Deep Insight in the Processes Occurring During Early Stages of the Formation and Room Temperature Evolution of the Core(Amorphous SiO2)@Shell(Organocations) Nanoparticles

Bosnar, Sanja; Antonić Jelić, Tatjana; Bronić, Josip; Dutour Sikirić, Maja; Šegota, Suzana; Čadež, Vida; Smrečki, Vilko; Palčić, Ana; Subotić, Boris (2018) Deep Insight in the Processes Occurring During Early Stages of the Formation and Room Temperature Evolution of the Core(Amorphous SiO2)@Shell(Organocations) Nanoparticles. Journal of Physical Chemistry C, 122 . pp. 9441-9454. ISSN 1932-7447

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Abstract

Following the assumption that the crucial processes governing the formation, properties and evolution of the core(amorphous silica)@shell(organocations) nanoparticles take place during short-time, room-temperature (rt) stirring/aging of the homogeneous reaction mixtures (HmRMs) formed by hydrolysis of TEOS (tetraethyl orthosilicate) in solutions of Org(OH)n, we investigated these processes by various experimental methods (pH, ionic conductivity, 29Si-NMR, dynamic light scattering and atomic force microscopy). The analysis of the data obtained by detail and careful investigation of the "model" HmRMs having the starting chemical composition: xTEOS:0.25TPAOH:20H2O (TPAOH = tetrapropylammonium hydroxide; x = 0.05 – 1), offer some new elements for the understanding of the mechanisms of formation and rt evolution of the core@shell silica nanoparticles: (1) There is a resolute evidence of the formation of the stable, about 1.2 nm sized core(amorphous SiO2)@shell(TPA+ ions) nanoparticles below the critical aggregation concentration (CAC). (2) Due to the intensive particulate processes (growth, aggregation, disaggregation, dissolution) which take place during the rt aging of the investigated HmRMs, the equilibrated core@shell silica nanoparticles do not exist as individual primary ones, but as the aggregates (about 2 nm to about 20 nm), composed of 1 – 2 nm sized "primary" nanoparticles. (3) In spite of the most frequent meaning that the nanoparticle shell is composed of the "free" TPA+ ions adsorbed on the surface of the nanoparticle core, the results of this study show that the nanoparticle shell can be formed mainly by attachment of the polysilicate anions (silicate oligomers), associated with TPA+ ions, on the surfaces of the nanoparticles cores.

Item Type:	Article
Uncontrolled Keywords:
Subjects:	NATURAL SCIENCES NATURAL SCIENCES > Chemistry NATURAL SCIENCES > Chemistry > Physical Chemistry NATURAL SCIENCES > Chemistry > Inorganic Chemistry
Divisions:	Division of Materials Chemistry
Depositing User:	Ana Palčić
Date Deposited:	15 Oct 2018 13:22
URI:	http://fulir.irb.hr/id/eprint/4184
DOI:	10.1021/acs.jpcc.8b00024

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