Oxygen vacancy engineering of ultra-small CuWO4 nanoparticles for boosting photocatalytic organic pollutant degradation.

Nanomaterials have attracted great interest in the field of photocatalytic degradation due to their larger specific surface area and efficient charge/mass transfer ability, which are beneficial for enhancing photocatalytic activity. However, the bandgap of photocatalysts would increase with the size reduction, weakening the photoabsorption ability. Thus the relationship between the size of catalysts and photoactivity should be balanced to achieve optimal photocatalytic performance. Herein, ultra-small CuWO4 nanoparticles (ca. 39 nm) with moderate oxygen vacancies (CuWO4-OVs) were synthesized by the cascade strategy (ligand confinement@fast calcination). The introduction of oxygen vacancies offset the deficiency of light absorption ability caused by the small size effect. Besides, oxygen vacancies could provide more reaction active sites, conducive to the adsorption and activation of dye molecules and H2O. Degradation experiments reveal that the optimized photocatalyst CuWO4-OVs 350 shows outstanding photocatalytic activity, and the removal ratio of methylene blue (MB) reaches over 90.26% in 70 min, exceeding that of pure CuWO4-air (37.66%). Additionally, the degradation performance of CuWO4-OVs 350 surpasses most of the other CuWO4-based photocatalytic systems. More importantly, the photocatalytic degradation activity of CuWO4-OVs 350 could remain at 88.26% even after five cycles, and high photostability was achieved. This work affords constructive inspiration for synergistic photoactivity enhancement and increase of catalyst reaction active sites to achieve eminent photocatalytic degradation performance.

Symmetry Breaking Enhancing the Activity of Electrocatalytic CO2 Reduction on an Icosahedron-Kernel Cluster by Cu Atoms Regulation.

Recently, CO2 hydrogenation had a new breakthrough resulting from the design of catalysts to effectively activate linear CO2 with symmetry-breaking sites. However, understanding the relationship between symmetry-breaking sites and catalytic activity at the atomic level is still a great challenge. In this study, a set of gold-copper alloy Au13 Cux (x=0-4) nanoclusters were used as research objects to show the symmetry-controlled breaking structure on the surface of nanoclusters with the help of manipulability of the Cu atoms. Among them, Au13 Cu3 nanocluster displays the highest degree of symmetry-breaking on its crystal structure compared with the other nanoclusters in the family. Where the three copper atoms occupying the surface of the icosahedral kernel unevenly with one copper atom is coordinately unsaturated (CuS2 motif relative to CuS3 motif). As expected, Au13 Cu3 has an excellent hydrogenation activity of CO2 , in which the current density is as high as 70 mA cm-2 (-0.97 V) and the maximum FECO reaches 99 % at -0.58 V. Through the combination of crystal structures and theoretical calculations, the excellent catalytic activity of Au13 Cu3 is revealed to be indeed closely related to its asymmetric structure.

Ultracompact Implantable Design With Integrated Wireless Power Transfer and RF Transmission Capabilities.

This paper presents an ultracompact design of biomedical implantable devices with integrated wireless power transfer (WPT) and RF transmission capabilities for implantable medical applications. By reusing the spiral coil in an implantable device, both RF transmission and WPT are realized without the performance degradation of both functions in ultracompact size. The complete theory of WPT based on magnetic resonant coupling is discussed and the design methodology of an integrated structure is presented in detail, which can guide the design effectively. A system with an external power transmitter and implantable structure is fabricated to validate the proposed approach. The experimental results show that the implantable structure can receive power wirelessly at 39.86 MHz with power transfer efficiency of 47.2% and can also simultaneously radiate at 2.45 GHz with an impedance bandwidth of 10.8% and a gain of -15.71 dBi in the desired direction. Furthermore, sensitivity analyses are carried out with the help of experiment and simulation. The results reveal that the system has strong tolerance to the nonideal conditions. Additionally, the specific absorption rate distribution is evaluated in the light of strict IEEE standards. The results reveal that the implantable structure can receive up to 115 mW power from an external transmitter and radiate 6.4 dB·m of power safely.

Analyses of negative refraction in the partial bandgap of photonic crystals.

