An effective CA–Ag SERS-active substrate was designed by first preparing cellulose acetate fiber pads and then coating them with Ag. The unique hydrophobicity of CA–Ag facilitates the enhancement and resolution of the SERS signal of R6G.

Current limitations in surface-enhanced Raman scattering (SERS) substrates fabrication stem from the rigidity of substrate materials, its potential toxicity, and complex costly fabrication processes. Herein, a simple and environmentally friendly cellulose acetate-assisted photoreduction strategy was developed to construct Au nanoparticles loaded-cellulose acetate fibers as flexible SERS substrates. Crucially, cellulose acetate was used both as capping molecule and reducing agent for generating Au nanoparticles without any additional chemicals. Furthermore, the morphology and particle size of Au nanoparticles can be facilely tuned by adjusting the HAuCl ₄ volume, photoreduction time and repeating photoreduction times. A key finding is that the SERS enhancement was controlled by an optimal trade-off between the size and density of Au nanoparticles on the cellulose acetate fibrous network. The optimized SERS-active substrate exhibited excellent sensitivity, good reproducibility and long-term stability to Rhodamine 6G molecules, revealing broad application prospects in SERS-based detection. This work not only provides a green, facile, and tunable method for constructing flexible SERS substrates but also offers new insights into sustainable sensor design.

In biological systems, DNA serves as the primary carrier of genetic information, and the stability of its structure is fundamental to cellular function. Metal ions and temperature are critical environmental factors that modulate DNA conformation and activity. However, the differential morphological effects of alkali, alkaline earth, and transition metal ions, especially when combined with thermal treatment, have not been systematically visualized and quantified. In this work, atomic force microscopy (AFM) was employed to investigate the effects of different metal ions (Na⁺, K⁺, Mg²⁺, Ca²⁺, Cu²⁺) and temperature on DNA structure. The results demonstrated that monovalent ions (Na⁺ and K⁺) neutralized the negative charges on the DNA backbone, thereby reducing intermolecular electrostatic repulsion and promoting DNA aggregation into dendritic structures. Divalent ions (Mg²⁺ and Ca²⁺) not only provided more effective charge screening but also formed ion bridges between DNA strands, leading to more compact and cross-linked networks. In contrast, Cu²⁺ ions directly coordinated with DNA bases, causing local structural distortion and strand scission. Elevated temperatures induced DNA melting, with distinct morphological transitions from extended double strands to condensed single-stranded globules observed at temperatures exceeding the melting point ($T_m$). These findings elucidate the mechanisms by which environmental factors govern DNA morphology, providing insights relevant to nanotechnology and molecular biology applications.

A flexible AuNI-CA SERS substrate was prepared by magnetron-sputtering Au onto electrospun cellulose-acetate fibers, which boosts SERS signals for sensitive detection of phenanthrene- and fluoranthene-type PAHs.