A silicon-based foam composed mostly of air. Often called "frozen smoke" or "blue smoke," aerogels have extremely low thermal conductivity, which gives them extraordinary insulating properties. They are the lowest-density solids known on earth.
A suspension of fine particles (0.01-10 microns) of a solid or liquid in a gas.
A collection of individual units or particles gathered together into a mass or body.
A group of soft, very reactive elements that includes lithium, sodium, and potassium.
A ceramic material made of aluminum oxide. Alumina is often used as a substrate, or underlying layer, for experiments. Alumina can be mixed with various amounts of titania (titanium dioxide) to change its properties as a substrate.
A silvery-white, metallic element with good conductive and thermal properties.
A scanning probe microscopy instrument capable of revealing the structure of samples. The AFM uses a sharp metal tip positioned over a conducting or non-conducting substrate and the surface topography is mapped out by measuring the mechanical force exerted on the tip. See scanning probe microscopy.
The study of the structure and function of biological substances to develop man-made systems that mimic natural ones; imitating, copying, or learning from biological systems to create new materials and technologies.
A polymer found in nature. DNA and RNA are examples of naturally occurring biopolymers. See also polymer.
A sensor used to detect a biological substance (for example: bacteria, blood gases, or hormones). Biosensors often make use of sensors that are themselves made of biological materials or of materials that are derived from or mimic biological materials.
The process by which living organisms produce chemical compounds.
Self-assembled material composed of long sequences of "blocks" of the same monomer unit, covalently bound to sequences of unlike type.
A nonmetallic element found in all living things. Carbon is part of all organic compounds and, in combined form, of many inorganic substances. Diamonds, graphite, and fullerenes are pure forms of carbon.
Long, thin cylinders of carbon, discovered in 1991 by S. Iijima. These large macromolecules are unique for their size, shape, and remarkable physical properties. They can be thought of as a sheet of graphite (a hexagonal lattice of carbon) rolled into a cylinder. The physical properties are still being discovered. Nanotubes have a very broad range of electronic, thermal, and structural properties that change depending on the different kinds of nanotube (defined by its diameter, length, and chirality, or twist). To make things more interesting, besides having a single cylindrical wall (Single Walled Nanotubes or SWNTs), nanotubes can have multiple walls (MWNTs)--cylinders inside the other cylinders. Sometimes referred to simply asnanotubes.
A small, usually microscopic, membrane-bound structure that is the fundamental unit of all living things. Organisms can be made up of one cell (unicellular; bacteria, for example) or many cells (multicellular; human beings, for example, which are made up of an estimated 100,000 billion cells.)
The bonding of cells to surfaces or to other cells. Protein molecules at the surface of cells are generally the glue involved in cell adhesion.
The process by which a cell in a multicellular organism interprets its surroundings.
Analysis of critical features of an object or concept.
A technique used to deposit thin layers of coatings on a substrate . In CVD, chemicals are vaporized and then applied to the substrate using an inert gas such as nitrogen as a carrier. CVD is used in the production of microchips, integrated circuits, sensors, and protective coatings.
A technique similar to CVD used to grow crystal structures.
The process by which a liquid or gas is chemically bonded to the surface of a solid.
Very fine solid particles that will not settle out of a solution or medium. Smoke is an example of a colloid, being solid particles suspended in a gas. Colloids are the intermediate stage between a truly dissolved particle and a suspended solid, which will settle out of solution.
A material made from two or more components that has properties different from the constituent materials. Composite materials have two phases: matrix (continuous) phase, and dispersed phase (particulates, fibers). For example, steel-reinforced cement is a composite material. The concrete is the matrix phase and the steel rods are the dispersed phase. The composite material is much stronger than either of the phases separately.
A branch of theoretical chemistry with the goal of creating computer programs to calculate the properties of molecules (such as total energy, dipole moment, and vibrational frequencies) and to apply these programs to concrete chemical objects.
The process of using more than one type of monomer in the production of a polymer , resulting in a product with properties different from either monomer. See monomer,polymer.
The process of growing crystals.
A polymer with multiple branches. Dendrimers are synthetic 3-D macromolecular structures that interact with cells, enabling scientists to probe, diagnose, treat, or manipulate cells on the nanoscale. From the Greek word dendra, meaning tree.
