Glassy carbon electrodes modified with single walled carbon nanotubes and cobalt phthalocyanine and nickel tetrasulfonated phthalocyanine: Highly stable new hybrids with enhanced electrocatalytic performances

We report here a fast procedure to modify glassy carbon (GC) electrode using commercially available unsubstituted cobalt phthalocyanine (CoPc) and tetrasulfonated substituted nickel phthalocyanine (NiTSPc) simply adsorbed on oxidized single walled carbon nanotubes SWCNT. The electrocatalytic activity of the resulting SWCNT-MPc nanocomposite materials was evaluated toward the oxidation of two biologically relevant molecules, namely 2-mercaptoethanol (2-ME) and nitric oxide (NO). The obtained electrodes are highly stable under hydrodynamic conditions and the tailored hybrid surfaces allow enhancing electron transfer for the electrocatalytic oxidation of 2-ME and NO.     

Electrochemical Detection of Nitric Oxide on a SWCNT/RTIL Composite Gel Microelectrode

Single walled carbon nanotubes (SWCNT) and room temperature ionic liquid (RTIL) were used to make a gel microelectrode for studies of the oxidation of nitric oxide (NO). The Faraday response of the gel microelectrode was contributed from two components: an outside‐surface microdisk and a thin‐layer cell formed by inner porous electrode materials, and enhanced by the thin‐layer effect. An EC mechanism, electrochemical NO oxidation followed by a chemical oxidation, was proposed. The gel microelectrode with a Nafion coating eliminated interferences from nitrite and some biomolecules, improved stability, and had a linear response range from 100 nM to 100 μM.     

A multiwall carbon nanotubes film-modified carbon fiber ultramicroelectrode for the determination of nitric oxide radical in liver mitochondria

A novel chemically modified electrode based on the multiwall carbon nanotubes (MWNTs) film-coated carbon fiber ultramicroelectrode (CFUE) has been described for the determination of nitric oxide radical (.NO). The electrochemical behaviors of MWNTs-modified CFUE have been characterized in 0.2 mmol L(-1) K(4)Fe(CN)(6) and 0.1 mol L(-1) KCl solution. The Nafion film was used to avoid some electroactive interferences. The amount of Nafion was optimized, and some possible interferents [such as nitrite (NO(2)(-)), nitrate (NO(3)(-)), ascorbate, dopamine (DA), l-arginine (l-Arg), etc.] were tested and evaluated. The oxidation peak current of .NO increases significantly at the MWNT/Nafion-modified CFUE, in contrast to that at the bare and the Nafion-modified CFUE, and the oxidation peak potential is at 0.78 V (vs. SCE), which can be used for the detection of .NO. The oxidation peak current is linearly with the concentration of .NO from 2x10(-7) to 8.6x10(-5) mol L(-1), and the detection limit is 2x10(-8) mol L(-1). The liver mitochondria in Carassius auratus were isolated and .NO release from mitochondria was monitored by using this ultramicroelectrode system.     

Electrooxidation of Nitric Oxide at a Glass Carbon Electrode Modified with Functionalized Single-walled Carbon Nanotube

The electrocatalytic oxidation of nitric oxide(NO) at a glass carbon electrode(GC) modified with functionalized single-walled carbon nanotubes(SWCNTs) was investigated by cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS).It was found that the SWCNT modified electrode could speed greatly up the electron transfer rate compared with the bare GC electrode.After the SWCNT was treated with alkali or mixed acids,the reaction rate and activation energy of NO electrooxidation were changed to different extent.Chemical modification of the SWCNT surface is one of the most powerful methods to change the sensitivity of NO electrooxidation reaction.The modified electrode with SWCNT obtained by the firstly alkali treatment and then the mixed acids treatment was the best one for NO electrooxidation,the result of CV was also confirmed by that of EIS.The anodic processes of NO were recognized more clearly by exploring the reaction mechanism of NO electrooxidation at the SWCNT modified electrode.     

