Sharif Digital Repository

Dye-sensitized solar cells (DSCs) with nanotubular TiO2 electrodes of varying thicknesses are compared to DSCs based on conventional nanoparticulate electrodes. Despite the higher degree of order in one-dimensional nanotubular electrodes, electron transport times and diffusion coefficients, determined under short-circuit conditions, are comparable to those of nanoparticulate electrodes. The quasi-Fermi level, however, is much lower in the nanotubes, suggesting a lower concentration of conduction band electrons. This provides evidence for a much higher diffusion coefficient for conduction band electrons in nanotubes than in nanoparticulate films. The electron lifetime and the diffusion length... 

In this study, adsorption of important pollutant cations on the surface of graphitic carbon nitride (g-C3N4) was investigated by density functional theory. The calculations indicated that N6 cavity surrounded by triazine units is the most probable adsorption site on this surface. The structural optimizations also predicted a planar surface for Cr3+, and Ni2+/g-C3N4 systems while the structure of the surface for other systems indicated a considerable distortion with strong dependency on the cation size. Also, g-C3N4 surface exhibited the high adsorption energies for Cr3+, As3+, and Sb3+ ions in the gas phase. However, formation energies of the metal-aquo complexes of these cations indicated... 

We have investigated the surface-enhanced resonance Raman spectroscopy (SERRS) for 4,4′-diaminotolane absorbed on silver experimentally and theoretically. Experimental observation shows greatly enhanced bg symmetric modes ν26 and ν27, which are silent in normal Raman spectroscopy and SERS on gold. The dependence of the surface-enhanced Raman spectroscopy (SERS) spectra on five excitation lines has also been registered and classified for single bands into three profiles referring to the different contributions of resonant transitions. Theoretical calculations based on the time-dependent path integral formalism by including the Herzberg-Teller correction reproduce the experimental spectra with... 

Ni/SiC nanocomposite coatings were electrodeposited using Watts type bath and different SiC particle size. The electrodeposition behavior of Ni/SiC nanoelectrocomposites was studied using electrochemical techniques such as impedance spectroscopy (EIS) and voltammetry. In this study it was shown that SiC particles modify the EIS diagram and voltammograms as well as surface morphology of electrodeposited layers. Experimental results showed that SiC particles not only affect the formation of intermediate species and decrease charge transfer resistance but also increase the nucleation sites for nickel electrodeposition and thus affect the microstructure of electrodeposited Ni/SiC nanocomposites.... 

A series of bithiazole-based dye sensitizers have been designed by employing various electron-rich moieties as π-spacer, which are based on the reported experimentally synthesized dye T-BT, to shed a light on the impact of both the nature and position of electron-rich moiety on the efficiency of dyes in DSSCs. To evaluate the efficiency of these dyes, various key parameters associated with overall conversion efficiency (η), including electronic and optical properties of free dyes are calculated, based on the computational methods. Besides, the dye/TiO2 structures have been taken into account to investigate the interfacial features of the dye sensitizers adsorbed on TiO2 semiconductor and... 

Argon is often considered as an innocent probe that can be attached and detached to study the structure of a particular species without perturbing the species too much. We have investigated whether this assumption also holds for small copper cationic clusters and demonstrated that small but significant charge transfer from argon to metal changes the remaining binding positions, leading in general, to weaker binding of other argon atoms. The exception is binding to just one copper ion, where the binding of the first argon facilitates the binding of the second. © 2020 American Chemical Society  

The mononuclear complexes of Zn(II), Cd(II) and Hg(II), [Zn(phen-dione)Cl2], [Cd(phen-dione)Cl2] and [Hg(phen-dione)Cl2], where phen-dione = 1,10-phenanthroline-5,6-dione, have been synthesized and characterized by elemental analysis and IR, 1H NMR and electronic absorption spectroscopies. The ν(C=O) of coordinated phen-dione ligands in these complexes shows that the phen-dione is not coordinated to metal ion from its C=O sites. Electronic spectra of the complexes show two absorption bands for intraligand transitions. These absorption bands show dependence on the dielectric constant of solvents. These complexes exhibit an intense fluorescence band around 545 nm in DMSO when the excitation... 

Abstract: Surface-nanostructured TiO2 nanorods were synthesized hydrothermally at 180 °C. Such nanorods have ‘crack-like’ surfaces that resemble burnt charcoal. Compared to nanorods with relatively smoother surfaces, the charcoal-like nanorods have higher-specific surface areas. By using the nanorods as a light-scattering layer in double-layered dye-sensitized solar cells, the cells based on the charcoal-like nanorods have 20 % higher dye loading and also higher diffuse reflectance compared with cells utilizing ‘smooth’ nanorods. The efficiency of a screen-printed double-layer dye-sensitized solar cell based on the charcoal-like nanorods is higher at 7.29 %. Electrochemical... 

