Shape Dependence of Pressure-Induced Phase Transition in CdS Semiconductor Nanocrystals

Abstract

Understanding structural stability and phase transformation of nanoparticles under high pressure is of great scientific interest, as it is one of the crucial factors for design, synthesis, and application of materials. Even though high-pressure research on nanomaterials has been widely conducted, their shape-dependent phase transition behavior still remains unclear. Examples of phase transitions of CdS nanoparticles are very limited, despite the fact that it is one of the most studied wide band gap semiconductors.Here we have employed in situ synchrotron wide-angle X-ray scattering and transmission electron microscopy (TEM) to investigate the high-pressure behaviors of CdS nanoparticles as a function of particle shapes. We observed that CdS nanoparticles transform from wurtzite to rocksalt phase at elevated pressure in comparison to their bulk counterpart. Phase transitions also vary with particle shape: rod-shaped particles show a partially reversible phase transition and the onset of the structural phase transition pressure decreases with decreasing surface-to-volume ratios, while spherical particles undergo irreversible phase transition with relatively low phase transition pressure. Additionally, TEM images of spherical particles exhibited sintering-induced morphology change after highpressure compression. Calculations of the bulk modulus reveal that spheres are more compressible than rods in the wurtzite phase. These results indicate that the shape of the particle plays an important role in determining their high-pressure properties. Our study provides important insights into understanding the phase−structure−property relationship, guiding future design and synthesis of nanoparticles for promising applications.

Harvesting Cool Daylight in Hybrid Organic–Inorganic Halides Microtubules through the Reservation of Pressure‐Induced Emission

“…[13,14] Pressure is a powerful strategy to profoundly reduce interatomic distances and modify bonding patterns, thus creating fascinating materials not accessible under atmospheric conditions. [15][16][17][18][19][20][21][22][23] Pressure-induced emission (PIE) was first identified in compressed 0D perovskite Cs 4 PbBr 6 nanocrystals. [24] Thereafter, this exotic PIE was also discovered in 1D C 4 N 2 H 14 SnBr 4 , C 4 N 2 H 14 PbBr 4 and 2D (CH 3 (CH 2 ) 3 NH 3 ) 4 AgBiBr 8 .…”

The Effect of Particle Size and Composition on the Optical and Electronic Properties of CdO and CdS Rocksalt Nanoparticles

“…[44][45][46] The preparation of rocksalt CdS nanoparticles involves the application of pressures in excess of 5 GPa to 5-10 nm zincblende CdS nanoparticles. [18][19] Using evGW-BSE here differences in the optical and electronic properties of ~ 1 nm MgO, CdO and CdS rocksalt particles (see Fig. 2) are studied, as well as the (de)localisation of the states responsible for these properties, and how these properties change with particle size.…”

“…Moreover, nanostructures of some of the materials that under ambient conditions crystallise in the wurtzite structure (CdS, CdSe) convert under pressure into the rocksalt structure, which can be subsequently recovered back to ambient conditions. [17][18][19] Another advantage of rocksalt materials as model systems is that even for small nanostructures and even in the absence of capping agents the experimentally relevant nanostructures are generally simple cuts from the bulk crystal structure exposing simple, typical <001>, crystal faces, which is not necessarily true for their wurtzite and zincblende counterparts. Indeed, global optimisation calculations in the absence of capping agents predict that the global minima of MgO, CaO and SrO are cuts from the rocksalt structure, [20][21][22] while those for ZnS and CdS nanostructures do not resemble the bulk zincblende or wurtzite structures.…”

In Situ Investigation of the Phase Transition at the Surface of Thermoelectric PbTe with van der Waals Control

“…To keep the structure stable and obtain excellent performance, both phase-transition conditions and processes were studied in depth. The trigger factors for phase-structure transformation include temperature, irradiation with an electron beam, and pressure [ 12 – 14 ]. In addition, the surface interface and dislocation defects also affect the phase-structure transition significantly [ 15 – 17 ].…”