Liquid Crystalline Template Research Articles

Influence of Ionic Liquid and Light Intensity on a Polymer Nanostructure Formed in Lyotropic Liquid Crystalline Templates.

Utilizing self-assembled lyotropic liquid crystal (LLC) templates with radical photopolymerization shows promise in controlling polymer structure on the nanometer scale This control of nanostructure allows tailoring and enhancement of material properties not attainable in traditional polymerization in applications including hydrogels and stimuli-responsive systems. However, thermodynamically driven phase separation between the polymer and LLC templates often hinders the control of local polymer order and resultant polymer properties. This study investigates an alternative method to control the hydrogel nanostructure and avoid phase separation using imidazolium ionic liquids (ILs) in the LLC template while modulating the light intensity used in photopolymerization. The addition of the IL improves the thermodynamic stability and enhances the polymerization rate in the LLC system. The degree of LLC nanostructure retention is increased by increasing light intensities during polymerization. In addition, intermediate concentrations of cross-linker allow a balance between phase stability and cross-linking to lock in LLC morphology. With enhanced retention, the maximum water uptake is significantly higher compared with isotropic controls. These results demonstrate a method to increase the structure on the nanometer scale of a polymer by combining the addition of ILs with the proper selection of light intensity and cross-link density that allows access to unique hydrogel properties. These templated polymers demonstrate enhanced swelling and a stimuli response that show promise in applications ranging from drug delivery to water remediation.

Clustering triggered emissive liquid crystalline template for dual mode upconverted and downconverted circularly polarized luminescence.

Liquid crystalline materials have attracted significant attention in chiroptical research due to their ability to form long range ordered helical superstructures. Research focus has been on exploiting the unique properties of liquid crystalline materials to demonstrate highly dissymmetric circularly polarised luminescent (CPL) systems. In this study, we present a thermally driven, facile approach to fabricate CPL-active materials utilizing cholesteryl benzoate as the active substrate. Cholesteryl benzoate, a well-known thermotropic liquid crystal, has been found to manifest intriguing optical characteristics upon subjecting to repeated heating-cooling cycles. Despite the absence of conventional fluorescent moieties, the material exhibited luminescence through aggregation induced clustering triggered emission mechanism. Systematic investigations revealed excitation-dependent CPL for solid cholesteryl benzoate films when subjected to multiple thermal cycles. The excited state chiroptical investigation performed after multiple thermal cycles showed a luminescence anisotropy (glum) of 8 × 10-2, which is a high value for simple organic molecules. Moreover, upon co-assembly with lanthanide-based upconversion nanophosphors (UCNPs), the hybrid system demonstrated upconverted circularly polarised luminescence (UC-CPL). Benefiting from the ability to endow upconversion nanoparticles of various sizes, fabrication of UCNP-ChB hybrid nanocomposites exhibiting multicoloured upconversion CPL was demonstrated. These findings highlight the potential of liquid crystalline materials for diverse applications, including 3D optical displays and anticounterfeiting technologies.

Electrochemical studies of catechol at ordinary and mesoporous platinum electrodes via convolutive voltammetry and numerical simulation methods

On the normal platinum electrode and mesoporous Pt electrode, the electrochemical behaviour of catechol was studied using convolutive cyclic voltammetry and numerical simulation. The nanostructured mesoporous platinum structure was electrochemically deposited from the hexadic liquid crystalline template of C16EO8 surfactant. The electrocatalytic feature and reversibility of the mesoporous platinum electrode within the oxidation of catechol in 1.0 M HClO4 have been found to be extraordinary. At ordinary and mesoporous platinum electrodes, the separation between the peaks (∆Ep) became reduced from 430 to 75 mV vs. SCE. Catechol cyclic voltammograms show one anodic peak inside the forward scan, but the corresponding cathodic one disappears in the reverse direction, and a new peak is observed at a lower potential value at the ordinary Pt electrode. In the case of the mesoporous Pt electrode, the voltammogram gives one anodic peak inside the first scan of potential and one cathodic peak inside the reverse direction. On the basis of the electrochemical behaviour, we conclude an ECEC mechanism for the electrochemical oxidation of catechol in 1.0 M HClO4 at each electrode. A numerical simulation was used to verify the proposed electrode response.Graphical

Quantitative determination of hydroquinone via electrochemical methods at nano-architecture platinum electrode

