Photoelectrochemical immunoassay of interleukin-6 based on covalent reaction-triggered photocurrent polarity switching of ZnO@fullerenol.

We report here a novel photocurrent polarity switching strategy for a photoelectrochemical immunoassay driven by the covalent reaction between fullerenol (COH) and chloranilic acid (CA). The sensitive detection of interleukin-6 is achieved by using CA-encapsulated liposome as the label and COH-coated ZnO as the photoactive material, with a detection limit of 1.0 fg mL-1.

Aggregation behavior of aqu/nC60 produced via extended mixing: Influence of sunlight and agitation intensity.

Aggregation of C60, as an important process governing its mobility and toxicity, has been quantitatively investigated. However, effects of sunlight and agitation intensity on the aggregation behavior of aqu/nC60 produced via extended mixing, have not been clarified. Therefore, in the present study, the aggregation behavior of aqu/nC60 produced at 500 and 800 rpm in the absence and presence of sunlight was investigated. Aggregation with increasing concentrations could be accelerated, while changes of Zave and zeta potential were not obvious. Critical coagulation concentrations (CCCs) of aqu/nC60 obtained at 800 rpm in the absence/presence of sunlight and that at 500 rpm under sunlight were 330, 205 and 170 mM NaCl, and 10.0, 2.6 and 3.1 mM CaCl2, respectively. These CCCs indicated that the aqu/nC60 prepared by the extended mixing were more stable than those produced by other methods. Salt-induced aggregation occurred more easily for aqu/nC60 formed under sunlight than that formed in the dark. Extra surface oxidation induced by high agitation intensity remarkably increased the stability of aqu/nC60 in NaCl solutions. In contrast, in CaCl2 solutions, aqu/nC60 formed at high agitation intensity had similar stability or even inadequate stability to that obtained at low agitation intensity due to the charge neutralization and cross-link bridging.

Simultaneous Unlocking Optoelectronic and Interfacial Properties of C60 for Ultrasensitive Immunosensing by Coupling to Metal-Organic Framework.

Due to exceptional electron-accepting ability, light-absorption, and a delocalized conjugated structure, buckminsterfullerene (C60) has attracted fascinating interest in the field of organic solar cells. However, poor delocalization and accumulation of electrons for pristine C60 in physiological aqueous solution and difficulties in conjugation with biomolecules limit its extended photovoltaic applications in bioassay. Herein, we reported the noncovalent coupling of C60 to an electronically complementary porphyrin-derived metal-organic framework (PCN-224) with carboxyl-group terminals. Such assembly not only offered a friendly interface for bioconjugation but also resulted in a long-range ordering C60@PCN-224 donor-acceptor system that demonstrated an unprecedented photocurrent enhancement up to 10 times with respect to each component. As an example, by further cooperating with Nanobodies, the as-prepared C60@PCN-224 was applied to a photoelectrochemical (PEC) immunosensor for S100 calcium-binding protein B with by far the most promising detection activities. This work may open a new venue to unlock the great potential of C60 in PEC biosensing with excellent performances.

Monitoring of Low-Intensity Exposures via Luminescent Bioassays of Different Complexity: Cells, Enzyme Reactions, and Fluorescent Proteins.

The current paper reviews the applications of luminescence bioassays for monitoring the results of low-intensity exposures which produce a stimulative effect. The impacts of radioactivity of different types (alpha, beta, and gamma) and bioactive compounds (humic substances and fullerenols) are under consideration. Bioassays based on luminous marine bacteria, their enzymes, and fluorescent coelenteramide-containing proteins were used to compare the results of the low-intensity exposures at the cellular, biochemical, and physicochemical levels, respectively. High rates of luminescence response can provide (1) a proper number of experimental results under comparable conditions and, therefore, proper statistical processing, with this being highly important for "noisy" low-intensity exposures; and (2) non-genetic, i.e., biochemical and physicochemical mechanisms of cellular response for short-term exposures. The results of cellular exposures were discussed in terms of the hormesis concept, which implies low-dose stimulation and high-dose inhibition of physiological functions. Dependencies of the luminescence response on the exposure time or intensity (radionuclide concentration/gamma radiation dose rate, concentration of the bioactive compounds) were analyzed and compared for bioassays of different organization levels.

