Shanghai JiaoTong University School of Medicine, Shanghai , People s Republic of China.

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1 Electronic Supplementary Material (ESI) for Nanoscale. This journal is The Royal Society of Chemistry 2017 Phase and Morphological Control of MoO 3-x Nanostructures for Efficient Cancer Theragnosis Therapy Bo Li a, Xin Wang a, Xiaoyu Wu a, Guanjie He b *, Ruoyu Xu c,xinwu Lu a *,Feng Ryan Wang c, Ivan P. Parkin b * a Department of Vascular Surgery, Shanghai Ninth People s Hospital Affiliated to Shanghai JiaoTong University School of Medicine, Shanghai , People s Republic of China. luxinwu@shsmu.edu.cn b Christopher Ingold Laboratory, Department of Chemistry, University College London, London WC1H 0AJ, UK. guanjie.he.14@ucl.ac.uk; i.p.parkin@ucl.ac.uk c Department of Chemical Engineering, University College London, London WC1E 7JE, U.K. Experimental Part Material Synthesis MoO 3-x with controlled phases and morphologies can be synthesized by one pot hydrothermal process. All the reagents were purchased from Sigma Aldrich (U.K.) and used without further purification. In a typical synthesis, g of (NH 4 ) 6 Mo 7 O 24 was dissolve in 10 ml of 0.6 M hydrochloric acid and 30 ml of deionized water (or 25 ml of distilled water and 5 ml of polyethylene glycol 400) with magnetic stirring for 30 min. The solution was moved to a 50 ml Teflon lined autoclaves and heated between 90 ~ 180 o C for 12 h. The precipitate was collected by centrifugation, washed with ethanol and deionized water for three times. The samples were freeze-dried for further use.

2 Characterization The morphology of the samples was characterized by scanning electron microscope (SEM, JSM-6700F) and transmission electron microscope (TEM, JEM-2100). The phases and chemical compositions were recorded by a STOE SEIFERT diffractometer (Mo source radiation) and X-ray photoelectron spectroscopy (XPS; Thermo scientific K-alpha photoelectron spectrometer). The photoluminescence spectrum was measured at room temperature using a fluorescence spectrophotometer (FP-6600, JASCO). Nitrogen adsorption-desorption isotherms were measured at 77 K (Micromeritics VacPrep 061), and the BET method was used to identify the specific surface area (SSA) by a five-point nitrogen adsorption isotherm. Dynamic light scattering test was performed on a DelsaMax PRO instrument (BECKMAN COULTER). The 808 nm semiconductor lasers were purchased from Shanghai Xilong Optoelectronics Technology Co. Ltd., China, the power could be adjusted externally (0-2 W). The output power of lasers was independently calibrated using a hand-held optical power meter (Newport model 1918-C, CA, USA). To measure the photothermal performance, solution of MoO 2 nanoclusters with various concentrations were irradiated by the 808 nm laser devices at a safe power density of 0.5 W cm -2 (~ 189 mw for a spot size of ~ 0.38 cm 2 ) for 5 min. The temperature was monitored and imaged simultaneously by a thermal imaging camera (FLIR A300, USA). To evaluate the photothermal performance of the MoO 2 nanoclusters, the photothermal transduction efficiency of the nanoclusters (100 ppm) was measured. Nanocluster dispersions were continuously illuminated by an 808-nm laser with a power density of 0.5 W cm 2 (~ 189 mw for a spot size of ~ 0.38 cm 2 ) until reaching a steady-state temperature increase. The irradiation source was then shut off and the temperature decrease was monitored to determine the rate of heat transfer from the system. The photothermal conversion efficiency, following Eq. 1: T, was calculated using the ha(t max - T amb ) Q0 T = A I(1 10 ) (1)

