Red emitting Eu:ZnO nanorods for highly sensitive optical ratiometric temperature sensing by following the fluorescence intensity ratio technique.

Hydrothermally synthesized MoS2 NFs have been employed as an efficient photocatalyst for the degradation of MB and CV dyes under sunlight.

Grafting metal nanoparticles (NPs) on flexible platforms is being increasingly attempted to advance their usage in the field of catalysis, sensing, energy storage, etc. However, anchoring NPs on substrates is nontrivial as it involves surface modification of the NPs and/or the substrate, which makes the whole process tedious. Here, we extend the classical “silver-mirror” reaction to unmodified filter paper achieving a controllable deposition of Ag NPs. The Ag NPs/filter paper thus obtained was employed as an enhanced Raman scattering (SERS) substrate achieving detection limits down to picomolar (10–12 M) and nanomolar (10–9 M) concentrations for rhodamine 6G and rhodamine B, with an enhancement factor (EF) of 1.42 × 1010 and 0.659 × 106, respectively. To check its usage for practical applications, the substrate was extended to detect trace amounts of illicit dyes used on common vegetables and contaminants in rain, pond, and tap water with excellent reproducibility. Moreover, the as-prepared Ag–paper can be directly employed for 4-nitrophenol reduction, which can be completely reduced to 4-aminophenol (4-AP) in a single step within seconds. The substrate can be reused several times over without any noticeable change in its catalytic activity. Finally, we studied the chemical transformation of 4-nitrophenol to 4-aminophenol by studying the concomitant spectral response, thereby integrating catalysis and SERS on a single substrate. This method thus provides a facile avenue to low-cost paper-based functional substrates for multimodal applications.

We report the temperature-dependent photoluminescence and Raman spectra of In2O3 octahedrons synthesized by an evaporation-condensation process. The luminescence obtained here is due to the defect-related deep level emission, which shows highly temperature-dependent behavior in 83-573 K range. Both the position as well as the intensity varies with temperature. Similarly, Raman spectroscopy in 83-303 K range shows temperature-dependent variation in peak intensity but no change in the peak position. Interestingly, the variation of intensity for different peaks is consistent with Placzek theory which invokes the possibility of temperature sensing. We demonstrate the reversibility of peak intensity with temperature for consecutive cycles and excellent stability of the octahedrons toward cryogenic temperature sensing. Overall, both the temperature-dependent photoluminescence and Raman spectra can be explored to determine temperature in the cryogenic range at micro/nano length scales. As an example, we evaluate the temperature-dependent Raman spectra of WO3 that undergoes a phase transition around 210 K and temperature-dependent luminescence of Rhodamine 6G (Rh6G) where intensity varies with temperature.

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