Recent advances in peptide-based bioactive hydrogels for nerve repair and regeneration: from material design to fabrication, functional tailoring and applications.

The injury of both central and peripheral nervous systems can result in neurological disorders and severe nervous diseases, which has been one of the challenges in the medical field. The use of peptide-based hydrogels for nerve repair and regeneration (NRR) provides a promising way for treating these problems, but the effects of the functions of peptide hydrogels on the NRR efficiency have been not understood clearly. In this review, we present recent advances in the material design, matrix fabrication, functional tailoring, and NRR applications of three types of peptide-based hydrogels, including pure peptide hydrogels, other component-functionalized peptide hydrogels, and peptide-modified polymer hydrogels. The case studies on the utilization of various peptide-based hydrogels for NRR are introduced and analyzed, in which the effects and mechanisms of the functions of hydrogels on NRR are illustrated specifically. In addition, the fabrication of medical NRR scaffolds and devices for pre-clinical application is demonstrated. Finally, we provide potential directions on the development of this promising topic. This comprehensive review could be valuable for readers to know the design and synthesis strategies of bioactive peptide hydrogels, as well as their functional tailoring, in order to promote their practical applications in tissue engineering, biomedical engineering, and materials science.

Broadband long-wave infrared high-absorption of active materials through hybrid plasmonic resonance modes.

Broadband high absorption of long-wavelength infrared light for rough submicron active material films is quite challenging to achieve. Unlike conventional infrared detection units, with over three-layer complex structures, a three-layer metamaterial with mercury cadmium telluride (MCT) film sandwiched between an Au cuboid array and Au mirror is studied through theory and simulations. The results show that propagated/localized surface plasmon resonance simultaneously contribute to broadband absorption under the TM wave of the absorber, while the Fabry-Perot (FP) cavity resonance causes absorption of the TE wave. As surface plasmon resonance concentrates most of the TM wave on the MCT film, 74% of the incident light energy is absorbed by the submicron thickness MCT film within the 8-12 µm waveband, which is approximately 10 times than that of the rough same thickness MCT film. In addition, by replacing the Au mirror with Au grating, the FP cavity along the y-axis direction was destroyed, and the absorber exhibited excellent polarization-sensitive and incident angle-insensitive properties. For the corresponding conceived metamaterial photodetector, as carrier transit time across the gap between Au cuboid is much less than that of other paths, the Au cuboids simultaneously act as microelectrodes to collect photocarriers generated in the gap. Thus the light absorption and photocarrier collection efficiency are hopefully improved simultaneously. Finally, the density of the Au cuboids is increased by adding the same arranged cuboids perpendicular to the original direction on the top surface or by replacing the cuboids with crisscross, which results in broadband polarization-insensitive high absorption by the absorber.

sEMG-Based Gain-Tuned Compliance Control for the Lower Limb Rehabilitation Robot during Passive Training.

The lower limb rehabilitation robot is a typical man-machine coupling system. Aiming at the problems of insufficient physiological information and unsatisfactory safety performance in the compliance control strategy for the lower limb rehabilitation robot during passive training, this study developed a surface electromyography-based gain-tuned compliance control (EGCC) strategy for the lower limb rehabilitation robot. First, the mapping function relationship between the normalized surface electromyography (sEMG) signal and the gain parameter was established and an overall EGCC strategy proposed. Next, the EGCC strategy without sEMG information was simulated and analyzed. The effects of the impedance control parameters on the position correction amount were studied, and the change rules of the robot end trajectory, man-machine contact force, and position correction amount analyzed in different training modes. Then, the sEMG signal acquisition and feature analysis of target muscle groups under different training modes were carried out. Finally, based on the lower limb rehabilitation robot control system, the influence of normalized sEMG threshold on the robot end trajectory and gain parameters under different training modes was experimentally studied. The simulation and experimental results show that the adoption of the EGCC strategy can significantly enhance the compliance of the robot end-effector by detecting the sEMG signal and improve the safety of the robot in different training modes, indicating the EGCC strategy has good application prospects in the rehabilitation robot field.

Photodetection and Infrared Imaging Based on Cd3As2 Epitaxial Vertical Heterostructures.

Due to the nontrivial electronic structure, Cd3As2 is predicted to possess various transport properties and outstanding photoresponses. Photodetectors based on topological materials are mostly made up of nanoplates, yet monolithic in situ heteroepitaxial Cd3As2 photodetectors are rarely reported to date owing to the crystal mismatch between Cd3As2 and semiconductors. Here, we demonstrate Cd3As2/ZnxCd1-xTe/GaSb vertical heteroepitaxial photodetectors via molecule beam epitaxy. By constructing dual-Schottky junctions, these photodetectors show high responsivity and external quantum efficiency in a broadband spectrum. Based on the strong and fast photoresponse, we achieved visible light to near-infrared imaging using a one-pixel imaging system with a galvo. Our results illustrate that the integration of three-dimensional Dirac semimetal Cd3As2 with semiconductors has potential applications in broadband photodetection and infrared cameras.

