S.G. Rashid

Synthesis, morphology and antifungal activity of nano-particulated amphotericin-B, ketoconazole and thymoquinone against Candida albicans yeasts and Candida biofilm

In the current study, nano-particulated drugs—Amphotericin-B, Ketoconazole and Thymoquinone (an active ingredient of Nigella sativa)—were prepared using the ball milling technique, and their particle sizes were examined by transmission electron microscopy (TEM) and using a particle size analyzer. The grain sizes of the prepared compounds were found in between 5 to 20 nm, and exhibited quasi-spherical morphology. The antifungal activity of each nano-particulated drug was investigated in vitro against Candida albicans yeasts and Candida biofilm, and compared with their micro-structured conventional forms. Nano-sized drugs were found to be two to four times more effective in disinfecting both the Candida yeasts and Candida biofilm. The study is a first of its kind as nano-forms of drugs have not been studied against Candida and Candida biofilm before. Further investigations are required for the determination of the clinical significance of the nano-formulation of antifungal substances.

Synthesis, characterization and visible light photocatalytic activity of Cr3+, Ce3+ and N co-doped TiO2 for the degradation of humic acid

The synthesis, characterization and photocatalytic activity of Cr3+ and Ce3+ co-doped TiON (N-doped TiO2) for the degradation of humic acid with exposure to visible light is reported. The synthesized bimetal (Cr3+ + Ce3+) modified TiON (Cr–Ce/TiON), with an evaluated bandgap of 2.1 eV, exhibited an enhanced spectral response in the visible region as compared to pure and Ce3+ doped TiON (Ce/TiON). The XRD analysis revealed the insertion of Cr3+ and Ce3+ in the crystal lattice along with Ti4+ and N that resulted in the formation of a strained TiON anatase structure with an average crystallite size of ∼10 nm. Raman analysis also supported the formation of stressed rigid structures after bimetal doping. HRTEM confirmed the homogeneous distribution of both the doped metallic components in the crystal lattice of TiON without the formation of surface oxides of either Cr3+ or Ce3+. Electron energy loss spectroscopy (EELS) analysis revealed no change in the oxidation of either Cr or Ce during the synthesis. The synthesized Cr–Ce/TiON catalyst exhibited appreciable photocatalytic activity for the degradation of humic acid on exposure to visible light. Additionally, a noticeable mineralization of carbon rich humic acid was also witnessed. The photocatalytic activity of the synthesized catalyst was compared with pristine and Ce3+ doped TiON.

Photo-catalytic deactivation of sulfate reducing bacteria – a comparative study with different catalysts and the preeminence of Pd-loaded WO3 nanoparticles

Sulfate reducing bacteria (SRB), predominantly present in the produced water in oil fields is known for being an agent for degrading the quality of crude oil by introducing an elevated level of sulfur content, initiating oil souring and corroding the oil pipelines. In addition, this bacterium poses an immense health threat to the oil field workers due to the generation of radioactive barium sulfide. Photo-catalytic deactivation of the sulfate reducing bacteria in water with four different pure and palladium loaded photo-catalysts was carried out and their relative efficiencies are compared. It was found that n-Pd/WO3 at an optimum concentration, in conjunction with 355 nm pulsed laser radiation showed a substantial increase in the photo-catalytic deactivation of SRB in contaminated water. A 110 fold increase in the SRB deactivation rate, compared to UV radiation (in the absence of catalyst) and a 30 fold increase in the same, compared to pure WO3, and the bench mark catalyst (TiO2) under the same experimental conditions was observed. All the nano-structured photo-catalysts were synthesized, optically and morphologically characterized to optimize the function of each catalyst effective in the deactivation of harmful sulfate-reducing bacteria in water.

Synthesis and photoluminescence of metal coated ZnO nanoparticles

ZnO nanoparticles were prepared by precipitation method from zinc nitrate and ammonium carbonate solutions, and annealing at 500°C. The XRD pattern shows that the ZnO nanoparticles have pure wurtzite structure. ZnO nanoparticles were coated with Au, Ag and Pd atoms using wet chemical treatment. The effect of coating ZnO nanoparticles with Au, Ag and Pd atoms on the photoluminescence properties is investigated. Results show that ZnO-plasmonics can play an important role in emission enhancement. In particular, it was found that coating ZnO nanoparticles with metals enhances the ZnO band edge emission by about 11 to 20 %, depending on the type of metal, and quenches the visible emission by about 50 %.

Enhanced photo-catalytic activity of ordered mesoporous indium oxide nanocrystals in the conversion of CO2 into methanol

ABSTRACT Ordered mesoporous indium oxide nanocrystal (m-In2O3) was synthesized by nanocasting technique, in which highly ordered mesoporous silca (SBA-15) was used as structural matrix. X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halanda (BJH) studies were carried out on m-In2O3 and the results revealed that this material has a highly ordered mesoporous surface with reduced grain size, increased surface area and surface volume compared to the non porous indium oxide. The diffuse reluctance spectrum exhibited substantially improved light absorption efficiency in m-In2O3 compared to normal indium oxide, however, no considerable change in the band gap energies of these materials was observed. When m-In2O3 was used as a photo-catalyst in the photo-catalytic process of converting carbon dioxide (CO2) into methanol under the pulsed laser radiation of 266-nm wavelengths, an enhanced photo-catalytic activity with the quantum efficiency of 4.5% and conversion efficiency of 46.3% were observed. It was found that the methanol production yield in this chemical process is as high as 485 µlg−1 h−1 after 150 min of irradiation, which is substantially higher than the yields reported in the literature. It is quite clear from the results that the introduction of mesoporosity in indium oxide, and the consequent enhancement of positive attributes required for a photo-catalyst, transformed photo-catalytically weak indium oxide into an effective photo-catalyst for the conversion of CO2 into methanol.