CHROMATOGRAPHIC PURIFICATION OF Kr@C60

Unusual compounds have been reported to form by the incorporation of atoms into fullerene cages. The compounds in which a noble gas atom is trapped into a C₆₀ cage are very stable and only van der Waals interactions occur between the noble gas and the fullerene cage. The study of these compounds requires efficient chromatographic (or other) separations. We performed the isolation of Kr@C₆₀ and a study of its chromatographic separations on several HPLC columns using toluene : hexane mixtures as solvent. We found that the separation factor is small (1.09 to 1.12) with the highest separation factor on a Buckyprep column.     

CHROMATOGRAPHIC PURIFICATION OF Kr@C60

Unusual compounds have been reported to form by the incorporation of atoms into fullerene cages. The compounds in which a noble gas atom is trapped into a C₆₀ cage are very stable and only van der Waals interactions occur between the noble gas and the fullerene cage. The study of these compounds requires efficient chromatographic (or other) separations. We performed the isolation of Kr@C₆₀ and a study of its chromatographic separations on several HPLC columns using toluene : hexane mixtures as solvent. We found that the separation factor is small (1.09 to 1.12) with the highest separation factor on a Buckyprep column.     

Poly(β-Styryl)-(1,2-Methanofullerene-C60)-61-Formo Hydroxamic Acid for the Solid Phase Extraction, Separation and Preconcentration of Rare Earth Elements

A new fullerene derivatives poly(β-styryl)-(12-methanofullerene-C₆₀)-61-formo hydroxamic acid has been synthesized and applied for the solid phase extraction, separation, preconcentration and ICP-MS determination of Ce, La, Pr, Nd, Sm and Gd. The introduction of the fullerene moiety into poly(β-styryl)-hydroxamic acid enhances its reactivity, chemical stability and recycled for their determination. The various parameter, viz. kinetics of sorption, breakthrough studies, effect of eluents, etc., have been studied. The influence of several diverse ions is also discussed. The proposed method has been applied for the sequential chromatographic separation of rare earths in the presence of each from rocks, monazite sand and in environmental samples.     

INFLUENCE OF DESIGN AND OPERATIONAL PARAMETERS ON YIELD OF FULLERENES

Fullerene production by arc-discharge method using graphite electrodes has been studied with respect to influence of different design and operational parameters on fullerene yield in a constant arc fullerene reactor. The design parameters like reactor length, diameter, heat transfer area and operational parameters like voltage, current, pressure, coolant flow rate, graphite evaporation rate and electrode diameter etc. have been experimentally studied in detail to establish a relationship between these parameters and fullerene yield. All the parameters affecting the yield have been correlated by dimensional analysis and an equation to calculate the fullerene yield is derived. It was observed experimentally as well as by dimensional analysis that many favorable parameters for getting good yield are linked with other parameters which also get changed if the favorable parameters are changed and thus it is difficult to make a substantial change in the yield of fullerenes.  The relationship established between the yield and parameters is however useful in optimising fullerene yield in a reactor and also helpful in designing a futuristic fullerene reactor of improved yield and productivity. The fullerene yield from different designs of reactors is obtained in the range of 4% to 20%.     

Poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene)(MEH-PPV) /Nitrogen Containing Derivatives of Fullerene Composites: Optical Characterization and Application in Flexible Polymer Solar Cells

New soluble organofullerenes were synthesized by the reaction of organic amines and azides with the [60]fullerene. The comparative investigations of the IR- and optical absorption spectra of blends MEH-PPV/fullerene derivative in solutions and in films showed no ground-state interaction between the components. Photoluminescence (PL) experiments, and photocurrent-voltage measurements were performed on model photovoltaic (PV) cells. We found that PL of MEH-PPV is completely quenched by a small admixture of fullerene derivative which assumes a high efficiency of charge separation in the composite material. The photocurrent in the PV device containing fullerene derivative is two orders of magnitude higher than that in pure MEH-PPV. An attempt to observe the magnetic field spin effect (MFSE) on the photocurrent in MEH-PPV/fullerene composites was made.     

Poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene)(MEH-PPV)/Nitrogen containing derivatives of fullerene composites: Optical characterization and application in flexible polymer solar cells

New soluble organofullerenes were synthesised by the reaction of organic amines and azides with the [60]fullerene. The comparative investigations of the IR- and optical absorption spectra of blends MEH-PPV/fullerene derivative in solutions and in films showed no ground-state interaction between the components. Photoluminescence (PL) experiments, and photocurrent-voltage measurements were performed on model photovoltaic (PV) cells. We found that PL of MEH-PPV is completely quenched by a small admixture of fullerene derivative which assumes a high efficiency of charge separation in the composite material. The photocurrent in the PV device containing fullerene derivative is two orders of magnitude higher than that in pure MEH-PPV. An attempt to observe the magnetic field spin effect (MFSE) on the photocurrent in MEH-PPV/fullerene composites was made.     

INFLUENCE OF DESIGN AND OPERATIONAL PARAMETERS ON YIELD OF FULLERENES

ABSTRACT

Fullerene production by arc-discharge method using graphite electrodes has been studied with respect to influence of different design and operational parameters on fullerene yield in a constant arc fullerene reactor. The design parameters like reactor length, diameter, heat transfer area and operational parameters like voltage, current, pressure, coolant flow rate, graphite evaporation rate and electrode diameter etc. have been experimentally studied in detail to establish a relationship between these parameters and fullerene yield. All the parameters affecting the yield have been correlated by dimensional analysis and an equation to calculate the fullerene yield is derived. It was observed experimentally as well as by dimensional analysis that many favorable parameters for getting good yield are linked with other parameters which also get changed if the favorable parameters are changed and thus it is difficult to make a substantial change in the yield of fullerenes. The relationship established between the yield and parameters is however useful in optimising fullerene yield in a reactor and also helpful in designing a futuristic fullerene reactor of improved yield and productivity. The fullerene yield from different designs of reactors is obtained in the range of 4% to 20%.     

Influence of the processing conditions on charge transfer and transport properties in poly(2-methoxy-5-(2′-ethylhexyloxy)1-4-phenylenevinylene):C60 composites for photovoltaics

Polymer-based photovoltaic devices have been elaborated by blending the conjugated polymer, poly(2-methoxy-5-(2′-ethylhexyloxy)1-4-phenylenevinylene) (MEH-PPV) with the buckminsterfullerene, C₆₀. The solvent used has a main influence on the optical and electrical properties of the photoactive layers. This could be attributed to different dispersion abilities of C₆₀ in the polymer layers shown by Atomic Force Microscopy and Scanning Electron Microscopy. Its effect on the transfer and transport properties has been studied. Thin film processing conditions have been modified by the preparation of blends of solutions of the polymer in Tetrahydrofuran and fullerene in Ortho-dichlorobenzene. The resulting spin casted layers show improved morphologies implying better dispersion of the fullerenes and increased short circuit currents. A decrease in the fullerene critical concentration to form percolation paths has been demonstrated. The improvement of the photovoltaic properties of the MEH-PPV/C₆₀ composites has been attributed to the nanosized fullerene domains formed upon phase separation. We used optical spectroscopy to study the charge transfer efficiency and electrical measurements to investigate charge transport properties in MEH-PPV:C₆₀.     

Comparative process analysis of fullerene production by the arc and the radio-frequency discharge methods

In this work, comparative analysis of processes in carbon arc and radio frequency (RF) plasma during fullerene synthesis has been presented. The kinetic model of fullerene formation developed earlier has been verified in both types of plasma reactors. The fullerene yield depended on carbon concentration, velocity of plasma flame and rotational temperature of C2 radicals predominantly. When mean rotational temperature of C2 radicals was 3000 K, the fullerene yield was the highest regardless of the type of used reactor. The zone of fullerene formation is larger significantly in RF plasma reactor compared to arc reactor.     

The significance of fullerene electron acceptors in organic solar cell photo-oxidation

Stability of organic solar cells requires development before their commercialisation is possible. This review will give a brief overview of organic solar cells and their stability, before focussing on the photochemical stability of the active layer. The photo-oxidation of the donor polymers will be looked at first which has been studied quite extensively and then fullerene electron acceptors, such as widely used phenyl-C61-butyric acid methyl ester, which has been considerably less studied. It has been shown that oxidation of the fullerene cage on phenyl-C61-butyric acid methyl ester results in oxides with a deeper lowest unoccupied molecular orbital (LUMO) level than the fresh electron acceptor. These oxides act as electron traps, leading to deterioration of the blend photoconductivity. The significance of fullerene photo-oxidation on device stability has been indirectly shown via research on: photoconductivity; organic solar cells made with an oxidised fullerene derivative and organic field effect transistors. Techniques that could be developed to increase photochemical stability of fullerene electron acceptor resistance to photo-oxidation include: reducing its LUMO level; increasing its crystallinity or aggregation and changing its chemical structure. Improving the photochemical stability of organic solar cells would move us one step closer to a more accessible solar power.     

