Silver-Coated Cobalt Microtubes for Surface-Enhanced Raman Sensing

In this study, magneto-plasmonic Co@Ag microtubes were developed as controllable substrates for surface-enhanced Raman sensing. Cobalt microtubes were synthesized by template-assisted electrochemical deposition in track-etched polyethylene terephthalate membranes with an average pore diameter of 400 ± 20 nm, followed by template removal and electroless deposition of silver on the Co surface. The silver coating was performed using a solution containing AgNO₃, potassium sodium tartrate, and pyridine, resulting in the formation of nanostructured Ag layers on the cobalt microtube framework. The obtained structures’ morphology, elemental distribution, crystal structure, surface composition, and magnetic properties were investigated using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and vibrating sample magnetometry. The results confirmed the formation of hollow Co microtubes uniformly coated with a crystalline metallic Ag layer. Magnetic measurements showed that silver deposition changed the coercivity and squareness ratio of the microtubes while preserving their magnetic responsiveness. The Co core enabled external-field-assisted alignment and local organization of the microtubes on the substrate, whereas the Ag shell provided plasmonic activity and hot-spot formation for Raman signal enhancement. Using rhodamine 6G as a model analyte, the Co@Ag microtubes demonstrated surface-enhanced Raman detection down to 10^-9 M, with enhancement factors on the order of 106. These results highlight the potential of magnetoplasmonic Co@Ag microtubes as efficient and tunable platforms for surface-enhanced Raman spectroscopy applications

Cobalt microtubes; Magneto-plasmonic structures; Rhodamine 6G detection; Surface-enhanced Raman scattering; Track-etched membranes

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