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The chemical exfoliation of graphite in liquids is the choice method to produce few-layer graphenes with versatility and scalability. While physical mechanisms have been described, the understanding of the graphene-medium interactions at the molecular level is still a challenge. Here, a systematic experimental and theoretical investigation of factors that control the chemical exfoliation of graphite into graphene was performed using 1-cyclohexyl-2-pyrrolidone (CHP)/water mixtures as model systems. The “molecular wedge” structure of CHP and the reduction of graphene-CHP interfacial energy are critical factors in the exfoliation of graphite, but they are not sufficient for the stabilization of the isolated graphene sheets. We propose that such stabilization occurs by steric forces with the formation of a sandwich-like structure on the surface of graphene with two layers of water molecules interleaved with a monolayer of CHP, and by electrostatic forces resulting from the hybrid surface polarization due to the CHP/H2O-graphene interaction. This stabilization is hampered in CHP/H2O mixtures containing above 10 wt% CHP due to the formation of CHP–CHP aggregates.

Graphene-related materials (GRM) are promising materials to improve mechanical, electrical, and optical polymer properties. Adding multi-wall carbon nanotubes (MWCNT) on GRM nanocomposites promotes synergistic effects on its electrical properties and electromagnetic interference shielding effectiveness (EMI SE). This study focused on evaluating the addition of MWCNT on three different polycarbonate (PC)/acrylonitrile butadiene styrene (ABS)/GRM nanocomposites. These hybrid nanocomposites were prepared by melt mixing using extrusion and injection-mold processes. The morphologies of the nanocomposites were evaluated by field emission gun scanning electron microscopy (FEG-SEM), and their proprieties were characterized by X-ray diffraction (XRD), oscillatory rheological, dielectric spectroscopy, and EMI SE analyses. The electrical behavior of all hybrid nanocomposites was anisotropic due to the injection-molded preparation process. The lateral size, thickness, and production method of the GRM were indicated to be critical factors for the electrical and EMI SE behaviors of these composites. The nanocomposites with GRM2, which had the smallest lateral size and thickness (graphene nanoplatelets), promoted total attenuation levels around 20 dB with 1.5 wt% of MWCNT, matching the EMI SE required for some commercial applications.

The interaction between carbon nanotubes (CNTs) and biological molecules of diagnostic and therapeutic interest, as well as the internalization of the CNTs-biomolecules complexes in different types of cell, has been extensively studied due to the potential use of these nanocomplexes as multifunctional nanoplatforms in a great variety of biomedical applications. The effective use of these nanobiotechnologies requires broad multidisciplinary studies of biocompatibility, regarding, for example, the in vitro and in vivo nanotoxicological assays, the capacity to target specific cells and the evaluation of their biomedical potential. However, the first step to be reached is the careful obtainment of the nanoplatform and the understanding of the actual surface composition and structural integrity of the complex system. In this work, we show the detailed construction of a nanoplatform created by the noncovalent interaction between oxidized multi walled carbon nanotubes (MWCNTs) and a DNA aptamer targeting tumor cells. The excess free aptamer was removed by successive washes, revealing the actual surface of the nanocomplex. The MWCNT-aptamer interaction by π-stacking was evidenced and shown to contribute in obtaining a stable nanocomplex compatible with aqueous media having good cell viability. The nucleotide sequence of the aptamer remained intact after the functionalization, allowing its use in further studies of specificity and binding affinity and for the construction of functional nanoplatforms.

The industrial application of radiation processing involves high doses of gamma or electron radiation to cause structural changes in materials, such as rubber vulcanization and polymer degradation, among others. A reliable dosimetric system is necessary to guarantee the desired effects and also to avoid damages. Poly(vinylidene fluoride) [PVDF] homopolymer has been recently proposed for application in high gamma dose dosimetry. In this work, nanocomposites made of PVDF filled with zirconium oxide [ZrO2] nanoparticles and multiwalled carbon nanotubes [MWCNT] were studied for applications in high dose dosimetry, for doses ranging from 100.0 kG to 2.72 MGy. Pristine PVDF and PVDF/MWCNT-ZrO2 samples were exposed to a Co-60 source. FTIR spectra were collected 2 h, 30 and 60 days after exposure. The intensity of the radio-induced absorption bands centered at 1715 cm−1 and 1730 cm−1 were found to have an unambiguous relationship with the absorbed dose. The pristine PVDF samples show linear behavior in the dose range between 100 and 1000 kGy. However, the PVDF/MWCNT-ZrO2 samples show linearity in a larger range, i.e. between 500 and 2750 kGy interval. The melting latent heat, measured by Differential Scanning Calorimetry (DSC) and SEM micrographs revealed that PVDF/MWCNT-ZrO2 samples show increased resistance to the radio-induced damages, when compared to pure PVDF samples irradiated in the same conditions. The results indicate that the MWCNT-ZrO2 adds resistance to PVDF and improves its dosimetric properties.

