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Bio Nano Conjugation

NANO BIO-CONJUGATION

Bio Nano Conjugation is a chemical strategy to form a stable covalent link between two molecules, at least one of which is a biomolecule. Proteins and other biopolymers regulate and perform biological functions by binding to ligands. “Novel functional bio-materials make possible transformative new opportunities to impact society in a beneficial way.”

The ability to create functional biomolecules through bioconjugation has affected every discipline of life sciences. As new cross-linking techniques and reagent are developed, novel applications in ligand discovery, disease diagnosis, and high throughput screening are being advanced through the development of new unique bioconjugates. These methods owe their existence to the discovery of chemo selective reactions that enable bio nano conjugation under physiological conditions.

The initial enthusiasm over the attainment of complete genetic information about various organisms has, however, been tempered by the realization that the utility of this information is nearly inaction able without knowledge of the function of the encoded proteins. Elucidation of the functions of other biomolecules, such as RNA and carbohydrates, is likewise imperative. “Bioconjugation”, which refers to the covalent derivatization of biomolecules, provides a means to attain this goal.

Bio Nano Conjugation

Bio Nano Conjugation

We focus on modern methods for bioconjugation, and delineate both imperatives and means for making useful bioconjugates. We restrict our analysis to wild-type proteins composed of the 20 amino acids encoded by genetics, or close analogues thereof. Strategies involving the addition of an exogenous domain and its subsequent modification have been reviewed elsewhere.

Nanoshel provide the custom synthesis of the conjugation of different functionalized groups to nanoparticles is necessary for their stability, functionality, and biocompatibility and develops their application fields, and provides them with novel and improved properties. Nanoshel attached a range of functionalized groups to the nanoparticles including low molecular weight ligands, peptides, proteins, polysaccharides, polyunsaturated and saturated fatty acids, DNA, plasmids, and RNA.

Nanoparticles have been often studied due to their unique surface, chemical inertness, high electron density, and strong optical absorption. In recent decades, Nanoshel nanoparticles have been applied in genomics, clinical chemistry, vaccine development, immunoassay, biosensor, diagnosis, and microorganism’s control, cancer-cell imaging, and drug delivery. In addition, the Nanoparticles conjugated by prostate specific membrane antigen (PSMA) RNA aptamer after loading of doxorubicin can be useful as therapeutic agents for diagnosis and treating of prostate cancer.

Recently, bio-conjugated QDs have often become inevitable parts of biology and biotechnology for imaging of molecules, cells, tissues and animals. Covalent or noncovalent conjugates of QDs with antibodies, proteins, peptides, aptamers, nucleic acids, small molecules, and liposome’s can be considered as bioconjugated QDs, which are extensively used for direct and indirect labeling of extracellular proteins and sub cellular organelles. Bioconjugated QDs are ideal substitutes for organic dyes when photo stability or multiplexing is a requirement and excitation laser source is a limitation.

Applications of Bio Nano Conjugation

Biomolecules enabled their application to various fields like medicine and materials. Synthetically modified biomolecules can have diverse functionalities, such as tracking cellular events, determining protein biodistribution, revealing enzyme function, imaging specific biomarkers, and delivering drugs to targeted cells. Bioconjugation links biomolecules with different substrates.

Diagnostic Applications

Qualitative and quantitative detection of analytes in clinical samples is crucial for the early diagnosis of disease. The complexity and heterogeneity of clinical samples presents a challenging environment for the detection of individual molecules. Chromatographic purification of analyte prior to analysis is time-consuming and labor-intensive, and hence impractical. Accordingly, chemical and immunological methods have become favored for medical diagnoses.

Clinical chemistry exploits an intrinsic physicochemical property of the analyte to generate a unique signal, thus circumventing analyte purification. Examples of this approach include spectrophotometric detection of metal ions and chromogenic and fluorogenic substrate-based assays for characterizing enzymes of interest. Clinical chemistry approaches are limited to special cases because many analytes lack a unique signal-generating property. Moreover, clinical chemistry approaches are often not sensitive enough to be useful in clinical regimes.

