Abstract
The ability of noble metal-based nanoparticles (NPs) (Au, Ag) to drastically enhance Raman scattering from molecules placed near metal surface, termed as surface-enhanced Raman scattering (SERS), is widely used for identification of trace amounts of biological materials in biomedical, food safety and security applications. However, conventional NPs synthesized by colloidal chemistry are typically contaminated by nonbiocompatible by-products (surfactants, anions), which can have negative impacts on many live objects under examination (cells, bacteria) and thus decrease the precision of bioidentification. In this article, we explore novel ultrapure laser-synthesized Au-based nanomaterials, including Au NPs and AuSi hybrid nanostructures, as mobile SERS probes in tasks of bacteria detection. We show that these Au-based nanomaterials can efficiently enhance Raman signals from model R6G molecules, while the enhancement factor depends on the content of Au in NP composition. Profiting from the observed enhancement and purity of laser-synthesized nanomaterials, we demonstrate successful identification of 2 types of bacteria (Listeria innocua and Escherichia coli). The obtained results promise less disturbing studies of biological systems based on good biocompatibility of contamination-free laser-synthesized nanomaterials.
Highlights
Raman scattering is known to provide a variety of information on the structure and composition of the matter, based on its vibrational fingerprints, and this information can be used for highly precise identification of chemical or biological species [1]
We recently showed that contamination-free laser-synthesized Si NPs are well compatible with biological systems in vitro and in vivo [44, 45], but are biodegradable as they decay in aqueous environment into orthosilicic acid Si(OH)4 and excrete from biological systems without any harmful effects [46]
We explored the employment of bare Au-based nanomaterials, including pure Au NPs and Au-Si composite NPs, synthesized by methods of laser ablation in deionized water, as surfaceenhanced Raman scattering (SERS) probes for bacteria detection
Summary
Raman scattering is known to provide a variety of information on the structure and composition of the matter, based on its vibrational fingerprints, and this information can be used for highly precise identification of chemical or biological species [1]. Pulsed laser ablation in liquids (PLAL) has recently emerged as a physical alternative to conventional synthesis [28,29,30,31,32], which promises a solution of the contamination problem of chemically synthesized nanomaterials This method is based on laser radiative removal (ablation) of material from a solid target in a liquid ambience, leading to a natural production of nanoclusters and their subsequent coalescence to form colloidal NPs solutions [33, 34]. We employ bare (ligand-free) Au-based nanomaterials, including pure Au and AuSi core-shell NPs, synthesized by methods of laser ablation in deionized water, as SERS probes and access their efficiency in tasks of bacteria identification
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