FACTORS INFLUENCING FLUORESCENCE INTENSITY
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Transcript of FACTORS INFLUENCING FLUORESCENCE INTENSITY
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FACTORS AFFECTING FLUORESCENCE INTENSITY
Presented by;
Aiswarya . A. T,First year M.Pharm,Department of Pharmacy Practice,Grace college of Pharmacy.
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For a molecule;The ability & extend of
fluoresence or phosphorescence depends upon 2 major factors.
Intrinsic structure of a molecule
Environment of a molecule
1
2
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Intrinsic structure of a molecule
ConjugationUnsaturated molecule
absorption of UV/visible radiation
fluorescenceAromatic, Aliphatic & Alicyclic
compounds
Aromatic- No: of rings FI
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Nature of substituent group
EDG’s- FIEWG’s- FI
Groups increases FI NH2 OH, OH, OMe, OEt, CN, NHR, NH2, NR2, NO, NO2
Groups decreases FI COOH, CHO, COR, COOR, SH, F, Cl, Br, I
Groups having no effect on FI
SO3 H, NH4 +, Alkyl grp
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Rigidity of the structure
Heterocyclic compounds
Flexible- less FI
Rigid- more FI
No fluorescence; lonepair of e- enter triplet state by inter system crossing
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Environment of a molecule
Temperature temperature - collisions - FI
Viscosity viscosity - collisions – FI
Oxygen 1. Oxidise fluorescent subst. to non
fluorescent2. decreases fluorescence because
of paramagnetic property of molecular energy
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Polarity of solventreduced FI
Ph of solution
Phenols : acidic – undissociated- NO fluorescence
alkaline- dissociated- good fluorescence
Aniline : acidic- fluorecence in visible region
alkaline/neutral- fluorescence in UV region
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Adsorptionsensitive method- Dilute
solutions are usedLight
Monochromatic light is essential for excitation
Photochemical decompositionno fluorescence; to avoid
this, chose wavelength not strongly absorbed.
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Concentration of solution
Flu
ore
scen
ce
Concentration of
fluorescing speciesDeviations at higher concentrations can be
attributed to self-quenching or self-absorption.
Flu
ore
scen
ce
Concentration of
fluorescing species
Calibration curve(Low con)
calibration curve(High con)
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