Journal of Colloid And Interface Science (v.338, #2)
On the reactive adsorption of ammonia on activated carbons modified by impregnation with inorganic compounds
by Teresa J. Bandosz; Camille Petit (pp. 329-345).
Ammonia adsorption on different activated carbons is enhanced by impregnation. The extent of this improvement depends on various parameters: the nature of parent carbon, type of impregnates and experimental conditions.Ammonia adsorption was studied under dynamic conditions, at room temperature, on activated carbons of different origins (coal-based, wood-based and coconut-shell-based carbons) before and after their impregnation with various inorganic compounds including metal chlorides, metal oxides and polycations. The role of humidity was evaluated by running tests in both dry and moist conditions. Adsorbents were analyzed before and after exposure to ammonia by thermal analyses, sorption of nitrogen, potentiometric titration, X-ray diffraction and FTIR spectroscopy. Results of breakthrough tests show significant differences in terms of adsorption capacity depending on the parent carbon, the impregnates and the experimental conditions. It is found that surface chemistry governs ammonia adsorption on the impregnated carbons. More precisely, it was demonstrated that a proper combination of the surface pH, the strength, type and amount of functional groups present on the adsorbents’ surface is a key point in ammonia uptake. Water can have either positive or negative effects on the performance of adsorbents. It can enhance NH3 adsorption capacity since it favors ammonia dissolution and thus enables reaction between ammonium ions and carboxylic groups from the carbons’ surface. On the other hand, water can also reduce the performance from the strength of adsorption standpoint. It promotes dissolution of ammonia and that ammonia is first removed from the system when the adsorbent bed is purged with air. Ammonia, besides adsorption by van der Waals forces and dissolution in water, is also retained on the surface via reactive mechanisms such as acid–base reactions (Brønsted and Lewis) or complexation. Depending on the materials used and the experimental conditions, 6–47% ammonia adsorbed is strongly retained on the surface even when the bed is purged with air.
Keywords: Ammonia; Activated carbons; Adsorption; Impregnation; Porosity; Surface chemistry
Kinetic aspects and swelling changes of magnesium and cerium titano-antimonates in aqueous and mixed solvents
by Essam S. Zakaria; Ismail M. Ali; Hisham F. Aly (pp. 346-352).
Applying modified calculations at constant values of diffusion coefficient (D i) of cesium ion on magnesium and cerium titano-antimonates in mixed aqueous–solvents revealed insignificant swelling characters.Magnesium titano-antimonate (MgTi5Sb2O16·12.5H2O) and cerium titano-antimonate (Ce2.7Ti5Sb2O19·15.0H2O) were synthesized as new cation exchangers using the in situ precipitation technique. Physico-chemical investigations showed different behaviors for the obtained materials. The materials have significant stability at high acid concentration and temperature. The ion exchange capacity for Cs+ in the presence of different alcoholic solvents was found to increase and generally obey the order C2H5OH>CH3OH>H2O. Diffusion coefficients (D i) and thermodynamic parameters of Cs+ exchange in both magnesium and cerium titano-antimonates in aqueous and alcoholic solutions were calculated. The swelling ratios of the materials were predicted by applying modified calculations at constant values ofD i. The results showed insignificant swelling behavior in the presence of organic solvents.
Keywords: Titano-antimonate; Ion diffusion; Swelling behavior; Mixed solvents
Fe–Mn binary oxide incorporated into diatomite as an adsorbent for arsenite removal: Preparation and evaluation
by Fangfang Chang; Jiuhui Qu; Huijuan Liu; Ruiping Liu; Xu Zhao (pp. 353-358).
Fe–Mn binary oxide incorporated into diatomite (FMBO-diatomite) had high oxidation and adsorption efficiency for As(III) in solution. The As(III) adsorption capacity increased with an increase of temperature.Fe–Mn binary oxide incorporated into diatomite (FMBO-diatomite) was prepared by a simple coating method, and exhibited high oxidation and adsorption ability for arsenite [As(III)]. After being incorporated by Fe–Mn binary oxide, the surface area of diatomite increased 36%, and the pore volume increased five times. The pHzpc of FMBO-diatomite was determined to be 8.1. These characteristics are responsible for the increased As(III) adsorption efficiency. The adsorption equilibria of As(III) on FMBO-diatomite were described well by a Langmuir isotherm model due to the homogeneous distribution of Fe–Mn binary oxide on a diatomite surface. As(III) was oxidized into As(V), and then adsorbed by FMBO-diatomite. The oxidation and adsorption efficiencies for As(III) depended deeply on the pH of solution. When the pH was raised to 8.1, the As(III) adsorption efficiency of FMBO-diatomite was almost equal to the As(III) oxidation efficiency. Silicate and phosphate had negative effects on As(III) adsorption. Also the influence of silicate and phosphate with the pH variation was different.
Keywords: Arsenite; Fe–Mn binary oxide; Diatomite; Adsorption; Oxidation
Synthesis of MPTS-modified cobalt ferrite nanoparticles and their adsorption properties in relation to Au(III)
by Andrea Kraus; Kunawoot Jainae; Fuangfa Unob; Nipaka Sukpirom (pp. 359-365).
The surface of CoFe2O4 magnetic nanoparticles was modified by the ligand exchange reaction and condensation of (3-mercaptopropyl)trimethoxysilane. Their extraction of Au(III) in aqueous solution was investigated.Cobalt ferrite magnetic nanoparticles (Co-MNP) were prepared by a co-precipitation method and subsequently coated with (3-mercaptopropyl)trimethoxysilane (MPTS) for the extraction and recovery of Au(III) from aqueous chloride solutions. Physical characterization of the MPTS-modified particles (Co-MPTS) was performed using FT-IR, TGA, and SEM. Results from FT-IR confirmed that MPTS was present on the surface of the magnetic nanoparticles. The amount of MPTS was 0.36mmolg−1 of Co-MPTS, obtained by elemental analysis. SEM images revealed aggregates composed of nanocrystalline Co-MPTS particles. The extraction efficiency as a function of the pH, contact time, and initial Au(III) concentration was evaluated. The modified particles showed maximum adsorption in the pH range from 1.0 to 4.0. The adsorption behavior of Co-MPTS toward Au(III) followed a Langmuir isotherm and the maximum adsorption capacity was found to be 120.5mgg−1. The stability of the modified materials was improved as compared to that of bare Co-MNP. The subsequent desorption of gold could be achieved by using acidified thiourea solution; the highest gold recovery reached 85%.
Keywords: Magnetic nanoparticles; Ferrite; MPTS; Gold adsorption; Water treatment
Assembly of Pt nanoparticles on electrospun In2O3 nanofibers for H2S detection
by Wei Zheng; Xiaofeng Lu; Wei Wang; Zhenyu Li; Hongnan Zhang; Zhaojie Wang; Xiuru Xu; Shangyu Li; Ce Wang (pp. 366-370).
