Anuraj S. Kshirsagar

Photodegradation of organic dyes based on anatase and rutile TiO2 nanoparticles

The present work highlights a simple nanochemistry based clean and efficient process for effective degradation of various organic dyes by use of anatase and rutile TiO2 nanoparticles. Based on photodegradation studies it was observed that at certain experimental parameters, rutile TiO2 was as effective as anatase for the degradation of indigo carmine (IC) dye in aq. solution. However, anatase TiO2 was found to be much more efficient against methylene blue (MB), methyl orange (MO), rhodamine B (RB) and eriochrome black T (EBT) under short UV irradiation. The photodegradation study of these organic dyes was also performed under long UV irradiation employing both anatase and rutile titania and the results showed similar trends. However, only EBT photodegradation indicated equal photocatalytic activity by both phases. The catalytic degradation of the organic dyes was studied by degradation kinetics. The maximum degradation efficiency using anatase and rutile titania photocatalysts was found to be 88% and 77% in the case of MB under short UV irradiation while about 65% was found in the case of EBT under long UV irradiation. The reuse of photocatalyst even after five cycles retained the degradation efficiency of 83% and 71% respectively for anatase and rutile when tested against MB.

In situ SeO2 promoted synthesis of CdSe/PPy and Se/PPy nanocomposites and their utility in optical sensing for detection of Hg2+ ions

Avoiding the use of any external oxidising agent or initiator for the polymerisation process, pyrrole was successfully polymerised to polypyrrole (PPy) using SeO2 as an internal oxidant which leads to the in situ synthesis of selenium and cadmium selenide polypyrrole (Se/PPy and CdSe/PPy) nanocomposites by chemical and microwave methods. PPy formation during the reaction was monitored by UV-Visible absorption spectroscopy. XRD measurements indicated the formation of the confirmed CdSe/PPy and Se/PPy nanocomposites. SEM images show the aggregation of small particles in the form of large globules with smooth surfaces. HRTEM images reveal the presence of spherical CdSe and Se nanoparticles homogeneously embedded in the polypyrrole matrix with interplanar distances of 0.35 nm and 0.4 nm for the (111) and (100) atomic planes, respectively. The as-synthesized CdSe/PPy and Se/PPy nanocomposites were tested for the detection of heavy metal ions. CdSe/PPy and Se/PPy successfully detected mercury ions at 25, 50 and 100 ppm. This article also describes the use of pre-synthesized Se/PPy nanocomposites as precursors for the synthesis of CdSe/PPy nanocomposites.

Synthesis of shape and size controlled copper indium diselenide (CuInSe2) via extrusion of selenium from 1,2,3-selenadiazole

Extrusion of selenium from cyclohexeno-1,2,3-selenadiazole (SDZ) was successfully utilized for the synthesis of CuInSe2 nanoparticles. Changes in various reaction parameters such as reaction temperature, concentration of oleic acid (OLA) and various other capping agents showed changes in the physical characteristics of the CISe nanoparticles. The reactions performed at various temperatures resulted in alteration in physical appearance, shape and size of the CISe nanoparticles which was confirmed by XRD, Williamson Hall analysis, particle size analyzer, SEM and TEM analysis. The variation in the amount of OLA only affected the particle size. Optical studies of as-synthesized CISe NPs revealed band gap ranging between 1.1–1.7 eV. HRTEM analysis confirmed the presence of CISe with a variety of shapes and lattice spacings of 0.33 nm corresponding to the (112) crystal plane.

CdSe–PVP QDs for Degradation of Methylene Blue via Photocatalytic Oxidative Cleavage Under Mild Visible Light

Present article describes, synthesis of polyvinyl pyrrolidone (PVP) capped CdSe quantum dots (QDs) at pH 5, 7 and 9 under controlled atmosphere. Spherical CdSe QDs in the size domain of 2 nm to 10 nm revealed cubic crystal structure from XRD analysis. The CdSe QDs synthesized at pH 7 showed highest specific surface area as compared to those synthesized at pH 5 and 9. The photocatalytic activity of CdSe QDs was investigated against methylene blue (MB) in aqueous solution of different concentrations (5, 10 and 20 ppm) under irradiation of mild visible light (8 W lamp). Maximum of 64% degradation was obtained for 5 ppm MB solution catalyzed by CdSe QDs synthesized at pH 7.

Green Synthesis of Silver Nano-Particles by Use of Edible Oils

Avoiding use of environmentally hazardous reducing agents and surfactants like sodium borohydride, hydrazine hydrate, alkyl amines and alkyl phosphines, the current article describes successful synthesis of silver nanoparticles via green synthesis by employing coconut, Indian gooseberry (amla), almond and mustard oils as capping as well as reducing agents. The presence of various fatty acids in such edible oils act as capping agents through their carboxylic acid functionality and control the growth of nanoparticles. A single step, simple synthetic method yielded silver nanoparticles which were characterized by UV-Visible, fluorescence spectroscopy, XRD, TEM and particle size analysis. As-prepared particles showed surface plasmon resonance (SPR) between 410 nm to 430 nm with narrow peak width indicating formation of homogeneous sized particles. XRD revealed formation of face cantered cubic crystal structure of silver. TEM analysis of the samples showed spherical morphology with particle size typically between 10-20 nm.

Titanium Dioxide (TiO2) Decorated Silver Indium Diselenide (AgInSe2): Novel Nano-Photocatalyst for Oxidative Dye Degradation

Novel visible-NIR photocatalysts prepared via the hybridization of wide and small bandgap semiconductors involving silver indium diselenide (AgInSe2) and titanium dioxide by thermal and microwave methods are presented. The process revealed the formation of new hybrid nanostructured materials with remarkably different properties than the parent semiconductors. New catalysts were characterized by various advanced analytical tools such as UV-visible diffuse reflectance, Raman spectroscopy, XRD, SEM, EDS, TEM, XPS, and BET. Changes in the optical properties in comparison to the parent compounds, namely, AgInSe2 and TiO2, resulted in a broad absorption band covering the entire UV-visible region, which confirmed successful coupling. The XRD pattern revealed the presence of diffraction peaks from both the parent semiconductors. TEM showed spherical morphology with the presence of small TiO2 NPs on the surface of AgInSe2 NPs. In situ-formed silver selenide can also generate useful AgInSe2 in the hybridized form, which showed rather excellent photocatalytic performance. The so-prepared hybrid nanostructured materials were tested for photocatalytic activity against three organic dyes, namely, methylene blue (MB), methyl orange (MO), and rhodamine B (RhB). The photocatalytic degradation efficiency was 89% for AgInSe2/Ag2Se against MB, which was better than the parent semiconductors. AgInSe2/TiO2 showed almost no loss in the degradation efficiency even after reuse for five times, confirming its stability and effectiveness.