Controllable Self-Assembly of SERS Hotspots in Liquid Environment

Abstract

Controllable synthesis of novel metal nanoparticles and effective capture of hotspots are of great significance for SERS (surface-enhanced Raman spectroscopy) detection. Therefore, in this paper, a green controllable synthesis method of gold nanoparticle was achieved via epigallocatechin gallate reduction. Different morphologies of gold nanoparticles were synthesized just by changing the solution pH values, and the growth kinetics of AuNPs (gold nanoparticles) were systematically studied. The synthetic AuNPs were put in a droplet to study dynamic variations of self-assembly SERS hotspots from the liquid sol state to the solid dry state. The addition of halogen ions in the droplet can controllably regulate the self-assembly three-dimensional hotspot model of gold nanoparticles in the evaporation process of a droplet, during which the most enhancement effect can be easily captured. The dynamically changing images of nanoparticles in the process were graphically described based on the internal interaction forces of a droplet. Two stronger areas in the changes of SERS intensity were achieved with a high concentration of halogen ions, while only one maximum intensity area was obtained with a low concentration of halogen ions added. This method can effectively avoid complex and unpredictable microenvironments of SERS substrates in the liquid drop, further improving the reproducibility of SERS detection as well as broadening it to biological applications.

Controlling the Shrinkage of 3D Hot Spot Droplets as a Microreactor for Quantitative SERS Detection of Anticancer Drugs in Serum Using a Handheld Raman Spectrometer

“…The SEM images show densely packed spheres in shrunk sol. In comparison with the interfacial assembly of nanoparticles, the shrunk Ag droplet nanostructures can extend SERS hot spots along the z -axis to the 3D space and can also achieve effective laser interaction because of high-density hot spots on all spatial planes. , More importantly, more target molecules can be adsorbed and detected in the 3D space to realize highly sensitive sensing applications.…”

Recent Advances in the Use of Surface-Enhanced Raman Scattering for Illicit Drug Detection

“…For example, the self-assembly of nanoparticles can be achieved through the chemical attachment of nanoparticles to a solid substrate. Zhang et al achieved controlled self-assembly of gold nanoparticles into a 3D hotspot structure by regulating the addition of halogen ions [ 64 ]. Kang et al implemented a bottom-up approach to achieve self-assembly of a close-packed gold octahedral array that exhibited an intense electric field at the edges and sharp corners of the nanostructure [ 65 ].…”

Enhanced Surface Plasmon by Clusters in TiO2-Ag Composite

“…In the view of the classic physics [ 5 , 6 ], the coherent movements of the electrons driven by the electromagnetic field of incident light carry significant energy, which can be delivered to their surroundings by the relaxation process, resulting in the local energy enhancement around the nanostructures [ 7 , 8 ]. When the nanostructures are near to each other, the local electromagnetic fields tend to couple together, which leads to the significant enhancement of the localized energy on the nanometer scale named as hot spots [ 9 , 10 , 11 ]. The energy and the distribution of hot spots depend on many parameters of the nanostructures, such as the materials, the shapes, the chemical compositions, and the separations between the nanostructures, which are also the tunable choices to get the desired hot spots [ 12 , 13 ].…”