Ultrasensitive hybrid SERS substrate for rapid detection of trace chemicals

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We demonstrate here a simple and effective approach for fabricating surface-enhanced Raman spectroscopy substrates by hybridizing Au films with silver particle clusters. A trace amount of aqueous chemical is dropped on the Au film covered substrate, followed by the addition of colloidal Ag nanoparticles (Ag NPs). The combination of Ag clusters and Au film promotes the enhancement ability of the substrate, as confirmed by a finite difference time domain simulation. The electromagnetic field tends to concentrate at the junctions between the Ag NPs and the flat Au film, and yields additional ‘hot spots’. The detect limitation of the hybrid substrate is 10 pM, with an enhancement factor about 1.5 × 107 when rhodamine 6G is employed as the probe molecule. The hybrid substrate showed good homogeneity, with a relative standard deviation about 10.7%. Moreover, the hybrid substrate is utilized for melamine detection with a detection limit of 10 nM (1.2 ppb). The simple procedure, high sensitivity, and good homogeneity make the hybrid substrate a promising tool for trace chemical detection.