http://dspace.cus.ac.in/jspui/handle/1/6347 Mon, 13 Apr 2026 16:54:50 GMT 2026-04-13T16:54:50Z http://dspace.cus.ac.in/jspui/handle/1/6463 Title: Synthesis of Si/SiO2 nanoparticles using nanosecond laser ablation of silicate-rich garnet in water Authors: Rawat, R.; Tiwari, A.; Vendamani, V.S.; Pathak, A.P.; Rao, S. Venugopal; Tripathi, A. Abstract: During the nanosecond pulsed laser ablation of naturally occurring garnet in water, silicon and silicon dioxide nanoparticles are synthesized. These nanoparticles have an average size of 25 nm and 23 nm when the target is ablated for 20 and 30 min, respectively. The synthesized silicon nanoparticles are crystalline in nature and have cubic structure with 3.0 Å interplanar distance. The effects of laser ablation time on the yield of synthesized nanoparticles in the solution are investigated and it is observed that the optimum ablation time of 20 min is required for the efficient synthesis of silicon nanoparticles while operating at an input pulse energy of 90 mJ. We also report the elemental analysis of the garnet using laser induced breakdown spectroscopy. Mon, 01 Jan 2018 00:00:00 GMT http://dspace.cus.ac.in/jspui/handle/1/6463 2018-01-01T00:00:00Z http://dspace.cus.ac.in/jspui/handle/1/6386 Title: Effect of reaction parameters on morphology and photoluminescence of intrinsic and Mn-doped ZnS microspheres synthesized by hydrothermal method Authors: Chanu, T. Inakhunbi; Samanta, Dhrubajyoti; Tiwari, Archana; Chatterjee, Somenath Abstract: Intrinsic and Manganese (Mn)-doped ZnS microspheres have been synthesized by hydrothermal method. Thiourea and amino acid, and l-histidine have been used as sulfur source and capping agent, respectively. The synthesized materials have been characterized using x-ray diffraction, field emission scanning electron microscopy, photoluminescence (PL) and UV–Vis spectroscopy. The above-said characterizations conveyed the information regarding the crystallinity, existence of microspheres, size and optical properties of synthesized ZnS and Mn-doped ZnS samples. Formation of microspheres of intrinsic and Mn-doped ZnS has been observed when the reaction parameters are kept at 150 °C for 4 h, and similarly, the micropores have been noticed when reaction parameters are kept at 150 °C for 8 h. The PL of ZnS microspheres shows multiple defect emissions. The nature of PL for pure ZnS has been regulated based on reaction parameters. Doping of Mn in the ZnS enhances the PL emission. This study reveals the role of reaction parameters and effect of Mn doping on tuning the morphology and emission behavior of ZnS microspheres. Mon, 01 Jan 2018 00:00:00 GMT http://dspace.cus.ac.in/jspui/handle/1/6386 2018-01-01T00:00:00Z http://dspace.cus.ac.in/jspui/handle/1/6368 Title: Effects of swift heavy ion-irradiation on mica- and coal-based rocks of lower Himalayas in Sikkim, India Authors: Tiwari, Archana; Vadavalli, Saikiran; Tripathi, Ajay; Pathak, Anand P. Abstract: Naturally occurring mica schist and coal sedimentary sequence in Sikkimese Himalaya were collected and investigated by two micro-techniques: scanning electron microscopy/energy dispersive spectrometry and Raman spectroscopy. They were applied to identify the constituents and the structure of the minerals before and after swift heavy ion irradiation. Vibrational data and the constituents of abundantly found mica schist and coal-based rock were acquired at room temperature and were compared with those reported for their analogues in the previous reports. Tue, 01 Jan 2013 00:00:00 GMT http://dspace.cus.ac.in/jspui/handle/1/6368 2013-01-01T00:00:00Z http://dspace.cus.ac.in/jspui/handle/1/6367 Title: Water quality and quantity analysis in Sikkim, North Eastern Himalaya Authors: Tiwari, Archana Abstract: Sikkim is known for its substantial water resources. However, due to rapid growth in population and industry, water scarcity is increasing day by day adding stress on these resources, both quantitatively and qualitatively. A comparative field study performed during January 2011, of available water in Namchi, Gangtok and Singtam areas of Sikkim is presented here. The study illustrates the quality and quantity of water, and their time-dependent variations during the year. Data on pH and coliform were used to assess quality, whereas questionnaire modules were used to find out the abundance of water for domestic use on various scales. The findings regarding water management on the local scale reveal the degree of awareness and the measures taken for water conservation, health and safety. The survey also focuses on the large number of hydel power projects commissioned in the state. Sun, 01 Jan 2012 00:00:00 GMT http://dspace.cus.ac.in/jspui/handle/1/6367 2012-01-01T00:00:00Z