The existing temperature sensors using carbon nanotubes (CNTs) are limited by low sensitivity, complicated processes, or dependence on microscopy to observe the experimental results. Here we report the fabrication and successful testing of an ionization temperature sensor featuring non-self-sustaining discharge. The sharp tips of nanotubes generate high electric fields at relatively low voltages, lowering the work function of electrons emitted by CNTs, and thereby enabling the safe operation of such sensors. Due to the temperature effect on the electron emission of CNTs, the collecting current exhibited an exponential increase with temperature rising from 20 °C to 100 °C. Additionally, a higher temperature coefficient of 0.04 K⁻¹ was obtained at 24 V voltage applied on the extracting electrode, higher than the values of other reported CNT-based temperature sensors. The triple-electrode ionization temperature sensor is easy to fabricate and converts the temperature change directly into an electrical signal. It shows a high temperature coefficient and good application potential.

An aggregation or assembly of Ag triangular nanoplates (Ag TNPs) can cause dramatic changes in their optical properties, which is widely used in applications in the field of sensing. The assembly forms of nanoparticles are crucial for obtaining sensitive sensing signals, but it is unknown what kind of assembly dominates the aggregated Ag TNPs in aqueous solutions. Herein, using thiram-induced Ag TNP aggregation as a model, six different assembly models were established, including three planar (side-by-side, side-to-tip, and tip-to-tip) assemblies and three tridimensional (plane-to-plane, plane-to-tip, and plane-to-side) assemblies. The corresponding optical properties were then investigated. Both theoretical and experimental findings indicate that three-dimensional assemblies, especially plane-to-plane assembly, dominate the Ag TNPs aggregation solution, causing a blue shift of the absorption spectrum. Analysis of charge distribution patterns in Ag TNPs indicates that such a blue shift is caused by the electrostatic repulsive force in plane-to-plane assembly. Thus, we propose a simple colorimetric method for thiram detection using Ag TNPs as an indicator. The method exhibits a selective and sensitive response to thiram with a limit of detection of 0.13 μM in the range of 0.2–0.5 μM, as well as excellent performance in real samples like wheat.

The carbon nanotube (CNT) film based ionized temperature sensor is sensitive to gas temperature, and shows good sensitivity compared with other temperature sensors. But it is still unclear about the effect of CNT film on thermal emission and gas discharge at different temperatures. In this article, we established a gas discharge model of the CNT film temperature sensor. Field assisted thermal emission is simulated at the tip of CNTs by analysing the field enhancement effect and effective work function. Ionization collision, excitation, recombination collision, Penning ionization and quenching of argon are considered in order to obtain the interaction of various particles at different temperature. The current density-temperature characteristic of the temperature sensor was obtained at 24–80 V. The increase of the working voltage is helpful to improve the output current and sensitivity of the temperature sensor. Response time of the sensor will not change in the temperature range of 293–373 K. However, the change of temperature will affect the current density, secondary electron emission and reaction rate. In addition, the sensor has different temperature sensitivity in argon and helium. The above simulation results are helpful to understand the role of CNT film and temperature sensitivity of the ionized sensor. It can also be used to study and improve the sensitivity of this type of sensor.

Ionized gas sensors using nano materials show good sensitivity to gases. Therefore, the nano material structure has a great impact on the performance of sensors. However, the current researches have mainly focused on the influence of nanostructure on field enhancement factors without considering the gas discharge process in space. Therefore, these methods are not suitable for the research of ionized gas sensors. In this paper, a fluid model is established based on the principle of gas discharge. It consists with mass conservation equation, energy conservation equation, and Poisson equation. The influence of electrode separation, screening effects and nanostructure on the cathode current density was analyzed compared with the field enhancement factor. We not only discussed the influence of nanomaterial morphology, but also considered the influence of nanomaterial quantity on gas discharge, which made the research results somewhat different from the previous ones. The experimental results show that the simulation results obtained by the established model can correctly reflect the discharge characteristics of the ionized gas sensor. The methods and results presented in this paper are expected to be applied to the design of device based on gas discharge.