Alcoholic Dispersion Research Articles

Nanoparticles of calcium hydroxide for wood deacidification: Decreasing the emissions of organic acid vapors in church organ environments

Acetic and formic acid vapors emitted from woodwork in historical organs are very important corrosive agents for lead pipes. These acids are slowly released from the wood both during playing and when the pipes are silent. To inhibit this emission process, the wood surface can be modified, by creating a protective layer with alkaline features. However, a coating of wood is not recommended since this could modify the appearance and create a layer not perfectly compatible with the substrate. For this reason, we propose to use some innovative nanotechnology that has been successfully applied for the deacidification of wood samples coming from the Vasa shipwreck. Application of calcium (or magnesium) hydroxide nanoparticles, with sizes ranging from 30–150 nm, allowed a homogeneous distribution of particles through the surface layer of wood simply by soaking (or spraying) it in a alcoholic (or mixed with less polar solvents) dispersion of nanoparticles. Nanoparticles do not modify the wood appearance and distribute randomly within the first layers of wood. The small size of particles accounts for the high reactivity with CO2 from the air, to give the alkaline reserve of carbonates that provide high efficacy in the neutralization of gaseous acids. The emission of volatile organic compounds (VOC) from the treated wood was determined by using an emission test cell, Field and Laboratory Emission Cell (FLEC). The results show that the emissions of acetic acid vapor from nanoparticles treated wood was very low (< 70 μg/m2 h) during the first 13 month. In contrast, untreated wood emitted high concentrations of acetic acid vapor (200–400 μg/m2 h).

Synthesis of Au@SiO2 Core/Shell Nanoparticles and their Dispersion into an Acrylic Photocurable Formulation: Film Preparation and Characterization

AbstractAu core/silica shell (Au@SiO2) nanoparticles were synthesized by coating gold NPs with sol/gel silica in alcoholic solution. The alcoholic dispersion was added, in the range of 1–5 wt.‐%, to TPGDA and photocured by means of UV light. Transparent coatings were obtained and they can find suitable applications. It was shown that the NPs can restrict the segmental motion and decrease the free volume of the polymer network, with a consequent increase in glass transition temperature. TEM analysis put in evidence that the particles are well dispersed without any macroscopic agglomeration, and many particles are present as isolated particles.magnified image

Surface-initiated atom transfer radical polymerization from TiO2 nanoparticles

Two kinds of hydrophilic polymers, poly(oxyethylene methacrylate) (POEM) and poly(styrene sulfonic acid) (PSSA), were grafted from TiO2 nanoparticles via the surface-initiated atom transfer radical polymerization (ATRP) technique. Chlorine modified TiO2 nanoparticles (TiO2-Cl), the ATRP initiators, were synthesized by the reaction of –OH in TiO2 with 2-chloropropionyl chloride (CPC). FT-IR, UV–vis spectroscopy and X-ray photoelectron spectroscopy (XPS) clearly showed that the polymer chains were successfully grafted from the surface of TiO2 nanoparticles. The hydrophilically modified TiO2 nanoparticles have a better dispersion in alcohol than unmodified nanoparticles, as revealed by transmission electron microscopy (TEM). It was also found that the polymer grafting did not significantly alter the crystalline structure of the TiO2 nanoparticles according to the X-ray diffraction (XRD) patterns. Grafting amounts were 10% of the weight for both TiO2-POEM and TiO2-PSSA nanoparticles, as determined by thermogravimetric analysis (TGA).

Electrically Conductive Polymeric Nanocomposites Prepared in Alcohol Dispersion of Multiwalled Carbon Nanotubes

In this study, electrically conductive microspheres were prepared by the adsorption of multiwalled carbon nanotubes (MWCNTs) on the surfaces of polymeric microspheres (polystyrene and poly(methylmethacrylate)) in MWCNT-dispersed alcohols (methanol, ethanol, and isopropanol) without surfactants. The stability of the MWCNT dispersions was measured using a recently developed multiple light scattering measurement instrument (Turbiscan). The individual MWCNTs on the surfaces of the microspheres were observed by scanning electron microscopy. The contents of MWCNTs in the composites were determined by thermogravimetric analysis and were found to range from 1.6 wt% to 4.5 wt%. The electrical conductivity and surface charge of the composite microspheres were also investigated.

