Touchable 3D hierarchically structured polyaniline nanoweb for capture and detection of pathogenic bacteria.

A bacteria-capturing platform is a critical function of accurate, quantitative, and sensitive identification of bacterial pathogens for potential usage in the detection of foodborne diseases. Despite the development of various nanostructures and their surface chemical modification strategies, relative to the principal physical contact propagation of bacterial infections, mechanically robust and nanostructured platforms that are available to capture bacteria remain a significant problem. Here, a three-dimensional (3D) hierarchically structured polyaniline nanoweb film is developed for the efficient capture of bacterial pathogens by hand-touching. This unique nanostructure ensures sufficient mechanical resistance when exposed to compression and shear forces and facilitates the 3D interfacial interactions between bacterial extracellular organelles and polyaniline surfaces. The bacterial pathogens (Escherichia coli O157:H7, Salmonella enteritidis, and Staphylococcus aureus) are efficiently captured through finger-touching, as verified by the polymerase chain reaction (PCR) analysis. Moreover, the real-time PCR results of finger-touched cells on a 3D nanoweb film show a highly sensitive detection of bacteria, which is similar to those of the real-time PCR using cultured cells without the capturing step without any interfering of fluorescence signal and structural deformation during thermal cycling.

Facile Formation of a LiF-Carbon Layer as an Artificial Cathodic Electrolyte Interphase through Encapsulation of a Cathode with Carbon Monofluoride.

Lithium batteries that utilize a lithium anode and a high voltage cathode are highly required to meet the growing demand for electrification of transportation. High voltage lithium cobalt oxide (LiCoO2, LCO) can be a promising choice for lithium batteries with high energy and power. However, intrinsic structural instability at high voltages (>4.2 V) leads to significant capacity loss during the repeated cycles of charge-discharge. Herein, a simple and effective method has been proposed to prepare an artificial protective layer of LCO, enabling the LCO to achieve long-term cycle stability at 4.5 V. It is found that carbon monofluoride reacts with LCO via defluorination at 400 °C to form a LiF-C layer on LCO, which suppresses side reactions at the electrolyte/electrode interface. Moreover, the LiF-C layer plays a key role in not only facilitating charge transport but also restricting Co dissolution from the cathode. The Li//LiF-C coated LCO cells deliver an initial discharge capacity of 186 mAh g-1 at 0.1C and exhibit excellent cycling and rate performance: 161 mAh g-1 after 180 cycles (90% of the initial value at 0.5C) and 115 mAh g-1 at 10C (63.2% of the 0.1C capacity).

Development and characterization of waste equine bone-derived calcium phosphate cements with human alveolar bone-derived mesenchymal stem cells.

Calcium phosphate cements (CPCs) are regarded as promising graft substitutes for bone tissue engineering. However, their wide use is limited by the high cost associated with the complex synthetic processes involved in their fabrication. Cheaper xenogeneic calcium phosphate (CaP) materials derived from waste animal bone may solve this problem. Moreover, the surface topography, mechanical strength, and cellular function of CPCs are influenced by the ratio of micro- to nano-sized CaP (M/NCaP) particles. In this study, we developed waste equine bone (EB)-derived CPCs with various M/NCaP particle ratios to examine the potential capacity of EB-CPCs for bone grafting materials. Our study showed that increasing the number of NCaP particles resulted in reductions in roughness and porosity while promoting smoother surfaces of EB-CPCs. Changes in the chemical properties of EB-CPCs by NCaP particles were observed using X-ray diffractometry. The mechanical properties and cohesiveness of the EB-CPCs improved as the NCaP particle content increased. In an in vitro study, EB-CPCs with a greater proportion of MCaP particles showed higher cell adhesion. Alkaline phosphatase activity indicated that osteogenic differentiation by EB-CPCs was promoted with increased NCaP particle content. These results could provide a design criterion for bone substitutes for orthopedic disease, including periodontal bone defects.

Performance of the nasal photoplethysmographic index as an analgesic index during surgery under general anaesthesia.

