Search

The thermostable GH78 family α-L-rhamnosidase DthRha from Dictyoglomus thermophilum DSM3960 was found to have the ability to remove the α-L-rhamnose moiety that was directly linked to the aglycone by an α-1-rhamnosidic bond at the C-3 position of epimedium flavonoids. It exhibited high specific activity on p-nitrophenyl-α-L-rhamnopyranoside (pNPR) (281.06 U/mg), followed by epimedin C (30.42 U/mg), icariin (9.74 U/mg), baohuoside I (1.02 U/mg) and 2’-O-rhamonosylicariside II (3.74 U/mg). In addition, the thermostable glucosidase Dth3 from Dictyoglomus thermophilum DSM3960, which exhibits β-xylosidase activity and β-glucosidase activity, was purified. The main enzymatic properties of the two thermostable glycosidases were compared, and these glycosidases were successfully utilized in the preparation of pharmacologically active icaritin from the total flavonoid extract of epimedium. Finally, 5 g/L of the total flavonoid extract of epimedium was completely transformed into 207.95 mg/L icaritin at pH 5.5 and 80 °C for a total of 4 h. This is the first report on the efficient biotransformation of the total flavonoid extract of epimedium into icaritin by two thermostable enzymes with high productivity. The cost of icaritin preparation will be substantially reduced by converting all the major ingredients in the total flavonoid extract of epimedium.

The thermostable GH3 family β-glucosidase DthBgl3 and thermostable GH78 family α-l-rhamnosidase DthRha from Dictyoglomus thermophilum DSM3960 were successfully immobilized by industrial amino resin 1000NH. The optimal reaction temperature and pH of 1000NH-DthBgl3 was 85 °C and pH 5.0. Over 65% residual enzyme activity maintained for 1000NH-DthBgl3 after a 3-h incubation under 85 °C, while about 20% residual enzyme activity maintained for free DthBgl3. The optimal reaction temperature and pH of 1000NH-DthRha was 95 °C and pH 6.5. Over 90% residual enzyme activity maintained for 1000NH-DthRha after a 3-h incubation under 90 °C, while about 22% residual enzyme activity maintained for free DthRha. Meanwhile, immobilized 1000NH-DthBgl3 and 1000NH-DthRha were successfully and could completely transform all major ingredient of 10 g/L total flavonoids extract from Epimedium (TFEE) into icaritin. After 15 cycles (45 h) of repeated use at 85 °C, 3 U 1000NH-DthBgl3 showed a molar conversion rate of 73.12%, initial activity of 30.09% and productivity of 124 mg/L/h, while 15 U 1000NH-DthRha showed a molar conversion rate of 88.50%, initial activity of 85.31% and productivity of 75 mg/L/h after ten cycles (60 h) of repeated use at 85 °C. The cooperation of two immobilized enzymes showed a molar conversion rate of 87.21% and productivity of 141 mg/L/h after 15 cycles of repeated use at 85 °C. This is the first report on immobilization of two thermostable glycosidases from thermophilic bacteria and their cooperated biocatalysis of all major ingredients of TFEE into icaritin with high productivity under a high substrate concentration.

The α-L-rhamnosidase BtRha from Bacteroides thetaiotao VPI-5482 is a specific enzyme that selectively hydrolyzes the α-1,2 glycosidic bond between rhamnose and rhamnose, allowing the bioconversion of epimedin C to icariin. In this study, BtRha was molecularly modified using B-factor-saturation mutagenesis strategy and the introduction of disulfide bonds, resulting in a mutant with significantly improved catalytic efficiency, S592C, and two thermally stable mutants, E39W and E39W-S592C. The results showed that the half-lives of E39W and E39W-S592C at 55 °C were 10.4 and 9.4-fold higher, respectively, than that of the original enzyme, The mutant S592C showed a 63.3% reduction in K

