Exhaled human breath analysis is a very promising field of research work having great potential for diagnosis of diseases in non-invasive way. Breath analysis has attracted huge attention in the field of medical diagnosis and disease monitoring in the last two decades. VOCs/gases (Volatile Organic Compounds) in exhaled breath bear the finger-prints of metabolic and biophysical processes going on in human body. It’s a non-invasive, fast, non-hazardous, cost effective, and point of care process for disease state monitoring and environmental exposure assessment in human beings. Some VOCs/gases in exhaled breath are bio-markers of different diseases and their presence in excess amount is indicative of un-healthiness. Breath analysis has the potential for early detection of diseases. However, it is still underused and commercial device is yet not available owing to multiferrious challenges. This review is intended to provide an overview of major biomarkers (VOCs/gases) present in exhaled breath, importance of their analysis towards disease monitoring, analytical techniques involved, promising materials for breath analysis etc. Finally, related challenges and limitations along with future scope will be touched upon.

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Electrical and optical properties of MoO 3 -TeO 2 amorphous films prepared by vacuum deposition method were investigated. X-ray diffraction patterns show an amorphous structure. The dc conductivity of the films was measured in the temperature range 323-523 K and follows a non-adiabatic small polaron hopping conduction mechanism between Mo 4þ and Mo 5þ , confirmed by X-ray photoelectron spectroscopy measurements. Conductivity of the films increases with increase of MoO 3 content. The Seebeck coefficient indicates the films to be n-type semiconductor. Optical absorption edge analysis gave a band gap energy of 2.7-2.9 eV depending on composition. The Urbach tail analysis gave the width of localized states between 0.23 and 0.25 eV.

Nickel–silica nanocomposites were prepared by the sol-gel route. By subjecting these to an oxidation treatment in the temperature range 723–1023 K, nickel oxide films of estimated thicknesses in the range 0.5–1.5 nm were grown on the nickel nanoparticles. dc electrical resistivity was measured in the temperature range 300–570 K. The data indicate that an amorphous phase in the interfacial region of the oxide-coated nickel nanoparticles determines the electrical conduction. A small polaron hopping conduction is found to be operative. The humidity sensing properties of these nanocomposites were measured at 300 K in the range of relative humidity (RH) from 3% to 87%. Electrical conductance in all specimens showed an increase of about three orders of magnitude as the RH was raised. Specimens subjected to higher oxidation treatment showed a higher conductance for a specific value of RH. This is ascribed to the presence of a larger number of Ni3+ ions in such specimens.