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Surface-enhanced Raman scattering (SERS) is a highly effective analytical technique for ultrasensitive detection of chemical and biological species. Hybrid plasmonic-semiconductor systems are particularly notable for their reproducibility and multifunctionality. Ag/ZnO/AZO heterostructures achieve enhancement factors (EFs) of about 10⁷ and detection limits as low as 10⁻¹² M [1]. Ag-decorated ZnO nanorods show EFs of 2.7 × 10⁸ for Rhodamine 6G [2], while ZnO nanoplate-Ag hybrids enable low-concentration detection of indigo carmine, supported by charge-transfer mechanisms [3].
We conducted a study on the wavelength-dependent surface-enhanced Raman scattering (SERS) of Methyl Orange (MO) using Ag/ZnO/AZO heterostructures. Raman spectra at 488, 514, and 633 nm showed significant enhancement at shorter wavelengths, revealing strong vibrational features (ν(N=N), ν(C–C), δ(C–H)) and additional ZnO E2 and N/Ag modes, indicating plasmon–exciton coupling.
The analytical enhancement factor (AEF) ranged from 10¹² to 10¹⁴, aligned with high-performance Ag/ZnO composites that achieved approximately 10¹¹. This sensitivity enabled reliable detection of MO at very low concentrations. The enhancement is attributed to the combined electromagnetic effects of Ag plasmonic hot spots and chemical charge transfer from ZnO. These findings highlight Ag/ZnO/AZO heterostructures as wavelength-tunable SERS platforms, useful for detecting dyes, biomolecules, and environmental pollutants.
References:
[1] Samriti, Kumar, P., Kuznetsov, A. Y., Swart, H. C., & Prakash, J. (2024). Sensitive, stable, and recyclable ZnO/Ag nanohybrid substrates for surface-enhanced Raman scattering metrology. ACS Materials Au, 4(4), 413-423.
[2] Li, N., Xu, G., Yan, M., Chen, B., Yuan, Y., & Zhu, C. (2023). Fabrication of vertically aligned ZnO nanorods modified with dense silver nanoparticles as effective SERS substrates. Chemosensors, 11(4), 210.
[3] Pham, T. T. H., Lan, N. T., Trang, T. T., Dien, N. D., Vuong, T. X., Nguyen, T. T. T., & Vu, X. H. (2025). Facile synthesis of a ZnO nanoplate/Ag nanoparticle hybrid as a highly sensitive SERS substrate for indigo carmine detection. RSC advances, 15(17), 13095-13110.
[4] Sun, Z., Fang, X., Kang, C., Han, Y., Zha, L., & Zhang, X. (2022). Plasmonic Ag/ZnO nanoscale villi in microstructure fibers for sensitive and reusable surface-enhanced Raman scattering sensing. ACS Applied Nano Materials, 6(1), 714-719.
[5] Behera, R., & Nag, A. (2025). Semiconductor‐Bimetallic Plasmonic Heterojunction ZnO− Ag− Cu as Reusable SERS Substrate with Attomolar Detection Limit. Chemistry–An Asian Journal, 20(9), e202401580.