In comparison to chemical methods, immunological approaches are often more sensitive. The high specificity of antibody–antigen interactions avoids sample purification. Moreover, since antibodies can be generated against almost any analyte, this method is widely applicable.

Industrial Applications

Immobilized enzymes are used as industrial catalysts. The first commercial application of immobilized enzymes was the resolution of amino acids by an aminocyclase. Applications in the food industry include use of fumarase to catalyze the isomerization of fumaric acid to malic acid. The pharmaceutical industry employs immobilized enzymes for the synthesis of drugs. For example, immobilized penicillin amidase is used in the preparation of 6-aminopenicillanic acid. Applications of bioconjugation are also prevalent in the chemical industry. One prominent example is the use of immobilized nitrile hydratase for the production of acryl amide from acrylonitrile.



Carbon Nanotubes Dispersion (CNT)

CNT DISPERSIONS

Carbon nanotubes dispersion are strong and flexible but very cohesive. They are difficult to disperse into liquids, such as water, ethanol, oil, polymer or epoxy resin. Carbonnanotubes (CNT) are used in adhesives, coatings and polymers and as electrically conductive fillers in plastics to dissipate static charges in electrical equipment and in electrostatically paintable automobile body panels. By the use of nanotubes, polymers can be made more resistant against temperatures, harsh chemicals, corrosive environments, extreme pressures and abrasion. There are two categories of carbon nanotubes: Single-wall nanotubes (SWNT) and multi-wall nanotubes (MWNT).

Currently two approaches are widely used in carbon nanotubes dispersion—the mechanical approach and the chemical approach. The mechanical approach includes ultrasonication and high-shear mixing. These processes are time-consuming and less efficient. Furthermore, ultrasonication can result in fragmentation of CNTs, in turn, decreasing their aspect ratio. Besides this, the stability of the dispersion is poor. On the other hand, the chemical approach includes both covalent and non covalent methods. Covalent methods involve functionalization with various chemical moieties to improve solubility in solvents.

Carbon Nanotubes Dispersion

Carbon Nanotubes Dispersion

However aggressive chemical functionalization at high temperature creates defects at the nanotube surface, consequently altering the electrical properties of carbon nanotubes. In contrast, a non covalent approach involves adsorption of the chemical moieties onto the nanotube surface, either via π–π stacking interaction such as in DNA, uncharged surfactants, etc., or through coulomb attraction in the case of charged chemical moieties. The non covalent approach is superior in the sense that it does not alter the π-electron cloud of graphene, in turn preserving the electrical properties of carbon nanotubes.

Properties of CNTs

The chemical bonding of CNTs is composed entirely of sp2 carbon– carbon bonds. This bonding structure – stronger than the sp3 bonds found in diamond – provides CNTs with extremely high mechanical properties. It is well known that the mechanical properties of CNTs exceed those of any existing materials. Although there is no consensus on the exact mechanical properties of CNTs, theoretical and experimental results have shown unusual mechanical properties of CNTs with Young’s modulus as high as 1.2 TPa and tensile strength of 50–200 GPa. These make CNTs the strongest and stiffest materials on earth. In addition to the exceptional mechanical properties associated with CNTs, they also possess other useful physical properties and chemical properties.

Applications of Carbon Nanotubes Dispersion

CNTs can be used as a flame-retardant additive to plastics; this effect is mainly attributed to changes in rheology by nanotube loading. These nanotube additives are commercially attractive as a replacement for halogenated flame retardants, which have restricted use because of environmental regulations. Some other commercial applications of Carbon Nanotubes Dispersion are:

Coatings and Films

Leveraging Carbon Nanotubes Dispersion, functionalization, and large-area deposition techniques, CNTs are emerging as a multifunctional coating material. For example, MWNT-containing paints reduce biofouling of ship hulls by discouraging attachment of algae and barnacles. They are a possible alternative to environmentally hazardous biocide-containing paints. Incorporation of CNTs in anticorrosion coatings for metals can enhance coating stiffness and strength while providing an electric pathway for cathodic protection. Widespread development continues on CNT based transparent conducting films as an alternative to indium tin oxide (ITO). A concern is that ITO is becoming more expensive because of the scarcity of indium, compounded by growing demand for displays, touch-screen devices, and photovoltaic’s. Besides cost, the flexibility of CNT transparent conductors is a major advantage over brittle ITO coatings for flexible displays. Further, transparent CNT conductors can be deposited from solution (e.g., slot-die coating, ultrasonic spraying) and patterned by cost-effective non lithographic methods (e.g., screen printing, micro plotting).

