Someshwar Pola

Synthesis, Characterization and Photocatalytic Activity of KAl0.33W1.67O6 and Sn0.5Al0.33W1.67O6xH2O

Nano sized defect pyrochlore, KAl0.33W1.67O6 (KAW), is prepared through sol–gel method. Divalent tin‐doped KAW is obtained at room temperature by ion exchange method using acidified SnCl2 and parent KAW. These materials are characterized by powder X‐ray diffraction, thermogravimetric analysis (TGA), scanning electron microscopy—energy dispersive spectra (SEM‐EDS), Raman Spectroscopy and X‐ray photo electronic spectroscopy. The composition of tin‐doped KAW is obtained from chemical analysis, SEM‐EDS and TGA methods and written as Sn0.5Al0.33W1.67O6 xH2O (x = 1.4–1.5) (SnAW). It crystallizes in cubic lattice with Fd3¯m space group. The band gap energies are found to be 2.82 and 2.21 eV for KAW and SnAW respectively. The observed reduction in the band gap with the introduction of Sn2+ in defect pyrochlore lattice is due to mixing of 5s state of Sn2+ with O 2p states leading to an upward shift in the valence band. The Raman spectra of these materials gave more bands than the number expected for defect pyrochlores due to substitutional disorder in 16c sites and displacive disorder of A ions. The photoactivity of SnAW is higher compared to KAW.

New photocatalyst for allylic aliphatic C–H bond activation and degradation of organic pollutants: Schiff base Ti(IV) complexes

Schiff base metal complexes have attracted significant attention due to their alternative applications in the environment, such as the mineralization of organic pollutants to less harmful byproducts and oxygen generation via such processes as photosynthesis. The Ti4+ complexes obtained from Schiff base ligands reacted with donor atoms such as S and N under solvothermal conditions. These complexes were characterized using microanalysis, conductivity studies, and different spectral techniques. These data reveal that the compounds show distorted octahedral geometries with ligand coordination via azomethine nitrogen and thiol sulfur atoms. Oxidation of the allylic methyl group examined the photocatalytic activity of [Ti(L)O] under ambient conditions and oxidative cyclization under visible light irradiation. The Ti(DCMPPT)O complex is a very efficient catalyst due to the very short span of time it takes to produce aldehydes from allylic compounds. Aldehydes readily react with 2-aminophenol or 2-aminobenzenethiol to produce (E)-2-styrylbenzo[d]oxazoles and (E)-2-styrylbenzo[d]thiazoles due to the suitability of the bandgap energy to the generation of ˙OH radicals during the catalytic reaction. This results in a higher oxidation rate. [Ti(DCMPPT)O] is a very efficient photocatalyst for the degradation of MB, due to its large surface area which suggests a lower recombination energy mechanism.

Compact TiO2 films with sandwiched Ag nanoparticles as electron-collecting layer in planar type perovskite solar cells: improvement in efficiency and stability

Fabrication of perovskite solar cells (PSCs) in a simple way with high efficiency and stability remains a challenge. In this study, silver nanoparticles (Ag NPs) were sandwiched between two compact TiO2 layers through a facile process of spin-coating an ethanolic AgNO3 solution, followed by thermal annealing. The presence of Ag NPs in the electron-transporting layer of TiO2 improved the light input to the device, the morphology of the perovskite film prepared on top, and eliminated leakage current. Photoluminescence and electron mobility studies revealed that the incorporation of Ag NPs in the ETL of the planar PSC device facilitated the electron–hole separation and promoted charge extraction and transport from perovskite to ETL. Hysteresis-free devices with incorporated Ag NPs gave a high average short-circuit current density (Jsc) of 22.91 ± 0.39 mA cm−2 and maximum power conversion efficiency of 17.25%. The devices also showed enhanced stability versus a control device without embedded Ag NPs. The possible reasons for the improvement are analyzed and discussed.

Synthesis and Characterization of Contorted Pentabenzo-Fused Coronenes as Semiconducting Materials

Here, we report the synthesis and characterization of a series of contorted, yet noncentrosymmetrical, polycyclic aromatic hydrocarbons with a pentabenzo-fused coronene as the core framework. The parent pentabenzo[a,d,g,j,m]coronene (PBC) compound is shown to exhibit a shifted and rotated type of π-π stacking interactions, which render this series a semiconducting material. Single-crystal-based field-effect transistor devices of PBC exhibited efficient charge transport behavior, giving a p-channel field-effect mobility of 0.42 cm2 V-1 s-1 and an on/off ratio of 105.

Synthesis of new fused heterocyclic aromatic hydrocarbons via C–S and C–C bond formation by C–H bond activation in the presence of new Pd(II) Schiff's base complexes

The Schiffs base aza-macrocyclic Pd(DPTTP)Cl2 and Pd(TPTTP)Cl2 complexes are efficient photocatalysts for the activation of the C–H bond and the formation of both intramolecular C–C bond and C–S bonds to obtain the fused heterocyclic system. Both ligands and Pd(II) complexes are well characterized by experimental and theoretical techniques such as microanalyses, mass, surface area, SEM, TGA, XPS, IR, UV-visible, 1H-NMR, DFT and TDDFT methods. C–H bond activation was confirmed by sequential reactions and the data were supported by a one-pot synthesis product. Optimization of the intensity of visible light of the photocatalytic reactions. Finally, the sp2-H bond activation via the formation of the C–S and intramolecular C–C bonds in the presence of both the complexes were performed under visible light irradiation to obtain the new fused system, pyrido[3′,2′:6,7][1,4]thiazepino[2,3-h][1,6]naphthyridine. It is also shown that the performance of the Pd(TPTTP)Cl2 is better than that of Pd(DPTT)Cl2 due to its high surface area and low bandgap energy.