SERS/RRS Detection Of Co²⁺ And Pb²⁺ In Gold Nanosols Based On Catalytic Amplification Of Iron-doped Carbon Dotsy

Carbon dots（CDs）,a new type of carbon nanomaterial,have gained great attention due to their high quantum yield,good water solubility,low toxicity,high stability,excellent tunable photoluminescence,very small size,low cost,and ease of modification.At the same time,due to the environmental friendliness of CDs,their basic research and applications are also popular in materials,chemistry,and other interdisciplinary fields.The main methods for the preparation of carbon dots are microwave,arc discharge,laser etching,and hydrothermal methods,of which hydrothermal is a classical method for the preparation of CDs and doped CDs,benefiting from high speed and the use of harmless water as a solvent is widely used.The abundance of carbon sources and the variety of synthesis methods have resulted in the diversity of CDs,and in recent years there has been an increase in research on heteroatomic doping of CDs,as this approach can improve the chemical composition and structural properties of CDs.This paper focuses on the preparation and catalytic amplification of iron-doped carbon dots(CD_Fe)and iron-nitrogen-doped carbon dots(CD_BFe).Catalytic amplification of HAu Cl₄-glyoxal/D-galactose nanoparticle by CD_Fe/CD_BFe and specific recognition of various environmental pollutants by aptamer（Apt）,quantitative analysis of surface enhanced Raman scattering（SERS）/resonance Rayleigh scattering（RRS）based on gold nanosol,reported an analytical method for the detection of Co²⁺,Hg²⁺,As³⁺,Pb²⁺,carbendazim（CBZ）and profenofos（PF）was developed.The details are as follows:In the second chapter,highly catalytically active iron-doped carbon dots(CD_Fe)were prepared by the muffle furnace hydrothermal method using only ferrocene as precursor and water as solvent,and characterized by electron microscopy and molecular spectroscopy.It was found that CD_Fe showed the excellent catalytic effect on the reduction of HAu Cl₄ by glyoxal/D-galactose to form gold nanoparticles（Au NPs）,and the addition of the corresponding aptamer（Apt）would adsorb and wrap CD_Fe,weakening its catalytic effect,thus reducing the production of Au NPs and decreasing the SERS and RRS signals of the system.When the target is added to the solution,Apt will bind specifically to the target and the CD_Fe is released and its catalytic effect is restored,increasing the concentration of the desorbed carbon site resulting in a linear increase in the Au NPs produced by the HAu Cl₄-glyoxal/D-galactose system.The resulting Au NPs possess very strong RRS signals and SERS activity,and the addition of the Victoria Blue B（VBB）molecular probe results in a strong SERS signal at 1613 cm^-1,which increases linearly with the concentration of the target.By coupling this novel nanocatalytic amplified double scattering indicator reaction with a specific aptamer（Apt）reaction,an aptamer-mediated iron-doped carbon dot nanocatalytic amplified-SERS/RRS analytical platform was constructed and used for the analysis of Co²⁺,Hg²⁺,As³⁺,Pb²⁺,CBZ and PF in samples with satisfactory results.The linear range for Co²⁺-CD_Fe-HAu Cl₄-acetaldehyde was 1.3-13 p M with detection limits of 0.5 p M（SERS）and 0.7 p M（RRS）respectively.The third chapter deals with carbon dot catalytic amplification as a new way to improve sensitivity.The preparation of highly catalytically active and stable iron-doped nitrogen carbon dot(CD_BFe)sols and their application in aptamer analysis have not yet been reported.As a molecular probe,nucleic acid aptamer has the advantages of easy synthesis and modification,high affinity for target molecules,good stability,etc.It has a very high recognition ability for the target and has great application in the fields of analytical detection,environmental monitoring,and clinical medical diagnosis.In this paper,a novel method for the facile hydrothermal preparation of CD_BFe was constructed using 2,2’-bipyridine-Fe²⁺complexes as precursors,and CD_BFe was found to be strongly catalytic for the indicated reaction of the reduction of HAu Cl₄ by glyoxal（C₂H₂O₂）to form gold nanoparticles（Au NP）.A new rapid and sensitive CD_BFe catalytic amplification-nanogold SERS/RRS aptamer detection method for the analysis of ultra-trace lead ions by using the generated Au NP as an indicator component of RRS spectroscopy mediated by lead ion aptamer reaction.The results showed a good linear relationship between SERS intensity and Pb（II）concentration in the range of 1.3-16 p M,with a detection limit of 1 p M.