Surface modification and characterization of SEBS films obtained by in situ and ex situ oxidization with potassium permanganate

The surface morphologies and compositions of the asymmetric films of polystyrene‐b‐poly(ethylene‐co‐butylene)‐b‐polystyrene (SEBS) prepared by in situ and ex situ oxidization with the KMnO₄ aqueous solution and KMnO₄/H₂SO₄ mixed solution were investigated by using scanning electron microscope, atomic force microscope (AFM), X‐ray photoelectron spectroscopy (XPS) and attenuated total reflectance infrared spectroscopy (ATR‐FTIR). The effect of the oxidization reagents on morphological changes and the influence of in situ and ex situ preparation methods on surface compositions were discussed. Different from the in situ oxidation by degrading the copolymers to form a gradient film, the ex situ oxidation preferentially degraded the uppermost layer of the film. Although both the KMnO₄ oxidation and the KMnO₄/H₂SO₄ oxidation gave hierarchical structures, distinctive differences were found that large ridges and smaller granules were fabricated in the former film and the latter produced large and deep ravines and fine sponge‐like morphologies. Additionally, the oxygen concentration and the oxo‐species implanted by these oxidation treatments were characterized and evaluated to provide a quantitative comparison. Oxygen, as well as manganese was found to be implanted in the surface layer of the oxidized film, forming predominantly O? C and O? C?O groups, as well as a small fraction of O? H and Mn? O compounds. Changes in contact angle of water on these films and total surface oxygen content are related but not directly. The hystereses of water contact angle at a value of 119 ± 3° due primarily to surface roughness and at a value of 63 ± 3° due primarily to chemical heterogeneity are led by different oxidation degrees and oxidation methods. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Structure and properties of the regenerated cellulose membranes prepared from cellulose carbamate in NaOH/ZnO aqueous solution

Regenerated cellulose (RC) membranes were prepared from cellulose carbamate—NaOH/ZnO aqueous solutions by coagulating with H₂SO₄ solution. Structure, morphology and properties of the membranes were investigated by using scanning electron micrograph (SEM), X-ray diffraction, Fourier transform infrared spectroscopy, flow rate method, and tensile testing. The results from SEM and water permeability revealed that the pore size and water permeability of the membranes in wet state changed drastically as a function of the concentration of H₂SO₄ and coagulation temperature, whereas they hardly changed with the coagulation time. RC membranes coagulated with the relatively dilute H₂SO₄ solution at relatively low temperature exhibited better mechanical properties. This work provided a promising way to prepare cellulose membranes with different pore sizes and good physical properties.     

Surface modification of PDMS by surface-initiated atom transfer radical polymerization of water-soluble dendronized PEG methacrylate

The current paper reports the synthesis of a highly hydrophilic, antifouling dendronized poly(3,4,5-tris(2-(2-(2-hydroxylethoxy)ethoxy)ethoxy)benzyl methacrylate) (PolyPEG) brush using surface initiated atom transfer radical polymerization (SI-ATRP) on PDMS substrates. The PDMS substrates were first oxidized in H₂SO₄/H₂O₂ solution to transform the Si-CH₃ groups on their surfaces into Si-OH groups. Subsequently, a surface initiator for ATRP was immobilized onto the PDMS surface, and PolyPEG was finally grafted onto the PDMS surface via copper-mediated ATRP. Various characterization techniques, including contact angle measurements, attenuated total reflection infrared spectroscopy, and X-ray photoelectron spectroscopy, were used to ascertain the successful grafting of the PolyPEG brush onto the PDMS surface. Furthermore, the wettability and stability of the PDMS-PolyPEG surface were examined by contact angle measurements. Anti-adhesion properties were investigated via protein adsorption, as well as bacterial and cell adhesion studies. The results suggest that the PDMS-PolyPEG surface exhibited durable wettability and stability, as well as significantly anti-adhesion properties, compared with native PDMS surfaces. Additionally, our results present possible uses for the PDMS-PolyPEG surface as adhesion barriers and anti-fouling or functional surfaces in biomedical applications.     

