Conjugate polymer-based membranes for gas separation applications: current status and future prospects

Conjugate polymers provide the possibility of exploiting both the chemical and physical attributes of the polymers for membrane-based gas separation. The presence of delocalized π electrons provides high chain stiffness with low packing density, thus making the membrane a rigid structure that favors facilitated transport. Historically, the polymeric membranes were constrained by the tradeoff relationship between gas permeability and gas selectivity. So, different methods were investigated to prepare the membranes that can overcome the limitation. In recent years, electroconductive polymeric membranes have gained attention with their enhanced transportation properties combining the separation behavior depending on both molecular size discrimination as well as the facilitated transport. They offer better selectivity toward polar gases such as CO₂ because of the increased solubility. This review is aimed to provide a literature survey on gas separation using conjugate polymers such as polyaniline, polypyrrole, and some derivatives of polythiophenes. It contains various methods used by different researchers to enhance the gas separation properties of the membranes with improved mechanical and thermal stability such as changing the morphology and membrane preparation methods. In addition, it provides the pros and cons of various factors affecting the conjugate polymer membrane performance. The major challenges and future work that can be done in improving the transportation properties through the membrane to achieve viable membranes are also discussed so that they can be used for commercial and practical applications in the future.     

Design and application of stimulus-responsive droplets and bubbles stabilized by phospholipid monolayers

Biomimetic colloidal particles are promising agents for biosensing, but current technologies fall far short of Nature's capabilities for sensing, assessing, and responding to stimuli. Phospholipid-containing cell membranes are capable of binding and responding to an enormous variety of biomolecules by virtue of membrane organization and the presence of receptor proteins. By tuning the composition and functionalization of simulated membranes, soft colloids such as droplets and bubbles can be designed to respond to various stimuli. Moreover, because lipid monolayers can surround almost any hydrophobic phase, the interior of the colloid can be selected to provide a sensitive readout, for example in the form of optical microscopy or acoustic detection. In this work, we review some advances made by our group and others in the formulation of lipid-coated particles with different internal phases such as fluorocarbons, hydrocarbons, or liquid crystals. In some cases, binding or displacement of stabilizing lipids gives rise to conformational changes or disruptions in local membrane geometry, which can be amplified by the interior phase. In other cases, multivalent analytes can promote aggregation or even membrane fusion, which can be utilized for an optical or acoustic readout. By highlighting a few recent examples, we hope to show that lipid monolayers represent a versatile biosensing platform that can react to and detect biomolecules by leveraging the unique capabilities of phospholipid membranes.     

Surfactants – Compounds for inactivation of SARS-CoV-2 and other enveloped viruses

We provide here a general view on the interactions of surfactants with viruses, with a particular emphasis on how such interactions can be controlled and employed for inhibiting the infectivity of enveloped viruses, including coronaviruses. The aim is to provide to interested scientists from different fields, including chemistry, physics, biochemistry, and medicine, an overview of the basic properties of surfactants and (corona)viruses, which are relevant to understanding the interactions between the two. Various types of interactions between surfactant and virus are important, and they act on different components of a virus such as the lipid envelope, membrane (envelope) proteins and nucleocapsid proteins. Accordingly, this cannot be a detailed account of all relevant aspects but instead a summary that bridges between the different disciplines. We describe concepts and cover a selection of the relevant literature as an incentive for diving deeper into the relevant material. Our focus is on more recent developments around the COVID-19 pandemic caused by SARS-CoV-2, applications of surfactants against the virus, and on the potential future use of surfactants for pandemic relief. We also cover the most important aspects of the historical development of using surfactants in combatting virus infections. We conclude that surfactants are already playing very important roles in various directions of defence against viruses, either directly, as in disinfection, or as carrier components of drug delivery systems for prophylaxis or treatment. By designing tailor-made surfactants, and consequently, advanced formulations, one can expect more and more effective use of surfactants, either directly as antiviral compounds or as part of more complex formulations.     

