDs provides a new strategy for facilitating effective endosomal escape to achieve spatiotemporally controlled drug delivery with enhanced efficacy.}, number={4}, journal={NANO LETTERS}, publisher={American Chemical Society (ACS)}, author={Lu, Yue and Lin, Yiliang and Chen, Zhaowei and Hu, Quanyin and Liu, Yang and Yu, Shuangjiang and Gao, Wei and Dickey, Michael D. and Gu, Zhen}, year={2017}, month={Apr}, pages={2138–2145} }
 @article{he_pan_liu_gao_2017, title={Graphene-Fiber-Based Supercapacitors Favor N-Methyl-2-pyrrolidone/Ethyl Acetate as the Spinning Solvent/Coagulant Combination}, volume={9}, ISSN={["1944-8244"]}, DOI={10.1021/acsami.7b05982}, abstractNote={One-dimensional flexible fiber supercapacitors (FSCs) have attracted great interest as promising energy-storage units that can be seamlessly incorporated into textiles via weaving, knitting, or braiding. The major challenges in this field are to develop tougher and more efficient FSCs with a relatively easy and scalable process. Here, we demonstrate a wet-spinning process to produce graphene oxide (GO) fibers from GO dispersions in N-methyl-2-pyrrolidone (NMP), with ethyl acetate as the coagulant. Upon chemical reduction of GO, the resulting NMP-based reduced GO (rGO) fibers (rGO@NMP-Fs) are twice as high in the surface area and toughness but comparable in tensile strength and conductivity as that of the water-based rGO fibers (rGO@H2O-Fs). When assembled into parallel FSCs, rGO@NMP-F-based supercapacitors (rGO@NMP-FSCs) offered a specific capacitance of 196.7 F cm-3 (147.5 mF cm-2), five times higher than that of rGO@H2O-F-based supercapacitors (rGO@H2O-FSCs) and also higher than most existing wet-spun rGO-FSCs, as well as those FSCs built with metal wires, graphene/carbon nanotube (CNT) fibers, or even pseudocapacitive materials. In addition, our rGO@NMP-FSCs can provide good bending and cycling stability. The energy density of our rGO@NMP-FSCs reaches ca. 6.8 mWh cm-3, comparable to that of a Li thin-film battery (4 V/500 μAh).}, number={29}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={He, Nanfei and Pan, Qin and Liu, Yixin and Gao, Wei}, year={2017}, month={Jul}, pages={24568–24576} }
 @article{pan_shim_pourdeyhimi_gao_2017, title={Highly Conductive Polypropylene-Graphene Nonwoven Composite via Interface Engineering}, volume={33}, ISSN={["0743-7463"]}, DOI={10.1021/acs.langmuir.7b01508}, abstractNote={Here we report a highly conductive polypropylene-graphene nonwoven composite via direct coating of melt blown polypropylene (PP) nonwoven fabrics with graphene oxide (GO) dispersions in N,N-dimethylformamide (DMF), followed by the chemical reduction of GO with hydroiodic acid (HI). GO as an amphiphilic macromolecule can be dispersed in DMF homogeneously at a concentration of 5 mg/mL, which has much lower surface tension (37.5 mN/m) than that of GO in water (72.9 mN/m, at 5 mg/mL). The hydrophobic PP nonwoven has a surface energy of 30.1 mN/m, close to the surface tension of GO in DMF. Therefore, the PP nonwoven can be easily wetted by the GO/DMF dispersion without any pretreatment. Soaking PP nonwoven in a GO/DMF dispersion leads to uniform coatings of GO on PP-fiber surfaces. After chemical reduction of GO to graphene, the resulting PP/graphene nonwoven composite offers an electrical conductivity of 35.6 S m-1 at graphene loading of 5.2 wt %, the highest among the existing conductive PP systems reported, indicating that surface tension of coating baths has significant impact on the coating uniformity and affinity. The conductivity of our PP/graphene nonwoven is also stable against stirring washing test. In addition, here we demonstrate a monolithic supercapacitor derived from the PP-GO nonwoven composite by using a direct laser-patterning process. The resulted sandwich supercapacitor shows a high areal capacitance of 4.18 mF/cm2 in PVA-H2SO4 gel electrolyte. The resulting highly conductive or capacitive PP/graphene nonwoven carries great promise to be used as electronic textiles.}, number={30}, journal={LANGMUIR}, author={Pan, Qin and Shim, Eunkyoung and Pourdeyhimi, Behnam and Gao, Wei}, year={2017}, month={Aug}, pages={7452–7458} }
 @article{babaahmadi_montazer_gao_2017, title={Low temperature welding of graphene on PET with silver nanoparticles producing higher durable electro-conductive fabric}, volume={118}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2017.03.066}, abstractNote={Conductive fabrics have been the basic building blocks in various applications such as static dissipation, EMI shielding and wearable electronics, where high conductivity and good durability are essential. This work describes a new method to improve the conductivity and durability of modified polyethylene terephthalate (PET) fabrics via low-temperature welding of silver nanoparticles (AgNPs) and reduced graphene oxide (rGO) on the PET fiber surfaces. A layer of rGO-AgNPs on the fiber surface was formed by coating aqueous mixture of graphene oxide (GO) and AgNO3 and the subsequent reduction with hydrazine. Interfusing of rGO-AgNPs and fibers has been achieved via thermal annealing at relatively low temperatures (<200 °C), thanks to the depressed melting point of Ag in the nanoparticle form. Electrical conductivity and wash fastness have been significantly enhanced after annealing. To our best knowledge, our fabric bares the highest electrical conductivity among those reported in similar textile systems. In addition, we report good durability of rGO coating on PET via a series of wash fastness and bending tests.}, journal={CARBON}, author={Babaahmadi, Vahid and Montazer, Majid and Gao, Wei}, year={2017}, month={Jul}, pages={443–451} }
 @article{pan_shim_pourdeyhimi_gao_2017, title={Nylon-Graphene Composite Nonwovens as Monolithic Conductive or Capacitive Fabrics}, volume={9}, ISSN={["1944-8244"]}, DOI={10.1021/acsami.7b00471}, abstractNote={Here we describe a nylon-graphene nonwoven (NGN) composite, prepared via melt-blowing of nylon-6 into nonwoven fabrics and infiltrate those with graphene oxide (GO) in aqueous dispersions, which were further chemically reduced into graphene to offer electrical conductivity. The correlation between the conductivity and the graphene loading is described by the percolation scaling law σ = (p - pc)t, with an exponent t of 1.2 and a critical concentration pc of 0.005 wt %, the lowest among all the nylon composites reported. Monolithic supercapacitors have been further developed on the nylon-GO nonwoven composites (NGO), via a programed CO2-laser patterning process. The nylon nonwoven works as an efficient matrix, providing high capacity to GO and ensuring enough electrode materials generated via the subsequent laser patterning processes. Our best monolithic supercapacitors exhibited an areal capacitance of 10.37 mF cm-2 in PVA-H2SO4 electrolyte, much higher than the 1-3 mF cm-2 reported for typical microsupercapacitors. Moreover, our supercapacitors were able to retain a capacitance density of 5.07 mF cm-2 at an ultrahigh scan rate (1 V s-1), probably due to the facilitated ion migration within the highly porous nonwoven framework. This is the first report of highly functional nylon-6 nonwovens, fabricated via industrially scalable pathways into low-cost conductive polymer matrices and disposable energy storage systems.}, number={9}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Pan, Qin and Shim, Eunkyoung and Pourdeyhimi, Behnam and Gao, Wei}, year={2017}, month={Mar}, pages={8308–8316} }
