The electromagnetic spectrum, broken by a specific pattern of dark lines or bands, which are observed when electromagnetic radiation traverses a particular absorbing medium. An absorption spectrum is, in a sense, the opposite of an emission spectrum.
Adenine (symbol A) is one of the constituent bases of DNA (and RNA), which pairs with thymine (and uracil).
In chemistry, alcohol is used as a more general term to signify any organic compound in which a hydroxyl group (OH) is bound to a carbon atom, which in turn is bound to other hydrogen and/or carbon atoms. The simplest and most commonly used alcohols are methanol and ethanol.
Any of a class of highly reactive chemical compounds containing a carbon atom linked to oxygen and a hydrogen atom. They are mainly used for the manufacture of synthetic resins, dyestuffs, flavourings, perfumes, and other common chemicals.
Simple organic compounds, in which a carbon atom is connected to an oxygen and a nitrogen atom. Twenty amino acids serve as building blocks (basic units) of protein molecules. The arrangement of amino acids in a protein is called amino acid sequence. The shape and function of each protein are determined by the kind of amino acids involved in its making and their arrangement in its structure.
Fibrous and insoluble aggregates of misfolded proteins. Abnormal structures of amyloid proteins found in the brain are called amyloid plaques. The formation of amyloid plaques is thought to contribute to the degradation of brain neurons (nerve cells) and is linked to the emergence of degenerative diseases such as the Alzheimer's disease.
A type of protein. The body's immune system produces antibodies when it detects harmful substances, called antigens. Each type of antibody is unique and defends the body against one specific type of antigen.
A colorless, odorless, tasteless, nontoxic gaseous element constituting approximately one percent of the Earth's atmosphere. It remains inert under most conditions and forms no confirmed stable compounds at room temperature.
The mixture of gases and particles which cover the surface of the earth. This natural body of air is composed of approximately 21% oxygen, 78% nitrogen, and 1% other gases.
The presence in the air of one or more contaminants in such a concentration and of such duration as to cause a nuisance or to be injurious to human life, animal life or vegetation.
The smallest particle of an element that can exist either alone or in combination, consisting of electrons, protons, and neutrons. Early theories on the composition of matter begin in 400 B.C., with the ancient Greek philosopher Democritus who thought matter could not be divided indefinitely.
The arrangement and number of smaller particles (protons, neutron, electrons) of an atom.
Time unit equal to one quintillionth of a second (10-18s) or one thousandth of a femtosecond.
The difference in energy in a substance between electron orbitals in which the electrons are not free to move (the valence band) and orbitals in which they are relatively free and will carry a current (the conduction band).
Chemical activity in living cells that allows them to grow, multiply, and do their daily tasks.
The chemistry of biochemical reactions. Biochemical reactions refer to chemical activities in living cells that allows them to grow, multiply, and do their daily tasks.
Particles being biologically compatible by not producing a toxic, injurious, or immunological response in living tissue.
The application of the principles of the natural sciences, especially biology and physiology, to clinical medicine.
Mimicking biological systems.
A chemical compound found in living organisms. They are composed mainly of carbon, hydrogen, oxygen, nitrogen, sulfur and phosphorus. Biomolecules are the building blocks of life that perform important functions in the living organisms. There are several types of biomolecules but the most well known are the proteins and the DNA.
The four blood types (A, B, AB, and O) are differentiated on the basis of the proteins present in each of them. If certain proteins are missing from the blood, or if the wrong proteins are present, health problems may arise, such as haemophilia (blood does not clot properly, and cuts do not heal).
Α colorless gas, dangerously reactive and a valuable reagent in organic synthesis. It is used in the refining of aluminium, magnesium, zinc, and copper alloys to remove nitrides, carbides, and oxides from molten metal.
Any illness occurring when one of the body's own cells starts growing out of control. The name comes from ancient Greek and it means "crab". The Greeks thought that clusters of cancer cells looked like the legs of a crab!
A product of combustion of organic matter with insufficient oxygen supply. Carbon monoxide is a significantly toxic gas, colorless, odorless, tasteless, and non-irritating.
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst.
The structural, functional and biological unit of all organisms.
A selectively permeable biological membrane that encloses the cell and maintains differences between the cell contents and the outside environment.
Force by which atoms or ions are bound in a molecule or crystal.
The branch of physics that studies chemical processes from the point of view of physics.
Any of a material's properties that becomes evident during a chemical reaction; that is, any quality that can be established only by changing a substance's chemical identity.
Any chemical process in which substances are changed into different ones, with different properties, as distinct from changing position or form. Energy is released or is absorbed, but no loss in total molecular weight occurs in going from reactants to products.