Extended free radical network from condensed cyanuric chloride with p-phenylenediamine: An EPR/FMR study

A covalent layered network was obtained by condensation of cyanuric chloride with bridging paraphenylenediamine. The local chemical environment of the layered solid can be changed by a redox reaction to obtain new reconstructed derivatives. A blue product was obtained by treating an alcoholic dispersion of the layered solid with ferric nitrate or potassium persulfate, indicating the possible formation of an extended free radical. When iron nitrate was used as oxidant, the temperature-dependent magnetic resonance spectra were measured in the 290–4K region. The magnetic resonance measurements showed the coexistence at room temperature of two spectra arising from two different magnetic centers: a narrow line centered at g=2.0038(1) with linewidth of ΔH=7.42(2) G (free radical) and a broad line centered at g=2.254(1) with linewidth of ΔH=1300(5) G (magnetic iron-oxide cluster). A new sample was prepared so that the broader line was more intense. The temperature dependence of the magnetic resonance lines was subject to intense changes in both cases. The integrated intensities decreased with decreasing temperatures in both spectra in the high temperature region. This type of behavior is similar to that of magnetic nanoparticles in non-magnetic matrices. Upon reducing the temperature with the gradient of ΔHr/ΔT=1.5(1) G/K, the resonance field of the broad line was shifted towards lower magnetic fields, while the narrow line was shifted towards higher magnetic fields with ΔHr/ΔT=0.020(1) G/K. The linewidth of the broader line increased with decreasing temperature, while the narrow line remained almost constant. The magnetic iron-oxide clusters could produce an internal magnetic field acting on free radicals. This field could compel free radicals to form a magnetic ordered state at high temperatures.

The preparation and characterization of anti-VEGFR2 conjugated, paclitaxel-loaded PLLA or PLGA microspheres for the systemic targeting of human prostate tumors

The objective of this study was to manufacture paclitaxel (PTX) loaded polymeric microspheres, that were surface conjugated with antibodies to vascular endothelial growth factor receptor 2 (anti-VEGFR2), for systemic targeting to angiogenic sites in prostate tumors. Microspheres were manufactured in the 1-3 microm size range from poly (l-lactic acid) (PLLA) or poly (lactide-co-glycolide) (PLGA) by a modified solvent evaporation method using Polytron homogenization followed by high speed dispersion in poly vinyl alcohol. Antibodies were conjugated to the surface of these microspheres using cyanogen bromide activation of the polymer surface. Cell Binding was determined using human umbilical vein endothelial cells (HUVECs) in vitro. Efficacy determinations were made using human prostate tumors (PC-3) grown subcutaneously in mice. Antibodies were effectively bound to the surface of PLLA and PLGA microspheres. Anti-VEGFR2 conjugated PLLA microspheres bound strongly to HUVEC's. Pilot efficacy studies in mice showed variability but demonstrated a significant inhibition of tumor growth following the systemic administration of a single dose of PTX-loaded anti-VEGFR2 conjugated PLLA microspheres as compared to non-antibody-conjugated PTX-loaded microspheres. Anti-VEGFR2 conjugated PLLA microspheres containing PTX may offer an effective way of administering a controlled release formulation of the drug to target prostate tumors.

