Single-walled Carbon Nanotubes Hybrid Research Articles

All-Automated Fabrication of Freestanding and Scalable Photo-Thermoelectric Devices with High Performance.

Flexible photo-thermoelectric (PTE) devices have great application prospects in the fields of solar energy conversion, ultrabroadband light detection, etc. A suitable manufacturing process to avoid the substrate effects as well as to create a narrow transition area between p-n modules for high-performance freestanding flexible PTE devices is highly desired. Herein, an automated laser fabrication (ALF) method is reported to construct the PTE devices with rylene-diimide-doped n-type single-walled carbon nanotube (SWCNT) films. Thewet-compressing approach is developed to improve the thermoelectric power factors and figure of merit (ZT) of the SWCNT hybrid films. Then, the films are cut and patterned automatically to make PTE devices with various structures by the proposed ALF method. The freestanding PTE device with a narrow transition area of ≈2-3 µm between the p and n modules exhibits a high-power density of 0.32 µW cm-2 under the light of 200 mW cm-2, which is among the highest level for freestanding-film-based PTE devices. The results pave the way for the automatic production process of PTE devices for green power generation and ultrabroadband light detection.

Three Dimensionally Printed Biobased Electrodes: Ionic Liquid and Single-Walled Carbon Nanotube Hybrids in a Vegetable Oil Matrix for Soft Robotics

Three Dimensionally Printed Biobased Electrodes: Ionic Liquid and Single-Walled Carbon Nanotube Hybrids in a Vegetable Oil Matrix for Soft Robotics

Enhancing Intracellular Optical Performance and Stability of Engineered Nanomaterials via Aqueous Two-Phase Purification.

Supramolecular hybrids of DNA and single-walled carbon nanotubes (SWCNTs) have been introduced in numerous biosensing applications due to their unique optical properties. Recent aqueous two-phase (ATP) purification methods for SWCNTs have gained popularity by introducing specificity and homogeneity into the sensor design process. Using murine macrophages probed by near-infrared and Raman microscopies, we show that ATP purification increases the retention time of DNA-SWCNTs within cells while simultaneously enhancing the optical performance and stability of the engineered nanomaterial. Over a period of 6 h, we observe 45% brighter fluorescence intensity and no significant change in emission wavelength of ATP-purified DNA-SWCNTs relative to as-dispersed SWCNTs. These findings provide strong evidence of how cells differentially process engineered nanomaterials depending on their state of purification, lending to the future development of more robust and sensitive biosensors with desirable in vivo optical parameters using surfactant-based ATP systems with a subsequent exchange to biocompatible functionalization.

Nonlinear Optical Response of Dispersed Medium Based on Conjugates Single-Walled Carbon Nanotubes with Phthalocyanines

Nanosecond lasers have recently been widely involved in human activity. However, high-intensity laser radiation can cause severe damage to organs of vision and expensive photonic devices. Radiation in the near UV range is especially dangerous for human eyes, since it is strongly absorbed by biological media and is also invisible, i.e., the reaction time of the eye to such radiation is much lower than that of visible light. Passive limiters have high transmission (>70%) at a low light intensity and begin to “darken” only when the threshold value of the laser radiation intensity is reached. In this work, we studied liquid nanodispersed nonlinear optical limiters based on hybrids of single-walled carbon nanotubes (SWCNTs) with metal-free tetra(hydroxy)phthalocyanine (OH)4PcHH). The value of the hydrodynamic radius of separate particles after (OH)4PcHH binding increased from 288 ± 55 nm to 350 ± 60 nm, which confirms the attachment of phthalocyanine complexes to nanotubes. The third harmonic of a Nd:YAG nanosecond laser (355 nm, 20 ns) was used to study the nonlinear optical response. Based on a Z-scan with open-aperture and input-output dependence curves, third-order nonlinear optical absorption coefficients of 149, 236, and 229 cm/GW were obtained for dispersions of composites of SWCNTs and (OH)4PcHH in water, dimethylformamide (DMF), and dimethylsulfoxide (DMSO), respectively. Threshold values did not exceed 100 mJ/cm2. The Z-scan showed a gradual decrease in the duration of the laser pulse by 53%; however, near the focus, there was a sharp increase in the duration of the transmitted pulse, reaching a value of 29 ns in z = 0. This phenomenon confirms the occurrence of reverse saturable absorption in the investigated media and can be used in photonic devices to control the temporal characteristics of the signal. Thus, the possibility of protection of sensitive photonic devices and human eyes from nanosecond laser pulses in the near UV range by nanodispersed liquid media based on composites of SWCNTs with (OH)4PcHH has been discussed in this paper.

