Theoretical and Experimental Investigations on High-Precision Micro-Low-Gravity Simulation Technology for Lunar Mobile Vehicle.

With the development of space technology, the functions of lunar vehicles are constantly enriched, and the structure is constantly complicated, which puts forward more stringent requirements for its ground micro-low-gravity simulation test technology. This paper puts forward a high-precision and high-dynamic landing buffer test method based on the principle of magnetic quasi-zero stiffness. Firstly, the micro-low-gravity simulation system for the lunar vehicle was designed. The dynamic model of the system and a position control method based on fuzzy PID parameter tuning were established. Then, the dynamic characteristics of the system were analyzed through joint simulation. At last, a prototype of the lunar vehicle's vertical constant force support system was built, and a micro-low-gravity landing buffer test was carried out. The results show that the simulation results were in good agreement with the test results. The sensitivity of the system was better than 0.1%, and the constant force deviation was 0.1% under landing impact conditions. The new method and idea are put forward to improve the micro-low-gravity simulation technology of lunar vehicles.

Flexible and Reusable Ag Coated TiO2 Nanotube Arrays for Highly Sensitive SERS Detection of Formaldehyde.

Quantitative analysis of formaldehyde (HCHO, FA), especially at low levels, in various environmental media is of great importance for assessing related environmental and human health risks. A highly efficient and convenient FA detection method based on surface-enhanced Raman spectroscopy (SERS) technology has been developed. This SERS-based method employs a reusable and soft silver-coated TiO2 nanotube array (TNA) material, such as an SERS substrate, which can be used as both a sensing platform and a degradation platform. The Ag-coated TNA exhibits superior detection sensitivity with high reproducibility and stability compared with other SERS substrates. The detection of FA is achieved using the well-known redox reaction of FA with 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (AHMT) at room temperature. The limit of detection (LOD) for FA is 1.21 × 10-7 M. In addition, the stable catalytic performance of the array allows the degradation and cleaning of the AHMT-FA products adsorbed on the array surface under ultraviolet irradiation, making this material recyclable. This SERS platform displays a real-time monitoring platform that combines the detection and degradation of FA.

Direct Dynamic Evidence of Charge Separation in a Dye-Sensitized Solar Cell Obtained under Operando Conditions by Raman Spectroscopy.

Interfaces play an important role in enhancing the energy conversion performance of dye-sensitized solar cells (DSCs). The interface effects have been studied by many techniques, but most of the studies only focused on one part of a DSC, rather than on a complete solar cell. Hence, monitoring the interface evolution of a DSC is still very challenging. Here, in situ/operando resonance Raman (RR) spectroscopic analyses were carried out to monitor the dynamics of the photovoltaic conversion processes in a DSC. We observed the creation of new species (i.e., polyiodide and iodine aggregates) in the photosensitization process. We also obtained molecular-scale dynamic evidence that the bands from the C=C and C=N bonds of 2,2'-bipyridyl (bpy), the S=C=N bonds of the NCS ligand, and photochemical products undergo reasonably strong intensity and frequency changes, which clearly demonstrates that they are involved in charge separation. Furthermore, RR spectroscopy can also be used to quickly evaluate the performance of DSCs.

Environmental contamination and health risk assessment of potentially toxic trace metal elements in soils near gold mines - A global meta-analysis.

Gold mining is the most important anthropogenic source of heavy metal emissions into the environment. Researchers have been aware of the environmental impacts of gold mining activities and have conducted studies in recent years, but they have only selected one gold mining site and collected soil samples in its vicinity for analysis, which does not reflect the combined impact of all gold mining activities on the concentration of potentially toxic trace elements (PTES) in nearby soils at a global scale. In this study, 77 research papers from 24 countries were collected from 2001 to 2022, and a new dataset was developed to provide a comprehensive study of the distribution characteristics, contamination characteristics, and risk assessment of 10 PTEs (As, Cd, Cr, Co, Cu, Hg, Mn, Ni, Pb, and Zn) in soils near the deposits. The results show that the average levels of all 10 elements are higher than the global background values and are at different levels of contamination, with As, Cd, and Hg at strong contamination levels and serious ecological risks. As and Hg contribute to a greater non-carcinogenic risk to both children and adults in the vicinity of the gold mine, and the carcinogenic risks of As, Cd, and Cu are beyond the acceptable range. Gold mining on a global scale has already caused serious impacts on nearby soils and should be given adequate attention. Timely heavy metal treatment and landscape restoration of extracted gold mines and environmentally friendly approaches such as bio-mining of unexplored gold mines where adequate protection is available are of great significance.

