Laser photolysis of carboxymethylated chitin derivatives in aqueous solution. Part 2. Reaction of OH* and SO4*- radicals with carboxymethylated chitin derivatives.
ABSTRACT The reactions of OH* or SO4*- radicals with carboxymethyl chitin (CM-chitin) and its deacetylated product, carboxymethyl chitosan (CM-chitosan), were investigated in aqueous solutions using a laser photolysis technique. The rate constants of the reactions of OH* and SO4*- radicals with CM-chitosan are always higher than those for CM-chitin, indicating that the amino-group could increase the reactivity of carboxymethylated chitin derivatives. The rate of the reactions of CM-chitin and CM-chitosan with OH* radical was found to decrease at lower pH when polymers chains tend to the coiled conformation. In comparison, the rate constant of the reaction of SO4*- radicals with CM-chitin or CM-chitosan decreased with pH, indicating that CM-chitin or CM-chitosan has a higher reactivity with the SO4*- radical at low pH due to the protonation of the amino group.
Article: Noncovalently modified carbon nanotubes with carboxymethylated chitosan: a controllable donor-acceptor nanohybrid.[show abstract] [hide abstract]
ABSTRACT: We report here the modification of multiwalled carbon nanotubes (MWNTs) with a kind of polysaccharide, carboxymethylated chitosan (cmCs), and their potential usage as donor-acceptor nanohybrids. The modified composites (cmCs/MWNTs) were characterized by high-resolution TEM, FT-IR, TGA and time-resolved spectroscopy. The time-resolved spectroscopic experiments revealed that interfacial electron transfer readily takes place between MWNTs and surface immobilized cmCs chains. The forward electron transfer is fast (< 20 ns) while the backward recombination is slow. The recombination process strongly depends on the chain length of carboxylmethylated chitosan, i.e. a shorter recombination lifetime (~1.1 micros) for the shorter-chain cmCs coated MWNTs against that of the longer-chain cmCs coated MWNTs (~3.5 micros). The results demonstrated that the cmCs/MWNTs composite may be applied as a controllable donor-acceptor nanohybrid.International Journal of Molecular Sciences 03/2008; 9(2):120-30. · 2.60 Impact Factor