The nanocomposites of gold nanoparticles/reduced graphene oxide (AuNPs/rGO) have attracted a lot of attention due to their excellent synergic properties. However, a green and low-cost synthesis method without suffering from solvent toxicity, labor-consuming, or high-temperature processes is still highly desirable. In this work, we demonstrated the preparation of AuNPs/rGO nanocomposite films by a one-step dual reduction of graphene oxide (GO) and chloroauric acid (HAuCl4) using argon (Ar) plasma. The oxygen functional groups on GO anchored the Au ions and the electrons generated in Ar plasma reduce these ions into metallic Au. By controlling the time of plasma treatment and concentration of HAuCl4 precursor, the size and density of AuNPs on GO can be widely tuned. The underlying mechanism for the size- and density-tunability was also discussed. The AuNPs/rGO nanocomposite films were used as Raman substrates and achieved strongly enhanced signals with excellent reproducibility and stability. The nanocomposites were also successfully applied to the catalytical reduction of toxic 4-nitrophenol (4-NP) into non-toxic 4-aminophenol (4-AP) with a reduction rate constant as high as 0.422 min−1. This work paves the way towards the green and low-cost industrial production of AuNPs/rGO nanocomposites which have great potentials in a variety of application fields.

The lack of highly efficient blue‐emitting perovskite nanocrystals limits their development for optoelectronic applications. In article number 2001698, Bartomeu Monserrat, Shuyu Zhang, and co‐workers develop blue‐emitting neodymium‐doped CsPbBr3 nanocrystals with high photoluminescence quantum yield (PLQY) and narrow spectral width. First principles calculations reveal the microscopic mechanisms for the blueshift of photoluminescence and the enhancement of PLQY upon doping. [Image: see text]

Ginkgo tea is a kind of health food produced from Ginkgo biloba leaves. The market of Ginkgo tea encountered many difficulties because of its bad palatability and vague function statement. In this study, two kinds of glycosidase were used to improve the flavor of Ginkgo tea, and three kinds of bioactivities were selected to investigate the health care function of the tea infusion. The aroma components extracted by headspace absorb (HSA) method during the making of Ginkgo tea were analyzed by GC-MS. The flavonoids and ginkgolides released into the tea infusion were studied by HPLC. A combination of &beta, glucosidase (&beta, G) and &alpha, rhamnosidase (&alpha, R) was applied during the making of the tea. The contents of characteristic aroma components and the release of total flavonoids and ginkgolides were increased significantly by adding &beta, G and &alpha, R. The composition of flavone glycosides was changed greatly. The free radical scavenging, inhibition of inflammatory cell activation, and tumor cytotoxicity activities of the tea were demonstrably improved. According to the release of active components, Ginkgo tea can be brewed repeatedly for at least three times. The enzymes used here show potential application prospects in the making of Ginkgo tea or tea drink to get higher contents of flavonoids, ginkgolides, and aroma components.

Colloidal CsPbX3 (X = Br, Cl, and I) perovskite nanocrystals exhibit tunable bandgaps over the entire visible spectrum and high photoluminescence quantum yields in the green and red regions. However, the lack of highly efficient blue‐emitting perovskite nanocrystals limits their development for optoelectronic applications. Herein, neodymium (III) (Nd3+) doped CsPbBr3 nanocrystals are prepared through the ligand‐assisted reprecipitation method at room temperature with tunable photoemission from green to deep blue. A blue‐emitting nanocrystal with a central wavelength at 459 nm, an exceptionally high photoluminescence quantum yield of 90%, and a spectral width of 19 nm is achieved. First principles calculations reveal that the increase in photoluminescence quantum yield upon doping is driven by an enhancement of the exciton binding energy due to increased electron and hole effective masses and an increase in oscillator strength due to shortening of the PbBr bond. Putting these results together, an all‐perovskite white light‐emitting diode is successfully fabricated, demonstrating that B‐site composition engineering is a reliable strategy to further exploit the perovskite family for wider optoelectronic applications.

