盐酸克伦特罗在纳米ZnO和多壁碳纳米管修饰玻碳电极上的电化学行为

制备了纳米ZnO与多壁碳纳米管(MWNTs)复合修饰玻碳电极(ZnO-MWNTs/GCE),考察了盐酸克伦特罗(CLB)在该修饰电极上的电化学行为。实验结果表明:纳米ZnO与MWNTs显著增强了修饰电极对盐酸克伦特罗的伏安响应,增加了电极的有效表面积,改善了电极的导电性和电催化活性。在2~30μmol·L-1和30~500μmol·L-1浓度范围内,CLB在所制备的修饰电极上的电流响应与其浓度线性关系良好,且该电极具有较好的重现性和稳定性。     

电化学方法制备石墨烯-铁氰化镍复合物及对抗坏血酸的电催化氧化研究

采用电化学还原方法制备了铁氰化镍-石墨烯复合薄膜电极,扫描电子显微镜(SEM)表征电还原石墨烯和铁氰化镍-石墨烯复合材料的表面形貌。采用循环伏安和计时电流技术研究了该修饰电极对抗坏血酸(AA)的电催化氧化性能,据此建立了一种测定AA的电化学分析新方法。由于石墨烯和铁氰化镍纳米颗粒之间的协同效应,使得该复合修饰电极对抗坏血酸具有优异的电催化活性。在0.1 mol/L pH 7.00的PBS溶液中,抗坏血酸的催化氧化电流与其浓度在1.0×10-4~7.0×10-4mol/L范围内呈良好的线性关系,检出限为3.1×10-5mol/L(S/N)。     

聚合物—石墨复合材料电极

用石墨粉填充ＡＳ树脂，挤出成型制备了ＡＳ－复合导电材料电极，电极具有较好的导电性，机械强度和操作稳定性，在多种底液中具有比玻碳电极更高的氢电压值和小的残余电流。电极成功地用于Ｃｕ、Ｉｎ、Ｐｂ、Ａｂ的测定并显示较好的选择性，稳定性和再现性；并可采用浸涂法方便地进行甲基蓝修饰，得到具有稳定电化学性的修饰电极。     

Pt微粒修饰纳米纤维聚苯胺电极对甲醇氧化电催化

以脉冲电流法制备的纳米纤维状聚苯胺(PANI)为Pt催化剂载体，用它制备了甲醇阳极氧化的催化电极Pt/（nano-fibular PANI）.研究结果表明, Pt/（nano-fibular PANI）电极对甲醇氧化具有很好的电催化活性,并有协同催化作用.在相同的Pt载量条件下， Pt/（nano-fibular PANI）电极比Pt微粒修饰的颗粒状聚苯胺电极Pt/(granular PANI)具有更好的电催化活性.此外， Pt的电沉积修饰方法同样影响Pt/（nano-fibular PANI）电极对甲醇氧化的催化活性.脉冲电流法沉积Pt形成的复合电极较循环伏安法电沉积得到的Pt复合电极具有更优异的催化活性.     

离子束修饰对电极表面结构和析氢活性的影响

采用了离子束对工业钛电极进行表面改性，用电化学方法研究了改性电极在Ｈ２ＳＯ４溶液中的析氢活性，用表面能谱分析了电极表面的组分和结构。结果表明：通过离子束修饰在电极表面引入微量的活性元素即可明显改善工业纯钛电极的析氢催化活性；离子束修饰改变了电极表面的组分和相结构，从而达到了改性的目的。     

多壁碳纳米管负载铁氰化铜-铁修饰电极的制备及对亚硝酸根的测定

采用循环伏安法制备了多壁碳纳米管负载铁氰化铜-铁修饰复合陶瓷碳电极(CuFeHCF/MWCNT/CCE),研究了该修饰电极的电化学性质及对NO-2的电催化活性。 结果表明,该修饰电极对NO-2的电氧化具有强的催化活性,安培法检测NO-2的线性范围为2.0×10-7~1.4×10-3 mol/L,灵敏度为104.1 μA/(mmol·L-1),检出限（3sb）为5.0×10-8 mol/L。 利用该方法测定了土壤中NO-2的含量,结果令人满意。     

