Surface-enhanced Raman scattering (SERS) has been extensively applied for developing biological and environmental sensors to detect biomarkers and pollutants. Through amplification of electromagnetic field induced by photoexcitation of localized surface plasmons, SERS is possible to detect even at a single molecular level. In this regard, a variety of plasmonic structures have been utilized to enhance SERS performances in sensitivity, selectivity, and reproducibility aspects. However, conventional methods for fabricating SERS-active plasmonic structures usually required complex, time-consuming steps, and expensive instruments for conducting lithography and metal deposition. Herein, we present a novel way to detect strong SERS signals from liquid samples via photothermal convection based real-time and pin-point colloidal assembly of plasmonic nanoparticles on any solid surface. Under resonant light illumination, plasmonic nanoparticles and small molecules in liquid are rapidly assembled together at the focused surface area due to photothermal convection of the plasmonic nanoparticles. For rapid and sensitive SERS measurement of small molecules, such assemblies are controlled and optimized by varying the shape of nanoparticles, dispersed media, the wavelength of light, and its power. Using those assemblies, finger-print spectra of small biomolecules such as peptides and nucleic acids dispersed in aqueous solution are quickly detected at low concentrations without labeling and sample drying steps. In addition, intrinsic SERS signals of water-insoluble environmental pollutants (<i>e.g.</i> polychlorinated biphenyl, polycyclic aromatic hydrocarbon) are detectable by using the proposed light-induced rapid colloidal assemblies in acetone. We expect this method can provide a new and practical way to detect biologically and environmentally important molecules easily, quickly and sensitively.

Sensitive SERS detection of small molecules by photothermal convection based real-time and pin-point colloidal assembly

2019 Fall National Meeting

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