Solutions Of C60 In Toluene Research Articles

The Study of the Optical Properties of C60 Fullerene in Different Organic Solvents

AbstractC60 fullerene exhibits unique optical properties that have high potential for wide photo-optical applications. To analyze the optical properties of C60, its excitation and emission properties were studied using UV-Vis absorption and photoluminescence (PL) spectroscopy, which were performed in various, non-polar organic solvents such as toluene, xylene, and trichloroethylene (TCE). The C60 solutions in toluene, xylene, and TCE displayed similar excitation bands at 625, 591, 570, 535, and 404 nm corresponding to Ag → T1u and Ag → T1g transitions. However, these bands differed from the solid C60 observed by UV-Vis diffuse reflectance spectroscopy. The two emission band energies of C 60 solution in toluene and xylene were nearly the same (1.78 and 1.69 eV), whereas the C60 solution in TCE was shifted to 1.72 and 1.65 eV. Because the polarity of TCE is higher than that of toluene and xylene, the PL spectrum of the C 60 solution in TCE was red-shifted. The PL spectroscopy had a better capability than UV-Vis absorbance spectroscopy to distinguish the different interactions between C60 and the organic solvents due to their different solvent polarities.

Synthesis of bipyramidal gold nanoparticle-[C60]fullerene nanowhisker composites and catalytic reduction of 4-nitrophenol

ABSTRACTThe seed solution was prepared by dissolving hydrogen tetrachloroaurate(III) trihydrate (HAuCl4·3H2O), trisodium citrate dihydrate (C6H5Na3O7·2H2O), and sodium borohydride (NaBH4) in distilled water. The resulting reddish-purple seed solution was stirred for 3 h at room temperature. The growth solution was prepared by mixing hydrogen tetrachloroaurate(III) trihydrate (HAuCl4·3H2O), cetyltrimethylammonium bromide (CTAB, (C16H33)N(CH3)3Br), silver nitrate (AgNO3), hydrochloric acid (HCl), and ascorbic acid (C6H8O6) in distilled water. Subsequently, 100 μL of this seed solution was transferred into 10 mL of the growth solution. The mixed solution was maintained at 30 °C for 3 h to obtain a solution of bipyramidal gold nanoparticles. The bipyramidal gold nanoparticle-[C60] fullerene nanowhisker composites were synthesized by applying the liquid-liquid interfacial precipitation (LLIP) method to a saturated solution of C60 in toluene, the solution of bipyramidal gold nanoparticles, and isopropyl alcohol. The prepared bipyramidal gold nanoparticle-[C60] fullerene nanowhisker composites were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The catalytic activity of these composites was confirmed in the reduction of 4-nitrophenol by UV-Vis spectroscopy.

Formation of new hybrid structures: Fullerene C60–amphiphilic copolymer of N-vinylpyrrolidone with (di)methacrylates in isopropyl alcohol

New hybrid structures of fullerene C60 and an amphiphilic copolymer of N-vinylpyrrolidone with lauryl methacrylate and triethylene glycol dimethacrylate have been obtained via solubilization of fullerene by individual macromolecules and their micelle-like aggregates that form in isopropyl alcohol. The volume ratios of copolymer and C60 solutions in toluene at which there is suppression of aggregation of fullerene and fullerene–polymer particles and the existence of stable hybrid structures in solution have been found. With the use of absorption electron spectroscopy, it has been shown that, with time, fullerene undergoes binding to donor groups of the copolymer and forms a donor–acceptor complex. According to the data of optical microscopy, fullerene is homogeneously distributed as spherical aggregates in the solid polymer matrix.

Preparation of colloidal dispersions of C60 fullerene

Stable aqueous colloidal dispersions of C60 fullerene free of organic solvents are prepared. A solvatochromic effect is revealed upon adding C60 solutions in toluene and chlorobenzene to a water-acetone mixture.

Two-Terminal Molecular Memories from Solution-Deposited C60 Films in Vertical Silicon Nanogaps

We demonstrate here two-terminal, charge-based memory from C60 films inside vertical 7 nm silicon nanogap devices. This testbed structure eliminated the possibility of metal migration in the nanostructure because the two electrodes are made solely of silicon; hence, the often troublesome and confusing possibility of filamentary metal formation is obviated. Saturated solutions of C60 in toluene, mesitylene, and 1-methylnaphthalene were each used to deposit these films at elevated temperatures. Electrical I-V measurements reveal a high yield (67%) of devices demonstrating bipolar, switchable hysteresis from both the mesitylene- and 1-methylnaphthalene-deposited devices, while the toluene-grafted devices display no such behavior. Pulse-based memory measurements of switching devices indicate high ON/OFF ratios (maximum approximately 1500), good stability (>100 cycles without device degradation) for molecular devices, and low operating currents (approximately 10(-11) A) in room temperature testing.

Effect of ultrasound treatment of C60 solutions on the crystalline structure of precipitated fullerite

The structure of fullerite precipitated from solutions of C60 in toluene, chlorobenzene, and 1,2-dichlorobenzene by adding isopropanol was studied. It was demonstrated that, irrespective of the nature of the solvent, the parameter of the fcc lattice of precipitated fullerite decreases markedly when the process occurs in the presence of a ultrasound field. No effect of ultrasound sonication on the size of the precipitated crystallites was observed.

