Jatindra Nath Ganguli

Tuning the band gap of mesoporous Zr-doped TiO2 for effective degradation of pesticide quinalphos.

This paper has focused on the synthesis and modification of TiO2 nanomaterial via an acid modified sol-gel process. ZrOCl2 was used as a source of Zr for doping titania. The nanomaterials were characterized by electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, N2 adsorption-desorption isotherms, UV-visible diffuse reflectance spectroscopy, etc. Changes in the band gap of the synthesized nanomaterials were studied with respect to the dopant amount, and the performance of the synthesized nanomaterials was evaluated as a photocatalyst to degrade pesticide quinalphos in aqueous solution under UV light. Anatase TiO2 nanocrystallites with an average size of ca. 8-11 nm were obtained depending on the amount of dopant. The results showed that the amount of dopant significantly altered the band gap as well as the surface properties of the hybrid nanomaterials which resulted in high photocatalytic activity.

A novel synthetic approach for the preparation of sulfated titania with enhanced photocatalytic activity

A novel approach was used to synthesize sulfated titania (TiO2) nanoparticles using 15% titanium trichloride and thiophene, in the presence and absence of oxalic acid. The catalyst structure has been characterized by using a combination of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), UV-visible diffused reflectance spectroscopy (DRS), transmission electron microscopy (TEM), cyclic voltammetry analysis (CV), BET surface area analysis, Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR). X-ray powder diffractometry showed that the catalysts are composed of only an anatase phase. DRS revealed that the sulfur doped titania catalysts showed a red shift of optical absorption. The results of both XRD and TEM revealed a decrease in the size of the sulfated titania particles. XPS provides conclusive evidence for Ti–O–S bond formation. The performance of the synthesized nanomaterial was evaluated as a photocatalyst to degrade 2,7-dichlorofluorescein dye in aqueous solution under UV light. Synthesized sulfated titania photocatalysts were found to be better than undoped and commercial titania.

Hydrogenation by nanoscale ruthenium embedded into the nanopores of K-10 clay

Ruthenium(0) nanoparticles in the size range 1–4 nm were generated in the nanopores of the fine fraction of Montmorillonite K-10 clay by in situ glycol reduction of RuCl3·3H2O impregnated clay. The synthesized catalyst was characterized by Powder XRD, SEM, TEM, DRS and BET surface area determination. TEM/HRTEM/SAED images revealed the growth of well dispersed Ru(0) nanoparticles having lattice fringes with interplanar spacing 0.21 nm corresponding to the [101] plane of hexagonal close packed ruthenium. The catalytic activity of the synthesized catalyst was tested for hydrogenation of cyclohexene to cyclohexane. The clay embedded Ru nanoparticles act as an efficient and recyclable environmentally friendly catalyst in hydrogenation of dextrose and phenol in aqueous medium under mild reaction conditions. Turn over frequency (TOF) of the catalyst was also calculated considering true active sites calculated on the basis of surface statistics and a model for full shell clusters.

Synthesis, characterization and photocatalytic reactions of phosphated mesoporous titania

Mesoporous titania nanoparticles with a well-defined mesostructure was prepared by hydrothermal process, using nonionic triblock copolymer P123 as surfactant template, modified with phosphoric acid and followed by calcination at 600°C. The sol–gel titania was modified by in situ phosphorylation using phosphoric acid and thereby incorporating phosphorous directly into the framework of TiO2. The resulting materials were characterized by XRD, SEM, TEM, nitrogen adsorption, TGA and DRS. It was found that the structural and optical properties of titania samples are strongly influenced by their phosphate modification. In case of calcined samples a positive effect on the specific surface area for the in situ phosphated sample was found. Mesoporous structure of phosphated titania did not collapse even after calcination at 600°C. The enhanced photocatalytic activity of the synthesized phosphate nanomaterials were evaluated through a study of the decomposition of fluorescein under UV light excitation and compared with undoped titania nanomaterial as well as with commercial titania.

Hibiscus sabdariffa L. leaf extract mediated green synthesis of silver nanoparticles and its use in catalytic reduction of 4-nitrophenol

ABSTRACT In the present study, the authors explored the green synthesis of silver nanoparticles (AgNP) using Hibiscus sabdariffa, L. leaf extract as reducing agent and nanoparticles stabilizer. The silver nanoparticles were formed at room temperature in a short period of time using the leaf extracts of H. sabdariffa and silver nitrate at room temperature. The resulting nanoparticles were characterized by UV-visible spectroscopy, transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. UV-visible spectroscopy shows characteristic surface plasmon resonance band of spherical silver nanoparticles. The synthesized AgNPs were effective in catalyzing the reduction of 4-nitrophenol.

Removal of a Basic Dye from Aqueous Solution by a Natural Kaolinitic Clay — Adsorption and Kinetic Studies

The < 25 μm fraction of natural clay containing kaolinite, chlorite, illite and illite/smectite mixed layered clay minerals was characterized and used as a potential adsorbent for the removal of Rhodamine B (RB) dye from aqueous solution. Adsorption experiments were carried out in batch mode by varying the following parameters: pH, temperature, initial dye concentration, adsorbent dosage and time of contact. The equilibrium data were well fitted by both the Langmuir and Freundlich adsorption isotherms. The Langmuir monolayer adsorption capacity was found to be 4.77 mg/g, which was better than the value reported for kaolinite (1.95 mg/g). The adsorption process followed pseudo-second-order kinetics. Negative ΔG0 values indicated that adsorption onto this clay was a spontaneous process. A maximum dye uptake of > 90% was achieved at 313 K employing an initial dye concentration of 4.8 × 10−6 M, a pH value of 2 and an adsorbent dosage of 1 g/ℓ.