http://dspace.cus.ac.in/jspui/handle/1/1455 Mon, 06 Apr 2026 17:14:36 GMT 2026-04-06T17:14:36Z http://dspace.cus.ac.in/jspui/handle/1/6522 Title: Femtosecond laser-induced, nanoparticle-embedded periodic surface structures on crystalline silicon for reproducible and multi-utility SERS platforms Authors: Hamad, Syed; Moram, Sree Satya Bharati; Yendeti, Balaji; Podagatlapalli, G. Krishna; Rao, S. V. S. Nageswara; Pathak, Anand Prakash; Mohiddon, Mahamad Ahamad; Soma, Venugopal Rao Abstract: Fabrication of reproducible and versatile surface-enhanced Raman scattering (SERS) substrates is crucial for real-time applications such as explosive detection for human safety and biological imaging for cancer diagnosis. However, it still remains a challenging task, even after several methodologies were developed by various research groups, primarily due to (a) a lack of consistency in detection of a variety of molecules (b) cost-effectiveness of the SERS substrates prepared, and (c) byzantine preparation procedures, etc. Herein, we establish a procedure for preparing reproducible SERS-active substrates comprised of laser-induced nanoparticle-embedded periodic surface structures (LINEPSS) and metallization of silicon (Si) LINEPSS. LINEPSS were fabricated using the technique of femtosecond laser ablation of Si in acetone. The versatile SERS-active substrates were then achieved by two ways, including the drop casting of silver (Ag)/gold (Au) nanoparticles (NPs) on Si LINEPSS and Ag plating on the Si LINEPSS structures. By controlling the LINEPSS grating periodicity, the effect of plasmonic nanoparticles/plasmonic plating on the Si NPs embedded periodic surface structures enormously improved the SPR strength, resulting in the consistent and superior Raman enhancements. The reproducible SERS signals were achieved by detecting the molecules of Methylene Blue (MB), 2,4-dinitrotoluene (DNT), and 5-amino-3-nitro-l,2,4-triazole (ANTA). The SERS signal strength is determined by the grating periodicity, which, in turn, is determined by the input laser fluence. The SERS-active platform with grating periodicity of 130 ± 10 nm and 150 ± 5 nm exhibited strong Raman enhancements of ∼108 for MB and ∼107 for ANTA molecules, respectively, and these platforms are demonstrated to be capable, even for multiple usages. Mon, 01 Jan 2018 00:00:00 GMT http://dspace.cus.ac.in/jspui/handle/1/6522 2018-01-01T00:00:00Z http://dspace.cus.ac.in/jspui/handle/1/6465 Title: Defect mediated magnetic transitions in Fe and Mn doped MoS2 Authors: Singh, Manish Kumar; Chettri, Prajwal; Tripathi, Ajay; Tiwari, Archana; Mukherjee, Bratindranath; Mandal, R. K. Abstract: We report single-phase syntheses of undoped 2H-MoS2 as well as Mn and Fe doped MoS2 by a facile hydrothermal route. The formation of the 2H-MoS2 phase was confirmed by XRD and was corroborated with Raman spectra. The morphology of the doped and undoped MoS2 nanostructures comprised sheets, as revealed by TEM and STEM images. The fine granular structure was observed by high resolution TEM micrographs. The STEM-EDS results show dopant concentrations of ∼1 atom% corresponding to Mn and Fe in doped MoS2. The undoped MoS2 revealed diamagnetic behavior at room temperature and paramagnetic behavior in the range (100 to 300 K). The Mn-MoS2 sample displayed ferromagnetism below 20 K with a coercive field of ∼50 Oe. Such a sample may be utilized for magnetic switching purposes at low temperatures. The onset of the antiferromagnetic interaction was observed below 145 K in Fe-MoS2 samples. They have been understood in terms of long-range magnetic interactions amongst the dipole moments mediated via surface defects as well as the interaction between the dipoles and the surface charges. The findings are corroborated with the help of EPR studies. Mon, 01 Jan 2018 00:00:00 GMT http://dspace.cus.ac.in/jspui/handle/1/6465 2018-01-01T00:00:00Z http://dspace.cus.ac.in/jspui/handle/1/6464 Title: Temperature and pressure induced Raman studies of C60 oxide Authors: Mondal, Trisha; Tripathi, Ajay; Tiwari, Archana; Zhang, Jinying; Shripathi, Thoudinja; Shinohara, Hisanori Abstract: We present temperature, laser power, and pressure dependent Raman spectral analysis of C60 oxide (C60O) thin films prepared by the photolysis method. The first order temperature, laser power, and pressure coefficients of the Raman frequencies are evaluated and are utilized for evaluating the thermal conductivity of C60O. Its thermal conductivity is found to be 0.7 W m−1 K−1 which is marginally higher than that of bulk C60. Raman frequencies corresponding to C–O and C–C bonds blueshift with a decrease in temperature which is attributed to the thermal contraction of C60O molecules. The density functional measurements have been performed to optimize C60O structure. The contraction in the C–O bond length has been corroborated with the experimental Raman shifts at different temperatures and is used to evaluate the linear expansion coefficient of C60O. Pressure induced compression and polymerization of C60O clusters are also illustrated. This study highlights the interplay between thermal and mechanical transformations in the C60O cluster which may regulate its thermoelectric properties by tuning the intermolecular interactions. Mon, 01 Jan 2018 00:00:00 GMT http://dspace.cus.ac.in/jspui/handle/1/6464 2018-01-01T00:00:00Z 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