Gas-solid interfacial charge transfer in volatile organic compound detection by CuCrO2nanoparticles

Simultaneously Engineering Oxygen Defects and Heterojunction into Ho-Doped ZnO Nanoflowers for Enhancing n-Propanol Gas Detection

Lung cancer poses a serious threat to people's lives and health due to its high incidence rate and high mortality rate, making it necessary to effectively conduct early screening. As an important biomarker for lung cancer, the detection of n-propanol gas suffers from a low response value and a high detection limit. In this paper, flower-like Ho-doped ZnO was fabricated by the coprecipitation method for n-propanol detection at subppm concentrations. The gas sensor based on the 3% Ho-doped ZnO showed selectivity to n-propanol gas. Its response value to 100 ppm n-propanol was 341 at 140 °C, and its limit of detection (LOD) was about 25.6 ppb, which is lower than that of n-propanol in the breath of a healthy person (150 ppb). The calculation results show that the adsorption of n-propanol on a Ho-doped ZnO surface releases more energy than isopropanol, ethanol, formaldehyde, acetone, and ammonia. The enhanced gas-sensing properties of the Ho-doped ZnO material can be attributed to the fact that the Ho-doping distorts the crystal lattice of the ZnO, increases the specific surface area, and generates a large amount of oxygen defects. In addition, the doped Ho partially forms a Ho2O3/ZnO heterojunction in the material and improves the gas-sensing properties. The 3% Ho-doped ZnO material is expected to be a promising candidate for the trace detection of n-propanol gas.

Detection of n-Propanol Down to the Sub-ppm Level Using p-Type Delafossite AgCrO2 Nanoparticles

As an important biomarker of lung cancer, n-propanol at the sub-ppm level is still challenging to be detected for a simple and immediate early diagnosis. In this work, a new n-propanol gas sensor with an ultralow detection limit down to 100 ppb is presented using AgCrO₂ nanoparticles synthesized by a simple hydrothermal method. Compared with the congeneric CuCrO₂ and commercial SnO₂, AgCrO₂ exhibits prevailing performances, including a higher selectivity, dynamic response, and logarithmical linearity but lower working temperature. The first-principles calculation and the energy band theoretical analysis are combined to elucidate the sensing mechanism, in which the chemical adsorption of gaseous molecules to silver followed by the dehydrogenation on chromium on the surface of AgCrO₂ is responsible for the outstanding susceptibility toward n-propanol. The proposed metal oxide semiconductor gas sensor capable of sub-ppm n-propanol detection provides a route to design and optimize the sensitive material system for the advanced trace detection of the volatile organic compounds.

Crystalline-to-Amorphous Phase Transformation in CuO Nanowires for Gaseous Ionization and Sensing Application

We report a dramatic reduction of operation voltage of a CuO nanowire-based ionization gas sensor due to the crystalline-to-amorphous phase transformation. The structural change is attributed to the ion bombardment and heating effect during the initial discharge, which brings about the formation of abundant nanocrystallites and surface states favoring gaseous ionization. The gas-sensing properties of the CuO nanowire sensor are confirmed by differentiating various types or concentrations of volatile organic compounds diluted in nitrogen, with a low detection limit at the ppm level. Moreover, a sensing mechanism is proposed on the basis of charge redistribution by electron-gas collision related to the specific ionization energy. The insightful study of the electrode microstructure delivers an exploratory investigation to the effect of gas ionization toward the discharge system, which provides new approaches to develop advanced ionization gas sensors.