Cationic Moieties Research Articles

Novel urea/thiourea-betaine inclusion compounds consolidated by host-guest hydrogen bonds

Two new inclusion compounds, (CH3)3N+CH2 COO−·2(NH2)2CS (1) and (CH3)3N+ CH2COO−·2(NH2)2CO (2), have been prepared and characterized by X-ray crystallography. In the crystal structure of 1, the cationic moieties are trapped in the channel-like lattice with quasi-rectangular section constructed from the linkage of the carboxyl anionic moieties and thiourea ribbons formed by the centrosymmetric hydrogen-bonded thiourea dimers. In the honeycomb-like stereo host lattice of two that are built by urea molecules, each channel is parallel to the b axis, and every two cationic moieties lie in the same column but link different ribbons with host-guest hydrogen bonds.

(Invited) Tuning Triblock Co-Polymer Silver Interactions on the Nanoscale to Enhance Transport in Electrodes for Electrochemical Devices Based on Anion Exchange Membranes

Anion exchange membranes (AEMs) have recently attracted interest for applications in fuel cells, electrolyzers, redox flow batteries, reverse electrodialysis, and water purification. In contrast to proton exchange membranes (PEMs), AEMs operate in base instead of acid and facilitate the transport of anionic species. In fuel cells and electrolyzers, this allows for more facile kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) respectively. Therefore, AEM-based devices provide the opportunity to utilize non-precious metal catalysts to achieve similar performance to Pt-based catalysts and a substantially reduced cost. The electrodes of these devices are comprised of a heterogeneous mixture of conductive carbon support, catalyst particles, and ionomer, which form a triple-phase boundary where the electrochemical reactions take place. The ionomer is an alkaline polymer electrolyte similar to the AEM which transports OH- and water to/from the catalyst surface and promotes reactant transport.The electrode layers in PEM-based fuel cells were developed empirically, and it was not until recently that research efforts were dedicated to investigating the heterogeneous microstructure and triple-phase boundary that form. Currently, the catalyst layer as it exists in an operating device is not well understood due to its complex nature; however, model interfaces between ionomers and catalyst particles have been used to provide valuable insight on ionomer-catalyst interfacial interactions. It is known from studies with Nafion® that restructuring of the polymer morphology can occur when it exists as an ionomer thin film at a catalyst interface. The behavior of the thin film ionomer changes compared to its bulk characteristics, which ultimately affects electrode kinetics by altering the nature of its microstructure, leading to shifts in morphology, water uptake properties, and ionic and water transport networks.Initial work was driven by the overarching hypothesis that the polymer-catalyst interfacial interactions could be modified by changing the ionomer chemistry. This was investigated by studying interactions between silver nanoparticles and anion exchange ionomers functionalized with two different quaternary ammonium cations, using our previously reported block copolymer backbone polychloromethylstyrene-b-polycyclooctene-b-polychloromethylstyrene (PCMS-b-PCOE-b-PCMS) functionalized with either trimethylammonium (TMA) or methylpiperidinium (MPRD) quaternary ammonium cations. Our early findings indicated there were interactions between silver nanoparticles and C=C groups in the polycyclooctene midblock of the polymer backbone. This motivated the development of a modified anion exchange polymer by hydrogenating the PCOE midblock in PCMS-b-PCOE-b-PCMS to synthesize a polyethylene (PE) midblock. Hydrogenation was achieved through a reaction with p-toluenesulfonyl hydrazide. The improved characteristics of the PE-based membrane have prompted studies investigating the comparison of saturated and unsaturated ionomers.A uniquely tunable polymer system was developed which has enabled further investigations of ionomer thin films on silver substrates. The thin film geometry allows for the use of grazing incidence small angle x-ray scattering (GISAXS) and atomic force microscopy (AFM) to study the interfacial morphology as a function of ionomer chemistry. Restructuring of the polymer morphology compared to its bulk properties has been confirmed, and our initial findings on the contribution of different cationic moieties will be discussed in the results of this report.