The Pt nanoparticles loaded on In2O3 nanofibers with diameters of 60–100nm are fabricated by electrospinning. The sensor based on Pt/In2O3 nanofibers exhibits excellent gas properties to H2S.In this paper, we presented a simple and effective solution route to deposit Pt nanoparticles on electrospun In2O3 nanofibers for H2S gas detection. The morphology and chemical structure of the as-prepared samples were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectra (XPS). The results showed that large quantities of In2O3 nanofibers with diameters about from 60 to 100nm were obtained and the surface of them was decorated with Pt nanoparticles (5–10nm in size). The In2O3 nanofibers decorated by Pt nanoparticles exhibited excellent gas sensing properties to H2S, such as high sensitivity, good selectivity and fast response at relatively low temperature.
Keywords: Indium oxide; Electrospinning; Sensor; Hydrogen sulfide; Nanofibers; Nanoparticles
Recovery of palladium using chemically modified cedar wood powder
by Durga Parajuli; Koichi Hirota (pp. 371-375).
Chemically modified wood powder exhibited strong Pd(II) preconcentration ability.Japanese cedar wood powder (CWP) was chemically modified to a tertiary-amine-type adsorbent and studied for the selective recovery of Pd(II) from various industrial waters. Batch adsorption tests performed from 0.1M to 5M HCl and HNO3 systems reveal stable performance with better results in HNO3 medium. The maximum loading capacity for Pd(II) was studied in HCl as well as in HNO3. A continuous-flow experiment taking a real industrial solution revealed the feasibility of using modified CWP for the selective uptake and preconcentration of traces of palladium contained in acidic effluents. In addition, stable adsorption performance even on long exposure to γ-irradiation and selective recovery of palladium from simulated high-level liquid waste (HLW) are important outcomes of the study.
Keywords: Cedar wood powder; Palladium; Fission-palladium
Synthesis and characterization of Fe2O3/SiO2 nanocomposites
by V.M. Bogatyrev; V.M. Gun’ko; M.V. Galaburda; M.V. Borysenko; V.A. Pokrovskiy; O.I. Oranska; E.V. Polshin; O.M. Korduban; R. Leboda; J. Skubiszewska-Zięba (pp. 376-388).
Fe2O3/SiO2 nanocomposites are characterized by low bulk density, high specific surface area and narrow distributions of both primary and secondary particles.Fe2O3/SiO2 nanocomposites based on fumed silica A-300 ( SBET=337m2/g) with iron oxide deposits at different content were synthesized using Fe(III) acetylacetonate (Fe(acac)3) dissolved in isopropyl alcohol or carbon tetrachloride for impregnation of the nanosilica powder at different amounts of Fe(acac)3 then oxidized in air at 400–900°C. Samples with Fe(acac)3 adsorbed onto nanosilica and samples with Fe2O3/SiO2 including 6–17wt% of Fe2O3 were investigated using XRD, XPS, TG/DTA, TPD MS, FTIR, AFM, nitrogen adsorption, Mössbauer spectroscopy, and quantum chemistry methods. The structural characteristics and phase composition of Fe2O3 deposits depend on reaction conditions, solvent type, content of grafted iron oxide, and post-reaction treatments. The iron oxide deposits on A-300 (impregnated by the Fe(acac)3 solution in isopropanol) treated at 500–600°C include several phases characterized by different nanoparticle size distributions; however, in the case of impregnation of A-300 by the Fe(acac)3 solution in carbon tetrachloride only α-Fe2O3 phase is formed in addition to amorphous Fe2O3. The Fe2O3/SiO2 materials remain loose (similar to the A-300 matrix) at the bulk density of 0.12–0.15g/cm3 and SBET=265–310m2/g.
Keywords: Nanosilica; Iron oxide deposits; Fe; 2; O; 3; /SiO; 2; nanocomposite; Phase composition; Structural characteristics; Electronic structure
The adsorption of salicylic acid onto γ-alumina and kaolinite from solution in hexane studied using diffuse reflectance infrared Fourier transform spectroscopy (DRIFT)
by Joan E. Thomas; Michael J. Kelley (pp. 389-394).
Solvent influences amount (only) of salicylic acid adsorbed onto γ-alumina, the loading from hexane (upper curve) being 4× that from water (lower solid). Water washing a sample with maximum coverage from hexane, decreases the level to the maximum observed from water (lower dashed).It was possible to determine the maximum loading of salicylic acid adsorbed onto γ-alumina and kaolinite clay after exposure to salicylic acid dissolved in hexane by examination using diffuse reflectance infrared Fourier transform infrared spectroscopy (DRIFTS). The maximum surface loading of salicylic acid (which resisted washing with fresh hexane) on γ-alumina was four times that observed using water as a solvent (approximately 3.0 compared with 0.7molecules/nm2). Washing the sample with water removed the organic which was in excess to the maximum level observed for samples prepared with aqueous solution. The spectra of samples prepared with a loading up to the maximum observed with aqueous solution showed no significant differences to those of samples where the organic had been adsorbed from hexane (with the same surface loading). New peaks were observed for loadings greater than 1molecules/nm2, but the salicylic acid was still present as carboxylate (with no clear evidence for the carbonyl group). Salicylic acid adsorbed more readily to the surface of kaolinite from solution in hexane than from aqueous solution (up to maximum average loading of 2molecules/nm2). Washing the samples with water removed the organic to a loading in the region of 0.2molecules/nm2, independent of the initial loading. Salicylic acid was adsorbed onto kaolinite as the carboxylate. The findings indicate that uptake is mediated by a surface water layer even in the absence of bulk water.
Keywords: Infrared spectroscopy; DRIFTS; γ-Alumina; Kaolinite; Adsorption; Hexane solvent; Salicylic acid; Surface water
In situ ATR-IR investigation ofL-lysine adsorption on montmorillonite
by Norio Kitadai; Tadashi Yokoyama; Satoru Nakashima (pp. 395-401).
ATR-IR spectral investigation revealed the fundamental aspects of the adsorption in lysine/montmorillonite system, as the driving force of the adsorption and the orientation of the lysine on montmorillonite.The adsorption behavior of lysine on montmorillonite in aqueous solution was investigated by in situ attenuated total reflectance infrared (ATR-IR) spectroscopy. To distinguish the protonation states of α-amino group, side-chain amino group and carboxyl group in lysine structure using ATR-IR spectra (i.e., NH2 versusNH3+ and COO− versus COOH), pH-induced spectral changes of dissolved lysine were firstly measured and correlated with the thermodynamically calculated dissociation states of lysine (di-cationic, cationic, zwitterionic and anionic states). The obtained result was applied to interpret the ATR-IR spectra of lysine adsorbed on montmorillonite. We found that the adsorbed lysine was dominantly present as cationic state over the whole range of tested pH (pH=4.9–9.7). This indicates that the adsorption is mainly driven by electrostatic interaction between the negatively charged montmorillonite surface and positively charged cationic lysine. We also found that lysine interacts with montmorillonite surface through the protonated side-chain amino group. This result suggests that lysine has a preferred vertical orientation, with the side-chain amino group pointing toward the surface.