The functionalization of graphene oxide with organosilanes is an important strategy to yield graphene-silica composites as well as to create nanomaterials for use as reinforcement in polymer nanocomposites and corrosion-inhibiting coatings for metals, among other uses. However, depending on the reaction conditions used, the organosilanes tend to self-condense, encapsulating the graphene oxide in a silica-like layer which can impair its properties by hiding its real surface and two-dimensionality. In this paper we describe a facile route for the functionalization of commercial graphene oxide with (3-aminopropyl) triethoxysilane using low concentrations and mild reaction conditions, and yielding amine and silanol surface-modified graphene nanohybrids while preserving its two-dimensional characteristics. The material obtained was characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), potentiometric titration, thermogravimetric analysis and electronic microscopy, evidencing the covalent and superficial nature of the functionalization.

The production and use of graphene-based nanomaterials is rapidly increasing. However, few data are available regarding the toxicity of these nanomaterials in aquatic organisms. In the present study, the toxicity of few-layer graphene (FLG) (obtained by chemical exfoliation) was evaluated in different tissues of the shrimp Litopenaeus vannamei following exposure to FLG through a diet for four weeks. Transmission electron microscopy and dynamic light scattering measurements showed a distribution of lateral sheet sizes between 100 and 2000 nm with the average length and width of 800 and 400 nm, respectively. Oxidative stress parameters were analyzed, indicating that FLG exposure led to an increase in the concentration of reactive oxygen species, modulated the activity of antioxidant enzymes such as glutamate cysteine ligase and glutathione-S-transferase, and reduced glutathione levels and total antioxidant capacity. However, the observed modulations were not sufficient to avoid lipid and DNA damage in both gill and hepatopancreas tissues. Furthermore, graphene exposure resulted in morphological changes in hepatopancreas tissues. These results demonstrate that exposure to FLG through the diet induces alterations in the redox state of cells, leading to a subsequent oxidative stress situation. It is therefore clear that nanomaterials presenting these physico-chemical characteristics may be harmful to aquatic biota.

Two different types of multi walled carbon nanotubes (MWCNT) were introduced in a calcium aluminate refractory castable used in steelmaking process. The first MWCNT was purchased from Cheap Tubes (USA), a hydroxyl (-OH) functionalized, outer diameter of 50-80 nm, length of 10-20 μm, and, the second one was supplied by Nanocyl (Belgium), not functionalized, outer diameter of 9.5 nm, and length of 1.5 μm. Both types of MWCNT were incorporated into the dry castable mixture before water addition. The workability and properties of the final product, such as apparent density, apparent porosity and hot modulus of rupture were evaluated. The nanocarbons were characterized by SEM, TEM, TGA and Raman spectroscopy. In both cases, the incorporation of MWCNT had a negative effect on the rheology of wet castables, decreasing their workability. No significant improvements on mechanical properties of the castables were observed with the incorporation until MWCNT concentration reached 0.15 % (m/m), except for the increase of hot modulus of rupture observed for Cheap Tubes MWCNT introduction.

Carbon nanomaterials (CNM), such as graphene oxide (GO), have been the focus of study in several areas of science mostly due to their physical-chemical properties. However, data concerning the potential toxic effects of these CNM in bivalves are still scarce. When present in the aquatic systems, the combination with other contaminants, as well as pH environmental variations, can influence the behavior of these nanomaterials and, consequently, their toxicity. Thus, the main goal of this study was to evaluate the effect of exposure of clam Ruditapes philippinarum to GO when acting alone and in the combination with copper (Cu), under two pH levels (control 7.8 and 7.3). A 28-day exposure was performed and metabolism and oxidative stress-related parameters were evaluated. The effects caused by GO and Cu exposures, either isolated or co-exposed, showed a direct and dependent relationship with the pH in which the organisms were exposed. In clams maintained at control pH (7.8), Cu and GO + Cu treatments showed lower lipid peroxidation (LPO) and lower electron transport system (ETS) activity, respectively. In clams maintained at low pH, glutathione-S-transferases (GSTs) activities were increased in Cu and Cu + GO treatments, whereas reduced glutathione (GSH) levels were increased in Cu treatment and ETS activity was higher in GO + Cu. Thus, it can be observed that clams responses to Cu and GO were strongly modulated by pH in terms of their defense system and energy production, although this does not result into higher LPO levels.

The use of carbon nanomaterials (CNMs) is growing in different technological fields, raising concern on their potential impacts on the environment. Given its diverse nanothenological applications, graphene oxide (GO) stands out among the most widely used CNMs. Its hydrophilic capacity enables it to remain stable in suspension in water allowing that GO can be accessible for accumulation by aquatic organisms through ingestion, filtration and superficial dermal contact when present in aquatic ecosystems. Considering that the effects induced to aquatic organisms may depend on environment characteristics, such as temperature, salinity, water pH as well as the presence/absence of sediment, the present study aimed to investigate the influence of sediment on the impacts caused by GO exposure. For this, oxidative stress parameters were measured in the clam Ruditapes philippinarum, exposed to different GO concentrations (0.01, 0.1 and 1 mg/L), in the presence and absence of sediment, for a 28-days experimental period. The results here presented showed that regardless the presence or absence of sediment, most of the biochemical parameters considered were altered when clams were exposed to the highest concentration. The present findings further revealed that in the presence of sediment, clams mostly invested in non-enzymatic defenses (such as reduced glutathione, GSH), while animals exposed to GO in the absence of sediment favored their enzymatic antioxidant defense capacity (catalase, CAT and superoxide dismutase, SOD). This study highlights the relevance of environmental variations as key factors influencing organisms' responses to pollutants.

