Protonated Amine Groups Research Articles

Synthesis of carbon disulfide modified chitosan resin and its adsorption properties for palladium(Ⅱ) in wastewater

A novel chitosan resin microsphere (CDCR) adsorbent, which was synthesized by secondary crosslinking and carbon disulfide modification, and was evaluated for its efficacy in recovering palladium from wastewater. The physicochemical properties and adsorption mechanism of CDCR were determined using scanning electron microscope energy dispersive system (SEM-EDS), fourier-transform infrared spectroscopy (FTIR), simultaneous thermal analyzer (TG-DSC), X-ray photoelectron spectroscopy (XPS), etc. The experimental results showed that its saturated adsorption capacity was about 204.34 mg/g. And the adsorption process of Pd(Ⅱ) was found to be in accordance with the pseudo-second-order kinetic model and the Freundlich model. Thermodynamic analysis indicated that the reaction between CDCR and Pd(Ⅱ) was a spontaneous endothermic process. CDCR showed good reusability, maintaining a Pd(Ⅱ) removal efficiency of 99.99% after eight adsorption–desorption cycles. In the multi-ion coexistence solution, CDCR also exhibited excellent selectivity towards Pd(Ⅱ) adsorption. Furthermore, the adsorption of Pd(Ⅱ) by CDCR was primarily attributed to electrostatic interaction with protonated amine groups and complexation with sulfur groups.

Efficient removal of anionic dye by protonated APTES modified hydrochar: The effect of cold‐activation

AbstractThe study focused on determining the effect of acidic and basic cold activation on hydrochar (HC) for the removal of methyl orange (MO). HC was prepared by hawthorn seeds (HS) under hydrothermal carbonization. HC was cold‐activated with HCl and NaOH, respectively, and they were grafted with aminopropyltriethoxysilane (APTES) and protonated to obtain AHC‐N+ (acid‐activated and modified HC) and BHC‐N+ (base‐activated and modified HC) to determine the effect of acidic and basic activation. They were characterized by elemental analysis, IR, thermal analysis, zeta potential, N2 adsorption–desorption measurements, and SEM–EDX analysis. The prepared adsorbents displayed MO adsorption due to abundant protonated amine groups. BHC‐N+ showed higher MO adsorption than AHC‐N+. The result showed that more protonated APTES groups grafted on the surface of HC via NaOH activation. The obtained data had a good fitting with the Langmuir isotherm and pseudo‐second‐order kinetic. The maximum adsorption capacity of BHC‐N+ was 250.38 mg g−1. The adsorption mechanism could be attributed to the electrostatic interactions between MO and protonated amine groups of APTES and hydrogen bonding.

Targeting of platinum capture under 1+1 aqua regia using robust and recyclable polymeric polyamine resin: Adsorption performance and mechanism

The targeted capture of platinum from complex and harsh acidic digests such as those platinum-containing secondary resources is essential from the perspectives of green development. Here, a polyamine chelating resin (CMPs-PEI) with excellent selectivity and acid resistance was prepared by a nucleophilic substitution reaction using chloromethylated polystyrene as the parent and polyethyleneimine as the modifier. The experimental results revealed that the adsorbent showed excellent adsorption effect on platinum under different acidities, and its maximum adsorption capacity was up to 337 mg/g at pH 2. More impressively, a rather high capacity of 162.41 mg/g was achieved in 1 + 1 aqua regia (pH −0.7), which was much higher than other adsorbent materials under the same conditions. In addition, the recovery of platinum by CMPs-PEI in practical platinum-containing iron concentrate abatement solution was 100 %. Mechanistic studies showed that the protonated amine groups on CMPs-PEI bound PtCl62− and partially reduced PtCl42− by electrostatic attraction. Meanwhile, the excellent regeneration performance of CMPs-PEI indicated that it showed great potential for green and economic recovery of precious metal ions.

Protonation of Strained Epoxy Resin under Wet Conditions via First-Principles Calculations Using the H+-Shift Method.

