Modification Of Single-walled Carbon Nanotubes Research Articles

Guanine Functionalization of SWCNTs Using Metalloporphyrin Photosensitizers

Chemical modifications of single-wall carbon nanotubes (SWCNT) have opened new areas in the creation of quantum defects and the tailoring of optical properties for these one-dimensional semiconducting materials. Recent research has revealed a novel and controllable chemical functionalization reaction in which guanine nucleobases of ssDNA coatings react covalently with the SWCNT side wall in the presence of singlet oxygen. Generation of singlet oxygen through photosensitizer optical excitation is a key part of this process. To further explore guanine functionalization of SWCNTs, we have investigated reaction kinetics under various conditions. We replaced the rose bengal photosensitizer by metalloporphyrin dyes. These have greater photostability and more intense and shorter wavelength absorptions, allowing them to be used at micro- to nanomolar concentrations and leaving a wider spectral transparency window for reaction monitoring. Excitation was at 405 nm. Our kinetic studies show that the rates of change of E11 and E22 energies depend linearly on sensitizer concentration, which implies that guanine functionalization is a first order reaction with respect to singlet oxygen. Using a series of oligos with the same length but different guanine contents, we find E11 spectral shifts that increase sub-linearly to an asymptotic value. To help understand the structure of the guanine covalent adduct, we also performed semi-empirical quantum chemistry simulations. These suggest that the lowest energy structure is bonded to two adjacent carbon atoms of the SWCNT sidewall, and that reaction exothermicity is larger for smaller diameter nanotubes. Computations will also be presented for presumed intermediate adducts of guanine peroxide bonded to (6,5) SWCNTs in different orientations relative to the nanotube axis.

Modification of SWCNTs with hybrid materials ZnO–Ag and ZnO–Au for enhancing bactericidal activity of phagocytic cells against Escherichia coli through NOX2 pathway

Zinc oxide-silver (ZnO–Ag), and zinc oxide-gold (ZnO–Au) nano-composites were prepared through wet chemical process and laced into single-walled carbon nanotubes (SWCNTs) to yield ZnO–Ag-SWCNTs, and ZnO–Au-SWCNTs hybrids. These nano-composite-laced SWCNTs hybrids were characterized using Raman spectroscopic, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses. The hybrids were evaluated for their effects on phagocytic cells and bactericidal activity against the gram-negative bacteria E. coli. Their phagocytic cell activities and intracellular killing actions were found to be significantly increased, as the ZnO–Ag-SWCNTs and ZnO–Au-SWCNTs nano-hybrids induced widespread clearance of Escherichia coli. An increase in the production of reactive oxygen species (ROS) also led to upregulated phagocytosis, which was determined mechanistically to involve the phagocyte NADPH oxidase (NOX2) pathway. The findings emphasized the roles of ZnO–Ag- and ZnO–Au-decorated SWCNTs in the prevention of bacterial infection by inhibiting biofilm formation, showing the potential to be utilized as catheter coatings in the clinic.

Azide modification forming luminescent sp2 defects on single-walled carbon nanotubes for near-infrared defect photoluminescence.

Azide functionalization produced luminescent sp2-type defects on single-walled carbon nanotubes, by which defect photoluminescence appeared in near infrared regions (1116 nm). Changes in exciton properties were induced by localization effects at the defect sites, creating exciton-engineered nanomaterials based on the defect structure design.

Carbon Nanotube Sensor Passivation Mitigates Inflammatory Response in Microglia

Non-covalent functionalization of single-walled carbon nanotubes (SWCNTs) has enabled advances in biomolecule imaging. In particular, modification of SWCNTs with select sequences of single-stranded DNA (ssDNA) produces near infrared optically active sensors for neurotransmitters such as dopamine, enabling high spatiotemporally resolved optical recording of synaptic and extrasynaptic signaling. However, the carbon lattice surface of SWCNT induces activation of the innate immune system, leading to an inflammatory response. Activation of microglia, the brain’s resident immune cells, is of particular relevance to imaging neuromodulation. Here, we show that non-covalent ssDNA-SWCNT nanosensor passivation with a PEGylated phospholipid can mitigate microglial activation while maintaining the nanosensor’s response towards dopamine. To do so, we screen a candidate library of PEGylated biomolecules, nonionic surfactants, and block copolymers against their ability to mitigate the microglial immune response as measured by transcriptomic analysis. We find that PEGylated phospholipids are capable of adsorption to ssDNA-SWCNTs without significant ssDNA displacement, with moderate reduction in nonspecific protein adsorption. These trends are recapitulated by a reduction in inflammatory response of SIM-A9 microglial cells, marked by lowered expression of cytokines CXCL2 and IL-6, mitigated morphological change, and decreased cytotoxicity. Taken together, these results suggest noncovalent passivation improves biocompatibility of DNA-SWNCT nanosensors and provides the groundwork for implementing similar passivation methods for other optical probes of this class.