Pressure and temperature are powerful tools applied to perovskites to achieve recrystallization. Lamination, based on recrystallization of perovskites, avoids the limitations and improves the compatibility of materials and solvents in perovskite device architectures. In this work, we demonstrate tightly compacted perovskite laminates on flexible substrates via hot-pressing and investigate the effect of hot-pressing conditions on the lamination qualities and optical properties of perovskite laminates. The optimized laminates achieved at a temperature of 90 °C and a pressure of 10 MPa could sustain a horizontal pulling pressure of 636 kPa and a vertical pulling pressure of 71 kPa. Perovskite laminates exhibit increased crystallinity and a crystallization orientation preference to the (100) direction. The optical properties of laminated perovskites are almost identical to those of pristine perovskites, and the photoluminescence quantum yield (PLQY) survives the negative impact of thermal degradation. This work demonstrates a promising approach to physically laminating perovskite films, which may accelerate the development of roll-to-roll printed perovskite devices and perovskite tandem architectures in the future.

Visible light communication (VLC) is becoming an important and promising supplement to the existing Wi-Fi network for the coming 5G communications. Organic light-emitting semiconductors present much fast fluorescent decay rates compared to those of conventional colour-converting phosphors, therefore capable of achieving much higher bandwidths. Here we explore how nanopatterned organic semiconductors can further enhance the data rates of VLC links by improving bandwidths and signal-to-noise ratios (SNRs) and by supporting spatial multiplexing. We first demonstrate a colour-converting VLC system based on nanopatterned hyperbolic metamaterials (HMM), the bandwidth of which is enhanced by 50%. With regard to enhancing SNRs, we achieve a tripling of optical gain by integrating a nanopatterned luminescent concentrator to a signal receiver. In addition, we demonstrate highly directional fluorescent VLC antennas based on nanoimprinted polymer films, paving the way to achieving parallel VLC communications via spatialmultiplexing. These results indicate nanopatterned organic semiconductors provide a promising route to high speed VLC links.

Visible light communication (VLC) is a promising candidate for high-speed wireless communication with numerous unlicensed spectrum. To achieve high-speed data communication, it requires intense light signals concentrated on a tiny fast photodiode. The common way of using focusing optics reduces the field of view (FoV) of the photodiode due to the conservation of etendue. Luminescent solar concentrators (LSC) provide a solution to enhance the signals without affecting the FoV. In this paper we demonstrate nanopatterned LSCs fabricated on flexible plastics that achieve a doubling of optical gain compared to its traditional rectangular counterparts. These LSCs can free VLC detectors from complex active pointing and tracking systems, making them compatible with smart mobile terminals in a simple fashion.

Organic light-emitting semiconductors present much shorter lifetimes compared to conventional phosphor colour converters, therefore capable of achieving much higher bandwidths in visible light communications. This talk focuses on addressing two of the coming challenges for organic semiconductors: spatial multiplexing and bandwidth enhancement, and explores the roles of photonic nanostructures as a solution to both challenges. The appealing features of visible light communications (VLC), including fast speed, numerous unregulated bandwidth and high security, make VLC an important and promising supplement to the existing Wi-Fi network for the coming 5G communications [1-4]. So far most of the fast VLC links are based on micro-LEDs or laser diodes (LD) which have bandwidths at GHz level, however, in order to achieve high-quality white light, a practical and simple way is to combine a colour converter with the fast-modulated blue LED/LD backlight. Conventional phosphors have bandwidths of only several MHz, so the overall bandwidths of white light sources are severely limited. Organic light-emitting semiconductors have demonstrated intriguing capabilities of boosting bandwidths due to their nanosecond-scale lifetimes [5-10]. For example, conjugated polymers demonstrate bandwidths of over 200 MHz, which are enhanced by two orders of magnitude compared to those of conventional phosphors. This talk focuses on addressing two of the coming challenges for organic semiconductors: i) Can organic semiconductors be applied for parallel communications like multiple-in-multiple-out (MIMO)? ii) Are there potential solutions to further improve the bandwidths of organic semiconductors if the molecular design of fast organic emitters has reached its bottleneck? Colour tuning for organic semiconductors is facile, so parallel communications based on wavelength division multiplexing can be easily realised. On the contrary, organic semiconductors are not born for spatial multiplexing, since they are generally Lambertian emitters. Our strategy to overcome this problem is to use photonic.