Single-wall carbon nanotubes functionalized with polyethylene glycol (SWCNT-PEG) are promising materials for biomedical applications such as diagnostic devices and controlled drug-release systems. However, several questions about their toxicological profile remain unanswered. Thus, the aim of this study was to investigate the action of SWCNT-PEG in Danio rerio zebrafish embryos at the molecular, physiological and morphological levels. The SWCNT used in this study were synthesized by the high-pressure carbon monoxide process, purified and then functionalized with distearoyl phosphatidylethanolamine block copolymer-PEG (molecular weight 2 kDa). The characterization process was carried out with low-resolution transmission electron microscopy, thermogravimetric analysis and Raman spectroscopy. Individual zebrafish embryos were exposed to the SWCNT-PEG. Toxic effects occurred only at the highest concentration tested (1 ppm) and included high mortality rates, delayed hatching and decreased total larval length. For all the concentrations tested, the alkaline comet assay revealed no genotoxicity, and Raman spectroscopy measurements on the histological slices revealed no intracellular nanotubes. The results shown here demonstrate that SWCNT-PEG has low toxicity in zebrafish embryos, but more studies are needed to understand what mechanisms are involved. However, the presence of residual metals is possibly among the primary mechanisms responsible for the toxic effects observed, because the purification process was not able to remove all metal contamination, as demonstrated by the thermogravimetric analysis. More attention must be given to the toxicity of these nanomaterials before they are used in biomedical applications. Copyright © 2016 John Wiley & Sons, Ltd.

Poly(vinylidene fluoride – tryfluorethylene) [P(VDF-TrFE)] copolymers were mixed with zirconia nanoparticles. The investigation was conducted with the intention to produce nanocompounds with potential to be used as protective patient shielding in radiological procedures. Polymer based nanocomposites with 1, 2, 3, 5 and 10 wt% of ZrO2 nanoparticles were prepared using sol-gel route with zirconium butoxide as the precursor for zirconium oxide nanoclusters. UV-Vis and FTIR spectrometry and differential scanning calorimetry (DSC) were used to characterize the composite samples. We observed a more homogeneous distribution of ZrO2 nanoparticles encapsulated by methyl methacrylate (MMA) into the polymeric matrix, when compared to composites made without the use of surface modifiers from methacrylate group. Apparently, this property is related to the absence of the strong MMA absorption band at 1745 cm-1, attributed to C=O bond, in the P(VDF-TrFE)/ZrO2-MMA nanocomposites. The radiation damage due to high dose exposuring was performed for gamma doses ranging from 100 kGy to 1,000 kGy. The radiation shielding characterization conducted using x-rays with effective energy of 40 keV has demonstrated that composites with 10% of ZrO2,and only 1.0 mm thick, can attenuate 60% of the x-rays beam.

The influence of extensive purification on oxidized multiwalled carbon nanotube surface composition was studied through the characterization and differentiation of the actual surface submitted to three oxidation methods: microwave-assisted acid oxidation, hydrogen peroxide reflux, and Fenton reaction. The oxidized samples were purified by a multi-step procedure including the sequential use of basic reflux and dispersion in dimethylformamide (DMF). The results showed a significant increase in the amount of oxidation debris with hydrogen peroxide and Fenton reaction times longer than 8 h and strong surface characteristic modification. With regard to sample purification, basic reflux led to a reduction in oxygenated group concentration of only 10% in the samples treated by acid oxidation. On the other hand, the subsequent use of DMF led to a further decrease in concentration of 39%, proving to be a more efficient method for the removal of oxidation debris.

Multi-layer graphene (MLG) sheets were obtained by exfoliation of natural graphite flakes in chloroform. Dispersions with concentration up to 19 mg/mL were prepared. Statistical measurements of MLG sheet sizes by transmission electron microscopy showed average width and length of ~340 nm and 860 nm, respectively. MLG/chloroform dispersions were used to prepare poly(lactic acid) (PLA)/MLG composite fibrillar membranes by electrospinning. A homogeneous distribution of MLG into the fibers was observed by optical and scanning electron microscopies. The presence of MLG leads to the decrease in the diameter distribution of the fibers, which presented average diameter values below 500 nm. Isothermal kinetic crystallization of PLA showed to be influenced by the electrospinning process and the content of MLG sheets, which acts as nucleating agents.