A method for nanoscale patterning of surfaces by the transfer of a material from the tip of an atomic force microscope onto the surface. Developed by Professor Chad A. Mirkin, the DPN allows researchers to precisely lay down or “write” chemicals, metals, biological macromolecules, and other molecular “inks” with nanometer dimensions and precision on a surface.
The molecule that encodes genetic information, found in the cell's nucleus.
The cutting or breaking of a DNA strand.
The ability of one DNA molecule to “recognize” and attach to another molecule that has a complementary shape.
The process of making copies of DNA strands prior to cell division using existing DNA as a template for the newly created strands.
DNA frameworks occurring in nature: i.e., double helix, cruciforms, left-handed DNA, multistranded structures. Also, microarrays of small dots of DNA on surfaces.
In electronics, the addition of impurities to a semiconductor to achieve a desired characteristic, often altering its conductivity dramatically. Also known as semiconductor doping.
The use of physical, chemical, and biological components to deliver controlled amounts of a therapeutic agent.
Experimental methods used to study the physical and chemical phenomena associated with electron transfer at the interface of an electrode and a solution. Electrochemical methods are used to obtain analytical or fundamental information regarding electroactive species in solution. Four main types of electrochemical methods include potentiometry, voltammetry, coulometry, and conductimetry.
The characteristics of materials that occur when a) an electric current is passed through a material and produces chemical changes and b) when a chemical reaction is used to produce an electric current, as in a battery.
The light produced by some materials — mainly semiconductors — when exposed to an electric field. In this process, the electric field excites electrons in the material, which then emit the excess energy in the form of photons. Light-emitting diodes (LEDs) are the most well known example of EL.
A surface science technique used to examine solids by firing a beam of electrons at a sample and observing the electron deflection from the sample’s atomic nuclei.
The visual examination of very small structures with a device that forms greatly magnified images of objects by using electrons rather than light to create an image. An electron microscope focuses a beam of electrons at an object and detects the actions of electrons as they scatter off the surface to form an image.
The passage of an electron from one constituent of a system to another, as from one molecule or ion to another. Applications include photography, xerography, and dye-sensitized injection solar cells.
The manipulation of individual electrons. Nanolithography techniques allow single electrons to be transported at very low temperatures in specially designed circuits.
The passage of electrons through a barrier that, according to the principles of classical mechanics, cannot be breached. An example of electron tunneling is the passage of an electron through a thin insulating barrier between two superconductors. Electron tunneling is a pure quantum mechanical effect that cannot be explained by a classical theory.
The study of the influence of an electric field on the optical properties of matter — especially in crystalline form — such as transmission, emission, and absorption of light. Also known as optoelectronics.
A method of separating large molecules, such as DNA fragments or proteins, from a mixture of similar molecules by passing an electric current through a medium containing the molecules. Depending on its electrical charge and size, each kind of molecule travels through the medium at a different rate, allowing separation.
The condition of being enclosed or the process of enclosing.
The growth of a crystal layer of one mineral on the crystal base of another mineral in such a manner that the crystalline orientation of the layer mimics that of the substrate.
In quantum mechanics, all levels of energy above the lowest or ground state (also known as equilibrium). Excited states are ranked in order of increasing energy; that is, the second excited state has higher energy than the first.
Crystalline substances that have a permanent spontaneous electric polarization (electric dipole moment per cubic centimeter) that can be reversed by an electric field.
A fluid in which fine particles of iron, magnetite or cobalt are suspended, typically in an oil. A ferrofluid is superparamagnetic and can create liquid seals held in position by magnetic fields. One application of ferrofluids is to keep dust off of the drive shafts of magnetic disk drives. Ferrofluids were invented by NASA as a way to control the flow of liquid fuels in space.
Substances, including a number of crystalline materials, that are characterized by a possible permanent magnetization.
A phenomenon by which a material can exhibit spontaneous magnetization. One of the strongest forms of magnetism, ferromagnetism is responsible for most of the magnetic behavior encountered in everyday life and is the basis for all permanent magnets.
The local change from the normal value produced by an electric field in the charge-carrier concentration of a semiconductor.
The emission of electrons from the surface of a metallic conductor into a vacuum (or into an insulator) under influence of a strong electric field. In field emission, electrons penetrate through the potential surface barrier by virtue of the quantum-mechanical tunnel effect. Also known as cold emission. See also electron tunneling.
