The combined catalytic action of solid acids with nickel for the transformation of polypropylene into carbon nanotubes by pyrolysis

The effects of both organically modified montmorillonite (OMMT) and Ni2O3 on the carbonization of polypropylene (PP) during pyrolysis were investigated. The results from TEM and Raman spectroscopy showed that the carbonized products of PP were mainly multiwalled carbon nanotubes (MWNTs). Surprisingly, a combination of OMMT and Ni2O3 led to high-yield formation of MWNTs. X-ray powder diffraction (XRD) and GC-MS were used to investigate the mechanism of this combination for the high-yield formation of MWNTs from PP. Bronsted acid sites were created in degraded OMMT layers by thermal decomposition of the modifiers. The resultant carbenium ions play an important role in the carbonization of PP and the formation of MWNTs. The degradation of PP was induced by the presence of carbenium ions to form predominantly products with lower carbon numbers that could be easily catalyzed by the nickel catalyst for the growth of MWNTs. Furthermore, carbenium ions are active intermediates that promote the growth of MWNTs from the degradation products with higher carbon numbers through hydride-transfer reactions. The XRD measurements showed that Ni2O3 was reduced into metallic nickel (Ni) in situ to afford the active sites for the growth of MWNTs.

Dissolution, characterization and photo functionalization of carbon nanotubes

A simple method to disperse carbon nanotubes (CNTs) has been achieved, which gives two photofunctionalized CNTs, hydrazine nanotubes (h-CNTs) and 1,3,4-oxadiazole nanotubes (o-CNTs). Results from FTIR, H-1 NMR spectroscopy and TEM observations showed that the functionalization was successful. The modified nanombes can dissolve in most of the nonpolar organic solvents and no precipitate was observed in the solution of the nanombes even after 2 months. The functionalized nanotubes showed photo-electronic properties, which is due to the attachment of the function groups to them as proved by steady-state fluorescence spectroscopy. Both h-CNTs and o-CNTs showed good thermal stability below 300 C and might be used as functional materials.

Conductive property of multiwall carbon nanotubes-PEO-salt nanocomposite film

By adding a small amount of multiwall carbon nanotubes (MWNTs) to polyethylene oxide (PEO) and a salt system, a new type of nanocomposite film was constructed. At ambient temperature, the conductivity of the PEO-salt-0.5 wt % MWNTs was nearly three orders of magnitude higher than that of the PEO-salt system. The conductive property of the nanocomposite film was characterized by ac impedance and the differential scanning calorimetry technique.

Noncovalent functionalization of multiwalled carbon nanotubes: Application in hybrid nanostructures

We developed a reproducible, noncovalent strategy to functionalize multiwalled carbon nanotubes (MWNTs) via embedding nanotubes in polysiloxane shells. (3-Aminopropyl)triethoxysilane molecules adsorbed to the nanotube surfaces via hydrophobic interactions are polymerized simply by acid catalysis and form a thin polysiloxane layer. On the basis of the embedded MWNTs, negatively charged gold nanoparticles are anchored to the nanotube surfaces via electrostatic interactions between the protonated amino groups and the gold nanoparticles. Furthermore, these gold nanoparticles can further grow and magnify along the nanotubes through heating in HAuCl4 aqueous solution at 100 degrees C; as a result these nanoparticles are joined to form continuous gold nanowires with MWNTS acting as templates.

Facile preparation of amperometric laccase biosensor with multifunction based on the matrix of carbon nanotubes-chitosan composite

The carbon nanotubes-chitosan (CNTs-CS) composite provides a suitable biosensing matrix due to its good conductivity, high stability, and good biocompatibility. Enzymes can be firmly incorporated into the matrix without the aid of other cross-linking reagents. The composite is easy to form insoluble film in solution above pH 6.3. Based on this, a facilely fabricated amperometric biosensor by entrapping laccase into the CNTs-CS composite film has been developed. At pH 6.0, the fungi laccase incorporated into the composite film remains better catalytic activity than that dissolved in solution. The system is in favor of the accessibility of substrate to the active site of laccase, thus the affinity to substrates is improved greatly, such as 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS), catechol, and 0, with K. values of 19.86 mu M, 9.43 mu M, and 3.22 mM, respectively. The major advantages of the as-prepared biosensor are: detecting different substrates (ABTS, catechol, and 02), possessing high affinity and sensitivity, durable long-term stability, and facile preparation procedure. On the other hand, the system can be applied in fabrication of biofuel cells as the cathodic catalysts based on its good electrocatalysis for oxygen reduction.

