A flexible hybrid substrate was developed by affixing gold nanoparticles (AuNPs) onto the surface of two-dimensional nanomica platelets (NMPs). The substrate was successfully used in biosensors with high efficiency and high selectivity through surface-enhanced Raman scattering (SERS). By controlling the amphiphilicity of the hybrid substrate, the flexible substrate was made highly selective toward biomolecules. Four different SERS substrate systems were constructed, including intercalated mica, exfoliated NMPs, hydrophilic exfoliated NMPs, and hydrophobic exfoliated NMPs. NMPs were only 1 nm thick. AuNPs adsorbed on both sides of NMPs and thus created excellent threedimensional hot junction effects in the z-axis direction. For the detection of adenine in DNA, a satisfactory Raman enhancement factor (EF) of up to 8.9 × 10 6 was achieved with the detection limit as low as 10 −8 M. Subsequently, the AuNP/NMP hybrids were adopted to rapidly detect hydrophilic Staphylococcus hominis and hydrophobic Escherichia coli. The AuNP/PIB−POE−PIB/NMP nanohybrid was concurrently hydrophilic and hydrophobic. This amphiphilic property greatly enhanced the detection selectivity and signal intensity for hydrophilic or hydrophobic bacteria. Overall, AuNPs/PIB−POE−PIB/NMPs developed as SERS substrates enable rapid, sensitive biodetection.
Gold nanorods (AuNRs) with different aspect ratios were prepared by the seed-mediated growth method and combined with three carbon-based nanomaterials of multiple dimensions (i.e., zero-dimensional (0D) carbon black (CB), onedimensional (1D) carbon nanotubes (CNTs), and two-dimensional (2D) graphene oxide (GO)). The AuNR/carbon-based nanomaterial hybrids were utilized in dynamic surface-enhanced Raman scattering (D-SERS). First, cetyltrimethylammonium bromide (CTAB) was used to stabilize and coat the AuNRs, enabling them to be dispersed in water and conferring a positive charge to the surface. AuNR/carbon-based nanomaterial hybrids were then formed via electrostatic attraction with the negatively charged carbon-based nanomaterials. Subsequently, the AuNR/carbon-based nanomaterial hybrids were utilized as large-area and highly sensitive Raman spectroscopy substrates. The AuNR/GO hybrids afforded the best signal enhancement because the thickness of GO was less than 5 nm, which enabled the AuNRs adsorbed on GO to produce a good three-dimensional hotspot effect. The enhancement factor (EF) of the AuNR/GO hybrids for the dye molecule Rhodamine 6G (R6G) reached 1 × 10 7 , where the limit of detection (LOD) was 10 −8 M. The hybrids were further applied in D-SERS (detecting samples transitioning from the wet state to the dry state). During solvent evaporation, the system spontaneously formed many hotspots, which greatly enhanced the SERS signal. The final experimental results demonstrated that the AuNR/GO hybrids afforded the best D-SERS signal enhancement. The EF value for R6G reached 1.1 × 10 8 after 27 min, with a limit of detection of 10 −9 M at 27 min. Therefore, the AuNR/GO nanohybrids have extremely high sensitivity as molecular sensing elements for SERS and are also very suitable for the rapid detection of single molecules in water quality and environmental management.
Triangular gold nanoplates (TAuNPs) were prepared by a one-step rapid growth method and then reduced and stabilized on two-dimensional nano mica nanoplatelets (NMPs). We also prepared TAuNP/NMP nanohybrids with a...
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.
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