Fullerene Concentration Research Articles

Morphology of F8T2/PC71BM Blend Film as Investigated by Scanning Transmission X-ray Microscope (STXM)

Clarification of the morphology of bulk heterojunction (BHJ) is indispensable for true comprehension of the organic solar cells. Here, we performed scanning transmission X-ray microscopy (STXM) for a poly-(9,9-dioctylfluorene-co-bithiophene) (F8T2)/[6,6]-phenyl C71-butyric acid methyl ester (PC71BM) blend film annealed at various temperatures (Tan). We found that the fullerene concentration within the polymer-rich domain decreases with Tan while the domain size (∼230 nm) is essentially unchanged. We will discuss the interrelation between the film morphology and the photovoltaic performance.

Efficient small molecule-based bulk heterojunction photovoltaic cells with reduced exciton quenching in fullerene

Most highly efficient small molecule-based bulk heterojunction (BHJ) photovoltaic cells contain a large concentration of fullerene in their blend active layers. However, the excitons generated in fullerene can seriously quench at the surface of the commonly used MoO3 buffer layer, becoming a key limitation to the photovoltaic performance of these cells. In this study, we’ve investigated various anode buffer layers in the thermally evaporated tetraphenyldibenzoperiflanthene (DBP) and C70-based BHJ cells with high C70 concentration. It’s been found that obviously enhanced power conversion efficiency (PCE) of up to 6.26% can be obtained in DBP and C70-based BHJ cells via simply replacing the MoO3 buffer by poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS), which is also a commonly used anode buffer material in polymer-based BHJ cells. Photoluminescence spectra results have confirmed the suppression of exciton quenching at the anode interface by inserting this PEDOT: PSS buffer. Moreover, after adding a C70 interlayer for better electron extraction and the further suppression of exciton quenching, the DBP and C70-based M-i-n photovoltaic cells show a remarkable PCE of 7.04% under illumination with 100mW/cm2, AM 1.5G simulated solar light.

Step-Wise Concentration Influence of Fullerenes C60 and C70 on the Various Parameters of Condensed Systems

A step-wise changing concept is developed of the influence of fullerenes C60and C70 on various properties of condensed systems, liquid, and solid. In this, Part I is considered the step-wise character for three parameters: (1) the density of solutions; (2) the boiling points of solutions, and (3) the coefficient of the surface tension of solutions. The sharp drop of the density of solutions at very small fullerene concentrations is pointed out and considered. A step change in the coefficients of the surface tension of fullerene solutions with concentration were determined and are discussed. In Part II, to follow, the influence of fullerene concentrations on the freezing and melting of solutions will be considered.

Step-Wise Concentration Influence of Fullerenes C60 and C70 on the Various Parameters of Condensed Systems

A step-wise concept has been proposed for description of the influence of the concentration of fullerenes on various properties of their solutions in a series of single-ring solvents: benzene, toluene, xylenes, o-dichlorobenzene, and bromobenzene. In a previous report, with increase of fullerene concentration, the step-wise character was observed for changes of such parameters as the density of solutions, their boiling points, Tb, and coefficients of their surface tensions. In this report, we show that the step-wise concept can also be used for control and correction of the melting process of various frozen fullerene-containing solutions in two of the solvents.

ИССЛЕДОВАНИЕ ЭФФЕКТИВНОСТИ РЕЗОНАНСНО-ТУННЕЛЬНОГО МЕТОДА ДЛЯ КОНТРОЛЯ КОНЦЕНТРАЦИИ ФУЛЛЕРЕНОВ В КРЕМНИЙОРГАНИЧЕСКИХ КОМПОЗИТАХ

ИССЛЕДОВАНИЕ ЭФФЕКТИВНОСТИ РЕЗОНАНСНО-ТУННЕЛЬНОГО МЕТОДА ДЛЯ КОНТРОЛЯ КОНЦЕНТРАЦИИ ФУЛЛЕРЕНОВ В КРЕМНИЙОРГАНИЧЕСКИХ КОМПОЗИТАХ

Investigation of the dissolution kinetics of fullerene C60 in solvents with different polarities by UV-Vis spectroscopy

The dissolution kinetics of fullerene C60 in solvents with different polarities, including toluene, benzene, and N-methylpyrrolidone (NMP), at varying concentrations and temperatures of the solution, and conditions of preparation, is studied by UV-Vis spectroscopy. For a polar C60/NMP solution, stable peaks in the absorption spectrum were not found; the evolution of the spectra is determined by the kinetics of the formation of charge-transfer complexes in the solution. It is shown that the dissolution of fullerene in low-polar toluene and benzene is described by the Noyes-Whitney equation; the fullerene concentration in a solution is determined by the absorption peak at λ = 408 nm. The parameters in the dissolution equations for different conditions are determined.

