Surface-Enhanced Raman Spectroscopy of Organic Molecules and Living Cells with Gold-Plated Black Silicon.

Abstract
Black silicon (bSi) refers to an etched silicon surface comprising arrays of microcones that effectively suppress reflection from UV to near-infrared (NIR) while simultaneously enhancing the scattering and absorption of light. This makes bSi covered with a nm-thin layer of plasmonic metal, i.e., gold, an attractive substrate material for sensing of bio-macromolecules and living cells using surface-enhanced Raman spectroscopy (SERS). The performed Raman measurements accompanied with finite element numerical simulation and density functional theory analysis revealed that at the 785 nm excitation wavelength, the SERS enhancement factor of the bSi/Au substrate is as high as 108 due to a combination of electromagnetic and chemical mechanisms. This finding makes the SERS-active bSi/Au substrate suitable for detecting trace amounts of organic molecules. We demonstrate the outstanding performance of this substrate by highly sensitive and specific detection of a small organic molecule of 4-mercaptobenzoic acid and living C6 rat glioma cell nucleic acids/proteins/lipids. Specifically, the bSi/Au SERS-active substrate offers a unique opportunity to investigate the living cells' malignant transformation using characteristic protein disulfide Raman bands as a marker. Our findings evidence that bSi/Au provides a pathway to the highly sensitive and selective, scalable, and low-cost substrate for lab-on-a-chip SERS biosensors that can be integrated into silicon-based photonics devices.

Citation
Golubewa, L., Karpicz, R., Matulaitiene, I., Selskis, A., Rutkauskas, D., Pushkarchuk, A., … Kuzhir, P. (2020). Surface-Enhanced Raman Spectroscopy of Organic Molecules and Living Cells with Gold-Plated Black Silicon. ACS Applied Materials & Interfaces. doi:10.1021/acsami.0c13570

Acknowledgements
This work was supported by Horizon 2020 RISE DiSeTCom Project 823728, the Academy of Finland (Flagship Programme, Photonics Research and Innovation (PREIN), no 320166, and projects nos 298298 and 334370), joint project no. S-LB-19-4 from the Research Council of Lithuania Foundation, and the Belarusian Republican Foundation for Fundamental Research (BRFFR) project F19LITG-003. P.K. is supported by Horizon 2020 IF TURANDOT project 836816. D.M. and D.L. are supported by KAUST baseline funding. The authors are grateful to Dr. Martynas Skapas and Mr. Martynas Talaikis (Center for Physical Sciences and Technology, Vilnius, Lithuania) for assistance in TEM and Raman measurements, respectively, and to Alesia Paddubskaya (Institute for Nuclear Problems, Belarusian State University, Minsk, Belarus) for valuable discussions and interest to the work.

Publisher
American Chemical Society (ACS)

Journal
ACS applied materials & interfaces

DOI
10.1021/acsami.0c13570

PubMed ID
33107725

Additional Links
https://pubs.acs.org/doi/10.1021/acsami.0c13570

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