Reusable gold-coated black silicon enables sensitive SERS detection of organic molecules

What is it about?

In this study, we propose a fast, low-cost method to fabricate Au-coated black Si-based SERS-active substrates with an enhancement factor of 10^6. A lace-like Si surface with uniformly distributed nanometer-thin gold islands enables high Raman signal enhancement, while the open Si zones allow normalization of the Raman peak intensity, enabling quantitative analysis. The substrates show uniformity with less than 6% signal variation over large areas. When stored under ambient conditions, the SERS signal decreases by less than 3% in 1 month and by less than 40% in 20 months. In addition, the developed substrates can be successfully reused after oxygen plasma purification. After 10 cycles of reuse, the Raman signal of the target molecules was still only 4 times lower than that of the molecules detected with a freshly prepared substrate. A case study showed reproducible detection of 10^(-5) M drug doxorubicin after reuse.

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Photo by Joshua Sortino on Unsplash

Photo by Joshua Sortino on Unsplash

Why is it important?

Gold-coated black silicon substrates enable both qualitative and quantitative monitoring of analytes. Quantitative analysis is often a weak point of SERS measurements due to the enormous signal fluctuations caused by substrate non-uniformity and the limited possibilities of SERS signal normalization, which significantly limit its applicability, e.g. for the determination of analyte concentrations. The proposed gold-coated black silicon structures overcome these obstacles and have been shown to be suitable for doxorubicin concentrations from 10^(-9) to 10^(-4) M.

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