Nanomaterials MWCNTs

Miodek A, Mejri N, Gomgnimbou M, Sola C, Korri-Youssoufi H. E-DNA sensor of Mycobacterium tuberculosis based on electrochemical assembly of nanomaterials (MWCNTs/PPy/PAMAM). Analytical Chemistry 2015 87 9257-64. http //dx.doi.org/ 10.1021/acs.analchem.5b01761. 

It is thus evident that the characteristics of nanocarbons (conductivity, local structure, presence of defects and functional groups, morphology, etc.) are critical to determining the properties of the hybrid nanomaterial with the semiconductor. However, most of the literature studies put emphasis on the analysis of semiconductor characteristics, while often nanocarbons are only described in generic terms (CNT, for example). Yet, it is well known how the properties of nanocarbons can be considerably different from case to case (depending on details in preparation), even if the structure is formally the same (MWCNT, for example). 

However, the exceptional size-specific behavior of nanomaterials in combination with their relatively large surface-to-volume ratio might result in potential risk for human health and the environment [26-28]. For example, fullerene (C60) particles suspended in water are characterized by antibacterial activity against Escherichia coli and Bacillus subtilis [29] and by cytotoxicity to human cell lines [30]. Single- and multiwalled carbon nanotubes (CWCNTs and MWCNTs) are toxic to human cells as well [31, 32]. Nano-sized silicon oxide (Si02), anatase (Ti02), and zinc oxide (ZnO) can induce pulmonary inflammation in rodents and humans [33-35],... 

Biological functionalization of nanomaterials has become to be of significant interest in recent years owing to the possibility of developing detector systems. Noncovalent immobilization of biomolecules on carbon nanotubes motivated the use of the tubes as potentially new types of biosensor materials [207-210] (a review on carbon nanotube based biosensors was recently published by Wang [211]). So far, only limited work has been carried out with MWCNTs [207-210]. Streptavidin was found to adsorb on MWCNTs, presumably via hydro-phobic interactions between the nanotubes and hydrophobic domains of the proteins [210]. 

In addition to the size, also the shape of NMs was shown to play a role in induction of toxicity. NMs made of the same material but in different shapes can be differently internalized into the cells, react with cell membranes, and produce different oxidative effects [6, 14]. Carbon nanomaterials with different geometric structures (single-walled carbon nanotubes [SWCNTs], MWCNTs, and fullerenes) were shown to exhibit quite different cytotoxicity and bioactivity in vitro [15]. The uptake of Au nanospheres and nanorods was also significantly different, illustrating the role of the shape on NM internalization [6, 48],... 

Alternatively, PNIPAAm was grafted on to aligned MWCNTs, generating a smart surface with thermal-responsive suprahydrophilic and suprahydropho-bic transition behavior.CNT-initiated ATRP of another acrylamide class of monomers has rarely reported yet, leaving space for the future work. Preparation of smart nanomaterials with both temperature and pH responsibility and exploration of the application of the smart nanowires are especially expected. 

MWCNTs Raw tubes, as prepared by the EA method, contain about one third of other nanomaterial. This material is best removed by oxidation. Pure tubes can thus be prepared, although the procedure is wasteful. The pmest tubes are obtained when 99% is oxidised but when 95% is oxidised only 10-20% of product contains pure nanotubes. A ground raw sample is placed in an oven and the temperature is raised to 750° in air or oxygen for 30 minutes until 1% is left. This consists mostly of pure tubes with length/diameter ratios that exceed 100, and traces of open cylinders with the ratio of 20. [Ebbesen et al. Nature 367 519 1994, see also Chen et al. Adv Mater % 1012 1996.]... 

Information about surface morphology is also obtained from SEM studies. In general, the intercalated clay layers show an intense peak in the range of 1.5° ° (29 value), whereas exfoliated systems have no distinct peak in that range for their loss of structural integrity shown in the XRD pattern of the nanocomposites. XRD studies indicate that there is no infiu-ence of nanomaterial on poly(e-caprolactone)diol PCL crystallinity in sunflower oil-based hyperbranched polyurethane/silver nanocomposite, but that crystallinity is enhanced in castor oil or Mesua ferrea oil-based hyperbranched polyurethane/MWCNT nanocomposites. ... 

The hierarchy of nanomaterials contains the considerable list of various groups, such as, (i) fuUerenes and their derivatives, (ii) single wall carbon nanotubes (SWCN) (iii) multi walls carbon nanotubes (MWCNT) (iv) graphene (v) micro-electro-mechanical systems (MEMS) (vi) metal nano oxides (vii) quantum dots, and others. One can expect that in the near future this list will be extended owing to intensive work of experimentahsts. 

Recently, Ling et al. [45] reported the use of the dispersion of MWCNT-Plys as a bio-nanomaterial in apphcations such as sensing, nanoelectronics, and drug delivery systems based on the pH response of the dispersion. 

Carbon nanotubes (CNTs) are one-dimensional nanomaterials with cylindrical structures consisting of sp carbon bonds [9]. It is believed that CNTs are ideal nanofillers due to its super mechanical [10], thermal [11, 12], and electrical properties. Two main commercial players for PNCs are multiwalled carbon nanotubes (MWCNTs) with a diameter range from 4 to 30 nm and single-walled carbon nanotubes (SWCNTs) with a diameter range from 0.4 to 2-3 nm. This section will follow the in-situ approaches to incorporate CNTs into PU elastomer, solvent-based and waterborne PU. 

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