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

Document Type : Original Research Paper


1 Department of Physics, University of Sistan and Baluchestan, Zahedan, Islamic Republic of Iran

2 Department of Physics, University of Zabol, Zabol, P. O. Box. 98613-35856, Islamic Republic of Iran

3 Department of Chemistry, Jadavpur University, Kolkata 700032, India



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 investigated at two higher 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 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 largely at high concentrations compared to that at low