NO在碳纳米管(CNTs),Rh/CNTs,Rh/Al_2O_3上的分解(英文)

甲烷在预还原的ＬａＣｏＯ３催化剂上分解生成碳纳米管（ＣＮＴｓ）。研究了稳态下ＮＯ在ＣＮＴｓ,Ｒｈ／ＣＮＴｓ,Ｒｈ／Ａ１２Ｏ３上的分解,温度区间为５７３Ｋ～９７３Ｋ,原料气为６０００ｐｐｍ的ＮＯ,Ｈｅ为平衡气。程序升温还原结果表明：（１）Ｒｈ的负载显著降低了ＣＮＴｓ的氢吸收量;（２）负载于ＣＮＴｓ上的Ｒｈ比负载于Ａ１２Ｏ３上的Ｒｈ更易还原。在５７３Ｋ时ＮＯ即能与预还原后的ＣＮＴｓ,Ｒｈ／ＣＮＴＳ,Ｒｈ／Ａｌ２Ｏ３中存储的氢反应;随着氢的消耗,反应活性逐渐降低,当储存的氢消耗完后,ＮＯ的直接催化反应发生。在８７３ Ｋ及以上,Ｒｈ／ＣＮＴｓ中的ＣＮＴｓ能彼ＮＯ分解产生的氧氧化为ＣＯ。在９７３Ｋ时,ＮＯ在ＣＮＴｓ上几乎能１００％分解,连续反应１５０ｍｉｎ后其反应活性不降低,且未观察到ＣＯ或ＣＯ２的生成。在９７３Ｋ时ＣＮＴｓ本身可作为ＮＯ分解的催化剂,这是一个非常有意义的结果。     

Hybrid Materials from Carbon Nanotubes,Nickel Tetrasulfonated Phthalocyanine and Thin Polymer Layers for the Selective Electrochemical Activation of Nitric Oxide in Solution

The elaboration of hybrid materials from single‐wall carbon nanotubes (SWCNT) and tetrasulfonated nickel phthalocyanine (NiTSPc) was electrochemically performed to obtain chemically modified electrodes with improved electrocatalytic activity towards the electrooxidation of nitric oxide (NO). The characterization of these hybrid electrodes was achieved by cyclic voltammetry and AFM. The electrochemical performances of the electrodes towards the oxidation of NO were then analyzed by chronoamperometry and the obtained results show that the presence of SWCNT greatly enhances the electrocatalytic performances in terms of current intensity. Additional coatings were then electrodeposited over the hybrid electrodes to act as selective membranes against four major interfering analytes: nitrite, ascorbate, hydrogen peroxide and L ‐arginine. Several polymer coatings were tested to achieve the best balance between sensitivity to NO and selectivity against interferents.     

Long synthetic nanotubes from calix[4]arenes

We report the synthesis and encapsulation properties of long (up to 5 nm) molecular nanotubes 1-4, which are based on calix[4]arenes and can be filled with multiple nitrosonium (NO(+)) ions upon reaction with NO(2)/N(2)O(4) gases. These are among the largest nanoscale molecular containers prepared to date and can entrap up to five guests. The structure and properties of tubular complexes 1(NO(+))(2)-4(NO(+))(5) were studied by UV/Vis, FTIR, and (1)H NMR spectroscopy in solution, and also by molecular modeling. Entrapment of NO(+) in 1(NO(+))(2)-4(NO(+))(5) is reversible, and addition of [18]crown-6 quickly recovers starting tubes 1-4. The FTIR and titration data revealed enhanced binding of NO(+) in longer tubes, which may be due to cooperativity. The described nanotubes may serve as materials for storing and converting NO(x) and also offer a promise to further develop supramolecular chemistry of molecular containers. These findings also open wider perspectives towards applications of synthetic nanotubes as alternatives to carbon nanotubes.     

