Radially oriented mesoporous TiO2 microspheres with single-crystal–like anatase walls for high-efficiency optoelectronic devices

Highly crystalline mesoporous materials with oriented configurations are in demand for high-performance energy conversion devices. We report a simple evaporation-driven oriented assembly method to synthesize three-dimensional open mesoporous TiO2 microspheres with a diameter of ~800 nm, well-controlled radially oriented hexagonal mesochannels, and crystalline anatase walls. The mesoporous TiO2 spheres have a large accessible surface area (112 m2/g), a large pore volume (0.164 cm3/g), and highly single-crystal–like anatase walls with dominant (101) exposed facets, making them ideal for conducting mesoscopic photoanode films. Dye-sensitized solar cells (DSSCs) based on the mesoporous TiO2 microspheres and commercial dye N719 have a photoelectric conversion efficiency of up to 12.1%. This evaporation-driven approach can create opportunities for tailoring the orientation of inorganic building blocks in the assembly of various mesoporous materials.State Key Basic Research Program of China (2013CB934104 and 2012CB224805), the National Science Foundation (21210004), the Science and Technology Commission of Shanghai Municipality (08DZ2270500), the Shanghai Leading Academic Discipline Project (B108), King Abdulaziz City for Science and Technology (project no. 29-280), and Deanship of Scientific Research, King Saud University–The International Highly Cited Research Group Program (IHCRG#14-102). Y.L. also acknowledges the Interdisciplinary Outstanding Doctoral Research Funding of Fudan University (EZH2203302/001)

Low-cost and biodegradable thermoelectric devices based on van der Waals semiconductors on paper substrates

We present a method to fabricate handcrafted thermoelectric devices on standard office paper substrates. The devices are based on thin films of WS2, Te, and BP (P-type semiconductors) and TiS3 and TiS2 (N-type semiconductors), deposited by simply rubbing powder of these materials against paper. The thermoelectric properties of these semiconducting films revealed maximum Seebeck coefficients of (+1.32 ± 0.27) mV/K and (-0.82 ± 0.15) mV/K for WS2 and TiS3, respectively. Additionally, Peltier elements were fabricated by interconnecting the P-type and N-type films with graphite electrodes. A thermopower value up to 6.11 mV/K was obtained when the Peltier element is constructed with three junctions. The findings of this work show proof-of-concept devices to illustrate the potential application of semiconducting van der Waals materials in future thermoelectric power generation as well as temperature sensing for low-cost disposable electronic device

Regulating C2H2/CO2 adsorption selectivity by electronic-state manipulation of iron in metal-organic frameworks

Article reports a metal electronic-state manipulation strategy to construct a pair of isostructural and interconvertible Fe-MOFs featuring open Fe centers with different electron densities for efficient C₂H₂/CO₂ separation. The authors show that the presence of Fe[II] centers with a medium-spin-state trail plays a crucial role in the enhanced C₂H₂ selective adsorption

Polymer-Based Electrospun Nanofibers for Biomedical Applications

Electrospinning has been considered a promising and novel procedure to fabricate polymer nanofibers due to its simplicity, cost effectiveness, and high production rate, making this technique highly relevant for both industry and academia. It is used to fabricate non-woven fibers with unique characteristics such as high permeability, stability, porosity, surface area to volume ratio, ease of functionalization, and excellent mechanical performance. Nanofibers can be synthesized and tailored to suit a wide range of applications including energy, biotechnology, healthcare, and environmental engineering. A comprehensive outlook on the recent developments, and the influence of electrospinning on biomedical uses such as wound dressing, drug release, and tissue engineering, has been presented. Concerns regarding the procedural restrictions and research contests are addressed, in addition to providing insights about the future of this fabrication technique in the biomedical field

Freestanding eggshell membrane-based electrodes for high-performance supercapacitors and oxygen evolution reaction

A type of freestanding, light-weight eggshell membrane-based electrode is demonstrated for supercapacitors and for oxygen evolution reaction (OER) catalysis. As a widely available daily waste, eggshell membranes have unique porous three-dimensional grid-like fibrous structures with relatively high surface area and abundant macropores, allowing for effective conjugation of carbon nanotubes and growth of NiCo2O4 nanowire arrays, an effective supercapacitor material and OER catalyst. The three-dimensional fibrous eggshell membrane frameworks with carbon nanotubes offer efficient pathways for charge transport, and the macropores between adjacent fibers are fully accessible for electrolytes and bubble evolution. As a supercapacitor, the eggshell membrane/carbon nanotube/NiCo2O4 electrode shows high specific capacitances at current densities from 1 to 20 A g-1, with excellent capacitance retention (>90%) at 10 A g-1 for over 10 000 cycles. When employed as an OER catalyst, this eggshell membrane-based electrode exhibits an OER onset potential of 1.53 V vs. the reversible hydrogen electrode (RHE), and a stable catalytic current density of 20 mA cm-2 at 1.65 V vs. the RHE. The Royal Society of Chemistry.Scopu

Nickel oxide carbon nanofiber composite for electrochemical oxidation of methanol

Electrospun fibers of a mixture of polyvinylpyrrolidone (PVP), polyaniline (PANI) and graphene were stabilized for 2 h at 200 °C and then carbonized at 800 °C for 5 h. Composites were prepared by depositing Ni(OH)2 on the carbon nanofibers (CNFs) and calcining them at different temperatures. The composites were characterized using XRD, TEM and SEM. The effect of the calcination temperatures on the electrochemical catalytic properties towards methanol (MeOH) oxidation was studied using cyclic voltammetry and electrochemical impedance spectroscopy. The analysis of the chronoamperometry measurements confirmed a significant increase in the real surface area for the CNF/NiO composite as the calcination temperature increases. The real surface area is increased at calcination temperatures of 400 and 500 oC more than 20 times higher than that calcined at 300 oC. The oxidation of MeOH was not found to be a purely diffusion controlled process. The CNF/NiO composite has shown, not only, a good stability as the potential was cycled between a large potential window, but also, the electrocatalytic properties was enhanced which was attributed to the surface activation during the cyclic process. The impedance parameters were calculated from the EIS measurements proved that this system has two time constants: one for the adsorption and the other for the charge transfer.Scopu

