Category Archives: news

Some of the researchers have invented a production method for oxidation resistant copper alloy nanoparticles for printed electrodes. These new copper alloy nanoparticles can be used as main component of affordable conductive inks with high oxidation resistance. These high performance conductive inks will contribute to the advancement of printed electrodes.

CeO2 Nanoparticles Dispersion

CeO2 Nanoparticles Dispersion

Nanomaterials are being applied across a wide range of high-tech industries and advanced technologies due to their excellent optical, magnetic, catalytic and electronic properties. The properties of nanomaterials depend greatly on their structure, shape, and size.

Cerium is a Block F, Period 6 element. It is the most abundant of the rare earth elements, and is found in minerals bastnasite, synchysite, hydroxylbastnasite, sallanite, monazite, rhabdophane, and zircon. It is malleable and oxidizes very readily at room temperature.

CeO2 Nanoparticles Dispersion: Cerium (IV) oxide, also known as ceric oxide, ceric dioxide, ceria, cerium oxide or cerium dioxide, is an oxide of the rare-earth metal cerium. It is a pale yellow-white powder with the chemical formula CeO2. It is an important commercial product and an intermediate in the purification of the element from the ores. The distinctive property of this material is its reversible conversion to a non stoichiometric oxide.

Ceria (cerium oxide, CeO2) nano dispersion finds applications in the precision polishing of most semiconductor substrate materials including silicon, sapphire, GaAs, etc. Ceria dispersion has been shown to not only demonstrate tremendous advantages in the planarization process of most semiconductor materials but glassy materials employed in photonic applications as well.

CeO2 Nanoparticles Dispersion

CeO2 Nanoparticles Dispersion

Today, cerium oxide is largely used in the catalysis field (mainly for diesel engines), and in chemical and mechanical polishing (CMP). However, cerium oxide is also well known for its optical properties and ability to filter ultraviolet (UV) rays. Moreover, expertise ensures good size control from 5-nm diameter up to 100 nanometers. Researchers are able to obtain stable sols of cerium oxide nanoparticles with diameters of 10 nm. These sols appear as a clear liquid, since the particles are small enough to be totally transparent. For instance, at the same solid concentration (1g/l) and for similar particle size, a titanium dioxide sol appears milky.

Water-repellence and water-barrier properties are of primary importance for the durability and the stability of the coatings. The action of rain and humidity on outdoor constructions is a key factor in the degradation of the coatings because photo-degradation and final failure of the protective coating is the result of the combined action of UV, oxygen and water molecules. Moreover, water penetration in the coating leads to a lack of adherence of the coating onto the wood substrate, causing macroscopic failure. In this respect, a water absorption test on pine panels was performed, comparing a reference to a cerium oxide colloid modified alkyd formulation. The water absorption of the reference is 72 g/m2 and decreased to 45 g/m2 for the cerium oxide containing coating.

Application to Coatings

Cerium oxide nanoparticles, properly dispersed in coating formulations using the specific chemistry described previously, combine the advantages of organic ultraviolet (UV) absorbers with those of mineral additives. The cerium oxide nanoparticles ensure the durability of the UV absorption function whilst improving the hardness and strengthening the organic binders currently used in wood technology. Since the nanoparticles do not scatter light, the coating remains transparent. The transparency (i.e. no coloration, no whitening) is an important requirement for the wood coating industry; since wood is a natural material, the coating must be as neutral as possible. When the durability is targeted, colored pigments are often added to help in this way, but this negatively impacts the aesthetics of the end product. Organic UV absorbers are also efficient, but their actions are limited because of progressive destruction of active molecules (migration, leaching, photochemical activity).

Biological Applications:

Cerium Nanomaterials have unique regenerative properties owing to their low reduction potential and the coexistence of both Ce(3+)/Ce(4+) on their surfaces. Defects in the crystal lattice due to the presence of Ce(3+) play an important role in tuning the redox activity of Cerium nanomaterials. The surface Ce(3+):Ce(4+) ratio is influenced by the microenvironment. Therefore, the microenvironment and synthesis method adopted also plays an important role in determining the biological activity and toxicity of Cerium nanodispersions. The presence of a mixed valance state plays an important role in scavenging reactive oxygen and nitrogen species. They found to be effective against pathologies associated with chronic oxidative stress and inflammation. Also they are well tolerated in both in vitro and in vivo biological models, which make cerium nano dispersions well suited for applications in nanobiology and regenerative medicine.

 



Silver Paste

Applications of Silver Paste

In nanoscience, silver nanoparticles have been the subjects in the many works due to its specific properties on the optical, electronic, catalytic, and antibacterial materials research. The research on the synthesis of silver nanoparticles was rapidly developed for last decade. It has been known as chemical reduction, electrochemical reduction, irradiation reduction, or micro emulsion methods. Through these methods, it has been possible to prepare the conducting metal nanoparticles which could be applied for metal paste, conducting ink, and conducting adhesive.