Chemical compass behaviour at microtesla magnetic fields strengthens the radical pair hypothesis of avian magnetoreception.

The fact that many animals, including migratory birds, use the Earth's magnetic field for orientation and compass-navigation is fascinating and puzzling in equal measure. The physical origin of these phenomena has not yet been fully understood, but arguably the most likely hypothesis is based on the radical pair mechanism (RPM). Whilst the theoretical framework of the RPM is well-established, most experimental investigations have been conducted at fields several orders of magnitude stronger than the Earth's. Here we use transient absorption spectroscopy to demonstrate a pronounced orientation-dependence of the magnetic field response of a molecular triad system in the field region relevant to avian magnetoreception. The chemical compass response exhibits the properties of an inclination compass as found in migratory birds. The results underline the feasibility of a radical pair based avian compass and also provide further guidelines for the design and operation of exploitable chemical compass systems.

Fullerene Radiolysis in Astrophysical Ice Analogs: A Mass Spectrometric Study of the Products.

The γ-radiolysis of fullerenes (C60 and C70) was performed to investigate the role of fullerenes as a carbon source in building organic molecules in astrophysical ice analog media. Mass spectrometric analyses and the sequential collision-induced dissociation processes enabled us to determine the plausible chemical structure of new products originated during γ-irradiation of fullerenes. The radiolytic products are grouped into six principal compound families. We assessed the relative yield, as percentage, for each new radiolytic compound, and designed the reaction schemes that lead to γ-irradiation products. The reactions start with the formation of primary radicals due to the radiolysis of solvents that react with the fullerenes' structures, forming fullerene radical adducts. The fate of these fullerene radical adducts depends on two factors: (i) the nature of radicals formed by irradiation of solvents and consequently by their ability to give secondary reactions, (ii) whether the onset of thermalization energy processes occurs or does not occur. Here, we present the results regarding the fragmentation processes that lead to functionalized carbonaceous chains characterized by lower molecular weight. We identify the chemical nature of functionalized chain products, propose the reaction schemes, and quantify their relative yields.

C60@C3N4 nanocomposites as quencher for signal-off photoelectrochemical aptasensor with Au nanoparticle decorated perylene tetracarboxylic acid as platform.

Herein, a novel signal-off photoelectrochemical (PEC) aptasensor was proposed for sensitive detection of thrombin on the basis of C60@C3N4 nanocomposites as quencher and Au nanoparticles (depAu) decorated perylene tetracarboxylic acid (PTCA) as sensing platform. Owing to the excellent membrane-forming of PTCA and superior conductivity of depAu, the PTCA between two depAu layers can simply and effectively produce an extremely high initial photocurrent to afford a precondition for sensitive biodetection. Thereafter, the assembly of C60@C3N4 nanocomposites on electrode via typical sandwich reaction enabled the generation of a significantly decreased photocurrent. Here, the C3N4 with high surface area not only provided massive binding sites for C60 immobilization, but also partly competed with PTCA in light absorption for producing a significantly smaller photocurrent in the presence of electron donor ascorbic acid (AA). Additionally, both the C3N4 and C60 have the poor conductivity, which could inhibit the electron transfer to achieve a further decreased photocurrent, effectively improving the sensitivity of proposed biosensor. As a result, the PEC biosensor in a "signal-off" mode showed an extremely low detection limit down to 1.5 fM, providing a sensitive and universal strategy for protein detection.

Incubation of solid state C60 fullerene under UV irradiation mimicking environmentally relevant conditions.

