For the sake of simplicity, here, we focus our comparison to curve C because in curve B, the polymer peak P is overlapped to the main CdS diffraction peak, but as can be easily seen, the conclusion and findings will be identical for find more curve B. Figure 6 shows the experimental WAXS pattern that corresponds to curve C in Figure 5, and the calculated WAXS pattern of CdS nanocrystals of particle diameter of 3 nm of zinc blende (curve z) and wurtzite (curve w) crystallographic structure, respectively. The X-ray diffraction patterns are calculated using the
model of Langford  and assuming particles of spherical shape and, for simplicity, without size dispersion. For comparison, together with the calculated patterns, the Bragg peaks are also shown (their angular position and relative intensities) in accordance with the ICDD cards for the cubic (PDF nr. 80–0019) and hexagonal (PDF nr. 80–0006) CdS phase [JCPDS-ICDD ©2000]. Figure 6 Experimental WAXS pattern (curve C in Figure 5 ) and calculated X-ray diffraction patterns.
For CdS nanocrystals of cubic (zinc blende, labelled as ‘z’) and hexagonal (wurtzite, ‘w’) crystallographic phase. The nanocrystals are assumed to be of spherical shape and having particle selleck kinase inhibitor size (diameter) of 3 nm. For this kind of polymer nanocomposite samples, it is not very easy to perform quantitative X-ray analyses; nevertheless, by comparing Thymidylate synthase the calculated patterns with experimentally Akt inhibitor measured patterns, we find a much better agreement for the wurtzite phase of the CdS nanocrystals. This is particularly evident for the shape of the main diffraction peak (convolution of more Bragg peaks) at about 2θ = 27.6° and for the broad peak at about 2θ = 47°. Nevertheless, we cannot exclude the presence and coexistence of CdS nanocrystals of zinc blende phase within the hybrid nanocomposite. In order to further investigate the structure of CdS/MEH-PPV nanocomposites,
the thermolysis process was performed directly on thin composite films deposited on carbon-coated copper grids for TEM observations. In Figure 7a,b, TEM images of CdS/MEH-PPV nanocomposites obtained at 185°C, for the sample with a weight/weight ratio of 1:4, show the formation of CdS NCs with a regular spherical shape and a very homogeneous distribution in MEH-PPV matrix. Nevertheless, the density of nanocomposite is very low for application in photovoltaic and light detection devices; in fact, the average distance among the CdS NCs is above 50 nm. Further experiments were performed using a respective weight/weight ratio between precursor and polymer of 2:3. This ratio percentage allows to obtain a dense regular network of CdS NCs inside MEH-PPV without evident agglomerates, as shown in Figure 7c,d.