Fs30 ultrasonic cleaner

Carbon dots were synthesized using citric acid and β-alanine according to a previous report [8 (link)] with a slight modification, outlined in Figure 1. We used citric acid monohydrate (Fisher #A104-500, Pittsburg, PA, USA) as a carbon source instead of anhydrous citric acid (Fisher #BP339-500, Pittsburg, PA, USA) at the same molar ratio and observed similar results. Briefly, CDs were synthesized by mixing 1:2 molar ratio of citric acid and β-Alanine, where one gram of citric acid was mixed with 0.9 g of β-Alanine in 10 mL of distilled water (pH 3) in a conical flask. The mixture was homogenized using an Ultrasonicator (Ultrasonic Cleaner FS30, Fisher Scientific, Pittsburg, PA, USA) until completely dissolved and then heated for 3 min in a commercial microwave oven (Model#JES2251SJ02, GE Appliance, Louisville, KY, USA) at 70% power level to proceed to carbonization and surface passivation. The obtained brownish solid was then dissolved in 10 mL of distilled water (pH 3).

Carbon dots were synthesized using citric acid and β-alanine according to previous reports^{6 ,16 (link)} with slight variations. Briefly, CDs were synthesized by mixing 1:2 molar ratio of citric acid and β–Alanine. 2.1 g of citric acid monohydrate was mixed with 1.8 g β-alanine in 10 mL water (pH3) in a conical flask. The mixture was homogenized using Ultrasonicator (Ultrasonic Cleaner FS30, Fisher Scientific, Pittsburg, PA) and heated using commercial microwave oven (1200 W#JES2251SJ02, GE Appliance, Canada) at 70% power level for 3 min to complete the carbonization and surface passivation steps. The brownish solid was then dissolved in 10 mL of distilled water.

Nanoparticle stock suspensions were obtained monodispersed in MQ water or sodium bicarbonate buffer (Online Resource 2). FW exposure media was prepared by dissolving 0.26 g/l Instant Ocean salts (Aquatic Ecosystems, Apopka, FL) in reverse osmosis water and adjusting the pH to 7.2 ± 0.2 using ~0.01 g sodium bicarbonate (conductivity 480–600 μS/cm). Prior to dilution in FW, stocks were bath sonicated (120 V) using a Fisher Scientific FS30 Ultrasonic Cleaner (without heating) for 25 s to break up agglomerates as per the manufacturer’s recommendation. Serial dilutions were mixed by inverting prior to making the subsequent dilutions. The concentrations used for the exposures were based on preliminary dose responses to a wide range (0.02–250 μg/ml), and based on the total mass of the material provided by nanoComposix. Suspension concentrations used for the commercial and custom-made ~70 nm AgSi and Si NPs were 0.5, 1, 5, 10, 25, 50, and 100 μg/ml; for the bare Ag NPs: 0.02, 0.08, 0.4, 2, 10, 50, and 250 μg/ml; and for the custom-made ~20 nm AgSi NP: 0.1, 0.5, 1, 10, 25, and 50 μg/ml.