Mr. Khattab,

I do not know how you have operated with this theory, because of, m1 and m2 are obtained by experimental slopes of two different equations (eqs. (1) and (2), attachment). Once when you have calculated those values, you can compute GS and ES dipole moments (mug and mue) by the corresponding set of two independent equations to m1 and m2, respectively (eqs (3) and(4). In other words you have two equations and two unidentified values yielding to eq. (5) (attachment).

In spite of the comment stated above, negative mug value, however, arises the following questions:

1. Are relationships, using solvatochromic methods about plot (hia-nif)=f(f) and (nia+nif) = f(f+2g) linear within whole range of f(e,n) and g(n) values or not (Eqs. (1) and (2))?

2. Is absorption and fluorescence patterns very complex, meaning overlapped? Because of you can obtain large error's values determining band positions in absorption and fluorescence spectra (nia and nif values in Eqs. (1) and (2)). This error contributes to errors, determining m1 and m2 from the corresponding slopes as well.

3. How many solvents you have used? Because of, m1 and m2 are values of slopes as mentioned above. From a chemometric standpoint, there is meaningful information, operating with a set of 10-15 solvents, for example, in order to obtain accurate data. When the number of points (solvents in your case) is small, then the inaccuracy of m1 and m2 values increases in.

4. How much is the concentration? Because of, using those solvatochromic approaches, you approximate that there is not change of refractive index and dielectric constant with increasing in concentration of analyte (particles). Or you operate with very diluted solutions. Generally, however, if you operate with relatively high concentrations, you cannot neglect the change of dielectric constants and refractive indexes. In other words you should recalculate the f(e,n) and phi(n,e) values with corresponding values of dielectric constants and refractive indexes of the concentrated solutions. Such as recalculations yield to new m1 and m2 values, and thus - to new mue and mug quantities.

Please bear in mind that if you have measured nanoparticles, for example, you should avoid aggregation and sedimentation. In other words nano-colloids should be measured freshly prepared.

There is better as well as to compute mug and mue theoretically, by methods of the quantum chemistry. Because of, negative mug value can occur in inorganic crystals with differently charged layers. Is your crystal perovskite, for example? Or is there possible in your system surface redox process? Negative mug means that there is most probably phase transition. Such conclusion, however, need confirmation by other computations at different theoretical levels in order to avoid discrepancy, first, due to inaccuracy of the corresponding theoretical level, because of some methods can give such discrepancy; and second, due to discrepancy between theoretical data and experimental errors of measurements/chemometrics according the comments associated with questions 1-4.

Thanks so much!

Actually, the is no overlapping between the absorption and emission spectra. Sample concentration is 0.3 uM (very dilute). I noticed that authors convert the -ve sign of m2 to be +ve. i did so as well. but as i mentioned above, the numerical value of m1 is bigger than m2 even after using the +ve valus of m2. hence, the ES dipole moment woul be -ve.