Room Temperature Ionic Liquids Research Articles

DFT-based investigation of solvation of Nd(III)/Yb(III) cations in room-temperature ionic-liquid

We report a DFT study on the solvation of bare rare-earth (RE) cations [Nd(III) and Yb(III)] in the room-temperature ionic-liquid (RTIL) based on 1,3-dimethyl-imidazolium+, PF6−, [MMI][PF6]. In the present article, we aim to investigate whether the chosen RTIL can preferentially solvate any of the RE cations under study. First, the RTIL binding to the RE cation is studied in the gas phase, and then explored with continuum solvation model employing RTIL parameters. First, we considered the formation of the first solvation shell, where the PF6− anions directly bond with the Ln(III) cation. We then further surrounded the first solvation shell with [MMI]+ cations to form the second solvation shell. The stability of PF6− coordinated complexes is studied by calculating the binding energy values. The number of PF6− anions for both Ln(III) cations starts with three ligands and goes until the maximum binding energy in the RTIL medium is reached. The coordination number and binding modes of PF6− depend on the size of the RE cation. Comparing the binding energy values between the RE cations for the first solvation shell complexes, it is noticed that Yb-complexes have relatively greater binding energy than Nd-complexes. We have further performed a Boltzmann population analysis to find out the most dominant conformer among each category of PF6− coordinated complexes. A study using Natural Population Analysis shows that after complexation with PF6− the charge on the Yb-centers lower to a greater extent than Nd-centers, implying stronger bonding between Yb and PF6−, which is in harmony with the binding energy analysis. Overall, the computational investigation provides an in-depth understanding of the complexation phenomena of RE cations in RTIL, which can be useful for the practical separation of RE cations using RTIL.

Synthesis and properties of long-lived room-temperature phosphorescent liquid crystal polymers based on “Jacketing” effect

Polymerization is one of the most widely used strategies to achiever RTP. To date, various polymer-based RTP materials have been reported. However, how to improve the phosphorescence lifetime of polymer-based RTP materials still needs to be further researched. In this article, we proposed a new strategy to realize long-lived room-temperature phosphorescence by utilizing the “jacketing” effect of mesogen-jacketed liquid crystal polymers. Two polymers PMJ0DFM and PMJ6DFM with different flexible spacer length were synthesized, and their liquid crystal phase structures and photo-physical properties were systematically investigated. PMJ0DFM formed columnar nematic phase while PMJ6DFM formed a more ordered hexagonal columnar phase liquid crystal. For PMJ0DFM without spacer length, due to the strong “Jacketing” effect, the thermal motion of the chromophore was suppressed, and it was also more conducive to the aggregation and planarization of the chromophores. Therefore, PMJ0DFM film showed longer phosphorescence lifetime and more red-shifted phosphorescence spectrum than PMJ6DFM film. The phosphorescence lifetimes of PMJ0DFM and PMJ6DFM were 355 ms and 247 ms, respectively. In addition, we also explored their application in linearly polarized luminescent materials. When oriented, PMJ0DFM and PMJ6DFM film could emit efficient linearly polarized room temperature phosphorescence.

Pyrazino[2,3-g]quinoxaline core-based organic liquid crystalline semiconductor: Proficient hole transporting material for optoelectronic devices

Hole transport materials (HTMs) have a significant impact on the effectiveness of organic electronic devices; therefore, we present a molecular architecture of pyrazino[2,3-g]quinoxaline (PQ10)-based room-temperature organic liquid crystalline semiconductor (OLCS) as an alternative HTM. The PQ10 compound exhibits three different rectangular columnar (Colr) phases offering an impressive hole mobility of 8.8 × 10−3 cm2V−1s−1 which is found to be dexterous than most of existing polymeric hole transport materials. The charge transport mechanism is governed by the hole polarons hopping through H-aggregates of the PQ10 molecules and the hole mobility remains nearly constant throughout the mesophase range, but it decreases with increasing applied electric field. The current-voltage characteristics of the PQ10 have also been investigated in all three Colr phases and explained via the Poole-Frenkel conduction mechanism. The dielectric spectroscopy has been eventually carried out to understand the nature of dielectric permittivity and conductivity as a function of temperature and a correlation is established between the molecular architecture of the Colr phases and aforementioned physical properties. Solar cell simulation has been additionally performed to demonstrate that the PQ10 material can be a better choice as HTM for organic electronics and photovoltaic applications.

