The synthesis of nucleus-shell Cd(OH)<Subscript>2</Subscript>/CdS structures by chemical precipitation from aqueous solutions

The region of stable coexistence of Cd(OH)₂ and CdS as a function of pH and the concentration of the complex-forming agent (ammonia) was determined by thermodynamic analysis with the purpose of the preparation of Cd(OH)₂ cadmium hydroxide particles surrounded by cadmium sulfide CdS shells. In this region, powders were obtained by chemical precipitation during various precipitation times from aqueous solutions. X-ray diffraction was used to track the growth of the CdS nanophase of a disordered structure and hexagonal Cd(OH)₂ phase consumption with time. It was found by complexonometry that part of cadmium formed insoluble structures as a result of the formation of continuous nanosized CdS shells on single crystalline Cd(OH)₂ particles. A comparative analysis of the experimental data was used to determine the kinetics of formation of nucleus-shell Cd(OH)₂/CdS particles in the system.     

Fabrication of strawberry-like nano-CdSe thin films for photoelectrochemistry by selenizing Cd(OH)<Subscript>2</Subscript> deposits obtained from the anodization of Cd

CdSe is an important semiconductor for photoelectrochemistry. Here, we propose a two-step method for preparing thin films of aggregated CdSe nanoparticles on Cd electrodes. We first anodized the Cd electrode in an aqueous solution of 0.2 M KNO₃ at ?0.9 V (vs. Hg|Hg₂SO₄(s)|K₂SO₄ (saturated)) into a porous and layered structure covered with Cd(OH)₂ precipitation, and then selenized the Cd(OH)₂ deposited on the Cd anode in an aqueous solution of 0.2 M Na₂SeSO₃. The resulting CdSe nanoparticles self-assembled into strawberry-like nanoaggregates. The anodization time and selenization time were optimized separately. Under our experimental conditions, the optimized anodization time was 80 s, whereas the optimized selenization time ranged from 15 to 60 min, corresponding to the partial or complete conversion of the deposited Cd(OH)₂ into smaller and larger strawberry-like CdSe nanoaggregates, respectively. The optimized partially and completely selenized films showed photocurrent responses that were enhanced in different ways but demonstrated comparable performances. They presented an anodic photocurrent density as high as 3.2 mA cm^?2 at ?0.3 V with good stability under visible light illumination of 100 mW cm^?2 in a solution containing a sacrificial reagent of ascorbic acid.

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Graphical Abstract Strawberry-like CdSe nanoaggregates were prepared by selenizing the anodization film of Cd(OH)₂ on Cd electrode and they demonstrated enhanced photoelectrochemical performance.

     

Moisture and solvent responsive cellulose/SiO<Subscript>2</Subscript> nanocomposite materials

Water responsive SiO₂/cellulose nanocomposite hydrogels and films were constructed, for the first time, by dispersing SiO₂ nanoparticles into cellulose solution in LiOH/urea solvent, and then by crosslinking with epichlorohydrin or regeneration in coagulation bath, respectively. The cellulose nanocomposite materials were characterized by Field emission scanning electron microscopy, FTIR, dynamic rheology, wide angle X-ray diffraction and mechanical test. The SiO₂/cellulose nanocomposites at wet state or in water displayed unique behaviors, showing higher light transmittance than those before contacting with water. The results revealed that strong hydrogen-bonding interaction among water, cellulose and SiO₂ led the good dispersion of SiO₂ nanoparticles in the cellulose matrix. The incorporation of SiO₂ nanoparticles improved the transmittance and mechanical strength of the cellulose hydrogels, and also enhanced the mechanical strength of the films. Especially, the cellulose/SiO₂ nanocomposite films were milky at dry state, and changed to transparent after being soaked in water, different from the cellulose film without the SiO₂ nanoparticles. In our findings, SiO₂ and cellulose with water could form strong hydrogen bonding to create a homogenous network structure. The cellulose/SiO₂ composite as a smart material exhibited moisture and solvent responsiveness, showing potential applications in moisture detection.     

TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> hybrid nanomaterials: synthesis and variable UV-blocking properties

Silica and core–shell structured titania/silica (TiO₂/SiO₂) nanoparticles with particles size ranging from tens to hundreds of nanometers were prepared and deposited onto cotton fabric substrates by sol–gel process. The morphologies of the nanoparticles were characterized by field-emission scanning electron microscope (FE-SEM). The photocatalytic decomposition properties as well as UV-blocking properties of the fabrics treated with SiO₂ and TiO₂/SiO₂ nanoparticles were investigated.     

