Preparation Of Chiral And Fluorescent Nanostructures And The Application In Detecting Food Risk Factors

In this paper, a series of chiral nanostructures were constructed using achiral nanomaterials and chiral molecules, and take advantage of these nanostructures, we established a variety of chiral biosensors with high sensitivity and high specificity. In addition, we also prepared a new class of chiral nanocrystals with interior nanogaps. Finally, a new fluorescent sensor based on fluorescence resonance energy transfer(FRET) for detection of heavy metal ions in aqueous solution was fabricated.First, the diverse discrete chiral Au NR-NP heterodimers bridged by DNA molecules were reported. The experimental result revealed that plasmonic CD responses were in the region from 520 nm to 750 nm, which was in agreement with the theoretical simulation. Importantly, the CD band could be regulated by controlling the gaps between adjacent NCs and altering the building blocks of the assemblies. These results show that the plasmonic chiroptical response of NP-NR heterodimers could come from the finger-crossed chiral construction of adjacent NC in the heterodimers and the formation of plasmonic hot-spots in the assemblies could further enhance the plasmonic CD.Secondly, gold nanorods(Au NRs) and gold nanoparticles(Au NPs) were assembled into core-satellites(Au NR-Au NPs) nanostructures using DNAs as linkers. With the aid of endonuclease and its inhibitor, the CD changes of nanostructures were carried out in detail to further illustrate the origin of chirality, which might due to the chiral arrangement of building blocks and the Coulomb dipole-dipole interactions between them may give rise to the PCD effect. And the inhibitor can be sensitively screened using the chirality of core-satellites superstructures.Thirdly, we fabricate a chiral sensor based on Au NP pyramids to probe the endonuclease activity employing DNase I as a model analyte. The limit of detection(LOD) for DNase I was 0.0036 U/m L.Fourthly, chiral oligomers of Au NP assemblies which were totally different from Au NP dimers were applied to the quantitative detection of antibiotics(using SDM as a model antibiotic) residues in water, the limit of detection reached 0.014 ng/m L. The advantage of this chiroptical oligomers sensor is as follows: facilitate preparation with convenient control of structure complexity, while it is an extreme challenge to control the complexity of NPs agglomeration that could affect repeatability and stability of the assay.Fifthly, we report the synthesis of a new class of GGS NPs with a nanobridge-supported interior nanogap using D/L/D,L-cysteine(D/L/D,L-cys). The GGS-L/D(L/D represents L/Dcys) NPs showed strong and reversed chiroptical activity in the Ag plasmonic region. The plasmonic chirality of GGS NPs may originate due to the following two aspects:(1) a chiral cysteine-plasmon dipolar interaction;(2) plasmonic hot-spot-induced CD amplification.Lastly, a simple sensing platform for highly sensitive and selective detection of Ag+ and Hg2+ based on the FRET between luminescent Cd Te quantum dots(QDs) and dye-labeled single-strand DNA(DNA-dye) probes. Furthermore, the assay can also simultaneously detect Ag+ and Hg2+ in water media with the limit of detection(LOD) of 2.5 nmol/L and 1.8 nmol/L, separately.