Environmental Engineering Reference
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Fig. 5
TEM images of pyrite nanocrystal growth progression. Reprinted with permissions from
[ 53 ]
of the separated nanocrystals the particles' overall size does not change dramati-
cally over time, which also suggests that Ostwald ripening is not a major factor in
pyrite nanosynthesis. Absorbance of these particles shows a typical absorbance
shoulder around 550 nm. Thin films were created from these particles by layer-by-
layer deposition, and then sintered to try to improve the properties of the material
by removing sulfur deficiencies. This sintering also had the effect of increasing
grain size that can be seen in Fig. 6 that left many voids in the film layer and also
increased the roughness of the top surface. Although sintering may not have
helped to create the best films for devices, synthesis of nanosphere particles with
narrow size distribution was achieved.
In our lab, we have also taken to utilizing the hot injection method for pyrite
nanocrystal synthesis [ 24 , 54 ]. It has been observed that both cubes and nano-
spheres can be made for pyrite nanomaterial, but from the use of different synthetic
routes. Being able to create both cubes and nanospheres using the same method
would useful in the future testing of the material in devices. With this motivation, a
model was conceived to achieve shape control with the most studied iron precursor
FeCl 2 . Figure 7 shows the proposed model. Since it has been shown that the {100}
face is lower in surface energy than the {111} face, simply changing the tem-
perature of the injection reaction could dictate the final shape. The task was then
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