MOLECULAR ORGANIZATION AND CONFORMATIONAL CHANGES OF HUMIC ACIDS IN DEPENDENCE ON THEIR CONCENTRATION IN VARIOUS AQUEOUS SOLUTIONS

1 KLUČÁKOVA Martina
Co-authors:
1 VĚŽNÍKOVÁ Kateřina
Institution:
1 Brno University of Technology, Faculty of Chemistry, Materials Research Centre, Purkynova 118/464, 612 00 Brno, Czech Republic, klucakova@fch.vutbr.cz
Conference:
7th International Conference on Nanomaterials - Research & Application, Hotel Voronez I, Brno, Czech Republic, EU, October 14th - 16th 2015
Proceedings:
Proceedings 7th International Conference on Nanomaterials - Research & Application
Pages:
639-644
ISBN:
978-80-87294-59-8
ISSN:
2694-930X
Published:
11th January 2016
Proceedings of the conference were published in Web of Science and Scopus.
Metrics:
21 views / 2 downloads
Abstract

Conformational changes of humic acids in different aqueous solutions were studied by means of two novelty methods: high resolution ultrasound spectrometry (HRUS) and micro-rheology (μR). Obtained results were compared with those of more conventional method of dynamic light scattering (DLS).The HRUS method is based on the measurement of parameters of ultrasonic waves propagating through the sample. The attenuation describes the decay of the amplitude of the ultrasonic wave with the distance travelled. The velocity is the speed of this wave and is related to the wavelength and the frequency of oscillation of the deformation. It is determined by the density and elasticity of the sample, which is strongly influenced by the molecular arrangement. The μR technics (in contrast to conventional rheology) relies on tracking the motions of the micro-sized tracer particles embedded in the sample. It can give information about a local inhomogeneity especially in the ultra-small scale materials.Our results showed that the organization of particles in diluted and concentrated solutions of humic acids is different. The conformational arrangement was strongly influence both the concentration and the character of surrounding medium. The decrease in compressibility indicated the formation of a more rigid structure, which could lead to the decrease in the binding ability of humic acids. Changes in sizes of particles detected using DLS resulted in their different mobility and obtained micro-rheological parameters. It was confirmed that both novelty methods employed were very sensitive and could be utilized as indicators of conformational changes in humic systems.

Keywords: Humic substances, molecular organization, conformation, ultrasound spectrometry, micro-rheology
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