Constructio And Application Of Spectral Analysis System Based On Gold Nanomaterials

Gold nanomaterials have a high molar extinction coefficient and adjustable longitudinal localized surface plasmon resonance absorption,and they have broad application prospects in spectral analysis.The introduction part of this article mainly introduces the research progress of the preparation and application of gold nanomaterials;In the experimental part,based on the fluorescence quenching effect of gold nanoparticles and the surface plasmon resonance absorption characteristics of gold nanorods,new spectral analysis methods for the detection of biological thiols,ellagic acid,dopamine and uric acid were constructed.(1)Gold nanoparticles(AuNPs)were prepared by reducing chloroauric acid by sodium citrate.The AuNPs were characterized by transmission electron microscopy(TEM)and ultraviolet absorption spectroscopy.AuNPs were spherical in shape and had good dispersibility,with strong characteristic peak at520 nm.Biothiols(cysteine,homocysteine and glutathione)can bind to AuNPs through sulfhydryl groups,leading to the aggregation of AuNPs.Owning to their inner filter effect,AuNPs can weaken or even quench the fluorescence of fluorescein.However,the introduction of biothiols to fluorescein-AuNPs leads to the recovery of fluorescein fluorescence.Thus,a simple and reliable turn on fluorescence method was developed for monitoring biothiols with fluorescein-AuNPs as a probe.Under the optimal conditions,sensitive sensing of Cys,HCys and GSH was achieved.The detection limits for Cys,GSH,and HCys were0.027,0.023,and 0.030??,respectively.This method was used to the determination of Cys in human serum samples with high precision and accuracy,indicating the potential of the method in practical applications with simple operation,good accuracy and high sensitivity.(2)The surface plasmon resonance characteristics of AuNPs are quite sensitive to their morphology,size and composition.Ag⁺ions were reduced by EA to Ag atoms,which deposited on the surfaces of AuNPs to form Au@AgNPs in situ,the local surface plasmon resonance(LSPR)peak shifts from 520 nm to410 nm,along with an obvious color change from pink to yellow.Carbon quantum dots(CQDs)were prepared from trifolium leaves via hydrothermal method;the fluorescence of CQDs was quenched by Au@AgNPs,attributing to inner filter effect(IFE).Thus,a fluorometric and colorimetric double signal probe based on CQDs-gold nanoparticles(AuNPs)-AgNO₃ system was constructed for the detection of ellagic acid(EA).Under the optimal conditions,sensitive assay of EA was achieved,with the limit of detection(LOD)of 0.41?M for fluorescence analysis and 0.22?M for colorimetric assay.The changes of fluorescence and absorbance correlated well with EA concentration in the range of 0.50-25.0?M.In addition,the double signal probe also exhibited high selectivity toward EA.The feasibility of the probe was confirmed in commercial cosmetics analysis with satisfactory results.(3)Gold nanorods(AuNRs)were prepared by reducing chloroauric acid with hydroquinone.The AuNRs were characterized by TEM and ultraviolet absorption spectroscopy.The aspect ratio of the prepared AuNRs was about 5:1,and the longitudinal localized surface plasmon resonance LSPR absorption peak Located at 980 nm.AuNRs have tunable surface plasmon resonance optical properties.Iodine(I₂)etching can change the aspect ratio?the maximum LSPR peak and the color change of AuNRs solution.A colorimetric analytical method,with wavelength change as a response,was developed for highly sensitive determination of dopamine(DA)based on the AuNRs.Even though AuNRs were unable to be etched by KIO₃,however,they surrendered to I₂ generated from IO₃^-in the presence of DA.This could result in a blue shift of their absorption peak of longitudinal localized surface plasma resonance(LSPR),accompanied by obvious color change of solution from wine red to blue.Under the optimum conditions such as KIO₃ concentration of 0.7 mmol/L,reaction temperature at 50°C,pH 2.6 and incubation time of 6 min,the amount of blue shift of AuNRs absorption wavelength was linear to DA concentration in the range of 0.80-60.0?mol/L and the detection limit was 0.62?M(3?/k).Furthermore,the common substances in urine did not interfere in the determination and the DA recovery rate in actual urine samples ranged from103%to 110.8%.(3)MnO₂ nanosheets(MnO₂ NS)were prepared by stirring at room temperature and characterized by TEM,X-ray photoelectron spectroscopy,X-ray diffraction and other methods.The prepared MnO₂ NS had a two-dimensional ultra-flaky structure.The longitudinal direction of AuNRs would be gradually etched by I₂,as an oxidant,generated by the reaction between MnO₂NS and I^-.Benefitted from the length change,the localized surface plasmon resonance(LSPR)peak of AuNRs showed an obvious blue shift,accompanied by color change of the solution.Once uric acid(UA)was introduced,MnO₂ NS was reduced to Mn²⁺rapidly.As a result,the formation of I₂ was reduced and the etching of AuNRs was inhibited.Thus,a method for sensitive detection of UA was achieved with UV-vis spectroscopy and bare eyes,respectively.LSPR absorption peak shift(??)of AuNRs before and after inhibition was used to quantitative determination of UA.Under the optimal conditions,the shift of LSPR peak correlated well with UA concentration in the range of 0.8-30?M and 30-300?M,with a detection limit of 0.76?M and 2.04?M,respectively.The proposed method has been used for determining UA in clinical samples with satisfactory results.