 @article{he_yildiz_pan_zhu_zhang_bradford_gao_2017, title={Pyrolytic-carbon coating in carbon nanotube foams for better performance in supercapacitors}, volume={343}, ISSN={["1873-2755"]}, url={https://publons.com/publon/19584407/}, DOI={10.1016/j.jpowsour.2017.01.091}, abstractNote={Nowadays, the wide-spread adoption of supercapacitors has been hindered by their inferior energy density to that of batteries. Here we report the use of our pyrolytic-carbon-coated carbon nanotube foams as lightweight, compressible, porous, and highly conductive current collectors in supercapacitors, which are infiltrated with chemically-reduced graphene oxide and later compressed via mechanical and capillary forces to generate the active electrodes. The pyrolytic carbon coatings, introduced by chemical vapor infiltration, wrap around the CNT junctions and increase the surface roughness. When active materials are infiltrated, the pyrolytic-carbon coatings help prevent the π-stacking, enlarge the accessible surface area, and increase the electrical conductivity of the scaffold. Our best-performing device offers 48% and 57% higher gravimetric energy and power density, 14% and 23% higher volumetric energy and power density, respectively, and two times higher knee frequency, than the device with commercial current collectors, while the “true-performance metrics” are strictly followed in our measurements. We have further clarified the solution resistance, charge transfer resistance/capacitance, double-layer capacitance, and Warburg resistance in our system via comprehensive impedance analysis, which will shed light on the design and optimization of similar systems.}, journal={JOURNAL OF POWER SOURCES}, publisher={Elsevier BV}, author={He, Nanfei and Yildiz, Ozkan and Pan, Qin and Zhu, Jiadeng and Zhang, Xiangwu and Bradford, Philip D. and Gao, Wei}, year={2017}, month={Mar}, pages={492–501} }
 @article{wang_babaahmadi_he_liu_pan_montazer_gao_2017, title={Wearable supercapacitors on polyethylene terephthalate fabrics with good wash fastness and high flexibility}, volume={367}, ISSN={["1873-2755"]}, DOI={10.1016/j.jpowsour.2017.09.047}, abstractNote={All solid-state micro-supercapacitors (MSC) have emerged as attractive energy-storage units for portable and wearable electronics. Here, we describe a textile-based solid-state MSC via laser scribing of graphene oxide (GO) coatings on a flexible polyethylene terephthalate (PET) fabric. The laser-scribed graphene oxide layers (LGO) possess three-dimensionally porous structure suitable for electrochemical-double-layer formation. To improve the wash fastness and the flexibility of the as-prepared MSCs, glutaraldehyde (GA) was employed to crosslink the GO layers and PVA-gel electrolyte onto the PET fabric. The resultant all solid-state MSCs exhibited excellent flexibility, high areal specific capacitance (756 μF·cm−2 at 20 mV·s−1), and good rate capability when subject to bending and laundering. Furthermore, the MSC device showed a high power density of about 1.4 W·cm−3 and an energy density of 5.3 × 10−5 Wh·cm−3, and retained 98.3% of its initial capacitance after 1000 cycles at a current density of 0.5 mA·cm−2. This work is the first demonstration of in-plane MSCs on PET fabric surfaces with enhanced durability and flexibility.}, journal={JOURNAL OF POWER SOURCES}, author={Wang, Guixia and Babaahmadi, Vahid and He, Nanfei and Liu, Yixin and Pan, Qin and Montazer, Majid and Gao, Wei}, year={2017}, month={Nov}, pages={34–41} }
 @article{pan_chung_he_jones_gao_2016, title={Accelerated Thermal Decomposition of Graphene Oxide Films in Air via in Situ X-ray Diffraction Analysis}, volume={120}, ISSN={["1932-7455"]}, DOI={10.1021/acs.jpcc.6b05031}, abstractNote={Thermal decomposition of graphene oxide (GO) has been extensively investigated in the past decade, but the detailed reaction kinetics remains elusive so far. Here we employ an in situ X-ray diffraction (XRD) analysis to clarify the kinetics of GO decomposition in different atmospheres and sample morphologies. The XRD peak (002), which is the major diffraction peak corresponding to the interlayer distance in GO samples, shifted from 11.5° to 23° along with significant decrease in intensity when samples were heated from 25 to 350 °C. The decomposition in air exhibits a higher reaction rate compared with that in pure nitrogen gases because the O2 molecules in air facilitate the oxidation of carbon atoms, leading to the evolution of CO and CO2. Free-standing films of GO also decompose significantly faster than GO powders, owing to their slower heat dissipation into the environment and higher thermal conductivity within the well-stacked lamella. This study has provided new insights into the reaction kinetics o...}, number={27}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Pan, Qin and Chung, Ching-Chang and He, Nanfei and Jones, Jacob L. and Gao, Wei}, year={2016}, month={Jul}, pages={14984–14990} }
 @article{gao_havas_gupta_pan_he_zhang_wang_wu_2016, title={Is reduced graphene oxide favorable for nonprecious metal oxygen-reduction catalysts?}, volume={102}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2016.02.054}, abstractNote={Reduced graphene oxide (rGO), as a newly emerged carbon material, has attracted great attention concerning its applications for electrocatalysts. Presently, there are mixed opinions regarding the advantages to using rGO as a support for preparing nonprecious metal catalysts for the oxygen reduction reaction (ORR). The primary goal of this work is to determine whether rGO would be favorable for non-precious metal catalysis of oxygen reduction or not. In the case of Fe-free catalysts, when polyaniline (PANI) was used as nitrogen/carbon precursor, the PANI-rGO catalyst is superior to the PANI-Ketjenblack (KJ) carbon black catalyst in terms of ORR activity and H2O2 yield. When comparing the ORR activity of PANI-Fe-rGO to the traditional PANI-Fe-KJ, in more challenging acidic electrolyte, PANI-Fe-rGO performed no better than PANI-Fe-KJ. However, rGO does indeed enhance stability of the Fe–N–C catalyst in acidic media. In addition, in an alkaline electrolyte, ORR activity was significantly improved when using rGO in comparison to the KJ-supported Fe–N–C catalysts. Based on detailed comparisons of structures, morphologies, and reaction kinetics, the traditional KJ support with dominant microporous is able to accommodate more FeNx moieties that are crucial for the ORR in acid. Oppositely, the richness of nitrogen-doped graphene edge sites provided by rGO facilitates the ORR in the alkaline electrolyte.}, journal={CARBON}, author={Gao, Wei and Havas, Dana and Gupta, Shiva and Pan, Qin and He, Nanfei and Zhang, Hanguang and Wang, Hsing-Lin and Wu, Gang}, year={2016}, month={Jun}, pages={346–356} }
