Answer:
it involves the detection of light emitted by a sample after it has absorbed light of a specific wavelength.
Step-by-step:
Fluorescence spectroscopy is more sensitive than UV-Vis absorption spectroscopy because it involves the detection of light emitted by a sample after it has absorbed light of a specific wavelength. This emission of light is called fluorescence.
In UV-Vis absorption spectroscopy, the amount of light absorbed by a sample is measured as a function of wavelength. The amount of light absorbed is proportional to the concentration of the absorbing species in the sample, but the sensitivity of this technique is limited by the intensity of the incident light and the path length of the sample.
On the other hand, fluorescence spectroscopy measures the emission of light that occurs when the excited molecules return to their ground state. This emitted light is typically at a longer wavelength than the absorbed light, and it is much weaker than the incident light. However, the sensitivity of fluorescence spectroscopy is enhanced by the fact that the emitted light is measured at right angles to the excitation light, which reduces background noise from scattered light and improves the signal-to-noise ratio.
Additionally, fluorescence spectroscopy can be more selective than UV-Vis absorption spectroscopy because it can detect specific molecular species based on their unique fluorescence spectra. This selectivity is due to the fact that the fluorescence emission spectra of different molecules can be quite distinct, even for molecules with similar UV-Vis absorption spectra.
Overall, the increased sensitivity and selectivity of fluorescence spectroscopy make it a powerful technique for the detection and quantification of trace amounts of fluorescent molecules in complex samples.
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