A STUDY ON THE THERMAL STABILITY TO 1000°C OF VARIOUS CARBON ALLOTROPES AND CARBONACEOUS MATTER BOTH UNDER NITROGEN AND IN AIR

The thermal behavior of graphite, C₆₀ fullerene, fullerene black (carbon soot containing fullerenes), extracted fullerene black and diamond has been analyzed to 1000°C by TGA-DTA (thermogravimetric analysis and differential thermal analysis) under a nitrogen flow at a heating rate of 20°C/min. Very small weight losses have been recorded in the case of graphite and diamond. Furthermore no diamond graphitization has been observed. The sublimation of pure C₆₀ and the fullerene fraction of fullerene black (both pristine and extracted) has been observed and discussed.

The combustion reaction in air flow of graphite, C₆₀ and C₇₀ fullerenes, fullerene black (both unextracted and extracted), carbon nanotubes and diamond has been studied by TGA-DTA at a heating rate of 20°C/min. C₇₀ fullerene and fullerene black have been found to be the most reactive carbon materials with O₂. The role played by C₇₀ in the degradation of fullerites has been discussed. Among the carbon materials examined, the best resistance to O₂ attack has been shown by diamond and carbon nanotubes. The behavior of graphite is intermediate between diamond and fullerene blacks. The behavior of C₆₀ fullerene appears closer to that of graphite although it appears to be more reactive with O₂. Samples of graphite and carbon blacks N375 and N234 have been studied by TGA-DTA in air flow before and after a radiation treatment with neutrons or γ radiation. The effect of the radiation damage in the combustion reaction of these carbon materials has been discussed.     

用富勒烯残余烟灰制备炭分离膜的初步研究

以富勒烯残余烟灰为原料,采用粘结成型炭化法制备出炭分离膜,目的在于考察富勒烯残余烟灰的有效利用途径。实验结果表明,富勒烯残余烟灰可以用来制备炭分离膜,制备工艺条件对膜性能有较大影响。     

FORMATION OF FULLERENES AND CARBON CLUSTERS BY LASER IRRADIATION OF POLYMERIC FULLERENE OXIDE (FULLERENE OZOPOLYMER)

Polymeric fullerene oxide (PFO) prepared by prolonged ozonation of C₆₀ fullerene has been laser irradiated and the resulting products formed have been studied by ion cyclotron resonance mass spectrometry. It has been found that PFO produces a complete set of carbon clusters from C₆₀ up to C₁₆₄. The mechanism of formation of this set of fullerenic clusters implies necessarily a laser-induced carbonization step of the PFO substrate. Once the PFO target has been changed into the opportune carbon nanostructure by the laser radiation, the sequence of fullerene carbon clusters has been produced.     

Progress in Fullerene Chemistry: From Exohedral Functionalization to Heterofullerenes

Various types of cycloaddition such as [2+1], [2+3], and Diels-Alder reactions have been investigated for the purpose of exohedral functionalization of [60]fullerene and also in few cases of [70]fullerene. Thermal and photochemical activation have been used and lead to a variety of new fullerene derivatives which may be further functionalizable. In addition, a new approach to aza-heterofullerenes has been developed starting from an exohedrally activated fullerene.     

FORMATION OF FULLERENES AND CARBON CLUSTERS BY LASER IRRADIATION OF POLYMERIC FULLERENE OXIDE (FULLERENE OZOPOLYMER)

ABSTRACT

Polymeric fullerene oxide (PFO) prepared by prolonged ozonation of C₆₀ fullerene has been laser irradiated and the resulting products formed have been studied by ion cyclotron resonance mass spectrometry. It has been found that PFO produces a complete set of carbon clusters from C₆₀ up to C₁₆₄. The mechanism of formation of this set of fullerenic clusters implies necessarily a laser-induced carbonization step of the PFO substrate. Once the PFO target has been changed into the opportune carbon nanostructure by the laser radiation, the sequence of fullerene carbon clusters has been produced.     

