Room-temperature lasing based on low-dimensional GaAs nanowires (NWs) is one of the most critical and challenging issues in realizing near-infrared lasers for nanophotonics. In this article, the random lasing characteristics based on GaAs NW arrays have been discussed theoretically. According to the simulation, GaAs/AlGaAs core-shell NWs with an optimal diameter, density, and Al content in the shell have been grown. Systematic morphological and optical characterizations were carried out. It is found that the GaAs NWs with the additional growth of the AlGaAs shell exhibit improved emission by about 2 orders of magnitude at low temperatures, which can be attributed to the suppression of crystal defects. At room temperature, lasing was observed with a threshold around 70.16 mW/cm2, and the random lasing mechanism was discussed in detail. This work is of great significance for the design of random cavities based on semiconductor NWs, which is important for optoelectronic integration.

OBJECTIVE: This work aimed to evaluate the effect of artificial aging on the translucency and color difference (ΔE) of ultra-translucent zirconia and provide a reference for clinical application.
METHODS: The discs of ultra-translucent zirconia from six brands (Wieland, 3M ESPE, Amann Girrbach, Kuraray Noritake, Upcera, and Besmile) were cut and sintered according to each manufacturer\'s product instructions; the experimental groups were named ZNT, LVP, AG, KAT, UPC, and BSM, respectively. IPS e.max Press was used as the control group (PLT). The specimens (n=6) were prepared with a diameter of 14 mm and a thickness of 1 mm. The specimens were subjected to artificial aging treatment according to the following conditions: in an autoclave at 134 ℃ at 0.2 MPa for 4, 8, and 12 h. According to the CIE1976Lab system, the CIE L*, a*, and b* values of the specimens before and after aging were measured by a co-lorimeter. The translucency parameter (TP) and ΔE were calculated.
RESULTS: The mean TP values of each group before aging inorder were PLT>KAT>AG>ZNT>BSM>UPC>LVP. We found no significant difference in translucency in all experimental groups after aging for 4 and 8 h compared with those before aging. After 12 h of aging, the TP values of the KAT and ZNT groups were not significantly different from those before aging, but the TP values of the AG, BSM, LVP, and UPC groups were significantly lower than those before aging (P<0.05). The TP value of the control group was significantly higher than that of the other experimental groups at different stages (P<0.05). ΔE=3.3 was considered the visible color difference, and ΔE was less than 3.3 in all groups after 4 h of aging. After aging for 8 h, ΔE of the UPC group was slightly higher than 3.3. ΔE of the BSM and UPC groups was greater than 3.3 after 12 h of aging.
CONCLUSIONS: The TP and ΔE of different brands of ultra-translucent zirconia may change after various aging times. The translucency of some zirconia showed a decreasing trend and the color difference showed an increasing trend with the aging time.
目的: 探究多种常用超透氧化锆陶瓷在人工老化前后半透性和颜色的改变，为临床应用提供参考。方法: 分别将6种不同品牌（Wieland、3M ESPE、Amann Girrbach、Kuraray Noritake、爱尔创和贝施美）的超透氧化锆按照厂商产品说明进行切割及烧结，分别以ZNT、LVP、AG、KAT、UPC和BSM命名实验组，以义获嘉铸瓷作为对照组（PLT），制备成直径14 mm、厚度1 mm的试件（n=6），置于立式压力蒸汽灭菌器中，在134 ℃、0.2 MPa的标准环境下分别对各组试件进行4、8、12 h三个时段人工老化处理。采用CIE1976Lab色度系统，用电脑比色仪测量各组试件人工老化前及人工老化4、8、12 h后的CIE L*、a*、b*值，并计算半透明度（TP）及色差（ΔE）。结果: 老化前各组的TP值从大到小分别为PLT>KAT>AG>ZNT>BSM>UPC>LVP。老化4 h及8 h后，所有实验组的TP值和老化前相比差异均无统计学意义；老化12 h后，KAT组和ZNT组的TP值与老化前相比差异无统计学意义，但AG组、BSM组、LVP组和UPC组的TP值与老化前相比出现了显著性降低（P<0.05）。对照组TP值在不同阶段均显著高于实验组（P<0.05），且不受老化影响。以ΔE=3.3为肉眼可见色差，老化4 h后所有组∆E均小于3.3，老化8 h后仅有UPC组ΔE略大于3.3，老化12 h后BSM组和UPC组ΔE大于3.3。结论: 各品牌超透氧化锆在不同老化时间后，半透性和色差可能会有改变，部分氧化锆材料随着老化时间的增加半透性呈下降趋势，色差呈上升趋势。.

