Density functional theory(DFT)was utilized to simulate the reactions occurred in the mixture solution of cysteine and Hg(II)ions with the ratio\2.Simulation result shows that Hg ions will coordinate to cysteine by the thiol groups with the form of S–Hg2and S–Hg3,and moreover,the content of free Hg ions can only be reduced by these two forms.OH-plays an important role in the growth of b-HgS,because its nucleophilic substitution reaction supplies plenty of Hg–S–Hg radicals,which will be adsorbed onto the surface of liquid mercury ball and form the precursor of b-HgS(111)plane.Three valent bonds adsorption of Hg–S–Hg radicals onto the surface of Hg ball has more adsorption energy(-32.768 kcal mol-1)than that of two valent bond adsorption(-20.882 kcalmol-1).Hg balls will stop growing after completely covered with Hg–S–Hg radicals and their size will be limited.The growth direction of b-HgS is parallel to the‘‘repelling’’force,that is[111]direction in b-HgS lattice.The calculated results are in good agreement with the experimental observations,demonstrating that the DFT method can be taken as a very useful tool to interpret the solution reactions that cannot be solved by conventional methods.
Understanding the evolution process and formation mechanism of nanoscale structures is crucial to controllable synthesis of inorganic nanomaterials with well-defined geometries and unique functionalities. In addition to the conventional Ostwald ripening process, oriented aggregation has been recently found to be prevalent in nanocrystal growth. In this new mechanism, primary small nanocrystals firstly spontaneously aggregate in the manner of oriented attachment, and then the large crystalline materials are formed via the process of interparticle recrystallization. Furthermore, controllable fabrication of the ordered nanocrystal solid materials that has shown specific collective properties will promote the application of inorganic nanocrystal in devices. Therefore, investigation of the mechanism of oriented aggregation is essential to controllable synthesis of nanocrystals and ordered nanocrystal solid materials. In this review, we summarize recent advances in the preparation of nanocrystal materials, which are mostly focused on our work about the role of self-assembly in construction of inorganic nanostructural materials.
