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Multi-walled carbon nanotubes were chemically functionalized with methacrylic acid and methacrylated bovine serum albumin by free radical grafting reaction to obtain novel nanocomposites. The nanotubes were synthesized by aerosol-assisted chemical vapor deposition, and then the monomers were directly grafted by the action of hydrogen peroxide/ascorbic acid redox pair which allows operating in water-compatible and eco-friendly environment without the generation of any toxic reaction by-product. A multi-technique approach was used to evaluate the effectiveness of the grafting process employing Fourier transform infrared, Raman, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analyses. Considering the high importance of methacrylate polymers and bovine serum albumin, the proposed nanocomposites could be of great applicability in biomedical and pharmaceutical fields.

We report the encapsulation of the antiferromagnetic and magnetoelectric oxide Cr2O3 inside both multi - and single-walled carbon nanotubes. This is achieved by a two step post-synthesis filling process which involves the filling of nanotubes with CrO3 either from aqueous solution or from the molten phase, followed by appropriate annealing sequences. TEM imaging confirms significant filling rates for both multi- and single-walled carbon nanotubes. Analytical transmission electron microscopy implies that after secondary annealing Cr2O3 is formed inside the nanotubes.

Objectives To prove the possibility of covalently functionalizing multi-walled carbon nanotubes (CNTs) by free radical grafting of gallic acid on their surface with the subsequent synthesis of materials with improved biological properties evaluated by specific in-vitro assays. Methods Antioxidant CNTs were synthesized by radical grafting of gallic acid onto pristine CNTs. The synthesis of carbon nanotubes was carried out in a fixed-bed reactor and, after the removal of the amorphous carbon, the grafting process was performed. The obtained materials were characterized by fluorescence and Fourier transform infrared spectroscopy (FT-IR) analyses. After assessment of the biocompatibility and determination of the disposable phenolic group content, the antioxidant properties were evaluated in terms of total antioxidant activity and scavenger ability against 2,2′-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl and peroxyl radicals. Finally the inhibition activity on acetylcholinesterase was evaluated. Key findings The covalent fuctionalization of CNTs with gallic acid was confirmed and the amount of gallic acid bound per g of CNTs was found to be 2.1 ± 0.2 mg. Good antioxidant and scavenging properties were recorded in the functionalized CNTs, which were found to be able to inhibit the acetylcholinesterase with potential improved activity for biomedical and pharmaceutical applications. Conclusions For the first time, a free radical grafting procedure was proposed as a synthetic approach for the covalent functionalization of CNTs with an antioxidant polyphenol.

The electrical percolation behaviour of five different kinds of carbon nanotubes (CNTs) synthesised by two CVD techniques was investigated on melt mixed composites based on an insulating polyamide 6.6 matrix. The electrical percolation behaviour was found to be strongly dependent on the properties of CNTs which varied with the synthesis conditions. The lowest electrical percolation threshold (0.04 wt.%) was determined for as grown multi-walled carbon nanotubes without any purification or chemical treatment. Such carbon nanotubes were synthesised by the aerosol method using acetonitrile as ferrocene containing solvent and show relatively low oxygen content near the surface, high aspect ratio, and good dispersability. Similar properties could be found for nanotubes produced by the aerosol method using cyclohexane, whereas CNTs produced by the fixed bed method using different iron contents in the catalyst material showed much higher electrical percolation thresholds between 0.35 and 1.02 wt.%.

Aim: In this paper, carbon nanotubes (CNTs) are presented as feasible carriers for carboplatin, a therapeutic agent for cancer treatment. The drug was introduced into CNTs to demonstrate that they are suited as nanocontainers and nanocarriers and can release the drug to initialize its medical virtue. Method: The filling was accomplished by a wet-chemical approach after the CNTs were opened. The effect on cell proliferation and cytotoxicity of the carboplatin-filled CNT was investigated by using a viability assays. Results: Using different analysis methods such as electron energy loss spectroscopy and x-ray photoelectron spectroscopy the structure of carboplatin incorporated into the CNTs was found to be retained. In vitro studies showed that carboplatin-filled CNTs inhibited growth of bladder cancer cells whereas unfilled, opened CNTs barely affected cancer cell growth. Conclusion: A reversible filling–emptying process could be performed successfully within this work. This highlights the potential of CNTs for applications in the field of drug delivery.

