Supporting Information Wiley-VCH 29 69451 Weinheim, Germany Voltage-Induced Payload Release and Wettability Control on O 2 and O 2 Nanotubes** Yan-Yan Song, Poulomi Roy, Indhumati Paramasivam, and Patrik Schmuki* ange_295111_sm_miscellaneous_information.pdf
Experimental details: O 2 nanotube and layer formation. O 2 layers were formed by anodization of. For this, sheets (99.6% purity, Advent Materials, UK) of.1 mm thickness were degreased by sonicating the samples in acetone and ethanol, followed by rinsing with deionized (DI) water and drying in a nitrogen stream. To provide smooth, polished surface for XPS analysis, titanium sheets were mechanically ground, lapped, and finally polished (New Lam System). Anodization was carried out using a two-electrode configuration with platinum gauze as a counter electrode. For the fabrication of O 2 nanotube arrays, cleaned foils were anodized in an electrolyte of glycerol/water/nh 4 F at 2 V for 4 h to grow a ~1.1 µm thick O 2 nanotube layer with a diameter of approx. 1 nm (SI 1). The sheets were anodized at 2V in 1 M H 2 SO 4 for 2 min to grow the amorphous O 2 compact layer. In order to investigate the influence of the crystal structure, some anodized samples were annealed in ambient air at 45 o C for 1 h to produce a defined anatase structure. The conversion was confirmed using XRD characterization. attachment. The O 2 samples were placed in a flask which was sealed and top equipped with a water cooling system and a Teflon stir bar. A hydrophobic monolayer was attached to the samples by refluxing the samples in 2 mm octadecylphosphonic acid ()-toluene solution at 7 C for 24 h. HRP grafting. HRP grafting was achieved by silanization on the O 2 layer with 3-Aminopropyltriethoxysilane (APTES) and using a vitamin C linker for covalent attachment of HRP. First the samples were refluxed in 1 mm APTES-toluene solution for 24 h at 7 o C, which lead to a saturated APTES monolayer. According to the method reported by Berlin and coworkers, [2] the APTES modified O 2 surface were then dipped into concentrated ascorbic acid (Vitamin C)- dimethyl sulfoxide (DMSO) solution and incubated for 3 min. Then, horseradish peroxidase (HRP, 4 unit/ml) was attached chemically to the remaining keto group of the dedydroascorbic acid (product of oxidation of ascorbic acid) from a 5 mm phosphate buffer solution (PBS, ph 6.) by immersion of the O 2 samples for 24 h at 4 C. Voltage induced chain scission. All voltage induced experiments were carried out in a three-electrode system. Voltage induced hydrophobic molecule chain scission were performed in.1 mm (NH 4 ) 2 SO 4. Drug release experiments were carried out in 5 mm PBS, which was used as surrounding solution. After applying voltages for different times (platinum as counter electrode and Ag/AgCl as reference electrode),.1 ml of surrounding PBS was taken out by a micropipette and transferred into a quartz glass cuvette containing 2 ml PBS solution,.3% H 2 O 2 and.5 M 2,2 -azino- bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS). The latter reagent served as the HRP release color indicator. To quantify the release amounts, absorption spectra were measured by a UV-vis spectrometer Lambda Bio XLS after 2 min stirring. Photocatalytic and corresponding dark experiments. Voltage induced and photocatalytic decomposition was studied using a model pollutant Acid Orange 7 (AO7, C 16 H 11 N 2 O 4 SNa, Cinitial = 2.5 x1-5 mol L -1 ) and flat O 2 (anatase) layers (Area = 3.2 cm 2 ). Platinum was used as counter electrode. An applied voltage of 5 V was kept on the flat O 2. The change in the concentration with respect to time was measured using an UV-vis absorption spectrophotometer (Lambda Bio XLS). Fig. 1E shows the plots of the absorption decay for 1 V, 5 V and also the photocatalytic behavior while shining a UV-light (He Cd, Kimmon, Japan λ = 325 nm, I light = 6 mw cm²) that was defocused to irradiate the whole immersed surface of the samples. Detection of OH - radicals. Terephthalic acid (TA) was used without further purification. An aqueous solution containing.1 M NaOH,.1 M KCl and 3 mm TA was prepared, and then O 2 samples were mounted in a home made bottom-cell as the working electrode in 5 ml of above solution. The cell was placed in a dark box, and different voltages were applied for
