Ionic liquids are remarkable chemical compounds, which find applications in many areas of modern science. Because of their highly tunable nature and exceptional properties, ionic liquids have become essential players in the fields of synthesis and catalysis, extraction, electrochemistry, analytics, biotechnology, etc. Apart from physical and chemical features of ionic liquids, their high biological activity has been attracting significant attention from biochemists, ecologists, and medical scientists. This Review is dedicated to biological activities of ionic liquids, with a special emphasis on their potential employment in pharmaceutics and medicine. The accumulated data on the biological activity of ionic liquids, including their antimicrobial and cytotoxic properties, are discussed in view of possible applications in drug synthesis and drug delivery systems. Dedicated attention is given to a novel active pharmaceutical ingredient-ionic liquid (API-IL) concept, which suggests using traditional drugs in ...

Biological Activity of Ionic Liquids and Their Application in Pharmaceutics and Medicine.

The thermal and physicochemical properties of protic ionic liquids (PILs) are reported. It is highly evident that there has been an extensive range of alkylammonium, imidazolium, and heterocyclic cations paired with many organic and inorganic anions that have been employed to prepare PILs. There has been strong interest in modifying the properties of PILs through the addition of water or other molecular solvents. For many applications, the presence of some water in the PILs is not detrimental, and instead leads to enhanced solvent properties such as lower viscosity, higher conductivities, and lower melting points. It remains an issue of definition though of how to refer to these resulting protic solutions. There is also an ongoing difficulty surrounding how to describe the proton activity in the PILs, analogous to pH in aqueous systems. For a broad range of applications, it has been reported that the acidity/basicity of the PIL or PIL-solvent system is crucial for their beneficial properties. It is expected that the fundamental properties of PILs will continue to be explored, along with continued interest in many existing and new applications, such as in electrochemistry, organic and inorganic synthesis, and biological applications. In particular, there has been a significant interest in a broad- range of PILs for use as electrolytes and incorporation in polymer electrolytes for fuel cells, and other energy storage devices.

Protic Ionic Liquids: Evolving Structure–Property Relationships and Expanding Applications

Metal-organic frameworks (MOFs) are a class of distinctive porous crystalline materials constructed by metal ions/clusters and organic linkers. Owing to their structural diversity, functional adjustability, and high surface area, different types of MOF-based single metal sites are well exploited, including coordinately unsaturated metal sites from metal nodes and metallolinkers, as well as active metal species immobilized to MOFs. Furthermore, controllable thermal transformation of MOFs can upgrade them to nanomaterials functionalized with active single-atom catalysts (SACs). These unique features of MOFs and their derivatives enable them to serve as a highly versatile platform for catalysis, which has actually been becoming a rapidly developing interdisciplinary research area. In this review, we overview the recent developments of catalysis at single metal sites in MOF-based materials with emphasis on their structures and applications for thermocatalysis, electrocatalysis, and photocatalysis. We also compare the results and summarize the major insights gained from the works in this review, providing the challenges and prospects in this emerging field.

Metal-Organic Framework-Based Catalysts with Single Metal Sites.