Branch of science concerned with the properties, composition, and structure of substances (molecules) and the changes they undergo when they combine or react under specified conditions.
A characteristic of any object which cannot be superimposed upon its reflection. Chirality is used to denote the existence of left/right opposition between objects.
Part of a molecule responsible for its colour.
A macro-molecule made of deoxyribonucleic acid (or DNA), which contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. A normal human body has 23 pairs of chromosomes (46 total chromosomes).
A condition caused by two waves whose electric field components are 90 degrees out of phase, causing an effective rotation of the electric field about an axis in direction of propagation.
The most abundant protein in the body and one of the main constituents of skin, bones, tendons, cartilage, and ligaments. It forms fibres that bind together and strengthen these tissues.
Relating to quantitative chemical analysis by color.
The conversion efficiency of a solar cell is the proportion of sunlight energy that the cell converts to electrical energy.
A solid having, in all three dimensions of space, a regular repeating internal unit of structure.
The arrangement of atoms, ions, or molecules in a crystal.
A family of compounds made up of sugar molecules bound together in a ring.
Cytocine (symbol C) is one of the constituent bases of DNA and RNA, which pairs with guanine.
DDL is a cyclic compound, i.e. a compound in which a series of carbon atoms are connected to form a loop or ring [3,5-diacetyl-1,4-dihydrolutidine].
Loss of brain function that occurs with certain diseases or trauma. It affects memory, thinking, language, judgment, and behaviour.
Abbreviation that stands for ‘DeoxyriboNucleic Acid’. The DNA plays a central role in protein synthesis, and is responsible for the transmission of hereditary characteristics from parents to offspring.
Essential building block of the DNA molecule. DNA contains four complementary bases: adenine (A), which pairs with thymine (T), and cytosine (C), which pairs with guanine (G). The human genome is made of a sequence of roughly three billion of these bases.
A succession of letters representing the DNA bases, which are the basic subunits of a DNA molecule.
A laser that makes use of organic dyes and emits light in the visible light spectrum.
The space where a charged particle experiences force.
Property of matter, carried by elementary particles (protons are positively charged, electrons are negatively). Electric charge, which can be positive or negative, occurs in discrete natural units and is neither created nor destroyed.
By this term we refer to the numerous phenomena that result from the directed motion of electrons due to the presence of an electric field.
The conversion of electricity directly into light.
The electromagnetic fields are spaces where invisible forces occur anytime electricity is being used.
Emission or transmission of energy through space or through a material medium in the form of electromagnetic waves.
Elementary (subatomic) particle of the atom that travels around the nucleus, being contained within fixed regions of space termed orbitals (energy levels or shells). Electrons are negatively charged.
A collective scattering phenomenon with electrons being (nearly elastically) scattered by atoms in a regular array (crystal).
An electron hole (usually referred to simply as a hole) is the absence of an electron from the otherwise full valence band.
A unit of energy equal to the energy acquired by an electron falling through a potential difference of one volt.
The particular distribution of electrons among available shells or orbitals.
The movement of an electron in an atom or molecule from a lower energy state (an orbital closer to the nuclei) to a higher energy state.
A branch of technology involving components, devices and systems which operate by modification of the optical properties of a material by an electric field.
Any substance that cannot be broken up into simpler substances by chemical means. Currently 115 elements have been observed and are displayed in the Periodic Table of Elements. Gold, silver, iodine, oxygen and nickel are examples of elements.
Two nonsuperimposable objects which are mirror images of each other are. The term enantiomer is synonymous with enantiomorph. For example, the letters b and d are enantiomers of each other.
The position in which electrons orbit around the nucleus. Each energy level (or shell) can hold a set number of electrons.
A protein that functions as a catalyst meaning that it speeds up the rate of reaction between substances.
Laboratory methods for studying enzyme activity
The addition of the amount of energy (excitation energy) necessary to a system that results in its alteration, ordinarily from the condition of lowest energy (ground state) to one of higher energy (excited state). Talking in detail, electrons in an atom may absorb the photons' energy and jump to a higher energy level in outer shells. When this happens, the atom is said to be "excited". Very soon, the electrons lose the extra energy and return to a lower level shell -a process called “de-excitation” of the atom. If the photon energy is too high, the electrons may even escape from the material (case of the photoelectric effect).
A discrete amount of energy needed to be absorbed in order an electron of the particlar atom to excite.
The study of chemical reactions on a very short time scale, often using pulsed lasers.
Unit of time equal to one quadrillionth of a second (10-15s) or one thousandth of a nanosecond.
A laser that emits ultra-fast radiation (ultrashort pulses of light).
