High Cationic Density Research Articles

PH-Responsive Charge Convertible Hyperbranched Poly(ionic liquid) Nanoassembly with High Biocompatibility for Resistance-Free Antimicrobial Applications.

As a potential alternative to antibiotics, hyperbranched poly(ionic liquid)s (HPILs) have demonstrated significant potential in combating bacterial biofilms. However, their high cation density poses a high risk of toxicity, greatly limiting their in vivo applications. In this study, we constructed a biocompatible HPIL (HPIL-Glu) from a hyperbranched polyurea core with modified terminals featuring charge-convertible ionic liquids. These ionic liquid moieties consist of an ammonium-based cation and a gluconate (Glu) organic counter. HPIL-Glu could form a homogeneous nanoassembly in water and exhibited a pH-responsive charge conversion property. Under neutral conditions, Glu shielded the positively charged surface, minimizing the toxicity. In a mildly acidic environment, Glu protonation exposes cationic moieties to biofilm eradication. Comprehensive antimicrobial assessments demonstrate that HPIL-Glu effectively kills bacteria and promotes the healing of bacteria-infected chronic wounds. Furthermore, prolonged exposure to HPIL-Glu does not induce antimicrobial resistance.

Room temperature intercalated poly(diallyldimethylammonium chloride)@montmorillonite as an ultrasensitive mangiferin electrochemical sensor component

A high cationic density polymer (poly(diallyldimethylammonium chloride)) intercalated montmorillonite (PDDA@Mt) was prepared at room temperature and employed as an electrode modifier for the sensitive electrochemical determination of the bioactive molecule mangiferin. X-ray diffraction analysis (XRD) analysis showed an increase in d-spacing from 1.34 nm in Na+-Mt to 1.49 nm in PDDA@Mt, thus ascertaining successful intercalation. A significant charge transfer resistance drop was noted when PDDA@Mt was used as an electrode modifier. Under optimum experimental conditions, the peak current of mangiferin varied linearly with concentration in the range from 1 to 2591.1 nM. From the slope of the calibration curve and the blank standard deviation, a detection limit of 0.63 nM was found (3 S/N). The developed methodology was successfully applied to the electrochemical sensing of mangiferin in the presence of some potential organic interferent species. The results herein show that room temperature intercalated clays could be cost-effective and less energy demanding electrochemical sensor components.

Super-adsorbent microspheres based on a triallyl isocyanurate-maleic anhydride copolymer for the removal of organic pollutants from water.

Owing to the frequent occurrence of diclofenac sodium (DS) in fresh aquatic environments and its potential toxicity towards living organisms, the effective removal of DS has attracted worldwide attention. Herein, a green and efficient strategy to fabricate crosslinked microspheres with interconnected mesoporous structures and abundant adsorption active sites was developed. With this strategy, triallyl isocyanurate (TAIC)-maleic anhydride (MAH) copolymer microspheres (TMs) with a diameter of 1.19-1.35 μm were first prepared by self-stabilized precipitation (2SP) polymerization, and the TMs possess a large amount reactive anhydride groups (62.5-71.8 mol%), a specific surface area of 51.6-182.4 m2 g-1 and a mesoporous structure (average pore size: 3.4-3.8 nm). Then the TMs were further functionalized with polyethylenimine (PEI) to give rise to cationic microspheres (Cat-TMs), which showed excellent adsorption performance to DS with a rapid adsorption rate (reached equilibrium within 30 min), a very high equilibrium adsorption capacity (1421 mg g-1) and excellent recyclability. The pseudo-second-order model and Langmuir model were a good fit for the adsorption kinetic and isotherm process, respectively. Furthermore, due to the high cation density (4.291 mmol g-1) and excellent pH buffer capacity of Cat-TMs, the adsorption capacity can be maintained at a high level within the pH range of 6-10. The regenerated Cat-TMs showed only a slight loss (<5%) in the adsorption capacity even after 5 adsorption-desorption cycles. In short, Cat-TMs can be considered as a highly promising adsorbent for the rapid and ultra-efficient removal of anionic organic contaminants and have significant potential to be applied in wastewater treatment.

Vapor deposition of CsPbBr3 thin films by evaporation of CsBr and PbBr2

Thin films of the inorganic halide perovskite, CsPbBr3, find applications in various optoelectronic devices, including solar cells, radiation detectors, light-emitting diodes, photodetectors, and lasers. Physical vapor deposition (PVD) by coevaporation of CsBr and PbBr2 onto a substrate is a scalable solventless approach to forming high purity large-grained polycrystalline films. Herein, we investigate the effects of deposition temperature, between 26 and 162 °C, and postdeposition annealing, between 250 and 350 °C, on the structure, texturing, and morphology of orthorhombic CsPbBr3 films formed by PVD. All films, regardless of the stable phase at the deposition temperature, transform to orthorhombic upon cooling to room temperature. The films deposited as orthorhombic or tetragonal CsPbBr3 below 130 °C were textured in the orthorhombic structure's ⟨202⟩ direction, while cubic CsPbBr3 films deposited above 130 °C were textured in the orthorhombic structure's ⟨121⟩ direction. This texturing favors the growth of high cation density planes of the stable phase at the deposition temperature. The orthorhombic ⟨202⟩ texturing also dominates after annealing as long as the films have ⟨202⟩ aligned grains before annealing.