Adsorption of lanthanide double-decker phthalocyanines on single-walled carbon nanotubes: structural changes and electronic properties as studied by density functional theory

ContextMolecular modeling of carbon nanotubes and lanthanide double-decker phthalocyanines hybrids is challenging due to the presence of 4f-electrons. In this paper, we analyzed the trends in structural changes and electronic properties when a lanthanide (La, Gd, and Lu) bisphthalocyanine molecule is adsorbed on the surface of two single-walled carbon nanotubes (SWCNTs) models: armchair and zigzag. The density functional theory (DFT) computations showed that the height of bisphthalocyanines complexes (LnPc2) when adsorbed on a nanotube (LnPc2+SWCNT) is the structural feature which is most affected by the nanotube model. The formation energy of the LnPc2+SWCNT hybrid depends on the metal atom and the nanotube chirality. LaPc2 and LuPc2 bind stronger to the zigzag nanotube, while for GdPc2, bonding to the armchair nanotube is the stronger one. The HOMO-LUMO gap energy (Egap) shows a correlation between the nature of lanthanide and the nanotube chirality. In the case of adsorption on armchair nanotube, Egap tends to match the gap of isolated LnPc2, whereas for adsorption on the zigzag nanotube, it is closer to the value for the isolated nanotube model. The spin density is localized on the phthalocyanines ligands (plus on Gd in the case of GdPc2), when the bisphthalocyanine is adsorbed on the surface of the armchair nanotube. For bonding to zigzag nanotube (ZNT), it extends over both components, except for LaPc2+ZNT, where spin density is found on the nanotube only.MethodAll DFT calculations were carried out using the DMol3 module of Material Studio 8.0 software package from Accelrys Inc. The computational technique chosen was the general gradient approximation functional PBE in combination with a long-range dispersion correction developed by Grimme (PBE-D2), the double numerical basis set DN, and the DFT semi-core pseudopotentials.

Hybridization of papain molecules and DNA-wrapped single-walled carbon nanotubes evaluated by atomic force microscopy in fluids

Although various conjugates of single-walled carbon nanotubes (SWNTs) and biomolecules, such as nanobiosensors and nanobiodevices, have been reported, the conjugation of papain and SWNTs have not been reported because of the formation of unexpected aggregates. In this study, atomic force microscopy (AFM) in liquid was used to investigate the interactions between papain and DNA-wrapped SWNTs (DNA–SWNTs) at two different pH values (pH 3.0 and 10.5). The direct AFM observation of the mixture of papain and DNA–SWNTs confirmed the aggregation of papain molecules with DNA–SWNTs in the buffer solutions. The numerous and non-uniform adsorption of papain molecules onto DNA–SWNTs was more pronounced at pH 3.0 than that at pH 10.5. Furthermore, thick conjugates appeared when papain and DNA–SWNTs were simultaneously mixed. The near-infrared photoluminescence spectra of the SWNTs drastically changed when the papain molecules were injected into the DNA–SWNT suspension at pH 3.0. Thus, the regulation of electrostatic interactions is a key aspect in preparing optimal conjugates of papain and DNA–SWNTs. Furthermore, although previous papers reported AFM images of dried samples, this study demonstrates the potential of AFM in liquid in evaluating individual bioconjugates of SWNTs.