Ionic liquids synthesis and applications: An overview

This paper reviews the state of the art of anodized titanium dioxide nanotubes (TiO2 NTs), with an emphasis on the growth mechanism leading to their formation and the effect of heat treatment on their structure and properties. The discussion is primarily focused on TiO2 NTs grown in fluoride containing electrolytes, although the mechanism of formation of NTs in fluoride free solutions via Rapid Breakdown Anodization (RBA) is briefly covered. After an initial overview of progress made on the synthesis of anodized TiO2 NTs the review provides an analysis of the factors affecting the anodizing process (fluoride concentration, electrolyte type, applied potential and anodizing time). Details of the current-time transient, the chemistry of the process and the chemical composition of the anodic films are described which provide key information to unveil the nanotube growth mechanism. The main debate is whether NTs growth in fluoride containing solutions occurs via field-assisted plastic flow (i.e. a constant upward displacement of the oxide to form the NTs) combined with field-assisted ejection of the Ti4+ ions (i.e. ions are ejected into the electrolyte without oxide formation) or via field-assisted dissolution (i.e. preferential dissolution at the pore base where the field is stronger) or whether both processes play a role. Whenever anodization takes place in organic solutions the experimental evidence supports the plastic flow model, whereas in aqueous media field-assisted (and chemical) dissolution occur. The mechanism of rib formation on the walls of the NTs is also reviewed, and it clearly emerges that the applied potential and water content in the electrolyte are key factors in determining whether the NTs are ribbed or smooth. There also appears to be a relationship between the presence of ribs and the evolution of oxygen bubbles at the anode. The impact of thermal treatment on the properties of the NTs is also described. A variety of crystalline structures are present in the NTs (i.e. anatase or rutile), depending on the heat treatment temperature and atmosphere and the resulting electrical properties can be varied from dielectric to semi-metallic. A heat treatment temperature limit ranging from 500 to 800 °C exists, depending on preparation history, above which sintering of nanoscale titania particles occurs leading to collapse of the NTs structure. Future work should aim at using annealing not just to influence the resulting crystalline phase, but also for generating defects to be exploited in specific applications (i.e. photocatalysis, water splitting and photovoltaics).

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A review of growth mechanism, structure and crystallinity of anodized TiO2 nanotubes

Synthesis and application of task-specific ionic liquids used as catalysts and/or solvents in organic unit reactions

The formation processes of barrier anodic alumina (BAA) and porous anodic alumina (PAA) are discussed in detail. The anodizing current J(T) within the oxide includes ionic current j(ion) and electronic current j(e) during the anodizing process. The j(ion) is used to form an oxide and the j(e) is used to give rise to oxygen gas or sparking. The j(e) results from the impurity centers within the oxide. For a given electrolyte, the j(e) is dependent on the impurity centers and independent of the J(T). The formation of nanopores can be ascribed to the oxygen evolution within the oxide. Oxygen gas will begin to be released at the critical thickness d(c). The manner of the development of PAA is in accordance with that of BAA. The differences between PAA and BAA are the magnitude of j(e) or the continuity of oxygen evolution. There are two competitive reactions, i.e. oxide growth (2Al3 + 3O2- --> Al2O3) and oxygen evolution (2O2- --> O2 up arrow + 4e). The former keeps the wall of the channel lengthened, the latter keeps the channel open. By controlling the release rate of oxygen gas under different pressures, the shape of the channels can be adjusted. The present results may open up some opportunities for fabricating special templates.

https://iopscience.iop.org/article/10.1088/0957-4484/20/47/475303/pdf

Electronic currents and the formation of nanopores in porous anodic alumina.

Electrochemical investigation of a new Cu-MOF and its electrocatalytic activity towards H2O2 oxidation in alkaline solution

We discovered a unique formation of serrated nanopore in porous anodic alumina (PAA). A new growth model is proposed for the formation mechanism of PAA. The model emphasizes the close relationship between pore generation and oxygen evolution. The initial pore formation is ascribed to oxygen bubble mould effect. Our model provides a satisfactory explanation for the growth process of PAA, alleviating the difficulties encountered in existing theories. These findings represent a decisive new step towards the full understanding of the nature of PAA films. The serrated nanopore arrays in PAA could also be used in a wide range of future nanostructure fabrications.

Lin Liu

Papers

Synthesis and application of task-specific ionic liquids used as catalysts and/or solvents in organic unit reactions

Electronic currents and the formation of nanopores in porous anodic alumina.

Electrochemical investigation of a new Cu-MOF and its electrocatalytic activity towards H2O2 oxidation in alkaline solution

Oxygen bubble mould effect: serrated nanopore formation and porous alumina growth

Oxygen evolution and porous anodic alumina formation