The Preparation Of CQDs And CdS QDs And Their Application In Ion Detection And Photocatalytic H2 Evolution

Compared with bulk materials,nanomaterials has diameter smaller than 100 nm at least in one dimensional scale,and the surface area increased greatly,the corresponding energy level structure has also changed with the size of materials decreased into nanometer,these unusual properties make the Nanomaterials special.Especially the Zero-dimensional quantum dots,whose size on the three-dimensional scale is smaller than twice the excitons Boolean radius,has excellent quantum size effect,surface effect,small size effect,and excellent optical properties.Therefore,it is vital to modify and develop novel preparation method in order to investigate the application of quantum dots in photoelectric properties,molecular devices and photocatalysis,etc.This dissertation is make up of three parts as follows:Chapter ?,the introduction of research background.On one hand,we introduced the classification and mechanism of fluorescent probes,especially highlighted the application of carbon quantum dot fluorescent probes in the detection of heavy metal ions.On the other hand,we summarized the application of nano-semiconductor materials,and focused on the preparation of CdS and its modification in photocatalytic hydrogen evolution.Finally,the objective and the scientific significance of this dissertation are presented based on the above introduction.Chapter ?,ionic liquid-functionalized carbon quantum dots as fluorescent probes for sensitive and selective detection of iron ion and ascorbic acid.In this section,we obtained CQDs fluorescent probe by one-step hydrothermal treatment using citric acid and 1-Aminopropyl-3-iethylixnidazolium.This probe can detect Fe3+ with sensitivity and selectivity.Fluorescence titration assay shows that there is a good linear relationship between the fluorescence intensity of CQDs and the concentration of Fe3+in the range of 0-300 ?M(R2=0.99)with a detection limit of 13.68 ?M.Besides,when added different biomolecules into the hybrid solution after the fluorescence of CQDs were quenched by Fe3+,only ascorbic acid can recover the fluorescence of CQDs,this indicates that the CQDs-Fe3+ hybrid-solution can serve as a fluorescence probe for the detection of ascorbic acid.It is expected that our strategy may offer a new approach for developing rapid,low cost and sensitive CQDs-based sensors for environmetal and biological sensing applications.Chapter ?,coordination self-assembly mineralized CdS QDs with sustainable photocatalytic hydrogen evolution.In this section,we develop a facile and effective method to fabricate CdS QDs hierarchical structure by cystine and Cd2+ coordination self-assembly.Firstly,SEM,TEM,XPS and titration experiment prove that cystine and Cd2+ bind together with molar ratio 1:1 through coordination.The forming structure can further serve as a template for the generate of CdS QDs with the addition of Na2S.The results(HR-TEM,XRD,FL and Uv-vis)indicate that we can obtain CdS nanoparticles with different size by regulating the amount of Na2S.In the presence of sacrificial agent,the sample with best light capture and catalytic performance can transfer electrons to the in-situ mineralized Pt,thus improve the hydrogen evolution efficiency(The bubbles can be seen with the naked eye).Due to the stability of the CdS/Cd template,the structure can be reused during five cycles without degradation and decrease of catalytic performance.Our coordination self-assembly method is expected to provide a simple and feasible idea for the preparation of other sulfide nanoparticles.At the same time,the template method in-situ mineralization quantum dots may provide a solution for the synthesis of novel photocatalysts.