Ⅱ-Ⅵ族半导体纳米器件在液体和光照下降解失效的研究

Unraveling the phase selection mechanisms of semiconductor nanowires (NWs) is critical for the applications in future advanced nanodevices. In this study, the atomistic vapor-solid-liquid growth processes of Sn-catalyzed wurtzite (WZ) and zinc blende (ZB) ZnO are directly revealed based on the in situ transmission electron microscopy. The growth kinetics of WZ and ZB crystal phases in ZnO appear markedly different in terms of the NW-droplet interface, whereas the nucleation site as determined by the contact angle ϕ between the seed particle and the NW is found to be crucial for tuning the NW structure through combined experimental and theoretical investigations. These results offer an atomic-scale view into the dynamic growth process of ZnO NW, which has implications for the phase-controllable synthesis of II-VI compounds and heterostructures with tunable band structures.

The development and utilization of inorganic material biosynthesis have evolved into single macromolecular systems. A putative cystathionine γ-lyase of bacteria Stenotrophomonas maltophilia (smCSE) is a newly identified biomolecule that enables the synthesis of nanomaterials. Due to the lack of structural information, the mechanism of smCSE biosynthesis remains unclear. Herein, we obtain two atomic-resolution smCSE-form X-ray structures and confirm that the conformational changes of Tyr108 and Lys206 within the enzyme active sites are critical for the protein-driven synthesis of metal sulfide quantum dots (QDs). The structural stability of tetramer and the specificity of surface amino acids are the basis for smCSE to synthesize quantum dots. The size of QD products can be regulated by predesigned amino acids and the morphology can be controlled through proteolytic treatments. The growth rate is enhanced by the stabilization of a flexible loop in the active site, as shown by the X-ray structure of the engineered protein which fused with a dodecapeptide. We further prove that the smCSE-driven route can be applied to the general synthesis of other metal sulfide nanoparticles. These results provide a better understanding of the mechanism of QD biosynthesis and a new perspective on the control of this biosynthesis by protein modification.

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Cancer research has experienced astonishing advances recently, but cancer remains a major threat because it is one of the leading causes of death worldwide. Glioblastoma (GBM) is the most malignant brain tumor, where the early diagnosis is vital for longer survival. Thus, this study reports the synthesis of novel water-dispersible ternary AgInS2 (AIS) and quaternary AgInS2-ZnS (ZAIS) fluorescent quantum dots using carboxymethylcellulose (CMC) as ligand for multiplexed bioimaging of malignant glioma cells (U-87 MG). Firstly, AgInS2 core was prepared using a one-pot aqueous synthesis stabilized by CMC at room temperature and physiological pH. Then, an outer layer of ZnS was grown and thermally annealed to improve their optical properties and split the emission range, leading to core-shell alloyed nanostructures. Their physicochemical and optical properties were characterized, demonstrating that luminescent monodispersed AIS and ZAIS QDs were produced with average sizes of 2.2 nm and 4.3 nm, respectively. Moreover, the results evidenced that they were cytocompatible using in vitro cell viability assays towards human embryonic kidney cell line (HEK 293T) and U-87 MG cells. These AIS and ZAIS successfully behaved as fluorescent nanoprobes (red and green, resp.) allowing multiplexed bioimaging and biolabeling of costained glioma cells using confocal microscopy.

The contamination and pollution of wastewater with a wide diversity of chemical, microbiological, and hazardous substances is a field of raising environmental concern. In this study, we developed, for the first time, new hybrid multifunctional nanoplexes composed of ZnS semiconductor quantum dots (ZnS QDs) chemically biofunctionalized with epsilon-poly-l-lysine (ɛPL) and coupled with magnetic iron oxide nanoparticles (MION, Fe3O4) stabilized by carboxymethylcellulose (CMC) for the photodegradation (ZnS) of organic molecules and antibacterial activity (ɛPL) with a potential of recovery by an external magnetic field (Fe3O4). These nanosystems, which were synthesized entirely through a green aqueous process, were comprehensively characterized regarding their physicochemical properties combined with spectroscopic and morphological features. The results demonstrated that supramolecular colloidal nanoplexes were formed owing to the strong cationic/anionic electrostatic interactions between the biomacromolecule capping ligands of the two nanoconjugates (i.e., polypeptide in ZnS@ɛPL and polysaccharide in Fe3O4@CMC). Moreover, these nanosystems showed photocatalytic degradation of methylene blue (MB) used as a model dye pollutant in water. Besides MB, methyl orange, congo red, and rhodamine dyes were also tested for selectivity investigation of the photodegradation by the nanoplexes. The antibacterial activity ascribed to the ɛPL biomolecule was confirmed against Gram-positive and Gram-negative bacteria, including drug-resistance field strains. Hence, it is envisioned that these novel green nanoplexes offer a new avenue of alternatives to be employed for reducing organic pollutants and inactivating pathogenic bacteria in water and wastewater treatment, benefiting from easy magnetic recovery.

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Luminescent quantum dot (QD) ink is currently a powerful tool for generating hidden information on paper substrates. Herein, we fabricated a nanohybrid ink of bacterial cellulose nanocrystal (BCNC) and UV-responsive ZnO QD via electrostatic self-assembly for improving solvent resistance and message encryption process. Under investigations on the printed areas, the nanohybrid can slightly infiltrate into the paper fibers and form a thin layer on the top of paper substrates, conferring an enhanced print permanence against wetting conditions while maintaining the daylight unobservability and its luminescent stability. The water resistance of the proposed nanohybrid ink enables developing a higher security level that the prints can be submerged in CuCl2 aqueous solutions to quench the luminescent message. The concealed message can eventually be revealed under UV light again after submerging in EDTA solution. Our ZnO QD/BCNC nanohybrid with eco-friendly nature therefore exhibits great potential as security marking ink for counterfeit protection with sustainable uses.

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High quality Mn2+-doped CdTe quantum dots (QDs), Co2+-doped CdTe QDs and Mn2+&Co2+ co-doped CdTe QDs were successfully synthesized via an aqueous phase method with mercaptopropanoic acid (MPA) ligands. The doped QDs maintain the same zinc blende structure of CdTe by X-ray diffraction (XRD). The Mn2+-doped CdTe QDs and Co2+-doped CdTe QDs both show a red-shift on absorption and photoluminescence (PL) spectra compared to pure CdTe QDs. In addition, Mn2+-doped CdTe QDs show a significant increase in the PL lifetime due to an orbitally forbidden d–d transition, which is of benefit to the reduction of electron recombination loss. Co2+ doping has a more matched doping energy level. In view of this, Mn2+&Co2+ co-doped CdTe QDs were applied as sensitizers for quantum dot sensitized solar cells, resulting in a significantly enhanced efficiency.

We present light harvesting of aqueous colloidal quantum dots to nonradiatively transfer their excitonic excitation energy efficiently to dye molecules in water, without requiring ligand exchange. These as-synthesized CdTe quantum dots that are used as donors to serve as light-harvesting antennas are carefully optimized to match the electronic structure of Rhodamine B molecules used as acceptors for light harvesting in aqueous medium. By varying the acceptor to donor concentration ratio, we measure the light harvesting factor, along with substantial lifetime modifications of these water-soluble quantum dots, from 25.3 ns to 7.2 ns as a result of their energy transfer with efficiency levels up to 86%. Such nonradiative energy transfer mediated light harvesting in aqueous medium holds great promise for future quantum dot multiplexed dye biodetection systems.