Surface spin canting has been studied for high quality magnetite nanoparticles in terms of size and shape uniformity. Particles were prepared by thermal decomposition of organic precursors in organic media and in the presence of oleic acid. Results are compared to spin canting effect for magnetic iron oxide nanoparticles of similar size prepared by coprecipitation and subsequently coated with silica. Magnetic characterization and Mössbauer spectroscopy at low temperature and in the presence of a magnetic field have been used in this study. Transmission electron microscopy images and x-ray diffractograms show that iron oxide nanoparticles synthesized by thermal decomposition are more uniform than those prepared by coprecipitation, and they have higher crystal order. Magnetic measurements show superparamagnetic behavior for both samples at room temperature but particles synthesized by thermal decomposition shows higher saturation magnetization and lower coercivity at low temperature. The imaginary part of the ac susceptibility has been used to support the presence of mainly magnetite instead of maghemite in these iron oxide nanoparticles. Mössbauer measurements with and without field demonstrate surface spin canting, only in the octahedral positions for the coprecipitation particles. However, high synthesis temperature and the presence of oleic acid molecules covalently bonded at the particle surface, accounting for the lack of spin canting in particles prepared by thermal decomposition, which justifies the high saturation magnetization and low coercivity at low temperature.

Carbon nanomaterials with a different character of the chemical bond—graphene (sp²) and nanodiamond (sp³)—are the building bricks for a new class of all-carbon hybrid nanomaterials, where the two different carbon networks with sp³ and sp² hybridization coexist, interacting and even transforming into one another. The extraordinary physiochemical properties defined by the unique electronic band structure of the two border nanoallotropes ensure the immense application potential and versatility of these all-carbon nanomaterials. The review summarizes the status quo of sp² – sp³ nanomaterials, including graphene/graphene-oxide—nanodiamond composites and hybrids, graphene/graphene-oxide—diamond heterojunctions, and other sp²–sp³ nanocarbon hybrids for sensing, electronic, and other emergent applications. Novel sp²–sp³ transitional nanocarbon phases and architectures are also discussed. Furthermore, the two-way sp² (graphene) to sp³ (diamond surface and nanodiamond) transformations at the nanoscale, essential for innovative fabrication, and stability and chemical reactivity assessment are discussed based on extensive theoretical, computational and experimental studies.