In-situ photo-induced synthesis of Ag nanocubes based on nanocellulose film and its SERS application.

Conventional synthetic routes to Ag nanocubes (AgNCs) often leave reagent residues on the particle surface, thereby compromising analyte accessibility and surface-enhanced Raman scattering (SERS) sensitivity. Here, AgNCs were grown in-situ on two-dimensional (2D) nanocellulose films via a photo-induced reduction process, yielding surfactant-free particles with tunable morphology. No additional reducing agents or surfactants were introduced during synthesis, reducing surfactant-derived surface coverage and improving the accessibility of the resulting AgNCs. Notably, the dissolved oxygen in the reaction solution played an important etching role in eliminating the twins during the nucleation process and generating AgNCs with a single crystal structure. The nanocellulose film served both as a photo-reactive substrate, where surface hydroxyl groups acted as reductive sites for the photo-induced conversion of Ag(I) to Ag(0), and as a 2D support that stabilized interfacial nucleation and growth. In addition, the in-situ synthesized AgNCs were uniformly distributed across the nanocellulose film surface, enabling one-step fabrication of flexible SERS substrates under mild conditions. The optimized substrate enabled highly sensitive detection of Rhodamine 6G (R6G), with a limit of detection of 6.24 × 10-12 g L-1, approximately fivefold lower than that of the same substrate after surfactant adsorption. This strategy provides a simple platform for constructing nanocellulose-based SERS substrates for trace detection.