Nanocomposites, composed of organic and inorganic building blocks, can combine the properties from the parent constituents and generate new properties to meet current and future demands in functional materials. Recent developments in nanoparticle synthesis provide a plethora of inorganic building blocks, building the foundation for constructing hybrid nanocomposites with unlimited possibilities. The properties of nanocomposite materials depend not only on those of individual building blocks but also on their spatial organization at different length scales. Block copolymers, which microphase separate into various nanostructures, have shown their potential for organizing inorganic nanoparticles in bulk/thin films. Block copolymer-based supramolecules further provide more versatile routes to control spatial arrangement of the nanoparticles over multiple length scales. This review provides an overview of recent efforts to control the hierarchical assemblies in block copolymer-based hybrid nanocomposites.
Due to the bicontinuous phase structure of Nafion® with small hydrophilic channels, formation of composites with silica colloids to improve thermal stability, hydration and proton conductivity should be influenced by size and surface functionality of the colloids. To test this hypothesis we prepared batches of silica particles between 20 - 400 nm in diameter with narrow polydispersities using a modified Stöber procedure. Some particles were subsequently surface modified using mercaptopropyltriethoxysilane. Enough particles were mixed with Nafion® in alcohols to achieve 5wt% silica in the final membranes, which were made by casting and drying. Membrane top and bottom surface and cross-section morphologies were examined with AFM and SEM to determine how the particles were dispersed. We discovered that casting the membranes from dispersions with viscosities less than 65 Centapoise led to larger particles floating to the top surface of the membrane where they were easily dislodged from the dry membrane. Membranes cast from more viscous solutions exhibited homogeneous distributions of particles. Water up-take was over 60% higher in nanocomposites with un-modified silica particles than for Nafion® and about 15% higher than for Nafion® with in situ generated silica particles, but showed no trend in water uptake correlating with changing particle size. Surface silated particles of all sizes appeared to have reduced water uptake relative to Nafion® alone.
The combination of magnetic particles and layered double hydroxide (LDHs) materials leads to the formation of hierarchical composites that can take full advantages of each component; this is an effective approach for achieving multifunctional materials with intriguing properties. This Concept article summarizes several important strategies for the fabrication of magnetic-core/LDH-shell hierarchical nanocomposites, including direct coprecipitation, layer-by-layer assembly, and in situ growth methods. The obtained nanocomposites exhibit excellent performance as multifunctional materials for promising applications in targeted drug delivery, efficient separation, and catalysis. The fabrication and application of magnetic-core/LDH-shell nanocomposite materials represent a new direction in the development of LDH-based multifunctional materials, which will contribute to the progress of chemistry and material science.
Graphene-based polymer nanocomposites have attracted increasing interest because of their superior physicochemical properties over polymers. Semiconductor conjugated polymers (CPs) with excellent dispersibility and stability, and efficient electronic and optical properties have been recently integrated with graphene to form a new class of functional nanomaterials. In this minireview, we will summarize the recent advances in the development of graphene-CP nanocomposites for electronic device applications.
- Journal of biomedical materials research. Part B, Applied biomaterials
- Published about 6 years ago
Bone is a nanocomposite composed of organic (mainly collagen) and inorganic (nanocrystalline hydroxyapatite) components, with a hierarchical structure ranging from nano- to macroscale. Its functions include providing mechanical support and transmitting physio-chemical and mechano-chemical cues. Clinical repair and reconstruction of bone defects has been conducted using autologous and allogeneic tissues and alloplastic materials, with functional limitations. The design and development of biomaterial scaffolds that will replace the form and function of native tissue while promoting regeneration without necrosis or scar formation is a challenging area of research. Nanomaterials and nanocomposites are promising platforms to recapitulate the organization of natural extracellular matrix for the fabrication of functional bone tissues because nanostructure provides a closer approximation to native bone architecture. Nanostructured scaffolds provide structural support for the cells and regulate cell proliferation, differentiation, and migration, which results in the formation of functional tissues. Unique properties of nanomaterials, such as increased wettability and surface area, lead to increased protein adsorption when compared with conventional biomaterials. Cell-scaffold interactions at the cell-material nanointerface may be mediated by integrin-triggered signaling pathways that affect cell behavior. The materials selection and processing techniques can affect the chemical, physical, mechanical, and cellular recognition properties of biomaterials. In this article, we focused on reviewing current fabrication techniques for nanomaterials and nanocomposites, their cell interaction properties and their application in bone tissue engineering and regeneration. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2012.
