Supporting Information. Near infrared light-powered Janus mesoporous silica nanoparticle motors

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1 Supporting Information Near infrared light-powered Janus mesoporous silica nanoparticle motors Mingjun Xuan,, Zhiguang Wu,, Jingxin Shao, Luru Dai, Tieyan Si,, * and Qiang He, * State Key Laboratory of Robotics and System (HIT), Micro/Nanotechnology Research Centre, Harbin Institute of Technology, Harbin , China CAS Key Lab for Biomedical Effects of Nanomaterials and Nanosafety, National Center for Nanoscience and Technology, Beijing , China * tieyansi@hit.edu.cn; qianghe@hit.edu.cn Movie Information Video 1. The motion movie of 50 nm JMSNMs upon the 16.3 W/cm 2 NIR light. Video 2. The motion movie of 80 nm JMSNMs upon the 16.3 W/cm 2 NIR light. Video 3. The motion movie of 120 nm JMSNMs upon the 16.3 W/cm 2 NIR light. Video 4. In the absence of NIR light, the Brownian motions of 50 nm JMSNMs. Video 5. In the absence of NIR light, the Brownian motions of 80 nm JMSNMs. Video 6. In the absence of NIR light, the Brownian motions of 120 nm JMSNMs. Video 7. The power on/off motion of 80 nm JMSNMs upon 3W/cm 2 NIR light. S1

2 Experimental Section Materials Tetraethyl orthosilicate (TEOS), 3-aminopropyltrimethoxysilane (APTES), hexadecyltrimethylammonium bromide (CTAB), and fluorescein isothiocyanate (FITC) were purchased from Sigma-Aldrich. NaOH, ethanol, and ammonium hydroxide were purchased from Beijing Chemical Works. Phosphate buffer solution (PBS, ph = 7.4) and fetal bovine serum (FBS) were purchased from Life Technologies Corporation. These chemical reagents were employed without further purification. All chemicals were used as received without further purification, and all the solutions were freshly prepared. In addition, deionized water (Millipore, Milli-Q Plus 185 purification) with a resistivity of 18.2 MΩ was used in this work. Equipment A scanning electron microscope (SEM, Hitachi S4800) and a transmission electron microscope (TEM, FEI, Tecnai G 2 F20) were used to image the morphology of the nanoparticles. Au half-coated MSNs were prepared by a sputter coating machine (K575; EMITECH). The near-infrared absorption properties of the nanomotors were investigated using a UV-Vis-NIR spectrophotometer (Perkin Elmer, Lambda 950). Importantly, a two-photon confocal laser scanning microscope (TP-CLSM, Olympus, FV 1000) and an 808-nm fiber-coupled diode laser system (BWT, Beijing) were employed to provide a continuous-wave near-infrared laser to trigger or anchor the nanomotors. The diffusion coefficients of the nanomotors were measured by a dynamic light scattering system (Malvern, Zetasizer Nano ZS). Preparation of the Janus mesoporous silica nanomotors (JMSNMs) JMSNMs with a diameter of 80 nm were prepared according to our previous method. CTAB (250 mg), as the cationic surfactant, and NaOH (70 mg) were jointly dissolved in deionized water (120 ml). The mixture was heated to 80 C. TEOS (1.25 ml) was S2

3 introduced to the surfactant solution and allowed to react for 2 h at 80 C. Furthermore, MSNs with diameters of approximately 50 nm and 120 nm were synthesized and fabricated by changing the amount of NaOH (30 mg and 100 mg, respectively). The as-prepared MSNs were dispersed in a water/ethanol solution (V/V = 1:1), dropped on a piranha solution-treated silicon wafer to form a monolayer structure and dried in a vacuum. Subsequently, a 10-nm gold layer was deposited on the surface of the MSNs by chemical vapor deposition. Finally, the JMSNs were released from the substrate by weak ultrasonic treatment and were fluorescence-functionalized with FITC for the motion tracking observations. The FITC-labeled JMSNMs were observed via CLSM, as shown in Figure S3. Motion characterization of JMSNMs TP-CLSM was employed with an 808-nm fiber-coupled femtosecond laser to supply the NIR light source to trigger the motion and to record the motion frames of the JMSNMs. An in-house-designed program in MATLAB 7.0 was employed to acquire motion coordinate information on the JMSNMs. These coordinate data were utilized in conducting mathematical statistics and motion analysis. In the microfluidic experiment, a microfluidic chip (width of 200 µm) was designed to create a voyage line for examining the collective movement of the JMSNMs upon the gradient NIR light irradiation. In addition, MATLAB 7.0 and ImageJ were frequently employed in analyzing the nanomotor motion. Motion analysis for the bare MSN and Au whole-shell coated MSN Au whole-shell coated MSNs (AuWS-MSNs) were specially prepared by seed-mediated growth. In both the absence and presence of 16.3-W/cm 2 NIR light, the motions of bare MSNs and AuWS-MSNs were recorded by TP-CLSM, and the corresponding diffusion coefficients were calculated accordingly. To investigate the influence of increased temperature on motion, the motion of the AuWS-MSNs was analyzed at different temperatures (25 C, 30 C, 35 C, and 40 C) in the absence of S3

