Research Of The Formaldehyde And The Toluene Gas Sensor

In recent years, with the exaltation of the living level along with thepeople, indoors repair increasingly universal. Formaldehyde and toluene whichreleasing from the decorative material has became the main air pollutionindoors. One study showed that the formaldehyde and toluene have themightiness cancer-causing function. Therefore it is necessary to examine theair pollution indoors.This paper began with the synthesization of SnO₂ and In2O3 materialwhich are the basic material mixed mainly with La₂O₃,ZnO,CuO andWO3.This paper researched formaldehyde and toluene sensor with goodsensitivity, selectivity and stability.SnO₂ and In2O3 material was prepared by sol-gel method. XRD,TEMwas used to character the structure and grain size of the resulting materials.The result indicates that by controlling the PH value is 3 and sintertemperature is 500℃pure SnO₂ nanocrystalline can be prepared, and bycontrolling the PH value is 7 and sinter temperature is 500℃pure In2O3nanocrystalline can be prepared.The formaldehyde sensor is based on the SnO₂ nano-powder. The doping3wt%ZnO and5wt% La₂O₃ of can obviously improve the sensitivity of theelement to the formaldehyde. When heat temperature is about 140℃,formaldehyde concentration is 10×10-6, the sensitivity of the element is 2.With the modification of 4A molecule-sifter layer,the selectivity of theelement is improved. The change of the resistance of the element is found tobe within 10% in the 60 days. And the response and recover time of theelement to 10×10-6 formaldehyde gas is 12s and 120s respectively.The toluene sensor is based on the SnO₂ nano-powder The doping of5wt%CuO and 0.5wt%WO3 can obviously improve the sensitivity and stabilityof the element to the toluene. When heat temperature is about 175℃, tolueneconcentration is 30×10-6, the sensitivity of the element is 3. The change of thesensitivity of the element is found to be within 10% in the 90 days. And theresponse and recover time of the element to 30×10-6 Toluene gas is 8s and15s respectively.The formaldehyde sensor is based on the In2O3 nano-powde The dopingof 5wt%La2O3 can obviously improve the sensitivity of the element to theformaldehyde. When heat temperature is about 145 ℃ , formaldehydeconcentration is 10×10-6, the sensitivity of the element is 4. With themodification of 4A molecule-sifter layer,the selectivity of the element isimproved. The change of the Sensitivity of the element is found to be within10% in the 90 days. And the response and recover time of the element to 10×10-6 formaldehyde gas is 10s and 40s respectively.The formaldehyde sensor is based on the In2O3 nano-powder prepared bySol-gel as the basic material mixed with NASICON.10wt% NASICON whichthe cost of x is 2 can obviously improve the sensitivity and stability of theelement to the formaldehyde.The change of the resistance of the element isfound to be within 5% in the 60 days and found the element mixed withNASICON has much better sensitivity to ethanol.