The process in which molecules or matter absorb high energy photons and then emit lower energy photons. The difference in energy causes molecular vibrations.
A technique to measure the interaction of radiant energy with matter by passing emitted fluorescent light through a monochromator to record the fluorescence emission spectrum.
A stain used for tagging and labeling biological cells to detect structures, molecules, or proteins within the cell. Also single-stranded pieces of DNA, with enzymatically incorporated fluorescent tags, affixed in a microscopic array (DNA microarray).
An electrical cell that converts the intrinsic chemical free energy of a fuel into direct-current electrical energy in a continuous catalytic process. Fuel cells extract the chemical energy bound in fuel and, in combination with air as an oxidant, transform it into electricity. Researchers are hoping to develop fuel cells that could take the place of combustion engines, thereby reducing the world dependence on fossil fuels.
A molecular form of pure carbon that takes the form of a hollow cage-like structure with pentagonal and hexagonal faces. The most abundant form of fullerenes is C60 (carbon-60), a naturally occurring form of carbon with 60 carbon atoms arranged in a spherical structure that allows each of the molecule's 60 atomic corners to bond with other molecules. Larger fullerenes may contain from 70 to 500 carbon atoms. Named for R. Buckminster Fuller for his writing on geodesic domes; also referred to as “buckyballs.”
A class of chemical reactions that occur in a single gaseous phase based on the physical state of the substances present. Examples include the combination of common household gas and oxygen to produce a flame.
The transcription, translation, and phenotypic manifestation of a gene.
Technology used to interpret the sequence of the nucleotides (adenine, cytosine, guanine, and thymine) in a DNA sample from bands on an X-ray film image. Scientists use a combination of lasers, high-precision optics, and computer software to determine the sequence of fluorescently tagged DNA molecules.
Techniques that allow experimenters to manipulate specific genes within an organism and determine the effect this has on the functioning of the organism.
The study of the genetic content of organisms.
The use of chemical products and processes that reduce or eliminate substances hazardous to human health or the environment, creating no waste or generating only benign waste.
A chemical process in which the catalyst and the reactant are present in separate phases. Usually the catalyst is a solid, the reactants and products are in gaseous or liquid phases, and the catalytic reaction occurs on the surface of the solid.
An assortment of technologies used to identify small molecules. HTS is often used in drug development to screen potential sources for novel molecules. It is capable of processing a wide variety of input samples and track data for each.
A process in which a catalyst is in the same phase — usually a gas or liquid — as the reactant. Catalysis of the transformation of organic molecules by acids or bases is one of the most widespread types of homogeneous catalysis.
The interaction of a hydrogen atom with another atom, influencing the physical properties and three-dimensional structure of a chemical substance. Hydrogen bonding generally occurs between atoms of hydrogen and nitrogen, oxygen, or fluorine. An important example of a hydrogen bonding is the formation of the DNA double helix.
Having an affinity for, attracting, adsorbing, or absorbing water. Hydrophilic effect occurs when a liquid comes in contact with another phase — typically a solid substrate, if it attracts the liquid molecules — causing the liquid to attain a relatively large contact area with the substrate.
Lacking an affinity for, repelling, or failing to adsorb or absorb water. Hydrophobic effect occurs when a liquid comes in contact with another phase — typically a solid substrate, if it exerts a repulsive force onto the liquid — causing the liquid to retract from the surface, with relatively little contact area between liquid and substrate.
A technique in which infrared light is passed through matter and some of the light is absorbed by inciting molecular vibration. The difference between the incident and the emitted radiation reveals structural and functional data about the molecule.
A protein-coated pore in a cell membrane that selectively regulates the diffusion of ions into and out of the cell, allowing only certain ion species to pass through the membrane.
The discharge of charged particles in a fluid electrolyte to conduct an electrical current.
In electronics, the interface between two different types of materials within diodes, transistors, and other semiconductor devices.
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Miniaturized analytical systems that integrate a chemical laboratory on a chip. Lab-on-a-chip technology enables portable devices for point-of-care (or on-site) medical diagnostics and environmental monitoring.