Energy Storage and Environment

CNTs are widely used in lithium ion batteries for notebook computers and mobile phones, marking a major commercial success. In these batteries, small amounts of MWNT powder are blended with active materials and a polymer binder, such as 1 wt % CNT loading in LiCoO2 cathodes and graphite anodes. CNTs provide increased electrical connectivity and mechanical integrity, which enhances rate capability and cycle life. Many publications report gravimetric energy storage and power densities for unpackaged batteries and super capacitors, where normalization is with respect to the weight of active electrode materials. The frequent use of low areal densities for active materials makes it difficult to assess how such gravimetric performance metrics relate to those for packaged cells, where high areal energy storage and power densities are needed for realizing high performance based on total cell weight or volume.

Biotechnology

Ongoing interest in CNTs as components of biosensors and medical devices is motivated by the dimensional and chemical compatibility of CNTs with biomolecules, such as DNA and proteins. At the same time, CNTs enable fluorescent and photo acoustic imaging, as well as localized heating using near-infrared radiation. SWNT biosensors can exhibit large changes in electrical impedance and optical properties in response to the surrounding environment, which is typically modulated by adsorption of a target on the CNT surface. Low detection limits and high selectivity require engineering the CNT surface (e.g., functional groups and coatings) and appropriate sensor design (e.g., field effects, capacitance, Raman spectral shifts, and photoluminescence).



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.



Indium Arsenide Nanoparticles

Indium Arsenide Nanoparticles

InAs is a semiconductor material made of arsenic and indium. The semiconductor has a melting point of 942 °C and appears in the form of grey crystals with a cubic structure. It is very similar to gallium arsenide and is a material having a direct bandgap. Indium arsenide is popular for its narrow energy bandgap and high electron mobility.

InAs, or indium monoarsenide, is a semiconductor composed of indium and arsenic. It has the appearance of grey cubic crystals with a melting point of 942 °C.

InAs is used for construction of infrared detectors, for the wavelength range of 1–3.8 µm. The detectors are usually photovoltaic photodiodes. Cryogenically cooled detectors have lower noise, but InAs detectors can be used in higher-power applications at room temperature as well. Indium arsenide is also used for making of diode lasers.

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Indium Arsenide Nanoparticles

Indium Arsenide Nanoparticles

Indium arsenide is similar to gallium arsenide and is a direct bandgap material. Indium arsenide is sometimes used together with indium phosphide. Alloyed with gallium arsenide it forms indium gallium arsenide – a material with band gap dependent on In/Ga ratio, a method principally similar to alloying indium nitride with gallium nitride to yield indium gallium nitride.

InAs is well known for its high electron mobility and narrow energy bandgap. It is widely used as a terahertz radiation source as it is a strong photo-Dember emitter.

Quantum dots can be formed in a monolayer of indium arsenide on indium phosphide or gallium arsenide. The mismatches of lattice constants of the materials create tensions in the surface layer, which in turn leads to formation of the quantum dots. Quantum dots can also be formed in indium gallium arsenide, as InAs dots sitting in the gallium arsenide matrix.

Indium Arsenide Quantum Dots:

With the emergence of applications based on short-wavelength infrared light, indium arsenide quantum dots are promising candidates to address existing shortcomings of other infrared-emissive nanomaterials. However, III–V quantum dots have historically struggled to match the high-quality optical properties of II–VI quantum dots.

Technological improvements in the fabrication of short-wavelength infrared (SWIR, 1,000–2,000 nm) detector technology have recently inspired a new wave of optical fluorescence imaging, as longer imaging wavelengths promise increased spatiotemporal resolution, penetration depths and unprecedented sensitivity.