Physiologically-Regulated Adhesion of Hydrogels for Wound Dressing

Adhesion is an essential function of wound dressing materials, which allows the close contact with skin surface. However, the dressing replacement inevitably causes the secondary damage to unhealed wound. A wound dressing material having physiologically-regulated adhesion is thus expected to avert the secondary damage to patients. Herein, we report a hydrogel by covalently introducing cationic moieties into an elastic network. The cationic moieties are capable of electron-withdrawing that promotes a strong electrostatic interaction with polar groups of protein (high electron cloud density) from the wound skin tissue, enabling the adhesion of hydrogel on the skin surface. With the tissue metabolism, the nucleophilic skin surface forms a lipid layer that gradually destroys the electrostatic interaction and weakens the interfacial affinity. The adhesion energy can be reduced from 60 to <10 J/m 2 in seven days, so that the dressing material can be removed from the wound area without bringing in the secondary damage. The cationic moieties also endow the hydrogel a high water swelling ratio, reaching 25200%, making it capable of absorption of a large amount of tissue exudate. In addition, the cationic moieties have an antibacterial effect that can decrease the infection possibility of the wound. The in-vivo tests demonstrate that the wound on a mouse back reaches physiological 100% healing after the hydrogel dressing treatment for 12 days. All results show that the introduction of cationic moieties makes the hydrogel more promising as a wound dressing.

Synthesis and Anion Conductivity of Anion-exchange Membrane with Fused Expanded Pyridinium Structure as Cationic Moiety

We develop a cationic polymer that contains a fused expanded pyridinium (FEP) moiety with a large planar π-conjugated system. This new FEP monomer is synthesized via photochemical pericondensation of a bromo-substituted FEP precursor, and subsequent introduction of the vinyl group. The polymers show a conductivity of 55.2 and 23.7 mS cm−1 at 80% relative humidity and 80 °C for OH− and Cl− forms, respectively. Weak interactions between the FEP cation and anions might be the reason for high anion conductivity.

Gemini Thermotropic Smectic Liquid Crystals for Two-Dimensional Nanostructured Water-Treatment Membranes.

We have developed a two-dimensional (2D) liquid-crystalline (LC) nanostructured water-treatment membrane showing high virus rejection ability (over 99.99997% for bacteriophage Qβ) and improved water permeation. Polymerizable gemini amphiphiles have been designed and synthesized. They have H-shaped gemini-type structures of thermotropic smectic liquid crystals composed of cationic imidazolium moieties. One of the gemini amphiphiles shows a smectic A phase with an interdigitated bilayer structure. A cross-linked self-standing 2D nanostructured polymer film has been obtained by in situ photopolymerization of the gemini amphiphile in the smectic phase. The length of linkers in gemini amphiphiles affects the formation of LC phases. The 2D nanostructured membrane also showed selective salt rejection.

Tuning Ni-MoO2 Catalyst-Ionomer and Electrolyte Interaction for Water Electrolyzers with Anion Exchange Membranes.

Tailoring catalyst–ionomer and electrolyte interaction is crucial for the development of anion exchange membrane (AEM) water electrolysis. In this work, the interaction of Ni–MoO2 nanosheets with ionomers and electrolyte cations was investigated. The activity of Ni–MoO2 nanosheets for the hydrogen evolution reaction (HER) increased when tested in 1 M NaOH compared to 1 M KOH; however, it decreased when tested in 0.01 M KOH compared to 1 M KOH electrolyte. The capacitance minimum associated with the potential of zero free charge (pzfc) was shifted negatively from 0.5 to 0.4 V versus RHE when KOH concentration increased from 0.1 mM to 1 M KOH, suggesting a softening of the water in the double-layer to facilitate the OH– transport and faster kinetics of the Volmer step that lead to improved HER activity. The catalyst interaction with cationic moieties in the anion ionomer (or organic electrolytes) can also be rationalized based on the capacitance minimum, because the latter indicates a negatively charged catalyst during the HER, attracting the cationic moieties leading to the blocking of the catalytic sites and lower HER performance. The HER activity of Ni–MoO2 nanosheets is lower in benzyltrimethylammonium hydroxide (BTMAOH) than in tetramethylammonium hydroxide (TMAOH). Anion fumion ionomer and electrolytes with organic cations with benzyl group adsorption (such as BTMAOH) lead to decreased HER activity in comparison with TMAOH and Nafion. By utilizing Ni–MoO2 nanosheet electrodes as a cathode in a full non-platinum group metal (PGM) AEM electrolyzer, a current density of 1.15 A/cm2 at 2 V cell voltage in 1 M KOH at 50 °C was achieved. The electrolyzer showed exceptional stability in 0.1 M KOH for 65 h at 0.5 A/cm2.

