[Show abstract][Hide abstract] ABSTRACT: The growth of iron filled multiwalled carbon nanotubes (Fe-MWCNT) using chemical vapour deposition (CVD) has been widely studied. Considering the remarkable magnetic and structural properties of Fe-MWCNT, these materials have been applied in numerous areas. In particular their biomedical application has been explored, where Fe-MWCNT can be used in hyperthermia, acting as a local nano-heater at cellular level. Regarding this aim, the reproducible and highly purified ferromagnetically filled samples of carbon nanotubes are still required. There are several parameters during the synthesis process that influence the properties of the nanotubes. The most favourable temperature of the CNT growth is probably one of the most important issues and its optimisation is crucial. In the current study, the Fe-MWCNT were grown at different temperatures ranging from 650 °C to 1050 °C. Additionally, a comparison between two different CVD systems and two carbon sources are also here presented. The Fe-MWCNT were characterised using diverse techniques regarding the evaluation of their morphology, filling ratio, and purity. Observations showed a strong influence of the growth temperature on the morphology and properties of the Fe-MWCNT. The samples characterisation was performed using Raman spectroscopy, thermogravimetric analysis (TGA), X ray diffraction (XRD), and transmission electron microscopy analysis (TEM).
[Show abstract][Hide abstract] ABSTRACT: Double-walled carbon nanotubes (DWNTs) prepared by catalytic chemical vapour deposition were functionalized in such a way that they were optimally designed as a nano-vector for the delivery of small interfering RNA (siRNA), which is of great interest for biomedical research and drug development. DWNTs were initially oxidized and coated with a polypeptide (Poly(Lys:Phe)), which was then conjugated to thiol-modified siRNA using a heterobifunctional cross-linker. The obtained oxDWNT-siRNA was characterized by Raman spectroscopy inside and outside a biological environment (mammalian cells). Uptake of the custom-designed nanotubes was not associated with detectable biochemical perturbations in cultured cells, but transfection of cells with DWNTs loaded with siRNA targeting the green fluorescent protein (GFP) gene, serving as a model system, as well as with therapeutic siRNA targeting the survivin gene, led to a significant gene silencing effect, and in the latter case a resulting apoptotic effect in cancer cells.
[Show abstract][Hide abstract] ABSTRACT: Nanotechnology is a broad scientific field but one of the most explored materials in nanotechnology is carbon nanotube (CNT).
A large proportion of research on CNTs is focused on their huge potential for biomedical applications. Within this context,
the synthesis of carbon nanotubes filled with magnetic materials has been widely investigated, especially with iron due to
its excellent ferromagnetic characteristics. Pure iron-filled carbon nanotubes (Fe-CNT) can be prepared following diverse
routes. Here, an overview of the different preparation routes of Fe-CNT, using the chemical vapour deposition (CVD) synthesis
method will be presented. Several working parameters were varied and investigated, the most significant being the pressure
of the system, the iron and the carbon sources. The consequence of these modifications is reflected in the structure of the
final material, which varies in respect of the amount of iron encapsulated in the cavity, tube diameter and the number of
graphitic walls forming the CNT. The filling of hollow CNT through wet chemistry reactions (as a post-synthesis route) and
CVD process (filling during the synthesis of CNTs) will also be addressed in this chapter.
[Show abstract][Hide abstract] ABSTRACT: Efforts to develop carbon nanotubes (CNTs) as nano-vehicles for precise and controlled drug and gene delivery, as well as markers for in vivo biomedical imaging, are currently hampered by uncertainties with regard to their cellular uptake, their fate in the body, and their safety. All of these processes are likely to be affected by the purity of CNT prepn., as well as the size and concn. of CNTs used, parameters that are often poorly controlled in biol. expts. It is demonstrated herein that under the exptl. conditions of std. transfection methods, DWNTs are taken up by cultured cells but are then released after 24 h with no discernable stress response. The results support the potential therapeutic use of CNTs in many biomedical settings, such as cancer therapy. [on SciFinder(R)]
[Show abstract][Hide abstract] ABSTRACT: One of the most interesting molecular hybrid based on Multi-wall Carbon Nanotubes (MWCNTs) in respect of their medical applications (such as hyperthermia or drug delivery) is iron filled MWCNTs (Fe-MWCNTs). The significant barrier to realize this potential utilization of Fe-MWCNTs is their natural tendency to aggregate in aqueous buffers. Therefore here, we present a novel route to create a stable suspension of this system in a biocompatible aqueous solution of glicolipid Psychosine (Galactosyl-β1-sphingosine). This step was performed via the covalent linkage of the glicolipid and the external moieties of the tubes. It is worth noting that the functional groups on Fe-MWCNTs surface have been formed using a mild and non-invasive treatment employing galactose in order to preserve the ferromagnetic properties of the iron filled tubes.
