Three-dimensional Ni foam supported NiCoO2@Co3O4 nanowire-on-nanosheet arrays with rich oxygen vacancies as superior bifunctional catalytic electrodes for overall water splitting.

Earth abundant transition metal oxide (EATMO)-based bifunctional catalysts for overall water splitting are highly desirable, but their performance is far from satisfactory due to low intrinsic activities of EATMOs toward electrocatalysis of both oxygen and hydrogen evolution reactions and poor electron transfer and transport capabilities. A three-dimensional (3-D) Ni-foam-supported NiCoO2@Co3O4 nanowire-on-nanosheet heterostructured array with rich oxygen vacancies has been synthesized, showing OER activity superior to most reported catalysts and even much higher than Ru and Ir-based ones and HER activity among the highest reported for non-noble-metal-based catalysts. The excellent activities are ascribed to the highly dense, ultrathin nanowire arrays epitaxially grown on an interconnected layered nanosheet array greatly facilitating electron transfer and providing numerous electrochemically accessible active sites and the high content of oxygen vacancies on nanowires greatly promoting OER and HER. When adopted as bifunctional electrodes for overall water splitting, this heterostructure shows an overvoltage (at 10 mA cm-2) lower than most reported electrolyzers and high stability. This work not only creates a 3-D EATMO-based integrated heterostructure as a low-cost, highly efficient bifunctional catalytic electrode for water splitting, but also provides a novel strategy to use unique heteronanostructures with rich surface defects for synergistically enhancing electrocatalytic activities.

Doping molybdenum oxides with different non-metal atoms to promote bioelectrocatalysis in microbial fuel cells.

The sluggish extracellular electron transfer has been known as one of the bottlenecks to limit the power density of microbial fuel cells (MFCs). Herein, molybdenum oxides (MoOx) are doped with various types of non-metal atoms (N, P, and S) by electrostatic adsorption, followed by high-temperature carbonization. The as-prepared material is further used as MFC anode. Results indicate that all different elements-doped anodes can accelerate the electron transfer rate, and the great enhancement mechanism is attributed to synergistic effect of dopped non-metal atoms and the unique MoOx nanostructure, which offers high proximity and a large reaction surface area to promote microbe colonization. This not only enables efficient direct electron transfer but also enriches the flavin-like mediators for fast extracellular electron transfer. This work renders new insights into doping non-metal atoms onto metal oxides toward the enhancement of electrode kinetics at the anode of MFC.

Carbon microspheres built of La2O3 quantum dots-implanted nanorods: Superb hosts with ultra-long Li2Sn-catalysis durability.

Practical utilization of Li-sulfur batteries (LSBs) is still hindered by the sulfur cathode side due to its inferior electrical conductivity, huge volume expansion and adverse polysulfide shuttling effects. Though using polar catalysts coupled with mesoporous carbons may well surmount these barriers, such unsheltered catalysts rarely survive due to oversaturated polysulfide adsorption and extra sulfuration side reactions. To overcome above constrains, we herein propose to implant highly reactive nanocatalysts into carbon matrix with few nanometers insertion depth for mechanical protection. As a paradigm study, we have embedded La2O3-quantum dots (QDs) into carbon nanorods, which are then assembled into carbon microspheres (CMs). As evaluated, La2O3 QDs-CMs can help elevate the cathode redox reaction kinetics and sulfur utilization ratios, delivering a large capacity of 1392 mAh g-1 at 0.25C and high-capacity retention of 76% after total cycling. The thin carbon layers on La2O3 QDs exert a key role in impeding excess polysulfide accumulation on catalysts and thus prevent their deactivation/failure. Our strategy may guide a smart way to make catalysts-involved sulfur cathode systems with ultra-long working durability for LSBs applications.

Construction of BiVO4/NiCo2O4 nanosheet Z-scheme heterojunction for highly boost solar water oxidation.

