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Indicator Electrodes, Potentiometry, Electrochemistry, Electrode Kinetics, Electrogravimetry, Polarography, Square Wave Voltammetry, Wavelength Selection, Types of Spectroscopy, Detectors, Theory of Molecular Absorption, Absorption by Organic Molecules, Applying UV-vis Spectroscopy are major topics of this course. Main points from these slides are: Luminescence, Phosphorescence, Fluorescence, Photoluminescence, Bioluminescence, Chemiluminescence, Triboluminescence, Electroluminescence, Jablonski
Typology: Slides
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Luminescence
levelsa transition from higher to lower energy
screens (CRTs) & “fluorescent” lightsglow in the dark key chains, televisionby photons) often exhibited by solids likephotoluminescence (excited state generatedPhosphorescence – example of
analytical applicationsquinine that is added to tonic water manywhich is usually observed in solution likeFluorescence – also photoluminescence
by fireflies, some algae & fishbiologically (enzymatic process) exhibitedBioluminescence – excited state induced
some analytical applicationsoften oxidation & used for light sticks &induced chemically by bond breakage,Chemiluminescence – excited state
mechanicallyTriboluminescence – excited state induced
bite down on hard candy,
also Curad bandaids
found in some polymers & electric pickleElectroluminescence – electrical excitation
1 = absorption, 2 = vibrational relaxation, 3 = fluorescence, 4 & 7 =
radiationless deactivation, 5 = intersystem crossing, 6 = phosphorescnce
refer to this diagramThe following slides
StateTripletExcited
StateGround StateSingletExcitedFirst
Jablonski Energy Level Diagram
When absorption of a photon occurs
(process #1), several things can happen:
Vibrational Relaxation (VR) - is a non-
electronic energy state (very fast ~ 10lowest vibrational level in a givenvibrational levels lose energy & go to theradiative process (#2) by which the upper
s)
Internal Conversion (IC) - non-radiative
electronic energy level followed by VRto upper vibrational level of lowerprocess (#4) where excited state couples
Radiationless Deactivation
(#4) – return
collisional deactivationby internal conversion or some sort ofto ground state giving up energy as heat,
Intersystem Crossing
(#5) – lowest
a photon =ground state radiationlessly or by emittingOnce formed the triplet state can go tostate followed by vibrational relaxationcouples to upper vibrational level of tripletvibrational level of first excited singlet
phosphorescence
The transition T
1
o (G) with emission of a
probability and a slow ratephoton is spin forbidden, has a low
Fluorescence involves a spin allowed
transition
very probable
fast rate &
short lifetime (typically 1-20 nsec)
Phosphorescence involves spin forbidden
transition
not so probable
slower
rate & longer lifetime ( from 10
4
Moderately interesting website showing an
phosphorescence, etc.absorption, VR, fluorescence,animated Jablonski Diagram for
http://micro.magnet.fsu.edu/primer/java/jablo
nski/lightandcolor/
phosphorescence intensity (at fixedExcitation Spectrum – fluorescence or
λ ) as
a function of excitation
λ
or absorption
λ
fluorescence emission intensity vs.Fluorescence Emission Spectrum -
λ for
a fixed excitation
λ
(= absorption
λ , max.)
λ phosphorescence emission intensity vs.Phosphorescence Emission Spectrum –
for a fixed excitation
λ
(= absorption
λ ,
max.)
