Water contact angle (WCA) values were obtained with a Theta Lite 101 optical tensiometer (Biolin Scientific, UK) using the sessile-drop method with an 8 μL droplet of the background electrolyte solution. The immediate WCA was recorded at 10 ms from droplet contact and reported values are the average of 4 -12 measurements for every PS loading at each surface (see details about PS-goethite and PS-diamond surface preparation below). The drop shape was analyzed using the Young-Laplace equation. The relative humidity of the laboratory air during air-drying and measurements was about 30% at room temperature.