Investigating the Multiple Roles of Polyvinylpyrrolidone for a General Methodology of Oxide Encapsulation

Abstract

Growing oxide shells on seed nanoparticles requires the control of several processes: (a) the nucleation and growth of the shell material; (b) the "wetting" of the shell material on the seeds; and (c) the aggregation of the nanoparticles. These processes are influenced by a number of factors, many of which are related. Without understanding the interdependence of these contributing factors, it is difficult to circumvent problems and achieve rational synthesis. We first did a case study on encapsulating Au nanoparticles with ZnO to understand the multiple roles of polyvinylpyrrolidone (PVP) and their dependence on other factors. We developed a general method for coating ZnO on a variety of seeds, including metals, oxides, polymer nanoparticles, graphene oxide, and carbon nanotube. This method can be further extended to include Fe3O4, MnO, Co2O3, TiO2, Eu2O3, Tb2O3, Gd2O3, β-Ni(OH)2, ZnS, and CdS as the shell materials. The understanding obtained in this systematic study will aid rational design and synthesis of other core-shell nanostructures.

Self-assembled one-dimensional MnO2@zeolitic imidazolate framework-8 nanostructures for highly efficient arsenite removal

“…28 In this case, ZIF-8 nuclei prefer to self-aggregate together to minimize surface energy for subsequent growth. 29 While methanol as protic solvent provides opportunities for forming hydrogen bonds with MnO 2 NWs, this results in lowering the surface energy of …”

Synthesis of gold/rare-earth-vanadate core/shell nanorods for integrating plasmon resonance and fluorescence

“…For the growth of oxides on metal nanocrystals, the use of metal salts may generally cause aggregation of the seed particles [17]; it is a great challenge to find a compatible ligand/surfactant for simultaneously stabilizing the products and tuning the interface between two dissimilar materials. The addition of multiple additives is a suggested efficient method; however, this addition often makes the synthesis complicated and difficult to control.…”

“…However, the large interfacial energy induced by the lattice mismatch between Au and the shell materials is the main obstacle to nanoscale integration. One efficient route to solve this problem is the introduction of a compatible ligand/surfactant between Au and the shell materials (e.g., a sulfide or oxide) to achieve an interface tuning so that the lattice mismatch can be neglected [16,17]. Another route is to use the pre-grown Ag layer as a "bridge" to decrease the lattice mismatch, facilitating the subsequent growth of the sulfide and selenide shells [18,19].…”

Synthesis mechanism, enhanced visible-light-photocatalytic properties, and photogenerated hydroxyl radicals of PS@CdS core–shell nanohybrids

“…Only large amounts of CdS particles deposited randomly on the surface of PS microspheres and no continuous CdS shell was observed, which might be due to the extensive growth and aggregation of pure CdS NPs. Typically, there was a large interfacial energy between a polymer and a Sulfide, mainly because of their lattice mismatch and lack of chemical interaction (Sun et al 2013). When the PSCdS interface was not improved, it was extremely difficult to form PS-CdS into complete core-shell structure (thermodynamically unfavorable).…”

“…(3) PVP has enhanced the bonding strength between CdS NPs and PS microspheres; this was due to the fact that methylene groups of PVP connected polymer via chemical bonds besides physical adsorption so as to reduce the PS-CdS interfacial energy (Sun et al 2013), resulting in as-prepared PS@CdS CSNPs having higher mechanical strength.…”