Carbon-based nanomaterials, such as C60 fullerenes, are expected to accumulate in soil due to direct release and deposition from the atmosphere. However, little is known about the environmental fate of these nanoparticles which may be susceptible to photochemical and microbial degradation. In the present work, C60 was incubated for a period of 28 days and irradiated with UVA light. Three experiments were carried out where the fullerenes were either spiked onto a glass surface or added to quartz sand or sandy soil samples. At specific time intervals the samples were extracted and analysed by liquid chromatography coupled to UV or high resolution mass spectrometric (HRMS) detection. The fullerenes were degraded in all the treatments and the decay followed a pseudo-first-order rate law. In absence of a solid matrix, the half-life (t1/2) of the C60 was 13.1 days, with an overall degradation of 45.1% that was accompanied by the formation of functionalized C60-like structures. Furthermore, mass spectrometric analysis highlighted the presence of a large number of transformation products that were not directly related to the irradiation and presented opened cage and oxidized structures. When C60 was spiked into solid matrices the degradation occurred at a faster rate (t1/2 of 4.5 and 0.8 days for quartz sand and sandy soil, respectively). Minor but consistent losses were found in the non-irradiated samples, presumably due to biotic or chemical processes occurring in these samples. The results of this study suggest that light-mediated transformation of the fullerenes will occur in the environment.

Increased Photovoltaic Performance in Polymer-Oligothiophene-[6,6]-Phenyl-C61 -Butyric Acid Methylester Ternary Blend Films.

The introduction of oligothiophenes (b-5T and b-5TB) improved the performance of F85TB:PCBM bulk heterojunction OPV cells due to improved UV-vis absorption and the well-matched cascade energy levels between components.

Multi-functional liposomes showing radiofrequency-triggered release and magnetic resonance imaging for tumor multi-mechanism therapy.

Recently, nanoplatforms with multiple functions, such as tumor-targeting drug carriers, MRI, optical imaging, thermal therapy etc., have become popular in the field of cancer research. The present study reports a novel multi-functional liposome for cancer theranostics. A dual targeted drug delivery with radiofrequency-triggered drug release and imaging based on the magnetic field influence was used advantageously for tumor multi-mechanism therapy. In this system, the surface of fullerene (C60) was decorated with iron oxide nanoparticles, and PEGylation formed a hybrid nanosystem (C60-Fe3O4-PEG2000). Thermosensitive liposomes (dipalmitoylphosphatidylcholine, DPPC) with DSPE-PEG2000-folate wrapped up the hybrid nanosystem and docetaxel (DTX), which were designed to combine features of biological and physical (magnetic) drug targeting for fullerene radiofrequency-triggered drug release. The magnetic liposomes not only served as powerful tumor diagnostic magnetic resonance imaging (MRI) contrast agents, but also as powerful agents for photothermal ablation of tumors. Furthermore, a remarkable thermal therapy combined chemotherapy multi-functional liposome nanoplatform converted radiofrequency energy into thermal energy to release drugs from thermosensitive liposomes, which was also observed during both in vitro and in vivo treatment. The multi-functional liposomes also could selectively kill cancer cells in highly localized regions via their excellent active tumor targeting and magnetic targeted abilities.

Leveraging electrokinetics for the active control of dendritic fullerene-1 release across a nanochannel membrane.

General adoption of advanced treatment protocols such as chronotherapy will hinge on progress in drug delivery technologies that provide precise temporal control of therapeutic release. Such innovation is also crucial to future medicine approaches such as telemedicine. Here we present a nanofluidic membrane technology capable of achieving active and tunable control of molecular transport through nanofluidic channels. Control was achieved through application of an electric field between two platinum electrodes positioned on either surface of a 5.7 nm nanochannel membrane designed for zero-order drug delivery. Two electrode configurations were tested: laser-cut foils and electron beam deposited thin-films, configurations capable of operating at low voltage (≤1.5 V), and power (100 nW). Temporal, reproducible tuning and interruption of dendritic fullerene 1 (DF-1) transport was demonstrated over multi-day release experiments. Conductance tests showed limiting currents in the low applied potential range, implying ionic concentration polarization (ICP) at the interface between the membrane's micro- and nanochannels, even in concentrated solutions (≤1 M NaCl). The ability of this nanotechnology platform to facilitate controlled delivery of molecules and particles has broad applicability to next-generation therapeutics for numerous pathologies, including autoimmune diseases, circadian dysfunction, pain, and stress, among others.

Synergistic photogeneration of reactive oxygen species by dissolved organic matter and C60 in aqueous phase.