Hydroquinone (HQ) was electrochemically measured using convolutive cyclic voltammetry and differential pulse voltammetry (DPV) on a nano-architecture mesoporous platinum film electrochemically grown from a hexagonal liquid crystalline template of C16EO8 surfactant in 1.0 mol/l HClO4. The HQ cyclic voltammograms produced one oxidative peak in the forward sweep of potential and one reductive peak in the reverse sweep. The effect of HQ concentration was investigated using the different electrochemical methods mentioned above. The modified platinum electrode exhibits good sensitivity for the determination of the HQ compound in 1.0 mol/l HClO4. The best executive was found for the i-t curve method developed from cyclic voltammetry of HQ. It exhibits a linear peak current response over the concentration range of 8 to 55 µmol/l, with a detection limit of 0.5726 µmol/l and a quantification limit of 1.9088 µmol/l, confirming the accuracy and sensitivity of this quick, cheap, and easy method.

Emergence of Structural Phosphorescence in Free-Standing, Laterally Organized Polymer Nanofiber Membranes

In the past decade, the phosphorescence of metal-free confined polymer structures has generated interest in optoelectronics due to their sustainability, low toxicity, and deployment in sensing applications. Herein, a free-standing array of laterally organized nanofibers was prepared via templated chemical vapor deposition polymerization into a liquid crystalline (LC) phase, and their optical properties were compared to compositionally identical films. The fibers converge into laterally aligned membranes that maintain a high internal order despite the surfaces of the membranes remaining uniform and closed. The membranes consisted of hourglass-shaped nanofibers with features in the micro- and nanometer regime. Free-standing nanofiber membranes differ from polymer films of equivalent chemical composition in several key features: (1) Anisotropic growth of polymer nanofibers with constraint and compliance to an LC template, (2) a high surface-to-volume ratio, and (3) the occurrence of a long-lived emission in the blue region, which persists for multiple seconds after excitation. This study constitutes the first report of long-lived emission from solid-state poly(p-xylylenes) nanofibers. Prospective applications of morphologically controlled polymer arrays with structural luminescence include organic sensors and optoelectronic devices.

Quantitative Determination of Catechol via Cyclic Voltammetry, Convolution-Deconvolution Voltammetry, and Differential Pulse Voltammetry at a Mesoporous Nanostructured Platinum Electrode

The electrochemical quantification of catechol (CC) was performed via cyclic voltammetry (CV), convolution-deconvolution voltammetry, and differential pulse voltammetry (DPV) at nanostructured mesoporous platinum film electrochemically deposited from a hexagonal liquid crystalline template of C16EO8 surfactant in 1.0 M HClO4.The cyclic voltammograms of catechol produced one oxidative peak in the forward sweep of potential coupled with a reductive peak on the reverse sweep potential. The effect of catechol concentration was examined using the various electrochemical methods mentioned before. The modified platinum electrode exhibits good sensitivity for the determination of catechol compound in 1.0 M HClO4. The best performance was found for i-t curve method developed from cyclic voltammetry of CC. It manifests a linear peak current response over the concentration range of 3 to 50 μM, with a detection limit of 2.11 μM and a quantification limit of 7.04 μM confirming the accuracy and sensitivity of this fast and simple method.

A Low-Temperature Hydrothermal Synthesis of Prussian Blue Nanocrystal and Its Application in H2O2 Detection

Uniform Prussian blue Fe3[Fe(CN)6]2 nanocrystals were synthesized by a direct dissociation and reduction of the single-Fe(III)-source precursor K3Fe(CN)6 under low-temperature hydrothermal conditions. UV-visible absorption spectrum, Fourier transform infrared spectrum, X-ray diffraction, field emission scanning electron microscope, X-ray photoelectron spectra, high-resolution transmission electron microscopy, and electrochemical testing were used to characterize and verify the synthesized Prussian blue nanocrystal product. The size of the synthesized product had a strong dependence on the acidity condition and the concentration of K3Fe(CN)6 solution. This result may facilitate not only the exploration of preparing Fe3[Fe(CN)6]2 nanocrystals for particular applications but also an in-depth explanation of the nature of the hydrothermal reaction. The Prussian blue nanocrystals were deposited onto an electrode support through lyotropic liquid crystalline templates to detect hydrogen peroxide (H2O2) by reduction reaction. Cyclic voltammograms showed that the Prussian blue modified electrode was of excellent electrocatalytic activity for H2O2. This electrode demonstrated a detection limit (1 × 10−7 M) and a linear range starting from the detection limit and extending over 6 orders of magnitude of H2O2 concentrations (1 × 10−7 to 1 × 10−1 M), which was of excellent performance in detecting H2O2.

