Noncovalent Functionalization Of Single-walled Carbon Nanotubes Research Articles

Flexible Chemiresistive Cyclohexanone Sensors Based on Single-Walled Carbon Nanotube-Polymer Composites.

We report a chemiresistive cyclohexanone sensor on a flexible substrate based on single-walled carbon nanotubes (SWCNTs) functionalized with thiourea (TU) derivatives. A wrapper polymer containing both 4-vinylpyridine (4VP) groups and azide groups (P(4VP-VBAz)) was employed to obtain a homogeneous SWCNT dispersion via noncovalent functionalization of SWCNTs. The P(4VP-VBAz)-SWCNT composite dispersion was then spray-coated onto an organosilanized flexible poly(ethylene terephthalate) (PET) film to achieve immobilizing quaternization between the pyridyl groups from the polymer and the functional PET substrate, thereby surface anchoring SWCNTs. Subsequent surface functionalization was performed to incorporate a TU selector into the composites, resulting in P(Q4VP-VBTU)-SWCNT, for the detection of cyclohexanone via hydrogen bonding interactions. An increase in conductance was observed as a result of the hydrogen-bonded complex with cyclohexanone resulting in a higher hole density and/or mobility in SWCNTs. As a result, a sensor device fabricated with P(Q4VP-VBTU)-SWCNT composites exhibited chemiresistive responses (ΔG/G0) of 7.9 ± 0.6% in N2 (RH 0.1%) and 4.7 ± 0.4% in air (RH 5%), respectively, upon exposure to 200 ppm cyclohexanone. Selective cyclohexanone detection was achieved with minor responses (ΔG/G0 < 1.4% at 500 ppm) toward interfering volatile organic compounds (VOC). analytes. We demonstrate a robust sensing platform using the polymer-SWCNT composites on a flexible PET substrate for potential application in wearable sensors.

Synthesis and structural characterization of single-walled carbon nanotubes functionalized with fluorinated phosphonate analogues of phenylglycine, as promising materials for synthetic and biomedical applications

Through chemical functionalization the prerequisites for possible applications of such nanostructures as single-walled carbon nanotubes (SWCNTs) are established. In this study, modifications of SWCNTs by fluorinated phosphonate analogue of phenylglycine, compound belonging to important group of natural amino acid mimetics, using two approaches are presented. The first one was based on noncovalent functionalization of SWCNTs with the phosphono-perfluorophenylglycine analogue. In the second approach, SWCNTs were covalently bonded to the fluorinated α-aminophosphonates in one-step or multi-step reactions. The investigation of the functionalization effect on the dispersibility, thermal properties and the structure of SWCNTs was performed by using of X-Ray spectroscopy, TGA and Raman spectroscopy. Both approaches indicated promising methods for fast and efficient modification of carbon nanotubes (CNTs) also with other representatives of previously synthesized fluorinated aminophosphonates. Functionalized with such compounds CNTs can constitute materials for synthetic and biomedical applications. Due to their biological activity and structural analogy to corresponding α-amino acids, fluorinated α-aminophosphonates provide an important source for drug discovery. Therefore functionalization of SWCNTs with such molecules can provide an important platforms for drug delivery applications. Due to the presence of perfluorinated phenyl rings various nucleophiles can be introduced by nucleophilic aromatic substitution reactions to the functionalized SWCNTs leading to obtaining completely new materials.

3D, covalent and noncovalent hybrid materials based on 3-phenylcoumarin derivatives and single walled carbon nanotubes as gas sensing layers

In this work, the effect of different types of functionalization of single walled carbon nanotubes (SWCNT) with 3-phenylcoumarin derivatives on the chemiresistive sensor response to ammonia (10–50 ppm) was studied. Covalent functionalization of SWCNT was performed according to the Huisgen reaction of azide-alkyne 1,3-dipolar cycloaddition between mono alkyne-substituted 3-phenylcoumarin and single walled nanotubes modified by azide groups. Covalent functionalization was shown by IR- and X-ray photoelectron spectroscopy. To obtain the 3D hybrid material, the dialkyne functionalized 3-phenylcoumarin molecules were used as linkers between nanotubes. Third hybrid material was prepared by noncovalent functionalization of SWCNT, namely by adsorption of 7-propinyloxy-3-(p-propinyloxyphenyl)coumarin on SWCNT surface. It was shown that the 3D hybrid and the hybrid obtained by covalent functionalization exhibit 2 and 4 times higher sensor responses to ammonia compared to noncovalently functionalized SWCNT. The value of sensor response is in good correlation with the degree of functionalization of SWCNTs with coumarin molecules.

