SERS Effect on Spin-Coated Seeding of Tilted Au-ZnO Nanorods for Low-Cost Diagnosis

Abstract

Uniformly parallel Au-coated ZnO nanorods have previously been shown to amplify local Raman signals, providing increased sensitivity to disease markers in the detection of inflammation and cancer. However, practical and cost-effective fabrication methods of substrates for surface-enhanced Raman spectroscopy (SERS) fail to produce highly uniform surfaces. Here, the feasibility of Raman enhancement on less-uniform substrates is assessed. ZnO nanorod structures were fabricated by hydrothermal synthesis, starting from spin-coated seed substrates. Following analysis, the nanostructures were coated with Au to create stochastically variant substrates. The non-uniformity of the fabricated Au-coated ZnO nanorod structures is confirmed morphologically by FE-SEM and structurally by X-ray diffraction, and characterized by the angular distributions of the nanorods. Monte Carlo finite element method simulations matching the measured angular distributions and separations predicted only moderate increases in the overall Raman enhancement with increasing uniformity. Highly variant substrates exhibited approximately 76% of the Raman enhancement of more uniform substrates in simulations and experiments. The findings suggest that, although highly inhomogeneous Au-coated ZnO nanorod substrates may not attain the same Raman enhancement as more uniform substrates, the relaxation of fabrication tolerances may be economically viable.

Emerging SERS biosensors for the analysis of cells and extracellular vesicles

“…The trend is similar to that previously describedthere is a need for strong, reliable and accurate Raman measurement that is achieved through increased EM enhancement. 237,238 Haldavnekar et al developed a label-free SERS approach for the specific detection of biomolecules on the cells by using extremely small ZnO NPs (sub 10 nm). 228 ZnO is a wide band gap material, hence a good candidate for biomolecular sensing applications.…”

AgNPs decorated 3D bionic silicon nanograss arrays pattern with high-density hot-spots for SERS sensing via green galvanic displacement without additives

“…But it should also be emphasized that, even a small amount of organic additives (such as reductants, surfactants, coupling agents, and other functional agents), originating from the synthesis of noble metal/semiconductor (Au-ZnO, 14,15 Ag-Fe 3 O 4 , [16][17][18][19] Pt-TiO 2 , 20,21 et al), still diminish the plasmonic activity of the SERS substrates and causing a loss of probe binding sites. Besides, they may bring extra interferential bands, if the target analytes have similar Raman spectral response with the organic additives.…”