Articles

Intracellular Reactive Oxygen Species and Genotoxicity of Nanosized Polyamidoamine (PAMAM) dendrimers in fish cells (PLHC-1) in vitro.

Pratap Naha et al. — Mon, 04 Mar 2013 01:15:52 PST

Polyamidoamine (PAMAM) dendrimers elicit systematically variable cyto- and eco-toxic responses, promising the basis for structure activity relationships governing nanotoxicological responses. Increased production of intracellular reactive oxygen species (ROS), genotoxicity and apoptosis due to in-vitro exposure of hepatocellular carcinoma cells to dendrimer generations G-4, G-5 and G-6 is demonstrated. A generation dependent increase in ROS and genotoxicity was observed, consistent with our previous studies. The responses correlate well with the number of surface amino groups per generation. Although ROS production initially increases approximately linearly, it saturates at higher doses. Notably, normalised to molar dose of surface amino groups, the dose-dependent ROS production for different generations overlap exactly, indicating that the response is due to these functional units. The percentage tail DNA formation is related to the generation and dose dependent production of intracellular ROS, at low levels. At the higher ROS levels, increased DNA damage is associated with the onset of necrosis.

Reactive Oxygen Species Mediated DNA Damage In Human Lung Alveolar Epithelial (A549) Cells From Exposure To Non-Cytotoxic MFI-Type Zeolite Nanoparticles

Kunal Bhattacharya et al. — Thu, 03 Jan 2013 02:05:40 PST

Increasing utilization of engineered nanoparticles in the field of electronics and biomedical applications demands an assessment of risk associated with deliberate or accidental exposure. Metal based nanoparticles are potentially most important of all the nanoparticles in terms of health risks. Microporousalumino-silicates and pure silicates named as zeolites and zeo-type materials with variety of structures, chemical compositions, particle sizes and morphologies have a significant number of industrial uses such as in catalysis, sorption and ion-exchange processes. In particular, the nanosized particles due to their unique properties are used in hybrid organic-inorganic materials for photography, photonics, electronics, labeling, imaging, and sensing. The aim of the current study is to investigate pure silica MFI-type zeolitesnanoparticles with sizes of 50 nm and 100 nm (samples MFI-50 and MFI-100) under suspended conditions and their toxicological effects on human lung alveolar (A549) cells under in vitro conditions.

Live cell imaging showed that the nanoparticles precipitated from the colloidal suspension of cell culture media as large agglomerates, coming in contact with the cell surface through sedimentation. A cellular proliferative capacity test showed the zeolite nanoparticles to exhibit no significant cytotoxicity belowa concentration of 100 µg/ml.However, both the MFI-50 and MFI-100 nanoparticles induced high intracellular reactive oxygen species (ROS) generation and elevated mitochondrial membrane potential in the A549 cells over the measured time period of 12 hours and at concentrations up to ≤50 µg/ml. DNA fragmentation analysis using the comet assay showed that the MFI-50 and MFI-100 nanoparticles cause genotoxicity in a concentration dependent manner. Furthermore, the rate at which maximum genomic damage was caused by MFI-100 nanoparticles in the A549 cells was found to be high as compared to the MFI-50 nanoparticles. However, the damage caused by the MFI-50 nanoparticles was found to accumulate over a longer period of time as compared to MFI-100 nanoparticles.

The study therefore points towards the capability of the non-cytotoxic zeolite nanoparticles to induce oxidative stress resulting in short-term altered cellular metabolism up-regulation and genomic instability. Although the damage was found to be short-lived, its persistence over longer durations, or stabilization cannot be neglected. Further studies are in progress to yield a better understanding of the mechanisms for oxidative stress and resulting cascade of events leading to genetic damage in the human lung alveolar epithelial cells following exposure to zeolite nanoparticles of different sizes.

Effects of Salinity on the Toxicity of Ionic Silver and Ag-PVP Nanoparticles to Tisbe Battagliai and Ceramium Tenuicorne

Ailbhe Macken et al. — Thu, 03 Jan 2013 01:38:00 PST

The toxic effects of polyvinylpyrrolidone (PVP) coated silver nanoparticles (Ag-NP_PVP) and ionic Ag, to Tisbe battagliai (Tb) and Ceramium tenuicorne (Ct) were investigated and the usefulness of standardised marine guidelines for ENP risk assessment were assessed. The toxicity of Ag-NP_PVP [CtEC₅₀ = 26.6 µg/L, TbEC₅₀ = 7.9 µg/L] and Ag⁺ [CtEC₅₀ = 2312.2µg/L, Tb EC₅₀ = 90.9 µg/L] to both test species differed, with the silver ENPs being more toxic. In contrast to Ag⁺the toxicity of Ag-NP_PVP increased significantly with increasing salinity, however, after thorough characterisation it was not possible to correlate the behaviour of the particles with an increase in toxicity and salinity. The results suggest that the observed toxicity is being elicited by the free ionic silver complexing in solution and also from an unknown potential particle related effect.