氧化环境和比例对改性Hummers法制备GO的影响

以鳞片石墨(GR)为原料,采用改性Hummers法液相氧化方法制备氧化石墨,通过超声剥离的方法剥离出片状的氧化石墨烯(GO),探讨了H₂SO₄环境与H₂SO₄+H₃PO₄混酸环境和KMnO₄与GR的比例对GO制备的影响。采用FTIR、UV、TG、XRD、SEM和XPS等分析手段对制备的GO进行分析。结果表明：GO外貌是呈褶皱片状,在片层上主要有C=O、C-OH、-COOH和C-O-C等官能团,以共价键形式存在石墨层间;通过TG与XPS数据分析表明在H₂SO₄ H₃PO₄混酸环境下制备的GO含氧官能团较多,并且(KMnO₄)与鳞片石墨的最佳比例是1:4。     

Effect of H2SO4 Solution Treatment on Adhesion,Charge Transfer,and Catalytic Performance of Screen-Printed PEDOT:PSS

Post-treatment was performed for poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films screen-printed on fluorine-doped tin oxide (FTO) substrates, to improve their charge transfer efficiency. Different H₂SO₄ solutions, including concentrated H₂SO₄ and H₂SO₄ diluted with H₂O or dimethyl sulfoxide (DMSO), were adopted during the post-treatment. The adhesion of the as-treated films was evaluated by adhesive tape peeling tests, the surface morphology and vertical charge transfer from the films to the substrates were investigated by current-sensing atomic force microscopy, and the catalytic activities toward I₃⁻ reduction of PEDOT:PSS films were characterized by electrochemical measurements. It is discovered that selecting proper H₂SO₄ solutions is crucial to improve the charge transfer efficiency and catalytic performance while maintaining reliable adhesion of the film on the substrates, with H₂SO₄/DMSO performing best as the solution for post-treatment. A mechanistic explanationis proposed based on different interactions among solution, PEDOT:PSS, and the substrate for various post-treatment solutions.     

Mechanism for the radiolytic conversion of sulphur dioxide to sulphuric acid

The present paper describes the radiolytic oxidation of 10^-4M K₄[Fe(CN)₆] aqueous aerated solution in the presence of different concentrations of SO₂. In the absence of SO₂, ferrocyanide is oxidized to ferricyanide with a G value of 7.2. In this solution two O₂^- react to form H₂O₂. Ferrocyanide is oxidized by OH and H₂O₂ both. At low concentration of SO₂, O₂^- reacts with SO₂ forming first SO₄^._, which leads to chain oxidation of SO₂. The G [Fe(CN)₆^3-) decrease from 7.2 to 4.5. At higher concentrations of SO₂, H₂O₂ also reacts with SO₂ and the G(Fe(CN)₆^3-] further reduces to 2.7. In the presence of chloride ions, SO₄^._ converts them to chloride atoms which react with H₂O₂ and ferrocyanide and the G[Fe(CN)₆^3-] is again increased to 4.3. The reaction of OH with SO₂ was observed only at high concentrations of SO₂ since the reaction of OH with ferrocyanide is very fast. The importance of water and ammonia in the conversion of sulphur dioxide to sulphuric acid probably lies in their reaction with SO₄^2- to form H₂SO₄ or (NH₄)₂SO₄.     

Quecksilberbestimmung in Wasser-, Fisch-, Pflanzen- und sedimentproben mit Hilfe der Atom-Absorptions-Spektroskopie

Zusammenfassung Quecksilber wurde in Flußwasser, Fischen, Pflanzen und Sedimenten durch Atom-Absorptions-Spektroskopie bestimmt. In Wasserproben wurden die Hg-Verbindungen mit H₂SO₄ aufgeschlossen und mit KMnO₄ oxidiert. Nach der Beseitigung des entstandenen MnO₂-Niederschlags bzw. des überschüssigen Permanganats mit HONH₃Cl wurde das Quecksilber mit SnCl₂ reduziert, durch einen Luftstrom in eine Vorlage mit bidest. Wasser+H₂SO₄ +KMnO₄ eingeleitet und damit angereichert. Quecksilber wurde nach Zusatz von SnCl₂ mit Hilfe eines Luftstroms in die Meßzelle eingeleitet und gemessen. Fisch-, Pflanzen- und Sedimentproben wurden mit H₂SO₄+HNO₃ aufgeschlossen und das Hg mit KMnO₄ allein (beim Fisch) oder KMnO₄+K₂S₂O₈ (bei Pflanzen und Sediment) oxidiert. Bei diesen Analysen wurden der MnO₂-Niederschlag und das überschüssige KMnO₄ ebenfalls mit HONH₃Cl beseitigt. Die Bestimmung wurde in einem geschlossenen System durchgeführt. Bei diesem System sind die Nachweisempfindlichkeit und die Reproduzierbarkeit besser als beim offenen System. Der mittlere relative Fehler beträgt 13,7% für Wasser, 1,9% für Fisch, 4,9% für Pflanzen und 5,6% für Sediment. Die Wiederfindung des Quecksilbers beträgt 91–122%.

