Interfacial engineering of surface-functionalized hydroxyapatite@Ag nanohybrids for sensitive SERS detection

An interfacial engineering strategy was developed to fabricate polymer-functionalized hydroxyapatite@Ag (HA@Ag) nanohybrid substrates using poly(vinyl alcohol) (PVA) and polyethylene glycol-polypropylene glycol-polyethylene glycol (PEPE) as interfacial modifiers for surface-enhanced Raman scattering (SERS). By maintaining identical fabrication conditions, the effects of the two polymers on the morphology and SERS performance of HA@Ag substrates were systematically compared. Physicochemical characterization demonstrated that polymer functionalization altered the surface morphology and Ag nanoparticle distribution of the HA framework. PVA produced a more homogeneous surface with improved nanoparticle dispersion, whereas PEPE generated a rougher hierarchical architecture with more densely distributed Ag nanodomains. These structural differences were reflected in the SERS performance using methylene blue as a model probe under 532 nm laser excitation. Compared with pristine HA@Ag, both polymer-functionalized substrates exhibited enhanced Raman responses. HA/PVA@Ag achieved the best analytical reproducibility, with a linear response (R² = 0.93846), spatial reproducibility (RSD = 4.3%), and long-term stability (RSD = 2.7% after 75 days). In contrast, HA/PEPE@Ag exhibited the highest Raman signal intensity and the best linearity (R² = 0.96742), indicating enhanced sensing sensitivity. These results demonstrate that polymer-assisted interfacial modification provides an effective approach for tailoring the surface characteristics and analytical performance of HA-based SERS substrates, offering a promising platform for sensitive and reproducible Raman sensing.