Tuning Tailored Single-Walled Carbon Nanotubes by Highly Energetic Heavy Ions

Carbon-based nanomaterials have attracted a lot of interest lately due to their highly promising applications. Here we report on the modifications of single-walled carbon nanotubes (SWCNTs) induced by swift (highly energetic) heavy ions. Using scanning force microscopy and Raman spectroscopy, we observe a dramatic change in the structure of the irradiated SWCNTs, accompanied by an increase of the adhesion force as a function of ion fluence and electronic energy loss. With increasing ion fluence, the SWCNTs exhibit a partial transformation from metallic to more semiconducting. Moreover, at high fluence they break into segments 10--20 nm long.

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.

Oxygen Evolution Reaction on Single‐Walled Carbon Nanotubes Noncovalently Functionalized with Metal Phthalocyanines

AbstractThis work reports the facile preparation of single‐walled carbon nanotubes (SWCNTs) noncovalently functionalized with 3d transition metal (II) phthalocyanines MPcs (M=Mn, Fe, Co and Ni) and their electrochemical evaluation towards the oxygen evolution reaction (OER) in alkaline media. The modification of SWCNTs with MPcs improved the potential required for the oxygen evolution reaction in 0.1 M and 1 M KOH by lowering the potential by approximately 120 mV in comparison with unmodified SWCNTs, at a current density of 10 mA cm−1. The onset potential of the hybrids is close to the bulk Ni electrode in 1 M KOH and significantly outperforms Ni and Ir black electrodes in 0.1 M KOH solution. Nickel, cobalt and iron phthalocyanines showed auto‐activation during extended cyclic voltammetry and long‐term chronoamperometric measurements in both KOH concentrations. The excellent electrocatalytic activity of hybrids obtained and the straightforward method of their synthesis opens the possibility of exploring the proposed materials for applications in anion exchange membrane water electrolysis (AEMWE).

Carbon-nanotube-based Photocatalysts for Water Splitting in Cooperation with BiVO4 and [Co(bpy)3]3+/2+

Physical modifications of single-walled carbon nanotubes (SWCNTs) with fullerodendrons, followed by complexation with RuCl3 leads to the formation of CNT-photocatalysts that exhibit high quantum yi...

Noncovalent Modification of Single-Walled Carbon Nanotubes Using Thermally Cleavable Polythiophenes for Solution-Processed Thermoelectric Films.

Four thermally cleavable polythiophene derivatives containing carbonate and solubilizing groups were synthesized for noncovalent modification of single-walled carbon nanotubes (SWCNTs). A well-dispersed polythiophene/SWCNTs composite was obtained by adsorption of the polymer at the SWCNT surface. The solution-processed composite film exhibited solid-state thermal cleavage of the insulating solubilizing group through decarboxylation, producing an insoluble composite film. The thermally cleavable composite film was evaluated for potential application as a thermoelectric (TE) material. The electrical conductivity (σ) of the thermally treated composite film was up to 250 times higher than that of the as-prepared composite film. The increased σ contributed to an increase in the power factor (PF). The ethanol-processed composite film could be applicable for green processing of a TE material using the less-toxic solvent. The substrate-free polythiophene/SWCNTs composite film prepared by simple solvent evaporation yielded a figure-of-merit of 3.1 × 10-2 with a PF of 28.8 μW m-1 K-2 at 25 °C. This solution-processed methodology is beneficial for the development of a flexible TE material.

