@article{hussain_islam_bedja_gupta_han_el-shafei_2014, title={A comparative study of Ru(II) cyclometallated complexes versus thiocyanated heteroleptic complexes: thermodynamic force for efficient dye regeneration in dye-sensitized solar cells and how low could it be?}, volume={16}, ISSN={["1463-9084"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84903529744&partnerID=MN8TOARS}, DOI={10.1039/c4cp00907j}, abstractNote={Although cyclometallation may produce significantly better light harvesting, a driving force <0.25 eV is not sufficient for effective dye regeneration in DSSCs.}, number={28}, journal={PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, author={Hussain, Maqbool and Islam, Ashraful and Bedja, Idriss and Gupta, Ravindra Kumar and Han, Liyuan and El-Shafei, Ahmed}, year={2014}, pages={14874–14881} }
 @article{dong_calzolari_felice_el-shafei_hussain_nardelli_2014, title={Optical Enhancement in Heteroleptic Ru(II) Polypyridyl Complexes Using Electron-Donor Ancillary Ligands}, volume={118}, ISSN={["1932-7455"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84899829963&partnerID=MN8TOARS}, DOI={10.1021/jp409733a}, abstractNote={Organic dyes are a viable alternative to silicon for energy conversion. Using simulations from first-principles, we show that chemical manipulation is a powerful tool for tuning the optical absorption spectra of a special class of dyes in a way that is convenient for exploitation in dye-sensitized solar cells. Specifically, we have carried out density functional theory calculations on three Ru(II) polypyridyl complexes with electron-donor ancillary ligands. These complexes were recently developed to study how different electron-donor ancillary ligands affect the photophysical and electrochemical properties of these dyes for light harvesting and photon-to-electron conversion efficiency. We found that the electron-donor ancillary ligands significantly enhance the light harvesting in the visible and the near-infrared regions relative to the reference dye N3. Furthermore, we detected a decrease in the ionization potential, which improves the energy alignment with the redox potentials of the electrolyte. These...}, number={17}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Dong, Rui and Calzolari, Arrigo and Felice, Rosa and El-Shafei, Ahmed and Hussain, Maqbool and Nardelli, Marco Buongiorno}, year={2014}, month={May}, pages={8747–8755} }
 @article{el-shafei_hussain_islam_han_2014, title={Structure-property relationship of hetero-aromatic-electron-donor antennas of polypyridyl Ru (II) complexes for high efficiency dye-sensitized solar cells}, volume={22}, ISSN={["1099-159X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84906283126&partnerID=MN8TOARS}, DOI={10.1002/pip.2349}, abstractNote={ABSTRACT}, number={9}, journal={PROGRESS IN PHOTOVOLTAICS}, author={El-Shafei, Ahmed and Hussain, Maqbool and Islam, Ashraful and Han, Liyuan}, year={2014}, month={Sep}, pages={958–969} }
 @article{el-shafei_hussain_islam_han_2013, title={Influence of cyclic versus acyclic oxygen-containing electron donor ancillary ligands on the photocurrent, photovoltage and photostability for high efficiency dye-sensitized solar cells}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84886923554&partnerID=MN8TOARS}, DOI={10.1039/c3ta12748f}, abstractNote={Three novel heteroleptic amphiphilic polypyridyl Ru-complexes, MH01, MH03, and MH05, with oxygen-containing-electron-donor stilbazole-based ancillary ligands were synthesized to study the influence of the cyclic-electron-donor (MH01), the presence of the cyclic electron donor coupled to acyclic electron-donor auxochromes (MH03) ortho to the CHCH bridge of stilbazole, and the presence of only acyclic electron-donor methoxy group (MH05) on molar extinction coefficient, light harvesting efficiency (LHE), ground and excited state oxidation potentials, and photovoltaic performance for DSSCs. Although MH05 has three electron donor methoxy groups, it achieved the lowest molar extinction coefficient of 18 250 M−1 cm−1 and exhibited the lowest photocurrent. The highest photocurrent density (JSC) was observed for the longest interatomic distance between the CHCH bridge of the stilbazole moiety and cyclic-electron-donor auxochromes (MH01). It was also shown that while incorporation of acyclic electron-donor auxochromes ortho to the CHCH bridge (MH03) has little effect on the ground and excited state oxidation potentials, λmax of the low energy MLCT, and molar absorptivity, the lowest photovoltage and %η were observed. When compared under the same experimental device conditions using 0.3 M tert-butylpyridine (TBP), only MH01-TBA achieved 18% more in JSC and 8.6% greater in η than the benchmark dye N719. To probe the interrelationship among the cyclic-vs.-acyclic oxygen-containing electron donors of the ancillary ligands, photocurrent and photovoltage of these dyes, the equilibrium molecular geometries of the ancillary ligands were calculated using DFT. The HOMO distribution on cyclic-vs.-acyclic electron donors and the position of OMe in the ancillary ligands rationalized the fundamental science behind the photovoltaic performance and photostability of these dyes.}, number={43}, journal={Journal of Materials Chemistry A}, author={El-Shafei, A. and Hussain, M. and Islam, A. and Han, L.}, year={2013}, pages={13679–13686} }
