Article

Three Steps of Hierarchical Self Assembly Toward a Stable and Efficient Surface Enhanced Raman Spectroscopy Platform

Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
Institute of High Pressure Physics Unipress, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw, Poland
Chem. Mater., 2012, 24 (19), pp 3667–3673
DOI: 10.1021/cm3008914
Publication Date (Web): August 31, 2012
Copyright © 2012 American Chemical Society
*Fax: 48 22343 3333. Tel.: 48 223433228. E-mail: akamin@ichf.edu.pl (A.K.). Fax: 48 223433333. Tel.: 48 223433102. E-mail: rholyst@ichf.edu.pl or robert.holyst@gmail.com (R.H.).

Abstract

Abstract Image

We report an innovative application of a true “bottom-up” approach for preparation of functional material. Three consecutive self-assembly steps were utilized for formation of a complex surface enhanced Raman spectroscopy (SERS) platform. First the Langmuir–Blodgett technique was used to deposit gold nanoparticles on a solid substrate. Thus prepared surfaces were afterward used as substrates in the chemical vapor deposition process of gallium nitride (GaN) nanowire growth. On such scaffolding, a third step of material fabrication was performed. Gold microflowers (Au MFs) deposited from solution preferably appeared at the top of the GaN nanowires and not in the cavities in between. The obtained morphology of the final material was controlled at each step of the preparation process to tailor its properties for desired purposes. Prepared surfaces were tested as SERS platforms. The enhancement factor was around 107 in case of p-mercaptobenzoic acid (p-MBA). The platforms were also suitable for biological and biomedical applications. We demonstrated the label free detection of DNA. The substrates gave reproducible SERS spectra both across a single platform and between different platforms. The average spectral correlation coefficients (Γ) was 0.87. Moreover, the obtained material proved to be very stable. The presented complex structure demonstrated therefore had the advantages of the two surface functionalization concepts it comprised: (1) GaN nanowire growth and (2) Au MF deposition, eliminating their major drawbacks. Presented material combined high SERS enhancement factor of Au MFs deposited on a flat surface and good durability of microflowers deposited on a surface completely covered with nanowires, which were almost SERS inactive. The final product provided truly exceptional stability and repeatability of SERS results, maintaining an enhancement factor comparable to the best commercially available platforms.

Figures S1–S5. This material is available free of charge via the Internet at http://pubs.acs.org.

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Received 21 March 2012
Published online 31 August 2012
Published in print 9 October 2012