Fullerenol-d Solubility in Fullerenol-dâInorganic SaltâWater Ternary

Article pubs.acs.org/IECR

Fullerenol‑d Solubility in Fullerenol‑d−Inorganic Salt−Water Ternary Systems at 25 °C Konstantin N. Semenov,*,† Nikolai A. Charykov,‡ Victor A. Keskinov,‡ Andreii S. Kritchenkov,† and Igor V. Murin† †

Saint Petersburg State University, Universitetskii pr. 26, St. Petersburg, Russia 198504 Saint Petersburg State Technological Institute (Technical University), Moskovskii pr. 26, St. Petersburg, Russia, 190013

‡

S Supporting Information *

ABSTRACT: In this work, solubility in ternary systems fullerenol-d−NaCl−H2O, fullerenol-d−Pr (NO3) 3−H2O, fullerenol-d− YCl3−H2O, fullerenol-d−uranyl sulfate−water, and fullerenol-d−CuCl2−water at 25 °C by the method of isothermal saturation in ampules was studied; a description of the results is presented.

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INTRODUCTION

The discovery of the fullerene opened a new field of science because of its unique physicochemical properties. There are many possible uses of this particle, either individually or as a modifier.1−5 However, poor solubility limits its application. Water-soluble forms of fullerene derivatives may find the widest application in mechanical engineering (in water-soluble cooling and antifriction mixtures), in building (as soluble additives for cements and concretes), in medicine and pharmacy (due to their compatibility with water, physiological salt solutions, blood, lymph systems, and stomach juices, etc.), and in cosmetics (specifically those that have water and water−alcohol bases), as well as in science and technology. This causes particular interest in finding accessible and simple methods for the synthesis of water-soluble fullerene derivatives on an industrial scale. Polyhydroxylated fullerene, so-called fullerenol, has a simple structure, convenient for practical use (Figure 1), low toxicity; and the possibility of further modification. It is considered the most promising water-soluble fullerene derivative.6−20 It should be pointed out that (i) currently the term “fullerenol” includes not only the fullerenols C60(OH)x, which are the derivatives of fullerene C60 (the most easily accessible from all of the fullerenes) but also hydroxy derivatives of all other individual fullerenes Cn(OH)x (n = 60, 70, 76, 78, 84, 90); (ii) besides the hydroxyl groups, fullerenols can also include some other nonhydroxylic groups, such as oxygen groups (O, -O-) Cn(OH)xOy, and salt type groups, such as [Cn(OH)xOy](ONa)z, etc.; and (iii) finally, to fullerenol also are referred mixtures of individual fullerenol of different composition or individual fullerenols of low purity (for example, less than 95 wt %). To the best of our knowledge, in the literature, there are few works devoted specifically to the solubility of fullerenols. We note a series of papers (see refs 13, 14, 16, and 19) devoted to the study of the solubility of fullerenols of different types (corresponding to the light fullerene C60) in water under polythermic conditions. © 2013 American Chemical Society

Figure 1. Structural formula of the C60(OH)24 fullerenol (blue circles, carbon atoms; red circles, oxygen atoms; white circles, hydrogen atoms).

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EXPERIMENTAL SECTION In this paper the authors used fullerenol-d, the most available of known light fullerenols.12,19 It is established that fullerenol-d synthesized by direct catalytic oxidation of C60 is not a single compound but a mixture of closely related forms of average composition [C60(OH)18‑20O0‑3](ONa)2±1. Fullerene C60 of mass fraction purity 99.9%, with the main detectable impurity C70 (ω = 0.001) was used for synthesis of fullerenol-d. The reagent was produced at ZAO “ILIP” (St. Petersburg). The other reagents used were reagent grade 10% tetrabutylammonium hydroxide (TBAH) solution, benzene, methanol, and NaOH (purchased from Vecton Ltd., St. Petersburg). Received: Revised: Accepted: Published: 16095

May 20, October October October

2013 22, 2013 24, 2013 24, 2013

dx.doi.org/10.1021/ie401590g | Ind. Eng. Chem. Res. 2013, 52, 16095−16100

Industrial & Engineering Chemistry Research

Article

In the case of ternary systems fullerenol-d−NaCl−H2O and fullerenol-d−UO2SO4−H2O, we carried out spectrophotometric determination of the concentration of fullerenol-d in a saturated solution. The electronic spectrum of an aqueous solution of fullerenol-d relative to pure water in the visible and near-ultraviolet regions of the spectrum is shown in Figure 2.

