Preparation of high-capacity substrates from polycrystalline silver chloride for the selective detection of tyrosine by surface-enhanced infrared absorption (SEIRA) measurements

Abstract

In this work, stacked but isolated silver nanoparticles (AgNPs) on silver chloride were prepared in order to create sensitive substrates that could be used to determine analytes in aqueous solution by performing surface-enhanced infrared absorption (SEIRA) measurements. These substrates have a high loading capacity, which improves sensitivity, thus allowing the detection of biospecies such as weak infrared absorbers (including amino acids) in aqueous solution. AgNPs were obtained by converting the surface layers of the silver chloride crystals into stacked but isolated AgNPs using reducing agents. To optimize the conditions used to prepare the SEIRA substrates, the roles of four common reducing agents-hydrazine, sodium borohydride, glucose, and formaldehyde-were explored by probing the finished substrates with para-nitrobenzoic acid (PNBA). Factors that influence the morphologies of the AgNPs were examined systemically. These factors include the pH of the reducing solution, the reaction time, and the concentration of the reducing agent. Results indicate that the concentration of the reducing agent and the pH of the solution strongly influence the AgNP morphology and hence the SEIRA signals. Under optimized conditions, the resulting substrates showed intense SEIRA spectra from PNBA, with enhancement factors of around two orders of magnitude compared to conventional transmission methods. The new substrates offer a high loading capacity and good heat tolerance, allowing the direct infrared detection of tyrosine in aqueous solution.

A single-loop fiber attenuated total reflection sensor enhanced by silver nanoparticles for continuous glucose monitoring

“…Vacuum evaporation [17,18] and sputtering [19,20] are two traditional dry process to grow nanoparticles, but these methods are limited on flat substrates and very difficult to apply on a cylindrical surface, especially on the cylindrical surface of a single-loop fiber ATR sensor. Wet chemical processes offers some advantages over dry processes, such as lower cost and easier operation during preparation [21][22][23]. A reduction method as one type of wet chemical process has been studied to grow AgNPs on flat substrates of silver chloride; Silver ions of the substrate that were dissolved in solution were reduced by agents such as N 2 H 4 and NaBH 4 in the alkaline condition of sodium hydroxide [22].…”

“…Wet chemical processes offers some advantages over dry processes, such as lower cost and easier operation during preparation [21][22][23]. A reduction method as one type of wet chemical process has been studied to grow AgNPs on flat substrates of silver chloride; Silver ions of the substrate that were dissolved in solution were reduced by agents such as N 2 H 4 and NaBH 4 in the alkaline condition of sodium hydroxide [22]. Though AgNPs could be grown on the cylindrical surface of the fiber ATR sensor by this reduction method, the surface of fiber might be partly corroded by the sodium hydroxide, which might lead to light leakage and the reduction of the measurement resolution of fiber ATR sensor.…”

“…Silver has good biocompatibility, and in this paper, we will further improve the sensitivity and measurement resolution of fiber ATR sensor with surface modification by AgNPs on the cylindrical surface of fiber. There are many methods to grow nanoparticles for different applications [17][18][19][20][21][22][23][24]. Vacuum evaporation [17,18] and sputtering [19,20] are two traditional dry process to grow nanoparticles, but these methods are limited on flat substrates and very difficult to apply on a cylindrical surface, especially on the cylindrical surface of a single-loop fiber ATR sensor.…”

Surfactant-assisted electroless deposition of silver nanoparticles on Ge crystal for ultra-sensitive detection by surface-enhanced infrared absorption spectroscopy

“…[2][3][4][5] The applying of SEIRA effect for analytical purposes have been addressed and successful results have been documented. [6][7][8][9][10] However, the applications of this technique for practical usages rely on the methods to prepare sensitive SEIRA substrates, which should be simple and feasible for massive productions. Several types of methods have been developed for preparation of SEIRA substrates including vapor deposition (PVD), 5,10,11 lithographic fabrication, [12][13][14][15] electroless deposition, 6,16,17 chemical reductions, 18 and electrochemical deposition.…”

“…[6][7][8][9][10] However, the applications of this technique for practical usages rely on the methods to prepare sensitive SEIRA substrates, which should be simple and feasible for massive productions. Several types of methods have been developed for preparation of SEIRA substrates including vapor deposition (PVD), 5,10,11 lithographic fabrication, [12][13][14][15] electroless deposition, 6,16,17 chemical reductions, 18 and electrochemical deposition. 19,20 The reported enhancement factors of the prepared SEIRA substrates by these methods are comparable and ranged from one to two orders of magnitude.…”