Abstract
Nanostructure, chemical composition and size distribution of aerosols have prime important effects on their efficiency in heterogeneous ice nucleation (HIN). The ice nucleation usually requires active sites in the aerosols in order to act as ice nuclei (IN). In this study, HIN and probable active sites of the graphene-graphene oxide nanoparticles (GGON), obtained from graphite oxide by low temperature thermal shock (LTTS), were investigated. Characteristics and size distribution of the GGON were identified using scanning electron microscope (SEM) and image processing of the results, Fourier transform infrared spectroscopy (FTIR), Raman spectra and X-ray diffraction (XRD) of their sheets. The FTIR spectra indicate stronger carbon-oxygen bonds in the samples obtained by LTTS. In addition, maximum size distribution of the GGON was ranged around 160–180 nm. After introducing these particles in the cloud chamber, HIN has occurred and ice crystals were formed. Size distribution of crystals were obtained from image processing of the plates, where covered by a thin layer of Formvar, showed the number of ice crystals in the GGON were increased as temperature increased from −20 °C to −10 °C. In addition, two possible mechanisms of asymmetry and deformation in ice crystals of the GGON were described.
Highlights
Cloud-aerosol interactions in the Earth’s atmosphere have several important effects on weather and climate system
The G band shows the presence of sp[2] carbon-type structures within the sample, the D band is associated with the presence of defects in the hexagonal graphitic layers and 2D-band is attributed to the development of graphene structure (Fig. 1a)
These GGO sheets in ice nuclei (IN), where they make hydrophobic hexagonal island in hydrophilic the structure, can make active sites onto the IN and be activated in the cloud chamber. Formation of these active sites on the graphene-graphene oxide nanoparticles (GGON) are very important in heterogeneous ice nucleation (HIN) and cloud micro-physics, and mechanism of water adsorption on them should be clarified more
Summary
Cloud-aerosol interactions in the Earth’s atmosphere have several important effects on weather and climate system. The organic molecular nature, rotational symmetry, hydrogen bonding groups matching to ice are of important features of active sites in the organic IN. There are some limited substances and biogenically driven organic aerosols in the atmosphere that can act as IN in Bergeron process[18,19] Both primary and secondary organic particles have been shown to nucleate ice despite their amorphous nature which seems to be in contrast to the concept of rotational symmetry and matching of hydrogen bonding groups[15]. Studies on mineral materials showed quartz- and feldspar-containing of desert dust are preferential ice nucleating sites in the IN in mixed-phase cloud conditions at lower temperature (T < –15). Laboratory study of IN activity of idealized organic particles is a reliable approach to understand the complexities and contradictions in characteristics of the ambient organic and mineral IN activity
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