Sol-gel synthesis of nanocomposite materials based on lithium niobate nanocrystals dispersed in a silica glass matrix

With the final goal to obtain thin films containing stoichiometric lithium niobate nanocrystals embedded in an amorphous silica matrix, the synthesis strategy used to set a new inexpensive sol-gel route to prepare nanocomposite materials in the Li₂O-Nb₂O₅-SiO₂ system is reported. In this route, LiNO₃, NbCl₅ and Si(OC₂H₅)₄ were used as starting materials. The gels were annealed at different temperatures and nanocrystals of several phases were formed. Futhermore, by controlling the gel compositions and the synthesis parameters, it was possible to obtain LiNbO₃ as only crystallizing phase. LiNbO₃-SiO₂ nanocomposite thin films on Si-SiO₂ and Al₂O₃ substrates were grown. The LiNbO₃ average size, increasing with the annealing temperature, was 27 nm for a film of composition 10Li₂O-10Nb₂O₅-80SiO₂ heated 2 h at 800 °C. Electrical investigation revealed that the nanocrystals size strongly affects the film conductivity and the occurrence of hysteretic current-voltage curves.     

A new hybrid nanocomposite prepared by graft copolymerization of butyl acrylate onto chitosan in the presence of organophilic montmorillonite

Organophilic montmorillonite (OMMT) was synthesized by cationic exchange between Na-MMT and tricetadecylmethyl ammonium bromide in an aqueous solution. A new nanocomposite consisting of poly(butyl acrylate)-modified chitosan and OMMT was prepared by γ-ray irradiation polymerization in acetic acid aqueous solution. The degree of dispersion and the intercalation spacing of these nanocomposites were investigated using X-ray diffraction. The enhanced thermal stabilities of nanocomposites were characterized by the thermal gravimetric analysis. The improved mechanical properties of nanocomposites were characterized by static tensile studies and dynamic mechanical analysis. The nanocomposites showed improved resistance to water absorption.     

Biodegradable polymer matrix nanocomposites for tissue engineering: A review

Nanocomposites have emerged in the last two decades as an efficient strategy to upgrade the structural and functional properties of synthetic polymers. Aliphatic polyesters as polylactide (PLA), poly(glycolides) (PGA), poly(?-caprolactone) (PCL) have attracted wide attention for their biodegradability and biocompatibility in the human body. A logic consequence has been the introduction of organic and inorganic nanofillers into biodegradable polymers to produce nanocomposites based on hydroxyapatite, metal nanoparticles or carbon nanotructures, in order to prepare new biomaterials with enhanced properties. Consequently, the improvement of interfacial adhesion between the polymer and the nanostructures has become the key technique in the nanocomposite process. In this review, different results on the fabrication of nanocomposites based on biodegradable polymers for specific field of tissue engineering are presented. The combination of bioresorbable polymers and nanostructures open new perspectives in the self-assembly of nanomaterials for biomedical applications with tuneable mechanical, thermal and electrical properties.     

Synthesis and physical properties of new layered double hydroxides based on ionic liquids: Application to a polylactide matrix

Ionic liquids based on tetraalkylphosphonium salts combined with different anions (decanoate and dodecylsulfonate) have been used as intercalating agents of layered double hydroxides (LDHs) by ion exchange. The synthesized phosphonium-treated LDHs display a dramatically improved thermal degradation and a significant increase in the interlayer distance as confirmed by thermogravimetric analysis (TGA) and X-ray Diffraction (XRD), respectively. To highlight the effect of thermostable ionic liquids, a very low amount of LDHs has been introduced within a polylactide (PLA) matrix and PLA/LDHs nanocomposites have been processed in melt by twin-screw extrusion. Then, transmission electron microscopy (TEM) analysis has been used to investigate the influence of ILs on the different morphologies of these nanocomposites. Even though the thermal stability of PLA matrix decreased, an excellent stiffness-toughness compromise has been obtained.     

