title: Ultrasensitive Detection of Volatile Organic Compounds by a Pore Tuning Approach Using Anisotropically Shaped SnO2Nanocrystals.
abstract: Gas sensing with oxide nanostructures is increasingly important to detect gaseous compounds for safety monitoring, process controls, and medical diagnostics. For such applications, sensor sensitivity is one major criterion. In this study, to sensitively detect volatile organic compounds (VOCs) at very low concentrations, we fabricated porous films using SnO2nanocubes (13 nm) and nanorods with different rod lengths (50-500 nm) that were synthesized by a hydrothermal method. The sensor response to H2increased with decreasing crystal size; the film made of the smallest nanocubes showed the best sensitivity, which suggested that the H2sensing is controlled by crystal size. In contrast, the responses to ethanol and acetone increased with increasing crystal size and resultant pore size; the highest sensitivity was observed for a porous film using the longest nanorods. Using the Knudsen diffusion-surface reaction equation, the gas sensor responses to ethanol and acetone were simulated and compared with experimental data. The simulation results proved that the detection of ethanol and acetone was controlled by pore size. Finally, we achieved ultrahigh sensitivity to ethanol; the sensor response (S) exceeded S = 100 000, which corresponds to an electrical resistance change of 5 orders of magnitude in response to 100 ppm of ethanol at 250 °C. The present approach based on pore size control provides a basis for designing highly sensitive films to meet the criterion for practical sensors that can detect a wide variety of VOCs at ppb concentrations.
authors.affiliation: Division of Materials Science, Faculty of Advanced Science and Technology, Kumamoto University , Kumamoto 860-8555, Japan.
authors.forename: Tetsuya
authors.identifier: http://orcid.org/0000-0001-9357-9557
authors.initials: T
authors.lastname: Kida
authors.affiliation: Chemical and Textile Research Institute , Fukuoka Industrial Technology Center, Fukuoka 818-8540, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Suematsu
authors.affiliation: Institute of Multidisciplinary Research for Advanced Materials, Tohoku University , Sendai, Miyagi 980-8577, Japan.
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Hara
authors.affiliation: Institute of Multidisciplinary Research for Advanced Materials, Tohoku University , Sendai, Miyagi 980-8577, Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Kanie
authors.affiliation: Institute of Multidisciplinary Research for Advanced Materials, Tohoku University , Sendai, Miyagi 980-8577, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Muramatsu
keywords: Knudsen diffusion; SnO2; gas sensor; nanocubes; nanorods; pore control