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Developing an efficient approach to decompose ground-level O

The accumulation of antibiotics in river watersheds and lakes could induce the spread of antibiotic-resistance genes in drinking water, causing damage to human health. An OH equipment, that produces OH by strong ionization discharge combined with water jet cavitation effect, was installed in a drinking water treatment system of 12,000 m3 per day in Xiang’an water plant, Xiamen of China. The NFX as a model antibiotic was mixed into a branched pipe at a flow rate of 1.0 m3 h−1 for OH mineralization. As a result, the OH after coagulation sedimentation at 1.0 mg L−1 and after sand filtration at 0.5 mg L−1 degraded NFX to not detected within only 20 s. Moreover, the OH mineralizes the NFX into CO2 and H2O by breaking the C F bond, and opening the piperizine, nalidixic, and benzene rings, while NaClO only opens the piperizine ring and adversely forms chlorinated intermediates. By OH disinfection at 0.5 mg L−1 in the main pipe of 500 m3 h−1, all algae blooms were inactivated; the tests of 106 drinking water quality indicators satisfied the Chinese Standards; any disinfection by-products, such as bromate and trihalomethanes (THMs) were not be detected. By NaClO disinfection, the total THMs increased to 190 μg L−1, which is 2.4 times higher than the limit regulated by Environmental Protection Agency (80 μg L−1). To prevent the spread of antibiotic-resistance genes in humans, OH advanced oxidation based on strong ionization discharge could be apply to mineralize antibiotics during practical drinking water treatment.

Nanocrystal superlattices are typically fabricated by either solvent evaporation or destabilization methods that require long time periods to generate highly ordered structures. In this paper, we report for the first time the use of electric fields to reversibly drive nanocrystal assembly into superlattices without changing solvent volume or composition, and show that this method only takes 20 min to produce polyhedral colloidal crystals, which would otherwise need days or weeks. This method offers a way to control the lattice constants and degree of preferential orientation for superlattices and can suppress the uniaxial superlattice contraction associated with solvent evaporation. In situ small-angle X-ray scattering experiments indicated that nanocrystal superlattices were formed while solvated, not during drying.

The structure of nanocrystal superlattices has been extensively studied and well documented, however, their assembly process is poorly understood. In this work, we demonstrate an in situ space- and time-resolved small angle X-ray scattering measurement that we use to probe the assembly of silver nanocrystal superlattices driven by electric fields. The electric field creates a nanocrystal flux to the surface, providing a systematic means to vary the nanocrystal concentration near the electrode and thereby to initiate nucleation and growth of superlattices in several minutes. Using this approach, we measure the space- and time-resolved concentration and polydispersity gradients during deposition and show how they affect the superlattice constant and degree of order. We find that the field induces a size-selection effect that can reduce the polydispersity near the substrate by 21% leading to better quality crystals and resulting in field strength-dependent superlattice lattice constants., How nanocrystals assemble into superlattices is poorly understood, given the difficulty of probing these processes in real time, in a controlled environment. Here, the authors use space- and time-resolved in situ small angle X-ray scattering to monitor the ordering of nanocrystal superlattices by electric field, which allows them to extract quantitative information about the assembly process.

Two families of strongly luminescent silicon nanocrystals (SiNCs) cofunctionalized with dodecyl chains and pyrene chromophores perform as light-harvesting antennae and interact with carbon allotropes. The energy harvested in the SiNC core can thus be used to populate, for example, the lowest triplet excited state of C-60.

Auger recombination lifetimes, absorption cross sections, and the quantum yields of carrier multiplication (CM), or multiexciton generation (MEG), were determined for solvent-dispersed silicon (Si) nanorods using transient absorption spectroscopy (TAS). Nanorods with an average diameter of 7.5 nm and aspect ratios of 6.1, 19.3, and 33.2 were examined. Colloidal Si nanocrystals of similar diameters were also studied for comparison. The nanocrystals and nanorods were passivated with organic ligands by hydrosilylation to prevent surface oxidation and limit the effects of surface trapping of photoexcited carriers. All samples used in the study exhibited relatively efficient photoluminescence. The Auger lifetimes increased with nanorod length, and the nanorods exhibited higher CM quantum yield and efficiency than the nanocrystals with a similar band gap energy Eg. Beyond a critical length, the CM quantum yield decreases. Nanorods with the aspect ratio of 19.3 had the highest CM quantum yield of 1.6 ± 0.2 at 2....