The sluggish water oxidation process is a severe obstacle for solar-driven water splitting. Therefore, it is imperative to develop a suitable photocatalyst with reduced energy barrier for strong oxidation. In this study, a Z-scheme BiVO4/NiCo2O4 (BVO/NCO) heterojunction system was designed by decorating ultrathin nickel-cobalt (NiCo2O4) spinel nanosheets on BiVO4 as an efficient photocatalyst for water oxidation. The unique structure of the system significantly reduced the energy barrier and improved the oxidation ability of BiVO4 to efficiently enhance the separation and transfer of the photogenerated carriers. Thus, the photocatalyst delivered an excellent O2 evolution performance of 1640.9 µmol∙g-1∙h-1 and showed 124% improved efficiency as compared to pristine BiVO4 and a quantum efficiency of 5.39% at 400 nm for O2 evolution. Additionally, the theoretical calculations revealed that the formation of *OOH was the rate-determining step for water oxidation. The decoration with NiCo2O4 significantly reduced the energy barrier between *O and *OOH, which eventually improved the photocatalytic performance of BVO/NCO. The results hold great promise for the potential application of spinel-based materials in efficient photocatalytic O2 evolution and offer fundamental insights into the design of efficient water oxidation heterojunctions.

Facile method to produce sub-1 nm pore-rich carbon from biomass wastes for high performance supercapacitors.

Sub-1 nm pores can lead to an anomalous increase in the supercapacitive performance [1], but it still faces great challenges from its relatively low sub-1 nm pore content, complicated preparation process, low yield and high cost. Here we successfully prepared a sub-1 nm pore-rich carbon from biomass wastes using a facile method by pre-treating walnut shell powder at 380 ℃ in air for different times to delicately tailor carbon defects, followed by KOH activation at 700 ℃. The as-prepared optimal material delivers the highest sub-1 nm pore content (Vsub-1 nm = 0.57 cm3 g-1, Vsub-1 nm/Vt = 58.4 %) among all reported porous carbons. A supercapacitor made from the material accomplishes an ultrahigh specific capacitance of 298.7F g-1 at 1 A g-1 in a two-electrode device, excellent rate capability (78.8 % retention from 1 to 10 A g-1) and long-cyclic life (94 % retention after 10,000 cycles at 10 A g-1) in KOH. Even in Et4NBF4 electrolyte that is often used in commercial supercapacitors, a high energy density of 82.8 Wh kg-1 at 7 kW kg-1 and excellent cycling performance (90 % retention after 10,000 cycles at 5 A g-1) can be achieved, ranking the best among all reported carbon-based electrical double layer capacitors tested in the same electrolyte. More importantly, it drives a light-emitting-diode (LED) to operate for as long as 20 min, vividly demonstrating the great potential of sub-1 nm pore-rich carbon-based high performance supercapacitors in practical applications.

11,11,12,12-tetracyano-9,10-anthraquinonedimethane as a high potential and sustainable cathode for organic potassium-ion batteries.

We fabricated a potassium-ion battery by using 11,11,12,12-tetracyano-9,10-anthraquinonedimethane (TCAQ) as the cathode for the first time. Owing to the unique molecular structure and configuration of ionic liquid electrolytes, TCAQ shows a high redox potential of 2.6 V vs. K+/K while delivering a capacity of 88 mAh g-1 at a current density of 17 mA g-1 and a capacity retention of 61% after 50 cycles. The mechanism of the reaction of TCAQ with K was investigated. The results prove that TCAQ holds great promise for broad applications in potassium-ion batteries while revealing new scientific insights into K+-organic cathode batteries.

Rationally tuning ratio of micro- to meso-pores of biomass-derived ultrathin carbon sheets toward supercapacitors with high energy and high power density.

The carbon pore structure could have a significant effect on supercapacitor performance; however, this effect has not yet been systematically studied. A facile approach for synthesizing porous, ultrathin carbon sheets while rationally tuning the ratio of micro-to meso-pores via partial corrosion has been developed for the fabrication of high-performance devices. The prepared carbon from biomass with an optimal ratio of micro- to meso-pores has a large specific surface area of 1785 m2 g -1, a high specific capacitance of 447F g -1 at 0.5 A g-1, a high energy density of 15.5-9.7 Wh kg-1, and an excellent power density of 0.062-6.24 kW kg-1. After 10,000 charge-discharge cycles, the capacitance retention was maintained at 95%, which exceeded most of the biomass-carbon-based capacitors. Volcano relationships were found to exist through plots of both specific surface area and specific capacitance versus the micro-to meso-pore ratio. An enhancement mechanism with a rational pore structure is proposed, which not only networks micropores to remove died-end micropores to achieve the largest specific active surface area and high specific capacitance but also realizes fast mass-transport channels, resulting in high power density. This work provides an effective approach based on waste re-use by tuning a rational pore structure for achieving high energy/power density toward green energy applications with universal significance.

Synthesis of merit-combined antimony tetroxide nanoflowers/reduced graphene oxide to synergistically boost real-time detection of nitric oxide released from living cells for high sensitivity.

