Halloysite-Based Nanorockets with Light-Enhanced Self-Propulsion for Efficient Water Remediation.

Halloysite-based tubular nanorockets with chemical-/light-controlled self-propulsion and on-demand acceleration in velocity are reported. The nanorockets are fabricated by modifying halloysite nanotubes with nanoparticles of silver (Ag) and light-responsive α-Fe2O3 to prepare a composite of Ag-Fe2O3/HNTs. Compared to the traditional fabrication of tubular micro-/nanomotors, this strategy has merits in employing natural clay as substrates of an asymmetric tubular structure, of abundance, and of no complex instruments required. The velocity of self-propelled Ag-Fe2O3/HNTs nanorockets in fuel (3.0% H2O2) was ca. 1.7 times higher under the irradiation of visible light than that in darkness. Such light-enhanced propulsion can be wirelessly modulated by adjusting light intensity and H2O2 concentration. The highly repeatable and controlled "weak/strong" propulsion can be implemented by turning a light on and off. With the synergistic coupling of the photocatalysis of the Ag-Fe2O3 heterostructure and advanced oxidation in H2O2/visible light conditions, the Ag-Fe2O3/HNTs nanorockets achieve an enhanced performance of wastewater remediation. A test was done by the catalytic degradation of tetracycline hydrochloride. The light-enhanced propulsion is demonstrated to accelerate the degradation kinetics dramatically. All of these results illustrated that such motors can achieve efficient water remediation and open a new path for the photodegradation of organic pollutions.

Fabrication of Pd/Mg2 P2 O7 via a Struvite-Template Way from Wastewater and Application as Chemoselective Catalyst in Hydrogenation of Nitroarenes.

A highly efficient heterogeneous catalyst Pd/Mg2 P2 O7 was fabricated by combining palladium nanoparticles (PdNPs) and mesoporous Mg2 P2 O7 fibers/rods. Mg2 P2 O7 fibers with ultra-high specific surface area were prepared from struvite as templates, which were synthesized from waste water containing N- and P-containing pollutants. This strategy provided a novel pathway for developing advanced catalysts from eutrophication-polluted water. The composite Pd/Mg2 P2 O7 showed brilliant performance in selective hydrogenation of nitro aromatics to give anilines. As an example of nitrobenzene hydrogenation, the conversion to aniline and selectivity were found to reach almost 100 % at a temperature of T=90 °C and under a pressure of P H 2 =2.0 MPa. The superior performance was found to originate from PdNPs, which were boosted by electron transfer afforded by the nanofiber Mg2 P2 O7 supports. The favorable adsorption of withdrawing groups (-NO2 ) was realized by synergistic effects between Pd and oxygen vacancies provided by pyrolysis of struvite. The catalyst remained stable after cycles of reuse with little degradation in catalytic performance.

Prolonged-Photoresponse-Lifetime Ni2P Nanocrystalline with Highly Exposed (001) for Efficient Photoelectrocatalytic Hydrogen Evolution.

Seeking highly efficient non-preference electrocatalytic materials that serve photoelectrochemical (PEC) water splitting in acidic systems is expectant in the context of environmentally friendly production. We designed Ni2P electrocatalysts synthesized in oil phases via the hot-bubbling method with superb stability in air and sulfuric acid solution for PEC, which were found with excellent hydrogen evolution performance. A tunable particle size and highly exposed (001) planes of Ni2P nanocrystals were achieved. The designed catalysts achieved a notable promotion in the hydrogen evolution reaction activity compared to that of Ni2P synthesized in the water phase. More specifically, the electrode prepared by self-assembled Ni2P nanoparticles was found to have decent over-potential of η10 = 164 mV in darkness and was further decreased to 129 mV with irradiation of visible light. The cyclic stability tests manifested brilliant durability in 0.5 M H2SO4. Measurement of the transient photocurrent response and PEC water splitting catalytic performance indicated that the Ni2P had high carrier concentration upon irradiation, lower carrier recombination probability, and prolonged photo-response lifetime (3.03-3.14 s).