In the context of this work, the most simple and repeatable method of direct fullerenol synthesis was chosen.12 Initially the fullerene solution in benzene (600 mg of C60 and 800 mL of benzene) was prepared. The saturation of the solution was carried out in a temperature-controlled shaker at 25 ± 0.05 °C over the course of 20 h. After that, the solution was filtered on the Schott filter (porosity factor, 10). Then the water solution of NaOH (20 g of NaOH/(20 mL of H2O)) and 20% tetrabutylammonium hydroxide solution (1.5−2 mL) was added to the C60 solution in benzene up to the decoloration of the benzene solution. Then the benzene was distilled by means of a vacuum (5 mmHg) from the reaction mixture, and a supplementary quantity of distilled water (100 mL) was added. The reaction mixture obtained was stirred with a magnetic stirrer for 12−15 h. During this process, the extraction of the fullerenol to the water phase was realized. Later the additional quantity of water (200 mL) was added for the completion of the reaction. The mixture obtained was filtered on the Schott filter (porosity factor, 10), and the solution was evaporated using the rotary evaporator up to 50 mL. After that, 500 mL of methanol was added and the fullerenol was precipitated from the water solution in the form of a brown flaky precipitate (the reprecipitation procedure was repeated 3 times). Then the precipitate was separated from the solution and additionally neutralized by chlorohydric acid up to a neutral value of pH = 7 ± 1. After that, it was washed by methanol and dried in a vacuum at t = 40 °C and p = 0.1 mmHg. As a result the reddish-brown fine crystals of the fullerenol were obtained; the yield of the reaction was equal to 72% (600 mg). The identification of the fullerenol obtained was carried out using UV and IR spectroscopy, mass spectrometry, and elemental analysis methods.12 The solubility in the ternary systems fullerenol-d−salt−H2O at 25 °C was studied by an isothermal saturation method in ampules. In the curve of a two-phase equilibrium saturated solution−fullerenol-d in a heterogeneous mixture comprising water and a notorious excess of fullerenol-d (5 g/(10 g of H2O)) were consequently added various amounts of inorganic salts, providing complete dissolution of the latter. Into the curve of a two-phase equilibrium saturated solution−inorganic salt in a heterogeneous mixture comprising water and an excess of salt (depending on the solubility of the latter) were consequently added various amounts of fullerenol-d, leading to complete dissolution of the latter. Saturation conditions were as follows: the saturation time (t) was 4 h, the saturation temperature was maintained to within 25 ± 0.05 °C, and saturation was under conditions of a shaker-thermostat at a shaking frequency ω ≈ 2 s−1. After shaking, the ampules were left to stand in a thermostatic mode for 30 min. Then there was sampling for the following operations: (a) for determination of the total concentration of components of solution [the identification was performed after calcination of weighing bottles with solutions to dryness under atmospheric pressure and at the temperature T ≈ 200 ± 10 °C for 2 h; such conditions are sufficient for the nondestructive decomposition of crystalline hydrates of fullerenol-d;13,19 the authors of refs 13 and 19 reported about the composition of equilibrium crystalline hydrate of fullerenol-d−fullerenol-d·30H2O]; (b) for picnometric determination of the density of triple saturated solutions fullerenol-d + inorganic salt + H2O with an accuracy of temperature control at T ≈ 25 ± 0.05 °C; (c) for determination of the concentration of inorganic salt (or fullerenol) in a saturated solution.

Figure 2. Optical spectrum of fullerenol-d in water. D is optical density; λ is wavelength.

