Advances In Synthesis Methods Research Articles

Polydopamine Nanomaterials: Recent Advances in Synthesis Methods and Applications.

Polydopamine (PDA), the final oxidation product of dopamine or other catecholamines, attracted much attention as versatile coatings that can be used to cover the surface of almost all materials with a conformal layer of adjustable thickness ranging from a few to about 100 nm. These PDA layers can be subsequently modified with molecules carrying nucleophilic groups or with metallic nanoparticles from solutions containing metallic cations. However, during the deposition of PDA film on the surfaces, the reaction products that are simultaneously obtained from the oxidation of catecholamines in solution precipitate. Hence, some recent effort has been devoted to produce PDA in the form of nanoparticles. The aim of this short review is to give a comprehensive description of the synthesis methods yielding of PDA nanoparticles in the absence or in the presence of templating agents (polymers, polyelectrolytes, surfactants, proteins, and even some small organic molecules). We will also describe the use of thin PDA layers to coat already synthesized nanoparticles or nanotubes. Finally, several first applications of the obtained PDA nanoparticles will be described.

Recent advances in methods of synthesis and applications of bacterial cellulose/calcium phosphates composites in bone tissue engineering

Bacterial cellulose (BC) is a nanofibrous biomaterial biosynthetized by a series of acetic bacteria with unique properties with application in many tissue engineering purposes. Calcium phosphates (CPs), mainly hydroxyapatite, are bioceramics that possess similar composition of host bones and are able to stimulate osteoconduction and osteointegration to living tissues.Bacterial cellulose-calcium phosphates composites have caught the attention of researchers by their excellent mechanical properties and biocompatibility, being considered an excellent proposal to development of new synthetic grafts to bone tissue engineering. The minireview presented here focuses on various fabrication methods used to prepare and novel applications of BC-CPs composites and their applications in BTE.

Magnetic Fe3O4@Mesoporous Silica Composite Microspheres: Synthesis and Biomedical Applications

With the development of nanotechnology, multifunctional nanoparticles have attracted great attention in the field of biomedicine in recent years. Magnetic Fe3O4@mSiO2composite microspheres (MMS), consist of magnetic Fe3O4cores and mesoporous silica shells, are considered as promising biomedical materials. In this review, we focused on the current advances in synthesis methods and biomedical applications of MMS. At First, we outlined different structures of MMS such as core–shell, hollow and rattle type MMS, and their structures, synthesis approaches and properties were discussed in detail. Combining with the magnetism of Fe3O4and the mesopores of mSiO2, MMS were wildly applied in biomedical. Then, we summarized the biomedical applications of MMS, including drug loading and release, MRI, tumour targeted therapy, hyperthermia, multimodal cancer therapies and bioseparation. At last, the great potentials of MMS as multifunctional diagnose and therapy platforms were discussed.

Recent advances in the synthesis, biological activities and various applications of ferrocene derivatives

Ferrocene derivatives constitute an important class of organometallic compounds with not only an extensive range of biological activities but also diverse industrial as well as material science applications. These stimulating features of ferrocene derivatives spurred us to review the recent advances in synthesis methods and biological and other applications reported in the latest literature. An effort has been made to summarize the recent developments in synthetic methods providing access to ferrocene scaffolds and the useful medicinal and material applications, including agricultural, catalytic, polymer, conducting, redox mediating, ferrocenyl stationary phase, rocket propellant and ion sensing applications. Ferrocene‐based bulky metallocenes are also discussed.

Recent advances in high-performance bulk thermoelectric materials

Thermoelectric (TE) materials facilitate direct heat-to-electricity conversion. The performance of a TE material is characterised by its figure of merit zT (=S2σT/κ) that depends on both electronic transport properties, i.e. the Seebeck coefficient S and the electrical conductivity σ, and on thermal transport properties, i.e. the thermal conductivity κ of a material. The intrinsically counter-correlated behaviour between electronic and thermal transport properties makes the enhancement of zT a very challenging task. In the past 10 years, the zTs in bulk TE materials have been significantly enhanced due to intensive exploratory efforts, the discovery of new physical phenomena and effects, and applications of advanced synthesis methods. In this review, we summarise the recent progress in bulk TE materials. After the introduction of fundamental principles of thermoelectricity, the recently achieved enhancements in the TE performance encompassing the use of electronic band structure engineering, lattice phonon engineering and nanostructure tailoring will be emphasised. Next, the highlights of typical TE materials will be presented, focusing especially on the great progress achieved during the past decade. Finally, new techniques and approaches developed to fabricate TE materials will be outlined and their impact on the performance and economic viability of large-scale TE applications will be considered. The progress made during the past dozen or so years provides great opportunities for the use of bulk TE materials in a much broader range of applications and bodes well for a more efficient utilisation of energy.

Stable amorphous georgeite as a precursor to a high-activity catalyst.