Indium arsenide (InAs) quantum dots (QDs) are among the most promising SWIR probes to address these challenges as they exhibit size-tunable emission, broad absorption spectra, and show higher QYs than rare earth nanocrystals (NCs) silver chalcogenide NC, or organic SWIR dyes. While much recent SWIR imaging has focused on carbon nanotubes (CNTs) the low QYs (<0.1%) and broad emission profiles of as-synthesized CNT ensembles have rendered imaging in narrow spectral windows and multiplexed imaging applications challenging. In contrast to other SWIR QDs, such as PbS or Ag2S, InAs QDs can exhibit higher QYs and probe stability after transfer from the organic phase to aqueous media. This is mostly attributed to the zincblende crystal structure of InAs QDs that allows the straightforward overcoating with a higher band gap shell consisting of established II–VI QD materials, which isolates the InAs core from the environment.

Applications of Indium Arsenide

A member of the III–V family of semiconductors, indium arsenide offers several advantages as an alternative to silicon including superior electron mobility and velocity, which makes it an oustanding candidate for future high-speed, low-power electronic devices.

Indium arsenide is used for construction of infrared detectors, for the wavelength range of 1–3.8 µm. The detectors are usually photovoltaic photodiodes. Cryogenically cooled detectors have lower noise, but InAs detectors can be used in higher-power applications at room temperature as well. Indium arsenide is also used for making of diode lasers.

Indium arsenide is similar to gallium arsenide.

InAs is sometimes used together with indium phosphide. Alloyed with gallium arsenide it forms indium gallium arsenide – a material with band gap dependent on In/Ga ratio, a method principally similar to alloying indium nitride with gallium nitride to yield indium gallium nitride.

InAs is well known for its high electron mobility and narrow energy bandgap. It is widely used as terahertz radiation source as it is a strong Photo-dember emitter.

Quantum dots can be formed in a monolayer of indium arsenide on indium phosphide or gallium arsenide. The mismatches of lattice constants of the materials create tensions in the surface layer, which in turn leads to formation of the quantum dots. Quantum dots can also be formed in indium gallium arsenide, as indium arsenide dots sitting in the gallium arsenide matri

 


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Colloidal Silica (Silicon Dioxide Nanoparticles Dispersion)

COLLOIDAL SILICA – SiO2 Nanoparticles Dispersion

Colloidal Silica is suspensions of silicon dioxide nanoparticles in water or various organic solvents such as ethanol or mineral oil. Nanoshel manufactures oxide nanopowders and nanoparticles with typical particle sizes ranging from 10 to 200nm and in coated and surface functionalized forms.

Nanoparticles have some special properties in optical, electric, thermal, and magnetic aspects. SiO2 is not only an important kind of semi conductive material but also used as the filler of plastic, rubber, coating and gooey because of its good properties of heat-resistance, weather ability and chemical stability. At present there are many preparation methods, but most of them concentrate on preparing SiO2 nanoparticles in solid state or dispersed in organic solvent. These methods are suitable for preparing the polymer-base composite material but difficult to prepare SiO2 nanoparticles/polymer emulsion coating or adhesive because nanoparticles are not easy to disperse uniformly in water system because of their strong hydrophilic properties.

SiO2 nanoparticles dispersed in water can be prepared from silicon by the way of “formation in situ” and “surface-modification in situ “. This kind of preparation method would be widely adopted because of being simple and convenient and cheap in price and effectively resolving dispersion stability of SiO2 nanoparticles in water.

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Colloidal Silica

Silicon Dioxide Dispersion

The chemical and physical characteristics of the different types of amorphous silicon dioxide dispersions contribute to the versatility of these compounds in a variety of commercial applications. Traditionally, silica has had a broad spectrum of product usage including such areas as viscosity control agents in inks, paints, corrosion-resistant coatings, etc. and as excipients in pharmaceuticals and cosmetics. In the food industry, the most important application has been as an anticaking agent in powdered mixes, seasonings, and coffee whiteners. However, amorphous silica has multifunctional properties that would allow it to act as a viscosity control agent, emulsion stabilizer, suspension and dispersion agent, desiccant, etc. The utilization of silica’s in these potential applications, however, has not been undertaken, partially because of the limited knowledge of their physiochemical interactions with other food components and partially due to their controversial status from a toxicological point of view.