Do Ionic Liquids Slow Down in Stages?

High impact recent articles have reported on the existence of a liquid-liquid (L-L) phase transition as a function of both pressure and temperature in ionic liquids (ILs) containing the popular trihexyltetradecylphosphonium cation (P666,14+), sometimes referred to as the "universal liquifier". The work presented here reports on the structural-dynamic pathway from liquid to glass of the most well-studied IL comprising the P666,14+ cation. We present experimental and computational evidence that, on cooling, the path from the room-temperature liquid to the glass state is one of separate structural-dynamic changes. The first stage involves the slowdown of the charge network, while the apolar subcomponent is fully mobile. A second, separate stage entails the slowdown of the apolar domain. Whereas it is possible that these processes may be related to the liquid-liquid and glass transitions, more research is needed to establish this conclusively.

Effects of operating temperature on Li-O2 battery with ionic liquid-based binary electrolyte

Awaiting a breakthrough, the Li-oxygen battery (LOB) is considered a promising candidate to meet the high energy demands in the future. Among various critical challenges which hamper its development, the mystery of the electrolyte with optimal properties remains unsolved to this day. In this study, we comprehensively investigated the effects of operating temperature (20C, 40 °C and 60 °C) on the electrochemical performance of LOBs incorporated with room temperature ionic liquid (RTIL) and organic solvent binary electrolyte. We designed and investigated 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2C1im][Tf2N]) RTIL and dimethyl sulfoxide (DMSO) organic solvent at various volume ratios ((4:1), (1:1), (1:4)). Among the binary electrolytes, ([C2C1im][Tf2N]/DMSO (1:4)) delivered the highest discharge capacities of 3.70 Ah g− 1 (20 °C), 4.0 Ah g− 1 (40 °C) and 3.65 Ah g− 1 (60 °C) as compared with pure [C2C1im][Tf2N] and DMSO. Cycling stability tests showed superior stability of the binary electrolyte ([C2C1im][Tf2N]/DMSO (1:4)) irrespective of the operating temperature. From viscosity and ionic conductivity measurements (at 20–60 °C), [C2C1im][Tf2N]/DMSO (1:4) exhibited the highest ionic conductivity and the lowest viscosity compared with other binary electrolytes (even with pure electrolytes) at any given temperature. Cyclic voltammetry (CV) tests revealed the highest reaction rates for [C2C1im][Tf2N]/DMSO (1:4) binary electrolytes than pure electrolytes. The superior performance of [C2C1im][Tf2N]/DMSO (1:4) binary electrolyte was ascribed to enhanced stability against reactive intermediate species during oxygen reduction reaction (ORR), increased ionic conductivity, low viscosity (comparable with organic electrolytes), improved oxygen solubility, and relatively low evaporation rates.

Harnessing the power of iron-alumina-based ionic liquid composites for simultaneous removal of Congo red dye and microplastics

