Fluorescence, Phosphorescence, and Photoluminescence Spectroscopy
Fluorescence, phosphorescence, and photoluminescence occur when a sample is excited by absorbing photons and then emits them with a decay time that is characteristic of the sample environment. Fluorescence is a term used by chemists when the absorbing and emitting species is an atom or molecule. Phosphorescence is similar to fluorescence, except that the time between absorption and emission is much longer than in fluorescence. Photoluminescence is the term physicists use to describe the absorption and emission of light by things such as semiconductors and nanotubes. Regardless of the terminology, when samples absorb photons and then emit them at a different wavelength the resultant light can be dispersed by a spectrograph, the spectrum can be detected by a device such as a CCD, and information can be gleaned about the sample.
As illustrated in the diagram at right, fluorescence occurs when a chemical species absorbs a photon and is excited to a singlet electronic excited state, relaxes via non-radiative mechanisms, emits a lower-energy photon, and then transitions to the ground electronic state. In fluorescence, the time between absorption and emission is on the order of nanoseconds. The spectrum of the wavelengths emitted can be used to identify atoms and molecules, as well as to determine chemical structures. The intensity of the photons emitted can be used to determine the concentration of chemical species.
Since absorption is a requirement for the fluorescence process, molecules and functional groups that are strong UV-Vis absorbers can be strong fluorescers. For example, molecules with extended pi-electron systems, including aromatic and conjugated aromatic rings, make excellent fluorescers (known as fluorophores). In biology, fluorophores are attached to molecules such as proteins, are excited, and the resultant fluorescence used to image molecules and cells. Spectral analysis of this fluorescence can give chemical information about biological systems.
A near-infrared fluorescence spectrum of a collection of carbon nanotube
Fluorescing samples typically produce enough photons for a standard silicon-based CCD to detect a spectrum. Since fluorescence peaks are inherently broad, high-resolution spectra are not necessarily needed to obtain useful data.
High-Sensitivity, Large-Format CCD Camera -Enable Multidimensional Characterization of Soil-Grown Root Systems
GLO-Roots employs luminescence-based reporters and a pair of Princeton Instruments back-illuminated CCD cameras to enable studies of root architecture and gene expression patterns in soil-grown, light-shielded roots. Custom-designed image analysis algorithms allow the spatial integration of soil properties, gene expression, and root system architecture traits.
Ground breaking software to control your Princeton Instruments systems. Now with Windows 10 support. It's like nothing you have ever experienced!
with near-diffraction-limited image quality."
Rashid Zia - Brown University
Featured Product for Fluorescence, Phosphorescence, and Photoluminescence Spectroscopy
Award-winning imaging spectrographs with superior performance over Czerny-Turner traditional designs, available with 203 mm and 320 mm focal length designs.