Diamond and Related Materials 07/2010; DOI:10.1016/j.diamond.2010.02.013 · 1.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Iron filled carbon nanotubes have been widely used for numerous applications due to their remarkable magnetic and structural
properties. One very important example is the biomedical application, where iron filled multiwalled carbon nanotubes (Fe-MWCNT)
can be used in anticancer therapies, acting as local nano-heaters, at the cellular level. Regarding this aim the systematic
study of the Fe-MWCNT preparation was required. Therefore, in this contribution a chemical vapour deposition (CVD) process
was employed to perform a comparative study on Fe-MWCNT synthesis using two carbon feedstock (cyclohexane and ethanol), and
different catalyst mixtures. The homogeneity, filling ratio, and purity of the samples were analysed, and the optimal conditions
for the bulk sample preparation were achieved. The samples were characterised concerning their quality, diameter range, number
of walls, and amount of iron encapsulated in the nanotubes cavity. The characterisation was performed using Raman spectroscopy,
transmission electron microscopy (TEM), and thermogravimetric analysis (TGA).
Physics of Condensed Matter 05/2010; DOI:10.1140/epjb/e2010-00070-1 · 1.46 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Here, a study on Cisplatin (cis-Diammineplatinum(II)
dichloride – CDDP) insertion within multiwalled carbon nanotubes (MWCNTs)
via capillary forces is presented. The employment of MWCNTs as anticancer
drug nano-vectors is suggested by the harmful side effects occurring after
the chemotherapeutic treatment due to the lack of selectivity of the
chemotherapeutic agents in general. Cisplatin is widely used as a powerful
cell-killer but without any cell-specificity. Via high resolution
transmission electron microscopy (HR-TEM) CDDP clusters inserted into MWCNTs
were detected. Energy dispersive X-ray spectroscopy (EDX) revealed the
signal of CDDP constitutive elements. Raman Spectroscopy and InfraRed analysis excluded
the presence of the drug on the tubes outer shell. Thermogravimetric (TGA)
study was exploited to evaluate the purity of the material and to calculate
the amount of CDDP incorporated into the tubes. A time dependent release of
CDDP indicated that the outflow took place in the range between 12 and 48 h. After this time ~95% of the drug previously embedded
The European Physical Journal B 05/2010; 75(2):141-146. DOI:10.1140/epjb/e2010-00037-2 · 1.46 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Carbon-encapsulated magnetic nanoparticles are a new class of materials where the core magnetic nanoparticle is protected
from reactions with its environment by graphite shells. Having a structure similar to carbon nanotubes, these nanoparticles
could be potentially functionalized using methods which are already applied to those structures. We present the effects of
acidic treatments based on HCl, HNO3, and H2SO4 on these nanoparticles highlighting the impact on their magnetic and surface properties. We show that acidic treatments based
on HNO3 can be successfully applied for the generation of carboxylic groups on the surface of the nanoparticles. Using methylamine
as a model, we demonstrate that these functional groups can be used for further functionalization with amino-containing biomolecules
via diimide-activated amidation.