Universality of mesoporous coal gasification slag for reinforcement and deodorization in four common polymers.

Mesoporous adsorbents and polymer deodorants are difficult to implement on a large scale because of their complicated preparation methods. Herein, a mesoporous adsorbent (CGSA) with a specific surface area of 564 m2g-1and a pore volume of 0.807 cm3g-1was prepared from solid waste coal gasification slag using a simple acid leaching process. The adsorption thermodynamics and adsorption kinetics results verified that the adsorption mechanism of propane on CGSA was mainly physisorption. Then the universality of CGSA in different polymers was investigated by introducing CGSA and its commercialized counterparts (CaCO3, and zeolite) into four common polymers. When the filler content was 30 wt%, the average reinforcement effect of CGSA on the tensile, flexural, and impact strengths of the four polymers was 46.68%, 83.62%, and 211.90% higher than that of CaCO3, respectively. Gas chromatography results also showed that CGSA significantly decreased total volatile organic compound emissions from the composites, and its optimal deodorization performance reached 69.58%, 81.33%, and 91.09% for different polymers, respectively, far exceeding that of zeolite. Therefore, this study showed that low-cost, high-performance, and multifunctional mesoporous polymer fillers with excellent universality can be manufactured from solid contaminants.

Hydrogen-bonding-mediated synthesis of atomically thin TiO2 films with exposed (001) facets and applications in fast lithium insertion/extraction.

Ultrathin two-dimensional (2D) crystalline materials show high specific surface area (SA) of high energy (HE) facets, imparting a significant improvement in their performances. Herein we report a novel route to synthesize TiO2 nanofilms (NFs) with atomic thickness (<2.0 nm) through a solvothermal reaction mediated by the hydrogen-bonding networks constructed by hydroquinone (HQ). The resultant TiO2 NFs have nearly 100 % exposed (001) facets and give an extremely high SA up to 487 m(2) g(-1) . The synergistic effect of HQ and choline chloride plays a vital role in the formation of TiO2 NFs and in the exposure of HE (001) facets. Because of its ultrathin feature and exposed (001) facet, the N2 -annealled TiO2 NFs showed fast kinetics of lithium insertion/extraction, demonstrating foreseeable applications in the energy storage.

Emissive ZnO@Zn3 P2 nanocrystals: synthesis, optical, and optoelectrochemical properties.

ZnO@Zn3 P2 quantum dots (QDs) are synthesized, with emission from yellow to red. Photoelectrochemical investigations reveal that the current and voltage of the QD-derivatized electrodes show a response upon illumination. A photocurrent of ca. 8 nA cm(-2) for a monolayer of ZnO@Zn3 P2 QDs deposited on indium tin oxide (ITO) electrode is recorded.

Highly Stable and Recyclable Sequestration of CO2 Using Supported Melamine on Layered-Chain Clay Mineral.

A type of highly stable and recyclable clay-based composite was developed for sequestration of CO2, which was synthesized by loading melamine (MEL) onto attapulgite (ATT) via a wet impregnation method. The synthesized materials were characterized by N2 adsorption-desorption, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), and transmission electron microscopy (TEM). By means of thermal and acidic treatments more active sites of ATT were exposed, and large surface areas were obtained. The MEL molecules were well combined with those exposed sites, which enhanced stability and cyclability for CO2 sequestration. On the basis of CO2 adsorption-desorption measurements, the composite of ATT-MEL was found to have a higher CO2 adsorption capacity (4.91 cm3/g) which was much higher than that of CO2 absorption on bare MEL (1.30 cm3/g) at 30 °C. After ten cycles of reusing, the composite exhibited even higher capacity for CO2 adsorption by an increased percentage of 5.91% (30 °C) and 5.77% (70 °C) compared to the capacity in the first cycle. The reason lies in the strong interaction between melamine and attapulgite matrix which was further confirmed by DFT calculations. The MEL was validated to have advantages over aliphatic amines (TEPA) in modifying ATT to get high stability of CO2-adsorbents.