Keywords: Adsorption; Amino acids; ATR-IR spectroscopy; Lysine; Montmorillonite
Phenol removal from aqueous solution by adsorption and ion exchange mechanisms onto polymeric resins
by Michelle Caetano; César Valderrama; Adriana Farran; José Luis Cortina (pp. 402-409).
This figure represents experimental phenol removal by AuRIX 100 and Dowex XZ resins at pH 3 and 11, as well as the calculations done with the theoretical combined model (adsorption and ion exchange mechanisms).The removal of phenol from aqueous solution was evaluated by using a nonfunctionalized hyper-cross-linked polymer Macronet MN200 and two ion exchange resins, Dowex XZ (strong anion exchange resin) and AuRIX 100 (weak anion exchange). Equilibrium experimental data were fitted to the Langmuir and Freundlich isotherms at different pHs. The Langmuir model describes successfully the phenol removal onto the three resins. The extent of the phenol adsorption was affected by the pH of the solution; thus, the nonfunctionalized resin reported the maximum loading adsorption under acidic conditions, where the molecular phenol form predominates. In contrast both ion exchange resins reported the maximum removal under alkaline conditions where the phenolate may be removed by a combined effect of both adsorption and ion exchange mechanisms. A theoretical model proposed in the literature was used to fit the experimental data and a double contribution was observed from the parameters obtained by the model. Kinetic experiments under different initial phenol concentrations and under the best pH conditions observed in the equilibrium experiments were performed. Two different models were used to define the controlling mechanism of the overall adsorption process: the homogeneous particle diffusion model and the shell progressive model fit the kinetic experimental data and determined the resin phase mechanism as the rate-limiting diffusion for the phenol removal. Resins charged after the kinetic experiments were further eluted by different methods. Desorption of nonfunctionalized resin was achieved by using the solution (50% v/v) of methanol/water with a recovery close to 90%. In the case of the ion exchange resins the desorption process was performed at different pHs and considering the effect of the competitive ion Cl−. The desorption processes were controlled by the ion exchange mechanism for Dowex XZ and AuRIX 100 resins; thus, no significant effect for the addition of Cl− under acidic conditions was observed, while under alkaline conditions the total recovery increased, specially for Dowex XZ resin.
Keywords: Phenol removal; Adsorption; Ion exchange; Kinetic; Diffusion coefficients; Industrial aqueous effluents
Adsorption and inactivation behavior of horseradish peroxidase on cellulosic fiber surfaces
by Sabina Di Risio; Ning Yan (pp. 410-419).
Sketches of HRP adsorption behavior on cellulosic fiber surfaces with different surface energy (left) and surface charge density (right) as examined in this paper.The physical immobilization behavior of horseradish peroxidase (HRP) on cellulosic fiber surfaces was characterized using adsorption and inactivation isotherms measured by the depletion method followed by fitting of Langmuir’s and Freundlich’s models to the experimental data. The adsorption and inactivation behavior of simpler and relatively non-porous high and low crystalline cellulosic substrates (microcrystalline cellulose and regenerated cellulose) as well as more complex and porous cellulosic pulp fibers (bleached kraft softwood fibers) were investigated. The effect of the sorbent surface energy on HRP adsorption was demonstrated by increasing the hydrophobicity of the cellulosic fibers using an internal sizing agent. The influence of the fiber surface charge density on HRP adsorption was studied via modification of the cellulosic fibers using TEMPO (2,2,6,6-tetramethyl-1-piperidiniloxy radical)-mediated oxidation methods. Results showed that hydrophobic interactions had a much larger effect on HRP adsorption than electrostatic interactions. More hydrophobic fiber surfaces (lower polar surface energy) result in larger enzyme-fiber binding affinity constants and higher binding heterogeneity. It was also found that oxidation of the cellulosic fiber substrate reduces enzyme adsorption affinity but significantly increases the loading capacity per unit weight of the surface.
Keywords: Abbreviations; ABTS; 2,2′-azino-di-(3-ethylbenzthiazoline) 6-sulfonate; BKSW; bleached kraft softwood pulp; DP; degree of polymerization; HRP; horseradish peroxidase; MCC; microcrystalline cellulose; RC; regenerated cellulose; SEM; scanning electron microscopy; SSA; specific surface area; TEMPO; 2,2,6,6-tetramethyl-1-piperidiniloxy radical; XPS; X-ray photoelectron spectroscopyCellulosic fibers; Horseradish peroxidase; Enzyme adsorption; Enzyme activity; Hydrophobicity; Oxidation; Crystallinity
Study of micellar and phase separation behavior of mixed systems of triblock polymers
by Durgesh Nandni; Kulwinder Kumar Vohra; Rakesh Kumar Mahajan (pp. 420-427).
In the present work, investigations on micellization and demicellization properties of triblock polymer mixtures (F88/F127+P85/P123) have been undertaken using cyclic voltammetric and cloud point measurements.Cyclic voltammetric (CV) techniques have been employed to study the mixed micellar behavior of binary mixtures of triblock polymers (TBP) such as F127+P85, F127+P85, F88+P85, and F88+P123 using 2,2,6,6-tetramethyl-1-piperidinyloxy (Tempo) as an electroactive probe. Critical micellar concentration (cmc) has been obtained for pure triblock polymers and their mixed systems from the plots of peak current ( ip) variation versus the total concentration. Diffusion coefficients of the electroactive species have been determined from the Randles–Sevcik equation. The interaction parameter ( β) for the mixed micelles was obtained from the regular solution theory. The values of β suggest that the synergism does exist especially with the F88+P123 system. Cloud point measurements have also been made on the binary mixtures of triblock polymers following similar mixing criteria. An effort has been made to correlate the micellar behavior and phase separation (cloud point) phenomenon. From the correlation, it can be concluded that in the systems studied, an increase in cmc increases the cloud point of mixed systems of triblock polymers.
Keywords: Triblock polymer; Cyclic voltammetry; Cloud point; Mixing and demixing; Synergism
Characterization of patterned poly(methyl methacrylate) brushes under various structures upon solvent immersion
by Jem-Kun Chen; Chih-Yi Hsieh; Chih-Feng Huang; Po-min Li (pp. 428-434).
