Bismuthoxyiodide Nanoflakes/Titania Nanotubes. Arrayed p-n Heterojunction and Its Application for. Photoelectrochemical Bioanalysis

Transcription

1 Supplementary Information Bismuthoxyiodide Nanoflakes/Titania Nanotubes Arrayed p-n Heterojunction and Its Application for Photoelectrochemical Bioanalysis Wei-Wei Zhao 1, Zhao Liu 2, Shu Shan 1, Wen-Wen Zhang 2, Jing Wang 1, Zheng-Yuan Ma 1, Jing-Juan Xu 1* & Hong-Yuan Chen 1* 1 State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing , China, 2 Department of Vascular Surgery, Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, Nanjing, China. *Tel/Fax: xujj@nju.edu.cn. *Tel/Fax: hychen@nju.edu.cn SI-1

2 Materials and Apparatus. Vascular endothelial growth factor (VEGF, Ag) was purchased from Sino Biological Inc. (Beijing, China), two polyclonal antibodies to VEGF (primary capture antibody (Ab 1 ) and biotinylated secondary detection antibody (biotin-ab 2 )) were purchased from Beijing Biosynthesis Biotechnology Co., Ltd (Beijing, China). Streptavidin was from Amresco (USA). Glucosedehydrogenase (GDH) was from Sigma-Aldrich (Shanghai) and then biotinylated by Beijing Biosynthesis Biotechnology Co., Ltd. Human VEGF ELISA Kit was from Beijing 4A Biotech Co., Ltd. Ti sheets (99.99%), chitosan powder (from crab cells, 85% deacetylation), bovine serum albumin (BSA), nicotinamide adenine dinucleotide (NAD + ) were purchased from Sigma-Aldrich (Shanghai). Tween 20 was purchased from Amresco. Glutaraldehyde (GLD) (25% aqueous solution) was obtained from Sinopharm Chemical Reagent Co., Ltd (China). Other chemicals were of analytical reagent grade and used as received M phosphate buffer solution (PBS, ph 7.4) was used for the preparation of antigen (Ag) and antibody (Ab) stock solutions. The washing buffer solution was 0.01 M PBS (ph 7.4) containing 0.05 % Tween 20. The blocking buffer was 0.01 M PBS (ph 7.4) containing 3% (w/v) BSA. All aqueous solutions were prepared using ultra-pure water (Milli-Q, Millipore). PEC measurements were performed with a homemade PEC system equipped with a 500 W Xe lamp and a monochromator. Photocurrent was measured on a CHI 750a electrochemical workstation (China) with a three-electrode system: a modified TiO 2 NTs electrode with a geometrical area of 0.25 ± 0.01 cm 2 as the working electrode, a Pt wire as the counter electrode and a saturated Ag/AgCl electrode as the reference electrode. ELISA result was acquired from ELx800 Absorbance Microplate Reader (Biotek, USA) according to the recommended procedure with the plasma sample (with 5 times dilution before test) taken from author Zhao Liu. Scanning electron microscopic (SEM) images were recorded by a Hitachi S4800 scanning electron microscope (Hitachi Co., Japan). Figure S1 displays the digital images of the different electrodes. Figure S1 A and B shows the images of bare Ti foil and as-annealed TiO 2 NTs. As shown in Figure S1 D-F, with the increase of SILAR cycles SI-2

3 from 15 to 45, the color on the electrode appears varied from transparent pale yellow to dark orange, implying more BiOI with changed sizes has been loaded onto the TiO 2 NTs. Besides, comparing Figure S1 C and Figure S1 E would find that the color of 30 SILAR cycles of BiOI on the bare Ti foil was brighter than that on TiO 2 NTs, which could be attributed to the presence of TiO 2 NTs layer. Figure S2 provides detailed insight into the effect that the SILAR cycles has on the location and growth density of crossed BiOI flakes on TiO 2 NTs. TiO 2 NTs was formed uniformly on the Ti foil after electrochemical anodization. As shown in Figure S2 A, after 3 cycles of SILAR, a few dispersed flakes of BiOI was appeared on the TiO 2 NTs electrode. When underwent 5 cycles of SILAR, as shown in Figure S2 B, a 3D BiOI film in the morphology of crossed flakes array was formed, with average thickness of ~10 nm and lateral dimension of several micrometers. Close examination of Figure S2 B (and also Figure S2 C) would find that the unique layered structures of BiOI were perpendicular to the electrode surface and the pores of the underlying TiO 2 NTs still existed. As shown in S2 C-F, with the SILAR cycles increased from 10 to 45, the flakes, with enhanced growth density, became robust enough to stand more vertically on the surface. Figure S1: Digital images of the electrodes. Above (from left to right): bare Ti foil, the annealed TiO 2 NTs and 30 cycles of BiOI on bare Ti foil; below (from left to right): 15, 30, 45 cycles of BiOI on TiO 2 NTs. SI-3

4 Figure S2: SEM images of (A F) 3, 5, 10, 15, 30, 45 cycles BiOI on TiO 2 NTs. X-ray photoelectron spectroscopy (XPS) was performed to study the surface chemical compositions and oxidation states of BiOI flakes/tio 2 NTs. The peak positions of the existed atoms were determined by internally referencing the adventitious carbon at a binding energy of ev. The obtained survey spectrum has been depicted in Figure 1C, revealing that the sample contain Ti, O, Bi, I and C elements. The peak for C 1s (284.8 ev) is attributed to the adventitious hydrocarbon from the XPS instrument. Figure S3 illustrates the corresponding high-resolution XPS spectra of Bi 4f, O 1s and I 3d. As shown in Figure S3 A, two peaks at and ev should be assigned to Bi 4f 7/2 and Bi 4f 5/2, respectively, characteristic of Bi 3+ in BiOI. Figure S3 B shows the high-resolution XPS spectrum of the O 1s region, which can be fitted into three peaks: the peaks at ev, ev, ev should be assigned to the Bi-O bonds in [Bi 2 O 2 ] slabs of BiOI layered structure, the Ti-O of TiO 2, and the hydroxyl group, respectively. Figure S3 C demonstrates two peaks at ev and ev that should be ascribed to I 3d 5/2 and I 3d 3/2, respectively, corresponding to I - in pure BiOI. These results, SI-4

5 together with XRD measurements, confirm the coexistence of BiOI and TiO 2 in the as fabricated sample and no existence of other impurities. Figure S3: the high-resolution XPS spectra of Bi 4f, O 1s and I 3d. SI-5