Formation Of Hybrid Materials Research Articles

Encapsulation of Nanoparticles in Block Copolymer Micellar Aggregates by Directed Supramolecular Assembly

Incorporation of inorganic nanoparticles (NPs) into selfassembled block copolymers offers a powerful route for the formation of hybrid materials with desired optical, electronic, and magnetic properties through the choice of NPs and their distribution in polymer assemblies. Nanostructured block copolymer domains act as a scaffold that directs not only the position of the NPs but also their orientation. NPs/polymer hybrid materials have been prepared in solution by incorporating one or multiple hydrophobic NPs into a hydrophobic core of spherical amphiphilic block copolymer micelles. Careful control of micellization conditions will allow other hydrophobic ingredients to co-assemble with the amphiphilic polymers, resulting in micelles that encapsulate therapeutic molecules and NPs for imaging and targeting. Cylindrical or wormlike micelles show particular interest in drug delivery because of their large core volume (per carrier) and elongated structures, which offer additional opportunities to control biodistribution and release profiles of therapeutic agents. The “precipitation method”, which is a practical way to incorporate NPs into micelles, does not easily allow the growth of extended wormlike micelles with NPs encapsulated in the core. Several groups have reported the successful incorporation of NPs into hydrophilic portions of wormlike micelles through electrostatic interaction of corona-forming blocks with NPs. Recently, we reported the encapsulation of iron oxide NPs within wormlike micelle cores through interfacial instabilities of emulsion droplets containing amphiphilic polymers. However, it is hard to achieve high loading and uniform dispersion of NPs in wormlike micelle cores. So far, precise control over NPs position in wormlike micelle cores with homogeneous distribution remains a challenge. Herein we introduce a simple, yet versatile approach for the encapsulation of NPs within wormlike micelle cores through directed supramolecular assembly. The concept for preparation of the hybrid nano-objects is illustrated in Figure 1a. Typically, polystyrene–poly(4-vinylpyridine) (PS20k–P4VP17k, volume fraction of PS fPS= 56%) and pentadecylphenol (PDP) were dissolved in chloroform to form PS–P4VP(PDP)x (x represents the ratio of PDP to 4VP

Preparation of zinc sulfide nanocrystallites from single-molecule precursors

Zinc sulfide nanocrystallites were prepared using Zinc(II) thiosemicarbazone complexes of the types Zn(L) 2 and ZnCl 2(LH) 2 (where, LH=thiosemicarbazones of cinnamaldehyde, 4-chlorobenzaldehyde, indol-3-carboxaldehyde and thiophene-2-carboxaldehyde) as single source precursors by solvothermal decomposition in ethylene glycol and ethylene diamine in few cases. The materials were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction, energy dispersive X-ray analysis and UV–vis and IR spectroscopy. Solvothermal decomposition in ethylene glycol resulted in the formation of hexagonal ZnS (JCPDS: 36-1450) as evident from the XRD patterns. However, XRD shows formation of hybrid material, ZnS 0.5EN in case of solvothermal decomposition in ethylenediamine. Infrared spectra authenticate the capping of ethylene glycol and ethylenediamine on ZnS and ZnS 0.5EN, respectively. TEM images showed formation of spherical nanoparticles for the materials obtained from ethylene glycol, whereas plate-like morphology is observed in case of materials obtained from ethylene diamine. The blue shift of absorption bands compared to bands of bulk materials in the UV–vis spectra supports the formation of smaller particles.

Mn3O4−Graphene Hybrid as a High-Capacity Anode Material for Lithium Ion Batteries

We developed two-step solution-phase reactions to form hybrid materials of Mn(3)O(4) nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Selective growth of Mn(3)O(4) nanoparticles on RGO sheets, in contrast to free particle growth in solution, allowed for the electrically insulating Mn(3)O(4) nanoparticles to be wired up to a current collector through the underlying conducting graphene network. The Mn(3)O(4) nanoparticles formed on RGO show a high specific capacity up to ∼900 mAh/g, near their theoretical capacity, with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn(3)O(4) nanoparticles grown atop. The Mn(3)O(4)/RGO hybrid could be a promising candidate material for a high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for the design and synthesis of battery electrodes based on highly insulating materials.