various times. Fluorescence spectra of the liquid were measured with an optical meter (Newport 183-C) at 426 nm using a 5 mw He-Cd laser (325 nm) as the excitation source. Surface Analysis. The morphology of the formed porous layers was characterized using a field-emission scanning electron microscope (Hitachi FE-SEM S48). XRD patterns were acquired on an X Jpert Philips PMD diffractometer with a Panalytical X celerator detector, using graphite-monochromatized Cu Kα radiation (λ=1.5456 K). X-ray photoelectron spectra (XPS) were recorded on a Perkin-Elmer Physical Electronics 56 spectrometer using Al Kα radiation at 13 kv as excitation source. The takeoff angle of the emitted photoelectrons was 45 o (the angle between the plane of sample surface and the entrance lens of the detector). The binding energy of the target elements (O 1s, C 1s, N 1s, P 2p, 2p, Si 2p) was determined at pass energy of 23.5 ev, with a resolution of.1 ev, using the binding energy of 2p signal (458. ev) as the reference. Atomic concentration data (Si and ) were determined with a resolution of.2 ev. Background subtraction was carried out according to the Shirley approach (implemented in the Phi 56 software package). Additional experiments: To verify that long term anodization and gas evolution at the electrodes did not affect the results, we conducted experiments with 2 compartment cells (using salt bridges) and measured induced ph changes. No effect due to ph changes could be found even for 5 V anodization for 24 h.
A A 2 nm 1.1 µm 1 µnm m 1 A 8 B 7 Counts 6 5 A 4 R A AA R A A A anatase 3 2 1 2 3 4 5 6 7 as-formed 8 2θ(degree) SI1. SEM images of O2 nanotube layers anodized in glycerol/water/nh4f at 2 V for 8h (A), and the corresponding XRD spectra of the layers as-formed and after annealing at 45oC for 1 h (B).
5 4 3 2 1. O1s 14 12 1 8 6 1. C 1s 4 1 2 534 532 53 528 526 292 29 288 286 284 282 28 4 32 24 16 8 1. 2p 468 466 464 462 46 458 456 454 18 17 16 15 14 13 12 11 1 9 1. 135 134 133 132 131 13 129 P2p SI 2. XPS characterization of the release process induced by voltages on anatase flat O 2 foil (carried out on compact, smooth 5 nm thick O 2 layers, followed by annealed at 45 o C for 1h). These data confirm the successful voltage induced chain scission in Fig. 3C on anatase samples.
before before anodazation anodiazation OCP 15 h 1.5 V 15 h 5 V 15 h SI3. Optical images of a water droplet on amorphous O 2 nanotube layers modified with after applied different voltage on monolayer for 16h. (This demonstrates that no chain scission occurs on amorphous surfaces.)
2 1 18 16 14 12 1 8 1. O 1s 8 6 4 1.5 V 15h C 1s 6 4 2 2 534 532 53 528 526 292 29 288 286 284 282 28 16 13 14 12 1 8 6 4 2 1. 468 466 464 462 46 458 456 454 2p 12 11 1 9 8 7 6 1. P 2p 135 134 133 132 131 13 129 SI4. XPS characterization of the release process induced by voltages on amorphous flat O 2 foil (carried out on asformed compact, smooth 5 nm thick O 2 layers). These data confirm absence of the voltage induced chain scission for amorphous O 2.
4 32 35 3 25 2 HRP_OCP 2 h HRP_1.5 V 2 h HRP_5 V 2 h N 1s 28 24 2 16 12 HRP_OCP 2 h HRP_1.5 V 2 h HRP_5 V 2 h 2p 15 8 1 4 5 44 42 4 398 396 468 466 464 462 46 458 456 454 15 14 13 12 11 1 9 8 7 HRP_OCP 2 h HRP_1.5 V 2 h HRP_5 V 2 h 16 14 12 1 98 Si 2p 45 4 35 3 25 2 15 1 5 HRP_OCP 2 h HRP_1.5 V 2 h HRP_5 V 2 h O 1s 536 534 532 53 528 526 524 SI 5. XPS characterization of the HRP voltage induced release process on anatase flat O 2 foil (carried out on compact, smooth 5 nm thick O 2 layers after anneal at 45 o C for 1h). These data confirm the success of the HRP released by chain scission mechanism at 5V: (Decrease of N from HRP, increase of substrate and O, Si maintained on surface).