To address the global energy shortage and mitigate greenhouse gas emissions on a massive scale, it is critical to explore novel and efficient photocatalysts for the utilization of renewable resources. Bi-based metal oxide (BixMOy) semiconductors composed of bismuth, transition metal, and oxygen atoms have demonstrated improved photocatalytic activity and product selectivity. The vast number of element combinations available for BixMOymaterials provides a huge compositional space for the rational design and isolation of promising photocatalysts for specific applications. In this study, we have systematically investigated the electronic and optical properties over Bi2O3and a series of selected BixMOygroup materials (BiVO4, BiFeO3, BiCoO3, and BiCrO3) by calculating band structure, basic optical property features, mobility and separation of charge carriers. It is clearly noted that the band gap and band edge position of the BixMOygroup materials can be tuned in a wide range in comparison to Bi2O3. Similarly, the light response of BixMOyalso can be broadened from the ultraviolet to the visible light region by adjusting the selection of transition metals. Additionally, the analysis of the effective mass of charge carriers of these materials further confirms their possibility in photocatalytic reaction applications because of the appropriate separation efficiency and mobility of carriers. A selection of experimental investigations on the crystal structure, composition, and optical properties of Bi2O3, BiVO4, and BiFeO3as well as their catalytic performance in the degradation of methylene blue over was also conducted, which agree well with the theoretical predictions.

Transparent silica aerogel, serving as one typical porous and transparent material, possesses various unique features (e.g., large amounts of pores and interfaces, super-lightweight, super thermal insulation, low refractive index similar to gas), and it has attracted great attention in the fields of science, technology, engineering, art, and others. Transparency is one important evaluation index of transparent silica aerogel, and it was influenced by various factors such as raw materials, sol-gel reactions, phase separation, and drying methods. The structure design and fabrication of transparent silica aerogel is one huge and fine engineering. In this review, the optical/chemical guidance and design for the preparation of transparent silica aerogels are discussed, and typical applications, such as Cherenkov detectors, solar energy collection, lighting systems, and transparent fabric, also were discussed. Finally, a future outlook on the opportunities and challenges of transparent silica aerogels was proposed.

Scalable and highly efficient bamboo whitening remains a great challenge. Herein, an effective bamboo whitening strategy is proposed based on photocatalyzed oxidation, which involves H2O2 infiltration and UV illumination. The as-prepared white bamboo well maintains the nature structure of natural bamboo and demonstrates high whiteness and superior mechanical properties. The absorbance value is significantly decreased to 3.5 and the transmittance is increased to 0.04 % in UV-visible wavelength range due to the removal of light-absorbing chromospheres of lignin, resulting in a high whiteness when the UV illumination time is 8 h. In addition, the white bamboo displays a high tensile strength of 30 MPa and a high flexural strength of 36 MPa due to the well-preserved lignin units (lignin preservation is about 89 %). XRD patterns and analysis show that photocatalyzed oxidation has no effect on the crystal parameters of cellulose. Compared with the traditional bamboo whitening technology, our photocatalyzed oxidation strategy demonstrates significant advantage including chemical and time conservation, high efficiency, environment friendliness, and mechanical robustness. This highly efficient and environmentally friendly photocatalyzed oxidation strategy for the fabrication of white bamboo may pave the way of bamboo-based energy-efficient structural materials for engineering application.

The composition of melanoidins in dried apple that affects quality remains unclear. The composition and structure of melanoidins in dried apple slices by hot air drying (HAAM), instant controlled pressure drop drying (DICAM), and vacuum freeze-drying (FDAM) were investigated. It showed that the melanoidins were highly heterogeneous mixtures with a light-yellow color and blue-green fluorescence, belonging to polysaccharide-type melanoidins. Specifically, HAAM had a large molecular weight (929.5 g/mol) and wide molecular weight distribution, with more double-bond conjugated systems. DICAM (610.9 g/mol), possessing the strongest fluorescence intensity, was mainly composed of compounds with fewer π-conjugated structures and more electron-donating groups. As a control, the low level of Maillard reaction in FDAM resulted in the formation of the smallest molecular weight (458.6 g/mol) with weak fluorescence intensity. Moreover, 10 compounds were tentatively identified in apple melanoidins. This study provides the foundation for the future functional preparation of apple melanoidins.

