title: Photophysical and redox properties of molecule-like CdSe nanoclusters.
abstract: Advancing our understanding of the photophysical and electrochemical properties of semiconductor nanoclusters with a molecule-like HOMO-LUMO energy level will help lead to their application in photovoltaic devices and photocatalysts. Here we describe an approach to the synthesis and isolation of molecule-like CdSe nanoclusters, which displayed sharp transitions at 347 nm (3.57 eV) and 362 nm (3.43 eV) in the optical spectrum with a lower energy band extinction coefficient of ~121,000 M(-1) cm(-1). Mass spectrometry showed a single nanocluster molecular weight of 8502. From this mass and various spectroscopic analyses, the nanoclusters are determined to be of the single molecular composition Cd34Se20(SPh)28, which is a new nonstiochiometric nanocluster. Their reversible electrochemical band gap determined in Bu4NPF6/CH3CN was found to be 4.0 V. There was a 0.57 eV Coulombic interaction energy of the electron-hole pair involved. The scan rate dependent electrochemistry suggested diffusion-limited transport of nanoclusters to the electrode. The nanocluster diffusion coefficient (D = 5.4 × 10 (-4) cm(2)/s) in acetonitrile solution was determined from cyclic voltammetry, which suggested Cd34Se20(SPh)28 acts as a multielectron donor or acceptor. We also present a working model of the energy level structure of the newly discovered nanocluster based on its photophysical and redox properties.
authors.affiliation: Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202, United States.
authors.forename: Sukanta
authors.initials: S
authors.lastname: Dolai
authors.forename: Amala
authors.initials: A
authors.lastname: Dass
authors.forename: Rajesh
authors.initials: R
authors.lastname: Sardar
mesh_terms: D019187:Cadmium Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D055664:Electrochemical Techniques; D049329:Nanostructures / Q000737:chemistry*; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D018036:Selenium Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D013696:Temperature
chemical_list: D019187:Cadmium Compounds; D018036:Selenium Compounds; C058667:cadmium selenide