Experimental technique used for the study of photochemical reactions. It allows following the time evolution of intermediate species which play an important role in the formation of the reaction products.
A device so constructed that appropriate measurements (as of absorbance) may be made on a flowing liquid.
A probe molecule which reacts selectively with formaldehyde to form a cyclic compound called DDL.
The luminescence of a substance when excited by light or other forms of electromagnetic radiation. In most cases, fluorescence occurs when a molecule absorbs light photons from an ultraviolet (or visible) light source (this is known as excitation) and then rapidly emits light photons back, as it returns to its ground state. Fluorescence phenomena are therefore based on the property of molecules to absorb light at a particular wavelength and to subsequently emit light of longer wavelength after a brief interval.
Measurement based on detecting the light emitted as a result of fluorescence.
Fluorescence spectroscopy is used by scientists in order to identify and analyze fluorescent samples at very low concentration (in the parts per billion range) and also to draw information on the structure, formulation, and stability of the fluorescent substances. Fluorescence spectra are produced when ions or molecules absorb electromagnetic radiation at short wavelengths (higher energy), which then radiate back at longer wavelengths (lower energy).
The simplest aldehyde, H2CO, and a central building block in the synthesis of many other compounds. At standard temperature and pressure it is a flammable, poisonous, colourless gas with a suffocating odour. Formaldehyde was discovered by Wilhelm Von Hofmann and Alexander Butlerov in 1867. It was not until 1892, though, when Friedrich Von Stradonitz managed to isolate and purify this substance.
A 10% solution of formaldehyde in water used as a disinfectant or to preserve biological specimens.
One of the three states of matter, along with solids, and liquids. In any gas, molecules are only weakly attracted to each other and move freely in the available space. The term gas was introduced to the chemical vocabulary by John Baptist Van Helmont (1577-1644) who produced “gas silvestre” (i.e. “gas that is wild and dwells in out-of-the-ways places”). The gas he discovered was carbon dioxide (CO2) even though he was not aware of it at the time.
One state in which matter can exist (the other two common states are solids and liquids).
One of the three states of matter, along with solids, and liquids. In gases, distances between each molecule or atom are large, giving them a great mobility in space. Atmosphere for instance, is composed of a mixture of gases. In any gas, molecules are only weakly attracted to each other and move freely in the available space.
The basic unit of inheritance that exists within the chromosomes. Genes consist of a sequence of DNA that encodes information about how to make an individual protein thus determining a particular hereditary characteristic in an organism. All organisms are equipped with a certain number of genes which varies among species and which is for humans around 20.000 – 25.000 genes.
The complete set of genes that constitutes the genetic identity of a species.
A naturally occurring process that results in heating the Earth's surface and atmosphere through re-absorption of infrared radiation emitted from the Earth’s surface by atmospheric constituents, notable water vapour and carbon dioxide.
One of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine. Guanine is named for its occurrence in guano, a natural fertilizer composed mainly of the excrement of sea bird.
Any of a group of five non-metallic elements with similar chemical bonding properties: fluorine, chlorine, bromine, iodine, and astatine. They all have coloured vapours and are poisonous. The term "halogen" originates from 18th century scientific French nomenclature based on adaptations of Greek roots: hals (sea) or halas (salt), and gen (to generate) —referring to elements which produce a salt in union with a metal.
A product of the decomposition of hemoglobin. Also called hemoporphyrin is a porphyrin that does not contain iron.
Ensemble of proteins which functions as the oxygen transporting component of red blood cells.
Hydrophobic literally means “water fearing” [from the Greek “hydro” (water) and “phobos” (fear)]. Hydrophobic molecules do not mix readily with water because they are not able to form hydrogen bonds with water molecules. On the contrary, hydrophilic molecules, meaning “water loving”, do mix readily with water molecules (in Greek, “φÎ¯λος”, pronounced as philos, means “friend”).
Invisible radiation which has a longer wavelength than the red colour of the visible spectrum, and which is commonly associated to heat.
Notable features or qualities of a person transmitted through the genes from parent to offspring.
An attraction or repulsion between molecules. Intermolecular forces are much weaker than chemical bonds.
Weak forces (either attraction or repulsion) between molecules. The attractive forces are collectively called "van der Waals forces". Intermolecular forces may be feeble (in fact much weaker than intra-molecular forces, i.e. chemical bonds within an individual molecule), but without them life as we know it would be impossible. Water, for example, could not condense from vapour into solid or liquid forms.
An atom or group of atoms that has either lost one or more electrons, making it positively charged (a cation), or gained one or more electrons, making it negatively charged (an anion).
