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Hyper-Rayleigh Scattering and Fluorescence of CdS-ZnS Nanoparticle Composites

Published online by Cambridge University Press:  11 February 2011

Yu Zhang
Affiliation:
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, P. R. China National Laboratory of Molecular and Biomolecular Electronics, Southeast University, Nanjing 210096, P. R. China
Xin Wang
Affiliation:
National Laboratory of Molecular and Biomolecular Electronics, Southeast University, Nanjing 210096, P. R. China
Ming Ma
Affiliation:
National Laboratory of Molecular and Biomolecular Electronics, Southeast University, Nanjing 210096, P. R. China
Degang Fu
Affiliation:
National Laboratory of Molecular and Biomolecular Electronics, Southeast University, Nanjing 210096, P. R. China
Haiqian Zhang
Affiliation:
National Laboratory of Molecular and Biomolecular Electronics, Southeast University, Nanjing 210096, P. R. China
Ning Gu
Affiliation:
National Laboratory of Molecular and Biomolecular Electronics, Southeast University, Nanjing 210096, P. R. China
Juzheng Liu
Affiliation:
National Laboratory of Molecular and Biomolecular Electronics, Southeast University, Nanjing 210096, P. R. China
Zuhong Lu
Affiliation:
National Laboratory of Molecular and Biomolecular Electronics, Southeast University, Nanjing 210096, P. R. China
Yi Ma
Affiliation:
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, P. R. China
Ling Xu
Affiliation:
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, P. R. China
Jun Xu
Affiliation:
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, P. R. China
Kunji Chen
Affiliation:
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, P. R. China
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Abstract

Hyper-Rayleigh scattering (HRS) or incoherent second-order light scattering technique has been used to investigate the second-order optical nonlinearities of nanoparticles and seems sensitive to nanoparticle aggregation. In the present work, CdS and ZnS nanoparticle colloids are prepared by the method of colloidal chemistry. From absorption spectra their average diameters are determined to be 5.0 nm for CdS and 2.5 nm for ZnS. Composite CdS-ZnS colloids are obtained by mixing the two colloids at different concentration ratio. The formation of the composites is confirmed by fluorescence measurement. The reduction of emission intensity of the ZnS colloid at 428 nm is observed with increasing CdS concentration, due to fluorescence quenching of the ZnS colloid after forming CdS-ZnS composites. The apparent combining constant of the two nanoparticles is determined to be 8.1×104 mol−1.L by fitting the relative fluorescence intensity of F0/F vs. the added CdS concentration. Upon 1064 nm laser pulse excitation, HRS signal is determined at frequency-doubling wavelength (532 nm) using photomultiplier tube (PMT). HRS experiments show that the composite CdS-ZnS colloids exhibit stronger HRS signal than both CdS and ZnS colloids, and a maximum of HRS signal appears at concentration ratio of [CdS]/[ZnS]=1. This is attributed to that the composite CdS-ZnS nanoparticles have lower symmetry which contributes substantially to the second-order optical nonlinearity of nanoparticles in the electric dipole approximation.

Type
Research Article
Copyright
Copyright © Materials Research Society 2003

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References

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