Ultrathin films (monolayers and isolated molecular layers) created by nanofabrication. An LB-film can consist of a single layer or many, up to a depth of several visible-light wavelengths. The term Langmuir-Blodgett comes from the names of a research scientist and his assistant, Irving Langmuir and Katherine Blodgett, who discovered unique properties of thin films in the early 1900s. Such films exhibit various electrochemical and photochemical properties. This has led some researchers to pursue LB-films as a possible structure for integrated circuits (ICs). Ultimately, it might be possible to construct an LB-film memory chip in which each data bit is represented by a single molecule. Complex switching networks might be fabricated onto multilayer LB-films chips.
In crystallography, a regular periodic arrangement of atoms in three-dimensional space.
A semiconductor device that converts electrical energy into electromagnetic radiation. The LED emits light of a particular frequency (hence a particular color) depending on the physical characteristics of the semiconductor used. See electroluminescence.
A type of nanoparticle made from fat molecules surrounding a core of water. Liposomes were the first nanoparticles used to create unique therapeutic agents.
A method of extracting one liquid from another, generally through the use of solvents.
The process of imprinting patterns on materials. Derived from Greek, the term lithography means literally "writing on stone.” Nanolithography refers to etching, writing, or printing at the microscopic level, where the dimensions of characters are on the order of nanometers (units of 10 -9 meter, or millionths of a millimeter).
Cool light emitted by sources as a result of the movement of electrons from more energetic states to less energetic states. There are many types of luminescence. Chemiluminescence is produced by certain chemical reactions. Electroluminescence is produced by electric discharges, which may appear when silk or fur is stroked or when adhesive surfaces are separated. Triboluminescence is produced by rubbing or crushing crystals.
A very large molecule composed of hundreds or thousands of atoms.
The force of attraction or repulsion between various substances, especially those made of iron and certain other metals. Magnetism is the result of the motion of electrons in the atoms.
A device used to identify the kinds of molecules present in a given substance: the molecules are ionized and passed through an electromagnetic field. The way in which they are deflected is indicative of their mass and identity.
A technique that uses a silicone stamp to deposit molecules on surfaces in patterns with microscale features.
A device that has one or more channels with at least one dimension less than 1 mm. Common fluids used in microfluidic devices include whole blood samples, bacterial cell suspensions, protein or antibody solutions and various buffers. The small amounts of samples needed and relative inexpensiveness of microfluidic devices make them attractive for biomedical research and creating clinically useful technologies. One of the long term goals in the field of microfluidics is to create integrated, portable clinical diagnostic devices for home and bedside use, thereby eliminating time consuming laboratory analysis procedures.
A multidisciplinary field that studies the behavior of fluids at volumes thousands of times smaller than a drop. Microfluidic components form the basis of “lab-on-a-chip” devices capable of performing several different functions. Microfluidics is critical in the development of gene chip and protein chip technology.
The use of standard semiconductor technologies along with special processes to fabricate miniature mechanical devices and components on silicon and other materials. See micromolding.
An method of fabricating microsystems using tiny molds to cast materials. Micromolding serves as an alternative to micromachining. See micromachining.
A technique for growing thin layers of compound semiconductors in which metal-organic compounds are decomposed near the surface of a heated substrate wafer.
Method used to grow layers of materials of atomic-scale thickness on surfaces.
A process by which functional monomers are allowed to self-assemble around a template molecule and locked into place. The template molecule is then removed, leaving behind a cavity that is complementary in shape and functionality as the template molecule, which will bind molecules identical to the template.
A small molecule that may become chemically bonded to other monomers to form a polymer; from Greek mono "one" and meros "part".
The understanding of the chemical and physical properties of atomic and nanoscale materials.
Materials that result from the intimate mixture of two or more nanophase materials. See composite.
Solids with small domains of crystallinity within the amorphous phase. Applications include optical electronics and solar cells.
A generic term to describe nanoscale electrical/mechanical devices.
A polymer membrane formed by electrospinning, with filament diameters of 150–200 nanometers. Also called nanomesh, it is used in air and liquid filtration applications.
The control of nanoscale amounts of fluids.
Writing nanoscale patterns. See Lithography.
The process of manipulating items at an atomic or molecular scale in order to produce precise structures.
Nanoscale particles, films, and composites designed and assembled in controlled ways.
