Alkaline Coprecipitation Research Articles

A comparative physicochemical, morphological and magnetic study of silane-functionalized superparamagnetic iron oxide nanoparticles prepared by alkaline coprecipitation

The characterization of synthetic superparamagnetic iron oxide nanoparticle (SPION) surfaces prior to functionalization is an essential step in the prediction of their successful functionalization, and in uncovering issues that may influence their selection as magnetically targeted drug delivery vehicles (prodrugs). Here, three differently functionalized magnetite (Fe3O4) SPIONs are considered. All were identically prepared by the alkaline coprecipitation of Fe2+ and Fe3+ salts. We use X-ray photoelectron spectroscopy, electron microscopy, time-of-flight SIMS, FTIR spectroscopy and magnetic measurements to characterize their chemical, morphological and magnetic properties, in order to aid in determining how their surfaces differ from those prepared by Fe(CO)5 decomposition, which we have already studied, and in assessing their potential use as drug delivery carriers.

Layered Zinc Hydroxide Salts Intercalated with Anionic Surfactants and Adsolubilized with UV Absorbing Organic Molecules

Two anionic surfactants, dodecylsulfate (DDS) and dodecylbenzenesulfonate (DBS), were intercalated into layered zinc hydroxide salts (LHS) using the direct alkaline co-precipitation method, and characterized by powder X-ray diffraction (PXRD), Fourier-transform infrared (FTIR) and thermogravimetric analysis/differential thermal analysis (TGA/DTA). Different UV-absorbing organic molecules, like salicylates, cinnamates and benzophenones, were adsolubilized in the LHS interlayer following two different procedures (conventional microwave treatment and microwave with hydrothermal treatment). The adsolubilized products were investigated by PXRD, FTIR, diffuse reflectance UV-Vis (DRUV-Vis) and luminescence spectroscopies before and after exposure to UV radiation. Most of the products showed a good absorption in the UV region, from UVC to UVA, and good stability under UV radiation. The photodegradation tests showed that DDS-intercalated compounds were more stable than those intercalated with DBS. Adsolubilization in LHS can be an interesting alternative to immobilize neutral molecules with UV absorption capability, to prepare materials to be used in sunscreen formulations.

An efficient and highly versatile synthetic route to prepare iron oxide nanoparticles/nanocomposites with tunable morphologies.

We report a versatile synthetic method for the in situ self-assembly of magnetic-nanoparticle-functionalized polymeric nanomorphologies, including spherical micelles and rod-like and worm-like micelles and vesicles. Poly(oligoethylene glycol methacrylate)-block-(methacrylic acid)-block-poly(styrene) (POEGMA-b-PMAA-b-PST) triblock copolymer chains were simultaneously propagated and self-assembled via a polymerization-induced self-assembly (PISA) approach. Subsequently, the carboxylic acid groups in the copolymers were used to complex an iron ion (Fe(II)/Fe(III)) mixture. Iron oxide nanoparticles were then formed in the central block, within the polymeric nanoparticles, via alkaline coprecipitation of the iron(II) and (III) salts. Nanoparticle morphologies, particle sizes, molecular weights, and chemical structures were then characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), size exclusion chromatography (SEC), and (1)H NMR measurements. TEM micrographs showed that the average size of the magnetic nanoparticles was ∼7 nm at the hydrophobic/hydrophilic nexus contained within the nanoparticles. In addition, XRD was used to confirm the formation of iron oxide nanoparticles. Importantly, the polymeric nanoparticle morphologies were not affected by the coprecipitation of the magnetic nanoparticles. The hybrid nanoparticles were then evaluated as negative MRI contrast agents, displaying remarkably high transverse relaxivities (r2, greater than 550 mM(-1) s(-1) at 9.4 T); a result, that we hypothesize, ensues from iron oxide nanoparticle clustering at the hydrophobic-hydrophilic interface. This simple synthetic procedure is highly versatile and produces nanocarriers of tunable size and shape with high efficacy as MRI contrast agents and potential utility as theranostic delivery vectors.

Removal of phenol from aqueous solutions by adsorption onto Mn–Ce–K solids

Mn–Ce solids were used for the adsorption of phenol from aqueous solution at 25 and 50 °C. The samples were prepared with a Mn–Ce molar ratio between 0 and 100 % by the alkaline co-precipitation method (KOH). Structural studies showed the formation of cryptomelane, Mn2O3, Mn5O8, Mn3O4 and CeO2. The formation of different phases is a function of the Ce concentration. The adsorption isotherms of phenol were determined and modelled with Langmuir and Freundlich equations. Sample 7/3 had a high adsorption capacity. Thermodynamic parameters, in flat and vertical position of phenol, were calculated. These parameters indicated that the adsorption of phenol onto Mn–Ce was spontaneous and exothermic. The DRIFTS study detected of both phenol and phenolate species adsorbed on the surface and the aromatic ring of phenol is parallel to the surface. The interaction between Mn and Ce enhanced the reducibility of the oxides and activated oxygen, which is favorable for the adsorption process.

