Abstract
For surface-enhanced Raman scattering (SERS) sensors, one of the important issues is the development of substrates not only with high SERS-activity but also with strong ability to capture analytes. However, it is difficult to achieve the two goals simultaneously especially when detecting small molecules. Herein a compact battery-controlled nanostructure-assembled SERS system has been demonstrated for capture and detection of trace small molecule pollutants in water. In this SERS fluidic system, an electrical heating constantan wire covered with the vertically aligned ZnO nanotapers decorated with Ag-nanoparticles is inserted into a glass capillary. A mixture of thermo-responsive microgels, Au-nanorods colloids and analyte solution is then filled into the remnant space of the capillary. When the system is heated by switching on the battery, the thermo-responsive microgels shrink, which immobilizes the analyte and drives the Au-nanorod close to each other and close to the Ag-ZnO nanotapers. This process has also created high-density “hot spots” due to multi-type plasmonic couplings in three-dimensional space, amplifying the SERS signal. This integrated device has been successfully used to measure methyl parathion in lake water, showing a great potential in detection of aquatic pollutants.
Highlights
When a compact surface-enhanced Raman scattering (SERS) device is used for real-time detection of trace toxic pollutants in the environment, the key to success of SERS analysis is to construct a substrate that has high SERS activity and strong capability of capturing the analyte[11,12]
To enable the detection of small molecules in the environmental samples, sealed apparatuses have been reported to prevent from volatilization, in which the plasmonic Ag/Au nanoparticles (NPs) and the analytes were blended and confined/enclosed in a microfluidic system[14,15,16]; and the analyte solution was injected into the microfluidic channel decorated with SERS active Ag-covered nanopillar arrays[17]
A radial ZnO-nanotaper (ZnO-NT) array was electrodeposited on an electric heating constantan-wire, the high-density Ag-NPs were decorated onto each ZnO-NT
Summary
When a compact SERS device is used for real-time detection of trace toxic pollutants in the environment, the key to success of SERS analysis is to construct a substrate that has high SERS activity and strong capability of capturing the analyte[11,12]. When the system was heated to a given temperature, the thermo-responsive pNIPAM shells were collapsed, leading to mechanically trapping of the analytes in the proximity to the plasmonic Au-NPs core for the enhanced SERS signal[18].
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