Increased water shortage due to industrialization and population increase requires immediate action to address water contamination. Using dimethyl sulfate as a common anion, we synthesized imidazolium-based cations with varying chain lengths (Imidazole, 2-methyl imidazole, 2-ethyl imidazole, and 2-isopropyl imidazole). This allowed us to create novel room-temperature ionic liquids (RTILs) that can be stored and transported at room temperature. These RTILs were further modified to magnetic ionic liquid composites (MILCs) by adding iron-alumina composites. The synthesized RTILs and MILCs were further characterized using H-NMR, FTIR, TGA, SEM, and EDX techniques. The process of adsorption at varying parameters was studied for the removal of Congo red (CR) and microplastics using these materials. MILC-4 in results, demonstrated excellent adsorption effectiveness by reaching a high removal rate of 90% at a concentration of 10 ppm for CR. Furthermore, 10-μm polystyrene beads were successfully destroyed by the MILCs in about 30 min. Following the completion of 40 experimental data, an Artificial Neural Network (ANN) model with three layers was used to accurately predict the removal of CR dye from an aqueous solution by MILCs. For the prediction and modeling of CR dye removal, the minimal mean squared error (MSE) of 0.051 and coefficient of determination (R2) of 0.97 were discovered. These numerical findings demonstrate the amazing effectiveness of the synthesized MILCs in combating water pollution issues. Overall, the study emphasizes the necessity of cleaner production methods and sustainable solutions provided by MILCs for CR dye and microplastics removal from water bodies.

Phase Behavior and Structure of Poloxamer Block Copolymers in Protic and Aprotic Ionic Liquids.

Ionic liquids are promising media for self-assembling block copolymers in applications such as energy storage. A robust design of block copolymer formulations in ionic liquids requires fundamental knowledge of their self-organization at the nanoscale. To this end, here, we focus on modeling two-component systems comprising a Poly(ethylene oxide)-poly (propylene oxide)-Poly(ethylene oxide) (PEO-PPO-PEO) block copolymer (Pluronic P105: EO37PO58EO37) and room temperature ionic liquids (RTILs): protic ethylammonium nitrate (EAN), aprotic ionic liquids (1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), or 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4). Rich structural polymorphism was exhibited, including phases of micellar (sphere) cubic, hexagonal (cylinder), bicontinuous cubic, and lamellar (bilayer) lyotropic liquid crystalline (LLC) ordered structures in addition to solution regions. The characteristic scales of the structural lengths were obtained using small-angle X-ray scattering (SAXS) data analysis. On the basis of phase behavior and structure, the effects of the ionic liquid solvent on block copolymer organization were assessed and contrasted to those of molecular solvents, such as water and formamide.

Influence of thermodynamically consistent data on artificial neural network modeling: Application to NH3 solubility data in room temperature ionic liquids

A general thermodynamic consistency of temperature, pressure, and solubility (T-P-x) data for binary mixtures including, ammonia + Room Temperature Ionic Liquids (ILs), has been studied. Experimental data taken from the literature for 24 binary mixtures of NH3 + ILs including, 108 isothermal data sets altogether. This study set out two main purposes 1) model dependency of thermodynamic consistency analysis applied by equations of state including Generic Redlich Kwong (GRK)/Van der waals berthelot (VdWB), Peng Robinson Stryjek Vera (PRSV)/Panagiotopoulos-Reid (PR) and that done using Peng Robinson / Kwak Mansoori (PR/KM) EoS in other work, Faúndez et al. (2013). 2) Impact of the discarding thermodynamically inconsistent data on Multilayer Perceptron (MLP)-Artificial Neural Network (ANN) modeling precision. The GRK/VdWB model was found to characterize themean averagepressure deviation as less than 2.0 % and the maximum average pressure deviation as 8.5 %, which is an improvement over PRSV/PR (which has deviations of 2.6 % and 9.7 %. The results of the MLP-ANN were categorized into two groups1) MLP-ANN tests were conducted for all data points and 2) MLP-ANN tests were done for excluded thermodynamically inconsistent (TI) data. Themaximum deviationfrom experimental data in the modeling of all data was found to be 13.213 % for the wholeIL + NH3systems, while the maximum deviation for modeling data without TI data was 9.9979 %. Thestatistical characteristicsused to evaluate the agreement between experimental data and modeling data, including R2, MSE, MAE, ARD, and MRD, indicate that the agreement is better for the excluded thermodynamically inconsistent data than for the total data set.