Nanocomposites with superparamagnetic behavior based on a vegetable oil and magnetite nanoparticles

The direct reaction of unmodified tung oil and styrene initiated by boron trifluoride diethyl etherate allowed obtaining thermoset polymers with valuable properties like shape memory behavior. On the other hand, the addition of magnetite nanoparticles (MNPs) to the tung oil/styrene copolymer was considered, in order to improve/modify its properties. MNPs were synthesized by the method of alkaline coprecipitation, followed by coating with oleic acid in order to hydrophobize their surfaces and make them more compatible with the polymeric matrix. Thus, superparamagnetic polymer nanocomposites were prepared from the inclusion of the MNPs to the cationically copolymerized tung oil (TO) and styrene (St) networks. The morphology, dynamic–mechanical and mechanical properties of the copolymers as well as magnetic behavior were significantly affected by the variation of the concentration of the MNPs.

Biotinylated magnetic nanoparticles for pretargeting: synthesis and characterization study.

In this paper, we have proposed a simple method to covalently conjugate biotin to magnetic nanoparticles, which can be targeted to the tumour sites by using pretargeting approach with avidin or streptavidin. Magnetic nanoparticles of manganese ferrite were synthesized by alkaline coprecipitation of ferric chloride hexahydrate, ferrous sulphate heptahydrate and manganese sulphate monohydrate using ammonium hydroxide. The synthesized magnetic nanoparticles were then successfully surface modified by using 3-aminopropyl trimethoxysilane, and the amount of aminopropylsilane bound to the surface of magnetic nanoparticles was quantified by measuring the absorbance of a purple-coloured complex (Ruhemann’s purple) formed between amine group and ninhydrin at 576 nm. The aminated magnetic nanoparticles were then conjugated to biotin by reacting them with N-hydroxysuccinimide–biotin in dimethylsulphoxide. The successful conjugation of biotin to magnetic nanoparticles was confirmed by Fourier transform infrared spectroscopy. The size, phase and magnetic nature of the synthesized nanoparticles were analysed by using various techniques like transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy and vibrating sample magnetometry.

Preparation of magnetic microspheres with thiol-containing polymer brushes and immobilization of gold nanoparticles in the brush layer

Narrow-disperse magnetic microspheres were prepared by alkaline coprecipitation of Fe 2+ and Fe 3+ ions within poly(acrylic acid–divinylbenzene) microspheres that were prepared by distillation–precipitation copolymerization. Magnetic microspheres with polymer brushes that contain epoxy groups were prepared by graft copolymerization of glycidyl methacrylate and glycerol monomethacrylate via atom transfer radical polymerization (ATRP) from the magnetic microsphere surfaces. Subsequently, magnetic microspheres with thiol-containing polymer brushes were prepared by treating the epoxy group-containing magnetic microspheres with sodium hydrosulfide. Gold nanoparticles were immobilized in the brush layer of the thiol-containing magnetic microspheres through Au–S coordination. The catalytic activity of the gold nanoparticle-immobilized magnetic microspheres was investigated using the reduction of 4-nitrophenol to 4-aminophenol with sodium borohydride as a model reaction. The catalyst could be reused for over 10 cycles without noticeable loss of catalytic activity.

Effect of confinement of anionic organic ultraviolet ray absorbers into two-dimensional zinc hydroxide nitrate galleries

Anionic ultraviolet (UV) ray absorbers (4-methoxybenzoate, N-acetylanthranilate, 4-methoxycinnamate and 4,4'-diamino-2,2'-stilbenedisulfonate) were intercalated into zinc hydroxide nitrate, either by direct alkaline co-precipitation or topotactic exchange reactions. The intercalation was confirmed by X-ray powder diffractometry (XRPD), Fourier transform infrared spectroscopy (FTIR), thermal analysis (TGA/DTA), scanning electron microscopy (SEM), selected area electron diffraction (SAED), elemental analysis and ultraviolet visible (UV-Vis) spectroscopy. In the co-precipitation reactions full intercalation was achieved, while during the exchange reactions nitrate anions were not completely replaced by the organic anions. After the intercalation, the UV absorption capacity was similar to that of the solid salts and acids, the effect being attributed to the confinement of the anionic species in the host two-dimensional gallery. This observation opens new opportunities for the use of organic anions immobilized in alternative layered matrixes for the formulation of sunscreens.

