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Controlled Nucleation and Growth of CDS Nanoparticles by Turbulent Dispersion and Statistical Processin of Light Scattering From Nanoparticles

SHayeganfar, Farzaneh | 2010

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 47964 (04)
  4. University: Sharif University of Technology
  5. Department: physics
  6. Advisor(s): Rahimitabar, Mohammad Reza; Taghavinia, Nima
  7. Abstract:
  8. In this thesis, We propose and test a method for controlling the size of nanoparticles, which plays a fundamental role in their electrical, optical, and mechanical properties. The method utilizes turbulent mixing, and is applicable to the fabrication of any type of nanoparticle that uses a solution environment in the preparation process. We show by well-controlled experiments on the CdS nanoparticles, which are semiconducting materials, that the average size < d > of the particles decreases with Reynolds number Re. To gain a deeper understanding of the phenomena reported here, we have carried out molecular dynamics simulations of the processes. In second investigation, We provide a simple interpretation of non-Gaussian nature of the light scattering-intensity fluctuations from an aging colloidal suspension of Laponite using the multiplicative cascade model, Markovian method, and volatility correlations. The cascade model and Markovian method enable us to reproduce most of recent empirical findings: long-range volatility correlations and non-Gaussian statistics of intensity fluctuations. We provide evidence that the intensity increments x(τ ) = I(t + τ ) − I(t), upon different delay time scales , can be described as a Markovian process evolving in . Thus, the dependence of the probability density function p(∆x, τ ) on the delay time scale can be described by a Fokker-Planck equation. We also demonstrate how drift and diffusion coefficients in the FokkerPlanck equation can be estimated directly from the data. Last investigation is related to The existence of the important similarities between gelation and glass transition makes it hard to distinguish between the two types of nonergodic states experimentally. Here, we report on a stochastic analysis of the scattered light intensity through a colloidal particles suspension during the gel and glass formation. In this analysis, we exploit the methods developed for complex hierarchical systems, such as turbulence. Using the multiplicative log-normal cascade models, we ,provide a criterion to distinguish gels from glasses
  9. Keywords:
  10. Turbulence ; Light Scattering ; Nanoparticles Size ; Statistical Investigation ; Nanoparticles Suspension

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