Number Of Sulfonic Acid Groups Research Articles

Complex extraction of sulfonate dyes from wastewater and the effect of dye structure on extraction performance

ABSTRACT In this study, the influences of sulfonate dye structure on the extraction rate, the reaction mechanism, and the complex ratio were studied. The parent structure and the number of sulfonic acid groups of sulfonate dyes have a great effect on extraction performance, whilst the molecular weight has a small effect on extraction performance. The results indicate that the extraction rate of azo dyes remains above 80% at the aqueous-organic phase ratio of 7:1, but the extraction rate of two anthraquinone dyes decreases to 54.9% and 34.9%, respectively; and the fewer the number of sulfonic acid groups of the dye, the better the extraction performance under the condition of insufficient extractant, the extraction rate of Direct Grey D and Acid Red M is over 82%. A complete set of methods for determining the ratio of the extractant and the dye was determined using the distribution coefficient method. The interaction between Telon Yellow 4 R and trioctylamine is ionic association and hydrogen bonding association, and the complex ratio between the dye and the extractant is about 2:1. In summary, dye structure has a big impact on the extraction performance, which should be taken into account in actual application.

Novel sulfonated rGOHfO2/PVDF hybrid nanocomposite ultrafiltration membrane towards direct potable reuse water production

Using wastewater to produce safe and reliable reclamation water is a sustainable means of reducing water scarcity. Membrane technology can be a viable path for producing advanced treated water from wastewater. Numerous three-dimensional metal oxide nanoparticles with graphene oxide (GO) have been evaluated in membrane fabrication. On the other hand, there are no reports on the use of GO combined with hafnium oxide (HfO2) for the fabrication of ultrafiltration (UF) membranes to produce direct potable reuse (DPR) water. In this study, rGOHfO2 (reduced GOHfO2) was synthesized using a microwave method. A novel sulfonated rGOHfO2 (SrGOHfO2) nanocomposite was fabricated and added to the polyvinylidene fluoride (PVDF) to develop advanced nanohybrid UF membranes toward the production of DPR water and improve dispersibility and hydrophilicity. The incorporation of SrGOHfO2 into PVDF membranes had very positive effects on hydrophilicity, MWCO, and morphology. The P-SGOHf-2 membrane (0.2 wt % SrGOHfO2) exhibited excellent pure water flux of approximately 301 ± 3% and 133.3 ± 2% than PVDF and P-GOHf membrane, respectively. The P-SGOHf-2 membrane showed high separation efficiency up to 94 ± 1% and 98 ± 04% towards humic acid (HA) and bovine serum albumin (BSA), respectively. The superior antifouling properties were observed in the SrGOHfO2 incorporated membranes compared to the P-GOHf and PVDF membranes, with a 2.9% irreversible fouling ratio (Rir) and a 97.1% flux recovery ratio (FRR) for the P-SGOHf-2 membrane. The excellent performance of the P-SGOHf-2 membrane was attributed to the larger number of sulfonic acid groups (-SO3H) in the SrGOHfO2 nanocomposite. In the tertiary UF membrane filtration mode operation using the secondary effluent of the field-scale wastewater treatment plant, the P-SGOHf-2 membrane performed high flux with reliable effluent quality (154 ± 5L m−2 h−1, 0.26 ± 0.03 NTU, no pathogens), while it exhibited lower membrane resistances during filtration. These advanced nanohybrid membranes can be a sustainable, viable alternative technology compared to the traditional tertiary treatment processes that utilize expensive and complex multi-step processes to produce DPR water.

Mesoscale Simulation Based on the Dynamic Mean-Field Density Functional Method on Block-Copolymeric Ionomers for Polymer Electrolyte Membranes.

