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Au nanoparticles for SERS: Temperature-controlled nanoparticle morphologies and their Raman enhancing properties.

ABSTRACT: Quasi-fractal gold nanoparticles can be synthesized via a modified and temperature controlled procedure initially used for the synthesis of star-like gold nanoparticles. The surface features of nanoparticles lead to improved enhancement of Raman scattering intensity of analyte molecules due to the increased number of sharp surface features possessing numerous localized surface plasmon resonances (LSPR). The LSPR is affected by the size and shape of surface features as well as inter-nanoparticle interactions, as these affect the oscillation modes of electrons on the nanoparticle surfaces. The effect of the particle morphologies on the localized surface plasmon resonance (LSPR) and on the surface-enhancing capabilities of these nanoparticles is explored by comparing different nanoparticle morphologies and concentrations. We show that in a fixed nanoparticle concentration regime, quasi-fractal gold nanoparticles (gold nanocaltrop) provide the highest level of surface enhancement, whereas spherical nanoparticles provide the largest enhancement in a fixed gold concentration regime. The presence of highly branched features enables these nanoparticles to couple with a laser wavelength, despite having no strong absorption band and hence no single surface plasmon resonance. This cumulative LSPR may allow these nanoparticles to be used in a variety of applications in which laser wavelength flexibility is beneficial, such as in medical imaging applications where fluorescence at short laser wavelengths may be coupled with non-fluorescing long laser wavelengths for molecular sensing.

SUBMITTER: Darienzo RE

PROVIDER: S-EPMC7665167 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Au nanoparticles for SERS: Temperature-controlled nanoparticle morphologies and their Raman enhancing properties.

Darienzo Richard E RE Chen Olivia O Sullivan Maurinne M Mironava Tatsiana T Tannenbaum Rina R

Materials chemistry and physics 20190918

Quasi-fractal gold nanoparticles can be synthesized via a modified and temperature controlled procedure initially used for the synthesis of star-like gold nanoparticles. The surface features of nanoparticles lead to improved enhancement of Raman scattering intensity of analyte molecules due to the increased number of sharp surface features possessing numerous localized surface plasmon resonances (LSPR). The LSPR is affected by the size and shape of surface features as well as inter-nanoparticle ...[more]

PMID: 33191968

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Project description:In this study, we assessed the controlled synthesis and efficacy of surface-enhanced Raman scattering (SERS) on two distinct types of star-like Au@Ag core-shell nanoarrays. These nanoarrays were designed based on gold nanostars (AuNSs), which were synthesized with and without CTAB surfactant (AuNSs-CTAB and AuNSs-FS, respectively). The AuNS-FS nanoparticles were synthesized via a novel modification process, which helped overcome the previous limitations in the free-surfactant preparation of AuNSs by significantly increasing the number of branches, increasing the sharpness of the branches and minimizing the adsorption of the surfactant on the surface of AuNSs. Furthermore, the differences in the size and morphology of these AuNSs in the created nanoarrays were studied. To create the nanoarrays, a three-step method was employed, which involved the controlled synthesis of gold nanostars, covering them with a silver layer (AuNSs-FS@Ag and AuNSs-CTAB@Ag), and finally self-assembling the AuNS@Ag core-shelled nanoparticles via the liquid/liquid self-assembly method. AuNSs-FS@Ag showed higher ability in forming self-assembled nanoarrays than the nanoparticles prepared using CTAB, which can be attributed to the decrease in the repulsion between the nanoparticles at the interface. The nano-substrates developed with AuNSs-FS@Ag possessed numerous "hot spots" on their surface, resulting in a highly effective SERS performance. AuNSs-FS featured a significantly higher number of sharp branches than AuNSs-CTAB, making it the better choice for creating nanoarrays. It is worth mentioning that AuNSs-CTAB did not exhibit the same benefits as AuNSs-FS. The morphology of AuNSs with numerous branches was formed by controlling the seed boiling temperature and adding a specific amount of silver ions. To compare the SERS activity between the as-prepared nano-substrates, i.e., AuNS-CTAB@Ag and AuNS-FS@Ag self-assembled nanoarrays, low concentrations of crystal violet aqueous solution were characterized. The results showed that the developed AuNSs-FS@Ag could detect CV at trace concentrations ranging from 1.0 ng mL-1 to 10 ng mL-1 with a limit of detection (LOD) of 0.45 ng mL-1 and limit of quantification (LOQ) of 1.38 ng mL-1. The nano-substrates remained stable for 42 days with a decrease in the intensity of the characteristic Raman peaks of CV by less than 7.0% after storage. Furthermore, the spiking method could detect trace amounts of CV in natural water from the Dong Nai River with concentrations as low as 1 to 100 ng mL-1, with an LOD of 6.07 ng mL-1 and LOQ of 18.4 ng mL-1. This method also displayed good reproducibility with an RSD value of 5.71%. To better understand the impact of CTAB stabilization of the Au@Ag star-like nanoparticles on their surface-enhanced Raman scattering (SERS) performance, we conducted density functional theory (DFT) calculations. Our research showed that the preparation of AuNSs-FS@Ag via self-assembly is an efficient, simple, and fast process, which can be easily performed in any laboratory. Furthermore, the research and development results presented herein on nanoarrays have potential application in analyzing and determining trace amounts of organic compounds in textile dyeing wastewater.

Dataset Information

Au nanoparticles for SERS: Temperature-controlled nanoparticle morphologies and their Raman enhancing properties.

Publications

Au nanoparticles for SERS: Temperature-controlled nanoparticle morphologies and their Raman enhancing properties.

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