Model zen3600

The mean hydrodynamic size and zeta potential of suspended PdNPs in water and culture media were measured by DLS by using Zetasizer Nano-ZS equipped with 4.0 mW, 633 nm laser (Model ZEN3600, Malvern Instruments Ltd., Malvern, UK).

The average hydrodynamic size (Z average), size distribution (% number distribution), and zeta potential of GNPs-Pep-A as a colloidal suspension were measured using dynamic light scattering (DLS) and a Zetasizer [Nano-ZS model equipped with 4.0 mW, 633 nm laser, Model ZEN3600, serial no. MAL1024433, Malvern Instruments Ltd., Malvern, UK]. The particle size was determined based on the Brownian motion relating to the size of the particles suspended in a liquid.

Hydrodynamic diameter (Z-average size), polydispersity index (PDI), and zeta potential measurements were always performed at room temperature using a Zetasizer Nano ZS instrument (Model ZEN3600, Malvern Instruments Ltd., UK) fitted out with a solid state HeNe laser (λ = 633 nm) at a scattering angle of 173°.

TEM characterizations were carried out with a JEOL Jem 1011 microscope, operating at an accelerating voltage of 100 kV (JEOL USA, Inc, Peabody, MA, USA). TEM samples were prepared by dropping a dilute solution of NPs in water on carbon-coated copper grids (Formvar/Carbon 300 Mesh Cu). DLS and ζ-potential measurements were performed on a Zetasizer Nano-ZS equipped with a 4.0 mW HeNe laser operating at 633 nm and an avalanche photodiode detector (Model ZEN3600, Malvern Instruments Ltd., Malvern, UK). Measurements were performed at 25 °C in aqueous solution (pH 7).
ImageJ open source software (NIH image) version 1.47 was used with a suite of analysis routines used for particle analysis to test the circularity values of NPs measured on TEM acquisition. Sorting based on circularity and including only those with circularity values > 0.8 will ensure any aggregates are not included in the measurement [38 (link)].

Dynamic light scattering (DLS) and electrophoretic light scattering (ELS) methodology was employed to measure the hydrodynamic diameter, zeta potential and polydispersity index of NP using ZetaSizer Nano ZS (Malvern Instruments, Malvern, UK) equipped with the 4.0 mW 633 nm laser (Model ZEN3600; 173° angle). NP samples (10 mg metal/L) were incubated for 0 h, 48 h, and 144 h at the toxicity test conditions and vortexed before the measurement.
The dissolution of NP was measured as initially described elsewhere [39 (link)]. Briefly, NP suspensions were prepared at 10 mg metal/L and incubated for 48 h (the duration of the Daphnia magna acute toxicity test) in OECD 202 AFW, Lake Raku water and Lake Ülemiste water with (7.5 × 10⁶ cells/mL) and without added algae. The samples were then ultracentrifuged at 362,769 × g for 30 min (duration of the whole cycle 60 min). For metal recovery control, salt solutions were always used in parallel. Metal concentrations in the supernatants were measured using graphite furnace atomic absorption spectroscopy (GF-AAS) analysis in the accredited laboratories of the Institute of Medical Research and Occupational Health (Zagreb, Croatia) and Estonian University of Life Sciences (Tartu, Estonia).