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Determination of mercury in water, fish, plant and sediment samples by atomic-absorption spectroscopy

Summary Organic and inorganic Hg-compounds in water samples were decomposed with H₂SO₄ +KMnO₄. Precipitated MnO₂ and excess of permanganate were destroyed with HONH₃Cl. Mercury was reduced by SnCl₂ and driven by an air stream into an absorption solution containing KMnO₄ and H₂SO₄. This solution was treated with SnCl₂, and mercury was aerated into the measuring cell. Fish, plant and sediment samples were digested with H₂SO₄ +HNO₃. For the oxidation of all forms of mercury to Hg(II) ions, KMnO₄ was added to the fish samples and KMnO₄+K₂S₂O₈ to the plant and sediment samples. Precipitated MnO₂ and excess of permanganate were destroyed with HONH₃Cl, too. Mercury was determined by using a closed, recirculating air stream. Sensitivity and reproducibility of the closed-system were better than those of the open-system. The coefficient of variation was 13.7% for water, 1.9% for fish, 4.9% for plant and 5.6% for sediment samples. Recovery rate of mercury ranged from 91 to 122%.

     

Sequential distillation of fission-produced radioiodine and radioruthenium from sulfuric acid solutions

Fission-produced ¹³¹I and ¹⁰³Ru radionuclides have been separated sequentially by distillation from H₂SO₄ of controlled chemical composition. The thermal-neutron irradiated uranium trioxide targets were digested in 2M NaOH solution and then, the supernatant solution was acidified to 20% H₂SO₄ with addition of a few drops of H₂O₂ solution. On boiling for 3.5 hours, ≥99.99%¹³¹I was volatilized, passed through 3M H₂SO₄ traps, and then collected in 0.1M NaOH + 0.01% Na₂S₂O₃ solution with a recovery yield of 73.6%. The product radionuclide had high radiochemical and radionuclidic purities. After separation of ¹³¹I, the fission-product solution was acidified to 40% H₂SO₄ acid containing KMnO₄ as an oxidant and boiled for 40 minutes. Ruthenium nuclides were volatilized and collected in 0.1M NaOH solution. Gamma-ray spectrometry showed that the separation and the recovery yields of ¹⁰³Ru were ≥99.99 and 65%, respectively, with ~92% radionuclidic purity, measured immediately after separation. The radionuclides of ¹³²I and ¹⁰⁶Rh were the main contaminants detected in the obtained ¹⁰³Ru product solution. This revised version was published online in July 2006 with corrections to the Cover Date.     

Measurement of the relaxation transitions of nitrocellulose based gunpowder

The formation of a new sulfate compound K₄H₂(SO₄)₃ is obtained by evaporation at 25°C of an aqueous solution, which was formed by a mixture of K₂SO₄ and H₂SO₄. The characterization of this solid is carried out by X-ray diffraction, thermal and infrared analyzes. The heat treatment was carried out in interval 25–700°C; the end product of the thermal evolution is K₂SO₄. The vibration bands relating to SO₄ and OH groups were highlighted by the infrared spectroscopy.Moreover, one study of ionic conductivity on this solid compound was carried out according to the temperature in interval 25–80°C. Its activation energy is 0.47 eV. The X-ray intensities collection obtained on a monocrystal of K₄H₂(SO₄)₃ gives the following cell parameters: a=7.035(5), b=19.751(4), c=23.466(2) Å, β=95.25(1)°.     

The standard enthalpy of formation of (XeF5)2[MnF6](cr)

The enthalpies of interaction of (XeF₅)₂[MnF₆](cr) with a 0.0524 m solution of KOH and a 0.0300 m solution of H₂SO₄, the enthalpy of solution of KMnO₄(cr) in a 0.0440 m solution of KOH, and the enthalpy of mixing of aqueous KF with alkaline KMnO₄ were measured in isothermic-shell calorimeters at 298.15 K. The standard enthalpy of formation of the compound at 298.15 K was calculated by two independent procedures using the experimental values and literature data (Δ_f H ^o = −1185 ± 18 kJ/mol). Original Russian Text ? S.N. Solov’yov, A.A. Firer, A.Ya. Dupal, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 4, pp. 798–800.     