Here, we report on utilizing a photoactive protein, bacteriorhodopsin (bR), as a light harvester in combination with TiO2 nanoparticles in biosensitized solar cell application. Experiments have been conducted to investigate the capability of surface adsorption of bR on nanoparticular TiO2photoanodes. Different pretreatment processes have been done to modify the interface of TiO2 nanoparticles and bR as a biophotosensitizer. Our results indicate the feasibility of efficient immobilization and photoinduced charge transfer of bR to the nanostructured TiO2 photoelectrode. Under illumination of simulated AM1.5 sunlight, the solar-light-to-electricity... 

Cadmium sulfide (CdS) thin film was electrodeposited on indium tin oxide (ITO) by chronoamperometry. The SEM images showed that hexagonal sheets of CdS deposited on the ITO surface. The X-ray diffraction (XRD) analysis confirmed this structure for CdS crystals and the average of crystalline size and the lattice constant parameters are approximately 39.54 and a = 0.4136, c = 0.6696 nm respectively. Photo-electrochemical investigations were performed by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) techniques. CdS band edges and density of states (DOS) were determined by CV technique. The band gap energy (Ebg) was measured... 

A three-dimensional (3D) graphene/Nickel oxide (ERGO/NiO) composite electrode have been fabricated directly on a Nickel foam substrate via a one-step electrochemical co-deposition in an aqueous solution containing Nickel nitrate and GO. By using this simple and one-step electrochemical deposition, it is possible to produce binder-free composite electrodes with improved electrochemical properties using a low-cost, facile and scalable technique. It is observed from FE-SEM images that graphene oxide sheets affect the electrodeposition of nickel oxide. The optimized ErGO/NiO electrode developed in this work exhibits high charge storage capacity with a specific capacitance of 1715.5 F g−1 at... 

Demand for more efficient energy storage devices stimulates efforts to search and develop new materials and composites with promising properties. In this regard, composite materials, including carbonaceous materials and metal oxides have attracted a great attention due to better electrochemical performance as compared to their single material analogues. For the first time, herein, we report a new and simple procedure for preparing porous highly oriented pyrolytic graphite/nickel hydroxide composite (P-HOPG/Ni(OH)2) via a fast and simple two-step electrochemical method including potentiostatic routes. In the first step, a low anodic potential (2 V) was applied to pristine HOPG in 0.5 M H2SO4... 

Lithium ion batteries as one of the most important energy storage equipments, have several challenges including capacity drop as number of cycles increases. Cathode particle coating is an effective approach in improvement of electrochemical performance of the batteries. In this study, TiO2-Ag coating was used to improve NCM cathode performance. The microstructure and crystal structure properties of coated NCMs were evaluated by the FE-SEM and XRD. Electrochemical behavior of the batteries was investigated by cycling performance analysis and EIS. TiO2 coating was deposited as a uniform layer and Ag coating was precipitated as dispersed nanoparticles. The results shows that using of TiO2-Ag... 

A series of thiophene-based donor-acceptor-donor (D-A-D) oligomer substituted metalloporphyrins (MPors) with different 3d central metal-ions (M = Co, Ni, Cu, and Zn) were systematically investigated to screen efficient hybrid photocatalysts for CO2 reduction based on density functional theory (DFT) and time-dependent DFT simulations. Compared with base MPors, the newly designed hybrid photocatalysts have a lower bandgap energy, stronger and broader absorption spectra, and enhanced intermolecular charge transfer, exciton lifetime, and light-harvesting efficiency. Then, the introduction of D-A-D electron donor (ED) groups into the meso-positions of MPors is a promising method for the... 

The bond valence sum method has been developed to high pressures considering B0(p) for calculating the valences of atoms. This approach has the advantages of finding a universal B0(P) for all the atoms -at least in YBCO, ability to evaluate the valency of each atom, and charge neutrality requirement of the unit cell. As a result, a new structural refinement has led to a more exact structural detail. The position of apical oxygen is found to be specially crucial for hole distribution between the superconducting CuO2 planes and Cu-O charge reservoir chains. Under pressure, the hole concentration in CuO2 planes increases, but in the Cu-O chains decreases, consistent with the pressure induced... 

Electronic structure calculations for two isofamilies, YBa 2Cu3O7 (YBCO) and YSr2Cu 3O7 (YSCO) high Tc cuprates, have been done for ambient and high pressures (-15 GPa