Design of Physicochemical Factors for Regulating the Retention Mechanism of 4-Aminothiophenol in Surface-Enhanced Raman Scattering toward Nitrite Sensing

Abstract

The extensive use of 4-aminothiophenol (4-ATP) as a Raman-active molecule is attributed to ease in its functionalization and use for potential sensing in surface-enhanced Raman scattering (SERS) research. However, its SERS spectrum is susceptible to be influenced and chemically affected by several experimental factors. Thus, the current study focuses on theoretically and experimentally investigating such physicochemical factors and its counteractive stimulus to discriminate the SERS signal arising from the analyte of interest and interferents. The sensing mechanism of nitrite-triggered 4-ATP that might induce its oxidation and/or dimerization and the conditions inhibiting or generating abnormal type b2 bands (1142, 1388, and 1432 cm–1) were discussed. The factors covered were as follows: (i) solvent effect; (ii) laser power; (iii) nature of the substrate; (iv) reaction media; (v) reaction kinetics; and (vi) influence of air or any oxygen (dissolved)-containing moiety. The activation of 4-ATP by any factor forms 4,4-dimercaptoazobenzene with characteristic symmetric b2 bands in nearly all the literature, whereas, herein, the species formed between nitrite and 4-ATP was differentiated and confirmed by basic electronic assignments along with their respective binding mechanism toward 1-naphthylamine. The retention mechanism of 4-ATP was assigned and controlled at pH < 2.0, where the protonation of amine and unavailability of necessary precursors in the presence of excess H+ greatly resists its oxidation, making it independent of many potential factors. Moreover, a highly stable platform for nitrite sensing has been established with exceptional selectivity (in the presence of potent interferences) and sensitivity (0.3 × 10–8 M).

Quaternary Alloy Quantum Dots as Fluorescence Probes for Total Acidity Detection of Paper-Based Relics

“…Figure S1 shows the UV absorption spectra of the ethanol eluent of CdZnSeS-OA QDs after being treated by pATP. The UV absorption peak at 212 and 253 nm are assigned to the K band and B band of pATP respectively, and the two bands are derived from π–π* transition of the conjugated substituted benzene structure of pATP [ 26 ]. The UV absorption spectra indicate that both peaks at 212 and 253 nm gradually reduce with washing times of ethanol, and the absorbance spectrum for the seventh ethanol eluent is almost the same as that of ethanol [ 27 ], indicating that pATP physically absorbed on surfaces of CdZnSeS-pATP QDs could be removed through ethanol washing.…”

Point-of-Care Detection of Salivary Nitrite Based on the Surface Plasmon-Assisted Catalytic Coupling Reaction of Aromatic Amines

“…Lately, the similar sensing scheme was adopted by many groups to detect nitrite, but using more complex SERSactive nanoparticles (such as Ag Nanopyraid, Au nanostar, Fe 3 O 4 /Au, Fe 3 O 4 /Au@Ag, etc.) to improve the sensitivity [37,[39][40][41][42], which could also increase the time and difficulties for preparing the sensing probers. Other approaches to improve the sensitivities include by adding an additional reactant (1-naphthylamine) to boost the signal (the Griess reaction) [46][47][48][49].…”

“…Despite that, inspired by the high selectivity of the above NO2 − triggered catalysis reaction, a fast and straightforward nitrite screening method was firstly developed by our group [33] and used by other groups [37,[39][40][41][42]. However, the detection limit of the proposed can be achieved about 10 µM.…”

“…To understand the size effect on surface plasmons, the 3D finite-difference time-domain (FDTD) method is used to simulate the surface plasmons (see the Materials and Despite that, inspired by the high selectivity of the above NO 2 − triggered catalysis reaction, a fast and straightforward nitrite screening method was firstly developed by our group [33] and used by other groups [37,[39][40][41][42]. However, the detection limit of the proposed can be achieved about 10 µM.…”

Headspace Solid-Phase Microextraction Following Chemical Vapor Generation for Ultrasensitive, Matrix Effect-Free Detection of Nitrite by Microplasma Optical Emission Spectrometry

“…Numerous techniques have been developed for the determination of nitrite, including colorimetry, spectrophotometry, − chromatography, capillary electrophoresis, , fluorescence assay, , chemiluminescence, electrochemical methods, , Raman spectrometry, , and other methods. − Although some of these methods provide enough sensitivity for the quantification of nitrite in complex samples, most of them usually suffer from severe matrix interference such as color and turbidity, thus limiting their further application for the field analysis of nitrite. However, the field analysis allows both immediate identification of the toxicity induced from nitrite and in situ evaluation of its seriousness, which is conducive to making a correct decision as soon as possible.…”