Behaviors of Perfluorocarbon Emulsion during Dissolution of Oxide Layers

This study investigates the dissolution behavior of oxide layers containing radionuclides using perfluorocarbon (PFC) emulsion as a reusable medium. Chemicals such as PFC, anionic surfactant, and H₂SO₄ are used for preparing the PFC emulsion, and emulsified using an ultrasonication process. The FTIR results show O–H stretching that is formed by the interaction of the carboxyl group of the anionic surfactant with the hydroxyl group of water containing H₂SO₄, and find that the H₂SO₄ can be homogeneously dispersed in the PFC–anionic surfactant–H₂SO₄ emulsion. The dissolution test of the simulated Cr₂O₃ specimen is conducted using PFC emulsion containing KMnO₄. Through the weight losses of specimens and Scanning Electron Microscope-Energy Dispersive X-ray Spectrometer (SEM-EDS) analysis, it is confirmed that the Cr₂O₃ layer on the SUS304 specimen is easily dissolved using PFC emulsion. During the dissolution of the Cr₂O₃, it is observed that the dispersed H₂SO₄–KMnO₄ became unstable and separated from PFC emulsion. Based on these results, the behavior of the PFC emulsion during the dissolution of the oxide layer is explained.     

Chitosan/N-methylol nylon 6 blend membranes for the pervaporation separation of ethanol–water mixtures

Blend membranes of chitosan and N-methylol nylon 6 were prepared by solution blending. Their pervaporation performances for the separation of ethanol–water mixtures were investigated in terms of acid (H₂SO₄) post-treatment, feed concentration, blend ratio and temperature. The pervaporation performance of the blend membranes was significantly improved by ionizing with H₂SO₄. The blend ratio of chitosan and N-methylol nylon 6 plays a different role at feed solutions of low and high water content. At a feed solution having low water content, an increase in chitosan content caused a decrease in permeability and an increase in separation factor. At a feed solution having high water content, the permeability increases with an increase in chitosan content, while the separation factor shows a maximum value around 60 wt% chitosan. It is proposed that extra permeation channels generated from the phase separation boundary between ionized chitosan and N-methylol nylon 6 account for the abnormal temperature dependence of pervaporation performance of the blend membranes.     

Oxidations with potassium permanganate in the presence of fluoride

Summary The titration of ferrous iron in presence of fluoride ions in acid medium gives fleeting end points and erroneous results. A method is deviced to overcome this difficulty by oxidising the ferrous with an excess of KMnO₄ in alkaline medium. After mixing the reactants the excess of KMnO₄ is reduced by an excess of Hg₂ ²⁺ ions in presence of H₂SO₄ and fluoride. The remaining mercurous is then titrated with standard KMnO₄ solution.Part III: Issa, I. M., and M. Hamdy: Z. analyt. Chem. 174, 418 (1960).     

Electrochemical and In Situ FTIR Studies of Adsorption and Oxidation of Dimethyl Ether on Platinum Electrode

Dissociative adsorption and electrooxidation of dimethyl ether (DME) on a platinum electrode in different pH solutions were studied using cyclic voltammetry (CV) and in situ FTIR reflection spectroscopy. The coverage of the dissociative adsorbed species was measured about 70% from hydrogen adsorption-desorption region (0.05-0.35 V (vs RHE)) of steady-state voltammogram recorded in 0.1 mol·L⁻¹ H₂SO₄ solution. It was found that the electrochemical reactivity of DME was pH dependent, i.e., the larger the pH value was, the less the reactivity of DME would be. No perceptible reactivity of DME in 0.1 mol·L⁻¹ NaOH solution could be detected. It was revealed that the protonation of the oxygen atom in the C-O-C bond played a key role in the electrooxidation of DME. In situ FTIR spectroscopic results illustrated that linearly bonded CO (CO_L) species determined at low potential region were derived from the dissociative adsorption of DME and behaved as ‘poisoning’ intermediate. The CO_L species could be oxidized to CO₂ at potential higher than 0.55 V (vs RHE) and in the potential range from 0.75 to 1.00 V (vs RHE) DME was oxidized simultaneously via HCOOH species that were identified as the reactive intermediates.     

The study of self-assembled films of triazole on iron electrodes using electrochemical methods,XPS, SEM and molecular simulation

3-Alkyl-4-amino-5-mercapto-1,2,4-triazole (AAMT) has been evaluated as corrosion inhibition for iron in 0.1 M H₂SO₄ when the films of AAMT were self-assembled on the surface of iron. The films of AAMT inhibitor were characterized by electrochemical impedance spectroscopy, electrochemical polarization curves Results revealed that AAMT performed excellently as a corrosion inhibitor for iron in H₂SO₄ solution. Surface analysis was carried out using X-ray photoelectron spectroscopy and scanning electron microscope. The mechanism of adsorption was discussed using molecular simulation.     

