The fluorescence phenomenon has been observed for thousands of years. However, it was not until today that we understand this phenomenon and have been able to control and make use of the process.
Phenomenons now known as fluorescence and phosphorescence were mentioned in Chinese books as far back as 1500 BC.
Nicolás Monardes, a Spanish physician and botanist publishes in 1565 the "Historia medicinal de las cosas que se traen de nuestras Indias Occidentales" in which he describes the bluish opalescence of the water infusion from the wood of a small Mexican tree. When made into cups and filled with water, a peculiar blue tinge was observed. He observed the luminescence for the first time in an extract of Lignum nephriticum a drug recommended at the time for the treatment of kidney diseases.
Around the same time, Bernardino de Sahagún (1499-1590), a Franciscan missionary, independently described the wood called “coatli” by the Aztecs in the Florentine Codex.
In this book "Ars Magna Lucis et Umbrae", Athanasius Kircher (1602-1680) describes the effect of a wood extract (lignum nephriticum) in water and discussed the application of fireflies to illuminate houses. Light passing through an aqueous infusion of this wood appeared more yellow while light reflected from the solution appeared blue.
Recent studies by Ulises Acuña indicate that the original blue emission observed by the Aztecs was probably due to the conversion of Coatline B, under mildly alkaline conditions, to a strongly blueemitting compound - resembling fluorescein - with an emission maximum near 466nm and with a quantum yield near 0.8
In 1603, Vincenzo Casciarolo, a Bolognian shoemaker who was dreaming of producing gold, discovered that a stone, after being baked, emitted a purple-blue light in the dark. Most likely, the stone, named lapis solaris, was barium sulfate. The discovery starts a lively debate between scientists at the time.
Galileo Galilei (1612) described the emission of light (phosphorescence) from the famous Bolognian stone, "It must be explained how it happens that the light is conceived into the stone, and is given back after some time, as in childbirth."
Robert Boyle (1664) was inspired by Monardes’ report and investigated this system more fully.
He discovered that after many infusions the wood lost its power to give color to the water and concluded that there was some “essential salt” in the wood responsible for the effect.
He also discovered that addition of acid abolished the color and that addition of alkali brought it
back.
David Brewster (1833) described that when a beam of white light passed through an alcohol solution
of leaves a red beam could be observed from the side (which was of course chlorophyll fluorescence). He considered the effect due to “dispersion”.
John Herschel (1845) made the first observation of fluorescence from quinine sulfate, he termed this phenomenon “epipolic dispersion”.
Edmond Becquerel (1842) reports the emission of light from Calcium sulphate upon excitation in the
UV (Ultra-Violet Light). He notes that the emission occurs at a wavelength longer than that of the incident light.
Later on (1858) builds the first phosphoroscope enabling him to measure the decay times of phosphorescence.
The term fluorescence was coined by Sir George Gabriel Stokes (1819–1903). In 1843, he described the luminescence in calcium fluoride as fluorescence.
George Gabriel Stokes (1852) published his massive treatise “On the Change of Refrangibility of Light” more than 100 pages. He initially using the term “dispersive reflection” to describe the phenomenon presented by quinine sulphate.
Stokes used the light from the sun as the source of excitation. Sunlight was first passed through a filter composed of a solution of cupric hydroxide in an aqueous solution containing ammonia, then the filtered light was focused onto the specimen, and the emitted light together with the filtered excitation sunlight was passed through an yellow filter composed of an aqueous solution of potassium dichromate.
Stokes used a prism to disperse the solar spectrum and illuminate a solution of quinine. He noted that there was no effect until the solution was placed in the ultraviolet region of the spectrum.
Stokes observed the fluorescence with his eyes. In what became known as "Stokes law", the phenomenon of fluorescence is often characterized by the wavelength of the emitted light that is of a longer wavelength than the wavelength of the exciting light (1852).
This observations led Stokes to proclaim that fluorescence is of longer wavelength than the exciting light, which led to this displacement being called the Stokes Shift.
He also seems to have been the first to propose, in 1864, the use of fluorescence as an analytical tool, in a lecture "On the application of the optical properties to detection and discrimination of organic substances”.