Electrogenerated chemiluminescence sensing platform using Ru(bpy)(3)(2+) doped silica nanoparticles and carbon nanotubes

An effective electrogenerated chemiluminescence (ECL) sensor was developed by coimmobilization of the Ru(bpy)(2)(3+)-doped silica (RuDS) nanoparticles and carbon nanotubes (CNTs) on glassy carbon electrode through hydrophobic interaction. The uniform RuDS nanoparticles were prepared by a water-in-oil (W/O) microemulsion method and Ru(bpy)(3)(2+) doped inside could still maintain its high ECL efficiency. With such unique immobilization method, a great deal of Ru(bpy)(3)(2+) was immobilized three-dimensionally on the electrode , which could greatly enhance the ECL response and result in the increased sensitivity. On the other hand, CNTs played dual roles as matrix to immobilize RuDS nanoparticles and promoter to accelerate the electron transfer between Ru(bpy)(3)(2+) and the electrode. The as-prepared ECL sensor displayed good sensitivity and stability.

Electrochemical characteristics of facile prepared carbon nanotubes-ionic liquid gel modified microelectrode and application in bioelectrochemistry

The carbon nanotubes (CNTs) based microelectrode (ME) by modifying CNTs-room temperature ionic liquid (IL) gel at carbon fiber microelectrode (CFME) is easily prepared, which exhibits the typical cyclic voltammogram of ME with sigmoid shape and possesses good stability, high conductivity and enlarged current response and tunable dimension. The direct electron transfer of glucose oxidase has been greatly promoted showing reversible electrochemical behavior even at high scan rate. In addition, the CNTs based ME also exhibits effectively electrocatalytic oxidized ability to biomolecules, e.g. dopamine (DA), ascorbic acid (AA) and dihydronicotinamide adenine dinucleotide. The obvious separation of oxidized peak potential for DA and AA makes it possible to selectively determine DA in presence of AA. These phenomena show that the CNTs based ME has promising potential to detect various species in vivo and in vitro.

Polypeptide modification of multiwalled carbon nanotubes by a graft-from approach

Covalent surface functionalization of carbon nanotubes with polypeptides is promising for possible medical applications. This work presents a graft-from approach to perform the polypeptide modification of multiwalled carbon nanotubes (MWTNs). The raw MWNTs are first amine-functionalized. The amine-functionalized MWNTs are then used as the initiator to initiate the ring-opening polymerization of gamma-benzyl-L-glutamate N-carboxyanhydride (BLG- NCA), to results in the polypeptide-grafted MWNTs. FT-IR, XPS, and TGA data demonstrate that the functionalization is successful. The TEM images of the products show that the thickness of the polypeptide shell of the PBLG-MWNT is about 4.5-22 nm. Using the facile route developed here, carbon nanotubes functionalized with other types of polypeptides can be easily fabricated using the corresponding NCAs.

Preparation and layer-by-layer self-assembly of positively charged multiwall carbon nanotubes

The report described a method of more stably dispersing oxidized carbon nanotubes (CNTs) by forming complex with polycation and the layer-by-layer self-assembly behavior of the complex with polyanion was studied. The properties of the self-assembled multilayer film containing carbon nanotubes were studied. Cyclic voltammetry, UV-vis-NIR spectroscopy, electrochemical impedance spectroscopy and scanning electron microscopy were used for characterization of film assembly. UV-vis-NIR spectroscopy and cyclic voltammetry study indicated the uniform growth of the film. Electrochemical impedance spectroscopy results showed that incorporating of carbon nanotubes in the polyelectrolyte multilayers; decreased in the electron-transfer resistance R, indicating more favorable electrochemical reaction interface. The electrocatalytic property of the multilayer modified electrode to NADH was investigated mainly with different numbers of the bilayers; and the results showed that along with the increase of the assembled bilayers the overpotential of NADH oxidation decreased. The detection lit-nit Could reach 6 mu M at a detection potential of 0.4 V.

