Atomic force microscopy study of fullerene-based colloids (original) (raw)
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Chemical Physics Letters, 2002
Two types of fullerene-water colloidal systems: molecular-colloidal C 60 solution in water (C 60 FWS) and typical monodisperse C 60 hydrosol are compared in this work. It was confirmed that C 60 FWS consists of isolated C 60 molecules in hydrated state, C 60 @fH 2 Og n , and of their small spherical C 60 clusters of different sizes. It was shown that C 60 FWS simultaneously has the properties of both true solutions and colloidal systems. The origin of supramolecular complexes C 60 @fH 2 Og n stabilization is explained both by the weak donor-acceptor interactions of unpaired electrons of H 2 O oxygen atoms with fullerene molecule and by formation of ordered, H-bounded and sphere-like hydrated shells around the fullerene. Spectra of surface enhanced infrared absorption (SEIRA) of C 60 on gold substrate were recorded in FTIR reflectance mode. In the 400-900 cm À1 region some additional vibration bands of C 60 , which are forbidden in IR spectra, have been registered. Earlier the similar bands had been observed in inelastic neutron scattering.
Stable Dispersions of Fullerenes, C 60 and C 70 , in Water. Preparation and Characterization
Langmuir, 2001
Stable aqueous dispersions of fullerenes, C60 and C70, were prepared by simply injecting into water a saturated solution of fullerene in tetrahydofuran (THF), followed by THF removal by purging gaseous nitrogen. To our knowledge, this is the first report of the stable dispersion of C70 in water. Fullerenes are dispersed as monodisperse clusters in water, 60 nm in diameter. High resolution transmission electron microscopy revealed the polycrystalline nature of the cluster. The preparation of the dispersion is very easy to perform, and the dispersions thus obtained are of excellent colloidal stability even though no stabilizing agent is used. It was found that the surface of the cluster is negatively charged and the electrostatic repulsion between the negatively charged cluster surfaces is important for the stability of the dispersions.
Facile preparation of aqueous fullerene C60 nanodispersions
Nanotechnologies in Russia, 2014
Aqueous solutions of the fullerene C 60 (nC 60) were prepared by simple mixing of the solution of C 60 in N-methylpyrrolidone (MP) with deionized water or an aqueous solution of a low molecular weight natural substance (L amino acids, monosaccharides, peptides, or glycerol) used as stabilizing agents (SAs) followed by exhaustive dialysis against distilled water. During dialysis, all low molecular weight compounds are removed through the pores and the fullerene clusters remain in the solution. The efficiency of conversion of C 60 from the crystalline state to the solution approaches the quantitative value, and solutions with a C 60 concentration of up to 250 mg/L can be obtained; moreover, these solutions are stable for at least 10-12 months. The formation of insoluble aggregates has been observed when basic and acidic organic com pounds were used as SA. The UV-VIS spectra of solutions have a profile characteristic of nC 60 solutions obtained by other well known procedures (maxima at 220, 265, 340, and 450 nm). Mass spectra of aqueous solutions and FTIR spectra of dried nC 60 samples were indicative of the possible partial hydroxylation of the fullerene. A measurement of the sizes and ζ potential of the C 60 particles in solutions by the dynamic light scattering method showed that their average diameter is about 100 nm and the charge is-30 mV, whereas the electron microscopy data demonstrated that the particles have a typical size of approximately 20 nm and con tain both crystalline and amorphous phases. The proposed method is promising for the preparation of solu tions of endofullerenes and, probably, higher fullerenes.
Structure and toxicity of aqueous fullerene C60 solutions
Journal of Surface Investigation. X-ray, Synchrotron and Neutron Techniques, 2015
In this paper, two types of fullerene C 60 solutions are compared with respect to their structural fea tures and toxic properties. The results are discussed in terms of their potential in medical and biological appli cations. The fullerene cluster state at the nanoscale in these solutions is analyzed by small angle neutron scat tering. Experiments on the cytotoxicity of these systems on Chinese hamster V 79 cells showed no toxic effects of the solutions.
