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Hernández Cifre, José Ginés

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Hernández Cifre, José Ginés
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Universidad de Murcia. Departamento de Química Física
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    Aggregation behaviour of gold nanoparticles in presence of chitosan
    (Springer, 2015-06-13) Fernández Espín, Vanesa ; Pamies, Ramón ; García de la Torre, José; García Montalbán, Mercedes; Collado-González, Mar; Hernández Cifre, José Ginés; Díaz Baños, F. Guillermo; Víllora Cano, Gloria; Ingeniería Química
    Chitosan (CS) is a biocompatible polysaccharide with positive charge that is widely used as a coating agent for negatively charged nanoparticles. However, the types of structures that emerge by combining CS and anoparticles as well as their behaviour are still poorly understood. In this work, we characterize the nanocomposites formed by gold nanoparticles (AuNPs) and CS and study the influence of CS in the expected aggregation process that should experience those nanoparticles under the favourable conditions of low pH and high ionic strength. Thus, at the working CS concentration, we observe the existence of CS structures that quickly trap the AuNPs and avoid the formation of nanoparticle aggregates in environmental conditions that, otherwise, would lead to such an aggregation.
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    Aggregation behaviour of gold nanoparticles in saline aqueous media
    (Springer, 2014-04-01) Pamiés, Ramón ; Fernández Espín, Vanesa ; García de la Torre, José; Hernández Cifre, José Ginés; Díaz Baños, F. Guillermo; Collado-González, Mar; Química Física
    The evaluation of the effect of saline aqueous media in the aggregation of colloidal gold nanoparticles (AuNP) suspensions has been followed by means of both dynamic light scattering and UV–Vis spectroscopy techniques. A wide range of ionic strengths from 0 to 1 M has been covered for suspensions of AuNPs with a hydrodynamic radius of 6.5 nm. The growth of the clusters over time is described by a power law whose exponent varies with the ionic strength. Two main aggregation regimes are found in qualitative agreement with predictions of the DLVO theory. At low ionic strength, AuNPs form small aggregates that are long-term stable. When a critical electrolyte concentration is exceeded, big clusters are formed rapidly and then colloidal suspension becomes unstable and precipitation occurs. That so-called critical coagulation concentration was estimated by analyzing the time evolution of both the nanoparticle size (determined by DLS) and the plasmon peak (determined by UV–Vis spectroscopy), thus showing the validity of both techniques for such a purpose. The stability is also studied in terms of the zeta potential which approaches zero when salt concentration is above the critical coagulation concentration.
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