Surface-analyte interaction as a function of topological polar surface area of analytes in metal (Cd, Al, Ti, Sn) sulfide, nitride and oxide based chemiresistive materials

Abstract

Material surface - analyte interactions play important roles in numerous surface mediated processes including gas sensing. However, effects of topological polar surface area (TPSA) of target analytes on surface interactions during gas sensing have been so far largely disregarded. In this work, based on experimental observations on cross-sensitivity in cadmium sulfide (CdS) nanoparticle based room temperature gas sensor, we found that for reactions with similar Energy Rate of Surface Interaction (ERSI), unexpected quadratic correlation exists between sensing response of CdS and TPSA of analytes. From general understanding and as reported earlier in case of drug absorption through surface of membranes, it is expected that surface interactions would decrease with increasing TPSA of analytes. Our results imply that for certain TPSA range, sensor surface-analyte interactions actually increase with increasing TPSA before it finally starts decreasing. Further experiments on four other diverse material systems like AlN, SnO2, TiO2 (Anatase) and Vanadium-doped SnO2 showed similar trend, revealing generalized picture of TPSA dependence of sensor surface-analyte interactions. A physical explanation behind the parabolic relation has been provided based on electrostatic energy minimization of interacting polar fields. Above finding is anticipated to pave way to achieve improved surface interactions and highly selective sensing performances consecutively.