3D Natural Mesoporous Biosilica-Embedded Polysulfone Made Ultrafiltration Membranes for Application in Separation Technology.

Diatoms are the most abundant photosynthetic microalgae found in all aquatic habitats. In the extant study, the spent biomass (after lipid extraction) of the centric marine diatom Thalassiosira lundiana CSIRCSMCRI 001 was subjected to acid digestion for the extraction of micro composite inorganic biosilica. Then, the resulting three-dimensional mesoporous biosilica material (diatomite) was used as a filler in polysulfone (PSF) membrane preparation by phase inversion. The fabricated PSF/diatomite composite membranes were characterized by SEM-EDX, TGA, and ATR-IR, and their performances were evaluated. The number of pores and pore size were increased on the membrane surface with increased diatomite in the composite membranes as compared to the control. The diatomite composite membranes had high hydrophilicity and thermal stability, lower surface roughness, and excellent water permeability. Membranes with high % diatomite, i.e., PSF/Dia0.5, had a maximum water flux of 806.8 LMH (Liter/m2/h) at 20 psi operating pressure. High-diatomite content membranes also exhibited the highest rejection of BSA protein (98.5%) and rhodamine 6G (94.8%). Similarly, in biomedical rejection tests, the PSF/Dia0.5 membrane exhibited a maximum rejection of ampicillin (75.84%) and neomycin (85.88%) at 20 Psi pressure. In conclusion, the mesoporous inorganic biosilica material was extracted from spent biomass of diatom and successfully used in filtration techniques. The results of this study could enhance the application of natural biogenic porous silica materials in wastewater treatment for water recycling.

Preparation and characterization of carrageenan-embedded lanthanum iron oxide nanocomposite for efficient removal of arsenite ions from water.

Arsenic (As) contamination in drinking water has grown into a global concern in recent years, which demands the development of various As remediation approaches. In this study, a new magnetic nanocomposite, carrageenan-embedded LaFeO3 nanoparticles (abbreviated as CA-LaFeNPs) was synthesized by a sol-gel process and used to remove arsenite [As(III)] from water. The synthesized magnetic adsorbent was characterized by powder XRD, SEM, FTIR, VSM, and TGA. The adsorbent gel, CA-LaFeNP was mainly with LaFeO3 in nanoscale particles with a saturation magnetization of 13.33 emu g-1 and could be easily separated from water with a simple hand-held magnet in 2 minutes. The adsorption outcomes of the CA-LaFeNPs could be finely interpreted by Langmuir, Freundlich, and Tempkin isotherm models. The Langmuir isotherm model appears to have good regression coefficients, and maximum adsorption capacity was estimated to be 91 mg g-1 for CA-LaFeNPs at 27 °C and pH 7. The removal efficiency observed for CA-FeNPs was 91% up to the As(III) concentration of 700 mg L-1, while it decreased to 85% when the As(III) concentration was above 1200 mg L-1. This low-cost and environmentally-friendly magnetic nanocomposite, CA-LaFeNPs could be more appropriate for real-world applications and also a substitute for the traditional magnetic nanoparticles.

Ionic Liquid-Based Colloidal Formulations for the Synthesis of Nano-MOFs: Applications in Gas Adsorption and Water Desalination.

Microemulsions (MEs) comprising choline dioctylsulfosuccinate [Cho][AOT], a biobased ionic liquid (IL) surfactant as an emulsifier, (R)-(+)-limonene (RL) as a nonpolar phase, and ethylene glycol (EG)/ethanolammonium formate (EOAF) as an organic solvent/low-viscosity IL polar component were constructed. Spontaneous aggregation of [Cho][AOT] was observed with a negative ΔH form using isothermal titration calorimetry. The aggregates of [Cho][AOT] in RL showed a critical micellar concentration (cmc) of ∼5.49 mM, EG (cmc ∼3.99 mM), and EOAF (cmc ∼1.56 mM), and these are further characterized by various techniques. These novel IL-based MEs have been used as nanoreactors for the sustainable synthesis of uniform nanosized metal-organic frameworks (N-MOFs), such as MIL-53(Al), HKUST-1, UIO-66-NH2, and ZIF-8, with a precise control over size and morphology at room temperature. Characterization of N-MOFs has been performed using scanning electron microscopy, powder X-ray diffraction, and Fourier transform infrared spectroscopy. The synthesized N-MOFs have been used to prepare stable and uniform thin film nanocomposite nanofiltration membranes, suitable for desalination of brackish water with excellent flux (31.8 LMH/bar) and rejection (99.0%) of divalent salts.

