▎ 摘　　要

Surface-enhanced Raman scattering (SERS) and graphene-mediated surface-enhanced Raman scattering (G-SERS) are attractive analytical techniques for the detection of chemical and biological molecules at a single-molecule level registering their chemical fingerprints. Graphene-based surface enhancement (or G-SERS) boosted traditional SERS phenomenon producing signal enhancement from both electromagnetic (EM) and chemical enhancement (CE) mechanisms. Thus, graphene oxide (GO) nanosheets coated with silver (Ag [30 nm]) and gold (Au [40 nm]) nanoparticles smart array platforms, for direct detection and differentiation of DNA bases, namely, adenine (A), cytosine (C), guanine (G), thymine (T), and environmental relevant beta-carotene (beta-C) and malachite green (MG) biomolecules, are developed. The size and interparticle gap were controlled via dispersion and loading on GO surface to achieve optimal enhancement factors. The morphology of these substrates was characterized by scanning electron microscopy and atomic force microscopy. The Raman spectra consisted of discrete bands occurring at (A: 732.8 cm(-1); C: 792 cm(-1); G: 658 cm(-1); T: 796 cm(-1); beta-C: 1416 cm(-1); MG: 1174 cm(-1)) that are characteristic of molecular modes of vibration and serve as chemical fingerprint of three-dimensional structure, intramolecular interaction and steady-state dynamics, of biomolecule ensemble. The GO-decorated nanoparticles are capable of sensitive biomolecular detection over a broad concentration range 100 nM to 100 mu M with limit of detection (LOD) noted at <1 ppm for A, C, G, T, beta-C, and MG. Moreover, the experimental results illustrated five to six orders of magnitude signal enhancement in the following order: GO/Ag30 > GO/Au40 > Ag30 > Au40 > GO. Moreover, ssDNA probe and complementary target C-ssDNA were monitored simultaneously during hybridization on the same substrates assigned confidently to base, local chemical structure, and global conformation of resulting dsDNA. The experimental findings suggest a strong GO-nanoparticle coupling leading to interfacial orbital hybridization (charge transfer) and polarization affected by biomolecule orientation, and it will help in designing ultrasensitive platforms covering range of inorganic nanoparticles and nanostructured surfaces for a wealth of biomedicine and environmental applications.