Polystyrene−Silica Colloidal Nanocomposite Particles Prepared by Alcoholic Dispersion Polymerization

Micrometer-sized silica-stabilized polystyrene latex particles and submicrometer-sized polystyrene−silica nanocomposite particles have been prepared by dispersion polymerization of styrene in alcoholic media in the presence of a commercial 13 or 22 nm alcoholic silica sol as the sole stabilizing agent. Micrometer-sized near-monodisperse silica-stabilized polystyrene latexes are obtained when the polymerization is initiated with a nonionic AIBN initiator. These particles are stabilized by silica particles that are present on the latex surface at submonolayer concentration. The total silica content is no greater than 1.1 wt %, which corresponds to a silica sol incorporation efficiency of less than 1.3%. Reduction of the initial silica sol concentration led to a systematic increase in the mean latex diameter. In contrast, submicrometer-sized polystyrene-silica nanocomposite particles are obtained when the polymerization is initiated with a cationic azo initiator. The silica contents of these nanocomposite particles are significantly higher, ranging up to 29 wt %. Zeta potential measurements, XPS, and electron spectroscopy imaging by transmission electron microscopy (ESI/TEM) studies reveal a well-defined core−shell morphology for these particles, whereby the core is polystyrene and the shell comprises the silica sol. After calcination, these nanocomposite particles can form hollow silica capsules. Variation of the initial silica sol and initiator concentration has relatively little effect on the final particle size and silica content of these polystyrene−silica nanocomposite particles, but indicates silica sol incorporation efficiencies up to 72%.

Preparation and characterization of Pluronic-colloidal silicon dioxide composite particles as liquid crystal precursor

The purpose of this study was to produce spray-dried Pluronic-colloidal silicon dioxide (Aerosil) composite particles as a liquid crystal precursor that would form a liquid crystalline phase upon hydration. A Pluronic-colloidal silicon dioxide dispersion in isopropyl alcohol was spray-dried to obtain composite particles using different concentrations of Aerosil. Polarizing microscopy, gelation, gel melting, and rheological studies were employed to characterize the composite particles. The composite particles obtained were irregular, with concave depression. Gelation was found to decrease with the addition of Aerosil, while gel melting was found to increase with the concentration of Aerosil. Rheological studies showed an increase in elasticity as well as viscosity with an increase in the concentration of Aerosil. Composite particles showed improved gelation and rheological properties. These composite particles and the process by which they were obtained may be useful for designing various drug delivery systems.

Rheology and structure of aqueous bentonite-polyvinyl alcohol dispersions

The influence of polymer on flow behaviour of Balikesir, Turkey bentonite dispersions (2%, w/w) was studied for non-ionic polymer, polyvinyl alcohol (PVA). In a range of 3.3 × 106 −3.3 × 105 mol/l, PVA was added to the bentonite dispersions in different concentrations and its behaviour was observed on rheology parameters. Thixotropy was detected by a hysteresis loop of the flow curves. The data were interpreted taking into account the interactions of colloidal clay particles, bentonitic clay concentrations, structure, and concentrations of added PVA. The particle size analysis was explained by surface orientation of PVA to the clay particles dispersed in aqueous solution. Zeta potential determination also emphasized that PVA molecules got attached on the face and edge surface of clay particles. The morphology of bentonite dispersions was analysed by scanning electron micrograph (SEM). FTIR studies carried out in parallel to rheology studies showed that hydrogen bonds were formed between surface of the clay, and absorbed PVA molecules and adsorbed water. The presence of PVA did not prevent extensive swelling of bentonite.

Polystyrene−Silica Nanocomposite Particles via Alcoholic Dispersion Polymerization Using a Cationic Azo Initiator