Metallocene-Filled Single-Walled Carbon Nanotube Hybrids

In this paper, the growth mechanism, structure, growth processes, growth kinetics, and optical, vibronic and electronic properties of metallocene-filled single-walled carbon nanotubes (SWCNTs) are considered. A description of the procedures used to fill the nanotubes is provided. An investigation of doping effects on metallicity-mixed SWCNTs filled with metallocenes by Raman spectroscopy, near edge X-ray absorption fine structure spectroscopy, photoemission spectroscopy, and optical absorption spectroscopy is described. The studies of doping effects on metallicity-sorted SWCNTs filled with metallocenes are discussed. Doping effects in metallicity-mixed and sorted SWCNTs upon the chemical transformation of encapsulated molecules are analyzed. A discussion of the modification of the electronic properties of filled SWCNTs is presented. Applications of metallocene-filled SWCNTs in electrochemistry, thermoelectric power generation, chemical sensors, and magnetic recording are discussed.

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.

Rotating Flow and Heat Transfer of Single-Wall Carbon Nanotube and Multi-Wall Carbon Nanotube Hybrid Nanofluid with Base Fluid Water over a Stretching Sheet

In this article, numerical simulations of the rotational flow of water-based magnetohydrodynamic (MHD) nanofluid containing single-wall carbon nanotube (SWCNT) and hybrid nanofluid containing single- and multiple-wall carbon nanotube (SWCNT-MWCNT) over a stretching sheet are performed. The primary goal is to improve thermal transport efficiency due to CNTs extraordinary thermal conductivity. The 3D governing equations for microorganism concentration, energy, momentum, concentration, and mass conservation are transformed into 1D ordinary differentiation via similarity transformations. In a MATLAB environment, the resultant system of equations (ODEs) are then solved using Runge–Kutta fourth order with the shooting process. Tables and graphs were used to show the results of physical parameters. According to our findings, enhancing the rotational parameter λ and the magnetic field M reduce the base fluid velocity along the x-axis, and on the other hand, the opposite tendency is shown along the y-axis. Furthermore, the velocities, temperature, and microorganism concentration profiles of hybrid nanofluid (SWCNT−MWCNT/H2O) are found to be higher than those of mono nanofluid (H2O+SWCNT), while the concentration profile is found to be lower.

Synthesis and characterization of a novel silver nanoparticles decorated functionalized single-walled carbon nanotubes nanohybrids embedded polyaniline ternary nanocomposites: thermal, dielectric, and sensing properties

ABSTRACT The recent research paper describes the synthesis of the silver nanoparticles (AgNPs) coated functionalized single-walled carbon nanotubes (f-SWNTs) hybrid nanofillers reinforced polyaniline (PANI) (PANI/Ag@f-SWNTs) nanocomposites, which was carried out through in situ polymerization process to analyze its thermal, dielectric, and sensing properties. The Fourier transform infrared (FTIR) spectroscopy showed the occurrence of interphase interactions within the Ag@f-SWNTs hybrid nanofillers and PANI matrix. The Raman spectroscopy indicated the blue shift with increase in intensity of the band that confirms the decoration of AgNPs on the surface of the f-SWNTs. The structural behavior of the PANI/Ag@f-SWNTs nanocomposites was investigated via X-ray diffraction (XRD) spectroscopy, which revealed the presence of the face centered cubic (FCC) crystal structure of the AgNPs. X-ray photoelectron spectroscopy (XPS) evaluated the chemical composition and bond structure of the nanocomposites. The morphology of the nanocomposites is studied from scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which displayed the well decoration of the AgNPs on the surface of the f-SWNTs. The thermal and dielectric properties of the PANI/Ag@f-SWNTs nanocomposites were examined by using thermogravimetry-differential scanning calorimetry (TG-DSC) and dielectric relaxation spectroscopy (DRS), respectively. The thermal and dielectric properties of the PANI/Ag@f-SWNTs nanocomposites were significantly enhanced owing to the development of robust interphase interactions between the Ag@f-SWNTs hybrid nanofillers and PANI matrix that arises due to the homogeneous dispersion of the Ag@f-SWNTs nanohybrids within the PANI matrix through in situ polymerization process. The Cr(VI) metal ion sensing behavior of the PANI and PANI ternary nanocomposites was studied through UV-Vis spectroscopy, which indicates significant improvement in sensing behavior of the PANI/Ag@f-SWNTs ternary nanocomposites as compared to the pure PANI matrix.