Noncovalent functionalization of pristine CVD single-walled carbon nanotubes with 3d metal(II) phthalocyanines by adsorption from the gas phase

Noncovalent hybrids of carbon nanotubes (CNTs) with phthalocyanines (Pcs) is a subject of growing research effort focused on the development of new efficient organic photovoltaic cells, heterogeneous catalysts, lithium batteries, gas sensors, field effect transistors, among other possible applications. The main advantage of using unsubstituted Pcs is their very moderate cost and easy commercial availability. Unfortunately, the deposition of unsubstituted Pcs onto CNT sidewalls via the traditional liquid-phase strategy proves to be very problematic due to an extremely poor solubility of Pcs. At the same time, unsubstituted free-base H2Pc ligand and many of its transition metal complexes exhibit high thermal stability and volatility under reduced pressure, which allows for their physical vapor deposition onto solid surfaces. In the present work, we demonstrated the possibility of simple, fast, efficient and environmentally friendly noncovalent functionalization of single-walled CNTs (SWNTs) with a series of 3d metal(II) phthalocyanines Me(II)Pc, where Me = Co, Ni, Cu and Zn. The functionalization can be performed at 400–500 °C under moderate vacuum, and takes about 2–3 h only. The nanohybrids obtained were characterized by means of Fourier-transform infrared, Raman, UV–vis and energy-dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), scanning and transmission electron microscopy. TGA suggested that Pc weight content is 30%, 17% and 35% for NiPc, CuPc and ZnPc, respectively (CoPc exhibited anomalous behavior), which is close to the estimates from EDS spectra of 24–39%, 27–36% and 27–44% for CoPc, CuPc and ZnPc, respectively. A strong increase in intensity of D band in the Raman spectra of SWNT‒Pc hybrids, as compared to that of pristine nanotubes, was interpreted as very strong interactions between Pc molecules and SWNT sidewalls. Very high absolute values of binding energies of 32.46–37.12 kcal/mol and the patterns of HOMO and LUMO distribution, calculated at the PBE-D/DNP level of density functional theory, also suggested that the interactions between metal phthalocyanines studied and nanotube sidewalls are very strong.

Abstract 5374: Effect of carbon nanotube amount and subcellular location on the near infrared (NIR) photothermal ablation of cells

Abstract Background and Objective: Single-walled carbon nanotubes (SWNTs) are readily taken up by cells, strongly absorb in the NIR (700-1100 nm) region, and efficiently convert absorbed NIR into heat. These properties have made SWNTs an interesting facilitator for the NIR mediated thermal ablation of cancer cells. In the application of SWNTs to thermal ablation, it is not known what amount of cell-associated SWNTs is required to achieve a defined level of cell killing upon NIR irradiation. In addition, it has not been quantitatively demonstrated whether SWNTs bound to the plasma membrane or internalized into vesicles are more efficient in killing cells. The overall objective of this project is to assess NIR mediated killing as a function of cell-associated SWNT amount and SWNT subcellular location. Methods: The study was performed in three phases. The first phase involved non-covalent functionalization of SWNTs by bovine serum albumin. Non-targeted uptake and NIR irradiation of cells was performed to find the optimal laser power density, NIR exposure time and SWNT concentration to kill cells. SWNTs associated with cells were then extracted and quantified by a sodium dodecyl sulfate-polyacrylamide gel electrophoresis technique (Wang et al., 2009, Anal. Chem. 81:2944-2952) and the SWNT amount was correlated with cell killing. The second phase included the non-covalent functionalization of SWNTs with phospholipid-PEG conjugated folic acid (PL-PEG-FA) as a targeting ligand. The SWNTs were internalized by receptor-mediated endocytosis at 37°C, the optimum laser conditions were determined as in the first phase, and the amount of internalized SWNTs were quantified and correlated with NIR-mediated cell killing. In the third phase, cells were incubated with the PL-PEG-FA SWNTs at 4°C to allow binding to the cell surface without internalization, followed by measuring the amount of surface-bound SWNTs. The amount of surface-bound SWNTs was then correlated with NIR-mediated cell death. Results: An increase in killing of cells incubated with SWNTs was observed in both the non-targeted and targeted systems as a function of NIR laser power density, NIR exposure time and incubated SWNT concentration. With the folate targeted system, there was more cell death when SWNTs were internalized into vesicles compared to when an equivalent amount of SWNTs were confined to the cell surface. Conclusion: SWNTs internalized by cells, either by fluid phase endocytosis, or by receptor-mediated endocytosis via the folate receptor, were effective in killing cells upon NIR irradiation. However, SWNTs confined to the cell surface after binding to folate receptors at low temperature were not as efficient in killing cells upon NIR irradiation. This suggests that NIR-mediated thermal ablation therapy will be more effective when SWNTs are targeted to a receptor and are internalized by receptor-mediated endocytosis. Citation Format: Vasanth Siruvallur Murali, Carole Mikoryak, Ruhung Wang, Rockford K. Draper. Effect of carbon nanotube amount and subcellular location on the near infrared (NIR) photothermal ablation of cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5374. doi:10.1158/1538-7445.AM2014-5374