Controlled synthesis and enhanced bacteriostatic activity of Mg(OH)<Subscript>2</Subscript>/Ag nanocomposite

Silver nanoparticles have good sterilization performance due to their small size and large specific surface area, while the small size also brings about reunification and reduces the sterilization activity. To resolve the problem, magnesium hydroxide [Mg(OH)₂] microsphere was designed as a supported material to load silver particles on its surface. Mg(OH)₂ microspheres were successfully synthesized under the control of a biotemplate of eggshell membrane. X-ray diffraction, thermal gravimetric analysis/differential scanning calorimetry, and transmission electron microscopy were performed to characterize the Mg(OH)₂ microspheres. The results indicate that the Mg(OH)₂ microspheres of average size ~ 2 μm were formed from nanoflakes. The silver nanoparticles were loaded on the surface of Mg(OH)₂ microspheres to form Mg(OH)₂/Ag nanocomposite, which exhibited enhanced antibacterial effect compared to that of silver nanoparticles. The enhanced antibacterial mechanism was investigated in detail.     

Fabrication and characterization of TiO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript> composite nanoparticles and polyurethane/(TiO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript>) nanocomposite films

TiO₂–SiO₂ composite nanoparticles were prepared by a sol–gel process. To obtain the assembly of TiO₂–SiO₂ composite nanoparticles, different molar ratios of Ti/Si were investigated. Polyurethane (PU)/(TiO₂–SiO₂) hybrid films were synthesized using the “grafting from” technique by incorporation of modified TiO₂–SiO₂ composite nanoparticles building blocks into PU matrix. Firstly, 3-aminopropyltriethysilane was employed to encapsulate TiO₂–SiO₂ composite nanoparticles’ surface. Secondly, the PU shell was tethered to the TiO₂–SiO₂ core surface via surface functionalized reaction. The particle size of TiO₂–SiO₂ composite sol was performed on dynamic light scattering, and the microstructure was characterized by X-ray diffraction and Fourier transform infrared. Thermogravimetric analysis and transmission electron microscopy (TEM) employed to study the hybrid films. The average particle size of the TiO₂–SiO₂ composite particles is about 38 nm when the molar ratio of Ti/Si reaches to1:1. The TEM image indicates that TiO₂–SiO₂ composite nanoparticles are well dispersed in the PU matrix.     

Mechanical and Electrochemical Properties of New Nanocomposite Polymer Electrolytes Based on Poly(vinylidene fluoride-co-hexafluoropropylene) and SiO<Subscript>2</Subscript> Addition

Nanocomposite polymer electrolytes based on the system poly(vinylidene fluoride-co-hexafluoropropylene)–liquid electrolyte 1 mol/L LiBF₄ in gamma-butyrolactone which is modified by introducing up to 10 wt % of SiO₂ nanopowder (an average particle size of 7 nm) are synthesized and characterized. The introduction of SiO₂ nanoparticles worsens the elasticity of films but increases their fracture stress to 24 MPa. The conductivity of the nanocomposite electrolytes containing SiO₂ nanoparticles is higher than that without SiO₂ and attains 3.7 mS/cm at 20°C for the electrolyte containing 1.25 wt % SiO₂. Upon the introduction of SiO₂ nanoparticles, the electrochemical stability of electrolytes grows by 0.50–0.85 V and attains 6.7 V relative to Li/Li⁺.     

Conducting properties of nanocomposite polymer electrolytes based on polyethylene glycol diacrylate and SiO<Subscript>2</Subscript> nanoparticles at the interface with a lithium electrode

Nanocomposite polymer electrolytes based on polyethylene glycol diacrylate and 1 M LiBF₄ solution in γ-butyrolactone with addition of SiO₂ nanoparticles were synthesized and studied. Resistance measurement at the Li/electrolyte and Li/nanocomposite electrolyte interface by the time-resolved electrochemical impedance showed its significant decrease in the presence of SiO₂ nanoparticles. Charge-discharge cycling of prototypes of Li/LiFePO₄ batteries for 50 cycles also showed the advantage of using nanocomposite polymer electrolytes over electrolytes without SiO₂ additives.     

