Brookhaven 90plus

Measurements of hydrodynamic particle diameters were carried out on a Brookhaven 90 Plus instrument, at a fixed angle (90°). Light intensity fluctuations were recorded using the Brookhaven90 Plus correlator (Brook haven Instruments Company, Holtsville, NY, USA). To process the obtained data and calculate the particle diffusion coefficients, the software provided by the device manufacturer was used. The hydrodynamic radii were calculated using the Stokes equation in the approximation of spherical particles

The mean size and polydispersity index (PDI) of the Nps were determined using dynamic light scattering (DLS) via the Brookhaven 90 Plus instrument (Brookhaven Instruments Corp., Holtsville, NY, USA). The samples were diluted in ultrapure water (1:100) and placed in a cuvette with a lid. Zeta potential was determined from the electrophoretic mobility of the suspended Nps. The measurements were carried out using the ZetaSizer equipment (ZS-Malvern^®, Malvern, UK). The samples were diluted (1:100) in a 1 mM KCl aqueous solution and placed in the electrophoretic cell, where a potential of ±150 mV was established. Throughout both tests, the pH of the nanoparticle solutions was consistently maintained at approximately 4.5. This was conducted to ensure the pH closely matched the final pH of the Nps suspension obtained, which was also approximately 4.5, thus ensuring consistent conditions for analysis.

Dynamic light scattering of QRs in water was employed to determine the apparent hydrodynamic size of the QRs and to check for particle aggregation. Measurements were carried out on a Brookhaven 90Plus (BrookHaven, Holtsville, NY, USA) particle sizer equipped with a red laser (659 nm) and an APD detector placed at 90°. Samples were enclosed in a PMMA cell and placed in a temperature-controlled (25 °C) measurement camera. The measured autocorrelation functions were fitted with the non-negatively constrained least squares algorithm (NNLS) to extract the diffusion coefficients of the particles as an average of 5 independent measurements. Diffusion coefficients were then converted into apparent hydrodynamic size through the Stokes–Einstein law. Zeta-potentials of QRs in an aqueous solution were obtained via phase analysis light scattering (PALS) using a Brookhaven ZetaPALS instrument. The apparatus consisted of a laser operating at 659 nm and an APD detector placed at 15°. The recorded electrophoretic mobilities (as an average of 5 independent measurements) were converted into ζ-potential values through the Helmholtz–Smoluchowski equation.