An atom or group of atoms that has either lost one or more electrons, making it positively charged (a cation), or gained one or more electrons, making it negatively charged (an anion).
An atom or group of atoms that has either lost one or more electrons, making it positively charged (a cation), or gained one or more electrons, making it negatively charged (an anion).
The physical process by which an atom or a molecule converts to an ion (it possess electric charge) by gaining or loosing electron(s).
The energy required for the ionization process to take place. The ionization energy is greater in small atoms because their electrons are strongly attracted to the nucleus. On the contrary, removing electrons from bigger atoms requires less ionization energy.
Add or remove electrons from an element so that it becomes an ion.
Chemical compounds with the same number of atoms but different physical and chemical properties due to the different arrangement of their atoms (same molecular but different structural formulas). Isomers are named after the Greek words “isos” meaning equal and “meros” meaning part.
The process by which one molecule is transformed into another molecule (isomers), which has exactly the same atoms but in different arrangement.
The branch of mechanics that studies the motion of a body or a system of bodies without consideration given to its mass or the forces acting on it.
An abbreviation that stands for “Light Amplification by the Stimulated Emission of Radiation”. The laser device produces a very narrow, highly concentrated beam of light with specific properties.
Electromagnetic radiation (partly electric, partly magnetic) that flows in straight lines. The part of light that can be detected by the human eye corresponds to the “visible spectrum” and is made up of seven different colours: red, orange, yellow, green, blue, indigo and violet. Different colours correspond to different amounts of energy. Light can also be described as particles, called photons.
A narrow projection of light energy radiating from a source into a beam.
The emission of light as a result of the excitation of atoms by energy other than heat. Bioluminescence, fluorescence, and phosphorescence are examples of luminescence that can be produced by biological or chemical processes.
Referring to a cyclic macro-molecule (molecule comprised of a large number of atoms) or a macromolecular cyclic portion of a molecule.
A region of space near a body possessing magnetism or carrying an electric current in which magnetic forces can be detected.
An imaging technique used, inter alia, in medicine, to visualize the internal structure and of the body. It uses a powerful magnetic field to align the nuclear magnetization of (usually) hydrogen atoms in water within the body.
Parasitic disease transmitted by certain kinds of mosquito. Malaria is characterized by fever and enlargement of the spleen. Each year, there are approximately 515 million cases of malaria, killing between one and three million people.
Visualization of internal body organs, tissues, or cavities using specialized instruments and techniques for diagnostic purposes.
In chemistry, a methyl group is a functional group derived from methane (CH4) and occurring in many important organic compounds. It contains one carbon atom bonded to three hydrogen atoms, -CH3.
The branch of nanotechology dealing with the study and application of molecular building blocks for the fabrication of electronic components.
The manner in which the molecule constituents are arranged to form this molecule. Molecular structures are determined by many factors including (1) chemical bonds (i.e. the way atoms are connected to each other), (2) forces that apply between the atoms not directly connected (e.g. between positive and negative charges for electrostatic forces), (3) the current environmental conditions (temperature, salinity, acidity) etc.
The smallest unit of a substance that retains its characteristic chemical properties, consisting of two or more atoms bonded together. Molecules vary in size, from diatomic (two atoms) hydrogen molecules to DNA molecules that feature thousands of atoms. Their chemical properties are influenced by the way their atoms are linked together.
Monoclonal antibodies are laboratory produced substances that can locate and bind to specific molecules. They can mimic the antibodies that the body naturally produces as part of the immune system's response to various invaders.
Formation or development of a mutation.
Α permanent transmissible change in the DNA helix. It can be an insertion or deletion of genetic information, or an alteration in the original genetic information.
A protein present in muscle, which shows a higher affinity for oxygen than haemoglobin of the blood.
Scientific prefix meaning “one - billionth” (1/1.000.000.000). It comes from the Greek word “nanos” (dwarf).
Material whose components are mixed at a nanometer scale.
Crystalline particle with at least one dimension measuring less than 1000 nanometers (=1 micron). Nanocrystals are aggregates of anywhere from a few hundred to tens of thousands of atoms that combine into a crystalline form of matter known as a "cluster".
A unit of length in the metric system equal to one billionth of a meter (10-9m).
A unit of length in the metric system equal to one billionth of a meter (10-9m). A sheet of paper is about 100.000 nanometers thick. A human hair measures roughly 50.000 to 100.000 nanometers across. Our fingernails grow one nanometer every second.
A microscopic particle whose size is measured in nanometers (nm). It is defined as a particle with at least one dimension less than 100nm.
A material with a porous structure, where pores are by definition roughly in the nanometre range.
