Syntheses And Properties Of Charge-transfer Cadmium Chalcogenido Clusters

CdS/CdSe nanomaterials with semiconductor property have been arousedworldwide attention because of their potential application in the area of photoelectricity,electric, catalysis and biology. Great progress has been made in solar cell,photochemical sensor and biosensor with CdS/CdSe quantum dots. Now one of the keysin this field is to introduce functional organic/inorganic groups into CdS/CdSe materialsto expand the applied area of those materials and further to investigate the relationshipbetween the properties and structures at microscopic structure level. The syntheticchallenge in this field is how to control size distribution of quantum dots. CdS/CdSeclusters could serve as models of CdS/CdSe nanomaterials because of theirhomogeneous dimensions, definite structures and arrangement. Therefore, to studyCdS/CdSe clusters has both theoretical and practical significance.The content of this paper includes the synthesis and characterization of functionalCdS/CdSe clusters and investigating the functional CdS/CdSe clusters’ propertiescontaining fluorescence spectrum, UV-visible spectroscopy, thermal analysis,electrochemical and photocurrent properties.（1） Three anion–cation compounds1–3with formula[M（phen）₃][Cd₄（Sph）₁0] Sol (M=Ru²⁺, Fe²⁺, and Ni²⁺, Sol=MeCN and H2_O) havebeen synthesized and characterized by single–crystal analysis. Important inter ion’sinteractions are found in the crystals, such as π···π stacking and C–H···π contact.Both spectroscopic and theoretical calculated results indicate that there isanion–cation charge-transfer （ACCT） in the Ru-phen complex dye and Cd–Sphcluster co-assembled compound. The intensity of fluorescent emission of the[Ru（phen_）3]²⁺is enhanced when titrated with [Cd₄（Sph）₁0]^2–. The mechanism for theenhancement of photoluminescence has been proposed. （2） Large cadmium chalcogenido C2(Cd₃₂) and C1(Cd₁₇) CdQ （Q=S, Se） clusterswith [Ru（Phen/Bpy）₃]²⁺cations were prepared under solvothermal conditions, using thethiourea and selenourea as S and Se sources （Bpy=2,2’–bipyridine, Phen=1,10–phenanthroline）. The high condensed3-D C2–CdSeSRuBpy （4）,C2–CdSeSRuPhen （5）, and C2–CdSSRuPhen （6） were obtained at higher temperaturecomparing with that of the0-D C1–CdSeSRuBpy （7）, C1–CdSeSRuPhen （8）, andC1–CdSSRuBpy （9）. Clusters in4and5can be considered as homosized nanoCdS/CdSe core-shell particles （Cd₃2cluster, ac2.0nm radius） with Cd4Se10core. Theemission spectra showed a red-shift and enhancement due to the interaction between[Ru（Phen/Bpy）₃]²⁺cations and CdQ cluster anions. The photocurrent responses of theseclusters on ITO electrodes are systematically studied, and the results are （1） the currentintensity of the3–D C2clusters is larger than that of the0–D C1clusters,（2） the currentintensity of the selenide clusters is larger than that of the sulfide clusters,（3） darkcurrent was clearly found for the selenide clusters.（3） Halide-substituted cadmium chalcogenido C1(Cd₁₇) and P1（Cd₈） withcation MV²⁺were obtained by solvothermal reaction at low temperature（compounds10–12）. Infrared spectrum and Raman spectrum helped us to comfirm that MV²⁺exists in these clusters. Cyclic voltammetry experiment of compoud12in DMFshowed that redox potential was shifted to more negative positon, proving that thereare interactions and charge transfer between cadmium chalcogenido anion andMV²⁺cation in the solution of compound12. We studied the photocurrentproperties of the compouds11and12, and the result displays that the photoresponsein the visible area for compoud11and12is superior to cadmium chalcogenidocluster only with quarternary ammonium salt cation.