What is Stokes shift used for?
What is Stokes shift used for?
The Stokes shift is the term used to describe the difference in the wavelength at which a molecule emits light is relative to the wavelength at which the molecule was excited.
Why is the Stokes shift important in fluorescence?
The presence of appreciable Stokes shift is principally important for practical applications of fluorescence because it allows to separate (strong) excitation light from (weak) emitted fluorescence using appropriate optics.
What are the applications of fluorescence spectroscopy?
Examples of the use of fluorescence spectroscopy include the study of fluorescent dyes that are widely used with biological samples, both in routine assays and in advanced research. It is also employed in material science to characterize luminescent materials.
Why is a large Stokes shift important?
A larger Stokes shift eliminates spectral overlap between absorption and emission and allows detection of fluorescence while reducing interference. This also eliminates quenching of fluorescence and gives a stronger signal when used for biological imaging.
How did Stokes discover fluorescence?
The phenomenon of fluorescence was known by the middle of the nineteenth century. Stokes first made the observation that the mineral fluorspar exhibits fluorescence when illuminated with ultraviolet light, and he coined the word “fluorescence”.
What is fluorescence give its principle & application?
Basic Principle of Fluorescence Fluorescence is a three-stage process that takes place in molecules known as fluorescent dyes, or fluorophores. During absorption, the electrons in the molecule are excited by a high energy light, which leads to the transition of electrons from the ground state to the excited state.
What are the application of fluorescence in medicine?
Fluorescence spectroscopy is an emerging diagnostic tool for various medical diseases including pre- malignant and malignant lesions. Fluorescence spectroscopy is a noninvasive technique and has been applied successfully for the diagnosis of multisystem cancers with high sensitivity and specificity.
What are Stokes and anti Stokes lines?
Stokes lines are of longer wavelength than that of the exciting radiation responsible for the fluorescence or Raman effect. Thus, anti-Stokes lines are always of shorter wavelength than that of the light that produces them.
What is the difference between Stokes and anti-Stokes?
When the radiation is absorbed, a molecule jumps to a higher vibrational or rotational energy level. If the emitted radiation is of lower frequency than the incident radiation, then it is called Stokes scattering. If it is of higher frequency, then it is called anti-Stokes scattering.
How Stokes lines are created?
, i.e., the frequency of scattered light is less than the frequency of the incident light, this results in the formation of Stokes lines in Raman spectra. , i.e., the frequency of scattered light is more than the frequency of the incident light, this results in the formation of Anti Stokes lines in Raman spectra.
What is Stokes shift in spectrophotometer?
Stokes Shift in Fluorescence Spectroscopy In fluorescence spectroscopy, the Stokes shift is the difference between the spectral position of the maximum of the first absorption band and the maximum of the fluorescence emission and can be expressed in either wavelength or wavenumber units as shown in Figure 2. 3,4
What is meant by the term Stokes shift?
Stokes shift is the difference (in wavelength or frequency units) between positions of the band maxima of the absorption and emission spectra ( fluorescence and Raman being two examples) of the same electronic transition. It is named after Irish physicist George Gabriel Stokes. When a system (be it a molecule or atom)…
What is meant by Stokes fluorescence?
Stokes fluorescence. Stokes fluorescence is the emission of a longer-wavelength photon (lower frequency or energy) by a molecule that has absorbed a photon of shorter wavelength (higher frequency or energy). Both absorption and radiation (emission) of energy are distinctive for a particular molecular structure.
What determines the extent of the Stokes shift in fluorophores?
The extent of the Stokes shift depends on the particular fluorophore and its solvation environment, with more polar solvents typically giving larger Stokes shifts. The emission and absorption spectra of two fluorophores with a small and large Stokes shift are shown in Figure 3.
