Asymmetric Core–Shell Gold Nanoparticles and Controllable Assemblies for SERS Ratiometric Detection of MicroRNA

Abstract

Janus nanogap gold nanoparticles (JAuNNPs) with varying proportions of Au shell coverage of (ca. 100/75/50/25 %) are presented. The internal nanogap between the partial Au shell and core caused asymmetric optical behavior; tunability depends on the degree of Au shell coverage and structural asymmetry. The shell‐to‐shell or core‐to‐core JAuNNDs(50 %) were self‐assembled from amphiphilic JAuNNPs(50 %) by tuning the hydrophilic and hydrophobic polymer brushes on the Au core or shell. The positions of electromagnetic field enhancement of JAuNNDs varied with geometrical configurations because of hybridized plasmonic coupling effects. Furthermore, DNA linkers were utilized to form JAuNND12(50 %). By combining with Raman molecules, ratiometric SERS signals could be generated, enabling JAuNND12(50 %) to image the distribution of miR‐21 in living cells and tumors. Asymmetric JAuNNPs allowed facile conjugation of various linkage molecules to fabricate dimeric nanostructures.

Highly Sensitive Colorimetric/Surface-Enhanced Raman Spectroscopy Immunoassay Relying on a Metallic Core–Shell Au/Au Nanostar with Clenbuterol as a Target Analyte

“…The SERS signal generally relies on the SERS tag, which combines metallic plasmonic nanoparticles and organic Raman reporter molecules . Typically, gold nanoparticles (AuNPs) have received extensive applications in SERS tags due to their unique localized surface plasmon resonance property, which could produce a strong local electromagnetic field and rich hot spots. , However, Raman reporter molecules absorbed on the surface of AuNPs are easily disturbed by environmental interference, resulting in desorption and inaccurate detection signals. − Besides, the SERS enhancement of AuNPs is relatively weak, which is further limited in trace analysis. Therefore, it is still a challenge to develop a signal probe for a SERS-based immunoassay biosensor.…”

Emergence of Responsive Surface‐Enhanced Raman Scattering Probes for Imaging Tumor‐Associated Metabolites

“…As a crucial component of high sensitivity, the permutation and combination of different substrate materials and different geometries of the metal substrate can produce different effects. [23] The substrate materials can be noble metals (gold, [24][25][26][27] silver, [28][29][30] copper, [31][32][33] etc.) and inorganic nanomaterials (graphene, [34][35][36] boron nitride, [37][38][39] semiconductor, [40][41][42] etc.).…”

Symmetry-Reduced Metal Nanostructures Offer New Opportunities in Plasmonics and Catalysis

“…Adding more complexity to NPs through symmetry reduction is an additional method for promising platforms for SERS. For example, a hollow Au shell on spherical Au seeds can be achieved through growing a silver shell on the exposed Au surface of a Au seed partially capped with a silica shell . Following the deposition of Ag, galvanic replacement is used where Au replaces the Ag shell, forming a hollow Au shell .…”

“…For example, a hollow Au shell on spherical Au seeds can be achieved through growing a silver shell on the exposed Au surface of a Au seed partially capped with a silica shell . Following the deposition of Ag, galvanic replacement is used where Au replaces the Ag shell, forming a hollow Au shell . Depending on the amount of surface coated in silica, the symmetry of the final product can be modified, with both concentric (quasi- D ∞ symmetry, Figure C) and 50% coating with the hollow shell (quasi- C ∞ v symmetry, Figure D) .…”

“…, D ∞ versus C ∞ v allows for different ways for electron density to be polarized, yielding different hotspot generations (Figure E,F). The hotspot generation of the symmetry-reduced NPs could then be used for SERS detection of 4-MBN; however, the SERS signal could be further increased through linking the particles core-to-core, generating an intense hotspot in the interparticle gap . These examples illustrate the increased capabilities of symmetry-reduced NPs for SERS; the ability to tune the LSPR maximum through NP symmetry facilitates the wavelength-dependent study of SERS …”