Effects of peak current density on the structure and property of PbO<Subscript>2</Subscript>–CeO<Subscript>2</Subscript> nanocomposite electrodes prepared by pulse electrodeposition

PbO₂–CeO₂ nanocomposite electrodes were prepared by pulse electrodeposition method in the lead nitrate solution containing CeO₂ nanoparticles with different peak current density. The content of CeO₂ nanoparticles in the electrodes increase with the increase of peak current density. The effects of peak current density on the morphology and structure of PbO₂–CeO₂ nanocomposite electrodes were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The SEM and XRD results show that the increase of peak current density can make the morphology finer and more compact, and the crystal size decreases with the increase of peak current density. The oxygen evolution overpotential and stability of PbO₂–CeO₂ nanocomposite electrodes enhance with the increase of peak current density. The electrocatalytic property of PbO₂–CeO₂ nanocomposite electrodes was examined for the electrochemical oxidation of rhodamine B (RhB). The results show that the RhB removal efficiency on PbO₂–CeO₂ nanocomposite electrodes increase with the increase of peak current density, which can be attributed to the higher oxygen evolution overpotential and CeO₂ content in the composite electrodes.     

Synthesis and Characterization of Al(OH)<Subscript>3</Subscript>, Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Nanoparticles and Polymeric Nanocomposites

Applying of the most toxic halogenated and aromatic flame retardants is limited with respect to the environmental requirements. Nontoxic Al(OH)₃ nanoparticles were synthesized via a simple surfactant-free precipitation reaction at room temperature. The effect of various precipitation-agents on the morphology of the products was investigated. Al(OH)₃ nanoparticles were added to the polysulfone and poly styrene (PS) matrices. Electron microscope images show excellent dispersion of aluminium hydroxide in PS matrix. Nanoparticles appropriately enhanced both thermal stability and flame retardant property of the polymeric matrices. The enhancement of flame retardancy is due to endothermic decomposition of Al(OH)₃ that absorbs heat and simultaneously releases of water (makes combustible gases diluted and cold). Dispersed nanoparticles play the role of a barrier layer against flame, oxygen and polymer volatilization. Al(OH)₃ was converted to Al₂O₃ and its photo-catalyst property in degradation three different organic dyes as pollutants was investigated.     

Nanosized TiO<Subscript>2</Subscript> particles decorated on SiO<Subscript>2</Subscript> spheres (TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript>): synthesis and photocatalytic activities

Nanosized TiO₂ and nano-anatase TiO₂ decorated on SiO₂ spherical core shells were synthesized by using a sol–gel method. The synthesized pure TiO₂ nano particle and TiO₂ grafted on SiO₂ sphere with various ratios have been characterized for their structure and morphologies by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrophotometry (FTIR) and transmission electron microscopy (TEM). Their surface areas were measured using the BET method. The photocatalytic activity of all nanocomposites was investigated using methylene blue as a model pollutant. The synthesized TiO₂/SiO₂ particles appeared to be more efficient in the degradation of methylene blue pollutant, as compared to pure TiO₂ particles.     

Single-Step Synthesis of SiO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript> Hydrophobic Core–Shell Nanocomposite by Hydrothermal Method

The objective of this work is the synthesis and characterization of an appropriate hydrophobic nanoparticle as a collector for flotation of hematit in Gol-E-Gohar Iron Mine Iran. In this investigation, SiO₂–TiO₂ nanocomposites have been successfully synthesized by hydrothermal process. The morphology, structure, and composition of the as-synthesized nanostructures have been investigated by scanning electron microscopy and transmission electron microscopy. The ability of SiO₂–TiO₂ nanocomposite to facilitate the froth flotation of pyrite was correlated to the hydrophobicity of the nanoparticles. Furthermore, the efficiency of the mineral flotation process was evaluated in terms of final recovery and grade of S in Gol-e Gohar Iron Ore Complex, Sirjan, Iran.     

Effects of duty cycle on the preparation and property of PbO<Subscript>2</Subscript>-CeO<Subscript>2</Subscript> nanocomposite electrodes