 @article{pino_gyoergy_logofatu_puigmarti-luis_gao_2015, title={Laser-induced chemical transformation of graphene oxide-iron oxide nanoparticles composites deposited on polymer substrates}, volume={93}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2015.05.078}, abstractNote={Ultraviolet laser irradiation of films composed of graphene oxide (GO) and GO–magnetite (Fe3O4) nanoparticles deposited on polydimethylsiloxane substrates is carried out. The irradiations are performed in vacuum and ammonia-rich gas environments. Electron and scanning probe microscopies reveal a rippling process in GO sheets as the accumulation of laser pulses proceeds, being the effect more pronounced with the increase of laser fluence. X-ray photoelectron spectroscopy analyses point to laser-induced chemical reaction pathways in GO completely different depending on the environment and the presence or absence of Fe3O4 nanoparticles. It is demonstrated that GO-based films with diverse type of oxygen- and nitrogen-containing chemical groups can be obtained by means of laser irradiation processes. The sheet resistance of these materials is also correlated to their structure and composition.}, journal={CARBON}, author={Pino, Angel and Gyoergy, Eniko and Logofatu, Constantin and Puigmarti-Luis, Josep and Gao, Wei}, year={2015}, month={Nov}, pages={373–383} }
 @article{sharp_kuntz_brubaker_amos_gao_gupta_mohite_farrar_mascareñas_2014, title={Crack detection sensor layout and bus configuration analysis}, volume={23}, ISSN={0964-1726 1361-665X}, url={http://dx.doi.org/10.1088/0964-1726/23/5/055021}, DOI={10.1088/0964-1726/23/5/055021}, abstractNote={In crack detection applications large sensor arrays are needed to be able to detect and locate cracks in structures. Emerging graphene-oxide paper sensing skins are a promising technology that will help enable structural sensing skins, but in order to make use of them we must consider how the sensors will be laid out and wired on the skin. This paper analyzes different sensor shapes and layouts to determine the layout which provides the preferred performance. A ‘snaked hexagon’ layout is proposed as the preferred sensor layout when both crack detection and crack location parameters are considered. In previous work we have developed a crack detection circuit which reduces the number of channels of the system by placing several sensors onto a common bus line. This helps reduce data and power consumption requirements but reduces the robustness of the system by creating the possibility of losing sensing in several sensors in the event that a single wire breaks. In this paper, sensor bus configurations are analyzed to increase the robustness of the bused sensor system. Results show that spacing out sensors in the same bus as much as possible increases the robustness of the system and that at least 3 buses are needed to prevent large segments of a structure from losing sensing in the event of a bus failure. This work is a preliminary effort toward enabling a new class of ‘networked materials’ that will be vitally important for next generation structural applications. ‘Networked materials’ have material properties related to information theoretic concepts. An example material property is ‘bandwidth’ per unit of material that might indicate the amount of information the material can provide about its state-of-health.}, number={5}, journal={Smart Materials and Structures}, publisher={IOP Publishing}, author={Sharp, Nathan and Kuntz, Alan and Brubaker, Cole and Amos, Stephanie and Gao, Wei and Gupta, Gautam and Mohite, Aditya and Farrar, Chuck and Mascareñas, David}, year={2014}, month={Apr}, pages={055021} }
 @article{li_xu_gao_ma_zhang_cao_cho_wang_wu_2014, title={Graphene/Graphene-Tube Nanocomposites Templated from Cage-Containing Metal-Organic Frameworks for Oxygen Reduction in Li-O2 Batteries}, volume={26}, ISSN={0935-9648}, url={http://dx.doi.org/10.1002/ADMA.201304218}, DOI={10.1002/ADMA.201304218}, abstractNote={Nitrogen-doped graphene/graphene-tube nanocomposites are prepared by a hightemperature approach using a newly designed cage-containing metal-organic framework (MOF) to template nitrogen/carbon (dicyandiamide) and iron precursors. The resulting N-Fe-MOF catalysts universally exhibit high oxygen-reduction activity in acidic, alkaline, and non-aqueous electrolytes and superior cathode performance in Li-O2 batteries.}, number={9}, journal={Advanced Materials}, publisher={Wiley}, author={Li, Qing and Xu, Ping and Gao, Wei and Ma, Shuguo and Zhang, Guoqi and Cao, Ruiguo and Cho, Jaephil and Wang, Hsing-Lin and Wu, Gang}, year={2014}, month={Mar}, pages={1378–1386} }
 @article{gao_wu_janicke_cullen_mukundan_baldwin_brosha_galande_ajayan_more_et al._2014, title={Ozonated Graphene Oxide Film as a Proton-Exchange Membrane}, volume={53}, ISSN={1433-7851}, url={http://dx.doi.org/10.1002/ANIE.201310908}, DOI={10.1002/ANIE.201310908}, abstractNote={Graphene oxide (GO) contains several chemical functional groups that are attached to the graphite basal plane and can be manipulated to tailor GO for specific applications. It is now revealed that the reaction of GO with ozone results in a high level of oxidation, which leads to significantly improved ionic (protonic) conductivity of the GO. Freestanding ozonated GO films were synthesized and used as efficient polymer electrolyte fuel cell membranes. The increase in protonic conductivity of the ozonated GO originates from enhanced proton hopping, which is due to the higher content of oxygenated functional groups in the basal planes and edges of ozonated GO as well as the morphology changes in GO that are caused by ozonation. The results of this study demonstrate that the modification of dispersed GO presents a powerful opportunity for optimizing a nanoscale material for proton-exchange membranes.}, number={14}, journal={Angewandte Chemie International Edition}, publisher={Wiley}, author={Gao, Wei and Wu, Gang and Janicke, Michael T. and Cullen, David A. and Mukundan, Rangachary and Baldwin, Jon K. and Brosha, Eric L. and Galande, Charudatta and Ajayan, Pulickel M. and More, Karren L. and et al.}, year={2014}, month={Feb}, pages={3588–3593} }
 @article{galande_gao_mathkar_dattelbaum_narayanan_mohite_ajayan_2014, title={Science and Engineering of Graphene Oxide}, volume={31}, ISSN={0934-0866}, url={http://dx.doi.org/10.1002/PPSC.201300232}, DOI={10.1002/PPSC.201300232}, abstractNote={Functional and synthesis diversity of graphene oxide (GO) has led to various fundamental and applied scientific explorations. GO can be viewed as an in‐plane, hybrid 2D lattice consisting of sp2 and sp3 carbon regions. Engineering the type and distribution of sp3 regions can tune the physical properties of resultant GO. This article reviews the development in the field of GO since the 19th century, with a thorough discussion on its status after the discovery of graphene in last decade. Detailed structure, optical properties, electrochemical behavior, and its viability for biological applications are discussed from both a scientific and technological perspective and a future outlook for GO research is presented.}, number={6}, journal={Particle & Particle Systems Characterization}, publisher={Wiley}, author={Galande, Charudatta and Gao, Wei and Mathkar, Akshay and Dattelbaum, Andrew M. and Narayanan, Tharangattu N. and Mohite, Aditya D. and Ajayan, Pulikel M.}, year={2014}, month={Feb}, pages={619–638} }