Soft-x-ray photoemission spectroscopy and ab initio studies on the adsorption of NO2 molecules on defective multiwalled carbon nanotubes

The adsorption of NO(2) molecules on defective multiwalled carbon nanotubes has been studied by soft-x-ray photoemission. The valence band and carbon core-level spectra have been acquired before, during, and after NO(2) exposure. The spectra show a reversible decrease of the density of states at the top of the valence band when NO(2) molecules are adsorbed on the (carbon nanotubes) CNTs. No shift of the C 1s spectra has been observed. Theoretical calculations, using density-functional theory, have been performed on the CNT + NO(2) system, considering semiconducting nanotubes with different diameters and introducing a Stone-Wales [Chem. Phys. Lett. 128, 501 (1986)] defect. The calculation confirms the decrease of the density of states at the top of the valence band in the CNT + NO(2) system, while close to the adsorption site new states appear very close to the Fermi level.     

Eletrodeposited nickel oxide on a film of carbon nanotubes for monitoring nitric oxide release from rat kidney and drug samples

Nickel oxide nanoparticles (NiO-NPs) were electrodeposited on a film of multi-walled carbon nanotubes to improve the electro-oxidation of nitric oxide (NO). The resulting sensor film exhibits excellent electrocatalytic activity towards NO and was used for the construction of an amperometric sensor for NO that was applied to monitoring the release of NO from sodium nitroprusside in rat kidney. Key operational parameters such as the conditions for deposition, kind of electrolyte and pH value were optimized. The nano-structured sensor possesses numerous active sites for oxidation of NO and thus exhibits good performance including wide linearity, simple operation, and good stability. The response to NO is linear in the concentration range from 80.0?nmol·L^?1 to 0.117?mmol·L^?1, the limit of detection is 20.0 n mol·L^?1. The sensor was developed for real-time monitoring of NO.

Pt/C和Pt/CNTs电极的电化学稳定性研究

采用恒电位氧化法研究了Pt/C和Pt/CNTs电极的电化学稳定性. 相同条件下, Pt/C电极的氧化电流大约为Pt/CNTs电极的2倍; 120 h氧化后, Pt/C电极Pt的电化学表面积下降了21.3%, 而Pt/CNTs电极仅下降了7.6%, 表明Pt/CNTs电极性能衰减较慢. X射线光电子能谱(XPS)分析表明, Pt/C的载体碳黑表面氧增加量大于Pt/CNTs中碳纳米管(CNTs)表面氧的增加量, 说明碳黑的被氧化程度较高, 电化学稳定性差; Pt的表面化学状态没有发生变化; 碳纳米管本身的抗电化学氧化性也大于碳黑. 所以, 载体的被氧化程度不同是两种电极性能衰减不同的主要原因之一, 并且排除了Pt表面状态的影响.     

TiO2纳米管阵列负载MnOx复合催化剂的脱硝性能

研究了TiO2纳米管阵列负载的MnOx复合物选择性催化还原NOx的性能.结果显示,在150～250℃下该催化剂脱除NOx的效率达90%以上(200℃下为99%以上),表现出优异的中低温脱硝性能.当反应温度更高时,有可能使反应进入努森扩散控制状态,从而在一定程度上抑制了催化反应的进行.     

Chirality- and diameter-dependent reactivity of NO2 on carbon nanotube walls

We report the density-functional calculations of NO2 adsorption on single-walled carbon nanotube walls. A single molecular adsorption was endothermic with an activation barrier, but a collective adsorption with several molecules became exothermic without an activation barrier. We find that NO2 adsorption is strongly electronic structure- and strain-dependent. The NO2 adsorption on metallic nanotubes was energetically more favorable than that on semiconducting nanotubes and furthermore the adsorption became less stable with increasing diameters of nanotubes. The adsorption barrier height shows similar dependence on the electronic structure and diameter to the adsorption energy. Our theoretical model can be a good guideline for the separation of nanotubes by electronic structures using various adsorbates.     

