Self-assembly of noble metallic spherical aggregates from monodisperse nanoparticles: their synthesis and pronounced SERS and catalytic properties

Abstract

Here, an oil-in-water emulsion method was used to assemble monodisperse noble metallic nanoparticles (NPs) in the oil phase into aggregates in the aqueous phase. The original size of the NPs is an essential factor in determining the final morphology: beyond the critical size, spherical aggregates with the original NPs can be formed; otherwise, complex aggregates with coarsing NPs come into being. The aggregation level of NPs and consequent properties of the as-constructed spherical assemblies can be optimized through tuning the evaporation rate of the organic solvent. The fabricated assemblies can serve as highly sensitive surface-enhanced Raman scattering (SERS) platforms for the detection of chemical or biological molecules, showing significantly high SERS activity toward rhodamine 6G (R6G) dye and 4-aminothiophenol (4-ATP) molecules. In addition, we further demonstrate the use of these highly sensitive SERS-active substrates to identify melamine at 1 Â 10 À7 M to insure food safety and biosecurity. Furthermore, the catalytic reduction of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) in the presence of excess NaBH 4 was also investigated, in which the as-prepared silver assemblies exhibited excellent catalytic activities due to their special 3D architecture and large number of active catalytic sites.

Dual-Functional Grafted Electrospun Polymer Microfiber Scaffold Hosted Palladium Nanoparticles for Catalyzing Redox Reactions

“…The comparison of catalytic activity of Pd, Ag, and Au NPs reported in literature with that obtained in the present work given in Table clearly indicated that the Fiber@Pd had reasonably good initial catalytic activity ( k i ) in the reduction of PNP with borohydride . However, the catalytic activity in the later stage ( k l ) was considerably higher than those listed in Table .…”

Selective Surface Enhanced Raman Scattering for Quantitative Detection of Lung Cancer Biomarkers in Superparticle@MOF Structure

“…Surface plasmon oscillations in gold nanoparticles can greatly enhance Raman scattering upon optical excitation, and aggregated gold nanoparticles can yield even larger enhancements . The nanoscale gaps between adjacent metallic nanostructures are referred to as electromagnetic hotspots, generating intense local electromagnetic fields and highly efficient Raman scattering . The gaps between gold nanoparticles in a GSP were highly consistent to induce high‐intensity electromagnetic fields (Figure S6, Supporting Information) .…”

Facile synthesis of hollow hierarchical Ni@C nanocomposites with well-dispersed high-loading Ni nanoparticles embedded in carbon for reduction of 4-nitrophenol

“…[40][41][42][43][44] The high activity arises from the synergistic effect of carbon matrix and embedded Ni NPs, explained as follows: (1) carbon layers has high adsorption ability towards 4-NP via p-p stacking interactions. This provides a high concentration of 4-NP near to the Ni nanoparticles embedded in carbon matrix, leading to highly efficient contact between them; and (2) the synergistic effect of Ni nanocrystals and well-graphitized carbon matrix, facilitating the uptake of electrons by 4-NP molecules.…”