Two-dimensional photonic crystals as selective filters for thermophotovoltaic applications.

The optical properties and performance of the two-dimensional photonic crystal (2D PhC) filters at normal incidence were simulated, and the best geometric parameters were obtained with the help of a global optimization program. The honeycomb structure has better performance, including high in-band transmittance, high out-band reflectance, and low parasitic absorption. The power density performance and conversion efficiency can reach 80.6% and 62.5%. Furthermore, the deeper cavity structure and multi-layer structure were designed to improve the performance of the filter. The deeper one can reduce the influence of transmission diffraction, increases the power density performance and conversion efficiency. The multi-layer structure reduces the parasitic absorption significantly and increases the conversion efficiency to 65.5%. These filters have both high efficiency and high power density, avoid the challenge of high-temperature stability faced by emitters, also easier and cheaper to fabricate compared to the 2D PhC emitters. These results suggest that the 2D PhC filters can be used in thermophotovoltaic systems for long-duration missions to improve the conversion efficiency.

[Screening and identification of a Burkholderia strain and optimization of its phosphate solubilizing capacity]. / ä¸€æ ªä¼¯å ‹éœå°”å¾·èŒçš„ç­›é€‰é‰´å®šåŠæº¶ç£·æ€§èƒ½ä¼˜åŒ–.

In order to solve the problem that soil soluble phosphorus content in most cultivated land in China is insufficient and the plant growth is inhibited, a phosphate solubilizing microorganism (PB) was screened and identified, and its phosphate solubilizing performance was optimized. The results showed that the PB strain was belonged to Burkholderia stabilis. It had the ability of nitrogen fixation and indole-3-acetic acid (IAA) secretion, as well as a certain inhibitory effect on Escherichia coli. It could maintain high activity and phosphorus solubilizing ability at pH 8.0-10.0, indicating good alkali resistance. The results of phosphorus dissolving performance optimization showed that the phosphate solubilizing capacity of strain PB reached the best at 30℃, pH 7.0, 180 r·min-1, using glucose as carbon source, ammonium sulfate as nitrogen source, tricalcium phosphate as phosphorus source and adding 50 µmol·L-1 lysine. The amount of dissolved phosphorus was 569.33 mg·L-1, which was 1.9 times of that before optimization. The strain mainly secreted citric acid, malonic acid, and glucuronic acid during metabolism. After adding lysine, the type of organic acids secreted by the strain did not change, but the content increased significantly. Results from pot experiments showed that the application of PB bacterial fertilizer could significantly improve the growth and physiological indicators of garlic seedlings, and that the promotion effect was more obvious after adding lysine. Compared with the control, the height of seedling was increased by 18.6%, seedling diameter was increased by 16.7%, aboveground fresh and dry weight were increased by 22.1% and 15.7%, and belowground fresh and dry weight were increased by 22.0% and 28.7%, respectively in PB with lysine treatment. Soil available phosphorus content was 2.1 and 2.3 times of the control in PB and PB+lysine treatments, indicating that PB could improve soil available phosphate content. Adding lysine could strengthen such function.

Size-controlled synthesis of metal-organic frameworks and their performance as fluorescence sensors.

Metal-Organic Frameworks (MOFs) are of bright promise as new fluorescence sensors because of their accurate framework structure and unique fluorescence properties. Many MOFs have been reported as fluorescence sensors, including bulk-MOF-crystals and nano-MOF-powder. Obviously, the sensing performance of these MOF sensors should be diverse due to their different sizes. However, bulk-MOF-crystals and nano-MOF-powder have completely different dispersibility in solvents, and the effects of this difference on the analytical performance like precision and sensitivity are significant but have not been discussed systematically. To investigate such effects, rodlike bulk-MOFs and nano-MOFs with the same structure but different sizes are required. In this work, we obtained MOFs with a crystal width ranging from 9.7 µm to 170 nm by controlled synthesis, and then proved that they have the same structure by PXRD, SEM, TGA and FTIR analysis. After that, taking folic acid as the target molecule, fluorescent sensing experiments were carried out to compare the sensing performance between bulk-MOFs and nano-MOFs. From the results, we found that nano-MOFs have obviously better dispersity, a lower precipitation speed, a smaller standard deviation, ten times higher fluorescence intensities and a much lower LOD than bulk-MOFs. Finally, we draw a conclusion that nano-MOFs are more in line with the requirements of analytical performance as fluorescence sensors, and the size of MOFs as fluorescence sensors should be as small as possible.