Self-Propelled Nanojets for Fenton Catalysts Based on Halloysite with Embedded Pt and Outside-Grafted Fe3O4.

Taking inspirations from nature, we endeavor to develop catalytically self-propelled nanojets from a type of tubular clay minerals, halloysite nanotubes (HNTs), and utilize them as catalysts targeted for catalysis where the traditional means of mechanical agitation cannot be implemented. Nanojets of Fe3O4@HNTs/Pt were prepared by impregnating platinum nanoparticles (Pt NPs) in lumens of HNTs and selective grafting of magnetite (Fe3O4) particles on the external surface. The HNT-based nanojets were validated to be highly suitable both in free bulk solution and in microfluidic flow. An example of Fenton degradation catalyzed by these jets was demonstrated. The powerful movement of Fe3O4@HNTs/Pt (368 ± 50 µm·s-1) fueled by 5.0% wt. H2O2 was found to follow a bubble propulsion mechanism, and the motion exhibits collective behavior as swarms. The clay tubes were for the first time observed to self-assemble into fish-like aggregates during swimming, reflecting natural occurrence of motion-evolution philosophy. Guided motion was realized by employing magnetic manipulation which makes jets feasible for reactors with complex microchannels/reactors.

Synthesis and characterization of cadmium phosphide quantum dots emitting in the visible red to near-infrared.

The synthesis of high-quality cadmium phosphide quantum dots with emission wavelength maxima in the range from 1200 to approximately 760 nm are reported. The results demonstrate that the nucleation and growth linked with the optical properties can be controlled by the temperature, the growth time, and the addition of ligands such as oleylamine and trioctylphosphine. Photoelectrochemical investigations revealed that the cadmium phosphide QD-derivatized electrodes show an optical response and that photocurrents of several nanoamperes per square centimeter can be obtained upon illumination.

Three-component Langmuir-Blodgett films consisting of surfactant, clay mineral, and lysozyme: construction and characterization.

The Langmuir-Blodgett (L-B) technique has been employed for the construction of hybrid films consisting of three components: surfactant, clay, and lysozyme (Lys). The surfactants are octadecylammonium chloride (ODAH) and octadecyl ester of rhodamine B (RhB18). The clays include saponite and laponite. Surface pressure versus area isotherms indicate that lysozyme is adsorbed by the surfactant-clay L-B film at the air-water interface without phase transition. The UV-visible spectra of the hybrid film ODAH-saponite-Lys show that the amount of immobilized lysozyme in the hybrid film is (1.3+/-0.2) ng mm(-2). The average surface area (Omega) per molecule of lysozyme is approximately 18.2 nm(2) in the saponite layer. For the multilayer film (ODAH-saponite-Lys)(n), the average amount of lysozyme per layer is (1.0+/-0.1) ng mm(-2). The amount of lysozyme found in the hybrid films of ODAH-laponite-Lys is at the detection limit of about 0.4 ng mm(-2). Attenuated total reflectance (ATR) FTIR spectra give evidence for clay layers, ODAH, lysozyme, and water in the hybrid film. The octadecylammonium cations are partially oxidized to the corresponding carbamate. A weak 1620 cm(-1) band of lysozyme in the hybrid films is reminiscent of the presence of lysozyme aggregates. AFM reveals evidence of randomly oriented saponite layers of various sizes and shapes. Individual lysozyme molecules are not resolved, but aggregates of about 20 nm in diameter are clearly seen. Some aggregates are in contact with the clay mineral layers, others are not. These aggregates are aligned in films deposited at a surface pressure of 20 mN m(-1).

Effective removal of aromatic pollutants via adsorption and photocatalysis of porous organic frameworks.

