Nanomaterials and Nanocomposites
Nanomaterials and Nanocomposites
Introduction for Nanomaterials and Nanocomposites: State of Art, New Challenges, and Opportunities
P. M. Visakh
1.1 Chemistry of Nanoscience and Technology
Science uses methodologies from synthetic chemistry and materials chemistry to obtain nanomaterials in specific sizes and shapes, with specific surface properties, defects, and self-assembly properties, designed to accomplish specific functions and uses . Nanoscale is usually defined as being smaller than 1/10th of a micrometer in at least one dimension; this term is also used for materials smaller than 1 µm. An important aspect of nanomaterials is the vast increase in the surface area to volume ratio, which incorporates the possibilities of new quantum mechanical effects in such materials. Suspensions of nanoparticles are possible because the interaction of the particle surface with the solvent molecules is strong enough to overcome differences in density, which usually results from a material either sinking or floating in a liquid. Nanoparticles often have unexpected visual properties because they are small enough to confine their electrons and produce quantum effects. Nanostructured materials are classified as zero-dimensional, one-dimensional, two-dimensional, three-dimensional nanostructures. Nanomaterials are materials that are characterized by an ultrafine grain size (<50 nm) or by a dimensionality that is limited to 50 nm. Nanomaterials can be created with various modulation dimensionalities as defined by Richard W. Siegel: zero (atomic clusters, filaments, and cluster assemblies), one (multilayers), two (ultrafine-grained overlayers or buried layers), and three (nanophase materials consisting of equiaxed nanometer-sized grains). Recently, researchers are using a modified CVD technique for the fabrication of 0D Nanostructured materials (NSMs) [2, 3].
Palgrave and Parkin  used the aerosol-assisted CVD technique to fabricate the Au nanoparticles on a glass substrate. Toluene is used as a precursor to deposit gold nanoparticles onto glass. The sizes of Au nanoparticles are 100 nm. Boyd et al .  developed a new CVD process that can be used to selectively deposit materials of many different types. In this technique, they used the Plasmon resonance in nanoscale structures to create the local heating, which is crucial in order to initiate deposition when illuminated by a focused low-power laser . Elihn et al .  synthesized the iron nanoparticles enclosed in carbon shells by laser-assisted chemical vapor decomposition (LCVD) of ferrocene (Fe(C5H5)2) vapor in the presence of the Ar gas. One-dimensional nanomaterials have nanoscale sizes along two-dimensions and a rod-like or wire-like appearance. In such nanomaterials, quantum confinement and surface area-related nanoscale effects are more pronounced compared to 2D nanomaterials. Lyotropic liquid crystal (LLC) template-assisted synthesis is one of the most facile and most applied methods for the synthesis of 1D NSMs such as nanowires, nanorods, nanotubes, nanobelts, nanoribbons, and nanospindles [8-12]. Kijima et al .  fabricated the platinum, palladium, and silver nanotubes, with inner diameters of 3-4 nm and outer diameters of 6-7 nm, by the reduction of metal salts confined to lyotropic mixed Liquid Crystals (LCs) of two different sized surfactants.
Electrodeposition processes have a wide range of advantages such as low cost, low energy consumption, high growth rate at relatively low temperatures, being environmentally friendly, and having good control of the deposition thickness, shape, and size. Xia et al .  fabricated the MnO2 nanotube and nanowire arrays via an electrochemical deposition technique using porous alumina templates. Tang et al .  prepared the Si nanowires on Si substrates by the hydrothermal deposition route under low temperature and pres