Surface modification of single-walled carbon nanotubes by functional nitrogen-containing groups and study of their properties

Treatment of single-walled carbon nanotubes (SWCNT) in a gaseous 40%NH3–1%С2Н2–C2H4 mixture at 600 and 700°С led to “nitrogen-containing carbon coating–single-wall carbon nanotubes” composites. Single-walled carbon nanotubes after etching in aqua regia (SWCNTetch) and doped with nitrogen (N-SWCNT) were studied by XPS, electron microscopy, and IR spectroscopy. It was found that the initial SWCNTetch surface contains various oxygen-containing functional groups. Treatment of SWCNTetch in a 40%NH3–1%С2Н2–C2H4 mixture led to the formation of a thin carbon coating on the carbon nanotube surface due to polymerization and condensation of hydrocarbons. After treatment at 600°C, the formation of nitrogen-containing functional groups is insignificant; however, when the treatment temperature is increased to 700°C, the nitrogen content reaches 0.5 at % of the weight of the N-SWCNT sample.

Using a fluorescence quenching method to detect DNA adsorption onto single-walled carbon nanotube surfaces

Surface modification of single-walled carbon nanotubes (SWNTs) with DNA molecules has attracted much attention in recent years to increase SWNT solubility and make various SWNT-based nanobiodevices. Therefore, there is a critical need to quantify the interaction between DNA molecules and SWNT surfaces, particularly the intermediate structures during DNA adsorption. In this study, we demonstrate the ability to detect the adsorption of DNA oligomers on SWNT surfaces by fluorescence spectroscopy. Fluorescein-labelled, 30mer, thymine oligonucleotides (F-T30) were employed as a fluorescent probe to study the interaction of DNA with SWNTs. A clear quenching effect was observed when F-T30 was adsorbed onto SWNT surfaces. Using this method, the amount of DNA adsorbed onto the SWNT surfaces was measured under different sonication conditions to correlate adsorption efficiency with sonication strength and duration. When a bath-type sonicator was used, mild adsorption of F-T30 on SWNT surfaces was observed. Furthermore, a two-step adsorption was observed in this condition. In contrast, we observed rapid adsorption of F-T30 to SWNT surfaces at the higher sonication amplitude (60% maximal) using a probe-type sonicator, while only slight adsorption of DNA molecules was observed at the lower amplitude (20% maximal). Our data revealed that the quenching effect can be used to evaluate DNA adsorption onto SWNT surfaces. In addition, atomic force microscopy (AFM) and photoacoustic spectroscopy (PAS) were conducted to provide complementary information on the DNA-SWNT nanoconjugates.

Electronic properties of prismatic modifications of single-wall carbon nanotubes

Abstract The article shows the possibility of target modifying the prismatic single-walled carbon nanotubes (SWCNTs) by regular chemisorption of fluorine atoms in the graphene surface. It is shown that the electronic properties of prismatic SWCNT modifications are determined by the interaction of π- and ρ(in-plane)-electron conjugation in the carbon-conjugated subsystems (tracks) formed in the faces. The contributions of π- and ρ(in-plane)-electron conjugation depend on the structural characteristics of the tracks. It was found that the minimum of degree deviation of the track from the plane of the prism face and the maximum of the track width ensure the maximum contribution of the π-electron conjugation, and the band gap of the prismatic modifications of the SWCNT tends to the band gap of the hydrocarbon analog of the carbon track. It is established that the maximum of degree deviation of the track from the plane of the prism face and the maximum of track width ensure the maximum contribution of the ρ(in-plane) electron interface, and the band gap of the prismatic modifications of the SWCNT tends to the band gap of the unmodified carbon nanotube. The calculation of the model systems has been carried out using an ab initio Hartree–Fock method in the 3-21G basis.

Biophysical and electrochemical properties of Self-assembled noncovalent SWNT/DNA hybrid and electroactive nanostructure