Graphene has been shown to induce toxicity in mammals and marine crustaceans; however, information regarding oxidative stress in fish is scarce. The aim of this study was to evaluate the mechanism of graphene toxicity in different tissues of Danio rerio, considering different parameters of stress. Animals were injected intraperitoneally (i.p.) with 10 μL of suspensions containing different graphene concentrations (5 and 50 mg/L); the gills, intestine, muscle and brain were analysed 48 h later. There was no significant difference in the expression of the gclc (glutamate cysteine ligase catalytic subunit) and nrf2 (nuclear factor (erythroid-derived 2)-like 2) genes after exposure. In contrast, glutamate cysteine ligase (GCL) and glutathione-S-transferase (GST) activities were modulated and the glutathione (GSH) concentration was reduced in different tissues and at different concentrations. Lipid damage was observed in the gills. Histological analyses were performed to observe if the exposure could induce pathological damage in these tissues. The results showed pathological effects in all tissues, excluding the intestine, after exposure to both concentrations. Overall, these results indicate that graphene induces different grades of toxicological effects that are dependent on the analysed organ, with distinct pathological effects on some and oxidative effects on others. However, the brain and gills seem to be the primary target organs for graphene toxicity.

BACKGROUND AND OBJECTIVE In this mini-review, we have compiled the most recent and comparable information to shed light on the action of PEGylation in the biodistribution of carbon nanotubes (CNT) in the central nervous system (CNS). It is well known that due to the complexity of the CNS and the severity of the outcome following changes in this system, this is one of the areas where there are more investments in research to develop new technologies and approaches for more effective and less invasive treatments. The CNS is highly protected against toxic and invasive microorganisms thanks to the blood brain barrier (BBB), but this protection also prevents the passage of potentially beneficial molecules for the treatment of neurological disorders. Nanotechnology attempts to develop nanocompounds that are biocompatible and non-immunogenic, and that are able to cross the BBB in therapeutic amounts without causing damage and to diffuse through nerve tissue. These compounds should also be cleared and biodistributed properly, being capable of performing drug delivery exclusively for CNS pathologies, such as neurodegenerative diseases (Parkinson's and Alzheimer's) and brain tumors. CONCLUSION In this way, this review focuses on CNT PEGylation, aiming to help in the development of viable and effective nanomedicines for neuroscience applications.

Functionalization of single-walled carbon nanotubes (SWCNT) with polyethylene glycol (PEG) is among the most promising strategies to avoid SWCNT aggregation in aqueous media, improving its interactions with biological systems. However, the best molecular PEG weight and functionalization strategy remain under investigation. In this work we assessed the toxicological effects of SWCNT functionalized with PEG at 600 Da in zebrafish embryos. Embryos were exposed to SWCNT at 0.01, 0.1 and 1 mg/L from 3 to 96 h post-fertilization (hpf). At the highest concentration, SWCNT led to toxic effects at several endpoints, including mortality, delayed hatching, malformations, reduced body length, increased ROS production and DNA damage. Even with these effects, SWCNT could not be detected within the bodily tissues of the larvae. Our results give evidence that the tested PEGylation approach was unsuitable to avoid SWCNT aggregation in aqueous media, and that SWCNT can induce toxicity even without being absorbed by the organism by obstructing the chorion pores.

The industrial application of radiation processing involves high doses of gamma or electron radiation to cause structural changes in materials, such as rubber vulcanization and polymer degradation, among others. A reliable dosimetric system is necessary to guarantee the desired effects and also to avoid damages. Poly(vinylidene fluoride) [PVDF] homopolymer has been recently proposed for application in high gamma dose dosimetry. In this work, nanocomposites made of PVDF filled with zirconium oxide [ZrO

Carbon nanotubes (CNT) are promising materials for biomedical applications, especially in the field of neuroscience; therefore, it is essential to evaluate the neurotoxicity of these nanomaterials. The present work assessed the effects of single-walled CNT functionalized with polyethylene glycol (SWCNT-PEG) on the consolidation and retrieval of contextual fear memory in rats and on oxidative stress parameters in the hippocampus. SWCNT-PEG were dispersed in water at concentrations of 0.5, 1.0, and 2.1 mg/mL and infused into the rat hippocampus. The infusion was completed immediately after training and 30 min before testing of a contextual fear conditioning task, resulting in exposure times of 24 h and 30 min, respectively. The results showed that a short exposure to SWCNT-PEG impaired fear memory retrieval and caused lipid peroxidation in the hippocampus. This response was transient and overcome by the mobilization of antioxidant defenses at 24 h. These effects occurred at low and intermediate but not high concentration of SWCNT-PEG, suggesting that the observed biological response may be related to the concentration-dependent increase in particle size in SWCNT-PEG dispersions.

Raman spectra of octadecylamine (ODA) molecules covalently bound to the surface of single walled carbon nanotubes were obtained by varying the laser excitation energy from 1.92 to 3.81 eV. A strong dependence of the Raman intensity on the excitation energy was observed and, under specific conditions of resonance, the Raman signal from the amide linkage can become even stronger than the resonant Raman signal of the carbon nanotubes. This result is explained in terms of a chemical enhancement mechanism due to charge transfer between the ODA molecules and the nanotubes. The enhancement factor was up to 100 times higher than the value typically reported for the chemical Surface Enhanced Raman Scattering (SERS) effect. Our results show that carbon nanotubes may contribute to the still controversial understanding of the ‘chemical’ effects to the enhancement in SERS, extending the scope of application of this analytical tool in strategic areas such as biomedicine, catalysis and environmental analysis.