聚乙烯醇用于碳纳米管的开口及修饰研究

在低温(250 ℃)下,用聚乙烯醇(polyvinyl alcohol, PVA)和提纯后的碳纳米管(carbon nanotubes, CNTs)的混合物在空气中加热,以研究聚乙烯醇对碳纳米管的修饰作用,并采用TEM对不同条件下所得的产物进行了形态分析.结果发现,碳纳米管的顶端被打开,随着时间的增加,弯曲的碳纳米管断裂成较短的碳纳米管.聚乙烯醇对碳纳米管的氧化及修饰在实验中得到证实.讨论分析了氧化和修饰机理,认为可能是聚乙烯醇在空气中分解所得的产物的一种或几种在氧化和修饰过程中起主要作用.     

Demonstration of the advantages of using bamboo-like nanotubes for electrochemical biosensor applications compared with single walled carbon nanotubes

The modification of glassy carbon electrodes with random dispersions of nanotubes is currently the most popular approach to the preparation of carbon nanotube modified electrodes. The performance of glassy carbon electrodes modified with a random dispersion of bamboo type carbon nanotubes was compared with single walled carbon nanotubes modified glassy carbon electrodes and bare glassy carbon electrodes. The electrochemical performance of all three types for electrode were compared by investigating the electrochemistry with solution species and the oxidation of guanine and adenine bases of surface adsorbed DNA. The presence of edge planes of graphene at regular intervals along the walls of the bamboo nanotubes resulted in superior electrochemical performance relative to SWNT modified electrodes from two aspects. Firstly, with solution species the peak separation of the oxidation and reduction waves were smaller indicating more rapid rates of electron transfer. Secondly, a greater number of electroactive sites along the walls of the bamboo-carbon nanotubes (BCNTs) resulted in larger current signals and a broader dynamic range for the oxidation of DNA bases.     

新型微盘传感器的研制及用于单细胞释放NO监测

首次提出了一种新型碳纳米管修饰方法, 采用精确的空间操纵, 在碳纤维微盘电极盘面上修饰单壁碳纳米管, 得到新型高灵敏的NO微盘传感器, 与未修饰电极相比, 灵敏度提高10倍, NO检出限达到4.3 nmol/L, 已被成功地应用于实时动态监测单个人脐静脉内皮细胞中NO的释放.     

Oxidation of CO by NO on planar and faceted Ir(210)

Oxidation of CO by pre-adsorbed NO has been studied on planar Ir(210) and nanofaceted Ir(210) with average facet sizes of 5 nm and 14 nm by temperature programmed desorption (TPD). Both surfaces favor oxidation of CO to CO(2), which is accompanied by simultaneous reduction of NO with high selectivity to N(2). At low NO pre-coverage, the temperature (T(i)) for the onset of CO(2) desorption as well as CO(2) desorption peak temperature (T(p)) decreases with increasing CO exposure, and NO dissociation is affected by co-adsorbed CO. At high NO pre-coverage, T(i) and T(p) are independent of CO exposure, and co-adsorbed CO has no influence on dissociation of NO. Moreover, at low NO pre-coverage, planar Ir(210) is more active than faceted Ir(210) for oxidation of CO to CO(2): T(i) and T(p) are much lower on planar Ir(210) than that on faceted Ir(210). In addition, faceted Ir(210) with an average facet size of 5 nm is more active for oxidation of CO to CO(2) than faceted Ir(210) with an average facet size of 14 nm, i.e., oxidation of CO by pre-adsorbed NO on faceted Ir(210) exhibits size effects on the nanometer scale. In comparison, at low O pre-coverage planar Ir(210) is more active than faceted Ir(210) for oxidation of CO to CO(2) but no evidence has been found for size effects in oxidation of CO by pre-adsorbed oxygen on faceted Ir(210) for average facet sizes of 5 nm and 14 nm. The TPD data indicate the same reaction pathway for CO(2) formation from CO + NO and CO + O reactions on planar Ir(210). The adsorption sites of CO, NO, O, CO + O, and CO + NO on Ir are characterized by density functional theory.     

