Liquid-Crystalline Suspensions of Photosensitive Paramagnetic CeF₃ Nanodiscs

Abstract

The design of high-performance energy-converting materials is an essential step for the development of sensors but the elaboration of the bulk materials currently used remains costly and difficult. Therefore, a different approach based on the self-assembly of nanoparticles has been explored. We report on the preparation by solvothermal synthesis of highly crystalline CeF 3 nanodiscs. Their surface modification by bisphosphonate ligands led to stable, highly concentrated, colloidal suspensions in water. Despite the low aspect ratio of the nanodiscs (~ 6), a liquid-crystalline nematic phase spontaneously appeared in these colloidal suspensions. Thanks to the paramagnetic character of the nanodiscs, the nematic phase was easily aligned by a weak (0.5 T) magnetic field, which provides a simple and convenient way of orienting all the nanodiscs in suspension in the same direction. Moreover, the more dilute, isotropic, suspensions displayed strong (electric and magnetic) field-induced orientation of the nanodiscs (Kerr and Cotton-Mouton effects), with fast enough response times to make them suitable for use in electro-optic devices. Furthermore, emission study showed a direct relation between fluorescence intensity and magnetic field induced orientation of the colloids. Finally, with their fast radiative recombination decay rates, the nanodiscs show luminescence properties that compare quite favourably with those of bulk CeF 3 . Therefore, these CeF 3 nanodiscs are very promising building blocks for the development and processing of photosensitive materials for sensor applications.

Experimental probing of dynamic self-organized columnar assemblies in colloidal liquid crystals

“…Similar SAXS profiles suggesting two short-range orders were previously observed in columnar nematic phases for plate-like particles such as Al(OH) 3 nanoplates, 39 Sb 3 P 2 O 14 3− nanosheets, 40 and CeF 3 nanodisks. 42 A Schlieren texture similar to that in Fig. 4b was also observed by POM in a columnar nematic phase of lyotropic discotic liquid crystals.…”

Morphology and optical properties of CeF3 and CeF3:Tb nanocrystals: The dominant role of the reaction thermal mode

“…So, for CeF3 NCs synthesized at 160 °C, the PL emission spectrum consists of two bands with PL maxima at 361 nm and 500 nm. The PL band at "perturbed" Ce 3+ [26,42,43]. At the same time, for CeF3 NCs synthesized at 230 °C, the PL emission spectrum is represented by a single band with a maximum at 381 nm.…”

Properties of cerium (III) fluoride nanopowder obtained by pulsed electron beam evaporation

“…The magnetic behavior of CeF 3 crystals was studied relatively little and was described with the help of several models: the theory of a crystalline field [52], the mixed valence Ce 3+ -Ce 4+ behavior [53] and the superexchange interaction of cerium ions [54]. The study at T 50 K showed abnormal magnetic susceptibility behavior in CeF 3 nanodisks, which was explained by defects and/or dimensional effects [55]. Work [56] reports on the structural, magnetic, and optical properties of Tb 3+ -doped CeF 3 nanocrystals prepared via a polyol-assisted route, followed by calcinations.…”