Block copolymers generally have peculiar morphological characteristics, such as strong phase separation. They have been actively applied to polymer electrolyte membranes for proton exchange membrane fuel cells (PEMFCs) to obtain well-defined hydrophilic regions and water channels as a proton pathway. Although molecular simulation tools are advantageous to investigate the mechanism of water channel formation based on the chemical structure and property relationships, classical molecular dynamics simulation has limitations regarding the model size and time scale, and these issues need to be addressed. In this study, we investigated the morphology of sulfonated block copolymers synthesized for PEM applications using a mesoscale simulation based on the dynamic mean-field density functional method, widely applied to investigate macroscopic systems such as polymer blends, micelles, and multi-block/grafting copolymers. Despite the similar solubility parameters of the monomers in our block-copolymer models, very different morphologies in our 3D mesoscale models were obtained. The model with sulfonated monomers, in which the number of sulfonic acid groups is twice that of the other model, showed better phase separation and water channel formation, despite the short length of its hydrophilic block. In conclusion, this unexpected behavior indicates that the role of water molecules is important in making PEM mesoscale models well-equilibrated in the mesoscale simulation, which results in the strong phase separation between hydrophilic and hydrophobic regions and the ensuing well-defined water channel. PEM synthesis supports the conclusion that using the sulfonated monomers with a high sulfonation degree (32.5 mS/cm) will be more effective than using the long hydrophilic block with a low sulfonation degree (25.2 mS/cm).

A Maximization of the Proton Conductivity of Sulfonated Poly(Ether Ether Ketone) with Grafted Segments Containing Multiple, Flexible Propanesulfonic Acid Groups.

To enhance the proton conductivity of sulfonated poly(ether ether ketone) (SPEEK), proton-conducting groups are required to be covalently connected to SPEEK and form proton-conducting channels. Herein, SPEEK fully grafted with segments containing multiple, flexible propanesulfonic acid groups (MS-SPEEK-102) is successfully prepared. Compared with SPEEK, MS-SPEEK-102 exhibits a higher proton conductivity of 8.3×10-2 Scm-1 at 80°C with 98% relative humidity, and consequently a greater power density of 0.530Wcm-2 at60°C. These can be ascribed to the increased number of sulfonic acid groups, and ample, uninterrupted proton-conducting channels constructed by the movement of the maximum content, flexible side-chain segments. This approach offers an idea for obtaining a proton exchange membrane with good proton conductivity based on SPEEK.

A novel strategy toward the advancement of proton exchange membranes through the incorporation of propylsulfonic acid-functionalized graphene oxide in crosslinked acid-base polymer blends

Propylsulfonic acid-functionalized graphene oxide (PrSGO) was introduced into the sulfonated poly(ether ether ketone) (SPEEK)-sulfonated poly(benzimidazole) (SPBI) blend in this study to understand the impact on glass transition temperature (Tg), structural properties, increase mechanical properties, proton conductivity, and single-cell performance. At different loadings of PrSGO, atomistic molecular dynamics (MD) simulations of SPEEK/SPBI, cross-linked SPEEK/SPBI (XSPEEK/SPBI), and XSPEEK/SPBI/PrSGO composite systems were performed. Tg was increased after cross-linking the polymer systems and increasing the loading percent of PrSGO filler and SPBI in the polymer systems. The mechanical properties, chemical and thermal stability of the XSPEEK/SPBI/PrSGO nanocomposite membranes significantly increased PrSGO loading because of the strong interfacial interaction between PrSGO and the XSPEEK/SPBI matrix. XSPEEK/SPBI/PrSGO nanocomposite membrane at 4 wt % PrSGO loading demonstrated a considerable improvement in proton conductivity up to 0.17 S/cm at 100% relative humidity (RH) at 90 °C. Furthermore, the XSPEEK/SPBI/PrSGO nanocomposite membrane at 4 wt% PrSGO loading demonstrated good fuel cell (FC) performance with a maximum power density of ∼0.82 W/cm2 at 100% RH, 80 °C. Incorporating PrSGO nanofillers in the polymer matrix considerably improved proton conductivity of the membranes, other significant properties, and overall FC performance due to their hygroscopic nature, a higher number of sulfonic acid groups, and excellent interaction of the acid functionalized fillers with the cross-linked SPEEK/SPBI-based matrix.