Generally, a thick-film silver paste contains a functional phase consisting of particles of different shapes (flake or spherical) and sizes (micrometer, submicron, or nanometer), and these particles are dispersed in an organic vehicle by high-energy ball milling, ultrasonic vibration, and/or mechanical stirring.

A homogeneous thick-film silver paste is a stable system in which all the components are soluble in solvent and no solid or particle phase is excluded. The paste is able to avoid thoroughly the sedimentation and/or agglomeration of the particles applied in conventional pastes and eliminates the constraints of the particle size on fine patterns dispensing.

Silver Paste

Silver Paste

In recent years, the demand for flexible print circuit (FPC) has been increasing. Ordinary FPC is produced using circuits composed of plastic films onto which copper foil is laminated. In addition, silver printing circuit board (membrane circuit board, MB) that has a structure in which conductive silver paste is screen printed on a PET (polyethylene terephthalate) film to form circuits is available.

Silver conductive paste for screen printing used for formation of circuits in the MB uses silver material in conductive particles. Although silver has a disadvantage that ion migration can occur easily, it is handled with ease since it is more resistant to oxidization compared to copper, which has specific resistance of a similar level, and hence this material is used widely.

Polymer-type conductive paste utilized in the MB is specific in that low-temperature baking at less than 150°C (PET film circuit board is capable of withstanding this temperature) is possible. Silver conductive particles are dispersed in organic binder (polymer) and if printed or baked, conductive silver particles make contact each other thereby ensuring good electrical conductance. However, with this conductive mechanism, there are many contact resistance between conductive particles, specific resistance of the circuit being formed is more than 4.0 × 105 Ω cm which is more than 30 times that of bulk silver.

Conductive paste used in the ceramics substrate is composed by conductive silver particles and glass frit, and its baking temperature is more than approximately 500°C. After baking, conductive particles are sintered and contact resistance between conductive particles is greatly reduced. Therefore, it is possible to form a low-resistance circuit having specific resistance of the order of 106 Ω cm.

As one of applications, current collection wiring of transparent conductive glass substrate (transparent conductive glass) for dye-sensitized solar cells (DSC), which has been attracting attention recently as the next generation solar cells, is cited. With DSC, power is taken out through transparent conductive glass used as the window electrode. Since it has a certain resistance, the power generated is lost in part while the internal resistance of the battery is increased. In order to prevent this, efforts have been made in such a way that current collection wiring is provided to transparent conductive glass so as to reduce the loss to a minimal level.



Transition Metal Nanoparticles

Transition Metal Nanoparticles

The elements in the periodic table are often divided into four categories: (1) main group elements, (2) transition metals, (3) lanthanides, and (4) actinides. The main group elements include the active metals in the two columns on the extreme left of the periodic table and the metals, semimetals, and nonmetals in the six columns on the far right. The transition metals are the metallic elements that serve as a bridge, or transition, between the two sides of the periodic table. The lanthanides and the actinides at the bottom of the table are sometimes known as the inner transition metals because they have atomic numbers that fall between the first and second elements in the last two rows of the transition metals.

Transition metals are like main group metals in many ways: They look like metals, they are malleable and ductile, they conduct heat and electricity, and they form positive ions. The fact the two best conductors of electricity are a transition metal (copper) and a main group metal (aluminum) shows the extent to which the physical properties of main group metals and transition metals overlap.

There are also differences between these metals. The transition metals are more electronegative than the main group metals, for example, and are therefore more likely to form covalent compounds.

Transition Metal Nanoparticles

Transition Metal Nanoparticles

Another difference between the main group metals and transition metals can be seen in the formulas of the compounds they form. The main group metals tend to form salts (such as NaCl, Mg3N2, and CaS) in which there are just enough negative ions to balance the charge on the positive ions.

The transition metals form similar compounds [such as FeCl3, HgI2, or Cd(OH)2], but they are more likely than main group metals to form complexes, such as the FeCl4-, HgI42-, and Cd(OH)42- ions, that have an excess number of negative ions.

The use of transition metal nanoparticles (NPs) in catalysis is crucial as they mimic metal surface activation and catalysis at the nanoscale and thereby bring selectivity and efficiency to heterogeneous catalysis. Transition metal NPs are clusters containing from a few tens to several thousand metal atoms, stabilized by ligands, surfactants, polymers or dendrimers protecting their surfaces. Their sizes vary between the order of one nanometer to several tens or hundreds of nanometers, but the most active in catalysis are only one or a few nanometers in diameter, i.e. they contain a few tens to a few hundred atoms only. This approach is also relevant to homogeneous catalysis, because there is a full continuum between small metal clusters and large metal clusters, the latter being also called colloids, sols or NPs. NPs are also well soluble in classic solvents (unlike metal chips in heterogeneous catalysis) and can often be handled and even characterized as molecular compounds by spectroscopic techniques that are well known to molecular chemists, such as  H and multinuclear NMR, infrared and UV – vis spectroscopy and cyclic voltammetry.

