title: Photocatalytic applications with CdS • block copolymer/exfoliated graphene nanoensembles: hydrogen generation and degradation of Rhodamine B.
abstract: Amphiphilic block copolymer poly(isoprene-b-acrylic acid) (PI-b-PAA) was used to stabilize exfoliated graphene in water, allowing the immobilization of semiconductor CdS nanoparticles forming CdS • PI-b-PAA/graphene. Characterization using high-resolution transmission electron microscopy and energy-dispersive x-ray spectroscopy proved the success of the preparation method and revealed the presence of spherical CdS. Moreover, UV-Vis and photoluminescence assays suggested that electronic interactions within CdS • PI-b-PAA/graphene exist as evidenced by the significant quenching of the characteristic emission of CdS by exfoliated graphene. Photoillumination of CdS • PI-b-PAA/graphene, in the presence of ammonium formate as a quencher for the photogenerated holes, resulted in the generation of hydrogen by water splitting, monitored by the reduction of 4-nitroaniline to benzene-1,4-diamine (>80 ± 4% at 20 min; 100% at 24 min), much faster and more efficient compared to when reference CdS • PI-b-PAA was used as the photocatalyst (<30 ± 3% at 20 min; 100% at 240 min). Moreover, Rhodamine B was photocatalytically degraded by CdS • PI-b-PAA/graphene, with fast kinetics under visible light illumination in the presence of air. The enhancement of both photocatalytic processes by CdS • PI-b-PAA/graphene was rationalized in terms of effective separation of holes and electrons, contrary to reference CdS • PI-b-PAA, in which rapid recombination of the hole-electron pair is inevitable due to the absence of exfoliated graphene as a suitable electron acceptor.
authors.affiliation: Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vassileos Constantinou Avenue, 11635 Athens, Greece.
authors.forename: T
authors.initials: T
authors.lastname: Skaltsas
authors.forename: N
authors.initials: N
authors.lastname: Karousis
authors.forename: S
authors.initials: S
authors.lastname: Pispas
authors.forename: N
authors.initials: N
authors.lastname: Tagmatarchis
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D002384:Catalysis; D006108:Graphite / Q000138:chemical synthesis*; D006801:Humans; D006859:Hydrogen / Q000737:chemistry; D055668:Photochemical Processes; D011108:Polymers; D045663:Quantum Dots / Q000737:chemistry* / Q000648:ultrastructure; D012235:Rhodamines / Q000737:chemistry; D013440:Sulfides / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D011108:Polymers; D012235:Rhodamines; D013440:Sulfides; C034939:cadmium sulfide; D006108:Graphite; D006859:Hydrogen; C029773:rhodamine B