Nanocomposite Assembly Research Articles

Potentiometric determination of Pb2+ ions using hybrid assembly of zinc oxide@polyaniline nanocomposites

ABSTRACT Over the recent years, the detection and determination of level of pollutant in environment have become indispensable. This allows for the adoption of various methods to evade the pollution caused by these toxicant entities. This has enhanced the interest of researchers to develop sustainable sensors to determine the trace level concentration of harmful target species. Although the list of these pollutants is undoubtedly too long, toxic metal ions, like Pb2+ ions beyond certain limit, can severely endanger the whole ecosystem. Therefore, the present study is dedicated toward the development of Pb2+ ion-selective electrode based on the membrane of zinc oxide/polyaniline nanocomposites. Nanocomposite assembly was synthesized using in-situ chemical oxidative polymerization method and characterized using spectroscopic techniques, such as energy‐dispersive spectroscopy, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, dynamic light scattering, etc. The proposed potentiometric sensor exhibits excellent selectivity toward Pb2+ ions with detection limit of 2.239 × 10−6 M, Nernstian slope of 23.31 ± 2.5 mV decade−1 and a wide linear concentration range of 1.0 × 10−5 M to 1.0 × 10−1 M. Moreover, the designed Pb2+ ion-selective electrode was successfully examined for its practical applicability in Pb2+−EDTA complexometric titration as well as potentiometric determination of concentration of Pb2+ ions in real-life samples.

A Comparative Study of ZnS–ZnO Nanocomposite Assembly for Photocatalytic Removal of Crystal Violet Dye

Herein, the effect of composition on the optical and photocatalytic performance of ZnS–ZnO composite is described. The composite samples are synthesized by chemical precipitation method using (NaOH + Na2S) mixture as the precipitating agent. The chemical composition of precipitating agent results in in situ formation of ZnO and ZnS. Lower content of NaOH in precipitating agent solution (1:3 by volume) exhibits the formation of ZnS, while, its higher concentration induces the phase separation with higher volume fraction of ZnO as observed from X‐ray diffraction patterns. Optical studies suggest the enhancement of visible absorption along with redshift in the absorption edge of composites as compared with bare ZnS nanoparticles (NPs). Moreover, the incorporation of ZnO with ZnS is also supported by optical emission spectra in which intense emission around 507 nm is associated with S‐species. ZnO encapsulation on ZnS NPs exhibits higher emission associated with O‐ defects as compared to S‐species. Since both are near‐UV excited semiconductors, both contribute toward the generation of charge carriers to produce radicals and hence photo‐oxidation of crystal violet dye. Further, little concentration of ZnO with ZnS NPs exhibits comparable photocatalytic efficiency (≈88%) that is observed with other ZnS–ZnO nanocomposite samples.

Preparation and Photocatalytic/Photoelectrochemical Investigation of 2D ZnO/CdS Nanocomposites

Properties of heterotructured semiconductors based on ZnO/CdS nanosheets are investigated for their possible application in photocatalytic and photoelectrochemical reactions. Semiconductor material is the main active coating of photoanodes, which triggers the half-reaction of water oxidation and reduction, which entails the purifying or splitting of water. This article explains nanocomposite assembly by convenient and simple methods. The study of the physicochemical properties of semiconductor layers is carried out using electron microscopy, X-ray diffractometry, and UV-visible spectroscopy. Studies of electrochemical properties are carried out by potential static methods in electrochemical cells.

Electrochemical sensor based on ion-selective membrane of silica/polyaniline nano-composites for selective determination of uranyl ions