PAF-45 with a wholly aromatic framework, intrinsic microporosity and π-π conjugation system shows excellent performance in aromatic pollutant removal. It exhibits a high adsorption capacity for the benzene series and moderate photocatalytic performance. As an adsorbent, PAF-45 can adsorb 35 wt% benzene and 68 wt% chlorobenzene in static adsorption experiments at room temperature and pressure. In benzene simulation wastewater, PAF-45 also shows excellent adsorption capacity, without significant reduction after 10 cycles of the adsorption-desorption process. Moreover, PAF-45 exhibits an impressive photocatalytic degradability of aromatic compounds, like aniline and phenol, under visible light illumination.

Flexible Multifunctional Porous Nanofibrous Membranes for High-Efficiency Air Filtration.

Particulate matter (PM) discharged along with the rapid industrialization and urbanization hazardously threatens ecosystems and human health. Membrane-based filtration technology has been proved to be an effective approach to capture PM from the polluted air. However, the fabrication of filtration membranes with excellent reusability and antibacterial activity has rarely been reported. Herein, the flexible multifunctional porous nanofibrous membranes were fabricated by embedding Ag nanoparticles into the electrospun porous SiO2-TiO2 nanofibers via an impregnation method, which integrated the abilities of PM filtration and antibacterial performance. Compared with the reported air filters, the resultant membrane (Ag@STPNM) with high surface polarity and porous structure possessed the low density, high removal efficiency, and small pressure drop. For instance, the removal efficiency and the pressure drop of Ag@STPNM with a basis weight of only 3.9 g m-2 for PM2.5 reached 98.84% and 59 Pa, respectively. In terms of the excellent thermal stability of Ag@STPNM, the adsorbed PM could be removed simply by a calcination process. The filtration performance of Ag@STPNM kept stable during five purification-regeneration cycles and the long-time filtration for 12 h, exhibiting excellent recyclability and durability. Furthermore, the embedded Ag nanoparticles could achieve the effective resistance to the breeding of bacteria on Ag@STPNM, giving the bacteriostatic rate of 95.8%. Therefore, Ag@STPNM holds promising potentials as a highly efficient, reusable, and antibacterial air filter in the practical purification of the indoor environment or personal air.

Amino-Functionalized Porous Nanofibrous Membranes for Simultaneous Removal of Oil and Heavy-Metal Ions from Wastewater.

Both oil spill and heavy-metal ions in the industrial wastewater cause severe problems for aquatic ecosystem and human health. In the present work, the electrospun superamphiphilic SiO2-TiO2 porous nanofibrous membranes (STPNMs) comprised of intrafiber mesopores and interfiber macropores are modified by an amino-silanization reaction, which affords the membrane (ASTPNMs) the ability to simultaneously remove the oil contaminants and the water-soluble heavy-metal ions from wastewater. The underwater superoleophobicity of ASTPNMs facilitates the highly efficient separation of water and various oils, even emulsifier-stabilized emulsion. Meanwhile, an optimal modification time (15 min, ASTPNM-15) is important for maintaining the under-oil superhydrophilicity of the membrane, based on which the oil contaminant in membrane can be easily cleaned by water alone, showing excellent self-cleaning performance. The adsorption of Pb2+ over ASTPNM-15 reaches equilibrium at around 20 min, and the monolayer adsorption capacity is 142.86 mg g-1 at pH = 5 at 20 °C. In the breakthrough processes, the permeation volume of ASTPNM-15 for the purification of Pb2+ (5 ppm, pH = 5) reaches 160 mL when the concentration of Pb2+ in the filtrate increases to 0.05 ppm. The separation efficiencies of ASTPNM-15 for simulated wastewater containing both oil spill and various heavy-metal ions (Pb2+, Cr3+, Ni2+) are larger than 99.5%. In addition, the separation capacity keeps stable over five purification-regeneration cycles without obvious decrease, proving excellent recyclability and reusability of ASTPNM-15 for practical applications.

Swelling suppression of black cotton soil by means of liquid immersion and surface modification.