Synergistic Strengthening in Graphene Oxide and Oxidized Single-walled Carbon Nanotube Hybrid Material for use as Electrolytes in Proton Exchange Membrane Fuel Cells.

Herein, we report an efficient proton exchange membrane formed from a synergistic combination of graphene oxide (GO) and oxidized single-walled carbon nanotube (CNTOX) by the freeze-drying route that gives rise to enhanced fuel cell power density. At 25 °C and 100% relative humidity (RH), the 3DGO-CNTOX hybrid shows remarkably high out-of-plane and in-plane proton conductivities of 6.64×10-2 and 5.08 S cm-1 , respectively. Additionally, the measured performance using prepared films as proton conduction membranes in a proton exchange membrane fuel cell (PEMFC) exhibited a peak power density of 117.21 mW cm-2 . The high performance of these films can be ascribed to the freeze-dried-driven structural morphology of 3DGO-CNTOX that facilitates higher water retention capacity as well as the synergistic strengthening effect between GO and CNTOX with a highly interconnected proton conduction network. The current results imply that the new 3DGO-CNTOX hybrid material has potential for wide application as a proton exchange membrane.

Integrated, Highly Flexible, and Tailorable Thermoelectric Type Temperature Detectors Based on a Continuous Carbon Nanotube Fiber.

As possible alternatives to traditional thermoelectric (TE) materials, carbon nanomaterials and their hybrid materials have great potential in the future application of flexible and lightweight temperature detection. In this work, an integrated, highly flexible, and tailorable TE temperature detector with high performance has been fabricated based on a continuous single-walled carbon nanotube (SWCNT) fiber. The detector consists of more than one pairs of thermocouples composed of p-type SWCNT fiber and n-type SWCNT hybrid fiber in situ doped by polyethylenimine. Due to the node contact mechanism of the detection, the sensitivity of the detector can be improved with the increase of the number of p-n thermocouples, independent of the length of the thermocouple. The temperature detection process of the detector has been studied in detail. In particular, the integrated and flexible detector can be divided into several sub-detectors easily by cutting, illustrating the prospect of large-scale preparation of this kind of novel temperature detectors. Its high flexibility ensures the detector to maintain excellent detection performance after 15000 bending circles. Furthermore, the as-designed TE type temperature detector demonstrates a great application promise for real-time temperature detection and temperature change sensing even in complex surface and harsh environment.

Coumarin bearing asymmetrical zinc(II) phthalocyanine functionalized SWCNT hybrid nanomaterial: Synthesis, characterization and investigation of bifunctional electrocatalyst behavior for water splitting

A novel asymmetrical zinc(II) phthalocyanine (Coum-Pc) bearing three 7-ethynyl-3-(3,4,5-trimethoxyphenyl) coumarin and one ethyloxy azido groups was synthesized and characterized for the first time. This novel asymmetric Coum-Pc was covalently attached to single walled carbon nanotube (SWCNT) containing terminal ethynyl groups via the azide-alkyne Huisgen cycloaddition (Click) reaction for preparation of coumarin bearing zinc(II) phthalocyanine functionalized SWCNT hybrid nanomaterial (SWCNT-Coum-Pc). Hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalyst for water splitting behavior of SWCNT-Coum-Pc hybrid nanomaterial were evaluated. The SWCNT-Coum-Pc hybrid reduced the onset potential required for HER by approximately 200 mV compared to SWCNT catalyst in acidic medium. The SWCNT-Coum-Pc catalyst reduced the HER overpotential of 570 mV at a current density of 10 mA cm−2 in alkaline medium. It also exhibited outstanding activity in OER, required only an overpotential of 330 mV at a current density of 10 mA cm−2. Heterogeneous rate constants of the electrodes from impedance analysis were used to calculate the value of charge transfer resistance and the conductivity of the composite film. The presence of Coum-Pc groups on the SWCNT surface increased for both the conductivity and electron transfer rate of the SWCNT. Therefore, SWCNT-Coum-Pc hybrid significantly improved the performance of OER and HER for water splitting. The present work provided a promising ground for the of SWCNT-Coum-Pc hybrid as a bifunctional electrocatalyst for water splitting.