Life threatening impacts of uranium have necessitated its detection and determination in economically feasible way before it arrives in living bodies. Therefore, a new form of UO22+ ion-selective electrode has been fabricated based on membrane of silica/polyaniline core-shell nano-composites, in-spite of traditionally used ionophores, because of intrinsically conducting nature of polyaniline. For the synthesis of these nano-composites, silica has been extracted from rice straw in its cristobalite form, whereas the layer of polyaniline shell has been grafted on silica nanoparticles through in-situ chemical oxidative polymerization technique by cautiously maintaining the electro-active nature of these core-shell nano-composites. The chemical composition, purity, topography, morphology and surface polarity of this nano-composite assembly have been studied through various spectroscopic techniques such as, FT-IR, EDS, FESEM, UV–Vis, DLS and Raman spectroscopy. The results confirm that silica/polyaniline nano-composites have been synthesized with desired semi-cavities and electrostatic surface charge, which is responsible for binding with target cation, i.e., UO22+for its potentiometric determination in aqueous medium even in the presence of interfering metal ions. The designed potentiometric sensor has shown fast and stable linear response in concentration range of 1 × 10−6 to 1 × 10−2 M with the limit of detection of 1.4 × 10−7 M which is 100-folds lower than the detection limit calculated using spectrofluorometry. In addition to this, the proposed UO22+ion-selective electrode has been successfully employed as an indicator electrode for the determination of uranyl ions in complexometric titration and for the estimation of UO22+ions in real life based environmental sample, i.e., soil.

A Lipid-Coated Nanoconstruct Composed of Gold Nanoparticles Noncovalently Coated with Small Interfering RNA: Preparation, Purification and Characterization.

There is an urgent need to develop systems for nucleic acid delivery, especially for the creation of effective therapeutics against various diseases. We have previously shown the feasibility of efficient delivery of small interfering RNA by means of gold nanoparticle-based multilayer nanoconstructs (MLNCs) for suppressing reporter protein synthesis. The present work is aimed at improving the quality of preparations of desired MLNCs, and for this purpose, optimal conditions for their multistep fabrication were found. All steps of this process and MLNC purification were verified using dynamic light scattering, transmission electron microscopy, and UV-Vis spectroscopy. Factors influencing the efficiency of nanocomposite assembly, colloidal stability, and purification quality were identified. These data made it possible to optimize the fabrication of target MLNCs bearing small interfering RNA and to substantially improve end product quality via an increase in its homogeneity and a decrease in the amount of incomplete nanoconstructs. We believe that the proposed approaches and methods will be useful for researchers working with lipid nanoconstructs.

High-energy Al/graphene oxide/CuFe2O4 nanocomposite fabricated by self-assembly: Evaluation of heat release, ignition behavior, and catalytic performance

As part of our ongoing search for high-performance nanoenergetic materials, we herein used self-assembly guided by negatively charged graphene oxide (GO) to fabricate a high-energy Al/GO/CuFe2O4 nanocomposite with a dense layered structure featuring evenly mixed Al and CuFe2O4 nanoparticles uniformly loaded on the GO surface. Investigation of the effects of the equivalence ratio (Φ ​= ​1.00–1.75) showed that the heat release achieved at the optimal value of Φ ​= ​1.50 (3175 ​± ​65 ​J·g−1) exceeded that of most known thermites, while the fierce ignition process of this composite was characterized by an ignition delay time of (0.025 ​± ​0.002) s, a flame propagation speed of (14.3 ​± ​3.8) m·s−1, and a continuous reaction duration of (33 ​± ​0.58) ms. In addition, the nanocomposite with Φ ​= ​1.00 effectively catalyzed the thermal decomposition of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) and ammonium perchlorate (AP), decreasing their decomposition temperatures by 7.4 and 64.8 ​°C, respectively, reducing their apparent activation energies of decomposition by 118.7 and 18 ​kJ·mol−1, respectively. And the constant-volume combustion enthalpies of RDX and AP increase with the addition of Al/GO/CuFe2O4. The reason of this enhanced performance was probed by analyzing the nanocomposite assembly process, and a plausible assembly mechanism was proposed.

