Binary mixtures of varying concentrations comprised of cetylpyridinium chloride/formamide are prepared via a self-assembly process. Polarizing optical microscopy analysis reveals that all the binary ...mixture exhibits lamellar layered mesophase. Lamellar phases are explored for the degradation of the acid red-18 (AR18) and direct green-6 (DG-6) dyes under ultraviolet dark conditions, light (UV) irradiation, and photolysis. The concentrations of the used dyes are fixed at 0.001% and 0.01% for degradation experiments. Higher dye degradation efficiency ~94% and ~88% is obtained for lamellar phases (C5) contain a higher content of amphiphiles doped with AR18 and DG6 (0.001%). A probable dye degradation mechanism may be attributed to the attractive electrostatic pull caused by the excited pyridinium ring (NH
+
bond) of cetylpyridinium chloride which may break N=N bond (chromophore group) of the dye molecule. Pure and dye-doped lamellar phases demonstrate high ionic conductivity in the range of 5.37 to 14.64 mS/cm. The studied lamellar mesophase shows weak electrolytic behaviour as computed from Kohlrausch’s law and the degree of the dissociation parameter value. These phases can be seen as potential candidates for photocatalytic and electrolytic applications.
Soft self-assembled systems with smart functions have been explored over the past decades for diverse applications. However, the toxicity of synthetic surfactant based self-assembled systems and ...their stability always remain a point of concern. There is always a great quest to find an alternative to overcome such shortcomings of self-assembled systems. Hence, in this context, we made an effort to engineer self-assembled lyotropic liquid crystals (LLCs) using different concentrations of the medicinal plant Glycyrrhiza glabra L. in the nonaqueous polar media of glycerol, ethylene glycol and formamide. These nonaqueous solvents with considerable polarity, high cohesive energy, dipole moment and hydrogen bonding ability, not only offer the perfect environment for self-assembly, but also provide longtime stability. Nematic lyotropic ordering is obtained for studied systems at different concentrations of Glycyrrhiza glabra L./ nonaqueous solvents as confirmed via polarising optical microscopy (POM) and X-ray diffraction (XRD) analysis. Electrostatic and hydrogen bonding interactions among polar solvents and amphiphilic Glycyrrhiza glabra L. molecules could be responsible for nematic ordering. FTIR spectroscopy is employed to confirm the hydrogen bonding in LLCs. The prepared LLCs are studied through static, dynamic rheology under the shear range 1–100 s-1 to explore their fluidic behaviour and establish correlation with structural parameters. The studied LLC systems from three solvents exhibit non-Newtonian shear thinning behaviour at all concentrations. The dynamic rheology tests indicate the elastic behaviour of all LLC systems. LLCs derived from glycerol exhibit soft-solid gel-like behaviour, while weak gel-type behaviour is observed for ethylene glycol and formamide-based LLCs. Considering the medicinal value of prepared LLCs, their antibacterial activity has been checked against the gram-positive bacteria Bacillus subtilis. LLC phases show strong antibacterial activity, about 2–3 times better than that of the standard drug streptomycin used for this study.
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In this context, formamide is explored as an efficient solvent for the dispersion of GO sheets and preparation of graphene oxide lyotropic liquid crystals (GOLLCs). Polarizing optical microscopy ...(POM) studies confirm that GO/formamide dispersion shows smectic phase at lower concentration (< 2 mg/mL) and nematic phase up to 300 mg/mL. GOLLCs are found stable for up to 24 months. Probably it is the first report on the formation of GOLLCs in formamide and their long-term stability up to 24 months. GOLLCs are studied for steady and dynamic rheological behavior at room temperature. All the GOLLCs exhibit shear-thinning fluid behavior under the shear rate 1–100 s−1. Dynamic rheology reveals that GOLLCs follow solid viscoelastic behavior till 20 mg/mL concentration and then depict long range viscoelastic behavior at higher concentrations. Complex moduli behavior of GOLLCs has been studied to predict their elasticity. The scaling analysis of tunable viscoelastic GOLLCs is computed from Er=Ax−xc4.43. The free-standing film is prepared via thermal treatment method from 2 mg/mL GOLLCs and studied for structural and photocatalytic degradation behavior. rGO film shows 99.18% and 97.87% degradation efficiency for malachite green and methyl orange organic dyes respectively under UV light and is found stable up to 3 cycles.