In a previous study, we developed a new analgesic index using nasal photoplethysmography (nasal photoplethysmographic index, NPI) and showed that the NPI was superior to the surgical pleth index (SPI) in distinguishing pain above numerical rating scale 3. Because the NPI was developed using data obtained from conscious patients with pain, we evaluated the performance of NPI in comparison with the SPI and the analgesia nociception index (ANI) in patients under general anaesthesia with target-controlled infusion of propofol and remifentanil. The time of nociception occurrence was defined as when the signs of inadequate anaesthesia occurred. The median values of NPI, SPI, and ANI for 1 minute from the time of the sign of inadequate anaesthesia were determined as the value of each analgesic index that represents inadequate anaesthesia. The time of no nociception was determined as 2 minutes before the onset of skin incision, and the median value for 1 minute from that time was defined as the baseline value. In total, 81 patients were included in the analysis. NPI showed good performance in distinguishing inadequate anaesthesia during propofol-remifentanil based general anaesthesia. NPI had the highest value in terms of area under the receiver operating characteristic curve, albeit without statistical significance (NPI: 0.733, SPI: 0.722, ANI: 0.668). The coefficient of variations of baseline values of NPI, SPI, and ANI were 27.5, 47.2, and 26.1, respectively. Thus, the NPI was effective for detecting inadequate anaesthesia, showing similar performance with both indices and less baseline inter-individual variability than the SPI.

Effects of Methyl Acetate as a Co-Solvent in Carbonate-Based Electrolytes for Improved Lithium Metal Batteries.

In lithium metal batteries (LMBs), electrolytes composed of salts and organic solvents play a significant role in transporting Li+ ions and creating the surface film on Li-metal anodes. Herein, the effect of methyl acetate (MA) as a co-solvent is reported, which enables the facilitated Li+ transport and formation of a robust solid electrolyte interphase (SEI) on the Li-metal anode. The symmetrical Li//Li cell tests show remarkable cycle stability of MA-based electrolytes at 3 mA/cm2 without obvious voltage fluctuation. At 5 mA/cm2, the Li//Li cells in MA-based electrolytes can still run up to 110 h with lower overpotential, compared to the cell cycled with MA-free electrolytes. Furthermore, the LMBs consisting of the Li anode and LiNi0.8Co0.15Al0.05O2 (NCA) cathode deliver the high capacity (∼200 mA h/g), good cycling stability up to 300 cycles, excellent rate capability (10 C), and low self-discharging rates (8.5%) with MA-based electrolytes. Especially, the capacity of the Li//NCA cells with MA30 electrolytes at -35 °C is as high as 144 mA h/g, which is higher than that of the cells in MA-free electrolytes. It demonstrates that the MA is beneficial for the LMB operation at high rate and low temperature.

Studies on mass production and highly solar light photocatalytic properties of gray hydrogenated-TiO2 sphere photocatalysts.

In this paper, it is first reported that gray hydrogenated TiO2 sphere photocatalysts (H-TiO2) with high reactivity to solar light are mass produced within a few minutes using an underwater discharge plasma modified sol-gel method at room temperature and atmospheric pressure. This plasma modified system is an easy one-step in-situ synthetic process and the crystallinity, hydrogenation, and spherical structure of H-TiO2 are achieved by the synergy effect between the continuous reaction of highly energetic atomic and molecular species generated from the underwater plasma and surface tension of water. The resultant H-TiO2 demonstrated high anatase/rutile bicrystallinity and extended optical absorption spectrum from the ultraviolet (UV) to visible range. Furthermore, various defects including oxygen vacancies and hydroxyl species on the TiO2 surface permitted the enhancement of the photocatalytic performance. It was demonstrated that H-TiO2 photocatalysts showed significant degradation efficiencies for reactive black 5 (RB 5), rhodamine B (Rho B), and phenol (Ph) under solar light irradiation, up to approximately 5 times higher than that of commercial anatase TiO2 (C-TiO2), which resulted in good water purification. Notably, it was also possible to cultivate HepG2 cells using such well-purified water (to degrees up to 76%), with minimal cytotoxicity. Considering all these results, we believe that this novel plasma technology is promising for important environmental applications.

High performance electrochemical glucose sensor based on three-dimensional MoS2/graphene aerogel.

Two-dimensional (2D) nanosheets have been extensively explored as electrode materials for the development of high-performance electrochemical biosensors due to their unique structural characteristics. Nevertheless, 2D nanosheets suffer from sheet aggregation issues limiting the electrical conductivity of layered metal sulfides or hydroxides. Here, we report high-performance glucose biosensors based on a three-dimensional (3D) aerogel composed of interconnected 2D MoS2 and graphene sheet. 3D MoS2/graphene aerogel (MGA) provides a large surface area for the effective immobilization of enzymes, and continuous framework of electrically conductive graphene sheets. Flow-injection amperometric evaluation of the glucose biosensor using a 3D MGA electrode exhibits a rapid response (∼4s), a linear detection range from 2 to 20mM, a sensitivity of 3.36µA/mM, and a low limit of detection of 0.29mM. Moreover, the interference response from oxidizable species, such as ascorbic acid, uric acid and dopamine is negligible at an operating potential of -0.45V.