Monitoring of Aqueous Fullerene Dispersions by Thermal-Lens Spectrometry

Aqueous fullerene solutions (dispersions) are very promising materials of biomedicine and biotechnology. Of importance are the traceability of their production and characterization of their optical and colloidal properties. Thermal-lens spectrometry, as a method suitable for both optical and thermophysical studies, was used to elucidate the forms of non-modified fullerenes in their aqueous dispersions and to determine low concentrations of $$\hbox {C}_{60}$$ and $$\hbox {C}_{70}$$ fullerenes. It was shown that the residual amounts of toluene in aqueous fullerene dispersions made according to the solvent-exchange protocol could be detected by thermal lensing. As a result, the technique for the production of aqueous fullerene dispersions was improved compared to the existing data providing higher fullerene concentrations. The limits of detection of $$\hbox {C}_{60}$$ and $$\hbox {C}_{70}$$ fullerenes are approximately $$100\,\hbox {ng}{\cdot }\hbox {mL}^{-1}$$ , which are 20-fold lower compared to conventional spectrophotometry. The distinction between aqueous fullerene dispersions in comparison with organic solutions of fullerenes caused by the formation of large clusters is shown by the comparison of transient and steady-state calibration curves for aqueous and organic fullerene solutions and model reference systems under various thermal-lens excitation conditions. The advantages of thermal lensing for such colloidal systems are discussed.

Nanoparticle tracking analysis characterisation and parts-per-quadrillion determination of fullerenes in river samples from Barcelona catchment area.

In the present work, the analysis of seven fullerenes (C60 and C70 fullerenes and five functionalised fullerenes) has been performed in river samples collected in the vicinities of Barcelona (Catalonia, NE of Spain). The results of 48 samples (25 river waters, 12 river sediments and 11 wastewater effluents) are presented. Extracts of river water, river sediments and wastewater effluents were analysed by liquid chromatography (LC), using a pyrenylpropyl group bonded silica based column, coupled to a high-resolution mass spectrometer (HRMS), using a dual ion source, atmospheric pressure photoionisation/atmospheric pressure chemical ionisation source (APPI/APCI). The novel methodology presents good chromatographic separation, excellent selectivity and instrumental limits of quantification (ILOQ) in the femtogram order. Method limits of quantification (MLOQ) ranged from 2.9 to 17 pg/l and from 3.2 to 31 pg/l in surface waters and wastewaters, respectively. In wastewater effluents, the sums of C60 and C70 ranged from 0.5 to 9.3 ng/l. In surface waters, C60 fullerene was the most ubiquitous compound, being detected in 100% of the samples in concentrations from 31 pg/l to 4.5 ng/l, while C70 concentrations ranged from less than the method limits of detection (MLOD) to 1.5 ng/l. The presence of fullerenes in both the large particulate (diameter Ø > 450 nm) and the colloidal (Ø < 450 nm) fractions of surface waters should be noticed. In sediments, the concentrations of fullerenes were between the MLOD and 34.4 pg/g. In addition, nanoparticle tracking analysis (NTA) was used for the characterisation of water samples in terms of nanoparticle number concentration and size distribution. As far as our knowledge is concerned, this is the first time that NTA has been used for the characterisation of complex river waters with an environmental focus.

Antimicrobial photodynamic inactivation with decacationic functionalized fullerenes: Oxygen-independent photokilling in presence of azide and new mechanistic insights

