@article{abdellah_yildirim_el-shafei_2023, title={Low-cost novel X-shaped hole transport materials for efficient perovskite solar cells: Molecular modelling of the core and schiff base effects on photovoltaic and photophysical properties}, volume={296}, ISSN={["1879-3312"]}, url={https://doi.org/10.1016/j.matchemphys.2022.127188}, DOI={10.1016/j.matchemphys.2022.127188}, abstractNote={Eight molecules with D-π-D molecular motifs coded HTM(1-4)a,b were designed as efficient symmetric hole transporting materials for perovskite solar cells. These HTMs are composed of different core moieties, such as spiro [fluorene-9,9′-xanthene]-diol (SFO), spiro [fluorene-9,9′-xanthene]-dimethoxy (SFM), benzo [c][1,2,5]thiadiazole (BTD), and biphenyl (BP) and are gaining lot of attention because of their low-cost, reproducible electrical and optical properties in device performance. Detailed information about the energetic of molecular levels (GSOP/ESOP), first singlet excitation energy (E0-0), equilibrium molecular geometry, charge separation, charge transfer, reorganization energies, polarizability and hyperpolarizability, density of states (DOS), solubility and stability of these molecules was attained by systematically performing molecular modeling calculations using density functional theory (DFT) and time dependent-DFT calculations utilizing hybrid density functional B3LYP using the basis set 6–31g(d,p) level of theory as a successful method for predicting the photophysical and photovoltaic properties of these conjugated systems. The results showed that not only the core moieties, but also Schiff-base linkage extended conjugation, have an effect on the photophysical and photovoltaic properties of the proposed HTMs. It was demonstrated that HTMs incorporating SFO (HTM1a,b), SFM (HTM2a,b), and BP (HTM4a,b) achieved better charge transport, high stability values (η a = 2.11–2.40 eV), low electron-hole binding energy (Eb = 0.16–0.21 eV) than HTM3a,b with BTD core, which improves hole mobility and decreases recombination, all of which improved device photocurrent, which can be attributed to the extended π-conjugation in SFO, SFM and BP cores. These findings are strikingly similar to those of Spiro-OMeTAD (η a = 2.45 eV, Eb = 0.16 eV), indicating that these HTMs are promising candidates for efficient and cost-effective PSCs. Interestingly, when the stability of HTM(1-4)a and HTM(1-4)b was compared, it was clear that HTM(1-4)a has lower stability than HTM(1-4)b, which could be attributed to the presence of Schiff base CN bonds in HTM(1-4)b, which reduces the molecules stability when compared to HTM(1-4)b, owing to a strong C–C linkage. Meanwhile, HTM(1-4)a outperforms HTM(1-4)b in terms of electronic performance and hole mobility.}, journal={MATERIALS CHEMISTRY AND PHYSICS}, author={Abdellah, Islam M. and Yildirim, Erol and El-Shafei, Ahmed}, year={2023}, month={Feb} }
 @article{kobaisy_elkady_abdel-moneim_yildirim_el-shafei_el-khouly_2023, title={Optical Properties of Cationic Perylenediimide Nanowires in Aqueous Medium: Experimental and Computational Studies}, ISSN={["1573-4994"]}, DOI={10.1007/s10895-023-03253-9}, abstractNote={Abstract}, journal={JOURNAL OF FLUORESCENCE}, author={Kobaisy, Ahmed M. M. and Elkady, Marwa F. F. and Abdel-Moneim, Ahmed A. A. and Yildirim, Erol and El-Shafei, Ahmed and El-Khouly, Mohamed E. E.}, year={2023}, month={Jun} }