PVA nanocomposites reinforced with Zn2Al LDHs, intercalated with orange dyes

Zn2Al-layered double hydroxides (LDH) were intercalated with anions of the dyes Orange G, Orange II, and Methyl Orange by alkaline co-precipitation of aqueous solutions of zinc chloride and aluminum nitrate simultaneously in the presence of dye sodium salts. Transparent, homogeneous, and colored nanocomposite films were obtained by casting after dispersing the dye-intercalated LDHs (pigments) into commercial poly(vinyl alcohol) (PVA). The films were characterized by X-ray diffraction, ultraviolet–visible spectroscopy, thermal analysis (thermogravimetric analysis (TGA)) and differential thermal analysis (DTA)), and mechanical testing. Mechanical reinforcement of the PVA compounded with the dye-intercalated LDHs was achieved, and reasonable increases in Young’s modulus and ultimate tensile strength were observed with as little as 0.5% added filler, while larger amounts tended to decrease the reinforcement effect. These results demonstrate the onset of a new range of potential applications for layered double hydroxide intercalated with dyes in the preparation of polymer composite multifunctional materials.

Immobilization of enzymatic extract from Penicillium camemberti with lipoxygenase activity onto a hybrid layered double hydroxide

A Zn/Al layered double hydroxide was synthesized by alkaline co-precipitation with azelate ions ( −OOC(CH 2) 7COO −). The interlayer space of the layered material is occupied by organic ions as confirmed by X-ray diffraction and FTIR spectroscopy. The resulting hybrid material was tested as support for Penicillium camemberti enzymatic extract, containing lipoxygenase (LOX) activity. The optimal condition for LOX immobilization is done with 0.6 mol L −1 potassium phosphate buffer and pH 6.0. The affinity for the substrate is the same after immobilization, however the specific activity slightly decreases. The immobilization enhanced the thermal stability, which was evident with incubation at 60 °C where the immobilized enzyme retains 68% of specific activity while the free enzyme is inhibited. Recycling assays showed that after eight reaction cycles, the immobilized enzyme retains 60% of the activity.

Magnetic and pH-responsive nanocarriers with multilayer core–shell architecture for anticancer drug delivery

A multifunctional nanocarrier with multilayer core–shell architecture was prepared by alkaline coprecipitation of ferric and ferrous ions in the presence of a triblock copolymer, methoxy poly(ethylene glycol)-block-poly(methacrylic acid)-block-poly(glycerol monomethacrylate) (denoted MPEG-b-PMAA-b-PGMA), in aqueous solution. The core of the nanocarrier is a superparamagnetic Fe3O4 nanoparticle, on which the PGMA block of the triblock copolymer is attached. The PMAA block forms the inner shell and the MPEG block forms the outermost shell. The anticancer agent adriamycin (ADR), as a model drug with an amine group and a hydrophobic moiety, was loaded into the nanocarrier at pH 7.4 by combined action of ionic bonding and hydrophobic interaction. The hydrophobic main chain of PMAA and the hydrophobic microenvironment created by MPEG contribute to the hydrophobic interaction. The synergistic effect between the ionic bond and the hydrophobic interaction significantly enhances the loading capacity. At endosomal/lysosomal acidic pH (<5.5), protonation of polycarboxylate anions of PMAA (pKa = 5.6) breaks the ionic bond between the carrier and ADR, leading to the release of ADR because the hydrophobic interaction alone is very weak due to the relatively hydrophilic character of the nanocarrier.

Synthesis and Sintering of Lanthanum Chromite Solid Solutions Prepared by the Alkaline Coprecipitation Method

In the present work, three different solid solutions of lanthanum chromite, La 0.8 Ca 0.2 Cr 1-x Al x O 3 , where Al= 5 y 10 % molar; and LaCr 0.9 Al 0.1 O 3 , were prepared by the alkaline coprecipitation method. The preparation of the precursor gel was carried out by mixing solutions of Cr(NO 3 ) 3 and AlCl 3 at two volumetric ratios (9.5:0.5 and 9:1). The pH of the main solution was adjusted to a value 13 by adding a 0.5 M NaOH solution. The admixture of LaCl 3 and CaCl 2 was then added to the latter solution, resulting in the coprecipitation of a precursor gel. Thermal analysis of the precursor gels showed that the crystallization peak of the amorphous gel occurred below 750°C. Thus, crystallization of the gel was carried out at 900°C for 3 hours in air. Pellets were prepared by cold isostatic pressing at 200 MPa, and sintering was carried out at different temperatures between 1300-1500°C for reaction intervals between 1-5 hours in air. The maximum apparent density achieved on each of the lanthanum chromite solid solutions doped with Ca was 95% of the theoretical density.