The spectrum was obtained by a spectrophotometer SPECORD M-32 in quartz cuvettes “KB-1” of a width of 1 cm in the wavelength range of 200−900 nm. As can be seen from Figure 2, in all, the investigated spectral range of the electronic spectrum fullerenol-d does not have any visible absorption bands. However, it is quite suitable for determining the concentration of fullerenol-d, according to the Beer− Lambert−Bouguer law, on noncharacteristic wavelengths, for example, at wavelengths from the 300 to 400 nm region. The applicability of the Bouguer−Lambert−Beer law at wavelength λ ≈ 350 nm is shown in Figure 3. In the case of ternary system fullerenol-d−CuCl2−H2O, spectrophotometric determination of the concentration of CuCl2 was carried out. Figure 4 shows the electronic absorption spectrum of an aqueous solution of CuCl2 in relatively pure water. Figure 4 clearly shows a pronounced peak of absorption of light in the long-wave visible

Figure 3. Concentration dependence of the optical densities of the fullerenol-d solutions in water. D is optical density; S is the solubility of the fullerenol-d. 16096



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were added into the flask. Immediately before the titration 2−3 drops of 1% solution of xylenol orange indicator was also added in the flask. The solution was then titrated slowly dropwise with vigorous stirring until the color changed from violet to lemon yellow. If the pH of the solution does not correspond to the pH of the buffer, a few additional cm3 of the buffer should be added in a titration flask (the buffer capacity of the system may be exhausted due to leakage acidifying reactions: Na2H2EDTA + Pr3+ (Y3+) = Pr(Y)EDTA + 2Na+ + 2H+). Further, the data on the volume concentration of fullerenol (salts) were converted into the data on the weight concentration using data of the density of the saturated solutions.

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DISCUSSION OF RESULTS Fullerenol-d−Pr(NO3)3−H2O and Fullerenol-d−YCl3− H2O. Solubility diagrams in the systems fullerenol-d−Pr(NO3)3−H2O and fullerenol-d−YCl3−H2O at 25 °C are shown in Figures 6 and 7. As seen from Figures 6 and 7,

Figure 4. Optical spectra of the CuCl2 in water. D is optical density; λ is wavelength.

region of the spectrum (at λ > 800 nm) of solutions of CuCl2. Aqueous solutions of fullerenol-d (Figure 2) in this region are almost clear. This allows the authors to carry out the determination of the volume concentration of CuCl2 in ternary saturated solutions by the spectrophotometric method (preliminarily determining the density of the solutions). Dependence of the optical density of a solution of CuCl2 concentration at λ = 833 nm and l = 1 cm, D833(CCuCl2), is shown in Figure 5.

Figure 6. Solubility diagram in the ternary system fullerenol-d + Pr(NO3)3 + H2O at 298 K. The solid line corresponds to the crystallization of Pr(NO3)3·6H2O; the dashed line corresponds to crystallization of C 60 (OH) 22−24 ·30 H 2 O. w(Pr(NO 3 ) 3 ) and w(C60(OH)22−24) are the mass fractions of the fullerenol and salt in water solution. The open circle (○) corresponds to simultaneous saturation of the two solids.

solubility diagrams in both systems are very similar. For example, the diagrams consist of two branches, corresponding to the crystallization of crystalline hydrate fullerenol-d·30H2O and crystalline hydrates Pr(NO3)3·6H2O and YCl3·6H2O. The diagrams contain one invariant point of eutonic type, corresponding to a joint saturation by both the pointed out above pairs of the solid phases.21−24 Thus, on the branches of crystallization of crystallohydrates of salts of rare earth metals, solubility of the latter passes through a pronounced minimum, i.e., consequently salt-out effect and then salt-in effect are observed, and on the branches of the crystallization of the crystallohydrate of fullerenol-d, there is almost total independence from the solubility of the concentration of salts of praseodymium and yttrium. Change of the effects from salt-out effect to salt-in effect on the branches of the crystallization of crystallohydrates of salts of rare earth metals, in principle, is not surprising (though we did not observe such a situation in systems with NaCl and CuCl2). Such a passage of solubility through a minimum with increasing concentration of fullerenol can be associated with

Figure 5. Concentration dependencies of the optical densities of the CuCl2 solutions in water at λ = 833 nm. D is optical density; S is the solubility of CuCl2.

