Single-particle SERS Substrate:Application In Detection And In Situ SERS Monitoring Photocatalytic Degradation Process Of Pollutants

Surface enhanced Raman spectroscopy(SERS)is a promising and powerful analytical technique.It has attracted enormous attentions for its outstanding qualitative and quantitative abilities to ultratrace target molecules,since it provides abundant vibrational and rotational fingerprint information of target molecule,as well as ultra-high sensitivity with the assistance of SERS substrate(typically noble metal nanostructure).Nowadays,the development of SERS technique meets two bottlenecks: fabrication of ideal SERS substrate and extentional applications of SERS technique.In this dissertation,a micro/nano structural single-particle silver-based hollow cube SERS substrate was fabricated and applied to the fast and sensitive determination of two illegal pigments: crystal violet(CV)and auramine O(AO).By altering the preparation conditions of the above silver-based micro/nano hollow cube,we prepared another bifunctional Ag@AgCl single-particle micro reactor as a in situ SERS monitoring platform of the visible light photocatalytic degradation process of Nile blue.Main results were listed as below:(1)We designed micro/nano Ag based hollow cube as a single particle SERS substrate,which possessed strong SERS enhancing effect(EF ? 1.2×109 when crystal violet was applied as SERS probe),good reproducibility(RSD = 7.9% within ten different batchs)and reliable stability(less than 10% SERS signal decay was observed after the substrate stored in ethanol after one month).We applied the Ag micro/nano cage as SERS platform for the detection of several artificial pigments,crystal violet and auramine O,and received good linearity in the range of 0.001 ~ 1 mg/L and 0.1 ~ 10 mg/L with a detection limit of 10-5 mg/L and 0.1 mg/L,respectively.Finally,we successfully respectively determined the concentrations of the two artificial pigments in a spiked lakewater sample with the recovery rate from 84% ~ 128%(CV)and 80% ~ 127%(AO).(2)Based on the former micro/nano Ag hollow cube SERS substrate,we fabricated micro–nano Ag@AgCl hollow cube as a single particle reactor by tuning the in situ chemical reduction process,which possessed high photocatalytic activity and strong SERS enhancing effect(EF ? 2.4×108).The as-prepared micro-nano structure exhibited both good photocatalytic activity and strong SERS performances.Moreover,the micro-scale structural ensemble was large enough to act as a single particle reactor,which could conduct the in situ SERS monitoring of a photocatalytic degradation process of NB.On the basis of a kinetic monitoring,a deeply insight into photocatalytic degradation pathway was achieved by rationally analyzing the acquired fingerprint spectra,which revealed the cleavage of the C–O–C and C–N=C bond,and the directly oxidative cleavage of naphthalene during the photocatalytic degradation process.