Colloidal Multiscale Assembly via Photothermally Driven Convective Flow for Sensitive In‐Solution Plasmonic Detections

Abstract

The assembly of metal nanoparticles and targets to be detected in a small light probe volume is essential for achieving sensitive in‐solution surface‐enhanced Raman spectroscopy (SERS). Such assemblies generally require either chemical linkers or templates to overcome the random diffusion of the colloids unless the aqueous sample is dried. Here, a facile method is reported to produce 3D multiscale assemblies of various colloids ranging from molecules and nanoparticles to microparticles for sensitive in‐solution SERS detection without chemical linkers and templates by exploiting photothermally driven convective flow. The simulations suggest that colloids sub 100 nm in diameter can be assembled by photothermally driven convective flow regardless of density; the assembly of larger colloids up to several micrometers by convective flow is significant only if their density is close to that of water. Consistent with the simulation results, the authors confirm that the photothermally driven convective flow is mainly responsible for the observed coassembly of plasmonic gold nanorods with either smaller molecules or larger microparticles. It is further found that the coassembly with the plasmonic nanoantennae leads to dramatic Raman enhancements of molecules, microplastics, and microbes by up to fivefold of magnitude compared to those measured in solution without the coassembly.

Challenges and Recent Analytical Advances in Micro/Nanoplastic Detection

“…In this view, plasmonic photothermal effects of the Raman laser on LSPR metallic nanoparticles have been suggested (Figure 3d). 99 The absorbed light energy on the metallic nanoparticles' LSPR excitation is converted into thermal energy for local heating. The temperature gradient generates convective flow that collects MNPs toward the Raman laser spot site and assembles them together with the SERS nanoparticles.…”

Manipulation of Convection Using Infrared Light Emitted from Human Hands

“…[6,7] Convection most of the time leads to the energy exchange and the mass transfer, and is widely used in many different systems, [8][9][10] including motion systems [11,12] and heat transfer systems. [13,14] Convection can also carry specific nanoparticles or DOI: 10.1002/advs.202307020 targeting molecules for directional transportation, which further broadens the application of convection in bio/chemical sensing systems [15,16] and separation systems. [17] Generally, the formation of the convection is the result of the nonequilibrium state inside the liquid.…”

Aptamer-Modified Porous Anodized Aluminum Substrate for Rapid and Ultrasensitive Detection of Tetracycline via Surface Enhanced Raman Spectroscopy Couple with Electric Field Enrichment

“…To solve these problems, selectively concentrating targets on the detection zone is an effective strategy. Several methods have been explored, such as electrophoresis, thermo-diffusion, convection, and immiscible oil–water interfaces. , However, these approaches require additional devices and cannot be widely used. Electrokinetic preconcentration technology has been used for rapid separation and preconcentration of samples on the electrode surface. ,, Yang et al found that molecules could be loaded on the SERS substrate under electrostatic force guidance .…”

“…To solve these problems, selectively concentrating targets on the detection zone is an effective strategy. Several methods have been explored, such as electrophoresis, 23 thermo-diffusion, 24 convection, 25 and immiscible oil−water interfaces. 26,27 However, these approaches require additional devices and cannot be widely used.…”