Ecotoxicological Assessment of Silica and Polystyrene Nanoparticles Assessed by a Multitrophic Test Battery

Maria Casado et al. — Mon, 03 Dec 2012 09:41:14 PST

The acute ecotoxicity of different diameters of silica and polyethyleneimine polystyrene (PS-PEI)nanoparticles (NPs)was assessed on a test battery of aquatic organisms representing different trophic levels. Daphnia magna, Thamnocephalus platyurus, Pseudokirchneriella subcapitata and Vibrio fischeri, were employed in a series of standard acute ecotoxicity tests and work was complemented with two cytotoxicological end points on a rainbow trout gonadal cell line (RTG-2). Physico-chemical characterization of the NPs was performed in the different test media employed, using dynamic light scattering (DLS) and zeta potentiometry. In contrast to silica NPs exposure, for which no effect was observed for concentrations up to 1000 µg ml^-1 for all in vivo aquatic organisms tested, significant toxicity was detected after exposure to PS-PEI NPs at concentrations from 0.40 µg ml^-1 to 416.5 µg ml^-1. Differing sensitivities for each NP diameter for the different organisms was observed as: P. subcapitata > D. magna > T. platyurus > V. fischeri. The effects observed were dependent in some cases on the NP size, a higher effect being observed for the larger NPs. Finally, cytotoxicity studies showed an effect at the highest concentrations for both sets of NPs which was greater in the case of the PS-PEI NPs. However, as agglomeration and sedimentation of the nanoparticles was observed at these concentrations, the cytotoxicity studies were found not to be a reliable ecotoxicity test model.

Polyamidoamine Dendrimer Nanoparticle Cytotoxicity, Oxidative Stress, Caspase Activation and Infammatory Response: Experimental Observation and Numerical Simulation

Sourav Prasanna Mukherjee et al. — Fri, 30 Nov 2012 07:10:36 PST

Mechanisms underlying the in vitro cytotoxicity of Polyamidoamine nano-dendrimers in human keratinocytes are explored. Previous studies demonstrated a systematic, dendrimer-generation-dependent cytotoxicity, oxidative stress, and genotoxicity. The emerging picture is of dendrimer endocytosis, endosomal rupture and subsequent mitochondrial attack and cell death. To understand the underlying mechanisms, the evolution of reactive oxygen species, intracellular glutathione, caspase activation, mitochondrial membrane potential decay, and inflammatory responses have been examined. Early-stage responses are associated with endosomal encapsulation, later-stage with mitochondrial attack. In all cases, the magnitude and evolution of responses depend on dendrimer generation and dose. The early-stage response is modelled using a rate equation approach, qualitatively reproducing the time, dose and generation dependences, using only two variable parameters. The dependence of the response on the nanoparticle physicochemical properties can thus be separated from internal cellular parameters, and responses can be quantified in terms of rate constants rather than commonly employed effective concentrations.

Role Of Polymeric Excipients On Controlled Release Profile of Glipizide from PLGA and Eudragit RS 100 Nanoparticles

Pratap Naha et al. — Tue, 27 Nov 2012 02:45:39 PST

Polylactic-co-glycolic acid (PLGA) 50:50 and Eudragit RS 100 nanoparticles entrapping glipizide along with excipients were prepared using single emulsion solvent evaporation method. The objective was to develop single oral dose glipizide nano particles for reducing blood sugar level in diabetes induced experimental animals. Incorporation of Polyethylene glycol (PEG) (0.5%), Hydroxypropyl methylcellulose (HPMC) (0.5%) and Tween 20 (0.5%) in the organic phase during particle formulation improved release profile of glipizide from the polymer particles. Entrapment efficiency of glipizide in all the polymeric formulations was around ~70 %. Around 80 % of glipizide was released from both PLGA and Eudragit RS 100 nanoparticles when 0.5% of PEG and Tween 20 were added during preparation. Incorporation of amphiphilic polymer during particle formulation not only improved entrapment efficiency of glipizide but also resulted in uniform stabilized nanoparticles having desired control release characteristics. Both PLGA and Eudragit nanoparticles were biocompatible to SW 480 adenocarcinoma human cell line at concentration ranges from 12.5 to 500 µg/ml. The efficacy of glipizide loaded particle formulations were evaluated in female out breed Wistar rats. Significant reduction of blood glucose level was observed (p ≤ 0.05) for 24 hours from a single oral dose using stabilized nanoparticles formulations.