Single Molecule Detection of Nitric Oxide Enabled by d(AT)(15) DNA Adsorbed to Near Infrared Fluorescent Single-Walled Carbon Nanotubes

We report the selective detection of single nitric oxide (NO) molecules using a specific DNA sequence of d(AT)(15) oligonucleotides, adsorbed to an array of near-infrared fluorescent semiconducting single-walled carbon nanotubes (AT(15)-SWNT). While SWNT suspended with eight other variant DNA sequences show fluorescence quenching or enhancement from analytes such as dopamine, NADH, l-ascorbic acid, and riboflavin, d(AT)(15) imparts SWNT with a distinct selectivity toward NO. In contrast, the electrostatically neutral polyvinyl alcohol enables no response to nitric oxide, but exhibits fluorescent enhancement to other molecules in the tested library. For AT(15)-SWNT, a stepwise fluorescence decrease is observed when the nanotubes are exposed to NO, reporting the dynamics of single-molecule NO adsorption via SWNT exciton quenching. We describe these quenching traces using a birth-and-death Markov model, and the maximum likelihood estimator of adsorption and desorption rates of NO is derived. Applying the method to simulated traces indicates that the resulting error in the estimated rate constants is less than 5% under our experimental conditions, allowing for calibration using a series of NO concentrations. As expected, the adsorption rate is found to be linearly proportional to NO concentration, and the intrinsic single-site NO adsorption rate constant is 0.001 s(-1) μM NO(-1). The ability to detect nitric oxide quantitatively at the single-molecule level may find applications in new cellular assays for the study of nitric oxide carcinogenesis and chemical signaling, as well as medical diagnostics for inflammation.     

Dispersible Shortened Boron Nitride Nanotubes with Improved Molecule‐Loading Capacity

The oxidation process of boron nitride nanotubes was thoroughly investigated, and a slow oxidation characteristic was clearly revealed. Subsequently, the controllable oxidation process was utilized to break the sturdy structure of the boron nitride nanotubes to fabricate shortened nanotubes. The shortened boronnitride nanotubes were found to possess good solubility in water and many organic solvents. Further experiments demonstrated remarkably improved molecule‐loading capacity of the shortened boron nitride nanotubes. These dispersible shortened boron nitride nanotubes might have the potential to be developed as effective delivery systems for various molecules, which may find applications in bio‐related fields.     

负载Cu氧化铝纳米管合成及在NO+CH4反应中催化性能研究

采用过氧化氢调节反应条件,在水热体系中合成了新型的勃姆石纳米管,经520℃焙烧2h后,晶型由AlOOH转化为γ-Al2O3;采用XRD、氮吸附、TEM等对合成的纳米管进行表征.结果表明,合成的γ-Al2O3纳米管长约300nm,外径20nm,比表面积达到230m2/g以上.以此为载体,采用等体积浸渍法用Cu(NO3)2...     

共沉淀法制备的MnOx-CeO2在含NO气氛中氧化碳烟的研究

用共沉淀法制备的复合氧化物MnOx-CeO2,其程序升温氧化(TPO)结果显示,1 000 mL.m-3NO和10%O2条件下MnOx-CeO2对应的碳烟起燃温度Ti为250~303℃,远低于无催化剂时的Ti(402℃)及CeO2的Ti(334℃);也低于无NO下MnOx-CeO2的Ti(346~360℃);与MnOx的Ti(290℃)相当,但MnOx-CeO2的Tm(413~441℃)仍比MnOx的Tm(441℃)稍低。明显地,NO促进了碳烟的氧化,MnOx-CeO2比CeO2和MnOx的活性都要高。NO-TPD、FT-IR及原位DRIFTs表明,MnOx-CeO2表面对NO吸附能力强,更易促进NO氧化和NOx储存,从而有利于碳烟的氧化。可能的机理为,富氧条件下气相O2推动催化剂中氧物种(如超氧O2-,化学弱吸附氧O-与晶格氧O2-)的形成(含相互转化)与迁移,推进了NO或NO2-的氧化;储存的NOx在低温下生成硝酸根离子,在高温时则释放出高活性的NO2*和O-,促进碳烟氧化,其中间产物包括C-NO2复合物与C(O)复合物。