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Stress formation during the recording and bleaching of photopolymer holograms results in distortion of the internal diffractive structure and causes many undesirable effects. This is especially important in the case of holographic solar concentrators and similar holographic optical elements that are supposed to meet stringent specifications. We report a new digital holographic method to measure and study stress formation in photopolymers during hologram recording. A glass substrate, with one of its sides diffusely reflecting, is effectively applied to facilitate the recording of good digital holograms captured using a CMOS camera. A green-sensitive photopolymer is used for the study. Digital holograms recorded in successive time intervals of exposure were overlaid and numerically reconstructed. High-contrast stress fringes were generated, and the preliminary results are presented.

Molybdenum disulfide (MoS2), as a layered transition metal dichalcogenides (TMDCs) has profound applications in electronic devices, sensors, Li-ion batteries, solar cells, water purification, photo catalysis etc. Layered TMDCs are obtained through exfoliation of bulk material. There are various methods for synthesizing layered TMDCs from their respective bulk form. In this paper, we report hydrothermal method as the easiest and environmentally friendly way of preparing stacked MoS2 nanosheets from its bulk form. Here we confirm the structural and morphological properties of these stacked nanosheets by X-ray diffraction and electron microscopy. Energy dispersive X-ray analyzer confirms the elemental composition of the prepared MoS2 nanolayer. Optical properties of the stacked MoS2 were characterized by UV–Vis spectroscopy and photoluminescence spectroscopy (PL). The CIE chromaticity diagram identifies the color of the emission using PL data.

Surface-enhanced Raman spectroscopy (SERS) has emerged as one of the thrust research areas that could find potential applications in bio and chemical sensing. We developed colloidal SERS active substrate with excellent sensitivity and high reproducibility using silver nanocube (AgNC) synthesized via the solvothermal method. Finite-difference time-domain simulation was carried out in detail to visualize dipole generation in the nanocube during localized surface plasmon resonance and to locate the respective hot spots in AgNC responsible for the huge Raman enhancement. The prediction is verified by the SERS analysis of the synthesized nanocubes using Rhodamine 6G molecule. An excellent sensitivity with a detection limit of 10^−17 M and a very high enhancement factor of 1.2×10^8 confirms the “hot spots” in the nanocube. SERS activity is also carried out for crystal violet and for food adulterant Sudan I molecule. Finally, label-free DNA detection is performed to demonstrate the versatility of SERS as a potential biosensor. Published version

Development of cost-effective, highly reproducible non-conventional fabrication techniques for anisotropic metal nanostructures is essential to realizing potential applications of plasmonic devices, photonic devices, and surface enhanced Raman scattering (SERS) phenomenon based sensors. This report highlights the fabrication of nanotriangle arrays via nanoimprinting to overcome difficulties in creating large-area SERS active substrates with uniform, reproducible Raman signals. Electron beam lithography of anisotropic nanostructures, formation of arrays of nanotriangles in silicon and the transfer of triangular shapes to polymethylmethacrylate (PMMA) sheets via nanoimprinting have not been reported elsewhere. The reuse of silicon masters offers potential for production of low cost SERS substrates. The SERS activity and reproducibility of nanotriangles are illustrated and a consistent average enhancement factor of up to ~2.9 × 1011, which is the highest value reported for a patterned SERS substrate, is achieved.