Engineering 3D Multi-Branched Nanostructures for Ultra- Sensing Applications

Abstract

The fabrication of plasmonic nanostructures with sub-10 nm gaps supporting extremely large electric field enhancement (hot-spot) has attained great interest over the past years, especially in ultra-sensing applications. The "hot-spot" concept has been successfully implemented in surface-enhanced Raman spectroscopy (SERS) through the extensive exploitation of localized surface plasmon resonances. However, the detection of analyte molecules at ultra-low concentrations, i.e., down to the single/few molecule level, still remains an open challenge due to the poor localization of analyte molecules onto the hot-spot region. On the other hand, three-dimensional nanostructures with multiple branches have been recently introduced, demonstrating breakthrough performances in hot-spot-mediated ultra-sensitive detection. Multi-branched nanostructures support high hot-spot densities with large electromagnetic (EM) fields at the interparticle separations and sharp edges, and exhibit excellent uniformity and morphological homogeneity, thus allowing for unprecedented reproducibility in the SERS signals. 3D multi-branched nanostructures with various configurations are engineered for high hot-spot density SERS substrates, showing an enhancement factor of 10 11 with a low detection limit of 1 fM. In this view, multi-branched nanostructures assume enormous importance in analyte detection at ultra-low concentrations, where the superior hot-spot density can promote the identification of probe molecules with increased contrast and spatial resolution.

Sensitive and Homogeneous Surface‐Enhanced Raman Scattering Detection Using Heterometallic Interfaces on Metal–Organic Framework‐Derived Structure

“…[ 10,11 ] Moreover, 3D plasmonic structures contain a greater number of hot spots in the probe volume than 2D plasmonic substrates, which is favorable for collecting strong SERS signals. [ 12–15 ] However, common 3D plasmonic structures with porosity encounter difficulties in measuring a uniform SERS signal over a large surface area due to the irregular pore sizes of the templates and uneven generation of electric hotspots around the plasmonic nanostructures. [ 16–18 ] To this end, 3D templates with highly ordered porosity and excellent electric properties would be good candidates for fabricating 3D SERS‐active structures.…”

Star-shaped colloidal PbS nanocrystals: structural evolution and growth mechanism

“…22 Nevertheless, these branched structures possess a high surface area, porosity, mechanical strength and exposed margins, making them favored candidates as active sites in electro-catalysis, 23 sensitizers in solar cells 24 and sensing applications. 25,26 However, only limited procedures have been proposed for the growth of the IV-VI branched nanostructures compared to the lower dimension counterparts (0D, 12,27,28 1D 19,29 and 2D 17,30 ). In 2002, the Cheon group 31 rst introduced a method for obtaining PbS nanostars (NSs) that involved a high injection temperature of 230 C. In 2006, Zhao and Qi 32 advanced the procedure, producing highly uniform PbS NSs at a low temperature of 80 C in an aqueous solvent of mixed cationic/anionic surfactants.…”

Plasmon Hybridization in Compressible Metal–Insulator–Metal Nanocavities: An Optical Approach for Sensing Deep Sub‐Wavelength Deformation

“…[ 53 ] Through the exploitation of plasmon gap‐mode hybridization, it is indeed possible to realize extremely miniaturized optical resonators (i.e., nanocavities with dimensions much smaller than the illuminating wavelength of light—on the order of λ 3 /1000), operating into a deep sub‐wavelength regime, with intimate consequences for the production of highly sensitive nanometrology tools and disposable nanosensors. In particular, the inborn plasmonic essence of the proposed architecture can synergistically combine into a single platform multi‐purpose functionalities such as ultrasensitive spectroscopy, [ 54–56 ] remote temperature readout, [ 57 ] and advanced control of chemical reactions [ 58,59 ] thus envisioning exciting scenarios for the nanoscale decoration/progress of lab‐on‐a‐chip devices and total analysis systems.…”