Absence Of Single-walled Carbon Nanotubes Research Articles

Study on the series resistance of crystal violet dye-based organic photovoltaic device in presence of single walled carbon nanotubes

The series resistance (Rs) of any organic photovoltaic device (OPV) plays an important role on the device performance. Generally, the electrode and the presence of traps at the interface contribute the high Rs. In this present work, we have studied the Rs of crystal violet dye-based OPV device and its variation in the presence of single walled carbon nanotubes (SWCNT). From the dark current voltage (I–V) characteristics, we have extracted Rs by using the Cheung–Cheung method. It is observed that the trap energy (Ec) and the value of Rs are decreased in the presence of SWCNT. The values of Rs and Ec are about 0.246 MΩ and 0.085 eV in the absence of SWCNT and these values change to 0.124 MΩ and 0.060 eV, respectively, in the presence of SWCNT. The light I–V characteristics of the devices have also been studied to find out the Rs of the device under illumination. Under illumination, the charge transport process is governed by the incident photon energy (Em) which is absorbed by the OPV device. So we have extracted the Em from the light I–V characteristics and estimated the Rs by using area method under light illumination in the absence and presence of SWCNT. It is observed that the extracted values of Rs under illumination are low compared to the values of Rs measured from dark I-V characteristics.

Ni@Ni3C Nanochain-SWCNT Composite with Comparable Electrocatalysis of Benchmark Pt/C for Hydrogen Evolution Reaction

Developing robust and low-cost electrocatalysts for efficient hydrogen evolution reaction (HER) through facile methods is of great significance to the energy and environment sustainability. Herein, a simple one-pot solvothermal method has been developed to synthesize a hybrid material of nickel@nickel carbide (Ni@Ni3C) nanochain embedded in a network of single-walled carbon nanotubes (SWCNTs). The electrochemical experiments indicate that the composite of Ni@Ni3C-SWCNTs has the HER electrocatalytic performance comparable to that of Pt/C in an acidic medium (0.5 M H2SO4). The overpotential to reach a current density of 10 mA cm−2 in 0.5 M H2SO4 is only −74 mV with a Tafel slope of 46.9 mV dec−1. Compared to Ni@Ni3C in the absence of SWCNTs, the enhanced HER performance of Ni@Ni3C-SWCNTs can be attributed to the increased intrinsic activity, improved electronic conductivity, and the electron coupling effect between Ni@Ni3C and SWCNTs. The Ni@Ni3C-SWCNTs composites also show high stability at the overpotential of −0.2 V for 24 h. This work provides guidance for the synthesis of high-performance non-precious metal electrocatalysts for HER.

Incident photon-to-current efficiency of thermally treated SWCNTs-based nanocomposite for dye-sensitized solar cell

This study focuses on incident photon-to-current efficiency (IPCE) performance of In2O3-SWCNTs for dye-sensitized solar cell (DSSC) application. The thin films were prepared by sol-gel method using spin-coating technique annealed at 400, 450, 500, 550, and 600 °C. Morphology transition of In2O3 from spherical to cubic and then octahedral structure occurred as the annealing temperature rises. The photoanode annealed at 450 °C (cubic structure) provides a stable phase of cubic structure with large surface area and optimum thickness for effective dye adsorption. However, the IPCE value does not solely depends on the dye adsorption of photoanodes (light harvesting efficiency (LHE)) but the electron injection efficiency (ηinj) and the collection efficiency (ηcoll). Smaller energy bandgap of photoanodes favors the injected electrons with higher driving force to the conduction band (CB) of the photoanode, which in turn increases the ηinj from the LUMO of dye to the In2O3-SWCNTs CB. Besides that, the absence of single-walled carbon nanotubes (SWCNTs) above 500 °C caused the energy bandgap to increase and leads to lower driving force of injected electrons. In addition, SWCNTs are capable of absorbing visible light faster than other materials. Therefore, the cubic structure-based photoanode (450 °C) exhibited better electron transport with larger driving force on injected electron (ηinj) that decreased the electron recombination rate and increased electron lifetime and subsequently obtained larger charge collection efficiency (ηcoll) of almost 99%. Consequently, the IPCE performance of DSSC was enhanced.

Electropolymerized Pyrrole-Based Conductive Polymeric Ionic Liquids and Their Application for Solid-Phase Microextraction.

