Fabrication of polydimethylsiloxane (PDMS)-Based Flexible Surface-Enhanced Raman Scattering (SERS) Substrate for Ultrasensitive Detection.

This article presents a fabrication method for a flexible substrate designed for Surface-Enhanced Raman Scattering (SERS). Silver nanoparticles (AgNPs) were synthesized through a complexation reaction involving silver nitrate (AgNO3) and ammonia, followed by reduction using glucose. The resulting AgNPs exhibited a uniform size distribution ranging from 20 nm to 50 nm. Subsequently, 3-aminopropyl triethoxysilane (APTES) was employed to modify a PDMS substrate that had been surface-treated with oxygen plasma. This process facilitated the self-assembly of AgNPs onto the substrate. A systematic evaluation of the impact of various experimental conditions on substrate performance led to the development of a SERS substrate with excellent performance and an Enhanced Factor (EF). Utilizing this substrate, impressive detection limits of 10-10 M for R6G (Rhodamine 6G) and 10-8 M for Thiram were achieved. The substrate was successfully employed for detecting pesticide residues on apples, yielding highly satisfactory results. The flexible SERS substrate demonstrates great potential for real-world applications, including detection in complex scenarios.

Optical metasurfaces for multiplex high-performance grating-type structural colors.

Optical metasurfaces provide a significant approach for the production of structural colors due to their excellent optical control abilities. Herein, we propose trapezoidal structural metasurfaces for achieving multiplex grating-type structural colors with high comprehensive performance originating from the anomalous reflection dispersion in the visible band. Single trapezoidal metasurfaces with different x-direction periods can tune the angular dispersion regularly from 0.036 rad/nm to 0.224 rad/nm to generate various structural colors, and composite trapezoidal metasurfaces with three kinds of combinations can achieve multiplex sets of structural colors. The brightness can be controlled by adjusting the distance between the trapezoids in a pair accurately. The designed structural colors have higher saturation than traditional pigmentary colors, whose excitation purity can reach 1.00. The gamut is about 158.1% of the Adobe RGB standard. This research has application potential in ultrafine displays, information encryption, optical storage, and anti-counterfeit tagging.