Spectral Cross Correlation as a Supervised Approach for the Analysis of Complex Raman Datasets: The Case of Nanoparticles in Biological Cells

Mark E. Keating et al. — Wed, 31 Oct 2012 08:41:08 PDT

Spectral Cross-correlation is introduced as a methodology to identify the presence and subcellular distribution of nanoparticles in cells. Raman microscopy is employed to spectroscopically image biological cells previously exposed to polystyrene nanoparticles, as a model for the study of nano-bio interactions. The limitations of previously deployed strategies of K-means clustering analysis and principal component analysis are discussed and a novel methodology of Spectral Cross Correlation Analysis is introduced and compared with the performance of Classical Least Squares Analysis, in both unsupervised and supervised modes. The previous study demonstrated the feasibility of using Raman spectroscopy to map cells and identify polystyrene nanoparticles in a lipid rich environment, which is suggestive of the membrane rich endoplasmic reticulum. However, short comings in identification of all nanoparticle signatures in the cell using K-means clustering are apparent, as highlighted by principal component analysis of the identified clusters which demonstrates that K-means clustering does not identify all regions where spectral signatures of the nanoparticles are evident. Thus, two more sophisticated analytical approaches to the extraction of the nanoparticle signatures from the Raman spectral data sets, namely classical least squares analysis and cross correlation analysis, were employed and are demonstrated to improve the identification of spectroscopic signatures characteristic of polystyrene nanoparticles in a cellular environment. Additionally, to investigate the local biochemical environment in which the nanoparticles are trafficked, a pure spectrum of 3-sn-phosphatidyl ethanolamine was cross correlated against the Raman data set, further suggesting the particles are indeed localized in a lipid rich environment. Furthermore, to demonstrate the robustness and versatility of the analysis method, a spectrum of pure RNA was used to demonstrate that a differentiation could be made between DNA of the nucleus and RNA of the nucleolus using the supervised spectral cross-correlation technique.

Nonlinear Optical Properties of Carbon Nanotube Hybrids in Polymer Dispersions

Jun Wang et al. — Mon, 03 Sep 2012 02:50:35 PDT

A series of double-walled carbon nanotubes (DWNTs) and multi-walled nanotubes (MWNTs) functionalized with selected organic chromophores, fluorescein 5(6)-isothiocyanate (FITC), rhodamine B isothiocyanate (RITC) and fullerene (C₆₀) were synthesized by covalently linking these electron-donor groups to the metallic nanotubes. These versatile carbon nanotube composites show remarkable nonlinear optical (NLO) performance, due to a merged effect of the complementary NLO characteristics of the moieties of the composites. The hybrids were characterized by UV-Vis spectroscopy and Raman spectroscopy. Evidence suggests charge transfer species are formed between the chromophores and the nanotubes. The optical limiting performance of the DWNT, MWNT hybrids and carbon NanoBuds is found to be superior to that of single-walled nanotubes. Thermally induced light scattering from nanotube moieties is the primary mechanism dominating the NLO response. Reverse saturable absorption from fullerene moieties makes a significant contribution to the NLO response of fullerene containing hybrids and NanoBuds. Photoinduced charge transfer from the fullerenes or the organic chromophores (FITC and RITC) to nanotubes followed by absorption in the charge separated excited state may enhance the nonlinear absorption, thus an effective optical limiting response.

A Systematic Study of the Dispersion of SWNTs in Organic Solvents

Qiaohuan Chen et al. — Mon, 26 Mar 2012 01:37:56 PDT

Dispersions of as-produced HiPco single-walled carbon nanotubes (SWNTs) in a series of organic solvents were prepared by dilution with the aid of tip sonication. Mild centrifugation (~ 945 g) was carried out to remove large bundles. Atomic force microscopy (AFM) studies revealed that the bundle size decreased as the dispersion was diluted. By measuring the UV-vis-NIR absorption before and after centrifugation as a function of the concentration, the dispersion limit of SWNTs in each solvent can be determined. Correlations between the dispersion limit and solvent solubility parameters, including the Hildebrand solubility parameter and three dimensional Hansen solubility parameters, are explored, demonstrating that SWNTs are easily dispersed in solvents with Hildebrand solubility parameter range from ~22-24 MPa^1/2 and Hansen polarity component (δ_P) ~12-14 MPa^1/2. No clear correlation between dispersion limits and the dispersion force (δ_D) or hydrogen bonding force (δ_H) are evident. It is found, however, that the degree of dispersion depends critically on sample preparation conditions and in particular sonication time. Increased sonication times increase the amount of SWCNTs debundled and solubilised but do not appear to affect the dispersion limit. However, increased sonication also induces discernible changes to the SWNTs themselves and in itself influences their solubility, under which conditions no clear solubility parameters can be determined.

