Highly Efficient Laser Bidirectional Graphene Printing: Integration of Synthesis, Transfer and Patterning.

Graphene has tremendous potential in future electronics due to its superior force, electrical, and thermal properties. However, the development of graphene devices is limited by its complex, high-cost, and low-efficiency preparation process. This study proposes a novel laser bidirectional graphene printing (LBGP) process for the large-scale preparation of patterned graphene films. In LBGP, a sandwich sample composed of a thermoplastic elastomer (TPE) substrate, carbon precursor powder, and a glass cover is irradiated by a nanosecond pulsed laser. The laser photothermal effect converts the carbon precursor into graphene, with partial graphene sheets deposited directly on the TPE substrate and the remaining transferred to the glass cover via a laser-induced plasma plume. This method simultaneously prepares two face-to-face graphene films in a single laser irradiation, integrating synthesis, transfer, and patterning. The resulting graphene patterns demonstrate good performance in flexible pressure sensing and Joule heating, showcasing high sensitivity (7.7 kPa-1), fast response (37 ms), and good cycling stability (2000 cycles) for sensors, and high heating rate (1 °C s-1) and long-term stability (3000 s) for heaters. It is believed that the simple, low-cost, and efficient LBGP process can promote the development of graphene electronics and laser manufacturing processes.

Production of bacterial cellulose-based peptidopolysaccharide BC-L with anti-listerial properties using a co-cultivation strategy.

Bacterial cellulose (BC) has been found extensive applications in diverse domains for its exceptional attributes. However, the lack of antibacterial properties hampers its utilization in food and biomedical sectors. Leucocin, a bacteriocin belonging to class IIa, is synthesized by Leuconostoc that demonstrates potent efficacy against the foodborne pathogen, Listeria monocytogenes. In the current study, co-culturing strategy involving Kosakonia oryzendophytica FY-07 and Leuconostoc carnosum 4010 was used to confer anti-listerial activity to BC, which resulted in the generation of leucocin-containing BC (BC-L). The physical characteristics of BC-L, as determined by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA), were similar to the physical characteristics of BC. Notably, the experimental results of disc diffusion and growth curve indicated that the BC-L film exhibited a potent inhibitory effect against L. monocytogenes. Scanning electron microscopy (SEM) showed that BC-L exerts its bactericidal activity by forming pores on the bacterial cell wall. Despite the BC-L antibacterial mechanism, which involves pore formation, the mammalian cell viability remained unaffected by the BC-L film. The measurement results of zeta potential indicated that the properties of BC changed after being loaded with leucocin. Based on these findings, the anti-listerial BC-L generated through this co-culture system holds promise as a novel effective antimicrobial agent for applications in meat product preservation and packaging.

Laser-Induced Skin-like Flexible Pressure Sensor for Artificial Intelligence Speech Recognition.

Skin-like flexible pressure sensors with good sensing performance have great application potential, but their development is limited owing to the need for multistep, high-cost, and low-efficiency preparation processes. Herein, a simple, low-cost, and efficient laser-induced forming process is proposed for the first time to prepare a skin-like flexible piezoresistive sensor. In the laser-induced forming process, based on the photothermal effect of graphene and the foaming effect of glucose, a skin-like polydimethylsiloxanes (PDMS) film with porous structures and surface protrusions is obtained by using infrared laser irradiation of the glucose/graphene/PDMS prepolymer film. Further, based on the skin-like PDMS film with a graphene conductive layer, a new skin-like flexible piezoresistive sensor is obtained. Due to the stress concentration caused by the surface protrusions and the low stiffness caused by the porous structures, the flexible piezoresistive sensor realizes an ultrahigh sensitivity of 1348 kPa-1 at 0-2 kPa, a wide range of 200 kPa, a fast response/recovery time of 52 ms/35 ms, and good stability over 5000 cycles. The application of the sensor to the detection of human pulses and robot clamping force indicates its potential for health monitoring and soft robots. Furthermore, in combination with the neural network (CNN) algorithm in artificial intelligence technology, the sensor achieves 95% accuracy in speech recognition, which demonstrates its great potential for intelligent wearable electronics. Especially, the laser-induced forming process is expected to facilitate the efficient, large-scale preparation of flexible devices with multilevel structures.

Highly Sensitive Flexible Pressure Sensors with Hybrid Microstructures Similar to Volcano Sponge.