Designing Ionic Liquid-Derived Polymer Composites from Poly(Ionic Liquid)–Ionene Semi-interpenetrating Networks

While the solvating power of ionic liquids (ILs) for a variety of solute types including polymers is well-known, the use of ILs as solvents for ionenes—charged polymers with cationic moieties withi...

Comparison of the effects of dendrimer, micelle and silver nanoparticles on phospholipase A2 structure

The interaction of nanoparticles (NP) with proteins (the so-called 'protein corona') is a huge challenge in attempting to apply them in personalized nanomedicine. We have analyzed the interaction between A) two 'soft' NPs (a cationic phosphorus dendrimer of generation 3; a cationic phosphorus amphiphilic dendron of generation 2), and B) one 'hard' nanoparticle (silver NP covered with cationic carbosilane dendritic moieties); and membrane-bound protein phospholipase A2 from bovine pancreas. The hard and soft NPs have differences in the nature of their interactions with phospholipase A2. This enzyme surrounds hard AgNP, whereas dendrimer and amphiphilic dendron form aggregates/micelles with phospholipase A2. There is a difference in action of phospholipase A2 bound to the core of dendrimer, and of micelles formed from non-covalent interactions between the amphiphilic dendron. These data are important in understanding the nature of interaction between different kinds of nanoparticles and proteins.

Modes of Micromolar Host-Guest Binding of β-Cyclodextrin Complexes Revealed by NMR Spectroscopy in Salt Water.

Multitopic supramolecular guests with finely tuned affinities toward widely explored cucurbit[n]urils (CBs) and cyclodextrins (CDs) have been recently designed and tested as functional components of advanced supramolecular systems. We employed various spacers between the adamantane cage and a cationic moiety as a tool for tuning the binding strength toward CB7 to prepare a set of model guests with KCB7 and Kβ-CD values of (0.6-5.0) × 1010 M-1 and (0.6-2.6) × 106 M-1, respectively. These accessible adamantylphenyl-based binding motifs open a way toward supramolecular components with an outstanding affinity toward β-cyclodextrin. 1H NMR experiments performed in 30% CaCl2/D2O at 273 K along with molecular dynamics simulations allowed us to identify two arrangements of the guest@β-CD complexes. The approach, joining experimental and theoretical methods, provided a better understanding of the structure of cyclodextrin complexes and related molecular recognition, which is highly important for the rational design of drug delivery systems, molecular sensors and switches.

Self-Assembled Binaphthyl-Bridged Amphiphilic AABB Phthalocyanines: Nanostructures for Efficient Antimicrobial Photodynamic Therapy.