Template assisted nano-structured nickel for efficient methanol oxidation

Nanoporous nickel has been prepared by electrodeposition using non-ionic surfactant based liquid crystalline template under optimized processing conditions. Physicochemical properties of nanoporous nickel are systematically characterized through XRD, SEM and AFM analyses. Comparison of electrocatalytic activity of nanoporous nickel with smooth nickel was interrogated using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) analyses. Distinctly enhanced electrocatalytic activity with improved surface poisoning resistance related to nanoporous nickel electrode towards methanol oxidation stems from unique nanoporous morphology. This nanoporous morphology with high surface to volume ratio is highly beneficial to promote active catalytic centers to offer readily accessible Pt catalytic sites for MOR, through facilitating mass and electron transports.

Controlling phase and rheological behaviours of hexagonal lyotropic liquid crystalline templates for nanostructural administration and retention

Introducing polymerizable monomers into a binary hexagonal lyotropic liquid crystalline (LLC) template is a straightforward way for retaining the nanostructure but will decrease attractive intra- and inter- aggregate interactions. It is therefore crucial to understand the interfacial interactions at nanoscale after introducing the monomers but prior to polymerization. Herein, active species, poly (ethylene glycol) diacrylate (PEGDA) and 2-hydroxyethyl methacrylate (HEMA), were introduced into hexagonal LLC of dodecyl trimethylammonium bromide and water to explore the structural variables, dimensional stability, and dynamic property. At a proper volume ratio of PEGDA/HEMA (1/4), the system presents excellent homogeneity with a higher dimensional stability and lower dynamic property from rheological assessments, thereby achieving robust, free-standing, and transparent membranes after photo-polymerization. The unique property of the system also lies in the much lower order–disorder transition temperature (45 °C) that facilitates the reorientation of mesochannels. They are in contrast inaccessible for the ternary system only with PEGDA, though the nanostructure for both systems could be retained. An insight into subtle variations in these parameters allows us to prepare a polymerizable template possessing higher dimensional stability and suitable flexibility via molecular design, thereby enabling simultaneous structural alignment and retention for the development of functional nanomaterials.

Self-assembly of ionic and non-ionic surfactants in type IV cerium nitrate and urea based deep eutectic solvent.

Understanding and manipulating micelle morphology are key to exploiting surfactants in various applications. Recent studies have shown surfactant self-assembly in a variety of Deep Eutectic Solvents (DESs) where both the nature of surfactants and the interaction of the surfactant molecule with the solvent components influence the size, shape, and morphology of the micelles formed. So far, micelle formation has only been reported in type III DESs, consisting solely of organic species. In this work, we have explored the self-assembly of cationic surfactant dodecyl trimethylammonium nitrate/bromide (C12TANO3/C12TAB), anionic surfactant sodium dodecyl sulfate (SDS), and non-ionic surfactants hexaethylene glycol monododecyl ether (C12EO6) and octaethylene glycol monohexadecyl ether (C16EO8) in a type IV DES comprising metal salt, cerium (III) nitrate hexahydrate, and a hydrogen bond donor, urea, in the molar ratio 1:3.5. C12TANO3, C12TAB, C12EO6, and C16EO8 form spherical micelles in the DES with the micelle size dependent on both the surfactant alkyl chain length and the head group, whereas SDS forms cylindrical micelles. We hypothesize that the difference in the micelle shape can be explained by counterion stabilization of the SDS headgroup by polycations in the DES compared to the nitrate/bromide anion interaction in the case of cationic surfactants or molecular interaction of the urea and the salting out effect of (CeNO3)3 in the DES on the alkyl chains/polyethoxy headgroup for non-ionic surfactants. These studies deepen our understanding of amphiphile self-assembly in this novel, ionic, and hydrogen-bonding solvent, raising the opportunity to use these structures as liquid crystalline templates to generate porosity in metal oxides (ceria) that can be synthesized using these DESs.

Template assisted nano-structured nickel for efficient methanol oxidation

Nanoporous nickel has been prepared by electrodeposition using non-ionic surfactant based liquid crystalline template under optimized processing conditions. Physicochemical properties of nanoporous nickel are systematically characterized through XRD, SEM and AFM analyses. Comparison of electrocatalytic activity of nanoporous nickel with smooth nickel was interrogated using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) analyses. Distinctly enhanced electrocatalytic activity with improved surface poisoning resistance related to nanoporous nickel electrode towards methanol oxidation stems from unique nanoporous morphology. This nanoporous morphology with high surface to volume ratio is highly beneficial to promote active catalytic centers to offer readily accessible Pt catalytic sites for MOR, through facilitating mass and electron transports.

