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.

Sorption of polar organic solvents CH 3 OH, C 4 H 8 O (THF), CH 3 CN, C 3 H 7 NO (DMF) , C 2 H 6 OS (DMSO), C 5 H 9 NO (NMP) and water was quantitatively evaluated for Hummers (H-GO) and Brodie (B-GO) graphite oxides at T=298K and at melting temperature (Tm) of the solvents. H-GO showed stronger sorption compared to B-GO for all studied solvents and the increase of sorption upon lowering temperature was observed for both H-GO and B-GO. Thermodynamic equations allowed to explain earlier reported "maximums" of swelling/sorption in the binary systems H-GO -solvent at Tm. The specific relation between the values of enthalpies of sorption and melting leads to the change of sign in enthalpies of sorption at Tm and causes maximal swelling/sorption. The same thermodynamic explanation was given for the "maximum" on the swelling vs. pressure dependence in B-GO and H-GO -H 2 O systems earlier reported at pressure of phase transition "liquid water-ice VI". Notably higher sorption of H 2 O was observed for H-GO compared to H-GO membrane (H-GOm) at high relative humidity (RH), RH>0,75. Experimental sorption isotherm of H-GOm was used to simulate permeation rates of water through H-GOm and to estimate effective diffusion coefficient of water through the membrane.

Detonation nanodiamond (ND) is a suitable source material to produce unique samples consisting of almost uniform diamond nanocrystals (d = 3-5 nm). Such samples exist in the form of long stable aqueous dispersions with narrow size distribution of diamond particles. The material is finding ever increasing application in biomedicine. The major problem in producing monodispersed diamond colloids lies in the necessity of deagglomeration of detonation soot and/or removing of clusters formed by already isolated core particles in dry powders. To do this one must have an effective method to monitor the aggregation state or dispersity of powders and gels prior to the preparation of aqueous dispersions. In the absence of dispersity control at various stages of preparation the reproducibility of properties of existing ND materials is poor. In this paper we introduce differential scanning calorimetry (DSC) as a new tool capable to distinguish the state of aggregation in dry and wetted ND materials and to follow changes in this state under different types of treatment. Samples with identical X-ray diffraction patterns (XRD) and high resolution transmission electron microscopy (HRTEM) images gave visibly different DSC traces. Strong correlation was found between dynamic light scattering (DLS) data for colloids and DSC parameters for gels and powders of the same material. Based on DSC data we improved dispersity of existing ND materials and isolated samples with the best possible DSC parameters. These were true monodispersed easily dispersible fractions of ND particles with diameters of ca. 3 nm.

The nanosized water phase has been discovered while studying differential scanning calorimetry (DSC) of the aqueous gel of nano-diamond particles (diameter ca. 5 nm). Two endothermic peaks were observed in the DSC traces of frozen gel upon warming; a broad peak appeared at 265 K before the melting of bulk water, which is attributed to the melting of nanophase water adsorbed onto the surface of nano-diamond particles. The events can be reproduced in exothermic fashion upon cooling the same sample. The mass of nanophase water per one nano-diamond particle and the melting enthalpy of nanophase water were derived from the DSC data. Similar nanophase water was observed earlier in gels prepared from an aqueous dispersion of C 60 clusters with an average diameter of 68 nm, but the effect was not as distinct as with nano-diamond particles. These results demonstrate that DSC could be a versatile tool to study the stability of carbon nanoparticles in liquid media.

Graphite oxide (GO) in liquid acetonitrile undergoes a transition from an ordered phase around ambient temperatures to a gel-like disordered phase at temperatures below 260K, as demonstrated by in-situ x-ray diffraction. The stacking order of GO layers is restored below the freezing point of acetonitrile (199K). The reversible swelling transition between a stacked crystalline phase and an amorphous delaminated state observed upon cooling provides an unusual example of increased structural disorder at lower temperatures. The formation of the gel-like phase is attributed to the thermo-responsive conformational change of individual GO flakes induced by stronger solvation. Scanning force microscopy demonstrates that GO flakes deposited onto a solid substrate from acetonitrile dispersions at a temperature below 260K exhibit corrugations and wrinkling not observed for the flakes deposited at ambient temperature. The thermo-responsive transition between delaminated and stacked phases reported here can be used for sonication-free dispersion of graphene oxide, micro-container applications, or the preparation of new composite materials.

Graphite oxide is selectively intercalated by methanol when exposed to liquid water/methanol mixtures with methanol fraction in the range 20–100%. Insertion of water into the GO structure occurs only when the content of water in the mixture with methanol is increased up to 90%. This conclusion is confirmed by both ambient temperature XRD data and specific temperature variations of the GO structure due to insertion/deinsertion of an additional methanol monolayer observed upon cooling/heating. The composition of GO–methanol solvate phases was determined for both low temperature and ambient temperature phases. Understanding of graphite oxide structural properties in binary water/methanol mixtures is important for understanding the unusual permeation properties of graphene oxide membranes for water and alcohols. It is suggested that graphite oxide prepared by Brodie’s method can be used for purification of water using selective extraction of methanol from water/alcohol mixtures.

In the present study the scaled particle theory (SPT) along with the polarizable continuum model (PCM) were used to describe the thermodynamics of solvation of the fullerenes C60 and C70 in aromatic solvents, hexane, and water. The various contributions to the solute−solvent interaction were calculated within PCM based on effective Hamiltonians. The cavitation energy was calculated within the SPT formalism. The model was able to reproduce the trends in solution behavior of C60 along a series of aromatic solvents. The solvation and solution properties of fullerenes C60 and C70 were compared with the model developed. The estimations of solvation properties were further extended to higher fullerenes.

Differential scanning calorimetry, solution calorimetry, and room-temperature single-crystal X-ray diffraction were used to study the thermodynamic and structural properties of a solvated crystal C60·2C6H5Br. In the monoclinic solvate, two orientations of C60 were observed with fractional populations of 0.71 and 0.29. The enthalpy of solution of pure C60 in bromobenzene was determined to be Δsol H[C60(s)] = −11.5 ± 2.0 kJ/mol. The enthalpy of solution of the solvated crystal was Δsol H[C60·2C6H5Br(s)] = +28 ± 1 kJ/mol. The phase diagram of the system C60−C6H5Br for T < 423 K was constructed. It predicts the existence of a maximum in the temperature−solubility relationship for C60 in bromobenzene at 350 K. The activity of bromobenzene vapor over the solvated crystal is predicted to be reduced from its value over the pure liquid by a factor of 3.5.