Short Silk Nanoribbons Decorated by Au Nanoparticles as Substrates for Sensitive and Uniform Surface-Enhanced Raman Spectroscopy Detection

The optimal design of "hot spot" nanostructures governs the sensitivity and uniformity of surface-enhanced Raman scattering (SERS) substrates. Au–silk nanoribbon (SNR) aggregates have achieved excellent SERS sensitivity with SNR as hot spot reservoirs but are inferior to complicated laser ablation and electrochemical deposition systems. Here, nanostructures of SNR were designed to further enrich the hot spots of Au-SNR substrates via blending of Au nanoparticles (AuNPs) and SNR in aqueous solutions to achieve better sensitivity. The materials were on par with some of the best complex SERS systems previously reported. The length of the SNR templates was shortened from 2000 nm to 100–400 nm through ultrasonic treatment to minimize steric hindrance, facilitating the formation of hot spot structures. More than 4 times the amount of AuNPs adhered on these shortened SNRs, resulting in superior SERS sensitivity of 10–15–10–16 M, up to 100-fold higher than previous Au-SNR substrates. The reproducibility in detection was improved with a relative standard deviation (RSD) of 9.5%, superior to most solution-based systems. Similar to our previous Au-SNR substrates, the optimized Au-SNR assemblies exhibited excellent cytocompatibility, strengthening potential utility in biomedical applications. Ultrafast SERS imaging of cells could be completed within 8 s through these modified probe-laden Au-SNR assemblies. Considering the superior SERS performance and cytocompatibility, along with the simple, controllable, and green aqueous fabrication process, the present Au-SNR SERS substrates offer significant advantages in versatile applications.