Poly(aryl ether ketone) membrane with controllable degree of sulfonation for organic solvent nanofiltration

The separation of organic solvents can be improved in a sustainable way by implementing membranes produced via streamlined processing. However, conventional membranes are not typically used in organic solvents, and thus require further chemical cross-linking before use. This process is complicated, and cross-linking agents are harmful to the environment. This study investigated the synthesis of a sulfonated poly(aryl ether ketone) (SPAEK) copolymer with a controlled degree of sulfonation via molecular design as a novel nanofiltration membrane in organic solvent. The introduction of a suitable number of sulfonic acid groups improved the hydrophilicity and surface charge of the membrane compared to conventional poly(aryl ether ketone) (PAEK), leading to excellent performance in separating alcoholic solvents and negatively charged dyes. The membrane still exhibited good separation performance, and no obvious damage to its microstructure was found by FESEM after the membrane was soaked in N,N-dimethylformamide (DMF) for 7 days. Consequently, the ethanol permeance and dye rejection of the membrane was maintained. PEK-SPEDEK membrane has potential applications in OSN under complex and harsh conditions such as printing, dyeing and pharmaceuticals.

Preparation of Functionalized Carbon-Coated Cobalt Nanoparticles with Sulfonated Arene Derivatives, a Study on Surface Functionalization and Stability.

The functionalization of magnetic nanoparticles has been an important field in the last decade due to the versatile applications in catalysis and biomedicine. Generally, a high degree of functionalities on the surface of the nanoparticles is desired. In this study, covalent functionalization of various aromatic sulfonic acids on carbon-coated cobalt nanoparticles are investigated on surface functionalization yield and stability. The nanoparticles are prepared via covalent linkage of an in situ generated diazonium on the graphene-like surface. Adsorption and wash experiments were performed to confirm a covalent bonding of the naphthalene derivatives on the nanoparticle surface. With an increased number of sulfonic acid groups on the aromatic compound a significantly lower loading is observed on the corresponding functionalized nanoparticles. This can be counteracted by a change of nitrite species. With this method, nanoparticles with a high number of sulfonic acid groups can be produced.

Mechanical Properties and Chemical Durability of Nafion/Sulfonated Graphene Oxide/Cerium Oxide Composite Membranes for Fuel-Cell Applications.

To improve both the mechanical and chemical durability of Nafion membranes for polymer electrolyte membrane fuel-cells (PEMFCs), Nafion composite membranes containing sulfonated graphene oxide (SGO) and cerium oxide (CeO2; ceria) were prepared by solution casting. The structure and chemical composition of SGO were investigated by FT-IR and XPS. The effect of the sulfonation, addition of SGO and ceria on the mechanical properties, proton conductivity, and chemical stability were evaluated. The addition of SGO gave rise to an increase in the number of sulfonic acid groups in Nafion, resulting in a higher tensile strength and proton conductivity compared to that of graphene oxide (GO). Although the addition of ceria was found to decrease the tensile strength and proton conductivity, Nafion/SGO/ceria composite membranes exhibited a higher tensile strength and proton conductivity than recast Nafion. Measurement of the weight loss and SEM observations of the composite membranes after immersing in Fenton’s reagent indicate an excellent radical scavenging ability of ceria under radical degradation conditions.

Fracture Behavior of Solid Polymer Electrolyte Membranes with Different Ion Exchange Capacity for Fuel Cell

