I'm preparing organic nanoparticles and using it for sensing cation ions. After addition of cation solution the fluorescence intensity enhanced. How can I interpret the fluorescence lifetime studies for the same. Do any changes occur in fluorescence lifetime?
Have you been able to come up with a reason for this fluorescence enhancement ? If not, then you must do that first before thinking about fluorescence lifetimes. Is it only enhancement nor there are other changes involved such as spectral broadening or narrowing, spectral shift etc. ? Usually when we observe enhancement fluorescence intensity of probes such as due to binding in proteins etc. we associate it to decreased non-radiative loss. In these cases, radiative lifetime increases. Hope this helps.
You may try to analyze the fluorescent lifetime to see if it is single exponential decay. This will tell some information about the interaction between nano-particles and cations. In addition, the increase of fluorescence intensity usually comes from the decrease of non-emissive decay channels or the formation of complex. You have to find the reason of that fluorescence enhancement before you measure the lifetime. You may find one of my publications on Cryst. Groth & Design for your reference. (http://pubs.acs.org/doi/abs/10.1021/cg200920d) It shows the hydrogen bond can ignite a bright fluorescence.
Fluorescence lifetime (t) is composed of two components- radiative decay rate and non radiative decay rate ( 1/t = 1/tr +1/tnr). Enhancement of fluorescence can occur due to increased radiative recombination or decrease in non radiative recombination. For nanoparticles, since the surface to volume ratio is high lot of surface states and dangling bonds exist which contribute to non radiative loss of excited charges. If nanoparticle surface is passivated, non radiative recombination is decreased and fluorescence can be enhanced. Hence fluorescence lifetime in such cases may be correlated to fluorescence lifetime.
Dear Rupashree madam
i had already done the experiments of enhacement of nanoparticle fluorescence intensity and lifetime too.... both are increses in as i added a analyte to nanoparticles. whats the reasons.... please give refernces if u have
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