Ubaldo Ortiz Méndez

Ultrasmall particles and nanocomposites: state of the art

Synthesis, properties, and applications of ultrasmall particles (USPs, size/diameter <10 nm), so-called “ultrasmall nanoparticles”, are reviewed. USPs mainly consist of nanoparticles (with or without functionalization) of metallic gold, as well as iron and gadolinium oxides, all of which have important biomedical applications. Several other elemental metals and non-metals, oxides, salts, a few polymers and coordination compounds have also been obtained as USPs. Their main applications include biomedical uses {Magnetic Resonance Imaging (MRI) contract agents, virus inactivation, immunoassay labeling, etc.}, varieties of catalysis, hydrogen sorption, as magnetic devices, ultrasmall transistors, sensors for gases or biological objects, parts of solar cells and batteries, among others. Recent approaches, such as size-focusing methodology, for obtaining USPs and preventing their further agglomeration, are discussed.

Microwave Hydrothermal and Solvothermal Processing of Materials and Compounds

Hydrothermal synthesis (or hydrothermal method) includes the various techniques of fabrication or crystallizing substances from high-temperature aqueous solutions at high vapor pressures. In case of crystallization processes, the hydrothermal synthesis can be defined as a method of synthesis of single crystals that depends on the solubility of minerals in hot water under high pressure. The crystal growth is performed in an apparatus consisting of a steel pressure vessel called autoclave, in which a nutrient is supplied along with water. A gradient of temperature is maintained at the opposite ends of the growth chamber so that the hotter end dissolves the nutrient and the cooler end causes seeds to take additional growth.

Ultrasound in Nanochemistry: Recent Advances

Applications of ultrasound in the synthesis of nanomaterials, nanocomposites, and nanoforms of chemical compounds are reviewed here. Ultrasonic treatment is widely used to produce nanostructures/nanocomposites containing elemental metals, alloys, carbon nanoforms, metal oxides, salts, and coordination compounds, macrocycles, and polymers, as well as for obtaining nanoemulsions and nanogels. Nanocatalysts can be prepared or function more actively in conditions of ultrasonic irradiation, in particular, in the degradation of organic pollutants. Ultrasonically prepared nanomaterials are also applied for tumor treatments and drug delivery purposes.

Direct electrochemical synthesis of metal complexes of phthalocyanines and azomethines as model compounds: advantages and problems of this method versus traditional synthetic techniques

A comparison of traditional and electrochemical synthetic techniques for obtaining metal complexes of azomethine and phthalocyanine is reported. It is shown that the electrochemical method affords azomethinic coordination compounds free of anions of precursors and with higher yields at ambient temperature. Electrolysis in a solid phase of phthalonitrile using a high-surface platinum cathode leads to metal-free phthalocyanine and metal phthalocyaninates at 0–25°C. The typical problems of the electrosynthetic procedures in different conditions are discussed in detail.

Coordination and organometallic compounds as precursors of classic and less-common nanostructures: recent advances

The synthesis of various classic and less-common inorganic nanostructures (nanoparticles, microflowers, nanourchins, nanofilms, nanorods, nanoleaves, nanowires, etc.) consisting mainly of elemental metals, intermetallics, oxides and sulfides from metal complexes as precursors is reviewed. To prepare nanoparticles/nanostructures, a series of complexes of N–, O–, S–, N, O–, N, S(Se)–, and N, P-containing ligands, as well as σ- and π-organometallic compounds of mainly transition metals have been treated using pyrolysis, laser, ultrasonic irradiation, CVD techniques, electron beam irradiation, and related sophisticated techniques from 100 to 700 °C. The obtained nanoparticles possess a series of useful applications, in particular as catalysts, sensors, sorbents, and remediation agents.

A Review on Less-common Nanostructures

Less-comon nanostructures (nanoforms) such as “nanodumbbells”, “nanorices”, “nanolines”, “nanotowers”, “nanoshuttles”, “nanobowlings”, “nanowheels”, “nanofans”, “nanopencils”, “nanotrees”, “nanoarrows”, “nanonails”, “nanobottles”, or “nanovolcanoes”, among many others, have been reviewed. A considerable part of these nanoforms corresponds to gold, zinc oxide, and several binary inorganic compounds that are widely used in electronics. Synthesis methods for obtaining less-common nanoforms include wet-chemistry and electrochemical techniques, laser ablation, ultrasonic treatment, electron and ion beam irradiation, arc discharge, lithography, CVD and related routes, among others.