MnO2 Nanowire/Biomass-Derived Carbon from Hemp Stem for High-Performance Supercapacitors.

Hierarchical 3D nanostructures based on waste biomass are being offered as promising materials for energy storage due to their processabilities, multifunctionalities, environmental benignities, and low cost. Here we report a facile, inexpensive, and scalable strategy for the fabrication of hierarchical porous 3D structure as electrode materials for supercapacitors based on MnO2 nanowires and hemp-derived activated carbon (HC). Vertical MnO2 wires are uniformly deposited onto the surface of HC using a one-step hydrothermal method to produce hierarchical porous structures with conductive interconnected 3D networks. HC acts as a near-ideal 3D current collector and anchors electroactive materials, and this confers a specific capacitance of 340 F g-1 at 1 A g-1 with a high rate capability (88% retention) of the 3D MnO2/HC composite because of its open-pore system, which facilitates ion and electron transports and synergistic contribution of two energy-storage materials. Moreover, asymmetric supercapacitors fabricated using 3D HC as the anode and 3D MnO2/HC as the cathode are able to store 33.3 Wh kg-1 of energy and have a power delivery of 14.8 kW kg-1.

Hierarchical porous microspheres of the Co3O4@graphene with enhanced electrocatalytic performance for electrochemical biosensors.

The integration of organic and inorganic building blocks into hierarchical porous architectures makes potentially desirable electrocatalytic materials in many electrochemical applications due to their combination of attractive qualities of dissimilar components and well-constructed charge transfer pathways. Herein, we demonstrate the preparation of the hierarchical porous Co3O4@graphene (Co3O4@G) microspheres by one-step hydrothermal method to achieve high electrocatalytic performance for enzyme-free biosensor applications. The obtained Co3O4@G microspheres are consisted of the interconnected networks of Co3O4 and graphene sheets, and thus provide large accessible active sites through porous structure, while graphene sheets offer continuous electron pathways for efficient electrocatalytic reaction of Co3O4. These structural merits with synergy effect of Co3O4 and graphene lead to a high performance of enzyme-free detection for glucose: high sensitivity, good selectivity, and remarkable stability.

Yolk-Shell Polystyrene@Microporous Organic Network: A Smart Template with Thermally Disassemblable Yolk To Engineer Hollow MoS2/C Composites for High-Performance Supercapacitors.

Yolk-shell-type polystyrene@microporous organic network (Y-PS@MON) materials were prepared by the Sonogashira coupling of tetra(4-ethynylphenyl)methane and 1,4-diiodobenzene on the surface of PS@SiO2 and by the etching of SiO2. The diameter of PS yolk spheres and the thickness of MON shells were 150 and ∼10 nm, respectively. The thickness of the void space between the PS yolk and the MON shell was ∼30 nm. Y-PS@MONs were used as templates for the synthesis of MoS2/C composite materials. Because of the microporosity of the MON shells and the void space between the yolk and the shell, MoS2 precursor compounds were efficiently incorporated into Y-PS@MONs. The heat treatment under argon resulted in the formation of hollow MoS2/C composites. The contents of MoS2 in the composites were systematically controlled by changing the amounts of precursor. MoS2/C with 58 wt % of MoS2 showed the best energy storage performance with a capacitance of 418 F/g at a 0.5 A/g current density as an electrode material of a coin cell supercapacitor, which is attributable to its hollow structure, high surface area, and the good distribution of the sliced MoS2 in the carbon matrix. Also, the MoS2/C-58 composite showed excellent retention of capacitances during 5000 cycles.

Flexible and Disposable Sensing Platforms Based on Newspaper.

The flexible sensing platform is a key component for the development of smart portable devices targeting healthcare, environmental monitoring, point-of-care diagnostics, and personal electronics. Herein, we demonstrate a simple, scalable, and cost-effective strategy for fabrication of a sensing electrode based on a waste newspaper with conformal coating of parylene C (P-paper). Thin polymeric layers over cellulose fibers allow the P-paper to possess improved mechanical and chemical stability, which results in high-performance flexible sensing platforms for the detection of pathogenic E. coli O157:H7 based on DNA hybridization. Moreover, P-paper electrodes have the potential to serve as disposable, flexible sensing platforms for point-of-care testing biosensors.

