Andrew Kavanagh

An Electrochromic Ionic Liquid: Design, Characterization, and Performance in a Solid-State Platform

This work describes the synthesis and characteristics of a novel electrochromic ionic liquid (IL) based on a phosphonium core tethered to a viologen moiety. When integrated into a solid-state electrochromic platform, the viologen modified IL behaved as both the electrolyte and the electrochromic material. Platform fabrication was achieved through in situ photo-polymerization and encapsulation of this novel IL within a hybrid sol–gel. Important parameters of the platform performance, including its coloration efficiency, switching kinetics, and optical properties were characterised using UV–vis spectroscopy and cyclic voltammetry in tandem. The electrochromic platform exhibits a coloration efficiency of 10.72 cm2 C–1 and a varied optical output as a function of the incident current. Despite the rather viscous nature of the material, the platform exhibited approximately 2 orders of magnitude faster switching kinetics (221 s to reach 95 % absorbance) when compared to previously reported electrochromic ILs (18 000 s).

Photo-patternable hybrid ionogels for electrochromic applications

This work describes the development of photopatternable ionogels based on a hybrid organic/inorganic sol–gel material and both phosphonium (trihexyltetradecylphosphonium dicyanamide [P6,6,6,14][dca], trihexyltetradecylphosphonium bis(trifluoromethanesulfonyl)-amide [P6,6,6,14][NTf2]) and imidazolium (1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate [emIm][FAP]) room temperature ionic liquids (RTILs). Ionogels were prepared via a two step process with the RTIL content varied between 40 and 80 w/w%, and characterised via Raman and Electrochemical Impedance Spectroscopy. 1 and 2 photon polymerisation was performed on the hybrid ionogels using photolithography, resulting in three dimensional structures that were characterised using scanning electron microscopy. Electrochromic ionogels were prepared by addition of ethyl viologen dibromide (EV) to an ionogel containing [emIm][FAP] and hybrid sol–gel material. This composition was photo-polymerised on ITO electrodes by UV irradiation and subsequentially characterised viaUV/Vis spectroelectrochemistry. It was also possible to fabricate a solid state electrochromic device based on EV and switch between the colourless (oxidised) and blue (reduced) forms using a perturbation signal of 1 V.

Graphene-doped photo-patternable ionogels: tuning of conductivity and mechanical stability of 3D microstructures

This work reports for the first time the development of enhanced-conductivity, graphene-doped photo-patternable hybrid organic-inorganic ionogels and the effect of the subsequent materials condensation on the conductivity and mechanical stability of three-dimensional microstructures fabricated by multi-photon polymerisation (MPP). Ionogels were based on photocurable silicon/zirconium hybrid sol–gel materials and phosphonium (trihexyltetradecylphosphonium dicyanamide) [P6,6,6,14][DCA] ionic liquid (IL). To optimise the dispersion of graphene within the ionogel matrices, aqueous solutions of graphene were prepared, as opposed to the conventional graphene powder approach, and employed as catalysts of hydrolysis and condensation reactions occurring in the sol–gel process. Ionogels were prepared via a two step process by varying the hydrolysis degree from 25 to 50%, IL content between 0–50 w/w%, and the inorganic modifier (zirconate complex) concentration from 30 to 60 mol.% against the photocurable ormosil and they were characterised via Raman, Electrochemical Impedance Spectroscopy and Transmission Electron Microscopy. MPP was performed on the hybrid ionogels, resulting in three-dimensional microstructures that were characterised using scanning electron microscopy. It is clearly demonstrated that the molecular formulation of the ionogels, including the concentration of graphene and the zirconate network modifier, plays a critical role in the conductivity of the ionogels and influences the resulting mechanical stability of the fabricated three-dimensional microstructures. This work aims to establish for the first time the relationship between the molecular design and condensation of materials in the physico-chemistry and dynamic of ionogels.

Temperature and pH triggered release characteristics of water/fluorescein from 1-ethyl-3-methylimidazolium ethylsulfate based ionogels

A crosslinked poly(N-isopropylacrylamide) ionogel encapsulating an ionic liquid exhibits improved transmittance properties, enhanced water uptake/release, greater thermal actuation behaviour and distinct solvatomorphology over its hydrogel equivalent. It was also found that the rate of release of fluorescein pre-loaded into membranes was considerably enhanced for ionogels compared to equivalent hydrogels, and could be triggered through changes in pH and temperature.

On-Body Chemo/Bio-Sensing - Opportunities and Challenges

In recent years, there has been significant progress in a number of sensing technologies related to on-body measurements, such as platforms for monitoring respiration, heart rate, location and movement. In these cases, the sensing element (s) are based on highly effective transducers that are increasingly integrated into garments such that they are becoming innocuous to the user. In contrast, the area of on-body chemical sensing remains highly under-developed. In this paper, we will address the significant challenges that are inhibiting the practical realisation of reliable chemical sensors and biosensors capable of generating accurate data in real time.