Copper and zinc form an important group of hydroxycarbonate minerals that include zincian malachite, aurichalcite, rosasite and the exceptionally rare and unstable--and hence little known and largely ignored--georgeite. The first three of these minerals are widely used as catalyst precursors for the industrially important methanol-synthesis and low-temperature water-gas shift (LTS) reactions, with the choice of precursor phase strongly influencing the activity of the final catalyst. The preferred phase is usually zincian malachite. This is prepared by a co-precipitation method that involves the transient formation of georgeite; with few exceptions it uses sodium carbonate as the carbonate source, but this also introduces sodium ions--a potential catalyst poison. Here we show that supercritical antisolvent (SAS) precipitation using carbon dioxide (refs 13, 14), a process that exploits the high diffusion rates and solvation power of supercritical carbon dioxide to rapidly expand and supersaturate solutions, can be used to prepare copper/zinc hydroxycarbonate precursors with low sodium content. These include stable georgeite, which we find to be a precursor to highly active methanol-synthesis and superior LTS catalysts. Our findings highlight the value of advanced synthesis methods in accessing unusual mineral phases, and show that there is room for exploring improvements to established industrial catalysts.

Design of Polymorphic Operators for Efficient Synthesis of Multifunctional Circuits

Systematic effort dedicated to the exploration of feasible ways how to permanently come up with even more space-efficient implementation of digital circuits based on conventional CMOS technology node may soon reach the ultimate point, which is mostly given by the constraints associated with physical scaling of fundamental electronic components. One of the possible ways of how to mitigate this problem can be recognized in deployment of multifunctional circuit elements. In addition, the polymorphic electronics paradigm, with its considerable independence on a parti- cular technology, opens a way how to fulfil this objective through the adoption of emerging semiconductor materials and advanced synthesis methods. In this paper, main attention is focused on the introduction of polymorphic operators (i.e. digital logic gates) that would allow to further increase the efficiency of multifunctional circuit synthesis techniques. Key aspect depicting the novelty of the proposed approach is primarily based on the intrinsic exploitation of components with ambi- polar conduction property. Finally, relevant models of the polymorphic operators are presented in conjunction with the experimental results

Novel Approach To Synthesis of Logic Circuits Based on Multifunctional Components

Abstract Multifunctional logic continuously becomes an important way how to implement compact and cheap circuits with intrinsic reconfiguration features. Polymorphic electronics concept with its substantial technological independency opens a way to fulfil this objective through the adoption of emerging semiconductor technologies and advanced synthesis methods. The paper comes with a proposal of a novel synthesis method oriented on the exploitation of polymorphic electronics principles. Key part of it is based on Boolean divisor identification and function kernelling technique. The proposed method is evaluated with several test circuits.

From thermoelectric bulk to nanomaterials: Current progress for Bi2Te3 and CoSb3

Bi2Te3 and CoSb3 based nanomaterials were synthesized and their thermoelectric, structural, and vibrational properties analyzed to assess and reduce ZT‐limiting mechanisms. The same preparation and/or characterization methods were applied in the different materials systems. Single‐crystalline, ternary p‐type Bi15Sb29Te56, and n‐type Bi38Te55Se7 nanowires with power factors comparable to nanostructured bulk materials were prepared by potential‐pulsed electrochemical deposition in a nanostructured Al2O3 matrix. p‐type Sb2Te3, n‐type Bi2Te3, and n‐type CoSb3 thin films were grown at room temperature using molecular beam epitaxy and were subsequently annealed at elevated temperatures. This yielded polycrystalline, single phase thin films with optimized charge carrier densities. In CoSb3 thin films the speed of sound could be reduced by filling the cage structure with Yb and alloying with Fe yielded p‐type material. Bi2(Te0.91Se0.09)3/SiC and (Bi0.26Sb0.74)2Te3/SiC nanocomposites with low thermal conductivities and ZT values larger than 1 were prepared by spark plasma sintering. Nanostructure, texture, chemical composition, as well as electronic and phononic excitations were investigated by X‐ray diffraction, nuclear resonance scattering, inelastic neutron scattering, Mössbauer spectroscopy, and transmission electron microscopy. For Bi2Te3 materials, ab‐initio calculations together with equilibrium and non‐equilibrium molecular dynamics simulations for point defects yielded their formation energies and their effect on lattice thermal conductivity, respectively.Current advances in thermoelectric Bi2Te3 and CoSb3 based nanomaterials are summarized. Advanced synthesis and characterization methods and theoretical modeling were combined to assess and reduce ZT‐limiting mechanisms in these materials.

Magnetic titanium dioxide based nanomaterials: synthesis, characteristics, and photocatalytic application in pollutant degradation

Recent advances in synthesis methods, structure and enhanced photoactivity of magnetic titanium dioxide based photocatalysts are highlighted in this review.