PbO₂-CeO₂ nanocomposite electrodes were prepared by pulse electrodeposition in the lead nitrate solution containing CeO₂ nanoparticles with different duty cycles. The effects of duty cycle on the morphology and phase structure were investigated by scanning electronic microscopy (SEM) and X-ray diffraction (XRD), respectively. The SEM and XRD results show that the decrease of duty cycle can reduce the grain size of PbO₂-CeO₂ nanocomposite electrodes and make the electrodes more compact. The CeO₂ content in composite electrodes increases with the decrease of duty cycle. The steady-state polarization curves and accelerated life tests demonstrate that the oxygen evolution overpotential and service life of PbO₂-CeO₂ nanocomposite electrodes increase with the decrease of duty cycle. The service life of PbO₂-CeO₂ nanocomposite electrodes prepared with 25 % duty cycle reaches 218 h which is 1.8 times longer than that of PbO₂-CeO₂ nanocomposite electrodes prepared by direct electrodeposition. The bulk electrolysis shows that the degradation of malachite green (MG) on the PbO₂-CeO₂ nanocomposite electrodes is the pseudo-first-order reaction and the MG and chemical oxygen demand (COD) removal efficiency on PbO₂-CeO₂ nanocomposite electrodes increases with the decrease of duty cycle, which can be attributed to the higher oxygen evolution overpotentials, electrochemical active surface area, and CeO₂ content in the composite electrodes.     

Solution,Solid-State Two Step Synthesis and Optical Properties of ZnO and SnO<Subscript>2</Subscript> Nanoparticles and Their Nanocomposites with SiO<Subscript>2</Subscript>

Nanostructure luminescent ZnO and SnO₂ materials are prepared by a two-step solid-state method based on the solution preparation of the macromolecular precursors ZnCl₂·Chitosan and SnCl₂·Chitosan having different ratios (1:1, 1:5 and 1:10), their pyrolysis under air at 800 °C. The pyrolytic ZnO and SnO₂ nanomaterials show a dependence of the particle size, morphology and luminescent properties with the ratio [metal/polymer] in the MCl₂·Chitosan precursors. Thus, ZnO semiconductor materials exhibit luminescence spectra with several emission at 440 nm corresponds to a radiative transition of an electron from the shallow donor level of oxygen vacancies, and the zinc interstitial, to the valence band. On the other hand, the photoluminescence spectrum of the nanostructured SnO₂ shows an intense blue luminescence at a wavelength of 420 nm which may be attributed to oxygen-related defects that have been introduced during the growth process of the nanoparticles. Additionally, whereas SnO₂ was successfully incorporated into SiO₂ structure (SnO₂//SiO₂) by pyrolysis of solid-state mixtures of the precursors SnCl₂·Chitosan in the presence of SiO₂, the same reaction carried out with ZnCl₂·Chitosan precursors led to a mixture of Zn₂SiO₄ and SiO₂. Thus, this new methodology yields nanostructured semiconductor materials, ZnO and SnO₂, suitable for optoelectronic and sensor solid-state devices.     

Thermal preparation and stabilization of crystalline silver particles in SiO<Subscript>2</Subscript>-based coating solutions

Ag/SiO₂ coating solutions for antimicrobial functionalisation can be prepared by a thermal reaction (reflux or solvothermal conditions) of mixtures of tetraethoxysilane, alkylamine compounds and AgNO₃. These coating solutions are especially useful for antimicrobial refinement of temperature sensitive materials like textiles or wood. Moreover coating application onto substrates such as glass or metal, as well as preparation of micrometer sized bulk particles by using a spray-drying process is also feasible. The efficiencies of AgNO₃ reduction in the presence of different amine compounds like triethanolamine, triethylamine or diethanolamine are compared. SiO₂ nanoparticles are formed by basic hydrolysis of tetraethoxysilane and stabilize the crystalline silver particles in the solution. The antimicrobial effect of silver containing coatings on textile fabrics is investigated.     

Facile Synthesis of Polyethylenimine and Nano-TiO<Subscript>2</Subscript> Particles Functionalized PolyHIPE Beads for CO<Subscript>2</Subscript> Capture

Polyethylenimine (PEI) and titanium dioxide nanoparticles (nano-TiO₂) functionalized poly- HIPE beads were synthesized by suspension polymerization of styrene/divinylbenzene high internal phase emulsion (HIPE) containing PEI and nano-TiO₂ particles in inner phase. The products are uniform and spherical beads with average diameter of 1 mm. Characterization results showed good thermal stability and desired mechanical strength. CO₂ adsorption tests were performed with CO₂/H₂O/N₂ (1 : 1 : 8) gas mixture. Nano-TiO₂ particles distinctly improved the CO₂ adsorption performance of the polyHIPE beads, resulting in enhanced CO₂ adsorption capacity and fast adsorption/desorption kinetics. Besides, the functionalized polyHIPE beads exhibited remarkable cycle stability.     

