As toxic gas emissions continue to rise, it is ever more important that gas detection improve to sense these gases at or below toxicity levels that many sensors currently are unable to reach. Tin(IV) oxide (SnO2) nanomaterials are exceptional platforms for gas sensing applications. The combination of dual valency (Sn2+ and Sn4+) in SnO2 with high surface area creates diverse surface chemistry advantageous for sensing applications. These properties result in increased adsorbed oxygen, which enhances gas-surface interactions that in turn alters charge transfer through the SnO2 material. Such changes in charge flow are used to determine gas specific sensitivity and selectivity of SnO2. Our initial efforts focus on improving sensitivity by plasma treating SnO2 nanoparticles and in-house chemical vapor deposition (CVD)-grown nanowires. Plasma treatment is a unique surface modification method as it can be tailored for specific applications and exhibits an extensive parameter space. In particular, Ar/O2 and H2O plasmas were chosen to modify SnO2 nanoparticles and nanowires with the intent to create surface oxygen vacancies that ultimately result in increased oxygen adsorption. By compiling surface characterization data from plasma treatments and their corresponding resistances, we can gain a comprehensive view into enhancement of material sensitivity and selectivity toward targeted gases. This portfolio will allow us to fabricate tuned sensors for our desired sensing environment. Resistance data show that, when exposed to air, untreated ZrO2, SnO2 nanoparticles, and SnO2 nanowires all decrease in resistance with increasing temperature from 25 to 300 °C. Notably, the materials exhibit the same resistance at all temperatures ≥100 °C when also decreasing the temperature from 300 to 25 °C. Further, resistance of SnO2 nanoparticles and nanowires are the same as ZrO2, within error, at temperatures ≥100 °C. Upon plasma treatment, the surface chemistry of the nanomaterials changes dramatically, with significant increases in surface oxygen. Thus, these results suggest that upon plasma treatment, the modified SnO2 nanomaterials will exhibit larger changes in resistance upon heating, indicating enhanced sensing capabilities. Additional results from both materials characterization studies as well as sensing data using target analytes such as benzene (≤100 ppm) and CO (≤100 ppm) will be presented.

Resistance measurements for Ar/O2 and H2O plasma modified SnO2 nanomaterials for enhanced gas sensing

249th National Meeting (2015)

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