Journal of Nanoparticle Research 01/2010; 12(2):513-519. DOI:10.1007/s11051-009-9773-0 · 2.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A comparative study will be presented on the effect of strong acid treatments in both single-walled (SWCNT) and multi-walled carbon nanotubes (MWCNT). The effects were studied by Raman spectroscopy. The results show that in SWCNT the raw sample shows a broader G band, well fitted by a Breit-Wigner-Fano line in comparison with the acid treated sample, which can be fitted using a Lorentzian lineshape. The original shape of this feature is recovered after the annealing step. In MWCNT samples, a two-peak G' band profile was observed after the acid treatment, originated by an exfoliation effect. [GRAPHICS] Schematic illustration of the effects of acid treatment. On SWCNT, phase I corresponds to the intercalation in the interstitial channels of the bundles, while phase II is assigned to the intercalation between the walls of neighbouring nanotubes. On MWCNT, intercalation into the walls and consequent exfoliation is represented. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
[Show abstract][Hide abstract] ABSTRACT: Singlewalled carbon nanotubes (SWCNT) exhibit very unique properties. As an electronic system they undergo amphoteric doping effects (n-type and p-type) which can be reversed. These processes affect the optical and vibronic properties of the carbon nanotubes. The most common and widely used procedure which changes the properties of the SWCNT is acid treatment applied as a purification procedure. This effect has been widely studied but not fully understood so far. Here, we present a study, in which a diameter sensitive effect has been observed. Therefore, two kinds of SWCNT samples have been studied: (i) produced via chemical vapour deposition with a broad diameter distribution, and (ii) synthesised by the laser ablation technique which is commonly known to result in narrow diameter distribution bulk SWCNT samples. Resonance Raman spectroscopy, optical absorption spectroscopy, and Fourier transform middle-infrared spectroscopy have been applied for the characterisation of the samples.
Journal of Alloys and Compounds 11/2009; 486(1):386-390. DOI:10.1016/j.jallcom.2009.06.177 · 2.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Here we present a comparative study on Raman spectroscopy and optical absorption spectroscopy (OAS) as two main techniques being used for the purity evaluation of singlewall carbon nanotubes (SWCNT). The raw material was produced by the standard laser ablation technique using cobalt and nickel as catalysts (40wt.% SWCNT). The presence of impurities influences the measurement of the properties of the carbon nanotubes. Therefore, the systematic purification study and its comparative estimation using the above mentioned characterization tools are presented. In order to reduce the catalyst particles content the diluted aqua regia was applied. In order to eliminate the amorphous carbon and fullerenes (unwanted forms of carbon) the high temperature annealing was used. The measurements were performed in suspension (dimethylformamide (DMF)) and on thin film deposited on potassium bromide crystal. This gave additional information about the effect of the sample preparation technique sensitivity on the purity of SWCNT evaluation.
Energy Conversion and Management 09/2008; 49(9):2490-2493. DOI:10.1016/j.enconman.2008.01.037 · 3.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Here, we present a study on the synthesis of different nanostructures with one single-step in situ filling (encapsulation) via carbon vapor deposition (CVD). Ferrocene, acetylferrocene and iron (II) nitrate as iron precursors were explored. The application of each of these compounds resulted in different carbon nanomaterials such as: iron filled multiwalled carbon nanotubes with a low filling ratio (Fe-MWCNT), iron filled nanocapsules and unfilled MWCNT. The as-produced samples were purified by high temperature annealing and acid treatment. The purified materials were characterised using transmission electron microscopy (TEM) and Raman spectroscopy.
Energy Conversion and Management 09/2008; DOI:10.1016/j.enconman.2008.01.040 · 3.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Application of Raman spectroscopy to analyse carbon nanotubes has been presented. Having a mixture of various carbon nanotube samples, one can easily distinguish, in a quick experiment, presence of singlewalled, doublewalled and multiwalled carbon nanotubes (SWCNT, DWCNT, MWCNT, respectively). The so-called G-line is a characteristic feature of the graphitic layers and corresponds to the tangential vibration of carbon atoms. Another characteristic mode is a typical sign of defective graphitic structures (D-line). A comparison of the intensity ratios of these two peaks gives a measure of the quality of the bulk samples. In addition, there is a third mode, named the radial breathing mode (RBM) which is very sensitive to the diameter of SWCNT and DWCNT. Additional option is application of Raman microscopy for mapping analysis and depth profiling to view the changes of intensity in various directions in the sample.