A humidity-sensitive nanocomposite solid ion conductor: sulfonated poly-ether-ether-ketone in nanotubular TiO2 or ZrO2 matrix

Journal of Solid State Electrochemistry - A nanocomposite solid ion conductor was prepared by infiltrating zirconia or titania nanotube arrays, made by electrochemical anodization of Zr or Ti...     

Partial Carbamoylation of Cellulose Microspheres:a New Method to Prepare Adsorbents for Liquid Chromatography简

Micron-sized cellulose microspheres were prepared through sol-gel method using NaOH/urea solution to dissolve cellulose, then cross-linked by 1,6-hexanylene diisocyanate （HDI）, toluene 2,4-diisocyanate （TDI） and 1,4-phenylene diisocyanate （PDI）, respectively. The reaction conditions for partial modification of the microspheres were studied. The degree of substitution （DS） in cellulose was controlled by adjusting the reaction conditions. HDI-crosslinked microspheres were partially modified with phenyl isocyanate to obtain chiral stationary phases （CSPs）. The CSPs of a lower degree of crosslinking （DC） showed better chiral recognition ability than those of a higher DC. Meanwhile the CSPs prepared by pre- modification exhibited better chiral recognition ability than those prepared by pre-crosslinking.     

A new protection group strategy for cellulose in an ionic liquid: simultaneous protection of two sites to yield 2,6-di-O-substituted mono-p-methoxytrityl cellulose

Increased reactivity of cellulose in ionic liquids was revealed when cellulose was protected with a 4-methoxytrityl moiety in the imidazolium-based ionic liquid, 1-allyl-3-methylimidazolium chloride ([amim]Cl). Selectively protected 2,6-di-O-(4-methoxytrityl)cellulose was obtained in one reaction step with a DS of close to 2, and was characterised by NMR.     

De-aggregation of a polyfluorene derivative in clay nanocomposites: A photophysical study

The de-aggregation of a very luminescent polyfluorene derivative poly(9,9-di-hexylfluorenediyl divinylene-alt-1,4-phenylenevinylene), which has a high tendency to π-stacking aggregation was achieved through the interaction of the polymer with clay in clay/polymer nanocomposites. The mixing of diluted toluene polymer solutions with kaolinite was enough to promote the de-aggregation, even without the indication of polymer intercalation, indicating that the polymer de-aggregation was obtained due to its interactions with clay platelet surfaces. The photoluminescence observed for the dispersed polymer on clays showed an increase in intensity and a blue-shift of the photoluminescence, when compared with pure pristine material in thin film form. The results presented bring the possibility to produce more efficient polymer based devices and to carry single molecule studies using nanocomposite film formation.     

The first normal stress difference and viscosity in shear of liquid crystalline solutions of hydroxypropylcellulose: new experimental data and theory

The constitutive equations for liquid crystalline polymers recently proposed by one of us [1] are applied here to interpret the behaviour of the shear viscosity η and the first normal stress difference N₁() measured for liquid crystalline (LC) solutions of hydroxypropylcellulose in acetic acid. N₁( ) is observed to change from positive to negative and again to positive, as the shear rate increases, at lower concentrations, in the LC phase. The -values at which N₁ changes sign depend on the molecular mass (degree of polymerization) and on the concentration. η shows a small Newtonian plateau at low shear rates and a strong shear-thinning at higher values of . The rate of decrease of η in this region shows an “hesitation” similar to one previously observed in LC solutions of poly-γ-benzyl-L-glutamate PBLG. All these observations can be rationalized within the frame-work of Martins' theory. The expressions for N₁() and η derived from this theory fit very well (quantitatively) to the experimental data and some fundamental viscoelastic parameters of the system under study are thereby obtained for the first time.     