High-stability room temperature ionic liquids: enabling efficient charge transfer in solid-state batteries by minimizing interfacial resistance

Currently, intensive research is underway to develop stable electrolyte systems that can significantly enhance the performance of rechargeable batteries. Recent advances in solid electrolytes have led to new types of promising systems owing to their high conductivity. This has generated considerable interest in the practical applications of safe batteries. Considering the safety concerns associated with rechargeable batteries, solid electrolytes have become indispensable for the advancement of next-generation battery technologies. However, the increased interfacial resistance at solid-solid interfaces has become a critical challenge. To address this problem, room-temperature ionic liquids (RTILs) have been investigated as functional materials for mitigating the interfacial resistance in solid-state batteries (SSBs). The special properties of RTILs, such as their non-volatility, non-flammability, and high safety characteristics, make them highly promising candidates for safe batteries. Various approaches have been explored for the effective utilization of ionic liquids in SSBs. This review provides a comprehensive discussion on the application of RTILs as electrolytes, considering their electrochemical properties and incorporation into composites to minimize resistance in SSBs.

Room-Temperature Liquid Metals for Flexible Electronic Devices.

Room-temperature gallium-based liquid metals (RT-GaLMs) have garnered significant interest recently owing to their extraordinary combination of fluidity, conductivity, stretchability, self-healing performance, and biocompatibility. They are ideal materials for the manufacture of flexible electronics. By changing the composition and oxidation of RT-GaLMs, physicochemical characteristics of the liquid metal can be adjusted, especially the regulation of rheological, wetting, and adhesion properties. This review highlights the advancements in the liquid metals used in flexible electronics. Meanwhile related characteristics of RT-GaLMs and underlying principles governing their processing and applications for flexible electronics are elucidated. Finally, the diverse applications of RT-GaLMs in self-healing circuits, flexible sensors, energy harvesting devices, and epidermal electronics, are explored. Additionally, the challenges hindering the progress of RT-GaLMs are discussed, while proposing future research directions and potential applications in this emerging field. By presenting a concise and critical analysis, this paper contributes to the advancement of RT-GaLMs as an advanced material applicable for the new generation of flexible electronics.

Synthesis and Properties of Room-Temperature Phosphorescent Liquid Crystal Copolymers with Linearly Polarized Luminescence Characteristic.

Room-temperature phosphorescent (RTP) liquid crystal materials have garnered considerable attention because of their significant applications in organic light emitting diodes, polarized light emitting materials, and so forth. How to efficiently synthesize pure organic RTP liquid crystals and regulate their performance is of great significance. In this article, we propose a simple and feasible method to synthesize RTP liquid crystals and manipulate their properties through copolymerization. We constructed RTP liquid crystal copolymers by copolymerizing a phosphorescent monomer bearing biphenyl mesogen with a phosphorescent monomer bearing a dibenzofuran chromophore. All the synthesized copolymers show a liquid crystal property because of the introduction of biphenyl mesogen. Meanwhile, by changing the composition of copolymers, it is possible to regulate their RTP performance, including luminescence color and lifetime. As the content of the PMDFM0C component in copolymers increases, the phosphorescence lifetime gradually increases. For poly(MDFM0C(0.46)-co-MBi18C(0.54)), the phosphorescence lifetime can reach 463.0 ms. Moreover, the phosphorescence color of the PMDFM0C component in copolymers changes with the copolymer composition, which can induce variable room-temperature phosphorescence. In addition, when oriented, liquid crystal copolymer films can emit linearly polarized fluorescence and linearly polarized phosphorescence. The linearly polarized phosphorescence dichroic ratio and polarization ratio values of the oriented poly(MDFM0C(0.46)-co-MBi18C(0.54)) film are 3.33 and 0.50, respectively.

Insights into the structure and Ion transport of pectin-[BMIM][PF6] electrolytes.

