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Nonaromatic Unsaturated Hydrocarbons. Luminescence is rare in nonaromatic hydrocarbons. Possible if highly conjugated due to p – p * transitions. Seyhan Ege, Organic Chemistry , D.C. Heath and Company, Lexington, MA, 1989. Aromatic Hydrocarbons. Fluorescent.

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slide1

Nonaromatic Unsaturated Hydrocarbons

Luminescence is rare in nonaromatic hydrocarbons.

Possible if highly conjugated due to

p – p* transitions.

Seyhan Ege, Organic Chemistry, D.C. Heath and Company, Lexington, MA, 1989.

aromatic hydrocarbons
Aromatic Hydrocarbons

Fluorescent

Low lying p – p* singlet state

Phosphorescence is weak because there are no n electrons

Ingle and Crouch, Spectrochemical Analysis

heterocyclic aromatics
Heterocyclic Aromatics

Aromatics containing carbonyl or heteroatoms are more likely to phosphoresce

n – p* promotes intersystem crossing.

Fluorescence is often weaker.

Skoog, Hollar, Nieman, Principles of Instrumental Analysis, Saunders College Publishing, Philadelphia, 1998.

aromatic substituents
Aromatic Substituents
  • Electron donating groups usually increase fF.
  • Electron withdrawing groups usually decrease fF.

Ingle and Crouch, Spectrochemical Analysis

halogen substituents
Halogen Substituents

Internal Heavy Atom Effect

Promotes intersystem crossing.

fF decreases as MW increases.

fP increases as MW increases.

tP decreases as MW increases.

Ingle and Crouch, Spectrochemical Analysis

increased conjugation
Increased Conjugation

fF increases as conjugation increases.

fP decreases as conjugation increases.

Hypsochromic effect and bathochromic shift.

Ingle and Crouch, Spectrochemical Analysis

rigid planar structure
Rigid Planar Structure

fF = 1.0

fF = 0.2

fF = 0.8

not fluorescent

Ingle and Crouch, Spectrochemical Analysis

Skoog, Hollar, Nieman, Principles of Instrumental Analysis, Saunders College Publishing, Philadelphia, 1998.

metals
Metals

Metals other than certain lanthanides and actinides (with f-f transitions) are usually not themselves fluorescent.

A number of organometallic complexes are fluorescent.

Skoog, Hollar, Nieman, Principles of Instrumental Analysis, Saunders College Publishing, Philadelphia, 1998.

fluorescence and phosphorescence
Fluorescence and Phosphorescence

Which effect is used more regularly?

SciFinder Scholar Citations

Fluorescence Phosphorescence

… Labels/Tags60642 231

… Dyes86673 412

www.wikipedia.org

fluorescence or phosphorescence labels answer from a commercial view
Fluorescence or Phosphorescence Labels?Answer from a Commercial View

http://www.invitrogen.com/

fluorescence or phosphorescence commercially available phosphorescence labels
Fluorescence or Phosphorescence?Commercially Available Phosphorescence Labels

Erythrosin derivative Eosin derivative

http://www.invitrogen.com/

fluorescence or phosphorescence publications in analytical chemistry
Fluorescence or Phosphorescence?Publications in Analytical Chemistry
  • Fluorescence … Phosphorescence…
  • 10847 7927
  • Phosphorescence is rarer than fluorescence => Higher selectivity.
  • Phosphorescence: Analysis of aromatic compounds in environmental samples.
solvent effects

nonequilibrium

excited state

Solvent Effects

Increased viscosity can increase luminescence intensity.

H-bonding and dipole interactions with the solvent contribute to the Stokes shift.

Ashutosh Sharma and Stephen Schulman, Fluorescence Spectroscopy, John Wiley & Sons, New York, 1999.

solvent polarity
Solvent Polarity

Increasing solvent polarity usually causes a red-shift in fluorescence.

http://micro.magnet.fsu.edu/primer/techniques/fluorescence/fluorescenceintro.html

solvent polarity15
Solvent Polarity

Joseph Lakowicz, Principles of Fluorescence Spectroscopy, Kluwer Academic / Plenum Publishers, New York, 1999.

temperature
Temperature

Increasing temperature increases ks

Joseph Lakowicz, Principles of Fluorescence Spectroscopy, Kluwer Academic / Plenum Publishers, New York, 1999.

slide17

Decreasing temperature can induce a blue-shift in fluorescence.

Joseph Lakowicz, Principles of Fluorescence Spectroscopy, Kluwer Academic / Plenum Publishers, New York, 1999.

shpol skii spectroscopy
Shpol’skii Spectroscopy
  • Analytical potential of fluorescence spectroscopy often limited by unresolved band structure (5-50 nm)
    • homogeneous band broadening – depends directly on radiative deactivation properties of the excited state (usually 10-3 nm)
    • inhomogeneous band broadening – various analyte microenvironments yields continuum of bands (usually few nm)
  • Solution: Incorporate molecules in rigid matrix at low temperature to minimize broadening
  • Result: Very narrow luminescence spectra with each band representing different substitution sites in the host crystalline matrix
shpol skii spectroscopy19
Shpol’skii Spectroscopy
  • Requirements:
  • T < 77K with rapid freezing rate
  • Matrix with dimension match
  • Low analyte concentration
  • Instrumentation:
  • Xe lamp excitation
  • Cryogenerator with sample cell
  • High resolution monochromator with PMT

Analytes: polycyclic aromatic compounds in environmental, toxicological, or geochemical systems

Garrigues and Budzinski, Trends in Analytical Chemistry, 14 (5), 1995, pages 231-239.

epi fluorescence microscopy
Epi-Fluorescence Microscopy
  • Light Source - Mercury or xenon lamp (external to reduce thermal effects)
  • Dichroic mirror reflects one range of wavelengths and allows another range to pass.
  • Barrier filter eliminates all but fluorescent light.

http://micro.magnet.fsu.edu/primer/techniques/fluorescence/fluorosources.html

fluorescence microscopy
Fluorescence Microscopy

Need 3 filters:

Exciter Filters

Barrier Filters

Dichromatic Beamsplitters

http://microscope.fsu.edu/primer/techniques/fluorescence/filters.html

are you getting the concept
Are you getting the concept?

You plan to excite catecholamine with the 406 nm line from

a Hg lamp and measure fluorescence emitted at 470 ± 15

nm. Choose the filter cube you would buy to do this.

Sketch the transmission profiles for the three optics.

http://microscope.fsu.edu/primer/techniques/fluorescence/fluorotable3.html

fluorescence microscopy objectives
Fluorescence Microscopy Objectives

Image intensity is a function of the objective numerical

aperture and magnification:

Fabricated with low fluorescence glass/quartz with anti-

reflection coatings

http://micro.magnet.fsu.edu/primer/techniques/fluorescence/anatomy/fluoromicroanatomy.html

fluorescence microscopy detectors
Fluorescence Microscopy Detectors

No spatial resolution required: PMT or photodiode

Spatial resolution required: CCD

http://micro.magnet.fsu.edu/primer/digitalimaging/digitalimagingdetectors.html

special fluorescence techniques
Special Fluorescence Techniques

LIF

TIRF

http://microscopy.fsu.edu/primer/techniques/fluorescence/tirf/tirfintro.html