Anchoring of liquid crystal molecules on multi-walled carbon nanotubes and their effects on enhanced photoluminescence dynamics, fluorescence decay and distinctive electrical properties

Abstract

In the present work, self-organized non-polar liquid crystalline (LC) molecules (3b, 3c) were anchored by multi-walled carbon nanotubes (MWCNTs) to enhance optical and electrical properties. The 3b, 3c@MWCNTs LC-intercalated systems (IS) exhibited co-axial distribution of MWCNTs with orderly arrangement showing well-aligned interference colors with banded patterns in the textures, as observed using a polarizing optical microscope. Steady state photoluminescence studies unveiled sharp emission peaks around blue, yellow and red bands, and a broad emission peaks around violet band for 3b, 3c@MWCNTs LC-IS. Further, the Stoke's shifts were observed larger indicating that LC-IS can be used for display applications with high contrast ratio. Fluorescence decay studies demonstrated that average lifetime (τ) was in the range of 0.200ns–0.089ns and 0.087–0.139ns for 3b@MWCNTs and 3c@MWCNTs LC-IS, respectively and were lower than pure 3b, 3c LCs. Due to which it influenced the faster recombination of the excited photons, enabling effective charge transfer rates, and aid in the attainment of quantum equilibrium states quickly in the LC matrix. Furthermore, capacitance-voltage measurements of 3b@MWCNTs LC-IS showed quasi-static complete alignment at 42 °C and 3.2V, however, stable at 10V with relative dielectric permittivity of 0.023. The polarization studies confirmed asymmetric nature of 3b@MWCNTs LC-IS, showing saturation value of 41.8 μC/cm² with remnant polarization of 21.4 μC/cm². PFUND studies evidenced that polarization of 3b@MWCNTs LC-IS followed the rate of pulse and the delay at 40 °C and 42 °C with 2V of bias voltage. In contrast, 3c@MWCNTs LC-IS mild reorientation was seen at 2.4V and 7V with breakdown at 10V and polarization didn't follow rate of pulse and delay at any applied voltages. From the reported research work a new pathway has been opened for further exploration of electro-optical properties of various LC molecules, and can serve as a reference to improve electrical and optical properties of LC-IS systems for advanced display applications.