4 NIR light. Measurement of the translational diffusion coefficient and rotational diffusional coefficient for the NIR light-powered nanomotors The translational diffusion coefficient and rotational diffusion coefficient of the JMSNMs were measured by a dynamic light scattering system (Malvern, Zetasizer Nano ZS). Nanoparticle water solutions of JMSNMs (1 mg/ml) and MSNs (1 mg/ml) with three diameters (50 nm, 80 nm, and 120 nm) were dispersed in 3-mL disposable cuvettes, and a fiber-coupled diode NIR laser system was simultaneously used to adjust the power irradiation for propulsion of the nanomotors. All the measurements were taken at a scattering angle of 173 with a constant temperature (25 C). Corresponding analysis results were simultaneously acquired from the 7.02 software version of Malvern Zetasizer. Measurement and physical simulation of the temperature variation First, prepared nanomotors with diameters of 50 nm (0.15 mg), 80 nm (0.39 mg), and 120 nm (0.95 mg) were dispersed in glass tubes containing 300 µl of water. The number of nanomotors for each of the three sizes in the corresponding glass tubes was approximately based on our calculation. The average distance between the centers of these nanoparticles is approximately 262 nm. Three samples were irradiated for 5 minutes in 3-W/cm 2 NIR light. The temperature variations were measured and recorded by a sensitive electric coupling thermometer at an indoor temperature (25 C). Based on the temperature variation data, the temperature distribution and thermophoresis force of a single JMSNM were theoretically computed according to a physical simulation. S4

5 Figure S1. SEM (a-c) and TEM (d-f) images of 50 nm, 80 nm and 120 nm mesoporous silica nanoparticles (MSNs). Scale bars are 200 nm (a-c) and 50 nm (d-f), respectively. Figure S2. UV-Vis-NIR spectra of bare MSNs in three sizes (50 nm, 80 nm, and 120 nm). S5

6 Figure S3. CLSM images of FITC-labeled 80 nm JMSNMs. (a) Fluorescence image. (b) Bright field. Scale bars = 10 µm. Figure S4. The Brownian motion of JMSNMs without NIR laser irradiation: (a) 50 nm JMSNM, (b) 80 nm JMSNM, (c) 120 nm JMSNM. Scale bars = 20 µm. S6

7 Figure S5. The motion of bare MSNs upon NIR laser irradiation (16.3 W/cm 2 ): (a) 50 nm MSN, (b) 80 nm MSN, (c) 120 nm MSN. Scale bars = 20 µm. Figure S6. The mean square displacement (MSD) of bare MSNs in three sizes with or without NIR laser illumination (16.3 W/cm 2 ). S7

8 Figure S7. Time-lapse images of the motion of the 80 nm AuW-MSNs. Scale bars = 20µm. The inset is the TEM image of an AuWS-MSN. Scale bar = 50 nm. Figure S8. Diffusion coefficients of bare MSNs, AuWS-MSNs, and JMSNMs in the presence of NIR light (16.3 W/cm 2 ). S8

9 Figure S9. Diffusion coefficients of the AuWS-MSNs at different temperatures in the absence of NIR light. Figure S10. The voyaging images of JMSNMs (80 nm) in phosphate buffer solution (PBS) at ph 7.4 and fetal bovine serum (FBS) solution. Scale bars = 20 µm. S9