As-prepared Composite Particles Research Articles

Biosynthesis Effect of Egg White on Formation and Characteristics of NiO/NiCo2O4 Nanocomposites

For the successful production of NiO/NiCo2O4 nanocomposites, the environmentally friendly method of egg white supplementation has been used. Several analytical techniques were employed to characterize the morphology, purity, and crystal structure of the as-prepared nanocomposites. These techniques included transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The physical adsorption and magnetic properties of the investigated composite were determined using the Brunauer–Emmett–Teller (BET) method and a vibrating-sample magnetometer (VSM), respectively. The results have shown that the as-prepared composite particles had diameters of about 10–25 nm, with uniform distribution. The XRD analysis showed that the as-synthesized composites consisted entirely of cubic structures of both NiO and spinel NiCo2O4 nanoparticles, with a space group of Fd3m. The FTIR analysis showed characteristic vibration modes related to metal oxides, confirming the formation of composites containing NiO and NiCo2O4 crystallites. The investigated composites’ saturation magnetization (MS) and coercivity (HC) were easily controllable because of the ingredients’ ferromagnetic (NiCo2O4) and antiferromagnetic (NiO) characteristics. The excellent combination of the NiO/NiCo2O4 nanocomposites’ properties is anticipated to make this system suitable for a wide range of applications.

Realization of thorough photodegradation of the A-ring of tetracycline over urail-doped g-C3N4/Bi2WO6/chitosan using the synergistic effect of nonmetal dopants, the Z-scheme heterojunction and chitosan modification

It is well known that the toxicity of the widely used tetracycline (TC) mainly originates from the intermediates of its A-ring, which are difficult to thoroughly degrade. Therefore, it is critical to exploit an efficient method for fast and thorough degradation of the A-ring of TC. Herein, an urail-doped g-C3N4/Bi2WO6/chitosan (10UB-CS) composite was fabricated for the abovementioned purpose. Over 10UB-CS, A-ring and B, C, D- rings could be thoroughly decomposed into small molecules without toxicity after 100-min photodegradation for the first time owing to the following synergistic effects: (1) the substitution of diazine organic groups of uracil by partial tris-triazine units in g-C3N4 leads to a new channel beneficial to the transfer of photogenerated carriers and leads to a negative shift in ECB, resulting in the production of more •O2–. (2) The formed Z-scheme urail-doped g-C3N4/Bi2WO6 not only improves the separation of photoactivated electrons and holes but also causes a high redox potential. (3) Chitosan possesses superior surface-electron mobility so that the photoactivated electrons can easily migrate to the surface of the as-prepared composite particles, preventing the recombination of photoactivated electrons and hole pairs. Hence, more high-energy electrons react with O2 to produce more •O2–. This work has identified the roles of •O2– and h+ in photodegrading the A-ring of TC by comparing the active-species-trapping-experiments results for the first time. This work also finds for the first time that the fracture of A-ring in TC by h+ could realize through breaking the bonds which bridges B-ring and A-ring. This work is of great significance for rapidly and completely (100%) photodegrading the A ring of TC. This work has laid a solid foundation to effectively address the toxic issues of TC.

In situ formation and immobilization of silver nanoparticles using thermo-responsive microgel particles and their cytotoxicity evaluation

In this study, a simple environmentally greener “in situ” chemical synthesis has been developed to prepare silver nanoparticles (Ag NPs) from chemically reduced AgNO3 in an aqueous media of thermo-responsive microgel, using glucose as a reducing agent and by adopting a microwave irradiation technique. The thermo-responsive microgel poly-N-isopropylacrylamide-co-2-hydroxyethyl acrylate, poly (NIPAM-co-HEA) 200 nm in size was prepared by surfactant free emulsion polymerisation of a selected mixture of N-isopropylacrylamide, methylene-bis-acrylamide and 2-hydroxyethyl acrylate. This microgel acts as a mere support to immobilize Ag NPs. The formation of Ag NPs and the thermo-responsive properties of the mixture were studied using UV–visible Spectroscopy. Their structures were characterised by FE-SEM and TEM. The Ag NPs prepared by this approach appear to be monodispersed with sizes which are <15 nm. Excellent biocompatibility, cell viability and environmentally responsive properties suggested that as-prepared composite particles are ideal candidate for antibacterial, biosensors and drug delivery applications.