Fabrication of Flexible, Redoxable, and Conductive Nanopillar Arrays with Enhanced Electrochemical Performance.

Highly ordered and flexible nanopillar arrays have received considerable interest for many applications of electrochemical devices because of their unique mechanical and structural properties. Here, we report on highly ordered polyoxometalate (POM)-doped polypyrrole (Ppy) nanopillar arrays produced by soft lithography and subsequent electrodeposition. As-prepared POM-Ppy/nanopillar films show superior electrochemical performances for pseudocapacitor and enzymeless electrochemical sensor applications and good mechanical properties, which allowed them to be easily bent and twisted. Regarding electrochemical characteristics for pseudocapacitive electrodes, the POM-Ppy/nanopillar electrodes are capable of delivering high areal capacitance of 77.0 mF cm(-2), high rate performance, and good cycle life of ∼100% retention over 3500 cycles even when bent. Moreover, the study suggests that the POM-Ppy/nanopillar electrodes have an excellent electrocatalytic activity toward hydrogen.

Polyoxometalate-grafted graphene nanohybrid for electrochemical detection of hydrogen peroxide and glucose.

The electrochemical performances of electrochemical biosensors largely depend on electrode characteristics, such as size, composition, surface area, and electron and ion conductivities. Herein, highly efficient electrocatalytic polyoxometalate (POM) was directly deposited on polymeric ionic liquid (PIL)-functionalized reduced graphene oxide (rGO) in a simple manner. The nano-sized POM with PIL functional groups was uniformly distributed on the surface of rGO sheets. The unique nanostructure of the resultant POM-g-rGO nanohybrids enabled well-defined multiple redox reaction of POMs and rapid electron transfer. In particular, as-prepared nanohybrids demonstrated high electrocatalytic activity for the electrochemical detection of H2O2 and glucose molecules in flow-injection biosensor device with high sensitivity, rapid response time, and low detection limit.

Nanopillar films with polyoxometalate-doped polyaniline for electrochemical detection of hydrogen peroxide.

Design and fabrication of electrodes is key in the development of electrochemical sensors with superior electrochemical performances. Herein, an enzymeless electrochemical sensor is developed for detection of hydrogen peroxide based on the use of highly ordered polyoxometalate (POM)-doped polyaniline (PANI) nanopillar films. The electrodeposition technique enables the entrapment of POMs into PANI during electropolymerization to produce thin coatings of POM-PANI. Electrochemical investigations of the POM-PANI/nanopillar electrode showed well-defined multiple pairs of redox peaks and rapid electron transfer. The nanopillar structure facilitated the diffusion of the electrolyte and thus, enhanced the redox reaction. In particular, the POM-PANI/nanopillar electrode was incorporated into a flow injection biosensor and it demonstrates its electrocatalytic activity to detect hydrogen peroxide with high sensitivity, rapid response time, and low detection limit.

Hierarchical core/shell structure of MnO2@polyaniline composites grown on carbon fiber paper for application in pseudocapacitors.

Hierarchical core/shell structured arrays of MnO2@polyaniline (PANI) nanosheets are successfully deposited on the surface of carbon fiber paper (CFP) by a two-step method of a redox reaction-assisted deposition of MnO2 and post electrodeposition of PANI. The CFP is used as a three-dimensional (3D) current collector to ensure 3D transport of ions and electrons with a large surface area. In addition, the electrodeposition technique enables conformal and thin coating of a layer of PANI across the entire MnO2 nanosheet. The MnO2@PANI on the CFP shows a unique architecture for efficient ion diffusion pathways in hierarchical porous structures and rapid electron transfer through PANI coated layers. The MnO2@PANI/CFP can be applied as a binder- and carbon-free electrode for supercapacitors. Evaluation of the electrochemical performance revealed that the as-prepared electrodes have a high value of specific capacitance (437 F g(-1) at 1 A g(-1)), high rate capability (62.4% retention at 15 A g(-1)), and good cycle life (∼100% at sequential current densities of 1 and 5 A g(-1) over 3000 cycles).

Three-Dimensional Expanded Graphene-Metal Oxide Film via Solid-State Microwave Irradiation for Aqueous Asymmetric Supercapacitors.