The patterned PMMA brush is synthesised through ATRP and lithography system, which demonstrates mushroom- and brush-like structure after water and THF immersion, respectively.In this paper we describe a graft polymerization/solvent immersion method for generating various patterns of polymer brushes. We used a very-large-scale integration (VLSI) process and oxygen plasma system to generate well-defined patterns of polymerized methyl methacrylate (MMA) on patterned Si(100) surfaces through atom transfer radical polymerization (ATRP). After immersion of wafers presenting lines of these PMMA brushes in water and tetrahydrofuran, we observed mushroom- and brush-like regimes through grafting densities and surface coverages, respectively, for the PMMA brushes with various pattern resolutions. In the mushroom-like regime, the distance between lines of PMMA brushes was smaller than that of the lines patterned lithographically on the wafer; in the brush-like regime, this distance was approximately the same. This new strategy allows polymer brushes to be prepared through graft polymerization and then have their patterns varied through solvent immersion.
Keywords: ATRP; Grafting density; Surface coverage; Very-large-scale integration; PMMA brush
Exploring properties of Polyaniline–SDS dispersion: A rheological approach
by Rupali Gangopadhyay (pp. 435-443).
Highly stable aqueous dispersion of polyaniline was synthesized in presence of SDS. The modulus vs. frequency curve shows that under dynamic shear, this dispersion behaves like an entangled polymer solution.The paper describes steady and dynamic rheological characterization of a system in which polyaniline (PAn) is dispersed in aqueous medium by the effect of a surfactant sodium dodecyl sulphate (SDS). During polymerization of aniline in SDS medium, large and agglomerated micelle–polymer structures are formed (supported by TEM and DLS) resulting in high viscosity of the medium. On application of steady shear micellar entanglements are ruptured and the system exhibits yield properties followed by shear thinning. From the frequency dependence of storage and loss modulii ( G′ and G″) it seems that the system behaves more like a viscous fluid rather than an elastic liquid. Carrying out the same experiments on another dispersion in which PAn is stabilized by dodecyl benzenesulphonic acid (DBSA), very different viscoelastic response was received. DBSA molecules become counter-ions to PAn chains and this way large and interconnected PAn–DBSA structures are formed by mutual sharing of DBSA anions and PAn chains. This system therefore, exhibits gel like properties and encounters a gel to sol transition at larger deformation. Detailed studies have established that PAn–SDS is a stabilized dispersion that resembles entangled polymeric solutions to some extent while PAn–DBSA is a partially flocculated system. Therefore, rheological response of the system is mainly governed by the mutual orientation of PAn with respect to the micelles rather than the individual properties of the components. None of these systems, however, follow the established Maxwell’s model and a single relaxation time is not obtained. Rather, Rouse model of multiple relaxation times is partially applicable to PAn–SDS dispersion.
Keywords: Polyaniline; SDS; Dispersion; Rheology; Modulus; Viscosity
The thermodynamic stability of the mixtures of hyperbranched poly(ethyleneimine) and sodium dodecyl sulfate at low surfactant-to-polyelectrolyte ratios
by Róbert Mészáros (pp. 444-449).
At low surfactant-to-polyelectrolyte ratios kinetically stable colloidal dispersions of the PEI/SDS particles can be observed, which are stabilized by the uncompensated charges of the PEI molecules.The equilibrium nature of the association between the hyperbranched poly(ethyleneimine) (PEI) and sodium dodecyl sulfate (SDS) has been investigated in the presence of excess polyelectrolyte. It was found that the thermodynamic stability of the system considerably depends on the ionization degree of the PEI molecules. In the case of slightly charged PEI molecules, the PEI/SDS mixtures are thermodynamically stable solutions in the pre-precipitation concentration range. In contrast, at low and moderate pH kinetically stable colloidal dispersions of the positively charged PEI/SDS particles can be observed at low surfactant-to-polyelectrolyte ratios. These dispersions are stabilized by the uncompensated charges of the PEI molecules. In addition to the primary PEI/SDS particles, larger aggregates may also appear in the mixtures. The higher the protonation degree of the PEI molecules and the smaller the net charge of the primary PEI/SDS particles, the more likely the aggregate formation becomes.
Keywords: Polyelectrolyte; Surfactant; Colloidal dispersion; Thermodynamic stability; Kinetic stability
Direct measurements of interfacial interactions between pectin and κ-casein and implications for the stabilisation of calcium-free casein micelle mimics
by A. Cucheval; M.A. Al-Ghobashy; Y. Hemar; D. Otter; M.A.K. Williams (pp. 450-462).
Effect of the pectin degree of methylesterification (A: 78%, B: 28%, C: 90%) on the interfacial interaction between pectin (blue) and κ-casein (green) and the behaviour κ-casein coated latex particle in pectin solution at pH 4.6.Using Surface Plasmon Resonance (SPR) it has been shown that the fine structure of the anionic polysaccharide pectin strongly influences its interfacial interaction with a κ-casein layer coated onto a gold surface (via a dextran linker) in the pH range 3.5–6.8, with the highest SPR signal being observed for pectin with the lowest charge density tested (a degree of methylesterification (DM) around 90%).Furthermore, the Brownian motions of κ-casein coated polystyrene beads (used to provide calcium-free ‘model casein micelles’) were studied in pectin solutions using Diffusing Wave Spectroscopy (DWS) and microscopy, and were compared with measurements made on naked beads. At every pH value studied (with the exception of 3.5), bridging of the protein-covered probe particles was observed for pectins of both DM 28 and DM 78. However, no aggregated complexes were found in these model casein micelle systems when pectin of an unusually high DM was used (90%).It was hypothesised that having a limited number of binding regions of spatially limited extent maximises the number of chains binding to the protein layer (as found with the SPR measurement), encourages the formation of loops and trains, and additionally limits the potential for destabilisation via bridging.
Keywords: Abbreviations; DWS; diffusive wave spectroscopy; SPR; surface plasmon resonance; DM; degree of methylesterificationκ-Casein; Pectin; SPR; DWS; κ-Casein coated beads; Interfacial interactions
Hydrogen-bonding A(LS)2-type low-molecular-mass gelator and its thermotropic mesomorphic behavior
by Qiufei Hou; Shichao Wang; Libin Zang; Xiaoliang Wang; Shimei Jiang (pp. 463-467).
A hydrogen-bonding A(LS)2-type gelator shows fibrillar microstructure in xerogel (left) and fan-shaped texture in thermotropic mesophase (right).A unique cholesterol-based A(LS)2-type gelator, which is a hydrogen-bonding complex based on an ALS-type non-gelator molecule 3-cholesteryl 4-(trans-2-(4-pyridinyl)vinyl)phenyl succinate and a counterpart 3-cholesteryloxycarbonylpropanoic acid, shows strong gelation ability in alcohol and aromatic solvents. The formed gel has a high Tg at low gelation concentration, and its xerogel shows fibrillar microstructure revealed by scanning electron microscopy (SEM). FTIR confirms the existence of intermolecular hydrogen bond in the gelator, and X-ray diffraction (XRD) analysis reveals that the gelator possesses a folded conformation in gel and self-assembles into the fibrillar structure mainly by van der Waals interaction between cholesteryl moieties of the gelator. Further more, the thermotropic behavior of the xerogel is studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM), which shows typical optical textures of liquid crystals.
