| 1 IntroductionThe preparation procedure, spectral characteristics and its analytical application of gold and silver nanosol have been reviewed in this paper. The progress of gold and silver nanoparticles prepared by chemical and green synthesis procedures was introduced respectively. The feature of the surface plasmon resonance (SPR) absorption, resonance Rayleigh scattering (RRS), and surface-enhanced Raman scattering (SERS) of the gold and silver nanosol and its analytical applications were introduced emphatically. The propress of RRS and SERS based on the general chemical, immune, aptamer and other reactions was reviewed. The significance and propress of amino acid analysis were reviewed, and the feature of molecular spectral analysis of amino acid was compared. The main contents and significance of this paper were briefly described.2 RRS spectral analysis of amino acids using the ninhydrin-GO systemNon metallic nanomaterial graphene oxide (GO) has strong RRS effect that exhibited a strong RRS peak at 400 nm. In the presence of pH 7.2 KH2PO4-NaOH buffer solution and 85 ℃ water bath heating, ninhydrin reacted with glutamate to form blue-violet complex Ruhemann’s purple(RP) that reduced the RRS peak at 400 nm due to the RRS-energy transfer (RRS-ET) from the GO as donors to the RP as receptors. With the increase of glutamate concentration, the formed RP increased, and the RRS intensity quenched linearly at 400 nm due to the RRS-ET enhancing. The quenched intensity responds linearly with glutamate concentration in the range of 1.3-200 μmol/L. The RRS spectra of different kinds of amino acids and non metallic nanoparticles were investigated, and the absorption spectra, scanning electron microscope and laser scattering characteristics of the system were examined. Thus, a new non metallic nanomaterial RRS-ET method for the determination of trace amino acids was established with the detection limit of 1.0 fμmol/L. The new method was used to detect the content of amino acid in amino acid oral liquid, and the results were satisfactory.3 RRS spectral analysis of amino acids using ninhydrin-AuNF systemThe gold nanoflowers (AuNF) sol was prepared by reduction of gold chloride acid with 4-hydroxyethyl piperazine ethyl sulfonic acid as the buffer solution and reducing agent that exhibited a strong RRS peak at 555 nm. In the presence of pH 7.6 NaH2PO4-NaOH buffer solution and 85 ℃ water bath heating, ninhydrin reacted with glycine to form blue-violet complex RP that reduced the RRS peak at 555 nm due to the RRS-ET from the AuNP aggregates as donors to the RP as receptors. With the increase of glycine concentration, the formed RP increased, and the RRS intensity quenched linearly at 555 nm due to the RRS-ET enhancing. The quenched intensity responds linearly with glycine concentration in the range of 0.1-99.8 μmol/L. The RRS spectra and absorption spectra of different amino acids and metal nanoparticles were observed, and a kind of organic matter less interference, high sensitivity and good selectivity metal nanosol RRS-ET new method was developed for the determination of trace amino acids with the detection limit of 0.1 μmol/L. The method used in the detection of amino acids in water chestnut, tea and other agricultural products, and the results were satisfactory.4 SERS spectral analysis of amino acids in the substrate of AgNT solThe silver nanotriangle (AgNT) sol was prepared by reduction of silver ions with sodium borohydride and H2O2 in the presence of sodium citrate. Under the action of sodium chloride, AgNT gathered to form a highly active SERS substrate. In the presence of pH 6.0 Na2HPO4-NaH2PO4 buffer solution at 80 ℃ water bath, ninhydrin reacted with amino acids to form blue-violet complex RP, and the RP molecules adsorbed on the AgNT aggregated surface that exhibited strong SERS effects, which enhanced with the concentration of amino acids due to RP increasing. The intensity of SERS peak at 657 cm-1 increased linearly as amino acids concentration in the linear range of 0.7-99.8 μmol/L with a detection limit of 0.5 μmol/L. This new analytical systerm was investigated by SERS, RRS, absorption, transmission electron microscope and scanning electron microscope techniques, and a high selectivity SERS quantitative analysis method for detection of trace amino acids was established with RP molecular probe. This proposed method was applied to detect commercially available amino acids supplements samples, with satisfactory results.5 SERS spectral analysis of dopamine using acridine red-rGO/AgNT systemThe reduced graphene oxide/silver nanotriangle (rGO/AgNT) composite sol was prepared by using NaBH4 and H2O2 as reducing agents while sodium citrate was used as a stablizer. When the molecular probe of acridine red (AR) was added into the rGO/AgNT sol, it adsorbed on rGO sheets via noncovalent forces such as π-π stacking, hydrogen bonding, hydrophobic interactions and so on. It was difficult for AR to adsorb on the surface of AgNT aggregates that exhibited a weak SERS peak at 1506 cm-1. Upon addition of dopamine (DA), the competitive adsorption was occurred between DA and AR around the oxygen-containing groups of rGO sheets, that resulted in de-sorption of AR molecules from the rGO surface into the solution. The desorbed AR molecules could adsorb rapidly on the surface of AgNT aggregates that caused the intensity of SERS peak enhanced at 1506 cm’1. This new analytical systerm was investigated by SERS, RRS, fluorescence, absorption, laser scattering and scanning electron microscope techniques. Thus, a SERS quantitative analysis method was established for the determination of DA over 10-500 umol/L with the detection limit of 5.0 μmol/L, based on the label-free probe. This proposed method was applied to detect dopamine hydrochloride injection analysis, the result is satisfactory.6 ProspectsThe study significance and application of the RRS and SERS spectroscopy in the paper for detection trace amino acids and dopamine werre discussed which being used in high active substrate preparation and trace analysis. |
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