Xinghui Zhang

A new silver nanorod SPR probe for detection of trace benzoyl peroxide

The stable silver nanorod (AgNR) sol in red was prepared by the two-step procedure of NaBH4-H2O2 and citrate heating reduction. The AgNR had a transverse and a longitudinal surface plasmon resonance (SPR) absorption peak at 338 nm and 480 nm. Meanwhile, two transverse and longitudinal SPR Rayleigh scattering (SPR-RS) peaks at 340 nm and 500 nm were observed firstly using common fluorescence spectrometer. The SPR absorption, RS, surface enhanced Raman scattering (SERS) and electron microscope technology were used to study the formation mechanism of red silver nanorods and the SERS enhancement mechanism of nano-aggregation. The AgNR-BPO SPR absorption and AgNR-NaCl-BPO SPR-RS analytical systems were studied to develop two new simple, rapid, and low-cost SPR methods for the detection of trace BPO.

SERS Detection of Dopamine Using Label-Free Acridine Red as Molecular Probe in Reduced Graphene Oxide/Silver Nanotriangle Sol Substrate

The reduced graphene oxide/silver nanotriangle (rGO/AgNT) composite sol was prepared by the reduction of silver ions with sodium borohydride in the presence of H2O2 and sodium citrate. In the nanosol substrate, the molecular probe of acridine red (AR) exhibited a weak surface-enhanced Raman scattering (SERS) peak at 1506 cm−1 due to its interaction with the rGO of rGO/AgNT. Upon addition of dopamine (DA), the competitive adsorption between DA and AR with the rGO took place, and the AR molecules were adsorbed on the AgNT aggregates with a strong SERS peak at 1506 cm−1 that caused the SERS peak increase. The increased SERS intensity is linear to the DA concentration in the range of 2.5–500 μmol/L. This new analytical system was investigated by SERS, fluorescence, absorption, transmission electron microscope (TEM), and scanning electron microscope (SEM) techniques, and a SERS quantitative analysis method for DA was established, using AR as a label-free molecular probe.

A new and highly sensitive resonance Rayleigh scattering assay for lysozyme using aptamer-nanogold as a probe

Gold nanoparticles (GN), 10 nm in size, were modified by using lysozyme aptamer (Apt) to obtain a stable Apt–GN probe in pH 8.05 Tris/HCl buffer solutions containing 0.04 mol/L NaCl. Upon addition of lysozyme (LYS), it reacted with the Apt of the probe to form a very stable Apt–LYS complex and to release GNs, which aggregated to form large clusters with a resonance Rayleigh scattering (RRS) peak at 368 nm. The enhanced peak intensity, ΔI, was linear to the LYS concentration in the range 0.2–5.2 nmol/L, with a detection limit of 0.05 nmol/L. The influence of foreign substance was tested, and the results showed that this RRS method has high selectivity. This Apt–GN RRS method was applied to the analysis of LYS in a real sample, with satisfactory results.

A SERS nanocatalytic reaction and its application to quantitative analysis of trace Hg(II) with Vitoria blue B molecular probe

Trace mercury ions can be reduced by NaH2PO2 to form nanomercury that can catalyze the NaH2PO2 reduction of HAuCl4 to produce gold nanoparticles (AuNPs) with strong surface-enhanced Raman scattering (SERS) activity. Upon the addition of Vitoria blue B (VBB) as a molecular probe, it adsorbed on the surfaces of the AuNPs with a strong SERS peak at 1612 cm−1. With an increasing concentration of Hg2+, the SERS effect enhanced at 1612 cm−1 due to the formation of more AuNPs as substrate generated from the nanocatalytic particle reaction. This new SERS nanocatalytic indicator reaction was studied by SERS, resonance Rayleigh scattering, absorption spectrophotometry and scanning electron microscopy. Under the chosen conditions, 3.0 to 150 × 10−9 mol L−1 Hg2+ can be analyzed quantitatively using SERS, with a detection limit of 0.8 nmol L−1 Hg2+.

An ultrasensitive SERS method for the determination of ozone using a nanogold sol as substrate and rhodamine S as probe

In an aggregated gold nanoparticle (AuNP) sol substrate, rhodamine S (RhS) exhibited a surface-enhanced Raman scattering (SERS) peak at 1503 cm−1. Based on the ozone oxidization and RhS–I3 particle reactions, 1.56–62.5 nmol L−1 of O3 can be determined by SERS, with a detection limit of 0.9 nmol L−1.