Figure 5 clearly shows that, in the concentration range CCuCl2 ≤ 25 g/L and in the range of optical densities D833 ≤ 1.82 relative units at optical path length (l = 1 cm), the dependence is linear, which allows the calculation according to the formula CCuCl2 = 12.03D833. In the case of ternary systems fullerenol-d−Pr(NO3)3−H2O and fullerenol-d−YCl3−H2O the determination of the concentration of rare earth elements was performed by complexometric titration. We discuss this method in more detail. From a vial containing the rare earth salt solution and fullerenol an aliquot was transferred to a titration flask. Distilled water in an amount of 30−40 cm3 and then 5−10 cm3 of acetate buffer 16097



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UO2SO4·3H2O. As in previous cases, the diagram contains one invariant point of eutonic type corresponding to the joint saturation of both crystallohydrates. It should also be noted that the eutonic point is strongly pressed to the figurative point corresponding to binary system UO2SO4−H2O at 25 °C. On the branch of the crystallization of crystallohydrate of fullerenol-d a very strong salting-out effect is observed. Such results were not observed in the case of other salts (NaCl, CuCl2, YCl3·6H2O, Pr(NO3)3·6H2O). The latter effect can be effectively used to obtain fullerenol from saturated aqueous solutions by the salting-out of fullerenol with uranyl salts. Currently, this operation requires using an energy-intensive method − usually by salting-out with methanol, followed by evaporation to a paste consistency in a rotary vacuum evaporator and then vacuum drying. Fullerenol-d−CuCl2−Water. As can be seen from Figure 9 the diagram of solubility in the system fullerenol-d−CuCl2−

Figure 7. Solubility diagram in the ternary system fullerenol-d + YCl3 + H2O at 298 K. The solid line corresponds to the crystallization of YCl3·6H2O; the dashed line corresponds to the crystallization of C60(OH)22−24·30 H2O. w(YCl3) and w(C60(OH)22−24) are the mass fractions of the fullerenol and salt in water solution. The open circle (○) corresponds to simultaneous saturation of the two solids.

the simultaneous occurrence of two different processes: (a) a decrease in the share of the “free” water due to its efficient binding of water with fullerenol14 (this process should decrease the solubility of the second dissolved component (crystallohydrate of the salt of the rare earth element); (b) amplification of complexation in a pair of fullerenol−rare earth ion Pr3+ (Y3+) components (possibly with the participation of water and counterions NO3− (Cl−; such a process should certainly increase the solubility of the crystallohydrate of the salt of the rare earth element). Fullerenol-d−Uranyl Sulfate−Water. A diagram of solubility in the system fullerenol-d−uranyl sulfate−water at 25 °C is presented below in Figure 8. As can be seen from Figure 8, the diagram consists of two branches, corresponding to the crystallization of crystallohydrate of fullerenol-d and

Figure 9. Solubility diagram in the ternary system fullerenol-d + CuCl2 + H2O at 298 K. The solid line corresponds to the crystallization of CuCl2·2H2O; the dashed line corresponds to the crystallization of C60(OH)22−24·30 H2O. w(CuCl2) and w(C60(OH)22−24) are mass fractions of the fullerenol and salt in water solution. The open circle (○) corresponds to the simultaneous saturation of the two solids.

water consists of two branches, corresponding to the crystallization of crystallohydrate fullerenol-d·30H2O and copper chloride dihydrate, and contains one invariant point of eutonic type. On the branch of crystallization of fullerenol-d, the so-called salt-out effect is observed (i.e., decrease of the solubility of fullerenol-d with an increasing concentration of CuCl2), and on a branch of crystallization of CuCl2·2H2O, the salt-in effect is observed (i.e., increase of the solubility of CuCl2 with increasing concentration of fullerenol-d). The latter effect is relatively weak: the CuCl2 concentration in weight percent is increased from 43.1 to 50.6 wt %. Fullerenol-d−NaCl−Water. Study compatibility of fullerenol with aqueous solutions, in particular with water−salt solutions, has a practical importance. On the one hand, fullerenols have antibacterial, antiviral, antioxidative, and radioprotective activity.11 On the other hand, there is an evident need to study the compatibility of fullerenol not only with distilled water but also with different physiological fluids, the main components of which are water and mineral salts mainly haliteNaCl, and physiological solutions such as blood, lymph, and so on. As can be seen from Figure 10, the diagram consists of two branches, corresponding to the crystallization of

Figure 8. Solubility diagram in the ternary system fullerenol-d + UO2SO4 + H2O at 298 K. The solid line corresponds to the crystallization of UO2SO4·3H2O; the dashed line corresponds to the crystallization of C 60 (OH) 22−24 ·30 H 2 O. w(UO 2 SO 4 ) and w(C60(OH)22−24) are mass fractions of the fullerenol and salt in water solution. The open circle (○) corresponds to simultaneous saturation of the two solids. 16098



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ACKNOWLEDGMENTS

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REFERENCES

Article

The work was supported by the Russian Foundation of Fundamental Research (Projects No. 11-08-00219-a; 12-0331380−mol_a) and by a Grant of the President of the Russian Federation for supporting young scientists, MK-3151.2013.3.

