Surface-enhanced Raman spectrometry (SERS) represents a powerful method for analysis of a broad spectrum of analytes ranging from inorganic ions to biomolecules of high complexity. It combines the potential of Raman spectrometry for a definite identification of an analyte with remarkable sensitivity achieved by the surface enhancement effect occurring on metal nanoparticles. While low ionic strength influences positively the sensitivity of the SERS measurement, a higher level of inorganic salts leads to fast ruining of colloidal character, which completely devastates the effect of the surface enhancement. The common stabilization of nanoparticles by a layer of polymers has a negative impact on the SERS sensitivity since it shields the nanoparticle surface from the analytes. In this work, we aim at the development of the bi-ligand system of nanoparticles surface modification for improved stability of colloid in saline solution at sustaining the potential for sensitive SERS analyses. The proposed system relies on the binding of 3-mercaptopropionic acid and thiolated polyethylene glycol in a suitable ratio onto the nanoparticle surfaces. While the short chains of the acid sustain the accessibility of the surface for analytes, the polymeric structures act as a steric barrier preventing colloid aggregation.Keywords: Bi-ligand, nanoparticle, saline solution, stability, surface-enhanced Raman spectrometry
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