Pyromellitic-Based Low Molecular Weight Gelators and Computational Studies of Intermolecular Interactions: A Potential Additive for Lubricant.

Low molecular weight gelators (LMWG) have been extensively explored in many research fields due to their unique reversible gel-sol transformation. Intermolecular interactions between LMWG are known as the main driving force for self-assembly. During this self-assembly process, individually analyzing the contribution difference between various intermolecular interactions is crucial to understand the gel properties. Herein, we report 2,5-bis(hexadecylcarbamoyl)terephthalic acid (BHTA) as a LMWG, which could efficiently form a stable organogel with n-hexadecane, diesel, liquid paraffin, and base lubricant oil at a relatively low concentration. To investigate the contribution difference of intermolecular interactions, we first finished FT-IR spectroscopy and XRD experiments. On the basis of the d-spacing, a crude simulation model was built and then subjected to molecular dynamics (MD) simulations. Then, we knocked out the energy contribution of the H-bonding interactions and π-π stacking, respectively, to evaluate the intermolecular interactions significantly influencing the stability of the gel system. MD simulations results suggest that the self-assembly of the aggregates was mainly driven by dense H-bonding interactions between carbonyl acid and amide moieties of BHTA, which is consistent with FT-IR data. Moreover, wave function analysis at a quantum level suggested these electrostatic interactions located in the middle of the BHTA molecule were surrounded by strong dispersion attraction originating from a hydrophobic environment. Furthermore, we also confirmed that 2 wt % BHTA was able to form gel lubricant with 150BS. The coefficient of friction (COF) data show that the gel lubricant has a better tribological performance than 150BS base lubricant oil. Finally, XPS was performed and offered valuable information about the lubrication mechanism during the friction.

Miniaturized Low-Frequency Communication System Based on the Magnetoelectric Effect.

Recently, the realization of electromagnetic wave signal transmission and reception has been achieved through the utilization of the magnetoelectric effect, enabling the development of compact and portable low-frequency communication systems. In this paper, we present a miniaturized low-frequency communication system including a transmitter device and a receiver device, which operates at a frequency of 44.75 kHz, and the bandwidth is 1.1 kHz. The transmitter device employs a Terfenol-D (80 mm × 10 mm × 0.2 mm)/PZT (30 mm × 10 mm × 0.2 mm)/Terfenol-D glued composite heterojunction magnetoelectric antenna and the strongest radiation in the length direction, while the receiver device utilizes a manually crafted coil maximum size of 82 mm, yielding a minimum induced electromagnetic field of 1 pT at 44.75 kHz. With an input voltage of 150 V, the system effectively communicates over a distance of 16 m in air and achieves reception of electromagnetic wave signals within 1 m in simulated seawater with a salinity level of 35% at 25 °C. The miniaturized low-frequency communication system possesses wireless transmission capabilities, a compact size, and a rapid response, rendering it suitable for applications in mining communication, underwater communication, underwater wireless energy transmission, and underwater wireless sensor networks.

Geometry transformation of ionic surfactants and adsorption behavior on water/n-decane-interface: calculation by molecular dynamics simulation and DFT study.

Understanding the effect of surfactant structure on their ability to modify interfacial properties is of great scientific and industrial interest. In this work, we have synthesized four amide based ionic surfactants under acidic or basic conditions, including CTHA·HCl, CTEA·HCl, CTHA-Na+ and CTEA-Na+. Experiments have proved that the anionic surfactant with polyethylene oxide groups (CTEA-Na+) had the lowest surface tension on the water/n-decane interface. Molecular dynamics simulations have been applied to investigate the structural effect on the adsorption behavior of four different surfactants. The surface tension, interface thickness, interface formation energy, density profiles, order parameters, radial distribution function on the water/n-decane interfaces were calculated and compared. During the equilibrium states, we found that the interface configuration of two cationic surfactants are almost linear while the two anionic surfactants are changed to bending shapes due to the different positions of the hydrophilic head groups. Further DFT study and wavefunction analysis of surfactants have shown that CTEA-Na+ can form stronger vdW interactions with n-decane molecules due to a more neutral electrostatic potential distribution. Meanwhile, the introduction of polyethylene oxide groups has offered more H-bonding sites and resulted in more concentrated H-bonding interactions with water molecules. The difference of weak interactions may contribute to the conformational change and finally affect the interface properties of these ionic surfactants.

Titanosilicate Derived SiO2/TiO2@C Nanosheets with Highly Distributed TiO2 Nanoparticles in SiO2 Matrix as Robust Lithium Ion Battery Anode.