(1) Polotskaya, G. A.; Penkova, A. V.; Pientka, Z.; Toikka, A. M. Polymer membranes modified by fullerene C60 for pervaporation of organic mixtures. Desalin. Water Treat. 2010, 14, 83−88. (2) Matija, l.; Tsenkova, R.; Munćan, J.; Miyazaki, M.; Banba, K.; Tomić, M.; Jeftić, B. Fullerene based nanomaterials for biomedical applications: Engineering, functionalization and characterization. Adv. Mater. Res. 2013, 633, 224−238. (3) Penkova, A.; Toikka, A.; Kostereva, T.; Sudareva, N.; Polotskaya, G. Structure and transport properties of fullerene−polyamide membranes. Fullerenes, Nanotubes, Carbon Nanostruct. 2008, 16 (5− 6), 666−669. (4) Peyghan, A. A.; Soleymanabadi, H.; Moradi, M. Structural and electronic properties of pyrrolidine-functionalized [60]fullerenes. J. Phys. Chem. Solids 2013, 74, 1594−1598. (5) Polotskaya, G. A.; Gladchenko, S. V.; Pen’kova, A. V.; et al. Synthesis of fullerene−polyphenylene oxide membranes for separating aqueous−organic mixtures. Rus. J. Appl. Chem. 2005, 78, 1468−1473. (6) Sidorov, L. N.; Yurovskaya, M. A. Fullerenes; Ekzamen: Moscow, 2005. (7) Li, J.; Takeuchi, A.; Ozawa, M.; Li, X.; Saigo, K.; Kitazawa, K. C60 fullerol formation catalyzed by quaternary ammonium hydroxide. J. Chem. Soc., Chem. Commun. 1993, 22, 1784−1785. (8) Chiang, L. Y.; Bhonsle, J. B.; Wang, L.; Shu, S. R.; Chang, T. M.; Hwu, R. J. Efficient one-flask synthesis of water-soluble [60] fullerenols. Tetrahedron 1996, 52, 4963−4672. (9) Meier, M. S.; Kiegiel, J. Preparation and characterization of the fullerene diols 1,2-C60(OH)2, 1,2-C70(OH)2, and 5,6-C70(OH)2. Org. Lett. 2001, 3, 1717−1719. (10) Semenov, K. N.; Charykov, N. A.; Letenko, D. G.; Nikitin, V. A.; Postnov, V. N.; Krokhina, O. A. Synthesis and identification of fullerenol. Vestn. S.-Petersb. Univ., Ser. 4: Fiz., Khim. 2010, ASAP. (11) Piotrovskij, L. B.; Kiselev, O. I. Fullerenes in biology; Rostok: Saint Petersburg, 2006. (12) Pinteala, M.; Dascalu, A.; Ungurenasu, C. Binding fullerenol C60(OH)24 to dsDNA. Int. J. Nanomed. 2009, 4, 193−199. (13) Semenov, K. N.; Charykov, N. A.; Letenko, D. G.; Nikitin, V. A.; Krokhina, O. A. Synthesis and identification of fullerenol. Vestn. S.Peterb. Univ., Ser. 4: Fiz., Khim. 2010, 4, 79−86. (14) Semenov, K. N.; Charykov, N. A.; Letenko, D. G.; Nikitin, V. A.; Matuzenko, M.Yu.; Keskinov, V. A.; Postnov, V. N.; Kopyrin, A. A. Synthesis and identification of fullerenol obtained by direct oxidation method. Rus. J. Appl. Chem. 2010, 12, 1948−1952. (15) Letenko, D. G.; Nikitin, V. A.; Charykov, N. A.; Bitukov, A. R.; Semenov, K. N.; Puharenko, Yu. V. Fullerenol-d. Some properties and ways of application. Vestn. Grajdanskih Injenerov 2010, 4, 120−130. (16) Semenov, K. N.; Charykov, N. A.; Letenko, D. G.; Nikitin, V. A.; Matuzenko, M. Yu.; Keskinov, V. A.; Postnov, V. N.; Kopyrin, A. A. Solubility and Some Properties of Aqueous Solutions of Fullerenol-d and Crystal Hydrates. Russ. J. Appl. Chem. 2011, 1, 44−49. (17) Semenov, K. N.; Charykov, N. A.; Letenko, D. G.; Nikitin, V. A.; Matuzenko, M. Yu.; Keskinov, V. A.; Postnov, V. N.; Kopyrin, A. A. Electrochemical properties of aqueous solutions of fullerenol-d. Russ. J. Appl. Chem. 2011, 1, 79−83. (18) Letenko, D. G.; Nikitin, V. A.; Semenov, K. N.; Matuzenko, M. Yu.; Keskinov, V. A.; Gruzinskaya, E. G.; Tsvetkova, L. V. Study of Aqueous Solutions of Fullerenol-d by the Dynamic Light Scattering Method. Russ. J. Appl. Chem. 2011, 1, 50−53. (19) Semenov, K. N.; Charykov, N. A.; Keskinov, V. A. Fullerenol Synthesis and Identification. Properties of Fullerenol Water Solutions. J. Chem. Eng. Data 2011, 56, 230−239.

