optical properties

摘要： Radiative cooling can achieve cooling effect without consuming any energy by delivering energy into outer space(3K) through"atmospheric window"(8–13 μm). Conventional radiative cooling coating with multi-layer structure was severely restricted during application due to its complex preparation process and high cost. In this study, a single-layer radiative cooling coating with mixture of TiO_(2) particles and SiO_(2) particles was proposed. The algorithm for calculating the radiative properties of the multi-particle system was developed. Monte Carlo ray-tracing method combined with that algorithm was used to solve the radiative transfer equation(RTE) of the single-layer radiative cooling coating with mixture of TiO_(2) particles and SiO_(2) particles.The effects of particle diameter, volume fraction and coating thickness on radiative cooling performance were analyzed to obtain the best radiative cooling performance. The numerical results indicated that the average reflectivity of the single-layer radiative cooling coating with mixture of TiO_(2) particles and SiO_(2) particles in the solar spectrum can reach 95.6%, while and the average emissivity in the "atmospheric window" spectrum can reach 94.9% without additional silver-reflectance layer. The average reflectivity in the solar spectrum and average emissivity in the "atmospheric window" spectrum of the single-layer radiative cooling coating with mixture of TiO_(2) particles and SiO_(2) particles can increase 4.6% and 4.8% compared to the double-layer radiative cooling coating. This numerical research results can provide a theoretical guidance for design and optimization of single-layer radiative cooling coatings containing mixed nanoparticles.

摘要： Two-dimensional(2D)black arsenic phosphorus(b-AsP),as an alloy of black phosphorus(bP)with arsenic,has attracted great attention because of its outstanding electronic and optical properties,including high carrier mobility,tunable bandgap and in-plane anisotropy.B-AsP has a smaller bandgap(0.15–0.3 eV)than the b-P bandgap(0.3–2.0 eV),and thus can be used for mid-infrared photodetectors.In addition,both of them can form various van der Waals(vdW)heterojunctions with other 2D materials to realize novel functional optoelectronic devices.Here,we compare the basic characteristics of b-AsP and b-P,including crystal structure,optical properties,band structure,electrical properties and stability,and we summarize the update progress of b-AsP in photo detection,including representatives of phototransistor and photodiode devices.In the last part,the future research directions are discussed.

摘要： SnO_(2)-ZnO thin films consisting of nanoscale crystallites were obtained on glass and silicon substrates by solid-phase low-temperature pyrolysis.The synthesized materials were studied by XRD and SEM methods,electrophysical and optical properties were evaluated,as well as the band gap was calculated.It was shown that regardless of the phase composition all films were optically transparent in the visible range(310-1000 nm).The nanocrystallites’minimum size,the highest activation energy of the conductivity and the smallest band gap calculated for indirect transitions were shown for a thin film 50SnO_(2)-50ZnO.It was assumed that the band gap decreasing might be attributed to the existence of surface electric fields with a strength higher than 4×10^(5)V/cm.

摘要： The optical properties of polymethyl methacrylate(PMMA)with varying degrees of artificial scratches have been studied with the aim of reproducing the change of visibility of an aircraft’s PMMA optical windows after being damaged in their service environment.A novel maintenance method that can perfectly restore the optical property of PMMA has been identified and employed in the repair of the scratches that are formed on the surface of PMMA.This convenient and low-cost method entails polishing PMMA with different types of sandpaper to remove the scratches,and then spin-coating the repair solution in order to restore the optical properties of PMMA.The effect of this repair mechanism and parameters of the repair process were studied.The results indicated that the optical performance of PMMA is closely related to the mesh size of sandpaper,and improper parameter selection destroys the general effect of the repair.When the number of sandpaper mesh is low,the size of the abrasive particle is relatively larger,which can cause deeper friction marks on the surface of PMMA optical windows.Surface treatment using 5000 mesh sandpaper lowers surface roughness(R——a=0.566 nm),and optical transmittance in visible range can be restored to more than 88%.

摘要： A novel and simple solid-liquid chemical reaction route was proposed to synthesize ZnS nanoparticles.In the method,ZnS nanoparticles were prepared by reaction of ZnO and Na2S in water with ultrasonic radiation at low temperature.The effects of process parameters on the properties of ZnS particles were investigated.The products were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM),transmission electron microscopy(TEM),infrared spectroscopy(IR),thermogravimetrydifferential thermogravimetry(TG-DTG)and fluorescence emission spectroscopy.The results show that these particles are good crystalline zinc blende with average size of 35 nm,and possess good IR transmittance in the range of 400 to 4 000 cm1and good thermal stability in oxygen.

摘要： A novel imidazole derivative with functional group and π-conjugated system, 1- [trans-4-(4-diethylaminostyryl)phenyl]imidazole (abbreviated as L), and its CoII complex (CoCl2L4)2 (Co2C168H184N24Cl4, Mr = 2799.05 ) have been synthesized and the crystal structure of the latter was determined by X-ray diffraction. The crystal is of triclinic, space group P with a = 8.823(3), b = 18.799(7), c = 23.065(9) (A), α = 77.349(6), β = 83.128(7), γ = 80.942(3)°,V = 3671.5(12)(A)3, Z = 1, Dc = 1.266 g/cm3, μ = 0.361 mm-1, F(000) = 1482, the final R = 0.0587 and Wr = 0.1284 for 6562 observed reflections with Ⅰ ＞ 2б(Ⅰ). In the molecular structure of (CoCl2L4)2, there are two crystallographically unique units. The CoII atoms are six-coordinated by four N atoms from four imidazole ligands (L) and two Cl atoms to form a distorted octahedral geometry. The optical properties of complex (CoCl2L4)2 have been experimentally studied.

摘要： Amorphous Ta_2O_5 films were prepared on Si (100) substrates by thermal oxidization.The film consisted of amorphous Ta_2O_5 nanostructure that grew vertically and compactly at a large range.It was found that Ta_2O_5 films became crystalline when annealed at or above 650°Cand remained amorphous below 650°C.The effects of annealing on the optical properties of Ta_2O_5 film were also discussed.It is estimated that the refraction indexes and the optical energy gaps of both amorphous Ta_2O_5 film and crystal one are stable.The optical energy gap of as-deposited Ta_2O_5 film is about 4.81 eV.The above results indicate that Ta_2O_5 films have a promising application in the optical devices.

摘要： TiO2/ormosil planar waveguide was prepared by sol-gel method at low thermal treatment temperature ＜ 200 °C. Scanning electron microscope, FT-IR spectrometer, spectrophotometer, atomic force microscopy, thermal analyzer, and dark m-line spectroscopy were used with the method of scattering-detection to investigate optical and strucural properties. High optical quality waveguide film was obtained. The propagation loss of film was 0.569 dB/cm at a wavelength of 632.8 nm.