 @article{tian_li_wang_xiao_liu_li_li_gao_wu_2013, title={A Pd-free activation method for electroless nickel deposition on copper}, volume={228}, ISSN={0257-8972}, url={http://dx.doi.org/10.1016/J.SURFCOAT.2013.03.048}, DOI={10.1016/J.SURFCOAT.2013.03.048}, abstractNote={In this work, a Pd-free activation method for electroless nickel deposition on copper via an immersion nickel technique was developed. In the very solution we studied, high concentration of thiourea resulted in a negative shift of the steady potential of copper, making it possible to realize immersion nickel. The obtained immersion nickel layers were characterized by scanning electron microscopy, energy dispersive X-ray spectrometry and X-ray photoelectron spectroscopy, demonstrating a co-deposition of sulfur in the nickel layer. Importantly, the post-treatment in 1.0 M NaH2PO2 + 1.0 M NaOH solution was able to eliminate the adsorbed thiourea and stimulate the catalytic activity of the immersion nickel layer for electroless nickel deposition. A combination of open circuit potential measurements and morphology studies indicated that an incubation step was required during the electroless nickel deposition on the immersion nickel layers after post-treatment. Although the catalytic activity of this Ni-activation method was slightly lower as compared to the conventional Pd-activation, both obtained electroless Ni–P layers exhibited similar morphology, chemical composition, corrosion resistance, and adhesion strength. Thus, this work demonstrated that the newly developed Ni-activation method was cost-effective and could be a promising replacement to expensive Pd-activation method currently used in printed circuit board industries.}, journal={Surface and Coatings Technology}, publisher={Elsevier BV}, author={Tian, Dong and Li, De Y. and Wang, Fang F. and Xiao, Ning and Liu, Rui Q. and Li, Ning and Li, Qing and Gao, Wei and Wu, Gang}, year={2013}, month={Aug}, pages={27–33} }
 @article{song_khoerunnisa_gao_dou_hayashi_kaneko_endo_ajayan_2013, title={Effect of high-temperature thermal treatment on the structure and adsorption properties of reduced graphene oxide}, volume={52}, ISSN={0008-6223}, url={http://dx.doi.org/10.1016/j.carbon.2012.09.060}, DOI={10.1016/j.carbon.2012.09.060}, abstractNote={We present the study on the structure and adsorption properties of reduced graphene oxide subjected to thermal treatment in temperature range of 1100–2000 °C under flowing argon. The morphology and composition analyses reveal that the defective carbon materials remaining after volatilization of oxygen and hydrogen rearrange into highly ordered hexagonal carbon layers during thermal treatment at 2000 °C. The surface area of the resulting carbon layers increases to a value more than fourfold over that of the starting precursor materials. These results offer useful insights to understand the thermal behavior of the carbonaceous decomposition materials.}, journal={Carbon}, publisher={Elsevier BV}, author={Song, Li and Khoerunnisa, Fitri and Gao, Wei and Dou, Weihong and Hayashi, Takuya and Kaneko, Katsumi and Endo, Morinobu and Ajayan, Pulickel M.}, year={2013}, month={Feb}, pages={608–612} }
 @article{gao_song_guo_huang_yang_wang_zuo_fan_liu_gao_et al._2012, title={A simple method to synthesize continuous large area nitrogen-doped graphene}, volume={50}, ISSN={0008-6223}, url={http://dx.doi.org/10.1016/j.carbon.2012.05.026}, DOI={10.1016/j.carbon.2012.05.026}, abstractNote={Large area nitrogen (N)-doped graphene films were grown on copper foil by chemical vapor deposition. The as-grown films consisted of a single atomic layer that was continuous across the copper surface steps and grain boundaries, and could be easily transferred to a variety of substrates. N-doping was confirmed by X-ray photoelectron spectroscopy, Raman spectroscopy, and elemental mapping. N atoms were suggested to mainly form a “pyrrolic” nitrogen structure, and the doping level of N reached up to 3.4 at.%. The N-doped graphene exhibited an n-type behavior, and nitrogen doping would open a band gap in the graphene. This study presents use of a new liquid precursor to obtain large area, continuous and mostly single atom layer N-doped graphene films.}, number={12}, journal={Carbon}, publisher={Elsevier BV}, author={Gao, Hui and Song, Li and Guo, Wenhua and Huang, Liang and Yang, Dezheng and Wang, Fangcong and Zuo, Yalu and Fan, Xiaolong and Liu, Zheng and Gao, Wei and et al.}, year={2012}, month={Oct}, pages={4476–4482} }
 @article{gao_gao_cannuccia_taha-tijerina_balicas_mathkar_narayanan_liu_gupta_peng_et al._2012, title={Artificially Stacked Atomic Layers: Toward New van der Waals Solids}, volume={12}, ISSN={1530-6984 1530-6992}, url={http://dx.doi.org/10.1021/nl301061b}, DOI={10.1021/nl301061b}, abstractNote={Strong in-plane bonding and weak van der Waals interplanar interactions characterize a large number of layered materials, as epitomized by graphite. The advent of graphene (G), individual layers from graphite, and atomic layers isolated from a few other van der Waals bonded layered compounds has enabled the ability to pick, place, and stack atomic layers of arbitrary compositions and build unique layered materials, which would be otherwise impossible to synthesize via other known techniques. Here we demonstrate this concept for solids consisting of randomly stacked layers of graphene and hexagonal boron nitride (h-BN). Dispersions of exfoliated h-BN layers and graphene have been prepared by liquid phase exfoliation methods and mixed, in various concentrations, to create artificially stacked h-BN/G solids. These van der Waals stacked hybrid solid materials show interesting electrical, mechanical, and optical properties distinctly different from their starting parent layers. From extensive first principle calculations we identify (i) a novel approach to control the dipole at the h-BN/G interface by properly sandwiching or sliding layers of h-BN and graphene, and (ii) a way to inject carriers in graphene upon UV excitations of the Frenkell-like excitons of the h-BN layer(s). Our combined approach could be used to create artificial materials, made predominantly from inter planar van der Waals stacking of robust bond saturated atomic layers of different solids with vastly different properties.}, number={7}, journal={Nano Letters}, publisher={American Chemical Society (ACS)}, author={Gao, Guanhui and Gao, Wei and Cannuccia, E. and Taha-Tijerina, Jaime and Balicas, Luis and Mathkar, Akshay and Narayanan, T. N. and Liu, Zhen and Gupta, Bipin K. and Peng, Juan and et al.}, year={2012}, month={Jul}, pages={3518–3525} }
