Effect of beta-cyclodextrin on the photoinduced charge transfer in sodium 1-anilino-8-naphthalene sulfate (ANS)/CdS colloidal system

The S-center radical (ANS(.)) of sodium 1-anilino-8-naphthalene sulfate (AN S) generated by photoinduced charge transfer in ANS/CdS and ANS/CdS/beta -c yclodextrin(beta -CD) systems has been studied by using spin trapping elect ron spin resonance techniques, UV-visible spectroscopic methods, and fluore scence spectroscopic methods. It was found that the S-centered radical (ANS (.)) was produced by the charge transfer reaction between the ground state ANS and the positive hole h(+)(CdS) from the valence band of CdS colloids, by the charge transfer from the excited singlet state (1)ANS* to the conduc tion band of CdS colloids, or by both in the ANS/CdS and ANS/CdS/beta -CD s ystems. The ESR signal intensity of the spin adduct (5,5 ' -dimethyl-1-pyrr oline-N-oxide (DMPO)-ANS)(.), which is formed from ANS(.) trapped by DMPO, in the latter system is 15 times stronger than that in the former system. T he apparent association constants between ANS and CdS colloids in the absen ce and presence of P-CD determined from fluorescence quenching experiments are 1097 and 1606 M-1, respectively. From ESR and fluorescence results, it is estimated that the efficiency of photoinduced charge transfer from ANS t o CdS colloids in the ANS/CdS/beta -CD system is 12.5 times that in the ANS /CdS system. (C) 2001 Academic Press.