Supporting Information. Selective Metallization Induced by Laser Activation: Fabricating

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1 Supporting Information Selective Metallization Induced by Laser Activation: Fabricating Metallized Patterns on Polymer via Metal Oxide Composite Jihai Zhang, Tao Zhou,* and Liang Wen State Key Laboratory of Polymer Materials Engineering of China, Polymer Research Institute, Sichuan University, Chengdu , China. *Corresponding author. Tel.: ; Fax: ; address: (T. Zhou) S-1

2 1. Characterizations of CuO, Cr 2 O 3, and CuO Cr 2 O Powder X-ray diffraction (PXRD) Figure S1. (a) PXRD pattern of copper oxide (CuO) (red) and the reference PXRD peaks (represented as vertical blue bars) of CuO (JCPDS card no ); the inserted image is the corresponding model of CuO crystal. (b) PXRD pattern of chromium oxide (Cr 2 O 3 ) (blue) S-2

3 and the reference PXRD peaks (represented as vertical red bars) of Cr 2 O 3 (JCPDS card no ); the inserted image is the corresponding model of Cr 2 O 3 crystal. (c) PXRD pattern of copper chrome black (CuO Cr 2 O 3 ) (in black) and the reference PXRD peaks (represented as vertical blue bars) of CuO Cr 2 O 3 (JCPDS card no ); the inserted image is the corresponding model of CuO Cr 2 O 3 crystal X-ray photoelectron spectroscopy (XPS) Figure S2. (a) XPS pattern of CuO. (b) XPS pattern of Cr 2 O 3. (c) XPS pattern of CuO Cr 2 O 3. S-3

4 1.3. Thermal gravimetric analysis (TGA) Figure S3. TG curves of CuO, Cr 2 O 3, and CuO Cr 2 O 3 at 10 C/min upon heating from 30 C to 800 C in nitrogen atmosphere. TG analysis was carried out to investigate the thermal stability of CuO, Cr 2 O 3, and CuO Cr 2 O 3. It is revealed that CuO, Cr 2 O 3, and CuO Cr 2 O 3 appear a slight weight loss below 400 C. TG results demonstrate that CuO, Cr 2 O 3, and CuO Cr 2 O 3 are stable enough under the temperatures of melt bending with ABS and injection molding of polymer composites UV-vis-IR spectroscopy As shown in Figure S4, the absorptions of CuO, Cr 2 O 3, and CuO Cr 2 O 3 are very different at 1064 nm, which indicates the different absorption efficiency for 1064 nm NIR laser. The absorbance of CuO, Cr 2 O 3, and CuO Cr 2 O 3 at 1064 nm is 1.772, 0.067, and 4.260, respectively. S-4

5 Figure S4. UV-vis-IR spectra of CuO, Cr 2 O 3, and CuO Cr 2 O 3 in the region of nm. 2. Laser scanning experiments of a single line with different laser parameters Figure S5. Optical microscope images of laser scanning experiments of a single line on the ABS composites surface with 1064 nm NIR pulsed laser. (a) Different laser scanning speed (1000 mm/s, 2000 mm/s, and 3000 mm/s) at fixed laser power (8 W) and laser frequency (60 khz), and the top left corner is laser scanning speed. (b) Different laser power (1 W, 3 W, and 8 W) at fixed laser scanning (2000 mm/s) and laser frequency (60 khz), and the top left corner is laser power. (c) Different laser frequency (30 khz, 60 khz, and 100 khz) at fixed laser scanning speed (2000 mm/s) and laser power (8 W), and top left corner is laser frequency. Lower right corner in each image is scale bar: 100 μm. S-5

6 The optical microscopy images of laser scanning experiments of a single line on the ABS composites surface with 1064 nm NIR pulsed laser are shown in Figure S5. As shown in Figure S5 (a), with the increase of laser scanning speed from 1000 mm/s to 3000 mm/s, the surface morphology of the single line changes from a continuous line to discontinuous points, and it can be explained by the shortening interaction time between laser beam and ABS composites. As expected, in Figure S5 (b), the surface morphology has no obvious etching at lower laser power (10%=1 W), and the clear etching pits are formed on the surface with the increase of laser power (80%=8 W). This is because the fact that the lower laser energy is too weak to etch the surface. As illustrated in Figure S5 (c), at the fixed laser scanning speed and laser power, regardless of the laser frequency, the similar morphologies are observed on the surface of ABS composites. 3. Contact angles Figure S6. Surface contact angles of the samples after laser irradiation in the window of (60 khz, 80%) in Figure 3 and Figure 2(c). (a) Neat ABS; (b) ABS/CuO; (c) ABS/Cr 2 O 3 ; (d) ABS/CuO Cr 2 O 3. S-6