Study of the interaction of Pu(IV) and Np(IV,V,VI) with Fe hydroxides to predict the behavior of actinides in environmental media

A Mössbauer effect method was used to study the formation of mixed hydroxides in the alkaline coprecipitation of Pu(IV) or Np(IV) with Fe(III). The Mössbauer spectra of mixed 239Pu(IV)-Fe(III) and 237Np(IV)-Fe(III) hydroxide samples differ from that of pure α-FeO(OH) formed in aqueous basic solutions. Alkaline coprecipitation of Np(V) or Np(VI) with Fe(III) hydroxides does not produce the mixed hydroxides shown by Pu(IV) or Np(IV) with Fe(III). The general Mössbauer spectral parameters of the Np(V),(VI)-Fe(III) hydroxides are similar to those of pure α-FeO(OH).

The effect of oxides on stabilization of zirconium dioxide

The processes of coprecipitation of calcium, strontium, and cadmium salts are studied. It is shown that alkaline coprecipitation produces zirconates, which in heat treatment form stable solid solutions.

Preparation and Characterization of Garnet Phosphor Nanoparticles Derived from Oxalate Coprecipitation

Terbium-activated Y3Al5O12(YAG:Tb) phosphor nanoparticles with homogeneous grain size and crystallinity have been prepared at 1000°C by heat treatment of a metal oxalate precursor derived from an alkaline coprecipitation route. The diffraction profile of as-prepared YAG:Tb nanoparticles can be indexed as a garnet structure and exhibits peak broadening phenonmenon, as revealed by X-ray diffraction (XRD) data. Grains of YAG:Tb nanoparticles appear to be irregularly spherical or elliptical and their sizes range from 60 to 70 nm, as indicated by morphological studies from bright-field transmission electron microscopy (TEM) imaging. Furthermore, the photoluminescence (PL) spectra of the (Y2.9Tb0.1)Al5O12phase were investigated to determine the energy level of electron transition related to luminescence processes and the possible blue shift in the excitation or emission PL spectra.

Speciation of Cr in Leachates of a MSWI Bottom Ash Landfill

Cr concentrations and speciation were determined in leachate from a municipal solid waste incinerator bottom ash landfill both experimentally and by thermodynamic model calculations. Total dissolved Cr concentrations of 0.2 mmol L-1 were determined by GFAAS. Two orders of magnitude lower values were determined upon preconcentration by an in-situ solid-phase extraction technique based on the 8-HQ cation exchanger that is specific for Cr(III) but unspecific for Cr(VI). This suggests that chromate dominates the dissolved Cr concentrations in the leachates but was up to 5 orders of magnitude undersaturated with respect to the solubility of CaCrO4 or BaCrO4. Chromate adsorption by oxyhydroxides is less efficient in the highly alkaline environment, but coprecipitation and solid-solution formation with BaSO4 can explain the low chromate concentrations in the leachates. This model assumption was verified by EPMA/WDX measurement of Cr in secondary barite precipitates found in aged bottom ash. Scavenging by this secondary weathering product in landfilled MSWI ash can thus cause an efficient immobilization of the toxic chromate.

Catalytic properties of lanthanum strontium transition metal oxides (La1-xSrxBO3; B = manganese, iron, cobalt, nickel) for toluene oxidation

The alkaline coprecipitation method was employed to prepare La 1-x Sr x BO 3 (x = 0-1 and B = Mn, Fe, Co, Ni). The activities of the resulting catalysts for oxidizing toluene were measured by a differential flow reactor, and their physical properties were characterized by BET, XRD, AES, SIMS, XPS, SEM, TGA/DTGA, and stepwise oxygen desorption. The results indicate that substitution of La by Sr affects activity due to the oxygen vacancy. Among the Co and Fe series catalysts, those for which x=0.3 demonstrate the highest activity. The catalytic activity of the Mn series catalysts was found to increase not only with the quantity of Mn atoms but also with the sum of Mn and O atoms. In this series, the amount of chemically adsorbed oxygen, instead of the lattice oxygen, plays an important role in the catalytic activity, especially in the temperature range of toluene oxidation, with the catalytic activity for toluene oxidation increasing with the amount of oxygen chemically adsorbed. The activity of the Ni series catalysts does not increase with increasing amounts of NiO and La 2 NiO 4 ; the highest activity occurs at x=0.5. The experimental results are discussed in terms of the role played by various B-site cations, the influence of catalytic surface composition on catalytic activity, and the effect of lattice and chemically adsorbed oxygen. Four influencing factors on the catalytic activity of these four series catalysts were discriminated by analysis of the results of kinetic measurements and by surface characterization