Three-Dimensional Clustered Nanostructures for Microfluidic Surface-Enhanced Raman Detection

A materials fabrication concept based on a fluid construction strategy to create three-dimensional (3D) ZnO@ZnS-Ag active nanostructures at arbitrary position within confined microchannels to form an integrated microfluidic surface enhanced Raman spectroscopy (SERS) system is presented. The fluid-construction process allowed facile construction of the nanostructured substrates, which were shown to possess a substantial number of integrated hot spots that support SERS activity. Finite-difference time-domain (FDTD) analysis suggested that the 3D clustered geometry facilitated hot spot formation. High sensitivity and good recycle performance were demonstrated using 4-mercaptobenzoic acid (4-MBA) and a mixture of Rhodarnine 6G (R6G) and 4-MBA as target organic pollutants to evaluate the SERS microfluidic device performance. The 3D clustered nanostructures were also effective in the detection of a representative nerve agent and biomolecule. The results of this investigation provide a materials and process approach to the fabrication of requisite nanostructures for the online detection of organic pollutants, devices for real-time observation of environmental hazards, and personal-health monitoring.