On the Supermolecular Structure of Fullerene C60 Solutions

Small angle X‐ray scattering (SAXS) and wide angle X‐ray scattering (WAXS) techniques were used for investigation of fullerene C60 solutions in toluene and p‐xylene. On all SAXS curves, intensity decreases to some constant value of IC with increase of scattering angle. The value of IC depends on concentration non‐monotonically: it first slightly increases, then drops sharply to some minimal value, and then increases again. A qualitative explanation of such dependence is offered. It is supposed that the presence of fullerene C60 in solution suppresses thermal fluctuations of density in the solvent. In combination with the X‐ray data the results obtained for solutions of fullerene C60 by various others techniques (calorimetry, densimetry, etc.) are discussed. Possible models of a supermolecular structure of fullerene C60 solutions in good solvents are considered.

Chemiluminescence in Ozonolysis of Solutions of Fullerene C 60

We have discovered and studied chemiluminescence in ozone‐oxidation of the solutions of C60 in toluene, benzene, methylnaphthalene, tetrachloroethane, and CCl4 and photoluminescence of the products of ozonolysis. Irrespective of the nature of a solvent, the chemiluminescence and photoluminescence are attributed to radiation (λmax = 660 nm at maximum brightness of luminescence) of fullerene polyketones O=C60=[O] m (m = 1–19). The visually observed fluorescence of polyketones is much brighter than the well‐known fluorescence of C60 and of the majority of its derivatives. A hypsochromic shift of the maxima of the chemiluminescence spectra with increase in the time of ozonolysis is discovered, which is associated with decrease in the effect of the system of conjugated C=C bonds of the skeleton of C60 on radiating chromophore C=O*. Reactions with participation of oxofullerencarbonyloxide, i.e., intermediates of the ozonolysis of fullerene, are presumed as luminous stages of chemiluminescence.

UNSTABLE PRODUCTS FROM THE OZONATION OF C60 IN SOLVENTS

The ozonation of a solution of C60 in toluene results in the formation of several unstable compounds C60X and C60Y[1–5] which decay completely at room temperature within about 1 h. The products are oxides C60O[6,6], C60O2[I], C60O2[II], and possibly an isomer of C60O3. The transformations are not due to oxidation by atmospheric oxygen but are spontaneous. The ozonation of a solution of C60O[6,6] in toluene results in the formation of two unstable compounds C60Z[1–2] which also decay completely to C60O2[I] and C60O2[II]. It is suggested that all unstable “parents” are ozonides.

Calorimetric Studies of Solvates of C60 and C70 with Aromatic Solvents

To improve the understanding of the solution properties of C60 and C70 in aromatic solvents, binary systems of C60 and C70 with benzene, toluene, 1,2- and 1,3-dimethylbenzene, 1,2,4- and 1,3,5-trimethylbenzene, bromobenzene, and 1,2- and 1,3-dichlorobenzene were studied using differential scanning calorimetry, solution calorimetry, and thermogravimetry. Solid solvates with different compositions were identified in many of the systems. The solvates were characterized by composition and by the temperature and the enthalpy of the incongruent melting transition. Enthalpies of solution of C60 in toluene, 1,2-dimethylbenzene, 1,2- and 1,3-dichlorobenzene, and 1,2,4-trimethylbenzene and of C70 in 1,2-dimethylbenzene and in 1,2- and 1,3-dichlorobenzene were determined. The formation−incongruent melting of solid solvates causes maxima in the temperature−solubility curves of fullerenes in aromatic solvents. Trends in solubility behavior of fullerenes were discussed in terms of thermodynamics of solution and solvate formation.

Some Enthalpies of Solution of C60 and C70. Thermodynamics of the Temperature Dependence of Fullerene Solubility

The enthalpy of solution of C60 in toluene, carbon disulfide, decalin, and N,N-diethylaniline and of C70 in CS2 has been measured using an isoperibol solution calorimeter. Exothermic heats of solution are observed in all cases. The heat of solution of C60 in toluene is −8.6 ± 0.7 kJ mol-1; in carbon disulfide it is −20 ± 1 kJ mol-1. In decalin, slow dissolution prevents an accurate determination, but the heat of solution is less than −5 kJ mol-1. In N,N-diethylaniline, a fast exothermic step comparable to that observed in other systems is followed by a much larger heat evolution, implying that a chemical reaction is occurring. The heat of solution of C70 in CS2 is −9 ± 1 kJ mol-1. A thermodynamic theory of the temperature dependence of fullerene solubility is presented. The central idea is that the unusual temperature dependence of the solubilities of fullerenes is caused by the formation of solvated crystals. Conditions are derived under which a temperature maximum of solubility, caused by an incongruent...

Surface tension of C60 solutions in toluene

The surface tensions of toluene and benzene solutions of C60 were measured as a function of temperature and concentration. C60 was found to be surprisingly surface active; at the largest concentration studied C60 occupied nearly a monolayer as indicated by the ‘‘occupied’’ surface diameter of 14 Å.