DNA Functionalized Carbon Nanotubes for Nonbiological Applications

Functionalization of an inorganic nanomaterial like carbon nanotube (CNT) with biological macromolecules like deoxyribonucleic acid (DNA) leads to the formation of hybrid materials with fascinating properties. This article describes the structures of CNT and DNA, portrays the van der Waals force-dominant non-covalent π–π stacking interactions formed due to their self-assembly, and reviews the electronic, electrochemical, optical, and chemical properties of DNA-functionalized CNTs (DFCs). Current computational developments in simulating and predicting CNT-DNA interactions, alternate functionalization techniques, conformational changes of DNA bases, etc. are discussed. Various characterization techniques using scanning electron microscopy (SEM), scanning tunneling microscopy (STM), atomic force microscopy (AFM), UV-visible, Photoluminescence (PL) and Raman spectroscopy, etc. that help explain DFC properties are detailed. Potential applications for this hybrid material in nanoelectronics and chemical sensors as well as in chirality-based separation of metallic nanotubes from semiconducting ones are considered. The article concludes with current challenges, future directions of research, and prospective applications in this field.

Effect of processing on carbon molecular sieve structure and performance

Sub-micron sized carbon molecular sieve (CMS) materials were produced via ball milling for subsequent use in hybrid material formation. A detailed analysis of the effects of the milling process in the presence of different milling environments is reported. The milling process apparently alters the molecular scale structure and properties of the carbon material. Three cases: unmilled, air milled and nitrogen milled, were analyzed in this work. The property changes were probed using equilibrium sorption experiments with different gases. Furthermore, WAXD and BET results also showed differences between milling processes. Finally in order to improve the interfacial polymer-sieve region of hybrid membranes, the CMS surface was chemically modified with a linkage unit capable of covalently bonding the polymer to the sieve. A published single-wall carbon nanotube (SWCNTs) modification method was adopted to attach a primary aromatic amine to the surface. Several aspects including rigidity, chemical composition, bulky groups and length were considered in selecting the preferred linkage unit. Fortunately kinetic and equilibrium sorption properties of the modified sieves showed very little difference from unmodified samples, suggesting that the linkage unit is not excessively filling or obstructing access to the pores of the CMSs during the modification process.

Silver nanoparticles embedded phosphomolybdate–polyaniline hybrid electrode for electrocatalytic reduction of H2O2

Hybrid silver/phosphophomolybdate/polyaniline (Ag/PMo12/PAni) was obtained through one pot synthesis, and then, it was successfully fabricated on the glassy carbon electrode by simple casting method for electrocatalytic reduction of hydrogen peroxide (H2O2). The cyclic voltammetric studies of the Ag/PMo12/PAni hybrid electrode suggest that the electronic properties of the phosphomolybdate are retained even after the formation of hybrid material and in addition effectively electro-catalyzing the reduction of H2O2 with a less negative over potential. The Ag/PMo12/PAni-modified electrode showed the lowest detection limit (750 nM) for H2O2 reduction among the hybrid-modified electrodes already reported with a sensitivity of 4.398 nA μM−1. The prepared hybrid material was well characterized by using UV, XRD and TEM analysis.

Preparation and characterization of EP/SiO2 hybrid materials containing PEG flexible chain

EP/SiO2 hybrid materials, which contained flexible chain, were prepared by epoxy resin (EP) and polyethylene glycol (PEG)-grafted polysilicic acid (PSA), which was obtained by endcapping polyethylene glycol-1000 with toluene 2,4-diisocyanate (TDI), followed by a reaction with polysilicic acid. The formation of hybrid materials was confirmed by a wide-angle X-ray diffraction (WAXD) and atomic force microscopy (AFM) analysis. Results showed that the EP/SiO2 hybrid particles were nanosized and the average size was about 20–50 nm. The mechanical properties, dynamic mechanical properties, and thermal properties were evaluated and compared with the corresponding matrix. The improvement in impact properties in hybrid materials was explained in terms of the impact fracture surface analysis by scanning electron microscope (SEM).