Relating to or occurring on a scale of nanometers. Nanoscale is usually referring to measurements of 1 – 100 nanometers (nm). A virus is about 70 nm long. A cell membrane is about 9 nm thick. Ten hydrogen atoms lined up in a row would be about 1 nm long.
Τhe manipulation of materials that are a few nanometres long. As a nanometre is a millionth of a millimetre, this often means working with individual molecules. “Nano” is often used as shorthand to refer to nanoscience, nanoengineering and similar activities applied to the nanoscale. The nanoworld is a bridge between the world we live in and the world of atoms, where unexpected things happen. At the nanoscale, many common materials exhibit unusual properties, such as remarkably lower resistance to electricity, or faster chemical reactions. Designing and building things on a nanoscale makes design more precise and products which use nanotechnology more effective. For example, wires can be put closer together, and chemicals become more reactive. Norio Taniguchi (Tokyo Science University) was the first to define nanotechnology, in 1974. His definition still stands as the basic statement today: "Nanotechnology mainly consists of the processing of separation, consolidation, and deformation of materials by one atom or one molecule".
Cancer that forms in tissues of the nasopharynx (upper part of the throat behind the nose).
Inert gas which was referred to by the chemist Antoine Lavoisier as “mephetic air” or “azote”, from the Greek word “azotos” meaning lifeless.
The very dense region consisting of protons and neutrons, at the center of an atom. Atoms’ nuclei are positively charged (the number of positive charges is the atomic number of the atom, also known as the proton number).
A flexible optically transparent fiber, usually made of glass or plastic, through which light can be transmitted by successive internal reflections.
The field of technology that combines the physics of light with electricity. Optoelectronics encompasses the study, design and manufacture of devices that source, detect and control light converting electrical signals into photon signals and vice versa.
The path of an electron around the nucleus of an atom.
The branch of Chemistry devoted to the study of carbon element (symbol C), its compounds and their properties. The name organic came from the word organism as prior to 1828, all organic compounds had been obtained from organisms or their remains. There are over six million organic compounds characterized, including the foods we eat, furs and feathers, and the organisms they came from but also plastics, dyes and drugs, insecticides, petroleum products etc. Organic chemistry presents the biggest impact on daily life both because of the variety of practical applications and the possibility of better understanding life around us.
Chemical synthesis dealing with the synthesis of organic compounds via organic reactions.
The third most abundant element in the universe by mass after hydrogen and helium and the most abundant element by mass in the Earth’s crust. Diatomic oxygen gas constitutes 20.9% of the volume of air.
Ozone (O3) is a form of oxygen. It is a colourless gas that has a very pungent odour. It exists naturally at low concentrations in the stratosphere where it absorbs ultraviolet radiation. In the troposphere it exists naturally at extremely low concentrations. These concentrations increase when sunlight acts on various gases, coming mainly from vehicle exhausts, and ozone then becomes a pollutant in the troposphere. Ozone is a highly corrosive gas and is poisonous to most organisms. At concentrations as low as 0.00001 per cent (or 10 parts per hundred million), it can irritate the membranes lining the nose, throat and airways and can trigger or exacerbate asthma attacks.
A tumor suppressor protein, also known as the "Guardian of the Genome". It plays an important role in cell cycle control and apoptosis (the death of cell). Defective p53 could allow abnormal cells to proliferate, resulting in cancer. In normal cells, the p53 protein level is low. High level of p53 may also accelerate the aging process by excessive apoptosis.
A minute quantity or fragment, a tiny piece of matter.
Smaller than the atom. Proton, neutrons and electrons are the three main subatomic particles found in an atom.
Any agent capable of causing disease (from Greek word pathos meaning "suffering, passion", and gignomai meaning "give birth to").
PDT stands for PhotoDynamic Therapy, which is a medical treatment that uses a photosensitizing drug (a drug that becomes activated by light exposure) and a light source to activate the applied drug. PDT therapy is currently used in a number of medical fields including oncology, dermatology and cosmetic surgery.
Organic compound composed of a series of amino acids linked by chemical bonds (peptide bonds). Peptides are named after the Greek word peptos, meaning “digestible”.
A pH (potential of Hydrogen) measurement reveals if a solution is acidic or alkaline (also base or basic). If the solution has an equal amount of acidic and alkaline molecules, the pH is considered neutral. Very soft water is commonly acidic, while very hard water is commonly alkaline. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic, and a pH greater than 7 is basic.
The luminescence of a substance when it is excited by light. The process of phosphorescence occurs in a manner similar to fluorescence, as they both involve absorption of energy, but with a much longer excited state lifetime. "Glow-in-the-dark" light (phosphorescence) is not as bright as fluorescence but lasts much longer.