Polyethyleneimine-Stabilized Platinum Nanoparticles as Peroxidase Mimic for Colorimetric Detection of Glucose.

Colorimetric detection of glucose using enzyme-mimic nanoparticles (NPs) has been drawing great attention. However, many NPs lack good stability in solution, which results in reduced color change of substrates in colorimetric detection. Liner soluble macromolecules with high cationic density may be suitable candidates for the stabilization of NPs. Herein, we prepared polyethyleneimine-stabilized platinum NPs (Ptn-PEI NPs) for colorimetric detection of glucose. The platinum NPs (Pt NPs) used in this system had small size (from 3.21 to 3.70 nm) and narrow size distribution. Pt50-PEI NPs had high stability within one week with a hydrodynamic size of ∼25 nm and slightly positive zeta potential. Pt50-PEI NPs-catalyzed oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2, generating blue oxidized TMB (oxTMB), which indicated the peroxidase-like property of Pt50-PEI NPs. The optimal condition for this reaction was pH = 4.0 at 30 °C. More importantly, Pt50-PEI NPs were successfully used to detect glucose concentration by a colorimetric method with high selectivity. The established method had a linear concentration range from 10 to 5000 μM with a detection limit of 4.2 μM. For example, the concentration of glucose in saliva was tested to be 0.15 mM using our method. The high stability of Pt50-PEI NPs enhanced the high accessibility of the active center of Pt NPs for substrates and consequent excellent catalytic property. This established method has great potential to be used in various applications for glucose detection in the future.

Achieving high anion conductivity by densely grafting of ionic strings

To access highly ion-conductive membrane materials which are urgently desired by the technologies like fuel cells, flow batteries, electro-dialysis etc., a novel polymer architecture featured by the densely grafting of three ionic strings onto each benzene ring was developed. Compared with the previous densely functionalized AEMs prepared by closely attaching multiple cations onto polymer main chain, this study aims to achieve the improved nano-phase separation ability through combing the advantages of high cation mobility and high cation density. As a result, distinct ion conducting channels were observed by atomic force microscopy and high Br- conductivity of 50.6 mS/cm was achieved at 80 °C, suggesting the effectiveness of this strategy.

Vitamin B6 Cofactor Conjugated hPEI-AgNCs for Fluorescent Sensing of Metal Ions and its Application in Cells Imaging

Silver nanoclusters have been extensively used to construct fluorescent sensors for the detection of metal ions. Many synthetic strategies have been employed for development of these remarkable fluorescent materials by using different organic or biological templates such as proteins, peptides, polyelectrolyte, and DNAs. In the case of polyelectrolyte, polyethyleneimine (PEI) is a positively charged hyper-branched polyamine regarded as an ideal template to modify and stabilize nanoparticles based on several advantages: firstly, PEI contains primary, secondary and tertiary amine groups, which could efficiently chelate with metallic nucleus and stabilize these particles against flocculation by the strong columbic interaction due to the inherent high cationic density of the polymer.1 Considering the benefits of PEI-AgNCs, we have synthesized PEI-AgNCs using formaldehyde as the reducing agent and further bio-conjugated with the active form of vitamin B6 cofactor pyridoxal 5 -phosphate (PLP) to tune the sensing properties. Thus, the bio-conjugation of PLP with PEI-AgNCs (PLP_PEI-AgNCs) results in the formation of Schiff base that perceive significance complexation-induced turn-on fluorescent response in the presence of Zn2+ and Cd2+ with the detection limit down to 50.5 x 10-8 M for Zn2+ and 59.0 x 10-8 M for Cd2+, respectively. Also, low cost covalently anchored cellulose strips were prepared using the nano-assembly PLP_PEI-AgNCs for the easy on-site detection of Zn2+ and Cd2+. In addition, the nanoprobe was employed in live cell imaging for the detection of intracellular Zn2+ in live HeLa cells.2

Effect of Methylated Polybenzimidazole As an Electrolyte for Anion-Exchange Membrane Fuel Cells