Fluorescence superquenching of SYBR Green I in crowded DNA by gold nanoparticles

Gold nanoparticles (GNPs) are known to efficiently quench fluorescence with high constants (107-1011 M−1). Quenching efficiency is determined by GNPs parameters, the properties of dye complex with biomolecular substrate may also affect this efficiency. In the present work quenching of SYBR Green I fluorescence by 2.5 nm GNPs was investigated in an isotropic DNA solution and on cholesteric (DNA CLCD) and hexagonal (DNA HLCD) liquid crystalline dispersion templates obtained with polymer and salt-induced condensation. Superquenching of SYBR Green I fluorescence was observed in all investigated models. The quenching efficiency increased as the DNA molecules were spatially ordered: the greatest quenching was observed for DNA HLCD where DNA molecules are packed most densely. In the condensed DNA systems, unlike DNA solution, the mechanism of quenching was not only the formation of a nonfluorescent complex, but also energy transfer between dye molecules and GNPs. The Stern-Volmer and Perrin models were insufficient for description of quenching processes. The Perrin equation was in an agreement with experiment only for DNA in solution. The model of microphase separation most adequately described the SYBR Green I fluorescence quenching by GNPs in DNA solution as well as in the molecularly organized DNA CLCD and DNA HLCD.

Template Assisted Nano-structured Nickel for Efficient Methanol Oxidation

Nanoporous Nickel has been prepared by electrodeposition using non-ionic surfactant based liquid crystalline template under optimized processing conditions. Physicochemical properties of nanoporous nickel is systematically character-ized through XRD, SEM and AFM analyses. Comparison of electrocatalytic activity of nanoporous nickel with smooth nickel was interrogated using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) analyses. Distinctly enhanced electrocatalytic activity with improved surface poisoning resistance related to nanoporous nickel electrode towards methanol oxidation stems from unique nanoporous morphology. This nanoporous morphology with high surface to volume ratio is highly beneficial to promote active catalytic centers to offer readily accessible Pt catalytic sites for MOR, through facilitating mass and electron transports.

Preparation and Characterization of Mesoporous Nickel derived from Liquid crystalline Template and Evaluation of its Electro catalytic activity towards Methanol Oxidation

Mesoporous Nickel has been prepared by electrodeposition using non-ionic surfactant based liquid crystalline template under optimized processing conditions. Physico-chemical properties of mesoporous nickel is systematically characterized through XRD, SEM and AFM analyses. Comparison of electrocatalytic activity of mesoporous nickel with smooth nickel was interrogated using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) analyses. Distinctly enhanced electrocatalytic activity with improved surface poisoning resistance related to mesoporous nickel electrode towards methanol oxidation stems from unique mesoporous morphology. This mesoporous morphology with high surface to volume ratio is highly beneficial to promote active catalytic centers to offer readily accessible Pt catalytic sites for MOR, through facilitating mass and electron transports.

Highly effective and chemically stable surface enhanced Raman scattering substrates with flower-like 3D Ag-Au hetero-nanostructures

We demonstrated flower-like 3D Ag-Au hetero-nanostructures on an indium tin oxide glass (ITO glass) for surface enhanced Raman scattering (SERS) applications. The flower-like 3D Ag nanostructures were obtained through electrodeposition with liquid crystalline soft template which is simple, controllable and cost effective. The flower-like 3D Ag-Au hetero-nanostructures were further fabricated by galvanic replacement reaction of gold (III) chloride trihydrate (HAuCl4·3H2O) solution and flower-like Ag. The flower-like Ag-Au hetero-nanostructure exhibited stronger SERS effects and better chemical stability compared with flower-like Ag nanostructure. The localized surface plasmon resonance (LSPR) spectra, field emission scanning electron microscope (FESEM) photos and Ag-Au ratios were studied which show that the surface morphology and shape of the flower-like Ag-Au hetero-nanostructure play significant roles in enhancing SERS. The flower-like 3D Ag-Au hetero-nanostructures fabricated by electrodeposition in liquid crystalline template and galvanic replacement reaction are simple, cheap, controllable and chemical stable. It is a good candidate for applications in SERS detection and imaging.

Chitin Liquid-Crystal-Templated Oxide Semiconductor Aerogels.