 @article{peng_gao_gupta_liu_romero-aburto_ge_song_alemany_zhan_gao_et al._2012, title={Graphene Quantum Dots Derived from Carbon Fibers}, volume={12}, ISSN={1530-6984 1530-6992}, url={http://dx.doi.org/10.1021/nl2038979}, DOI={10.1021/nl2038979}, abstractNote={Graphene quantum dots (GQDs), which are edge-bound nanometer-size graphene pieces, have fascinating optical and electronic properties. These have been synthesized either by nanolithography or from starting materials such as graphene oxide (GO) by the chemical breakdown of their extended planar structure, both of which are multistep tedious processes. Here, we report that during the acid treatment and chemical exfoliation of traditional pitch-based carbon fibers, that are both cheap and commercially available, the stacked graphitic submicrometer domains of the fibers are easily broken down, leading to the creation of GQDs with different size distribution in scalable amounts. The as-produced GQDs, in the size range of 1-4 nm, show two-dimensional morphology, most of which present zigzag edge structure, and are 1-3 atomic layers thick. The photoluminescence of the GQDs can be tailored through varying the size of the GQDs by changing process parameters. Due to the luminescence stability, nanosecond lifetime, biocompatibility, low toxicity, and high water solubility, these GQDs are demonstrated to be excellent probes for high contrast bioimaging and biosensing applications.}, number={2}, journal={Nano Letters}, publisher={American Chemical Society (ACS)}, author={Peng, Juan and Gao, Wei and Gupta, Bipin Kumar and Liu, Zheng and Romero-Aburto, Rebeca and Ge, Liehui and Song, Li and Alemany, Lawrence B. and Zhan, Xiaobo and Gao, Guanhui and et al.}, year={2012}, month={Jan}, pages={844–849} }
 @article{wu_mack_gao_ma_zhong_han_baldwin_zelenay_2012, title={Nitrogen-Doped Graphene-Rich Catalysts Derived from Heteroatom Polymers for Oxygen Reduction in Nonaqueous Lithium–O2 Battery Cathodes}, volume={6}, ISSN={1936-0851 1936-086X}, url={http://dx.doi.org/10.1021/nn303275d}, DOI={10.1021/nn303275d}, abstractNote={In this work, we present a synthesis approach for nitrogen-doped graphene-sheet-like nanostructures via the graphitization of a heteroatom polymer, in particular, polyaniline, under the catalysis of a cobalt species using multiwalled carbon nanotubes (MWNTs) as a supporting template. The graphene-rich composite catalysts (Co-N-MWNTs) exhibit substantially improved activity for oxygen reduction in nonaqueous lithium-ion electrolyte as compared to those of currently used carbon blacks and Pt/carbon catalysts, evidenced by both rotating disk electrode and Li-O(2) battery experiments. The synthesis-structure-activity correlations for the graphene nanostructures were explored by tuning their synthetic chemistry (support, nitrogen precursor, heating temperature, and transition metal type and content) to investigate how the resulting morphology and nitrogen-doping functionalities (e.g., pyridinic, pyrrolic, and quaternary) influence the catalyst activity. In particular, an optimal temperature for heat treatment during synthesis is critical to creating a high-surface-area catalyst with favorable nitrogen doping. The sole Co phase, Co(9)S(8), was present in the catalyst but plays a negligible role in ORR. Nevertheless, the addition of Co species in the synthesis is indispensable for achieving high activity, due to its effects on the final catalyst morphology and structure, including surface area, nitrogen doping, and graphene formation. This new route for the preparation of a nitrogen-doped graphene nanocomposite with carbon nanotube offers synthetic control of morphology and nitrogen functionality and shows promise for applications in nonaqueous oxygen reduction electrocatalysis for Li-O(2) battery cathodes.}, number={11}, journal={ACS Nano}, publisher={American Chemical Society (ACS)}, author={Wu, Gang and Mack, Nathan H. and Gao, Wei and Ma, Shuguo and Zhong, Ruiqin and Han, Jiantao and Baldwin, Jon K. and Zelenay, Piotr}, year={2012}, month={Oct}, pages={9764–9776} }
 @article{singh_galande_miranda_mathkar_gao_reddy_vlad_ajayan_2012, title={Paintable Battery}, volume={2}, ISSN={2045-2322}, url={http://dx.doi.org/10.1038/srep00481}, DOI={10.1038/srep00481}, abstractNote={If the components of a battery, including electrodes, separator, electrolyte and the current collectors can be designed as paints and applied sequentially to build a complete battery, on any arbitrary surface, it would have significant impact on the design, implementation and integration of energy storage devices. Here, we establish a paradigm change in battery assembly by fabricating rechargeable Li-ion batteries solely by multi-step spray painting of its components on a variety of materials such as metals, glass, glazed ceramics and flexible polymer substrates. We also demonstrate the possibility of interconnected modular spray painted battery units to be coupled to energy conversion devices such as solar cells, with possibilities of building standalone energy capture-storage hybrid devices in different configurations.}, number={1}, journal={Scientific Reports}, publisher={Springer Science and Business Media LLC}, author={Singh, Neelam and Galande, Charudatta and Miranda, Andrea and Mathkar, Akshay and Gao, Wei and Reddy, Arava Leela Mohana and Vlad, Alexandru and Ajayan, Pulickel M.}, year={2012}, month={Jun} }
 @article{gao_liu_song_guo_gao_ci_rao_quan_vajtai_ajayan_2012, title={Synthesis of S-doped graphene by liquid precursor}, volume={23}, ISSN={0957-4484 1361-6528}, url={http://dx.doi.org/10.1088/0957-4484/23/27/275605}, DOI={10.1088/0957-4484/23/27/275605}, abstractNote={Doping is a common and effective approach to tailor semiconductor properties. Here, we demonstrate the growth of large-area sulfur (S)-doped graphene sheets on copper substrate via the chemical vapor deposition technique by using liquid organics (hexane in the presence of S) as the precursor. We found that S could be doped into graphene’s lattice and mainly formed linear nanodomains, which was proved by elemental analysis, high resolution transmission microscopy and Raman spectra. Measurements on S-doped graphene field-effect transistors (G-FETs) revealed that S-doped graphene exhibited lower conductivity and distinctive p-type semiconductor properties compared with those of pristine graphene. Our approach has produced a new member in the family of graphene based materials and is promising for producing graphene based devices for multiple applications.}, number={27}, journal={Nanotechnology}, publisher={IOP Publishing}, author={Gao, Hui and Liu, Zheng and Song, Li and Guo, Wenhua and Gao, Wei and Ci, Lijie and Rao, Amrita and Quan, Weijin and Vajtai, Robert and Ajayan, Pulickel M}, year={2012}, month={Jun}, pages={275605} }
