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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.

Photoluminescence (PL) spectra were measured for dodecene-capped Si nanocrystals with a wide range of average diameters, from 1.8 to 9.1 nm. Nanocrystals larger than 3 nm exhibited relatively high PL quantum yields of 30%−45%. Smaller nanocrystals exhibited lower quantum yields that decreased significantly with reduced size. Because smaller nanocrystals also have lower optical absorption there is a significant biasing of the PL spectra by the larger nanocrystals. We show that with proper accounting of polydispersity and size- dependent quantum yields and optical absorption the effective mass approximation (EMA) accurately estimates the average diameter of silicon (Si) nanocrystals from experimentally determined PL emission peak energies. A finite confinement model is presented that explains the decreased PL quantum yields of the smaller diameter nanocrystals.

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.

We recently observed that a disordered assembly of octadecanethiol-capped gold (Au) nanocrystals can order when heated from room temperature to 60 °C [Yu, Y.; Jain, A.; Guillaussier, A.; Voggu, V. R.; Truskett, T. M.; Smilgies, D.-M.; Korgel, B. A. Faraday Discuss. 2015, 181, 181–192]. This “inverse melting” structural transition was reversible and occurred near the melting-solidification temperature of the capping ligands. To determine the generality of this phenomenon, we studied by in situ grazing incidence small-angle X-ray scattering (GISAXS) the structure of assemblies of Au nanocrystals with shorter C12 and C5 alkanethiol capping ligands that form ordered superlattices at room temperature and have a ligand melting-solidification temperature below room temperature. Superlattices of dodecanethiol-capped Au nanocrystals disorder when cooled below 260 K, which is the melting-solidification temperature for dodecanethiol. Au nanocrystals capped with even shorter pentanethiol ligands that have a melting t...

Plastic photovoltaic devices (PVs) were fabricated by spray-depositing copper indium diselenide (CuInSe2) nanocrystals into micrometer-scale groove features patterned into polyethylene terephthalate (PET) substrates. Each groove has sidewall coatings of Al/CdS and Au and performs as an individual solar cell. These PV groove features can be linked electrically in series to achieve high voltages. For example, cascades of up to 15 grooves have been made with open-circuit voltages of up to 5.8 V. On the basis of the groove geometry, the power conversion efficiencies (PCEs) of the devices reached as high as 2.2%. Using the active area and photovoltaic response of devices determined from light-beam-induced current (LBIC) and photoreflectivity measurements gave PCE values as high as 4.4%.

Biomedical degradable polymer materials are widely used in medicine because of their excellent mechanical properties and degradation properties. The matching of strength change and degradation rate in the degradation process is a crucial consideration in the design of polymer devices. Establishing a strength model of the polymer degradation process can quantify the intensity evolution during the degradation process. In this research, the structural changes in the process of polymer erosion degradation are taken as the primary consideration, and the evolution of the phases of strength are reflected by the changes of structure. The concept of strength phase images is proposed. The images of the strength phase diagram are identified by the image processing method. The Near Neighbor-Boundary Enlargement Algorithm (NNBE) is put forward to identify features with the hole(block) and crack(strip) shape patterns. The strength model for different phase patterns is established. The model calculation is compared with the experimental data, and the model simulation value and the experimental value are well fitted, which indicates that the strength model and phase diagram feature extraction algorithm are feasible.

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.

A method was developed to create free-standing nanocrystal films in the form of solidified bubbles. Bubbles of octadecanethiol-capped gold nanocrystals were studied by in situ grazing incidence small-angle X-ray scattering (GISAXS) to determine how the absence of an underlying substrate influences a disorder–order transition of a nanocrystal superlattice. We find that the presence of the substrate does not significantly change the nature of the disorder–order transition but does lead to reduced interparticle separation and reduced thermal expansion. Bubble assemblies of silicon and copper selenide nanocrystals are also demonstrated.

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 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.

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).