We investigate the effect of pectin on the structure and ion transport properties of the room-temperature ionic liquid electrolyte 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) using molecular dynamics simulations. We find that pectin induces intriguing structural changes in the electrolyte that disrupt large ionic aggregates and promote the formation of smaller ionic clusters, which is a promising finding for ionic conductivity. Due to pectin in [BMIM][PF6] electrolytes, the diffusion coefficient of cations and anions is observed to decrease by a factor of four for a loading of 25 wt. % of pectin in [BMIM][PF6] electrolyte. A strong correlation between the ionic diffusivities (D) and ion-pair relaxation timescales (τc) is observed such that D ∼ τc-0.75 for cations and D ∼ τc-0.82 for anions. The relaxation timescale exponents indicate that the ion transport mechanisms in pectin-[BMIM][PF6] electrolytes are slightly distinct from those found in neat [BMIM][PF6] electrolytes (D∼τc-1). Since pectin marginally affects ionic diffusivities at the gain of smaller ionic aggregates and viscosity, our results suggest that pectin-ionic liquid electrolytes offer improved properties for battery applications, including ionic conductivity, mechanical stability, and biodegradability.

New stachydrine-derived ionic liquids enable the formation of robust cathode electrolyte interphase for improving the performance of LiFePO4 battery

In the present study, several new stachydrine-based room temperature ionic liquids ([Cn-Sta] ILs, n = 2, 3, 4 or 5) are prepared, characterized and applied as an electrolyte additive to significantly improve LiFePO4 battery performance. The Sta-based ILs are structurally homologous with the popular pyrrolidinium ILs combining a chiral ester group close to the N+ cationic center, leading to low symmetry for the absence of cold crystallization, a wide liquid range from about −60 °C (glass transition temperature) to 320 °C (thermal decomposition temperature) and a decent electrochemical stability window (∼4.5 V). These ILs are ready to decompose on the surface of LiFePO4 particles to form LiF-rich and robust cathode electrolyte interphase (CEI) passivation layers, according to an aggregate study of electrochemical and morphological evidence. As a result, the ILs are used as an efficient CEI-forming additive to improve the LiFePO4 battery performance, namely higher capacity and cyclic capacity retention, better high-current rate performance and lower initial resistance.

Amorphous TiO2 shells: an Essential Elastic Buffer Layer for High-Performance Self-Healing Eutectic GaSn Nano-Droplet Room-Temperature Liquid Metal Battery.

Gallium-based alloy liquid metal batteries currently face limitations such as volume expansion, unstable solid electrolyte interface (SEI) film and substantial capacity decay. In this study, amorphous titanium dioxide is used to coat eutectic GaSn nanodroplets (eGaSn NDs) to construct the core-shell structure of eGaSn@TiO2 nanodroplets (eGaSn@TiO2 NDs). The amorphous TiO2 shell (~6.5 nm) formed a stable SEI film, alleviated the volume expansion, and provided electron/ion transport channels to achieve excellent cycling performance and high specific capacity. The resulting eGaSn@TiO2 NDs exhibited high capacities of 580, 540, 515, 485, 456 and 426 mAh g-1 at 0.1, 0.2, 0.5, 1, 2 and 5 C, respectively. No significant decay was observed after more than 500 cycles with a capacity of 455 mAh g-1 at 1 C. In situ X-ray diffraction (in situ XRD) was used to explore the lithiation mechanism of the eGaSn negative electrode during discharge. This study elucidates the design of advanced liquid alloy-based negative electrode materials for high-performance liquid metal batteries (LMBs).

