Effect of Temperature Upon the Fluorescence of some Organic Solutions

Abstract

A spectrographic study has been made of the effect of temperature upon the fluorescence of alcoholic solutions of rhodamine B, eosin, tetrachlorofluorescein, and sulfonefluorescein. Fluorescein has been studied by means of a spectrometer. The effect of concentration has been studied for eosin and for rhodamine B. When observed, the temperature shift of the peak of the fluorescence bands is proportional to the change in temperature. The observed change is in the same direction as has been observed for absorption. The shift is not in the same direction for all substances. The shift, due to change in concentration, is proportional to the logarithm of the concentration. The shift is in the same direction as it is for absorption. Change in the width of the fluorescence band does not follow the same law as for absorption. In other respects the results caused by change in temperature or change in concentration seem to be the same for absorption as for fluorescence.Rhodamine B. Decrease in temperature or increase in concentration causes the peaks of the bands to shift to longer waves. Decrease in concentration causes a widening of the fluorescence band, but causes a narrowing of the absorption band.Eosin. Decrease in temperature causes a shift to shorter waves for fluorescence peaks. This is probably true for absorption. Concentration shifts were too slight to be accurately measured. Fluorescence is a maximum at room temperature.Fluorescein. Decrease in temperature causes a shift toward shorter waves. Fluorescence is a maximum at room temperature. Increase in temperature causes a widening of both the fluorescence and the absorption bands. Widening is greater on the red side of band.Tertachlorofluorescein. Shows so slight a shift that it could not be accurately measured. Lowering of temperature causes the appearance and growth of a new band on the red side of the main band.Sulfonefluorescein. Shows no appreciable shift of the peaks of the main bands as the temperature is lowered, but bands having shorter waves become relatively more prominent.