Functionalized fullerenes are gaining wide interest for mediating photodynamic therapy (PDT) of diseases such as cancers and infections. We recently reported the synthesis of two new decacationic fullerene monoadducts: C60[>M(C3N6+C3)2]–(I−)10(LC14) and its derivative with a light-harvesting antenna conjugated as a C60[>CPAF–(MN6+C3)2]–(I−)10 nanostructure (LC15). We studied the ability of these compounds to mediate PDT of human cancer cells in vitro when excited by UVA light or by white light. Here we report the synthesis of a new fullerene derivative C60[>M(C3N6+C3)2][>M(C3N6C3)2]–(I−)10 (LC16 derived from LC14), as a malonate bisadduct containing a covalently bound decatertiary amine arm. We investigated the relative abilities of the three compounds to generate singlet oxygen (1O2), hydroxyl radicals (HO·), and hydrogen peroxide (H2O2) after excitation by UVA or by white light. We used three different classes of pathogenic microbial cells (Gram-positive bacterium, methicillin-resistant Staphylococcus aureus (MRSA), Gram-negative bacterium Escherichia coli, and fungal yeast Candida albicans). LC15 was the most powerful broad spectrum antimicrobial fullerenyl photosensitizer (FPS) followed by LC16, and LC14 was least powerful. Killing depended on both fullerene monoadduct concentration and light fluence. UVA was five times more effective than white light for killing, but not for generation of ROS and relative absorption was greater in white spectral region. Bacterial killing was not much inhibited by addition of azide anions and in some cases was potentiated. In the absence of oxygen, microbial photokilling was highly potentiated (up to 5 logs) by the addition of azide anions. We conclude that molecular functional addends that encourage a type I electron-transfer mechanism increase the ability of photoactivated fullerene monoadducts to kill microbial cells. Oxygen-independent photokilling is possible with fullerene monoadducts in the presence of azide anions, probably mediated by azidyl radicals. UVA excitation may kill bacteria partly by an electron-transfer mechanism directly into bacteria as well as by ROS.

Вплив С60-фулерену на в’язко-еластичні властивості мембрани еритроцитів людини

The effect of C60 fullerene aqueous colloid solution (C60FAS) on viscoelastic properties of human erythrocytes membrane has been studied. It was established that the effect of C60FAS on erythrocytes depends on the medium osmolality and concentration of C60 fullerene in it. In particular, in isotonic solution (0,15 mol/l NaCl) adding C60 fullerene in concentrations from 0,7 to 28 μmol/l did not cause the hemolytic damage of cells. In hypotonic medium when introducing C60 fullerene (7 μmol/l concentration) at the beginning of erythrocyte hemolysis its stimulating effect was maximal and when adding C60FAS in 20 s after hemolysis start no this process stimulation is observed. This points to the changes in viscoelastic properties of erythrocyte membranes even during the first seconds of its interaction with C60 fullerene.

Charge transport and recombination in PDPP5T:[70]PCBM organic solar cells: The influence of morphology

The performance of organic bulk heterojunction solar cells is strongly dependent on the donor/acceptor morphology. Morphological parameters, such as the extent and the composition of donor- and acceptor-rich domains, influence both the charge generation and the charge transport throughout the active layer. This work focuses on a polymer:fullerene system based on a small bandgap diketopyrrolopyrrole–quinquethiophene alternating copolymer (PDPP5T) mixed with [6,6]-phenyl-C71-butyric acid methyl ester ([70]PCBM) that is capable of efficiencies higher than 6%. By changing the processing conditions, the morphology can be varied from a coarse separated morphology, with fullerene domains (blobs) embedded in a polymer-rich matrix, to a completely mixed layer.The charge carrier transport and the strength of the bimolecular recombination in PDPP5T:[70]PCBM blends with different morphologies and fullerene concentrations are experimentally characterized. The large difference in electron and hole mobility and the electric field dependency of the electron mobility are identified as the causes that limit the performance of devices with low [70]PCBM content. These effects are not present if the concentration of [70]PCBM is increased while keeping a fine phase separation by the addition of ortho-dichlorobenzene as a cosolvent.For the phase-separated blends, a model is proposed, based on a drift–diffusion approach that combines electrical and morphological parameters; with this model the contribution of each phase to the total current is quantified. Under operating conditions, most of the current comes from the interfacial region between the phases, with holes traveling through the matrix and the electrons through the blobs. This device model consistently connects morphological features to overall device performance.

Conformation and Interactions of Polystyrene and Fullerenes in Dilute to Semidilute Solutions

We report the polymer conformation and fullerene aggregation in a ternary system containing polystyrene, C60, and toluene measured by small angle neutron, static, and dynamic light scattering. We investigate polymer concentrations across the dilute and semidilute regime for five polymer molecular weights (Mw = 20 kg/mol to 1 Mg/mol), and fullerene concentrations below and above its miscibility threshold in toluene. We find that the polymer radius of gyration (Rgpoly), hydrodynamic radius (Rh), and the mixture correlation length (ξ) remain unchanged upon addition of C60. The miscibility of C60 in toluene, however, decreases upon addition of polystyrene forming aggregates with a time-dependent radius on the order of 100 nm, and this effect is amplified with increasing polymer Mw. Our findings are relevant to the solution processing of organic photovoltaics, which generally require the effective solubilization of fullerene derivatives and polymer pairs in this concentration range.