Preparing hybrid microstructures on flexible substrates is a crucial approach to achieving highly sensitive flexible pressure sensors. However, the preparation of hybrid microstructures on soft materials often faces complex, time-consuming, and costly problems, which hampers the advancement of highly sensitive flexible sensors. Herein, based on a 3D-printing template and a household microwave oven, a simple, green, and one-step microwave irradiation process using glucose porogen is applied to develop a flexible pressure sensor with a volcano-sponge-like porous dome structure based on porous polydimethylsiloxane (PDMS). Due to the easily deformable porous dome on the porous PDMS substrate, the flexible pressure sensor showcases exceptional sensitivity of 611.85 kPa-1 in 0-1 and 50.31 kPa-1 over a wide range of 20-80 kPa. Additionally, the sensor takes only 43 ms to respond, 123 ms to recover, and presents excellent stability (>1100 cycles). In application testing, the sensor effectively captures pulse signals, speech signals, tactile signals from a mechanical gripper, and gesture signals, demonstrating its potential applications in medical diagnosis and robotics. In conclusion, the microwave irradiation method based on template and glucose porogen provides a new way for the simple, low-cost, and green preparation of porous-surface hybrid microstructures on polymers and high-performance flexible pressure sensors.

One-Step Laser Direct-Printing Process of a Hybrid Microstructure for Highly Sensitive Flexible Piezocapacitive Sensors.

Microstructures can effectively improve the sensing performance of flexible piezocapacitive sensors. Simple, low-cost fabrication methods for microstructures are key to facilitating the practical application of piezocapacitive sensors. Herein, based on the laser thermal effect and the thermal decomposition of glucose, a rapid, simple, and low-cost laser direct-printing process is proposed for the preparation of a polydimethylsiloxane (PDMS)-based electrode with a hybrid microstructure. Combining the PDMS-based electrode with an ionic gel film, highly sensitive piezocapacitive sensors with different hybrid microstructures are realized. Due to the good mechanical properties brought about by the hybrid microstructure and the double electric layer induced by the ionic gel film, the sensor with a porous X-type microstructure exhibits an ultrahigh sensitivity of 92.87 kPa-1 in the pressure range of 0-1000 Pa, a wide measurement range of 100 kPa, excellent stability (>3000 cycles), fast response time (100 ms) and recovery time (101 ms), and good reversibility. Furthermore, the sensor is used to monitor human physiological signals such as throat vibration, pulse, and facial muscle movement, demonstrating the application potential of the sensor in human health monitoring. Most importantly, the laser direct-printing process provides a new strategy for the one-step preparation of hybrid microstructures on thermal curing polymers.

Structure, physicochemical properties, antioxidant, and hypoglycemic activities of water-soluble polysaccharides from millet bran.

This study aimed to investigate the composition, structure, in vitro antioxidant, and hypoglycemic activities of a novel water-soluble MBP-1, an extract from millet bran, isolated by DEAE-52 cellulose and purified by Sephadex G-100. The results showed that MBP-1 was mainly composed of xylose, mannose, galactose, rhamnose, and arabinose with a molar ratio of 0.72:0.59:76.26:1.04:0.83 and a molecular weight of 6.6×104  Da, and its purity was 98%, and the yield was 3.76%. MBP-1 has an irregular granular structure by atomic force microscopy and scanning electron microscopy, and the anomeric carbon in MBP-1 molecule has α-configuration and ß-configuration by NMR and FTIR. The in vitro scavenging abilities of MBP-1 for·OH, DPPH, O2·- , and ABTS+ were 73.5%, 80%, 69.8%, and 75.2%, respectively, and the chelating activity for Fe2+ was 50%, and the inhibition rates of α-glucosidase and α-amylase were 78.5% and 74.6%, respectively, which indicated that MBP-1 possessed strong antioxidant and hypoglycemic activities. The results indicated that MBP-1 have certain application prospects in food-related fields.

Antidiabetic Effect of Millet Bran Polysaccharides Partially Mediated via Changes in Gut Microbiome.