Carbon-coated SiO2/TiO2 (SiO2/TiO2@C) nanosheets consisting of TiO2 nanoparticles uniformly embedded in SiO2 matrix and a carbon-coating layer are fabricated by using acidified titanosilicate JDF-L1 nanosheets as template and precursor. SiO2/TiO2@C has unique structural features of sheetlike nanostructure, ultrafine TiO2 nanoparticles distributed in SiO2 matrix, and carbon coating, which can expedite ion diffusion and electron transfer and relieve volume expansion efficiently, and thus, the synergetic combination of these advantages significantly enhances its Li storage capability. As anode of lithium-ion batteries (LIBs), SiO2/TiO2@C nanosheets exhibit a high capacity of 998 mAh g-1 at 100 mA g-1 after 100 cycles. Moreover, an ultrahigh capacity of 410 mAh g-1 retains at 2000 mA g-1 after 400 cycles. A mixed reaction mechanism of capacitance and diffusion-controlled intercalation is revealed by qualitative and quantitative analysis.

Investigation of Y/SBA Composite Molecular Sieves Morphology Control and Catalytic Performance for n-Pentane Aromatization.

Using Y molecular sieve as the core, Y/SBA-15 composite molecular sieves were prepared by different crystallization methods in the paper. The growth process and morphologies of the composite molecular sieves were controlled by adjusting the synthesis factors. The structures and acidity of two kinds of composite molecular sieves were characterized by X-ray diffraction (XRD), N2 adsorption/desorption, transmission electron microscopy (TEM), and NH3-TPD. The catalysis performances of the composite molecular sieves were investigated in the aromatization reaction of n-pentane. The results indicated that the desired core-shell composite molecular sieves were obtained when the crystallization conditions were 36 hours, 100 °C and secondary crystallization. The aromatization results showed that core-shell composite molecular sieves had better selectivity for producing high application value xylenes compared to mixed-crystal composite molecular sieves.

Evaluation of three ornamental plants for phytoremediation of Pb-contamined soil.

Characteristics of accumulation and tolerance of lead (Pb) in Quamolit pennata, Antirrhinum majus L. and Celosia cristata pyramidalis were investigated to identify Pb-accumulating plants. In this study, pot culture experiment was conducted to assess whether these plants are Pb-hyperaccumulators or accumulators. The results indicated that the Pb enrichment factor (concentration in plant/soil) and Pb translocation factor (concentration in shoot/root) of these plants were principally <1 in pot culture and concentration gradient experiments. However, the Pb concentration in Celosia cristata pyramidalis shoots was higher than 1000 mg kg(-1), the threshold concentration for a Pb-hyperaccumulator. Shoot biomass of Celosia cristata pyramidalis had no significantly (p < 0.05) variation compared to the control. Based on these results, only Celosia cristata pyramidalis could be identified as a Pb-accumulator.

Adsorption and heterogeneous oxidation of As(III) on ferrihydrite.

Redox transformation of arsenic strongly influences its fate and transport in the environment. It is of interest to investigate heterogeneous oxidation of As(III) on the surface of major metal oxide in sediments. Whether As(III) can be oxidized on ferrihydrite and the role ferrihydrite plays as catalyst or oxidant are inconsistent in previous researches. In this work, oxidation of As(III) on ferrihydrite was studied by analysis of dissolved and adsorbed As(III) and As(V) quantitatively and qualitatively. X-ray absorption near edge spectroscopy (XANES) and pH(pznpc) (point of zero net proton charge) of ferrihydrite with adsorbed As(III) showed clear evidence for partial oxidation on ferrihydrite. Oxidation of As(III) occurred when it was brought to contact with ferrihydrite at high Fe/As molar ratio (i.e. 50, 200). The concentration of As(V) in solid phase increased gradually while adsorbed As(III) concentration dropped. Fe(II) was not detectable during the oxidation of As(III). These results showed that ferrihydrite had the catalytic effect on oxidation of As(III). Only a fraction of As(III) was oxidized even when the system was exposed to air. The effects of ferrihydrite aging, media pH, coexistence of ions on As(III) oxidation were also investigated. The results suggest that catalytic oxidation of As(III) on ferrihydrite may play a role in geochemical cycling of arsenic in environment.

Photocatalytic oxidation of arsenite by a composite of titanium dioxide and activated carbon fiber.

Preoxidation process is usually needed in the treatment of arsenic-containing drinking water because arsenite (i.e. As[III]) is less easily removed by adsorption. Nano-scale titanium dioxide is an efficient photocatalyst for arsenite oxidation but its application in water treatment is limited due to the difficulty of separation or packed-bed application of the tiny particles. This study synthesized a composite photocatalyst by loading titanium dioxide onto activated carbon fiber (TiO(2)/ACF). The effects of calcination temperature, photocatalyst dosage, pH, initial concentration of As(III) and common anions on the oxidation of As(III) were studied. Photocatalytic oxidation of As(III) took place in minutes and followed first-order kinetics. 0.80 mg L(-1) of As(III) could be entirely oxidized to As(V) within 30 min in the presence of 3.0 g L(-1) photocatalyst and under UV-light irradiation. The oxidation of As(III) occurred in a wide range of pH as examined from 2 to 10 with the oxidation efficiency increasing markedly with pH. The presence of phosphate and silicate significantly decreased As(III) oxidation at pH 7, while the effect of sulfate and chloride was small.