A significant challenge in adhesive bonding is the accelerated breaking of stretched adhesives under wet conditions, which is known as cohesive failure. One group of commonly used adhesives consists of the amine-cured epoxy resins. Based on deprotonation free-energy calculations of the unstrained resin in water, it has recently been proposed that these adhesives can undergo failure through breakage originating at the protonated amine group under neutral or acidic conditions [J. Phys. Chem. B 2021, 125, 8989-8996]. In this study, we comprehensively investigated the degree of protonation of the amine group under both stretched and compressed conditions by devising a robust first-principles protonation calculation method applicable to strained materials. It was found that the amine group was partially protonated in neutral water at 298 K and that the amine group was protonated when the epoxy resin was stretched to a greater extent in water, and vice versa. These findings support the physicochemical cause of cohesive failure due to protonation of the amine group in the stretched amine-cured epoxy resins.

Polyethyleneimine/polydopamine-functionalized self-floating microspheres for caramel adsorption: Interactions and phenomenological mass transfer kinetics

A polyethyleneimine/polydopamine-functionalized self-floating microsphere (EHGM/PDA/PEI) bears an etched hollow glass microsphere as a support, polydopamine as an interfacial cross-linking “glue”, and polyethyleneimine as a functional monomer was fabricated and used as a decolorization sorbent for sugarcane juice. The advantages of EHGM/PDA/PEI for sugarcane juice decolorization were attributed to its richness of target polyethyleneimine monomers, well-connected and abundant three-dimensional network-like aperture structure, and nontoxicity. Moreover, EHGM/PDA/PEI has excellent self-floating performance to allow separation from the adsorption system after decolorization and may have a faster separation speed and lower energy consumption than conventional solid–liquid separation methods. Synthetic caramels were used as model colorants of sugarcane juice to assess EHGM/PDA/PEI performance. The adsorption capacity of EHGM/PDA/PEI for caramels was 18.36 mg/g with a removal efficiency of 91.80% in the adsorption equilibrium state. The interaction mechanisms revealed that the caramel adsorption on EHGM/PDA/PEI was mostly mediated by protonated amine groups, followed by electron sharing. Two layers of caramels adhered onto EHGM/PDA/PEI were mainly mediated by electrovalent bonds between carboxylate and protonated amine. On average, one caramel molecule can be shared by 3–4 protonated amine groups of EHGM/PDA/PEI, which suggests a parallel sorption orientation. Four phenomenological mass transfer models [external diffusion resistance (EXTDR), internal diffusion resistance (INTDR), EXTDR–INTDR mixed, and adsorption onto active sites (AOAS)] proposed new and unique insights into the dynamic properties of the adsorption process.

Effective melanoidin adsorption of polyethyleneimine- functionalised molasses-based porous carbon: Adsorption behaviours and microscopic mechanisms

Sugar industry is an integral part of the food and agriculture sector of the national economy. Cane juice decolourisation is a crucial process in sugar production that directly impacts the final colour value of the sugar. However, the chemicals used in traditional methods may be harmful for food safety. Thus, advanced and effective alternatives methods should be developed to further address the problems on sugar production and quality. In this study, polyethyleneimine-functionalised molasses-based porous carbon (PMPC) was prepared from cane molasses, and was reversely applied to remove melanoidins from cane juice. The melanoidin removal efficiency by PMPC was 91.66% with the adsorption capacity of 550.00 mg/g in the adsorption equilibrium state. From the adsorption thermodynamics analysis, the adsorption process of melanoidins onto PMPC was spontaneous and endothermic. Analysis of the interaction mechanisms demonstrated that the successful adsorption of melanoidins by PMPC was mainly achieved through the electrostatic interations and other weak interactions (hydron-bond interaction), and a melanoidin molecule can be bonded with three to four protonated amine groups of PMPC. In addition, the mass transfer behaviour of the melanoidins adsorbed onto PMPC was determined using the mixed model of external and internal diffusion resistance, and the active-onto-site adsorption model. The results showed the melanoidins adsorbed by PMPC was a multilayer adsorption process dominated by chemisorption. Therefore, PMPC was proved to be an ideal adsorbent for cane juice decolourisation, with the advantages of green, high efficiency, and recyclability.