Chitin nanocrystals have been used as a liquid crystalline template to fabricate layered oxide semiconductor aerogels. Anisotropic chitin liquid crystals are transformed to sponge-like aerogels by hydrothermally cross-linked gelation and lyophilization-induced solidification. The hydrothermal gelation of chitin aqueous suspensions then proceeds with peroxotitanate to form hydrogel composites that recover to form aerogels after freeze-drying. The homogeneous peroxotitanate/chitin composites are calcined to generate freestanding titania aerogels that exhibit the nanostructural integrity of layered chitin template. Our extended investigations show that coassembling chitin nanocrystals with other metal-based precursors also yielded semiconductor aerogels of perovskite BaTiO3 and CuOx nanocrystals. The potential of these materials is great to investigate these chitin sponges for biomedicine and these semiconductor aerogels for photocatalysis, gas sensing, and other applications. Our results present a new aerogel templating method of highly porous, ultralight materials with chitin liquid crystals.

Synthesis of bimodal mesoporous silica with coexisting phases by co-hydrothermal aging route with P123 containing gel and F127 containing gel

Bimodal mesoporous silica materials with two coexisting phases were synthesized by co-hydrothermal aging (CHA) route. During the CHA process separately prepared P123 containing gel and F127 containing gel were mixed and the mixture underwent the hydrothermal aging together. The silica obtained through co-hydrothermal aging (CHAS) were characterized by XRD, N2 adsorption-desorption, TEM and SEM. CHAS was compared with the silica synthesized with the mixed templates (P123 and F127) through classic liquid crystalline templating route (LCTS). LCTS shows the regular mono-modal cylindrical mesopore, while CHAS shows obvious coexisting semi cubic arranged inkbottle small mesopores (2–5 nm) and hexagonal arranged cylindrical large mesopores (3–7 nm). Effects of synthetic conditions including the stirring time, the pH value and the mass ratio of P123 to F127 were studied in detail. It is found that CHAS can be synthesized within a wide range of stirring time before the mixing of the gels but too long stirring time after mixing will make the pore distribution of CHAS become wide. The mass ratio of P123 to F127 is an effective way to tailor the pore parameters of CHAS. The pH value control (below 3.0) is crucial for the formation of the bimodal mesoporous structure. The synthesis mechanism of the CHAS was suggested, the reaction step in the CHA process is decisive on the pore size of CHAS and the co-hydrothermal aging plays the key role in the formation of CHAS, in this step two phases were weaved together.

Arrangement and SERS Applications of Nanoparticle Clusters Using Liquid Crystalline Template

Manipulation of nanomaterials such as nanoparticles (NPs) and nanorods (NRs) to make clusters is of significant interest in material science and nanotechnology due to the unusual collective opto-electric properties in such structures that cannot be found in the individual NPs. This work demonstrates an effective way to arrange NP clusters (NPCs) to make the desired arrays based on removable and NP-guidable liquid crystalline template using sublimation and reconstruction phenomenon. The position of the NPCs is precisely controlled by the defect structure of the liquid crystal (LC), namely toric focal conic domains (TFCDs), during thermal annealing to construct the LC and corresponding NPC structures. As a proof of concept, the surface-enhanced Raman scattering (SERS) activity of a fabricated array of gold nanorod (GNR) clusters is measured and shown to have highly sensitive detection characteristics essential for potential sensing applications.

Highly effective surface-enhanced fluorescence substrates with roughened 3D flowerlike silver nanostructures fabricated in liquid crystalline phase

Highly effective surface-enhanced fluorescence substrates with roughened 3D flowerlike silver nanostructures were fabricated by electrodeposition in liquid crystalline template which is simple and controllable. Due to the localized surface plasmon resonance of silver nanostructures, the substrates were used as surface enhanced fluorescence substrates. The morphology and optical properties of the substrates were studied. The fluorescence experiments of the Rhodamine 6G on the substrates for different growth times were carried out and the best enhancement factor of 181 was achieved. Eight substrates with the same growth conditions were used to study the reproducibility of the substrate which shows that the fluctuations are within 9%. This substrate was used in organic distributed feedback lasers and the amplified spontaneous emission of poly(2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylenevinylene) was enhanced dramatically which means the reduced threshold and improved slope efficiency. Such easily fabricated flower-like silver nanostructure substrates with strong surface enhanced fluorescence effect and good reproducibility are good candidate for potential applications in optical imaging, biotechnology and material detections.

Lyotropic Supramolecular Polymer Systems with Anisotropic Functional Properties

SummaryWe have synthesized highly ordered nanostructured conducting PEDOT (poly (3,4ethylenedioxythiophene)) through chemical and electrochemical polymerization of bio based liquid crystalline templates and modified transducer used for the detection of ascorbic acid and nicotine.