 @article{hussain_el-shafei_islam_han_2013, title={Structure-property relationship of extended pi-conjugation of ancillary ligands with and without an electron donor of heteroleptic Ru(II) bipyridyl complexes for high efficiency dye-sensitized solar cells}, volume={15}, ISSN={["1463-9084"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84877693518&partnerID=MN8TOARS}, DOI={10.1039/c3cp51260f}, abstractNote={Two new heteroleptic Ru(II) bipyridyl complexes MH06 and MH11 were designed, synthesized and characterized for DSSCs. While the ancillary ligand of MH06 was molecularly engineered with a strong electron donating group coupled with an extended π-conjugated system, the ancillary ligand of MH11 contained a longer π-conjugated system only. Molecular modeling, photophysical, and photovoltaic properties were compared under the same experimental conditions against the benchmark N719. In an effort to understand the structure-property relationship, their photovoltaic and photoelectrochemical properties including Jsc, Voc, ground and excited state oxidation potentials, UV-Vis absorption, and molar extinction coefficients were studied. The UV-Vis results showed intense MLCT absorption peaks of MH06 and MH11 in the visible region with a red shift of 12 and 18 nm, respectively, with significantly higher molar extinction coefficients compared to N719. Tetrabutylammonium (TBA) substituted MH11-TBA demonstrated the most efficient IPCE of over 90% in the plateau region covering the entire visible spectrum and extending into the near IR region (ca. 890 nm), which showed a solar-to-power conversion efficiency (η) of 10.06%, significantly higher than that of the benchmark N719 dye (9.32%). The superior performance in terms of the IPCE and Jsc of MH11 can be attributed to the bulky and highly hydrophobic nature of the pyrene-based ancillary ligand, which behaves as a shielding barrier for hole-transport recombination between TiO2 and the electrolyte. In addition, the IMPS results showed that the contribution of dyes to the conduction band shift of the TiO2 level is almost similar, regardless of different substitutions on the bipy-moiety. This implies that the open-circuit photovoltage (Voc) increases with reduced charge recombination in the presence of a thick layer of tetrabutyl ammonium ions (TBA) of the dye anchored on the surface of TiO2.}, number={21}, journal={PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, author={Hussain, Maqbool and El-Shafei, Ahmed and Islam, Ashraful and Han, Liyuan}, year={2013}, pages={8401–8408} }
 @article{hussain_shamey_hinks_el-shafei_ali_2012, title={Synthesis of novel stilbene-alkoxysilane fluorescent brighteners, and their performance on cotton fiber as fluorescent brightening and ultraviolet absorbing agents}, volume={92}, ISSN={["1873-3743"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-80053923377&partnerID=MN8TOARS}, DOI={10.1016/j.dyepig.2011.06.034}, abstractNote={Two novel fluorescent brightening agents (compounds 3a–b shown in Figure 1) were synthesized, using a facile three-step synthetic route, from 4,4′-diamino-2,2′-disulfonic-stilbene, cyanuric chloride, and a readily cross-linkable 3-aminopropyltrimethoxy silane. The products contain hydrolytically active trimethoxysilyl, (–Si(OCH)3), functional groups that readily hydrolyze in the presence of water, and subsequently generate a water insoluble silicon cross-linked-network (Si–O–Si) via a condensation process. The cross-linked product hydrolyzes on treatment with hot aqueous sodium hydroxide to silanols (–Si(OH)3) to form compounds 4a–b which are readily water soluble and produce a clear fluorescent solution. The silanol forms of compounds 4a–b were used for further characterization and performance evaluation. The structures of compounds 4a–b were characterized by 1H-NMR, Fourier-Transform infrared (FT-IR) spectroscopy and negative electrospray ionization mass (−ESI-MS) spectroscopy. Compounds were applied to cotton fiber as fluorescent brightening agents and their performance was evaluated by measuring the degree of whiteness, ultraviolet protection factor (UPF), fluorescence and acid fastness. Results showed that application of 0.25% (o.w.f) of compounds 4a–b impart a high degree of whiteness (CIE WI = 144, 139) as well as good ultraviolet protection factor (UPF = 29, 27) on cotton fiber exhibiting a significant increase in whiteness and UV blocking properties compared to untreated substrate (CIE WI = 81, UPF = 5). Acid fastness tests of both compounds showed a slight change in fluorescence emission intensities as a function of pH. In acidic solutions, a shift in emission maximum occurs at pH 3 from 434 to 453 nm and from 435 to 457 nm, due to the protonation of amino and sulfonic groups of stilbene fluorophore which substantially reduces the quenching process.}, number={3}, journal={DYES AND PIGMENTS}, author={Hussain, Maqbool and Shamey, Renzo and Hinks, David and El-Shafei, Ahmed and Ali, Syed Ishrat}, year={2012}, month={Mar}, pages={1231–1240} }