Ultra-Bright Rhodamines with Sulfobutylether-β-Cyclodextrin: A Viable Supramolecular Dye Laser in Aqueous Medium

Area of Science:

• Supramolecular Chemistry
• Photophysics
• Laser Science

Background:

• Aqueous dye lasers are desirable but limited by dye aggregation in water, reducing optical output.
• Rhodamine 6G and rhodamine B are prominent laser dyes prone to aggregation in aqueous solutions.

Purpose of the Study:

• To investigate the noncovalent interactions between rhodamine dyes and sulfobutylether-β-cyclodextrin (SBE₇ βCD).
• To overcome the limitations of dye aggregation in water for practical aqueous dye laser applications.

Main Methods:

• Spectroscopic analysis (absorption, fluorescence) to study dye-host interactions.
• Photophysical measurements including fluorescence lifetime and anisotropy.
• Isothermal titration calorimetry to determine thermodynamic parameters and stoichiometry.
• Job's plot analysis to confirm complex formation.

Main Results:

• Evidence of complex formation between rhodamine dyes and SBE₇ βCD with binding constants around 10⁴ M^-1.
• 1:1 stoichiometric complex formation was confirmed through various photophysical and thermodynamic analyses.
• SBE₇ βCD effectively prevented dye aggregation and maintained rhodamine dyes in monomeric forms.
• Enhanced fluorescence yield and brightness of the dyes in the presence of SBE₇ βCD.

Conclusions:

• SBE₇ βCD acts as a host to stabilize rhodamine dyes in aqueous solutions, preventing aggregation.
• The developed supramolecular systems demonstrate cost-effective aqueous dye lasers with improved lasing efficiencies (up to 25% higher).
• These aqueous dye laser systems exhibit enhanced beam profiles and durability compared to conventional ethanol-based solutions.