A new thermoplastic vulcanizate (TPV)/organoclay nanocomposite: Preparation,characterization, and properties

The preparation, characterization, and properties of the new thermoplastic vulcanizate (TPV)/organoclay nanocomposites are reported in this article. The nanocomposites were prepared by the melt intercalation method. The organoclay was first treated with glycidyl methacrylate, which acts as a swelling agent for organoclays, as well as a grafting agent for TPV (in the presence of dicumyl peroxide) during the melt mixing. The nanocomposite was intercalated, as evidenced by X‐ray diffraction. The tensile modulus of the 5% TPV/organoclay nanocomposite was higher than that of the 20% talc‐filled microcomposite. The storage modulus of the nanocomposite was higher than that of the pristine TPV. The most important observation is obtained from dynamic mechanical analysis, which reveals that the glass‐transition temperature of the polypropylene phase of the nanocomposite increases (as compared to virgin TPV), whereas the ethylene–propylene–diene monomer phase remains almost the same. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2900–2908, 2004     

Parallel esterification of bio-based dicarboxylic acids in small scale film reactors: A high-throughput study

The applicability of polyesters across a wide range of fields creates a demand for novel polyester structures that can offer advanced product performance. Two critical factors to the development of unique polymer architectures are the speed at which new polymeric systems can be synthesized and the available selection of monomers from which polymers are designed. Herein, we successfully demonstrate the applicability of a high-throughput (HT) approach to polyesterification reaction between dicarboxylic acids and diols in reaction conditions similar to those used in industry. Furthermore, we apply our HT design to a series of bio-based monomers whose unique structures offer potential for enhanced properties in polyester-based systems. Using a custom-built array of small-scale film reactors, we conducted a parallel screening of 13 bio-based dicarboxylic acids as potential monomers in the synthesis of polyester polyols through copolymerization with 1,6-hexanediol. The polyester polyols were characterized for their molecular weight and thermal properties. Carrying out polyesterification reactions in small-scale film reactors is seen as a quick and powerful tool for screening the effectiveness of a series of potential monomers, as this method offers highly controllable and reproducible reaction conditions in every reactor coupled with the ability to use a minimum amount of reagents.     

A new hybrid nanocomposite prepared by emulsion copolymerization of ABS in the presence of clay

The preparation and characterizations of new hybrid organic–inorganic nanocomposites consisting of acrylonitrile–butadiene–styrene terpolymer and a Na⁺‐exchanged montmorillonite (MMT) are described by direct intercalation through one‐step emulsion polymerization. Those products were purified by successive hot acetone and toluene extraction, respectively, for more than 2 days. The IR spectra for the purified samples revealed the characteristic absorbances as a result of those of styrene, butadiene, acrylonitrile, and MMT. X‐ray diffraction spectra of the composites showed the enlarged 001 d‐spacing as much as 1.75 nm, but no signals were found for the partial insertion of copolymer chains. Moreover, it was evident that this direct intercalation was not accompanied by delamination of the clay interlayer. The thermogravimetric analytic measurement for the purified product confirmed that the onset temperature of decomposition was transferred to the higher temperature region as much as 40–50 °C. Morphological observations by transmission electron microscopy, scanning electron microscopy, and optical micrography demonstrated homogeneous dispersion of MMT particles in the copolymer matrix. The possible physical picture of this direct intercalation was discussed in terms of swelling characteristics of compacted bentonite and the monomer containing micelle sizes. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 719–727, 2001     

Versatile nanocomposites in phosphoproteomics: A review

Protein phosphorylation is one of the most important post-translational modifications. Phosphorylated peptides are present in low abundance in blood serum but play a vital role in regulatory mechanisms and may serve as casual factors in diseases. The enrichment and analysis of phosphorylated peptides directly from human serum and mapping the phosphorylation sites is a challenging task. Versatile nanocomposites of different materials have been synthesized using simple but efficient methodologies for their enrichment. The nanocomposites include magnetic, coated, embedded as well as chemically derivatized materials. Different base materials such as polymers, carbon based and metal oxides are used. The comparison of nanocomposites with respective nanoparticles provides sufficient facts about their efficiency in terms of loading capacity and capture efficiency. The cost for preparing them is low and they hold great promise to be used as chromatographic materials for phosphopeptide enrichment. This review gives an overview of different nanocomposites in phosphoproteomics, discussing the improved efficiency than the individual counterparts and highlighting their significance in phosphopeptide enrichment.     