Improving the contact properties of CdS-decorated TiO<Subscript>2</Subscript> nanotube arrays using an electrochemical/thermal/chemical approach

Decoration of TiO₂ nanotube films (TiO₂ nanotube arrays (TNAs)) with CdS nanoparticles has been pursued for a broad range of applications that goes from solar cells to biological sensors. In most synthesis methods, the scale-up of devices has been challenging due to the poor contact at the chalcogenide/oxide interface. In this work, we validate the electrochemical/thermal/chemical route as a superior strategy to sensitize TNAs with CdS nanoparticles when compared with conventional methods. The process consisted of (i) electrodeposition of cadmium on TNAs to ensure strong bonding between TiO₂ and Cd precursor particles, (ii) air annealing of Cd-decorated TNAs to thermally oxidize cadmium to cadmium oxide, and (iii) total sulfurization of cadmium oxide to obtain CdS in an hexagonal phase matching that of TNAs. X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) analyses indicated the complete transformation of cadmium precursor particles into CdS and a good surface coverage of the internal/external walls of TNAs. When compared to samples prepared by successive ionic layer adsorption and reaction (SILAR), electrochemical impedance spectroscopy data revealed the improvement of the electrical properties of the TNA matrix due to the sulfurization process and a lower contact resistance at the CdS/TNA interface. These improvements explain the superior photoelectrochemical response of CdS/TNA photoelectrodes obtained by the electrochemical/thermal/chemical route.     

Development of RuO<Subscript>2</Subscript>/Rutile-TiO<Subscript>2</Subscript> Catalyst for Industrial HCl Oxidation Process

Sumitomo Chemical has developed a low energy consuming and green process for the catalytic oxidation of HCl to Cl₂, especially when compared with the electrolysis process. The RuO₂/rutile-TiO₂ catalyst has high catalytic activity and thermal stability due to ultra-fine RuO₂ crystallites that cover the surface of the TiO₂ primary particles with strong interaction. In addition, the silica modified RuO₂/rutile-TiO₂ catalyst shows higher thermal stability by preventing the RuO₂ sintering due to using dispersed SiO₂ particles. With these catalysts, high reaction rates required for industrial applications are achieved, even at low temperatures.     

Novel nanocomposite membranes prepared with PVC/ABS and silica nanoparticles for C<Subscript>2</Subscript>H<Subscript>6</Subscript>/CH<Subscript>4</Subscript> separation

Composite membranes based on polyvinyl chloride and acrylonitrile butadiene styrene (ABS) copolymer have been prepared and then filled with 2–8 wt % of silica nanoparticles. Membranes were fabricated by solution casting method using dimethylacetamide. The performance of prepared membranes were studied for methane and ethane at the feed pressure of 1.0, 1.5, 2.0, and 3.0 bar at 35°C. By increasing the percentage of ABS, permeability of methane and ethane increased. In addition, by adding the silica nanoparticles in the membrane, permeability of gas increased in all cases. The highest gas pair selectivity for C₂H₆/CH₄ could be obtained from PVC/BS (20 wt %) which loaded with 8 wt % of silica nanoparticles. The results of this study suggest that high performance gas separation nanocomposite membranes can be attained by adopting a judicious combination of blending technique for polymeric membrane, optimized loading percentage, and feed operating conditions.     

Fabrication,characterization, and photocatalytic performance of TiO<Subscript>2</Subscript> hybridized with SiO<Subscript>2</Subscript>

Nanostructures TiO₂–SiO₂ photocatalysts were successfully synthesized using the sol-gel method, hydro-calcination, co-precipitation and room-temperature solid-phase synthesis technology. X-ray powder diffraction pattern (XRD), Fourier transform infrared spectrum (FTIR), photoluminescence (PL) spectra, thermal analyses (TG–DTA), scanning electron micrographs (SEM), X-ray photoelectron spectroscopy (XPS), and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) were used to characterize the as-synthesized catalysts. Photocatalytic performances of the catalysts were evaluated by the degradation of methyl orange (MO) under s imulated natural light and the degradation rate of MO is 97.2%. The composites showed a good stability: after five recycling runs there are no significant decreases in the photocatalytic activity. The photodegradation of methylene blue, rhodamine B, methyl violet, naphthol green B, basic fuchsin, malachite green, and methyl red were also tested, and the degradation rate of dyes could reach over 94.2 %. A possible mechanism for the photocatalysis with the TiO₂–SiO₂ was proposed.