Single-wall carbon nanotubes functionalized with polyethylene glycol (SWCNT-PEG) are promising materials for biomedical applications such as diagnostic devices and controlled drug-release systems. However, several questions about their toxicological profile remain unanswered. Thus, the aim of this study was to investigate the action of SWCNT-PEG in Danio rerio zebrafish embryos at the molecular, physiological and morphological levels. The SWCNT used in this study were synthesized by the high-pressure carbon monoxide process, purified and then functionalized with distearoyl phosphatidylethanolamine block copolymer-PEG (molecular weight 2 kDa). The characterization process was carried out with low-resolution transmission electron microscopy, thermogravimetric analysis and Raman spectroscopy. Individual zebrafish embryos were exposed to the SWCNT-PEG. Toxic effects occurred only at the highest concentration tested (1 ppm) and included high mortality rates, delayed hatching and decreased total larval length. For all the concentrations tested, the alkaline comet assay revealed no genotoxicity, and Raman spectroscopy measurements on the histological slices revealed no intracellular nanotubes. The results shown here demonstrate that SWCNT-PEG has low toxicity in zebrafish embryos, but more studies are needed to understand what mechanisms are involved. However, the presence of residual metals is possibly among the primary mechanisms responsible for the toxic effects observed, because the purification process was not able to remove all metal contamination, as demonstrated by the thermogravimetric analysis. More attention must be given to the toxicity of these nanomaterials before they are used in biomedical applications. Copyright © 2016 John WileySons, Ltd.

The combination of multi–walled carbon nanotubes (MWCNTs) with polymers offers an attractive route to reinforce the macromolecular compounds as well as the introduction of new properties based on morphological modifications or electronic interactions between the two constituents. As they are only a few nanometers in dimension, it offers ultra-large interfacial area per volume between the nano-element and polymer matrix. Nevertheless, the use of MWCNTs as a rough material in different applications has been largely limited by their poor processability, insolubility, and infusibility. Studies concerning the nanofiller reinforced polymer composites are justified in an attempt to overcome these limitations. This work presents one preliminary study of MWCNTs dispersion into the PVDF homopolymer. For preparation, the composite components were diluted in n,n-dimethylacetamide (DMAc) with mechanical agitation assistance. After complete dilution, followed by slow evaporation of the solvent at 60°C, the samples were dried. Films of about 80 μm were obtained. FTIR and UV-Vis spectroscopic techniques were used to characterize the nanocomposites. The appearance of absorption bands in the FTIR spectra of nanofilled samples, when compared to the spectrum of pristine PVDF samples, are discussed and compared with the UV-Vis measurements.

In this work, it is demonstrated how a novel technique based on temperature-programmed chemical vapor deposition (TPCVD) can be used to investigate the synthesis of carbon nanotubes (CNTs) from methane on a classic catalyst FeMo(x)/MgO (x = 0.07, 0.35 and 1.00). TPCVD monitors carbon deposition by measuring H2 formed during CH4 decomposition and affords information on the different catalytic species, deactivation process, reaction kinetics and carbon yields. The obtained results showed for FeMgO catalyst a simple TPCVD peak related to the production of carbon beginning at 760 degrees C with maximum at 800 degrees C followed by a rapid deactivation resulting in a low carbon yield. The addition of Mo to Fe/MgO catalyst completely changes the TPCVD profile with the formation of a new catalytic species active at temperatures higher than 900 degrees C, which is stable and continuously decomposes CH4 to produce high carbon yields. Raman, TG/DTG, Mössbauer, SEM, TEM, XRD and TPR analyses suggested that this active catalytic phase is likely related to Fe-Mo and Fe-Mo-C phases active to produce single wall and mainly multiwall carbon nanotubes.

This chapter addresses the initial steps one has to give to explore the unique properties of carbon nanotubes in biomedical applications, which are their synthesis, purification and functionalization. We start with a brief description of the structure and properties, and we summarize the synthesis methods. The major issues are then addressed, which are purification and functionalization for bioapplications. We review the different methods, highlighting their advantages and disadvantages.

A new composite electrode is described for anodic stripping voltammetry determination of Pb(II) at trace level in aqueous solution. The electrode is based on the use of multiwalled carbon nanotubes and Amberlite IR-120. The anodic stripping voltammograms depend, to a large extent, on the composition of the modified electrode and the preconcentration conditions. Under optimum conditions, the anodic peak current at around −0.57 V is linearly related to the concentration of Pb(II) in the range from 9.6 × 10−8 to 1.7 × 10−6 mol L−1 (R = 0.998). The detection limit is 2.1 × 10−8 mol L−1, and the relative standard deviation (RSD) at 0.24 × 10−6 mol L−1 is 1.7% (n = 6). The modified electrode was applied to the determination of Pb(II) using the standard addition method; the results showed average relative recoveries of 95% for the samples analysed.