A micromilled microgrid sensor with delaminated MXene-bismuth nanocomposite assembly for simultaneous electrochemical detection of lead(II), cadmium(II) and zinc(II)

A delaminated MXene-bismuth (Bi@d-Ti3C2) nanocomposite was synthesized for the construction of a microgrid electrochemical sensor via mechanical milling. The Bi@d-Ti3C2 nanocomposite was synthesized by accumulation of Bi(III) on the surface of delaminated Ti3C2 nanosheets through electrostatic attraction and subsequent in-situ growth of bismuth nanorods. Under optimized experimental conditions, the sensor exhibits (a) linear responses to Pb(II), Cd(II) and Zn(II) in the concentration range from 1 to 20μgL-1, (b) well separated peak potentials at -0.54V, -0.76V and - 1.15V vs. Ag/AgCl, (c) sensitivities of 0.98, 0.84 and 0.60μALμg-1, and (d) detection limits of 0.2, 0.4 and 0.5μgL-1, respectively. This performance is attributed to the uniform dispersion of Bi nanorods on electrically conductive delaminated Ti3C2 MXene, and to the enhanced diffusion due to the microgrid structure. Graphical abstractSchematic representation of a microgrid sensor based on delaminated MXene-bismuth (Bi@d-Ti3C2) nanocomposite for the simultaneous electrochemical determination of Pb(II), Cd(II) and Zn(II).

Poly(N‐octadecylaniline) Synthesized at the Air‐Water Interface: Aligned Nanofibers and Gold Nanocomposite Assembly via the Langmuir‐Blodgett Technique

AbstractMorphological and organizational control afforded by polymerization at the air‐water interface, and the unique structural features of poly(N‐alkylaniline)s are exploited in the fabrication of the polymer and polymer‐nanoparticle composites in micro and nanofiber (ultrathin film) forms. While ammonium peroxodisulfate as the oxidizer provides poly(N‐octadecylaniline) (PNOA), chloroauric acid leads to the nanocomposite, PNOA_Au. Experiments using relatively larger amounts of the monomer in a petri‐dish produced PNOA and PNOA_Au microfibers that could be characterized using spectroscopy, microscopy and electrical conductivity measurement. Polymerization in monolayer Langmuir films under surface pressure control in a Langmuir‐Blodgett (LB) trough, allowed the kinetics to be monitored, and ultrathin films of PNOA and PNOA_Au to be fabricated. The PNOA LB film shows nanofibers with twists, turns and helical segments, aligned parallel to the direction of monolayer compression; a computational model suggests a helical chain structure for PNOA formed at the interface. The polymer nanofibers are decorated with Au nanoparticles in the PNOA_Au film.

Mechanisms Underlying the Active Self-Assembly of Microtubule Rings and Spools.

Active self-assembly offers a powerful route for the creation of dynamic multiscale structures that are presently inaccessible with standard microfabrication techniques. One such system uses the translation of microtubule filaments by surface-tethered kinesin to actively assemble nanocomposites with bundle, ring, and spool morphologies. Attempts to observe mechanisms involved in this active assembly system have been hampered by experimental difficulties with performing observation during buffer exchange and photodamage from fluorescent excitation. In the present work, we used a custom microfluidic device to remove these limitations and directly study ring/spool formation, including the earliest events (nucleation) that drive subsequent nanocomposite assembly. Three distinct formation events were observed: pinning, collisions, and induced curvature. Of these three, collisions accounted for the majority of event leading to ring/spool formation, while the rate of pinning was shown to be dependent on the amount of photodamage in the system. We further showed that formation mechanism directly affects the diameter and rotation direction of the resultant rings and spools. Overall, the fundamental understanding described in this work provides a foundation by which the properties of motor-driven, actively assembled nanocomposites may be tailored toward specific applications.

Building a hybrid nanocomposite assembly of gold nanowires and thienyl-derivative fullerenes to enhance electron transfer in photovoltaics

We report the preparation and characterization of a novel nanocomposite assembly comprising metallic gold nanowires (Au NWs) and thienyl-C61-butyric acid methyl ester (ThCBM) fabricated by adsorbing ThCBM groups, via coordinate bonds involving sulfur functionalities, onto the Au(111) surfaces of Au NWs. The ThCBM-adsorbed Au NW nanocomposites displayed clear shifts in the plasmonic absorption band and in the binding energy of the gold relative to the pure gold NWs. A bulk heterojunction solar cell using the ThCBM-adsorbed Au NW nanocomposites displayed a good power conversion efficiency (PCE) of 3.12%, and a short circuit current density and fill factor that were significantly better than those of a reference cell prepared using ThCBM without Au NWs (with a PCE of 2.67%). The electron mobility in an electron-only device prepared using the ThCBM-adsorbed Au NW nanocomposites was significantly higher (by 35% or more) than the electron mobility in a device prepared with pure ThCBM. In conclusion, the hybrid composites proposed here, i.e., ThCBM-adsorbed Au NW nanocomposites, provide a promising approach to improving the performance of bulk heterojunction photovoltaic cells via improved electron transfer through the metallic nanowires as well as by enhanced ordering among the fullerenes assembled along the longitudinal axes of the gold nanowires.