Carbon-based electrochemical double-layer capacitors and pseudocapacitors, consisting of a symmetric configuration of electrodes, can deliver much higher power densities than batteries, but they suffer from low energy densities. Herein, we report the development of high energy and power density supercapacitors using an asymmetric configuration of Fe2O3 and MnO2 nanoparticles incorporated into 3D macroporous graphene film electrodes that can be operated in a safe and low-cost aqueous electrolyte. The gap in working potential windows of Fe2O3 and MnO2 enables the stable expansion of the cell voltage up to 1.8 V, which is responsible for the high energy density (41.7 Wh kg(-1)). We employ a household microwave oven to simultaneously create conductivity, porosity, and the deposition of metal oxides on graphene films toward 3D hybrid architectures, which lead to a high power density (13.5 kW kg(-1)). Such high energy and power densities are maintained for over 5000 cycles, even during cycling at a high current density of 16.9 A g(-1).

High density decoration of noble metal nanoparticles on polydopamine-functionalized molybdenum disulphide.

Here, we report a highly stable colloidal suspension of nanoparticles (i.e., Pt and Au)-deposited MoS2 sheets, in which polydopamine (PD) serves as surface functional groups. The adoption of polydopamine coating onto the MoS2 surface enables homogeneous deposition of nanoparticles in an aqueous solution. As-synthesized nanohybrids are thoroughly characterized by transmission electron microscopy (TEM), Raman spectroscopy, and X-ray diffraction (XRD) measurement. These intensive investigations reveal that noble metal nanocrystals are uniformly distributed on the surface of ultrathin MoS2 sheets (∼4 layers). Moreover, as-prepared Au/PD/MoS2 nanohybrids can be applied as a heterogeneous catalyst for reduction of 4-nitrophenol to 4-aminophenol, and they exhibit an excellent catalytic activity.

Polyoxometalate-mediated one-pot synthesis of Pd nanocrystals with controlled morphologies for efficient chemical and electrochemical catalysis.

Polyoxometalates (POMs), as inorganic ligands, can endow metal nanocrystals (NCs) with unique reactivities on account of their characteristic redox properties. In the present work, we present a facile POM-mediated one-pot aqueous synthesis method for the production of single-crystalline Pd NCs with controlled shapes and sizes. The POMs could function as both reducing and stabilizing agents in the formation of NCs, and thus gave a fine control over the nucleation and growth kinetics of NCs. The prepared POM-stabilized Pd NCs exhibited excellent catalytic activity and stability for electrocatalytic (formic acid oxidation) and catalytic (Suzuki coupling) reactions compared to Pd NCs prepared without the POMs. This shows that the POMs play a pivotal role in determining the catalytic performance, as well as the growth, of NCs. We envision that the present approach can offer a convenient way to develop efficient NC-based catalyst systems.

Multifunctional polyurethane sponge for polymerase chain reaction enhancement.

Selective filtering of target biomaterials from impurities is an important task in DNA amplification through polymerase chain reaction (PCR) enhancement and gene identification to save endangered animals and marine species. Conventional gene extraction methods require complicated steps, skilled persons, and expensive chemicals and instruments to improve DNA amplification. Herein, we proposed an alternative method for overcoming such challenges by imparting secondary functionality using commercially available polyurethane (PU) sponges and cost-effective fabrication approaches through polydopamine and polysiloxane coatings. The porous, highly flexible, and chemically modified superhydrophilic and superhydrophobic PU sponges allow large surface areas and mechanically stable frames for effective extraction of genomic DNA through selective filtering of fish tissues and oils. Furthermore, these chemically modified PU sponges allow separation of genes and improvement of PCR for DNA amplification for the identification of fish species. The combination of a simple fabrication method and functionalized PU sponges could be a useful platform for PCR enhancement and gene-based identification of species for practical applications.

Coaxial RuO2-ITO nanopillars for transparent supercapacitor application.

Supercapacitive properties of ruthenium oxide (RuO2) nanoparticles electrodeposited onto the indium tin oxide (ITO) nanopillars were investigated. Compared to conventional planar current collectors, this coaxially nanostructured current collector-electrode system can provide increased contact for efficient charge transport, and the internanopillar spacing allows easy access of electrolyte ions. The morphological and electrochemical properties depended on the thickness of the RuO2 layers, i.e., the number of electrodeposition cycles. A maximum specific capacitance, Csp, of 1235 F/g at a scan rate of 50 mV/s was achieved for the 30-cycle deposited RuO2-ITO nanopillars. The other capacitive properties such as electrochemical reversibility and Csp retention at high scan rates also improved greatly.