Au Nanorods on Carbon-Based Nanomaterials as Nanohybrid Substrates for High-Efficiency Dynamic Surface-Enhanced Raman Scattering

Abstract

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.

Surface Functionalization of Graphene Oxide with Polystyrene Sulfonic Acid Brushes to Fabricate Hierarchical Ag and Au Microstructures as SERS Substrates

“…The other two obvious peaks at 1362 and 1509 cm −1 are associated with aromatic stretching vibrations of the xanthene moiety [29] . These characteristic peaks are nicely consistent with those reported in literatures [28,29,40,41] …”

“…In this work, R6G as a detection molecule [28,29] is used to investigate the SERS performances of the GO‐g‐PSSA/Ag(Au) films. It is known that the sharp tips, corners, edges and nanogaps of noble‐metal particles can act as “hot spots”, dramatically enhancing Raman signals [30–39] .…”

“…[29] These characteristic peaks are nicely consistent with those reported in literatures. [28,29,40,41] In order to evaluate the limit of detection (LOD) of the GOg-PSSA/Ag SERS substrate, a series of R6G solutions with different concentration ranged from 1 × 10 À 6 m to 1 × 10 À 12 m are used and corresponding Raman signals are shown in Figure 6A. The Raman intensity decreases with decreasing the concentration of R6G from 10 À 6 to 10 À 12 m, and it can clearly identify the main characteristic peaks until the concentration of 10 À 12 m, implying the LOD of R6G on GO-g-PSSA/Ag film is as low as 10 À 11 m. Some of the recently reported Ag-based SERS substrates have same or much higher LOD values compared to our work.…”

“…In Figure 5(e), the diffraction peaks of (111), ( 200), (220), and (311) indicate that highly crystalline, pure Au NPs have been successfully achieved on the surface of the GO-g-PSSA film. [27] In this work, R6G as a detection molecule [28,29] is used to investigate the SERS performances of the GO-g-PSSA/Ag(Au) films. It is known that the sharp tips, corners, edges and nanogaps of noble-metal particles can act as "hot spots", dramatically enhancing Raman signals.…”

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

“…Recently, we have developed various metal nanoparticle/2D material nanohybrids as SERS substrates. − These SERS substrates exhibit significant sensitivity for the detection of single molecules and biomolecules. Additionally, the addition of two-dimensional materials can protect metal nanoparticles from oxidation and shield molecules from photoinduced damage .…”