Disposable capillary cuvettes

Zeta-potential was determined in diluted TiO₂ NP stock dispersions and TiO₂ NP/BSA dispersions (100 and 10 μg/ml) measuring electrophoretic mobility of the particles at 20 °C via laser Doppler velocimetry using a Zetasizer Nano-ZS apparatus (Malvern Instruments Ltd.) and disposable capillary cuvettes (Malvern Instruments Ltd.). Three consecutive measurements were taken of each sample. The number of runs was set automatically. The Smoluchowski approximation was used for calculation.

The hydrodynamic size distribution of the as-supplied aqueous dispersions of FLG inks (IA and IB) and ink powders in stock suspension (Milli-Q water) (IA+ and IB+) was determined by dynamic light scattering (DLS) analysis using a Zetasizer Nano-ZS apparatus (Malvern Instruments Ltd., Malvern, UK). The size distributions under test conditions (e.g., in aquarium water and cell culture medium) and over the specific test durations (e.g., over 96 h in aquarium water) were recorded to monitor their stability and/or any changes in properties (e.g., size, aggregation state, polydispersity index, zeta potential). At least four measurements (10 runs for each measurement, 10 s/run) were taken of each sample. The attenuator and the optimal measurement position were automatically determined in the first measurements of each concentration in each sample, and thereafter they were fixed and used to monitor stability (size distribution maintenance) [14 (link)]. Data were analyzed using Zetasizer Software version 6.34 (Malvern Instruments Ltd.). Z-potential measurements of some samples were also performed by electrophoretic light scattering using disposable capillary cuvettes (Malvern Instruments Ltd.). Three measurements were taken of each sample. The number of runs was set automatically by the device.

The hydrodynamic sizes of the particles in suspension were determined using a Zetasizer Nano-ZS (Malvern Instruments Ltd., Worcestershire, UK). Measurements were performed in the exposure suspensions at the maximum concentrations directly after preparation and at the end of the assays, 24 h for cytotoxicity assays in fish cell lines and 48 h for the Daphnia magna test. The hydrodynamic sizes of the NPs in the fish exposure tanks were also measured daily during the 96 h acute toxicity assay by taking aliquots from the water column. Medium without NPs was used as a control and to record any background signals that may arise from medium components. Before preparing the samples, the instrument temperature was set to the corresponding exposure condition temperature. Four independent measurements were taken with each measurement consisting of six runs of 20 s durations.
The ζ-potential was measured for the uncoated and coated (CIT and PEG) metal oxide NPs at the highest exposure concentration once dispersed in the media. Due to limitations in the stock concentration, this property was not measured for Ag NPs. ζ-potential measurements were performed using disposable capillary cuvettes (Malvern Instruments Ltd.). Three measurements were taken of each sample and the number of runs was set automatically.