Size and Strain of Zinc Sulfide Nanoparticles Altered by Interaction with Organic Molecules

Abstract

Nanosized zinc sulfides (nano-ZnS) have size-dependent and tunable physical and chemical properties that make them useful for a variety of technological applications. For example, structural changes, especially caused by strain, are pronounced in nano-ZnS < 5 nm in size, the size range typical of incidental nano-ZnS that form in the environment. Previous research has shown how natural organic matter impacts the physical properties of nano-ZnS but was mostly focused on their aggregation state. However, the specific organic molecules and the type of functional groups that are most important for controlling the nano-ZnS size and strain remain unclear. This study examined the size-dependent strain of nano-ZnS synthesized in the presence of serine, cysteine, glutathione, histidine, and acetate. Synchrotron total scattering pair distribution function analysis was used to determine the average crystallite size and strain. Among the different organic molecules tested, those containing a thiol group were shown to affect the particle size and size-induced strain most strongly when added during synthesis but significantly reduced the particle strain when added to as-formed nano-ZnS. The same effects are useful to understand the properties and behavior of natural nano-ZnS formed as products of microbial activity, for example, in reducing environments, or of incidental nano-ZnS formed in organic wastes.

A Critical Look at Colloid Generation, Stability, and Transport in Redox-Dynamic Environments: Challenges and Perspectives

“…However, no significant effect on crystallite domain size was observed for laboratory-synthesized nano-ZnS formed in the presence of serine, acetate, and histidine, which highlights that the impact on the colloid crystal growth is dependent on the binding energy of specific organic ligands on the colloid surface . Thus, the impact of binding organics on redox-generated colloid strain and size is directly dependent on the organic ligand functionality. ,, …”

“…For example, the nano-ZnS synthesized in the presence of organic molecules containing a thiol group, such as cysteine, exhibits both smaller average crystallite domain sizes and higher strain than the nano-ZnS synthesized under the same conditions in the absence of cysteine. 230 However, no significant effect on crystallite domain size was observed for laboratory-synthesized nano-ZnS formed in the presence of serine, acetate, and histidine, which highlights that the impact on the colloid crystal growth is dependent on the binding energy of specific organic ligands on the colloid surface. 235 Thus, the impact of binding organics on redox-generated colloid strain and size is directly dependent on the organic ligand functionality.…”

“…Also, if the surface energy decreases as a consequence of organic ligand binding, the system is thermodynamically more favorable for smaller crystal size colloids (reduced critical nucleus size) than an organic-ligand-free system. For example, the nano-ZnS synthesized in the presence of organic molecules containing a thiol group, such as cysteine, exhibits both smaller average crystallite domain sizes and higher strain than the nano-ZnS synthesized under the same conditions in the absence of cysteine . However, no significant effect on crystallite domain size was observed for laboratory-synthesized nano-ZnS formed in the presence of serine, acetate, and histidine, which highlights that the impact on the colloid crystal growth is dependent on the binding energy of specific organic ligands on the colloid surface .…”

“…235 Thus, the impact of binding organics on redox-generated colloid strain and size is directly dependent on the organic ligand functionality. 230,231,235 4.2.2. Interplay between NOM and Metal(loid)s in Redox-Dynamic Environments.…”

“…Strain (mineral structure change resulting in response to a stress) has been shown to be affected by surface chemistry and, in particular, by the strength of surface–ligand interactions. 229 As an example, Le Bars et al 230 showed that thiol functional groups can bind strongly to the nano-ZnS surface, reducing the internal strain regardless of particle size. The authors suggested that this strain release could result from a mechanism similar to that reported by Zhang et al, 231 that is, a decrease in internal energy and an increase in crystallinity induced by the interaction between water and the ZnS surface.…”