 @article{altay_yildirim_gursoy_hauser_el-shafei_2022, title={Synthesis of a Novel and More Sustainable Cationic Bleach Activator,N-[4-(N,N,N)-Triethylammoniumchloride-butanoyl] Butyrolactam, for Cotton: Optimization and Theoretical Limitations br}, volume={10}, ISSN={["2168-0485"]}, DOI={10.1021/acssuschemeng.1c07233}, abstractNote={Activated bleach systems have the potential to produce more efficient kinetically potent bleaching systems through increased oxidation rates with reduced energy cost and less time, hence causing less cellulose polymer chain damage or degradation than conventional hot peroxide bleaching. This article presents a study at the molecular level of a novel and more sustainable cationic bleach activator for cotton than aromatic-based cationic bleach activators using combined experimental and first-principles density functional theory (DFT) calculations. In this study, a novel and aliphatic-based cationic bleach activator, N-[4-(N,N,N)-triethylammoniumchloride-butanoyl] butyrolactam (TBUCB), was synthesized and applied for hot peroxide-cotton bleaching to optimize the bleaching conditions at lower temperatures. To improve the bleaching efficiency in the presence of TBUCB, the limitations of TBUCB, namely, the limitations of peracid generation in situ, have been identified using DFT calculations. First-principles density functional theory (DFT) calculations were performed to elucidate the reaction mechanism via identifying plausible transition state(s) of the nucleophilic attack of perhydroxyl anion (HOO–) at different carbonyl carbons and the advantages and limitations of the TBUCB activator for hydrogen peroxide bleaching for cotton. The results obtained showed that a whiteness index greater than 80 for cellulose can be achieved using an activated H2O2-TBUCB bleaching system at a lower temperature, providing reduced energy costs while maintaining the integrity of cellulose polymer chains.}, number={14}, journal={ACS SUSTAINABLE CHEMISTRY & ENGINEERING}, author={Altay, Pelin and Yildirim, Erol and Gursoy, Nevin Cigdem and Hauser, Peter J. and El-Shafei, Ahmed}, year={2022}, month={Apr}, pages={4415–4424} }
 @article{pang_yildirim_pasquinelli_wei_2021, title={Ammonia Sensing Performance of Polyaniline-Coated Polyamide 6 Nanofibers}, volume={6}, ISSN={["2470-1343"]}, url={https://doi.org/10.1021/acsomega.0c06272}, DOI={10.1021/acsomega.0c06272}, abstractNote={To understand the properties of polyaniline (PANI), aim gas, and the interaction between them in PANI-based gas sensors and help us to design sensors with better properties, direct calculations with molecular dynamics (MD) simulations were done in this work. Polyamide 6/polyaniline (PA6/PANI) nanofiber ammonia gas sensors were studied as an example here, and the structural, morphological, and ammonia sensing properties (to 50–250 ppm ammonia) of PA6/PANI nanofibers were tested and evaluated by scanning electron microscopy, Fourier transform infrared spectroscopy, and a homemade test system. The PA6/PANI nanofibers were prepared by in situ polymerization of aniline with electrospun PA6 nanofibers as templates and hydrochloric acid (HCl) as a doping agent for PANI, and the sensors show rapid response, ideal selectivity, and acceptable repeatability. Then, complementary molecular dynamics simulations were performed to understand how ammonia molecules interact with HCl-doped PANI chains, thus providing insights into the molecular-level details of the ammonia sensing performances of this system. Results of the radial distribution functions and mean square displacement analysis of the MD simulations were consistent with the dedoping mechanism of the PANI chains.}, number={13}, journal={ACS OMEGA}, publisher={American Chemical Society (ACS)}, author={Pang, Zengyuan and Yildirim, Erol and Pasquinelli, Melissa A. and Wei, Qufu}, year={2021}, month={Apr}, pages={8950–8957} }