Paramagnetic surface active ionic liquids: synthesis,properties, and applications

Paramagnetic surface active ionic liquids (PMSAILs) classify task-specific ionic liquids with magnetic properties by incorporating metal into the cationic or anionic part of the ionic liquid. Paramagnetic ionic liquids had long-chain either in cations or anions and showed excellent surface activity and magnetic properties without any need for the magnetic nanoparticles. These PMSAILs have inherent unique ionic liquid properties and self-assembled into various nano-aggregates such as micelles, vesicles, rod-like micelles, and etc., by modification in the structure of cations or anions. PMSAILs provide stimuli-responsive properties, which is one of the essential aspects of targeted applications. The appropriate functional tunability of anions and cations in PMSAILs leads to various multifaceted chemical and biological applications. A new emerging trend in PMSAIL research is hybridization with flexible materials. This review will mainly deal with the synthesis, characterization, and brief history of PMSAILs and their potential advantages in the various applications in micellar catalysis, purification and separation of biomolecules, compaction and decompaction of DNA, drug delivery, and other biomedical applications.     

Photocatalytic and antifouling properties of TiO2-based photocatalytic membranes

Photocatalysis has been extensively studied due to its potential ability to avoid the excessive use of chemical reagents and reduce the energy consumption by employing solar energy. Moreover, to alleviate the reduction in the membrane permeation selectivity, separation efficiency, and membrane service life caused by the emerging micro-pollutants and membrane fouling, membrane technology is often coupled with microbial, electrochemical, and catalytic processes. However, although physical/chemical cleaning and membrane module replacement can overcome the inherent limitations caused by membrane fouling and other membrane separation processes, high operating costs limit their practical applications. In this review, common preparation methods for TiO₂ photocatalytic membranes are described in detail, and the main approaches to enhancing their photocatalytic performance are discussed. More importantly, the mechanism of the TiO₂ photocatalytic membrane antifouling process is elucidated, and some applications of photocatalytic membranes in other areas are described. This review systematically outlines future research directions in the field of photocatalytic membrane modification, including metal and non-metal doping, fabrication of heterojunction structures, control over reaction conditions, increase in hydrophilicity, and increase in membrane porosity.     

Electrochemical disinfection – State of the art and tendencies

Electrochemical disinfection has gained increasing interest in many sectors of social and industrial life. The reason is the growing need to disinfect the air, water, and special surfaces of different nature such as drinking water, wastewater, pool water, and other water qualities or surfaces. New research studies are reported and discussed. A stronger orientation on engineering aspects is intended. Following tendencies can be identified - research on complex liquid systems, implementation of risks consideration seen from by-product formation, and better cooperation between researchers and industry oriented to improve cell design and disinfection technology. Partially, reaction kinetics is studied and discussed at higher levels of likelihood. Furthermore, it can be found that more and more research papers deal with hybrid technologies to create novelty, to use synergistic effects and to meet the demands of real system treatment under practical conditions. A major focus can be identified for wastewater treatment/disinfection emphasizing electrocoagulation and electro-photocatalysis.     

Nanoparticles: Properties,applications and toxicities

This review is provided a detailed overview of the synthesis, properties and applications of nanoparticles (NPs) exist in different forms. NPs are tiny materials having size ranges from 1 to 100 nm. They can be classified into different classes based on their properties, shapes or sizes. The different groups include fullerenes, metal NPs, ceramic NPs, and polymeric NPs. NPs possess unique physical and chemical properties due to their high surface area and nanoscale size. Their optical properties are reported to be dependent on the size, which imparts different colors due to absorption in the visible region. Their reactivity, toughness and other properties are also dependent on their unique size, shape and structure. Due to these characteristics, they are suitable candidates for various commercial and domestic applications, which include catalysis, imaging, medical applications, energy-based research, and environmental applications. Heavy metal NPs of lead, mercury and tin are reported to be so rigid and stable that their degradation is not easily achievable, which can lead to many environmental toxicities.     

