Sonication probe

The GO library was established using methods reported previously.^{4 (link)} Pristine GO was prepared by a modified Hummers’ method. We performed ICP-MS to determine the level of impurities and the results showed that all elements including metal impurities are negligible level (<0.04 wt. %) (data not shown). To prepare reduced GO, pristine GO was dispersed in NMP by ultrasonication for 1 h at 50% power (~55 W). The solution was heated to 150 °C with constant stirring in a silicone oil bath for 1 hour (rGO-1) or 5 h (rGO-2). For the preparation of hydrated GO, 10 mL pristine GO suspension (5 mg/mL) was diluted with 90 mL deionized (DI) water and mixed with 80 mg NaOH (0.02 M), using dispersal by a sonication probe (Sonics & Materials, USA) at 32 W for 10 s. The GO mixture was transferred into a round flask and refluxed at 50 or 100 °C in an oil bath with constant magnetic stirring for 24 h. 1 M HCl solutions were used to neutralize the reaction. The mixture was centrifuged at 50,000 rpm for 30 min to collect the hydrated GO pellets. After washing with DI water three times, the hydrated GO samples were dispersed in DI water and stored at 4 °C.

10 mL GO suspension (5 mg/mL) was diluted with 90 mL deionized (DI) water and mixed with 80 mg NaOH (0.02 M), using dispersal by a sonication probe (Sonics & Materials, USA) at 32 W for 10 min. The GO mixture was transferred into a round flask and refluxed at 50 or 100 °C in an oil bath with constant magnetic stirring for 24 h. 1 M HCl solutions were used to neutralize the reaction. The mixture was centrifuged at 50, 000 rpm for 30 min to collect the hydrated GO pellets. After washing with DI water three times, the hydrated GO samples were dispersed in DI water and stored at 4 °C.

CuO NPs were suspended in distilled, deionized H₂O at a concentration of 5 mg/mL. A water sonicator (Branson, Danbury, CT, USA, model 2510) was used to sonicate these suspensions at 100 W output with a frequency of 42 kHz for 15 min. The suspensions were used as stock solutions for further dispersion in RPMI1640 or BEGM media. An appropriate amount of each stock solution was added to cell culture media to achieve the desired final concentration. For RPMI 1640, the media were supplemented with 10% fetal bovine serum (FBS). For BEGM, BSA was added to the medium at 0.2 mg/mL, before the addition of CuO NPs to achieve a high dispersion. ^{19 (link)–20 (link), 23 (link)–24 (link)} The diluted CuO suspensions in cell culture media were dispersed using a sonication probe (Sonics & Materials, USA) at 32 W for 15 s before exposure to the cells.

Coated or uncoated UCNPs were suspended in DI H₂O at a concentration of 2 mg/mL as stock solutions. These stock solutions were sonicated for 15 min in a bath sonicator (Branson, Danbury, CT, USA, model 2510; 100 W output power; 42 kHz frequencey). An appropriate amount of each UCNP stock solution was added to cell culture media or PBS to achieve the desired final concentrations. The diluted UCNP suspensions were dispersed using a sonication probe (Sonics & Materials, USA) at 32 W for 15 s before introduction to cultured cells.