Diabetes is a type of metabolic disease associated with changes in the intestinal flora. In this study, the regulatory effect of millet bran on intestinal microbiota in a model of type 2 diabetes (T2DM) was investigated in an effort to develop new approaches to prevent and treat diabetes and its complications in patients. The effect of purified millet bran polysaccharide (MBP) with three different intragastric doses (400 mg/kg, 200 mg/kg, and 100 mg/kg) combined with a high-fat diet was determined in a streptozotocin (STZ)-induced model of T2DM. By analyzing the changes in indicators, weight, fasting blood sugar, and other bio-physiological parameters, the changes in gut microbiota were analyzed via high-throughput sequencing to establish the effect of MBP on the intestinal flora. The results showed that MBP alleviated symptoms of high-fat diet-induced T2DM. A high dosage of MBP enhanced the hypoglycemic effects compared with low and medium dosages. During gavage, the fasting blood glucose (FBG) levels of rats in the MBP group were significantly reduced (p < 0.05). The glucose tolerance of rats in the MBP group was significantly improved (p < 0.05). In diabetic mice, MBP significantly increased the activities of CAT, SOD, and GSH-Px. The inflammatory symptoms of liver cells and islet cells in the MBP group were alleviated, and the anti-inflammatory effect was partially correlated with the dose of MBP. After 4 weeks of treatment with MBP, the indices of blood lipid in the MBP group were significantly improved compared with those of the DM group (p < 0.05). Treatment with MBP (400 mg/kg) increases the levels of beneficial bacteria and decreases harmful bacteria in the intestinal tract of rats, thus altering the intestinal microbial community and antidiabetic effect on mice with T2DM by modulating gut microbiota. The findings suggest that MBP is a potential pharmaceutical supplement for preventing and treating diabetes.

High-Efficiency Copper Removal by Nitrogen Plasma-Assisted Picosecond Laser Processing.

Copper (Cu) removal efficiency is a key parameter in the processing of Cu-based electronic devices. Herein, a nitrogen plasma-assisted picosecond (ps) laser process for Cu removal is presented. Based on the cleaning and activation effect of nitrogen plasma on the surface of Cu film in ps-laser ablation, the removal efficiency can be significantly improved. Theoretically, the interaction mechanism between Cu and the ps-laser under the action of the plasma flow field is investigated by the dual temperature model (TTM) and finite element analysis (FEA). Meanwhile, the experimental results show that the angle of the plasma flow significantly affects the laser ablation of Cu. Small-angle plasma helps to improve the ps-laser processing precision of Cu, while large-angle plasma can effectively improve the ps-laser processing efficiency of Cu. Under the laser fluence of 2.69 J/cm2, the removal depth of the Cu film by a 30° plasma-assisted ps-laser is 148% higher than that by the non-plasma-assisted ps-laser, which indicates the application potential of nitrogen plasma in improving the laser ablation process.

Electrosynthesis of S-thiocarbamates with disulfides as a sulfur source.

An electrochemical oxidative synthesis of S-thiocarbamates by a carbamothioation reaction via a three-component coupling reaction (disulfide, water and isocyanide) is developed, which avoids the use of external oxidants and generates only hydrogen gas as the by-product. With NH4I as the mediator and electrolyte, the desired S-thiocarbamates were obtained in good yields in an undivided cell at room temperature.

Monodisperse Ultrahigh Nitrogen-Containing Mesoporous Carbon Nanospheres from Melamine-Formaldehyde Resin.

An aqueous emulsion polymerization self-assembly approach is demonstrated for the first time to synthesize ultrahigh nitrogen containing mesoporous polymer nanospheres, using melamine-formaldehyde resin oligomers as precursors. In the synthesis, change from alkaline to acidic conditions is critical for the formation of monodisperse mesostructured polymer nanospheres. Owing to unique structure of triazine stabilized in the covalent polymeric networks during the pyrolysis process, the derived mesoporous carbon nanospheres possess an ultrahigh nitrogen content (up to 15.6 wt%) even after pyrolysis at 800 °C, which is the highest nitrogen content among mesoporous carbon nanospheres. Furthermore, these monodisperse mesoporous carbon nanospheres possess a high surface area (≈883 m2 g-1 ) and large pore size (≈8.1 nm). As an anode for sodium-ion batteries, the ultrahigh nitrogen-containing mesoporous carbon nanospheres exhibit superior rate capability (117 mAh g-1 at a high current density of 3 A g-1 ) and high reversible capacity (373 mAh g-1 at 0.06 A g-1 ), indicating a promising material for energy storage.

Fabrication of a fluorescent probe for reversibly monitoring mitochondrial membrane potential in living cells.