Applications:

Silica oxide dispersions are common additive in food production, where it is used primarily as a flow agent in powdered foods, or to absorb water in hygroscopic applications. It is the primary component of diatomaceous earth. Colloidal silica is also used as a wine, beer, and juice fining agent. In pharmaceutical products, silica aids powder flow when tablets are formed.

In semiconductor and light-emitting-diode (LED) production, colloidal silica is a critical component for producing absolutely flat and uniform wafer surfaces. In both industries, colloidal silica performs equally well as a rough surface remover and final polishing additive, and eliminates the need for other surface preparation steps.

In chemical-mechanical planarization, colloidal silica is used to flatten out the irregularities in the films applied to the semiconductor substrates during integrated circuit fabrication. With colloidal silica, different substrates (e.g., silicon, aluminum and sapphire) can be polished to a surface roughness of nanometer, or if needed Angstrom level. In all cases, wafers can be polished to low-defect and ultra-flat surfaces.

Colloidal silica can be used as a binder in zinc-rich coatings to produce hard, durable, protective coatings that shield steel and prevent corrosion in construction environments. At the same time, colloidal silica is facilitating the conversion from Cr VI to Cr III in electroplating industries. For zinc-rich and shop-primer coatings, colloidal silica is an excellent binder for producing mechanically stronger coatings that possess excellent welding properties, as well as resist damage and corrosion. These protective coatings provide ideal protection for steel used in construction.

Paint filler (extender pigment), usually white or slightly colored, such as silicon dioxide dispersions, the refractive index is less than 1.7 of a class of pigments. It has a coating with basic physical and chemical properties of the pigment, but because of similar refractive index and film material, which is transparent in the coating, coloring power and do not have the ability to cover a coloring pigment, is an indispensable paint pigment. Since the vast majority of the filler from natural ore processing products, and its chemical stability, wear resistance, water resistance and other characteristics of a good, and inexpensive, play a role in skeleton in the paint. By increasing the thickness of the coating is filled to improve the mechanical properties of the coating, and can play durable, corrosion resistant, heat insulation, matting and so on. On the other hand it as a way of reducing the manufacturing cost of paint, using its low cost, the price is far lower than the color pigments; hiding under the premise of the film meet, appropriately added to supplement the extender pigment in paint color pigments should some volume.

 

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CuO Dispersion (Copper Oxide Dispersion)

CuO DISPERSION

CuO Dispersion: Nanodispersion are composites consisting of solid nanoparticles with sizes varying generally from 1 to 100 nm dispersed in heat transfer liquids such as water, ethylene glycol, propylene glycol and so on. In the last decade, nanofluids have gained significant attention due to their enhanced thermal properties. A great deal of energy is expended heating industrial and residential buildings in the cold regions of the world.

Cupric oxide (CuO) has been studied as a p-type semiconductor material with narrow band gap because of the natural abundance of its starting material, low cost production processing, nontoxic nature, and its reasonably good electrical and optical properties. CuO dispersions are of great interest due to its potential applications in a wide variety of areas including electronic and optoelectronic devices, such as microelectromechanical systems, field effect transistors, electrochemical cells, gas sensors, magnetic storage media, solar cells, field emitters, and nanodevices for catalysis. It has also been recently emphasized that apart from the size, the shape of the nanostructure is equally important for controlling different properties such as optical absorption in CuO nanostructures and the catalytic activities.

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CuO Dispersion

Copper Oxide Dispersion

In addition to some shared properties of metal oxide nanodispersions, such as TiO2, ZnO, WO3, and SnO2, CuO Dispersion have other unique magnetic and super hydrophobic properties. Furthermore, these nanostructures show very promising applications in heterogeneous catalysis in the complete conversion of hydrocarbons into carbon dioxide, enhancement of thermal conductivity of nanofluids, nanoenergetic materials, and super-hydrophobic surfaces or anode materials for lithium ion batteries (LIBs).