Removal of Pb from Contaminated Kaolin by Pulsed Electrochemical Treatment Coupled with a Permeable Reactive Barrier: Tuning Removal Efficiency and Energy Consumption.

Lead contamination in soil has emerged as a significant environmental concern. Recently, pulse electrochemical treatment (PECT) has garnered substantial attention as an effective method for mitigating lead ions in low-permeability soils. However, the impact of varying pulse time gradients, ranging from seconds to hours, under the same pulse duty cycle on lead removal efficiency (LRE) and energy consumption in PECT has not been thoroughly investigated. In this study, a novel, modified PECT method is proposed, which couples PECT with a permeable reaction barrier (PRB) and adds acetic acid to the catholyte. A comprehensive analysis of LRE and energy consumption is conducted by transforming pulse time. The results show that the LREs achieved in these experiments were as follows: PCb-3 s (89.5%), PCb-1 m (91%), PCb-30 m (92.9%), and PCb-6 h (91.9%). Importantly, these experiments resulted in significant reductions in energy consumption, with decreases of 68.5%, 64.9%, 51.8%, and 47.4% compared to constant voltage treatments, respectively. It was observed that LRE improved with an increase in both pulse duration and voltage gradient, albeit with a corresponding rise in energy consumption. The results also revealed that corn straw biochar as a PRB could enhance LRE by 6.1% while adsorbing migrating lead ions. Taken together, the present data highlights the potential of modified PECT technology for remediation of lead-contaminated soil, which provides an optimal approach to achieve high LRE while minimizing energy consumption.

Process design and validation of a new mixed eluent for leaching Cd, Cr, Pb, Cu, Ni, and Zn from heavy metal-polluted soil.

Chemical leaching, an emerging technology for treating heavy metal-polluted soils, requires a design for reasonable and new eluent and an evaluation of its efficiency on the simultaneous removal of different elements. In this study, the leaching effect and biodegradability of chelating agents were compared, and ethylenediamine disuccinic acid (EDDS) was selected to combine with ferric chloride (FeCl3) for the design of a mixed eluent (EDDS + FeCl3). Through batch experiments, the influences of the eluent concentration and solution pH on leaching were revealed, and leaching efficiencies of EDDS, FeCl3, and EDDS + FeCl3 on six heavy metals Cd, Cr, Pb, Cu, Ni, and Zn in the soil were separately analyzed. Results indicated that EDDS + FeCl3 showed advantages over both EDDS and FeCl3 alone, and it presented an excellent effect, especially for simultaneously leaching multiple heavy metals from the soil. The highest leaching efficiencies for Cd, Cr, Pb, Cu, Ni, and Zn reached up to 71.36%, 21.29%, 31.14%, 30.25%, 34.05%, and 4.96%, respectively. According to different soil types and target elements, the concentration, pH condition, and mass ratio of EDDS + FeCl3 could be adjusted for soil remediation. Fourier transform infrared spectroscopy proved that the better leaching effect of EDDS + FeCl3 was attributed to changes in the number and strength of functional groups in the solution, which enhanced the chelating ability of the mixed eluent and heavy metal ions. Therefore, chemical leaching by EDDS + FeCl3 for the remediation of multiple heavy metal-contaminated soil is a potential feasible strategy.

A highly selective fluorescent probe for Al3+ based on bis(2-hydroxy-1-naphthaldehyde) oxaloyldihydrazone with aggregation-induced emission enhancement and gel properties.

An efficient fluorescent probe, bis(2-hydroxy-1-naphthaldehyde) oxaloyldihydrazone (1), has been prepared for the selective sensing of Al3+ over other common metal ions in water-containing media. The 1:1 stoichiometry of 1 and Al3+ was determined from Job's plot and Benesti-Hildebrand plot. The binding constant was observed as 1.6×105M-1, and the limit of detection was found to be 0.36µM, which was far below the drinking water restriction of Al3+ by EPA (the maximum allowable value is 7.4µM). In addition, the inherent AIEE features of 1 were observed upon addition of water to DMSO solution due to the restriction of the intramolecular motion, which makes the molecular conformations rigid and planar. Moreover, 1 could act as a novel gelator to form thermo-reversible supramolecular organogel with significant green emission in DMSO-H2O (v/v, 9:1) solution.

