A SERS-based pH sensor utilizing 3-amino-5-mercapto-1,2,4-triazole functionalized Ag nanoparticles

Abstract

We report the first use of 3-amino-5-mercapto-1,2,4-triazole (AMT) to construct a surface-enhanced Raman scattering (SERS) based pH nano- and microsensor, utilizing silver nanoparticles. We optimize the procedure of homogenous attachment of colloidal silver to micrometer-sized silica beads via an aminosilane linker. Such micro-carriers are potential optically trappable SERS microprobes. It is demonstrated that the SERS spectrum of AMT is strongly dependent on the pH of the surroundings, as the transformation between two different adsorption modes, upright (A form) and lying flat (B form) orientation, is provoked by pH variation. The possibility of tuning the nanosensor working range by changing the concentration of AMT in the surrounding solution is demonstrated. A strong correlation between the pH response of the nanosensor and the AMT concentration in solution is found to be controlled by the interactions between the surface and solution molecules. In the absence of the AMT monomer, the performance of both the nano- and microsensor is shifted substantially to the strongly acidic pH range, from 1.5 to 2.5 and from 1.0 to 2.0, respectively, which is quite unique even for SERS-based sensors.

2-Mercaptoethanesulfonate (MES) anion-functionalized silver nanoparticles as an efficient SERS-based sensor of metal cations

“…Since total SERS intensities of the recorded spectra change with the concentration of the ion, internal normalization of the signal is needed. Our choice of two marker bands (strategy already used in our paper devoted to SERS pH sensing [11]) is therefore justified: even if total intensity of the spectrum changes, it affects both bands simultaneously and their intensity ratio remains independent of such fluctuations. If there are more cations able to interact with a sulfonate group, intensity of the higher-energy marker band rises and I 1040 /I 1051 ratio drops continuously.…”

“…Among SERS detectors of cations, sensors sensitive to pH value are studied the most extensively [4][5][6][7][8][9][10][11]. They have also been successfully employed in the intracellular investigations [4,6,[8][9][10].…”

Electrochemical Control of pH in Nanoliter Volumes

“…Optical methods do not have an impact in the footprint. Plasmonic devices using the enhancement of fluorophores or Raman signals associated to nanoparticles can report high intensities [28,29] but they require a long development for standardisation.…”

Absorption, fluorescence, Raman spectroscopic and density functional theoretical studies on the singlet and triplet excited state decay of 3-amino-5-mercapto-1,2,4-triazole

“…[5][6][7] Important structured features, such as the planarity (p) and lone pair of electrons on the hetero-atom, are attributed to their strong coordination on the metal surface. [8][9][10][11][12][13] In particular, 3amino-5-mercapto-1,2,4-triazole (AMT) can be considered as one pull-push electronic structure due to both electron donor (-NH 2 ) and acceptor (-S]C or -SH) groups bridged by one aromatic 1,2,4-triazole ring. Due to the donor-p-acceptor (Dp-A) structure, AMT demonstrates distinguished physical and chemical behaviour besides the above-mentioned characteristics.…”