A unit of measurement equal to one-billionth of one meter. The head of a pin is about 1 million nanometers across. A human hair is about 60,000 nanometers in diameter, and a DNA molecule is between 2-12 nanometers wide.
Particles ranging from 1 to 100 nanometers in diameter. Semiconductor nanoparticles up to 20 nanometers in diameter are often called quantum dots, nanocrystals, or Q-particles.
Engineered materials with nanoscale holes, used in filters, sensors, and diffraction gratings. In DNA sequencing, nanoporous materials have tiny holes that allow DNA to pass through one strand at a time. In biology, complex protein assemblies that span cell membranes allow ionic transport across the otherwise impermeable lipid bilayer.
A nanoparticle that has a metallic shell surrounding a semiconductor. Nanoshells are being investigated for use in treating cancer.
Structures made from nanomaterials.
Long, thin cylinders of carbon, discovered in 1991 by S. Iijima. These large macromolecules are unique for their size, shape, and remarkable physical properties. They can be thought of as a sheet of graphite (a hexagonal lattice of carbon) rolled into a cylinder. The physical properties are still being discovered. Nanotubes have a very broad range of electronic, thermal, and structural properties that change depending on the different kinds of nanotube (defined by its diameter, length, and chirality, or twist). To make things more interesting, besides having a single cylindrical wall (Single Walled Nanotubes or SWNTs), nanotubes can have multiple walls (MWNTs)--cylinders inside the other cylinders. Usually referred to as carbon nanotubes, also known as nanorods. Applications for carbon nanotubes include high-density data storage, nanoscale electronics, and flexible solar cells.
Analytical technique used to determine the structure of molecules. In NMR, the molecule is placed within a strong magnetic field to align the atomic nuclei. An oscillating electromagnetic field is applied, and the radiation absorbed or emitted by the molecule is measured. Not all atoms can be detected using NMR because the nuclei must have non-zero magnetic moments.
Interactions first recognized by J. D. van der Waals in the nineteenth century. In contrast to the covalent interactions, noncovalent interactions are weak interactions that bind together different kinds of building blocks into supramolecular entities. Also referred to as van der Waals interactions.
Process in which a molecule loses one or more electrons to another component of the reaction.
A part of a sample of matter that is in contact with other parts but is separate from them. Properties within a phase are homogeneous (uniform). For example, oil and vinegar salad dressing contains two phases: an oil-rich liquid, and a vinegar-rich liquid. Shaking the bottle breaks the phases up into tiny droplets, but there are still two distinct phases.
A map that shows which phases of a sample are most stable for a given set of conditions. Phases are depicted as regions on the map; the borderlines between regions correspond to conditions where the phases can coexist in equilibrium.
The movement of heat, mass, and momentum in a medium.
Light excited in a body by some form of electromagnetic radiation in the ultraviolet, visible, or infrared regions of the electromagnetic spectrum. See electroluminescence,LED, and luminescence.
Dielectric crystal that produce a voltage when subjected to mechanical stress or can change shape when subjected to a voltage.
A macromolecule formed from a long chain of molecules called monomers; a high-molecular-weight material composed of repeating sub-units. Polymers may be organic, inorganic, or organometallic, and synthetic or natural in origin. See biopolymer.
A technique for copying and amplifying the complementary strands of a target DNA molecule.
The property of a chemical substance crystallizing into two or more forms having different structures, such as diamond, graphite, and fullerenes from carbon. Also known as pleomorphism.
Large organic molecules involved in all aspects of cell structure and function.
The separation, identification, and characterization of the complete set of proteins present in the various cells of an organism; the design and construction of new proteins.
Atoms caged inside nanocrystals.
A nanoscale crystalline structure made from cadmium selenide that absorbs white light and then re-emits it a couple of nanoseconds later in a specific color. The quantum dot was originally investigated for possible computer applications. Recently, researchers are investigating the use of quantum dots for medical applications, using the molecule-sized crystals as probes to track antibodies, viruses, proteins, or DNA within the human body.
Analysis of the intensity of Raman scattering, in which light is scattered as it passes through a material medium and suffers a change in frequency and a random alteration in phase. The resulting information is useful for determining molecular structure.