Fabrication of Stable and Regenerable Amine Functionalized Magnetic Nanoparticles as a Potential Material for Pt(IV) Recovery from Acidic Solutions

MnFe2O4@SiO2-NH2 magnetic nanocomposite (AFMNC) adsorbent with a particle size of ∼50 nm was successfully synthesized using a facile approach. The as-prepared composite particles showed a fast binding of Pt(IV) with easy magnetic solid-liquid separation. The kinetic data were fitted to both pseudo-first and second-order rate models, indicating that AFMNC exhibited a much higher rate of Pt(IV) binding (0.125 g mg-1 min-1) compared to that of commercial ion-exchange resin Amberjet 4200 (0.0002 g mg-1 min-1). The equilibrium adsorption data were fitted to the Langmuir isotherm model with a relatively high sorption capacity of 380 mg/g. Scanning transmission electron microscopy analysis demonstrated the presence of platinum chloride after sorption on AFMNC, suggesting an adsorbate-adsorbent anion-exchange interaction. In addition, due to its magnetic characteristics, AFMNC can be easily separated from the aqueous medium after the sorption process. The novel nanocomposite may facilitate recovery of Pt(IV) from waste solutions.

Fuzzy, copper-based multi-functional composite particles serving simultaneous catalytic and signal-enhancing roles.

Multifunctional plasmonic particles serving simultaneously as catalysts and label-free reporting agents are highly pursued due to their great potential in enhancing reaction operational efficiencies. Copper is an abundant and economic resource, and it possesses practical applicability in industries, but no dual-functional copper-based catalytic and self-reporting particles have been reported so far. This study proposes a facile strategy to prepare high-performance dual-functional copper-based composite particles that catalyze reactions and simultaneously serve as a SERS (surface enhanced Raman spectra) active, label-free reporting agent. Polyelectrolyte-modified reduced graphene oxide particles are used as the reactive precursors in the fabrication method. Upon adding Cu(NO3)2 solutions into the precursor dispersions, composite particles comprised by copper/copper oxide core and polyelectrolyte-graphene shell were facilely obtained under sonication. The as-prepared composite particles efficiently catalyzed the conversion of 4-nitrophenol to 4-aminophenol and simultaneously acted as the SERS-active substrate to give enhanced Raman spectra of the produced 4-aminophenol. Taking advantage of the assembling capabilities of polyelectrolyte shells, the composite particles could be further assembled onto a planar substrate to catalyze organic reactions, facilitating their application in various conditions. We expect this report to promote the fabrication and application of copper-based multifunctional particles.

Fabrication of hierarchical hollow silica/silver/silica/titania composite particles

Hierarchical composite particles with hollow structure were fabricated in this work. The composite particles were composed of guest particles and host ones, which were achieved by Stober method, and a raspberry-like morphology was produced by the “anchoring” of guest particles on the surface of host ones. Moreover, the hollow structure was obtained by template-assisted approach. The raspberry-like morphology and hollow structure of composite particles were confirmed by scanning electron microscopy and transmission electron microscopy. As multiple distinct functional components were integrated into the raspberry-like particles, the obtained composite particles exhibited enhanced photocatalytic activity under visible light irradiation. The rate of degradation of the as-prepared composite particles was ca. 13 times faster than that of pure TiO2 under visible light irradiation. Furthermore, a brief photocatalytic mechanism was presented. The composite particles, combining hierarchical morphology and hollow structure, exhibit promising potential in self-cleaning and nanoreactor areas.

Fabrication of Electrically Conductive Nickel–Silver Bimetallic Particles via Polydopamine Coating

Inspired by adhesive proteins excreted by marine mussels, dopamine can act as a versatile surface modification agent for various organic and inorganic materials. By using adhesive polydopamine (PDA) as an intermediate layer, a simple and novel method for fabricating nickel-PDA-silver (Ni-PDA-Ag) bimetallic composite particles was developed. Ni-PDA-Ag bimetallic particles were fabricated by dispersing Ni particles in an aqueous dopamine solution followed by electroless Ag plating on the prepared Ni-PDA particles. A PDA layer with nano-meter thickness was deposited spontaneously on the surface of the Ni particles by oxidative self-polymerization of dopamine under alkaline conditions. Electroless Ag plating on the prepared Ni-PDA particles was carried out in the presence of a glucose solution as a reducing agent. Ni-PDA particles and Ni-PDA-Ag composite particles with a PDA intermediate layer were characterized by X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), field-emission transmission electron microscopy (FE-TEM), and X-ray diffraction (XRD). In addition, the electrical conductivity of as-prepared composite particles was evaluated by a 4-point probe. The PDA layer deposited on the surface of Ni was confirmed by XPS spectra, FT-IR spectroscopy, and FE-TEM. FE-SEM images demonstrated that Ag nanoparticles were successfully plated on the PDA layer-coated Ni particles after the electroless Ag plating process. XRD patterns also confirmed the presence of Ag in a metallic state. In addition, the sheet resistance of as-prepared composite particles showed a tendency to decrease with increasing AgNO3 concentration.

