““Cool Light”Cool Light”

Three types of “Cool Light”Three types of “Cool Light”

FluorescenceFluorescence:: higher energy radiation is absorbed by a species and stored

PhosphorescencePhosphorescence:: light is absorbed by a molecule which becomes excited to a higher singlet state.

Chemiluminescence:Chemiluminescence: the energy required to emit light comes from the energetics of the chemical

reaction.

ChemiluminescenceChemiluminescence

The non-thermal production of visible light The non-thermal production of visible light by a chemical reaction.by a chemical reaction.

Occurs when an energy releasing reaction Occurs when an energy releasing reaction produces a molecule in an electronically produces a molecule in an electronically excited state, as that molecule returns to excited state, as that molecule returns to the ground state it releases its energy as a the ground state it releases its energy as a photon of light.photon of light.

Rigid and Aromatic moleculesRigid and Aromatic molecules

Glow StickGlow Stick

Shows temperature dependence of Shows temperature dependence of chemical reaction involving chemical reaction involving chemiluminescencechemiluminescence

Energy transfer between an intermediate Energy transfer between an intermediate formed in the reaction between phenyl formed in the reaction between phenyl oxalate ester and hydrogen peroxideoxalate ester and hydrogen peroxide

Electronically Excited StateElectronically Excited State

Excited StateExcited State

The wavelength of light emitted by a The wavelength of light emitted by a molecule is related to the energy of its molecule is related to the energy of its excited state.excited state.

E=hc/E=hc/λλh= Plank’s constanth= Plank’s constantλ= wavelength of emitted light(m)λ= wavelength of emitted light(m)c= speed of lightc= speed of lightE= energy difference between emissive E= energy difference between emissive excited excited state and ground statestate and ground state

BioluminescenceBioluminescence

The production of The production of chemiluminescence chemiluminescence by living organismsby living organisms

Direct ChemiluminescenceDirect Chemiluminescence

AA** → A + light→ A + light

When the emissive excited state molecules are When the emissive excited state molecules are produced directly by the reaction mechanismproduced directly by the reaction mechanism

Sensitized ChemiluminescenceSensitized Chemiluminescence

AA** + B + B →→ A + B A + B**

When an acceptor molecule receives excitation When an acceptor molecule receives excitation energy from an excited state species, and energy from an excited state species, and releases the energy as a photon of light.releases the energy as a photon of light.

ApplicationsApplications

Latent fingerprintsLatent fingerprintsBlood/fluid testsBlood/fluid testsEntertainmentEntertainmentDNA testingDNA testingSpectroscopySpectroscopyPharmaceutical Industry (analysis and Pharmaceutical Industry (analysis and

quality control) quality control)

Oxidation of luminolOxidation of luminol1st report of chemiluminescence from luminol was made by Albrecht in 1928

ReferencesReferences http://agrippina.bcs.deakin.edu.au/bcs_courses/forensic/

Chemical%20Detective/index.htm http://www.shsu.edu/%7Echm_tgc/JPPdir/JPP1999/ http://www.shsu.edu/~chm_tgc/chemilumdir/

chemiluminescence2.html J. Org. Chem., Vol. 35, No. 7, 1970 http://dsc.discovery.com/fansites/onthecase/toolbox/

tool_01.html http://www.deakin.edu.au/forensic/Chemical

%20Detective/Luminol_test.htm Shakhashiri, Bassam; Chemical Demonstrations. Vol. 1

The University Of Wisconsin Press, 1983