Conventional Screening Overlooks Resistance Sources: Rootworm Damage of Diverse Inbred Lines and Their B73 Hybrids Is Unrelated

The western corn rootworm, Diabrotica virgifera virgifera (LeConte), is a major pest of maize, Zea mays L., in the United States and Europe, and it is likely to increase in importance as a trend toward increased nonrotated maize favors larger rootworm populations. Options for rootworm management in nonrotated maize in Europe and in nontransgenic "refuge" areas in countries that permit transgenic maize are limited to insecticides. Development of additional options for growers would be helpful. Screening maize germplasm (e.g., landraces, populations, inbreds) for native resistance to western corn rootworm is labor-intensive and is usually conducted on unfinished germplasm and not on hybrid materials. However, we have recently observed that topcrossed (hybrid) materials tend to have reduced western corn rootworm damage. To formally test whether rootworm damage to inbreds and associated hybrids were correlated, we evaluated 25 diverse inbred lines and their B73 hybrids for western corn rootworm damage in seven environments. Overall, hybrids had significantly less damage than inbreds, but unfortunately, the correlation between inbreds and hybrids was not significant. These findings have important implications regarding screening germplasm for western corn rootworm resistance, namely, that inbred materials and perhaps populations should be topcrossed to form hybrid materials before screening for western corn rootworm damage to ensure that valuable sources of resistance to western corn rootworm are not missed during the screening process.

Heterogeneous ring‐opening polymerization of lactones for biomedical applications

AbstractCatalysis of the ring‐opening reaction of L‐lactide and ε‐caprolactone to form the corresponding biodegradable polyesters is frequently performed using organometallic compounds such as tin(II) 2‐ethylhexanoate, which operates by a living, coordination insertion mechanism. For biomedical applications, non‐toxic calcium salts have been researched but these rarely approach the same efficiency. The use of heterogeneous immobilized catalysts offers an alternative approach, but competing reactions such as transesterification affect the final molecular weight and polydispersity. The formation of hybrid materials by using silica as the initiation site offers the prospect of biomaterials with novel properties. Copyright © 2009 Society of Chemical Industry

Meta‐Phosphonobenzoic Acid: A Rigid Heterobifunctional Precursor for the Design of Hybrid Materials

AbstractRigid meta‐phosphonobenzoic acid 2 possesses two functional groups (phosphonic acid and carboxylic acid) both having the aptitude to associate with a metallic precursor to form hybrid materials. The hydrothermal reactions of compound 2 with MnCl2·4H2O or Co(NO3)2·6H2O produce, respectively, the isostructural layered materials M(H2O)(PO3C6H4CO2H) (3, M = Mn; 4, M = Co) characterized by the presence of the free carboxylic acid groups in the interlayer space (space group P21/n). The reaction of Zn(CH3COO)2·2H2O with 2 produces two different materials depending on the pH of the reaction media. At low pH (pH < 4.1), the isostructural material Zn(H2O)(PO3C6H4CO2H) (5) is formed possessing ZnII atoms octahedrally coordinated. At higher pH, generated by the addition of urea in the hydrothermal reaction, Zn3(H2O)2)(PO3C6H4CO2)2 (6) is formed (orthorhombic; space group Pcan). In material 6, the phosphonic acid and the carboxylic acid groups are linked to the inorganic network. One of the two ZnII centres is tetrahedrally coordinated and the other is surrounded by a trigonal bipyramid. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Silica-based organic–inorganic hybrid materials prepared from chiral precursors

Abstract New organic–inorganic hybrid silica-based materials containing chiral moieties have been prepared by sol–gel hydrolysis–condensation of tartaramide enantiomer precursors. The new chiral precursors were characterized by means of FTIR, 13 C, 29 Si and 1 H NMR, specific rotation and elemental analysis. Their hydrolysis led to the formation of hybrid materials containing an organic (chiral)–inorganic (silica) network. The obtained chiral xerogels were studied using 13 C and 29 Si CP MAS NMR spectra, which indicated the insertion of the chiral precursors into the inorganic network, as well as condensation degrees higher than 73%. XRD was also applied in order to analyse the xerogel's organization, indicating that the catalyst played a fundamental role in the kinetics of these hybrid materials.

