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Portable and wearable gas sensors are required to judge and warn people about the condition of the air they walk into and thus deter accidents caused by gas leakage, saving life and machinery.Synthesis and characterization of CNT / metal oxide nanocomposites with two different compositions, namely SnO2 and ZnO are investigated in this paper. The nanocomposites are coated using a simple drop casting method over a flexible electrode with interdigitated geometry. The fabricated sensors are tested for CO2 gas in a custom-made test set up. It was observed that SnO2 and ZnO are n-type semiconductors in which resistance increased with increasing CO2 concentration. The facile hydrothermal synthesis process, ease of fabrication, and room temperature operability make metal oxide Nano composites with CNT as a good candidate for CO2 gas sensing.

Ultrathin graphene-like two-dimensional (2D) transition-metal dichalcogenides (TMDCs) due to their fundamentally intriguing properties have attracted a wide range of research interest in recent days. Combining different materials to obtain the elite properties of each compound and tuning them according to the prerequisite has been the grounds for the successful fabrication of a number of novel devices. In such a manner, various 2D materials can be brought together to concoct new devices for a broad range of applications. MoS2 and WS2 are two such TMDCs with excellent electronic and optical properties. Since these are atomically thin layered materials and are held by a weak van der Waals force, it is easier to peel them apart to form thin sheets, and hence the combined arrangement of different materials is named as van der Waals heterostructure. Our motive here is to make use of the mechanical exfoliation technique, which has the ability to yield a pure highly crystalline atomically thin layer of TMDCs (MoS2 and WS2). These layers are then stacked one above the other to form van der Waals heterostructure, whose fundamental properties are then studied in detail. The morphological and topographical properties are investigated from the data obtained from several microscopic techniques. Its optical and vibrational properties are scrutinized from various spectroscopic techniques. The data we acquired from optical imaging and Raman scattering, gives an insight into the thickness and edge effects of the flake. The absorption spectrum of MoS2, WS2, and their heterostructure reveal several interesting properties of the electronic band structure. These properties can then be explored and incorporated practically in several fields to fabricate energy storage devices, flexible and transparent electronics, thin electronics, switching devices, photodetectors, etc.