Facile synthesized zinc oxide nanorod film humidity sensor based on variation in optical transmissivity.

Variation in the transmitted light intensity from metal oxide thin films with moisture content provides a great opportunity to use them for humidity sensing. Herein, we have developed a novel and simple humidity sensor based on ZnO nanorod (ZNR) thin films which work as transmission-based sensing elements in an in-house fabricated sensing setup. The ZNR sensing element shows excellent linear sensing performance in the relative humidity (RH) range 10-90% and does not show any hysteresis. A maximum change in optical power of ∼95 µW is observed with the change in RH in the range 10-90%, for the sample with the smallest crystallite size (ZNR1) and highest pore diameter of the ZNR film. Also, a maximum sensitivity of 1.104 µW/% RH is observed for the ZNR1 sample which drops to 0.604 µW/% RH for the highest crystallite size sample (ZNR4). The presence of oxygen vacancies and the micro-porous nature of the film allow the absorption of water vapour on the film which deflects light at different angles that vary with the moisture content. The experimental results suggest that the ZNR film with a smaller crystallite size and larger pore diameter is more sensitive for humidity measurements. Further, an improved sensing performance is perceived in ZNRs because of the larger surface area of the nanorods. The ZNR based sensing elements do not suffer from ageing effects and exhibit high repeatability (88.74%). Further, the humidity sensor has a response time of 62 seconds and recovery time of 100 seconds which can be considered as a fairly quick response.

VO2 nanorods for efficient performance in thermal fluids and sensors.

VO2 (B) nanorods with average width ranging between 50-100 nm are synthesized via a hydrothermal method and the post hydrothermal treatment drying temperature is found to be influential in their overall phase and growth morphology evolution. The nanorods with unusually high optical bandgap for a VO2 material are effective in enhancing the thermal performance of ethylene glycol nanofluids over a wide temperature range as is indicated by the temperature dependent thermal conductivity measurements. Humidity and LPG sensors fabricated using the VO2 (B) nanorods bear testament to their efficient sensing performance, which can be partially attributed to the mesoporous nature of the nanorods.

NiO-based nanostructures with efficient optical and electrochemical properties for high-performance nanofluids.

NiO nanostructures were synthesized via a simple wet chemical solution method with varying calcination temperatures. The synthesized nanostructures were characterized by XRD, TG/DSC, FT-IR and high-resolution electron microscopy techniques. The nanostructures revealed dependence of particle size, stoichiometry, optical band gap and luminescence intensity on calcination temperatures. The materials exhibited efficient electrochemical properties with decent capacitance values. Ethylene-glycol-based nanofluids of these nanoparticles registered excellent thermal conductivity enhancement of 59-69% in the room temperature region and 125% enhancement at higher temperatures (80 ° C), establishing NiO to be a top-draw contender for high-performance heat transfer fluids.