Application Research Of Sulfur-based Quantum Dots In Environmental And Biological Analysis

The concept of quantum dots from the beginning is mainly applied to semiconductor quantum dots or alloy quantum dots.It is mainly composed of group II-VI,group III-V,group IV-VI elements,and group III element nitrides.Researchers then prepared a variety of zero-dimensional nanomaterials,such as carbon quantum dots,black phosphorus quantum dots,graphene quantum dots,sulfur quantum dots and other new materials.Quantum dots have received widespread attention in the fields of biological,chemical analysis,and medical research due to their superior optical properties and environmental friendliness.The biocompatibility of quantum dots is closely related to their surface properties.Since the specific surface activity of quantum dots is high,it is convenient for various functional modifications.Depending on the nature of the target analyte or the actual purpose,different chemical modifications can be performed.Therefore,through the preparation of new light-emitting quantum dots and the application of new functional modification pathways,a new horizon has been opened for the construction of more efficient and sensitive analysis technologies.Among them,the application of sulfur-based quantum dots in the field of analytical chemistry is particularly noticeable.In order to study the application potential of new materials,polyethylene glycol-passivated sulfur quantum dots and Mn-doped Zn S quantum dots coated with different materials(melamine,uridine triphosphate)were prepared using hydrothermal methods.Or an indirect method,a detection and analysis method based on luminescent nanomaterials was constructed.The main contents are summarized as follows:(1)Most pharmacological effects of clioquinol(CQ)are related to its high affinity for Zn²⁺.Indicator displacement assays based on the use of metal ions therefore have received much attention.A turn on–off fluorometric assay for CQ is described here.It is based on modulation of the fluorescence of sulfur quantum dots(SQDs;best measured at excitation/emission wavelengths of 360 nm/426 nm)by using the Zn²⁺-CQ affinity pair.Although the fluorescence enhancement effect of Zn²⁺on SQDs was not obvious,a good quenching modulation effect was observed in the presence of CQ.This resulted in a linear analytical range that is increased by two orders of magnitude(from 0.024?M to 0.24?M,and 0.62?M to 30?M),with a detection limit(3s)of 0.015?M.The selectivity of the method is also improved.(2)A turn-off room-temperature phosphorescence(RTP)sensor for clenbuterol(CB)based on melamine(MA)-modulated mercaptopropionic acid(MPA)-capped Mn-doped Zn S quantum dots(QDs)was described in this paper.Introduction of CB into the solution of MPA-capped Mn-doped QDs in the presence of MA could increase the surface defects of the QDs and lead to their reaction aggregation due to the hydrogen-bonding interaction between CB and MA,so a process that MA-induced RTP enhanced and subsequent CB-induced RTP quenching could been observed,this phenomenon could build a solid base for us to develop a QDs-based turn-off RTP sensor for detecting CB.Under the optimal conditions,the detection limit for CB was3.2 ngmL^-1,the relative standard deviations was 2.9%while the recovery of the method was in the range of 97%to 104%.The coexisting substances including 2000-fold excesses of Na⁺and K⁺,1500-fold excesses of lysine,cysteine,ascorbic acid,uric acid,Vitamin B1,Vitamin B2,Mn²⁺,Mg²⁺,Ca²⁺,Zn²⁺and Al³⁺,500-fold excesses Cu²⁺and Ag⁺did not affect the determination of CB.The proposed method was successfully applied to biological fluids with satisfactory results.(3)RNA plays a crucial role in biochemical processes.RNAs with abasic sites(AP-RNA),as one of RNA lesions,will cause serious negative consequences.Efficient and sensitive detection of AP-RNA deserves but does not receive enough attention.Water-soluble uridine triphosphate(UTP)-capped Mn-doped Zn S quantum dots(QDs),which have excellent room-temperature phosphorescence(RTP)properties,were prepared by hydrothermal method.The UTP on the surface of QDs could form a precipitation complex with amiloride(AMI)to quench the RTP.Meanwhile,abasic double-stranded RNA(AP-ds RNA)with a high affinity to AMI could dissociate AMI from the surface of UTP-QDs,resulting in RTP recovery.In this process,a highly sensitive and selective RTP-detection system for AP-ds RNA was constructed with AMI as the modulation factor and UTP-QDs as the luminescence matrix.RTP was turned off and on for the determination of AP-ds RNA,and the interference of background fluorescence and scattered light was effectively avoided during complex formation and aggregation.Steric hindrance of the conformation of AP-ds RNA provided efficient selectivity.The detection limit for AP-ds RNA was 0.86 n M,the relative standard deviation was 2.1%,and the recovery of biological samples with AP-ds RNA addition ranged from 95%to 103%at optimal conditions.The system is expected to provide new methods for environmental monitoring,early disease screening,and evaluation of gene editing efficiency.