BACKGROUND: The structurals stability, electronic structure, density of states (DOS), and optical properties of B-doped arsenene under biaxial tensile and compressive strains were investigated using density functional theory (DFT) calculations. The doping system was found to exhibit good stability. The introduction of B atom transformed the originally indirect band gap of arsenene into a direct band gap. Under compressive strain, the band gap remained direct, gradually decreasing in value. In contrast, under tensile strain, the direct band gap occurred a transition into an indirect band gap, of which value initially increasing and then decreasing with an increasing strain. The static dielectric constant was increased under both compressive and tensile strains, but compressive strain had a stronger effect. Compressive strain led to an increase in the imaginary peak of the dielectric function, while tensile strain resulted in a decrease. Moreover, as compressive strain increased, the absorption and loss function peak initially blue-shifted and then red-shifted, while tensile strain caused a gradual red-shift of the absorption peak.
METHODS: All DFT calculations were performed using Quantum Espresso software; the structures were optimized using generalized gradient approximation (GGA-PBE), and electronic structure and optical properties are performed using Heyd-Sceria-Ernzerhof (HSE06). The cut-off energy was set as 70 Ry, the Monkhorst-Pack grid was set to 10 × 10 × 1, the atomic convergence criterion was set as 1.0 × 10-6 Ry, and the convergence criterion of interatomic force was set as 1.0 × 10-4 Ry/Bohr.

Based on the first-principles calculations, ferroelectricBi2O2X(X=S,Se,Te)monolayers with unequivalent in-plane lattice constants are confirmed to be the ground state, which is consistent with the experiment result (Ghoshet al2019Nano Lett.195703-09), and the anisotropic optical property is firstly investigated. We find that the polarizations ofBi2O2Xmonolayers points along the direction ofa-axis, andBi2O2Temonolayer process the largest polarization. Furthermore, both the biaxial and uniaxial strains are favor for the enhancement of polarization ofBi2O2Xmonolayers. It should be mentioned that the type of band gap will convert from indirect to direct forBi2O2Temonolayer when thea-axial tensile strain is larger than 2%. At last, the optical absorption coefficient forBi2O2Xmonolayers are calculated, and we obtain thatBi2O2Temonolayer has the strongest optical absorption within the range of visible light, the anisotropy and possible strain engineering to improve the optical absorption are discussed in detail. Our findings are significant in fields of optoelectronics and photovoltaics.

Si3N4 bioceramics were fabricated using GPS and SPS method with MgO-RE2O3 (RE = La, Nd, Gd, Ho and Lu) sintering additives. The effect of sintering methods and sintering additives on the grain growth, mechanical, antimicrobial properties and color of Si3N4 bioceramics were studied. Samples sintered with GPS are composed of β-Si3N4 and samples sintered with SPS are composed of α-Si3N4 and β-Si3N4. The growth of β-Si3N4 grains in samples sintered with GPS are more adequate. Samples sintered with GPS exhibit a S. aureus inactivation rate up to 98% and a bright color appearance with a hardness of about 13 GPa and a fracture toughness up to 7.5 MPa m1/2, suitable for dental implants. And samples sintered with SPS exhibit a hardness of about 17 GPa and a fracture toughness about 6 MPa m1/2.

OBJECTIVE: The paper aims to investigative the cacuses and impacts of In- and Vacancy-doped to 6H-SiC, expecting that improving optical properties of materials. Design-Using the first-principles calculations, we discuss the electronic structure and optical properties of different doped 6H-SiC systems.
RESULTS: The results show that In-doped 6H-SiC becomes a direct bandgap p-type semiconductor and the energy bandgap is reduced from the intrinsic 2.059 to 1.515 eV. We demonstrate the stability of the systems through the formation energy analysis, meanwhile identify their physical origins and discuss applications of all structures in electronic devices within optical analysis. Find the energy beginning values of the VSi-doped and VC-doped systems\' optical absorption spectrums and extend to 0.4 2 eV and 0.11 eV respectively compared with the original 3.23 eV. In the visible light region, the reflectivity images of the VC/VSi and (In, VSi)-codoped systems rise obviously.
CONCLUSIONS: The optical properties of all doping systems were analyzed to be improved compared with the intrinsic, all above mentioned provide a theoretical basis for the fabrication of spintronic and optical devices.