However, this material has not got attention of scientists at right level until recent years. Compared with other oxides of transition metal such as Fe2O3, TiO2, and ZnO only few reports have described the synthesis strategies adopted for CuO nanodispersions along with the introduction of their related applications.

 

Effect of Starting Materials

Solvent is one of the most important components of wet chemical methods as solvent has a crucial effect on the product. Due to the critical role of solvent, it is sometimes used to name a particular wet chemical approach, for example, alcohol-thermal synthesis or DMSO (dimethyl sulfoxide) route. Two primary criteria for the solvents used to synthesize CuO dispersion are as follows: (i) they dissolve copper and alkali hydroxide compounds and (ii) they can be washed away easily or decomposed during the washing and drying process without leaving any detrimental impurities or residues in the final nanoproduct. There are many secondary factors that great attention should be paid for the synthesis process such as viscosity, surface tension, volatility, reactivity, toxicity, and cost.

Salt and Alkali Metal Solution.

According to previous study, any kind of soluble copper salts could be used as precursor to prepare CuO nanodispersions without much difference or at least there seems to be no report on the influence of copper salt precursor. Various copper salts such as chloride, nitrate, sulfate, acetate were used to prepare CuO nanomaterials. However, particle size and uniformity of copper nanoparticles prepared from copper acetate seem better than those from inorganic copper salt. A reasonable explanation is that carboxylate groups are still adsorbed on the surface of the copper oxide nanoparticles and play the role of a surfactant and suppress nanoparticles from growth and aggregating process.

Field-Emission Properties of Copper Oxide Nanodispersion

Field emission, one of the most fascinating properties of nanostructured materials for the practical application in vacuum microelectronic devices such as field-emission displays, X-ray sources, and microwave devices, has been studied extensively in the past few decades. During this time, carbon-based materials, especially carbon nano-tubes, were studied as promising materials for field emitters due to their high mechanical stability, good conductivity, low turn-on field, and large emission currents. Importantly, it appeared that metal oxide nanostructures emitters, as compared to car-bon nanotubes emitters, are more stable in harsh environments and have controllable electrical properties.

Applications

CuO first attracted attention of chemists as a good catalyst in organic reactions but recently discovered applications of CuO such as high-Tc superconductors, gas sensors, solar cells, emitters, electronic cathode materials also make this material a hot topic for physicists and materials science engineers. Some of the most interesting applications of CuO nanomaterials are sensing, photo catalyst and super capacitor are as follows:

Sensing Applications: It is surface conductivity that makes CuO an ideal material for semiconductor resistive gas sensor applications and in fact CuO nanomaterials were used for detection of many different compounds such as CO, hydrogen cyanide, and glucose. As sensing properties closely relate to the chemical reaction on the surface of sensor, the specific area is a key factor to achieve high sensitivity sensor. Due to the high surface area/volume ratio, the sensing property of CuO Dispersion was enhanced greatly. The shape of CuO nanostructures was also believed to affect significantly the sensing properties of CuO nanomaterials; for example, spherical crystals often show higher sensitivity than columnar one.

Photo catalyst and Solar Energy Conversion: Water pollution due to organic wastage from industry production has become a serious problem in the world today. Most of organic compounds in waste water are toxic and cannot be decomposed naturally so they need to be treated with care before disposal. CuO is a promising candidate due to low cost and abundance As a p type semiconductor of narrow band gap in visible region, CuO is expected to be a good material for application in photo catalyst and solar energy conversion. However, some researchers reported that CuO shows almost no or very little photo catalyst properties under visible light. Adding some amount of H2O2 could help to greatly improve the photo catalyst efficiency under visible light.

 

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ZnO Dispersion (Zinc Oxide Dispersion)

ZnO DISPERSION

ZnO Dispersion: A stable colloidal dispersion is expected to remain without sedimentation even after prolonged periods of storage. The settling behavior of dispersions depends mainly on the size and density of the dispersed particles. Dispersion of nanopowders into liquids is a challenging task. The high surface area and surface energy which are responsible for the beneficial effects of Nanomaterials cause agglomeration of particles which leads to poor quality dispersions.

