Mercapto propyltrimethoxysilane- and ferrous sulfate-modified nano-silica for immobilization of lead and cadmium as well as arsenic in heavy metal-contaminated soil.

Nano-silica as an important part of soil is an ideal carrier of passivator material. In this paper, nano-silica was modified by silane coupling agent containing mercapto group and iron (II) salt to afford an organic-inorganic hybrid containing -S-Fe-S functional group (coded as RNS-SFe) on the surface of nano-silica. Results demonstrate that the RNS-SFe nanoparticle has network-like spheroidal shape and a primary particle size is about 18.0 nm. The RNS-SFe hybrid as a potential immobilization agent for heavy metal in soil shows excellent performance for the remediation of the contaminated soil. Specifically, with a dosage of 3.0% (mass ratio) in the soil, it can immobilize bioavailable Pb, Cd, and As by 97.1%, 85.0%, and 80.1%, respectively. Namely, the RNS-SFe hybrid can transform the bioavailable Pb, Cd, and As into insoluble mercapto metal compounds (-S-Pb-S- and -S-Cd-S-) and less soluble iron arsenate (Fe3(AsO4)2, FeAsO4) precipitate on the surface of nano-silica particle, thereby reducing the toxicity and mobility of the toxic contaminant fractions. In the meantime, the immobilized products of the Pb, Cd and As fractions have good resistance against acid leaching. These results are contributive to the application of RNS-SFe for the remediation of multi-heavy metal-contaminated soils in field.

Functional Janus-SiO2 Nanoparticles Prepared by a Novel "Cut the Gordian Knot" Method and Their Potential Application for Enhanced Oil Recovery.

Currently available methods (e.g., interfacial protection and phase separation) for preparing Janus nanoparticles are often complex and expensive. Furthermore, the preparation of Janus nanoparticles with a particle size below 10 nm is challenging. In this work, we combine an in situ surface-modification route with a chemical etching route to establish a novel "cut the Gordian knot" method for the preparation of functional Janus-SiO2 nanoparticles. Hydrophobic SiO2 nanoparticles with a three-dimensional network structure prepared via an in situ surface-modification route were dispersed in NaOH solution containing surfactant or ethanol to enable corrosion close to the modifier-nanoparticle interface with a relatively low content of surface modifiers. Thus, amphipathic Janus-SiO2 nanoparticles with a hydrophilic surface containing Si-OH species and a hydrophobic surface containing -CH3 fragments were generated. The as-prepared Janus-SiO2 nanoparticles with a size of 4-9 nm and a specific surface area of up to 612.9 m2/g can be easily dispersed in water, and they also can transfer from the water phase to the oil phase by tuning the surface polarity. Moreover, they can be tuned to achieve bidirectional regulation of surface wettability plus a reduction of the oil/water interface tension. Hence, a significant reduction (by 33∼50%) of water injection pressure and an enhanced oil recovery (EOR) (by 21.1% ∼ 26.6%) can be achieved. Apart from that, Janus-SiO2 nanoparticles are able to increase the viscosity of partially hydrolyzed polyacrylamide by 282.9% and significantly decrease its viscosity loss ratio in brine, causing an EOR of about 36.6%. With simple, low-cost, and scalable procedures, the following approach could be well applicable to fabricating Janus-SiO2 nanoparticles with a high potential for augmented water injection as well as EOR of low-permeability reservoirs.

Preparation of Cellulose/Graphene Oxide Composite Membranes and Their Application in Removing Organic Contaminants in Wastewater.

Cellulose/graphene oxide composite membranes (CGCMs) were prepared using a vacuum-filtration method. The CGCMs were then used as filters to remove organic pollutants from wastewater. It was found that the CGCM filters could efficiently and simultaneously achieve wastewater treatment and adsorbent separation. Their adsorption of Rhodamine B (RhB, an organic dye) varied with varying cellulose/graphene oxide mass ratios. The CGCM obtained at a cellulose/graphene oxide mass ratio of 8:1 exhibited the maximum removal efficiency for RhB. The maximum adsorption capacity of the CGCMs for RhB was found to be 86.4 mg/g. In addition, the CGCMs were easily regenerated and the regenerated CGCMs retained good abilities to remove contaminants, which could be significant for their application in wastewater treatment.