Single-wall carbon nanotubes dispersed in aqueous solutions of different surfactants are investigated by optical absorption and photoluminescence spectroscopies. The role played by the type of surfactant, surfactant concentration, and nanotube concentration on the efficiency of absorption and emission of light by the individualized nanotubes of different chiralities is discussed. By comparing the intensities of absorption and emission is possible to obtain the best nanotube and surfactant concentrations that optimize the light emission efficiency. Changes in the absorption and emission energies are observed and interpreted in terms of the variation of the environments screening on the exciton binding energies.

Single-wall carbon nanotube (SWNT) samples grown by the CoMoCAT method are investigated by resonance Raman scattering and optical absorption. The environment effects in the population of the different ( n , m ) nanotubes present in the samples are characterized for DNA-wrapped nanotubes and the results are compared with SDS-wrapped CoMoCAT nanotubes. A significant decrease in the Raman intensity of metallic nanotubes is observed in the DNA-wrapped sample as compared to the SDS-wrapped sample, supporting the DNA-based separation method. This result is confirmed by optical absorption measurements in both samples.

Resonance Raman and photoluminescence excitation (PLE) spectroscopies are used to study the optical properties of different types of carbon nanostructures such as carbon nanotube, nanoribbons, nanographites and graphite edges. In the resonance Raman experiments of carbon nanotubes, the ( n , m ) assignment is obtained by comparing the experimental and theoretical diameter and chirality dependence of the optical transitions. The influence of the environment on the optical transitions of the nanotubes is also obtained in the Raman experiments. The PLE measurements in different samples of carbon nanotubes show both direct and phonon-assisted optical transitions, and the results give new evidences that the optical transitions in nanotubes have an excitonic character, which is very strong for the low energy transitions. We also analyze the Raman spectra of nanoribbons and nanographites, showing that this technique is an important tool for defect characterization in graphitic materials, and can be used to distinguish the atomic structure of the graphite edges.

A molecule with a π conjugated backbone built from aromatic thiophene and dialkoxyphenylene units and substituted imidazolium groups (TPO) is designed to obtain ultra-stable single walled carbon nanotube (SWCNT) dispersion in aqueous medium. The proposed mechanism of non-covalent interaction is accompanied by individualization of SWCNT and comprises of dominant nondisruptive π-π and cation-π interaction between them and the TPO conjugated oligomer. The individualization of SWCNT and dispersibility and stability of the ultra-stable suspensions were estimated using high resolution transmission electron microscopy, UV-Visible-NIR absorption spectroscopy, Raman spectroscopy, photoluminescence and zeta potential measurement. Nuclear magnetic resonance data provides direct evidence toward possible cation-π interaction.

Carbon nanotubes are promising nanomaterials for the diagnosis and treatment of brain disorders. However, the ability of these nanomaterials to cross cell membranes and interact with neural cells brings the need for the assessment of their potential adverse effects on the nervous system. This study aimed to investigate the biopersistence of single-walled carbon nanotubes functionalized with polyethylene glycol (SWCNT-PEG) directly infused into the rat hippocampus. Contextual fear conditioning, Y-maze and open field tasks were performed to evaluate the effects of SWCNT-PEG on memory and locomotor activity. The effects of SWCNT-PEG on oxidative stress and morphology of the hippocampus were assessed 1 and 7 days after infusion of the dispersions at 0.5, 1.0 and 2.1 mg/mL. Raman analysis of the hippocampal homogenates indicates the biopersistence of SWCNT-PEG in the hippocampus 7 days post-injection. The infusion of the dispersions had no effect on the acquisition or persistence of the contextual fear memory; likewise, the spatial recognition memory and locomotor activity were not affected by SWCNT-PEG. Histological examination revealed no remarkable morphological alterations after nanomaterial exposure. One day after the infusion, SWCNT-PEG dispersions at 0.5 and 1.0 mg/mL were able to decrease total antioxidant capacity without modifying the levels of reactive oxygen species or lipid hydroperoxides in the hippocampus. Moreover, SWCNT-PEG dispersions at all concentrations induced antioxidant defenses and reduced reactive oxygen species production in the hippocampus at 7 days post-injection. In this work, we found a time-dependent change in antioxidant defenses after the exposure to SWCNT-PEG. We hypothesized that the persistence of the nanomaterial in the tissue can induce an antioxidant response that might have provided resistance to an initial insult. Such antioxidant delayed response may constitute an adaptive response to the biopersistence of SWCNT-PEG in the hippocampus.