Nitric oxide (NO) is an important bio-regulatory and signaling molecule associated with various physiological and pathophysiological pathways, but its sensitive real-time detection is still very challenging due to the low concentration, large diffusivity and fast decay in biological samples. Here an antimony tetroxide (Sb2O4) nanoflowers/reduced graphene oxide (rGO) nanocomposite is synthesized via a facile and eco-friendly solvothermal method to merit-combine highly electroactive Sb2O4 nanoflowers with large surficial rGO component for a strong synergistic effect on oxidation of NO. Results demonstrate that the Sb2O4/rGO-based sensor has a low detection limit, high sensitivity, excellent selectivity and fast response for NO detection. The real-time detected NO released from living cells showed significant difference between normal and tumor cells. The Sb2O4 nanoflowers/rGO nanocomposite sensor holds a great promise for important applications in biomedical research fields and clinical diagnosis.

Borate-ion intercalated NiFe layered double hydroxide to simultaneously boost mass transport and charge transfer for catalysis of water oxidation.

Borate ion-intercalated NiFe layered double hydroxide (NiFe LDH) is synthesized as a highly active electrocatalyst toward oxygen evolution reaction (OER) for the first time. With the intercalation of borate ions, the interlayer spacing and specific surface area of the NiFe LDH are increased, meanwhile the pore size distribution shifts to a larger pore size range. The borate ion-intercalated catalyst prepared at 20% of Fe content in presence of 0.05 M sodium borate additive exhibits the highest OER electrocatalytic activity, which shows a low onset overpotential of 270 mV and a Tafel slope of 42 mV dec-1. The high catalytic activity of intercalated OER catalyst can be attributed to the enhanced mass transport and charge transfer as well as the increased specific surface area due to the borate ion intercalation. In addition, the intercalated borate ions act as a proton-accepting agent help to promote OO bond formation during OER. This work would open up a novel strategy for the synthesis of ion-intercalated layered materials for high-performance water splitting applications.

One-pot synthesis of Co/N-doped mesoporous graphene with embedded Co/CoOx nanoparticles for efficient oxygen reduction reaction.

Exploration of sustainable electrocatalysts toward oxygen reduction reaction (ORR) with high catalytic activity remains a key challenge in the development of metal-air batteries and fuel cells. In this work, a hybrid electrocatalyst composed of cobalt (Co/CoOx) nanoparticles encapsulated in Co/N-doped mesoporous graphene (Co/CoOx@Co/N-graphene) is reported for efficient ORR catalysis. The catalyst is rationally designed and synthesized via a facile combination of spontaneous one-pot polymerization of dopamine in the presence of graphene oxide (GO) and Co2+ ions and the subsequent carbonization process. The morphology, doping nature and ORR activity of the as-prepared catalyst are systematically investigated. It is found that there are abundant Co/N active sites and Co/CoOx nanoparticles in this hybrid catalyst, leading to a synergistic enhancement effect for improved ORR activity. In an alkaline environment, this Co/CoOx@Co/N-graphene catalyst displays Pt/C-comparable ORR activity in terms of half-wave potential and four-electron reduction selectivity, and higher limiting current density, better methanol tolerant ability and long-term durability. When being evaluated in a Zn-air battery, it demonstrates superior performance to the commercial Pt/C catalyst.

Vancomycin-conjugated polythiophene for the detection and imaging of Gram-positive bacteria.

Bacterial infections can cause serious health problems. The rapid identification of bacteria plays a vital role in the treatment of bacterial infection at an early stage of the disease. In this work, an active polythiophene derivative containing reactive pentafluorophenyl (PFP) ester pendant groups was prepared via Fe3+-catalyzed oxidative polymerization. As far as we know, this is the first report of active polythiophene with reactive PFP ester moieties. The active polythiophene derivative was conjugated with vancomycin and α-methoxy-ω-amino poly(ethylene glycol) (mPEG-NH2) via a reactive ester-amine reaction, resulting in the formation of water-soluble and fluorescent vancomycin-containing polythiophene (PTPVan). Since vancomycin can selectively interact with Gram-positive bacteria and kill them, the antibacterial properties of PTPVan were evaluated. The detection of Gram-positive bacteria was carried out by observing the color change and the fluorescence response of bacteria upon incubation with PTPVan through the naked eye and a fluorescence spectroscope, respectively. The staining of Gram-positive bacteria was observed using a confocal laser scanning microscope (CLSM).