 @article{gao_singh_song_liu_reddy_ci_vajtai_zhang_wei_ajayan_2011, title={Direct laser writing of micro-supercapacitors on hydrated graphite oxide films}, volume={6}, ISSN={1748-3387 1748-3395}, url={http://dx.doi.org/10.1038/nnano.2011.110}, DOI={10.1038/nnano.2011.110}, abstractNote={Microscale supercapacitors provide an important complement to batteries in a variety of applications, including portable electronics. Although they can be manufactured using a number of printing and lithography techniques, continued improvements in cost, scalability and form factor are required to realize their full potential. Here, we demonstrate the scalable fabrication of a new type of all-carbon, monolithic supercapacitor by laser reduction and patterning of graphite oxide films. We pattern both in-plane and conventional electrodes consisting of reduced graphite oxide with micrometre resolution, between which graphite oxide serves as a solid electrolyte. The substantial amounts of trapped water in the graphite oxide makes it simultaneously a good ionic conductor and an electrical insulator, allowing it to serve as both an electrolyte and an electrode separator with ion transport characteristics similar to that observed for Nafion membranes. The resulting micro-supercapacitor devices show good cyclic stability, and energy storage capacities comparable to existing thin-film supercapacitors.}, number={8}, journal={Nature Nanotechnology}, publisher={Springer Science and Business Media LLC}, author={Gao, Wei and Singh, Neelam and Song, Li and Liu, Zheng and Reddy, Arava Leela Mohana and Ci, Lijie and Vajtai, Robert and Zhang, Qing and Wei, Bingqing and Ajayan, Pulickel M.}, year={2011}, month={Jul}, pages={496–500} }
 @article{gao_majumder_alemany_narayanan_ibarra_pradhan_ajayan_2011, title={Engineered Graphite Oxide Materials for Application in Water Purification}, volume={3}, ISSN={1944-8244 1944-8252}, url={http://dx.doi.org/10.1021/am200300u}, DOI={10.1021/am200300u}, abstractNote={Retaining the inherent hydrophilic character of GO (graphite-oxide) nanosheets, sp(2) domains on GO are covalently modified with thiol groups by diazonium chemistry. The surface modified GO adsorbs 6-fold higher concentration of aqueous mercuric ions than the unmodified GO. "Core-shell" adsorbent granules, readily useable in filtration columns, are synthesized by assembling aqueous GO over sand granules. The nanostructured GO-coated sand retains at least 5-fold higher concentration of heavy metal and organic dye than pure sand. The research results could open avenues for developing low-cost water purification materials for the developing economies.}, number={6}, journal={ACS Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Gao, Wei and Majumder, Mainak and Alemany, Lawrence B. and Narayanan, Tharangattu N. and Ibarra, Miguel A. and Pradhan, Bhabendra K. and Ajayan, Pulickel M.}, year={2011}, month={May}, pages={1821–1826} }
 @article{gupta_thanikaivelan_narayanan_song_gao_hayashi_leela mohana reddy_saha_shanker_endo_et al._2011, title={Optical Bifunctionality of Europium-Complexed Luminescent Graphene Nanosheets}, volume={11}, ISSN={1530-6984 1530-6992}, url={http://dx.doi.org/10.1021/nl202541n}, DOI={10.1021/nl202541n}, abstractNote={Graphene is an intriguing two-dimensional material, which could be modified for achieving tunable properties with many applications. Photoluminescence of graphene due to plasmonic emission is well-known, however, attempts to develop strong luminescent graphene have been difficult. Synthesis of a graphene-based material with a dual optical functionality, namely quenching the fluorescence of organic dyes while maintaining its own self-luminescence, is an interesting and challenging proposition. Here, we demonstrate this optical bifunctionality in a lattice-modified luminescent graphene, where europium(III) cations are complexed with graphene through oxygen functionalities. After excitation at 314 nm, a hypersensitive red emission is observed at 614 and 618 nm showing the complexation of europium(III) with graphene. We demonstrate dual functionality of this graphene by the quenching of luminescence of Rhodamine-B while displaying its own hypersensitive red emission. The decay lifetime observed through the time-resolved spectroscopy confirms its potential for applications in biosensing as well as optoelectronics.}, number={12}, journal={Nano Letters}, publisher={American Chemical Society (ACS)}, author={Gupta, Bipin Kumar and Thanikaivelan, Palanisamy and Narayanan, Tharangattu N. and Song, Li and Gao, Wei and Hayashi, Takuya and Leela Mohana Reddy, Arava and Saha, Avishek and Shanker, Virendra and Endo, Morinobu and et al.}, year={2011}, month={Dec}, pages={5227–5233} }
 @article{galande_mohite_naumov_gao_ci_ajayan_gao_srivastava_weisman_ajayan_2011, title={Quasi-Molecular Fluorescence from Graphene Oxide}, volume={1}, ISSN={2045-2322}, url={http://dx.doi.org/10.1038/srep00085}, DOI={10.1038/srep00085}, abstractNote={Aqueous dispersions of graphene oxide (GO) have been found to emit a structured, strongly pH-dependent visible fluorescence. Based on experimental results and model computations, this is proposed to arise from quasi-molecular fluorophores, similar to polycyclic aromatic compounds, formed by the electronic coupling of carboxylic acid groups with nearby carbon atoms of graphene. Sharp and structured emission and excitation features resembling the spectra of molecular fluorophores are present near 500 nm in basic conditions. The GO emission reversibly broadens and red-shifts to ca. 680 nm in acidic conditions, while the excitation spectra remain very similar in shape and position, consistent with excited state protonation of the emitting species in acidic media. The sharp and structured emission and excitation features suggest that the effective fluorophore size in the GO samples is remarkably well defined.}, number={1}, journal={Scientific Reports}, publisher={Springer Science and Business Media LLC}, author={Galande, Charudatta and Mohite, Aditya D. and Naumov, Anton V. and Gao, Wei and Ci, Lijie and Ajayan, Anakha and Gao, Hui and Srivastava, Anchal and Weisman, R. Bruce and Ajayan, Pulickel M.}, year={2011}, month={Sep} }
 @article{song_toth_wei_liu_gao_ci_vajtai_endo_ajayan_2011, title={Sharp burnout failure observed in high current-carrying double-walled carbon nanotube fibers}, volume={23}, ISSN={0957-4484 1361-6528}, url={http://dx.doi.org/10.1088/0957-4484/23/1/015703}, DOI={10.1088/0957-4484/23/1/015703}, abstractNote={We report on the current-carrying capability and the high-current-induced thermal burnout failure modes of 5–20 µm diameter double-walled carbon nanotube (DWNT) fibers made by an improved dry-spinning method. It is found that the electrical conductivity and maximum current-carrying capability for these DWNT fibers can reach up to 5.9 × 105 S m − 1 and over 1 × 105 A cm − 2 in air. In comparison, we observed that standard carbon fiber tended to be oxidized and burnt out into cheese-like morphology when the maximum current was reached, while DWNT fiber showed a much slower breakdown behavior due to the gradual burnout in individual nanotubes. The electron microscopy observations further confirmed that the failure process of DWNT fibers occurs at localized positions, and while the individual nanotubes burn they also get aligned due to local high temperature and electrostatic field. In addition a finite element model was constructed to gain better understanding of the failure behavior of DWNT fibers.}, number={1}, journal={Nanotechnology}, publisher={IOP Publishing}, author={Song, Li and Toth, Geza and Wei, Jinquan and Liu, Zheng and Gao, Wei and Ci, Lijie and Vajtai, Robert and Endo, Morinobu and Ajayan, Pulickel M}, year={2011}, month={Dec}, pages={015703} }