Improved biorefinery pathways of marine diatoms using a water miscible ionic liquid and its colloidal solution: efficient lipid extraction and in situ synthesis of fluorescent carbon dots for bio-imaging applications.

In this study, a water-miscible 'classic' ionic liquid (IL), 1-ethyl-3-methylimidazoliumacetate ([EMIM][Ac]), has been used for lipid extraction from marine diatoms Thalassiosira lundiana CSIR-CSMCRI 001 by following a non-polar solvent partition method. The composition of lipid was determined using gas chromatography-mass spectrometry (GC-MS). In total, 91.4 mg g-1 (dry wt) of lipid was produced, out of which the percentage of docosahexaenoic acids (DHA), myristic acid, palmitic acid, and arachidonic acid was 19.6%, 15.1%, 11.2%, and 10.4%, respectively. The IL-inseparable residual waste solution was directly used to generate green fluorescent carbon dots (FCDs) by constructing a colloidal solution with the help of a surface-active IL, choline dioctyl sulfosuccinate ([Cho][AOT]). The stability of colloidal FCDs was examined using FTIR, FT-NMR, and Raman spectroscopy. FCDs were extracted from the colloidal solutions via the demicellization process and characterized using HR-TEM (2 to 5 nm) and PXRD techniques. The optical properties of colloidal FCDs were measured using UV-Vis and fluorescence spectroscopy and showed a wide range of emission (λ 460 nm to λ 590 nm). Such FCD stabilized colloidal solutions could be effectively used in fluorescence imaging of yeast cells, thus making the biorefinery approach more sustainable.

Versatile surface-active ionic liquid: construction of microemulsions and their applications in light harvesting.

This article outlines a sustainable method towards the synthesis of advanced materials such as core/shell Quantum Dots (QDs) and their in situ stabilization using microemulsions (MEs). QDs are versatile materials which show unusual optical properties. We have constructed MEs consisting of an Ionic Liquid (IL) based surfactant i.e. choline dioctylsulfosuccinate, [Cho][AOT] as an emulsifier, toluene as a nonpolar phase and water as a polar phase. The system forms a large single-phase region in the phase diagram without any co-surfactant. Spontaneous formation of micelles has been observed and studied through tensiometry and fluorescence and isothermal titration calorimetry (ITC). The exceptional swelling behaviour of the MEs was studied using Dynamic Light Scattering (DLS) and small angle neutron scattering (SANS). In ME droplets, i.e. Reverse Micelles (RMs), we successfully synthesized spherical core/shell QDs (size ∼3 to ∼6 nm) with precise control over the size and morphology. The QDs have been characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Powder X-ray Diffraction (PXRD). QDs stabilized in MEs exhibited excellent optical properties and can be suitably used as light harvesting materials for diverse applications.

Aqueous systems of a surface active ionic liquid having an aromatic anion: phase behavior, exfoliation of graphene flakes and its hydrogelation.

Surface active ionic liquid (SAIL) induced hydrogelation, in the absence of additives, is important considering the properties of soft-hydrogels that can be utilized in different applications. The present study is concerned with the phase behavior and hydrogelation of a SAIL, 1-hexadecyl-3-methylimidazolium p-toluenesulfonate, [C16mim][PTS]. The obtained information about the phase behavior along with the surfactant like behavior of the SAIL was exploited for effective exfoliation of graphene-flakes from graphite in aqueous medium that remain stable for at least one month. Thus the obtained dispersion of graphene-flakes was subsequently hydrogelated exploiting the observations made from the phase behavior of the SAIL, via entanglement of long worm-like micelles of the SAIL formed at higher concentration. The obtained graphene-flake based hydrogels were found to be equally stable as compared to the blank hydrogel as well as against centrifugation. The low melting point of hydrogel facilitates the extraction of graphene-flakes from the hydrogel matrix by heating and diluting the gel and there is no sign of agglomeration in the extracted graphene-flakes even if the extraction is carried out after a period of three months. The present work is an exemplary study on exfoliation, hydrogelation and extraction of graphene-flakes from a hydrogel, when required, using a SAIL and is expected to provide a new platform for utilization of SAILs for efficient graphene exfoliation and subsequent preparation of functional materials.

