Stable and Reusable Lace-like Black Silicon Nanostructures Coated with Nanometer-Thick Gold Films for SERS-Based Sensing

Abstract

We propose a simple, fast, and low-cost method for producing Aucoated black Si-based SERS-active substrates with a proven enhancement factor of 10 6 . Room temperature reactive ion etching of silicon wafer followed by nanometer-thin gold sputtering allows the formation of a highly developed lacetype Si surface covered with homogeneously distributed gold islands. The mosaic structure of deposited gold allows the use of Au-uncovered Si domains for Raman peak intensity normalization. The fabricated SERS substrates have prominent uniformity (with less than 6% SERS signal variations over large areas, 100 × 100 μm 2 ). It has been found that the storage of SERS-active substrates in an ambient environment reduces the SERS signal by less than 3% in 1 month and not more than 40% in 20 months. We showed that Au-coated black Si-based SERS-active substrates can be reused after oxygen plasma cleaning and developed relevant protocols for removing covalently bonded and electrostatically attached molecules. Experiments revealed that the Raman signal of 4-MBA molecules covalently bonded to the Au coating measured after the 10th cycle was just 4 times lower than that observed for the virgin substrate. A case study of the reusability of the black Si-based substrate was conducted for the subsequent detection of 10 −5 M doxorubicin, a widely used anticancer drug, after the reuse cycle. The obtained SERS spectra of doxorubicin were highly reproducible. We demonstrated that the fabricated substrate permits not only qualitative but also quantitative monitoring of analytes and is suitable for the determination of concentrations of doxorubicin in the range of 10 −9 −10 −4 M. Reusable, stable, reliable, durable, low-cost Au-coated black Si-based SERS-active substrates are promising tools for routine laboratory research in different areas of science and healthcare.

SERS-based microdevices for use as in vitro diagnostic biosensors

“…198–230 3D bottom-up self-assembly nanostructures are described owing to facile preparation and cost-effectiveness. 231–251 Combinatory detection is used for synergetic enhancements. 252–266…”

CMOS-Compatible Wafer-Level Double-layer Silicon Nanograss through Reactive Ion Etching for Applications in Optics

“…A micro-nano structure grown on the surface of a silicon wafer emerges as black silicon, enabling absorption of incident light (appears black) . Black silicon is prepared by dry etching, wet etching, or laser irradiation and viable for applications in optics such as sensing, solar cells, ,,, infrared-transmitting windows, optical alignment marks, etc. Different methods are used to develop different surface shapes of black silicon, such as holes, needles, spikes, columns, and grasslike .…”