Distance distributions of photogenerated charge pairs in organic photovoltaic cells.

Strong Coulomb interactions in organic photovoltaic cells dictate that charges must separate over relatively long distances in order to circumvent geminate recombination and produce photocurrent. In this article, we measure the distance distributions of thermalized charge pairs by accessing a regime at low temperature where charge pairs are frozen out following the primary charge separation step and recombine monomolecularly via tunneling. The exponential attenuation of tunneling rate with distance provides a sensitive probe of the distance distribution of primary charge pairs, reminiscent of electron transfer studies in proteins. By fitting recombination dynamics to distributions of recombination rates, we identified populations of charge-transfer states and well-separated charge pairs. For the wide range of materials we studied, the yield of separated charges in the tunneling regime is strongly correlated with the yield of free charges measured via their intensity-dependent bimolecular recombination dynamics at room temperature. We therefore conclude that populations of free charges are established via long-range charge separation within the thermalization time scale, thus invoking early branching between free and bound charges across an energetic barrier. Subject to assumed values of the electron tunneling attenuation constant, we estimate critical charge separation distances of ∼3-4 nm in all materials. In some blends, large fullerene crystals can enhance charge separation yields; however, the important role of the polymers is also highlighted in blends that achieved significant charge separation with minimal fullerene concentration. We expect that our approach of isolating the intrinsic properties of primary charge pairs will be of considerable value in guiding new material development and testing the validity of proposed mechanisms for long-range charge separation.

Material profile influences in bulk-heterojunctions

The morphology in mixed bulk-heterojunction films are compared using three different quantitative measurement techniques. We compare the vertical composition changes using high-angle annular dark-field scanning transmission electron microscopy with electron tomography and neutron and x-ray reflectometry. The three measurement techniques yield qualitatively comparable vertical concentration measurements. The presence of a metal cathode during thermal annealing is observed to alter the fullerene concentration throughout the thickness of the film for all measurements. However, the absolute vertical concentration of fullerene is quantitatively different for the three measurements. The origin of the quantitative measurement differences is discussed.

High Polymer/Fullerene Ratio Realized in Efficient Polymer Solar Cells by Tailoring of the Polymer Side‐Chains

The introduction of “double aromatic side-chains” to the existing polymer backbone is an effective approach to obtain high performance polymer solar cells with low fullerene and additive concentrations, leading to improved absorbance for thin film and more environment-friendly processing. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Dielectric and Microwave Properties of Natural Rubber Based Composites Containing Fullerene Black

It is expected that filling a rubber with a small amount of fullerene could lead to a new set of properties, bringing to the composite advantages over the rubbers in use. In the present work, the dielectric and microwave properties of natural rubber (SMR10) based composites containing various concentration of fullerene black (0-7,5 phr), rich in fullerenes (7,5%) were investigated in the 1-12 GHz frequency range. It has been established that within the range used for the experiments the increasing frequency and fullerene filler amount lead to an increase in the values of relative dielectric permittivity, dielectric loss angle tangent, reflection coefficient and attenuation of electromagnetic waves, while the values for shielding effectiveness get lower. That is due to the fact that under the experimental conditions the change in the reflection coefficient is greater than that in the attenuation of electromagnetic waves. The dielectric properties of the composites (especially the dielectric loss angle tangent) are more affected by fullerene black filler than their microwave properties. Further change in the properties could also occur at higher concentrations of fullerene black but the cost of rubber compound would be much higher

Unequal Partnership: Asymmetric Roles of Polymeric Donor and Fullerene Acceptor in Generating Free Charge

Natural photosynthetic complexes accomplish the rapid conversion of photoexcitations into spatially separated electrons and holes through precise hierarchical ordering of chromophores and redox centers. In contrast, organic photovoltaic (OPV) cells are poorly ordered, utilize only two different chemical potentials, and the same materials that absorb light must also transport charge; yet, some OPV blends achieve near-perfect quantum efficiency. Here we perform electronic structure calculations on large clusters of functionalized fullerenes of different size and ordering, predicting several features of the charge generation process, outside the framework of conventional theories but clearly observed in ultrafast electro-optical experiments described herein. We show that it is the resonant coupling of photogenerated singlet excitons to a high-energy manifold of fullerene electronic states that enables efficient charge generation, bypassing localized charge-transfer states. In contrast to conventional views, our findings suggest that fullerene cluster size, concentration, and dimensionality control charge generation efficiency, independent of exciton delocalization.

