This document discusses phosphorescence and quenching of phosphorescence. Phosphorescence involves the slow emission of light from a substance after exposure to radiation. Unlike fluorescence, which is a faster emission, phosphorescence can last from milliseconds to years. The document defines phosphorescence and the Jablonski diagram. It describes how quenchers like chloride ions can reduce the intensity of phosphorescence through collisional or other quenching processes. The presence of quenchers is studied to better understand phosphorescence mechanisms.

1. Phosphorescence in the
present of quencher
By:
Rashid Khan F2017067044
Saqib Noor F2017067056

2. Introduction of Phosphorescence
In simple terms, phosphorescence is a process in which
energy absorbed by a substance is released relatively slowly
in the form of light. This is in some cases the mechanism
used for "glow-in-the-dark" materials which are "charged" by
exposure to light.
Phosphorescence, emission of light from a
substance exposed to radiation and
persisting as an afterglow after the exciting
radiation has been removed. Unlike
fluorescence, in which the absorbed light is
spontaneously emitted about 10-8 second
after excitation, phosphorescence requires
additional excitation to produce radiation
and may last from about 10-3 second to
days or years, depending on the
circumstances.

3. History of Phosphorescence
Around 1604, Vincenzo Casciarolo discovered a "lapis solaris"
near Bologna, Italy. Once heated in an oxygen-rich furnace,
it thereafter absorbed sunlight and glowed in the dark.
Phosphorescence was first
observed in the 17th cent. but was
not studied scientifically until the
19th cent. According to the theory
first advanced by Philipp Lenard,
energy is absorbed by a
phosphorescent substance, causing
some of the electrons of the
crystal to be displaced.

5. Key term that are included in jablonski diagram?
Fluorescence?
Phosphorescence?
Internal Conversion?
Intersystem Crossing?
Explanation Of Diagram

6. Definition of Phosphorescence
Atoms, molecules, or solids that are excited to high
energy levels can decay to lower levels by emitting
radiation (emission or luminescence).
In fluorescence, an electron is raised from a certain
baseline energy known as the ground level to an
excited level by a light photon or other radiation.
Transition of the electron back to the ground level can
occur spontaneously with radiation of the same energy
as that which was absorbed.

7. Phosphorescence, emission of light from a substance
exposed to radiation and persisting as an afterglow after
the exciting radiation has been removed. The substance
which shows phosphorescence is called phosphorescent
substance. Phosphorescence is chiefly caused by
ultraviolet and visible light. It is generally shown by solids.
Unlike fluorescence, in which the absorbed light is
spontaneously emitted about 10-8 second after excitation,
phosphorescence requires additional excitation to produce
radiation and may last from about 10-3 second to days or
years, depending on the circumstances.

8. Quenching of Phosphorescence
Quenching refers to any process that reduces the
Phosphorescence intensity of a given substance.
This may occur due to various
factors like pH, concentration,
temperature, viscosity,
presence of oxygen, heavy
metals or, specific chemical
substances etc.
Quenching of quinine
Phosphorescence in presence of
chloride ions

9. Example of quenching agents Quenching
agents
 Thiocyanate
 Anthracene
 Chloride
 Quinine
 Iodide
 Tryptophan
 Disulfide
 Tyrosine
 Nitric oxide
 Naphthalene

10. Types of quenching process
Collisional
quenching
Static quenching
 Concentration
quenching
Chemical
quenching

11. In the present of quencher
𝑻 𝟏 + 𝐐
𝑲 𝒒
𝑺 𝟎 + Q
Delay rate of [𝑻 𝟏] is

14. Conclusion
In the usual case, quenching is an undesirable effect
and the possibility of encountering this type of
interference should always be evaluated in developing a
fluorometric assay. However, this phenomenon can be
used as an analytical means for determining the
concentration of the compounds known to quench
fluorescence. Quenching study can also be used to
reveal the localization of fluorophores in proteins or,
membranes and their permeability to the quenchers.

15. References
Leslie G. Chatten , Pharmaceutical
Chemistry Theory and Application (volume-
2), CBS publishers and distributors, 2014
revised edition, page: 180,181,182,183.
Joseph R. Lakowicz, Principles of
Fluorescence Spectroscopy, 3rd edition
(2006), Springer Science publication, page:
278,282,283