Stabilization of metal oxide nanoparticles are extensively studied over the past few years. As a promising semiconductor material, ZnO finds lot of applications in optoelectronic devices, photo catalysts, cosmetics, pigments, paints, ceramics, solar cells, varistors, sensors etc. The properties of ZnO can be tailor made by reducing the size, whereby the specific surface area gets increases which increases the chemical activity.

Zinc oxide in a dispersed form is used in a number of formulations which contain Water. Such formulations include sun screening preparations, cosmetics and veterinary products. The preparation of these formulations is greatly eased if the Zinc oxide is available in the form of an aqueous dispersion which can be readily incorporated into the formulation. However, stable dispersions of Zinc oxide are difficult to prepare and the Zinc oxide may dissolve at low or high pH values.

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ZnO Dispersion

Zinc Oxide Dispersion

In particular, the unique properties and utility of nanoparticles also arise from a variety of attributes, including the similar size of nanoparticles and biomolecules such as proteins and polynucleic acids. Additionally, nanoparticles can be fashioned with a wide range of metals and semiconductor core materials that impart useful properties such as fluorescence and magnetic behavior. Moreover, unlike their bulk counterparts, nanoparticles have reduced size associated with high surface/volume ratios that increase as the nanoparticles size decreases. As the particle size decreases to some extent, a large number of constituting atoms can be found around the surface of the particles, which makes the particles highly reactive with prominent physical properties. Nanoparticles of particular materials have unique material properties, hence, manipulation and control of the material properties via mechanistic means is needed.

Dispersing property: Additives can improve the degree of zinc oxide dispersion in a given medium and prevent reagglomeration of the aggregates. A 1-3% addition (in reference to zinc oxide) of polyacrylic acid (sodium salt; MW 2100) performs well for dispersion stabilization in most aqueous systems.

Zinc oxide (ZnO) nanopowders are available as powders and dispersions. These nanodispersions exhibit antibacterial, anti-corrosive, antifungal and UV filtering properties. Zinc is a Block D, Period 4 element while Oxygen is a Block P, Period 2 element. Some of the synonyms of zinc oxide nanoparticles dispersions are oxydatum, zinci oxicum, permanent white, ketozinc and oxozinc.

Applications of ZnO dispersion

The zinc oxide dispersions can be used as a UV-absorber, for catalytic applications, electronic applications, production of antifungal or antibacterial materials, sensors, actuators, photovoltaic devices, conductive coatings, among other applications.

  1. Rubber tires: zinc oxide dispersion for silicon rubber, boots, rubber gloves and other labor products, it can greatly extend the life of the products, and improve their appearance and color. It is irreplaceable in by other traditional carbon black surfactant in the use of clear or colored rubber products. Zinc oxide dispersion can also greatly improve products wear resistance and sealing effect.
  2. Paint coating: zinc oxide dispersion can make coating with UV shielding to absorb infrared rays and sterilization Antifungal and improve paint with stain resistance, resistance to artificial aging, water-alkali resistance, abrasion resistance, hardness and adhesion, and other traditional mechanical properties.
  3. Pottery field: ZnO dispersion sinters the temperature which can be reduced 40-60 centigrade in pottery field.
  4. Fiber and textile: ZnO dispersion effectively protects the fiber and clothes from the ultraviolet radiation and infrared ray.
  5. Sun proof cosmetic: Zinc Oxide is used in cosmetics primarily as a skin protectant and for UV attenuation. It is ideal for formulating mild or hnypoallergenic sun care products for UVA/UVB protection for babies and people with sensitive skin. Zinc Oxide is available in a wide range of primary particle sizes and varying optical properties. Notwithstanding, zinc oxide is not supplied as individual grains, but as aggregates of primary particles. The degree of aggregation is a function of the primary particle size and manufacturing process, similar to the case with TiO2. These large aggregates may reduce the protection of the formula against UV light, and likewise scatter visible light, increasing whitening when sun care products are applied on skin.

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