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Fluorometer
A fluorometer, fluorimeter or fluormeter is a device used to measure parameters of visible spectrum fluorescence: its intensity and wavelength distribution of emission spectrum after excitation by a certain spectrum of light. These parameters are used to identify the presence and the amount of specific molecules in a medium. Modern fluorometers are capable of detecting fluorescent molecule concentrations as low as 1 part per trillion. Fluorescence analysis can be orders of magnitude more sensitive than other techniques. Applications include chemistry/biochemistry, medicine, environmental monitoring. For instance, they are used to measure chlorophyll fluorescence to investigate plant physiology. Components and Design Typically fluorometers utilize a double beam. These two beams work in tandem to decrease the noise created from radiant power fluctuations. The upper beam is passed through a filter or monochromator and passes through the sample. The lower beam is passed through an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorimeter
A fluorometer, fluorimeter or fluormeter is a device used to measure parameters of visible spectrum fluorescence: its intensity and wavelength distribution of emission spectrum after excitation by a certain spectrum of light. These parameters are used to identify the presence and the amount of specific molecules in a medium. Modern fluorometers are capable of detecting fluorescent molecule concentrations as low as 1 part per trillion. Fluorescence analysis can be orders of magnitude more sensitive than other techniques. Applications include chemistry/biochemistry, medicine, environmental monitoring. For instance, they are used to measure chlorophyll fluorescence to investigate plant physiology. Components and Design Typically fluorometers utilize a double beam. These two beams work in tandem to decrease the noise created from radiant power fluctuations. The upper beam is passed through a filter or monochromator and passes through the sample. The lower beam is passed through an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chlorophyll Fluorescence
Chlorophyll fluorescence is light re-emitted by chlorophyll molecules during return from excited to non-excited states. It is used as an indicator of photosynthetic energy conversion in plants, algae and bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am .... Excited chlorophyll dissipates the absorbed light energy by driving photosynthesis (photochemical energy conversion), as heat in non-photochemical quenching or by emission as fluorescence radiation. As these processes are complementary processes, the analysis of chlorophyll fluorescence is an important tool in plant research with a wide spectrum of applications. The Kautsky effect Upon illumination of a dark-adapted leaf, there is a rapid rise in fluorescence from Photosystem II (PSII), followed by a slow decline. Fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spectrofluorometer
A spectrofluorometer is an instrument which takes advantage of fluorescent properties of some compounds in order to provide information regarding their concentration and chemical environment in a sample. A certain excitation wavelength is selected, and the emission is observed either at a single wavelength, or a scan is performed to record the intensity versus wavelength, also called an emission spectrum. The instrument is used in fluorescence spectroscopy. Operation Generally, spectrofluorometers use high intensity light sources to bombard a sample with as many photons as possible. This allows for the maximum number of molecules to be in an excited state at any one point in time. The light is either passed through a filter, selecting a fixed wavelength, or a monochromator, which allows a wavelength of interest to be selected for use as the exciting light. The emission is collected at the perpendicular to the emitted light. The emission is also either passed through a filter or a mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, than the absorbed radiation. A perceptible example of fluorescence occurs when the absorbed radiation is in the ultraviolet region of the electromagnetic spectrum (invisible to the human eye), while the emitted light is in the visible region; this gives the fluorescent substance a distinct color that can only be seen when the substance has been exposed to UV light. Fluorescent materials cease to glow nearly immediately when the radiation source stops, unlike phosphorescent materials, which continue to emit light for some time after. Fluorescence has many practical applications, including mineralogy, gemology, medicine, chemical sensors (fluorescence spectroscopy), fluorescent labelling, dyes, biological detectors, cosmic-ray detection, vac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Excitation Spectrum
