During the fluorescence measurement of a plant material taken in two different forms powder and juice, we have observed that a most intense peak appeared at 380 nm in powder form of the sample was blue shifted by 35 nm and noticed at 345 nm when the sample was in juice form. Water was used as a solvent. Kindly let me know the plausible reason for this shifting... I will appreciate your efforts.
Regards
If the fluorescence you are observing is coming from the same chemical in both cases (see above answer by Peter Kapusta), then one possible reason for the shift in emission peak could be the change in the dielectric constant of the environment of the fluorophore from a more hydrophilic environment in the powder (red shift) to a more hydrophobic environment (blue shift) in the solution (which seems backwards, but you never can tell). Another possibility is that you are seeing excimer fluorescence in the powder due to the high concentration, which is not seen when the substance is diluted in water.
If the fluorescence you are observing is coming from the same chemical in both cases (see above answer by Peter Kapusta), then one possible reason for the shift in emission peak could be the change in the dielectric constant of the environment of the fluorophore from a more hydrophilic environment in the powder (red shift) to a more hydrophobic environment (blue shift) in the solution (which seems backwards, but you never can tell). Another possibility is that you are seeing excimer fluorescence in the powder due to the high concentration, which is not seen when the substance is diluted in water.
Consider Adam Shapiro's answer. It is entirely possible that self-absorbance in the more concentrated powder form is red-shifting that spectrum.. You can confirm this by diluting the solution and seeing how both the fluorescence and absorption spectra respond.
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