Excited-State Proton Transfer of Weak Photoacids Adsorbed on Biomaterials: Proton Transfer on Starch
1Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel.
Abstract:
Steady-state and time-resolved fluorescence techniques were employed to study the excited-state proton transfer (ESPT) from a photoacid adsorbed on starch to a nearby water molecule. Starch is composed of ∼30% amylose and ∼70% amylopectin. We found that the ESPT rate of adsorbed 8-hydroxy-1,3,6-pyrenetrisulfonate (HPTS) on starch arises from two time constants of 300 ps and ∼3 ns. We explain these results by assigning the two different ESPT rates to HPTS adsorbed on amylose and on amylopectin. When adsorbed on amylose, the ESPT rate is ∼3 × 10(9 )s(-1), whereas on amylopectin, it is only ∼3 × 10(8) s(-1).
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