Noncovalent Functionalization of SWNTs with Azobenzene-Containing Polymers: Solubility, Stability, and Enhancement of Photoresponsive Properties

Azobenzene-derived photoactive polymers (P1−P3) containing pyrene pendants were designed and synthesized (Mw ∼ 30 000) for the noncovalent functionalization of single-walled carbon nanotubes (SWNTs). P1−P3 were found to be highly effective for the solubilization of SWNTs in common organic solvents, resulting in hybrid materials with enhanced thermal stability. The solubilization process was mostly driven by the π−π stacking interactions of pyrene with SWNTs. It also brings the azobenzene chromophores to the vicinity of nanotube surface, thereby allowing the electronic interactions between them. In addition to that, stacking of the pyrene and subsequent wrapping of the polymer around CNT surface provides more volume for the photoisomerization of azobenzene. These effects eventually accelerate the kinetics of photoisomerization of azobenzene in the polymer−SWNT composite. The photoalignment property of the composite was also increased when compared to that of the parent polymer which was studied by means of...

Use of Polyimide-graft-Bisphenol A Diglyceryl Acrylate as a Reactive Noncovalent Dispersant of Single-Walled Carbon Nanotubes for Reinforcement of Cyanate Ester/Epoxy Composite

Dispersion of single-walled carbon nanotubes (SWNTs) into individuals or small bundles and strong nanotube/matrix interfacial strength remain as challenges in exploiting the excellent mechanical properties of SWNTs in structural composites. Noncovalent functionalization of SWNTs is an attractive option for compatibilization of nanotubes with the matrix as it does not destroy the nanotube graphene structure. We have designed and successfully synthesized a new reactive comb-like polymer, polyimide-graft-bisphenol A diglyceryl acrylate (PI-BDA), which is shown to be highly effective in dispersing SWNTs into individual nanotubes or small bundles, as evidenced by transmission electron microscopy (TEM) and UV−vis−NIR absorption spectra. SWNTs dispersed with PI-BDA were added to a thermosetting resin blend of cyanate ester and epoxy (CE-EP) (70/30, w/w) and composite fibers with SWNT loading ranging from 0 to 1.5 wt % were successfully fabricated. The strong π−π interaction between SWNTs and PI-BDA backbone was ...

Lyotropic Liquid‐Crystalline Solutions of High‐Concentration Dispersions of Single‐Walled Carbon Nanotubes with Conjugated Polymers

The 1D structure of single-walled carbon nanotubes (SWNTs) leads to unique physical properties, which have been investigated extensively. Numerous applications and device prototypes have been demonstrated; however, most have used SWNTs grown in situ by chemical vapor deposition. This limits throughput and choice of substrate owing to the high growth temperatures involved. Solution-based postsynthesis device fabrication, typically involving purification, solubilization, chemical functionalization, cutting, and/ or controlled assembly of SWNTs, is more desirable because of low cost, scalability to large areas, and compatibility with flexible plastic substrates. Unfortunately, SWNTs are not readily soluble, and chemical functionalization strategies for their solubilization usually alter their electronic properties. Furthermore, to take full advantage of the anisotropic charge-transport properties of SWNTs and to enhance their performance in high-strength composite materials, it is necessary to align them over a large area. Noncovalent functionalization of SWNTs is a particularly attractive avenue for dispersion because it enables modification of material properties without altering the chemical structure of the nanotubes. To date, most high-concentration dispersions (>1mg mL ) have been obtained in aqueous solutions by mixing SWNTs with surfactants, doubleor