Minimal Analytical Characterisation of Engineered Nanomaterials Needed for Hazard Assessment in Biological Matrices

Hans Bouwmeester et al. — Mon, 26 Mar 2012 01:33:15 PDT

Background: This paper presents the outcomes from a workshop of the European Network on the Health and Environmental Impact of Nanomaterials (NanoImpactNet) held in June 2008. During this workshop 45 experts in the field of safety assessment of engineered nanomaterials from academia, non-profit organizations and industry addressed a list of essential metrics of engineered nanomaterials that need to be characterized as a minimum.

Results: The group discussed the need to systematically study sets of engineered nanomaterials to generate a dataset that allows for the establishment of dose-response data related to specific metrics of engineered nanomaterials. Concomitantly the availability of analytical methods to determine the physicochemical characteristics was discussed. Given the measurement challenges specific for engineered nanomaterials the issue of harmonizing protocols was raised.

Conclusion: The group concluded that international cooperation and worldwide standardization of terminology, reference materials and protocols are needed to make progress in establishing lists of essential metrics. The need for high quality data necessitates the development of harmonized study approaches and adequate reporting of data. Priority metrics can only be based on well-characterized dose-response relations (as regards biological interactions and physiochemical characteristics) of engineered nanomaterials. This requires the systematic study of the biokinetics and biointeractions of nanomaterials at both organism and (sub)cellular levels. Additionally, much effort needs to be put into the standardization and validation of analytical methods to determine these metrics. Especially for the characterization of engineered nanomaterials in a complex matrix much work needs to be done.

Comparison of Micro- and Nanoscale Fe+3-Containing (Hematite) Particles for their Toxicological Properties in Human Lung Cells In Vitro

Kunal Bhattacharya et al. — Mon, 05 Mar 2012 01:09:33 PST

The specific properties of nanoscale particles, large surface-to-mass ratio and highly reactive surfaces, have increased their commercial application in many fields. However, the same properties are also important for the interaction and bio-accumulation of the non-/biodegradable nanoscale particles in a biological system and are a cause for concern. Hematite (α-Fe2O3), being a mineral form of Fe(III) oxide, is one of the most used iron oxides besides magnetite. The aim of our study was the characterization and comparison of biophysical reactivity and toxicological effects of α-Fe2O3 nano- (d < 100 nm) and microscale (d < 5 μm) particles in human lung cells. Our study demonstrates that the surface reactivity of nanoscale α-Fe2O3 differs to that of microscale particles with respect to the state of agglomeration, radical formation potential, and cellular toxicity. The presence of proteins in culture medium and agglomeration were found to affect the catalytic properties of the hematite nano- and microscale particles. Both the nano- and microscale α-Fe2O3 particles were actively taken up by human lung cells in vitro, although, they were not found in the nuclei and mitochondria. Significant genotoxic effects were only found at very high particle concentrations (> 50 μg/ml). The nanoscale particles were slightly more potent in causing cyto- and genotoxicity as compared to their microscale counterparts. Both types of particles induced intracellular generation of reactive oxygen species. This study underlines that α-Fe2O3 nanoscale particles trigger different toxicological reaction pathways than microscale particles. However, the immediate environment of the particles (biomolecules, physiological properties of medium) modulates their toxicity on the basis of agglomeration rather than their actual size.

Water-soluble bis(1,10-phenanthroline) Octanedioate Cu2+ and Mn2+ Complexes with Unprecedented Nano and Picomolar in Vitro Cytotoxicity: Promising Leads for Chemotherapeutic Drug Development

Andrew Kellett et al. — Tue, 19 Jul 2011 03:11:34 PDT

Dinuclear Cu^II and Mn^II bis-phenanthroline octanedioate complexes exhibit rapid, unprecedented nano and picomolar in vitro cytotoxicity against colorectal cancer lines and are less toxic than cisplatin when examined in vivo. The complexes are potent generators of cellular reactive oxygen species, avid DNA binders and induce O₂ dependent cleavage of DNA. The Cu(II) complex was found to have self-cleaving nuclease activity.

