Using the Transient Response of WO3 Nanoneedles under Pulsed UV Light in the Detection of NH3 and NO2

Abstract

Here we report on the use of pulsed UV light for activating the gas sensing response of metal oxides. Under pulsed UV light, the resistance of metal oxides presents a ripple due to light-induced transient adsorption and desorption phenomena. This methodology has been applied to tungsten oxide nanoneedle gas sensors operated either at room temperature or under mild heating (50 °C or 100 °C). It has been found that by analyzing the rate of resistance change caused by pulsed UV light, a fast determination of gas concentration is achieved (ten-fold improvement in response time). The technique is useful for detecting both oxidizing (NO2) and reducing (NH3) gases, even in the presence of different levels of ambient humidity. Room temperature operated sensors under pulsed UV light show good response towards ammonia and nitrogen dioxide at low power consumption levels. Increasing their operating temperature to 50 °C or 100 °C has the effect of further increasing sensitivity.

Decoupling the Conflicting Roles of Photoactivation and Boosting Chemiresistor Response by Pulsed UV Light Modulation

“…Figures and demonstrate the universal applicability of the present PULM methodology in boosting the response of semiconductor chemiresistors toward trace vapors at RT. In addition, quantitative discrimination and enhanced response kinetics , have also been demonstrated by PULM, respectively. Therefore, PULM offers us a facile approach to designing high performance RT chemiresistors for emerging indoor/outdoor air quality IoT monitoring.…”

Light Activation of Nanocrystalline Metal Oxides for Gas Sensing: Principles, Achievements, Challenges

“…The widespread use of low-power UV LEDs to activate the sensor sensitivity of semiconductor oxides has led to increased publication activity in this area since the 2010s. To date, numerous studies have been published on the effect of UV radiation on the activation of the sensor sensitivity of semiconductor oxides, such as SnO 2 [ 35 , 36 ], In 2 O 3 [ 37 , 38 , 39 , 40 , 41 , 42 , 43 ], ZnO [ 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ], WO 3 [ 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 ], and TiO 2 [ 60 , 61 , 62 , 63 , 64 ], of various morphologies. Despite the fact that in some cases the obtained materials demonstrated high sensor sensitivity, many authors noted the low selectivity of materials based on individual binary metal oxides.…”

Photoresistive gas sensor based on nanocrystalline ZnO sensitized with colloidal perovskite CsPbBr3 nanocrystals

“…However, the investigation of gas sensitivity under light illumination can be carried out in stationary conditions that do not require establishing electrical conductivity values. Turning periodically the light source on and off at regular intervals t light and t dark , the observed graph σ(t) will show the alternating increase and decay of photoconductivity [66,67]. In this way, the atmosphere effect on the photoconductivity is determined by kinetics of light-induced effects, such as photoadsorption, photodesorption, photocatalytic processes and relaxation of photogenerated carriers.…”