Studies of aqueous colloidal solutions of fullerene C60 by electron microscopy
Chemical Physics Letters, 1999
Ž . The systems of fullerene C in water C FWS , i.e. aqueous colloidal solutions of buckminsterfullerenes, have been 60 60 studied using transmission electron microscopy. The C FWS are shown to be molecular-colloid systems, containing both 60 single fullerene molecules and their fractal clusters in a hydrated state. q
Environmental Science & Technology, 2009
The stability and aggregation kinetics of two different suspensions of fullerene (C 60 ) nanoparticles and their relation to nanoparticle charge (electrokinetic) properties were investigated. The two synthesis methods employedsa solvent exchange method involving sonication of fullerene initially dissolved in toluene and prolonged stirring of bulk fullerene in watersproduce negatively charged fullerene nanoparticles. With an increase in electrolyte (KCl) concentration, the electrophoretic mobilities of both fullerene nanoparticles became less negative, while the corresponding aggregation rates increased until maximum rates were reached at their respective critical coagulation concentrations. This behavior is consistent with the classic Derjaguin-Landau-Verwey-Overbeek (DLVO) theory for the stability of charged colloidal particles. The nanoparticles prepared by prolonged stirring of bulk fullerene in water were much more stable than those prepared by sonication in toluene, as evident from their significantly higher critical coagulation concentration (166 and 40 mM KCl, respectively). A comparison of the aggregation kinetics with predictions based on DLVO theory yielded the same Hamaker constant (8.5 × 10 -21 J) for both fullerene nanoparticles, indicating that they have the same material composition. Further investigation shows that both fullerene nanoparticles are more negatively charged and stable at higher pH conditions, suggesting that dissociation of surface functional groups contributes to surface charge for both nanoparticles. This hypothesis is further supported by oxidation which occurs on the surface of bulk fullerene that has been exposed to water over a prolonged period of time, as detected through X-ray photoelectron spectroscopy (XPS). However, since both nanoparticles remain negatively charged at pH 2, it is likely that there are other contributing factors to the surface charge of fullerene nanoparticles.
Colloidal structure and stabilization mechanism of aqueous solutions of unmodified fullerene C60
Crystallography Reports, 2007
Despite the inability of fullerenes to be directly dissolved in water, there are methods for preparing stable dispersions of fullerenes in water without any particular modifications of the fullerene or addition of stabilizers. The colloidal properties of such systems prepared by replacing the solvent and structural changes in them during coagulation have been studied. The coagulation dynamics has been investigated by spectroscopy and small-angle neutron scattering. The results obtained confirm the colloidal nature of such systems. During coagulation, particles retain a large volume of water around them, an indication of interaction between fullerene and water during solution stabilization.
Effect of solvent polarity on the aggregation of fullerenes: a comparison between C60 and C70
Chemical Physics Letters, 2002
Effect of solvent polarity on the aggregation behaviour of C 70 has been investigated in several mixed solvents using optical absorption, fluorescence, dynamic light scattering and scanning electron microscopic measurements and compared with those observed for the other fullerene analogue, C 60. It is seen that similar to C 60 , aggregation of C 70 also requires the solvent polarity to exceed some critical value. In terms of solvent dielectric constant the critical solvent polarity, required for C 70 aggregation is found to be in the range of 27−31,whichismuchhigherthanthatrequiredforC60aggregation(27-31, which is much higher than that required for C 60 aggregation (27−31,whichismuchhigherthanthatrequiredforC60aggregation(12-14). The large difference in the critical solvent polarity required for C 60 and C 70 aggregation has been rationalized on the basis of the molecular shapes and the polarizabilities of two fullerene molecules.
Journal of Nanoparticle Research, 2013
The present study was carried out to evaluate transformation kinetics of derivatized fullerene species by simulating natural aquatic processes, which will help elucidate biological effects of waterstirred nano-C 60 (aqu-nC 60 ). Physicochemical analyses of aqu-nC 60 included molecular and agglomeratescale characterization, surface charge analysis through examination of electrophoretic mobility, and chemical composition analysis using spectroscopy. Detailed analysis of aqu-nC 60 transformation over a 28-day stirring period in both light and dark conditions indicated aqu-nC 60 agglomerate concentrations can be estimated as a time-function using a predictor model (R 2 [ 0.99). Number-weighted agglomerate size did not differ significantly over the 28-day stirring period regardless of photocondition, although size distributions were more uniform as stirring time increased. The total number of surface groups identified through XPS indicated increased derivatization as a function of time with additions assigned to monooxygenated carbon moieties while the number of dioxygenated moieties declined. Earlier-phase stirring (t B 14 days) products were shown to contain epoxide surface groups, which were absent in later-phase (t [ 14 days) suspensions, suggesting specific pathways to derivatization with preferential mono-oxygenated states. Filter residue, a by-product of the aqu-nC 60 synthesis process, demonstrated high hydrophobicity and FTIR spectra similar to underivatized material, suggesting synthesis process inefficiencies.