The process of activating a substance by means of radiant energy and especially light.
Sensitivity to light that causes allergic reactions.
Photocatalysis comes from the Greek words photo meaning light and catalysis, which is the process of a substance (the so called catalyst) accelerating chemical reactions without itself being altered or consumed. Photocatalysts mediate chemical reactions and are activated by light energy.
Any chemical reaction caused by absorption of light (including visible, ultraviolet, and infrared). The light excites atoms and molecules (shifts some of their electrons to a higher energy level) thus making them more reactive.
The branch of Chemistry that deals with the chemical reactions initiated by light. A molecule changes photochemically only if it absorbs a photon, or received energy from another molecule that absorbed a photon already. The energy needed for the chemical reaction is provided by photons.
A molecule that can change its atomic structure and therefore its properties, when exposed to electromagnetic radiation.
The phenomenon of reversible transformation of molecules between two structural forms with different absorption spectra. Photochromism is practically observed as the process of inducing color changes in a medium using light (i.e. electromagnetic radiation).
Phenomenon in which electrically charged particles are released from or within a material when it absorbs electromagnetic radiation. The effect is often defined as the ejection of electrons from a metal plate when light falls on it.
An electron released in photoemission, i.e. due to the interaction with electromagnetic radiation.
The ejection of electrons from matter following the absorption of one or more photons.
A very small quantity (quantum) of electromagnetic radiation containing a discrete amount of energy. Photon may be also considered as a particle of light.
The physics of light, especially of its interaction with matter.
The process in which light energy is converted into chemical energy in the form of carbohydrates.
Adverse reaction to ultraviolet light or sunlight caused by chemicals, such as the furanocoumarins.
A non mechanical device (in particular, a specialized semiconductor diode) usually made of silicon alloys that convert sunlight directly into electricity.
The basic physical process through which a photovoltaic cell (PV cell) converts sunlight into electricity. When photons of sunlight strike a PV cell they may be reflected, absorbed, or pass through the cell. The absorbed photons may generate electricity through the emission or ejection of electrons from the surface of the cell, in response to the light. The term photovoltaic comes from the Greek words “photo” (light) and “voltaic”, which refers to electricity.
The branch of Chemistry that studies chemical processes from the point of view of Physics.
One trillionth (10-12) of a second.
It is sometimes regarded as the fourth state of matter (the first three being solid, liquid, and gas) mainly consisting of nuclei and electrons. More than 99% of the matter in the universe may exist in the plasma state.
A substance that pollutes, especially a waste material that contaminates air, soil, or water.
A material constructed of smaller molecules of the same substance that are chemically bonded to form larger molecules (from a Greek word meaning "many parts").
The study of the synthesis, structure and properties of polymers.
A widely used plastic; it is a polymer of styrene. Polystyrene is a colorless, transparent thermoplastic that is produced either as a solid or as a foamed plastic (commonly marketed under the trade name Styrofoam). Its many uses include electrical and thermal insulation, translucent window panels, storage-battery cases, and toilet articles.
Porphyrins are biological pigments (i.e. substances that impart color to materials) found in both, animal and plant cells. Their name comes from a Greek word reffering to the purple colour.
Any identifiable substance that is used to detect, isolate, or identify another substance.
A molecule deliberately added to a system which changes a property, for example fluorescence, in response to a stimulus, which may be biological or chemical (e.g. the presence of a pollutant).
A substance that forms as a result of a chemical reaction.
A biological macromolecule made of 20 basic building blocks called amino acids. Proteins are named after the Greek word protos, meaning “primary” or “first rank of importance”.
The physical process by which a protein folds into its characteristic three-dimensional structure.
The process in which cells build proteins. The “central dogma” of molecular biology as articulated by the British molecular biologist Francis Crick, put it simply as: “DNA makes RNA makes protein, proteins make us.”
A particle with a positive charge commonly found in the nucleus of atoms.
Psoriasis is a chronic autoimmune disease that appears on the skin. It occurs when the immune system sends out faulty signals that speed up the growth cycle of skin cells.
A therapy used for skin diseases such as severe psoriasis, atopic dermatitis, vitiligo, vesicular eczema etc. PUVA stands for psoralen (P) and ultraviolet A light (UVA), a therapy in which the patient is exposed first to psoralens (drugs containing chemicals that react with ultraviolet light) and then to UVA light.
A very small quantity, a discrete packet of energy (electromagnetic radiation).
The branch of Chemistry that applies the laws of Quantum Mechanics to chemical systems.
The change of electronic and optical properties when the material sampled is of sufficiently small size -typically 10 nanometers or less.
