One-Step Synthesis of Roughened Ag Nanoshells with Internal Standards for Label-Free SERS Detection of Environmental Contaminants

Various plasmonic structures incorporating internal standards (ISs) have been developed as quantitative and reliable nanoprobes for the surface-enhanced Raman spectroscopy (SERS)-based detection of environmental contaminants. However, despite the inherently high SERS activity of roughened silver (Ag)-based nanoparticles, limited research has focused on the integrating ISs to improve detection accuracy. In this study, we propose a simple synthesis method for elongated rod Ag nanoshells (ERNS) that serve as effective SERS substrates. The ERNS structures are designed to embed Raman label molecules as ISs, enabling reliable and quantitative detection. The rough Ag nanoshell surfaces are formed via the naturally slow reduction of silver ions mediated by hexadecylamine. By controlling the surface roughness and the position of the embedded Raman labels, it is demonstrated that ERNS with ISs exhibit superior SERS performance compared to spherical Ag nanoshells. The ERNS nanoprobe enabled the sensitive detection of thiram (1.2 × 10 –7 M), crystal violet (3.8 × 10 –8 M), and malachite green chloride (2.9 × 10 –7 M). Additionally, the introduction of ISs reduces the relative standard deviation of the detection signal to 1.94%, significantly enhancing reproducibility. The applicability of ERNS to real-world samples is demonstrated through the successful detection of contaminants on fruit surfaces. Given the ease of synthesis and high performance, the proposed ERNS-based SERS probes hold strong potential for environmental monitoring in agricultural and wastewater applications.