Degnerate Four-Wave Mixing in Rhodamine Doped Epoxy Waveguides

B. Rossi et al. — Thu, 16 Jun 2011 09:09:26 PDT

Self-diffraction from laser-induced gratings is observed in a 13 pm-thick film of rhodamine I3 doped epoxy. The decay of the grating is measured to be 2.05 ns. Degenerate forward four-wave mixing in a guided geometry is observed by coupling out all beams after nronagation over 1 mm. At 595 nm the third-order nonlinear susceptibility of the film is measured to be 1.5~10-‘~ m2Ve2.

Fourier Transform Infrared Microspectroscopy and Multivariate Methods for Radiobiological Dosimetry

Aidan Meade et al. — Thu, 03 Mar 2011 08:31:25 PST

The scientific literature contains an ever-growing number of reports of applications of vibrational spectroscopy as a multivariate non-invasive tool for analysis of biological effects at the molecular level. Recently, Fourier transform infrared microspectroscopy (FTIRM) has been demonstrated to be sensitive to molecular events occurring in cells and tissue after exposure to ionizing radiation. In this work the application of FTIRM in the examination of dose-dependent molecular effects occurring in skin cells after exposure to ionizing radiation with the use of partial least-squares regression (PLSR) and generalized regression neural networks (GRNN) was studied. The methodology is shown to be sensitive to molecular events occurring with radiation dose and time after exposure. The variation in molecular species with dose and time after irradiation is shown to be non-linear by virtue of the higher modeling efficiency yielded from the non-linear algorithms. Dose prediction efficiencies of approximately ±10 mGy were achieved at 96 h after irradiation, highlighting the potential applications of the methodology in radiobiological dosimetry.

A Model Compound Study: The Ecotoxicological Evaluation of five Organic Contaminants with a Battery of Marine Bioassays

Ailbhe Macken et al. — Wed, 26 Jan 2011 03:25:04 PST

This paper describes the ecotoxicological evaluation of five organic contaminants frequently detected in marine sediments (tributyltin, triphenyltin, benzo[a]pyrene, fluoranthene, and PCB 153) using three marine species (Vibrio fischeri, Tetraselmis suecica, and Tisbe battagliai). The sensitivity of each species varied for all compounds. The triorganotins were consistently the most toxic to all species. The applicability of each test system to assess the acute toxicity of environmental contaminants and their use in Toxicity Identification Evaluation (TIE) is discussed. Suitability of the Microtox and T. battagliai tests for employment in TIE studies were further assessed through spiking experiments with tributyltin. Results demonstrated that the most effective treatment to remove organotin toxicity from the sample was the C18 resin. The results of this study have important implications for risk assessment in estuarine and coastal waters in Ireland, where, at present the monitoring of sediment and water quality is predominantly reliant on chemical analysis alone.

A Test Battery Approach to the Ecotoxicological Evaluation of Cadmium and Copper Employing a Battery of Marine Bioassays

Ailbhe Macken et al. — Wed, 26 Jan 2011 03:25:01 PST

The main aim of this study was to investigate the sensitivity of the battery to two recognised metal pollutants of the marine environment and rank species sensitivity accordingly.

An integrated Approach to the Toxicity Assessment of Irish Marine Sediments Application of Porewater Toxicity Identification Evaluation (TIE) to Irish Marine Sediments