Herein, the photodynamic activity of phthalocyanine (pc)-assembled nanoparticles against bacterial strains is demonstrated. The photosensitizers (PS) studied in this work are two chiral ZnII Pcs (PS-1 and PS-2), with an AABB geometry (where A and B refer to differently substituted isoindole constituents). They contain differently functionalized, chiral binaphthyloxy-linked A isoindole units, which determine the hydrophobicity of the system, and cationic methyl pyridinium moieties in the other two isoindoles to embody hydrophilicity. Both compounds have the ability to self-assemble into nanoparticles in aqueous media and have proved efficient in the photo-inactivation of Staphylococcus aureus and Escherichia coli, selected as models of Gram-positive and Gram-negative bacteria. The average size of the nanoparticles was determined by substitution at the binaphthyl core and, in turn, influences the toxicity of the PS. Thus, PS-1, presenting a nonsubstituted binaphthyl core, forms larger nanoparticles with a larger cationic surface than the octyl-functionalized PS-2. Although both PSs present similar structure and photophysical features, the self-assembled nanostructures of PS-1 are more effective at killing both types of strain, showing an outstanding photo-inactivation capacity with the Gram-negative E. coli.

Heating Profile of Long Alkyl Chain Ionic Liquid Doped Solvents Under Ultrasound Irradiation

In this work, the heating profile of water, dimethyl sulfoxide (DMSO), acetonitrile (CH3CN) and ethanol (EtOH) and their solutions containing monocationic (CnMIMBr, n = 4, 6, 8, 10, 12, 14 and 16) and dicationic (di-CnMIMBr, n = 4, 6, 8 and 10) imidazolium-based ionic liquids (ILs) were evaluated under ultrasound irradiation. Similarly, ILs (CnMIMBr, n = 4, 8 and 14) with the BF 4 − anion and inorganic salts, such as NaBr and NaCH3CO2 were also evaluated. The results showed that water and DMSO have a linear heating profile; while CH3CN and EtOH have a logarithmic profile. In general, the IL-containing solutions heated up a little faster than the pure solvents, which indicates that the cationic moiety of the ILs did not cause notable changes in the heating profile of the solvents. The IL concentration and the consequent dissociation effects on this were not observed in any of the experimental conditions tested. The addition of NaBr and NaCH3CO2 changed the heating profile of EtOH, resulting in a linear profile. Additionally, our results confirmed that experimental parameters, such as irradiation amplitude and solution volume, significantly change the heating profile of solvents. Finally, under conventional heating and stirring (silent experiments), the heating profile of the pure solvents and the IL-containing solvents indicated that, under ultrasound, the cavitation process makes the heating faster and more efficient. Determination of the dissipated power reflected the solvent’s heating profile more than its heat capacity; therefore, the heating rate in ultrasound reveals the cavitation effects in the particular medium. These results are important because they show that the catalytic effects of ILs in chemical reactions or the solvent effects in micro extraction processes under ultrasound irradiation can be retained without raising the temperature and without decomposition of the ILs or products.

Cationic starch: an effective flocculant for separating algal biomass from wastewater RO concentrate treated by microalgae

Microalgae can remove nutrients and organic contaminants from municipal wastewater reverse osmosis concentrate (ROC) and enable resource recovery via biomass production. Two cationic starch flocculants (starch-graft-poly cationic moiety 2-methacryloyloxyethyl trimethyl ammonium chloride (St-g-PDMC) and starch-graft-poly cationic moiety 2,3-epoxypropyl trimethyl ammonium chloride (St-GTA)) were synthesized and tested as potential greener and lower cost alternatives to conventional chemical flocculants for harvesting Chlorella vulgaris and Nannochloropsis salina from the algae-treated ROC. St-GTA achieved up to 97% separation (based on optical density) for both algal species at the dosage of 5–10 mg g−1 dry cell weight (DWC) compared to alum (69% at 10 mg g−1 DWC) and PolyDADMAC (93% at 35 mg g−1 DWC). The overall better performance of St-GTA was attributed to its higher intrinsic viscosity, positive surface charge, and solubility. The harvesting efficiency was influenced by algal growth phases, which led to differences in the levels of negative charge and functional groups on the algal surfaces. The effectiveness of the flocculants was primarily associated with their respective level of positive surface charge (R2 = 0.87) that facilitated charge neutralization as indicated by apparent surface charge of the algal flocs (R2 = 0.97). Flocculation using St-GTA removed 40% TP, 25% TN, and 20% DOC from the residual contaminants of the algae-treated ROC. Overall, the study indicated that cationic starch could be an environmentally benign and cost-effective approach for harvesting microalgae from the treated ROC, and beneficial to the subsequent utilization of the harvested biomass.