Keywords: Hydrogen-bonding; Gelator; A(LS); 2; Organogel; Liquid crystal
p-Aminophenylacetic acid-mediated synthesis of monodispersed titanium oxide hybrid microspheres in ethanol solution
by Hongye Zhang; Yun Xie; Zhimin Liu; Ranting Tao; Zhenyu Sun; Kunlun Ding; Guimin An (pp. 468-473).
Monodispersed TiO2 hybrid microspheres were prepared via the hydrolysis of titanium isopropoxide (TTIP) in ethanol solution containing p-aminophenylacetic acid (APA), and their size could be tuned from 380 to 800nm by changing the molar ratio of APA: TTIP and water content in the reaction medium.Monodispersed TiO2 hybrid microspheres were prepared via the hydrolysis of titanium isopropoxide (TTIP) in ethanol solution containing p-aminophenylacetic acid (APA). The effects of the APA:TTIP molar ratio, water content, reaction time and reaction temperature on the morphology of the resultant spheres were investigated. The products were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. It was demonstrated that the diameters of the resultant TiO2 spheres could be tuned in the range of 380–800nm by changing the APA:TTIP molar ratio (1:3 to 3:1) and water content (1–3v/v%) in the reaction medium, and that increasing the APA:TTIP molar ratio led to larger TiO2 hybrid spheres while increasing the water content decreased their size. The loading content of APA in the hybrid spheres could reach 20wt.% as they were prepared with the APA:TTIP ratio of 3:1. The possible formation mechanism of the hybrid spheres was also investigated. It was found that APA slowed down the hydrolysis rate of the titanium precursor so that resulted in the formation of the TiO2 spheres. In addition, the APA present in TiO2 spheres acted as a reducing agent to in situ convert HAuCl4 into metallic Au on the surface of the TiO2 spheres. The catalytic activity of the resultant Au/APA–TiO2 composite was examined using transfer hydrogenation of phenylacetone with 2-propanol, and it was indicated that the catalyst displayed high efficiency for this reaction.
Keywords: TiO; 2; Hybrid; Spheres; Synthesis
Dehydrated halloysite intercalated mechanochemically with urea: Thermal behavior and structural aspects
by Keller Paulo Nicolini; Cristiane Regina Budziak Fukamachi; Fernando Wypych; Antonio Salvio Mangrich (pp. 474-479).
Dehydrated halloysite was mechanochemically intercalated with urea and submitted to heat treatments at different temperatures. Detail: 20% of urea and heated at 200°C.Urea has been intercalated mechanochemically into dehydrated halloysite and analyzed by X-ray powder diffraction (XRPD), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance ultraviolet/visible spectroscopy (DRUV–VIS), thermal analysis (TGA/DTA), transmission electron microscopy (TEM), and electron paramagnetic resonance (EPR). The basal distance expands from 7.4 to 10.7 Å and the interaction of urea to adjacent layers of halloysite through hydrogen bonds increases the structural order of the matrix. After heat treatment in air at different temperatures, decomposition products begin to appear starting from 100°C. Although the basal distance remains constant up to 160°C and collapses to the original value at 200°C, urea and the decomposition products are still present in the sample. Starting from 125°C, urea decomposition products reduce halloysite structural Fe3+ centers to Fe2+, as indicated by DRUV–VIS and EPR spectroscopy.
Keywords: Urea; Halloysite; Mechanochemical intercalation; Heat treatment
Role of electrolytes in the preparation of nanoparticles via the emulsion polymerization of vinyl pivalate
by Kenji Kikuchi; Mayuka Kitawaki; Atsushi Suzuki; Takeo Oku (pp. 480-485).
The 15-nm particles of PVPi were the main products. Aggregates of the particles having a diameter of ∼80nm were formed by the aggregate of ∼15-nm particles.By controlling both the kind of ion and the ionic strength of electrolytes in an emulsion polymerization system of vinyl pivalate containing about 1% sodium lauryl sulfate as a surfactant, nanoparticles of polyvinylpivalate having a diameter of about 25nm were successfully prepared. The use of high concentrations of lithium chloride and lithium sulfate (∼1.0molL−1) prevented the nanoparticles from aggregating and produced nanoparticles sizes of 25–50nm. Ammonium acetate and sodium acetate, on the other hand, accelerated the aggregate of the nanoparticles. These phenomena were examined in detail and found to be similar to the Hofmeister phenomena and the combination rule proposed by Craig et al.
Keywords: Emulsion polymerization; Polyvinylpivalate; Nanoparticle; Hofmeister; Ionic strength
Synthesis and characterization of AgBr nanocomposites by templated amphiphilic comb polymer
by Joo Hwan Koh; Jin Ah Seo; Jung Tae Park; Jong Hak Kim (pp. 486-490).
A novel amphiphilic graft copolymer, i.e. poly(vinylidene fluoride- co-chlorotrifluoroethylene)- g-poly(4-vinyl pyridine) (P(VDF- co-CTFE)- g-P4VP) was synthesized via atom transfer radical polymerization (ATRP) and silver halide nanoparticles were in situ generated within the graft copolymer.A novel amphiphilic graft copolymer, poly(vinylidene fluoride- co-chlorotrifluoroethylene)- g-poly(4-vinyl pyridine) (P(VDF- co-CTFE)- g-P4VP) at 65:35wt.%, respectively, was synthesized via atom transfer radical polymerization (ATRP), as confirmed by nuclear magnetic resonance (1H NMR) and transmission electron microscopy (TEM). Silver bromide (AgBr) nanoparticles were in situ generated within the self-assembled P(VDF- co-CTFE)- g-P4VP graft copolymer. TEM, UV–visible spectroscopy and X-ray diffraction (XRD) analyses support the successful formation of P(VDF- co-CTFE)- g-P4VP nanocomposites consisting of stabilized AgBr nanoparticles mostly 20–40nm in size, which is presumably due to the capping action of the coordinating pyridine groups of the graft copolymer. The wavenumber of pyridine nitrogen in FT-IR spectra and the glass transition temperature ( Tg) of the graft polymer measured by DSC shifted upon the formation of AgBr nanoparticles, indicating specific interactions between the nanoparticles and the graft copolymer matrix.