Pyrrole was covalently bonded to 1-methyl and 1-benzylimidazolium ionic liquids (ILs) via an N-substituted alkyl linkage to prepare electropolymerizable IL monomers with excellent thermal stability. The methylimidazolium IL, [pyrrole-C6MIm]+, was then electropolymerized on macro- and microelectrode materials to form conductive polymeric IL (CPIL)-modified surfaces. Electrochemical characterization of a 1.6 mm diameter Pt disk electrode modified with poly[pyrrole-C6MIm]+ demonstrated a selective uptake for an anionic redox probe while rejecting a cationic redox probe. Furthermore, electropolymerization of [pyrrole-C6MIm]+ doped with single-walled carbon nanotubes (SWNT) on 125 μm platinum wires produced 42 μm thick poly[pyrrole-C6MIm]+/SWNT films compared to 17 μm in the absence of SWNT and 5 μm for the previously reported poly[thiophene-C6MIm]+ coatings. The poly[pyrrole-C6MIm]+/SWNT films were prepared with reproducible thicknesses as well as thermal properties sufficient for high-temperature applications, such as solid-phase microextraction (SPME) with gas chromatographic analysis. The utilization of the CPIL sorbent materials in SPME experiments provided excellent extraction efficiencies and selectivity toward organic aromatic analytes. The CPIL sorbent coatings also yielded outstanding fiber-to-fiber reproducibility on the basis of extraction efficiencies and improved response for a range of analytes relative to commercial 100 μm poly(dimethylsiloxane) fibers when normalized for differences in film thickness. Poly[pyrrole-C6MIm]+ CPIL coatings doped with SWNT are therefore promising new sorbent materials for SPME analyses.

Sonocatalytic degradation coupled with single-walled carbon nanotubes for removal of ibuprofen and sulfamethoxazole

This study examined the degradation of pharmaceuticals ((PhACs), ibuprofen (IBP) and sulfamethoxazole (SMX)) using an ultrasonic (US) reactor at a 1000kHz frequency in the absence and presence of single walled carbon nanotubes (SWNTs). In the absence of SWNTs, maximum degradation of PhACs were achieved under high temperature; 55>35>25>15°C. In addition, the relatively higher degradation of IBP and SMX was obtained under acidic condition at pH 3.5 than pH 7 and 9.5; >99%, 79%, and 72% for IBP and >99%, 75%, and 65% for SMX, respectively. However, H2O2 production increased from 77μM (no SWNTs) to 115μM in the presence of SWNTs (45mg/L) at pH 7. In addition, the removal of IBP and SMX significantly increased under US/SWNTs reaction conditions than US and SWNTs only reactions. The removal of IBP and SMX was 57% and 48% under SWNTs (adsorption) reactions, 77% and 70% under US reactions, and 97% and 92% under US/SWNTs reactions, respectively. This study evaluated the effect of temperature, pH, SWNTs, and physiochemical properties of selected PhACs under US process. In addition, the adsorption molecular modeling was validated with the experimental results.

Enzymatic formation of carbohydrate rings catalyzed by single-walled carbon nanotubes.

Macrocyclic carbohydrate rings were formed via enzymatic reactions around single-walled carbon nanotubes (SWNTs) as a catalyst. Cyclodextrin glucanotransferase, starch substrate and SWNTs were reacted in buffer solution to yield cyclodextrin (CD) rings wrapped around individual SWNTs. Atomic force microscopy showed the resulting complexes to be rings of 12-50 nm in diameter, which were highly soluble and dispersed in aqueous solution. They were further characterized by Raman and Fourier transform infrared spectroscopy and molecular simulation using density functional theory calculation. In the absence of SWNT, hydrogen bonding between glucose units determines the structure of maltose (the precursor of CD) and produces the curvature along the glucose chain. Wrapping SWNT along the short axis was preferred with curvature in the presence of SWNTs and with the hydrophobic interactions between the SWNTs and CD molecules. This synthetic approach may be useful for the functionalization of carbon nanotubes for development of nanostructures.

Reducing background signal of G-quadruplex–hemin DNAzyme sensing platform by single-walled carbon nanotubes

The G-quadruplex–hemin DNAzyme has shown potential as a new catalytic label for the development of various biosensors. But the typical problem of high background induced by excess hemin itself limits the application of the method. In this work, we found that single-walled carbon nanotubes (SWNTs) can effectively decrease the background of G-quadruplex–hemin DNAzyme sensing platform. The method relies upon the strong affinity of SWNTs with hemin. In the presence of SWNTs, superfluous hemin is arrested the surface of SWNTs, and then is removed though centrifugation It was proved that SWNTs reduce the background of G-quadruplex–hemin DNAzyme sensing platform by ABTS–H 2O 2 colorimetric. Moreover, we detected K + with the AGRO100 as the sensing element. The present limit of detection for K + is 2 nM, and the sensitivity for analyzing K + is improved by about 10-fold as compared with the reported colorimetric counterpart in the absence of SWNTs.

