Preparation and characterization of Fe_3O_4/Au composite particles

Colloid gold with different sizes has been widely used in immunoassay and nucleic acid detection mainly because of their properties for immobilization of biomolecules, such as antibodies and oligonucleo-tides, through chemical reactions via active group SH on the biomolecules. Magnetic particles modified with various chemical groups on their surface can not only exhibit good magnetic responsiveness to an external magnetic field but also immobilize biomolecules through these chemical groups. As…     

Characterization of Fe3O4/poly(styrene-co-N-isopropylacrylamide) magnetic particles with temperature sensitivity

 The average diameter, diameter distribution and surface morphology of Fe₃O₄/poly(styrene-co-N-isopropylacrylamide)[P(St-NIPAM)] particles were characterized by scanning electron microscopy. The copolymer structure was confirmed by IR spectroscopy, differential scanning calorimetry and elemental analysis. The content of Fe₃O₄ entrapped in the particles was determined by atomic absorption spectrometry. A coarse structure was observed on the surface of the Fe₃O₄/P(St-NIPAM) particles. The hydrodynamic diameter of the Fe₃O₄/P(St-NIPAM) particles was found to exhibit about a 15% decrease in diameter on changing the temperature from 25 to 40 °C. The results also showed that Fe₃O₄/P(St-NIPAM) an advantage of exploited magnetic separation. Received: 6 August 1999 Accepted in revised form: 16 November 1999     

Fe3O4/poly (acrylic acid) nanoparticles as modifiers for improving rheological and filtration properties of water-based drilling fluids

Drilling fluid is a vital element and is often regarded as the “blood” in the oil industry. Although traditional oil-based drilling fluids have advantages in some harsh cases, the high cost and environmental pollution faced with them limit its application. Water-based drilling fluids (WBDFs) with environmental friendly, low cost, and high performance are important for drilling engineering to solve the problems of low efficiency and wellbore instability caused by poor rheological properties and large filtration loss in drilling operations. In this paper, Fe₃O₄ nanoparticles modified by poly (acrylic acid) (PAA) through 3-(trimethoxysilyl) proryl methacrylate (TMSPMA) were introduced into WBDFs for enhancing their rheological and plugging performance. Rheological tests indicated that the consistency coefficient (K) of the Fe₃O₄/PAA nanoparticles/WBDFs decreased at a higher concentration. Incorporated nanoparticles with a concentration of 0.05?wt %, the WBDFs will exhibit good shear-thinning behavior. The results showed that the best performance for Fe₃O₄/PAA nanoparticles being as a filtration additive in WBDFs was achieved at concentration as low as 0.1?wt %. These results demonstrated that Fe₃O₄/PAA nanoparticles are effective additives for WBDFs.     

分子印迹聚吡咯/Fe3O4复合材料的制备及其在识别色氨酸光学异构体中的应用

首先利用共沉淀法合成了磁性材料Fe3O4,再以吡咯为单体,L-色氨酸为模板分子,采用化学聚合法使吡咯在Fe3O4表面发生原位聚合,同时通过分子间的作用力以及氢键作用将模板分子掺杂到Fe3O4表面的聚吡咯中,从而制备了分子印迹聚吡咯/Fe3O4复合材料,并且利用该材料的磁性质实现固液分离。在1 mol/L的NaOH溶液中,通过施加1 V的电位使聚吡咯发生过氧化从而使L-色氨酸模板分子脱掺杂。根据分子印迹的原理,该分子印迹的复合材料可用于识别L-色氨酸光学异构体。将扫描电镜、X射线衍射及电化学法用于该分子印迹复合材料的表征。将该材料填入到多孔陶瓷管,将L-和D-色氨酸溶液分别流过该多孔陶瓷管,流出液用高效液相色谱检测,发现该复合材料对于L-色氨酸的富集能力接近D-色氨酸的两倍,说明该复合材料具有作为手性识别色谱固定相的潜力。     