Beneath the Skin: Nanostructure in the Sub‐Oxide Region of Liquid Metal Nanodroplets

AbstractLiquid metals (LMs) are emerging as unique fluids for a variety of applications, but their nanoscale solvation properties remain largely understudied. In this work, a combination of atomic force microscopy (AFM) and molecular dynamics (MD) simulations are used to investigate the structure of the interface between the bulk room temperature liquid metal (RTLM) and the LM oxide in nanodroplet systems of gallium, EGaIn (75.5% gallium, 24.5% indium), and Galinstan (68.5% gallium, 21.5% indium, 10% tin). Field's metal (51% indium, 32.5% bismuth, 16.5% tin) is also investigated, which melts at ≈62 °C, as a contrast to the other systems. AFM measurements reveal distinct sub‐oxide nanostructured layering in all three RTLM systems, and Field's metal above the melting point, to differing degrees. EGaIn and Galinstan show multiple penetration events between 20 and 30 nm, with smaller, less complex events in Ga. MD simulations suggest that this layering is a result of the near‐surface ordering of LM atoms beneath the oxide layer. Importantly, the atoms in this region do not behave as solids but are more ordered than in a pure disordered liquid system. The surface nanostructure elucidated here significantly expands the understanding of LM systems and their behavior at interfaces.

Experimental and Theoretical Studies on the Self-assembled Nano-structure of Nonionic Surfactant/ionic Liquid Hybrid Systems

The self-assembled structure of various Brij series nonionic surfactants (such as Brij-30, Brij-52, Brij-56, Brij-58, Brij-35, and Brij-700) hybridized with room-temperature ionic liquids (RTILs) was studied using small-angle X-ray scattering (SAXS) measurements and DFT calculations. The detailed characterization of the obtained self-assembled structure in nonionic surfactant/RTILs hybrid system was carried out using the combination of SAXS and DFT calculations. The SAXS result indicates that the alkyl chain length dependence on the spatial correlation corresponds to the interference peak angle. The addition of Brij surfactant to the [BMIm][PF6] results in a drastic change in the interference peak position. The DFT calculation result shows that a weak hydrogen bonding was formed between the −CH, −F of RTILs ([BMIm][PF6] and [OMIm][PF6]) and the polar site −OH, −O − of surfactants (Brij-30 and Brij-56). When the mixing molar ratio of ILs/Brij is 1:1, the absolute value of interaction energy (ΔE 0 BSSE) is 8.10-1.43 and 4.22-0.90 kcal·mol-1 for ILs/Brij-30 and ILs/Brij-56, respectively. Meanwhile, in the case of the ILs/Brij molar ratio equal to 2:1, ΔE 0 BSSE is 19.14-1.79 and 12.39-1.45 kcal·mol-1, respectively. It suggests that the stability of ILs/Brij hybridized system is higher for ILs/Brij-30 than for ILs/Brij56, and it has an increasing tendency to some extent with an increase of the molar fraction of ILs.

Preparation and electrochemical performance study of a self-healing electrode composite material with WSe2/liquid metal Galinstan for lithium-ion batteries

In this work, a room temperature liquid metal alloy (Galinstan) and tungsten diselenide (WSe2) composite anode (LMx@WSe2) were synthesized utilizing a one-step hydrothermal method. Through a comprehensive characterization process, including XRD, SEM, HRTEM, Raman spectroscopy, XPS, and BET, the structural and morphological properties of the synthesized composites were extensively explored. The liquid metal alloy was observed to combine effectively with WSe2 via electrostatic adsorption, coordination, and additional bonding methods. Furthermore, it displayed high fluidity, deformability, and chemical stability. Consequently, the alloy promoted the repair of cracked surface areas in the electrode material and reduced internal oxidation-reduction reactions, leading to improved electrochemical performance during repeated lithium-ion insertion and extraction cycles. After 500 cycles at a current density of 1 A g−1, this composite electrode retained a capacity of 224.5 mAh g−1. Impressively, at a low temperature of − 10 °C, it maintained a capacity of 290 mAh g−1 after 50 cycles at a current density of 0.2 A g−1. Our research may open avenues for addressing mechanical difficulties experienced in flexible electronic devices and self-healing electronic circuits exposed to chemical reaction processes.

