RESUMEN
Quantum dots (QDs) are semiconductor nanoparticles (NPs) that offer valuable functionality for cellular labeling, drug delivery, solar cells and quantum computation. In this study, we reported that CdSe QDs could be bio-synthesized in Bacillus licheniformis. After optimization, the obtained CdSe QDs exhibited a uniform particle size of 3.71±0.04nm with a maximum fluorescence emission wavelength at 550nm and the synthetical positive ratio can reach up to 87%. Spectral properties, constitution, particle sizes and crystalline phases of the CdSe QDs were systematically and integrally investigated. The CdSe QD-containing Bacillus licheniformis cells were further used as whole fluorescent bio-probes to detect copper (II) (Cu2+) in water, which demonstrated a low limit of detection (0.91µM). The assay also showed a good selectivity for Cu2+ over other ions including Al3+, Cd2+, Mg2+, K+, Na+, NH4+, Zn2+, CH3COO+, Pb2+ and I-. Our study suggests the fluorescent CdSe QDs-containing Bacillus licheniformis bio-probes as a promising approach for detection of Cu2+ in complex solution environment.
Asunto(s)
Bacillus licheniformis/metabolismo , Compuestos de Cadmio , Cobre/análisis , Puntos Cuánticos/metabolismo , Puntos Cuánticos/microbiología , Compuestos de Selenio , Agua/análisis , Colorantes Fluorescentes/química , Límite de Detección , Puntos Cuánticos/ultraestructura , Espectrometría de Fluorescencia , Contaminantes Químicos del Agua/análisisRESUMEN
We demonstrate highly antibacterial activities for killing off Staphylococcus aureus and Escherichia coli using ZnO nanowires decorated with ZnO quantum dots (so-called ZnO QDs/NWs) under visible-light irradiation and dark conditions. The average size of the ZnO QDs is in the range of 3-5 nm; these were uniformly dispersed on the ZnO nanowires' surface to form the ZnO QDs/NWs. A significant blue-shift effect was observed using photoluminescence (PL) spectra. The size of the ZnO QDs is strongly dependent on the material's synthesis time. The ZnO QDs/NWs exhibited an excellent photocatalytic activity under visible-light irradiation. The ZnO QDs' active sites (i.e. the O-H bond and Zn(2+)) accelerate the photogenerated-carrier migration from the QDs to the NWs. As a consequence, the electrons reacted with the dissolved oxygen to form oxygen ions and produced hydroperoxyl radicals to enhance photocatalytic activity. The antibacterial activities (as indicated by R-factor-inhibiting activity) of the ZnO QDs/NWs for killing off Staphylococcus aureus and Escherichia coli is around 4.9 and 5.5 under visible-light irradiation and dark conditions, respectively. The hydroxyl radicals served as an efficient oxidized agent for decomposing the organic dye and microorganism species. The antibacterial activities of the ZnO QDs/NWs in the dark may be attributed to the Zn(2+) ions that were released from the ZnO QDs and infused into the microbial solution against the growth of bacteria thus disrupting the microorganism. The highly antibacterial and photocatalytic activity of the ZnO QDs/NWs can be well implanted on a screen window, thus offering a promising solution to inhibit the spread of germs under visible-light and dark conditions.
Asunto(s)
Antibacterianos/síntesis química , Nanocables/química , Procesos Fotoquímicos , Puntos Cuánticos/química , Óxido de Zinc/química , Antibacterianos/administración & dosificación , Escherichia coli/efectos de los fármacos , Escherichia coli/ultraestructura , Nanocables/microbiología , Tamaño de la Partícula , Puntos Cuánticos/microbiología , Staphylococcus aureus/efectos de los fármacos , Staphylococcus aureus/ultraestructura , Óxido de Zinc/administración & dosificaciónRESUMEN
Metal monochalcogenide quantum dot nanocrystals of ZnS, CdS and SnS were prepared by anaerobic, metal-reducing bacteria using in situ capping by oleic acid or oleylamine. The capping agent preferentially adsorbs on the surface of the nanocrystal, suppressing the growth process in the early stages, thus leading to production of nanocrystals with a diameter of less than 5 nm.