Nanochitosan/carboxymethyl cellulose/TiO2 biocomposite for visible-light-induced photocatalytic degradation of crystal violet dye.

Development of novel bionanomaterials for water and wastewater treatment has gained increased attraction and attention in recent times. The present study reports an effective biocomposite-based nano-photocatalyst comprised of nanochitosan (NCS), carboxymethyl cellulose (CMC), and titanium dioxide (TiO2) synthesized by sol-gel technique. The as-prepared NCS/CMC/TiO2 photocatalyst was systematically characterized by X-ray diffraction, Fourier Transform Infrared spectroscopy, Scanning Electron Microscopy with energy dispersive X-beam spectroscopy, Differential scanning calorimetry (DSC), and Thermogravimetric analysis (TGA). Photocatalytic degradation of the crystal violet (CV) dye using this nano photocatalyst was studied by varying the irradiation time, catalyst dosage, feed pH, and initial dye concentration. Further, the kinetic analysis of dye degradation was explored using the Langmuir-Hinshelwood model, and a plausible photocatalytic mechanism was proposed. The modification of TiO2 using NCS and CMC accelerated photocurrent transport by increasing the number of photogenerated electrons and holes. Overall, the study indicated the excellent photocatalytic performance of 95% CV dye degradation by NCS/CMC/TiO2 than the bare inorganic TiO2 photocatalyst under visible light irradiation.

Synthesis of Culn(1-x)Ga(x)Se2 Nanoparticles by Thermal Decomposition Method with Tunable Ga Content.

Chalcopyrite Culn(1-x)Ga(x)Se2 (CIGS) nanoparticles were synthesized by mixing copper (I) chloride (CuCl), Indium (III) chloride (InCl3), gallium (III) chloride (GaCl3) and selenium (Se) in oleylamine (OLA) at 260 degrees C for 4 h under nitrogen atmosphere. The Ga/(In+ Ga) ratio was tuned across the entire stoichiometric range from 0 to 1. X-ray diffraction analysis (XRD) revealed chalcopyrite crystal structure for samples prepared with x = 0, 0.3, 0.5, 0.7 and 1. The lattice parameters a and c decreased linearly with increasing Ga concentration which is consistent with Vegard's law. Raman spectra exhibited A, optical phonon vibrational mode for synthesized nanoparticles which gradually shifted to higher wavenumber with increasing Ga content. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images showed irregular as well as hexagonal plate like morphologies in the size range of 100 to 400 nm. High-resolution transmission electron microscopy (HR-TEM) images showed well-defined lattice fringes and d-spacing correspond to (112) plane which gradually decreases with increasing Ga content. The material compositions of synthesized CIGS nanoparticles with x = 0, 0.3, 0.5, 0.7 and 1 were very close to the desired stoichiometry which was confirmed by energy dispersive X-ray analysis (EDAX). Ultraviolet visible near infrared (UV-VIS-NIR) absorption spectra of the synthesized CIGS nanoparticles revealed that the bandgap could be tuned over the range 1 to 1.7 eV by varying the Ga/(In+Ga) ratio.

Synthesis and Characterization of Cadmium Sulfide Nanoparticles by Chemical Precipitation Method.

Cadmium sulfide (CdS) nanoparticles were synthesized by chemical precipitation method using cadmium chloride (CdCl2), sodium sulfide (Na2S) and water as a solvent by varying temperatures from 20-80 degrees C. The nanoparticles were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), High-resolution transmission electron microscopy (HR-TEM) and UV-Visible spectroscopy. XRD pattern revealed cubic crystal structure for all the synthesized CdS nanoparticles. Raman spectra showed first and second order longitudinal optical (LO) phonon vibrational modes of CdS. The size of CdS nanoparticles was found to be in the range of 15-80 nm by FE-SEM analysis, in all cases. The atomic percentage of cadmium and sulfur was confirmed to be 1:1 from EDS analysis. TEM micrograph depicts the spherical shape of the particles and the size is in the range of 15-85 nm while HR-TEM images of CdS nanoparticles exhibit well-resolved lattice fringes of the cubic structure of CdS. The optical properties of CdS were examined by UV-Visible spectroscopy which showed variation in absorption band from 460-480 nm. The band gap was calculated from the absorption edge and found to be in the range of 3.2-3.5 eV which is greater than the bulk CdS.