Flexible fabric gas sensors based on PANI/WO3 p−n heterojunction for high performance NH3 detection at room temperature

A PANI/WO3@cotton thread-based flexible sensor that is capable of detecting NH3 at room temperature is developed here.A layer of WO3 with PANI nanoparticles can be deposited by in-situ polymerization.The morphology and structure of the specimens were investigated by utilizing TEM,SEM,XRD and FTIR.The sensing performance of the PANI/WO3@cotton sensors with different WO3 molar ratios to NH3 at room temperature was examined.The results show that the optimal sensor(10 mol%WO3)has a response of 6.0 to 100 ppm NH3,which is significantly higher than that of the sensors based on pristine PANI and other composites.The PANI/WO3@cotton sensor also displays excellent selectivity,gas response,and flexibility even at room temperature.The unique fiber structure,p-n heterojunction,and the increased protonation of PANI in the composites contribute to the enhanced sensing property.

Highly sensitive colorimetric detection of NH3 based on Au@Ag@AgCl core-shell nanoparticles

Abstract:As an important component of the atmosphere,ammonia(NH_(3))plays a very important role in maintaining the balance of environment.However,it is also one of the most toxic gases that can cause damage to the human respiratory system and mucous membranes even at low concentrations.As such,development of highly sensitive and selective NH_(3)sensors is of high significance for environmental monitoring and health maintenance.Herein,we have synthesized Au@Ag@Ag Cl core-shell nanoparticles(NPs)by oxidative etching and precipitating Au@Ag core-shell NPs using FeCl3 and further used them as optical probes for the colorimetric detection of NH_(3).The sensing mechanism is based on the fact that the etching of NH_(3)on AgCl and Ag shell leads to the variations of ingredients and core-to-shell ratio of the Au@Ag@AgCl NPs,thereby inducing noticeable spectral and color changes.By replacing the outmost layer of Ag with AgCl,not only is the stability of the sensor against oxygen significantly enhanced,but also is the sensitivity of the method improved.The method exhibits good linear relationship for the detection of NH_(3)from 0 to 5000 mmol/L with the limit of detection of 6.4 mmol/L.This method was successfully applied to the detection of simulated air polluted by NH_(3),indicating its practical applicability for environmental monitoring.This method shows great potential for on-site NH_(3)detection particularly in remote area,where a simple,fast,low-cost,and easy-to-handle method is highly desirable.