Improved Proton Adsorption and Charge Separation on Cadmium Sulfides for Photocatalytic Hydrogen Production

Cadmium sulfide has attracted wide attention in photocatalytic hydrogen production, due to its appropriate bandgap and band positions. However, high‐rate photogenerated electron–hole recombination and few active sites on CdS lead to its low photocatalytic activity. Herein, a PANI/NCPP/CdS (PANI/NiCoP/NiCoPi/CdS) hybrid as a noble metal‐free visible light‐driven photocatalyst is reported, with metal phosphides, metal phosphates, and polyaniline (PANI) as reduction and oxidation cocatalysts, respectively. This hybrid not only facilitates the charge separation and transfer owing to the formation of heterojunction, but also improves the local concentration of H+ on the surface of catalysts due to the formation of the protonated amine groups on PANI, beneficial to hydrogen evolution reaction. As a result, the as‐prepared photocatalyst could show a high hydrogen evolution rate of 170.3 mmol g−1 h−1 and an apparent quantum efficiency of 41.37% at 420 nm, representing one of the best performances of all‐CdS‐based photocatalysts.

Eco-friendly synthesis of durable aerogel composites from chitosan and pineapple leaf-based cellulose for Cr(VI) removal

Chromium (VI) oxyanion is one of the most toxic contaminants in water which causes cancer and genetic mutations in humans. In this work, the bio-based aerogels are successfully synthesized from pineapple leaves (PLs) and chitosan (CS) by an effective and eco-friendly method (including homogenizing, mixing, and freeze-drying) that is feasible for mass production to manage Cr(VI) pollution. The influences of different freezing approaches (refrigerator, isotropic and anisotropic freezing), solid concentrations, and weight ratios of cellulose to chitosan on the morphology, physical parameters, and Cr(VI) adsorption of the aerogels are comprehensively investigated. The fabricated aerogels are ultra-lightweight (20–30 mg/cm3), highly porous (above 97.5%), durable (Young’s modulus of 1.8–11.7 kPa), and strongly acid resistant (below 12% of weight loss at pH 3). The difference in pore size among freezing techniques is clarified by scanning electron microscopy, suggesting that anisotropic freezing is ineffective for non-nanoprecursors. The findings show the strong influence of chitosan content and pH of the medium on Cr(VI) adsorption of the PL/CS aerogels due to the electrostatic attraction between Cr(VI) oxyanions and protonated amine groups. The theoretical Langmuir maximum Cr(VI) uptake is up to 210.6–211.4 mg/g, which is generally comparable to carbon-based and costly metal-organic framework materials. The adsorption isotherm and kinetics of the samples are appropriate to the Langmuir model and the pseudo-second-order model, respectively. Furthermore, the Cr-absorption capacity retention rates of prepared aerogel are above 75% after 6 absorbing cycles by NaOH solution. Based on the results, the product cellulose/chitosan aerogel can be considered a potential adsorbent for Cr(VI) removal.

Surface modification of Cu nanoparticles coated commercial titanium in the presence of tryptophan: Comprehensive electrochemical and spectroscopic investigations

A combination of electrochemical and spectroscopic studies allows for understanding and describing the processes that occur on a nano-modified commercial pure Ti by Cu nanoparticles (CuNPs) in the presence and absence of tryptophan (Trp). The electrochemical results confirmed that the deposition of a thin CuNPs layer on the Ti substrate improves the corrosion resistance of the substrate under simulated physiological conditions. The addition of Trp to the corrosive environment accelerated the degradation of the CuNPs coating likely via the formation of a Cu-Trp complex. The degradation of the coating led to the formation of nano-galvanic sites at the substrate/ CuNPs coating interface, which in turn had a detrimental effect on the substrate and further increased the degradation of the coating. The conformational changes of Trp on the corroded CuNPs-Ti surface have been investigated by surface-enhanced vibrational techniques. Trp was adsorbed on the corroded CuNPs-Ti surface through the indole ring, which adopts a more/less horizontal orientation, and the protonated amine group in the presence of chloride and phosphate ions on the metallic surface. The application of a combination of infrared spectroscopy with atomic force microscopy (AFM-IR) proved that Trp covered the bimetal surface and caused the significant degradation of the surface.