 



Organic Compounds

ORGANIC COMPOUNDS

Organic compounds, any of a large class of chemical compounds in which one or more atoms of carbon are covalently linked to atoms of other elements, most commonly hydrogen, oxygen, or nitrogen. The few carbon-containing compounds not classified as organic include carbides, carbonates, and cyanides. See chemical compound.

The term ‘organic’ was originally coined to describe molecules associated with living organisms. This section of chemistry is therefore popularly termed “the chemistry of life”, as it was discovered and previously thought to flourish exclusively in living beings. However, this definition isn’t completely true and is not the only rule to determine whether a compound is organic or inorganic. For instance, carbon dioxide is based on carbon and is highly central to both animals and plants, but it’s far from being organic.

A popular consensus has been established, insisting that organic compounds are structures that contain carbon as well as hydrogen, bonded covalently together, collectively known as a ‘C-H’ group. This group is then further attached to nitrogen, oxygen, sulfur, silicon etc. to pave the way for a plethora of organic compounds.

The enormous amount of organic compounds and their versatile nature are the result of carbon’s promiscuity, a trait that can be attributed to its unique structure. Today, nearly 2 million organic compounds have been isolated or characterized.

Organic Compounds

Organic Compounds

Chemical synthesis is concerned with the construction of complex chemical compounds from simpler ones. A synthesis usually is undertaken for one of three reasons. The first reason is to meet an industrial demand for a product. For example, ammonia is synthesized from nitrogen and hydrogen and is used to make, among other things, ammonium sulfate, employed as a fertilizer; vinyl chloride is made from ethylene and is used in the production of polyvinyl chloride (PVC) plastic. In general, a vast range of chemical compounds are synthesized for applications as fibers and plastics, pharmaceuticals, dyestuffs, herbicides, insecticides, and other products.

Among the numerous types of organic compounds, four major categories are found in all living things: carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates

Almost all organisms use carbohydrates as sources of energy. In addition, some carbohydrates serve as structural materials. Carbohydrates are molecules composed of carbon, hydrogen, and oxygen; the ratio of hydrogen atoms to oxygen and carbon atoms is 2:1.

Simple carbohydrates commonly referred to as sugars, can be monosaccharides if they are composed of single molecules, or disaccharides if they are composed of two molecules. The most important monosaccharide is glucose, a carbohydrate with the molecular formula C6H12O6. Glucose is the basic form of fuel in living things. In multi cellular organisms, it is soluble and is transported by body fluids to all cells, where it is metabolized to release its energy. Glucose is the starting material for cellular respiration, and it is the main product of photosynthesis.

Lipids

Lipids are organic molecules composed of carbon, hydrogen, and oxygen atoms. The ratio of hydrogen atoms to oxygen atoms is much higher in lipids than in carbohydrates. Lipids include steroids (the material of which many hormones are composed), waxes, and fats.

Fat molecules are composed of a glycerol molecule and one, two, or three molecules of fatty acids. A glycerol molecule contains three hydroxyl (–OH) groups. A fatty acid is a long chain of carbon atoms (from 4 to 24) with a carboxyl (–COOH) group at one end. The fatty acids in a fat may all be alike or they may all be different. They are bound to the glycerol molecule by a process that involves the removal of water.

Nucleic acids

Like proteins, nucleic acids are very large molecules. The nucleic acids are composed of smaller units called nucleotides. Each nucleotide contains a carbohydrate molecule (sugar), a phosphate group, and a nitrogen-containing molecule that, because of its properties, is a nitrogenous base.

Living organisms have two important nucleic acids. One type is deoxyribonucleic acid, or DNA. The other is ribonucleic acid, or RNA. DNA is found primarily in the nucleus of the cell, while RNA is found in both the nucleus and the cytoplasm, a semi liquid substance that composes the volume of the cell.

Applications

Organic chemistry is a highly creative science in which chemists create new molecules and explore the properties of existing compounds. Organic compounds are all around us. They are central to the economic growth of the United States in the rubber, plastics, fuel, pharmaceutical, cosmetics, detergent, coatings, dyestuff, and agrichemical industries, to name a few. The very foundations of biochemistry, biotechnology, and medicine are built on organic compounds and their role in life processes. Many modern, high-tech materials are at least partially composed of organic -compounds.

Organic chemists spend much of their time creating new compounds and developing better ways of synthesizing previously known compounds.