In this study, a series of zinc (Zn)-based sorbents were prepared by high-pressure impregnation under different conditions of time and pressure, followed by fixed-bed pyrolysis using lignite as a precursor of support and zinc nitrate [Zn(NO3)2] as an active component precursor. The desulfurization performances of lignite and sorbents were measured. Moreover, they were characterized by X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), N2 adsorption, transmission electron microscopy–energy-dispersive X-ray (TEM–EDX), and scanning electron microscopy–energy-dispersive X-ray (SEM–EDX) techniques. The ambient conditions involved in hydrothermal synthesis are favorable for the efficient uploading of Zn(NO3)2 and the improvement of lignite texture during high-pressure impregnation. The content of Zn in prepared sorbent and the utilization rate of the active component can reach over 20 and 90%, respectively. The impregnation pressure and time are the main factors influencing the desulfurization perfo...

With lignite after vacuum drying as the raw material, a series of Zn-based sorbents were prepared by static impregnation, ultrasonic-assisted impregnation, bubbling-assisted impregnation and high-pressure impregnation. The physical properties and the desulfurization performances of Zn-based sorbents were studied systematically by XRD, BET, AAS characterization techniques and the fixed-bed desulfurization evaluation apparatus. The sorbents obtained by high-pressure impregnation method have a larger specific surface area, pore volume and pore diameter comparing with other methods, which is conducive to the sulfidation reaction of hydrogen sulfide gas in the sorbent. The effects of pressure during the high-pressure impregnation and concentration of Zn(NO 3 ) 2 precursor solution on the sorbents properties and desulfurization behavior were investigated. The higher the impregnation pressure and the concentration of impregnation solution are, the greater the amount of the active components are uploaded. However, overhigh impregnation pressure can cause collapse and blocking of the carrier pore. The optimal operating condition of high-pressure impregnation method for preparing the sorbents was the impregnation pressure of 20 atm and the solution concentration of 41%. Under that condition, the sorbent had the best desulfurization ability with a sulfur capacity of 13.94 g S /100 g sorbent and a breakthrough time of 54 h. Its desulfurization precision and efficiency of removing H 2 S before sorbent breakthrough from the middle temperature gases of 400 °C can reach 99%, respectively. Sorbents could be regenerated under the condition of 1 vol% O 2 , 20 vol% H 2 O, 0.5 vol%NH 3 , and N 2 balance gas. The regenerated sorbent could be used for repeated absorption of H 2 S with a slight decrease in desulfurization effect.

Room temperature recrystallization is an intriguing method of fabricating CsPbX3 perovskite quantum dots since it does not involve high temperature or inert atmosphere, offering a promising route to the mass production of CsPbX3 quantum dots at low cost. However, their performance stability during work was seldom investigated and was far from the requirements for practical applications. Here, we demonstrate a facile and low-cost method to significantly improve the thermal, photo- and water stability of room-temperature synthesized perovskite quantum dots by effectively suppressing the unfavored grain growth and surface trap states. The fabricated quantum dots of green-emitting CsPbBr3 and red-emitting CsPbBr1.2I1.8 were applied for quantum dot-converted white LEDs, which are capable of achieving a wide color gamut of 135% NTSC and 101% Rec. 2020.

This paper analyzes and studies of a threshold group signature scheme which is based on ElGamal type. In order to overcome the shortcomings of the scheme, a new threshold group signature scheme with privilege subjects based on ECC is proposed. The new scheme is able to prevent the fraud of key distribution center effectively. Only when the scheme satisfies (t, n) and (t1, n1) threshold signature, can the valid signature be generated. Thus the scheme reached the property of threshold. The program also satisfies the properties of anonymity, unforgeability, trace ability, reversibility and it can resist collusion attacks too.