Fluorescence spectroscopy (also known as fluorimetry or spectrofluorometry) is a type of electromagnetic spectroscopy that analyzes fluorescence from a sample. It involves using a beam of light, usually ultraviolet light, that excites the electrons in molecules of certain compounds and causes them to emit light; typically, but not necessarily, visible light. A complementary technique is absorption spectroscopy. In the special case of single molecule fluorescence spectroscopy, intensity fluctuations from the emitted light are measured from either single fluorophores, or pairs of fluorophores. Devices that measure fluorescence are called fluorometers. Theory Molecules have various states referred to as energy levels. Fluorescence spectroscopy is primarily concerned with electronic and vibrational states. Generally, the species being examined has a ground electronic state (a low energy state) of interest, and an excited electronic state of higher energy. Within each of these elec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight, and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights. Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack the energy to ionize atoms, it can cause chemical reactions and causes many substances to glow or fluoresce. Consequently, the chemical and biological effects of UV are greater than simple heating effects, and many practical applications of UV radiation derive from its interactions with organic molecules. Short-wave ultraviolet light damages DNA and sterilizes surfaces with which it comes into contact. F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monochromator
A monochromator is an optical device that transmits a mechanically selectable narrow band of wavelengths of light or other radiation chosen from a wider range of wavelengths available at the input. The name is from the Greek roots ''mono-'', "single", and ''chroma'', "colour", and the Latin suffix ''-ator'', denoting an agent. Uses A device that can produce monochromatic light has many uses in science and in optics because many optical characteristics of a material are dependent on wavelength. Although there are a number of useful ways to select a narrow band of wavelengths (which, in the visible range, is perceived as a pure color), there are not as many other ways to easily select any wavelength band from a wide range. See below for a discussion of some of the uses of monochromators. In hard X-ray and neutron optics, crystal monochromators are used to define wave conditions on the instruments. Techniques A monochromator can use either the phenomenon of optical dispersio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pasteurization
Pasteurization or pasteurisation is a process of food preservation in which packaged and non-packaged foods (such as milk and fruit juices) are treated with mild heat, usually to less than , to eliminate pathogens and extend shelf life. The process is intended to destroy or deactivate microorganisms and enzymes that contribute to food spoilage or risk of disease, including vegetative bacteria, but most bacterial spores survive the process. The process is named after the French microbiologist Louis Pasteur whose research in the 1860s demonstrated that thermal processing would deactivate unwanted microorganisms in wine. Spoilage enzymes are also inactivated during pasteurization. Today, pasteurization is used widely in the dairy industry and other food processing industries to achieve food preservation and food safety. By the year 1999, most liquid products were heat treated in a continuous system where heat can be applied using a plate heat exchanger or the direct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrolysis
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolysis is the cleavage of biomolecules where a water molecule is consumed to effect the separation of a larger molecule into component parts. When a carbohydrate is broken into its component sugar molecules by hydrolysis (e.g., sucrose being broken down into glucose and fructose), this is recognized as saccharification. Hydrolysis reactions can be the reverse of a condensation reaction in which two molecules join into a larger one and eject a water molecule. Thus hydrolysis adds water to break down, whereas condensation builds up by removing water. Types Usually hydrolysis is a chemical process in which a molecule of water is added to a substance. Sometimes this addition causes both the substance and water molecule to split into two parts. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorophore
A fluorophore (or fluorochrome, similarly to a chromophore) is a fluorescent chemical compound that can re-emit light upon light excitation. Fluorophores typically contain several combined aromatic groups, or planar or cyclic molecules with several π bonds. Fluorophores are sometimes used alone, as a tracer in fluids, as a dye for staining of certain structures, as a substrate of enzymes, or as a probe or indicator (when its fluorescence is affected by environmental aspects such as polarity or ions). More generally they are covalently bonded to a macromolecule, serving as a marker (or dye, or tag, or reporter) for affine or bioactive reagents ( antibodies, peptides, nucleic acids). Fluorophores are notably used to stain tissues, cells, or materials in a variety of analytical methods, i.e., fluorescent imaging and spectroscopy. Fluorescein, via its amine-reactive isothiocyanate derivative fluorescein isothiocyanate (FITC), has been one of the most popular fluorophores. F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and most abundant families of materials, existing as a compound of several minerals and as a synthetic product. Notable examples include fused quartz, fumed silica, silica gel, opal and aerogels. It is used in structural materials, microelectronics (as an electrical insulator), and as components in the food and pharmaceutical industries. Structure In the majority of silicates, the silicon atom shows tetrahedral coordination, with four oxygen atoms surrounding a central Si atomsee 3-D Unit Cell. Thus, SiO2 forms 3-dimensional network solids in which each silicon atom is covalently bonded in a tetrahedral manner to 4 oxygen atoms. In contrast, CO2 is a linear molecule. The starkly different structures of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