Effect of electric field on the wetting behavior of GaInSnBiZn high-entropy alloy in NaOH aqueous solution

The GaInSnBiZn low-melting-point high-entropy alloy exhibits promising prospects for utilization in the realm of flexible electronic devices, offering a promising alternative to common binary or ternary room-temperature liquid metals. By utilizing the sessile drop method, the wetting behavior of GaInSnBiZn/SiO2 was investigated, focusing on the effects of applied voltage and NaOH solution concentration. It was revealed that the alloy's electro-wetting is primarily influenced by the generation and dissolution of the surface oxide layer, as well as the interaction of the electric double-layer effect. The optimal response voltages for achieving the fastest wetting rate were found to be 16 V, 10 V, 18 V, and 8 V in 0.5 mol/L, 1.0 mol/L, 1.5 mol/L, and 2.0 mol/L concentrations, respectively, with 18 V at 1.5 mol/L concentration identified as the optimal process selection. The spreading behavior of the alloy in low-concentration NaOH solutions followed Tanner's Law, while in the 2.0 mol/L concentration, significant repellence and wetting angle saturation were observed. The wetting process of the alloy at various stages was described using the power-law equation R = atc, while the wetting mechanism of the alloy was elucidated through the application of the Lippmann equation and the electric double-layer effect equation.

Characterization of chemical composition distribution of ethylene-propylene-diene terpolymers by room temperature liquid adsorption chromatography and comparison to statistical approach

The chromatographic analysis of ethylene-propylene-diene (EPDM) terpolymers has hitherto been carried out only at high temperature, 120–160 °C. However, EPDM terpolymers are amorphous which could potentially allow to study their chromatographic behavior at room temperature (RT). To verify this hypothesis, cloud point measurements were realized to determine prospective solvent candidates. The identified solvents enabled injecting EPDM and model ethylene propylene norbornene terpolymers at RT.The retention of EPDM terpolymers on porous graphitic carbon (PGC) is a function at least two adsorbing comonomer components, ethylene and diene, in all tested chromatographic systems. This makes it difficult to characterize the chemical composition distribution (CCD) of terpolymers, which is of immense technical interest. Therefore, a modified form of LAC (LACm) was employed for determining the CCD of EPDM terpolymers using the identified solvents. Finally, the CCD obtained using different experimental methods was compared to the CCD determined using Monte Carlo simulations.

Tunable optical, electro-optical and dielectric properties of eco-friendly graphene quantum dots-nematic liquid crystal composites

ABSTRACT The changes in physical properties obtained by dispersing hydrophilic carboxylated graphene quantum dots (GQDs, <10 nm), which are non-toxic, biocompatible, and eco-friendly, into a room-temperature nematic liquid crystal, 5CB (4-pentyl-4ˈ- biphenylcarbonitrile) are described. Nematic–isotropic transition temperatures, polarising microscopy, electro-optic, photoluminescence, and dielectric investigations are reported for two composites having concentrations of GQDs of 0.25 and 1.0 wt.% in 5CB and compared to pristine 5CB. At the lower concentration (0.25%) of GQDs there is an enhancement in the order parameter by 5.49%, the birefringence by 1.28%, and the activation energy for dielectric relaxation by 4.4% compared to pure 5CB. However, at the higher concentration (1%), aggregation of GQDs occurs. This is apparent in optical textures and resulted in the deterioration of optical and electrical properties compared to 5CB. The photoluminescence spectrum of both concentrations of GQDs are centred at the same wavelength; however, the 1% GQD-5CB mixture exhibits significant quenching and may be suitable for some optical devices. Overall, our results support that, in addition to promoting sustainable, heavy-metal-free, and environmentally safe technologies, a low concentration of GQDs in LCs produces composites that have superior electrical and optical properties; thus, making them suitable for a variety of photonics and display applications.