Preparation of Graphene Sheets by Electrochemical Exfoliation of Graphite in Confined Space and Their Application in Transparent Conductive Films.

A novel electrochemical exfoliation mode was established to prepare graphene sheets efficiently with potential applications in transparent conductive films. The graphite electrode was coated with paraffin to keep the electrochemical exfoliation in confined space in the presence of concentrated sodium hydroxide as the electrolyte, yielding ∼100% low-defect (the D band to G band intensity ratio, ID/IG = 0.26) graphene sheets. Furthermore, ozone was first detected with ozone test strips, and the effect of ozone on the exfoliation of graphite foil and the microstructure of the as-prepared graphene sheets was investigated. Findings indicate that upon applying a low voltage (3 V) on the graphite foil partially coated with paraffin wax that the coating can prevent the insufficiently intercalated graphite sheets from prematurely peeling off from the graphite electrode thereby affording few-layer (<5 layers) holey graphene sheets in a yield of as much as 60%. Besides, the ozone generated during the electrochemical exfoliation process plays a crucial role in the exfoliation of graphite, and the amount of defect in the as-prepared graphene sheets is dependent on electrolytic potential and electrode distance. Moreover, the graphene-based transparent conductive films prepared by simple modified vacuum filtration exhibit an excellent transparency and a low sheet resistance after being treated with NH4NO3 and annealing (∼1.21 kΩ/□ at ∼72.4% transmittance).

Titanate Nanotubes Decorated Graphene Oxide Nanocomposites: Preparation, Flame Retardancy, and Photodegradation.

Most polymers exhibit high flammability and poor degradability, which restrict their applications and causes serious environmental problem like "white pollution." Thus, titanate nanotubes (TNTs) were adopted to decorate graphene oxide (GO) by a facile solution method to afford TNTs/GO nanocomposites with potential in improving the flame retardancy and photodegradability of flexible polyvinyl chloride (PVC). Results show that the as-prepared TNTs/GO can effectively improve the thermal stability and flame retardancy than TNTs and GO, especially, the peak heat release rate and total heat release were reduced by 20 and 29% with only 2.5 wt.% loading. And more, the TNTs/GO also improve the photodegradability of PVC compared with the neat PVC. The reasons can be attributed to synergistic flame-retardant and photocatalytic effects between TNTs and GO. The present research could contribute to paving a feasible pathway to constructing polymer-matrix composites with desired flame retardancy and photodegradability, thereby adding to the elimination of white pollution caused by polymers.

Simultaneous Surface Modification and Chemical Reduction of Graphene Oxide Using Ethylene Diamine.

We report a simple and facile method of reducing and modifying graphene oxide (GO) simultaneously using ethylene diamine (ED). The ED-modified and reduced GO (denoted as E-rGO) as well as the GO reduced by hydrazine hydrate (denoted as H-rGO) were characterized by Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), Raman spectra, Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM). It was found that as-prepared E-rGO exhibited good dispersibility in water and water-borne polyurethane (denoted as WPU) matrix and improve greatly the mechanical properties of WPU matrix. Moreover, E-rGO showed a high electric conductivity close to that of H-rGO after ultrasonic treatment for 12 h, which indicated that ED had the desired reducibility. The present approach could help to broaden the application field of graphene nanosheets and provide a new opportunity for developing high performance graphene/polymer-matrix composites.

Preparation of zinc hydroxystannate-decorated graphene oxide nanohybrids and their synergistic reinforcement on reducing fire hazards of flexible poly (vinyl chloride).

A novel flame retardant, zinc hydroxystannate-decorated graphene oxide (ZHS/GO) nanohybrid, was successfully prepared and well characterized. Herein, the ZHS nanoparticles could not only enhance the flame retardancy of GO with the synergistic flame-retardant effect of ZHS but also prevent the restack of GO to improve the mechanical properties of poly (vinyl chloride) (PVC) matrix. The structure characterization showed ZHS nanoparticles were bonded onto the surface of GO nanosheets and the ZHS nanoparticles were well distributed on the surface of GO. Subsequently, resulting ZHS/GO was introduced into flexible PVC and fire hazards and mechanical properties of PVC nanocomposites were investigated. Compared to neat PVC, thermogravimetric analysis exhibited that the addition of ZHS/GO into PVC matrix led to an improvement of the charring amount and thermal stability of char residue. Moreover, the incorporation of 5 wt.% ZHS/GO imparted excellent flame retardancy to flexible PVC, as shown by increased limiting oxygen index, reduced peak heat release rate, and total heat release tested by an oxygen index meter and a cone calorimeter, respectively. In addition, the addition of ZHS/GO nanohybrids decreased the smoke products and increased the tensile strength of PVC. Above-excellent flame-retardant properties are generally attributed to the synergistic effect of GO and ZHS, containing good dispersion of ZHS/GO in PVC matrix, the physical barrier of GO, and the catalytic char function of ZHS.