Figure 10. Solubility diagram in the ternary system fullerenol-d + NaCl + H2O at 298 K. The solid line corresponds to crystallization of NaCl; the dashed line corresponds to the crystallization of C60(OH)22‑24·30 H2O. w(NaCl) and w(C60(OH)22−24) are mass fractions of the fullerenol and salt in water solution. The open circle (○) corresponds to simultaneous saturation of the two solids.

crystallohydrate fullerenol-d·30H2O and anhydrous sodium chloride, and contains one invariant point of eutonic type. On the branch of crystallization of fullerenol-d the so-called salt-out effect is observed (i.e., decrease of the solubility of fullerenol-d by increasing the concentration of sodium chloride), and on the branch of crystallization of sodium chloride the salt-in effect is observed (i.e., increase of the solubility of sodium chloride with increasing concentration of fullerenol-d). The latter effect is very strong: the concentration of halite in weight percent increases by more than half.

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CONCLUSION (1) Developed were methods of investigating the phase equilibria in the fullerenol-d−inorganic salt−water systems (fullerenol-d−NaCl−H2O, fullerenol-d−Pr (NO3)3−H2O, fullerenol-d−YCl3−H2O, fullerenol-d−uranyl sulfate−water, and fullerenol -d−CuCl2−water). (2) It was determined that diagrams of solubility consist of two branches, corresponding to the crystallization of crystallohydrate fullerenol-d·30H2O and the inorganic salt crystallohydrate; all diagrams contain one invariant point of eutonic type corresponding to a joint saturation by both of the solid phases. (3) The potential ways of practical use of the investigated ternary systems have been described.

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ASSOCIATED CONTENT

S Supporting Information *

Table listing solubility in ternary systems fullerenol-d + inorganic salt + H2O at 25 °C. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*Tel.: (812)4284109. Fax: (812)2349859. E-mail: [email protected]. Notes

The authors declare no competing financial interest. 16099



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(20) Semenov, K. N.; Charykov, N. A.; Keskinov, V. A.; Letenko, D. G.; Nikitin, V. A.; Namazbaev, V. I. The Synthesis and Identification of Mixed Fullerenol Prepared by the Direct One-Stage Oxidation of Fullerenol Black. Russ J. Phys. Chem. 2011, 6, 1009−1015. (21) Storonkin, A. V. Thermodynamics of heterogeneous systems; Leningrad State University: Leningrad, Russia, 1967. (22) Mischenko, K. P.; Ravdel’, A. A. Abstract of physical-chemical properties; Khimija: Leningrad, Russia, 1974. (23) Pentin, Yu. A.; Vilkov, L. V. Physical methods in chemistry; Mir: Moscow, 2003. (24) Stromberg, A. G. Physical Chemistry; Visshaja Shkola: Moscow, 1973.

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Fullerenol-d Solubility in Fullerenol-dâInorganic SaltâWater Ternary

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Fullerenol-d Solubility in Fullerenol-dâInorganic SaltâWater Ternary