Nanoemulsions with All Ionic Liquid Components as Recyclable Nanoreactors.

Nanoemulsions (NEs) comprising ionic liquids (ILs); ethanolammonium formate (HO-EOAF), proliniumisopropylester dioctylsulfosuccinate ([ProC3][AOT]), and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, ([Bmim][NTf2]) as insoluble hydrophilic, surface active, and hydrophobic components have been constructed. This novel class of colloidal formulations exhibited several contrasting properties vis-à-vis conventional water-in-oil or water-in-ionic liquid or nonaqueous NEs such as (i) spontaneous formation, (ii) thermodynamic stability and isotropic nature, (iii) decrease of droplet size with increase in polar medium concentration, and (iv) high thermal and kinetic stability. Mechanisms and characteristics for such anomalies have been investigated by physical, spectroscopic, and imaging techniques. NEs have been demonstrated as versatile recyclable nanoreactors for user-friendly synthesis of materials such as metal-organic frameworks/light harvesting hybrid systems. We anticipate that this development will lead to the construction of several other need-based "all ionic-liquid nanoemulsions" in view of the flexibility provided by the tailoring nature of ILs.

Surface-Active Ionic Liquid Cholinium Dodecylbenzenesulfonate: Self-Assembling Behavior and Interaction with Cellulase.

The conventional sodium dodecylbenzenesulfonate (NaDBS) has been converted into an efficient and nontoxic anionic surface-active ionic liquid, cholinium dodecylbenzenesulfonate (Cho[DBS]). We have investigated its self-assembling behavior, interaction with the enzyme cellulase, and ecotoxicity. The surface-active properties at the air-liquid interface and the aggregation behavior of Cho[DBS] in water have been determined using tensiometry, isothermal titration calorimetry (ITC), conductometry, and dynamic light scattering (DLS). The enzyme activity was observed using dinitro salicylic acid analysis. The enhanced enzyme activity was explained through active-site exfoliation and structural constancy of cellulase in the micellar medium using the results from fluorescence, circular dichroism, DLS, and ITC. The nontoxic nature was confirmed by toxicity analysis on the freshwater microalgae Scenedesmus sp.

Illuminating microemulsions: ionic liquid-CdS quantum dots hybrid materials as potential white light harvesting systems.

Microemulsions (MEs) comprising of 2-hydroxyethylammonium formate, (HO-EAF), isooctane and dioctylsulfosuccinate proliniumisopropylester ([ProC3]AOT) have been constructed and used to prepare and stabilize CdS Quantum Dots (QDs) at room temperature. Such hybrid materials exhibited tunable light emission wherein the photoluminescence chromaticity could be precisely adjusted to pure white with a quantum efficiency (QE) of ∼43%, by adjusting the droplet size of MEs.

Spontaneous Formation of Multiarchitecture Vesicles of [C8mim]Br + [Na]DBS in Aqueous Medium: Synergic Interplay of Electrostatic, Hydrophobic, and π-π Stacking Interactions.

A mixture of a cationic surface active ionic liquid, [C8mim]Br and anionic surfactant, [Na]DBS has been shown to form unilamellar vesicles in water over an exceptionally wide mole fraction range of [C8mim]Br (x1 = 0.2 to 0.8). Formation of vesicles has been evidenced from transmission electron microscopy (TEM), cryo-TEM and atomic force microscopy (AFM) imaging. Cryo-TEM imaging of an equimolar mixture showed multiarchitectural unilamellar vesicles (spherical, tubular, and ribbon). Such complex architectures were earlier reported for Janus dendrimers of different structures (Science, 2010, 328, 1014). The synergism between oppositely charged single chain surfactants to form bilayer structures has been explained based on the evidence of π-π stacking interaction from 2D NOESY measurements, Coulombic interactions from zeta potential measurements and magnitude of interaction parameter from the critical aggregation concentration. The aggregation concentrations were measured from tensiometry and fluorescence using pyrene as a polarity probe. The phase behavior at different mixture compositions has been revealed from turbidity measurements and visual inspection. Hydrodynamic radii of self-assembled structures in the bulk solution phase were measured from dynamic light scattering. Vesicles formed have been explored as delivery vehicles for proteins using bovine serum albumin (BSA) as model.