We consider the conditions for negative refraction in the partial bandgap of photonic crystals and show that, in contrast to previously published studies, anisotropy is not a necessary condition for negative refraction, and that unrestricted imaging is possible. This analysis is made possible by the introduction of a negative local wavevector. In addition, we analyze the origins of the previously reported restricted and adjacent imaging properties and extend negative refraction to higher bands.

On the relationship between Bloch modes and phase-related refractive index of photonic crystals.

It has previously been shown that the phase-related refractive index is positive in photonic crystals that display negative refraction at higher bands. We hypothesize that the phase velocity is governed by a wave that can be related to the dominant Bloch mode. This dominant wave can be identified from an approximate solution of Maxwell Equations using a homogeneously averaged dielectric constant and the dominant wavevector is related to the fundamental wavevector and the reciprocal lattice vectors. We validate this hypothesis by numerical Fourier decomposition of the field in the entire simulation domain. It confirms that for negative refraction at higher bands, the phase-related refractive index is indeed positive and differs significantly from the negative value of effective refractive index calculated from the band structure.

Imaging properties of dielectric photonic crystal slabs for large object distances.

We extend the understanding of the imaging properties of dielectric photonic crystal slabs to object distances that are larger than the slab thickness. We specifically consider hexagonal crystal lattices in the second band. For object distances smaller than the slab thickness, the image distance is a negative linear function of the object distance as expected for negative refractive index materials. The effective refractive index extracted from this linear object-image relation is close to the negative unity value calculated for infinite photonic crystal using the plane wave expansion method. In contrast to previous predictions, we find that a real image can still be formed for object distances up to twice the slab thickness. In this regime the image distance changes little as the object distance increases, and can thus be described as the saturated image regime. Sub-wavelength resolution performance can be approximately maintained even for these larger object distances. The full-width half-maximum spot size at the image is approximately (0.43-0.55)lambda up to object distances 1.5 times the slab thickness. By evaluating the image angular frequency spectrum we show that this sub-wavelength resolution imaging at larger object distances is due to evanescent waves that arise within the slab, rather than being directly transferred from the object. The eventual loss of image resolution is due to interference side lobes which enter the image plane.

[Screening serum response special antibodies of U251 cell line from surface display phage antibody library].

U251 cell is a sensitive cell line to serum, which stops at G0 phase of cell cycle in no-serum medium, and recovers growth when the serum is added into no-serum medium. The cell can express corresponding proteins in different phase of cell cycle. Therefore it is very signification for the study of cell cycle regulation mechanism that explores these proteins. In this paper, the mouse antibody phage display library was added into the bottle in which the serum starvation U251 cells had been cultured, and the special antibody phages were absorbed. Then the absorbed antibody phages were amplified by adding E. coli TG1 and helper phage M13K07. Amplified antibody phages were added into bottle in which the serum cultured cell after serum starvation (follow named as serum recovered cells) were incubated, so that the cell absorbed the no-special antibody phages for the serum starvation cell and the special antibody phages were in supernatant. The remaining no-special antibody phages in the supernatant were discarded by repeating above program 3-4 times. The pure special antibody phages were gotten, and amplified by adding the host cell E. coli TG1 and helper phage M13K07. Then the host bacterium infected special antibody phage was spread on the plate medium with ampicillin, and the monoclonal antibody phages were gotten. Using same as above program, the monoclonal antibody phages absorbed specially for serum recovered U251 cells were obtained when the serum recovered cells instead of serum starvation cells and serum starvation cells instead of serum recovered cells. In this study, ninety-six positive monoclonal antibody phages that absorbed specially the serum starvation cells and eighty-two positive monoclonal antibody phages that absorbed specially the serum recovered cells were obtained. By using cell immunochemistry assay, two special signification antibodies were obtained. one (No.11) was the strong response in serum starvation cells, the other (No.2) was the strong response in serum recovered cells. The antibody No.2 had the distinctive response to the serum recovered cells in different incubation time (15min, 30min, 1h, 2h, 4h, 8h, 12h and 48h) after serum starvation. The results showed that No.2 antibody would be useful to research the factors of cell cycle regulation and apply to tumor diagnosis.