Ailbhe Macken et al. — Wed, 26 Jan 2011 03:24:59 PST

An integrated approach to the ecotoxicological assessment of Irish marine sediments was carried out between 2004 and 2007. Phase I Toxicity Identification Evaluation (TIE) of sediment porewaters from two sites on the east coast of Ireland were conducted. Initial Tier I screening of three Irish sites identified the need for TIE after significant toxicity was observed with Tisbe battagliai and the Microtox® assay at two of the assayed sites (Alexandra Basin and Dunmore East). Porewaters classified as toxic were characterised using four manipulations, ethylenediaminetetraacetic acid (EDTA) chelation, sodium thiosulphate addition, C18 Solid Phase Extraction (SPE) and Cation Exchange (CE) SPE. Prior to initial testing, and TIE manipulations, all porewater samples were frozen at −20 °C for several months until required. After initial Tier I testing Alexandra Basin porewater was classified as highly toxic by both assays while Dunmore East porewater only warranted a TIE with T. battagliai. Results of TIE manipulations for Alexandra Basin porewater and the Microtox® Basic test were inconclusive. The toxicity of the porewater in this assay was significantly reduced after freezing. Three experimental episodes were conducted with one month between each for the Alexandra Basin porewater. After each month of freezing the baseline toxicity was further reduced in the Microtox® assay, therefore it was not possible to draw accurate conclusions on the nature of the active contaminants in the sample. However, toxicity to T. battalgiai did not change after storage of the porewater. The C18 and CE SPE decreased the toxicity of Alexandra Basin porewater to the copepod indicating that both organic and cationic compounds (e.g. metals) were active in the sample. Dunmore East porewater was assayed with T. battalgiai and again a combination of organic and inorganic compounds were found to be partly responsible for the observed toxicity (C18, CE SPE and EDTA reduced toxicity). Results from these TIEs provide insight into the complexity of interpreting marine TIE data from porewater studies where mixtures of unknown substances are present.

A Systematic Study of the Dispersion of SWNTS in Organic Solvents

Qiaohuan Cheng et al. — Fri, 07 Jan 2011 08:59:09 PST

Dispersions of as-produced HiPco single-walled carbon nanotubes (SWNTs) in a series of organic solvents were prepared by dilution with the aid of tip sonication. Mild centrifugation (945 g) was carried out to remove large bundles. Atomic force microscopy (AFM) studies revealed that the bundle size decreased as the dispersion was diluted. By measuring the UV−vis−NIR absorption before and after centrifugation as a function of the concentration, the dispersion limit of SWNTs in each solvent can be determined. Correlations between the dispersion limit and solvent solubility parameters, including the Hildebrand solubility parameter and three-dimensional Hansen solubility parameters, are explored, demonstrating that SWNTs are easily dispersed in solvents with Hildebrand solubility parameter range from 22−24 MPa1/2 and Hansen polarity component (δP) 12−14 MPa1/2. No clear correlation between dispersion limits and the dispersion force (δD) or hydrogen bonding force (δH) are evident. It is found, however, that the degree of dispersion depends critically on sample preparation conditions and in particular sonication time. Increased sonication times increase the amount of SWNTs debundled and solubilized but do not appear to affect the dispersion limit. However, increased sonication also induces discernible changes to the SWNTs themselves and in itself influences their solubility, under which conditions no clear solubility parameters can be determined.

Ultrasound-Assisted SWNTs Dispersion: Effects of Sonication Parameters and Solvent Properties

Qiaohuan Cheng et al. — Fri, 07 Jan 2011 08:56:20 PST

Ultrasonication is widely used for preparing Single-Walled Carbon Nanotube (SWNT) dispersions in different solvent media and it has been shown to play a critical role in dispersing and debundling SWNTs. The strong shear force that can exfoliate the SWNT bundles during sonication comes from cavitation, which entails a process of bubble formation, growth, and collapse. The efficiency of the cavitation process is closely correlated to many solvent parameters, including vapor pressure, viscosity, and surface tension, as well as the sonication frequency, intensity, and time. In this study, SWNTs were dispersed in a range of organic solvents assisted by tip sonication. The effects of sonication intensity and time were investigated in o-dichlorobenzene (o-DCB) and dimethylformamide (DMF). The aggregation fraction below the dispersion limit of SWNTs in the range of organic solvents was found to be influenced by the solvent parameters, particularly solvent vapor pressure and viscosity. It is demonstrated that the parameters associated with the sonication process rather than solvent solubility parameters govern the dispersion process. It is further confirmed that significant degradation of the SWNTs is affected during the dispersion process.

A Comparative Study of the Interaction of Different Polycyclic Aromatic Hydrocarbons on Different Types of Single Walled Carbon Nanotubes

Sourabhi Debnath et al. — Fri, 07 Jan 2011 08:56:18 PST

A comparative study of the solubilising effect of polycyclic aromatic hydrocarbon (PAHs) on single walled carbon nanotubes (SWCNTs) produced by high pressure decomposition of carbon monoxide (HiPco) and the arc discharge (AD) method has been carried out with the aid of fluorescence and Raman spectroscopy. For this study, polyphenyl and polyacene PAHs of different lengths are used. From the study it has been found that the binding energy of PAHs with AD SWCNTs is the same as that with HiPco SWCNTs. Shorter PAHs molecules better solubilise SWCNTs and in general smaller diameter SWCNTs. Thus, given their smaller diameter profile, significantly larger amounts of HiPco SWCNTs are solubilised than AD SWCNTs.