Fe‐filled multi‐wall carbon nanotubes (MWNTs) were produced by pyrolysis of ferrocene in a dual furnace system. They grew vertically aligned on oxidized silicon substrates placed inside the reaction zone of a chemical vapor deposition reactor. A variation of the growth parameters has been performed in order to evaluate the possibility to control the Fe‐filled nanotube growth process and thereby the nanotube‐ and the filling length, diameter and yield, and also the nanotube alignment. Electron microscopy studies show nanotubes with quite different morphologies. The relation between the aligned Fe‐filled MWNTs growth and the most important growth parameters is discussed.

This paper presents melt mixed composites where two ways of introducing nanotubes in polymer matrices were used. In the first case, commercially available masterbatches of nanotube/polymer composites are used as the starting materials that are diluted by the pure polymer in a subsequent melt mixing process (masterbatch dilution method) while in the other case nanotubes are directly incorporated into the polymer matrix. As an example of the masterbatch dilution method, composites of polycarbonate with MWNT are presented which are produced using a Brabender PL‐19 single screw extruder. In this system, electrical percolation was found at about 0.5 wt% MWNT. The nanotube dispersion as observed by TEM investigations is quite homogeneous. The direct incorporation method is discussed in composites of polycarbonate with MWNT and SWNT. For commercial MWNT percolation was found between 1.0 and 3.0 wt% depending on the aspect ratio and purity of the materials. For HiPCO‐SWNT from CNI percolation occurred be...

Aligned Fe–Co alloy–filled multi-walled carbon nanotubes (MWNTs) were synthesized on silicon substrates via the pyrolysis of a ferrocene/cobaltocene mixture. The nanotubes are aligned normal to the substrate surface. The encapsulated metal nanowires have diameters of 10–20 nm and a length of up to a few micrometers. They consist of single crystals with BCC structure. Alternating gradient magnetometry investigations show that the magnetic wires exhibit a clear ferromagnetic behavior at room temperature. An enhanced coercivity of about 126 mT and uniaxial magnetic anisotropy with the easy axis of magnetization along the wire axis were observed.

We report on a method for the selective growth of aligned cobalt (Co)‐filled multi‐walled carbon nanotubes (MWNTs) using the pyrolysis of cobaltocene. The nanotubes grow preferentially on Fe structures patterned onto SiO2/Si substrates by a lift‐off process. The filling is discontinuous and forms a sequence of nanowire segments located along the tube. The nanowires consist of single crystalline grains with fcc structure. They have diameters of 10–20 nm and their length reaches several hundred nanometers. Our method allows the building of a system of oriented MWNTs filled with ferromagnets. It may be applied for fabricating nanotube‐based microelectronic devices.

Carpet-like flakes (area < 9 mm 2 ; thickness < 50 μm) of well-aligned Co-filled multi-walled carbon nanotubes were grown by decomposition of cobaltocene. The nanotubes have outer diameters of 50-90 nm and a metal core of 15-30 nm diameter. They are discontinuously filled with f.c.c.-Co nanowires of up to a few micrometers in length. Magnetometry studies show a weak uniaxial magnetic anisotropy with the easy axis along the nanowires and a high coercivity of about 59 mT. Electron holography provides information about the magnetic characteristics of individual nanowires.