Stimuli-responsive microgels with cationic moieties: characterization and interaction with E. coli cells.

Stimuli-responsive microgel copolymer networks with ionizable functional groups have important applications for encapsulation of drugs, peptides, enzymes, proteins, or cells. Rational design of such networks can be based on characterization of stimuli-induced volume phase transition and spatial distribution of neutral and charged monomer units in crosslinked polymer chains. In this work we successfully synthesized poly(N-vinylcaprolactam-co-1-vinyl-3-methylimidazolium) (poly(VCL-VIM+)) microgels carrying permanent positive charges and demonstrate that 1H high-resolution NMR spectroscopy in combination with transverse (T2) magnetization relaxometry allows investigating separately the behavior of each functional group in the microgel network. The information about comonomer transition temperatures, width of transition, and change in transition entropy were reported and correlated with the concentration of charged functional groups and resulting electrophoretic mobility. A two-state approach was used to describe the temperature-induced volume phase transition separately for neutral and charged polymer segments. The core-corona architecture specific to each functional group was detected revealing that the charged methylated vinylimidazolium groups (VIM+) are concentrated mainly in the corona of the microgel. These biocompatible PVCL-based microgels functionalized with permanent positive charges are shown to serve as an antibacterial system against Gram-negative E. coli strains, due to the positive charge of the incorporated VIM+ comonomer in the polymer network.

Effect of noncovalent interactions in ion pairs on hypervalent iodines: inversion of regioselectivity in sulfonyloxylactonization

The noncovalent interactions between the sulfonyloxy group and the cationic nitrogen-containing heterocyclic moiety substituted in hypervalent iodines caused specific regioselectivity in the sulfonyloxylactonization of 2-vinyl benzoic acids.

Pleiotropic Properties of Amphiphilic Dihydropyridines, Dihydropyridones, and Aminovinylcarbonyl Compounds.

Three groups of synthetic lipids are chosen for studies: (1) 1,4-dihydropyridines (1,4-DHPs) containing two cationic moieties and their analogues; (2) 3,4-dihydro-2(1H)-pyridones containing a cationic moiety; and (3) acyclic, open-chain analogues, i.e., 2-amino-3-alkoxycarbonylalkylammonium derivatives. 1,4-DHPs possessing dodecyl alkyl chains in the ester groups in positions 3 and 5 and cationic nitrogen-containing groups in positions 2 and 6 have high cytotoxicity in cancer cells HT-1080 (human lung fibrosarcoma) and MH-22A (mouse hepatoma), but low cytotoxicity in the noncancerous NIH3T3 cells (mouse embryonic fibroblast). On the contrary, similar compounds having short (methyl, ethyl, or propoxyethyl) chains in the ester groups in positions 3 and 5 lack cytotoxicity in the cancer cells HT-1080 and MH-22A even at high doses. Inclusion of fluorine atoms in the alkyl chains in positions 3 and 5 of the DHP cycle decreases the cytotoxicity of the mentioned compounds. Structurally related dihydropyridones with a polar head group are substantially more toxic to normal and cancerous cells than the DHP analogues. Open-chain analogues of DHP lipids comprise the same conjugated aminovinylcarbonyl moiety and possess anticancer activity, but they also have high basal cytotoxicity. Electrochemical oxidation data demonstrate that oxidation potentials of selected compounds are in the range of 1.6–1.7 V for cationic 1,4-DHP, 2.0–2.4 V for cationic 3,4-dihydropyridones, and 1.2–1.5 V for 2-amino-3-alkoxycarbonylalkylammonium derivatives. Furthermore, the tested cationic 1,4-DHP amphiphiles possess antiradical activity. Molecular topological polar surface area values for the tested compounds were defined in accordance with the main fragments of compound structures. The determined logP values were highest for dodecyl ester groups in positions 3 and 5 of the 1,4-DHP and lowest for short alkyl chain-containing amphiphiles.

