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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

Spectral Inspections on Molecular Configurations of Nile Blue A Adsorbed on the Elementary Clay Sheets.

Studies on the configuration of dye molecules are of great importance in revealing origins of the electronic bands as well as understanding their transitions. In this work, we utilized dye molecules named Nile blue A, which are a type of oxazine dyes, to study the molecular configurations when they are transferred from solutions to a solid surface. The Langmuir-Blodgett (LB) technique was employed to construct such an interface where the interaction between the dye molecules and solid supports can be pursued. Hybrid films were prepared via the LB depositions, and the dye molecules were assembled on the elementary clay sheets (laponite, saponite). The configuration of Nb reflected by the molecular orientation, packing density, phase behavior, and variances of the surface tension has been derived. The ex situ spectroscopy characterizations such as UV-vis absorption, fluorescence emission, and excitation spectra were carried out on these LB films to reveal the fact that the adsorbed Nb molecules are mainly assembled in two types of configurations. Adsorbed state I was found to be achieved at high concentrations (1-10 ppm) of clay dispersions and low surface pressure (∼5 mN/m). In this state the anionic oxazine rings of Nb are adsorbed on clay sheets sharing a large lift-off area. This configuration gives allowable fluorescence (λ = 550 nm). Lower clay concentration (<1 ppm) and high surface pressure (10-30 mN/m) yield the adsorbed state II in which the oxazine chromophores were arranged in a side-by-side style, and the dye molecules stand perpendicularly to the clay sheets. This conformation exhibits no photoluminescence.

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.

Conformational change of bovine serum albumin molecules at neutral pH in ultra-diluted aqueous solutions.

Surface chemical and electrochemical techniques were applied to reveal the unfolding of bovine serum albumin (BSA) molecules induced by concentrations in aqueous solution. Real-time surface pressures vs time (π-t) kinetic curves were recorded over an aqueous subphase (190 mL) by spreading BSA solutions of different concentrations but of the same amount (8.0 × 10(-4) mg) at the air/water (A/W) interface. A critical concentration (∼1.0 ppm) was discovered below which the surface pressure declines with time and the BSA is totally solubilized in the water subphase. Above this critical concentration (e.g., 8.0 ppm), the surface pressure goes up and the protein molecules assemble into a Langmuir monolayer at the A/W interface. These findings demonstrate that the BSA molecules have different conformations in the spreading protein solutions. The conformational transition in BSA molecules induced by concentrations was also confirmed by spectroscopy means and the catalytic hydrogen evolution reaction on a silver amalgam electrode by using constant current chronopotentiometric stripping. This discovery fills in gaps of Foster's N (normal) → F (fast) model, in which the unfolding of BSA molecules occurs at neutral pH values (8.0-4.3).

Ultrasmall SnO2 nanocrystals: hot-bubbling synthesis, encapsulation in carbon layers and applications in high capacity Li-ion storage.

Ultrasmall SnO2 nanocrystals as anode materials for lithium-ion batteries (LIBs) have been synthesized by bubbling an oxidizing gas into hot surfactant solutions containing Sn-oleate complexes. Annealing of the particles in N2 carbonifies the densely packed surface capping ligands resulting in carbon encapsulated SnO2 nanoparticles (SnO2/C). Carbon encapsulation can effectively buffer the volume changes during the lithiation/delithiation process. The assembled SnO2/C thus deliver extraordinarily high reversible capacity of 908 mA·h·g(-1) at 0.5 C as well as excellent cycling performance in the LIBs. This method demonstrates the great potential of SnO2/C nanoparticles for the design of high power LIBs.

One-pot hydrothermal synthesis of Co(OH)2 nanoflakes on graphene sheets and their fast catalytic oxidation of phenol in liquid phase.

A cobalt hydroxide (Co(OH)2) nanoflake-reduced graphene oxide (rGO) hybrid was synthesized by a one-pot hydrothermal method using glucose as a reducing agent for graphene oxide (GO) reduction. The structural and surface properties of the material were investigated by scanning and transmission electron microscopies, energy-dispersive X-ray spectrometry, powder X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Catalytic activities of GO, rGO, Co(OH)2 and Co(OH)2-rGO in aqueous phenol degradation using peroxymonosulfate as an oxidant were compared. A synergetic effect on the catalytic activity was found on the Co(OH)2-rGO hybrid. Although rGO has weak catalytic activity, Co(OH)2-rGO hybrid showed a higher catalytic activity than Co(OH)2. The phenol degradation on Co(OH)2-rGO was extremely fast and took around 10 min for 100% phenol removal. The degradation was found to follow the first order kinetics and a mechanism for phenol degradation was presented.

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.

Synthesis of monodisperse cadmium phosphide nanoparticles using ex-situ produced phosphine.

The synthesis of nanoparticles using a gas-liquid interfacial reaction, which for the first time is shown to result in highly monodisperse materials across a range of sizes, is presented. We demonstrate, using cadmium phosphide as the paradigm that this synthesis method can provide colloidal nanocrystals or quantum dots monodisperse enough so that for the first time multiple transitions in their absorbance spectra can be observed. Clear evidence is given that the resulting cadmium material is Cd(6)P(7) and not Cd(3)P(2), and a thorough investigation into the role of temperature and growth time and their effects on the optical properties has been conducted. This strategy can be extended to synthesize other relevant members of the binary component pnictide semiconducting family, and the chemistry of the pnictide compound formation using this synthetic methodology has been explained using the redox potential of the metals. The suitability of the resulting cadmium phosphide quantum dots for applications in light-emitting diodes (LEDs) has further been demonstrated.