Metal Complexes Containing Natural and Artificial Radioactive Elements and Their Applications

Recent advances (during the 2007–2014 period) in the coordination and organometallic chemistry of compounds containing natural and artificially prepared radionuclides (actinides and technetium), are reviewed. Radioactive isotopes of naturally stable elements are not included for discussion in this work. Actinide and technetium complexes with O-, N-, N,O, N,S-, P-containing ligands, as well π-organometallics are discussed from the view point of their synthesis, properties, and main applications. On the basis of their properties, several mono-, bi-, tri-, tetra- or polydentate ligands have been designed for specific recognition of some particular radionuclides, and can be used in the processes of nuclear waste remediation, i.e., recycling of nuclear fuel and the separation of actinides and fission products from waste solutions or for analytical determination of actinides in solutions; actinide metal complexes are also usefulas catalysts forcoupling gaseous carbon monoxide, as well as antimicrobial and anti-fungi agents due to their biological activity. Radioactive labeling based on the short-lived metastable nuclide technetium-99m (99mTc) for biomedical use as heart, lung, kidney, bone, brain, liver or cancer imaging agents is also discussed. Finally, the promising applications of technetium labeling of nanomaterials, with potential applications as drug transport and delivery vehicles, radiotherapeutic agents or radiotracers for monitoring metabolic pathways, are also described.

Microwave-Assisted Synthesis of Coordination and Organometallic Compounds

Microwave irradiation (MW) as a “non-conventional reaction condition” (Giguere, 1989) has been applied in various areas of chemistry and technology to produce or destroy diverse materials and chemical compounds, as well as to accelerate chemical processes. The advantages of its use are the following (Roussy & Pearce, 1995): 1. Rapid heating is frequently achieved, 2. Energy is accumulated within a material without surface limits, 3. Economy of energy due to the absence of a necessity to heat environment, 4. Electromagnetic heating does not produce pollution, 5. There is no a direct contact between the energy source and the material, 6. Suitability of heating and possibility to be automated. 7. Enhanced yields, substantial elimination of reaction solvents, and facilitation of purification relative to conventional synthesis techniques. 8. This method is appropriate for green chemistry and energy-saving processes. The substances or materials have different capacity to be heated by microwave irradiation, which depends on the substance nature and its temperature. Generally, chemical reactions are accelerated in microwave fields, as well as those by ultrasonic treatment, although the nature of these two techniques is completely distinct. Microwave heating (MWH) is widely used to prepare various refractory inorganic compounds and materials (double oxides, nitrides, carbides, semiconductors, glasses, ceramics, etc.) (Ahluwulia, 2007), as well as in organic processes (Oliver Kappe et al, 2009; Leadbeater, 2010): pyrolisis, esterification, and condensation reactions. Recent excellent reviews have described distinct aspects of microwave-assisted synthesis of various types of compounds and materials, in particular organic (Martinez-Palou, 2007; Oliver Kappe et al, 2009; Besson et al, 2006) and organometallic (Shangzhao Shi and Jiann-Yang Hwang, 2003) compounds, polymers, applications in analytical chemistry (Kubrakova, I.V., 2000), among others. Microwave syntheses of coordination and organometallic compounds, discussed in this chapter, are presented by relatively a small number of papers in the available literature in comparison with inorganic and organic synthesis. The use of microwaves in coordination chemistry began not long ago and, due to the highly limited number of results, these works can be considered as a careful pioneer experimentation, in order to establish the suitability of this technique for synthetic coordination chemistry. Classic ligands, whose numerous

Decoration of Carbon Nanotubes With Metal Nanoparticles: Recent Trends

Modern methods for external decoration of carbon nanotubes (CNTs) with elemental metal nanoparticles are reviewed. Carbon nanotubes can be decorated by indirect and direct physicochemical and physical methods mainly with noble and transition metals. The fabricated nanocomposites possess a series of useful applications in the fields of fuel cells, chemo/biosensors, solar cells, drug delivery, catalysis, and hydrogen storage. The first principal calculations and other related theoretical studies on these metal-CNTs nanohybrids are discussed.

Application of Functionalized SWCNTs for Increase of Degradation Resistance of Acrylic Paint for Cars

Physical properties of automotive acrylic paint are improved by incorporation of three different types of carbon nanotubes: single-wall carbon nanotubes (SWCNTs), OH-functionalized single-wall carbon nanotubes (OH-SWCNTs), and aniline-functionalized single-wall carbon nanotubes (aniline-SWCNTs). The formed composites are studied by electron miscroscopy methods and Raman spectrometry. It is found that the acrylic paints with addition of OH-SWCNTs and aniline-SWCNTs show better quality for their applications. In particular, the resistance against degradation by electron beam increased in ~500%.