Blue phase stabilization by CoPt-decorated reduced-graphene oxide nanosheets dispersed in a chiral liquid crystal

Abstract

We report on the effect of reduced-graphene oxide nanosheets decorated by CoPt nanoparticles on the blue phase range of a chiral liquid crystal. By means of high-resolution ac calorimetry and polarizing optical microscopy, it is demonstrated that a small concentration of these nanosheets induces the stabilization of a single blue phase structure in comparison to three blue phases existing in the pure compound. The results are compared with other liquid crystal-dispersed graphene studies, and, moreover, a short theoretical discussion of the stabilization effect is included.

Quantum Dot-Driven Stabilization of Liquid-Crystalline Blue Phases

“…The small spherical QDs of the present and previous studies [44,45] exhibit a minor shift of the BPIII-I transition temperature to slightly higher or lower values (depending on the QDs size, surface functionalization, and the LC host). On the contrary, large anisotropic NPs, such as graphene, laponite, and MoS 2 nanosheets, systematically upshift the BPIII-I transition temperature even at minute concentrations [55][56][57]67]. This trend confirmed by other studies [68,69] is attributed to the ordering of LC molecules induced within the I phase by the large surfaces of nanosheets.…”

“…This trend confirmed by other studies [68,69] is attributed to the ordering of LC molecules induced within the I phase by the large surfaces of nanosheets. It also explains why large anisotropic NPs with similar surface functionalization promote the stabilization of the more ordered BPI structure over the less ordered, macroscopically amorphous BPIII [55][56][57]67].…”

“…The outcomes of this work have been compared to other studies on QDs and other spherical and anisotropic NPs. The role of chemistry is very important since even moderate changes in the core composition and surface functionalization [56] have a noticeable impact on the stabilization effect. The results obtained so far have revealed certain trends, as well as the key mechanisms behind the BP stabilization.…”

“…They have a core diameter of 3.4 nm, and they are surfacefunctionalized by flexible oleyl amine and tri-octyl phosphine molecules [54]. The oleyl amine-based functionalization has proven very effective in obtaining high-quality dispersions of spherical and anisotropic NPs in LCs [44,45,[54][55][56][57]. Two mixtures of CE8 and CdSSe QDs have been prepared, with concentrations χ = 0.01 and χ = 0.05, where χ is defined as the ratio of the mass of QDs over the total sample mass (QDs and CE8).…”

A Bidimensional Gay-Berne Calamitic Fluid: Structure and Phase Behavior in Bulk and Strongly Confined Systems

“…Much research has been devoted to three-dimensional (3D) self-assembly [25], though a two-dimensional (2D) variant continues to be of interest from an exploratory perspective [47][48][49][50][51][52][53][54][55] as well as in applied technologies [1,56]. Optimal function is achieved via slab geometry in many devices, including optoelectronic/photonic materials [57][58][59][60][61], sensors [60,[62][63][64][65][66][67][68], display technologies [69][70][71], smart glass [72,73], spatial light modulators [74][75][76][77], and tunable filters [78][79][80][81]. However, dimensionality plays an essential role in the type and extent of structural order that a condensed phase can maintain [52,[82][83][84][85][86][87][88].…”