Polyamine-Functionalized 2'-Amino-LNA in Oligonucleotides: Facile Synthesis of New Monomers and High-Affinity Binding towards ssDNA and dsDNA.

Attachment of cationic moieties to oligonucleotides (ONs) promises not only to increase the binding affinity of antisense ONs by reducing charge repulsion between the two negatively charged strands of a duplex, but also to augment their in vivo stability against nucleases. In this study, polyamine functionality was introduced into ONs by means of 2'-amino-LNA scaffolds. The resulting ONs exhibited efficient binding towards ssDNA, ssRNA and dsDNA targets, and the 2'-amino-LNA analogue carrying a triaminated linker showed the most pronounced duplex- and triplex-stabilizing effect. Molecular modelling revealed that favourable conformational and electrostatic effects led to salt-bridge formation between positively charged polyamine moieties and the Watson-Hoogsteen groove of the dsDNA targets, resulting in the observed triplex stabilization. All the investigated monomers showed increased resistance against 3'-nucleolytic digestion relative to the non-functionalized controls.

Nano-graphene-platelet/Brilliant-green composite coated carbon paste electrode interface for electrocatalytic oxidation of flavanone Hesperidin

We have developed a nanodevice with the aid of adsorption strategy. The key factor being the extensive π-π interactions between sp2 carbons of nano-Graphene-platelets (nGp) and π-e- of cationic Brilliant green (Bg) at the electrode surface, that synergistically promoted Hesperidin (HES) oxidation. From our observations, electrochemical catalytic oxidation of HES significantly magnified on nGp-Bg/Modified carbon paste electrode (nGp-Bg/MCPE), under optimized experimental conditions, such as the volume of composite cast-coated, cationic active sites in the nGp-Bg film, and the pH of the buffer. Surface morphology was characterized using Field Emission Scanning Electron Microscopy (FESEM) and Electron Diffraction X-ray (EDX). Nyquist plots revealed the least charge transfer resistance at nGp-Bg/MCPE compared to other control electrodes. Further, at physiological pH, HES displayed an irreversible electrochemical charge transfer at nGp-Bg/MCPE. The cationic Bg moieties on nGp-Bg/MCPE portrayed a great affinity towards deprotonated HES and its accumulation on the electrode surface. Interactions between aromatic rings in nGp-Bg structure and HES molecules consequently enhanced total surface coverage concentration by 3.6-fold compared to control electrodes via adsorption-controlled-electron-transfer feature. We have demonstrated that the reaction capability of nGp-Bg/MCPE towards HES quantification via synergistic electrocatalytic effect, with the ability to lower the activation energy and hastened oxidation. Quantification of HES was performed using Differential Pulse Voltammetry (DPV). Gp-Bg/MCPE showed selective mediated oxidation current response with the lowest detection limit of 5.0 × 10−8 M in two linear ranges. We have successfully validated trace analysis of HES in fortified fruit juice samples, also extendable to various practical applications. Therefore, the present work has established simplicity in the principle of the novel approach in the development of an ultrasensitive voltammetric sensor for HES.