 @article{vaid_yildirim_pasquinelli_king_2021, title={Hydrolytic Degradation of Polylactic Acid Fibers as a Function of pH and Exposure Time}, volume={26}, ISSN={["1420-3049"]}, url={https://doi.org/10.3390/molecules26247554}, DOI={10.3390/molecules26247554}, abstractNote={Polylactic acid (PLA) is a widely used bioresorbable polymer in medical devices owing to its biocompatibility, bioresorbability, and biodegradability. It is also considered a sustainable solution for a wide variety of other applications, including packaging. Because of its widespread use, there have been many studies evaluating this polymer. However, gaps still exist in our understanding of the hydrolytic degradation in extreme pH environments and its impact on physical and mechanical properties, especially in fibrous materials. The goal of this work is to explore the hydrolytic degradation of PLA fibers as a function of a wide range of pH values and exposure times. To complement the experimental measurements, molecular-level details were obtained using both molecular dynamics (MD) simulations with ReaxFF and density functional theory (DFT) calculations. The hydrolytic degradation of PLA fibers from both experiments and simulations was observed to have a faster rate of degradation in alkaline conditions, with 40% of strength loss of the fibers in just 25 days together with an increase in the percent crystallinity of the degraded samples. Additionally, surface erosion was observed in these PLA fibers, especially in extreme alkaline environments, in contrast to bulk erosion observed in molded PLA grafts and other materials, which is attributed to the increased crystallinity induced during the fiber spinning process. These results indicate that spun PLA fibers function in a predictable manner as a bioresorbable medical device when totally degraded at end-of-life in more alkaline conditions.}, number={24}, journal={MOLECULES}, author={Vaid, Radhika and Yildirim, Erol and Pasquinelli, Melissa A. and King, Martin W.}, year={2021}, month={Dec} }
 @article{arangdad_yildirim_detwiler_cleven_burk_shamey_pasquinelli_freeman_el-shafei_2021, title={X-ray photoelectron spectroscopy study on the photodegradation of copolyester model compounds}, volume={138}, ISSN={["1097-4628"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85088566956&partnerID=MN8TOARS}, DOI={10.1002/app.49661}, abstractNote={Abstract}, number={2}, journal={JOURNAL OF APPLIED POLYMER SCIENCE}, author={Arangdad, Kiarash and Yildirim, Erol and Detwiler, Andrew and Cleven, Curtis D. and Burk, Christopher and Shamey, Renzo and Pasquinelli, Melissa A. and Freeman, Harold and El-Shafei, Ahmed}, year={2021}, month={Jan} }
 @article{arangdad_yildirim_detwiler_cleven_burk_shamey_pasquinelli_freeman_el-shafei_2019, title={Influence of UV stabilizers on the weathering of PETG and PCTT films}, volume={136}, ISSN={["1097-4628"]}, url={https://doi.org/10.1002/app.48198}, DOI={10.1002/app.48198}, abstractNote={ABSTRACT}, number={47}, journal={JOURNAL OF APPLIED POLYMER SCIENCE}, publisher={Wiley}, author={Arangdad, Kiarash and Yildirim, Erol and Detwiler, Andrew and Cleven, Curtis D. and Burk, Christopher and Shamey, Renzo and Pasquinelli, Melissa A. and Freeman, Harold S. and El-Shafei, Ahmed}, year={2019}, month={Dec} }
 @article{ashraf_yildirim_akhtar_siddiqi_el-shafei_2017, title={A comparative study of the influence of N, N '-dialkyl vs. N, N '-diaryl-based electron donor ancillary ligands on photocurrent and photovoltage in dye-sensitized solar cells (DSSCs)}, volume={19}, ISSN={["1463-9084"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85027680532&partnerID=MN8TOARS}, DOI={10.1039/c7cp02530k}, abstractNote={In this study, we report the synthesis of a novel heteroleptic Ru(ii)-sensitizer, denoted as SD-1; moreover, its photophysical, electrochemical, and photovoltaic performances were compared with those of N719 and K77-7.}, number={31}, journal={PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, author={Ashraf, Saba and Yildirim, Erol and Akhtar, Javeed and Siddiqi, Humaira M. and El-Shafei, Ahmed}, year={2017}, month={Aug}, pages={20847–20860} }
