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This paper reports on the high sensitivity of sub-spherical In 2 O 3 -Pt nanoparticles (NPs) for detecting ppb levels of acetone, a biomarker for diabetes. The In 2 O 3 -Pt NPs, in the form of monodisperse metal-oxide In 2 O 3 NPs with diameters of 6–8 nm, decorated with 2 wt% Pt metal NPs (2–3 nm) on the surface, were synthesized by a novel non-aqueous sol–gel route. NPs samples were investigated by X-ray powder diffraction (XRPD), using the advanced whole powder pattern modeling (WPPM) method, and high-resolution transmission electron microscopy (HR-TEM). The advantage of this preparative process is that it preserves metallic platinum NPs formed during the synthesis. The highly sensitive acetone sensor based on these NPs, showed a lower detection limit as low as 10 ppb or less, which is the lowest detection limit ever reported for any chemoresistive acetone sensors. This exceptional performance is likely due to the key role played by very small Pt metal NPs uniformly distributed in the In 2 O 3 -Pt nanostructure. The developed sensor would be suitable for use as a highly sensitive, practical breath acetone checker for daily diet and diabetes management and diagnosis. [ABSTRACT FROM AUTHOR]

Abstract: The light-enhanced NO2 sensing behavior of mesoporous In2O3 is measured and interpreted by means of a new sensing model. The model aims at explaining (i) the drop in electronic resistance of n-type semiconducting In2O3 under UV light exposure, (ii) the light-enhanced reaction to oxidizing gases, and (iii) the faster reaction and regeneration in mesoporous In2O3 as compared to non-porous material. Contrary to the conventional double Schottky model the dominating factor for the change in resistance is a change of oxygen vacancy donor states (0.18eV below the conduction band) in the bulk phase due to photoreduction, instead of chemisorption. For the faster reaction and regeneration we propose an explanation based on enhanced oxygen diffusion in the In2O3 crystal lattice, specifically dominant in the mesoporous structure. The response of ordered mesoporous In2O3 to NO2 is stronger than in case of unstructured bulk material (with an average grain size of ca. 40nm). The reaction is significantly accelerated by illuminating the samples with UV light. However, the response of the mesoporous material is weaker in the illuminated case. [Copyright &y& Elsevier]

Abstract: Crystalline SnO2/reduced graphene oxide (RGO) nanocomposites were synthesized by a one-pot microwave-assisted non-aqueous sol–gel method, in which partially reduction of the graphene oxide and nanoparticle formation occurs simultaneously. Composite samples with different SnO2 loadings on the RGO were prepared and characterized by TEM, XRD, TGA-DSC and FT-IR. Chemoresistive devices, consisting of a thick layer of the samples synthesized on alumina substrates provided with Pt interdigitated electrodes, were fabricated and their electrical and NO2 sensing characteristics investigated. The results obtained have shown the possibility of a fine tuning of the sensing characteristics of the devices fabricated by simply controlling the amount of metal oxide nanoparticles loaded onto the reduced graphene oxide sheets. This was explained on the basis of the critical role played by the n-SnO2/p-RGO heterojunction formed on the composite materials. [Copyright &y& Elsevier]