A quantum dot is a particle of matter so small that the addition or removal of an electron changes its properties. Quantum dots’ dimensions are typically measured in nanometers. They are also called quantum bits or gubits.
The branch of Physics that studies the dynamics (i.e. the motions, and energy and momentum exchanges) of systems of particles whose behaviour is governed by quantum mechanics.
The branch of Physics that describes the behavior of objects of atomic and subatomic size.
Quantum physics is a branch of science that deals with discrete, indivisible units of energy called quanta as described by the Quantum Theory.
Energy radiated or transmitted as rays, waves, in the form of particles (e.g. light).
The branch of chemistry that studies the chemical changes resulting from the absorption of high-energy, ionizing radiation, e.g. alpha particles, electrons, gamma ray, protons etc.
An atom, molecule, or ion with unpaired electrons that is likely to take part in chemical reactions.
The property possessed by some elements, e.g. uranium, of spontaneously emitting radiation (usually alpha or beta rays and sometimes also gamma rays) by the disintegration of the nuclei of atoms. Radioactivity was first discovered in 1896 by the French scientist Henri Becquerel, when he was working on phosphorescent materials.
A bow-shaped display in the sky of the colours of the visible light spectrum, caused by the refraction and reflection of the sun's rays through rain or mist.
A thin line or narrow beam of light or other radiant energy.
Substances initially present in a chemical reaction that are consumed during the reaction to make products.
Field within Physical Chemistry studying why chemical reactions occur, how to predict their behavior, and how to control them. Reaction Dynamics is mainly concerned with individual chemical events on atomic length scales and over very brief time periods.
The sequence of steps during which a chemical reaction occurs. A mechanism describes in detail what exactly takes place at each stage of a chemical transformation.
The environment where the reaction is taking place. It may be liquid, solid, heterogeneous etc.
A substance used in a chemical reaction to detect, measure, examine, or produce other substances.
The change in direction of a wave, such as a light or sound wave, away from a boundary the wave encounters. Reflected waves remain in their original medium rather than entering the medium they encounter.
Rickets, also called osteomalacia, is an abnormal bone formation in children primarly resulting from inadequate calcium in their bones.
Abbreviation that stands for RiboNucleic Acid. One of the two main types of nucleic acid (the other being DNA), which functions in protein synthesis in all living cells. RNA is mainly involved in translating into proteins the genetic information that is carried in DeoxyriboNucleic Acid (i.e. the DNA).
The ability of a sensor to measure only one parameter; in the case of a chemical sensor, to measure only one chemical species.
The ability of a sensor to detect the minimum amount of a substance under specified conditions.
The sensitizers commonly used in PDT are multi-ringed plate-like molecules like porphyrins, phthalocyanines, and pheophorbides.
Any device that records the level of a substance of interest or under investigation. When that record is done through chemical methods we are talking about chemical sensors.
A silicon-hydrogen compound. Silanes consist of a chain of silicon atoms covalently bound to hydrogen atoms.
The chemical compound silicon dioxide (from the Latin silex).
A non-metallic element occurring extensively in the Earth's crust, either as amorphous or as crystalline, and used in glass, semi-conducting devices, concrete, refractory bricks, pottery, and silicones. The word silicon comes from the Latin word silicus, which means “flint”.
A chemical compound, one of the most commonly encountered substances in both daily life and in electronics manufacturing. Under exposure to oxygen, a silicon surface oxidizes to form silicon dioxide (SiO2).
Singlet oxygen is a nonradical (does not have an unpaired electron) reactive oxygen species often associated with oxygen free radicals that has strong oxidising activity. Singlet oxygen (1O2) is an electronically excited and mutagenic form of oxygen.
Also known as chemical solution deposition, is a chemical synthesis technique widely used in the field of Materials Science for the fabrication of materials. It begins with the preparation of a solution (Sol) composed of various ingredients, which finally turns into a gel.
Energy emitted by the sun in the form of electromagnetic radiation.
The substance present in larger amount in a solution.
An optical instrument used within the spectroscopy field to measure properties of light over a specific portion of the electromagnetic spectrum.
The branch of science which measures the response of matter as it interacts with light and deals with the absorption, scattering, or emission of electromagnetic radiation by atoms or molecules. Its uses extend to weather monitoring, medical diagnostics such as MRI, household conveniences like the microwave oven and countless other facets of everyday life. Modern chemistry uses spectroscopic methods as a main tool for the identification of molecular structures, for monitoring reactions and controlling the purity of compounds.
A display or plot of component wavelengths of electromagnetic radiation (as a function of colour or energy).