Submicrometer-sized polystyrene-silica nanocomposite particles have been prepared by alcoholic dispersion polymerization of styrene using commercial alcoholic silica sols of 13 or 22 nm diameter as the sole stabilizing agent. The key to the formation of colloidally stable nanocomposite particles is the selection of a cationic azo initiator (use of nonionic or anionic initiators leads either to the formation of silica-stabilized polystyrene latex particles with very low silica contents or to the precipitation of polystyrene, respectively). Neither surface modification of the silica sol nor the addition of surfactant or polymeric stabilizers is required for successful nanocomposite syntheses. The purified polystyrene-silica nanocomposite particles have relatively narrow particle size distributions, with mean diameters ranging from 331 to 464 nm as judged by disk centrifuge photosedimentometry. Thermogravimetric analyses indicated mean silica contents of 13-26 wt. %, depending on the synthesis conditions. Calcination of the polystyrene-silica nanocomposite particles leads to the formation of hollow silica shells, which indicates a well-defined core-shell morphology for the original nanocomposite particles.

Conservation of acid waterlogged shipwrecks: nanotechnologies for de-acidification

Preservation of waterlogged wooden artifacts, and in particular ancient wrecks, is a challenge in cultural heritage conservation. Samples, from the Swedish warship Vasa, are under investigation in order to develop innovative methods for wood de-acidification and preservation. The Vasa represents a unique case in the study of ancient wrecks. In the past four years the problem of the acidity of wood emerged as a strong threat to its conservation. The production of sulphuric acid inside the ship wood might be the cause of both chemical damage through the acid hydrolysis of cellulose, and of physical damage of the wood’s pore structure, due to the crystallization of sulphate minerals in the wood pores. In this paper we show that wood acidity can be neutralized by the application of nanoparticles of alkaline-earth carbonates and/or hydroxides. The treatment provides an alkaline reservoir inside the wood. Nanoparticles absorbed in the wood from an alcoholic dispersion adhere to the wood wall and release hydroxyl ions leading to the wood neutralization. Oak and pine samples from the Vasa wreck were characterized and treated with alkaline magnesium or calcium nanoparticle dispersions in non-aqueous solvents. De-acidification was monitored by pH changes and thermal analysis, and all the treated samples were submitted to thermal artificial ageing in order to demonstrate the efficacy of the method. The results obtained opened a new perspective in wood conservation.

Spontaneous Formation of Core/Shell Bimetallic Nanoparticles: A Calorimetric Study

We showed recently that low entropy core/shell structured nanoparticles form spontaneously from the physical mixture of a dispersion of Ag nanoparticles and that of another noble metal (Rh, Pd, or Pt) at room temperature. Here we use isothermal titration calorimetry (ITC) and show that the initial step of such a spontaneous process is strongly exothermic. When the alcohol dispersion of poly(N-vinyl-2-pyrrolidone) (PVP)-protected Rh nanoparticles (average diameter 2.3 nm) was titrated into the alcoholic dispersion of PVP-protected Ag nanoparticles, a strong exothermic enthalpy change, DeltaH, was observed: DeltaH = -908 kJ/mol for Ag(S) nanoparticle (average diameter 10.8 nm) and -963 kJ/mol for Ag(L) nanoparticles (average diameter 22.5 nm). The strength of interaction increases in the order of Rh/Ag > Pd/Ag > Pt/Ag. This strong exothermic interaction is considered as a driving force to from low entropy bimetallic nanoparticles by simple mixing of two kinds of monometallic nanoparticles. We show also that exothermic interactions occur between a pair of noble metal nanoparticles themselves by using ITC.

Synthesis of Micrometer-Sized Silica-Stabilized Polystyrene Latex Particles

Micrometer-sized silica-stabilized polystyrene latexes have been readily prepared by alcoholic dispersion polymerization using a 13 or 22 nm commercial alcoholic silica sol as the sole stabilizing agent. These resulting surfactant-free polystyrene particles have relatively narrow particle size distributions and contain surprisingly low levels of silica (</=1.1% by mass), as judged by disk centrifuge photosedimentometry and thermogravimetry, respectively. Transmission electron microscopy studies indicate that the silica sol is located exclusively at the surface of the polystyrene latex particles at submonolayer coverage. The polymerization of styrene in the absence of the silica sol leads to macroscopic precipitation of the polystyrene. Hence, the presence of silica sol is essential for the colloid stability of these latexes, which presumably involves a charge stabilization mechanism.