Role of Chain Polarity on Ion and Polymer Dynamics: Molecular Volume-Based Analysis of the Dielectric Constant for Polymerized Norbornene-Based Ionic Liquids

Norbornene-based polymerized ionic liquids (PILs) were systematically prepared to understand the role of PIL architecture and linker on the ionic conductivity (σDC), segmental dynamics, and dielectric constant. In PILs with two- or one-armed imidazolium (Im⁺)-bis(trifluoromethanesulfonyl)imide (Tf₂N–) pendants, their dynamics and polarity were tuned by incorporating either oxyethylene [(OCH₂CH₂)ₓ = (OE)ₓ, x = 1 or 3] or alkylene [(CH₂)₂] moieties as linkers between the norbornene and imidazolium cation moieties and ethyleneoxy [(CH₂CH₂O)y = (EO)y, y = 2 or 3] terminal units on the imidazolium. All PILs exhibit three dipolar relaxations; the local chain β motions of the PIL pendants were observed below the glass transition temperature (Tg), while above Tg, the segmental α and slower ionic rearranging α₂ relaxations were observed. Unlike the alkylene linker, the OE linker incorporation speeds up the α and α₂ relaxations (consistent with the decrease in Tg), increases the relaxation strengths [leading to an increase in the static and Coulombic dielectric constants (eₛ and eC)], imparts a higher number density of simultaneously conducting ions (p), and boosts their mobility (μ). This is directly reflected in the OE-containing PILs having 10 times higher ionic conductivities (σDC) than the PIL with the alkylene linker. The Tg, eₛ, and σDC are significantly influenced by the repeat unit molecular volume (Vₘ), polarizability volume (Vₚ), and Keesom volume (VK), suggesting that the OE linker not only facilitates ion dissociation of Im⁺Tf₂N– but also promotes segmental motion, thereby leading to a strong correlation of ionic conductivity with the dielectric constant and glass transition temperature.

Design of Photosensitizing Agents for Targeted Antimicrobial Photodynamic Therapy.

Photodynamic inactivation of microorganisms has gained substantial attention due to its unique mode of action, in which pathogens are unable to generate resistance, and due to the fact that it can be applied in a minimally invasive manner. In photodynamic therapy (PDT), a non-toxic photosensitizer (PS) is activated by a specific wavelength of light and generates highly cytotoxic reactive oxygen species (ROS) such as superoxide (O2−, type-I mechanism) or singlet oxygen (1O2*, type-II mechanism). Although it offers many advantages over conventional treatment methods, ROS-mediated microbial killing is often faced with the issues of accessibility, poor selectivity and off-target damage. Thus, several strategies have been employed to develop target-specific antimicrobial PDT (aPDT). This includes conjugation of known PS building-blocks to either non-specific cationic moieties or target-specific antibiotics and antimicrobial peptides, or combining them with targeting nanomaterials. In this review, we summarise these general strategies and related challenges, and highlight recent developments in targeted aPDT.

Cation Effect in the Corrosion Inhibition Properties of Coumarate Ionic Liquids and Acrylic UV-Coatings.

Chromate free corrosion inhibitors are searched for to mitigate the economic loss caused by mid-steel corrosion. Here, we show metal-free organic inhibitors having free coumarate anions that can be used either as direct corrosion inhibitors or incorporated into a polymer coating obtained by UV-curing. Four different ionic liquid monomers and polymer coatings with hexoxycoumarate anion and different polymerizable counter cations were investigated. Potentiodynamic polarization, electrochemical impedance spectroscopy, and surface analyses have verified their corrosion inhibition performance on a mild steel AS1020 surface. In the case of the coumarate ionic liquid monomers, the most promising inhibitor is the one coupled with the ammonium cation, showing an inhibition efficiency of 99.1% in solution followed by the imidazolium, pyridinium, and anilinium. Next, the ionic liquid monomers were covalently integrated into an acrylic polymer coating by UV-photopolymerization. In this case, the barrier effect of the polymer coating is combined with the corrosion inhibitor effect of the pendant coumarate anion. Here, the best polymer coatings are those containing 20% imidazolium and pyridinium cations, presenting a greater impedance in the EIS (Electrochemical Impedance Spectroscopy) measurements and less evidence of corrosion in the scribe tests. This article shows that the cationic moiety of coumarate based ionic liquids and poly(ionic liquid)s has a significant effect on their excellent corrosion inhibition properties for a mild steel surface exposed to aqueous chloride solutions.