Metal Chalcogenides Semiconductors Nanocrystals Synthesised By Mechanical Alloying Process And Optical Performance Study

The main search contents of this paper is using a low-cost, simple, effective, environment friendly and general approach to synthesis the metal sulfide nanocrystals. Subsequent capping the surface of as-milled metal sulfide nanocrystals with organic-inorganic composite ligand (TOPO/TOP/NA) leads to a well disperse solutions. Furthermore, the optic properties of the as synthesized metal sulfide nanocrystals have also been investigated. The main results achieved in this paper are listed as below:1. The uniform-sized and well disperse hexagonal structure semi-conduct CuS nanocrystals are synthesized by mechanically alloying at room temperature with the Cu and S element powders to be a source. After only milling for 10 min, the pure hexagonal structure CuS nanocrystals was complete formed. We analysised the mechanism of the phase transition that the digenite Cu9S5 compounds, appeared at early stage, transferred to hexagonal CuS compound. Subsequent capping the surface of as-milled CuS nanocrystals synthesised from 3-40 hours with organic-inorganic composite ligand (TOPO/TOP/NA) leads to the formation of green dispersion solutions. The capped CuS nanocrystals show extremely high dispersion stability in the solution. The grain size of the capped CuS nanocrystals ranges from 2 to 10 nm observed by TEM analysis. The UV-vis absorption peaks of capped CuS nanocrystals locate within the range of 656 to 665 nm which blue shifts to shorter wavelength side with the longer milling time.2. The pure chalcocite phase Cu2S nanocrystals have been successful synthesized by mechanical alloyin the elemental Cu and S powders for 80hours at room temperature, which the atomic ratio of copper to sulfur was set to be 2.16:1. In this experiment, we found that the Cu1.96S compound was coexisted in the product until the mechanical alloying process was carried out for 80 hours when the Cu1.96S was fully transformed into Cu2S. The as-milled Cu2S nanocrystals were subsequently capped with trioctylphosphine oxide/trioctylphosphine/nitric acid (TOPO/TOP/NA). The TEM pictures show a good crystalline with chalcocite phase and the size of capped CU2S nanocrystals is in a narrow distribution ranging from 4 nm to 7 nm. The absorption peaks for capped CU2S nanocrystals locates within the range of 348 nm to 395 nm, showing a strong blue shifts with the longer milling time..3. The pure cubicβ-In2S3 nanocrystals have been firstly successful synthesized by mechanically alloying the In and S elemental powders. The phase structure ofβ-In2S3 compound was still growing from 2 to 10 hours. Further extending the ball milling time from 10h to 40h, no significant change happens, but the diffraction peaks are broadened. The capped P-In2S3 nanocrystals show extremely high dispersion stability in the light yellow dispersion solutions(TOPO/TOP/NA). The grain size of the cappedβ-In2S3 nanocrystals ranges from 2.8 to 8.8 nm observed by TEM. A 3-fold twins structure theβ-In2S3 was fortunately observed in the HRTEM. A wide and high UV-vis absorption spectra of the pure milledβ-In2S3 powders rangs from 200-600nm was observed using a UV-vis integrating-sphere photometer. The UV-vis absorption peaks of cappedβ-In2S3 nanocrystals are at about 395 nm. Compared to band gap in bulk In2S3, the obvious blue shift shows a the strong quantum size confinement effect.