Bubble sizes in agitated air–alcohol systems with and without particles: Turbulent and transitional flow

In heterogeneous catalytic processes, the relationship between bubble size and various process parameters is important in determining interfacial area, hence mass transfer rate. This paper presents the results of an experimental study of bubble sizes in air–alcohol dispersions with and without the presence of catalyst particles in a batch stirred reactor at different agitation speeds and mean specific energy dissipation rates. Factors investigated include catalyst type, particle size and concentration. It has been found that: • Since there are large differences in the viscosity of the various alcohols used, by dividing them into two groups based on the flow type (turbulent or transitional), a consistent correlation has been found for mean bubble size as a function of Weber number, We, for each region, though neither correlation agrees with the precise relationship suggested by Kolmogoroff's theory of locally, homogeneous, isotropic turbulence. • At the same We number, the size is bigger in transitional flow than in turbulent. The functionality of the correlation of d 32 / D versus We is similar whether particles are present or not. • In fully developed turbulent flow, the bubble size is slightly reduced when catalyst particles are present, independent of catalyst size or type. • In transitional flow, the effect of catalyst particles on bubble size is much stronger, the size being reduced by approximately 30%.

Polymer nanocomposites formation by the use of sodium montmorillonite dispersion in alcohol and a cationic surfactant

AbstractTo enhance the formation of nanocomposites, we pretreated montmorillonite clay with a high‐boiling‐point alcohol or a combination of the alcohol and a cationic surfactant prior to melt mixing. The polymer matrix was melt‐mixed with sodium montmorillonite treated with alcohol or a combination of the alcohol and a cationic surfactant, and then, the alcohol was removed. This new method was applied to polymethyl methacrylate, polystyrene, polyethylene, and polypropylene compounds. The dual use of a surfactant and an alcohol for the treatment of montmorillonite enabled a high degree of intercalation of montmorillonite layers by polymethyl methacrylate chains, which was not obtained in untreated clay or clay treated with either the surfactant or alcohol individually. The process was not as successful with the polyhydrocarbons. There was some evidence for slightly enhanced intercalation for polystyrene, but there was less evidence for polyethylene and polypropylene. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1951–1957, 2004

Preparation of monodisperse polystyrene spheres in aqueous alcohol system

The aqueous methanol/ethanol/ n-propyl systems have been exploited as dispersion medium in emulsion polymerizing of polystyrene (PS) using sodium lauryl sulfate and potassium persulfate as emulsifier and initiator, respectively. The diameter of PS spheres synthesized in aqueous methanol/ethanol/ n-propyl dispersion media is 80 nm–1.15 μm/150 nm–1.3 μm/260 nm–1.65 μm. The replacement of water dispersion medium with alcohol dispersion medium can lift the upper limit of PS spheres size from 1 to 1.65 μm. A seeded growth technique based on aqueous alcohol dispersion media was developed to improve spheric-shape and monodispersity as well as increasing PS spheres size. In this technique, the styrene added for the growth of seeds is diluted with four times volume absolute alcohol, which makes the swelling process of styrene in seed (which is necessary in the conventional two-step seed growth technique) unnecessary and consequently reduces dramatically the synthesis time.