Polymer electrolyte fuel cells (PEFCs) are considered to be one of the prospective power sources for automobile and domestic use due to their outstanding energy conversion efficiency and compactness. Recently, anion-exchange membrane fuel cells (AEMFCs) are promising due to the practicablity of eliminating the need for platinum-group metal catalysts, and employing non-precious metal electrocatalysts such as nickel, cobalt, silver are feasible, conducing a potentially low-cost technology. Also, an alkaline environment can inherently enhance the electrochemical kinetics of reaction such as the oxygen reduction reaction (ORR) on cathode, enabling higher power density and energy conversion efficiency. Hence, AMEFCs are attracting strong interest as the substitutes of proton-exchange membrane fuel cells requiring platinum-group metal catalysts[i]. However, the AEMFCs are still suffer from low performance and low OH- conductivities. In order to enhance the performance and durability, it’s required to enhance the ionic conductivity of anion-exchange electrolyte for both membrane and electrocatalyst. Typically, the fabrication of anion-exchange electrolyte is required for both polymer main chains and side chains which include cationic functional groups and charged anions[ii]. In order to enhance the anion conductivity, increasing the cationic density of anion-exchange electrolyte was considered to be one of the promising method for designing anion-exchange electrolyte with superior performance[iii].However, the critical drawback of anion-exchange electrolyte with high cationic density of side chains is their water solubility, due to their hydrophilicity of ionic moieties, which may cause the loss of anion-exchange electrolyte by leaching in water generated in the humidified AMEFCs cell. To overcome this issue, approach of hydrophobic part was introduced by condensation copolymerization to inhibit their water solubility and leaching, while, the reduction of ionic conductivity has been found. Also, another approach of crosslinking by directly casting on the electrode to insolubilize the electrolyte was reported[iv], while the uniform modification of the surface of the electrocatalyst is probably difficult. In our previous studies, we suggested an anchoring of the anion-exchange electrolyte on a polymer backbone, which can prevent the leaching of the anion-exchange electrolyte with high cationic density, uniformly and individually wrap on the surface of carbon supporting materials. We chose multi-walled carbon nanotubes (MWNT) as the carbon supporting material since they provide an outstanding electrical conductivity and lower impurities[v]. We used polybenzimidazole (PBI) as polymer backbone of anion-exchange electrolyte since we found that PBI can uniformly and individually wrap MWNT based on π-π interactions. Since high yield chemical modification of PBI on MWNT has already being reported, this strategy is expected to homogeneously decorate supporting material by anion-exchange electrolyte, which can probably offering a high ionic conductivity. Furthermore, PBI was chosen because Pt nanoparticles can be loaded onto the PBI wrapped MWNT (MWNT/PBI) with a homogeneous distribution in high yield. Based on this strategy, we studied on grafting approach by anchoring 1,4-diazabicyclo[2,2,2]octane (DABCO) polymer moieties as anion-exchange electrolyte onto MWNT/PBI (MWNT/PBI-g-DABCO), and loaded Pt nanoparticles onto MWNT/PBI-g-DABCO to fabricated MWNT/PBI-g-DABCO/Pt as an electrocatalyst for AEMFCs. This approach enabled to developed anion-exchange electrolyte for AEMFCs with high content of cationic moieties and water insolubility[vi]. In this study, instead of grafting approach, we designed a new approach to introduce cationic group by methylation of PBI, due to the advantages of convenient synthesis, high potential of ionic conductivity[vii], and excellent durability under alkaline environment[viii]. Hence, we fabricated methylated polybenzimidazole (mPBI) as electrolyte for AEMFCs electrocatalyst as well as the membrane (Fig. 1). Single cell test of membrane electrode assembly (MEA) using mPBI as electrocatalyst wrapped on MWNT was performed using H2 and conditioned air as the fuel for anode and cathode, respectively, and power density of 24.6 mWcm-2was obtained. [i] Z. Chen et al., Int. J. Hydrogen energy 2014, 39, 18405. [ii] K. Nijmeijer et al., J. Membrane Sci. 2011, 377, 1. [iii] M. A. Hickner et al., Macromolecules 2013, 46, 9270. [iv] Park et al., Int. J. Hydrogen Energy 2014, 39, 16556. [v] N. Nakashima et al., Small. 2009, 5, No. 6, 735. [vi] N. Nakashima. Submitted. [vii] Sun et al., Int. J. Hydrogen Energy 2011, 36, 11955. [viii] S. Holdcroft et al. J. Am. Chem. Soc. 2012, 134, 10753. Figure 1

Chapter Six - Chemical Modification of Chitosan for Efficient Gene Therapy

Gene therapy involves the introduction of foreign genetic material into cells in order to exert a therapeutic effect. Successful gene therapy relies on effective vector system. Viral vectors are highly efficient in transfecting cells, but the undesirable complications limit their therapeutic applications. As a natural biopolymer, chitosan has been considered to be a good gene carrier candidate due to its ideal character which combines biocompatibility, low toxicity with high cationic density together. However, the low cell specificity and low transfection efficiency of chitosan as a gene carrier need to be overcome before undertaking clinical trials. This chapter is principally on those endeavors such as chemical modifications using cell-specific ligands and stimuli-response groups as well as penetrating modifications that have been done to increase the performances of chitosan in gene therapy.