We investigated the photogeneration of reactive oxygen species (ROS) by C60 under UV irradiation, when humic acid (HA) or fulvic acid (FA) is present. When C60 and dissolved organic matter (DOM) were present as a mixture, singlet oxygen ((1)O2) generation concentrations were 1.2­1.5 times higher than the sum of (1)O2 concentrations that were produced when C60 and DOM were present in water by themselves. When C60 and HA were present as a mixture, superoxide radicals (O2(•­)) were 2.2­2.6 times more than when C60 and HA were present in water by themselves. A synergistic ROS photogeneration mechanism involved in energy and electron transfer between DOM and C60 was proposed. Enhanced (1)O2 generation in the mixtures was partly due to (3)DOM* energy transfer to O2. However, it was mostly due to (3)DOM* energy transfer to C60 producing (3)C60*. (3)C60* has a prolonged lifetime (>4 µs) in the mixture and provides sufficient time for energy transfer to O2, which produces (1)O2. The enhanced O2(•­) generation for HA/C60 mixture was because (3)C60* mediated electron transfer from photoionized HA to O2. This study demonstrates the importance of considering DOM when investigating ROS production by C60.

Fullerene derivatives as electron acceptors for organic photovoltaic cells.

Energy is currently one of the most important problems humankind faces. Depletion of traditional energy sources such as coal and oil results in the need to develop new ways to create, transport, and store electricity. In this regard, the sun, which can be considered as a giant nuclear fusion reactor, represents the most powerful source of energy available in our solar system. For photovoltaic cells to gain widespread acceptance as a source of clean and renewable energy, the cost per watt of solar energy must be decreased. Organic photovoltaic cells, developed in the past two decades, have potential as alternatives to traditional inorganic semiconductor photovoltaic cells, which suffer from high environmental pollution and energy consumption during production. Organic photovoltaic cells are composed of a blended film of a conjugated-polymer donor and a soluble fullerene-derivative acceptor sandwiched between a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)-coated indium tin oxide positive electrode and a low-work-function metal negative electrode. Considerable research efforts aim at designing and synthesizing novel fullerene derivatives as electron acceptors with up-raised lowest unoccupied molecular orbital energy, better light-harvesting properties, higher electron mobility, and better miscibility with the polymer donor for improving the power conversion efficiency of the organic photovoltaic cells. In this paper, we systematically review novel fullerene acceptors synthesized through chemical modification for enhancing the photovoltaic performance by increasing open-circuit voltage, short-circuit current, and fill factor, which determine the performance of organic photovoltaic cells.

Solvent-assisted self-assembly of fullerene into single-crystal ultrathin microribbons as highly sensitive UV-visible photodetectors.

The size, shape, and crystallinity of organic nanostructures play an important role in their physical properties and are mainly determined by the self-assembling kinetics of molecular components often involving the solvent conditions. Here, we reported a kinetically controlled self-assembly of C60 assisted by the solvent carbon bisulfide (CS2) into single-crystal ultrathin microribbons of 2C60·3CS2, upon mixing the poor solvent isopropyl alcohol with a C60/CS2 stock solution. Surface energy calculations reveal that these microribbons represent a kinetically favored high-energy state as compared with the thermodynamically stable shape of prismatic rods. High-resolution transmission electron microscopy observations clarify that association of CS2 at the nucleation stage helps to guide and rigidify the formation of π-π stacking 1D chains of C60 through the surrounding CS2 cage-like structures, which further act as glue, boosting lateral assembly of as-formed 1D chains into untrathin 2D microribbon single crystals. Precise control over the thickness, width, and length of 2C60·3CS2 microribbons was achieved by manipulation of the growth kinetics through adjusting the solvent conditions. Upon heating to 120 °C, sublimation of CS2 components results in fcc C60 microribbons. We found that both microribbons of solvated monoclinic 2C60·3CS2 and pure fcc C60 exhibit highly sensitive photoconductivity properties with a spectral response range covering UV to visible. The highest on/off ratio of two-terminal photodetectors based on single ribbons reaches around 250, while the responsitivity is about 75.3 A W(-1) in the UV region and 90.4 A W(-1) in the visible region.