Nanocomposite UV-cured coatings: Organoclay intercalation by an epoxy resin

Polymer layered silicate nanocomposites can be obtained using several methods. In this work in situ intercalative polymerisation is applied together with the ultraviolet (UV)-curing technique to produce hybrid materials in form of films. With this approach polymeric thermoset matrices can be obtained through a fast and environmentally safe process. Organophilic clays have been dispersed in UV-curable epoxy oligomers by ultrasonication. The suspension was added with a diol to improve curing kinetics and final conversion. The organic–inorganic hybrids obtained have been characterised by means of different techniques. The liquid resin mixed with clay and diol has been rheologically characterised in the linear viscoelastic region. In the presence of clays the epoxy monomer, which normally behaves as a Newtonian liquid, develops a solid-like behaviour in the low-frequency region. The diol addition determines an increase in the plateau modulus suggesting a better dispersion of the clay within the matrix.

Solvent effects in the formation of hybrid materials based on titanium alkoxide-polysiloxane precursors

Hybrid TiO2-polysiloxane nanoparticles as well as hybrid TiO2-polysiloxane gels were prepared and characterized applying solvent-induced aggregation effects of titanium alkoxide-modified polysiloxane block copolymers. The functionalized polymers were prepared by the covalent attachment of coordination sites that allow the binding to metal alkoxides (M(OR)4; M = Ti; R = ethyl, butyl, isopropyl). Composition and structure of the hybrid polymers were investigated by NMR and FT-IR spectroscopy. In a second step the metal-alkoxide functionalities were hydrolyzed to form the respective metal oxides. Depending on the solvent in which the hydrolysis took place, hybrid nanoparticles or gels were obtained as a result of the different compatibility of the polysiloxane blocks towards the polarity of the solvents. The formed materials were investigated by NMR, FT-IR, atomic force microscopy (AFM), electron microscopy, and dynamic light scattering (DLS).

Synthesis and characterization of nanoporous phospho-tungstate organic–inorganic hybrid materials

Nanoporous phospho-tungstate organic–inorganic hybrid materials have been synthesized from sodium tungstate and mono-n-dodecyl phosphate (MDP), which was used as both surfactant and phosphorus precursor. These hybrid materials were thoroughly characterized by N2 adsorption, elemental analysis, powder XRD, FTIR, Raman, TG, TEM and XPS and possess lamellar structures with interlayer spacings of 3.2 nm. A plausible method for formation of hybrid materials comprised of lacunary Keggin anions and micelles of surfactants is proposed.

A novel way to prepare luminescent hybrid materials derived from 5-chloromehtyl-8-hydroxyquinoline and silylated monomer with coordination to aluminum ion

In this article, a new method to synthesize novel metaloquinolate-contained electroluminescent hybrid materials is reported. The small molecule metal complex monomer was obtained from the reaction of 3-piperazinepropylmethyldimethoxysilane and 5-chloromethyl-8-quinolinol hydrochloride. Then the silylated metaloquinolate-contained monomer was complexed with aluminum ion and further introduced into silica matrices by Si–O bonds and formed hybrid materials after hydrolysis and polycondensation processes. FT–IR, UV, NMR, SEM, TGA, luminescence spectra and luminescence quantum yields were used to characterize the obtained hybrid materials. It was found from the scanning electron micrographs (SEM) results that no phase separation occurred in 8-hydroxyquinoline aluminum complexes-silicone hybrid materials. The target materials were thermally stable until 380 °C and exhibited high quantum yield (43%). Such materials should combine the fluorescent properties of metalloquinolate and good mechanical properties, stability, and processability of organosilicone to improve device efficiencies and work lifetimes, and should be of interest for OLED applications.

Cellulose‐Nanocomposites: Towards High Performance Composite Materials

AbstractSummary: Strong cellulose fibres, e.g. flax and hemp, are increasingly used for composites. Despite substantial advantages, the tensile strength of these fibres is limited due to their complex structure and the unavoidable imperfections of the cell wall, inherent from growth or induced by processing. Essential improvements are possible by using highly crystalline cellulose fibrils (“whiskers”) which can be isolated from the cell wall, thus eliminating the influence of adhesion and defects. Instead of complete fibrillation, which demands special time consuming processing, a partly fibrillation has been achieved by adapted textile finishing procedures which have the potential for mass production. By combining chemical and mechanical/hydro‐mechanical treatments it is possible to produce finest fibrils with diameters from below 1 µm down to the nanometer range. The problem of fibril agglomeration during drying has been avoided by forming homogenous fibrous sheets in a wet‐laid non‐woven process. These sheets can be impregnated with thermosetting resins. Alternatively thermoplastic polymers can be directly integrated to form hybrid materials ready for moulding. The resulting composites show greatly enhanced mechanical properties.