Keywords: Atom transfer radical polymerization (ATRP); Nanoparticle; Silver; Nano patterning; Graft copolymer
Preparation of silane-coated TiO2 nanoparticles in supercritical CO2
by Carlos A. García-González; Julio Fraile; Ana López-Periago; Concepción Domingo (pp. 491-499).
Titanium dioxide (TiO2) nanoparticles were coated with silane coupling agents using scCO2 as solvent. Five different alkylalkoxysilanes were studied: methyltrimethoxy, isobutyltriethoxy, octyltriethoxy, octyldimethylmethoxy and octadecyltrimethoxysilane.Nanometric inorganic pigments are widely used as fillers for hybrid composite materials. However, these nanometric powders are hydrophilic in nature and their surface must be functionalized before use. In this work, titanium dioxide (TiO2) nanoparticles were coated using silane coupling agents with alkyl functionality. A supercritical carbon dioxide (scCO2) method was used for surface silanization. Five alkylalkoxysilanes with different alkyl chain length and structure were studied: methyltrimethoxy, isobutyltriethoxy, octyltriethoxy, octyldimethylmethoxy and octadecyltrimethoxysilane. The microstructure and thermal stability of deposited monolayers were characterized using thermogravimetric analysis, ATR–IR spectroscopy, transmission electron microscopy, wettability characterization and low-temperature N2 adsorption/desorption analysis. The use of scCO2 as a solvent provided an effective approach to functionalize individual inorganic nanoparticles due to the enhanced diffusivity of the solution molecules in the aggregates interparticle voids. The trifunctional silanes employed here yielded surfaces with better thermal stabilities and greater hydrophobicities than the used monofunctional silane.
Keywords: Silane; Nanoparticles; Supercritical carbon dioxide; Wettability; Self-assembled; Monolayer
Photocatalytic property of a keggin-type polyoxometalates-containing bilayer system for degradation organic dye model
by Taohai Li; Shuiying Gao; Feng Li; Rong Cao (pp. 500-505).
POM-containing films via alternate adsorption of cationic L and anionic MW12 (M=P, Co) clusters were prepared on solid substrates. The photocatalytic property of the films was investigated.The photocatalytic activity composite films incorporating the Keggin-type polyoxometalates (POM) K6CoW12O40·16H2O and K3PW12O40· nH2O (MW12 (M=P, Co)) and [Cu(II)(1,8-dimethyl-1, 3, 6, 8, 10, 13-hexaazacycloteradecane)]2+(L) have been prepared by the layer-by-layer (LbL) self-assembly method. The experimental results show that the deposition process is linear and highly reproducible from layer to layer. Atomic force microscopy (AFM) images of the L/MW12 composite films indicate that the film surface is relatively uniform and smooth. In addition, the films show high photocatalytic activity to the degradation of organic dye model (methyl orange (MO)), attributed to the formation of an O→W charge-transfer excited state at W–O–W bridge bond, resulting in generating highly reactive holes and electrons; The photocatalytic efficiency of the films have little change after several times of photocatalytic cycle, indicating that the composite films are stable, reused and recovered.
Keywords: Polyoxometalate; Layer-by-layer self-assembly; Photocatalysis; Methyl orange; Degradation
Structural characterization of hierarchically porous alumina aerogel and xerogel monoliths
by Yasuaki Tokudome; Kazuki Nakanishi; Kazuyoshi Kanamori; Koji Fujita; Hirofumi Akamatsu; Teiichi Hanada (pp. 506-513).
Hierarchically porous alumina aerogel showing compositional dependences of structure both in micrometer and nanometer ranges.Detailed nanostructures have been investigated for hierarchically porous alumina aerogels and xerogels prepared from ionic precursors via sol–gel reaction. Starting from AlCl3·6H2O and poly(ethylene oxide) (PEO) dissolved in a H2O/EtOH mixed solvent, monolithic wet gels were synthesized using propylene oxide (PO) as a gelation initiator. Hierarchically porous alumina xerogels and aerogels were obtained after evaporative drying and supercritical drying, respectively. Macroporous structures are formed as a result of phase separation, while interstices between the secondary particles in the micrometer-sized gel skeletons work as mesoporous structures. Alumina xerogels exhibit considerable shrinkage during the evaporative drying process, resulting in relatively small mesopores (from 5.4 to 6.2nm) regardless of the starting composition. For shrinkage-free alumina aerogels, on the other hand, the median mesopore size changes from 13.9 to 33.1nm depending on the starting composition; the increases in PEO content and H2O/EtOH volume ratio both contribute to producing smaller mesopores. Small-angle X-ray scattering (SAXS) analysis reveals that variation of median mesopore size can be ascribed to the change in agglomeration state of primary particles. As PEO content and H2O/EtOH ratio increase, secondary particles become small, which results in relatively small mesopores. The results indicate that the agglomeration state of alumina primary particles is influenced by the presence of weakly interacting phase separation inducers such as PEO.
Keywords: Particle aggregation; SAXS; Alumina; Macropore; Mesopore; Monolith; Sol–gel
Dimensionless scaling methods for capillary rise
by N. Fries; M. Dreyer (pp. 514-518).
Different methods for scaling capillary rise are examined using the Buckingham π theorem.In this article the different dimensionless scaling methods for capillary rise of liquids in a tube or a porous medium are discussed. A systematic approach is taken, and the possible options are derived by means of the Buckinghamπ theorem. It is found that three forces (inertial, viscous and hydrostatic forces) can be used to obtain three different scaling sets, each consisting of two dimensionless variables and one dimensionless basic parameter. From a general point of view the three scaling options are all equivalent and valid for describing the problem of capillary rise. Contrary to this we find that for certain cases (depending on the time scale and the dominant forces) one of the options can be favorable. Individually the different scalings have been discussed and used in literature previously, however, we intend to discuss the three different sets systematically in a single paper and try to evaluate when which scaling is most useful. Furthermore we investigate previous analytic solutions and determine their ranges of applicability when compared to numerical solutions of the differential equation of motion (momentum balance).
Keywords: Dimensionless scaling; Capillary tube; Analytic solution; Capillary rise; Lucas–Washburn equation; Washburn equation; Imbibition; Liquid penetration
Equilibrium height of a liquid in a gap between corrugated walls under spontaneous capillary penetration
by G.J. Gutierrez; A. Medina; F.J. Higuera (pp. 519-522).
Equilibrium profiles attained by capillary penetration into a corrugated cell for a horizontal corrugation withδ=0.1 (solid). 0.4 (dashed) and 1 (dotted).A simple and general method is presented to calculate the equilibrium surface of a liquid that penetrates spontaneously, due to capillarity, in the gap between two vertical corrugated plates. Several properties of the equilibrium solution are discussed and the results are backed by a qualitative experiment.