Silicon nanorods are grown by trisilane decomposition in hot squalane in the presence of tin (Sn) nanocrystals and dodecylamine. Sn induces solution-liquid-solid nanorod growth with dodecylamine serving as a stabilizing ligand. As-prepared nanorods do not luminesce, but etching with hydrofluoric acid to remove residual surface oxide followed by thermal hydrosilylation with 1-octadecene induces bright photoluminescence with quantum yields of 4-5%. X-ray photoelectron spectroscopy shows that the ligands prevent surface oxidation for months when stored in air.

Silicon nanocrystals with an average diameter of 5nm and functionalized with 4,7-di(2-thienyl)-2,1,3-benzothiadiazole chromophores (TBT) and dodecyl chains exhibit near-infrared emission upon one-photon (1P) excitation at 515nm and two-photon (2P) excitation at 960nm. By using TBT chromophores as an antenna, we were able to enhance both 1P and 2P absorption cross-sections of the silicon nanocrystals to more efficiently excite their long-lived luminescence. These results chart a path to 2P-excitable imaging probes with long-lived oxygen-independent luminescence, a rare combination of properties that should allow for a substantial increase in imaging contrast.

Silicon (Si) nanocrystals are relatively strong light emitters, but are weak light absorbers as a result of their indirect band gap. One way to enhance light absorption is to functionalize the nanocrystals with chromophores that are strong light absorbers. By designing systems that enable efficient energy transfer from the chromophore to the Si nanocrystal, the brightness of the nanocrystals can be significantly increased. There have now been a few experimental systems in which covalent attachment of chromophores, efficient energy transfer and significantly increased brightness have been demonstrated. This review discusses progress on these systems and the remaining challenges.

Herein, we report the direct synthesis of micro–mesoporous silicas using unsaturated anionic surfactant α-linolenic acid as mesophase template. The self-assembly of α-linolenic acid, which could transform to a rigid mesophase template via inner-micellar polymerization when heated, was successfully leveraged to fabricate hydrothermally stable mesoporous silicas at high temperature, which retained a BET surface area of 678 m2 g−1 after hydrothermal treatment in boiling water for 5 days. Different analysis methods, e.g. X-ray diffraction, nitrogen physisorption, the non-local density functional theory (NLDFT) analysis and transmission electron microscopy, were employed to investigate the mesostructure of as-synthesized samples, which revealed a micro- and mesopores hybrid in one phase. 1H NMR was applied to characterize the α-linolenic acid micellar structure and confirmed that C C bonds have been opened up and polymerization occurred within micelles. The 29Si MAS NMR spectra indicated Q4 silicon is the dominating species, which explains well the high hydrothermal stability of the materials.

This is an open access article published under an ACS AuthorChoice License.-- et al., Uniform silicon nanocrystals were synthesized with cuboctahedral shape and passivated with 1-dodecene capping ligands. Transmission electron microscopy, electron diffraction, and grazing incidence wide-angle and small-angle X-ray scattering show that these soft cuboctahedra assemble into face-centered cubic superlattices with orientational order. The preferred nanocrystal orientation was found to depend on the orientation of the superlattices on the substrate, indicating that the interactions with the substrate and assembly kinetics can influence the orientation of faceted nanocrystals in superlattices., This research was funded by the Robert A. Welch Foundation (Grant F-1464 and F-1696) and the National Science Foundation (Grant CBET-1403768). CHESS is supported by the NSF & NIH/NIGMS via NSF award DMR-1332208. J.A. and M.d.l.M. acknowledge funding from Generalitat de Catalunya 2014 SGR 1638 and MINECO projects MAT2014-59961-C2-2-R and Severo Ochoa Program (Grant SEV-2013-0295).

The preparation of large MCM-41 single crystals as well as their controllable morphologies has very important meanings not only for their potential applications but also for the exploration of the new morphogenetic mechanism for some special mesoporous crystals. In this paper, a novel crystal form of hexagonal circular bicone of MCM-41 crystal, which is the combination form of thee hexagonal bipyramid and circular bicone forms, has been observed. The MCM-41 single crystals which originally remained the same can grow larger to nearly ∼10 micron via multiple-growth in extremely diluted ammonia solution, and were characterized by SEM, POM, TEM, XRDetc. The morphology of the MCM-41 crystal can also be controllably modulated by adding alkali salts to the synthetic system. Increasing the concentration of KCl can cause the aspect ratio and the conical angle to increase consistently and the result displays monotonicity with a certain statistical deviation. A fluctuation effect has an influence on the surface energy and eventually leads to the evolution from a single crystal to one with non-crystalline characteristics.