Novel ZnO–Al2O3 composite particles as sorbent for low temperature H2S removal

Abstract ZnO–Al2O3 composite particles composed of ZnO nanosheets (thickness of 40–80 nm) on alumina particles were prepared by heterogeneous precipitation method using bayerite seed particles. The as-prepared composite particles were characterized in terms of crystal structure, morphology, surface area and pore volume. The composite particles were used as sorbent for H2S adsorption at low temperature, and were compared with pure ZnO sorbent. The composite sorbent showed a greater sulfur adsorption capacity (0.052 g/g) than pure form of ZnO (0.028 g/g). This significant improvement was mainly attributed to higher surface area, more pore volume and unique morphology in nanoscale, which were also obtained by low cost presented method in this work for synthesis of ZnO sorbent supported on alumina particles.

Facile method to prepare Pd/Polystyrene composite microspheres and investigation on their catalytic properties

Nano-sized Pd/polystyrene composite nanoparticles were prepared via surfactant-free emulsion polymerization. The as-prepared composite particles were used as a catalyst for Suzuki reaction, and they showed excellent catalytic properties in the conversion and recyclability. First, polystyrene (PS) latex particles bearing carboxyl groups on the surfaces were synthesized via one-stage surfactant-free emulsion polymerization employing acrylic acid as the functional monomer. Thus, made the PS particles negatively charged and could attract positively charged Pd2+ ions. By adding PdCl2 solution to this functional polystyrene emulsion, Pd2+ ions were attached to the surfaces and reduced to zero valent particles by the reducing agent, NaBH4. Nano-sized Pd/PS composite particles could be synthesized via this facile method. The amount of the functional monomers, the Pd2+ content and the amount of the initiator played important roles to the final morphologies of the composite particles. The resulting composite microspheres were observed by TEM. Furthermore, catalytic properties of the as-prepared Pd/PS composite particles were studied via Suzuki reaction, and the results were characterized by FTIR and 1H-NMR. The Pd/PS composite particles showed excellent conversion and could be recycled easily for reuse. After each round of Suzuki reaction, the Pd/PS composite particles could be separated just by filtration, the conversion still remained as high as 70.2 %, even when used 5 times.

Synthesis of CoFe2O4/BaTiO3 Core-Shell Composite Nanoparticles

It is important to prepare ideal 0-3 type magnetoelectric nanocomposites for promoting the multiferroic technological applications; however, the processing technology has become a big challenge. The key point to achieve the synthesis of 0-3 type magnetoelectric composites is the creation of ferromagnetic/ferroelectric composite nanoparticles with core-shell structure. In this work, core-shell structured CoFe2O4/BaTiO3 nanoparticles were synthesized in two steps. CoFe2O4 nanoparticles were firstly prepared through a polyacrylamide gel method, and then were coated with BaTiO3 layers using the same gel route. It is demonstrated that the as-prepared composite particles are an evident core-shell structure, where the core and the shell are determined to be CoFe2O4 and BaTiO3, respectively. The composite particles are nearly spherical in shape with a narrow particle size distribution.

Complex Dielectric Permittivity and Magnetic Permeability of Fe/Fe3O4 Composite Particles in 2–18 GHz

In the present study, iron/iron oxide (with a ratio of 4/1, 1/1, and 1/4) composite particles were prepared by precipitation. The morphology and phase composition were examined by scanning electron microscopy and X-ray diffraction techniques. The as-prepared composite particles were mixed with epoxy resin to prepare microwave absorbers and the corresponding electromagnetic properties were evaluated. The experimental results showed that the composite powder exhibited a mixture of α-Fe (∼4 μm) and Fe3O4 (∼30 nm) phases. The amount of iron oxide plays an important role in the electromagnetic properties of microwave absorbers. In general, complex permittivity (ϵ’ and ϵ”) and permeability (μ’ and μ”) increased with increasing amount of iron oxide additions. The minimum reflection loss can reach −16.7 dB at 9.0 GHz for 50 wt% of Fe/Fe3O4 = 1/4 composite absorber with 3 mm in thickness.