Microstructure and Corrosion Behavior of Friction Stir-Welded 6061 Al/AZ31 Mg Joints with a Zr Interlayer.

Friction stir welding (FSW) with a Zr interlayer was employed to join dissimilar alloys of 6061 Al and AZ31 Mg. The microstructures of Al/Mg and Al/Zr/Mg joints were investigated by optical microscopy (OM), scanning electron microscopy (SEM), and energy dispersive X-ray spectrometer (EDS). The results showed that the central part of the Zr interlayer was smashed and intermixed with the base materials in the stir zone, whereas the undamaged part remained stable at the Al/Mg interface. The formation of Al-Mg intermetallic compounds (IMCs) was suppressed by the Zr interlayer due to its synergetic effects of chemical modification and thermal barrier. The electrochemical measurements revealed a differentiated corrosion behavior for each joint, where the corrosion rate of representative regions increased in the order of Al alloy < Mg alloy < heat-affected zone < stir zone. The immersion tests indicated an enhancement in corrosion resistance for the Al/Zr/Mg joint compared with the Al/Mg joint, which is owing to the mitigated galvanic corrosion between the base materials by the Zr interlayer.

Substituent effects on anion sensing of salicylidene Schiff base derivatives: Tuning sensitivity and selectivity.

A series of colorimetric anion sensors using the salicylidene Schiff bases with different substituents, including electron donating group (tert-butyl, in sensor 2), conjugated group (naphthyl, in sensor 3) and electron withdrawing group (chlorine, in sensor 4), respectively, have been developed. The substituents can not only impact chromogenic signal output, but also tune the sensitivity and selectivity of the anion sensing by their specific electron push-pull features. In particular, both 1 (without substituent) and 2 show high selectivity for F(-) over Cl(-), Br(-), I(-), AcO(-) and H2PO4(-), but the sensitivity of 2 is poorer than 1 due to the effect of electron donating groups. Sensor 3 exhibits higher sensitivity for F(-) than 1, but it is disturbed by the weak response to AcO(-) and H2PO4(-). Sensor 4 has the highest sensitivity for F(-), but shows the significant response to AcO(-) and H2PO4(-), which also decreases the selectivity for F(-). Finally, analytical applications of 1 for the detection of F(-) in aqueous medium and toothpaste have been studied.

A molecular half-subtractor with Zn2+ and UV-light as inputs.

The salen-type Schiff base (2,2'-bis(2-hydroxybenzylideneamino)-1,1'-binaphthyl (BHB)) has been synthesized and characterized. Exhibiting absorption and fluorescence changes in the presence of Zn(2+) in chloroform and ethanol mixed solution, BHB could be used as a fluorescent chemosensor for the detection of Zn(2+). Furthermore, by monitoring the fluorescence and absorbance as output signals, BHB can function as a combinatorial logic circuit for a molecular half-subtractor with Zn(2+) and UV irradiation as input variables.

Hydrogen-bonding A(LS)2-type low-molecular-mass gelator and its thermotropic mesomorphic behavior.

A unique cholesterol-based A(LS)2-type gelator, which is a hydrogen-bonding complex based on an ALS-type non-gelator molecule 3-cholesteryl 4-(trans-2-(4-pyridinyl)vinyl)phenyl succinate and a counterpart 3-cholesteryloxycarbonylpropanoic acid, shows strong gelation ability in alcohol and aromatic solvents. The formed gel has a high Tg at low gelation concentration, and its xerogel shows fibrillar microstructure revealed by scanning electron microscopy (SEM). FTIR confirms the existence of intermolecular hydrogen bond in the gelator, and X-ray diffraction (XRD) analysis reveals that the gelator possesses a folded conformation in gel and self-assembles into the fibrillar structure mainly by van der Waals interaction between cholesteryl moieties of the gelator. Further more, the thermotropic behavior of the xerogel is studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM), which shows typical optical textures of liquid crystals.