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Surface-enhanced Raman scattering (SERS) can provide ultrasensitive detection of chemical and biological analytes down to the level of a single molecule. The need for costly, nanostructured, noble-metal substrates, however, poses a major obstacle in the widespread application of the method. Here we present for the first time a novel type of metallic nanostructured substrates that, not only exhibit a remarkable SERS activity, but are also produced in a facile, cost-effective and nanofabrication-free manner. The substrates are formed through an electric field-guided assembly process of silver nanocolloids, which results in extended and interconnected dendritic nanoparticle structures with a high density of "hot spots". A unique and significant performance attribute of these nanostructures is their ability to also function as concentration amplification devices, thereby further enhancing their analyte detection efficiency. This major advantage against conventional SERS substrates is illustrated experimentally here with the concentration and detection of proteins from solution. Low limits of detection for illicit drugs, food contaminants and pesticides in relevant matrices are also demonstrated. The SERS-active dendrites are reusable and can be removed and replaced in a few minutes. The SERS substrates presented herein constitute a significant advance towards more effective and less expensive diagnostic tools.

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Using a handheld Raman spectrometer, we demonstrate how silver nanodendritic substrates formed using microelectrode platforms and a semi-batch process can be used for ultrasensitive detection and identification of target analytes.

Here, we demonstrated a facile method for growing nanofeatured silver (Ag) structures on a planar microelectrode platform. The nanostructures were assembled along the electrically insulating substrate, growing from the microelectrode edge with the electrodes acting as the template. This was done by (a) limiting the nucleation to the edges of the electrodes and (b) chemically functionalizing the insulating substrate to promote an interaction between itself and the growing metallic structures. These structures were able to reach lateral lengths greater than 100 μm. Additionally, we performed an extended investigation into how the nanostructure morphology can be changed from spherical aggregates to fractal dendrites by altering the electrical signal and solution composition. We determined citrate to be a necessary additive and showed that it acts as a supporting electrolyte, capping agent, and oxidizing/complexing agent. Next, using optimal deposition conditions, we assembled Ag surface-enhanced Raman scattering (SERS) substrates with an enhancement factor up to 4.55 × 10 6 . Finally, we demonstrated how these SERS nanostructures can also serve as concentration amplification devices, accelerating analyte deposition onto the detection site by means of electrohydrodynamics.