Constructing conductive titanium carbide nanosheet (MXene) network on polyurethane/polyacrylonitrile fibre framework for flexible strain sensor.

HYPOTHESIS: MXenes (two-dimensional early transition metal carbides and carbonitrides) possess both excellent conductivity and surface hydrophilicity, enabling more diverse potential applications. However, in flexible strain sensors, the flexible substrates are usually composed of hydrophobic elastomers such as thermoplastic polyurethane (TPU). To enhance the interactions between MXenes and hydrophobic. substrates, it is wiser to change the composition of the flexible substrate than to modify the surface of MXenes, so as to improve the interactions between the flexible substrate and MXenes without losing the excellent conductivity of MXene. EXPERIMENTS: We introduce polyacrylonitrile (PAN) into TPU, and then fabricate a flexible TPU/PAN mat through electrospinning. A highly conductive and stretchable Ti3C2 MXene/TPU/PAN mat was then prepared by a simple dip-coating process. The interaction mechanism between Ti3C2 MXene nanosheets and TPU/PAN mat was investigated by XPS and FT-IR. Finally, we build the MXene/TPU/PAN mat into a flexible strain sensor with excellent properties. FINDINGS: By introducing PAN into flexible substrate, the interaction between Ti3C2 MXene and the flexible substrate was effectively improved without compromising Ti3C2 MXene's excellent conductivity. The MXene/TPU/PAN strain sensor possesses a wide sensing range (0-80%), a fast response (<140.6 ms), a low limit of detection (<0.1%), splendid coating adhesion and excellent durability (>1750 cycles). All of these properties are demanded in wearable electronics.

High-level stable expression of gene for preparation of chlorothalonil hydrolytic dehalogenase and its application in elimination of chlorothalonil inhibition on bioconversion of lignocellulosic biomass.

To achieve the high-level stable expression of chlorothalonil hydrolytic dehalogenase (Chd), the gene chd was first integrated into the chromosome of Bacillus subtilis WB800. High generation stability was achieved by almost no gene lost after six generations but Chd activity decreased. aprE promoter alteration, translation initiation region modification and multi-copy chromosome integration were studied and these modifications could increase Chd activity by 270%, 2304% and 25%. Chlorothalonil residual exhibited inhibition on bioconversion of lignocellulosic biomass. The addition of Chd crude enzyme (60 µL per g wheat straw) could increase glucose production by 36.10% and 39.65% in synergistic hydrolysis and separate hydrolysis by laccase and cellulase with 120 mg/L residual chlorothalonil. Filter paper activity and carboxymethyl cellulase activity were enhanced by 12.84% and 23.95%, and biomass of Trichoderma reesei was increased by 76.67% under 50 µg chlorothalonil/g dry straw in solid-state fermentation. Thus, the high-level stable expressed Chd effectively eliminated chlorothalonil inhibition on enzymatic hydrolysis and solid-state fermentation. It showed promising potential for bioremediation of chlorothalonil pollution and improving conversion efficiency of lignocellulose.

Electrostatic wrapping of eupatorium-based botanical herbicide with chitosan derivatives for controlled release.

To avoid the negative effects of chemical herbicides and prepare herbicide with long-term efficacy, the active ingredients of eupatorium adenophorum spreng (AIEAS, negatively charged) were used as a botanical herbicide, and based on electrostatic attraction, the self-assembled hydroxyl isopropyl chitosan (HPCTS, positively charged) and carboxymethyl chitosan (CMC, with good water solubility) were successfully employed as degradable and water-soluble carrier for AIEAS to realize its controlled release. The release of AIEAS from the chitosan carrier in water could be divided into two stages. In the first stage, a fast release of AIEAS was detected and the total amount of the released AIEAS reached 41.5 %, while the release rate effectively slowed down in the second stage, indicating that good balance between fast control of weeds and long-term efficacy was achieved through this controlled delivery system. The release kinetics of AIEAS during the whole release process showed good fit to the Ritger-Peppas model with Fickian diffusion as the dominant release mechanism. Moreover, it found that the released AIEAS from chitosan carrier showed fine herbicidal effect on barnyard grass.

Effect of pesticide residues on simulated beer brewing and its inhibition elimination by pesticide-degrading enzyme.

Four different pesticide residues used in barley planting were selected to investigate their effects on simulated beer brewing. The influences were found to be different by varied agricultural chemicals. Among the four types of pesticides, at 25 µg/mL, triadimefon or carbendazim barely affected the brewing progress. However, ethametsulfuron-methyl and carbaryl (15 µg/mL and 2.5 µg/mL, respectively) exhibited slightly inhibition on saccharification and significantly negative impacts on yeast growth and alcohol fermentation. After pretreated by 50 µL carbaryl-degrading enzyme with the Kcat value of 2.12 s-1 at 30°C for 90 min, the negative influence on simulated beer brewing brought by carbaryl can be eliminated in the fermentation system containing 2.5 µg/mL carbaryl. The efficiency of ethanol fermentation was improved, and the removal rate of carbaryl in the brewing system was greatly accelerated. Taken together, this study suggested a potential method for solving the fermentation inhibition by pesticide residues.

A green approach for tunable fluorescent and superhydrophobic monodisperse polysilsesquioxane spheres.

