As a photoelectric material, the luminescent efficiency improvement of organic–inorganic perovskite material is a hot topic. This work fabricated a nanoporous distributed Bragg reflector based on GaN with a periodic structure using electrochemical etching methods. Considering the fact that hybrid perovskite materials are difficult to prepare on an inorganic GaN-based substrate, ultraviolet ozone treatment was implemented to enhance the surface activity of the prepared distributed Bragg reflector substrate. Cubic CH₃NH₃PbBr₃ crystals with smooth surfaces and precise edges were successfully prepared on the ozone-treated distributed Bragg reflector substrate by a two-step immersion method in the air environment. The structural property of the prepared CH₃NH₃PbBr₃ crystals was investigated using X-ray diffraction, scanning electron microscopy and Fourier-transform infrared spectroscopy. The structural analysis results showed that CH₃NH₃PbBr₃ crystals grown on the prepared distributed Bragg reflector and reference substrates have the same structure, with a good crystal quality. The photoluminescence intensity of CH₃NH₃PbBr₃ crystals grown on the distributed Bragg reflector was significantly enhanced. The enhancement is approximately 3.11-fold compared with CH₃NH₃PbBr₃ crystals grown on the unetched reference GaN substrate. Moreover, there is a 7.2 nm spectral blue shift. The enhancement of the photoluminescence intensity could be attributed to the out-coupling of emission light in the prepared crystals, and the blue shift could be attributed to the stress relaxation caused by the nanoporous GaN structure of the distributed Bragg reflector substrate.

The magnetic properties of π-conjugated bis (8-hydroxyquinoline) manganese (Mnq₂) crystals are investigated. Rod-shaped Mnq₂ crystals are prepared by using the physical vapor deposition method. Field emission scanning electronic microscopy spectra show that the Mnq₂ nanorods have perfect plane quadrangular ends. Energy dispersive spectrometer and X-ray photoelectron spectroscopy analysis demonstrates that the powders and nanorods are the same compound with a high purity. X-ray diffraction analysis shows the high crystal quality of the prepared Mnq₂ nanorods. The magnetic measurement, using alternating gradient magnetometer and magnetic property measurement system superconducting quantum interference device vibrating sample magnetometer, indicates that the prepared Mnq₂ nanorods show a paramagnetic property at room temperature. First-principles density functional theory (DFT) calculations are used to study the electronic structure and magnetic properties of the prepared Mnq₂ crystals. DFT calculations show that the magnetic moment of the Mnq₂ isolated molecule is 5 μ_B, which mainly comes from the localized Mn 3d orbital. The energy difference between the antiferromagnetic and ferromagnetic states of the Mnq₂ monoclinic cell is only 0.1 meV, which may explain the paramagnetic property observed in the prepared Mnq₂ nanorods and also indicates the difficulty of preparing intrinsic ferromagnetic Mnq₂ crystals.

The varying effects of temperature on SERS and plasmon-induced catalysis have been demonstrated with experimental methods.

As a new type of solar cell material that has attracted much attention, how to improve the environmental stability and photoluminescence property of organic-inorganic hybrid perovskite materials for large-scale commercial applications is a core issue. This work studied the effect of Br-doping and nanoporous GaN substrate on the environmental stability and photoluminescence property of CH₃NH₃PbI₃ film. The nanoporous GaN substrate was prepared by electrochemical etching method. The CH₃NH₃PbI₃ and CH₃NH₃PbI_xBr_3−x films were prepared by the spin coating/CVD method. Then the prepared CH₃NH₃PbI₃ and CH₃NH₃PbI_xBr_3−x films were exposed to the natural environment for different time without any protective measures to investigate the effect of Br doping on the environmental stability of the CH₃NH₃PbI₃ films. The morphology and structure of the two prepared films were investigated by using scanning electron microscopy, X-ray photoelectron spectrometer, and X-ray diffractometer. The result of X-ray photoelectron spectrometer showed that the I/Br ratio of the CH₃NH₃PbI_xBr_3−x film is approximately 2. The results of scanning electron microscopy and X-ray diffractometer showed that Br-doping significantly enhances the anti-degradation ability of the film. The result of photoluminescence spectroscopy showed that both Br-doping and nanoporous GaN substrate can increase the photoluminescence intensity of the CH₃NH₃PbI₃ film.