PVC-碳糊修饰电极的研制

研制了二茂铁修饰PVC-碳糊电极，采用循环伏安法研究了在pH7．4 KH2PO4-Na2HPO4缓冲溶液中该修饰电极的电化学特性和该修饰电极对抗坏血酸和邻苯二酚的电催化作用，测定结果具有较好的灵敏度和线性关系。研制了α-安息香肟修饰PVC-碳糊电极，研究了该电极对铜(Ⅱ)的特殊选择性。同时初步探讨了电极与铜(Ⅱ)的反应机理。     

纳米钯修饰电极在碱性条件下对过氧化氢的测定

采用单电位阶跃计时电流法制备了Pd纳米粒子修饰复合陶瓷碳电极(Pd/CCE)。研究了该修饰电极对H2O2的电催化氧化性能。结果表明,Pd/CCE修饰电极在碱性介质中对H2O2的氧化具有强电催化活性。在0.1 mol.L-1NaOH溶液中采用动态安培法检测H2O2,线性范围为2.0×10-6~2.6×10-3mol.L-1,r=0.999 3,检出限(3sb)为5.0×10-7mol.L-1,灵敏度为143.8μA.(mmol.L-1)-1。该法用于过氧化氢消毒液中H2O2的测定,结果满意。     

石墨烯-聚三聚氰胺修饰电极制备及对水果酸度测定

采用滴涂法和电聚合法,依次将石墨烯(GS)和三聚氰胺(Mel)修饰到玻碳电极表面,制备了电化学性能良好的石墨烯-聚三聚氰胺(GS/pMel)复合薄膜修饰电极。利用循环伏安法考察了该修饰电极在不同pH值的缓冲溶液中的电化学行为,在循环伏安图中可见与pH相关的一对氧化还原峰,且氧化峰电位与溶液的pH值在1.93～12.53范围内呈现良好的线性关系,相关系数为0.9969,响应斜率约为58 mV/pH。GS/pMel复合薄膜修饰电极成功地应用于果汁及水果活体的酸度测定,电极性能稳定,测量结果具有高度的重复性、稳定性和准确性。该修饰电极可广泛应用于果蔬活体酸度的直接测定。     

二氧化锰/石墨烯/N-取代羧基聚苯胺复合修饰电极对亚硝酸根的电化学催化研究

采用电聚合、静电吸附和恒电位还原的方法在玻碳电极上制备了均匀修饰的还原氧化石墨烯/N-取代羧酸聚苯胺(rGO/NPAN)复合膜。以其为支撑,利用滴涂法将高电催化活性的二氧化锰负载于复合膜上,形成MnO_2/rGO/NPAN复合修饰电极。通过扫描电镜(SEM)对复合膜的形貌进行表征,讨论了NPAN电聚合圈数、GO浓度、电还原时间和pH值等因素对电化学活性和电催化活性的影响。结果表明:该修饰电极具有低的检测电位和高的电化学响应,检测亚硝酸根的浓度范围为0.5×10~(-6)~5.13×10~(-2)mol/L,灵敏度为14.075μA·(mmol/L)~(-1),检出限(S/N=3)低至0.2μmol/L。     

Polymeric bilayer modified microelectrodes for in-vivo determination of neurotransmitter dopamine

A composite polymer carbon fiber electrode modified with Nafion and cellulose acetate is described.The modified electrode discriminates against both anionic reactants and big molecular organic compounds.The bilayer configuration is prepared in two steps.First,the carbon fiber electrode is coated with Nafion,then followed by air evaporation of the solvent,the electrode is dipped in a cellulose acetate solution and hydrolyzed for a selected time.The permeability of the film is explored by use of rotating disk electrode measurements.Parameters affecting the film electrochemistry are investigated.The resulting electrodes show high selectivity and stability in body fluids.For in-vivo voltammetry,the composite polymer modified electrode has been used for detection of the oxidative current of neurotransmitter dopamine in rat brain,while it inhabits the oxidation of anionic neurotransmitter metabolites and some electroactive compounds.     

