Physicochemical properties of surface charge-modified ZnO nanoparticles with different particle sizes

Abstract

In this study, four types of standardized ZnO nanoparticles were prepared for assessment of their potential biological risk. Powder-phased ZnO nanoparticles with different particle sizes (20 nm and 100 nm) were coated with citrate or L-serine to induce a negative or positive surface charge, respectively. The four types of coated ZnO nanoparticles were subjected to physicochemical evaluation according to the guidelines published by the Organisation for Economic Cooperation and Development. All four samples had a well crystallized Wurtzite phase, with particle sizes of ∼30 nm and ∼70 nm after coating with organic molecules. The coating agents were determined to have attached to the ZnO surfaces through either electrostatic interaction or partial coordination bonding. Electrokinetic measurements showed that the surface charges of the ZnO nanoparticles were successfully modified to be negative (about −40 mV) or positive (about +25 mV). Although all the four types of ZnO nanoparticles showed some agglomeration when suspended in water according to dynamic light scattering analysis, they had clearly distinguishable particle size and surface charge parameters and well defined physicochemical properties.

The Decoration of ZnO Nanoparticles by Gamma Aminobutyric Acid, Curcumin Derivative and Silver Nanoparticles: Synthesis, Characterization and Antibacterial Evaluation

“…This pH is intermediate between the pKa of the GABA carboxyl and amine groups, and thus the GABA is expected to be neutral. The fact that the zeta potential studies show that ZnO NPs-GABA is in fact positively charged is similar to the result obtained by Kim et al [46], who functionalized ZnO NPs with L-serine and measured a zeta potential of +26.8 mV at pH 7.0. After ZnO NPs-GABA was covalently attached with CurBF2, this value shifted to −9.8 ± 0.5 mV.…”

“…The pH solutions of all samples were determined as shown in Table S1. Wurtzite-type ZnO NPs are recognized to have positive surface charges in the as-prepared state [46]. The result showed that unmodified ZnO NPs showed zeta potential of 5.3 ± 1.1 mV while ZnO NPs modified by GABA demonstrated a zeta potential value of 24.9 ± 0.3 mV.…”

“…From the above results, the size of samples determined by TEM are always larger than those determined by XRD. We note that the size extracted from XRD via the Scherrer equation correspond to the average size of the crystalline domain in the particles [46] whereas that determined by TEM is the absolute size of the ZnO NPs. This suggests that at least some particles contain more than one crystalline domain, or that aggregation of ZnO nanocrystallites occurs [47].…”

Enhancement of Thermal Diffusivity in Phase-Separated Bismaleimide/Poly(ether imide) Composite Films Containing Needle-Shaped ZnO Particles

“…The monomodal dispersion observed after treatment is attributable to the size distribution of mono-dispersed n-ZnO particles (0.3–7 μm). The zeta potential of n-ZnO particles dispersed in ethanol was estimated as 26.3 ± 3 mV, which agrees well with the reference values of ZnO particles (24.0, 26.3 and 26.8 mV at pH 7) [ 9 , 10 ]. This positive and large zeta potential could facilitate homogenous dispersion of n-ZnO particles in polyimide and cured BMI matrices.…”

Photocatalytic performance of ZnO carbon composites for the degradation of methyl orange dye

“…Presence of -OH and C=O groups on the surface of CS make it hydrophilic in nature [38]. Herewith we propose that Zn 2+ produced during synthesis of ZnO using an aqueous solution of Zn(CH 3 COO) 2 can get coupled with such active sites especially where -OH group is present due to the electrostatic interactions [32,35,[39][40][41]. The Zn 2+ ions coupled at the surface of CS further reacts with the OH − ion present in the reaction solution to produce Zn(OH) 2 at the CS surface.…”