This document discusses types of fluorescence and quenching. There are three main types of fluorescence based on the excitation source: chemiluminescence, electrochemiluminescence, and photoluminescence. Quenching decreases fluorescence intensity and occurs via four main mechanisms: self-quenching, chemical quenching, static quenching, and collisional quenching. Factors like concentration, pH, presence of oxygen, halides, heavy metals, and temperature can also influence fluorescence by inducing quenching effects.

1. TYPES OF FLOURESCENCE & QUENCHING
Prepared by:-
SIMI JOJUK
M.PHARM 1st
YEAR
GRACE COLLEGE OF PHARMACY

2. Types of flourescence
1. Chemiluminescence (when excited by chemicals)
2. Electrochemiluminescence (when excited by
electrochemical reaction)
3. Photoluminescence (when excited by
electromagnetic radiation)
 Based on the wavelength of emitted radiation
1. Stroke’s flourescence wavelength of the emitted
radiation is longer than the absorbed
radiation(eg)as in conventional flourimetric
experiments.

3. Contd.
2. Anti-stroke’s Flourescence wavelength of emitted
radiation is shorter than absorbed radiation.This type is
uncommon and seen in thermally assisted fluorescence.
3. Resonance Flourescence When the wavelength of
emitted radiation = absorbed radiation(eg)mercury
vapour at 254nm.
 Based on Phenomena:
1. Sensitised flourescence :when elements like Th, Zn, Cd
or an alkali metal are added to mercury vapour these
elements are sensitised & thus gives fluorescence.
2. Thermally assisted Flourescence :the excitation is partly
by electromagnetic radiation and partly by thermal energy

4. 3) Direct line fluorescence:Where ,even after the emission of
radiation,the molecule remain in metastable state and finally
comes to ground state after loss of energy by vibrational
transition.ional transition.
4) Step wise fluorescence:This is nothing but the conventional
type of fluorescence,where a part of energy is lost by vibrational
transition before the emission of fluorescent radiation.

5. Decrease in fluorescence intensity due to specific
effects of constituents of the solution.
Due to concentration, pH, pressure of chemical
substances, temperature, viscosity, etc.
Types of quenchingTypes of quenching
1)1) Self quenchingSelf quenching
2)2) Chemical quenchingChemical quenching
3)3) Static quenchingStatic quenching
4)4) Collision quenchingCollision quenching

6. Fluorescence
Concentration of
fluorescing species
Deviations at higher concentrations can be
attributed to self-quenching or self-
absorption.
Fluorescence
Concentration of
fluorescing species
Calibration curve
(Low con)
calibration curve
(High con)

7. Here decrease in fluorescence intensity due to the
factors like change in pH,presence of oxygen, halides
&heavy metals.
 pH- aniline at pH 5-13 gives fluorescence but at pH
<5 &>13 it does not exhibit fluorescence.
 Halides- like chloride,bromide,iodide & electron
withdrawing groups like NO2,COOH etc. leads to
quenching.
 Heavy metals -leads to quenching, because of
collisions of triplet ground state.

8. This occurs due to complex formation.
e.g- caffeine reduces flourescence of riboflavin by
complex formation.
COLLISIONAL QUENCHING
It reduces fluorescence by collision. where no. of
collisions increased hence quenching takes place.