Carbon nanotubes (CNT) is one of the more abundant nanomaterial produced in the world. Therefore, it is desirable to access its effects in all environment compartments, in order to mitigate environmental distress. This study aims to verify the potential use of lichens - classical atmospheric pollution indicators - as biomonitors of carbon nanotubes aerosols. To examine cause-effect relationships, preserving environmental microclimatic parameters, the lichen Parmotrema tinctorum (Nyl.) Hale was transplanted to open top chambers where aerosols of CNT were daily added. Physiological parameters such as cell viability, photosynthetic efficiency, cell permeability as well as nanoparticle internalization were assessed. Carbon nanotubes exposure led to reduction on the cell viability of P. tinctorum. The treatment with 100µg/mL of MWCNT-COOH resulted in intracellular ion leakage, probably due to changes in membrane permeability. No alterations on photosynthetic efficiency were detected. Carbon nanotubes entrapment and internalization into the lichen thallus were observed. Short term exposition of CNT produced measurable physiological changes in P. tinctorum lichen. This suggests the possibility of use of lichens as models to assess the environmental impact (air related) of engineered nanomaterials.

Made available in DSpace on 2015-10-21T20:15:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-06-17. Added 1 bitstream(s) on 2015-10-22T09:48:16Z : No. of bitstreams: 1 WOS000356518200001.pdf: 803864 bytes, checksum: e41d7e36cd2e1f67d32a7945ba81b594 (MD5) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Gold is a noble metal that, in comparison with silver and copper, has the advantage of corrosion resistance. Despite its high conductivity, chemical stability and biocompatibility, gold exhibits high plasticity, which limits its applications in some nanodevices. Here, we report an experimental and theoretical study on how to attain enhanced mechanical stability of gold nanotips. The gold tips were fabricated by chemical etching and further encapsulated with carbon nanocones via nanomanipulation. Atomic force microscopy experiments were carried out to test their mechanical stability. Molecular dynamics simulations show that the encapsulated nanocone changes the strain release mechanisms at the nanoscale by blocking gold atomic sliding, redistributing the strain along the whole nanostructure. The carbon nanocones are conducting and can induce magnetism, thus opening new avenues on the exploitation of transport, mechanical and magnetic properties of gold covered by sp(2) carbon at the nanoscale. Univ Fed Minas Gerais, ICEx, Dept Fis, BR-31270901 Belo Horizonte, MG, Brazil Penn State Univ, Mat Res Inst, University Pk, PA 16802 USA Univ Fed Minas Gerais, Ctr Microscopia, BR-30123970 Belo Horizonte, MG, Brazil Ctr Desenvolvimento Tecnol Nucl, BR-31270010 Belo Horizonte, MG, Brazil Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13083970 Campinas, SP, Brazil Univ Estadual Paulista, UNESP, IGCE, Dept Fis, Rio Claro, SP 13506900, Brazil Univ Estadual Paulista, UNESP, IGCE, Dept Fis, Rio Claro, SP 13506900, Brazil FAPESP: 2013/08293-7 FAPESP: 2011/17253-3 FAPESP: 2013/09536-0

Nanotechnology has been proven to be increasingly compatible with pharmacological and biomedical applications. Therefore, we evaluated the biological interactions of single-wall carbon nanotubes functionalized with polyethylene glycol (SWNT-PEG). For this purpose, we analyzed biochemical, histological, behavioral and biodistribution parameters to understand how this material behaves in vitro and in vivo using the fish Danio rerio (zebrafish) as a biological model. The in vitro results for fish brain homogenates indicated that SWNT-PEG had an effect on lipid peroxidation and GSH (reduced glutathione) content. However, after intraperitoneal exposure, SWNT-PEG proved to be less biocompatible and formed aggregates, suggesting that the PEG used for the nanoparticle functionalization was of an inappropriate size for maintaining product stability in a biological environment. This problem with functionalization may have contributed to the low or practically absent biodistribution of SWNT-PEG in zebrafish tissues, as verified by Raman spectroscopy. There was an accumulation of material in the abdominal cavity that led to inflammation and behavioral disturbances, as evaluated by a histological analysis and an open field test, respectively. These results provide evidence of a lack of biocompatibility of SWNTs modified with short chain PEGs, which leads to the accumulation of the material, tissue damage and behavioral alterations in the tested subjects.

Photoluminescence (PL) measurements of porphyrin-doped single-walled carbon nanotubes (SWCNTs) were performed in sodium dodecylbenzenesulfonate (NaDDBS) aqueous dispersions. PL spectra were used to draw PL maps in which maxima correspond to absorption–emission excitonic processes related to (E11, E22) first Van Hove singularities of the SWCNT electronic structure. The influence of the net charge of the porphyrin is a determining factor in the energy map maximum shifts (EMMS) relative to that of a pristine NaDDBS/SWCNT dispersion. A non-interacting porphyrin is used as a reference to discard the influence of the dielectric constant of the medium in the EMMS.

Porphyrin-doped carbon nanotubes in sodium dodecylbenzenesulfonate (NaDDBS) aqueous solution were obtained from NaDDBS/carbon nanotube aqueous dispersions. Several phonon-assisted absorption and recombination processes seem to occur, including one-phonon and two-phonon processes, and remain present even upon porphyrin doping. Power-law scaling of exciton binding energies and environmental dielectric screening effects are used to infer the doping from photoluminescence maps. The dielectric constant of the 5,10,15,20-tetrakis(4-trimethylammonium phenyl) porphyrin (H2TTMAPP) in NaDDBS aqueous solution seems to be higher than the one of NaDDBS/aqueous solution apparently because the counterions have opposite net charges.