Inorganic–Organic Nanocomposite Assembly Using Collagen as a Template and Sodium Tripolyphosphate as a Biomimetic Analog of Matrix Phosphoprotein

Nanocomposites created with polycarboxylic acid alone as a stabilization agent for prenucleation clusters-derived amorphous calcium phosphate exhibit non-periodic apatite deposition. In the present study, we report the use of inorganic polyphosphate as a biomimetic analog of matrix phosphoprotein for directing polyacrylic acid-stabilized amorphous nanoprecursor phases to assemble into periodic apatite-collagen nanocomposites. The sorption and desorption characteristics of sodium tripolyphosphate to type I collagen was examined. Periodic nanocomposite assembly with collagen as a template was demonstrated with TEM and SEM using a Portland cement-based resin composite and a phosphate-containing simulated body fluid. Apatite was detected within the collagen at 24 hours and became more distinct at 48 hours, with prenucleation clusters attaching to the collagen fibril surface during the initial infiltration stage. Apatite-collagen nanocomposites at 72 hours were heavily mineralized with periodically-arranged intrafibrillar apatite platelets. Defect-containing nanocomposites caused by desorption of TPP from collagen fibrils were observed in regions lacking the inorganic phase.

有机阳离子-无机多阴离子复合物: 高分子体系中的组装及其自组装

Organic cation-encapsulated inorganic polyoxometalate polyanion supramolecular complexes exhibiting defined chemical composition and amphiphilic core-shell structure, which lead to tunable and synergetic structure and function of organic and inorganic components were summarized in this review. The self-assembly and polymer functional composite materials based on this type of complexes as pre-organization units were introduced to reveal a novel type of building block system for various supramolecular assemblies. The strategies to achieve the assembly and functionality in structure stable and well processable matrixes based on the pre-organization complexes were thought the key content of research in this field. It was believed highly important to assemble and functionalize the complexes in a well dispersed way in polymer materials. This review summarized the development of polymer nano-composite materials and assembly in solution based on the supramolecular complexes, and a perspective was anticipated.

Special method to prepare quantum dot probes with reduced cytotoxicity and increased optical property

Quantum dots (QDs) are widely used in the life sciences because of their novel physicochemical properties. However, the cytotoxity of these nonoparticles have attracted great attention recently because this has not been well resolved. Four probes were synthesized by chemical coupling and protein denaturation with CdSeZnS, CdTe QDs, and transferrin. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and capillary electrophoresis were used to verify the conjugation of these luminescent probes. The cytotoxicity of these four luminescent probes and the original QDs were evaluated in HeLa cells. The results showed that over 92% of HeLa cells were still alive after being exposed to 3.2-microM CdSeZnS QDs capped with denatured transferrin for 72 h. Furthermore, while the probe preparation was very simple, the photoluminescence quantum yield of this probe was 7% higher than the original CdSeZnS QDs. This provides a new way for exploiting QD probes with low cytotoxicity, which will expand applications of nanocomposite assembly in biolabeling and imaging.

Controlled nanoparticleassembly through protein conformational changes.

Selective surface recognition by proteins provides programmed bottom-up assembly of synthetic nanomaterials. We have investigated the controlled self-assembly of functionalized gold nanoparticles (Au-TAsp) with cytochrome c (Cyt c) and apoCyt c through complementary electrostatic interactions. Au-TAsp formed discrete, water-soluble adducts with native Cyt c, whereas unfolded apoCyt c induced nanocomposite formation at high Cyt c : Au-TAsp ratios. The binding of random-coil apoCyt c to Au-TAsp at low ratios induced α-helix formation in soluble nanocomposites, but at elevated ratios insoluble micron-scale aggregates were formed. The local structure of the assemblies was critically dependent on the Cyt c : Au-TAsp ratio. The dispersibility of apoCyt c-Au-TAsp was pH dependent, providing rapid and reversible control over nanocomposite assembly. The apoCyt c-Au-TAsp aggregates could likewise be disassembled through proteolytic cleavage of apoCyt c, demonstrating the ability to selectively remodel these hybrid materials.