Preparation and characterization of NiO(core)/Fe2O3(shell) composite particles

A novel hydrothermal coating process has been developed to deposit amorphous Ni(OH)₂·H₂O over octahedral α-Fe₂O₃ particles by treating aqueous dispersion of the preformed cores in Ni(NO₃)₂/CH₃COONa solution. NiO_(core)/Fe₂O_3(shell) composite particles were prepared by air sintering of the Ni(OH)₂·H₂O_(shell)/Fe₂O_3(core) particles at 200–500°C for 1–6 h. The changes of morphology, structure and weight of the hydrothermal and sintering products were studied by means of TEM, XRD, XPS, TG and IR analyzers. The nucleation and growth model was suggested for the non-isothermal decomposition of Ni(OH)₂·H₂O coatings and the kinetic equation was derived from the non-linear regression of the TG data. The activation in the thermal-decomposition process is 73.8 kJ mol⁻¹ and the pre-exponential factor is 1.95×10⁴ s⁻¹.     

Preparation of Fe3O4@Ag SERS substrate and its application in environmental Cr(VI) analysis

A novel sensitive and recyclable SERS substrate which can actively concentrate chromate (Cr(VI)) in water and substantially enhance Raman signal was synthesized as uniform Fe(3)O(4)@Ag nanoparticles. The surface morphology, structure, and magnetic properties were characterized using transmission electron microscopy, atomic force microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and vibrating sample magnetometry analysis. The closely spaced Fe(3)O(4)@Ag substrate with a core-shell structure exhibited a 25 nm surface roughness. The high saturation magnetization at 48.35 emu g(-1) enabled the complete and rapid separation of the substrate from the solution. The sensitivity and reproducibility of the substrate were confirmed using a common SERS probe molecule, rhodamine 6G. SERS spectra of Cr(VI) in simulated and real contaminated water showed that the symmetric stretching vibrations of Cr-O occurred at 796 cm(-1). This SERS peak area exhibited a linear dependence (R(2)=0.9992) on the Cr(VI) concentration between 5 and 100 μg L(-1). Coexisting anions such as sulfate, nitrate, chloride, carbonate, and humic acid could decrease the sensitivity of the SERS analysis. However, the adverse effect of the competing ions may be eliminated by proper dilution of the raw sample. This study provides a reliable method for qualitative and quantitative analysis of Cr(VI).     

Polyelectrolyte complex nanoparticles from chitosan and poly(acrylic acid) and Polystyrene‐block‐poly(acrylic acid)

Interpolymer polyelectrolyte complexes of chitosan (CS) with poly(acrylic acid) homopolymers and polystyrene‐block‐poly(acrylic acid) diblock copolymers were prepared and characterized. The influence of the positive/negative charge balance (charge ratio), pH, and ionic strength were thoroughly studied by dynamic light scattering. The existence of a strong polyelectrolyte effect was also highlighted in this study. Domains of stability, in which nanoparticle sizes are smaller than 100 and 200 nm for complexes of CS with the homopolymer and copolymer, respectively, were identified and confirmed by scanning electron microscopy and atomic force microscopy. The charged nature of the surface of the nanoparticles was evidenced by Zeta potential measurements. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

An investigation on polycaprolactone/chitosan/Fe3O4 nanofibrous composite used for hyperthermia

Hyperthermia is considered as an effective supplementary cancer treatment. However, the uneven temperature distribution is the major challenge in hyperthermia. Nanotechnology could solve this problem by applying magnetic nanoparticles directly or in nanofibers as implants. Low solubility, poor cancer targeting, and leakage are limitations of free magnetic nanoparticles. In this work, Fe₃O₄ nanoparticles were loaded into polycaprolactone/chitosan blended nanofibers in various contents. Magnetic, chemical, physical, and morphology of the derived nanofibrous composites were then studied. The results showed the magnetic properties of the nanocomposite had low coercivity, which was close to superparamagnetic particles. Chemical analysis showed that components had no interaction with each other. Nevertheless, Fe₃O₄ was slightly transformed to other iron oxides. However, the magnetic analysis showed this transformation had no significant effect on final magnetic content of the nanofibers. The results of X‐ray diffraction (XRD) (19.5 nm), transmittance electron microscopy (TEM) (21.6 nm), and vibration sample magnetometer (VSM) (17 nm) suggested that the magnetic nanoparticles were single domain. Thermal analysis results showed that 7% Fe₃O₄ nanofibers had more heat increase as oppose to other nanofibrous composites in the alternative magnetic field (AMF). Nonetheless, the heat performance of 3% Fe₃O₄ nanofibers was more than others according to its specific power absorption (SPA). Therefore, due to the importance of using nanoparticles in the least possible content, this method can be used as a postsurgical treatment by applying these nanofibrous composites as implants on the tumor site. Moreover, these nanofiber composites could carry anticancer drugs, which are applied as a multi‐mode treatment system.     

