Designing Nanowires with a Hidden Twist*

In this project, Ag@Ni–NiO nanowires were designed as core–shell structures, with a silver core and a nickel oxide shell, to improve their stability and long-term performance. While pure silver nanowires (Ag NWs) provide strong SERS signals, they are highly sensitive to air and moisture, leading to rapid oxidation and noticeable degradation within days to weeks. This surface oxidation reduces their efficiency for Raman enhancement over time. By contrast, the Ag@Ni–NiO core–shell nanowires overcome this limitation: the nickel oxide shell acts as a protective and stabilizing layer that significantly improves the stability of silver nanowires by preventing surface oxidation. As a result, Ag@Ni–NiO nanowires maintain their structural integrity and SERS activity for up to two months in ambient conditions, making them reliable for long-term applications. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analyses confirmed clear morphological differences between Ag NWs and Ag@Ni–NiO NWs. Since SERS is based on Raman spectroscopy—a technique that provides molecular vibrational fingerprints without labels or sample damage—this approach enables the detection of very low concentrations of cancer-related biomarkers with higher sensitivity, durability, and reproducibility.