Chongning Li

A surface enhanced Raman scattering quantitative analytical platform for detection of trace Cu coupled the catalytic reaction and gold nanoparticle aggregation with label-free Victoria blue B molecular probe

With development of economy and society, there is an urgent need to develop convenient and sensitive methods for detection of Cu2+ pollution in water. In this article, a simple and sensitive SERS sensor was proposed to quantitative analysis of trace Cu2+ in water. The SERS sensor platform was prepared a common gold nanoparticle (AuNP)-SiO2 sol substrate platform by adsorbing HSA, coupling with the catalytic reaction of Cu2+-ascorbic acid (H2A)-dissolved oxygen, and using label-free Victoria blue B (VBB) as SERS molecular probes. The SERS sensor platform response to the AuNP aggregations by hydroxyl radicals (•OH) oxidizing from the Cu2+ catalytic reaction, which caused the SERS signal enhancement. Therefore, by monitoring the increase of SERS signal, Cu2+ in water can be determined accurately. The results show that the SERS sensor platforms owns a linear response with a range from 0.025 to 25μmol/L Cu2+, and with a detection limit of 0.008μmol/L. In addition, the SERS method demonstrated good specificity for Cu2+, which can determined accurately trace Cu2+ in water samples, and good recovery and accuracy are obtained for the water samples. With its high selectivity and good accuracy, the sensitive SERS quantitative analysis method is expected to be a promising candidate for determining copper ions in environmental monitoring and food safety.

Resonance Rayleigh Scattering and SERS Spectral Detection of Trace Hg(II) Based on the Gold Nanocatalysis

Mercury (Hg) is a heavy metal pollutant, there is an urgent need to develop simple and sensitive methods for Hg(II) in water. In this article, a simple and sensitive resonance Rayleigh scattering (RRS) method was developed for determination of 0.008–1.33 µmol/L Hg, with a detection limit of 0.003 μmol/L, based on the Hg(II) regulation of gold nanoenzyme catalysis on the HAuCl4-H2O2 to form gold nanoparticles (AuNPs) with an RRS peak at 370 nm. Upon addition of molecular probes of Victoria blue B (VBB), the surface-enhanced Raman scattering (SERS) peak linearly decreased at 1612 cm−1 with the Hg(II) concentration increasing in the range of 0.013–0.5 μmol/L. With its good selectivity and good accuracy, the RRS method is expected to be a promising candidate for determining mercury ions in water samples.

A new silver nanochain SERS analytical platform to detect trace hexametaphosphate with a rhodamine S molecular probe

Using AgNO3 as the precursor, stable silver nanochain (AgNC) sols, orange-red in color, were prepared using hydrazine hydrate. A strong surface plasmon resonance Rayleigh scattering (RRS) peak occurred at 420 nm plus two surface plasmon resonance (SPR) absorption peaks at 410 nm and 510 nm. Rhodamine S (RhS) cationic dye was absorbed on the as-prepared AgNC substrate to obtain a RhS-AgNC surface-enhanced Raman scattering (SERS) nanoprobe that exhibited a strong SERS peak at 1506 cm(-1) and a strong RRS peak at 375 nm. Upon addition of the analyte sodium hexametaphosphate (HP), it reacted with RhS, which resulted in a decrease in the SERS and RRS peaks that was studied in detail. The decreased SERS and RRS intensities correlated linearly with HP concentration in the range of 0.0125-0.3 µmol/L and 0.05-1.0 µmol/L, with a detection limit of 6 nmol/L and 20 nmol/L HP respectively. Due to advantages of high sensitivity, good selectivity and simple operation, the RhS molecular probes were used to determine HP concentration in real samples.