We report the preparation of photovoltaic devices using modified single wall carbon nanotubes, SWNTs. Devices are produced stacking on top of fluorine-doped tin-oxide, an electrochemically deposited polybithiophene layer, a layer of SWNT blended with poly(3-octylthiophene) and an evaporated top metal contact, Ca/Al or Al. Ca/Al-top-electrode devices achieve open-circuit voltages of 1.81 V and average power conversion efficiency of 1.48% at irradiance of 15.5 W m–2, spectrally distributed following AM1.5. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Surface composition plays an important role in carbon nanotube dispersibility in different environments. Indeed, it determines the choice of dispersion medium. In this paper the effect of oxidation on the dispersion of HiPCO single-walled carbon nanotubes (SWNTs) in N-methyl-pyrrolidinone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMA), N-dodecyl-pyrrolidinone (N12P) and cyclohexyl-pyrrolidinone (CHP) was systematically studied. During the oxidation process, similar amounts of carboxylic acid and phenolic groups were introduced to mostly already existing defects. For each solvent the dispersion limits and the absorption coefficients were estimated by optical absorption analysis over a range of SWNT concentrations. The presence of acid oxygenated groups increased SWNT dispersibility in NMP, DMF and DMA, but decreased in N12P and CHP. The absorption coefficients, however, decreased for all solvents after oxidation, reflecting the weakening of the effective transition dipole of the ??? transition with even limited extension functionalization and solvent interaction. The analysis of the results in terms of Hansen and Flory?Huggins solubility parameters evidenced the influence of dipolar interactions and hydrogen bonding on the dispersibility of oxidized SWNTs.

Several techniques were recently reported for the bulk separation of metallic (M) and semiconducting (S) single wall carbon nanotubes (SWNTs), using optical absorption and resonance Raman spectroscopy (RRS) as a proof of the separation. In the present work, we develop a method for the quantitative evaluation of the M to S separation ratio, and also for the SWNT diameter selectivity of the separation process, based on RRS. The relative changes in the integrated intensities of the radial-breathing mode (RBM) features, with respect to the starting material, yield the diameter probability distribution functions for M and S SWNTs in the separated fractions, accounting for the different resonance conditions of individual SWNTs, while the diameter distribution of the starting material is obtained following the fitting procedure developed by Kuzmany and coworkers. Features other than the RBM are generally less effective for characterization of the separation process for SWNTs.

In this work, composite polymer electrolytes based on a thermoplastic polyurethane/LiClO4 amorphous system and on bare and functionalized zirconia nanoparticles as a filler are reported. The ceramic nanoparticles were synthesized via the sol-gel route using zirconium butoxide as the precursor for zirconium oxide nanoclusters and methacrylic acid as an organic modifier group. The salt concentration in the polymer phase was 17 wt% and fillers were added in the range between 2 and 10wt%. Scanning electron microscopy (SEM) was used to characterize the average size and the homogeneity of the nanoparticles in the polymer matrix, while impedance spectroscopy (IS) was used to evaluate the ionic conductivity of the composites. The addition of zirconia fillers results in an increase in ionic conductivity for all filled systems. The results also show that the functionalization of the zirconia nanoparticles promotes a significant increase in conductivity, suggesting that the interaction of the metracrylate-functionalized fillers with the polyurethane matrix was greatly improved. These results raise interest in the study of organically modified ceramic clusters as fillers for electrolyte polymers.

Since the discovery of single wall carbon nanotubes (SWNT) in 1991, this nanomaterial has received an enormous attention from the nanoscience and nanotechnology community, not only due to the clear prospects for applications such as novel nanoelectronic and nano-optoelectronic devices, but also because this unique one dimensional (1D) system offered a new possibility for the investigation of novel physical phenomena in low dimensions. In 2002 it was demonstrated that photoluminescence (PL) could be observed in suspensions of isolated SWNTs and, later on, that PL could also be observed from individual, suspended SWNTs. Since then, there has been an increasing amount of work directed towards the investigation of the optical properties of semiconducting SWNTs by PL and photoluminescence excitation spectroscopy (PLE), and the use of PL and PLE for the qualitative and quantitative identification of SWNTs species within and ensemble of carbon nanotubes. In 2005 it was shown that the observed optical transitions are associated to 1D excitons and, from the point of view of optical properties, the rich physics of excitons in SWNTs has received much attention. For instance, it is now clear that excitons and exciton-phonon interactions play a major role in the mechanisms responsible for the emission and the absorption of light in SWNTs. Also, the interaction of SWNTs with their vicinity, which includes the interaction with organic and inorganic molecules, and the modifications in the excitonic system caused by changes in the dielectric constant, can be readily investigated by PL and PLE. In this talk we presented an overview of our recent work in the optical spectroscopy of SWNTs.1–3 In particular, we showed some of our results on the investigation of the exciton-phonon interaction in semiconducting SWNTs and on the modifications in the PL and PLE spectra associated to the interactions with its surrounding environment. Note from Publisher: This article contains the abstract only.