C60 FULLERENE EFFECT ON THE DYNAMICS OF FATIGUE PROCESSES IN RAT SOLEUS MUSCLE AFTER ISCHEMIA-REPERFUSION

43 The purposeful application of bio compatible nanomaterials of low toxicity is a relevant problem in modern biotechnology. It is assumed that the use of nanoparticles will help to solve the problems of early disease diagnostics and targeted delivery of drugs into tissues and cells, as well as new methods of selective therapies. C60 fullerene has a prominent position among other potentially effective therapeutic agents [1]. It is known that C60 molecule normalizes cellular metabolism and neural processes, increases resistance to stress, exhibits antiviral properties, has pronounced anti-inflammatory and anti-allergic effects, enhances activity of enzymes and regenerative capacity of tissues [1]. Finally, C60 fullerene and its derivatives can be used for the treatment of cancer [2–4]. C60 fullerene can be readily dissolved in organic solvents, yet it is practically insoluble in water [5]. Poor solubility in water severely hampers investigation of physiological and pharmacological effects of C60 fullerene. As a consequence, a number of C60 fullerene derivatives with better solubility in polar solvents have been synthesized to date [5–6]. Pristine C60 fullerene aqueous solution (С60FAS) has been received by transferring C60 molecules from toluene to water followed by sonication [7–8]. The dark brown solution was identified to be a typical colloid system containing a single C60 molecule and spherical clusters with the diameter of 2–3 nm or more (depending on the C60 fullerene concentration in water) in a hydrated state [7–9]. Due to its nanoscale dimensions, the watersoluble pristine C60 fullerene can penetrate the cell membrane [10]. Toxicity is a major concern for the use of C60 fullerene-containing drugs for biomedical УДК 546.26.043

Interaction of Fullerene Nanoparticles With Biomembranes: From the Partition in Lipid Membranes to Effects on Mitochondrial Bioenergetics

Partition and localization of C60 and its derivative C60(OH)18-22 in lipid membranes and their impact on mitochondrial activity were studied, attempting to correlate those events with fullerene characteristics (size, surface chemistry, and surface charge). Fluorescence quenching studies suggested that C60(OH)18-22 preferentially populated the outer regions of the bilayer, whereas C60 preferred to localize in deeper regions of the bilayer. Partition coefficient values indicated that C60 exhibited higher affinity for dipalmitoylphosphatidylcholine and mitochondrial membranes than C60(OH)18-22. Both fullerenes affected the mitochondrial function, but the inhibitory effects promoted by C60 were more pronounced than those induced by C60(OH)18-22 (up to 20 nmol/mg of mitochondrial protein). State 3 and p-trifluoromethoxyphenylhydrazone-uncoupled respirations are inhibited by both fullerenes when glutamate/malate or succinate was used as substrate. Phosphorylation system and electron transport chain of mitochondria are affected by both fullerenes, but only C60 increased the inner mitochondrial membrane permeability to protons, suggesting perturbations in the structure and dynamics of that membrane. At concentrations of C60(OH)18-22 above 20 nmol/mg of mitochondrial protein, the activity of FoF1-ATP synthase was also decreased. The evaluation of transmembrane potential showed that the mitochondria phosphorylation cycle decreased upon adenosine diphosphate addition with increasing fullerenes concentration and the time of the repolarization phase increased as a function of C60(OH)18-22 concentration. Our results suggest that the balance between hydrophilicity and hydrophobicity resulting from the surface chemistry of fullerene nanoparticles, rather than the cluster size or the surface charge acquired by fullerenes in water, influences their membrane interactions and consequently their effects on mitochondrial bioenergetics.

Revealing the Active Layer Morphology within Complete Solar Cell Devices via Spectroscopic Ellipsometry

We used spectroscopic ellipsometry to simultaneously reveal the distribution of the fullerene component, as well as the formation of higher ordered polymer domains, within the active layer of organic solar cells. In contrast to other measurement techniques, both informations can be obtained nondestructively on postcathode annealed encapsulated solar cell devices. We observe a preferential attraction of [6,6]-phenyl-C61-butyric acid methyl ester toward the aluminum cathode, which is consistent with simple energetic considerations based on the estimated free surface energy of the cathode. Because of the increased nucleation rate in regions with high fullerene concentration and at the interfaces, we observed a reduction of the average domain size of ordered poly(3-hexylthiophene) regions in these areas, which manifests itself in a reduction of the volume fraction of highly ordered polymer domains.