7 4. X-ray photoelectron spectroscopy Figure S7. XPS patterns of Cu 2p of pure CuO Cr 2 O 3 after laser irradiation in the window of (60 khz, 80%). Figure S8. XPS patterns of ABS/CuO Cr 2 O 3 composites with different content of CuO Cr 2 O 3 after laser activation (irradiation) in the window of (60 khz, 80%). (a) 0.4 wt.% (ABS/CuO Cr 2 O 3 =99.6:0.4); (b) 0.6 wt.% (ABS/CuO Cr 2 O 3 =99.4:0.6). The XPS spectra are fitted using curve-fitting software (XPSPEAK v4.0). S-7

8 5. Performance of selective metallization with the different amount of CuO and CuO Cr 2 O 3 Figure S9. Digital photographs of ABS composites plates after NIR laser activation and 30 min electroless copper plating. (a) ABS incorporated with 1 wt.% CuO (ABS/CuO=99:1); (b) ABS incorporated with 3 wt.% CuO (ABS/CuO=97:3); (c) ABS incorporated with 1 wt.% CuO Cr 2 O 3 (ABS/CuO Cr 2 O 3 =99:1); (d) ABS incorporated with 3 wt.% CuO Cr 2 O 3 (ABS/CuO Cr 2 O 3 =97:3). 6. Performance of selective metallization with the different amount CuO Cr 2 O 3 Figure S10. Digital photographs of ABS/CuO Cr 2 O 3 composites plates with the different amount of CuO Cr 2 O 3 after NIR laser activation and 30 min electroless copper plating. (a) 0.2 wt.%; (b) 0.4 wt.%; (c) 0.6 wt.%; (d) 0.8 wt.%. S-8

9 Figure S11. Corresponding large squares (2 cm 2 cm) of ABS/CuO Cr 2 O 3 composites plates with different content of CuO Cr 2 O 3 after NIR laser activation and 30 min electroless copper plating. The laser activation parameters of these squares are the same as the windows of (60 khz, 80%) in Figure S10. (a) 0.2 wt.%; (b) 0.4 wt.%; (c) 0.6 wt.%; (d) 0.8 wt.%. 7. Estimation of the critical number of the Cu 0 atoms (per cm 2 ) to initiate the copper plating The required critical number of Cu 0 atoms (per cm 2 ) to initiate the copper plating can be conveniently obtained from the theoretical calculation combined with XPS analysis. Now, we give our steps as follows. Firstly, we calculate the total Cu present on the surface of ABS/CuO Cr 2 O 3 composites after laser activation (irradiation). In our work, the CuO Cr 2 O 3 (the relative molecular mass: g/mol) is completely uniformly dispersed throughout the polymer matrix (ABS) via melt blending. As shown in Figure 4(c), for the surface of ABS/CuO Cr 2 O 3 composite, the depth of laser radiation was determined at 26.9 μm. Thus, the volume of laser activation on the surface in per cm 2 are cm 3. It is believed that all the CuO Cr 2 O 3 within this depth (26.9 μm) involve in the reduction reaction during laser activation, and subsequently expose to the polymer surface. Then, the total Cu per cm 2 on the surface of ABS/CuO Cr 2 O 3 composite can be calculated according to the following equation: S-9

10 N = ρ V W N A where N is the total Cu per cm 2, and ρ is the density of ABS (1.03 g/cm 3 ). The V is the laser irradiated volume per cm 2 on the polymer composite surface. The W is amount of CuO Cr 2 O 3, and N A is Avogadro constant (N A = /mol). Thus, the total Cu per cm 2 on the surface of ABS/CuO Cr 2 O 3 composite is and when the amount of CuO Cr 2 O 3 are 0.4 wt.% and 0.6 wt.%, respectively. The specific calculations are below: ρ V W N = N A = = /cccc ρ V W N = N A = = /cccc Secondly, the XPS measurements of these two ABS/CuO Cr 2 O 3 composites after laser activation were carried out, and the results are shown in Figure S8. In Figure S8(a), through the fitting results of the Cu 2p 3/2 peak (areas of ev and ev), it is calculated that 47.4% Cu 2+ (933.6 ev) is reduced to Cu 0 (932.5 ev) in the polymer composite when the amount of CuO Cr 2 O 3 is 0.4 wt.%. In Figure S8(b), through the fitting results of the Cu 2p 3/2 peak (areas of ev and ev), it is calculated that 48.1% Cu 2+ (933.6 ev) is reduced to Cu 0 (932.5 ev) when the amount of CuO Cr 2 O 3 is 0.6 wt.%. Therefore, the critical Cu 0 atoms/cm 2 required for initiating electroless copper plating can be calculated as follows: N c = N R where N c is the critical Cu 0 atoms/cm 2, R is the reduction rate of CuO Cr 2 O 3. According to the above calculations, the total Cu atoms/cm 2 are and , respectively. Thus, in our work, the critical Cu 0 atoms/cm 2 required for initiating electroless copper plating is between /cm 2 and /cm 2. S-10

11 8. Photograph of CuO Cr 2 O 3 Figure S12. Digital photograph of pure CuO Cr 2 O 3 powder. S-11