Comparison between preparative methodologies of nanostructured carbon nitride and their use as selective photocatalysts in water suspension

Carbon nitride photocatalysts have been prepared by different methodologies, such as chemical ultrasonic irradiation (sonochemical treatment), hydrothermal and ball milling and thermoexfoliation, and have been used for the selective oxidation of 5-hydroxymethyl-2-furaldehyde (HMF) to form 2,5-furandicarboxyaldehyde (FDC) in water suspension both under UV and natural solar irradiation. The physico-chemical features of the photocatalysts have been studied by X-ray diffraction, infrared spectroscopy, UV–Vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, scanning electron microscopy, and specific surface area measurements. The results indicate that exfoliation of carbon nitrides can increase the conversion of HMF and the selectivity to FDC. In particular, samples exfoliated by both thermal and acidic ultrasonic irradiation treatments showed the best photocatalytic performance.     

Preparation of Cd(OH)2 nanostructures in water using a simple refluxing method and their photocatalytic activity

Nanostructures of Cd(OH)₂ were prepared using a simple template-free method in water by 4?h refluxing at about 95?°C without using any organic compound. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform-infrared and UV?Cvis diffuse reflectance spectroscopy techniques were applied for characterization of the nanostructures. The XRD pattern demonstrates that the nanostructures are crystallized in hexagonal phase. The SEM image shows that the nanostructures are nearly in plate form. The DRS of the nanostructures shows absorption maxima at about 315?nm. Photocatalytic activity of the nanostructures was investigated by degradation of methylene blue (MB) under UV irradiation. Moreover, the effects of refluxing time and calcination temperature on photocatalytic activity were studied.     

Simple and low temperature preparation and characterization of CdS nanoparticles as a highly efficient photocatalyst in presence of a low-cost ionic liquid

A simple and low temperature method is proposed for preparation of CdS nanoparticles in presence of 1-ethyl-3-methylimidazolium ethyl sulfate, [EMIM] [EtSO₄], a room-temperature ionic liquid (RTIL). The powder X-ray diffraction (XRD) studies display that the products are excellently crystallized in the form of cubic structure and size of the nanparticles prepared in presence of the RTIL is smaller than that prepared in water. Energy dispersive X-ray spectroscopy (EDX) investigations reveal that the products are very pure and nearly stoichiometric. The results obtained by scanning electron microscopy (SEM) demonstrate that the CdS nanoparticles prepared in presence of the RTIL have lower tendency for aggregation relative to the prepared sample in water. Diffuse reflectance spectra (DRS) of the product prepared in the neat RTIL, shows 1.52 eV blue shift relative to bulk CdS, which can be attributed to quantum confinement effect of the CdS nanoparticles. A possible formation mechanism for CdS nanoparticles in presence of the RTIL is presented. Photocatalytic activity of the CdS nanoparticles towards photodegradation of methylene blue (MB) using UV and visible lights was performed. The results demonstrate that observed firstorder rate constant for photodegradation of MB on CdS nanoparticles prepared in the neat RTIL are about 20 and 6 times greater than the prepared sample in water using visible and UV lights, respectively.     

Microwave-assisted method for preparation of Sb-doped ZnO nanostructures and their photocatalytic activity

Nanostructures of Sb-doped ZnO with 0.00, 0.03, 0.06, 0.10 and 0.15 mol fractions of Sb⁺³ ions were prepared by a one-pot method in water under microwave irradiation for 5 min. Powder X-ray diffraction studies display that the nanostructures are excellently crystallized in the form of Wurtzite hexagonal crystalline phase and doping Sb⁺³ ions does not change structure of ZnO. Moreover, size of the nanostructures decreases with increasing mole fraction of Sb⁺³ ions. Scanning electron microscopy and transmission electron microscopy images show that morphology and size of the nanostructures are changing with mole fraction of the dopant. In Fourier transform infrared spectra, intensity of the characteristic peak corresponding to Sb–O bond gradually increases with mole fraction of Sb⁺³ ions. UV–vis diffuse reflectance spectra of the nanostructures are similar to each other and they have a maximum of about 357 nm. Photocatalytic activity of the nanostructures was investigated by degradation of methylene blue under UV irradiation. For the nanostructures with 0.10 mol fraction of Sb⁺³ ions, the degradation rate constant increases nearly two times relative to pure ZnO. In addition, influence of various operational parameters on the degradation activity was investigated and the results were discussed.