Dual effect of L-Cysteine on the reorientation and relaxation of Fe3O4-decorated graphene oxide liquid crystals

Abstract

Recently, functional soft materials based on graphene oxide (GO) have attracted more attention due to their tunability and responsivity to external fields. From this point of view, exploring the magnetic effects on GO-dispersed colloidal liquid crystals (LCs) offers more opportunities to develop novel magnetically responsive systems. Specifically, controlling the orientational ordering of functionalized GOLC compounds is of great interest for both scientific purposes and technical applications. Here, we study the dynamics of Fe3O4-decorated L-Cysteine-functionalized GOLC director under an external magnetic field and analyze L-Cysteine's influence on the reorientation and relaxation time of the director. In particular, Fe3O4 nanoparticles were synthesized by solution-combustion method and added for altering orientational properties of GO which we synthesized electrochemically and functionalized by L-Cysteine. In addition, a comprehensive comparison of the director behaviour of GOLC and Fe3O4-decorated L-Cysteine-GOLC was undertaken to verify the tunability of the aforementioned systems. Furthermore, we demonstrate dual-effect of L-Cysteine on the magnetic field-induced alignment and relaxation time of GOLC systems, namely decrease in reorientation time and at the same time increase in relaxation time. Besides, micropattern creation and controlling in the drying drops of GOLC (net- and knit-like, flower-like, radial- and parallel-strip etc.) using a magnetic field were shown. The results of our studies could facilitate the fabrication of ordered and patterned tunable GOLC assemblies for a range of advanced applications.

Keywords

• Graphene oxide
• Graphene oxide liquid crystals
• L-Cysteine
• Iron oxide nanoparticle
• Magnetic field
• Reorientation