Biomimetic synthesis and assembly of HgS nanocrystals via a protein inducing process

Abstract

In this contribution, we report a simple protein-directed biomimetic strategy for fabricating HgS nano-assemblies in pepsin and bovine hemoglobin (BHb) aqueous solutions. Powder X-ray diffraction, transmission electron microscopy (TEM) and high-resolution transmission microscopy were used to characterize the structure and morphology of the nanocrystals, and track the whole growth process of HgS nano-assemblies. The prepared cubic phase HgS nano-assemblies were uniform and monodispersed with homogeneous sizes of around 60 nm (pepsin) and 50 nm (BHb), respectively. Time-dependent TEM results showed that the final products were formed via multi-level assembly by a large number of smaller nanoparticles under the confinement of protein molecules. The interaction between proteins and Hg2+/HgS was assessed by Fourier transform infrared and circular dichroism spectroscopy. Pepsin and BHb molecules have multiple functional groups, such as O–H, C=O and N–H, which could coordinate with Hg2+ ions to induce nucleation and control the growth of HgS nanocrystals. The formation of HgS–protein nanoconjugates resulted in the change of the secondary structure of the protein molecules. In addition, the HgS nanocrystals assembly process is discussed to investigate the growth mechanism.