Formation of luminescent nanocomposite assemblies via electrostatic interaction

A novel luminescent nanocomposite assembly was prepared in aqueous solutions, via the electrostatic interaction between poly(ethylene glycol)- b-poly( N , N -dimethylaminoethyl methacrylate) (PEG- b-PDMAEMA) double hydrophilic block copolymer (DHBC) and thioglycolic acid (TGA)-stabilized CdTe quantum dots (QDs). By tuning the molar ratios of QDs to DHBC, the nanocomposite assemblies could be well controlled and the dimension of these regular spherical QDs/PEG- b-PDMAEMA assemblies ranged from 40 to 75 nm in aqueous media. As the periphery of QDs/PEG- b-PDMAEMA nanocomposite assembly was composed of PEG segments when the PDMAEMA blocks and QDs were immobilized inside the assembly, the cytotoxicity of the assembly was significantly reduced, compared with that of pure PEG- b-PDMAEMA and QDs. The nanocomposite assembly also exhibited superior stability in salt solutions and remained strongly photoluminescent even when free radicals existed. Thus, the QDs/PEG- b-PDMAEMA nanocomposite assembly is potentially useful for a number of applications in biolabeling and imaging.

SYNTHESIS OF CALCIUM OXALATE ASSEMBLY STRUCTURE AND CONVERSION

The conversion from one assembly structure to other composite assembly structures is valuable to both theoretical research and actual application in the nano/micromaterials science. In this paper, firstly, the flower-like calcium oxalate assembly structure was synthesized using a supramolecule template; then, through a facile process, the calcium oxalate was converted to a sphere-cluster-like core/shell CaC 2 O 4/ CaWO 4 nanocomposite assembly structure. The converted product remained the basic structure of original product, and possessed some new optical properties such as fluorescence, etc.

Cover Picture: Macromol. Rapid Commun. 21/2006

Cover: An electrodeposition process is used to be an effective means of nanocomposite assembly directly onto Cu electrodes. This approach enables the simultaneous formation of the hybrid nanocomposite containing BaTiO3 nanoparticles covered with PMMA and Al metallic inclusions. Stabilization of colloidal BaTiO3 suspensions by the adsorbed PMMA is achieved. The hybrid three phase nanocomposites were assembled on Cu electrodes by incorporating Al nitrate salt into the suspension. Further details can be found in the article by D.‐W. Kim,* D.‐H. Lee, B.‐K. Kim, H.‐J. Je, and J.‐G. Park on page 1821.

Continuous self-assembly of organic–inorganic nanocomposite coatings that mimic nacre

Nanocomposite materials are widespread in biological systems. Perhaps the most studied is the nacre of abalone shell, an orientated coating composed of alternating layers of aragonite (CaCO3) and a biopolymer. Its laminated structure simultaneously provides strength, hardness and toughness: containing about 1 vol. % polymer, nacre is twice as hard and 1,000 times as tough as its constituent phases1. Such remarkable properties have inspired chemists and materials scientists to develop synthetic, ‘biomimetic’ nanocomposite assemblies2,3,4,5. Nonetheless, the efficient processing of layered organic–inorganic composites remains an elusive goal. Here we report a rapid, efficient self-assembly process for preparing nanolaminated coatings that mimic the structure of nacre. Beginning with a solution of silica, surfactant and organic monomers, we rely on evaporation during dip-coating to induce the formation of micelles and partitioning of the organic constituents into the micellar interiors6. Subsequent self-assembly of the silica–surfactant–monomer micellar species into lyotropic mesophases7 simultaneously organizes the organic and inorganic precursors into the desired nanolaminated form. Polymerization fixes this structure, completing the nanocomposite assembly process. This approach may be generalized both to other composite architectures and to other materials combinations.