A series of In₂O₃/Au nanorods (NRs) were fabricated and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X–ray diffractometer (XRD) and X–ray photoelectron spectroscopy (XPS). The length to diameter ratios of In₂O₃/Au NRs was periodically modulated in the range of 2.9–4.5 through controlling the initial content of indium salt and reaction time. Their gas sensing properties to volatile organic compounds (VOCs) were carefully studied and then applied in exhaled breath detection. The results demonstrate that In₂O₃/Au NRs gas sensor can effectively detect acetone at 250 °C and ethanol at 400 °C. The corresponding actual detection limit is as low as 0.1 ppm to acetone and 0.05 ppm to ethanol, respectively. Moreover, by using humidity compensation method, In₂O₃/Au NRs gas sensor can clearly distinguish the acetone and ethanol biomarkers in human breath. The main reason of the enhanced gas sensing properties was attributed to the “spillover effects” between Au and In₂O₃ NRs. The excellent sensing performance indicates that In₂O₃/Au NRs is a promising functional material to actual application in monitoring and detecting diabetes and safe driving area in a noninvasive and more accurate way.

Sensitive and selective detection of acetone in human exhaled breath plays an important role in the diagnosis of diabetes. However, obtaining a reliable response to ppb levels of acetone and avoiding cross-sensitivity due to the large amount of moisture in exhaled breath are still great challenges. In this work, a type of acetone sensor with ultrahigh sensitivity and moisture resistance is reported. Electrospun In₂O₃ nanowires with a controllable Pt core (Pt@In₂O₃ core-shell nanowires) are designed and prepared as sensitive layers. A mesoporous silica molecular sieve is further integrated as the moisture filter layer. The Pt@In₂O₃ core-shell nanowire-based sensor exhibits a highly improved response compared with a sensor based on pure In₂O₃ nanowires due to the probable increase in surface resistance and the introduction of p–n junctions after rational design of the structure. In addition, a good performance in terms of the fast dynamic process, selectivity and long-term stability is also achieved, and the detection limit can be as low as 10 ppb, which is much lower than the concentration level of 1.8 ppm in the exhaled breath of diabetic patients. The influence of the large amount of moisture is greatly weakened by using the molecular sieve as a moisture filter layer, leading to much improved sensitivity in clinical sample detection among healthy and diabetic patients. Based on the optimized composite structure of the Pt@In₂O₃ core-shell nanowire sensor and moisture filter layer, a simple portable sensing prototype is successfully fabricated. The reported Pt@In₂O₃ core-shell nanowires and the acetone sensing approach open up a new opportunity for a simple, inexpensive, and noninvasive diagnosis of diabetes.

Three-dimensional (3D) porous ZnO–CuO hierarchical nanocomposites (HNCs) nonenzymatic glucose electrodes with different thicknesses were fabricated by coelectrospinning and compared with 3D mixed ZnO/CuO nanowires (NWs) and pure CuO NWs electrodes. The structural characterization revealed that the ZnO–CuO HNCs were composed of the ZnO and CuO mixed NWs trunk (~200 nm), whose outer surface was attached with small CuO nanoparticles (NPs). Moreover, a good synergetic effect between CuO and ZnO was confirmed. The nonenzymatic biosensing properties of as prepared 3D porous electrodes based on fluorine doped tin oxide (FTO) were studied and the results indicated that the sensing properties of 3D porous ZnO–CuO HNCs electrodes were significantly improved and depended strongly on the thickness of the HNCs. At an applied potential of + 0.7 V, the optimum ZnO–CuO HNCs electrode presented a high sensitivity of 3066.4 μAmM−1cm−2, the linear range up to 1.6 mM, and low practical detection limit of 0.21 μM. It also showed outstanding long term stability, good reproducibility, excellent selectivity and accurate measurement in real serum sample. The formation of special hierarchical heterojunction and the well-constructed 3D structure were the main reasons for the enhanced nonenzymatic biosensing behavior.

3DIO macroporous In ₂ O ₃ films with additional via -hole architectures were fabricated and Au NPs were loaded, which were applied for detecting of acetone gas in exhaled breath.