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•Highly stable formamide/GO based GOLLCs are prepared considering intermolecular interactions.•Smectic and nematic LLCs phases are observed as a function of increasing GO concentration.•Shear and dynamic rheological behavior are correlated with the structural parameters considering the domain size concept.•Shear thinning, viscoelastic and long-range viscoelastic behavior of GOLLCs.•rGO film from GOLLCs has been developed and tested for photodegradation of organic dyes.
ZnO rice like nonarchitects are grafted on the graphene carbon core via a rapid microwave synthesis route. The prepared grafted systems are characterized via XRD, SEM, RAMAN, and XPS to examined the ...structural and morphological parameters. Zinc oxide grafted graphene sheets (ZnO‐G) are further doped in β‐phase of polyvinylidene fluoride (PVDF) to prepare the polymer nanocomposites (PNCs) via mixed solvent approach (THF/DMF). β‐phase confirmation of PVDF PNCs is done by FTIR studies. It is observed that ZnO‐G filler enhances the β‐phase content in the PNCs. Non‐doped PVDF and PNCs are further studied for rheological behavior under the shear rate of 1–100 s−1. Doping of ZnO‐G dopant to the PVDF matrix changes its discontinuous shear thickening (DST) behavior to continues shear thickening behavior (CST). Hydrocluster formation and their interaction with the dopant could be the reason for this striking DST to CST behavioral change. Strain amplitude sweep (10−3% ‐10%) oscillatory test reveals that the PNCs shows extended linear viscoelastic region with high elastic modulus and lower viscous modulus. Effective shear thickening behavior and strong elastic strength of these PNCs present their candidature for various fields including mechanical and soft body armor applications.
A simple and rapid microwave synthesis technique has been explored in this work to graft ZnO on the graphene carbon core. Further, these grafted materials are doped in the PVDF to prepare nanocomposites. Prepared nanocomposites exhibit continuous shear thickening behaviour (CST), extended linear viscoelastic region (LVER), high elastic modulus and lower viscous modulus. These nanocomposites are best suited for mechanical and soft body armour applications.
Scheme for the formation of lamellar smectic phases in GO/Glycerol dispersion.
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•Reporting first time the dispersion of GO in glycerol which is stable up to 120 days.•Formation of ...lamellar smectic structures with surface chirality.•In-situ reduction of GO to rGO during sonication within 1 h.•Higher viscosity of GOLLC systems and their viscoelastic behaviour.•G′/G′′ ratio lie between 1 and 2.4 which enable the spray coating and ink jet printing applications of studied GOLLC systems.
Herein, we report the dispersion and stabilization of graphene oxide (GO) in the polar organic solvent glycerol (C3H8O3). The GO/glycerol (0.5 mg/mL and 1 mg/mL) dispersions are found stable for about 4 months. Strong hydrogen bonding and electrostatic repulsive interactions amid solvent and solute may be responsible for the stable dispersion. Moreover, such interactions and the non-covalent bonding may also lead to the organization of GO sheets in the self-sustained anisotropic supramolecular lyotropic structures in glycerol. Two dimensional lamellar smectic lyotropic phases with surface chirality have been observed for 0.5 mg/mL and 1 mg/mL, GO/glycerol dispersions. Partial reduction of GO into rGO has been observed and confirmed by UV–Visible measurement. Graphene-based lyotropic structures exhibit ionic conductivity of micron order (S/cm) and also possesses conduction activation energy of range 13–14 kJ/mol. GO/glycerol-based Lyotropic dispersions show non-Newtonian behaviour along with the decrease in the viscosity as the GO concentration is increased. The maximum viscosity noted for these systems is ~630 mPa.s. Viscoelastic behaviour of lyotropic dispersion has been confirmed by dynamic rheology and G'/G'' G'(storage) and G'' (loss) modulus crossover. Rheological studies infer that such lyotropic dispersion with high viscosity can be explored for ink-jet printing and printing of flexible membrane.
