title: Charge separation in Pt-decorated CdSe@CdS octapod nanocrystals.
abstract: We synthesize colloidal CdSe@CdS octapod nanocrystals decorated with Pt domains, resulting in a metal-semiconductor heterostructure. We devise a protocol to control the growth of Pt on the CdS surface, realizing both a selective tipping and a non-selective coverage. Ultrafast optical spectroscopy, particularly femtosecond transient absorption, is employed to correlate the dynamics of optical excitations with the nanocrystal morphology. We find two regimes for capture of photoexcited electrons by Pt domains: a slow capture after energy relaxation in the semiconductor, occurring in tipped nanocrystals and resulting in large spatial separation of charges, and an ultrafast capture of hot electrons occurring in nanocrystals covered in Pt, where charge separation happens faster than energy relaxation and Auger recombination. Besides the relevance for fundamental materials science and control at the nanoscale, our nanocrystals may be employed in solar photocatalysis.
authors.affiliation: Dipartimento di Scienze Chimiche e Geologiche and INSTM, Università di Cagliari, Cittadella universitaria, I-09042 Monserrato, Italy.
authors.forename: Erika
authors.initials: E
authors.lastname: Conca
authors.forename: Mauro
authors.initials: M
authors.lastname: Aresti
authors.forename: Michele
authors.initials: M
authors.lastname: Saba
authors.forename: Maria Francesca
authors.initials: MF
authors.lastname: Casula
authors.forename: Francesco
authors.initials: F
authors.lastname: Quochi
authors.forename: Guido
authors.initials: G
authors.lastname: Mula
authors.forename: Danilo
authors.initials: D
authors.lastname: Loche
authors.forename: Mee Rahn
authors.initials: MR
authors.lastname: Kim
authors.forename: Liberato
authors.initials: L
authors.lastname: Manna
authors.forename: Anna
authors.initials: A
authors.lastname: Corrias
authors.forename: Andrea
authors.initials: A
authors.lastname: Mura
authors.forename: Giovanni
authors.initials: G
authors.lastname: Bongiovanni
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*; D018036:Selenium Compounds / Q000737:chemistry*; D012666:Semiconductors; D013440:Sulfides / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D018036:Selenium Compounds; D013440:Sulfides; C034939:cadmium sulfide; D010984:Platinum; C058667:cadmium selenide