INTRODUCTION: Fuel cells are known as one of power generation technologies with high efficiency, and are anticipated to be ecological and renewable energy. Polymer electrolyte membrane (PEM) fuel cells have excellent features including compact size and lightweight. Therefore, these are expected to be used in automotive and electric portable applications. PEMs are utilized as an ion conductive material between electrodes in the fuel cell. Perfluorosulfonic acid polymer is widely used as the electrolyte membrane because of its high proton conductivity. However, the major problem of PEMs is the mechanical degradation of the membrane. In this study, toughness properties were investigated to clarify the mechanical fracture behaviour of PEM. EXPERIMENTIAL: Flemion® CSH25 (Asahi Glass Co., Ltd) consisting of tetrafluoroethylene main chain and sulfonic acid group in the side chain was used. It exhibits good proton conductivity by dissociating protons from the side chain moiety. Three types of samples with different ion exchange capacity (IEC) were selected. The IEC is determined by the number of sulfonic acid groups which is one of the factors that greatly affect power generation efficiency of a fuel cell. These samples were prepared by casting method. Therefore, any residual strains were not observed in the optical strain gauge. Uniaxial tensile tests (Imoto Machinery Co., Ltd.) with dumbbell shape samples (JISK-6251-7) were performed at a stroke length of 15 mm, a temperature of 25.0 ± 1.0 °C, a test speed of 60 mm/ min, ambient conditions of 23 ± 1 °C, and 45 ± 5% RH. The essential work of fracture (EWF) was calculated from the load-displacement curve of the uniaxial tensile test result to evaluate fracture toughness. Double notches were applied to specimens at both ends of test pieces on parallel portions. A test speed of 5 mm/min and the ambient conditions were maintained the same as above tests. RESULTS AND DISCUSSION: Nominal stress-strain curves in uniaxial tensile tests were shown in Fig.1. With increasing the IEC, elastic modulus and yield stress of the samples were increased. Fig.2 show the results of EVF evaluation. The IEC 1.10 (the lowest IEC) showed the highest EWF (15.2 KJ / m2) compared with IEC 1.25 and IEC 1.43. In the uniaxial tensile test results without double notch, larger IEC showed higher mechanical properties, but it is opposite to the results of EWF. Figure 1

Studies of sulfonated poly(phenylene)-block-poly(ethersulfone) for proton exchange membrane fuel cell

The polymers were prepared by nickel catalyzed carbon–carbon coupling reaction of 1,4-dichloro-2,5-dibenzoylbenzene (DCDBB) and sulfone oligomer. DCDBB was synthesized from oxidation reaction of 2,5-dichloro-p-xylene and followed by Friedel–Craft reaction with benzene. DCDBB monomer had good reactivity in polymerization by electron withdrawing group as benzophenone. Sulfone group of oligomer had improving flexibility and solubility. Post sulfonation was carried out to add sulfonic acid groups by using chlorosulfuric acid. These polymers were presumably stable against nucleophilic attack by hydrogen peroxide, hydroxide anion, and radical generated by proton exchange membrane fuel cell operation system. The number of sulfonic acid groups were controlled by varying the mole ratio of 1,4-dichloro-2,5-dibenzoylbenzene in synthesized polymer. A series of membranes were studied by 1H NMR spectroscopy, thermo-gravimetric analysis, ion exchange capacity, water uptake, and proton conductivity. Also surface morphologies were assessed by atomic force microscope (AFM).

Novel polymeric humidity sensors based on sulfonated poly (ether ether ketone)s: Influence of sulfonation degree on sensing properties

Sulfonated poly (ether ether ketone)s (SPEEKs) with different values of sulfonation degree were successfully synthesized by a direct aromatic nucleophilic substitution polymerization of sulfonated monomers. By the direct-synthesis method, the number of sulfonic acid groups can be precisely controlled. They were then fabricated by spin coating on a ceramic substrate to be used as a novel polymeric humidity sensor. The morphology of the ionic polymers especially the microstructure of ionic clusters, water sorption and the complex impedance spectra of the sensors were investigated to explain the humidity sensing characteristics and the sensing mechanism under different relative humidity. In addition, SPEEK-6 polymer with sulfonation degree (Ds=1.18) was chosen as the optimal humidity sensing materials, which possessed high sensitivity and satisfactory linearity ranging from 11% RH to 97% RH. Furthermore, it exhibited a small hysteresis (less than 3% RH) during the sorption processes, an acceptable response/recovery time (100s response and 105s of recovery time) and an excellent repeatability. These results indicated SPEEKs could be promising for applications in humidity sensor.