3 Where h is the heat transfer coefficient, A is the surface area of the container. T max is the maximum system temperature, T amb is the ambient surrounding temperature, I is the laser power (in units of mw, 189 mw) and A λ is the absorbance ( ) at the excitation wavelength of 808 nm. Q 0 is the heat input (in units of mw) due to light absorption by the solvent. The lumped quantity ha was determined by measuring the rate of temperature drop after removing the light source. The value of ha is derived according to Eq. 2: mc D s ha D (2) where τ s is the sample system time constant, m D and C D are the mass (0.1 g) and heat capacity (4.2 J g -1 ) of deionized water used as solvent, respectively. The Q 0 was measured independently using a quartz cuvette cell containing pure water without themoo 2 nanoclusters and found to be mw. In Vitro Cell Viability Assay The in vitro cytotoxicity was evaluated using the Cell Counting Kit-8 (CCK-8) (Dojindo Laboratories, Kumamoto, Japan). TC71 cells were seeded into a 96-plate at 1x10 4 cells per well at 37 C in the presence of 5% CO 2. After incubation for 24 h, MoO 2 nanoclusters were then added into the wells at various concentrations and incubated for another 24 h. Cell viabilities were then detected using the CCK-8 assay. In vitro photothermal therapy of cancer cells TC71 cells were seeded into a 24-well plate at a density of 10, 000 cells/ml in RPMI culture medium at 37 C in the presence of 5% CO 2 for 24 h prior to treatment. After incubation, the cell medium was removed, and the cells were washed with PBS buffer solution for three times. 100 μl MoO 2 nanoclusters dispersed in a PBS solution was then added into the wells. After incubation for another 12 h, the cells were irradiated for 5 min, using a 808 nm laser with an output power density of 0.5 Wcm -2. Cell viabilities were then detected using the CCK-8 assay. In Vivo Photothermal Ablation

4 Severe combined immunodeficiency (SCID) nude mice were inoculated subcutaneously with TC71 cells for 20 days. When the tumors inside the mice had grown to 5-10 mm in diameter, the SCID nude mice were randomly allocated into four groups. The TC71 tumor-bearing nude mice were intratumorally injected with of the solution of MoO 2 nanoclusters (100 μl, 250 ppm) or saline solution. After 0.5 h post-injection, the mice with or without the injection of MoO 2 nanostructures were simultaneously irradiated with the 808-nm laser at a power density of 0.5 W cm - 2 power density for 5 min. During the laser irradiation, full-body infrared thermal images were captured using an IR camera from a photothermal therapy monitoring system (FLIR A300, USA). After the laser treatment, the SCID mice were killed, and tumors were removed, embedded in paraffin, and cryosectioned into 4 μm slices. The slides were stained with H&E. The slices were examined under a Zeiss Axiovert 40 CFL inverted fluorescence microscope, and images were captured with a Zeiss AxioCam MRc5 digital camera.

5 Figure S1. Nitrogen adsorption desorption isotherms of the MoO 2 nanostructures.

6 Figure S2. Dynamic light scattering (DLS) data of MoO 2 nanoclusters in water. Figure S3. SEM images of MoO 3 nanostructures.

7 Figure S4. XRD patterns of MoO 3 samples.

8 Figure S5. Crystal structures of (a) MoO 2 and (b) MoO 3.

9 Figure S6. X-ray photoelectron spectroscopy spectra of (a), (c) Mo 3d and (b), (d) O 1s, respectively for MoO 2 and MoO 3 nanostructures. The peaks in O 1s spectra at and ev for MoO 2 and MoO 3 can be assigned to lattice oxygen in the metal oxide. The peaks at ev in Figure S3b can be indexed to oxygen vacancies in the matrix of MoO 2. The peaks with largest binding energy are related to chemically absorbed oxygen sites in both samples. 1

10 Figure S7. Photoluminescence spectrum of MoO 2 sample, recorded at an excitation wavelength of 240 nm.

11 Figure S8. A camera picture of MoO 2 nanoclusters dispersed in water, PBS, and RPMI-1640 culture medium for a week, showing the good dispersion of NCs.

12 Figure S9. Plot of temperature change (T) over a period of 300 s versus the aqueous dispersion concentration of MoO 2 nanostructures

13 Figure S10. (a) Photothermal effect of 100 ppm MoO 2 nanoclusters upon being irradiated (808 nm, 0.5 W cm -2 ) for 300 s and shutting off the laser; (b) Time constant for heat transfer from the system is determined to be τ s = 86.4 s by applying the linear time data from the cooling period of panel (c) versus negative natural logarithm of driving force temperature.

14 Figure S11. UV-vis spectra of (a) the MoO 2 nanoclusters and (b) Au nanorods before and after the NIR light (808 nm, 2W) irradiation for 30 min.

15 Figure S12. (a) The TC71 cell viability incubated with the MoO 2 nanoclusters with different concentrations for 24 h. (b) The TC71 Cell viability after treatment with different concentrations of the MoO 2 nanoclusters and NIR laser irradiation for 5 min. References: 1. H. S. Kim, J. B. Cook, H. Lin, J. S. Ko, S. H. Tolbert, V. Ozolins and B. Dunn, Nat. Mater., 2017, 16,