Sunil Verma

Metal–support interaction plays important role in governing the activity and stability of Pt–carbon catalysts for hydrogen energy applications. In this work, a structure–property correlation of Pt catalysts supported on carbon aerogels synthesized via four different routes: water-based (CA-W), freeze-dried (CA-FD), isopropanol-based (CA-IPA), and nitrogen-doped (CA-N) are investigated. All the samples exhibit hierarchical micro–mesoporous structures measured by Gas adsorption technique, with CA-FD having highest surface area of ~1271 m²/g. Chemisorption analysis reveal superior Pt dispersion (>30%) for CA-FD. For atomic-scale insights, Pt coordination and electronic structure of these catalysts are investigated using synchrotron X-ray absorption spectroscopy. XANES spectra of Pt/CA samples display moderately enhanced white-line intensity which indicates a higher density of unoccupied Pt 5d states may be attributed to partial electron transfer from Pt to the carbon matrix. Two coordination regimes are identified by EXAFS analyses. Pt/CA-W and Pt/CA-IPA are dominated by Pt–C coordination, whereas Pt nano-domains are indicated for Pt/CA-FD and Pt/CA-N having mixed Pt–C and Pt–Pt coordination. The balance between metallic character and metal support interaction in Pt/CA-FD and Pt/CA-N makes them promising catalysts for hydrogen energy applications.

Trans-stilbene (TSB) crystals are important for the detection of high energy photons and neutrons through the process of scintillation. To fulfil the requirement of large area scintillator detector elements, TSB/PMMA composites have been developed. These plastic scintillator materials can be prepared in a relatively simpler manner as compared to the single crystals. The detailed optimization of the synthesis parameters has been reported. Using the optimal parameters, the TSB/PMMA composites having different TSB concentrations, up to a maximum of 35 wt% TSB, have been successfully fabricated. The fabricated composites were stable at room temperature, optically homogeneous, and transparent in a wide spectral range. The device relevant properties of the synthesized TSB/PMMA plastic scintillator, important for their deployment in optical imaging applications such as the index of refraction, UV–Vis–NIR transmission and photoluminescence properties have been characterized as a function of TSB concentration in the polymer matrix and the behavior observed has been analyzed. Thin wafers of 0.5 mm thickness having different TSB concentrations were fabricated and used for demonstrating x-ray imaging with a resolution of 100 μm, using x-ray imaging beamline of Indus-2 synchrotron radiation facility. In addition, samples of 5 mm thickness having two different concentrations were used for the detection of neutrons using thermal neutron beamline of Dhruva research reactor facility at BARC, Trombay. The results demonstrate that TSB/PMMA composite is a potential plastic scintillator material for x-ray imaging and neutron scintillation applications.