In analytical chemistry, the preparation of one or more subsamples from a sample of material that is to be analyzed chemically. In chemistry, reduction refers to the reaction of hydrogen with another substance or the chemical reaction in which an element gains an electron.
Elements used in performing photolithography experiments. Resists are polymer materials spun onto a substrate. When exposed to UV light, the polymer in the resist cross-links. When treated with a solvent, the cross-linked portion of the resist dissolves, leaving the desired pattern.
A long linear polymer of nucleotides found mainly in the cytoplasm of a cell that transmits genetic information from DNA to the cytoplasm and controls certain chemical processes in the cell.
Molecules that act as scaffolds upon which proteins are assembled to form functional ribosomes. RNA structures include a variety of single-stranded and double-stranded structures that result in complex three-dimensional structures.
Three-dimensional biodegradable polymers engineered for cell growth.
Experimental techniques used to image both organic and inorganic surfaces with (near) atomic resolution. Includes atomic force microscopes and scanning tunneling microscopes.
A scanning probe microscopy instrument capable of revealing the structure of samples. The STM uses a sharp metal tip positioned over a conducting substrate with a small potential difference applied between them. The gap between the tip and substrate surface is small enough so that electrons can tunnel between the tip and the surface. The tip is then scanned across the surface and adjusted to keep a contact current flowing. By recording the tip height at each location a "map" of the sample surface is obtained.
The light that results when a beam of monochromatic light hits an asymmetrical surface. The second harmonic light is at a frequency twice that of the incident light and allows the study of surface phenomena such as molecular adsorption, aggregation, and orientation as well as of buried interfaces.
Monomolecular films that form or self-assemble after immersing a substrate into a solution of an active surfactant.
At the molecular level, the spontaneous gathering of molecules into well-defined, stable, structures that are held together by intermolecular forces. In chemical solutions, self-assembly (also called Brownian assembly) results from the random motion of molecules and the affinity of their binding sites for one another. Self-assembly also refers to the joining of complementary surfaces in nanomolecular interaction. Developing simple, efficient methods to organize molecules and molecular clusters into precise, pre-determined structures is an important area of nanotechnology exploration.
A broad collection of methods used to study and analyze the behavior and performance of actual or theoretical systems. Simulation provides a mechanism for predicting computationally useful functional properties of systems, including thermodynamic, thermochemical, spectroscopic, mechanical, and transport properties.
The analysis of individual molecular properties in contrast with the study of bulk properties.
In materials science, the starting materials for semiconductor devices; powdered materials with uniform chemical composition throughout the mixture.
Gels, glasses, and ceramic powders synthesized through the sol-gel process; organic-inorganic composite materials.
A chemical synthesis technique for preparing gels, glasses, and ceramic powders generally involving the use of metal alkoxides.
Transformations that occur in and between solids and between solids and other phases to produce solids.
A wafer that is the basis for subsequent processing operations in the fabrication of semiconductor devices.
An object or substance that conducts electricity with zero resistance.
Extreme water repellence. See hydrophobic effect.
Any process or reaction for building up a complex compound by the union of simpler compounds or elements.
Techniques for the design and creation of new materials in the laboratory.
In cell and molecular biology, the macromolecular model for the synthesis of another macromolecule.
The engineered design and creation of materials of controlled size, shape, and surface chemistry.
A film one molecule thick; often referred to as a monolayer.
The use of electron high-energy beams to achieve magnification close to atomic observation. See electron microscopy.
Method to determine concentrations of an absorbing species in solution. This technique uses light in the visible and adjacent near ultraviolet (UV) and near infrared (NIR) ranges to achieve this quantitative analysis.
In cell biology, a relatively small and enclosed compartment, separated from the cytosol by at least one lipid bilayer. Vesicles store, transport, or digest cellular products and wastes.
In electronics, coating a contact surface with an adherent film of mercury. In metallurgy, wetting refers to spreading liquid filler metal or flux on a solid base metal. Wetting occurs if a liquid is in contact with another phase, typically a solid substrate, with the substrate exerting an attractive force on the liquid molecules.
The use of X-ray radiation to detect heavy elements in the presence of lighter ones, to give critical-edge absorption to identify elemental composition, and to identify crystal structures by diffraction patterns.
The scattering of x-rays from a crystal, resulting in an interference pattern used to determine the structure of the crystal.
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