DNA self-assembled hybrid nanostructures are widely used in recent research in nanobiotechnology. Combination of DNA with carbon based nanoparticles such as single-walled carbon nanotube (SWNT), multi-walled carbon nanotube (MWNT) and carbon quantum dot were applied in important biological applications. Many examples of biosensors, nanowires and nanoelectronic devices, nanomachine and drug delivery systems are fabricated by these hybrid nanostructures. In this study, a new hybrid nanostructure has been fabricated by noncovalent interactions between single or double stranded DNA and SWNT nanoparticles and biophysical properties of these structures were studied comparatively. Biophysical properties of hybrid nanostructures studied by circular dichroism, UV–vis and fluorescence spectroscopy techniques. Also, electrochemical properties studied by cyclic voltammetry, linear sweep voltammetry, square wave voltammetry, choronoamperometry and impedance spectroscopy (EIS). Results revealed that the biophysical and electrochemical properties of SWNT/DNA hybrid nanostructures were different compare to ss-DNA, ds-DNA and SWNT singly. Circular dichroism results showed that ss-DNA wrapped around the nanotubes through π-π stacking interactions. The results indicated that after adding SWNT to ss-DNA and ds-DNA intensity of CD and UV–vis spectrum peaks were decreased. Electrochemical experiments indicated that the modification of single-walled carbon nanotubes by ss-DNA improves the electron transfer rate of hybrid nanostructures. It was demonstrated SWNT/DNA hybrid nanostructures should be a good electroactive nanostructure that can be used for electrochemical detection or sensing.

Full range of wettability through surface modification of single-wall carbon nanotubes by photo-initiated chemical vapour deposition

Single-wall carbon nanotubes (SWCNTs) have various remarkable properties, which make them a promising candidate for many applications. However, their inherent hydrophobicity has limited their commercial use in optical, biological, and electrical applications. Photo-initiated chemical vapour deposition (PICVD) using syngas is proposed as a novel, affordable, and versatile method to tailor SWCNT wettability through the addition of oxygen-containing functional groups. Following PICVD surface treatment, X-ray photoelectron spectroscopy, water contact angle measurements (CA), thermogravimetric analysis, Raman spectroscopy and transmission electron microscopy confirm controlled oxygenation of the SWCNT surface. Indeed, this novel approach allows to reproducibly make SWCNTs having surfaces properties ranging from superhydrophilic (CA<5°) to superhydrophobic (CA>150°), including any intermediate values, by simply varying operational parameters such as molar ratio of the syngas precursor, photo-polymerization time and reactor pressure (about normal conditions).

Functionalized single-walled carbon nanotubes for the improved solubilization and delivery of curcumin

abstractThe surface modification of single-walled carbon nanotubes (SWCNTs) can enhance their solubility and stability in water and biological systems. The present study demonstrated the application of the functionalized SWCNTs (f-SWCNTs) as drug-delivery vehicles. In this study, f-SWCNTs were functionalized with one of four different chemical groups for the delivery of curcumin to splenic lymphocytes. Since free curcumin can modulate the proliferation of splenic lymphocytes, we compared the abilities of different f-SWCNTs for the delivery of water-insoluble curcumin to inhibit cell proliferation, which were stimulated with concanavalin A (Con A) and lipopolysaccharide (LPS). The results showed that curcumin can be loaded onto the f-SWCNTs surface through π−π stacking with a loading capacity of 235–327 mg/g (curcumin/f-SWCNTs). The f-SWCNTs-curcumin complexes display considerable cell proliferation inhibition efficacy when compared with free curcumin diluted in dimethyl sulfoxide (DMSO). Furthermore, curcumin loaded onto SWCNTs functionalized with poly(ethylene glycol) (SW-PEG) showed good dispersion and stability in water, confirming the excellent biocompatibility of SW-PEG as a drug carrier.

In vitro platelet activation, aggregation and platelet–granulocyte complex formation induced by surface modified single-walled carbon nanotubes

Surface modification of single-walled carbon nanotubes (SWCNTs) such as carboxylation, amidation, hydroxylation and pegylation is used to reduce the nanotube toxicity and render them more suitable for biomedical applications than their pristine counterparts. Toxicity can be manifested in platelet activation as it has been shown for SWCNTs. However, the effect of various surface modifications on the platelet activating potential of SWCNTs has not been tested yet. In vitro platelet activation (CD62P) as well as the platelet–granulocyte complex formation (CD15/CD41 double positivity) in human whole blood were measured by flow cytometry in the presence of 0.1mg/ml of pristine or various surface modified SWCNTs. The effect of various SWCNTs was tested by whole blood impedance aggregometry, too. All tested SWCNTs but the hydroxylated ones activate platelets and promote platelet–granulocyte complex formation in vitro. Carboxylated, pegylated and pristine SWCNTs induce whole blood aggregation as well. Although pegylation is preferred from biomedical point of view, among the samples tested by us pegylated SWCNTs induced far the most prominent activation and a well detectable aggregation of platelets in whole blood.