A new conception on the toughness of nylon 6/silica nanocomposite prepared via in situ polymerization

A novel method, in situ polymerization, was used for the preparation of nylon 6/silica nanocomposites, and the mechanical properties of the nanocomposites were examined. The results showed that the tensile strength, elongation at break, and impact strength of silica-modified nanocomposites exhibited a tendency of up and down with the silica content increasing, while those of silica-unmodified nanocomposites decreased gradually. It also exhibited that the mechanical properties of silica-modified nanocomposites have maximum values only when 5% silica particles were filled. Based on the relationship between impact strength of the nanocomposites and the matrix ligament thickness τ, a new criterion was proposed to explain the unique mechanical properties of nylon 6/silica nanocomposites. The nylon 6/silica nanocomposites can be toughened only when the matrix ligament thickness is less than τ_c and greater than τ_a, where τ_a is the matrix ligament thickness when silica particles begin to aggregate, and τ_c is the critical matrix ligament thickness when silica particles begin to toughen the nylon 6 matrix. The matrix ligament thickness, τ, is not independent, which related with the volume fraction of the inorganic component because the diameter of inorganic particles remains constant during processing. According to the observation of Electron Scanning Microscope (SEM), the process of dispersion to aggregation of silica particles in the nylon 6 matrix with increasing of the silica content was observed, and this result strongly supported our proposal. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 789–795, 1998     

Introducing a new pharmaceutical agent: Facile synthesis of CuFe12O19@HAp-APTES magnetic nanocomposites and its cytotoxic effect on HEK-293 cell as an efficient in vitro drug delivery system for atenolol

In this study, novel CuFe₁₂O₁₉@hydroxyapatite magnetic nanocomposites (CuFe₁₂O₁₉@HAp MNCs) as controlled target drug delivery were synthesized by ultrasound-assisted precipitation method for the first time. Then, the magnetic substrate was functionalized with APTES (CuFe₁₂O₁₉@HAp-APTES MNCs) to increase the efficiency of the drug delivery system. The crystallinity, size, morphology, and composition of the products were determined by FESEM, DLS, BET, TEM, XRD, EDS, and VSM. In order to investigate the drug loading ability of prepared nanocomposites, we chose antihypertensive drug (atenolol) as the model drug. After that, the release behavior of magnetic nanocomposites modified atenolol was investigated under stomach (pH value of 1.5–2) and intestine (pH value of 5.8–6.7) conditions. The results revealed that the highest entrapment efficiency was achieved by CuFe₁₂O₁₉@HAp-APTES MNCs (63.1%). Furthermore, the controlled-release potential for CuFe₁₂O₁₉@HAp-APTES MNCs was the highest compared with the pure CuFe₁₂O₁₉@HAp MNCs. Increased efficiency can be due to the binding of the amine group in APTES with the atenolol drug. The cytotoxicity of the ATL-loaded magnetic nanocomposites (ATL-CuFe₁₂O₁₉@HAp-APTES MNCs) was investigated on the HEK-293 cell line using MTT assay. Based on the results, we concluded that the synthesized magnetic nanocomposites could be effective vehicles for the sustained delivery of atenolol as an antihypertensive drug.     

A new kind of single Li-ion polyelectrolyte based on triazolate in a polyurea matrix: syntheses and properties

In this work, a new class of single Li-ion polyelectrolyte (SLIP) based on a polyurea matrix was developed from triazolate salt and diisocyanates with an aliphatic or aromatic moiety. The structure and chemical information were checked by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses. The aggregate structure, thermal stability, phase behavior and morphology were examined via X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry and scanning electron microscopy, respectively. It was found that the obtained SLIPs were disordered pore materials with amorphous structures and high stability, and the influence of varied isocyanate monomers on their properties was associated with hydrogen bonding derived from urea linkage. Furthermore, the electrochemical properties for the SLIPs absorbing dimethyl sulfoxide were determined by cyclic voltammetry, linear sweep voltammetry and electrochemical impedance spectroscopy, and the results showed that the electrolytes could endure an oxidation potential up to 4.2 V (vs. Li⁺/Li) and exhibited a practicable conductivity (10^?4 S cm^?1) at 30 °C. The cycling performance for an Li|Li cell was also tested preliminarily. The obtained results indicated that the developed SLIPs could be used as potential polyelectrolytes in lithium batteries.     