Preparation of Carbon-Encapsulated Alloy Nanomaterials by Detonation Decomposition of Nitrate Complex Explosives Containing Multi-Metallic Ions

Carbon-encapsulated iron-based alloy nanoparticles with a core-shell structure were prepared by detonation decomposition of nitrate complex explosives containing multi-metallic ions. The size and magnetic properties of the as-prepared composite particles were revealed by X-ray powder diffraction, transmission electron microscopy, energy dispersive X-ray detector and magnetic measurements. Results showed that the different sizes of the ferronickel and ferrocobalt nanocrystal core and the thickness of the carbon shell could be yielded by adjusting the component materials of the explosives. The composite particles had a gamma- or alpha- ferronickel or bcc-ferrocobalt nanocrystal core with a coating of graphitic carbon layers. Magnetic measurements indicated these composite nanoparticles were superparamagnetism at the room temperature, with some variation in the values of saturation magnetization, remanences and coercive forces.

Rapid synthesis of nanostructured Cu–TiO2–SiO2 composites for CO2 photoreduction by evaporation driven self-assembly

Nanostructured copper doped titania–silica (Cu–TiO2–SiO2) photocatalyst composite particles were directly formed in a rapid manner by evaporation driven self-assembly of nanocolloids in a furnace aerosol reactor (FuAR). Aqueous suspensions of nanosized TiO2 and SiO2 colloids and copper nitrate solution were used as precursors. The size, composition, and porosity of the composite particles were tailored by manipulating the precursor concentration, stoichiometric ratio, and synthesis temperature, respectively. The as-prepared composite particles were characterized by means of SEM, TEM, XRD, UV-VIS, and nitrogen physisorption measurements, to determine particle diameter, morphology, crystallinity, absorption band, surface area, and pore size. CO2 photoreduction was conducted inside a quartz reactor under illumination of UV light followed by GC analysis. The results revealed that the composite particles were submicrometre-sized mesoporous spheres with average pore sizes of 20 to 30 nm, having optimal molar percentages of TiO2 and Cu to the whole particle of 2% and 0.01%, respectively, achieving a relatively high CO2 conversion efficiency, i.e. a CO yield of approximately 20 μmol/g TiO2/h.

Synthesis and characterization of carbon-encapsulated iron/iron carbide nanoparticles by a detonation method

Carbon-encapsulated iron-based nanoparticles with a core–shell structure were produced by detonation decomposition of explosive mixture precursors containing iron ion components. The size and magnetic properties of the as-prepared composite particles were revealed by X-ray powder diffraction, transmission electron microscopy and magnetic measurements. Results showed that the different sizes of the iron-based nanocrystal core and the thickness of the carbon shell could be yielded by adjusting the component materials of the explosive precursors during the course of these detonation chemical reactions. The composite particles had a body-centered cubic iron or iron carbide core with a coating of graphitic or amorphous carbon layers. Magnetic measurements indicated these composite nanoparticles were magnetic at the room temperature, with some variation in the values of saturation magnetization, remanences and coercive forces that depend on the size and grain composition.

Anatase TiO 2 nanolayer coating on strontium ferrite nanoparticles for magnetic photocatalyst

TiO 2/SrFe 12O 19 composite nanoparticles with core-shell structure have been obtained. The core SrFe 12O 19 nanoparticles were synthesized by citrate precursor technique with Fe/Sr ratio of 10.8, and then the shell TiO 2 nanocrystals were derived via sol–gel technology. The presence of a small amount of polyethyleneimine (PEI) on the surface of the strontium ferrite nanoparticles facilitates this coating process. The morphology, crystalline structure, particle size and size distribution of TiO 2/SrFe 12O 19 composite nanoparticles were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and 3000HSA analyzer (MALVERN), respectively. Energy-dispersive spectroscopy (EDS) was utilized for the elemental analysis of the products. The as-prepared composite particles can be utilized as a magnetic photocatalyst, which can be fluidized and recovered by an applied magnetic field enhancing both separating and mixing efficiency for recyclable fluids. Magnetic properties and photocatalytic activities of these powders have been evaluated. The result of the experiments shows that the saturation magnetizations of titania-coated SrFe 12O 19 nanoparticles decrease as increasing the thickness of the titania coating, while the coercivity does not show any change after coating. Photocatalytic activities of these powders increase with increasing the thickness of TiO 2 coating layer.