Fluorescence biosensor based on silicon quantum dots and 5,5'-dithiobis-(2-nitrobenzoic acid) for thiols in living cells.

An efficient and stable fluorescent sensor is described for the detection and imaging of thiols. It is making use of silicon quantum dots (SiQDs) which can be rapidly prepared. They were characterized by transmission electron microscopy, X-ray power diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectrometry. The SiQDs have an absorption maximum at 300 nm and displayed blue-green fluorescence with excitation/emission maxima at 410/480 nm. A mixture of SiQDs and 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) exhibits strong fluorescence emission which however is quenched within 30 s of incubation with thiols. This is assumed to be due to an inner filter effect caused by the reaction of DTNB and thiols. The following thiols were tested: cysteine, homocysteine, and glutathione. The sensor has a linear response in the 3-100 µM thiol concentration range, and the LODs are between 0.80 and 0.96 µM. The sensor displays low cytotoxicity and was applied to fluorescence imaging of MCF-7 cells and Hela cells where it demonstrated excellent biocompatibility.

A dual-responsive fluorescent sensor for Hg2+ and thiols based on N-doped silicon quantum dots and its application in cell imaging.

In this study, a simple and rapid method was designed to synthesize N-doped silicon quantum dots (N-SiQDs) with a maximum excitation wavelength and maximum emission wavelength of 347 nm and 440 nm, respectively. The prepared N-SiQDs are colorless in aqueous solution with excellent dispersibility, and the fluorescence quantum yield is 28.8%. The fluorescence intensity of the N-SiQDs decreases rapidly within 30 s in response to Hg2+ to form the Hg2+-N-SiQD system. Under physiological conditions, glutathione can coordinate with Hg2+ in the Hg2+-N-SiQD system causing Hg2+ to detach from the surface of N-SiQDs, and the fluorescence of N-SiQDs is restored within 1 min. After optimization of the N-SiQD preparation conditions and the response conditions, the linear ranges for Hg2+ and glutathione detection are 0.1-4 µM and 0.1-5 µM with the detection limits of 24 nM and 55 nM, respectively. Besides, fluorescence imaging results indicate that the "on-off-on" Hg2+-N-SiQD fluorescent sensor can be successfully applied to the detection of biothiols in living cells.

Characterization and functional properties of mango peel pectin extracted by ultrasound assisted citric acid.

Pectin was extracted from 'Tainong No. 1' mango peels, using a chelating agent-citric acid as extraction medium by ultrasound-assisted extraction (UAE) and conventional extraction (CE) at temperatures of 20 and 80°C. Chemical structures, rheological and emulsifying properties of mango peel pectins (MPPs) were comparatively studied with laboratory grade citrus pectin (CP). All MPPs exhibited higher protein content (4.74%-5.94%), degree of methoxylation (85.43-88.38%), average molecular weight (Mw, 378.4-2858kDa) than the CP, but lower galacuronic acid content (GalA, 52.21-53.35%). CE or UAE at 80°C resulted in significantly higher pectin yield than those at 20°C, while the extraction time for UAE-80°C (15min) was significantly shorter compared to CE-80°C (2h) with comparable pectin yield. Moreover, MPPs extracted at 80°C were observed with higher GalA and protein content, higher Mw, resulting in higher viscosity, better emulsifying capacity and stability, as compared to those extracted at 20°C and the CP. Therefore, these results suggested that MPPs from 'Tainong No. 1' may become a highly promising pectin with good thickening and emulsifying properties, using ultrasound-assisted citric acid as an efficient and eco-friendly extraction method.