Promoted Mid-Infrared Photodetection of PbSe Film by Iodine Sensitization Based on Chemical Bath Deposition.

In recent years, lead selenide (PbSe) has gained considerable attention for its potential applications in optoelectronic devices. However, there are still some challenges in realizing mid-infrared detection applications with single PbSe film at room temperature. In this paper, we use a chemical bath deposition method to deposit PbSe thin films by varying deposition time. The effects of the deposition time on the structure, morphology, and optical absorption of the deposited PbSe films were investigated by x-ray diffraction, scanning electron microscopy, and infrared spectrometer. In addition, in order to activate the mid-infrared detection capability of PbSe, we explored its application in infrared photodetection by improving its crystalline quality and photoconductivity and reducing tge noise and high dark current of PbSe thin films through subsequent iodine treatment. The iodine sensitization PbSe film showed superior photoelectric properties compared to the untreated sample, which exhibited the maximum of responsiveness, which is 30.27 A/W at 808 nm, and activated its detection ability in the mid-infrared (5000 nm) by introducing PbI2, increasing the barrier height of the crystallite boundary and carrier lifetimes. This facile synthesis strategy and the sensitization treatment process provide a potential experimental scheme for the simple, rapid, low-cost, and efficient fabrication of large-area infrared PbSe devices.

Epitaxial Topological Insulator Bi2Te3 for Fast Visible to Mid-Infrared Heterojunction Photodetector by Graphene As Charge Collection Medium.

Three dimensional topological insulators have a thriving application prospect in broadband photodetectors due to the possessed topological quantum states. Herein, a large area and uniform topological insulator bismuth telluride (Bi2Te3) layer with high crystalline quality is directly epitaxial grown on GaAs(111)B wafer using a molecular beam epitaxy process, ensuring efficient out-of-plane carriers transportation due to reduced interface defects influence. By tiling monolayer graphene (Gr) on the as-prepared Bi2Te3 layer, a Gr/Bi2Te3/GaAs heterojunction array prototype was further fabricated, and our photodetector array exhibited the capability of sensing ultrabroad photodetection wavebands from visible (405 nm) to mid-infrared (4.5 µm) with a high specific detectivity (D*) up to 1012 Jones and a fast response speed at about microseconds at room temperature. The enhanced device performance can be attributed to enhanced light-matter interaction at the high-quality heterointerface of Bi2Te3/GaAs and improved carrier collection efficiency through graphene as a charge collection medium, indicating an application prospect of topological insulator Bi2Te3 for fast-speed broadband photodetection up to a mid-infrared waveband. This work demonstrated the potential of integrated topological quantum materials with a conventional functional substrate to fabricate the next generation of broadband photodetection devices for uncooled focal plane array or infrared communication systems in future.

Zinc uptake and replenishment mechanisms during repeated phytoextraction using Sedum plumbizincicola revealed by stable isotope fractionation.

Improving phytoremediation techniques requires a thorough understanding of the mechanisms of plant uptake and the replenishment of the bioavailable pool of the target element, and this may be effectively explored using stable isotope methods. A repeated phytoextraction experiment over five successive crops of cadmium (Cd) and zinc (Zn) hyperaccumulator Sedum plumbizincicola X.H. Guo et S.B. Zhou ex L.H. Wu (Crassulaceae) was conducted using four agricultural soils differing in soil pH and clay content. The isotopic composition of total Zn and NH4OAc-extractable Zn in soils before phytoextraction and after the fifth crop were determined, together with Zn in shoot samples in the first crop. S. plumbizincicola preferentially took up light Zn isotopes from the NH4OAc-extractable pool (Δ66Znshoot-extract = -0.42 to -0.16‰), indicating the predominance of Zn low-affinity transport. However, after long-term phytoextraction NH4OAc-extractable Zn became isotopically lighter than prior to phytoextraction in three of the soils (Δ66Znextract: P5-P0 = -0.39 to -0.10‰). This was resulted from the equilibrium replenishment of Zn bound to iron (Fe) and manganese (Mn) oxides based on Zn isotopic and chemical speciation analysis. Zinc showed opposite fractionation patterns to Cd in the same plant-soil system with heavy Cd isotope enrichment in S. plumbizincicola (Δ114/110Cdshoot-extract = 0.02-0.17‰) and in the NH4OAc-extractable pool after repeated phytoextraction (Δ114/110Cdextract: P5-P0 = 0.07-0.18‰). This indicates different mechanisms of membrane transport (high-affinity transport of Cd) and supplementation of the bioavailable pool in soil (Cd supplied mainly through complexation with root-derived organic ligands) of the two metals. The combination of chemical speciation and stable Zn isotope ratios in the plant and the bioavailable soil pool reveal that the Zn pool related to Fe and Mn oxides became increasingly bioavailable with increasing crop generations. Capsule: Stable isotope analysis indicates that soil Fe- and Mn-oxide bound Zn replenishment boosted Zn uptake by the hyperaccumulator Sedum plumbizincicola during long-term remediation.

