An insight to optical studies of acridine orange cationic dye within nanometer-sized microemulsions at fixed water content

Abstract

Cationic dye Acridine orange (AO) has wide applications especially in biological fields such as analysis of lysosomal and mitochondria content by flow cytometry and so on. In the current work, spectroscopy of acridine orange (AO) dye at both low concentrations (mdye/mwater=6.25*10-5, 3.12*10-5) and high concentrations (mdye/mwater=0.002, 0.001) was studied in confined water nanodroplets within water/AOT/n-hexane microemulsions (MEs) at a constant water content (W= [Water]/[AOT]=10) and as a function of mass fraction of droplet (MFD) using absorption and fluorescence spectroscopic techniques. The absorption spectra of the dye at high concentrations of Acridine orange (AO) dye molecules showed that the absorption spectra of the samples deviated from Beer's law, and are broadened at larger MFD due to the interactions of AO dye molecules. The fluorescence spectrum was investigated at two high concentrations (0.002, 0.001) and low concentrations (6.25*10-5, 3.12*10-5). At high concentration of the dye, quenching of fluorescence intensity was observed due to the accumulation of the dye molecules, coupled with a red shift with increasing MFD. However, in the lower concentration regime, enhancement of fluorescence intensity was observed with increasing MFD. The Stokes’ shift of the dye for both high and low concentrations increased with MFD, but to a greater extent at high concentrations compared to that at low concentrations.