Fluorescence and Phosphorescence - PHRM 2041

Is the wavelength of phosphorescence higher or lower than fluorescence?

Higher wavelength

What is the difference between fluorescence and phosphorescence?

In phosphorescence the release of light is delayed and occurs at a slower rate

What is fluorescence and phosphorescence?

It is the release of energy in the form of light

Is the wavelength of absorption longer or shorter than wavelength of fluorescence?

Longer

Why is the detector usually placed 90 degrees from the sample which is undergoing fluorescence?

To reduce the noise from the excitatory wavelength

Describe the pathway a molecule takes from resting state to undergoing phosphorescence and back to resting state

1. From resting/ground state (S0) the molecule undergoes absoption of energy from an excitation wavelength raising it to an excited state (S2) 2. The molecule then loses energy (S2 --> S1) and then undergoes intersystem crossing 3. The molecule then loses energy through phosphorescence (T1 --> S0)

Describe the pathway a molecule takes from resting/ground state to undergoing fluorescence and back to resting state

1. From resting/ground state (S0) the molecule undergoes absoption of energy from an excitation wavelength raising it to an excited state (S2) 2. The molecule then releases energy in the form of light and returns to the ground state (S2 --> S1 --> S0)

What types of molecules can fluoresce? (3)

1. Rigid molecules 2. Molecules which can absorb light (Aromatic rings) 3. Functional groups which can donate electrons (OH, NR2)

Why is fluorescence useful in drug analysis? (2)

1. Selective as not all molecules can fluoresce 2. Sensitive as it can be used to see small concentrations of substances