Optimization and Insights into the Mechanism of Formation of Mechanically Interlocked Derivatives of Single-Walled Carbon Nanotubes.

The mechanical bond provides a stable yet dynamic link between the submolecular components of mechanically interlocked molecules, such as rotaxanes and catenanes. We introduced the mechanical bond as a new tool for the chemical modification of single-walled carbon nanotubes (SWNTs), producing the first mechanically interlocked derivatives of nanotubes (MINTs). To do so, we used U-shaped molecules featuring two units of a SWNT-recognition unit, which were cyclized around the SWNT by means of ring-closing metathesis (RCM). Here we report optimized conditions for the synthesis of MINTs obtained by systematic investigation of the effect of the concentration of the U-shaped molecule 1, reaction time, and catalyst concentration. Analysis of the data also provides insights into the mechanism of formation of MINTs. In particular, the effect of the concentration of 1 supports the formation of a 1⋅SWNT complex. The kinetic data follow a pseudo-first-order behavior that validates the RCM as the rate-determining step. An excess of RCM catalyst leads to the formation of supramolecularly adsorbed linear oligomers of 1.

Synthesis and Cytotoxicity of POSS Modified Single Walled Carbon Nanotubes

Single walled carbon nanotubes (SWNTs) decorated with polyhedral oligomeric silsesquioxane (POSS) were synthesized via the amide linkages between the acid treated SWNTs and amine‐functionalized POSS. The successful modification of SWNTs with POSS was confirmed by Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and UV‐Vis spectra. The resulting SWNTs‐POSS can be dispersed in both water and organic solutions. The biocompatibility and cytotoxicity of the SWNTs and SWNTs‐POSS were evaluated by CCK‐8 viability assays, which indicated that SWNTs‐POSS exhibit very extremely low toxicity. The low toxicity of the POSS modified SWNTs leads to more opportunities for using carbon nanotubes in biomedical fields.

Study on modification of single-walled carbon nanotubes on the surface of monocrystalline silicon solar cells.

Modification of single-walled carbon nanotubes (SWNTs) on the surface of monocrystalline silicon solar cells was investigated. The modification was realized by dropping a well-distributed mixture of SWNTs and ethanol with different dosages on the surface of monocrystalline silicon solar cells in the same effective area. The experimental results showed that the increasing rates of conversion efficiency, short-circuit current, and fill factor were 4.37%, 2.18%, and 2.11%, respectively; the open circuit voltage and series resistance decreased by 0.11% and 9.37% compared with the bare solar cell without an antireflection (AR) layer, when the modification reached the best state by dropping a 0.5 mL mixture solution with a concentration of 0.08 g/L. With the energy-band diagrams of the heterojunction and p-n junction, the principles of the modification of SWNTs on monocrystalline silicon solar cells and the reasons for the change of electrical parameters were analyzed theoretically. Through experiments and theoretical analyses, the modification of SWNTs on solar cells is a potential and effective way to improve the performance of solar cells.

Electronic property modification of single-walled carbon nanotubes by encapsulation of sulfur-terminated graphene nanoribbons.

The use of carbon nanotubes (CNTs) as cylindrical reactor vessels has become a viable means for synthesizing graphene nanoribbons (GNRs). While previous studies demonstrated that the size and edge structure of the as-produced GNRs are strongly dependent on the diameter of the tubes and the nature of the precursor, the atomic interactions between GNRs and surrounding CNTs and their effect on the electronic properties of the overall system are not well understood. Here, it is shown that the functional terminations of the GNR edges can have a strong influence on the electronic structure of the system. Analysis of SWCNTs before and after the insertion of sulfur-terminated GNRs suggests a metallization of the majority of semiconducting SWCNTs. This is indicated by changes in the radial breathing modes and the D and G band Raman features, as well as UV-vis-NIR absorption spectra. The variation in resonance conditions of the nanotubes following GNR insertion make direct (n,m) assignment by Raman spectroscopy difficult. Thus, density functional theory calculations of representative GNR/SWCNT systems are performed. The results confirm significant changes in the band structure, including the development of a metallic state in the semiconducting SWCNTs due to sulfur/tube interactions. The GNR-induced metallization of semiconducting SWCNTs may offer a means of controlling the electronic properties of bulk CNT samples and eliminate the need for a physical separation of semiconducting and metallic tubes.