Additive manufacturing approaches for biological power generation

As the consequences of global warming continue to affect the climate, there is an increased need for technologies that decrease dependence on fossil fuel consumption and promote sustainability. Additive manufacturing (AM) not only enables the scale-up and mass production of renewable energy technologies but also reduces cost and lead time, minimizes waste, and uses less energy than traditional manufacturing processes. Moreover, AM brings design and innovation to the forefront by allowing for design strategy revision and rapid prototyping. Herein, AM approaches used to fabricate devices that enable biological power generation are described. Biological power generation is a process through which biocatalysts – electroactive bacteria, enzymes, or cyanobacteria – harvest electrons from chemical substrates or light. Device engineering directs electron transfer events to a conductive material and maximizes power output. This review covers recent AM approaches for biological power generation in the form of microbial fuel cells (MFCs), enzymatic fuel cells, and biophotovoltaic cells with an emphasis on MFCs. Fabrication methods and materials for electrodes, chambers, inserts, membranes, and biofilms are described, along with impacts on device performance.     

Probing the reaction of membrane proteins via infrared spectroscopies,plasmonics, and electrochemistry

Spectroelectrochemistry, in combination with plasmonic approaches and infrared spectroscopy, has emerged as a powerful tool in the study of membrane protein redox reactions, both for immobilized monolayer samples and those reintroduced into their native environment. Here the use of nanostructured electrodes for surface enhanced spectroelectrochemistry are discussed.     

Dynamics of liposomes in the fluid phase

We review the currently available material on the morphology and dynamics of phospholipids assembled into liposomes. Key information obtained from neutron scattering, nuclear magnetic resonance (NMR), and other techniques plays a crucial role in understanding the vital role of lipids in sustaining life in living organisms. We concentrate on the dynamics in the biologically important fluid phase in the time range from picoseconds to seconds, which includes a discussion of the center of mass diffusion of liposomes, membrane fluctuations; and lateral, rotational, and flip-flop motions of the lipids. We emphasize on the sensitivity of the dynamics on interactions with a variety of biologically relevant molecules such as cholesterol. By a comparison of data from literature, we witness a good agreement of the results from different techniques and studies.     

Improving the stability of photosystem I–based bioelectrodes for solar energy conversion

Isolated photosystem I (PSI) has been integrated into numerous technologies for solar energy conversion. Interest in PSI is a consequence of its high internal quantum efficiency, thermal stability, ease of extraction, and adaptability. While there has been success in improving performance to elevate PSI biohybrid technologies toward a practical realm, the stability of PSI bioelectrodes is also of critical importance. Commercial solar energy conversion technologies are expected to achieve lifetimes of the order of ten years; however, many research-scale PSI bioelectrodes have only been tested for tens of days. Key areas affecting PSI bioelectrode stability include the effects of reactive oxygen species, immobilization strategies, and the environment within solid-state PSI biohybrid photovoltaics. At the current state, further investigation of long-term stability is necessary in enabling the development of PSI bioelectrodes for both photoelectrochemical cells and solid-state biohybrid photovoltaics.     

Application of HPLC to measure vanadium in environmental,biological and clinical matrices

Vanadate and vanadium compounds exist in many environmental, biological and clinical matrices, and despite the need only limited progress has been made on the analysis of vanadium compounds. The vanadium coordination chemistry of different oxidation states is known, and the result of the characterization and speciation analysis depends on the subsequent chemistry and the methods of analysis. Many studies have used a range of methods for the characterization and determination of metal ions in a variety of materials. One successful technique is high performance liquid chromatography (HPLC) that has been used mainly for measuring total vanadium level and metal speciation. Some cases have been reported where complexes of different oxidation states of vanadium have been separated by HPLC. Specifically reversed phase (RP) HPLC has frequently been used for the measurement of vanadium. Other HPLC methods such as normal phase, anion-exchange, cation-exchange, size exclusion and other RP-HPLC modes such as, ion-pair and micellar have been used to separate selected vanadium compounds. We will present a review that summarizes and critically analyzes the reported methods for analysis of vanadium salts and vanadium compounds in different sample matrices. We will compare various HPLC methods and modes including sample preparation, chelating reagents, mobile phase and detection methods. The comparison will allow us to identify the best analytical HPLC method and mode for measuring vanadium levels and what information such methods provide with regard to speciation and quantitation of the vanadium compounds.     

