Fluorescence spectroscopy is a research method for analysing substances based on studying the fluorescence properties of a sample for the quantitative measurement of chemical products. What is fluorescence?
Fluorescence is a type of luminescence caused by the excitation of a molecule by a photon, which puts it in an electronically excited state.
Fluorescence spectroscopy uses a beam of light to excite electrons in the molecules of certain compounds, causing them to emit light. This light is directed to a filter and detector, which is used to measure and identify changes in the molecule or molecules.

What is fluorescence spectroscopy?

A fluorophore’s emission and excitation spectra are usually mirror images of each other. The steady-state fluorescence spectrum plots the fluorescence intensity versus the wavelength a molecule emits under excitation from a constant light source. The emission spectrum is the intensity versus wavelength obtained by scanning the emission wavelength at a fixed excitation wavelength;
The excitation spectrum is a scan of the excitation wavelength at a fixed emission wavelength, providing information on sample absorption. The emission spectrum is usually at a longer wavelength than the excitation spectrum. Both spectra observe changes in the sample in response to temperature, concentration, or interaction with other molecules, such as bursting, energy transfer, and sensitivity to solvent environments.

What types of molecules and materials fluoresce?

Fluorescent molecules and materials come in all shapes and sizes. Some are inherently fluorescent, such as chlorophyll. Others are specially synthesised stable organic dyes or labels that can be added to non-fluorescent systems.
Some classes of fluorescent molecules and materials include:
Amino acids (tryptophan, phenylalanine, tyrosine)
Fluorescent proteins (FP)
Solar cells
Chlorophyll (chlorophyll)
Organic dyes (fluorescein, rhodamine, N-amino coumarin and their derivatives)
Pigments, whitening agents
Semiconductors
Base pair derivatives (2-AP, 3-MI, 6-MI, 6-MAP, pyrrolo-C, tC)
Quantum dots
Single-walled carbon nanotubes (SWCNT)
Rare earth elements (lanthanides)
Fluorescent powders
And many more ……
Commonly used fluorescent samples include fluorescent proteins, semiconductors, phosphors and other molecules and materials such as rare earth elements. Of course, new materials are emerging all the time.

Principles and Theory of Fluorescence Spectroscopy

Fluorescence is a type of luminescence produced by the excitation of a molecule by a photon, causing it to enter an electronically excited state. It is triggered by the absorption of a photon in the singlet state ground state and is raised to the singlet excited state. When the excited state molecule returns to the ground state, it emits a photon of lower energy than the absorbed photon, corresponding to a longer wavelength. Fluorescence spectroscopy analyses the fluorescence of a molecule based on its fluorescence properties.
Fluorescence is a type of luminescence produced by the excitation of a molecule by a photon, placing it in an electronically excited state.

What is fluorescence lifetime?

Simply put, the fluorescence lifetime of a molecule is the average length of time it is in its excited state. It depends on the type of molecule and its local environment.

Conclusion

Fluorescence spectroscopy is a powerful and versatile tool for studying the properties of molecules, offering insights into their interactions, environments, and dynamics. By understanding the fundamentals of fluorescence, including the principles of excitation and emission, the significance of spectra, and the factors that influence fluorescence behavior, researchers can unlock detailed information about molecular systems. This knowledge forms the foundation for numerous applications in chemistry, biology, and material science, where fluorescence spectroscopy continues to play a crucial role in advancing scientific discovery.