Although the surface organic modification of smectite has been investigated widely, the swelling behavior of clays has been scarcely studied with consideration of civil engineering applications. In this work a facile strategy of liquid-immersion (dilute H2SO4 aqeuous solution) was proposed, and the 3-aminopropyltrimethoxysilane (APS) was utilized as surface modifier to suppress expansibility of black cotton soil (BCS) which is a type of highly swelling soils in tropical areas. Factors such as the incorporation dosage of APS, surface characters of soil treated by solution of H2SO4 or Na2CO3, and reaction temperatures/time were investigated to get lower swelling ratios. The treatment of BCS by H2SO4 was found more effective in immobilizing APS molecules, and hydronium ions were suppressed after the APS modification. The free swelling index (FSI) of BCS was decreased from 120% to 15% after treatment with H2SO4 and appropriate amount of APS modification. The reaction can be completed within several hours at the room temperature to ~80 °C. The soil samples were characterized by different means including the X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscope, thermogravimetric analysis and Zeta potential measurements. The APS molecules were found to react with -OH groups of the clay, and the hydrophobic groups provide surface hydrophobicity, which prevents hydration of cations within clay minerals. The APS was indicated to re-constructed lamellar structures of smectites after H2SO4 treatment, which suppressed the intra-crystalline and the subsequent osmotic swelling. This research highlights the liquid immersion and surface modification is applicable in diminishing swelling ratios of highly expansive black cotton soil.

One-pot synthesis of ZnS/polymer composites in supercritical CO2-ethanol solution and their applications in degradation of dyes.

A facile method to decorate the polymeric hollow spheres with ZnS nanoparticles has been presented. In this method, the precursors, Zn(Ac)(2)H(2)O and CH(3)CSNH(2), were first adsorbed by the polymer substrate in supercritical CO(2)-ethanol solution at 35 degrees C. Followed by heating the mixture at 100 degrees C for 2 h, ZnS/polymer composites were obtained. The as-produced ZnS/polymer composites were characterized by means of IR spectra, X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy. It was demonstrated that crystalline ZnS nanoparticles with size of 3-5 nm were uniformly decorated on the polymer spheres under suitable conditions. The resultant ZnS/polymer composites exhibited high efficiency for degrading eosin B, methyl orange and methylene blue under UV light irradiation.

Microtubular Fuel Cell with Ultrahigh Power Output per Footprint.

A novel realization of microtubular direct methanol fuel cells (µDMFC) with ultrahigh power output is reported by using "rolled-up" nanotechnology. The microtube (Pt-RuO2 -RUMT) is prepared by rolling up Ru2 O layers coated with magnetron-sputtered Pt nanoparticles (cat-NPs). The µDMFC is fabricated by embedding the tube in a fluidic cell. The footprint of per tube is as small as 1.5 × 10-4 cm2 . A power density of ≈257 mW cm-2 is obtained, which is three orders of magnitude higher than the present microsized DFMCs. Atomic layer deposition technique is applied to alleviate the methanol crossover as well as improve stability of the tube, sustaining electrolyte flow for days. A laminar flow driven mechanism is proposed, and the kinetics of the fuel oxidation depends on a linear-diffusion-controlled process. The electrocatalytic performance on anode and cathode is studied by scanning both sides of the tube wall as an ex situ working electrode, respectively. This prototype µDFMC is extremely interesting for integration with micro- and nanoelectronics systems.

Microwave-assisted synthesis of pt nanocrystals and deposition on carbon nanotubes in ionic liquids.

In this work, a simple, fast and efficient route is presented for the metal (such as Pt, Rh, etc.) nanocrystal synthesis and deposition on carbon nanotubes (CNTs) in ionic liquids (ILs) via microwave heating. In this method, inorganic salts (such as H2PtCl6.4H2O, RhCl3.2H2O, etc.) dissolved in ILs, 1,1,3,3-tetramethylguanidinium trifluoroacetate or 1,1,3,3-tetramethylguanidinium lactate, were reduced to metal nanoparticles by glycol with the aid of microwave heating, and the produced metal nanoparticles could be decorated on CNTs in the presence of CNTs in ILs. The resulting nanomaterials were characterized by means of transmission electron microscopy and X-ray diffraction. It was demonstrated that the homogeneously dispersed Pt nanocrystals with the size of 2-3 nm were obtained using H2PtCl6.4H2O as precursor, and they deposited on CNTs with the similar size when CNTs was present in ILs. This technique also can be extended to fabricate other noble metal nanocrystals (including Rh, Au, etc.) and corresponding CNT composites.