Exponential Matrix–Rational Approximation (EM-RA) Model for SWCNT Bundle and Hybrid Cu-CNT Interconnects

This article presents a variation-aware exponential matrix–rational approximation (EM-RA) model for the signal integrity analysis in single-walled carbon nanotube (SWCNT) bundle and hybrid copper-CNT (Cu-CNT) on-chip interconnects. The variations include temperature (300–500 K) only, and temperature (300–500 K) and dielectric surface roughness (10–180 pm) both. The transient analysis is carried out for the signal integrity parameters, crosstalk and propagation delay, estimation using the proposed EM-RA model. The results obtained using the proposed model are compared with the industry-level simulation program with an integrated circuit emphasis (SPICE) simulator. The comparison shows excellent agreement for the results with less than 1% error. The proposed model is also compared for the computational time complexity. It is observed that a speed-up factor of 74.24 and 48.35 is attained using the proposed temperature-parameterized model during the analysis of coupled-two and coupled-three interconnect lines, respectively. The speed-up further increases to 485.41 and 378.35 for coupled-two and coupled-three lines, respectively, when the temperature and dielectric surface roughness parametrized EM-RA model is used. This computational CPU time expense efficiency and the accuracy of the proposed model in comparison to the HSPICE simulator ensures immense possibility regarding its implementation in computer-aided design (CAD) tools for carrying out the transient analysis of SWCNT bundle and Cu-CNT interconnect lines. Encouraging results for the eye-diagram analysis reports 95.54% and 99.37% of the eye height and eye width for the SWCNT network, and 99.77% and 99.96% of the eye height and eye width for the Cu-CNT.

Covalent functionalization of single-walled carbon nanotubes using meso-tetra(4-aminophenyl) porphyrin and its zinc complex

Covalent linking of 5,10,15,20 meso tetra(4-aminophenyl) porphyrin (TAP) and its zinc complex with single-walled carbon nanotubes (SWCNTs) (nanohybrids A and B, respectively) has been reported. Significant decrease in the intensity of D-band and higher frequency shift of G-band of SWCNT-TAP in Raman spectrum reveals the improved graphitic sp2 hybridization of SWCNT as compared to SWCNT-ZnTAP. This is due to the functionalization of free base porphyrin (electron donating group) in the nanohybrid A. Shifting of carbonyl stretching frequency from 1700 cm−1 to 1680 cm−1 and further appearance of striking bands in the X-ray photoelectron spectroscopy (XPS) and FTIR spectra of nanohybrids A and B confirm the covalent linking of porphyrin chromophores with SWCNTs. XPS reveals that the extent of functionalization of nanohybrid A is more as compared to nanohybrid B. These nanohybrids demonstrate positive solvatochromism. Upon excitation at 450 nm, the nanohybrids A and B reveal ∼76% and 65% fluorescent quenching of emission bands at 686 and 632 nm, respectively. This is due to the energy or electron transfer from porphyrins to SWCNTs.

Multispectral Fingerprinting Resolves Dynamics of Nanomaterial Trafficking in Primary Endothelial Cells.

