title: In Situ Localized Growth of Ordered Metal Oxide Hollow Sphere Array on Microheater Platform for Sensitive, Ultra-Fast Gas Sensing.
abstract: A simple and versatile strategy is presented for the localized on-chip synthesis of an ordered metal oxide hollow sphere array directly on a low power microheater platform to form a closely integrated miniaturized gas sensor. Selective microheater surface modification through fluorinated monolayer self-assembly and its subsequent microheater-induced thermal decomposition enables the position-controlled deposition of an ordered two-dimensional colloidal sphere array, which serves as a sacrificial template for metal oxide growth via homogeneous chemical precipitation; this strategy ensures control in both the morphology and placement of the sensing material on only the active heated area of the microheater platform, providing a major advantage over other methods of presynthesized nanomaterial integration via suspension coating or printing. A fabricated tin oxide hollow sphere-based sensor shows high sensitivity (6.5 ppb detection limit) and selectivity toward formaldehyde, and extremely fast response (1.8 s) and recovery (5.4 s) times. This flexible and scalable method can be used to fabricate high performance miniaturized gas sensors with a variety of hollow nanostructured metal oxides for a range of applications, including combining multiple metal oxides for superior sensitivity and tunable selectivity.
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California, Berkeley , Berkeley, California 94720, United States.|Berkeley Sensor & Actuator Center, University of California, Berkeley , Berkeley, California 94720, United States.
authors.forename: Ameya
authors.identifier: http://orcid.org/0000-0003-4660-2077
authors.initials: A
authors.lastname: Rao
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California, Berkeley , Berkeley, California 94720, United States.|Berkeley Sensor & Actuator Center, University of California, Berkeley , Berkeley, California 94720, United States.|State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology , Wuhan 430074, China.
authors.forename: Hu
authors.initials: H
authors.lastname: Long
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California, Berkeley , Berkeley, California 94720, United States.|Berkeley Sensor & Actuator Center, University of California, Berkeley , Berkeley, California 94720, United States.
authors.forename: Anna
authors.initials: A
authors.lastname: Harley-Trochimczyk
authors.affiliation: Department of Materials Science and Engineering, University of California, Berkeley , Berkeley, California 94720, United States.|Department of Physics, University of California, Berkeley , Berkeley, California 94720, United States.|Materials Science Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Thang
authors.initials: T
authors.lastname: Pham
authors.affiliation: Department of Physics, University of California, Berkeley , Berkeley, California 94720, United States.|Materials Science Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Alex
authors.initials: A
authors.lastname: Zettl
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California, Berkeley , Berkeley, California 94720, United States.|Berkeley Sensor & Actuator Center, University of California, Berkeley , Berkeley, California 94720, United States.
authors.forename: Carlo
authors.initials: C
authors.lastname: Carraro
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California, Berkeley , Berkeley, California 94720, United States.|Berkeley Sensor & Actuator Center, University of California, Berkeley , Berkeley, California 94720, United States.
authors.forename: Roya
authors.initials: R
authors.lastname: Maboudian
keywords: SnO2; formaldehyde; gas sensor; hollow sphere; metal oxide; microheater; on-chip; tin oxide