Composite film of carbon nanotubes and chitosan for preparation of amperometric hydrogen peroxide biosensor

A new amperometric biosensor for hydrogen peroxide was developed based on cross-linking horseradish peroxidase (HRP) by glutaraldehyde with multiwall carbon nanotubes/chitosan (MWNTs/chitosan) composite film coated on a glassy carbon electrode. MWNTs were firstly dissolved in a chitosan solution. Then the morphology of MWNTs/chitosan composite film was characterized by field-emission scanning electron microscopy. The results showed that MWNTs were well soluble in chitosan and robust films could be formed on the surface. HRP was cross-linked by glutaraldehyde with MWNTs/chitosan film to prepare a hydrogen peroxide biosensor. The enzyme electrode exhibited excellent electrocatalytic activity and rapid response for H2O2 in the absence of a mediator. The linear range of detection towards H2O2 (applied potential: -0.2 V) was from 1.67 x 10(-5) to 7.40 x 10(-4) M with correction coefficient of 0.998. The biosensor had good repeatability and stability for the determination of H2O2. There were no interferences from ascorbic acid, glucose, citrate acid and lactic acid.

Preparation of cobalt hexacyanoferrate nanowires using carbon nanotubes as templates

A simple and convenient method for preparation of cobalt hexacyanoferrate (CoHCF) nanowires by electrodeposition was reported. Multiwall carbon nanotubes (MWNTs) were used as templates to fabricate CoHCF nanowires. MWNTs could affect the size of CoHCF nanoparticles and made them grow on the sidewalls of carbon nanotubes during the process of electrodeposition. Thus CoHCF nanowires could be obtained by this method. Field-emission scanning electron microscopy, UV-vis spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize these nanowires. These results showed the CoHCF nanowires could be easily and successfully obtained and it gave a novel approach to prepare inorganic nanowires.

Multilayer films of carbon nanotubes and redox polymer on screen-printed carbon electrodes for electrocatalysis of ascorbic acid

Multilayer films containing multiwall carbon nanotubes and redox polymer were successfully fabricated on a screen-printed carbon electrode using layer-by-layer (LBL) assembled method. UV-vis spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy and electrochemical method were used to characterize the assembled multilayer films. The multilayer films modified electrodes exhibited good electrocatalytic activity towards the oxidation of ascorbic acid (AA). Compared with the bare electrode, the oxidation peak potential negatively shifted about 350 mV (versus Ag/AgCl). Furthermore, the modified screen-printed carbon electrodes (SPCEs) could be used for the determination of ascorbic acid in real samples.

Synthesis and photoluminescence of Y2O3 : RE3+ (RE = Eu, Tb, Dy) porous nanotubes templated by carbon nanotubes

Y2O3:RE3+ (RE = Eu, Tb, Dy) porous nanotubes were first synthesized using carbon nanotubes as template. The morphology of the coated precursors and porous Y2O3:Eu3+ nanotubes was determined by scanning electron Microscopy (SEM) and transmission electron microscopy (TEM). It was found that the coating of precursors on carbon nanotubes (CNTs) is continuous and the thickness is about 15 nm, after calcinated, the Y2O3:Eu3+ nanotubes are porous with the diameter size in the range of 50-80 nm and the length in micrometer scale. X-ray diffraction (XRD) patterns confirmed that the samples are cubic phase Y2O3 and the photoluminescence studies showed that the porous rare earth ions doped nanotubes possess characteristic emission of Eu3+, Tb3+, and Dy3+. This method may also provide a novel approach to produce other inorganic porous nanotubes used in catalyst and sensors.

Assembly of Prussian blue onto SiO2 nanoparticles and carbon nanotubes by electrostatic interaction

Prussian blue (PB) was modified onto surface of SiO2 nanoparticles and multiwall carbon nanotubes (MWNTs) by electrostatic assembled method. SiO2 nanoparticles and MWNTs firstly modified by polyelectrolyte exhibited positive charges and negative charged PB could be assembled onto them. UV-vs spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), field-emitted scanning electron microscopy (FE-SEM) and electrochemical methods were used to characterize these composite nanomaterials. TEM and FE-SEM images showed that PB was easily assembled onto polyelectrolyte modified SiO2 nanoparticles and MWNTs. Moreover, PB on the surface of nanomaterials was stable and still kept its intrinsic electrochemical properties and high electrocatalytic activity towards hydrogen peroxide.