Mild surface modification of para-aramid fiber by dilute sulfuric acid under microwave irradiation

In aramid fiber-reinforced composites manufacturing, para-aramid fiber requires surface modification to improve its interfacial adhesion with matrix materials. In this study, aramid fiber was modified with dilute sulfuric acid, which was gradually concentrated under microwave irradiation. Results showed that the aramid fiber could be efficiently modified. Sulfonic acid groups were introduced on the surface of the aramid fiber, as confirmed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The breaking strength and thermal stability of the modified aramid fiber were not adversely affected. When the concentration of sulfuric acid was 30.0 g/L, the breaking strength of the aramid fiber remained at 90.7% of the original value, and the number of sulfonic acid groups of 1 g modified aramid fibers was 1.38 × 10–5 mol/g. Thermogravimetric and X-ray diffraction analyses showed that the main structure of the aramid fibers was not affected. The aramid fiber surface was not severely etched, as evidenced by scanning electron microscopy images. Therefore, this modifying method involving a gradual change in sulfuric acid concentration may be widely applied in many fields.

Removal of Cd(II) by poly(styrenesulfonic acid)-impregnated alginate capsule

In this study, a capsule type sorbent of poly(styrenesulfonic acid)-impregnated alginate capsule (PSSA-AC) was developed by using a simple and moderate method. PSSA was used as a model encapsulated material because of its large number of sulfonic acid groups which have high affinity toward Cd(II). PSSA-AC was prepared by dropping solution A (mixture of 10% (w/v) PSSA + 1% CaCl2) into B solution (0.6% (w/v) sodium alginate). Microscope images revealed that PSSA was well encapsulated inside of the alginate shell. The pH edge experiment indicated that Cd(II) sorption was influenced marginally by the experimental pH range. The maximum Cd(II) uptake by PSSA-AC was as high as 184.12 ± 6.30 mg/g. The kinetic and FTIR studies demonstrated that ion-exchange was the main sorption mechanism. The PSSA-AC could be regenerated by using 2% CaCl2 as a desorbing agent.

Using a Macroporous Silver Shell to Coat Sulfonic Acid Group-Functionalized Silica Spheres and Their Applications in Catalysis and Surface-Enhanced Raman Scattering.

In this paper, novel organic sulfonic acid group-functionalized silica spheres (SiO2-SO3H) were chosen as a template for fabricating core-shell SiO2-SO3H@Ag composite spheres by the seed-mediated growth method. The SiO2-SO3H spheres could be obtained easily by oxidation of the thiol group-terminated silica spheres (SiO2-SH) with H2O2. Due to the presence of sulfonic acid groups, the [Ag(NH3)2](+) ions were captured on the surface of the silica spheres, followed by in-site reduction to silver nanoseeds for further growth of the silver shell. By this strategy, the complete silver shell could be obtained, and the surface morphologies and structures of the silver shell could be controlled by adjusting the number of sulfonic acid groups on the silica spheres. A large number of sulfonic acid groups on the SiO2-SO3H spheres favored the formation of the macroporous silver shell, which was unique and exhibited good catalytic performance and a high surface-enhanced Raman scattering (SERS) enhancement ability.

Kinetic Study of Acetic Acid Esterification with Methanol Catalyzed by Gel and Macroporous Resins

The liquid-phase acetic acid esterification kinetics with methanol to methyl acetate and water catalyzed by gel (Lewatit K1221) and macroporous (Lewatit K2629) ion exchange resins have been investigated and compared with literature reported data acquired on Amberlyst 15. The effects of the resin swelling, the initial molar methanol to acetic acid ratio (1:1 – 10:1) and the temperature (303 – 333 K) on the reaction kinetics were investigated. The gel type resin exhibits a remarkably higher catalytic activity compared to the macroporous resins, despite its similar number of sulfonic acid groups. This can be attributed to the differences in active site accessibility during reaction and, hence, in resin swelling, especially when it is in contact with polar components, such as water and methanol. The differences in catalytic behavior between the considered resins have been assessed using an exchange based Eley-Rideal model in which it is assumed that (1) all the active sites are occupied, (2) the acid undergoes a proton exchange with the protonated methanol and (3) the reaction occurs according to an Eley-Rideal mechanism with the surface reaction between protonated acetic acid and methanol from the bulk as ratedetermining step. This model, which implicitly accounts for resin swelling, could describe the observed differences between the various resins. The activation energy was determined at 47 kJ mol−1, irrespective of the resin used.

