Recently, carbon nanomaterial-supported plasmonic nanocrystals used as high-performance surface-enhanced Raman scattering (SERS) substrates have attracted increasing attention due to their ultra-high sensitivity of detection. However, most of the work focuses on the design of 2-D planar substrates with traditional plasmonic structures, such as nanoparticles, nanorods, nanowires, and so forth. Here, we report a novel strategy for the preparation of high-yield Au nanohydrangeas on three-dimensional porous polydopamine (PDA)/polyvinyl alcohol (PVA)/carbon nanotube (CNT) foams. The structures and growth mechanisms of these specific Au nanocrystals are systematically investigated. PDA plays the role of both a reducing agent as well as an anchoring site for Au nanohydrangeas’ growth. We also show that the ratio of surfactant KBr to the gold precursor (HAuCl4) is key to obtain these structures in a manner of high production. Moreover, the substrate of the CNT foam–Au nanohydrangea hybrid can be employed as SERS sensors and can detect the analytes down to 10–9 M.
Uniform deposition of metal nanoparticles (NPs) on carbon-based substrates is of importance for practical applications as sensors, catalysts, devices, and so forth. Here, we report a one-step wet-chemistry approach that realizes the highly uniform decoration of gold NPs (Au NPs) onto carbon nanotube (CNT) sheets. We first use plasma treatment to make the CNT bundles separated, namely, applying the “debundling” effect onto the film. We also reveal that dimethyl sulfoxide (DMSO) not only promotes the CNT debundling, providing more interstitial space for gold deposition, but also attracts the gold cluster nucleation due to molecule interactions. The reproducibility of surface-enhanced Raman scattering (SERS) signals from this well-engineered CNT/Au NPs substrate is significantly enhanced, as the relative standard deviation from G and D peaks are decreased from 18.8 and 21.3% to 5.6 and 6.2%, respectively. We have fabricated a flexible SERS substrate based on Au NPs/CNT hybrid, which can effectively detect the analyte Rhodamine 6G (R6G) at a concentration as low as 1 × 10–8 M.
Surface-enhanced Raman scattering (SERS) is a powerful technique to detect analytes in a label-free and non-destructive way at extremely low concentrations, even down to the single-molecule level. In the present study, a series of anisotropic Au nanostructures are integrated onto the platforms of carbon nanomaterials, mainly including carbon nanotubes (CNTs) and graphene, in order to fabricate high-performance flexible SERS sensors. Sizes, dimensions, and shapes of Au nanostructures can be well controlled through this strategy, based on which Au nanowires, nanoribbons, nanoplates, nanobelts, and nanoframes are successfully deposited onto CNT films and graphene templates, respectively. Significantly enhanced plasmonic activity originates from these Au nanocrystals, which provide increased SERS signals of the analytes by many orders of magnitude, while CNT films or graphene substrates offer superior flexibility and accessibility. For instance, A flexible SERS sensor made of graphene supported Au nanoframes can detect the analyte R6G at the concentration as low as 10−9 M. The mechanism for the sensitivity enhancement could be attributed to the homogenous distribution of Au nanoframes on the graphene support as well as the strong molecule adsorption to the graphene nanoporous network.
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