Peptide Mesocrystals as Templates to Create an Au Surface with Stronger Surface‐Enhanced Raman Spectroscopic Properties

Abstract

The design and fabrication of various nanostructures with predefined geometry and composition is a big challenge of nanotechnology. Here we demonstrate an Au nanoflake film replicated from a self-assembled, well-ordered, dipeptide flower-like hierarchical architecture. Such morphology can give rise to useful and remarkable surface-enhanced Raman spectroscopy (SERS) properties. We obtained these nanostructures by using a scaffold of flake-built spherical dipeptide aggregations. Gold nanoparticles were sputtered on the surface of as-assembled dipeptide by an etching system. After removing the dipeptide templates by ethanol, a metal crust was left with a morphology similar to that of the dipeptide hierarchical structure. The different steps within the process were monitored by using electron microscopy, energy-dispersive spectrum (EDS) analysis and atomic force microscopy (AFM). Cyclic voltammetry and Raman spectra were employed to prove the SERS effect of the obtained Au substrates. The enhancement factor is estimated to be about 10(4) for 4-mercaptobenzoic acid (4-MBA) molecules on the Au nanoflake surfaces.

Mechanistic study on reduction reaction of nitro compounds catalyzed by gold nanoparticles using in situ SERS monitoring

“…Compared with UV-vis absorption spectroscopy and infrared spectroscopy, fingerprint vibrational information of the adsorbates on the surfaces can be obtained using SERS spectroscopy, as well as the conversion of reactants and the unstable transient reaction intermediates. Another promising advantage of SERS is the enormous enhancement factor up to 10 14 which brings the detection limit down to the level of single molecules [1][2][3][4]. Moreover, the transparency of water regarding the laser light used in Raman spectroscopy makes SERS especially suitable in aqueous environment.…”

Biomimetic and Bioinspired Synthesis of Nanomaterials/Nanostructures

“…For example, self‐assembled peptide frameworks can generate linear, networked Pd materials (Figure A) . A self‐assembled, well‐ordered, flower‐like hierarchical dipeptide architecture can serve as a template for the synthesis of Au nanoflake films with remarkable surface‐enhanced Raman spectroscopy properties (Figure C) . Based upon the Pd/peptide ratio, different Pd morphologies can be prepared, such as nanoparticles, linear nanoribbons, and complex nanoparticle networks (NPNs); enhanced reactivity was observed for the Pd nanoparticles and NPNs over nanoribbons.…”

“…C) Higher‐magnificatopm SEM image of the hierarchical flower‐like morphology of peptide mesocrystals. Reproduced with permission . Copyright 2011, Wiley‐VCH.…”

Ultrathin Hexagonal Hybrid Nanosheets Synthesized by Graphene Oxide‐Assisted Exfoliation of β‐Co(OH)2 Mesocrystals

“…[20] Interestingly, hierarchical 2D nanoplatelets of a definite shape, with thicknesses of several nanometers and widths on the micrometer scale, have been found to exist stably as an integral part of the 3D superstructure (e.g., peony flower-like mesocrystal). [21][22][23] These mesocrystal intermediates are typically formed through nonclassical nanoparticle-mediated crystallization involving a mesoscale transformation in polymer matrix, [24] in which crystallization of the inorganic phase is coupled with organic mesophase transitions to produce exceptional nanosheet building blocks with high crystallinity. [25] Therefore, it is interesting to investigate if such mesocrystals made up of ultrathin nanosheets building blocks could be exfoliated to yield ultrathin single-crystal nanosheets under appropriate conditions, similar to the exfoliation of bulk-layered materials.…”