Carbon quantum dots (CQDs) co-doped with N, P and S derived from expired milk was prepared by a simple hydrothermal method. By dipping pure cotton face towel (PCFT) into CQDs ink, a flexible all-biomass CQDs/PCFT sensor was prepared for the first time. Due to the heteroatom doping, extremely small particle size of CQDs and excellent permeability of CQDs/PCFT film, the flexible CQDs/PCFT sensor showed the high sensitivity and bending stability. In the range of 0–60° bending states, the responses of CQDs/PCFT sensor to four target analytes changed by less 5.0%. After 3000 bending of 60°, the maximum change of the response to the target analytes was only 6.4%. Interestingly, due to the abundant functional groups and defects of CQDs, the flexible CQDs/PCFT sensor displayed sensing curves of different shapes for different target analytes. In this way, by establishing a database of sensing curves of target analytes, multiple analytes can be detected discriminatively by relying only on single sensor with the help of image recognition. This work provided a reference for the development of cotton fiber based all biomass flexible gas sensor.
Based on the Einstein-Maxwell theory, the Joule-Thomson (J-T) expansion of charged dilatonic black holes (the solutions are neither flat nor AdS) in \begin{document}$ (n+1) $\end{document}-dimensional spacetime is studied herein. To this end, we analyze the effects of the dimension n and dilaton field α on J-T expansion. An explicit expression for the J-T coefficient is derived, and consequently, a negative heat capacity is found to lead to a cooling process. In contrast to its effect on the dimension, the inversion curve decreases with charge Q at low pressures, whereas the opposite effect is observed at high pressures. We can observe that with an increase in the dimension n or parameter α, both the pressure cut-off point and the minimum inversion temperature \begin{document}$T_{\rm min}$\end{document} change. Moreover, we analyze the ratio \begin{document}$T_{\rm min}/T_{\rm c}$\end{document} numerically and discover that the ratio is independent of charge; however, it depends on the dilaton field and dimension: for \begin{document}$ n=3 $\end{document} and \begin{document}$ \alpha=0 $\end{document}, the ratio is 1/2. The dilaton field is found to enhance the ratio. In addition, we identify the cooling-heating regions by investigating the inversion and isenthalpic curves, and the behavior of the minimum inversion mass \begin{document}$M_{\rm min}$\end{document} indicates that this cooling-heating transition may not occur under certain special conditions. 相似文献