A new potentiometric ibuprofenate ion sensor immobilized in a graphite matrix for determination of ibuprofen in tablets

The characteristics, performance, and application of an electrode, namely, Pt|Hg|Hg₂(IBP)₂|Graphite, where IBP stands for ibuprofenate ion, are described. This electrode responds to IBP with sensitivity of (58.6 ± 0.9) mV decade^− 1 over the range 5.0 × 10^− 5–1.0 × 10^− 1 mol L^− 1 at pH 6.0–9.0 and a detection limit of 3.8 × 10^− 5 mol L^− 1. The electrode is easily constructed at a relatively low cost with fast response time (within 15–30 s) and can be used for a period of 5 months without any considerable divergence in potentials. The proposed sensor displayed good selectivity for ibuprofen in the presence of several substances, especially concerning carboxylate and inorganic anions. It was used for the direct assay of ibuprofen in commercial tablets by means of the standard additions method. The analytical results obtained by using this electrode are in good agreement with those given by the United States Pharmacopeia procedure.     

1,8-Bis(dimethylamino)naphthalene/9-aminoacridine: A new binary matrix for lipid fingerprinting of intact bacteria by matrix assisted laser desorption ionization mass spectrometry

The effectiveness of a novel binary matrix composed of 1,8-bis(dimethylamino)naphthalene (DMAN; proton sponge) and 9-aminoacridine (9AA) for the direct lipid analysis of whole bacterial cells by matrix assisted laser desorption ionization mass spectrometry (MALDI MS) is demonstrated. Deprotonated analyte signals nearly free of matrix-related ions were observed in negative ion mode. The effect of the most important factors (laser energy, pulse voltage, DMAN/9AA ratio, analyte/matrix ratio) was investigated using a Box–Behnken response surface design followed by multi-response optimization in order to simultaneously maximize signal-to-noise (S/N) ratio and resolution. The chemical surface composition of single or mixed matrices was explored by X-ray photoelectron spectroscopy (XPS). Moreover, XPS imaging was used to map the spatial distribution of a model phospholipid in single or binary matrices.     

离子缔合型离子选择电极的研究 I: PVC膜铬(VI)离子选择电极的研制的和应用

A new Cr(VI)-selective electrode of PVC membrane based on triheptyl dodecyl ammonium iodide is described. The response of the electrode is Nernstian for Cr(VI) concentration down to 2X10-6M in 0.03-0.13N HF solution. Limit of detection is 5X10-7M. The plot of logarithms of selectivity coefficients vs. z/γ of various anions is essentially linear with a correlation coefficient of -- 0.88. Applications of the electrode in determination of total Cr in steels and copper alloys, and Cr(VI) in waste-water from chromium electroplating are reported.     

Designing and fabrication of a novel gold nanocomposite structure: application in electrochemical sensing of bisphenol A

In this article, a highly sensitive electrochemical sensor is introduced for direct electro-oxidation of bisphenol A (BPA). The novel nanocomposite was prepared based on multi-walled carbon nanotube/thiol functionalised magnetic nanoparticles (Fe₃O₄-SH) as an immobilisation platform and gold nanoparticles (AuNPs) as an amplifying electrochemical signal. The chemisorbed AuNPs exhibited excellent electrochemical activity for the detection of BPA. Some analysing techniques such as Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy and energy-dispersive x-ray diffraction exposed the formation of nanocomposite. Under optimum conditions (pH 9), the sensor showed a linear range between 0.002–240 μM, with high sensitivity (0.25 μA μM^?1) along with low detection limit (6.73 × 10^?10 M). Moreover, nanocomposites could efficiently decrease the effect of interfering agents and remarkably enhance the utility of sensor at detection of BPA in some real samples.