Applications versus properties of Mg–Al layered double hydroxides provided by their syntheses methods: Alkoxide and alkoxide-free sol–gel syntheses and hydrothermal precipitation

A tremendous number of studies have examined layered double hydroxides (LDH) for their technological applications in the ion exchange removal of toxic ions, recovery of valuable substances, catalysis, CO2 capture, as a layered host for storage/delivery of biologically active molecules, additives to plastics and building materials, and other functions. Numerous publications always conclude that the materials (prepared, as a rule, using the oldest synthesis method) are very promising for each investigated application; however, the main chemical industries producing these materials advertise them mainly (or only) as plastic additives. The authors performed extensive research using many of the appropriate methods to compare the structure, surface and adsorptive properties of three Mg–Al LHDs produced by advanced synthesis methods. One industrial sample (by Sasol, Germany) prepared by the alkoxide sol–gel method and two novel Mg–Al LDHs synthesised in-house by alkoxide-free sol–gel and hydrothermal precipitation approaches were investigated. Reasons for the very different adsorptive selectivity of the three LDHs towards arsenate, selenate, phosphate, arsenite and selenite have been provided, highlighting the role of speciation of the interlayer carbonate, aluminium, magnesium, interlayer hydration and moisture content in the adsorptive selectivity towards each toxic anion. This work is the first report presenting the regularities of the LDHs structure, surface and anion exchange properties as a function of their syntheses method. It establishes the links to potential technological applications of each investigated LDH and explains the necessary properties required to make the technological application cost-effective and efficient. The paper might accelerate industrial applications of these advanced materials.

Structural Characterization of Rotavirus-Directed Synthesis and Assembly of Metallic Nanoparticle Arrays

Self-assembled structures derived of viral proteins display sophisticated structures that are difficult to obtain with even advanced synthesis methods and the use of protein nanotubes for synthesis and organization of inorganic nanoarrays into well-defined architectures are here reported. Nanoparticle arrays derived of rotavirus VP6 nanotubes were synthesized by in situ functionalization with silver and gold nanoparticles. The size and morphology of metal nanoparticles were characterized by transmission electron microscopy (TEM) and high resolution TEM (HR-TEM). Processing of micrographs to obtain fast Fourier transforms (FFT) patterns of nanoparticles shown that the preferred morphologies are fcc-like and multiple twinned ones. Micrographs were used to assign structure and orientation, and the elemental composition analysis was performed with energy dispersive spectroscopy (EDS). Structural characterization of functionalized rotavirus VP6 demonstrated its utility for directed construction of hybrid anisotropic nanomaterials formed by arrays of metallic nanoparticles.

Conducting Material-incorporated Electrorheological Fluids: Core-shell Structured Spheres

Conducting material-based electro-responsive particles have become important as the smart soft matter in electrorheological (ER) fluids. These materials include conducting polymers, such as polyaniline, polypyrrole and poly(3,4-ethylenedioxythiophene), and carbon materials, such as carbon nanotubes and graphene oxide. Core-shell structured ER particles containing these materials as either core or shell species have attracted increasing interest owing to their outstanding advantages of an enhanced ER effect or diverse ER mechanism, lighter particulate density and lower cost. This paper summarizes the recent advances in synthesis methods as well as the critical characteristics of the core-shell structured particles, such as shear stress, yield stress and dielectric properties.

Advances in Light-Emitting Doped Semiconductor Nanocrystals

Insertion of just a few impurity atoms in a host semiconductor nanocrystal can drastically alter its phase, shape, and physical properties. Such doped nanomaterials now constitute an important class of optical materials that can provide efficient, stable, and tunable dopant emission in visible and NIR spectral windows. Selecting proper dopants and inserting them in appropriate hosts can generate many new series of such doped nanocrystals with several unique and attractive properties in order to meet current challenges in the versatile field of luminescent materials. However, the synthesis of such doped nanomaterials with a specific dopant in a predetermined host at a desired site leading to targeted optical properties requires fundamental understanding of both the doping process as well as the resulting photophysical properties. Summarizing up to date literature reports, in this Perspective we discuss important advances in synthesis methods and in-depth understanding of the optical properties, with an emphasis on the most widely investigated Mn-doped semiconductor nanocrystals.

IAEA Activities on Application of Nuclear Techniques in Development and Characterization of Materials for Hydrogen Economy

Hydrogen and fuel cells can greatly contribute to a more sustainable less carbon-dependent global energy system. An effective and safe method for storage of hydrogen in solid materials is one of the greatest technologically challenging barriers of widespread introduction of hydrogen in global energy systems. However, aspects related to the development of effective materials for hydrogen storage and fuel cells are facing considerable technological challenges. To reach these goals, research efforts using a combination of advanced modeling, synthesis methods and characterization tools are required. Nuclear methods can play an effective role in the development and characterization of materials for hydrogen storage. Therefore, the IAEA initiated a coordinated research project to promote the application of nuclear techniques for investigation and characterization of new/improved materials relevant to hydrogen and fuel cell technologies. This paper gives an overview of the IAEA activities in this subject.

TWO NEW ECONOMICAL COMPUTERS FOR THE DESIGN AND ANALYSIS OF SERVOMECHANISMS, NETWORKS, AMPLIFIERS, AND ANALOGOUS DYNAMICAL SYSTEMS

TWO NEW ECONOMICAL COMPUTERS FOR THE DESIGN AND ANALYSIS OF SERVOMECHANISMS, NETWORKS, AMPLIFIERS, AND ANALOGOUS DYNAMICAL SYSTEMS