We have shown that monodisperse cholesteric liquid crystal microspheres and microshells produced in a microfluidic pathway exhibit spherically symmetric visible Bragg reflection that generates, via photonic cross communication among microspheres collected arranged in a plane, what are likely to be unique dynamic patterns. These patterns could render such microspheres very useful in countless security applications if used as tags to identify and authenticate their carriers, mainly physical objects or persons. We demonstrated that such assemblies can be polymerized to obtain roboust and mechanicaly stable authentication "stickers".
COBISS.SI-ID: 2959460
Ferrofluids are familiar as colloidal suspensions of ferromagnetic nanoparticles in aqueous or organic solvents. The dispersed particles are randomly oriented but their moments become aligned if a magnetic field is applied, producing a variety of exotic and useful magnetomechanical effects. A longstanding interest and challenge has been to make such suspensions macroscopically ferromagnetic, that is having uniform magnetic alignment in the absence of a field. Here we report a fluid suspension of magnetic nanoplates that spontaneously aligns into an equilibrium nematic liquid crystal phase that is also macroscopically ferromagnetic. Its zero-field magnetization produces distinctive magnetic self-interaction effects, including liquid crystal textures of fluid block domains arranged in closed flux loops, and makes this phase highly sensitive, with it dramatically changing shape even in the Earth’s magnetic field.
COBISS.SI-ID: 29253927
We observed self-assembly of superparamagnetic colloidal particles in a rotating external magnetic field. Within a range of field frequencies, we observed dynamic large-scale structures, such as precessing chains, ribbons, and rotating vortices. We studied the stability of the vortices, which is due to the interplay of short-lived chain formations, many-body-induced interactions and intraparticle magnetic relaxation.
COBISS.SI-ID: 29511463
Dissolution of upconverting AYF4:Yb,Tm (A = Na or K) nanoparticles (UCNP) in aqueous media was studied in relation with the cation (A), particle size, temperature, pH, and aqueous medium composition. on the dissolution of the UCNPs were evaluated. The highest dissolution rate and degree was measured for the phosphate buffer saline, which is explained by formation of lanthanide phosphate compounds. The dissolution degree was lower in water and phthalate buffer, which was attributed to the release of F via hydrolysis of the UCNP surface.
COBISS.SI-ID: 29679655
We measured the refractive indices and the absorption in bulk single crystals of aluminum nitride, in the region from 1 to 8 THz. Additionally, we estimated the static dielectric constants to be 7.84 and 9.22, for the ordinary and extraordinary polarization, respectively. Our results are relevant in considering this material for terahertz applications.
COBISS.SI-ID: 28838439