Radiation-Induced Synthesis of Fullerene-Silica Hybrid Nanomaterials

C₆₀ fullerene has been radiation grafted on bare and functionalized silica surface with mercaptopropyl moieties in toluene solution. The resulting fullerene-silica hybrid nanomaterials have been characterized by FT-IR and solid state ¹³C CP-MAS NMR spectroscopy and compared to the radiolysis products of C₆₀ in toluene. It has been found that fullerene is grafted on silica surface but, because the radiation grafting has been conducted in toluene, fullerene results arylated from radicals derived from toluene radiolysis. The fullerene-silica hybrid nanomaterials cannot be extracted by warm decalin, demonstrating that the fullerene cage is chemically bonded on the silica surface. The thermal behavior of fullerene-silica hybrid nanomaterials has been studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA) in air flow.     

A STUDY ON THE THERMAL STABILITY TO 1000°C OF VARIOUS CARBON ALLOTROPES AND CARBONACEOUS MATTER BOTH UNDER NITROGEN AND IN AIR

ABSTRACT

The thermal behavior of graphite, C₆₀ fullerene, fullerene black (carbon soot containing fullerenes), extracted fullerene black and diamond has been analyzed to 1000°C by TGA–DTA (thermogravimetric analysis and differential thermal analysis) under a nitrogen flow at a heating rate of 20°C/min. Very small weight losses have been recorded in the case of graphite and diamond. Furthermore no diamond graphitization has been observed. The sublimation of pure C₆₀ and the fullerene fraction of fullerene black (both pristine and extracted) has been observed and discussed.

The combustion reaction in air flow of graphite, C₆₀ and C₇₀ fullerenes, fullerene black (both unextracted and extracted), carbon nanotubes and diamond has been studied by TGA–DTA at a heating rate of 20°C/min. C₇₀ fullerene and fullerene black have been found to be the most reactive carbon materials with O₂. The role played by C₇₀ in the degradation of fullerites has been discussed. Among the carbon materials examined, the best resistance to O₂ attack has been shown by diamond and carbon nanotubes. The behavior of graphite is intermediate between diamond and fullerene blacks. The behavior of C₆₀ fullerene appears closer to that of graphite although it appears to be more reactive with O₂. Samples of graphite and carbon blacks N375 and N234 have been studied by TGA–DTA in air flow before and after a radiation treatment with neutrons or γ radiation. The effect of the radiation damage in the combustion reaction of these carbon materials has been discussed.     

Progress in Fullerene Chemistry: From Exohedral Functionalization to Heterofullerenes

Abstract

Various types of cycloaddition such as [2+1], [2+3], and Diels-Alder reactions have been investigated for the purpose of exohedral functionalization of [60]fullerene and also in few cases of [70]fullerene. Thermal and photochemical activation have been used and lead to a variety of new fullerene derivatives which may be further functionalizable. In addition, a new approach to aza-heterofullerenes has been developed starting from an exohedrally activated fullerene.     

Fullerene Research at the University of New South Wales

This paper gives an overview of our group's involvement in fullerene research which has been focussed in the two areas of mass spectrometry and production of fullerenes. The early work was mainly concentrated on the observation of fullerene ions in laser ablation mass spectrometry. We have also tried to develop other carbon sources of fullerenes besides graphite. The fullerene work continues and has led us into other areas such as the study of the reactivity of small carbon anions.     

Grafting of buckminsterfullerene onto polythiophene: novel intramolecular donor-acceptor polymers

Conjugated polymer-fullerene composites have shown efficient photoinduced charge transfer. The attachment of a fullerene moiety to the conducting polymer backbone is expected to lead to materials with more intimate association of the donor/acceptor sites. Two approaches to the attachment of fullerenes onto polythiophene derivatives have been explored. In the first case, fullerene has been bonded to a bithiophene derivative which can be electropolymerized. In the second, solvent processable polythiophene copolymers were prepared and functionalized with fullerene. Both these systems exhibit electrochemical and optoelectrochemical properties for fullerene and the conducting polymer.