Synthesis and characterization of hard magnetic composite photocatalyst—Barium ferrite/silica/titania

Hard magnetic composite photocatalytic particles—barium ferrite (magnetic core)/silica (intermediate layer)/titania (photoactive shell) (B/S/T) were prepared by wet-chemical methods. Anatase titania nanoparticles were directly coated on the silica-coated barium ferrite forming photoactive titania shell by hydrolysis and condensation of titanium n-butoxide. The prepared hard magnetic composite photocatalyst can be magnetically fluidized and recovered by an applied magnetic field enhancing both the separation and mixing efficiency for remediating fluids. The prepared composite particles were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution TEM (HRTEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), BET specific surface area measurement and inductively coupled plasma (ICP) spectroscopy. The photocatalytic activity of the synthesized composite particles was tested by photodegradation of Procion red MX-5B dye under UV illumination (302 nm) and compared with that of titania nanoparticles. The as-prepared composite particles were photoactive, with enhanced photocatalytic activity after the heat-treatment at 500 °C for 1 h. The reusability of the composite photocatalytic particles was also tested and the recycled composite particles presented the photocatalytic activity comparable to the fresh composite particles.

Anatase TiO2 nanolayer coating on cobalt ferrite nanoparticles for magnetic photocatalyst

TiO2/CoFe2O4 composite nanoparticles with a core–shell structure have been obtained. The core CoFe2O4 nanoparticles were synthesized via co-precipitation method, and the shell TiO2 nanocrystals were derived via sol–gel technology followed by heat-treatment at 450 °C. The morphology and the crystalline structure of composite nanoparticles were characterized by transmission electron microscopy (TEM) and X-ray diffraction, respectively. The as-prepared composite particles can be utilized as a magnetic photocatalyst, which can be fluidized and recovered by an applied magnetic field enhancing both the separation and mixing efficiency for recyclable fluids. Magnetic properties and photocatalytic activities of these powders have been evaluated.

Anatase TiO2 Nanoparticle Coating on Barium Ferrite Using Titanium Bis-Ammonium Lactato Dihydroxide and Its Use as a Magnetic Photocatalyst

Photoactive anatase TiO2 nanoparticles with a size less than 10 nm were coated on barium ferrite forming complete coverage by the controlled hydrolysis and condensation of titanium bis-ammonium lactato dihydroxide in the presence of polyethyleneimine at a relatively low temperature (95 °C). The as-prepared composite particles (hard magnetic barium ferrite (core)−anatase TiO2 nanoparticles (shell)) can be utilized as a magnetic photocatalyst, which can be fluidized and recovered by an applied magnetic field enhancing both the separation and mixing efficiency for remediating fluids. The morphology of composite particles was characterized with scanning electron microscopy and transmission electron microscopy. The crystalline structure of TiO2 was characterized by X-ray diffraction and electron diffraction. Energy-dispersive spectroscopy was utilized for the elemental analysis of the products. The as-prepared TiO2−barium ferrite composite has higher photocatalytic activities than the TiO2−barium ferrite composite heat-treated at 500 °C for 1 h. The higher photoactivities of the unheated composite are ascribed to higher specific surface area and preservation of the surface hydroxyl groups on TiO2.

The synthesis of composite particles responsive to electric and magnetic fields

A new route to produce composite particles showing electric and magnetic response is presented in this paper. The particles comprised of Fe3O4/PSt magnetic polymer spheres as core and amorphous titania as shell were prepared in two steps. This method avoids three or more steps of multi-coating on glass spheres. The morphology and the structure of the particles were characterized by SEM, FT-IR and TG–DTA. The measured dielectric constant and conductivity of the composite particles were approximate to that of the pure amorphous titania particles. Meanwhile, the transmittance of the aqueous suspension of composite particles can reach 90% within 900 s under magnetic field, in contrast to that of 60% under no magnetic field. Furthermore, the particles suspended in silicon oil can quickly form chains structure when a 0.6 kV/mm electric or 1500 Gs magnetic field strength was applied. This indicates that the as-prepared composite particles are responsive to both electric and magnetic fields.