Keywords: Capillary penetration; Free surface flows; Micro- and nano-flows
Dissipation mechanisms in ionic liquids
by Erik J. Stalcup; Ralf Seemann; Stephan Herminghaus; Bruce M. Law (pp. 523-528).
Ionic liquid droplets dissipate energy via viscous flow and contact line friction as they spread across a molecular smooth silicon wafer.The spreading of ionic liquids on molecularly smooth solid surfaces has been little studied in the past. We show that the spreading behaviors of the two ionic liquids, [EMIM] ethyl sulfate and ECOENG™ 500, are well described by the combined molecular kinetic and hydrodynamic model of de Ruijter, de Coninck, and Oshanin [M.J. de Ruijter, J. de Coninck, G. Oshanin, Langmuir 15 (1999) 2209] with reasonable values for the molecular friction coefficient ζ, molecular displacement λ, and frequency K0 associated with contact line motion, as well as reasonable values for the microscopic cutoff a associated with hydrodynamic dissipation.
Keywords: Moving contact line; Dissipation; Contact angle; Ionic liquids
Counterion specificity of surfactants based on dicarboxylic amino acids
by Romain Bordes; Jürgen Tropsch; Krister Holmberg (pp. 529-536).
The behavior in solution of a series of amino acid-based surfactants having two carboxyl groups separated by a spacer of one, two, or three carbon atoms has been investigated. All three surfactants precipitated on addition of acid, but the aspartate surfactant (with a two-carbon spacer) was considerably more resistant to precipitation than the aminomalonate surfactant (one-carbon spacer) and the glutamate surfactant (three-carbon spacer). The interactions with the monovalent counterions lithium, sodium, and potassium were investigated by conductivity. It was found that lithium ions bound the strongest and potassium ions the weakest to the surfactant micelles. These results were interpreted using the hard and soft acid-base theory. Comparing the three surfactants with respect to binding of one specific counterion, sodium, showed that the aminomalonate surfactant, which has the shortest spacer, bound sodium ions the strongest and the glutamate surfactant, which has the longest spacer, had the lowest affinity for the counterion. Also that could be explained by the hard and soft acid-base concept. The glutamate surfactant was found to be considerably more resistant to calcium ions than the two other surfactants. This was attributed to this surfactant forming an intermolecular complex with the calcium ion at the air–water interface while the aminomalonate and the aspartate surfactants, with shorter distance between the carboxylate groups could form six- and seven-membered intramolecular calcium complexes.The study of a series of amino acid-based surfactants having two carboxyl groups separated by a spacer was carried out.
Keywords: Surfactant; Amino acid; Glutamate; Aspartate; Aminomalonate; Conductivity; Hard–soft
Mg2+-induced vesicles of tetradecyldimethylamine oxide and magnesium dodecyl sulfate
by Minmin Teng; Aixin Song; Jingcheng Hao (pp. 537-541).
A Mg2+-induced vesicle phase was observed in the mixed aqueous solution of tetradecyldimethylamine oxide and magnesium dodecyl sulfate.A Mg2+-induced vesicle phase was prepared from a mixture of tetradecyldimethylamine oxide (C14DMAO) and magnesium dodecyl sulfate [Mg(DS)2] in aqueous solution. Study of the phase behavior shows that at the appropriate mixing ratios, Mg2+–ligand coordination between C14DMAO and Mg(DS)2 results in the formation of molecular bilayers, in which Mg2+ can firmly bind to the head groups of the two surfactants. The area of the head group can be reduced because of the complexation. In this case, no counterions exist in aqueous solution because of the fixation of Mg2+ ions to the bilayer membranes. Therefore, the charges of the bilayer membranes are not shielded by salts. The birefringent solutions of Mg(DS)2 and C14DMAO mixtures consist of vesicles which were determined by transmission electron microscopy (TEM) images and rheological measurements. Magnesium oxide (MgO) nanoplates were obtained via the decomposition of Mg(OH)2 which were synthesized in Mg2+-induced vesicle phase which was used as the microreactor under the existence of ammonia hydroxide. The morphologies and structures of the obtained MgO nanoplates have been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that the crystal growth is along the (111) direction which can be affected by the presence of a vesicle phase having a fixation of Mg2+ ions to the bilayer membranes.
Keywords: Surfactants; Vesicles; Mg; 2+; -induced vesicles; Microreactors
Solubilization, microstructure, and thermodynamics of fully dilutable U-type Brij microemulsion
by S.K. Mehta; Gurpreet Kaur; Ruchi Mutneja; K.K. Bhasin (pp. 542-549).
A U-type microemulsion has been investigated for the effect of cosurfactant, oil chain length, and water solubilization capacity using conductivity, optical microscopy, dilution method, absorption, and FT-IR spectroscopy.A U-type microemulsion of Brij 96 has been characterized with respect to the change in cosurfactant, oil chain length on dilution, water solubility, and water solubilization capacity. The phase behavior of the systems has been mapped with different oils. Several techniques, viz., conductivity, optical microscopy, dilution method, absorption, and FT-IR spectroscopy, have been used for microemulsion analysis. The equilibrium within the microemulsion droplets and liquid crystals has been visualized using optical microscopy. The microemulsions have evidenced volume-induced conductance percolation in all the cosurfactants ( n2– n6 alcohols). The energetics of transfer of alcohol from the bulk oil to the interface has been determined through dilution method. To gain insight into the microenvironment of microemulsion, two optical probes, hydrophilic (Methyl orange) and hydrophobic (Nile red), have been utilized in absorption spectroscopy. Lastly, FT-IR has been explored to observe the state and dissolution behavior of water with increasing weight fraction.
Keywords: Brij microemulsion; Water solubilization capacity; Phase diagram; Microenvironment; Percolation; Dilution method
Rheological investigation of thermal transitions in vesicular dispersion
by Luigi Coppola; Mohamed Youssry; Isabella Nicotera; Luigi Gentile (pp. 550-557).
The 10mM DODAB dispersion is a threshold above which the vesicles are in coexistence with lamellar fragments as indicated by the peak at 52°C.The thermal behavior of unsonicated dispersions of a double-chained surfactant, Dioctadecyldimethylammonium bromide (DODAB), has been studied over a wide concentration range using DSC and dynamic rheology. All dispersions are characterized by the pre- and main transition peaks at 35°C and 43°C, respectively. But, only above 10mM DODAB, a third endotherm at 52°C appears which may correspond to the (ULVs+Lα fragments)→MLVs transition. The thermal-induced MLV’s size is proportionally dependent on the concentration. In addition, and in agreement with DSC data, dynamic rheology has proven to be an indirect way to elucidate the structural transitions in these DODAB vesicular dispersions.
Keywords: DODAB dispersions; Thermal-induced transition; Dynamic rheology; DSC
The detachment of particles from coalescing bubble pairs
by Seher Ata (pp. 558-565).