Choline chloride – Urea deep eutectic solvent an efficient media for the preparation of metal nanoparticles

Metal nanoparticles are nanosized structures that have different potential applications in biological, chemical, medical, and agricultural fields because of their exotic characteristics. Their size ranges from 1 to 100 nm. Metal nanoparticles are either purer forms of metals (eg: Gold, Silver, Copper, Iron, etc.) or their compounds (eg: sulfides, hydroxides, oxides, etc.). Ionic liquids are generally used in the extraction of nanoparticles but they are challenging because of their indigent bio-degradability, bio-compatibility, and sustainability. So Deep Eutectic Solvent (DES) is reported as an alternative to ionic liquids in the formation of nanoparticles. The DESs are a complex of quaternary ammonium salts and hydrogen donors or metal salt. DESs contain higher non-symmetric ions which have lower lattice energy and hence they have a lower melting point. This research utilizes a novel DES (choline chloride – urea) as an effective solvent to produce mercuric sulfide (HgS), zirconium oxide (ZrO), manganese oxide (MnO), and copper oxide (CuO) nanoparticles. As a result, the production of these metal nanoparticles using Choline Chloride (C₅H₁₄ClNO) – Urea DES can be treated as a promising way in chemical manufacturing. The nanoparticles have been analyzed using Ultra Violet Spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray Diffraction (XRD) and Energy Dispersive X-Ray Analysis (EDAX).     

Dynamic variations of bioactive compounds driven by enzymes in Psoralea corylifolia L. from growth to storage and processing

Fructus Psoraleae (FP), the dried ripe fruit of Psoralea corylifolia L., is a popular herbal medicine commonly applied for alleviating osteoporosis and vitiligo. But, until now, the dynamic variations of compounds in P. corylifolia have been less investigated during its growth, storage, and treatment by different temperatures, which is meaningful for guaranteeing the quality of FP. In this study, focused on these questions, with emphasis on the enzyme-driven dynamic transformation of coumarins, ultra-high performance liquid chromatography coupled with photodiode array detector (UHPLC-PDA) method was successfully established for the simultaneous determination of nine compounds. The distribution and accumulation of compounds were discussed and illuminated in different parts of P. corylifolia and samples harvested at different times. The characteristics of compounds' variation in flowers and fruits of P. corylifolia were identified. Through the market survey and quantitative study on FP, positive correlation was speculated between transformation from (iso)psoralenoside to (iso)psoralen via β-glucosidase and storage time, which was further confirmed by accelerated stability test. The effect of treated temperatures (40–210 °C) was unveiled on the enzyme activity and transformation from (iso)psoralenoside to (iso)psoralen in FP. And the focused compounds' transformation was mainly driven by β-glucosidase when the temperature was below 120 °C. Above 120 °C, β-glucosidase was completely inactivated, and the focused compounds' transformation was mediated by high-temperature, also the obvious degradation was found. Our results demonstrated that compounds' transformation characteristics arising from the growth, processing and storage of P. corylifolia are critical factors to ensure the quality of FP.     

Exogenous pulmonary surfactant: A review focused on adjunctive therapy for severe acute respiratory syndrome coronavirus 2 including SP-A and SP-D as added clinical marker

Type I and type II pneumocytes are two forms of epithelial cells found lining the alveoli in the lungs. Type II pneumocytes exclusively secrete ‘pulmonary surfactants,’ a lipoprotein complex made up of 90% lipids (mainly phospholipids) and 10% surfactant proteins (SP-A, SP-B, SP-C, and SP-D). Respiratory diseases such as influenza, severe acute respiratory syndrome coronavirus infection, and severe acute respiratory syndrome coronavirus 2 infection are reported to preferentially attack type II pneumocytes of the lungs. After viral invasion, consequent viral propagation and destruction of type II pneumocytes causes altered surfactant production, resulting in dyspnea and acute respiratory distress syndrome in patients with coronavirus disease 2019. Exogenous animal-derived or synthetic pulmonary surfactant therapy has already shown immense success in the treatment of neonatal respiratory distress syndrome and has the potential to contribute efficiently toward repair of damaged alveoli and preventing severe acute respiratory syndrome coronavirus 2–associated respiratory failure. Furthermore, early detection of surfactant collectins (SP-A and SP-D) in the circulatory system can be a significant clinical marker for disease prognosis in the near future.     