Removal of bisphenol A and 17α-ethinyl estradiol from landfill leachate using single-walled carbon nanotubes

In this study, the adsorption of bisphenol A (BPA) and 17α-ethinyl estradiol (EE2) from landfill leachate onto single-walled carbon nanotubes (SWCNTs) was investigated. Different leachate solutions were prepared by altering the pH, ionic strength, and dissolved organic carbon (DOC) in the solutions to mimic the varying water conditions that occur in leachate during the various stages of waste decomposition. The youngest and oldest leachate solutions contained varying DOC and background chemistry and were represented by leachate Type A (pH = 5.0; DOC = 2500 mg/L; conductivity = 12,500 μS/cm; [Ca 2+] = 1200 mg/L; [Mg 2+] = 470 mg/L) and Type E (pH = 7.5; DOC = 250 mg/L; conductivity = 3250 μS/cm; [Ca 2+] = 60 mg/L; [Mg 2+] = 180 mg/L). These solutions were subsequently combined in different ratios to produce intermediate solutions, labeled B–D, to replicate time-dependent changes in leachate composition. Overall, a larger fraction of EE2 was removed as compared to BPA, consistent with its higher log K OW value. The total removal of BPA and EE2 decreased in older leachate solutions, with the adsorptive capacity of SWCNTs decreasing in the order of leachate Type A > Type B > Type C > Type D > Type E. An increase in the pH from 3.5 to 11 decreased the adsorption of BPA by 22% in young leachate and by 10% in old leachate. The changes in pH did not affect the adsorption of EE2 in the young leachate, but did reduce adsorption by 32% in the old leachate. Adjusting the ionic strength using Na + did not significantly impact adsorption, while increasing the concentration of Ca 2+ resulted in a 12% increase in the adsorption of BPA and a 19% increase in the adsorption of EE2. DOC was revealed to be the most influential parameter in this study. In the presence of hydrophilic DOC, represented by glucose in this study, adsorption of the endocrine disrupting compounds (EDCs) onto the SWCNTs was not affected. In the absence of SWCNTs, hydrophobic DOC (i.e., humic acid) adsorbed 15–20% of BPA and EE2. However, when the humic acid and SWCNTs were both present, the overall adsorptive capacity of the SWCNTs was reduced. Hydrophobic (π-π electron donor-acceptor) interactions between the EDCs and the constituents in the leachate, as well as interactions between the SWCNTs and the EDCs, are proposed as potential adsorption mechanisms for BPA and EE2 onto SWCNTs.

Label‐Free Colorimetric Detection of Single Nucleotide Polymorphism by Using Single‐Walled Carbon Nanotube Intrinsic Peroxidase‐Like Activity

Single-walled carbon nanotubes (SWNTs) have been considered to be leading candidates for nanodevice applications and novel drug delivery. Intriguingly, recent studies have shown that SWNTs have catalytic activity even in the absence of catalytic factors. Since hydrogen peroxide is an important oxidizing agent in biological systems, the catalytic reaction of SWNTs with H2O2 has received much attention. The SWNT catalytic mechanism is much debated, but it has been suggested that it is related to trace amounts of metal catalyst in SWNTs. H2O2 is a major reactive oxygen species in living organisms, and its overproduction is implicated in the development of numerous inflammatory diseases, such as atherosclerosis, chronic obstructive pulmonary disease, and hepatitis. Furthermore, as a product of many enzyme-catalyzed reactions, H2O2 can act as an indicator to monitor the quantity of biologically important molecules, such as glucose. Therefore, studying the catalytic reaction of SWNTs with H2O2 might offer a promising application for disease diagnosis and for the design of SWNT-based sensors. In this work, we report that SWNTs possess intrinsic peroxidase-like activity. That the catalytic activity does not depend on trace amounts of metal catalyst in the SWNTs is evidenced by energy-dispersive X-ray (EDX) analysis. In the presence of H2O2, SWNTs catalyze the reaction of the peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) thereby producing a color change (Scheme 1). Our results indicate that the catalytic efficiency of SWNTs is strongly dependent on pH, temperature, and H2O2 concentration, similar to horseradish peroxidase (HRP). More importantly, we compared the catalytic efficiency of SWNTs containing different amounts of cobalt residues. The results clearly show that the observed “catalytic” effect of SWNTs can be attributed to their intrinsic properties rather than metal residues. Peroxidase activity has a great potential for practical application and has been used in the bioremediation of waste water or as diagnostic kits. As peroxidase mimics, SWNTs were used here for label-free colorimetric detection of disease-associated single-nucleotide polymorphism (SNP) with a direct detection limit of 1 nm based on the color reaction of TMB. It is well known that SNP detection is very important, and different kinds of detection methods have been reported; however, to our knowledge, this is the first demonstration of applying intrinsic SWNT peroxidase-like activity and color change for this purpose. This work will provide new insights into the utilization of SWNT peroxidase-like activity. To increase SWNT solubility in aqueous solution, we treated SWNTs with a mixture of concentrated sulfuric and nitric acids, as described previously. Figure S1 in the Supporting Information shows the mixed solution of H2O2 and TMB in the presence or absence of SWNTs. In the absence of SWNTs, the color of the solution does not change in 12 h; however, in the presence of SWNTs, the color changes from black to blue immediately. This result suggests that SWNTs can catalyze the reaction of TMB in the presence of [a] Y. Song, X. Wang, C. Zhao, K. Qu, Dr. J. Ren, Prof. X. Qu Laboratory of Chemical Biology Division of Biological Inorganic Chemistry State Key Laboratory of Rare Earth Resource Utilization Graduate School of the Chinese Academy of Sciences Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun, Jilin 130022 (China) Fax: (+86)431-85262656 E-mail : xqu@ciac.jl.cn Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.20090902643. Scheme 1. Schematic illustration of SWNTs catalyzing the reaction of peroxidase substrate TMB in the presence of H2O2 to give the blue product oxidized TMB (oxTMB).