Decoration carbon nanotubes with Pd and Ru nanocrystals via an inorganic reaction route in supercritical carbon dioxide-methanol solution.

This work describes a method to decorate carbon nanotubes (CNTs) with metallic Pd and Ru nanocrystals via inorganic reactions in supercritical (SC) CO2-methanol solutions. In this route, PdCl2 or RuCl3.3H2O dissolved in SC CO2-methanol solution acted as a metal precursor and CNTs functioned as a template to direct the deposition of produced nanoparticles. Methanol served as the reductant for the precursors as well as cosolvent to enhance the dissolution of precursors in SC CO2. Dry products were readily obtained through in situ extraction with SC CO2 after reactions. The products were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. It was demonstrated that the loading content and particle size of the nanoparticles deposited on CNTs could be tuned by changing the weight ratio of the precursor to CNTs. This simple and efficient approach may also be utilized to synthesize other high-purity materials using inorganic salt precursors in SC CO2-based solution.

Synthesis and characterization of ZnS-montmorillonite nanocomposites and their application for degrading eosin B.

Nanocomposites of zinc sulfide (ZnS) and montmorillonite (MMT) were prepared via a hydrothermal route. In this method, the MMT treated with hexadecyltrimethyl ammonium bromide (HTAB) aqueous solution was dispersed in the aqueous solution of thiourea and Zn(OOCHCH(3))(2)2H(2)O, and heated at 170 degrees C for about 4 h, resulting in ZnS-MMT composites. The as-prepared nanocomposites were characterized with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen sorption analysis. It was demonstrated that the interlayer space of MMT was enlarged from 0.98 to 3.77 nm after the treatment with HTAB aqueous solution, and the ZnS nanoparticles were deposited on the layers of MMT. Nitrogen sorption analysis demonstrated that the specific surface area of the samples decreased from 39.2 m(2)/g of the pristine MMT to 5.9 m(2)/g of the final ZnS-MMT composites. The resulting ZnS-MMT nanocomposites (50.0 mg) could degrade eosin B completely in aqueous solution (75 ml, 3.2x10(-5) M) within 20 min under UV irradiation.

High Efficiency Dye-sensitized Solar Cells Constructed with Composites of TiO2 and the Hot-bubbling Synthesized Ultra-Small SnO2 Nanocrystals.

An efficient photo-anode for the dye-sensitized solar cells (DSSCs) should have features of high loading of dye molecules, favorable band alignments and good efficiency in electron transport. Herein, the 3.4 nm-sized SnO2 nanocrystals (NCs) of high crystallinity, synthesized via the hot-bubbling method, were incorporated with the commercial TiO2 (P25) particles to fabricate the photo-anodes. The optimal percentage of the doped SnO2 NCs was found at ~7.5% (SnO2/TiO2, w/w), and the fabricated DSSC delivers a power conversion efficiency up to 6.7%, which is 1.52 times of the P25 based DSSCs. The ultra-small SnO2 NCs offer three benefits, (1) the incorporation of SnO2 NCs enlarges surface areas of the photo-anode films, and higher dye-loading amounts were achieved; (2) the high charge mobility provided by SnO2 was confirmed to accelerate the electron transport, and the photo-electron recombination was suppressed by the highly-crystallized NCs; (3) the conduction band minimum (CBM) of the SnO2 NCs was uplifted due to the quantum size effects, and this was found to alleviate the decrement in the open-circuit voltage. This work highlights great contributions of the SnO2 NCs to the improvement of the photovoltaic performances in the DSSCs.