Upon coalescing of a naked and coated bubble, some of the particles leave the surface due to the oscillation caused by coalescence process.This paper is concerned with the detachment of particles from coalescing bubble pairs. Two bubbles were generated at adjacent capillaries and coated with hydrophobic glass particles of mean diameter 66μm. The bubbles were then positioned next to each other until the thin liquid film between them ruptured. The particles that dropped from the bubble surface during the coalescence process were collected and measured. The coalescence process was very vigorous and observations showed that particles detached from the bubble surfaces as a result of the oscillations caused by coalescence. The attached particles themselves and, to some extent the presence of the surfactant had a damping affect on the bubble oscillation, which played a decisive role on the particle detachment phenomena. The behaviour of particles on the surfaces of the bubbles during coalescence was described, and implications of results for the flotation process were discussed.
Keywords: Froth flotation; Froth; Bubble coalescence; Particle detachment; Bubble oscillation
Surface potential of spherical polyelectrolyte brushes in the presence of trivalent counterions
by M. Hoffmann; A. Jusufi; C. Schneider; M. Ballauff (pp. 566-572).
The electrophoretic mobility of a negatively charged brush layer in the presence of trivalentEu3+ counterions is measured. The experimental(ζ) is compared to the theoretical(Ψtheo) surface potential derived from a simple statistical–mechanical model.We consider theζ-potential and the effective charge of spherical polyelectrolyte brushes (SPBs) in aqueous solution in the presence of trivalent europium ions. The SPB consists of a polystyrene core of ca. 250nm diameter onto which long chains of the strong polyelectrolyte poly(styrene sulfonate) are grafted (contour length: 82nm). At low concentration ofEuCl3 the chains are stretched to nearly full length. If the concentration of the trivalent ions is raised, the surface layer of the polyelectrolyte chains collapses. Theζ-potential of the SPB is calculated from the electrophoretic mobilities measured at different concentrations ofEuCl3. At the collapse,ζ decreases by the partial neutralization of the charges by the trivalent ions. The experimentalζ-potential thus obtained agrees with the theoretical surface potentialΨtheo calculated for the effective shear plane by a variational free energy model of the SPB.
Keywords: Electrophoretic mobility; Zeta-potential; Brush; Effective charge; Dynamic light scattering; Variational free energy calculation
Preparation of raspberry-like polypyrrole composites with applications in catalysis
by Tongjie Yao; Chuanxi Wang; Jie Wu; Quan Lin; Hui Lv; Kai Zhang; Kui Yu; Bai Yang (pp. 573-577).
Silver/polypyrrole composites were coated on the surface of silica spheres to form raspberry-like composites. They displayed excellent catalytic properties in the reduction of methylene blue dye.Raspberry-like composites were prepared by coating the silver/polypyrrole core/shell composites onto the surface of silica spheres via oxidation polymerization of pyrrole monomer with [Ag(NH3)2]+ ions as oxidants. The whole process allowed the absence of stabilizers, which greatly improved the quality of the conducting polymer composites. The morphology of the resulting composites was investigated, which can be described as raspberry-like; also, the structure and composition of the composites were characterized in detail. A possible formation mechanism was proposed. The present synthetic strategy substantially extended the scope of metal/conducting polymer composite synthesis. The raspberry-like composites exhibited excellent catalytic properties in the reduction of methylene blue dye with the reducing agent of sodium borohydride.
Keywords: Polypyrrole (PPy); Silver (Ag); SiO; 2; Composites; Catalysis
Study on the interaction between CdSe quantum dots and chitosan by scattering spectra
by Juanjuan Peng; Shaopu Liu; Lei Wang; Zhengwen Liu; Youqiu He (pp. 578-583).
The interaction between chitosan with CdSe QDs caused the RRS intensity greatly enhanced. Based on this, it is potentially to develop RRS methods to detect chitosan using QDs as probes.Two different stabilizing agents thioglycolic acid (TGA) andl-cysteine (l-Cys) capped CdSe QDs with the diameter of 2nm were synthesized, large amounts of stabilizing agents connected to CdSe QDs surface through Cd–S bond. The interaction between chitosan and QDs had been investigated, respectively. The interaction lead to the remarkable enhancement of RRS, RNLS and the enchantments were in proportional to the concentration of chitosan in a certain range. Under the optimal conditions, compared with TGA–CdSe QDs, the interaction betweenl-Cys–CdSe QDs with chitosan owned more broad linear range 0.042–3.0μgmL−1 and lower detect limits 1.2ngmL−1. The influences of factors on the interaction between chitosan with QDs and some foreign substances were all examined, which showed that the methods had a good sensitivity and selectivity. Based on this, it is hoped to build a method for the determination of chitosan using CdSe QDs as probes. Through Fourier transform infrared spectroscopy (FTIR) transmission electron microscopy (TEM), it was speculated that CdSe QDs interacted with chitosan to form a network structure aggregates through electrostatic attraction and hydrophobic forces. The reasons for the enhancement of RRS intensity were assumed as follows: resonance enhanced Rayleigh scattering effect, increase of the molecular volume, and hydrophobic effect.
Keywords: CdSe QDs; Thioglycolic acid; l; -Cysteine; Resonance Rayleigh scattering; Chitosan
Fabrication of superparamagnetic magnetite/poly(styrene- co-12-acryloxy-9-octadecenoic acid) nanocomposite microspheres with controllable structure
by Song Yang; Huarong Liu; Haofeng Huang; Zhicheng Zhang (pp. 584-590).
The superparamagnetic nanocomposite microspheres with controllable structure have been fabricated successfully through irradiation induced inverse emulsion polymerization.We herein report a novel and facile approach to the fabrication of the superparamagnetic magnetite/poly(styrene- co-12-acryloxy-9-octadecenoic acid) nanocomposite microspheres with controllable structure via γ-ray radiation induced inverse emulsion polymerization under room temperature and at ambient pressure. 12-Acryloxy-9-octadecenoic acid (AOA, containing part of sodium salts Na–AOA) as a surfactant can also copolymerize with the styrene. It is interesting that just by changing the added amount of styrene, the magnetic hollow spheres with different wall thickness and various sizes of core, up to the magnetic solid spheres, can be obtained. The final products were thoroughly characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron diffraction (TEM), field-emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA) which showed the formation of magnetite/poly(styrene- co-AOA) nanocomposite microspheres. Magnetic hysteresis loop measurements showed that the magnetic nanocomposite microspheres exhibited superparamagnetism, which should make them have potential applications in biotechnology and biomedicine. Furthermore, we also proposed a possible formation mechanism of these magnetic microspheres with different morphologies.
Keywords: Hollow microspheres; Superparamagnetic; Nanocomposite; Inverse emulsion; γ-Radiation