Preparation of metal-organic framework composite beads for selective adsorption and separation of palladium: Properties, mechanism and practical application

Separation and recovery of palladium from industrial waste is an environmental way to utilize the valuable secondary resources. Metal-organic framework (MOF) has a great potential for the adsorption of Pd(Ⅱ) from aqueous solutions, but the tiny powder form of MOF restricts its practical applications. In this work, a feasible and green method is developed to prepare novel MOF composite beads (B-MOF) with a stable cross-linked network. The adsorption performance of B-MOF for Pd(Ⅱ) was evaluated in acidic solutions. Comprehensive characterization results show that the structure of B-MOF is stable throughout the adsorption process. At pH 3.0, the adsorption capacity of Pd(Ⅱ) on B-MOF was high up to 334.68 mg.g−1, exhibiting superiority to most of the other congeneric adsorbents. The adsorption behavior accorded with the pseudo-second-order kinetic model and the Langmuir adsorption isotherm, which was a spontaneous and endothermic chemisorption process. Moreover, the adsorption performance of B-MOF persisted almost unchanged even after 12 regeneration cycles. B-MOF also demonstrated high selectivity to Pd(Ⅱ) in the presence of interfering ions, including Na(Ⅰ), K(Ⅰ), Ni(Ⅱ), Mg(Ⅱ), Cu(Ⅱ), Zn(Ⅱ), Co(Ⅱ), Ca(Ⅱ) and Al(III). Mechanism studies reveal that Pd(Ⅱ) can be adsorbed on B-MOF by the inner-sphere complexation to Zr-nodes and the electrostatic attraction with protonated amine groups. The recovery of Pd from a real industrial waste was successfully achieved with a recovery rate of 92.5 %. This study provides an effective method to improve the practicability of MOF-based materials and may open a new way for the disposal of industrial waste containing palladium.

Congo red removal by lanthanum-doped bismuth ferrite nanostructures

Phase-pure lanthanum (La)-doped bismuth ferrite (La–BFO) nanostructures with La contents of 0–15% were synthesised by a wet chemical method. The structural, morphological, elemental, and optical characteristics confirmed the phase purity and granular morphology of synthesised La–BFO. Zeta potential indicated a significant increase of surface charge of La–BFO with increasing doping content. The La–BFO nanostructures were used for adsorption of anionic Congo red (CR) from aqueous solution under different physio-chemical conditions. A removal efficiency of 95% was achieved in 135 min. The experimental results suggested that the increasing doping concentration of La increased the adsorption capacity and removal efficiency due to an electrostatic interaction between negatively-charged La–BFO nanostructures and the protonated amine group of CR. The adsorption capacity was strongly influenced by the initial pH of the CR solution.

Impact of Low-Pressure Plasma Treatment of Wool Fabric for Dyeing with PEDOT: PSS.

This study presents the effect of non-thermal plasma modification on the changes of surface morphology, color characteristics and electrical conductivity of wool fabric dyed with intrinsically conductive polymer (ICP) poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS). The wool fabric was treated with an aqueous dispersion of PEDOT: PSS, Clevios F ET, providing electrically conductive properties to textiles. The wool fabric, containing basic groups of amines (NH2), was pre-activated with low-pressure plasma of non-polymer forming nitrogen (N2) gas before exhaust dyeing with PEDOT: PSS at 90 °C was applied. This treatment imparted hydrophilicity, reduced felting, increased adhesion, improved dye ability and ensured that more PEDOT: PSS negatively charged sulfonate counter ions would be electrostatically bounded with the cationic protonated amine groups of the wool fiber. Initially, before (N2) plasma treatment and after fabrics were evaluated according to the test method for aqueous liquid repellency, the surface morphology of the plasma-modified and -unmodified wool dyed fabric was observed with scanning electron microscopy (SEM). The functional groups introduced onto the surface after N2 gas plasma treatment of wool fabric were characterized by X-ray photoelectron and FTIR-ATR spectroscopy. The results of color difference measurements show that N2 gas plasma treatments provide more intense color on Clevios F ET dyed wool fabric and retain its electrical conductivity.

