D

dendrimer

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.

dip-pen nanolithography (DPN)

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.

DNA (deoxyribonucleic acid)

The molecule that encodes genetic information, found in the cell's nucleus.

DNA cleavage

The cutting or breaking of a DNA strand.

DNA recognition

The ability of one DNA molecule to “recognize” and attach to another molecule that has a complementary shape.

DNA replication

The process of making copies of DNA strands prior to cell division using existing DNA as a template for the newly created strands.

DNA structures

DNA frameworks occurring in nature: i.e., double helix, cruciforms, left-handed DNA, multistranded structures. Also, microarrays of small dots of DNA on surfaces.

doping

In electronics, the addition of impurities to a semiconductor to achieve a desired characteristic, often altering its conductivity dramatically. Also known as semiconductor doping.

drug delivery

The use of physical, chemical, and biological components to deliver controlled amounts of a therapeutic agent.

E

electrochemical methods

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.

electrochemical properties

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.

electroluminescence (EL)

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.

electron diffraction

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.

electron microscopy

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.

electron transfer

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.

electron transport

The manipulation of individual electrons. Nanolithography techniques allow single electrons to be transported at very low temperatures in specially designed circuits.

electron tunneling

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.

electro-optics

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.

electrophoresis

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.

encapsulation

The condition of being enclosed or the process of enclosing.

epitaxy

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.

excited states

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.