 @article{li_gao_ci_wang_ajayan_2010, title={Catalytic performance of Pt nanoparticles on reduced graphene oxide for methanol electro-oxidation}, volume={48}, ISSN={0008-6223}, url={http://dx.doi.org/10.1016/j.carbon.2009.11.034}, DOI={10.1016/j.carbon.2009.11.034}, abstractNote={We have investigated a simple approach for the deposition of platinum (Pt) nanoparticles onto surfaces of graphite oxide (GO) nanosheets with particle size in the range of 1–5 nm by ethylene glycol reduction. During Pt deposition, a majority of oxygenated functional groups on GO was removed, which resulted in a Pt/chemically converted graphene (Pt/CCG) hybrid. The electrochemically active surface areas of Pt/CCG and a comparative sample of Pt/multi-walled carbon nanotubes (Pt/MWCNT) are 36.27 and 33.43 m2/g, respectively. The Pt/CCG hybrid shows better tolerance to CO for electro-oxidation of methanol compared to the Pt/MWCNT catalyst. Our study demonstrates that CCG can be an alternative two-dimensional support for Pt in direct methanol fuel cells.}, number={4}, journal={Carbon}, publisher={Elsevier BV}, author={Li, Yongjie and Gao, Wei and Ci, Lijie and Wang, Chunming and Ajayan, Pulickel M.}, year={2010}, month={Apr}, pages={1124–1130} }
 @article{li_guo_gao_xia_zheng_2009, title={Enhanced electrochemiluminescence efficiency of Ru(ii) derivative covalently linked carbon nanotubes hybrid}, ISSN={1359-7345 1364-548X}, url={http://dx.doi.org/10.1039/b916007h}, DOI={10.1039/b916007h}, abstractNote={The synthesized derivative Ru(bpy)(3) covalently linked CNTs hybrid shows good electrochemical activity and ca. 17 times higher luminescence quantum efficiency than the adsorbed derivative Ru(bpy)(3). The Ru-CNTs based ECL sensor exhibits high stability toward determination of TPA with a detection limit as low as 8.75 pM.}, number={48}, journal={Chemical Communications}, publisher={Royal Society of Chemistry (RSC)}, author={Li, Jing and Guo, Li-Rong and Gao, Wei and Xia, Xing-Hua and Zheng, Li-Min}, year={2009}, pages={7545–7547} }
 @article{ci_song_jariwala_elã­as_gao_terrones_ajayan_2009, title={Graphene Shape Control by Multistage Cutting and Transfer}, volume={21}, ISSN={0935-9648 1521-4095}, url={http://dx.doi.org/10.1002/adma.200900942}, DOI={10.1002/adma.200900942}, abstractNote={The fascinating properties of graphene render it very promising for electronics applications, such as field-effect transistors and interconnects. For these applications, appropriate processes are required to tailor graphene sheets into desired geometries with specific dimensions, smooth edges, and specific edge types. [1–5] By combining electron-beam lithography and plasma etching, [6,7] graphene nanoribbon devices have been fabricated and tested. However, the production of graphene devices with smooth edges, well-defined shapes, and controlled edge configuration (zigzag or armchair edged) is still a challenge. Nanocutting of graphene sheets has been realized using nanometer-sized nickel [8] or iron particles [9] in hydrogen atmosphere at high temperatures, a process referred to as catalytic hydrogenation. [10–13] This nanocutting process can generate various shapes of graphene pieces. The edges of these pieces are along specific crystallographic orientations, which can be controlled by the size of the catalyst particles. [8] Theoretically and experimentally, we have shown that the edges of cutting channels can be atomically smooth with zigzag or armchair terminations. It is well known that scattering of electrons, the charge carriers, at a rough graphene edge will decrease their mean free path. [7,14] Therefore, the catalytic cutting technique provides an efficient approach to fabricating graphene components with high electron conductivity. Another important finding in our previous work is that catalyst particles bounce back at angles of 60 8 or 120 8 when they approach a free edge, [8] which means that cutting always proceeds along the same crystallographic orientation. With the change in orientation occurring at 60 8 or 120 8 , it is possible to cut graphene pieces into various shapes with the same edge type, for example in triangles, and this could impact applications such as shape-enhanced magnetism in graphene materials. [15,16}, number={44}, journal={Advanced Materials}, publisher={Wiley}, author={Ci, Lijie and Song, Li and Jariwala, Deep and Elías, Ana Laura and Gao, Wei and Terrones, Mauricio and Ajayan, Pulickel M.}, year={2009}, month={Nov}, pages={4487–4491} }
 @article{gao_alemany_ci_ajayan_2009, title={New insights into the structure and reduction of graphite oxide}, volume={1}, ISSN={1755-4330 1755-4349}, url={http://dx.doi.org/10.1038/nchem.281}, DOI={10.1038/nchem.281}, abstractNote={Graphite oxide is one of the main precursors of graphene-based materials, which are highly promising for various technological applications because of their unusual electronic properties. Although epoxy and hydroxyl groups are widely accepted as its main functionalities, the complete structure of graphite oxide has remained elusive. By interpreting spectroscopic data in the context of the major functional groups believed to be present in graphite oxide, we now show evidence for the presence of five- and six-membered-ring lactols. On the basis of this chemical composition, we devised a complete reduction process through chemical conversion by sodium borohydride and sulfuric acid treatment, followed by thermal annealing. Only small amounts of impurities are present in the final product (less than 0.5 wt% of sulfur and nitrogen, compared with about 3 wt% with other chemical reductions). This method is particularly effective in the restoration of the π-conjugated structure, and leads to highly soluble and conductive graphene materials.}, number={5}, journal={Nature Chemistry}, publisher={Springer Science and Business Media LLC}, author={Gao, Wei and Alemany, Lawrence B. and Ci, Lijie and Ajayan, Pulickel M.}, year={2009}, month={Jul}, pages={403–408} }
 @article{song_ci_gao_ajayan_2009, title={Transfer Printing of Graphene Using Gold Film}, volume={3}, ISSN={1936-0851 1936-086X}, url={http://dx.doi.org/10.1021/nn9003082}, DOI={10.1021/nn9003082}, abstractNote={We report a facile transfer printing process for easily exfoliating prepatterned graphene from HOPG surfaces by using gold film as the transfer stamp. The transferred printed patterns consist of single- and few-layer graphene with macroscopic continuity. Raman spectra show that some defects appear along the edges of the graphene patterns, which were induced by the oxygen plasma-etching treatment of the HOPG surface. This transfer-printing technique paves a new and simple way to get large-scale graphene patterns on to any substrates.}, number={6}, journal={ACS Nano}, publisher={American Chemical Society (ACS)}, author={Song, Li and Ci, Lijie and Gao, Wei and Ajayan, Pulickel M.}, year={2009}, month={May}, pages={1353–1356} }
