Multiwalled CNTs functionalized

Pillai et al. described a comparison between two chemical functionalization strategies for the amine functionalization of multiwalled CNTs. The modified CNTs with optimum amine content were used to prepare PLA/CNT nanocomposites through solution casting method. The polymer nanocomposite thus prepared showed improved thermal properties when compared to the neat PLA [65]. 

Burke et al. injected pluronic F127 functionalized multiwalled CNTs (MWNTs) into kidney tumors and then ablated the tumors by 1064 nm laser irradiation (3 W cm , 3 min). The temperature of the tumor tissue was increased to 76 °C and the tumors were totally destroyed. In another report, Ghosh and coworkers demonstrated that DNA-encased MWNTs could also be used to safely eradicate PC3 xenograft tumors in vivo under 1064 nm laser irradiation (2.5 W cm , 70 s). ... 

Tan Y, Deng W, Ge B, Xie Q, Huang J, Yao S. Biofuel cell and phenolic biosensor based on acid-resistant laccase-glutaraldehyde functionalized chitosan-multiwalled CNTs nanocomposite film. Biosens Bioelectron 2009 24 2225-2231. 

An alternative approach to functionaUzed CNTs is direct surface functionalization of CNTs with reactive groups. For example, Theato and coworkers used partly oxidized multiwall CNTs to install PFP esters on the surface, which could be used for further surface functionaUzation or for use in the reactive LbL assembly of multilayer polymer films. It is worth noting that the obtained thin films were transparent and conductive, making them suitable candidates for solution-processed transparent electrodes [209]. 

Some potentially relevant work concerns the attachment of magnesium hydroxide nanoparticles onto multiwall carbon nanotubes (MWCNTs).92 These were prepared from water-in-oil emulsions specifically for conversion into MgO to functionalize and preserve the mechanical and the electrical properties of the CNTs, although not for fire-retardant purposes. However, although more speculative, this work may be of interest as it has been reported that combinations of M WCNT and micron-sized particles of ATH in EVA function as very efficient fire retardants through enhanced char formation and coherency.93... 

Double-walled carbon nanotubes (DWNTs), first observed in 1996, constitute a unique family of carbon nanotubes (CNTs). -2 DWNTs occupy a position between the single-walled carbon nanotubes (SWNTs) and the multiwalled carbon nanotubes (MWNTs), as they consist of two concentric cylinders of rolled graphene. DWNTs possess useful electrical and mechanical properties with potential applications. Thus, DWNTs and SWNTs have similar threshold voltages in field electron emission, but the DWNTs exhibit longer lifetimes.3 Unlike SWNTs, which get modified structurally and electronically upon functionalization, chemical functionalization of DWNTs surfaces would lead to novel carbon nanotube materials where the inner tubes are intact. The stability of DWNTs is controlled by the spacing of the inner and outer layers but not by the chirality of the tubes 4 therefore, one obtains a mixture of DWNTs with varying diameters and chirality indices of the inner and outer tubes. DWNTs have been prepared by several techniques, such as arc discharge5 and chemical vapor depo-... 

The most common method for the production of carbon nanotubes is hydrocarbon-based chemical vapor deposition (CVD) [97] and adaptations of the CVD process [98, 99], where the nanotubes are formed by the dissolution of elemental carbon into metal nanoclusters followed by precipitation into nanotubes [100]. The CVD method is used to produce multiwalled carbon nanotubes (MWCNTs) [101] and double-walled carbon nanotubes (DWCNTs) [102] as well as SWCNTs [103], The biomedical applications of CNTs have been made possible through surface functionalization of CNTs, which has led to drug and vaccine delivery applications [104,105],... 

CS-based mixed matrix membranes and nanocomposite membranes are much useful in heavy metal removal. Salehi et al. [82] synthesized amine functionalized multiwalled carbon nanotubes (F-MWCNTs) and utilized to prepare novel CS/polyvinyl alcohol (PVA) thin adsorptive membranes for copper ion removal from water. Copper ion adsorption on the membranes was more favorable at higher CNT contents as well as increased temperatures. The adsorption capacity of the membrane containing 2 wt.% CNTs (20.1 mg/g at 40°C) was almost twice as large as that of the plain membrane (11.1 mg/g). Salehi et al. [83] used PE glycol and amino-modified MWCNTs to modify CS/PVA thin adsorptive membranes for copper ion adsorption. Adsorption capacity of CS/PVA membrane was increased from 11 to 30 mg/g by the addition of 5 wt.% PEG to the blend. Addition of CNTs,... 

Hydroxyapatite (CajQ(P04)g(0H)2) has also attracted considerable interest as a catalyst support. In these materials, wherein Ca sites are surrounded by P04 tetrahedra, the introduction of transition metal cations such as Pd into the apatite framework can generate stable monomeric phosphate complexes that are efficient for aerobic selox catalysis [99]. Carbon-derived supports have also been utihzed for this chemistry, and are particularly interesting because of the ease of precious metal recovery from spent catalysts simply by combustion of the support. Carbon nanotubes (CNTs) have received considerable attention in this latter regard because of their superior gas adsorption capacity. Palladium nanoparticles anchored on multiwalled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs) show better selectivity and activity for aerobic selox of benzyl and cinnamyl alcohols [100, 101] compared to activated carbon. Interestingly, Pd supported on MWCNTs showed higher selectivity toward benzaldehyde, whereas activated carbon was found to be a better support in cinnamyl alcohol oxidation. Functionalized polyethylene glycol (PEG) has also been employed successfully as a water-soluble, low-cost, recoverable, non-toxic, and non-volatile support with which to anchor nanoparticulate Pd for selox catalysis of benzyl/cinnamyl alcohols and 2-octanol [102-104]. 

The surface modification can aim at different goals for example, the purpose could be the achievement of a superior chemical compatibility between the two phases through the addition of bridging agents [82]. The modification of the CNTs surface is frequently reported to increase their affinity with polymer solution. One example has been reported in the literature to obtain MMMs of multiwalled carbon nanotubes (MWNTs) in hydrophilic polymer blends for the synthesis of gas separation membranes. Acidification [62] and amino functionalization [56] of the fillers have been performed to increase their dispersability in an aqueous-based casting solution and to offer a reactive moiety for further crosslinking with polymer chains. 

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