Research the Several Organic Inhibitors Influence on Jamesonite and Marmatite

The study of flotation separation on two different mineral shows that inhibitors such as amino, hydroxyl, act. take no significant inhibitory effect on that kind of minerals; polyhydroxy compounds such as starch, tannic acid do not inhibit marmatite, but Jamesonite; the Congo red dye containing a number of sulfonic acid groups and amino can inhibit marmatite and Jamesonite, but especially for marmatite. The thioglycolic acid, containing thiol and carboxy, have a good selective adsorption, and adsorbent at the surface of marmatite, Selectively.

Low methanol permeable sulfonated poly(ether imide)/sulfonated multiwalled carbon nanotube membrane for direct methanol fuel cell

AbstractA novel organic/inorganic composite membrane synthesized with sulfonated multiwalled carbon nanotubes (s‐MWNTs) and sulfonated polyetherimide (s‐PEI) is prepared for use in a direct methanol fuel cell (DMFC). A solution casting method was used to prepare s‐MWNT/s‐PEI membranes (SPEI membranes) with various s‐MWNT contents. This composite membrane showed not only low methanol crossover and water swelling but also enhanced mechanical properties. The IEC and proton conductivity of SPEI membranes were increased by incrementing their s‐MWNT content. This is because the number of sulfonic acid groups (SO3−) increases as s‐MWNTs are added. The water uptake of SPEI membranes increased as s‐MWNT content was increased due to the hydrogen bonded interaction between sulfonic groups and carboxylic groups in s‐MWNTs and water molecules. However, the water uptake of SPEI membranes is remarkably low, compared with Nafion membranes. The methanol permeability of the SPEI membranes (8.8 × 10−8 cm2 s−1) in this study was also lower than that of the Nafion membrane. Therefore, SPEI membranes were expected to have potential applications in DMFCs. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Tetrasulfonated Poly(arylene biphenylsulfone ether) Block Copolymer and Its Composite Membrane Containing Highly Sulfonated Blocks

Among different types of fuel cells, proton exchange membrane (PEM) fuel cells show the highest power density and have been actively investigated for automobile applications. Although Nafion has been typically considered as a PEM for practical applications, there are still some limitations such as the high cost and the degradation of proton conductivity at high temperature (> 80 C). Several approaches have been examined to improve proton conductivity. The strategies have included changing the acidity and position of sulfonic acid groups and the control of membrane morphologies. Recently, highly sulfonated moieties or sequenced hydrophilic and hydrophobic groups as block copolymers were claimed to improve proton conductivity under high temperature. However, none of these alternative membranes could compete with Nafion membranes. Related to these reports, we wish to study the thermal and electrochemical properties and morphological characteristic of a block membrane enhanceing the number of sulfonic acid groups in a repeat unit of a polymer. Here, we report on highly sulfonated poly(arylene biphenylsulfone ether) block copolymer (5) made using tetrasulfonated 4,4'-bis[(4chloro-3-sulfonatophenyl)sulfony]biphenyl-2,2'-disulfonate (TsBCSBPD, 2) and its composite membrane using phosphotunstic acid (PWA). In the previous paper, we described the synthesis and characterization of tetrasulfonated poly(arylene biphenylsulfone ether) random copolymers made using TsBCSBPD (2). The block copolymer 4 was prepared as follows: First, hydrophobic oligomer 1 was made from 6F-BPA (4,4'-hexafluoroisopropylidene diphenol), DCDPS (4,4'-dichlorodiphenyl sulfone), and K2CO3 in dimethyl acetamide (DMAc). 7 Second, hydrophilic oligomer 3 was prepared from TsBCSBPD (2) and 6F-BPA in the same manner. Finally, we synthesized a block copolymer 4 from the hydrophobic 1 (Mw 10 kDa) and hydrophilic oligomer 3 (Mw 13 kDa) using a nuclephilic substitution reaction. This was then followed by hydrolysis with sulfuric acid (Scheme 1). The polymer had a high molecular weight (Mw 57 kDa), which supported the formation of a block structure. The H NMR spectrum of B37 copolymer is shown in Figure 1. H NMR analysis confirmed 37% sulfonation (the degree of sulfonation on each phenylene ring in the repeating unit). The B37 membrane was prepared by solution casting the acid form of the B37 copolymer in DMAc (10% w/v) and the B37-P30 (B37:PWA = 10:3, wt/wt) composite membrane was prepared by casting the acid form of the B37 and a commercial PWA (H3PWO40, Fluka Chemicals) in DMAc (10% wt/v). These castings were carried out onto a clean glass plate and then dried by a heat lamp at 80 C for 24 h. A summary of the thermal properties of the fabricated membranes is listed in Table 1. The TGA (thermogravimetric analysis) of B37, B37-P30, and Nafion N117 membranes

