Preparation and Gas Sensing Properties of In2O3/Au Nanorods for Detection of Volatile Organic Compounds in Exhaled Breath.

Ruiqing Xing,Dali Liu,Qingling Li,Jian Song,Hong Wei Song,Chunyang Zhou,Lin Xu

doi:10.1038/srep10717

Abstract

A series of In2O3/Au nanorods (NRs) were fabricated and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X–ray diffractometer (XRD) and X–ray photoelectron spectroscopy (XPS). The length to diameter ratios of In2O3/Au NRs was periodically modulated in the range of 2.9–4.5 through controlling the initial content of indium salt and reaction time. Their gas sensing properties to volatile organic compounds (VOCs) were carefully studied and then applied in exhaled breath detection. The results demonstrate that In2O3/Au NRs gas sensor can effectively detect acetone at 250 °C and ethanol at 400 °C. The corresponding actual detection limit is as low as 0.1 ppm to acetone and 0.05 ppm to ethanol, respectively. Moreover, by using humidity compensation method, In2O3/Au NRs gas sensor can clearly distinguish the acetone and ethanol biomarkers in human breath. The main reason of the enhanced gas sensing properties was attributed to the “spillover effects” between Au and In2O3 NRs. The excellent sensing performance indicates that In2O3/Au NRs is a promising functional material to actual application in monitoring and detecting diabetes and safe driving area in a noninvasive and more accurate way.

Highlights

A series of In2O3/Au nanorods (NRs) were fabricated and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X–ray diffractometer (XRD) and X–ray photoelectron spectroscopy (XPS)
The nucleation and growth of In(OH)CO3 stemmed from the precipitation of In3+ by OH− and CO32− ions
After addition of Au NRs which was positively charged because of residual CTAB on its surface, the negatively charged OH− and CO32− ions tended to gather around Au NRs, and induced the heterocoagulation process start from the surface of Au NRs and self–assembled to NR structure, that is to say, Au NRs played a role as template in forming the In2O3/Au NRs29

Summary

Introduction

A series of In2O3/Au nanorods (NRs) were fabricated and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X–ray diffractometer (XRD) and X–ray photoelectron spectroscopy (XPS). The length to diameter ratios of In2O3/Au NRs was periodically modulated in the range of 2.9–4.5 through controlling the initial content of indium salt and reaction time Their gas sensing properties to volatile organic compounds (VOCs) were carefully studied and applied in exhaled breath detection. By using humidity compensation method, In2O3/Au NRs gas sensor can clearly distinguish the acetone and ethanol biomarkers in human breath. The performances, including sensitivity, selectivity, and response time, and else, of conventional gas sensors generally could not satisfy the requirements for breath analysis because the gaseous biomarkers in exhaled breath were complex in contents and with low concentrations. In2O3/Au gas sensor can detect acetone lower to 10 ppb at 250 °C, and can detect ethanol lower to 50 ppb at 400 °C This sensor showed good anti–interference to humidity and could effectively detect gaseous acetone and ethanol in simulated exhale breath environment. A humidity compensation method was used to increase the detection accuracy and the clinic test was conducted

Methods

Results

Conclusion