In this study we report the enhancement of UV photodetection and wavelength tunable light induced NO gas sensing at room temperature using Au-ZnO nanocomposites synthesized by a simple photochemical process. Plasmonic Au-ZnO nanostructures with a size less than the incident wavelength have been found to exhibit a localized surface plasmon resonance (LSPR) that leads to a strong absorption, scattering and local field enhancement. The photoresponse of Au-ZnO nanocomposite can be effectively enhanced by 80 times at 335 nm over control ZnO. We also demonstrated Au-ZnO nanocomposite's application to wavelength tunable gas sensor operating at room temperature. The sensing response of Au-ZnO nancomposite is enhanced both in UV and visible region, as compared to control ZnO. The sensitivity is observed to be higher in the visible region due to the LSPR effect of Au NPs. The selectivity is found to be higher for NO gas over CO and some other volatile organic compounds (VOCs), with a minimum detection limit of 0.1 ppb for Au-ZnO sensor at 335 nm.

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Epidermal electronic systems for detecting electrophysiological signals, sensing, therapy, and drug delivery are at the frontier in man–machine interfacing for healthcare. However, it is still a challenge to develop multifunctional bioapplications with minimal invasiveness, biocompatibility, and stable electrical performance under various mechanical deformations of biological tissues. In this study, a natural silk protein with carbon nanotubes (CNTs) is utilized to realize an epidermal electronic tattoo (E‐tattoo) system for multifunctional applications that address these challenging issues through dispersing highly conductive CNTs onto the biocompatible silk nanofibrous networks with porous nature to construct skin‐adhesive ultrathin electronic patches. Individual components that incorporate electrically and optically active heaters, a temperature sensor (temperature coefficient of resistance of 5.2 × 10−3 °C−1), a stimulator for drug delivery (>500 µm penetration depth in skin), and real‐time electrophysiological signal detectors are described. This strategy of E‐tattoos integrated onto human skin can open a new route to a next‐generation electronic platform for wearable and epidermal bioapplications.

Sonication induced vertical fragmentation of two-dimensional (2D) WS nanosheets into highly luminescent, monodispered, zero-dimensional (0D) quantum dots (QDs) is reported. The formation of 0D structures from 2D sheets and their surface/microstructure characterization are revealed from their microscopic and spectroscopic investigations. Size dependent optical properties of WS nanostructures have been explored by UV-vis absorption and photoluminescence spectroscopy. Interestingly, it is observed that, below a critical dimension (∼2 nm), comparable to the Bohr exciton radius, the tiny nanocrystals exhibit strong emission. Finally, the electroluminescence characteristics are demonstrated for the first time, by forming a heterojunction of stabilizer free WS QDs and ZnO thin films. The signature of white light emission in the light emitting device is attributed to the adequate intermixing of emission characteristics of WS QDs and ZnO. The observation of white electroluminescence may pave the way to fabricate prototype futuristic efficient light emitting devices.

The growing demand for biomaterials for electrical and optical devices is motivated by the need to make building blocks for the next generation of printable bio-electronic devices. In this study, transparent and flexible resistive memory devices with a very high ON/OFF ratio incorporating gold nanoparticles into the Bombyx mori silk protein fibroin biopolymer are demonstrated. The novel electronic memory effect is based on filamentary switching, which leads to the occurrence of bistable states with an ON=OFF ratio larger than six orders of magnitude. The mechanism of this process is attributed to the formation of conductive filaments through silk fibroin and gold nanoparticles in the nanocomposite. The proposed hybrid bio-inorganic devices show promise for use in future flexible and transparent nanoelectronic systems.