Triangular Silver Nanoplates/Graphene Oxide Nanohybrids on Flexible Substrates for Detection of Bacteria via Surface-Enhanced Raman Spectroscopy

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 × 108 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 102 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.

Application of Nanohybrid Substrates with Layer-by-Layer Self-Assembling Properties to High-Sensitivity Surface-Enhanced Raman Scattering Detection

“…SERS performance is dependent on the strength of the electromagnetic field on the surfaces of noble metal particles, as well as chemical interactions between the analyte and SERS substrate. − Although GO is believed to enhance SERS signal intensity through chemical effects, the contribution of chemical effects to signal enhancement is usually only 10–10 3 -fold. − Compared with that provided by the electromagnetic effect, the enhancement factor provided by the 3D hot-junction effects of AuNP/copolymer/GO may be as high as 10 4 –10 7 . However, in the AuNP/copolymer/GO system, the copolymer is used for the prevention and control of aggregation.…”

“…Figure a depicts a comparison of SERS spectra for 10 –5 M R6G obtained with pre- and postannealed AuNP/copolymer/GO, indicating that the postannealed SERS substrate led to an approximately 3-fold increase in signal intensity. The enhancement factor (EF) was calculated using the following formula: − EF = ( I SERS / N SERS ) / ( I ref / N ref ) where I SERS and I ref are the integration of the signals of R6G at 613 cm –1 on glass and substrate, respectively, and N SERS and N ref are the corresponding detected concentrations of R6G. The EF achieved with AuNP/copolymer/GO annealed at 300 °C was 3.5 × 10 6 (Figure b).…”

“…In this study, we report the preparation of large-area, flexible, and high-sensitivity SERS substrates. Organic/inorganic nanohybrids – which demonstrated superior properties and a certain level of sensitivity in SERS detection after being developed in our previous work – served as the bases for SERS substrates. − An amphiphilic triblock copolymer with excellent dispersibility and applicability was also developed in this study. , However, the presence of strong sp 2 -hybridized bonds in the 2D hexagonal honeycomb lattice of GO poses a considerable challenge to the production of stable AuNP/copolymer/GO nanohybrids. We first stabilized the growth of AuNPs and enhanced their dispersibility by using a PIB–ED–PIB copolymer.…”

Enhancing SERS Sensitivity in N‐Graphene Hydrangea by Synergistic Charge‐Transfer and Excitation Light Absorption

“…enhancement generated by the plasmon resonance on the surface of metal nanostructures. [10][11][12][13] CM refers to charge transfer between molecules and the substrate surface. [14][15][16][17] As SERS technology evolved, its applications spanned various domains, including chemical analysis, materials science, biomedicine, environmental monitoring, and food safety.…”

Flexible nanohybrid substrates utilizing gold nanocubes/nano mica platelets with 3D lightning-rod effect for highly efficient bacterial biosensors based on surface-enhanced Raman scattering

“…In our previous work, well-established nanohybrids comprising noble metallic nanoparticles and 2D materials were used as the basis of the SERS substrate and exhibited extremely high sensitivity for detecting single molecules and biomolecules. 40–42 In this study, an improved seed-mediated method was used to prepare AuNCs, and the lightning-rod effect formed by AuNCs was employed to increase the SERS signal intensity for biomolecules. In addition, this study proposes the application of AuNCs in SERS bacterial detection for the first time, confirming the feasibility of AuNCs in bacterial molecular detection.…”