Experiments on Cu-isotope fractionation between chlorine-bearing fluid and silicate magma: implications for fluid exsolution and porphyry Cu deposits.

Hydrothermal fluid is essential for transporting metals in the crust and mantle. To explore the potential of Cu isotopes as a tracer of hydrothermal-fluid activity, Cu-isotope fractionation factors between Cl-bearing aqueous fluids and silicate magmas (andesite, dacite, rhyolite dacite, rhyolite and haplogranite) were experimentally calibrated. Fluids containing 1.75-14 wt.% Cl were mixed together with rock powders in Au95Cu5 alloy capsules, which were equilibrated in cold-seal pressure vessels for 5-13 days at 800-850°C and 2 kbar. The elemental and Cu-isotopic compositions of the recovered aqueous fluid and solid phases were analyzed by (LA-) ICP-MS and multi-collector inductively coupled plasma mass spectrometry, respectively. Our experimental results show that the fluid phases are consistently enriched in heavy Cu isotope (65Cu) relative to the coexisting silicates. The Cu-isotope fractionation factor (Δ65CuFLUID-MELT) ranges from 0.08 ± 0.01‰ to 0.69 ± 0.02‰. The experimental results show that the Cu-isotopic fractionation factors between aqueous fluids and silicates strongly depend on the Cu speciation in the fluids (e.g. CuCl(H2O), CuCl2 - and CuCl3 2-) and silicate melts (CuO1/2), suggesting that the exsolved fluids may have higher δ65Cu than the residual magmas. Our results suggest the elevated δ65Cu values in Cu-enriched rocks could be produced by addition of aqueous fluids exsolved from magmas. Together with previous studies on Cu isotopes in the brine and vapor phases of porphyry deposits, our results are helpful for better understanding Cu-mineralization processes.

Construction of core-shell structured WO3@SnS2 hetero-junction as a direct Z-scheme photo-catalyst.

An ideal photocatalyst not only offers high photo-generated electron-hole pairs separation ability, but also has suitable redox potential. Here, a direct Z-scheme core-shell structured WO3@SnS2 hetero-junction photo-catalyst was prepared via two-step hydrothermal method, in which the core-shell structure, rod morphology and micro-composition of hetero-junction were confirmed through X-ray diffraction (XRD) patterns, Fourier transform infrared (FTIR) spectra, field emission scanning electron microscope (FE-SEM), transmission electron microscope (FEI-TEM) and X-ray photoelectron spectra (XPS). Their enhanced photo-catalytic abilities were evaluated by photo-degradation of Rhodamine (RhB), photo-reduction of dichromate (Cr6+) solution and photo-catalytic H2 production through comparing with pure WO3, SnS2 or the mixture of WO3 and SnS2 (WO3/SnS2). The absorption spectra and electrochemical properties were used to estimate the band gap of samples, the expanded spectral absorption capacity and improved electron-hole separation ability, which are important factors for enhanced photocatalytic performance. Furthermore, the direct Z-scheme charge transfer mechanism of WO3@SnS2 hetero-junction was determined through the combination of theoretical calculation and experimental characterizations, which played a decisive role for retaining excellent redox potential and increasing photo-catalytic ability of WO3 and SnS2.

Influence of room temperature on magnesium isotope measurements by multi-collector inductively coupled plasma mass spectrometry.

RATIONALE: We observed that the accuracy and precision of magnesium (Mg) isotope analyses could be affected if the room temperature oscillated during measurements. To achieve high-quality Mg isotopic data, it is critical to evaluate how the unstable room temperature affects Mg isotope measurements by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). METHODS: We measured the Mg isotopes for the reference material DSM-3 using MC-ICP-MS under oscillating room temperatures in spring. For a comparison, we also measured the Mg isotopes under stable room temperatures, which were achieved by the installation of an improved temperature control system in the laboratory. RESULTS: The δ26 Mg values measured under oscillating room temperatures have a larger deviation (δ26 Mg from -0.09 to 0.08‰, with average δ26 Mg = 0.00 ± 0.08‰) than those measured under a stable room temperature (δ26 Mg from -0.03 to 0.03‰, with average δ26 Mg = 0.00 ± 0.02‰) using the same MC-ICP-MS system. CONCLUSIONS: The room temperature variation can influence the stability of MC-ICP-MS. Therefore, it is critical to keep the room temperature stable to acquire high-precision and accurate isotopic data when using MC-ICP-MS, especially when using the sample-standard bracketing (SSB) correction method.