Yanghe Luo

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 highly sensitive resonance Rayleigh scattering assay for detection of Hg(II) using immunonanogold as probe

The monoclonal antibody (mAb) against Hg2+ was produced by the hybridoma technique, and was labeled using nanogold (NG) to obtain an immunonanogold (ING) probe. The immunoreaction takes place to form an ING–Hg2+ immunocomplex that caused the resonance Rayleigh scattering peak at 580 nm to decrease, with a detection limit of 1.1 nmol L−1 Hg2+.

Quantitative analysis of trace Pb(II) by a DNAzyme cracking-rhodamine 6G SERRS probe on AucoreAgshell nanosol substrate

In pH 7.2 Tris-HCl buffer solution containing 0.09 mol/L NaCl at 80°C, the single-stranded substrate DNA hybrids with the enzyme DNA to form double-stranded DNA (dsDNA). The substrate chain of dsDNA could be cracked catalytically by Pb(2+) to produce a short single-stranded DNA (ssDNA) that adsorbed on the Au(core)Ag(shell) nanoparticle (Au/AgNP) surface to form stable Au/AgNP-ssDNA conjugate to prevent aggregation by NaCl, and it combined with rhodamine 6G (RhG) to form RhG-Au/AgNP-ssDNA probe that exhibited a strong surface-enhanced resonance Raman scattering (SERRS) peak at 1510 cm(-1). With the increase of Pb(2+) concentration, the SERRS peak increased linearly due to the more RhG-Au/AgNP-ssDNA probe forming. Under the selected conditions, the increased SERRS intensity ΔI was linear to Pb(2+) concentration in the range of 5.0×10(-8)-7.0×10(-7) mol/L, with a detection limit of 7×10(-9) mol/L Pb(2+).

Selective determination of trace boron based on resonance Rayleigh scattering energy transfer from nanogold aggregate to complex of boric acid–azomethine-H

The nanogold particles were aggregated to stable nanogold aggregates as nanoprobes that exhibited a resonance Rayleigh scattering (RRS) peak at 400 nm in the pH 5.6 NH4Ac–HAc buffer solutions and in the presence of azomethine-H (AMH). Upon addition of boric acid, it reacts with AMH to form AMH–boric acid (AMH–B) complexes. When the complexes (as receptors) are close to the nanogold aggregates (as donors), the RRS-energy transfer (ET) takes place, which results in the RRS signal quenching at 400 nm. The quenching intensity responds linearly with the concentration of boron over 5–500 ng mL−1 B.

A simple label-free rhodamine 6G SERS probe for quantitative analysis of trace As3+ in an aptamer–nanosol

Gold nanoparticles (NGs) were modified by the aptamer (ssDNA) to prepare a NGssDNA probe for As3+. In pH 8.0 HEPES buffer solution containing 50 mmol L−1 NaCl, rhodamine 6G (Rh6G) molecules adsorbed on the NGssDNA sol substrate exhibited a strong surface-enhanced Raman scattering peak (SERS) at 1358 cm−1. Upon addition of As3+, it reacts with the NGssDNA probe to form a stable As–ssDNA complex and release NGs that were aggregated to the NG aggregates (NGAs) as a substrate, in which Rh6G SERS activity is very weak. With the increase of As3+ concentration, the SERS peak decreased at 1358 cm−1 due to more NGAs forming. The decreased SERS intensity responds linearly with the concentration of As3+ over 0.288–23.04 ng mL−1, with a detection limit of 0.1 ng mL−1.

A simple resonance Rayleigh scattering method for determination of trace CA125 using immuno-AuRu nanoalloy as probe via ultrasonic irradiation.

AuRu nanoalloy (GR) with Au/Ru molar ratio of 32/1 was prepared by the sodium borohydride reduction method. It was used to label the CA125 antibody (Ab) to obtain an immunonanoprobe (GRAb) for cancer antigen 125 (CA125). In pH 7.0 citric acid-Na2HPO4 buffer solution and irradiation of ultrasound, the probes were aggregated nonspecifically to big clusters that showed a strong resonance Rayleigh scattering (RRS) peak at 278 nm. Upon addition of CA125, GRAb reacted specifically with CA125 to form dispersive immunocomplexes of CA125-GRAb in the solution and this process enhanced by the ultrasonic cavitation effect, which led to the RRS intensity decreased greatly. The decreased RRS intensity was linear to the concentration of CA125 in the range of 1.3-80 U/mL, with a detection limit of 0.6 U/mL. The proposed method was applied to detect CA125 in 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+.

A highly sensitive SERS method for the determination of nitrogen oxide in air based on the signal amplification effect of nitrite catalyzing the bromate oxidization of a rhodamine 6G probe

Rhodamine 6G adsorbed onto a triangular plate-type nanosilver aggregate exhibits a strong SERS peak at 1508 cm−1. Based on NO2− catalysis of the bromate oxidization of Rh6G and SERS peak quenching, trace nitrogen oxides in air samples were analyzed by a catalytic amplification SERS method.

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.

SERS quantitative detection of trace human chorionic gonadotropin using a label‐free Victoria blue B as probe in the aggregated immunonanogold sol substrate

Nanogold particles (NG) were modified by anti-rabbit antibody (RAb) against human chorionic gonadotropin to obtain an immunonanogold probe (ING). In pH 7.0 Na2HPO4-citrate buffer solution containing KCl, ING probes formed large aggregates in which Victoria blue B (VBB) molecules were adsorbed on the surface and which exhibited strong surface-enhanced Raman scattering (SERS) at a peak of 1612 cm(-1). After addition of human chorionic gonadotropin (hCG) an immune reaction with the ING probe occurred to form dispersive ING-hCG complexes with non-SERS activity that led to a decreased SERS peak at 1612 cm(-1). The decreased SERS intensity was linear to the concentration of hCG over 2.4-73.2 ng/mL. The ING reaction was studied in detail by SERS, scanning electron microscope (SEM), resonance Rayleigh scattering (RRS), surface plasmon resonance (SPR) absorption and laser scattering techniques. SERS quenching was observed and discussed.