The Effect of Nanoparticle-Enhanced Photoacoustic Stimulation on Multipotent Marrow Stromal Cells

In this article, we report a novel nanoparticle-enhanced biophysical technique that differentiates multipotent marrow stromal cells (MSCs) toward osteoblasts. We show that a brief (10 min) daily nanoparticle-facilitated exposure of MSCs to nanosecond pulse laser-induced photoacoustic (PA) stimulation enhances their differentiation toward osteoblasts. To observe osteodifferentiation under PA stimulation, tissue culture plates were seeded with MSCs without the osteogenic culture supplements (OS, 0.01 M beta-glycerophosphate, 50 mg/L ascorbic acid, 10(-8) M dexamethasone) in the presence and absence of single-walled carbon nanotubes (SWNTs) and gold nanoparticles (GNPs). The alkaline phosphatase activity, calcium content, and osteopontin secretion were monitored as indicators of MSCs' differentiation toward osteoblasts. The PA stimulated groups show up to 612% increase in calcium content compared to the controls cultured with osteogenic supplements (without PA stimulation) after 16 days. Among the PA stimulated groups, at day 16, MSCs incubated with SWNTs at 10 microg/mL concentrations showed up to 97% greater calcium content than those that did not contain SWNTs. The results demonstrated that PA stimulation not only promotes osteogenesis but also is synergistically enhanced by the presence of nanoparticles and, thus, has major implications for bone regeneration applications.

Direct Electron Transfer at Cellobiose Dehydrogenase Modified Anodes for Biofuel Cells

Cellobiose dehydrogenases (CDHs, EC 1.1.99.18) contain a larger flavin-associated (dehydrogenase) domain and a smaller heme-binding (cytochrome) domain. CDHs from basidiomycete fungi oxidize at an appreciable level cellobiose, cellodextrins, and lactose, and those from ascomycetes may additionally oxidize some monosaccharides to their corresponding lactones at the flavin domain. CDHs are able to communicate directly with an electrode via their heme domain. In this work, different types of CDHs have been adsorbed on graphite electrodes and studied with respect to their direct electron transfer (DET) properties. Electrochemical studies were performed in the presence and absence of single-walled carbon nanotubes (SWCNTs) using lactose as substrate. In the presence of SWCNTs, the electrocatalytic current for substrate oxidation based on DET between enzyme and electrode was significantly increased. Furthermore, the onset of the electrocatalytic current was at lower potential than in the absence of SWCNTs. The highest electrocatalytic activity toward oxidation of lactose was found for CDH from the basidiomycete Phanerochaete sordida. Based on CDH from Phanerochaete sordida, an anode for biofuel cells was developed. This anode using lactose as substrate was combined with a Pt black cathode for oxygen reduction as a model for a membrane-less biofuel cell in which the processes at both electrodes occur by DET.

Dramatic Effect of Dispersed Carbon Nanotubes on the Mechanical and Electroconductive Properties of Polymers Derived from Ionic Liquids

Free-radical polymerization of an imidazolium ion-based ionic liquid bearing a methacrylate group, gelling with single-walled carbon nanotubes (SWNTs), allows fabrication of a mechanically reinforced, electroconductive soft material (bucky plastic). A film sample of this material displays an excellent conductivity of 1 S cm(-1) and a 120-fold enhancement of the Young's modulus at a 7 wt % content of SWNTs. The conductivity is temperature-dependent in the range 5-300 K, suggesting that the conductive process involves carrier hopping. Scanning electron and atomic force micrographs of a bucky plastic film display the presence of crosslinked networks consisting of finely dispersed SWNTs. Such nanotube networks, developed in the polymer matrix, likely suppress slipping of entrapped polymer molecules via a strong interfacial interaction and also facilitate intertubular carrier transport. Although a bucky plastic derived from a vinylimidazolium ion-based ionic liquid monomer shows a comparable conductivity to that of the methacrylate version, the film is brittle irrespective of the presence or absence of SWNTs.