A pale yellow nonmetallic element occurring widely in nature in several free and combined allotropic forms. Through its major derivative, sulfuric acid, sulfur (S) ranks as one of the more-important elements used as an industrial raw material.
The spectrum of the electromagnetic radiation (light) coming from the sun.
Dealing with assembled molecular subunits or components.
The chemistry of molecular interactions between molecules that are not chemically bonded with each other.
The branch of Chemistry dealing with the formation of more complex chemical compounds from simpler substances.
DNA sequences at the end of chromosomes. Telomeres prevent chromosomes from losing base pair sequences at their ends, while also stopping them from fusing to each other. Geneticist Elizabeth Blackburn compared telomeres to the little plastic caps on the ends of the shoelaces. Without them, the laces would begin to unravel. The word telomere derives from the Greek “telos” meaning end.
Chaotic, random motion of molecules due to the temperature.
Thymine is one of the four DNA bases.
A nontoxic compound, widely prized for its opaque quality in coatings, plastics, high-gloss paints etc. It is commonly found in food coloring, toothpaste, paint, and sunblock. Known as titanium dioxide, titanium(IV) oxide or titania.
A protein which controls muscle stretching and contraction. Also known as connectin, it is the longest known protein containing 26.926 amino acids.
Capable of causing injury or death, especially by chemical means; poisonous.
The process of converting a form of energy into a different one.
The state corresponding to the highest energy during a chemical reaction. It is a brief intermediate stage in the transformation from reactants to products during which there is a combination of new and old chemical bonds.
Tuberculosis, or TB, is an infectious bacterial disease caused by Mycobacterium tuberculosis, which most commonly affects the lungs. It is transmitted from person to person via droplets from the throat and lungs of people with the active respiratory disease.
Radiation which occupies the segment of the electromagnetic wavelength spectrum between 10 to 400 nanometers, invisible to the human eye. That’s why UV lights are often referred to as “black” lights. Ultraviolet radiation is widely used in industrial processes and research practices. Ultraviolet radiation emitted by the sun or man-made sources (e.g. tanning beds or lamps, lasers, arc welding etc.) is considered as a cancer-causing agent.
UVA is a type of ultraviolet (UV) radiation. UVA radiation penetrates deep into the skin and is responsible for premature aging of the skin and skin cancer.
The outermost electrons of an atom that can be gained or lost in a chemical reaction. Valence electrons are very important in determining how an element reacts chemically with other elements.
Very weak forces that exist between molecules. The smaller the molecules, the weaker the Van der Waals forces. These forces were named after Johannes van der Waals (1837-1923), a carpenter’s son from Dutch who was trained as a physics teacher and later returned to the university to study the physical properties of the gases. Van der Waals’ research showed the existence of very weak forces between molecules, an interaction too feeble to be classified as “bonds”. Johannes van der Waals was awarded the 1910 Nobel Prize for physics. The first isolation of Van Der Waals molecules took place in the 1980s.
An oscillatory motion —a movement first in one direction and then back in the opposite direction. According to the famous physicist R.P. Feynmann “everything that living things do can be understood in terms of the jigglings and wigglings of atoms…”
Visible light coming from the sun is made up of seven different colours, which correspond to different electromagnetic waves. These colours are: red, orange, yellow, green, blue, indigo and violet. A rainbow is an arch of light comprised of all the colours of the visible spectrum in their order. We can also see the different colours of the visible light by using a prism (light analysis).
Chemical compounds that are light and can be readily vaporised but not easily dissolved in water. Many of them are human-made chemicals that are used and produced in the manufacture of paints, pharmaceuticals and refrigerants inducing short or long-term adverse health effects
Εlectrical potential energy per unit charge.
The wave-particle duality principle of quantum physics holds that light exhibit the behaviors of both waves and particles (energy particles called photons), depending upon the circumstances of the experiment.
The length of a wave, meaning the distance measured in the direction of the wave from any given point to the next point in the same phase, as from crest to crest. Humans can perceive different electromagnetic waves of the visible light as different colours, e.g. the longest wavelength corresponds to red colour while the shortest one to violet.
Light having the different colors (red, orange, yellow, green, blue, indigo and violet) in the same proportion as in the light coming directly from the sun, without having been decomposed, as by passing through a prism.
A technique used to determine the detailed, three-dimensional structure of molecules. It is based on the scattering of X-rays through a crystal of the molecule under study. The X-ray Crystallography was first applied in 1961 by J. Kedrew & M. Perutz. The technique was also used to define the shape and structure of proteins.
Short wavelength energy beams capable of penetrating most substances except heavy metals. X-rays are widely used in imaging and therapy.