Fabrication of Two- and Three-Dimensional Silica Nanocolloidal Particle Arrays

Monodispersed silica spheres with diameters of 100−500 nm were prepared by hydrolysis of tetraethyl orthosilicate (TEOS) in the presence of water and ammonia in ethanol medium. Silica colloidal sphere sizes were controlled by changing ammonium concentration at fixed TEOS and water concentrations. These silica spheres settle out from their alcoholic dispersion to form closely packed three-dimensional (3-D) particle arraysi.e., photonic crystals that exhibit vivid optical diffraction due to a high degree of ordering of the particles. The lattice constant of the opal photonic crystal structure, as determined by optical diffraction, was found to be in a good agreement with that observed by SEM measurements. Highly purified silica nanospheres could also self-assemble to form 3-D crystalline colloidal arrays (CCAs) in water, which give narrow and continuously tunable diffraction peaks in the visible range. By grafting hydrocarbon chains on silica surfaces using the silane coupling agent octadecyltrimethoxysilane, hydrophobic silica nanospheres were obtained, and they readily self-assemble at the air−water interface to form closely packed two-dimensional (2-D) particle arrays. Such 2-D particle arrays could be collected onto solid substrates to form monolayer or multilayer thin films with controlled film thickness according to the particle size.

A New Method for Consolidating Wall Paintings Based on Dispersions of Lime in Alcohol

-Dispersions of calcium hydroxide, Car OH) 2' in short-chain aliphatic alcohols were studied with the aim of establishing a new pre-consolidation and consolidation methodology for wall paintings. The choice of lime (a paste comprising calciun1 hydroxide plus water) as the consolidant was suggested by physicochemical compatibility criteria, as lime is the original binder in the wall paintings treated. Many problems are encountered when trying to apply calcium hydroxide to wall paintings. Saturated solutions are too weak to act as consolidant, due to the low solubility (1·7 gl–1) of Ca(0H)2 in water. In addition, suspensions of Ca(0H)2 in water are too unstable to be applied to unprotected painting surfaces. The use of Ca(OH)2 dispersions in propan-l-ol is proposed; these dispersions were characterized, and their kinetic stability investigated, by ultraviolet/visible spectrophotometry. The alcohol dispersions were found to be n1uch n10re stable than suspensions in water. The second part of the study evaluated the consolidating power of alcohol dispersions on specimens that simulate different degrees of decohesion. These were examined using X-ray diffractometry and Fourier transform infrared spectroscopy. Their surface properties were characterized by studying capillary rise, water permeability and mercury porosity. The mechanical properties of the specimens were determined using sclerometric resistance and the 'Scotch Tape test'. All the results indicated that the lime/alcohol dispersions produced excellent consolidation. Finally, the paper reports the positive results of tests using the lime/alcohol dispersion on wall paintings by Andrea da Firenze in the Cappellone degli Spagnoli, Chiostro Verde of Santa Maria Novella, Florence.

Spray-drying of solid lipid nanoparticles (SLN TM)

Aqueous dispersions of solid lipid nanoparticles (SLN TM) were converted by spray-drying into dry, reconstitutable powders which could be stored over a long period. After redispersion, the resulting granulates were still acceptable for i.v. administration with respect to the particle size distribution and toxicity. Therefore only physiologically acceptable excipients such as carbohydrates and alcohols (ethanol and methanol) were added to the SLN dispersions before spraying. The particle size was influenced by the applied spraying parameters and by the chemical nature of the lipid phase, the type of carbohydrate and the spraying, and the redispersion medium. An identical size distribution before and after the spraying process, followed by subsequent redispersion was achieved by: reducing the temperature by spraying alcoholic dispersions, reducing the lipid concentration while increasing the sugar concentration, and by redispersion in a poloxamer 188 solution.

Dry pressing boehmite gels for the fabrication of monolithic α-Al2O3

It is demonstrated that dense alpha alumina can be fabricated by pressing ethanol-dispersed, α-Al2O3 seeded boehmite. Green bodies were formed by uniaxially pressing either water or ethanol dispersed gel powder and then isostatically pressing the compacts at 280 MPa. Green microstructure and alumina densification are correlated with gel agglomerate size and dispersing medium. The ethanol-dispersed specimens showed better sinterability than the water-dispersed specimens, and sintered to more than 99% theoretical density at 1300°C. It is shown that softer gel agglomerates were obtained by alcohol dispersion and resulted in better green microstructure and higher sintered density.