From Water Oxidation to Reduction: Homologous Ni–Co Based Nanowires as Complementary Water Splitting Electrocatalysts

A homologous Ni–Co based nanowire system, consisting of both nickel cobalt oxide and nickel cobalt sulfide nanowires, is developed for efficient, complementary water splitting. The spinel-type nickel cobalt oxide (NiCo2O4) nanowires are hydrothermally synthesized and can serve as an excellent oxygen evolution reaction catalyst. Subsequent sulfurization of the NiCo2O4 nanowires leads to the formation of pyrite-type nickel cobalt sulfide (Ni0.33Co0.67S2) nanowires. Due to the 1D nanowire morphology and enhanced charge transport capability, the Ni0.33Co0.67S2 nanowires function as an efficient, stable, and robust nonnoble metal electrocatalyst for hydrogen evolution reaction (HER), substantially exceeding CoS2 or NiS2 nanostructures synthesized under similar methods. The Ni0.33Co0.67S2 nanowires exhibit low onset potential of −65, −39, and −50 mV versus reversible hydrogen electrode, Tafel slopes of 44, 68, and 118 mV dec−1 at acidic, neutral, and basic conditions, respectively, and excellent stability, comparable to the best reported non-noble metal-based HER catalysts. Furthermore, the homologous Ni0.33Co0.67S2 nanowires and NiCo2O4 nanowires are assembled into an all-nanowire based water splitting electrolyzer with a current density of 5 mA cm−2 at a voltage as 1.65 V, thus suggesting a unique homologous, earth abundant material system for water splitting.* National Key Basic Research Program of China. Grant Number: 2013CB934104 * Natural Science Foundation of China. Grant Numbers: 21322311, 21473038, 21071033 * Science and Technology Commission of Shanghai Municipality. Grant Number: 14JC1490500 Doctoral Fund of Ministry of Education of China. Grant Number: 20130071110031 * Program for Professor of Special Appointment * Deanship of Scientific Research at King Saud University. Grant Number: RG#1435-010Wiley Online librar

The Impact of AN Contribution on the Thermal Characteristics and Molecular Dynamics of Novel Acrylonitrile–Styrene–Styrene Sodium Sulfonate Terpolymers

We performed a free radical solution polymerization of new acrylonitrile (AN), styrene (St) and styrene sodium sulfonate (SSS) acceptor–donor acceptor monomer systems. The compositions and structures of the produced terpolymers were elucidated using CHNS elemental analysis, and Fourier transform infrared (FTIR) spectroscopies. Three terpolymers candidates were chosen for detailed thermal investigations, where the AN molar ratio varied almost threefold (from ~6.9% to ~17.4%) while the molar ratios of St and SSS varied slightly, at average values around 76.0% and 12.9%, respectively. The glass transition (Tg) values of the terpolymers were measured calorimetrically. In addition, thermal gravimetric analyses (TGA) of the samples were conducted in the temperature range from room temperature to 800 °C. All terpolymers exhibited a single Tg value, indicating random copolymerization of the monomeric species. TGA results revealed that variation of the AN molar ratio had a significant influence on the thermal stabilities of the terpolymers. The impact of AN contribution on the molecular dynamics of the glass transition in the terpolymers was explained quantitatively in a framework of a molecular model

Evaluation of the Cytotoxic Behavior of Fungal Extracellular Synthesized Ag Nanoparticles Using Confocal Laser Scanning Microscope

Silver nanoparticles have been synthesized by subjecting a reaction medium to a Fusarium oxysporum biomass at 28 °C for 96 h. The biosynthesized Ag nanoparticles were characterized on the basis of their anticipated peak at 405 nm using UV-Vis-NIR spectroscopy. Structural confirmation was evident from the characteristic X-ray diffraction (XRD) pattern, high-resolution transmission electron Microscopy (HRTEM) and the particle size analyzer. The Ag nanoparticles were of dimension 40 ± 5 nm and spherical in shape. The study mainly focused on using the confocal laser scanning microscope (CLSM) to examine the cytotoxic activities of fungal synthesized Ag nanoparticles on a human breast carcinoma cell line MCF7 cell, which featured remarkable vacuolation, thus indicating a potent cytotoxic activity

High electrocatalytic performance of nitrogen-doped carbon nanofiber-supported nickel oxide nanocomposite for methanol oxidation in alkaline medium

Nitrogen-Doped Carbon Nanofiber (N-CNF)–supported NiO composite was prepared by electrospinning a sol-gel mixture of graphene and polyaniline (PANi) with aqueous solutions of Polyvinylpyrrolidone (PVP) followed by a high-temperature annealing process. The electrospun was stabilized for 2 h at 280 °C, carbonized for 5 h at 1200 °C then loaded by 10% NiO. The electrocatalytic activities of the produced nanocomposite have been studied using cyclic voltammetry, and chronoamperometry. Also, N-CNF was characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), surface area (BET), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), and scanning-electron microscopy (SEM). The obtained N-doped carbon nanofiber was found to have a nitrogen content of 2.6 atomic% with a diameter range of (140–160) nm, and a surface area (393.3 m2 g−1). In addition, it showed a high electrocatalytic behavior towards methanol oxidation reaction in alkaline medium and high stability and resistivity to the adsorption of intermediates.Scopu