 @article{caydamli_yildirim_shen_fang_pasquinelli_spontak_tonelli_2017, title={Nanoscale considerations responsible for diverse macroscopic phase behavior in monosubstituted isobutyl-POSS/poly(ethylene oxide) blends}, volume={13}, ISSN={["1744-6848"]}, url={https://doi.org/10.1039/C7SM01788J}, DOI={10.1039/c7sm01788j}, abstractNote={Nanocomposites prepared by incorporating polyhedral oligomeric silsesquioxane (POSS) into polymer matrices afford versatile hybrid materials but are exquisitely sensitive to even POSS monofunctionalization.}, number={46}, journal={SOFT MATTER}, publisher={Royal Society of Chemistry (RSC)}, author={Caydamli, Yavuz and Yildirim, Erol and Shen, Jialong and Fang, Xiaomeng and Pasquinelli, Melissa A. and Spontak, Richard J. and Tonelli, Alan E.}, year={2017}, month={Dec}, pages={8672–8677} }
 @article{elsherbiny_yildirim_el-essawy_abdel-megied_el-shafei_2017, title={Structure-property relationships: Influence of number of anchoring groups in triphenylamine-carbazole motifs on light harvesting and photovoltaic performance for dye-sensitized solar cells}, volume={147}, ISSN={["1873-3743"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85028554215&partnerID=MN8TOARS}, DOI={10.1016/j.dyepig.2017.08.022}, abstractNote={Three novel organic sensitizers were molecularly designed and synthesized based on triphenylamine (TPA), as the core donor (DTPA), linked to one, two or three carbazole (DCarb) moieties with different number of anchoring groups (AG) to generate: DTPA-π-DCarb-A (DE1), DTPA(π-DCarb-A)2 (DE-2) and DTPA(π-DCarb-A)3 (DE-3). The primary goal of this study was to investigate the influence of bridging different number of DCarb and AG, through π-spacer, with TPA on the photovoltaic performance in DSSCs. The molar extinction coefficient increased with increasing the number of DCarb and A. DE-3 showed the greatest light harvesting in solution and when anchored onto TiO2. Hence, the increase in the number of DCarb and AG led to better light harvesting and stronger electronic coupling with TiO2, which reflected positively on the photovoltaic properties, and this is the first systematic study of its kind involving TPA-π-carbazole motif. DE-3 achieved the best efficiency of 5.44% and showed IPCE of 74% at 470 nm. The Voc increased with increasing the number of anchoring groups. Equilibrium molecular geometries and frontier molecular orbitals studied by DFT and TD-DFT calculations were in excellent agreement with experiments, which showed enhanced electronic coupling with TiO2 and photovoltaic performance as the number of anchoring groups increased.}, journal={DYES AND PIGMENTS}, author={Elsherbiny, Dalia and Yildirim, Erol and El-Essawy, Farag and Abdel-Megied, Ahmed and El-Shafei, Ahmed}, year={2017}, month={Dec}, pages={491–504} }
 @article{yildirim_yurtsever_wilkes_yilgor_2016, title={Effect of intersegmental interactions on the morphology of segmented polyurethanes with mixed soft segments: A coarse-grained simulation study}, volume={90}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2016.03.008}, abstractNote={Segmented thermoplastic polyurethanes, polyureas and polyurethaneureas (TPU) based on a given hard segment and two chemically different soft segments display interesting microphase morphologies and thermal, mechanical and surface properties. In these systems the final TPU morphology is mainly controlled by the structure, amount and molecular weight of the soft segment oligomers and the nature and extent of specific intermolecular interactions between the mixed soft segments themselves and with the urethane hard segments. These interactions lead to variable compatibilities between the soft and hard segments resulting in interesting TPU morphologies. The proper choice of the two chemically different soft blocks provides more flexibility in controlling the extent of microphase separation, size and shape of the microphase domains and offers new possibilities for controlling the properties of TPUs. In this study