Studies on cellulose acetate-carboxylated polysulfone blend ultrafiltration membranes--Part I

Hydrophilic polysulfone ultrafiltration (UF) membranes were prepared from blends of cellulose acetate with carboxylated polysulfone of 0.14 degree of carboxylation. The effects of blend polymer composition on compaction, pure water flux, water content and membrane hydraulic resistance (R_m), have been investigated to evaluate the performance of the membranes. The performance of the blend membranes of various blend polymer compositions were compared with that of membranes prepared from pure cellulose acetate and blends of cellulose acetate and pure polysulfone. The hydrophilic cellulose acetate-carboxylated polysulfone blend UF membranes showed better performance compared to membranes prepared from pure cellulose acetate and blends of cellulose acetate and pure polysulfone.     

Permeation of water as a tool for characterizing the effect of solvent, film thickness and water solubility in cellulose acetate membranes

Cellulose acetate membranes have been used in many applications; of particular interest are reverse osmosis systems, and as a neutral matrix for incorporation of different polymers (e.g., conducting polymers), inorganic ions (e.g., lanthanides) and organic (e.g., pharmaceutical) compounds. The properties of the new polymers derived from cellulose acetate or blends depend on those of cellulose acetate. This work presents an attempt to find links between thermodynamic and kinetic properties of cellulose acetate membranes in equilibrium with water. Water diffusion coefficients in cellulose acetate membranes are reported, measured with a simple water permeation technique. The comparison of these values with the percentage of water uptake and polymer thickness leads to interesting conclusions related with different polymer properties.     

Interactions underpinning the plasticization of a polymer matrix: a dynamic and structural analysis of DMP-plasticized cellulose acetate

This work establishes that the plasticization effect of a classical petrochemical plasticizer, dimethyl phthalate (DMP), on a polymer matrix, cellulose acetate (CA), is due to the development of intermolecular interactions of dipolar type. Plasticized cellulose acetate films are studied with regard to the interactions between the polymer and plasticizer at the macroscopic scale by thermogravimetric analysis and differential scanning calorimetry. At the molecular level, Fourier transform infrared spectroscopy and dielectric relaxation spectroscopy are used to elucidate the nature of interactions that are responsible for the plasticizing effects. These static and dynamic complementary analyses evidenced that DMP does not establish H-bonding interactions with the polymer chains of cellulose acetate but rather weaker interactions of dipolar type. These dipole–dipole interactions that develop between acetyl side groups of CA and the ester phthalate moieties of DMP increase the overall mobility of CA chains and also locally influence the molecular mobility and the water uptake tendency.     

Adsorption of carboxymethyl cellulose on polymer surfaces: evidence of a specific interaction with cellulose

The adsorption of carboxymethyl cellulose (CMC), one of the most important cellulose derivatives, is crucial for many scientific investigations and industrial applications. Especially for surface modifications and functionalization of materials, the polymer is of interest. The adsorption properties of CMC are dependent not only on the solutions state, which can be influenced by the pH, temperature, and electrolyte concentration, but also on the chemical composition of the adsorbents. We therefore performed basic investigation studies on the interaction of CMC with a variety of polymer films. Thin films of cellulose, cellulose acetate, deacetylated cellulose acetate, polyethylene terephthalate, and cyclo olefin polymer were therefore prepared on sensors of a QCM-D (quartz crystal microbalance) and on silicon substrates. The films were characterized with respect to the thickness, wettability, and chemical composition. Subsequently, the interaction and deposition of CMC in a range of pH values without additional electrolyte were measured with the QCM-D method. A comparison of the QCM-D results showed that CMC is favorably deposited on pure cellulose films and deacetylated cellulose acetate at low pH values. Other hydrophilic surfaces such as silicon dioxide or polyvinyl alcohol coated surfaces did not adsorb CMC to a significant extent. Atomic force microcopy confirmed that the morphology of the adsorbed CMC layers differed depending on the substrate. On hydrophobic polymer films, CMC was deposited in the form of larger particles in lower amounts whereas hydrophilic cellulose substrates were to a high extent uniformly covered by adsorbed CMC. The chemical similarity of the CMC backbone seems to favor the irreversible adsorption of CMC when the molecule is almost uncharged at low pH values. A selectivity of the cellulose CMC interaction can therefore be assumed. All CMC treated polymer films exhibited an increased hydrophilicity, which confirmed their modification with the functional molecule.     

