Category Archives: Spectroscopy

The “Spectrum” of Microscopic and Spectroscopic Techniques


Electromagnetic (EM) radiation is our main source of information about the world (i.e. “seeing is believing”). Most scientific techniques rely on some form of imaging/visualization (“microscopy”) and/or measurement of energy absorption or emission (“spectroscopy”) or both (for instance: fluorescence microscopy). In the figure above we outline the spectrum of electromagnetic radiation from x-rays to microwaves and the different scientific techniques that each type of radiation supports.

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Why are Emission and Excitation Spectra Mirror Images?

09 Emission-Excitation Spectra

In a follow-up to our introduction to fluorescence, we wanted to discuss a somewhat confusing(at least for us) detail of fluorescence spectroscopy: the fact that emission spectra and excitation spectra of the same fluorophore are mirror images of each other. It wasn’t until we drew out the diagram pictured above that we truly “got it.”

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Introduction to Fluorescence

07 Fluorescence Introduction

Fluorescence (i.e. the emission of light from a electronically excited substance) is one of the most utilized physical phenomena in chemistry and biology. Though humans have been aware of fluorescence for thousands of years (e.g. fireflies), it wasn’t until the discovery of quinine in 1845 that we really started to understand its chemical basis(see figure above). Interestingly, during World War II, the study of quinine’s anti-malarial properties led to the development of the first spectrofluorometers which enabled true quantitative study of fluorescence. Finally, in the 1980-1990’s, new tools in synthetic chemistry and molecular biology allowed rational engineering of chemical fluorophores into a critical class of probes in biophysics(microscopy), molecular biology(sequencing), cell-biology(flow cytometry) and even anatomy (histology)).

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