Synthesis and characterization of magnetic poly(divinyl benzene)/Fe3O4, C/Fe3O4/Fe, and C/Fe onionlike fullerene micrometer-sized particles with a narrow size distribution

Magnetic poly(divinyl benzene)/Fe(3)O(4) microspheres with a narrow size distribution were produced by entrapping the iron pentacarbonyl precursor within the pores of uniform porous poly(divinyl benzene) microspheres prepared in our laboratory, followed by the decomposition in a sealed cell of the entrapped Fe(CO)(5) particles at 300 °C under an inert atmosphere. Magnetic onionlike fullerene microspheres with a narrow size distribution were produced by annealing the obtained PDVB/Fe(3)O(4) particles at 500, 600, 800, and 1100 °C, respectively, under an inert atmosphere. The formation of carbon graphitic layers at low temperatures such as 500 °C is unique and probably obtained because of the presence of the magnetic iron nanoparticles. The annealing temperature allowed control of the composition, size, size distribution, crystallinity, porosity, and magnetic properties of the produced magnetic microspheres.     

Grafting of functionalized silica particles with poly(acrylic acid)

Two different methods to graft silica particles with poly(acrylic acid) (PAA) were studied. In the first method PAA was reacted with 1,1′‐carbonyldiimidazole to give functionalized PAA. The resulting activated carbonyl group reacted easily with 3‐aminopropyl‐functionalized silica at low temperatures. In the second method 3‐glycidoxypropyl‐functionalized silica particles were reacted directly with PAA by using magnesium chloride as a catalyst. Different molecular weights of PAAs were used in order to investigate the effect of molecular weight on grafting yields in both methods. The grafting yields were determined with thermogravimetric analysis (TGA). All products were also investigated with IR. The results showed that the yields of reactions performed at ambient temperature by using 1,1′‐carbonyldiimidazole‐functionalized PAA were the same as with a direct reaction of unfunctionalized PAA and 3‐aminopropyl‐functionalized silica performed at 153°C. Also in reactions between 3‐glycidoxypropyl‐functionalized silica and PAA the yields were satisfactory. Copyright © 2006 John Wiley & Sons, Ltd.     

Modification of porous silica particles with poly(acrylic acid)

The surface of porous silica particles was modified with poly(acrylic acid) by reacting the carboxyl groups on poly(acrylic acid) with the amino groups of pregrafted aminopropyltriethoxysilane (APS). The chemical modifications by APS and polymer were characterized by infrared spectroscopy and the amount of APS and poly(acrylic acid) grafted to the surface were determined by thermal gravimetric analyses. The wettability of the modified silica particles, based on the rate of water penetration, was pH‐dependent with PAA; at pH 1.5 the wettability increased but at pH 5.5 it decreased dramatically. The pore size and size distribution of the silica particles decreased with APS and polymer grafting. Copyright © 2000 John Wiley & Sons, Ltd.     

Preparation and electrochemical properties of Fe/Fe3O4@r-GO composite nanocage with 3D hollow structure

Journal of Solid State Electrochemistry - Fe/Fe3O4@r-GO composite nanocages with a hollow porous heterostructure, which look like “flower cluster,” are prepared by a mild, simple, and...     