coarse grained computer simulations were carried out to better understand the nature of intermolecular interactions and to elucidate the equilibrium microphase morphologies of TPUs with two different soft segments at 300 K. Model TPU systems investigated are comprised of poly(tetramethylene oxide) (PTMO) or poly(hexylethyl carbonate) (PHEC) and polydimethylsiloxane (PDMS) or polyisobutylene (PIB) soft segments with molecular weights in the range of 500–2500 g/mol. Hard segments consisted, in all cases, of diphenylmethane diisocyanate (MDI) based urethane repeat units and ranged from 25 to 50% by weight. Through coarse grained Dissipative Particle Dynamics (DPD) simulations it was demonstrated that by varying the composition and the chain lengths of the soft and hard blocks, quite different morphologies from homogeneous (or mixed) to gradient and to completely microphase separated structures were attainable. As expected, fairly hydrophobic soft blocks such as PIB and PDMS favored strong microphase separation when compared with relatively hydrophilic PHEC and PTMO segments. For comparison, morphologies of the TPUs based on single soft segments (PTMO, PHEC, PDMS and PEO) with varying molecular weights and hard segment contents were also simulated.}, journal={POLYMER}, author={Yildirim, E. and Yurtsever, M. and Wilkes, G. L. and Yilgor, I.}, year={2016}, month={May}, pages={204–214} }
 @article{zhu_yildirim_aly_shen_chen_lu_jiang_kim_tonelli_pasquinelli_et al._2016, title={Hierarchical multi-component nanofiber separators for lithium polysulfide capture in lithium-sulfur batteries: an experimental and molecular modeling study}, volume={4}, ISSN={["2050-7496"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84984804707&partnerID=MN8TOARS}, DOI={10.1039/c6ta04577d}, abstractNote={A multi-functional nanofiber membrane significantly improves the overall performance of Li–S batteries.}, number={35}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, publisher={Royal Society of Chemistry (RSC)}, author={Zhu, Jiadeng and Yildirim, Erol and Aly, Karim and Shen, Jialong and Chen, Chen and Lu, Yao and Jiang, Mengjin and Kim, David and Tonelli, Alan E. and Pasquinelli, Melissa A. and et al.}, year={2016}, pages={13572–13581} }
 @article{yildirim_dakshinamoorthy_peretic_pasquinelli_mathers_2016, title={Synthetic Design of Polyester Electrolytes Guided by Hydrophobicity Calculations}, volume={49}, ISSN={["1520-5835"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84994061022&partnerID=MN8TOARS}, DOI={10.1021/acs.macromol.6b01452}, abstractNote={Partition coefficients (LogP) help to quantify hydrophobicity, which can be used to guide the design of polymer electrolytes with targeted properties. Thus, this study combined synthetic experiments and molecular modeling to produce polyester electrolytes that solubilize lithium salts. These polyester electrolytes were derived from natural sources and polymerized with different ratios of polyols (diglycerol, glycerol, and diethylene glycol) and citric acid in the presence of lithium salts (LiTf and LiTFSI). The Fisher esterification produced homogeneous, cross-linked films with high optical transparency, whereas the lithium salts increased glass transition temperatures. The LogP values of monomers and the resulting polyesters were predicted using cheminformatics tools and indicate changing diglycerol to glycerol or diethylene glycol alters the hydrophobicity. Comparison of different molecular modeling methods with predicted LogP values demonstrate that LogP values are a reliable means of tailoring physica...}, number={20}, journal={MACROMOLECULES}, publisher={American Chemical Society (ACS)}, author={Yildirim, Erol and Dakshinamoorthy, Deivasagayam and Peretic, Matthew J. and Pasquinelli, Melissa A. and Mathers, Robert T.}, year={2016}, month={Oct}, pages={7868–7876} }