Enhanced SERS performance through defect-guided growth of 2D/3D AuAg nanoplates for chemical sensing and cellular imaging applications

Abstract

Background

Surface-enhanced Raman scattering (SERS) is a powerful analytical technique that utilizes localized electromagnetic fields to amplify molecular vibrational signatures. The effectiveness of SERS substrates relies on the presence of “hot spots,” where electromagnetic fields are highly concentrated. However, the fabrication of metal nanotemplates with optimal hot spot structures is often restricted by the continuous shell formation inherent in conventional synthesis methods, which limits the reproducibility and sensitivity of SERS-based analyses. This study addresses the significant challenge of developing a reliable method for creating SERS substrates with a high density of hot spots.

Results

We developed two-dimensional/three-dimensional (2D/3D) AuAg nanoplates by controlling pore formation within silver templates. This method enabled the selective deposition of gold and silver atoms at high-energy defect sites. The resulting 3D AuAg nanoplates displayed distinctive island-like structures with optimized gap spacings in nanogranule assembly, which led to significant shifts in surface plasmon resonance (SPR). The SERS performance of these 3D AuAg nanoplates, characterized by in-plane absorption, was enhanced, achieving a detection limit of 0.008 ppm for 4-nitrothiophenol, with enhancement factors 2 to 4 times greater than those of conventional nanocube and nanosphere structures. Additionally, functionalization with NTP:4-mercaptophenylboronic acid (MPBA) in a 1:3 ratio demonstrated excellent biocompatibility (>80 % cell viability) and effective cancer-targeting imaging capabilities in both SERS and dark-field microscopy. These findings highlight the crucial role of template morphology in enhancing electromagnetic fields, leading to improved SERS sensitivity for chemical and biological sensing.

Significance

This study conclusively demonstrates the importance of template morphology in optimizing SERS performance. It emphasizes the potential of 2D/3D AuAg nanoplates for advanced chemical sensing and biological diagnostics. The developed methodology provides a viable approach for creating highly sensitive and specific SERS probes, thereby advancing the field of analytical chemistry.