Luminescence Flashcards
is the emission of light by a substance
Luminescence
It occurs when an electron returns to the electronic ground state from an excited state and loses its excess energy as a photon.
Luminescence
Three types of luminescence
Fluorescence
Phosphorescence
Chemiluminescence
When a beam of light is incident on certain substances they emit visible light or radiations.
Fluorescence
starts immediately after the absorption of light and stops as soon as the incident light is cut off
Fluorescence
When light radiation is incident on certain substances they emit light continuously even after the incident light is cut off.
Phosphorescence
Measurement of the Fluorescence
Fluorometry
is the production of light from a chemical reaction
Chemiluminescence
The excitation of the substance does not involve electromagnetic radiation and no monochromators are needed, instead the excitation energy comes from a chemical or electrochemical reaction
Chemiluminescence
Light signal is measured against a completely dark background
Involves the_____ of an organic compound
oxidation
Chemiluminescence
is a physical phenomenon that results from the interaction of light with particles in solution.
Light scattering
Unlike fluorescence emission, the wavelength of the_____ light is the same as that of the incident light.
scattered
Measures the amount of light blocked in a particulate suspension
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V in light transmission
Turbidimetry
Measures the amount of light scattered in a particulate auspension at 90 degree angle
Nephelometry
the amount of light passing through a solution is measured.
Turbidimetry
The higher the____, the smaller the quantity of light transmitted (i.e. more light is absorbed).
turbidity
Any ________ or ______can be used as a turbidimeter, without modification.
spectrophotometer or photometer
useful method to determine the concentration of solutions that contains particles too large for absorption spectrometry
Nephelometry
the detecting cell is placed at right angles to the light source, to measure light scattered by particles.
Nephelometry
The instrument is called a ‘_______ or ________’ A spectrophotometer can be used, however, a special attachment is required for nephelometry.
Nephelometer’ or a ‘Nephelometric Turbidimeter
Mercury arc lamp
Nephelometry
Tungsten lamp
Turbidimetry
Scattered light is measured
Nephelometry
Light transmitted is measured
Turbidimetry
Measured at 90 deg angle
Nephelometry
Measured in a straight line
Turbidimetry
PMT is the detector
Nephelometry
Photocell is the detector
Turbidimetry
FACTORS THAT AFFECT LIGHT SCATTER
Particle size
Concentration of particles
MW of particles
Wavelength dependence
THREE (3) TYPES OF SCATTERED LIGHTS:
Rayleigh
MIE
Rayleigh Debye
Light symmetrically scattered around the particle
RAYLEIGH
Wavelength of light > particle size
Rayleigh
Light scatters backward but appears forward due to destruction out of phase background scatter
MIE
Wavelength of light < particle size
MIE
Antigen-antibody reactions
RAYLEIGH DEBYE
More forward light scatter
RAYLEIGH DEBYE
Wavelength of light = particle size
RAYLEIGH DEBYE