The glucocorticoid derivative with the phthalimide group cationic nanocrystal for ophthalmic application: a design space development approach

The glucocorticoid derivative of budesonide with a phthalimide group is a drug candidate to treat inflammatory eye diseases; nevertheless, it presents low water solubility. Drug nanocrystals have been proposed to overcome this hurdle. The development of an innovative ophthalmic anti-inflammatory nanosuspension was performed using a design space approach. We obtained the particle size reduction of this glucocorticoid derivative on a nanometer scale (approximately 165.0 nm), applying wet bead milling on a super reduced scale. The design of experiment supported the optimization of the formula evaluating the parameters that influence reducing the particle size and also allowed determining the design space. Considering the two statistical models developed and the size range obtained, we proposed that the optimized formulation for the glucocorticoid derivative nanosuspension may be 1.0 wt% glucocorticoid derivative and 0.092 wt% cetylpyridinium chloride. This formulation was characterized by the morphological, physical–chemical, and mucoadhesive in vitro test and showed potential for ophthalmic use with reduced frequency of product application, improved efficiency, and safety, which may promote better patient compliance.     

Predicting ion selectivity in water purification by capacitive deionization: Electric double layer models

Ion-selective water treatment is needed to address emerging problems in an energy- and cost-efficient manner. Capacitive deionization (CDI) is a membraneless water treatment technology, which relies on storing ions in charged electric double layers (EDLs) of micropores. CDI has shown remarkable selectivity, with local density approximations (LDAs) showing some success in guiding selective separations. However, many underlying processes are represented by lumped fitting parameters in LDA models, hindering further progress. Atomistic models help unravel selectivity mechanisms, but are difficult to integrate with cell-level CDI theory. Here, we review and extend LDA models for CDI, highlight a knowledge gap in connecting between LDA and atomistic models for CDI, and emphasize and build upon analogies between micropore EDLs and nanofiltration membranes.     

Nickel- and cobalt-based heterogeneous catalytic systems for selective primary amination of alcohol with ammonia

It is one of the critical fields of green chemistry to catalyze the selective conversion of biomass-derived alcohol and ammonia to primary amines with extensive application. Recently, catalytic systems consisting of non-noble metal nickel- and cobalt-based catalysts have been developed for catalytic alcohol amination. This paper reviewed these two types of catalytic systems, which are classified as skeleton Co and Ni catalytic systems, supported and modified Co and Ni catalytic systems, emphasized on catalysts and catalysis, and clearly explained where zero-valent cobalt or nickel is active species for catalytic reaction. In supported catalysts, the catalytic active sites constituted by the catalytic active species and its micro-environment can regulate the efficiency of catalytic the reaction. While in modified catalysts, modifiers such as metal Fe, Re and Bi may modulate the catalytic active sites and change the catalytic selectivity. There are differences in structure and size between catalysts prepared by different methods, resulting in distinct interface and electronic properties for alcohol amination, which determines the structure–activity relationships of the catalytic system.     

Tuning of graphitic carbon nitride (g-C3N4) for photocatalysis: A critical review

Graphitic carbon nitride (g-C₃N₄) is a remarkable semiconductor catalyst that has attracted widespread attention as a visible light photo-responsive, metal-free, low-cost photocatalytic material. Pristine g-C₃N₄ suffers fast recombination of photogenerated electron-hole pairs, low surface area, and insufficient visible light absorption, resulting in low photocatalytic efficiency. This review presents the recent progress, perspectives, and persistent challenges in the development of g-C₃N₄-based photocatalytic materials. Several approaches employed to improve the visible light absorption of the materials including metal and non-metal doping, co-doping, and heterojunction engineering have been extensively discussed. These approaches, in general, were found to decrease the material’s bandgap, increase the surface area, reduce charge carrier recombination, and promote visible light absorption, thereby enhancing the overall photocatalytic performance. The material has been widely used for different applications such as photocatalytic hydrogen production, water splitting, CO₂ conversion, and water purification. The work has also identified various limitations and weaknesses associated with the material that hinders its maximum utilization under visible illumination and presented state-of-the-art solutions that have been reported recently. The summary presented in this review would add an invaluable contribution to photocatalysis research and facilitate the development of efficient visible light-responsive semiconducting materials.