Electrophoretic mobility of poly(acrylic acid)-coated alumina particles

The effect of poly (acrylic acid) (PAA) adsorption on the electrokinetic behavior of alumina dispersions under high pH conditions was investigated as a function of polymer concentration and molecular weight as well as the presence, concentration and ion type of background electrolyte. Systems of this type are relevant to nuclear waste treatment, in which PAA is known to be an effective rheology modifier. The presence of all but the lowest molecular weight PAA studied (1800) led to decreases in dynamic electrophoretic mobility at low polymer concentrations, attributable to bridging flocculation, as verified by measurements of particle size distribution. Bridging effects increased with polymer molecular weight, and decreased with polymer concentration. Increases in background electrolyte concentration enhanced dynamic electrophoretic mobility as the polymer layers were compressed and bridging was reduced. Such enhancements were reduced as the cation was changed from K(+) to Na(+) to Cs(+).     

Complexation of poly(acrylic acid)s with uranyl ion

The complexation of uranyl ion (UO₂²⁺) in aqueous solution with polymers containing carboxylic acid groups was studied potentiometrically. Overall formation constants of the uranyl complexes with poly(methacrylic acid) and crosslinked poly(acrylic acid) were much larger than those with the corresponding low molecular carboxylic acids. Decrease in the viscosity of the polymer solution on adding uranyl ion indicated that poly(acrylic acid) forms intra-polymer chelates with uranyl ion. The crosslinked poly(acrylic acid) adsorbed uranyl ions at higher efficiency than transition metal ions.     

Preparation and swelling behavior of amphoteric superabsorbent composite with semi-IPN composed of poly(acrylic acid)/Ca-bentonite/poly(dimethyldiallylammonium chloride)

Amphoteric superabsorbent composite with semi-interpenetrating polymer networks (semi-IPN) composed of poly(acrylic acid) (PAA)/Ca-bentonite/poly(dimethyldiallylammonium chloride) (PDMDAAC) was prepared by a combination of intercalative polymerization and a sequential IPN method and the effects of reaction parameters on the swelling capacity were studied. PDMDAAC was used as a polycation to modify bentonite and form semi-IPN with lightly crosslinked PAA. FTIR and TG were used to characterize the amphoteric superabsorbent composites with semi-IPN. The thermal stability of the product was not degraded as in the case of using small molecular surfactant to modify bentonite. The contents of carboxylic groups and nitrogen had been determined. This indicated that the product with certain content of carboxylic groups and nitrogen is inclined to exhibit excellent swelling capacity. The presence of PDMDAAC improved the swelling capacity. The resulting amphoteric superabsorbent composite showed excellent swelling capacity of 1578 g/g in distilled water and 136 g/g in 0.9 wt% NaCl solution. Copyright © 2007 John Wiley & Sons, Ltd.     

Preparation and characterization of poly(acrylic acid)-based nanoparticles

The present investigation describes the synthesis and characterization of nanoparticles based on poly(acrylic acid) (PAA) intramolecularly cross-linked with diamine, 2,2′-(ethylenedioxy)bis(ethylamine), using water-soluble carbodiimide. The aqueous colloid dispersions of nanoparticles were clear or mildly opalescent depending on the ratio of cross-linking, pH of the solution, and the molecular weight of PAA, finding consistent with values of transmittance between 3% and 99%. The structure was determined by nuclear magnetic resonance spectroscopy, and the particle size was identified by dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements. It was found that particle size depends on the pH, and at a given pH, it was caused by the ratio of cross-linking and the molecular weight of PAA. Particle size measured by TEM varied in the range of 20 and 80 nm. In the swollen state, the average size of the particles measured by DLS was in the range of 35–160 nm.     

Preparation of polystyrene/poly (4-butyltriphenylamine) composite particles by chemical oxidative seeded dispersion polymerization

Polystyrene (PSt)/poly (4-butyltriphenylamine; PBTPA) composite particles was prepared by a chemical oxidative seeded dispersion polymerization of (4-butyltriphenylamine) with PSt seed particles that were prepared by nonaqueous dispersion polymerization of styrene. Monodisperse composite particles were obtained when the ratio of monomer to seed, the rate of monomer feed, and poly(N-vinyl pyrrolidone; PVP) concentration was appropriately selected. The introduction of PBTPA was confirmed by the presence of the characteristic absorption band attributed to PBTPA from a Fourier transform infrared spectra. The solvent extraction with ethyl acetate revealed that composite particles consisted of PSt core and PBTPA shell. Then two-dimensional arrays of composite particles were also fabricated.