 @article{ci_xu_wang_gao_ding_kelly_yakobson_ajayan_2008, title={Controlled nanocutting of graphene}, volume={1}, ISSN={1998-0124 1998-0000}, url={http://dx.doi.org/10.1007/S12274-008-8020-9}, DOI={10.1007/S12274-008-8020-9}, abstractNote={Rapid progress in graphene-based applications is calling for new processing techniques for creating graphene components with different shapes, sizes, and edge structures. Here we report a controlled cutting process for graphene sheets, using nickel nanoparticles as a knife that cuts with nanoscale precision. The cutting proceeds via catalytic hydrogenation of the graphene lattice, and can generate graphene pieces with specific zigzag or armchair edges. The size of the nanoparticle dictates the edge structure that is produced during the cutting. The cutting occurs along straight lines and along symmetry lines, defined by angles of 60° or 120°, and is deflected at free edges or defects, allowing practical control of graphene nano-engineering.}, number={2}, journal={Nano Research}, publisher={Springer Science and Business Media LLC}, author={Ci, Lijie and Xu, Zhiping and Wang, Lili and Gao, Wei and Ding, Feng and Kelly, Kevin F. and Yakobson, Boris I. and Ajayan, Pulickel M.}, year={2008}, month={Jul}, pages={116–122} }
 @article{gao_xia_xu_chen_2007, title={Three-Dimensionally Ordered Macroporous Gold Structure as an Efficient Matrix for Solid-State Electrochemiluminescence of Ru(bpy)32+/TPA System with High Sensitivity}, volume={111}, ISSN={1932-7447 1932-7455}, url={http://dx.doi.org/10.1021/jp0722814}, DOI={10.1021/jp0722814}, abstractNote={Tris(2,2‘-bipyridyl)ruthenium(II) (Ru(bpy)32+) is generally considered as the most valuable electrochemiluminescence agent. For better utilization of this agent, various immobilization methods in different matrixes have been developed. However, its application is still subject to low stability and low sensitivity. Herein, we report on the fabrication of a three dimensionally (3D) ordered macroporous gold film electrode as the matrix for efficient immobilization of Ru(bpy)32+ in zirconia-Nafion sol−gel film. The 3D macroporous gold film with good conductivity has a large active surface area and interconnected macroporous structure, which enhance loading of the electrochemiluminescence (ECL) agent and mass transport of the analytes. In addition, Ru(bpy)32+ immobilized on the macroporous gold electrodes is more electrochemically accessible than it is on flat gold electrodes. These effects enable us to obtain high sensitivity of the presented sensor. As a demonstration, tripropylamine (TPA) was used as the mo...}, number={33}, journal={The Journal of Physical Chemistry C}, publisher={American Chemical Society (ACS)}, author={Gao, Wei and Xia, Xing-Hua and Xu, Jing-Juan and Chen, Hong-Yuan}, year={2007}, month={Aug}, pages={12213–12219} }
 @article{zhang_gao_xia_chen_2006, title={Three-dimensional ordered macroporous platinum-based electrode for methanol oxidation}, volume={51}, ISSN={1001-6538}, url={http://dx.doi.org/10.1007/S11434-005-1351-Y}, DOI={10.1007/S11434-005-1351-Y}, number={1}, journal={Chinese Science Bulletin}, publisher={Springer Science and Business Media LLC}, author={Zhang, Dai and Gao, Wei and Xia, Xinghua and Chen, Hongyuan}, year={2006}, month={Jan}, pages={19–24} }
 @article{wang_yang_song_gao_xia_2005, title={Adsorption and Direct Electron Transfer from Hemoglobin into a Three-Dimensionally Ordered Macroporous Gold Film}, volume={15}, ISSN={1616-301X 1616-3028}, url={http://dx.doi.org/10.1002/adfm.200500048}, DOI={10.1002/adfm.200500048}, abstractNote={Application of protein‐based, direct electron communication in bioelectronic devices, biosensors, or biofuel cells usually requires high stability and function density of the immobilized proteins or enzymes. Traditional methods have been used to increase the function density using multilayer immobilization techniques at the expense of losing stability and electron‐communication rate, that is, generally only protein molecules near the electrode surface are electroactive. In order to overcome the above problems, a three‐dimensional, ordered, macroporous gold film electrode is synthesized electrochemically by an inverted colloidal crystal template technique. The uniform, three‐dimensional macroporous gold provides superior conductivity, high stability, and large surface area. Its interconnected macroporous structure, containing gold nanoparticles, significantly enhances the amount of adsorbed hemoglobin (Hb) molecules at the monolayer level and also provides a good microenvironment for retaining the biological activity of the adsorbed protein, as confirmed by electrochemical and attenuated total reflection Fourier‐transform infrared spectroscopy. Therefore, direct electron transfer between the adsorbed Hb and the electrode is achieved. Adsorption of Hb on the macroporous gold film electrode is monitored using electrochemical impedance spectroscopy. The saturated adsorption amount, Γ, of the Hb is determined to be 6.55×10–10 mol cm–2 with a surface coverage of 88.1 %. The electrochemical behavior and the adsorption mechanism of Hb on the macroporous gold film electrode are discussed on the basis of the experimental results.}, number={8}, journal={Advanced Functional Materials}, publisher={Wiley}, author={Wang, C. H. and Yang, C. and Song, Y. Y. and Gao, W. and Xia, X. H.}, year={2005}, month={Aug}, pages={1267–1275} }
 @article{song_zhang_gao_xia_2005, title={Nonenzymatic Glucose Detection by Using a Three-Dimensionally Ordered, Macroporous Platinum Template}, volume={11}, ISSN={0947-6539 1521-3765}, url={http://dx.doi.org/10.1002/chem.200400981}, DOI={10.1002/chem.200400981}, abstractNote={A three-dimensionally ordered, macroporous, inverse-opal platinum film was synthesized electrochemically by the inverted colloidal-crystal template technique. The inverse-opal film that contains platinum nanoparticles showed improved electrocatalytic activity toward glucose oxidation with respect to the directly deposited platinum; this improvement is due to the interconnected porous structure and the greatly enhanced effective surface area. In addition, the inverse-opal Pt-film electrode responds more sensitively to glucose than to common interfering species of ascorbic acid, uric acid, and p-acetamidophenol due to their different electrochemical reaction mechanisms. Results showed that the ordered macroporous materials with enhanced selectivity and sensitivity are promising for fabrication of nonenzymatic glucose biosensors.}, number={7}, journal={Chemistry - A European Journal}, publisher={Wiley}, author={Song, Yan-Yan and Zhang, Dai and Gao, Wei and Xia, Xing-Hua}, year={2005}, month={Mar}, pages={2177–2182} }