Nanoparticle vesicles were spontaneously assembled from homopolymer polyamine polyelectrolytes and water-soluble, citrate-stabilized quantum dots. The further addition of silica nanoparticles to a solution of quantum dot vesicles generated stable micrometer-sized hollow spheres whose walls were formed of a thick, inner layer of close-packed quantum dots followed by an outer layer of silica. The method employed here to assemble both the nanoparticle vesicles and the hollow spheres is in direct contrast to previous syntheses that use either tailored block copolymers or oil-in-water emulsion templating. We propose that the formation of charge-stabilized hydrogen bonds between the positively charged amines of the homopolymer polyelectrolytes and the negatively charged citrate molecules stabilizing the quantum dots is responsible for the macroscopic phase separation in this completely aqueous system. The ease and processibility of the present approach gives promise for the production of a diverse array of materials ranging in applications from drug delivery to catalysis to micrometer-scale optical devices. 相似文献
We report a tunable stimulated-Brillouin-scattering resonator that does not require a starting mirror or a wavelength selector. The resonator is based on the Bragg scattering from the dynamic grating within the active medium itself. The laser dye (Rhodamine 6G dissolved in ethanol) was utilized as the active medium and was pumped by a frequency-doubled Nd:YAG laser. The quality factor (M(2)) of the output beam was 2.2. A single short pulse (<1 ns) with a pumping efficiency of ~4% was observed. 相似文献
A stereoselective synthesis of cyathin A3 and cyathin B2 has been achieved by a Prins‐type reaction of a cycloalkenyl cyclopropanol. Particularly noteworthy is the use of a spirocyclobutanone moiety as a convenient scaffold for an efficient ring‐closing metathesis to stereoselectively construct a suitably functionalized seven‐membered ring (see scheme).
It is known that CdTe solar cells are often degraded under solar illumination. But the degradation mechanism is not fully proved because it does not appear consistently. The junction degradation in CdS/CdTe solar cells was investigated using a CdTe layer with Cd deficient composition, where Cd vacancy concentration is high. It was found that the Cu atoms easily filled the Cd vacancies in CdTe and transport to junction area from Cu back contact. PL measurement and spectral quantum efficiency measurement showed that the incorporation of Cu atoms in CdS forms a defect energy level at 1.55 eV below the conduction band in CdS. As a result, the junction built-in potential is decreased and light penetration into CdTe absorber is shielded. For reliable and stable CdTe cells, the formation of Cd vacancy in CdTe should be avoided by careful control of CdTe. 相似文献
Nb2O5/C nanosheets are successfully prepared through a mixing process and followed by heating treatment.Such Nb2O5/C based electrode exhibits high rate performance and remarkable cycling ability, showing a high and stable specific capacity of ~380 mAh g-1 at the current density of 50 mA g-1(much higher than the theoretical capacity of Nb2O5).Further more,at a current density of 500 mA g-1,the nanocomposites electrode still exhibits a specific capacity of above 150 mAh g-1 after 100 cycles.These results suggest the Nb2O5/C nanocomposite is a high performance anode material for lithium-ion batteries. 相似文献
During wastewater treatment, phosphate removal is an important and challenging process; thus, diverse technologies, including those derived from biological means, have been devised for efficient phosphate removal. Although conventional biological methods are effective in decreasing wastewater phosphate levels to ~1 mg/L, long periods of microbial adaptation are required for effective phosphate removal, and the removal efficiency of these methods is relatively poor at lower phosphate concentrations. In the present work, we constructed a recombinant Escherichia coli with periplasmic-expressed phosphate-binding protein (PBP) and investigated its biological removal ability for low phosphate levels. We found that the PBP-expressing recombinant E. coli cells showed efficient (> 94 %) removal of phosphate at low concentrations (0.2–1.0 mg/L) in a treated cell mass-dependent manner. Collectively, we propose that our PBP-expressing recombinant whole-cell system could be successfully used during wastewater treatment for the biological removal of low concentrations of phosphate. 相似文献