Effect of formaldehyde properties on SnO2 clusters gas sensitivity: A DFT study.

Formaldehyde (CH2O) properties such as flash point and autoignition temperature have a great effect on the temperature range of sensitivity of sensors applied to detect CH2O gas. Tin dioxide nanocrystal interaction with formaldehyde is investigated from room temperature to 500 °C using transition state and density functional theory. Gibbs free energy, enthalpy, and entropy of activation and reaction are evaluated as a function of temperature. The sensitivity and response time of SnO2 clusters towards formaldehyde are evaluated. Results show that the activation energy of SnO2 clusters with formaldehyde increases with the rise of temperature while the reaction energy decreases (in negative value) with the rise of temperature. Response time is inversely proportional to formaldehyde concentration. The highest CH2O gas-sensitive range of SnO2 is confined between the formaldehyde flash point at 64 °C and the autoignition temperature at 430 °C. The effect of partial oxidation and dissociation of formaldehyde is discussed.