Magnetically responsive chitosan-based nanoparticles for remediation of anionic dyes: Adsorption and magnetically triggered desorption

Chitosan-based nanoparticles (PGMA/mCHT) were prepared for the adsorption of anionic Reactive Red 120 (RR120) and Indigo Carmine (IC). The morphology and characteristics were clarified by using SEM-EDX, XRD, VSM, and FTIR. The adsorption of RR120 and IC on PGMA/mCHT was carried out in a batch process to determine the influence of initial dye concentration (5–600 mg/L), initial pH (3–9), temperature (5, 25, 35, and 45 °C) and contact time. Under acidic conditions, higher adsorption efficiencies of the PGMA/mCHT nanoparticles due to intermolecular interactions of dye molecules between the protonated amine groups and the sulfonyl groups. Bi-solute adsorption was also investigated revealing between dye molecules has no competitive effect at the same initial concentration. The kinetic results of RR120 and IC adsorption onto PGMA/mCHT nanoparticles fit well to the pseudo-second-order model. The desorption of dye molecules from PGMA/mCHT nanoparticles was also studied using an alternating magnetic field which is caused the superior desorption behavior demonstrating the magnetic nanoparticles can be acted as a nanoheater.

Evaluation of Speek |Chitosan As a Proton Exchange Membrane in Electrochemical Hydrogen Pumping

In recent years, climate change has become more evident, requiring the use of renewable energy sources. In this context, energy conversion advanced technologies demand greater attention of the scientific and industrial community for the transition to the so-called "Global Hydrogen Economy" based on the hypothesis that hydrogen can play a role as an energy carrier [1] due its high energy content per unit weight.Proton Exchange Membrane Technology (PEM-Technology) responds to different industrial issues through different systems such as PEM-Electrolyser to produce hydrogen [2] or Electrochemical Hydrogen Pumping / Compression (EHP / EHC) to purify or compress hydrogen to finally distribute it [3–5].In our previously reported works, we prepared SPEEK-Chitosan blends, and we demonstrate with physicochemical characterization (SEM-EDS, TGA-DSC, Water Uptake, Proton Conductivity, etc.). This time we evaluated the best membrane blend S-CS 10%(SPEEK with a 80% of sulfonation degree and 10% of chitosan) in chronopotentiometry at different current density. The S-CS 10% membrane was compared with pristine SPEEK and Nafion115. Our membrane blend exhibited low cell voltage at high current density.In the Figure 1, results obtained via chronopotentiometry are shown for three different membranes for a continuous operating time of t = 1 h at T = 37.5 ° C and 100% RH. From this graph, the Nafion 115 membrane, when demanding a current density of j=1 A cm-2 loses stability and is not able to cover the demanded current; however, it shows some stability when the current demand decreases (j= 0.8 A cm-2). On the other hand, SPEEK and SQ 10% synthesized membranes present a better stability with demanding currents up to j=1 A cm-2 and j=1.3 A cm-2, respectively. The better performance of S-CS 10% is probably due to as there are sulfonic groups interacting with the protonated amine group, a Zwitterion effect is created, causing the water molecules to remain strongly trapped in the membrane by an electrostatic effect, preventing the membrane from dehydrating when working at higher current densities and therefore it consumes less energy [6]. Figure 1

Surface adsorption and survival of SARS-CoV-2 on frozen meat

The first case of a severe acute respiratory syndrome caused by coronavirus-2 was reported in December 2019 in China. The disease spread globally quickly, causing the 2019–2021 COVID-19 pandemic. The meat industry became concerned over the possibility of transmitting the virus in the slaughterhouse environment. The level of air exchange strongly affects the distribution of SARS-CoV-2 aerosols within the slaughterhouses. The adsorption of the SARS-CoV-2 virus on the surface of the frozen meat is dictated mainly by the interplay of electrostatic forces between the virion and tissue (pH) and environmental conditions (temperature and humidity) in the vicinity of adsorption micro-location. Suppose the virus contaminates the meat surface, whereby pH is 5.5 or less. In that case, it firmly adsorbs due to bonds established by protonated amine group and a hydrogen bond between the COOH group of the viral protein and oxygen in hydroxyl groups present on meat surfaces. The meat surface, coated with a thin water film, interacts with the SARS-CoV-2 virions by establishing strong hydrogen bonds. Although there is no proof of COVID-19 contraction by food consumption, the strong surface adsorption and ability of SARS-CoV-2 to survive meat freezing indicate a potential risk of virus transmission by meat.

