Sharif Digital Repository

A new model to calculate electronic states of the diamond vacancies has been developed using many body techniques. This model is based on physical assumptions of previous molecular models but does not use configuration interaction. Present model allows an accurate and unified treatment of electronic levels and related eigen functions for diamond vacancies, in addition to transition energies of the first dipole-allowed transitions in the neutral (V0) and negatively charged (V-) vacancies, GR1 and ND1 band. For the first time, we calculated their optical transition intensities. For obtaining these results, we solved a generalized form of the Hubbard Hamiltonian, which consists of all... 

The visible band (band A) of photoluminescence spectra of high-purity synthesized diamond is analyzed by the deconvolution technique. A set of eight lines with distinct peak energies are found. The peak energy and the width of these lines were either constant or varied very slightly with temperature. The amplitude of the lines are significantly temperature dependent. The closeness of the temperature at which the amplitudes of these lines reach their minimum to the temperature at which the free-exiton emission is maximum, is an indication of the competition between these two effects  

The search for cathode materials with fast oxygen reduction reaction (ORR) catalytic activities and high ionic conductivity is the key obstacle to SOFCs commercialization and its operation at low temperatures. In order to search for a cathode with enhanced catalytic functionality, herein we report a single-phase CoFe2O4 (CFO) and CoGd0.2Fe1.80O4 (CGFO), which can be employed as an active cathode to improve electrocatalytic ORR functionalities at low temperature. It is found that CGFO having enriched oxygen vacancies exhibits the least polarization resistance (RP) of 0.42 Ωcm2 compared to the pure CFO which shows polarization resistance of 0.56 Ω cm2 under H2/air conditions. Furthermore,... 

Preparation of the defective TiO2 nanoparticles (NPs) have been recently in particular interest for its outstanding applications in visible-light active photocatalysis. In order to make TiO2 visible-light absorber, optical band gap should be modified especially via introducing structural defects like oxygen vacancies as an effective pathway. In this research, we prepared defective rutile TiO2 NPs with highly efficient photocatalytic activity under visible light. The NPs were synthesized by electric arc discharge in water as a cost-effective and environmentally friendly method with capability of defect formation which followed by heat treatment. The photocatalytic activity improvement... 

In this research, the potential of bismuth chromate (BCO), a new bismuth-based semiconductor belongs to the family of Bi2XO6 (X = Mo, W, or Cr), was introduced by a novel 1D/2D structure consist of BCO nanobelts and N2-freezed ultra-wrinkled graphitic carbon nitride (N–CN) nanosheets. To enhance intimate contact between BCO and N–CN (BCO/N–CN composite), surface oxygen vacancy (VO) was created as an efficient electron transfer highway using a simple alkaline-treatment-assisted method. Various characterization techniques, including XRD, FT-IR, EPR, FE-SEM, TEM, BET, DRS, PL, EIS, and photocurrent transient analyses were conducted to elucidate the physicochemical aspects of catalysts. The...