Size Dependence of a Temperature-Induced Solid–Solid Phase Transition in Copper(I) Sulfide

Abstract

Determination of the phase diagrams for the nanocrystalline forms of materials is crucial for our understanding of nanostructures and the design of functional materials using nanoscale building blocks. The ability to study such transformations in nanomaterials with controlled shape offers further insight into transition mechanisms and the influence of particular facets. Here we present an investigation of the size-dependent, temperature-induced solid-solid phase transition in copper sulfide nanorods from low-to high-chalcocite. We find the transition temperature to be substantially reduced, with the high chalcocite phase appearing in the smallest nanocrystals at temperatures so low that they are typical of photovoltaic operation. Size dependence in phase transformations suggests the possibility of accessing morphologies that are not found in bulk solids at ambient conditions. These otherwise-inaccessible crystal phases could enable higher-performing materials in a range of applications, including sensing, switching, lighting, and photovoltaics.

The mechanism of ultrafast structural switching in superionic copper (I) sulphide nanocrystals

“…The increase in intensity can be indexed to the (011) peak of the hightemperature hexagonal phase, consistent with previous work studying the thermally driven superionic phase transition in Cu 2 S (ref. 12). The large magnitude of the changes and the long-timescale recovery of the effect are consistent with the diffraction signature of the superionic phase transition in copper (I) sulphide.…”

“…2b, the time-resolved measurements (black, red, orange, pink and green traces, also indicated in Fig. 2c) show decreases in intensity by more than 15%, whereas a clear peak indexed to the high-temperature phase (blue trace) increases by a similar magnitude, indicating the expected change in crystallographic symmetry 12,22 . The full threedimensional pattern may be seen in Supplementary Fig.…”

“…Recent work in nanoscale superionics has shown that the transition temperature is reduced at small sizes and that polymer surface treatments enable stabilization of the superionic phase to room temperature 11,12 . Room-temperature superionic behaviour of lithium has recently been observed in Li 10 GeP 2 S 12 and can be stabilized close to room temperature in LiBH 4 , sparking increased interest in superionic materials for practical electrochemical devices [13][14][15][16] .…”

Reversible structure manipulation by tuning carrier concentration in metastable Cu 2 S

“…The transition temperature of the nanoplates (∼80°C), which occurs abruptly on heating and cooling, is somewhat lower than that of bulk Cu 2 S (∼100°C). The small suppression of the phase-transition temperature observed here for Cu 2 S nanoplates is consistent with previous studies on nanomaterials (14). The corresponding crystal structures of the L-s and H-i phases are displayed schematically in Fig.…”

From Cu2S nanocrystals to Cu doped CdS nanocrystals through cation exchange: controlled synthesis, optical properties and their p-type conductivity research

“…Many reports indicated that colloidal Cu 2 S NCs were prone to form as the hexagonal and cubic phase mixtures [19,31]. Herein, hexagonal phase chalcocite Cu 2 S NCs (JCPDS # 26-1116) with good purity and crystallization were synthesized successfully, as confirmed by XRD pattern and the indexed lattice spacing in Figs 1b and c. Then based on cation exchange process shown in Fig.…”