Intracellular vesicle trafficking involves a complex series of biological pathways used to sort, recycle, and degrade extracellular components, including engineered nanomaterials (ENMs) which gain cellular entry via active endocytic processes. A recent emphasis on routes of ENM uptake has established key physicochemical properties which direct certain mechanisms, yet relatively few studies have identified their effect on intracellular trafficking processes past entry and initial subcellular localization. Here, we developed and applied an approach where single-walled carbon nanotubes (SWCNTs) play a dual role-that of an ENM undergoing intracellular processing, in addition to functioning as the signal transduction element reporting these events in individual cells with single organelle resolution. We used the exceptional optical properties exhibited by noncovalent hybrids of single-stranded DNA and SWCNTs (DNA-SWCNTs) to report the progression of intracellular processing events via two orthogonal hyperspectral imaging approaches of near-infrared (NIR) fluorescence and resonance Raman scattering. A positive correlation between fluorescence and G-band intensities was uncovered within single cells, while exciton energy transfer and eventual aggregation of DNA-SWCNTs were observed to scale with increasing time after internalization. An analysis pipeline was developed to colocalize and deconvolute the fluorescence and Raman spectra of subcellular regions of interest (ROIs), allowing for single-chirality component spectra to be obtained with submicron spatial resolution. This approach uncovered correlations between DNA-SWCNT concentration, dielectric modulation, and irreversible aggregation within single intracellular vesicles. An immunofluorescence assay was designed to directly observe the DNA-SWCNTs in labeled endosomal vesicles, revealing a distinct relationship between the physical state of organelle-bound DNA-SWCNTs and the dynamic luminal conditions during endosomal maturation processes. Finally, we trained a machine learning algorithm to predict endosome type using the Raman spectra of the vesicle-bound DNA-SWCNTs, enabling major components in the endocytic pathway to be simultaneously visualized using a single intracellular reporter.

(Invited) Toward Spectral Homogeneity in Guanine Functionalized SWCNTs

Different chiralities of single-walled carbon nanotubes (SWCNTs) have distinct electronic and optical properties, with a range of band gaps that make them appropriate for several opto-electronic applications. Due to the unusually high mobility of charge carriers in SWCNTs,1 semiconducting SWCNTs may find use as logic gates in future high-speed nano-electronic circuits. With this in mind, controlled modulation of the optical and electronic properties of individual carbon nanotubes may be valuable in optoelectronic and nano-bioelectronic applications.It was recently discovered that when SWCNTs coated with single-stranded DNA are exposed to singlet oxygen, the guanine nucleobases in the DNA coatings form covalent bonds to the nanotube sidewalls.2 This alters the nanotube electronic and optical properties, allowing spatial and energetic control through selection of the DNA base sequence. However, the functionalized products display undesired spectral broadening interpreted as excess inhomogeneity compared to the pristine SWCNT reactants.Here we will present the results of efforts to understand and reduce this inhomogeneity. Our study has used molecular dynamics simulations of ssDNA – SWCNT hybrid structures, as well as analysis of experimental data. We have explored the effects of varied reaction conditions, including temperature, ionic strength, and pH on product yields and spectra. An unexpected inverse dependence of functionalization density on reaction temperature was uncovered. We will also present photophysical results extracted from spectral data via statistical modeling, including the energy depth of localized exciton quantum wells created by functionalization. The analysis points to fluorescence red shifts that reflect the random number of functionalization sites felt by excitons. Dürkop, T.; Getty, S. A.; Cobas, E.; Fuhrer, M. S. Extraordinary Mobility in Semiconducting Carbon Nanotubes. Nano Lett. 2004, 4, 35-39.Zheng, Y.; Bachilo, S. M.; Weisman, R. B. Controlled Patterning of Carbon Nanotube Energy Levels by Covalent DNA Functionalization. ACS Nano 2019, 13, 8222-8228.