Multifunctionalized reduced graphene oxide-doped polypyrrole/pyrrolepropylic acid nanocomposite impedimetric immunosensor to ultra-sensitively detect small molecular aflatoxin B1.

Aflatoxin B1 (AFB1), an aflatoxin is extremely toxic among mycotoxins in contaminated food products but it is very difficult to be quantitatively detected by existing methods. Impedimetric immunosensor is an advantageously label-free and fast assay. Nevertheless, its applications are limited by low sensitivity when the target molecule is small such as AFB1 due to relatively low impedance change during detection. Herein for the first time reduced graphene oxide (rGO) is nanocomposed with polypyrrole (PPy) and pyrrolepropylic acid (PPa) as a unique sensing platform, in which rGO greatly improves the conductivity and stability, PPa provides covalent linkers for probe immobilization and PPy endows the film electroactivity from its inherent electrochemical doping/dedoping property for impedance measurements, thus significantly improving the sensitivity to detect AFB1 in a range of 10 fg mL(-1) to 10 pg mL(-1) with high specificity and good reproducibility. This work demonstrates a novel method to sensitively detect small molecule by using immunoassay.

Novel short antibacterial and antifungal peptides with low cytotoxicity: Efficacy and action mechanisms.

Short antimicrobial peptides with nine and eleven residues were developed against several clinically important bacterial and fungal pathogens (specifically Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, and Fusarium solani). Twelve analogues of previously reported peptides BP76 (KKLFKKILKFL) and Pac-525 (KWRRWVRWI) were designed, synthesized, and tested for their antimicrobial activities. Two of our eleven amino acid peptides, P11-5 (GKLFKKILKIL) and P11-6 (KKLIKKILKIL), have very low MICs of 3.1-12.5microg ml(-1) against all five pathogens. The MICs of these two peptides against S. aureus, C. albicans and F. solani are four to ten times lower than the corresponding MICs of the reference peptide BP76. P9-4 (KWRRWIRWL), our newly designed nine-amino acid analogue, also has particularly low MICs of 3.1-6.2microg ml(-1) against four of the tested pathogens; these MICs are two to eight times lower than those reported for Pac-525 (6.2-50microg ml(-1)).These new peptides (P11-5, P11-6 and P9-4) also exhibit improved stability in the presence of salts, and have low cytotoxicity as shown by the hemolysis and MTT assays. From the results of field-emission scanning electron microscopy, membrane depolarization and dye-leakage assays, we propose that these peptides exert their action by disrupting membrane lipids. Molecular dynamics simulation studies confirm that P11-6 peptide maintains relatively stable helical structure and exerts more perturbation action on the order of acyl tail of lipid bilayer.

Evidence of harvesting electricity by exciton recombination in an n-n type solar cell.

Free electrons and holes bounded by weak interactions in organic molecules must be generated from excitons to produce photocurrent in organic solar cells. Free charge carriers, in either small molecule- or polymer-based solar cells, are generated so far by dissociation of excitons at the donor-acceptor interface through injecting electrons (holes) from a donor (acceptor) into an acceptor (donor) while leaving holes (electrons) in the donor (acceptor). Here we report a new way, intermolecular exciton recombination, to generate free carriers from organic semiconductors. Unlike the exciton dissociation between donor and acceptor, the recombination of electrons from perfluorinated hexadecafluorophthalo-cyaninatozinc (F16ZnPc) with holes from fullerene (C(60)) frees their counterpart carriers. A new organic solar cell based on this intermolecular exciton recombination at the interface is fabricated to clearly demonstrate this new way to produce free carriers and then harvest electricity from sunlight.

Polypyrrole Based Reporterless DNA/Protein Sensors.

Polypyrrole (PPy) is one of the important conductive polymers that are widely used in energy storage systems, biosensors and electronics. The electrochemical synthesis of PPy has advantages of simple process, mass production and low cost. In this study, polypyrolle were used to reporterlessly detect DNA and proteins. PPy thin films impregnated with probe molecules were deposited on both microelectrode and glassy carbon electrode surface by galvanostatic deposition method. Results demonstrated that PPy coated electrodes can be used for successful detection of DNA hybridization and antibody (Ab)-antigen (Ag) bindings. The experimental results also showed that the detection mechanism is probably due to the change of doping/undoping process of the conductive polymer after the DNA hybridization or antibody/antigen bindings.