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Formation of gold nanoparticle bilayers on gold sensors

Maciejewska-Prończuk, J., Oćwieja, M., Adamczyk, Z., Pomorska, A.
Colloids and surfaces 2019 v.560 pp. 393-401
adsorption, atomic force microscopy, chemical reduction, colloids, electrophoresis, electrostatic interactions, gold, ionic strength, models, nanogold, nanoparticles, pH, quartz, scanning electron microscopy, transmission electron microscopy
Formation of bilayers composed from oppositely charged gold nanoparticles and characterized by comparable size distribution was investigated using gravimetric and microscopic techniques. Positively (AuNPsCH(+)) and negatively charged (AuNPsTC(−)) gold nanoparticles were synthesized according to chemical reduction procedure. The transmission electron microscopy (TEM) revealed that the nanoparticle size was equal to 9.0 ± 3 nm and 14 ± 2 nm in the case of AuNPsCH(+) and AuNPsTC(−), respectively. The electrophoretic mobility measurements allowed to determine the electrokinetic properties of the nanoparticles and their stability under various conditions of pH and ionic strengths. Both the deposition kinetics of AuNPsCH(+) on gold sensors and the formation kinetics of second AuNPsTC(−) layer were determined using quartz microbalance (QCM) measurements. Additionally, the maximum coverage and bilayer structure were evaluated using atomic force microscopy (AFM) and scanning electron microscopy (SEM). In these measurements a negligible hydratation of AuNPsCH(+)/AuNPsTC(−) bilayers was confirmed. The significant increase in the maximum coverage of both supporting and external layers with ionic strength was interpreted as a results of decreasing range of repulsive electrostatic interactions among deposited nanoparticles. The experimental results were quantitatively interpreted in terms of the extended random sequential adsorption (eRSA) model.