A silver nanorod resonance rayleigh scattering-energy transfer analytical platform for trace tea polyphenols

The stable silver nanorod (AgNR) sol in red was prepared by the two-step procedure of NaBH4-H2O2 and citrate heating reduction, and it exhibited a strong resonance Rayleigh scattering (RRS) peak at 346 nm. In pH 3.8 HAc-NaAc buffer solution, tea polyphenols (TP) reacted with ammonium molybdate (AM) to form yellow organic molybdate (OM) as receptor that was closed to the donor of AgNR, the RRS energy transfer (RRS-ET) takes place, owing to the overlapping between the AgNR RRS spectra and OM absorption spectra. When TP concentration increased, the RRS intensity decreased due to the RRS-ET increasing. So, a simple and sensitive AgNR surface plasmon RRS-ET analytical platform was fabricated to detect trace TP in the range of 0.05-0.85 μg/mL, with a detection limit of 0.03 μg/mL TP. The TP in tea samples was analyzed by this RRS-ET analysis platform, with satisfactory results.

A simple and sensitive graphene oxide/gold nanoparticle surface plasmon resonance Rayleigh scattering-energy transfer analytical platform for detection of iodide and H2O2

Graphene oxide/gold nanoparticle (GO/GN) composites were prepared by citrate reduction that exhibited a strong resonance RS (RRS) peak at 370 nm. When KIO3 and H2O2 were added respectively, they reacted with KI to form I3− ions that adsorbed on the GO/GN surfaces and the RRS intensity decreased due to the RRS energy of GO/NG being transferred to the receptor I3− ions. So, a simple and sensitive GO/GN surface plasmon resonance (SPR) Rayleigh scattering (RS)-energy transfer (SPRRS-ET) analytical platform was fabricated and can be utilized to detect trace KIO3 and H2O2.

Resonance Rayleigh scattering detection of trace PDGF based on catalysis of an aptamer-modified nanogold probe in the Fehling reaction

Gold nanoparticles (GN) were modified by a platelet-derived growth factor (PDGF) aptamer to obtain stable aptamer-nanogold probes (Apt-GN). The probes specifically combined with PDGF-AA to form Apt-GN–PDGF-AA clusters that exhibited a resonance Rayleigh scattering (RRS) peak at 550 nm. The RRS intensity ΔI550nm was linear to the PDGF-AA concentration in the range of 0.33–40 ng mL−1. The probes exhibit strong catalysis of the Fehling reagent–glucose Cu2O particle reaction that can be monitored by the RRS technique at 610 nm, but the cluster is very weak. When PDGF-AA concentration increased, the Apt-GN decreased, and the RRS intensity at 610 nm decreased. The decreased RRS intensity ΔI610nm was linear to PDGF-AA concentration in the range of 0.03–26.67 ng mL−1. Accordingly, two new aptamer-nanogold RRS methods were established.

SERS quantitative analysis of trace HSA with a Coomassie brilliant blue G-250 molecular probe in nanogold sol substrate

Human serum albumin (HSA) is an important protein in human blood plasma and is commonly used in assays such as spectrophotometry, fluorescence and resonance Rayleigh scattering (RRS); however, its detection using SERS quantitative analysis methods is rarely reported. In this study, the as-prepared nanogold (NG) particles were aggregated to stable NG aggregates (NGA) with a strong resonance Rayleigh scattering effect in pH 6.6 phosphate buffer solution containing NaCl. On addition of Coomassie brilliant blue G-250 (CBB) as a molecular probe, it was absorbed on the surface of the NGA, which exhibited the strongest surface-enhanced Raman scattering (SERS) peak at 1171 cm−1, and 2.9 × 10−8–4.68 × 10−7 mol L−1 of CBB in aqueous solutions can be detected directly using the SERS sensor platform. Using this sensor platform to monitor the concentration changes of CBB in the SERS quenching reaction of HSA–CBB, a new simple and sensitive SERS method was developed for the quantitative analysis of 0.04–2.0 μg mL−1 HSA, which could be utilized to study the interaction of HSA with a dye.

A simple and sensitive fluorescence method for the determination of trace ozone in air using acridine red as a probe.

The ozone in an air sample was trapped by H3 BO3 -LK solution to produce iodine (I2) that interacted with excess I(-) to form I3(-). In pH 4.0 acetate buffer solutions, the I3(-) reacted with acridine red to form acridine red-I3 ion association particles that resulted in the fluorescence peak decreased at 553 nm. The decreased value ΔF553 nm is linear to the O3 concentration in the range 0.08-53.3 × 10(-6) mol/L, with a detection limit of 4 × 10(-8) mol/L. This fluorescence method was used to determine ozone in air samples, and the results were in agreement with that of indigo carmine spectrophotometry.