Immunocontrolling Graphene Oxide Catalytic Nanogold Reaction and Its Application to SERS Quantitative Analysis

The gold nanoreaction between HAuCl4 and H2O2 is very slow at 50 °C, and the nanoenzyme of graphene oxide (GO) greatly catalyzes the nanoreaction to form gold nanoparticles (AuNPs) with high SERS activity in the presence of Vitoria blue 4R (VB4r) molecular probes, strong resonance Rayleigh scattering (RRS), and surface plasmon resonance (SPR) absorption effect. With the increase of GO, the SERS, RRS, and SPR absorptions were enhanced linearly due to the formation of more AuNPs. The rabit antibody of human chorionic gonadotropin (RHCG) strongly adsorbed on the GO surface to inhibit its catalysis. Upon addition of human chorionic gonadotropin (HCG), the RHCG is separated from the GO surface due to the formation of HCG-RHCG specific immunocomplexes, which led to the recovery of GO catalysis. Using the new strategy of immunocontrolling GO catalysis, three types of resonance methods including SERS, RRS, and surface plasmon resonance (SPR) absorption have been developed for detection of HCG.

A Sensitive Gold Nanoplasmonic SERS Quantitative Analysis Method for Sulfate in Serum Using Fullerene as Catalyst

Fullerene exhibited strong catalysis of the redox reaction between HAuCl4 and trisodium citrate to form gold nanoplasmon with a strong surface-enhanced Raman scattering (SERS) effect at 1615 cm−1 in the presence of Vitoria blue B molecule probes. When fullerene increased, the SERS peak enhanced linearly due to formation of more AuNPs as substrate. Upon addition of Ba2+, Ba2+ ions adsorb on the fullerene surface to inhibit the catalysis of fullerene that caused the SERS peak decreasing. Analyte SO42− combined with Ba2+ to form stable BaSO4 precipitate to release free fullerene that the catalysis recovered, and the SERS intensity increased linearly. Thus, a new SERS quantitative analysis method was established for the detection of sulfate in serum samples, with a linear range of 0.03–3.4 μM.

Preparation of Highly Catalytic N-Doped Carbon Dots and Their Application in SERS Sulfate Sensing

Carbon dots (CD) have excellent stability and fluorescence activity, and have been widely used in fluorescence methods. However, there are no reports about using CD as catalysts to amplify SERS signals to detect trace sulfate. Thus, preparing CD catalysts and their application in SERS sulfate-sensing are significant. In this article, highly catalytic N-doped carbon dots (CDN) were prepared by a hydrothermal procedure. CDN exhibited strong catalysis of the gold nanoparticle (AuNP) reaction between HAuCl4 and H2O2. Vitoria blue 4R (VB4R) has a strong SERS peak at 1614 cm−1 in the formed AuNP sol substrate. When Ba2+ ions were added, they were adsorbed on a CDN surface to inhibit the CDN catalytic activity that caused the SERS peak decreasing. Upon addition of analyte SO42−, a reaction with Ba2+ produced stable BaSO4 precipitate and CDN, and its catalysis recovered to cause SERS intensity increasing linearly. Thus, an SERS method was developed for the detection of 0.02–1.7 μmol/L SO42−, with a detection limit of 0.007 μmol/L.

A facile and sensitive peptide-modulating graphene oxide nanoribbon catalytic nanoplasmon analytical platform for human chorionic gonadotropin

The nanogold reaction between HAuCl4 and citrate is very slow, and the catalyst graphene oxide nanoribbon (GONR) enhanced the nanoreaction greatly to produce gold nanoparticles (AuNPs) that exhibited strong surface plasmon resonance (SPR) absorption (Abs) at 550 nm and resonance Rayleigh scattering (RRS) at 550 nm. Upon addition of the peptide of human chorionic gonadotropin (hCG), the peptide could adsorb on the GONR surface, which inhibited the catalysis. When hCG was added, peptides were separated from the GONR surface due to the formation of stable peptide–hCG complex, which led to the activation of GONR catalytic effect. With the increase in hCG concentration, the RRS and Abs signal enhanced linearly. The enhanced RRS value showed a good linear relationship with hCG concentration in the range of 0.2–20 ng/mL, with a detection limit of 70 pg/mL. Accordingly, two new GONR catalytic RRS/Abs methods were established for detecting hCG in serum samples.