Detection And Application On Sulfate And Sulfite Ions With Surface-enhanced Raman Spectroscopy Based On Phenylboronic Acid Probe

As important reactants of life metabolism,ions play an irreplaceable role in many coures of physiological and metabolic reactions,but its physiological regulation and toxicity to the body are highly dependent on the concentration.The imbalance of ions in the body will disturb the metabolism and induce the occurrence and development of many chronic diseases.Therefore,strictly controlling the dose of ions in food and environment is an effective way to protect human health.Surface-enhanced Raman scattering（SERS）has become a highly sensitive detection technique developed rapidly in recent years.With the improvement of surface modification technology,ion sensors based on SERS technology have been continuously developed.However,the specific detection of highly hydrophilic anions is remained to be a major problem for the application of SERS technology.In order to address the problem of anion recognition and detection by SERS technology,in this paper,4-mercaptophenylboronic acid（4-MPBA）was used to be the sensing probe,and then a SERS sensing technology was developed combining with the self-assembly and surface modification technology for the detection of SO₄^2-and SO₃^2-ions.Subsequently,the response mechanism of the ion detection was discussed.The main research contents and conclusions were as follow:（1）Monolayer silver nanoparticles（Ag NPs）substrates with high SERS activity were constructed.Ag NPs were successfully synthesized by sodium citrate reduction,and then self-assembled on the glass substrate by means of the silanization technology.At the same time,Rhodamine 6G（R6G）was used as the probe molecule to characterize the SERS activity of the obtained substrate.The Ag NPs substrate showed a good sensitivity,reproducibility and storage stability,and its detection limit for R6G was down to 1×10^-12mol/L as well as the enhancement factor was 2.12×10⁸,at the same time,it can be stored for a long time.（2）Based on the coordination principle of Lewis acid-base reaction,an ultrasensitive quantitative SERS technology using 4-MPBA as the recognition probe was constructed for the detection of SO₄^2-ion.The specific coordination recognition of boron atom and oxygen atom in SO₄^2-ion will change the molecular structure of 4-MPBA.This identification reaction was directly reflected in the change of SERS spectra,and a quantitative equation was established for SO₄^2-ion based on the intensity ratio of the two characteristic peaks at 1382 cm^-1and1070 cm^-1.This technology had excellent selectivity and anti-interference for the SO₄^2-ion decetion with a fast response speed of 160 s,the linear response was range from 1×10^-4mol/L to 1×10^-8mol/L,and the detection limit was down to 1×10^-8mol/L.This method was used for standard addition experiments of the SO₄^2-ion in tap water,mineral water,beer and infant formula,the recoveries were between 98.12%and 110.12%,which proved that this method had good application potential for the detection of SO₄^2-ion in complex matrices.（3）Taking advantage of the characteristic of SO₃^2-ion being oxidized to SO₄^2-ion,a SERS chip-based micro-oxidation detection technology for SO₃^2-ion identification was further established.The effects of oxidant selection and oxidation products on substrates and probes were discussed,and then the nitric acid was determined as the optimal oxidant.The detection limit of the established method for SO₃^2-ion reached 5×10^-8mol/L,with the linear concentration ranged from 1×10^-3mol/L to 5×10^-8mol/L.Mineral water,white sugar and mutton were tested for the usability assessment,the technology showed a good detection stability with recoveries of the two materials were between 94.93%and 107.82%.These results proved that this method was suitable for the quantitative determination of SO₃^2-ion detection in some food.