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    Imidazole substituted Zinc(ii) phthalocyanines for co-catalyst-free photoelectrochemical and photocatalytic hydrogen evolution: influence of the anchoring group
    (Royal Soc Chemistry, 2021) Yuzer, A. Celil; Genc, Eminegul; Kurtay, Gulbin; Yanalak, Gizem; Aslan, Emre; Harputlu, Ersan; Ocakoglu, Kasim
    Novel zinc phthalocyanine derivatives, ZnPc-1 and ZnPc-2, consisting of one and four imidazole units, respectively, have been synthesized and utilized as panchromatic photosensitizers for photocatalytic and photoelectrochemical H-2 evolution. The effect of the imidazole-anchoring group on the photocatalytic H-2 production has been compared with ZnPc-3, which possesses a carboxylic acid unit as the anchoring group. ZnPc-1/TiO2 shows the best photoactivity with the highest H-2 evolution rate of 0.4006 mmol g(-1) h(-1), which is much higher than that of ZnPc-2/TiO2 and ZnPc-3/TiO2 (0.3319 mmol g(-1) h(-1) and 0.3555 mmol g(-1) h(-1), respectively). After 20 h of irradiation, ZnPc-1 produces an H-2 production rate of 3.4187 mmol g(-1) with a turnover number (TON) of 14863 and a solar-to-hydrogen energy (STH) conversion efficiency of 1.03%, without using a co-catalyst.
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    Öğe
    Improving the Photocatalytic Hydrogen Generation Using Nonaggregated Zinc Phthalocyanines
    (Amer Chemical Soc, 2021) Acar, Eminegul Genc; Yuzer, A. Celil; Kurtay, Gulbin; Yanalak, Gizem; Harputlu, Ersan; Aslan, Emre; Ocakoglu, Kasim
    In comparison to traditional solar cells, the dye-sensitized photocatalytic system is one of the most appealing artificial photosynthesis mechanisms due to its low cost and straightforward fabrication. Herein, the photoelectrochemical and photocatalytic hydrogen evolution reactions of Zn-based phthalocyanine (Pc) derivatives, abbreviated as ZnPc-1 and ZnPc-2, were primarily studied in the presence of TEOA sacrificial electron donor. To this aim, the PC activities of ZnPc-1/TiO2 and ZnPc-2/TiO2 photocatalysts were investigated in the absence and presence of a cocatalyst. For the first hour, the amount of hydrogen generated by ZnPc derivatives (ZnPc-1/TiO2 and ZnPc-2/TiO2) was determined to be 1.221 and 0.864 mmol g(-1) h(-1), respectively. Additionally, the solar-to-hydrogen conversion efficiencies of ZnPc-1/TiO2 and ZnPc-2/TiO2 were ascertained to be 3.15% and 2.22%, respectively. Interestingly, STH efficiencies of photocatalysts were increased about 4-fold in the presence of a cocatalyst. Consequently, to elucidate the structural properties of ZnPc-1 and ZnPc-2, density functional theory (DFT) and time-dependent DFT studies were also conducted, and it was discovered that noncovalent interactions and steric hindrance effects on ZnPc-2 are tightly related to the experimentally determined PC activity differences between ZnPc-1 and ZnPc-2.
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    Öğe
    Solution-processed small-molecule organic solar cells based on non-aggregated zinc phthalocyanine derivatives: A comparative experimental and theoretical study
    (Elsevier Sci Ltd, 2021) Yuzer, A. Celil; Kurtay, Gulbin; Ince, Tuncay; Yurtdas, Semih; Harputlu, Ersan; Ocakoglu, Kasim; Gullu, Mustafa
    A series of non-aggregated zinc phthalocyanine derivatives containing either bulky thiophenol or phenol substituents were synthesized as a novel donor component for bulk heterojunction (BHJ) solar cell applications. The molecular structure and photophysical properties of ZnPc derivatives were investigated by combined experimental and theoretical studies using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. In order to evaluate the physical properties of ZnPcs in the solvent environment, we applied the conductor-like polarizable continuum model (CPCM). Within this scope, light-harvesting efficiency (LHE), excited-state lifetime (?), maximum absorption wavelengths (?max), oscillator strength (f) and hyperpolarizability (? tensors) were calculated both in vacuum and chloroform (? = 4.9) medium. Furthermore, divergent types of global descriptors such as EHOMO, ELUMO, and bandgap (Egap) energies, ionization potential (I), electron affinity (A), hardness (?), and electrophilicity index (?) were also calculated. Our computational findings revealed that the linker heteroatoms [sulfur for the ZnPc (1?2); oxygen for the ZnPc (3?4) including the substituent type (isopropyl for the ZnPc (2?4), and phenyl for the ZnPc (1?3] severely affected the photophysical properties of the dyes. In relation, theoretical results are in good accordance with our experimental observations. Finally, ZnPc derivatives were used as a donor component and PC61BM as an acceptor material in BHJ solar cells, displaying a maximum power conversion efficiency of 0.8%. Compared with ZnPcs 1?2, ZnPc 3?4 based cells showed an inferior photovoltaic performance. These results are promising and should encourage further studies on BHJ solar cells using near-infrared absorbing and non-aggregated ZnPcs.
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    Öğe
    Subphthalocyanines for Visible-Light-Driven Hydrogen Evolution: Tuning Photocatalytic Performance with Molecular Design
    (Amer Chemical Soc, 2023) Guntay, Buket; Dogan, Sifa; Killi, Askin; Genc Acar, Eminegul; Demircioglu, Perihan Kubra; Aslan, Emre; Kurtay, Gulbin
    In this work, a series of subphthalocyanines (SubPcs)with a carboxylicacid anchoring group at the axial position were used as photosensitizersof TiO2 for photocatalytic hydrogen evolution from waterunder visible light irradiation. SubPc derivatives with various peripheralsubstituents were successfully prepared to systematically investigatethe dependence of photocatalytic performance on electron-donatingunits (i.e., bisthiophene or thioether) at the peripheral positionof the SubPcs. SubPc 2/TiO2/Pt shows the best photocatalyticactivity among the three dye-sensitized photocatalysts, with a hydrogenevolution rate of 1.104 mmol center dot g(-1)center dot h(-1). After 24 h irradiation, SubPc 2/TiO2/Ptachieved a remarkable catalytic activity for the production of H-2 (19.96 mmol center dot g(-1)) with a TON valueof 40 734 and a high STH efficiency of 2.1%. Density functionaltheory (DFT) and time-dependent DFT (TD-DFT) approaches were usedto elucidate further structural and electrical properties, includingthe interaction patterns of tailored SubPcs. It is worth noting thatthe theoretical computations exhibit good conformity with the empiricaldata. The predicted fluctuations in photocatalytic activity detectedin SubPc systems were shown to be closely associated with frontiermolecular orbital (FMO) characteristics, noncovalent interaction (NCI)patterns, and the electron-donating nature of the fragments locatedat the peripheral positions.