Sq I

s(q) = 2pqD, where q is the usual scattering vector, D is the diameter of the nanoparticle, Lm is the Lorentz polarization factor and mm and Fm are the multiplicity and structure factor of the hkl reflection, respectively. The calculated curves that better approximate the experimental data show that a mixture of both zb and w phases is present. With the hypothesis that each phase contributes to the total scattered intensity by 50%, we obtained a good fit of the experimental curves.

We report the results relative to the samples annealed at 240 and 300°C (Fig.5.6) where the nanoparticle diameter D is evaluated as 1.8 and 8 nm, respectively. This study,

Fig. 5.6 Theoretical simulations of the in situ synchrotron XRD data of C12/TP at annealing temperatures T = 240 °C (a) and 300 °C (b), by considering spherical CdS nanoparticles with zincblende (zb) and wurtzite (w) phases of diameter 0 = 1.8 nm (a) and 8.0 nm (b). In both (a) and (b): (i) the dots represent the experimental data points, the green curve is the calculated for nanoparticles with zb phase, the blue curve for nanoparticles with w phase, the red curve is obtained by considering 50% zb and 50% w mixed phase; (ii) the peaks are labelled by the relative Miller indexes of the zb and w phases. Reprinted with permission from [35]. Copyright © (2006) American Chemical Society q (nm"')

experimental data points simulation zfcH-w simulation zb simulation w

Fig. 5.6 Theoretical simulations of the in situ synchrotron XRD data of C12/TP at annealing temperatures T = 240 °C (a) and 300 °C (b), by considering spherical CdS nanoparticles with zincblende (zb) and wurtzite (w) phases of diameter 0 = 1.8 nm (a) and 8.0 nm (b). In both (a) and (b): (i) the dots represent the experimental data points, the green curve is the calculated for nanoparticles with zb phase, the blue curve for nanoparticles with w phase, the red curve is obtained by considering 50% zb and 50% w mixed phase; (ii) the peaks are labelled by the relative Miller indexes of the zb and w phases. Reprinted with permission from [35]. Copyright © (2006) American Chemical Society

Fig. 5.7 Schematic view of the chemical transformation of the thiolate precursors and the nucleation and growth of the CdS nanoparticles from the precursor thermolysis: (a) lamellae structure of the precursor from room temperature up to 100°C; (b) hexagonal structure due to the flexibility of the alkyl chains in the temperature range between 160 and 240 °C; (c) final state (above 240 °C) consisting of CdS nanoparticles only. The organic component has completely decomposed. The crystalline structure of the nanoparticles has been simplified in the sketch. Reprinted with permission from [35]. Copyright © (2006) American Chemical Society

Fig. 5.7 Schematic view of the chemical transformation of the thiolate precursors and the nucleation and growth of the CdS nanoparticles from the precursor thermolysis: (a) lamellae structure of the precursor from room temperature up to 100°C; (b) hexagonal structure due to the flexibility of the alkyl chains in the temperature range between 160 and 240 °C; (c) final state (above 240 °C) consisting of CdS nanoparticles only. The organic component has completely decomposed. The crystalline structure of the nanoparticles has been simplified in the sketch. Reprinted with permission from [35]. Copyright © (2006) American Chemical Society together with supporting analyses from TEM, PL and Gas chromatography/Mass spectrometry, allowed to draw a possible mechanism for the CdS nanoparticle formation from the thermolysis of the long-chain thiol precursors (Fig. 5.7) : below 100 °C, the precursor has a lamellae structure (a) that changes to an hexagonal lattice formed by the sulphur atoms (b) because of the flexibility of the organic chains induced by the increased temperature (160-240 °C). Above 240 °C, (c) the precursor molecules are completely decomposed and the CdS nanoparticles are grown dispersed in the polymer matrix.

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