Development of a chemosensor probe based on functionalised poly[β-(1→4)-2-amino-2-deoxy-D-glucopyranose]-cobalt nanoparticles for the selective detection of flunitrazepam

ABSTRACT Flunitrazepam abuse as ‘date-rape’ drug is on the increase. A colorimetric probe was developed by grafting cobalt nanoparticles (CoNPs) onto poly[β-(1→4)-2-amino-2-deoxy-D-glucopyranose] functionalized thymol blue (CFTB) backbone for the detection of flunitrazepam drug in human urine (ex-situ). Studies revealed an interaction between CFTB and Co with the formation of a five-membered ring chelated compound (FTIR), while high thermal stability properties were displayed by CFTB-CoNPs without any change in the composition of the material (TGA). The distribution of CoNPs showed an irregular spherical pore deposited on the surface of CFTB (SEM) in the dimension of 100 nm (TEM). The interaction between the CFTB-CoNPs probe and the flunitrazepam was due to ionic bonding between the protonated amine group in the biopolymer and the fluoro group of flunitrazepam. The highly selective and sensitive CFTB-CoNPs probe was able to detect at 1.00µg/L with an instant and distinct colour change from wine to orange.

Spectroscopic Investigations of 316L Stainless Steel under Simulated Inflammatory Conditions for Implant Applications: The Effect of Tryptophan as Corrosion Inhibitor/Hydrophobicity Marker

In this paper, the conformational changes of tryptophan (Trp) on the corroded 316 L stainless steel (SS) surface obtained under controlled simulated inflammatory conditions have been studied by Raman (RS) and Fourier-transform infrared (FT-IR) spectroscopy methods. The corrosion behavior and protective efficiency of the investigated samples were performed using the potentiodynamic polarization (PDP) technique in phosphate-buffered saline (PBS) solution acidified to pH 3.0 at 37 °C in the presence and absence of 10−2 M Trp, with different immersion times (2 h and 24 h). The amino acid is adsorbed onto the corroded SS surface mainly through the lone electron pair of the nitrogen atom of the indole ring, which adopts a more/less tilted orientation, and the protonated amine group. The visible differences in the intensity of the Fermi doublet upon adsorption of Trp onto the corroded SS surface, which is a sensitive marker of the local environment, suggested that a stronger hydrophobic environment is observed. This may result in an improvement of the corrosion resistance, after 2 h than 24 h of exposure time. The electrochemical results confirm this statement—the inhibition efficiency of Trp, acting as a mixed-type inhibitor, is made drastically higher after a short period of immersion.

Investigating how amine structure influences drug-amine ion-pair formation and uptake via the polyamine transporter in A549 lung cells

Transiently associating amines with therapeutic agents through the formation of ion-pairs has been established both in vitro and in vivo as an effective means to systemically direct drug delivery to the lung via the polyamine transport system (PTS). However, there remains a need to better understand the structural traits required for effective PTS uptake of drug ion-pairs. This study aimed to use a structurally related series of amine counterions to investigate how they influenced the stability of theophylline ion-pairs and their active uptake in A549 cells. Using ethylamine (mono-amine), ethylenediamine (di-amine), spermidine (tri-amine) and spermine (tetra-amine) as counterions the ion-pair affinity was shown to increase as the number of protonated amine groups in the counterion structure increased. The mono and diamines generated a single hydrogen bond and the weakest ion-pair affinities (pKFTIR: 1.32 ± 0.04 and 1.43 ± 0.02) whereas the polyamines produced two hydrogen bonds and thus the strongest ion-pair affinities (pKFTIR: 1.93 ± 0.05 and 1.96 ± 0.04). In A549 cells depleted of endogenous polyamines using α-difluoromethylornithine (DFMO), the spermine-theophylline uptake was significantly increased (p < 0.05) compared to non-amine depleted cells and this evidenced the active PTS sequestering of the ion-pair. The mono-amine and di-amine failed to enhance theophylline uptake in these A549 cells, but the tri-amine and tetra-amine both almost doubled the theophylline uptake into the cells when compared to the uptake of free drug. As the data indicated that polyamines with at least 3 amines were required to form ion-pairs that could enhance A549 cell uptake, it suggested that at least two amines were required to physically stabilise the ion-pair and one to interact with the PTS.