Unique Static Magnetic and Dynamic Electromagnetic Behaviors in Titanium Nitride/Carbon Composites Driven by Defect Engineering.

Recently, the defect-induced static magnetic behaviours of nanomaterials have been a cutting-edge issue in diluted magnetic semiconductor materials. However, the dynamic magnetic properties of nanomaterials are commonly ignored if their bulk counterparts are non-magnetic. In the present research, titanium nitride-carbon (TiN/C) nanocomposites were found to exhibit both static and dynamic magnetic properties that vary in the opposite trend. Moreover, novel unconventional electromagnetic resonance behaviour was demonstrated in TiN/C systems, and their permeability and permittivity show similar trend. This is challenging for the traditional understanding of electromagnetism and makes it possible to achieve an appropriate balance between the permeability and permittivity simultaneously in a simple system. Hopefully, the results could provide some valuable clues to revealing the magnetism and electromagnetism of nanostructures.

Superhydrophobic cuprous oxide nanostructures on phosphor-copper meshes and their oil-water separation and oil spill cleanup.

A simple aqueous solution-immersion process was established to fabricate highly dense ordered Cu2O nanorods on commercial phosphor-copper mesh, with which the preparation was accomplished in distilled water. The present method, with the advantages of simple operation, low cost, short reaction time, and environmental friendliness, can be well adopted to fabricate desired Cu2O nanostructures on the phosphor-copper mesh under mild conditions. After surface modification with 1-dodecanethiol, the Cu2O nanostructure obtained on the phosphor-copper mesh exhibits excellent superhydrophobicity and superoleophilicity. Besides, a "mini boat" made from the as-prepared superhydrophobic phosphor-copper mesh can float freely on water surface and in situ collect oil from water surface. This demonstrates that the present approach, being facile, inexpensive, and environmentally friendly, could find promising application in oil-water separation and off shore oil spill cleanup.

Preparation and characterization of layer-by-layer self-assembled polyelectrolyte multilayer films doped with surface-capped SiO2 nanoparticles.

SiO(2) nanoparticles capped with gamma-aminopropyltrimethoxysilane were doped into polyelectrolyte (poly(allylamine hydrochloride), PAH, and poly(acrylic acid), PAA) multilayer films via spin-assisted layer-by-layer self-assembly. The resulting as-prepared multilayer films were heated at a proper temperature to generate cross-linked composite films with increased adhesion to substrates. The tribological behavior of the multilayer films was evaluated on a microtribometer. It was found that SiO(2)-doped composite films had better wear resistance than pure polyelectrolyte multilayers, possibly because doped SiO(2) nanoparticles were capable of enhancing load-carrying capacity and had "miniature ball bearings" effect. Moreover, heat-treatment had significant effect on the morphology of the composite films. Namely, heat-treated (SiO(2)/PAA)(9) film had a larger roughness than the as-prepared one, due to heat-treatment-induced agglomeration of SiO(2) nanoparticles and initiation of defects. However, heat-treated (PAH/PAA)(3)/(SiO(2)/PAA)(3)(PAH/PAA)(3) film had greatly reduced roughness than the as-prepared one, and it showed considerably improved wear resistance as well. This could be closely related to the "sandwich-like" structure of the composite multilayer film. Namely, the outermost strata of composite multilayer film were able to eliminate defects associated with the middle strata, allowing nanoparticles therein to maintain strength and robustness while keeping soft and fluid-like exposed surface. And the inner strata were well anchored to substrate and acted as an initial "bed" for SiO(2) nanoparticles to be inhabited, resulting in good antiwear ability.