New Insights into the SnO2 Sensing Mechanism Based on the Properties of Shape Controlled Tin Oxide Nanoparticles

Abstract

We report on the sensing behavior of SnO2 shape controlled nanocrystals in order to evaluate the role of their exposed crystal surfaces in the sensing mechanism. Octahedral (OCT), elongated dodecahedral (DOD), and nanobar shaped (NBA) nanocrystals were synthesized by previously reported procedures and their performances were evaluated in the sensing toward CO. Singly ionized oxygen vacancies (VO•) were detected by electron spin resonance (ESR), and their abundance and reactivity were associated to the exposed crystal faces and, in turn, to the sensing responses of the nanocrystals. Results indicated that the electrical properties and the formation/reactivity of the VO• centers are interconnected and are relatable to the nanoparticle specific surfaces. Two different temperature-dependent sensing mechanisms were proposed, depending on the prevalence of the surface structure or of the specific surface area on the sensing ability of shape controlled SnO2 nanoparticles.