Complexes of Bifunctional DO3A-N-(α-amino)propinate Ligands with Mg(II), Ca(II), Cu(II), Zn(II), and Lanthanide(III) Ions: Thermodynamic Stability, Formation and Dissociation Kinetics, and Solution Dynamic NMR Studies.

The thermodynamic, kinetic, and structural properties of Ln3+ complexes with the bifunctional DO3A-ACE4− ligand and its amide derivative DO3A-BACE4− (modelling the case where DO3A-ACE4− ligand binds to vector molecules) have been studied in order to confirm the usefulness of the corresponding Gd3+ complexes as relaxation labels of targeted MRI contrast agents. The stability constants of the Mg2+ and Ca2+ complexes of DO3A-ACE4− and DO3A-BACE4− complexes are lower than for DOTA4− and DO3A3−, while the Zn2+ and Cu2+ complexes have similar and higher stability than for DOTA4− and DO3A3− complexes. The stability constants of the Ln(DO3A-BACE)− complexes increase from Ce3+ to Gd3+ but remain practically constant for the late Ln3+ ions (represented by Yb3+). The stability constants of the Ln(DO3A-ACE)4− and Ln(DO3A-BACE)4− complexes are several orders of magnitude lower than those of the corresponding DOTA4− and DO3A3− complexes. The formation rate of Eu(DO3A-ACE)− is one order of magnitude slower than for Eu(DOTA)−, due to the presence of the protonated amine group, which destabilizes the protonated intermediate complex. This protonated group causes the Ln(DO3A-ACE)− complexes to dissociate several orders of magnitude faster than Ln(DOTA)− and its absence in the Ln(DO3A-BACE)− complexes results in inertness similar to Ln(DOTA)− (as judged by the rate constants of acid assisted dissociation). The 1H NMR spectra of the diamagnetic Y(DO3A-ACE)− and Y(DO3A-BACE)− reflect the slow dynamics at low temperatures of the intramolecular isomerization process between the SA pair of enantiomers, R-Λ(λλλλ) and S-Δ(δδδδ). The conformation of the Cα-substituted pendant arm is different in the two complexes, where the bulky substituent is further away from the macrocyclic ring in Y(DO3A-BACE)− than the amino group in Y(DO3A-ACE)− to minimize steric hindrance. The temperature dependence of the spectra reflects slower ring motions than pendant arms rearrangements in both complexes. Although losing some thermodynamic stability relative to Gd(DOTA)−, Gd(DO3A-BACE)− is still quite inert, indicating the usefulness of the bifunctional DO3A-ACE4− in the design of GBCAs and Ln3+-based tags for protein structural NMR analysis.

54 cm2 Large-Area Flexible Organic Solar Modules with Efficiency Above 13.

Development of large-area flexible organic solar cells (OSCs) is highly desirable for their practical applications. However, the efficiency of the large-area flexible OSCs severely lags behind small-area devices. Here, efficient large-area flexible single cells with power conversion efficiency (PCE) of 13.1% and 12.6% for areas of 6 and 10 cm2 , and flexible modules with a PCE of 13.2% (54 cm2 ) based on poly(ethylene terephthalate)/Ag grid/silver nanowires (AgNWs):zinc-chelated polyethylenimine (PEI-Zn) composite electrodes are reported. The solution-processed flexible transparent electrode of AgNWs:PEI-Zn shows low surface roughness and good optoelectronic and mechanical properties. PEI-Zn is conductive and optically transparent. It can adhere to and wrap the AgNWs under electrostatic interaction between the negatively charged surface (AgNWs) and positively charged protonated amine groups (in PEI-Zn). It wraps the AgNWs networks and fills the void space to achieve a smooth surface. The flexible electrode is validated in both flexible OSCs and flexible quantum-dots light-emitting diodes (QLEDs). Small-area flexible OSCs show a PCE of 16.1%, and flexible QLEDs show an external quantum efficiency of 13.3%. In the end, a flexible module is demonstrated to charge a mobile phone as a flexible power source (shown in Video S1, Supporting Information).