Stability of polyynes in air and their degradation by ozonolysis

Polyyne solutions in n-hexane or other aliphatic hydrocarbons having C₆H₂, C₈H₂ and C₁₀H₂ as main components were found to be unstable at relatively high concentration (≈10⁻² M) and to separate in few hours a brown precipitate. This phenomenon does not occur in more dilute solutions. The precipitate recovered from the mentioned solutions was analysed by FT-IR spectroscopy and thermogravimetry and found to be constituted by polyyne chains crosslinked and oxidized by oxygen resembling in some way the product obtained by photolysing acetylene in water solution and in presence of air. Polyynes react very quickly with ozone producing as main product polymeric ozonides which are insoluble in hydrocarbons and which have been studied with FT-IR spectroscopy. The oxidized nature of the chains highly crosslinked by ozonides, peroxide and oxygen bridges has been confirmed. The oxidized polyyne fraction remaining in solution after ozonolysis was studied by electronic absorption spectroscopy and by liquid chromatography. Extensive chain breaking was found as expected although some degree of unsaturation was preserved even in the final oxidized products.     

The effect of electrochemically treated glassy carbon on the activity of supported Pt catalyst in methanol oxidation

Effect of electrochemical oxidation of glassy carbon on deposition of platinum particles and electrocatalytic activity of platinum supported on oxidized glassy carbon (Pt/GC_OX) were studied for methanol oxidation in H₂SO₄ solution. Platinum was potentiostatically deposited from H₂SO₄ + H₂PtCl₆ solution. Glassy carbon was anodically polarised in 0.5 M H₂SO₄ at 2.25 V vs. saturated calomel electrode (SCE) during 35 s. Electrochemical treatment of GC support, affecting not significantly the real Pt surface area, leads to a better distribution of platinum on the substrate and has remarkable effect on the activity. The activity of the Pt/GC_OX electrode for methanol oxidation is larger than polycrystalline Pt and for more than one order of magnitude larger than Pt/GC electrode. This increase in activity indicates the pronounced role of organic residues of GC support on the properties of Pt particles deposited on glassy carbon.     

向日葵盘果胶对碳钢的缓蚀性能研究

以向日葵盘为原料,利用纤维素酶制备果胶(SFP)。采用静态失重、极化曲线和交流阻抗技术研究SFP在1mol/L HCl及0.5mol/L H_2SO_4溶液中对碳钢的缓蚀性能,并探讨其在碳钢表面的吸附机理。结果表明,缓蚀效率随SFP浓度增大而增大,随温度升高而降低。在HCl和H_2SO_4溶液中,SFP的吸附方式分别服从Langmuir和Temkin等温式,属于物理吸附;极化曲线测试显示SFP是一种混合型缓蚀剂。本文的研究表明,向日葵盘果胶是碳钢的绿色高效缓蚀剂,且在HCl溶液中的缓蚀性能优于在H_2SO_4溶液中。     

Fabrication of a micro-direct methanol fuel cell using microfluidics

A direct-methanol fuel cell containing three parts: microchannels, electrodes, and a proton exchange membrane (PEM), was investigated. Nafion resin (NR) and polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (PS) were used as PEMs. Preparation of PEMs, including compositing with other polymers and their solubility, was performed and their proton conductivity was measured by a four point probe. The results showed that the 5 % Nafion resin has lower conductivity than the 5 % PS solution. The micro-fuel cell contained two acrylic channels, PEM, and two platinum catalyst electrodes on a silicon wafer. The assembled micro-fuel cells used 2 M methanol at the flow rate of 1.5 mL min^?1 in the anode channel and 5 × 10^?3 M KMnO₄ at the flow rate of 1.5 mL min^?1 in the cathode channel. The micro-fuel cell with the electrode distance of 300 ??m provided the power density of 59.16 ??W cm^?2 and the current density of 125.60 ??A cm^?2 at 0.47 V.     

Thorium adsorption on graphene oxide nanoribbons/manganese dioxide composite material

A functional graphene oxide nanoribbons/manganese dioxide composite material (MnO₂-GONRs) was synthesized by hydrothermal method using graphene oxide nanoribbons (GONRs) as raw material which were formed by longitudinal unzipping of multi-walled carbon nanotubes with KMnO₄ and H₂SO₄. The microstructure of MnO₂-GONRs was characterized by SEM and FT-IR. The various factors affecting the adsorption of Th(IV) in aqueous solution such as pH, solid–liquid ratio, contact time, initial concentration and temperature were investigated by batch static adsorption experiments, and the adsorption mechanism is also discussed. The results showed that MnO₂-GONRs had a good adsorption effect on Th(IV) with a maximum adsorption of 166.11 mg/g.