The standard molar enthalpy of combustion of hydrofullerene C 60 H 36 was determined by static bomb calorimetry, ∆ c H°m ) -(29769 ( 25) kJ‚mol -1 . Using this result and the standard molar enthalpy of sublimation, ∆ sub H°m ) (175 ( 5) kJ‚mol -1 , the values of the standard molar enthalpies of formation of C 60 H 36 in the crystalline and gaseous states were calculated: ∆ f H°m(C 60 H 36 , cr) ) (1013 ( 26) kJ‚mol -1 and ∆ f H°m(C 60 H 36 , g) ) (1188 ( 26) kJ‚mol -1 . The enthalpy of reaction C 60 H 36 (g) ) C 60 (g) + 36 H(g) was found to be (9196 ( 30) kJ‚mol -1 , or (255.4 ( 0.8) kJ‚mol -1 per one C-H bond. The enthalpy of reaction C 60 F 36 (g) + 36 H(g) ) C 60 H 36 (g) + 36 F(g) was calculated, ∆ r H°m ) (1421 ( 203) kJ‚mol -1 , or (39.5 ( 5.6) kJ‚mol -1 per one H atom. The enthalpies of bond breaking and of F to H replacement were compared with the analogous values in some other organic compounds.
Temperature dependence of vapor pressures for 12 dihalogen-substituted benzenes (halogen = F, Cl, Br, I) was studied by the transpiration method, and molar vaporization or sublimation enthalpies were derived. These data together with results available in the literature were collected and checked for internal consistency using structure-property correlations. Gas-phase enthalpies of formation of dihalogen-substituted benzenes were calculated by using quantum-chemical methods. Evaluated vaporization enthalpies in combination with gas-phase enthalpies of formation were used for estimation liquid-phase enthalpies of formation of dihalogen-substituted benzenes. Pairwise interactions of halogens on the benzene ring were derived and used for development of simple group additivity procedures for estimation of vaporization enthalpies, gas-phase, and liquid-phase enthalpies of formation of dihalogen-substituted benzenes.
The use of few-layer graphene coatings over nanoparticles is attractive, as it offers both long-term stability to the nanoparticles and renders them biocompatible due to the inert nature of the coating material. Moreover, graphitic coatings provide an easy platform for additional functionalization, making graphitic coated nanoparticles attractive candidates for multimodal therapeutics. Alternative strategies to coat nanoparticles often result in inhomogeneous coatings and unwanted contaminants that are hard to remove. In this work, we show the feasibility to use oleic acid as a precursor for the formation of multilayer graphene over iron oxide nanoparticles using a facile and clean route. The demonstrated graphitization process was driven by electron beam irradiation or thermal annealing. Thermal annealing leads to reduction of the iron oxide to pure iron and provides a means to tailor the magnetic properties of the multilayer graphene coated nanoparticles which are attractive as units for hyperthermia therapeutics. The graphitization process is also demonstrated over Si/SiO 2 wafers.
The employment of Ni–Mo films
has recently been shown to
yield strictly homogeneous single-layer graphene. In this study, we
systematically investigate the different stages of nucleation and
growth of graphene over Ni–Mo layers. The studies reveal that
the Ni film breaks up and diffuses into the underlying Mo foil, forming
a Ni–Mo intermetallic. Nucleation only occurs from Ni sites,
and thus, the nucleation density can be controlled by the Ni film
thickness. Both nucleation and growth of the graphene are shown to
be susceptible to very efficient self-termination processes to the
formation of molybdenum carbide, and this guarantees the formation
of large area graphene that consists entirely of
monolayer graphene.
Carbon : nickel (C : Ni) nanocomposite templates (NCTs) were used as catalyst precursors for diameter-controlled growth of single-walled carbon nanotubes (SWCNTs) by chemical vapor deposition (CVD). Two NCT types of 2 nm thickness were prepared by ion beam co-sputtering without (type I) or with assisting Ar(+) ion irradiation (type II). NCT type I comprised Ni-rich nanoparticles (NPs) with defined diameter in an amorphous carbon matrix, while NCT type II was a homogenous C : Ni film. Based on the Raman spectra of more than 600 individual SWCNTs, the diameter distribution obtained from both types of NCT was determined. SWCNTs with a selective, monomodal diameter distribution are obtained from NCT type I. About 50% of the SWCNTs have a diameter of (1.36 ± 0.10) nm. In contrast to NCT type I, SWCNTs with a non-selective, relatively homogeneous diameter distribution from 0.80 to 1.40 nm covering 88% of all SWCNTs are obtained from NCT type II. From both catalyst templates predominantly separated as-grown SWCNTs are obtained. They are free of solvents or surfactants, exhibit a low degree of bundling and contain negligible amounts of MWCNTs. The study demonstrates the advantage of predefined catalysts for diameter-controlled SWCNT synthesis in comparison to in situ formed catalysts.
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