Mitochondria are important organelles in cells, which play an important role in metabolism and many other vital biological events. Mitochondrial membrane potential (MMP) is a significant biological parameter participating in various procedures. However, fluorescent probes for monitoring MMP are rarely reported, which greatly limited the related studies. Herein, we present the rational design, synthesis, and living cell imaging studies of a fluorescent probe REP for monitoring MMP changes based on organic cationic fluorophores. In live cells with high MMP levels, REP can exclusively light up mitochondria with intense fluorescence. Upon the loss of MMP, the emission of intracellular REP evidently decreased. The reversible changes in MMP have been successfully monitored by REP, and the oxidative damages to live cells have been detected with the probe. The probe is expected to serve as a desired tool in studying MMP and related areas.

General Synthesis of Ultrafine Monodispersed Hybrid Nanoparticles from Highly Stable Monomicelles.

Ultrafine nanoparticles with organic-inorganic hybridization have essential roles in myriad applications. Over the past three decades, although various efforts on the formation of organic or inorganic ultrasmall nanoparticles have been made, ultrafine organic-inorganic hybrid nanoparticles have scarcely been achieved. Herein, a family of ultrasmall hybrid nanoparticles with a monodisperse, uniform size is synthesized by a facile thermo-kinetics-mediated copolymer monomicelle approach. These thermo-kinetics-mediated monomicelles with amphiphilic ABC triblock copolymers are structurally robust due to their solidified polystyrene core, endowing them with ultrahigh thermodynamic stability, which is difficult to achieve using Pluronic surfactant-based micelles (e.g., F127). This great stability combined with a core-shell-corona structure makes the monodispersed monomicelles a robust template for the precise synthesis of ultrasmall hybrid nanoparticles with a highly uniform size. As a demonstration, the obtained micelles/SiO2 hybrid nanoparticles display ultrafine sizes, excellent uniformity, monodispersity, and tunable structural parameters (diameters: 24-47 nm and thin shell thickness: 2.0-4.0 nm). Notably, this approach is universal for creating a variety of multifunctional ultrasmall hybrid nanostructures, involving organic/organic micelle/polymers (polydopamine) nanoparticles, organic/inorganic micelle/metal oxides (ZnO, TiO2 , Fe2 O3 ), micelle/hydroxides (Co(OH)2 ), micelle/noble metals (Ag), and micelle/TiO2 /SiO2 hybrid composites. As a proof of concept, the ultrasmall micelle/SiO2 hybrid nanoparticles demonstrate superior toughness as biomimetic materials.

A red-emissive and positively charged RNA ligand enables visualization of mitochondrial depolarization and cell damage.

In this work, a red-emissive RNA ligand bearing two positive charges were developed for the visualization of mitochondrial depolarization, via the subcellular localization of the ligand molecules. The ligand with quinolinium moiety and strong electronic donor displays red fluorescence peaked at 630 nm. Meanwhile, the probe is concentrated in mitochondria of live cells due to the high mitochondrial membrane potential, and re-localizes into nucleolus upon mitochondrial depolarization owing to the affinity to RNA. In this manner, the decrease of mitochondrial membrane potential could be real-timely and in-situ monitored with the red-emissive probe. Particularly, two cations were decorated on the probe, which enables the fast response to mitochondrial depolarization with elevated sensitivity. Cell damage induced by H2O2 was also successfully observed with the probe. We expect that the probe can promote researches on mitochondrial membrane potential, cell apoptosis, and relative areas.

Molecular Design Strategy for Ordered Mesoporous Stoichiometric Metal Oxide.

A molecular design strategy is used to construct ordered mesoporous Ti3+ -doped Li4 Ti5 O12 nanocrystal frameworks (OM-Ti3+ -Li4 Ti5 O12 ) by the stoichiometric cationic coordination assembly process. Ti4+ /Li+ -citrate chelate is designed as a new molecular precursor, in which the citrate can not only stoichiometrically coordinate Ti4+ with Li+ homogeneously at the atomic scale, but also interact strongly with the PEO segments in the Pluronic F127. These features make the co-assembly and crystallization process more controllable, thus benefiting for the formation of the ordered mesostructures. The resultant OM-Ti3+ -Li4 Ti5 O12 shows excellent rate (143 mAh g-1 at 30 C) and cycling performances (<0.005 % fading per cycle). This work could open a facile avenue to constructing stoichiometric ordered mesoporous oxides or minerals with highly crystalline frameworks.