Preparation and application of fluorocarbon polymer/SiO2 hybrid materials, part 1: Preparation and properties of hybrid materials

AbstractFor this study, we first prepared a fluorocarbon polymer and its hybrid materials. We found that fluorocarbon copolymers can produce hydrogen bonds with SiO2 to form hybrid materials. We also used thermogravimetric analyzer and tested the thermostabilities of the four products, which were ranked as follows: fluorocarbon copolymer/SiO2 hybrid material > fluorocarbon polymer/SiO2 hybrid material > fluorocarbon copolymer > fluorocarbon polymer. In addition, we found that, due to the inorganic SiO2 used, the number of pores and the specific surface areas of the hybrid materials both increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1140–1145, 2007

Genetically engineered polypeptides for inorganics: A utility in biological materials science and engineering

Adapting molecular biology to materials science we developed peptide-based protocols for the assembly and formation of hybrid materials and systems. In this approach of generating molecular scale biomimetic materials, peptides are designed, synthesized, genetically tailored and, finally, utilized as potential molecular linkers in self-assembly, ordered organization, and fabrication of inorganics for specific technological applications. The potential areas range from molecular and nanoscale functional materials to medical fields, e.g., from diagnosis to biosensors. Here, we describe a selection of inorganic binding polypeptides via directed evolution, post-selection modifications through genetic engineering, and utility in practical applications. The selection of the inorganic binders is accomplished through combinatorial biology based peptide libraries. The diversity of applications is highlighted in three case studies. First, the molecular and nanoscale recognition of the polypeptide is presented via nanosize gold particle immobilization onto a molecular template by gold binding polypeptide. Second, we present that the alkaline phosphatase fused with multiple repeats of gold binding polypeptide can still be enzymatically active when it is immobilized onto a solid substrate. Finally, we present silica biosynthesis in aqueous environment using engineered quartz-binding peptides.

Electrochemical Organization of Monolayer Protected Gold Nanoclusters on Single-Walled Carbon Nanotubes: Significantly Enhanced Double Layer Capacitance

This paper reports a novel electrochemical route for anchoring monolayer protected gold nanoclusters (size 8 +/- 0.2 nm) on single-walled carbon nanotube bundles, resulting in the formation of hybrid materials. Monolayer protected gold nanoclusters prepared by modified Brust synthesis route were organized on SWNT bundles by cycling the potential in dichloromethane between -1 to +1 V at a scan rate of 50 mV/s. Monolayer protected nanoclusters in electrolyte solutions possess ionic space charge around them (double layer charging), making them suitable for organization on nanotube bundles, by tuning the electrostatic interactions. More significantly, analysis of the double layer capacitance of these hybrid materials shows almost ten times increase in capacitance compared to that of bare SWNT bundles. We believe that these hybrid materials are potentially useful in nanoelectronics.

Using silica nanoparticles for modifying sulfonated poly(phthalazinone ether ketone) membrane for direct methanol fuel cell: A significant improvement on cell performance

Sulfonated poly(phthalazinone ether ketone) (sPPEK) with a degree of sulfonation of 1.23 was mixed with silica nanoparticles to form hybrid materials for using as proton exchange membranes. The nanoparticles were found homogeneously dispersed in the polymer matrix and a high 30 phr (parts per hundred resin) loading of silica nanoparticles can be achieved. The hybrid membranes exhibited improved swelling behavior, thermal stability, and mechanical properties. The methanol crossover behavior of the membrane was also depressed such that these membranes are suitable for a high methanol concentration in feed (3 M) in cell test. The membrane with 5 phr silica nanoparticles showed an open cell potential of 0.6 V and an optimum power density of 52.9 mW cm −2 at a current density of 264.6 mA cm −2, which is better than the performance of the pristine sPPEK membrane and Nafion ® 117.