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Aggregation of Shungite Carbon Nanoparticles

#2769


Complex Investigation of Aggregation of Carbon Nanoparticles and Their Role as Basic Elements of Nanotechnology in Systems: Shungites, Aqueous Dispersions of Shungites

Tech Area / Field

  • CHE-OTH/Other/Chemistry
  • CHE-THE/Physical and Theoretical Chemistry/Chemistry

Status
8 Project completed

Registration date
14.05.2003

Completion date
19.12.2006

Senior Project Manager
Endrullat B

Leading Institute
Institute of Geology, Karelian Research Center, Russia, Petrozavodsk

Supporting institutes

  • Russian Academy of Sciences / Physical Technical Institute, Russia, St Petersburg\nFEI (IPPE), Russia, Kaluga reg., Obninsk\nJoint Institute of Nuclear Research, Russia, Moscow reg., Dubna

Collaborators

  • NanoCarbon Research Institute Ltd., Japan, Chiba\nKyoto University / Graduate School of Engineering, Japan, Kyoto

Project summary

Carbonaceous materials of a new generation, such as fullerenes, nanotubes, ultradisperse diamonds etc., have a well-developed surface and high reactivity, and are, therefore, highly prospective in nanotechnology. At the same time, an excess of free energy at the highly developed interphase boundaries, disperse medium - disperse phase (nanocarbon), contributes to aggregation of carbon nanoparticles because surface energy decreases in this case. Many researchers have noted a similarity in the formation and morphology of С60 (fullerenes) and carbon nanoparticles of soot. However, the aggregation of fullerenes, unlike that of soot particles, has not been discussed yet.

The goal of this project is to study carbon nanoparticle aggregation and stabilization mechanisms for their subsequent use in nanotechnological processes. This study is expected to increase our knowledge of the genesis and formation mechanisms of shungite carbon (SC) nanoparticles in nature.

The target of study is native carbon from shungites in which fullerenes were found, but the main structural constituents of SC are nanosized (fullerene-like) units responsible for its properties. In spite of structural similarity, shungites from different deposits differ considerably in bulk morphology. Therefore, they have a wide range of useful properties such as porosity and surface area. We assume that water played an important role in the formation of SC structure. Our assumption was supported by the study of aqueous colloidal SC solutions produced using the procedure developed by G.V. Andrievsky et al. for preparing molecular-colloidal fullerene solutions. Shungites are widely used as adsorbents and filters in water purification and water treatment and their large-scale use in biomedicine is expected. Therefore, the properties of aqueous SC nanoparticle dispersions, primarily biological activity, should be studied in more detail.

Unlike X-ray and electron diffraction data, analysis of the scanning tunneling microscopy (STM) and atomic force microscopy (AFM) of shungite carbon gave large sizes of structural constituents (tens to hundreds of nanometers) that showed wide lognormal distribution. This distribution pattern was found to be typical for aggregates of colloidal particles in solidifying systems. SC morphology is thus expected to reflect differences in the degree and ways of aggregation of its nanoparticles. Unfortunately, existing model concepts of SC structure fail to explain their properties and high activity well enough to understand how they were generated and how these active particles could survive in nature for 2 billion years. We assume that the high activity of SC is related to fullerene-like structures. The aggregation of the nanosized constituents of SC can diminish activity, whereas their de-aggregation will result in the activation of SC.

Using modern research methods, such as spectroscopy in the UV- and visible field, Raman spectroscopy, IR-spectroscopy, electron spectroscopy, sedimentation analysis, dynamic and static light scattering, small-angle X-ray and neutron scattering, quasi-elastic neutron scattering etc., one can obtain comprehensive information on the structure and interaction of nano-objects. To efficiently solve the problems arising under the project, these methods should be combined. It should be noted that to understand particle stabilization mechanisms in colloidal solutions, various theoretical approaches must be used. Modern theoretical phase-transition physics provides some models to describe aggregation processes that will be further developed under the project in a supplement to the systems studied.

Small-angle neutron scattering experiments will give us data on the structure and interaction of objects with characteristic dimensions of the order of 1 - 100 nm. The elastic and inelastic slow neutron scattering method (NSNS) is an efficient tool that can be used to study the microdynamics of condensed matter and to obtain unique information on the diffusion characteristics and rotation-oscillation spectrum of water molecules that other methods cannot provide. Therefore, NSNS will be used to study aqueous dispersions of shungite nanoparticles to estimate the effect of nanoparticles on the microdynamic properties of surrounding water molecules.

The carbon nanoparticles synthesized in A.F.Ioffe Physical-Technical Institute RAS will be used as a standard.

To achieve the goal of the project (the study of the stabilization of carbon nanoparticles produced under artificial and natural conditions), we plan to use a colloidal-chemical approach, according to which aggregation can be prevented by both electrostatic and steric stabilization, including hydration. Water can also play an important role in the production of new composite materials from fullerene-like nanoparticles because water evaporation gives rise to considerable contracting forces. As a result, the durability and chemical resistance of carbon nanonets can be greatly increased. Films based on SC nanoparticles will be produced during project activities.

The success of the project will be ensured by:

- knowledge and experience in the study of the structure and physicochemical properties of shungite rocks and shungite carbon gained in the Shungite Laboratory of the Institute of Geology, Karelian Research Center, Russian Academy of Sciences;

- opportunity to conduct small-angle neutron scattering experiments on the IBR-2 high-flux pulsed reactor and long-term experience in carrying out such experiments and analyzing results in JINR;

- experience in conducting experiments in electron microscopy, spectroscopy, sedimentation analysis, dynamic scattering of light and small-angle X-ray scattering as well as analysis of experimental results in JINR, IPPE and IG, KarRC, RAS;

- experience in the production and analysis of fullerenes and fullerene soot in PTI;

- experience in experimental work with aqueous colloids of fullerenes and shungites and theoretical modeling and description of aggregation of nanoparticles in various systems in IG KarRC, RAS and JINR;

- experience in carrying out neutron-physical experiments to study the microdynamics of condensed matter on aqueous solutions of electrolytes and hydrophobic particles, data processing and extraction of physical information in SSC RF-IPPE.


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