We describe the preparation and the properties of Fe-filled multi-walled carbon nanotubes on Co-coated oxidized silicon substrates. The material was grown by pyrolysis of ferrocene, using a chemical vapor deposition process. Scanning and transmission electron microscopy studies indicate that the material consists of filled and aligned MWNTs. They have outer diameters of 40–100 nm and diameters of the metal core of 20–40 nm. Energy dispersive X-ray analysis of individual tubes reveals that their filling consists of pure Fe. Alternating gradient magnetometry investigations demonstrate the ferromagnetic behavior of the filled tubes. We observe unique magnetic properties differing from those of bulk Fe.

Thanks to their capillary-like structure CNTs provide a well-characterized container material for hosting miscellaneous fillings. Here we present basic studies on the use of CNTs for drug delivery. By introducing carboplatin, an anticancer drug, into the CNTs via a wet chemical approach, drug-filled nanotubes have been produced. The maintenance of the structure of carboplatin was proven using electron energy loss spectroscopy and X-ray photoelectron spectroscopy. It was shown that the drug is released into cell culture medium leading to cell death. Cell viability assays performed with bladder cancer cells EJ28 demonstrated the cytotoxicity of CNTs filled with carboplatin. For comparison a reference of unfilled, open ended CNTs did not affect the cell viability. These results point out the general capabilities of CNTs as nanocarriers for drug delivery.

Ferromagnetic-filled carbon nanotubes are new nanostructured materials with many possible applications. They can be synthesized using the thermal decomposition of metallocenes of the iron triad. Two different methods (solid and liquid source CVD) are suitable for producing, at very high filling rates, filled nanotubes on precoated Si substrates. The diameters of deposited filled nanotubes are particularly dependent on the size of catalyst particles on the substrate, while the lengths depend more on the sublimation and decomposition rate of metallocene. The growth mechanism of filled carbon nanotubes is based on the root growth mode. Multiwalled carbon nanotubes, filled with body-centered cubic Fe, show unusual magnetic properties. Aligned-growth nanotube ensembles can reach coercivities up to 130 mT (bulk iron 0.09 mT). Ferromagnetic-filled carbon nanotubes can be successfully used both as cantilever tips in magnetic force microscopy and as a nanocontainer for new therapies in medicine.

This paper presents melt mixed composites where two ways of introducing nanotubes in polymer matrices were used. In the first case, commercially available masterbatches of nanotube/polymer composites are used as the starting material which are diluted by the pure polymer in a subsequent melt mixing process (masterbatch dilution method) while in the other case nanotubes are directly incorporated into the polymer matrix. As an example of the masterbatch dilution method, composites of polycarbonate with MWNT are presented which are produced using different melt mixing equipments. The lowest percolation threshold was found at about 0.5 wt% MWNT using a Brabender PL‐19 single screw extruder. The nanotube dispersion as observed by TEM investigations is quite homogeneous. The direct incorporation method is discussed in composites of polycarbonate with MWNT and SWNT. The nanotube addition significantly changes the stress‐strain behavior of the composites: modulus and stress are increased; however, elongation is reduced especially above the percolation concentration.

We have performed morphological analysis of samples of Fe nanowires encapsulated into aligned multiwalled carbon nanotubes (Fe-MWCNTs) via Fe57 Mossbauer spectroscopy. The aligned Fe-MWCNTs were obtained by pyrolysis of ferrocene onto an oxidized Si substrate. Transmission Mossbauer spectroscopy (TMS) and backscattered conversion electron Mossbauer spectroscopy (CEMS) were applied in order to distinguish different Fe phases and their spatial distribution within the whole sample and along the tubes’ height. A characterization (on a large spatial scale) of the aligned CNT samples was performed by obtaining TMS spectra for selected spots positioned at different locations of the sample. While the total Fe content changes considerably from one location to another, the γ-Fe∕α-Fe phase ratio is constant onto a relatively large area. Using TMS and CEMS for all aligned Fe-MWCNT samples it is also shown that along the CNT axes, going to the top of the nanotube the relative content of the γ-Fe phase increases. Going...