A suitable humidity environment is of great significance to the healthy and comfortable life of urban residents, and the humidification effect of street trees is crucial for effectively regulating microclimates in big cities. Therefore, evaluating the humidification capacity among species is a rewarding research aiming at providing bases for selecting appropriate street tree species. The leaves of trees generate water vapor through transpiration to slowly increase the environmental humidity, and humidity sensors with giant response, excellent linearity, and reliable repeatability are more conducive to analyzing and evaluating the subtle process in detail. Here, the antisolvent method was adopted to simplify the synthesis process of lead-free K2CuBr3, and the fabricated impedance-type humidity sensor based on K2CuBr3 microrods satisfied these requirements. The all-inorganic lead-free halide K2CuBr3 overcomes two drawbacks, including the toxicity of Pb and the moisture instability of most reported halide perovskites used in the field of humidity sensing. The impedance variation exceeds 106 Ω (162 Ω to 182 MΩ), with the relative humidity varying from 12 to 95%. In addition, the analysis of the corresponding complex impedance spectroscopy revealed the sensing mechanism. The intrinsic properties of K2CuBr3 are reflected at low humidity, and the proton transfer gradually dominates the sensing paths with increasing humidity. Furthermore, the K2CuBr3 humidity-sensitive layer is employed to evaluate the transpiration of street trees for the first time, and the successful evaluation of the humidification effect indicates more applications of lead-free halides.
Lead halide perovskites have shown great X-ray scintillation properties. One big challenge is to find nontoxic replacements for practical applications. Moreover, the scintillator should contain less intrinsic radioactivity as possible to suppress the constant background signal. Here, we report K2CuBr3 with ultralow intrinsic radioactivity. The abundance of radioactive isotope 40K is 0.0118%, while Cu and Br do not contain stable radioactive isotopes. Thanks to the one-dimensional crystal structure and strong electron–phonon coupling, K2CuBr3 exhibits strong carrier confinement and high photoluminescence quantum yield (86.98%) for the violet emission (peak, 391 nm). Such a high PLQY value is among the highest for all kinds of violet emitters. For X-ray scintillation applications, we evaluate the light yield to be 23,806 photons per MeV, and the detection limit is 132.8 nGyair s–1.
Halide perovskites have recently emerged as potential humidity-detection materials due to their excellent chemical and physical properties. However, the toxicity of Pb and environmental instability of the lead halide perovskites restrict the application in humidity detection . Herein, a lead-free K 2 CuBr 3 microwires-based quartz crystal microbalance (QCM) humidity sensor was investigated, and the application in human respiratory monitoring was developed. Coupling the high humidity sensitivity of K 2 CuBr 3 with the high mass change sensitivity of QCM, the lead-free K 2 CuBr 3 coated QCM humidity sensor exhibited excellent logarithmic linearity response (R 2 = 0.98626, 11–95% RH). In addition, the sensor demonstrated excellent repeatability, fast response/recover time (10.63 s/4.31 s), and considerable stability. Moreover, the Fourier transform infrared spectra (FTIR) and Langmuir adsorption model were applied to reveal the corresponding humidity sensing mechanism. The results indicate the lead-free K 2 CuBr 3 -based QCM sensor reported in this work could be a promising candidate for real-time breath monitoring.
危险品化学品经营许可证（带存储）