The application of pyrolysis gas chromatography mass spectrometry for the identification of degraded early plastics in a sculpture by Naum Gabo

A study was carried out to characterise the materials of a highly degraded plastic sculpture by Naum Gabo in the collection of the Philadelphia Museum of Art. Samples from the sculpture were analysed using pyrolysis gas chromatography mass spectrometry (Py-GCMS) in conjunction with Fourier transform infrared microspectroscopy (MFTIR) and other techniques. Py-GCMS confirmed that Gabo had used cellulose acetate and cellulose nitrate plastics; the identification of the former was based on the detection of trace levels of 5-acetoxymethylfurfural and other characteristic carbohydrate-derived pyrolysis products bearing an acetyl group. Because of the unusually severe state of degradation of certain parts of the sculpture, the pyrolysis data were critical for identification of the cellulose acetate polymer, which could not be achieved using MFTIR. The original polymer has undergone almost complete reversion to a cellulose-like structure through hydrolysis and deacetylation.     

Effects of hydroxyvalerate contents in thermal degradation kinetic of cellulose acetate propionate/poly(3-hydroxyalkanoates) blends

Thermal stability of polymers is an important parameter that determines the application as well as the processing conditions. The green polymers have shown low thermal stability, such as the polyhydroxyalkanoates (PHAs). The PHAs with different comonomers containing hydroxyvalerate (HV) were studied. It was seen that the green polymer showed a fast thermal degradation process. The addition of the HV comonomer modified this profile and the thermal degradation kinetic. The blend prepared between the PHAs and other polymers can modify the thermal degradation process of the green polymers. In the present study, blends of cellulose acetate propionate and PHAs were prepared, and the thermal degradation kinetics of these blends were evaluated. It was observed that the cellulose acetate propionate (CAP) phase in the blends modified the thermal degradation process and kinetic profile of the PHA phase. In the blends, the thermal stability of the PHAs was slightly modified because of CAP reducing the reactivity of the PHAs. On the other hand, the thermal stability of the CAP phase in the blends is not largely modified by the PHA phase. However, the hydroxyvalerate comonomer decreases the reactivity of the CAP phase at the start of thermal degradation of the same. The interaction between the phases promotes the synergetic interaction, which slightly improves the thermal stability of the two polymers blends.     

Reactions with 1.3 propane sultone for the synthesis of cation-exchange membranes

For several reasons it is interesting for membrane technology to introduce strongly anionic groups in membranes. Therefore the possibilities of 1.3 propane sultone were studied to modify cellulose, cellulose acetate and polyacrylonitrile.The results showed that cellulose and cellulose acetate could be modified by a direct reaction of 1.3 propane sultone with the available hydroxyl groups. The nitrile groups in polyacrylonitrile had to be reacted first with hydrogen sulphide to give reactive thioamide groups, able to react with the sultone. These results give evidence for 1.3 propane sultone being a useful chemical for modification of polymers, its carcinogenic properties will however prevent applications.     

Characteristics of thin cellulose ester films spin-coated from acetone and ethyl acetate solutions

Spin-coated films of cellulose acetate (CA), cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB) and carboxymethylcellulose acetate butyrate (CMCAB) have been characterized by ellipsometry, atomic force microscopy (AFM) and contact angle measurements. The films were spin-coated onto silicon wafers, a polar surface. Mean thickness values were determined by means of ellipsometry and AFM as a function of polymer concentration in solutions prepared either in acetone or in ethyl acetate (EA), both are good solvents for the cellulose esters. The results were discussed in the light of solvent evaporation rate and interaction energy between substrate and solvent. The effects of annealing and type of cellulose ester on film thickness, film morphology, surface roughness and surface wettability were also investigated. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Modified cellulose acetate flat membranes for desalination

In this article, the radiation grafting of acrylamide on to cellulose acetate flat membranes using UV-irradiation on the initiator is described. The modified membranes thus obtained have been characterized by IR, DSC, and TGA. Their transport properties have been studied. The modified membranes exhibit higher salt rejection with slightly reduced water flux as compared with cellulose acetate membrane. The work is further extended to study the thermal stability of these modified membranes in a dry state. These modified membranes up to 330°C are stable.