Electrocatalytic Water Oxidation by a Water-Soluble Copper(II) Complex with a Copper-Bound Carbonate Group Acting as a Potential Proton Shuttle.

Water-soluble copper(II) complexes of the dianionic tridentate pincer ligand N,N'-2,6-dimethylphenyl-2,6-pyridinedicarboxamidate (L) are catalysts for water oxidation. In [L-CuII-DMF] (1, DMF = dimethylformamide) and [L-CuII-OAc]- (2, OAc = acetate), ligand L binds CuII through three N atoms, which define an equatorial plane. The fourth coordination site of the equatorial plane is occupied by DMF in 1 and by OAc- in 2. These two complexes can electrocatalyze water oxidation to evolve O2 in 0.1 M pH 10 carbonate buffer. Spectroscopic, titration, and crystallographic studies show that both 1 and 2 undergo ligand exchange when they are dissolved in carbonate buffer to give [L-CuII-CO3H]- (3). Complex 3 has a similar structure as those of 1 and 2 except for having a carbonate group at the fourth equatorial position. A catalytic cycle for water oxidation by 3 is proposed based on experimental and theoretical results. The two-electron oxidized form of 3 is the catalytically active species for water oxidation. Importantly, for these two oxidation events, the calculated potential values of Ep,a = 1.01 and 1.59 V vs normal hydrogen electrode (NHE) agree well with the experimental values of Ep,a = 0.93 and 1.51 V vs NHE in pH 10 carbonate buffer. The potential difference between the two oxidation events is 0.58 V for both experimental and calculated results. With computational evidence, this Cu-bound carbonate group may act as a proton shuttle to remove protons for water activation, a key role resembling intramolecular bases as reported previously.

Facile synthesis of sponge-like Ni3N/NC for electrocatalytic water oxidation.

Sponge-like Ni3N/NC was prepared through a facile approach and was examined as a catalyst for the oxygen evolution reaction (OER). This material can efficiently catalyze water oxidation to reach a current density of 10 mA cm-2 with a small overpotential of 310 mV in 1.0 M KOH aqueous solution. The high efficiency can be attributed to the good electronic conductivity, large specific surface area and fast mass diffusion ability of Ni3N/NC.

Surface Electrochemical Modification of a Nickel Substrate to Prepare a NiFe-based Electrode for Water Oxidation.

The slow kinetics of water oxidation greatly jeopardizes the efficiency of water electrolysis for H2 production. Developing highly active water oxidation electrodes with affordable fabrication costs is thus of great importance. Herein, a NiII FeIII surface species on Ni metal substrate was generated by electrochemical modification of Ni in a ferrous solution by a fast, simple, and cost-effective procedure. In the prepared NiII FeIII catalyst film, FeIII was incorporated uniformly through controlled oxidation of FeII cations on the electrode surface. The catalytically active NiII originated from the Ni foam substrate, which ensured the close contact between the catalyst and the support toward improved charge-transfer efficiency. The as-prepared electrode exhibited high activity and long-term stability for electrocatalytic water oxidation. The overpotentials required to reach water oxidation current densities of 50, 100, and 500 mA cm-2 are 276, 290, and 329 mV, respectively.

Phase-transfer synthesis of α-Co(OH)2 and its conversion to CoO for efficient electrocatalytic water oxidation.

Water splitting is an attractive way to produce recyclable hydrogen energy resource. The oxygen evolution reaction (OER) is the rate-determine step of water electrolysis. The exploring of low-cost, highly efficient and durable electrocatalysts for OER is thus extremely important. In this work, we developed a facile two-phase protocol to fabricate an α-Co(OH)2 using sodium oleate as the phase-transfer surfactant. The crystallinity and structure of the α-Co(OH)2 was regulated by heat treatments toward enhanced electrocatalytic OER activity. With the calcination of the as-prepared α-Co(OH)2 at 200°C, a networked and well-dispersed CoO nanoparticles were formed. The CoO sample afforded an OER current density of 10mAcm-2 under a low overpotential of 312mV in a 1molL-1 KOH aqueous solution. The high activity of the CoO material is believed to be associated with its ultra-small particle size and plentiful open spaces in the material, both of which can provide abundant surface catalytic sites.