A facile one-step solvothermal approach was developed to synthesize BiPO4-graphene (BP-RGO) nanocomposites using ethylene glycol/water as the solvent and reducing agent. During the solvothermal reaction, both the effective reduction of graphene oxide (GO) and the growth of rod-shaped BiPO4 as well as its deposition on graphene occurred simultaneously. The as-obtained BP-2%RGO nanocomposite showed the highest photocatalytic activity toward the photodegradation of methyl orange (MO), which was about 2.0 and 1.5 times as high as that of pure BiPO4 and physical mixture of BiPO4 and graphene, respectively. The enhanced photocatalytic activity of BP-2%RGO nanocomposite is attributed to a larger surface area, much increased adsorption capacity, and more effective charge transportations and separations arisen from the introduction of graphene along with the intimate interfacial contact between BiPO4 and graphene. This work highlights the significant effect of solvothermal method and introduction of graphene on the photoactivity of graphene-based nanocomposites. It is expected that this method could aid to fabricate more efficient graphene-based photocatalysts with improved interfacial contact and photocatalytic performance for environmental remediation.
It is highly desired to enhance the visible-excited charge separation of nano-sized BiVO4 for efficient solar utilization. Herein, different molar-ratio ZnO/BiVO4 nanocomposites are fabricated by simple wet-chemical processes, after nano-sized BiVO4 and ZnO are respectively synthesized by hydrothermal methods. It is shown by means of atmosphere-controlled steady-state surface photovoltage spectra (SS-SPS) and transient-state surface photovoltage (TS-SPV) responses that the photogenerated charges of resulting nanocomposite display longer lifetime and higher separation than those of BiVO4 alone. This leads to its superior photoactivities for water oxidation to produce O2 and for colorless pollutant degradation under visible irradiation, with about three times enhancement. Interestingly, it is suggested that the prolonged lifetime and promoted separation of photogenerated charges in the nanocomposite is attributed to the unusual spatial transfer of visible-excited high-energy electrons from BiVO4 to ZnO on the basis of the ultra-low-temperature EPR measurements and the photocurrent action spectra. Moreover, it is clearly demonstrated that the photogenerated charge separation of resulting ZnO/BiVO4 nanocomposite could be further enhanced after introducing the silicate bridges so as to improve the visible photoactivity greatly, attributed to the built bridge roles favorable to charge transfer. This work would provide a feasible way to enhance the solar energy utilization of visible-response semiconductor photocatalysts.
A process route to fabricate templated BiFeO3/CoFe2O4 (BFO/CFO) vertical nanocomposites is presented in which the self-assembly of the BFO/CFO is guided using a self-assembled triblock terpolymer. A linear triblock terpolymer was selected instead of a diblock copolymer in order to produce a square-symmetry template, which had a period of 44 nm. The triblock terpolymer pattern was transferred to a (001) Nb:SrTiO3 substrate to produce pits that formed preferential sites for the nucleation of CFO crystals, in contrast to the BFO which wetted the flat regions of the substrate. The crystallographic orientation and magnetic properties of the templated BFO/CFO were characterized.
Metal‒organic frameworks (MOFs) are a class of fascinating supramolecular soft matters but with relatively weak mechanical strength. To enforce MOF materials for practical applications, one possible way seems to be transforming them into harder composites with a stronger secondary phase. Apparently, such a reinforcing phase must possess larger porosity for ionic or molecular species to travel into or out of MOFs without altering their pristine physicochemical properties. Herein we report a general synthetic approach to coat microporous MOFs and their derivatives with an enforcing shell of mesoporous silica (mSiO2). Four well-known MOFs (ZIF-8, ZIF-7, UiO-66 and HKUST-1), representing two important families of MOFs, have served as a core phase in nanocomposite products. We show that significant enhancement in mechanical properties (hardness and toughness) can indeed be achieved with this “armoring approach”. Excellent accessibility of the mSiO2 wrapped MOFs and their metal-containing nanocomposites has also been demonstrated with catalytic reduction of 4-nitrophenol.
Polymer nanocomposites (PNCs) are important materials that are widely used in many current technologies and potentially have broader applications in the future due to their excellent property of tunability, light weight and low cost. However, expanding the limits in property enhancement remains a fundamental scientific challenge. Here, we demonstrate that well-dispersed, small (diameter ~1.8 nm) nanoparticles with attractive interactions lead to unexpectedly large and qualitatively new changes in PNC structural dynamics in comparison to conventional composites based on particles of diameter ~10-50 nm. At the same time, the zero-shear viscosity at high temperatures remains comparable to that of the neat polymer, thereby retaining good processibility and resolving a major challenge in PNC applications. Our results suggest that the nanoparticle mobility and relatively short lifetimes of nanoparticle-polymer associations open qualitatively new horizons in tunability of macroscopic properties in nanocomposites with high potential for the development of new functional materials.