Rhodamine amides are versatile derivatives of the xanthene dye rhodamine B that possess the ability to open or close depending on the surrounding environment. Higher levels of protonation that are associated with acidic environments encourage the open form of a rhodamine B dimer, which results in bright orange fluorescence. The basic profile of the dimer corresponds with the closed spirolactam form and does not generate any orange fluorescence, indicating there is a transitional pH range in which the molecular structure changes from open to closed. Synthesized samples of rhodamine B dimers were combined with diluted bases or acids to establish incremental pH levels in a variety of solvents, each of which influenced the observable fluorescence of the solutions. The excitation and emission wavelengths of these substances were collected from 3D fluorescence spectra through the use of fluorometry. Understanding the optimal conditions and trends for fluorescence in different pH and solvent environments will allow inexpensive fluorescent dyes such as rhodamine B to be utilized in sensors as effective visual indicators.

Analyzing the fluorescent behavior of rhodamine B regarding pH changes

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