Triangular Silver Nanoplates/Graphene Oxide Nanohybrids on Flexible Substrates for Detection of Bacteria via Surface-Enhanced Raman Spectroscopy
Yanfeng Chen, Wen-Ru Chang, Jui‐Hsin Wang, Chung‐Feng Jeffrey Kuo, Chih‐Chia Cheng, Chih‐Wei Chiu
Abstract
In this study, triangular silver nanoplates (TAgNPs) with various sizes were prepared using a seed-mediated growth method. The TAgNPs/GO and TAgNPs/rGO nanohybrids were synthesized by using graphene oxide (GO) and reduced graphene oxide (rGO), respectively. Furthermore, nanohybrid surface-enhanced Raman scattering (SERS) substrates with high sensitivity have been prepared that can be used for the SERS-based detection of biological targets. Our experimental results show that the SERS signals were enhanced when the TAgNPs have a shorter edge length. Such an enhancement was further promoted by the lightning rod effect at the sharp tips of the TAgNPs. Moreover, GO has good dispersibility in water, and the thickness of GO flakes is ∼5 nm. The TAgNPs/GO nanohybrid exhibits an improved signal enhancement effect when compared to the TAgNPs because of the hot spot excited along the z -axis. In addition, many oxygen-containing moieties on the surface of GO (e.g., hydroxyl, carboxylic, and epoxide moieties) can form hydrogen bonds with Pluronic F-127-coated TAgNPs, which improves the dispersion of the TAgNPs on the surface of GO. The π–π stacking interactions formed between GO and adenine can also improve the stability of the molecular structure, thereby increasing the adsorption of adenine molecules on the substrate. The limit of detection (LOD) and SERS enhancement factor for adenine were determined to be 10 –9 M and 1.09 × 10 8 using TAgNPs/GO (40:1 w/w), respectively. For the detection of bacteria, the SERS technique can effectively reduce the detection time and achieve good detection results, even with low detection limits. The LOD for Staphylococcus aureus is only 10 2 CFU/mL using TAgNPs/GO. This result revealed that TAgNPs/GO has great market potential as a SERS substrate and can be widely used for the detection of bacteria.