Preparation and photoluminescence investigation of the LaPO4:Eu3+ inverse opal structure.

The inverse opal LaPO4:Eu3+ was successfully fabricated by the sol-gel method, and characterized by the scanning electron microscopy, transmission electron microscopy, X-ray diffraction (XRD), and photoluminescence investigations. The inverse opal LaPO4:Eu3+ sample has a different emission in comparison with the ordinary luminescence emission bands of Eu3+ ion at 590, 615, and 695 nm. In the inverse opal structure, the strongest emission is the transition 5D0→7F4 at about 695 nm, which may be due to the fact that the emission in the plane decreases because of the photonic band structure and the corresponding emission in the vertical direction increases. For the emissions at 590 and 615 nm of the Eu3+, the results show that the emission ratio of 590 to 615 nm increases from 0.266 to 0.639 for the inverse opal sample in comparison with the ordinary sample, which means that the ratio increases about 2.4 times for the inverse opal sample. An appropriate reason is that in the inverse opal sample the magnetic dipole emission 5D0→7F1 will increase in comparison with the electric dipole emission 5D0→7F2.

Cu3BiS3/MXenes with Excellent Solar-Thermal Conversion for Continuous and Efficient Seawater Desalination.

Two-dimensional materials with unique physical and chemical properties have recently attracted widespread attention in the field of solar thermal conversion. However, affected by the Fresnel effect, traditional two-dimensional materials such as MXenes, graphene, transition metal disulfide often have relatively significant light reflection losses at the solid-liquid or gas interface. So how to improve the light absorption of the two-dimensional material performance has become a new challenge in photothermal conversion. Here, we use an improved thermal-injection method to uniformly grow Tricopper(I) Bismuth Sulfide (Cu3BiS3, CBS) on the surface of Ti3C2 nanosheets in a nonaqueous polar solvent environment. A three-dimensional nanoflower-nanosheet structure CBS-Ti3C2 for photothermal conversion has been constructed successfully. Owing to the excellent photothermal performance of Cu3BiS3 in the near-infrared region, the good thermal conductivity of Ti3C2, and the unique porous structure of the composite material, the composite achieves broadband absorption of light (more than 90% in the visible light region, more than 80% in the near-infrared region), which optical model and finite element simulation have theoretically verified. The composite material has obtained higher solar-to-heat conversion performance than similar material systems, and the steady-state temperature can reach 62.3 °C under 1 sun incident light intensity. CBS-Ti3C2 is expected to become a light-absorbing layer material for solar vapor generation devices due to its excellent light-to-heat conversion performance and good material flexibility. It still guarantees a reasonably high steam generation rate (1.32 kg·m-2·h-1) even with a thinner material thickness (0.48 mg·cm-2) and a comprehensive conversion efficiency higher than 90%. Besides, CBS-Ti3C2 also exhibits the characteristics of resisting surface salt accumulation, which is conducive to maintaining the long-lasting photothermal seawater evaporation process. The material's electronic structure and the charge transfer process of the heterojunction interface have been studied with the first-principles calculation. The high light absorption performance and good thermal conductivity of the composite material are theoretically explained and supported.

TM and TE propagating modes of photonic crystal waveguide based on honeycomb lattices.

The waveguide based on the honeycomb photonic crystal has propagating modes for both the TE and TM polarizations. The group index-normalized frequency curves are U-shaped for the two polarizations. The average group index of the TE mode is approximately 3, while the average group index of the TM mode is over 10, which implies that the TM mode is a slow light mode. With the shift value 0 ≤ δx ≤ 0.025a, the group index is over 10 and the normalized delay-bandwidth product is from 0.316 to 0.349, which is ideal for the slow light mode of the TM polarization. In the group velocity dispersion of the waveguide, there is a very large "zero" dispersion region for both the TM and TE modes, which is far larger than that of other photonic crystal waveguides. The TM mode of this kind of waveguide structure is a slow light mode with wide bandwidth and a large "zero" dispersion region.

Photoluminescence eigenmodes in a single ZnO nanobelt covering the ultraviolet and visible band.

The photoluminescence properties of a ZnO nanobelt are investigated. Both the band-edge emission and the green-yellow emission bands have a series of eigenmodes. The theoretical results demonstrate that in the band-edge emission region the photoluminescence modes are determined by the polariton modes. In the green-yellow band there is no coupling between the photons and excitons and the photoluminescence modes are determined by the transverse Fabry-Perot modes. The photoluminescence spectra at different spots confirm that the Fabry-Perot modes are determined by the transverse size. Furthermore, the fitting results show in the waveband in the ultraviolet and visible band the quality-factor Q of the cavity is decreased from 280 to 70 with the increase of the wavelength.