We observed a dye absorption blue shifted when deposited as a thin film from a solution. Also the spectra is broadened for film.
Any clarifications.
We performed the concentration dependent solution study and we dont see such peak shift and broadening. This is happening only in thin film. the thin film is deposited on glass substrate using the spin coating technique.
Check
http://www.dstuns.iitm.ac.in/teaching-and-presentations/teaching/undergraduate%20courses/cy306-structure-and-energetics-of-biomolecules/presentations/H-%20and%20J-%20Aggregates.pdf
Probably H-aggregates are formed..in the film???
In addition to Venugopal Rao Soma I want to add some thing. You have not observed any shift or broadening in the absorption of dye solution with concentration. It is surprising. Normally absorption spectra show a broadening as well as blue shift with an increase in the concentration of dye due to dimer formation. This is a type of aggregation. Another type of aggregation showing red shift has been noted when dyes are coated on Al2O3 surfaces. This indicates that different type of aggregation takes place when dyes are coated on surfaces. This is again due to effective increase in concentration. Following references may be helpful.
Pramana, J of Physics 23 215 (1984).
Appl. Opt. 27 2776 (1988).
In thin films light waves interfere and you can get color even without dyes. Maybe interference is responsible for the color change. What do you observe when you change the film thickness?
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