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