Nanocolloids are prepared via doping of 0.015 mg and 0.030 mg multiwalled carbon nanotubes (MWCNTs) in the lyotropic phases of cetylpyridinium chloride (CPC)/glycerol (2:98, 5:95, 10:90 and 20:80 ...wt%/wt%). Nanocolloids are characterised by polarising optical microscopy (POM) for structural confirmations. No phase change has been observed in any sample with MWCNTs doping concentrations. Non-doped lyotropic phases and nanocolloids are studied for static and dynamic rheology, frequency sweep and thixotropic behaviour. Shear rheology infers about the shear thinning to Newtonian till 10:90 CPC/glycerol concentration and shear thickening to Newtonian for 20:80 wt%:wt% system. The studied systems follow the nematodynamic concept. The frequency sweep test infers that lyotropic mesophases and nanocolloids exhibit viscoelastic behaviour. Further, the thixotropic measurements infer the weak gel nature of mesophases and nanocolloids. Lyotropic phases and nanocolloids show strong inhibition properties against the gram-negative Escherichia Coli (E. Coli.) bacteria. Lyotropic phases and nanocolloids can be used in microbial and lubrication applications. The unique antibacterial properties of these systems make them suitable for use in medical and pharmaceutical devices to prevent the spread of infection.
We report on the surfactant/additives free synthesis of single domain superparamagnetic Fe3O4 nanoparticles (FNPs) by rapid microwave synthesis method. X-Ray diffraction (XRD) and Scanning Electron ...Microscopy (SEM) studies reveal that FNPs were crystallized in the magnetite (Fe3O4) lattice and have granular shape with average particles size of ∼14 nm. The band gap of FNPs calculated from UV–Visible absorption spectrum is ∼2.3 eV. FNPs exhibit single domain superparamagnetic behaviour as confirmed from magnetic hysteresis loops. The nanocomposites of FNPs and β-phase of PVDF were prepared via mixed solvent approach using THF/DMF with different concentrations of FNPs. The rheological behaviour of the nanocomposites was studied with and without ageing in an applied magnetic field of 3500 Gauss for 3 h. Samples depicts shear thinning to shear thickening transition, decrease in zero shear viscosity and long frequency range viscoelastic behaviour as function of increasing FNP concentration. Increase in CST region, fluidity and complex modulus are the main consequences of magnetic aging. FNP-PVDF nanocomposites with such properties could find applications in flexible magnetic and mechanical films for soft body armor and memory storage.
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•Surfactant/additive free microwave synthesis of superparamagnetic Fe3O4 nanoparticles.•Controlled synthesis of granular shaped nanoparticles with uniform size distribution with average particles size ∼14 nm.•Tuning of shear and dynamic rheology of PVDF as a function of nanoparticle doping concentration and magnetic ageing.•PVDF: Fe3O4 nanocomposites may find applications in magnetic and mechanical films for soft body armor and memory storage.
Graphene quantum dots (GQDs) are prepared and characterized
via
X-ray diffraction (XRD), UV-Visible spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM) and ...photoluminescence (PL). GQDs are doped (5 mg and 10 mg) in the lyotropic liquid crystalline (LLC) lamellar and hexagonal phases to prepare GQD/LLC nanocolloids. Polarizing optical microscopy and X-ray diffraction measurement reveals that GQDs do not affect the lamellar and hexagonal LLC structures and may organize on their interface. Pure LLC phases and nanocolloids are studied for steady and dynamic rheological behavior. LLC phases and GQD/LLC nanocolloids possess shear thinning and frequency dependent liquid viscoelastic behavior. A complex moduli study of LLCs and GQD/LLC nanocolloids is carried out which indicates the gel to viscous transition in LLCs and GQD/LLC nanocolloids as a function of frequency. LLC phases and GQD/LLC nanocolloids are tested for antibacterial activity against
Listeria ivanovii.