Multi adducts of diphenylmethanofullerenes as electron acceptors for polymer solar cells: a quantum chemical study.

In the present study, quantum chemical methods were applied to investigate the energy levels of the frontier orbital of mono and multi adducts of diphenylmethanofullerenes (DPMs). Recently these molecules have been used as electron acceptors in polymer solar cells showing interesting properties compared to the widely used [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM). The geometries of all the investigated compounds were optimized with the density functional theory at the B3LYP/3-21G level of calculation. We studied the effect of electron-donating (methoxy and methyl thioether) and electron-withdrawing (fluorine) substituents (placed on the diphenylmethano addend in ortho, meta and para position of the phenyl rings), on the lowest unoccupied molecular orbital (LUMO) level of DPM. Afterward, we analysed all the possible isomers arising from bis and tris additions to fullerene cage. The LUMO level is significantly raised compared to the mono adduct but different isomers have different LUMO levels. Since the open circuit voltage (V(oc)) for polymer solar cells with ohmic contacts is proportional to the difference between the highest occupied molecular orbital (HOMO) of the donor polymer and the LUMO of the acceptor (fullerene), these bisadducts have the potential to increase the V(oc) of the corresponding devices.

Synthesis and characterization of novel soluble fulleropyrrolidine derivatives and their photovoltaic performance.

Currently, [60] fullerene derivatives are the focus of considerable research due to their important roles in many fields, especially material science. In this study, we synthesized the following two novel fulleropyrrolidine derivatives: C60-fused N-methyl-(4-hexyloxybenzen-2-yl) pyrrolidine, (p-HOPF) and C60-fused N-methyl-(2-hexyloxybenzen-2-yl) pyrrolidine, (o-HOPF). Structural assignments of the two fullerene derivatives were made through 1H NMR and FAB-MS. We also measured the optical and electrochemical properties of p-HOPF and o-HOPF through UV/Vis spectrophotometry and cyclic voltammetry. We found that the difference in the position of the alkoxyl substituent on the phenyl ring greatly affects the characteristics of the molecules. In particular, from the 1H NMR spectrum, we found that the hydrogen atoms on the carbons adjacent to the oxygens in p-HOPF and o-HOPF have completely different chemical environments. In order to study the effects of the substituent group positions on photovoltaic performance, photovoltaic devices were fabricated. The highest power conversion efficiency, 0.71%, was achieved when using o-HOPF as the electron acceptor.

Thermal annealing effect on poly(3-hexylthiophene): fullerene:copper-phthalocyanine ternary photoactive layer.

We have fabricated poly(3-hexylthiophene) (P3HT)/copper phthalocyanine (CuPc)/fullerene (C60) ternary blend films. This photoactive layer is sandwiched between an indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT/PSS) photoanode and a bathocuproine (BCP)/aluminium photocathode. The thin films have been characterized by atomic force microscope (AFM) and ultraviolet/visible spectroscopy in order to study the influence of P3HT doping on the morphological and optical properties of the photoactive layer. We have also compared the I-V characteristics of three different organic solar cells: ITO/PEDOT:PSS/CuPc0.5:C600.5/BCP/Al and ITO/PEDOT:PSS/P3HT0.3:CuPc0.3:C600.4/BCP/Al with and without annealing. Both structures show good photovoltaic behaviour. Indeed, the incorporation of P3HT into CuPc:C60 thin film improves all the photovoltaic characteristics. We have also seen that thermal annealing significantly improves the optical absorption ability and stabilizes the organic solar cells making it more robust to chemical degradation.

How redox conditions and irradiation affect sorption of PAHs by dispersed fullerenes (nC60).