Microwave assisted vacuum regeneration for CO2 capture from wet flue gas

Small scale processing of flue gas with the goal of enriching the stream in CO2 for sequestration or use is an interesting application area for adsorption technology. For example, boiler flue gas which may contain up to 10 % (v/v) CO2 in air can be readily enriched to a stream containing >70 % CO2 which may be ideal for use within a process such as acidification, precipitation, stripping, etc. The challenge in these applications is producing high purity CO2 without excessive energy use and handling high concentrations of water vapor without the added complication of a pre-drying stage. In this study we have examined the use of microwave assisted vacuum as a way of rapidly directing thermal energy to the adsorbent surface to liberate water and CO2. Preliminary “proof-of-concept” pump down experiments were conducted on a small transparent adsorption column of 13X zeolite pre-saturated with a 12 % CO2 in N2 gas mixture. Both wet and dry gas tests were conducted. The addition of microwave radiation improved the rapid desorption of CO2 and water and improved the integrated CO2 purity in the blowdown stream from 60 to 80 %. In the case of dry CO2 mixtures, the enhancement is due to microwave heating of the 13X zeolite facilitated by the high cation density in the faujasite structure. In the case of water and CO2 desorption, the temperature rise of the adsorbent upon microwave heating was much lower than that predicted by simple heating suggesting that the microwave radiation is absorbed primarily by the adsorbed water. A simplified energy analysis suggests that brief exposure of an adsorbent to microwave radiation will raise the required vacuum level for regeneration of high humidity flue gas streams and may lead to an overall lower energy penalty. The selective ability of microwave radiation to target different species provides scope for optimized, compact, flue gas treatment systems.

A Water‐Soluble π‐Conjugated Polymer with up to 100 mg · mL−1 Solubility

AbstractA cationic water‐soluble polyfluorene (P2) containing a high density of tetraalkylammonium side chains in polymer backbone was synthesized and characterized. The polymer shows excellent water solubility up to 100 mg · mL−1 as well as high photoluminescence (PL) quantum yield of 44% in water. The relatively high cationic density and appropriate side chain length of the polymer are the key factors to achieve such high water solubility. The reduction potential of P2 is decreased as compared with its neutral polymer, reflecting the enhanced electron injection abilities. The standard NPB/Alq3 device using such a polymer as the electron injection layer shows nearly three‐fold enhancement in the electroluminescence (EL) efficiency.magnified image

Macromol. Rapid Commun. 16/2007

Cover: A cationic water‐soluble polyfluorene with excellent solubility and high PL quantum yield in water has been prepared. The high cationic density and appropriate side chain length of the polymer are the key factors to achieve such high water solubility. Further details can be found in the article by H. Wang, P. Lu, B. Wang, S. Qiu, M. Liu, M. Hanif, G. Cheng, S. Liu, and Y. Ma on page 1645.

Interaction of N 2, CO and NO with Cu-exchanged ETS-10: a compared FTIR study with other Cu-zeolites and with dispersed Cu 2O

After a brief overview of the reasons why, in spite of the high fraction of framework Ti(IV) atoms, Engelhard titanosilicate (ETS-10) cannot be used as competitive catalyst in partial oxidation reactions, we draw the attention on the fact that the high cation density of ETS-10 can be the key property for potential new catalytic applications of this recent material. Among all, cation exchange with Cu 2+ can yield to Cu-ETS-10, a promising material for environmental catalysis. We so present a detailed characterization of this material using N 2, CO and NO as probe molecules. In spite of the rather high complexity of the obtained spectra, a comparison with similar experiments (described in the literature or ad hoc performed for this work) on other Cu-exchanged zeolites and on Cu 2O dispersed on silica and on MCM-41, allows a full interpretation of the spectroscopic properties. It is shown that copper is present both as counterion and in the form of Cu 2O nanoclusters dispersed in the ETS-10 channels and in the external surface. Finally, IR spectroscopy has been used to demonstrate that Cu-ETS-10 is active in the decomposition of NO.

Adsorption heat of ammonia on natural clinoptilolite

1. The high cation density in the narrow cavities of clinoptilolite determines its high adsorption capacity with respect to small polar molecules. 2. The clinoptilolite structure has sites where strongly coordination-unsaturated exchange cations are localized. NH3 molecules react with such cations by the ion-dipole mechanism, with an energy of 23 kcal/ mole.