**2. Thermogravimetric Analysis**

Thermogravimetric analysis was performed on a TA Q600-0348, model SDT Q600 (Thermofinnigan) using a temperature profile of 25–800 °C at 10 °C/min under N2 flow (10 mL/min) with sample masses ranging from 5-12 mg.

The TGA analysis of the inorganic nanotubes before and after carboxylation is displayed in Figure S2. Weight losses were 1.39% and 17.12% for the untreated and carboxylated WS2 INTs respectively, indicating that organic material is attached to the surface of the treated nanotubes.

#### **3. Zeta Potential**

Nanoparticle surface charge (ȟ potential) was determined using a Zetasizer Nano-ZS (Malvern Instruments Ltd. Worcestershire, UK) in water at 25 °C and 150 V. Dispersions were prepared with an ElmaSonic S30 sonicator (Elma GmbH & Co., Singen, DE).5 mg of WS2 INTs or carboxylated WS2 INTs were dispersed in 15 ml ultra-pure H2O (resitivity >18 Mohm•cm) by sonication for one minute. The Zeta potential was measured immediately after sonication. The analysis showed -27.8 mV and -17.3 mV for the carboxylated and untreated WS2 INTs, respectively.