HYPOTHESIS: Typically, calcination at high temperature could bring fluorescence to hybrid silica spheres prepared with 3-aminopropyltriethoxysilane and tetraethylorthosilicate, but they tended to be hydrophilic. Further extra modification is required to gain superhydrophobicity, which might probably block the fluorescence. Short side organic chains are very thermostable at high temperature. Therefore, it might be possible to produce superhydrophobic and fluorescent hybrid silica spheres through the co-condensation of organosilanes with short side organic chains and calcination at high temperature. EXPERIMENTS: Methyltrimethoxysilane (MTMS) and vinyltrimethoxysilane (VTMS) were co-condensed to prepare polysilsesquioxane (PSQ) spheres, which were subsequently calcinated at high temperature. The impact of MTMS/VTMS ratio on the chemical structures, fluorescence and wettability was investigated, and the applications of PSQ spheres were expanded. FINDINGS: The PSQ spheres with the ratio of MTMS/VTMS as 3/1 and 2/2 exhibited strong fluorescence, and the calcination did not destroy the superhydrophobicity for the remaining of abundant methyl, vinyl, or ethyl groups. Our study provides an extremely green, simple and effective approach to prepare thermostable, fluorescent and superhydrophobic monodisperse silica spheres without using rare earth element, gold, conjugated polymer, phorsphore, fluoride chemical or organic solvent.

Ti3C2 MXene as a new nanofiller for robust and conductive elastomer composites.

Ti3C2 MXene with a layered 2D structure was applied as a novel functional filler in rubber for the first time. A facile and green method was proposed to fabricate rubber/Ti3C2 nanocomposites via a freeze-drying & mechanical mixing process. It was found that Ti3C2 with ∼1 nm thickness fabricated by etching Al from Ti3AlC2 phases can be dispersed in styrene-butadiene rubber (SBR) evenly in a single-layered state. Mechanical strength and electrical and thermal conductivities of the rubber nanocomposites were remarkably enhanced by the incorporation of Ti3C2, showing dramatic improvement compared with reduced graphene oxide (rGO) reinforced rubber composites. For example, the thermal conductivity of SBR nanocomposites with 3 wt% rGO was 0.265 W m-1 k-1, while that of SBR nanocomposites with only 1.96 wt% Ti3C2 reached 0.477 W m-1 k-1. Meanwhile, the resistance of rubber/Ti3C2 nanocomposites was stable under complex deformation and their sensitivity was well recovered during stretching/shrinking cycles under large strain. Moreover, it was discovered that incorporating Ti3C2 in rubber nanocomposites dramatically improved the wet skid resistance and thermal stability without increasing the rolling resistance. Ti3C2 MXene with a distinctive structure and properties as well as uniform dispersion will have more potential for the preparation of high-performance rubber nanocomposites, especially for green tires and flexible sensors.

Immobilization of rubber additive on graphene for high-performance rubber composites.

It is still a challenge to achieve simultaneous improvements in aging resistance, mechanical strength, thermal conductivity and dielectric constant of rubber composites via incorporation of graphene obtained by conventional methods. Herein, an effective and green method was proposed to simultaneously reduce and functionalize graphene oxide (GO) with 2-mercaptobenzimidazole (antioxidant MB) via a one-pot method. GO was successfully reduced by MB which was also chemically grafted on the reduced GO (G-MB). G-MB sheets were uniformly dispersed in rubber with strong interfacial interaction, and graphene-graphene conductive paths were formed through intermolecular H-bonding between the grafted antioxidant molecules. Consequently, rubber composites with G-MB showed higher thermal conductivity, mechanical strength and dielectric constant than rubber composites with hydrazine hydrate reduced GO (rGO). Moreover, the thermo-oxidative aging resistance of rubber composites with G-MB was also superior to that of rubber composites with rGO because of the elimination of blooming effect of the grafted MB molecules. Thus, this work may open a new way for the eco-friendly functionalization and reduction of GO and may boost the development of high-performance, functional graphene-elastomer composites.

Functionalized Halloysite Nanotubes⁻Silica Hybrid for Enhanced Curing and Mechanical Properties of Elastomers.

Vulcanization and reinforcement are critical factors in governing the ultimate practical applications of elastomer composites. Here we achieved a simultaneous improvement of curing and mechanical properties of elastomer composites by the incorporation of a functionalized halloysite nanotubes-silica hybrid (HS-s-M). Typically, HS-s-M was synthesized by 2-mercapto benzothiazole (M) immobilized on the surface of halloysite nanotubes-silica hybrid (HS). It was found that the HS-s-M uniformly dispersed in the styrene-butadiene rubber (SBR) matrix, offering more opportunity for M molecules to communicate with rubber. In addition, the physical loss of accelerator M from migration and volatilization was efficiently suspended. Therefore, SBR/HS-s-M composites showed a lower curing activation energy and a higher crosslinking density than SBR/HS composites. Moreover, a stronger interfacial interaction between HS-s-M and SBR was formed by the cross-linking reaction, giving a positive contribution to the eventual mechanical properties. The possible vulcanization and reinforcement mechanisms of SBR/HS-s-M composites were also analyzed in detail.

Halloysite Tubes as Nanocontainers for Herbicide and Its Controlled Release in Biodegradable Poly(vinyl alcohol)/Starch Film.

Commercial herbicide atrazine (AT) was first loaded into the lumen of halloysite nanotubes (HNTs) in the amount of 9 wt %, and then the AT-loaded HNTs (HNTs-AT) were further incorporated into poly(vinyl alcohol)/starch composites (PVA/ST, with the weight ratio of 80/20) to construct a dual drug delivery system. AT loaded in nanotubes displayed much slower release from PVA/ST film in water than free AT; for example, the total release amount of AT from PVA/ST film with loaded AT was only 61% after 96 h, while this value reached 97% in PVA/ST film with free AT. The release behavior of AT from PVA/ST film with HNTs-AT was first dominated by the mechanism of matrix erosion and then by the mechanism of Fickian diffusion. In addition, combining HNTs and PVA/ST blends together in the controlled release of herbicide also reduced its leaching through the soil layer, which would be useful for diminishing the environmental pollution caused by pesticide.