The effect of surfactant concentration, LLC phase geometry and GQD concentration has been studied and discussed. A probable mechanism for the strong antimicrobial activity of LLCs and GQD/LLC nanocolloids is presented considering intermolecular interactions. The viscoelastic behavior and strong antibacterial activity (inhibition zone 49.2 mm) of LLCs and GQD/LLC nanocolloids make them valuable candidates for lubrication, cleaning, cosmetics and pharmaceutical applications.
Antibacterial study (a) control, negative control and GQDs (b) 10:90 wt% pure (S1) 5 mg (S2) and 10 mg (S3) GQDs/LLC nanocolloids (c) 30:70 wt% pure (S4), 5 mg (S5) and 10 mg (S6) GQDs/LLC nanocolloids and (d, e & f) Inhabitation image analysis.
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•Litchi Chinensis (LC) seed powder act as an excellent natural surfactant for lyotropic phases.•Bare litchi powder act as an excellent adsorbent to adsorb RhD dye with 52% ...efficiency.•LC seeds could be cost-effective and efficient adsorbent for the removal of toxic dyes from wastewater.
Aggregation behavior of biowaste Litchi Chinensis (LC) seed in three different solvents of varying polarity water (80), formamide (108), and glycerol (37) has been studied. Nematic liquid crystalline phase has been obtained for studied systems as confirmed by a polarizing optical microscope (POM). Potential of the LC seeds has been checked to remove the Rhodamine B (RhB) dye from the wastewater. Effect of dye varying concentration (1 mg/L, 3 mg/L, 5 mg/L, 7 mg/L and 10 mg/L) varying pH (3,6 and 9), and contact time (0 to120 sec) on adsorption process have been evaluated. About 52% of dye removal efficiency is achieved with bare 50 mg adsorbent at pH≈ 6. Pseudo-first-order kinetics is found best fitted for the adsorption process (R2~0.98). Freundlich isotherm is found best fitted to the adsorption data which is also vindicated by a greater value of R2~0.95. Hydrogen bonding, electrostatic interactions, and pi-pi interaction between RhB and LC seeds (saponin) could be responsible for the adsorption process. These results indicate that LC seed can act as a perfect surfactant for lyotropic assemblies and also an effectual natural adsorbent for the dye adsorption and cleaning of aquatic systems.
A new rapid microwave-assisted approach has been employed to prepare the γ-Fe
3
O
4
magnetic nanoparticles (γ-Fe
3
O
4
MNPs). The formation of spherical γ-Fe
3
O
4
MNPs with an average size of 45 nm ...and bandgap of 2.3 eV is confirmed by FESEM and UV-Visible spectroscopy. γ-Fe
3
O
4
is doped (0.01 wt% and 0.02 wt%) in the lyotropic liquid crystalline (LLC) lamellar phases of Pluronic F127/N,N dimethylformamide (DMF) to prepare the LLC nanocolloids. Polarizing optical microscopy measurement reveals that γ-Fe
3
O
4
doping does not affect the lamellar LLC structures except 0.02 wt% at 10:90 wt%:wt% system where lamellar to nematic LLC phase transition is observed. Pure LLC phases and nanocolloids are studied for steady and dynamic rheological behavior. LLC phases and LLC nanocolloids possess shear thinning and solid viscoelastic behavior. A complex moduli study of LLCs and LLC nanocolloids is done which indicates the highly elastic strength-based lamellar and nematic phases. Shear-thinning and highly viscoelastic nature of LLCs and LLC nanocolloids have future applications in lubrication, cleaning, cosmetics, and pharmaceutical.