Surface properties, dispersion state, and sorption behavior of carbon-based nanomaterials will change after being released into the environment. To study these processes, five different scenarios were considered to probe the impact of changes in surface properties of dispersed fullerenes (nC60) on their sorption potential due to irradiation and presence of oxygen. Sorption isotherms of pyrene by nC60 were determined at environmentally relevant concentrations applying a passive sampling method. Isotherms of all dispersion scenarios were best fit with the Dubinin-Ashthakov model. Sorption was strongest for nC60 kept under anoxic condition. Both the presence of oxygen and irradiation significantly decreased the sorption capacity of nC60, while commercially available polyhydroxy fullerenes had the smallest sorption. In addition, competition for sorption sites was never observed in multiple sorbate experiments with four polycyclic aromatic hydrocarbons at small concentration. A strong relationship between sorption coefficients and hydrophobic properties of sorbates suggests that hydrophobic interactions are of major importance. The results emphasize that aging of released fullerenes results in a reduced strength of interactions with nonpolar compounds and, thus, reduces the impact on the environmental transport of hydrophobic pollutants.

Effects of alkoxy chain length in alkoxy-substituted dihydronaphthyl-based [60]fullerene bisadduct acceptors on their photovoltaic properties.

A series of alkoxy-substituted dihydronaphthyl-based [60]fullerene bisadduct derivatives (Cn-NCBA, n = 1-6), with the alkoxy chain length from 1 to 6 carbon atoms, were synthesized as acceptors for polymer solar cells (PSCs), for the purpose of systematically investigating the effects of fullerene derivative structures on the photovoltaic properties of PSCs. Although the absorption spectra and electrochemical properties of Cn-NCBA are almost the same, the PSCs based on P3HT:Cn-NCBA showed different photovoltaic properties. The device based on the P3HT:C3-NCBA blend demonstrated the highest power-conversion efficiency (PCE) of ca. 4.1%, while those with shorter or longer alkoxy-substituted dihydronaphthyl-based [60]fullerene bisadduct derivatives showed relatively lower PCE values. C5-NCBA and C6-NCBA with longer alkoxy chain length showed relatively low electron mobilities, leading to relatively poor photovoltaic performance. More importantly, we found that the alkoxy chain length changes the hydrophobicity of Cn-NCBA and, thus, the interfacial interaction and miscibility with P3HT, which were analyzed by interfacial tension and atomic force microscopy (AFM) measurements. The hydrophobicity of Cn-NCBA increased as the alkoxy chain length increased. A distinct phase separation for the P3HT:C1-NCBA blend film due to the large interfacial tension and poor miscibility between P3HT and C1-NCBA could be one reason for the low PCE value of the C1-NCBA-based devices. C3-NCBA may provide the most appropriate combination of electron mobility and miscibility with P3HT to achieve optimal photovoltaic properties. The current study provides the molecular structure-device performance relationship, especially with respect to the alkoxy chain length of Cn-NCBA and their interfacial interactions with P3HT, and suggests a design rule for high-performance fullerene bisadduct acceptors for PSC applications.

[60]Fulleropyrrolidines bearing π-conjugated moiety for polymer solar cells: contribution of the chromophoric substituent on C60 to the photocurrent.

Two fullerene-terthiophene dyads without hexyl chains (3T-C60) and with hexyl chains (3TH-C60) on the terthiophene substituent are synthesized by 1,3-dipolar cycloaddition of corresponding azomethine ylides to C60. The cyclic voltammetry studies indicate no apparent electronic communication between the terthiophene pendent group and the fulleropyrrolidine core in the ground state. However, a significant florescence quenching is observed for 3T-C60 and 3TH-C60, compared to their fluorescent terthiophene (3T) and 3TH precursors, respectively, suggesting the occurrence of strong intramolecular electron/energy transfers in the photoexcited state. Furthermore, these new fulleropyrrolidine derivatives are applied as electron acceptors to fabricate poly(3-hexylthiophene) (P3HT) based bulk heterojunction solar cells. The incident photon-to-current efficiency (IPCE) value of the P3HT/3T-C60 device is significantly higher than that of the P3HT/PCBM cell in wavelengths of 350-420 nm. This finding provides direct evidence for the contribution of 3T excitons to the photocurrent. Replacing 3T-C60 with 3TH-C60 effectively improves the morphology of the photoactive layer and widens the window of optimal D/A ratios, raising the power conversion efficiency (PCE) from 2.14% to 2.54%. Importantly, these devices exhibit superior stability of PCE against high-temperature aging.