Suitable Labels for Molecular Imaging – Influence of Dye Structure and Hydrophilicity on the Spectroscopic Properties of IgG Conjugates

Aiming at the design of highly brilliant NIR emissive optical probes, e.g., for in vivo near-infrared fluorescence imaging (NIRF), we studied the absorption and fluorescence properties of the asymmetric cyanines Dy678, Dy681, Dy682, and Dy676 conjugated to the model antibody IgG. The ultimate goal was here to derive general structure-property relationships for suitable NIR fluorescent labels. These Dy dyes that spectrally match Cy5 and Cy5.5, respectively, were chosen to differ in chromophore structure, i.e., in the substitution pattern of the benzopyrylium end group and in the number of sulfonic acid groups. Spectroscopic studies of the free and IgG-bound fluorophores revealed a dependence of the obtained dye-to-protein ratios on dye hydrophilicity and control of the fluorescence quantum yields (Φ(f)) of the IgG conjugates by the interplay of different fluorescence reduction pathways like dye aggregation and fluorescence resonance energy transfer (FRET). Based upon aggregation studies with these dyes, the amount of dye dimers in the IgG conjugates was determined pointing to dye hydrophilicity as major parameter controlling aggregation. To gain further insight into the exact mechanism of dye dimerization at the protein, labeling experiments at different reaction conditions but constant dye-to-protein ratios in the reaction solution were performed. With Dy682 that displays a Φ(f) of 0.20 in PBS and 0.10 for moderate dye-to-protein ratio of 2.5, a low aggregation tendency, and a superior reactivity in IgG labeling, we identified a promising diagnostic tool for the design of NIR fluorescent probes and protein conjugates.

Ab initio molecular dynamics of proton networks in narrow polymer electrolytepores

It is well established that proton conductivity in fuel cell membrane materials such asNafion decreases strongly with decreasing water content. Proton transport in almost dry membranes isthought to proceed through narrow channels. In the present work we investigate proton structureand dynamics in two narrow cylindrical pores, which differ by their radius and the spacing ofSO3H groups inside the channel. Pores are modelled through eightCF3CF3 andfour CF3SO3H entities in a helical arrangement. The water contentλ (the ratio between the number of water molecules and the number of sulfonic acid groups) in thepores varies between 2.5 and 4.5. We observe a transition from the undissociated acid at very lowλ through more or lesslocalized H3O + entities to moredelocalized H5O2 + entities forthe investigated range of λ. In the narrower pore, where S–S distances vary in a more favourable range (between 6 and8.5 Å) than in the wider pore, we find that the molecular mobility is significantly higher, evenat a rather high density of water molecules inside the pore.