Study of adsorption kinetics of pristine and SnO2 functionalized carbon nanotubes as environment gas sensors for NO2 and NH3 gases

The pristine and functionalized single walled carbon nanotubes are studied as environmental gas sensors. The results for pristine Single walled carbon nanotubes (SWNT) and SnO2 functionalized SWNT hybrid nanostructures have been compared for their response towards the gases, i.e. NO2 and NH3 (for concentrations ranging from 2 to 20 ppm). To study the underlying phenomenon, the adsorption kinetics of pristine and SnO2 functionalized (SWNT) have been next investigated for their sensitivity towards both the prevalent gases. The electrical model of Carbon nanotubes (CNT) networks and its dependence on gas concentration has been investigated. Considering the physisorption of NH3 and NO2, Langmuir adsorption model has been applied to study the change in conductivity with varying gas concentration by fitting experimental data with Langmuir isotherm. Langmuir constants are indicative of adsorption capacity of SWNT surface as well as concentration of gas molecules adsorbed on CNT networks. An increment has been observed in the Langmuir constants from pristine to functionalized SWNT. The observed enhancement may be attributed to the improvement of surface adsorption kinetics when SWNT surface is modified with a functional group.

Sensing of epigallocatechin gallate and tannic acid based on near infrared optical spectroscopy of DNA-wrapped single-walled carbon nanotube hybrids

The optical responses of DNA-wrapped single-walled carbon nanotubes (DNA-SWNTs) caused by the addition of epigallocatechin gallate (EG) and tannic acid (TA) were investigated. Near infrared absorbance and photoluminescence spectra of pre-oxidized DNA-SWNTs were measured with and without EG and TA. Since both EG and TA have antioxidant abilities, the near infrared spectra changed after the addition of the chemicals. While detection of the antioxidant abilities of EG by DNA-SWNT hybrids has been previously reported, TA was employed for the first time. The changes in the absorbance caused by the addition of TA were found to saturate at 0.33 µM TA, although saturation was not observed even at 3.3 µM with the addition of EG. Oxidation of DNA-SWNT was suppressed by addition of TA or EG. The effects of TA were much greater than those of EG on the absorbance. The photoluminescence did not appear to saturate at 3.3 µM for either EG or TA. photoluminescence had a larger measurement capacity than NIR absorbance. Interestingly, the photoluminescence change caused by EG was much larger than that of TA at 3.3 µM, although the antioxidant property of TA was stronger at 0.33 and 0.033 µM, suggesting that the optical responses were not simple redox reactions. Peak shifts in the absorbance/photoluminescence spectra revealed unique differences according to the chirality of the SWNTs and the types of chemicals used. This suggests that the combination of absorbance/photoluminescence and peak intensity/peak shifts could detect multiple types of chemical information, not only redox reaction. A direct comparison between EG and TA was demonstrated for the first time in this novel study. In addition, sensing of EG and TA by near infrared spectra was made available using not only changes in intensity but also a variety of peak shifts of SWNTs.

Study on optical response sensitivity in hybrid of single-walled carbon nanotubes mixed with double-stranded DNA and carboxymethylcellulose

This study investigated the optical response sensitivity of a hybrid of single-walled carbon nanotubes (SWNTs) mixed with double-stranded DNA (dsDNA) and carboxymethylcellulose (CMC). The changes of optical response in SWNTs such as oxidation and antioxidant reactions can be measured using near infrared (NIR) absorbance spectra. The previous studies have not identified a sensitivity of mixture ratio of CMC and dsDNA for optical response of SWNTs. SWNTs hybrids prepared by mixing dsDNA and CMC were oxidized by H2O2 for 30 min (final concentration 0.03%), and then antioxidized by catechin (final concentration 15 μg/mL) hybrid for 10 min. The NIR absorbance of SWNT hybrids was shown to be sensitive even when mixed with dsDNA at a weight concentration (mg/mL) of 1% CMC. While the optical response of SWNTs was highly dependent on the mixture ratio of DNA and CMC, there was no significant difference in the height distribution of SWNTs hybrids examined by atomic force microscopy (AFM). This result suggests that the optical response performance of dsDNA/CMC-SWNTs hybrids sensor can be greatly controlled by the mixture ratio of dsDNA and CMC without changing the heights of the hybrids.