title: Excited-state proton transfer of weak photoacids adsorbed on biomaterials: 8-hydroxy-1,3,6-pyrenetrisulfonate on chitin and cellulose.
abstract: Time-resolved and steady-state florescence measurements were used to study the photoprotolytic process of an adsorbed photoacid on cellulose and chitin. For that purpose we used the 8-hydroxy-1,3,6-pyrenetrisulfonate (HPTS) photoacid which transfers a proton to water with a time constant of 100 ps, but is incapable of doing so in methanol or ethanol. We found that both biopolymers accept a proton from the electronically excited acidic ROH form of HPTS. The excited-state proton-transfer (ESPT) rate of HPTS adsorbed on chitin is greater than that on cellulose by a factor of 5. The ESPT on chitin also occurs in the presence of methanol or ethanol, but at a slower rate. The transferred protons can recombine efficiently with the conjugate excited base, the RO(-) form of HPTS.
authors.affiliation: Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University , Tel Aviv 69978, Israel.
authors.forename: Ron
authors.initials: R
authors.lastname: Simkovitch
authors.forename: Dan
authors.initials: D
authors.lastname: Huppert
mesh_terms: D000327:Adsorption; D002482:Cellulose / Q000737:chemistry*; D002686:Chitin / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D011522:Protons; D011721:Pyrenes / Q000737:chemistry*; D013451:Sulfonic Acids / Q000737:chemistry*
chemical_list: C538892:8-hydroxy-1,3,6-pyrenetrisulfonic acid; D011522:Protons; D011721:Pyrenes; D013451:Sulfonic Acids; D002686:Chitin; D002482:Cellulose