Supporting Information Potential-resolved Multicolor Electrochemiluminescence of N-(4-Aminobutyl)-N-ethylisoluminol/tetra(4-carboxyphenyl) porphyrin/tio 2 Nanoluminophores Jiangnan Shu, Zhili Han, Tianhua Zheng, Dexin Du, Guizheng Zou and Hua Cui* CAS Key Laboratory of Soft Matter Chemistry, ichem (Collaborative Innovation Center of Chemistry for Energy Materials), Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, China School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong 250100, China Corresponding author: Prof. H. Cui, Tel: +86-551-63600730 Fax: +86-551-63600730 Email: hcui@ustc.edu.cn S1
Table of Contents 1. Experimental Sections S3 1.1 Chemicals and Solutions S3 1.2 Synthesis of TiO 2 -TCPP Nanocomposites S3 1.3 Synthesis of TiO 2 -TCPP-ABEI Nanoluminophores S3 1.4 Characterization of TiO 2 -TCPP-ABEI Nanoluminophores S4 1.5 Electrochemical and ECL Measurement S4 1.6 Florescence Measurement S5 2. Results and Discussion S6 2.1 Characterization of TiO 2 -TCPP-ABEI Nanoluminophores S6 2.1.1 XPS Studies S6 2.1.2 FT-IR Spectra S7 2.1.3 XRD Studies S8 2.2 Effect of ph S9 2.3 Stability of TiO 2 -TCPP-ABEI Nanoluminophores S9 2.4 A Comparison of ECL Spectra S10 2.5 A Comparison of FL Spectra S10 2.6 Stacked ECL spectra of ECL-1, ECL-2 and ECL-3 S11 2.7 A Comparison of Cyclic Voltammograms S12 2.8 Partial Enlarged View of 3D ECL Spectrum S12 2.9 Comparisons of UV-Vis and FL Spectra with ECL Spectra S13 3. Reference S13 S2
1. Experimental Sections 1.1 Chemicals and Solutions N-(aminobutyl)-N-(ethylisoluminol) (ABEI) was purchased from TCI (Japan). A 4.0 mmol/l stock solution of ABEI was prepared by dissolving ABEI in 0.01 mol/l NaOH solution and was kept at 4 ºC. Titanium dioxide (TiO 2 ) nanoparticles and meso-tetra(4-carboxyphenyl)porphine (TCPP) were purchased from Aladdin Reagent (Shanghai, China). N-hydroxysuccinimide (NHS) and 1-ethyl-3-3(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) were purchased from Sigma Aldrich (USA). Supporting electrolyte was 0.02 M Britton-Robison (BR) buffer solution. All other reagents were of analytical grade. Ultrapure water was prepared by a Milli-Q system (Millipore, France) and used throughout. All glassware used in the following procedures was cleaned in a bath of freshly prepared 3:1 (v/v) HNO 3 -HCl, rinsed thoroughly in redistilled water, and dried prior to use. 1.2 Synthesis of TiO 2 -TCPP Nanocomposites TiO 2 -TCPP nanocomposites were synthesized according to the literature. 1 100 mg of TiO 2 nanoparticles was added to 100 ml of TCPP solution (0.05 mg/ml) in DMF and heated at 100 C for 5 h. The samples were then centrifuged at 11000 rpm for 10 min to remove unbound TCPP. After being washed with DMF and ultrapure water, respectively. TCPP-TiO 2 nanocomposites were obtained. 1.3 Synthesis of TiO 2 -TCPP-ABEI Nanoluminophores TiO 2 -TCPP nanocomposites were further functionalized by ABEI via amide reaction between NH 2 group in ABEI molecule and COOH group in TCPP. EDC/NHS was used to activate carboxyl group on the surface of TCPP-TiO 2 nanocomposites. Briefly, 2 ml of solution containing 10 mg/ml of NHS and 10 mg/ml of EDC were added to TiO 2 -TCPP nanocomposite suspension (1 mg ml -1 ) under magnetic stirring with 15 min for activating the carboxyl groups of TCPP and then activated TiO 2 -TCPP nanocomposites reacted with ABEI for 1 h at room temperature. The unbound ABEI S3
molecules were removed via centrifugation at 11000 rpm for 10 min and washed with ultrapure water to obtain TiO 2 -TCPP-ABEI nanoluminophores. 1.4 Characterization of TiO 2 -TCPP-ABEI Nanoluminophores The as-prepared TiO 2 -TCPP-ABEI nanoluminophores were subsequently characterized by transmission electron microscopy (TEM, JEOL Ltd, JEOL-2010, Japan), UV-visible spectroscopy (Agilent 8453 UV-visible spectrophotometer, USA), X-ray diffraction spectroscopy (XRD, a model D/max-rA diffractometer (Rigaku, Japan)), X-ray photoelectron spectroscopy (XPS, an ESCALABMK II electron spectrograph (VG Scientific, UK) with Al Ka radiation as the X-ray source), and Fourier transform infrared spectroscopy (FT-IR, a Bruker Vector-22 FTIR spectrometer (Bruker Instruments, Billerica, MA)). A centrifugation process was used for the purification of TiO 2 -TCPP-ABEI nanoluminophores to remove free ABEI molecules, so that true information about the surface of TiO 2 -TCPP-ABEI nanoluminophores could be obtained by various characterization methods. The precipitates were redispersed in the BR buffer for the measurement of UV-vis absorption spectra and in the alcohol solution for the characterization of TEM. The precipitates were dried under vacuum at room temperature for XRD, XPS and FT-IR detection. 1.5 Electrochemical and ECL Measurement A TiO 2 -TCPP-ABEI nanoluminophore modified F-doped tin oxide (FTO) electrode was used as working electrode, a platinum wire as the counter-electrode, and a silver wire as the quasireference electrode. An Ag quasi reference electrode (AgQRE) was used due to simplicity for cell construction and quick potential response. 3D ECL spectra was accomplished with an ECL spectrum system, consisting of an Acton SP2300i monochromator equipped with a liquid N 2 cooled PyLoN 400BR-eXcelon digital CCD detector and a CHI 832 electrochemical analyzer (Shanghai, China). FTO-coated glass slides were used as assembly electrodes owing to their stability, easy miniaturization, and compatibility with microfabrication. FTO electrodes with S4
dimensions of 6.0 cm 1.5 cm were cleaned by sequential sonication in neat acetone, ethanol, and ultrapure water (15 min each). The FTO substrate was reversibly bound to a punched poly(dimethylsiloxane) (PDMS) layer that was prepared by curing the mixture of PDMS monomer and the curing agent (10:1) in an oven at 75 C for 1.5 h. The effective electrode area was confined by a punched round hole of 8 mm in diameter, which was used as a reservoir for subsequent assembly. The suspension (50 µl, 1 mg ml -1 ) of TiO 2 -TCPP-ABEI nanoluminophores was coated onto the FTO electrode and dried in dark at room temperature to obtain a TiO 2 -TCPP-ABEI nanoluminophore modified FTO electrode. The TiO 2 and TiO 2 -TCPP nanoparticles modified electrodes were prepared similarly. 1.6 Florescence (FL) Measurement FL measurements were performed by using an F-7000 fluorometer (Hitachi, Japan) with a 150 W Xe lamp as the light source. S5
2. Results and Discussion 2.1 Characterization of TiO 2 -TCPP-ABEI Nanoluminophores 2.1.1 XPS Studies Figure S1 showed the survey spectrum and the Ti 2p X-ray photoelectron spectra of TiO 2, TiO 2 -TCPP and TiO 2 -TCPP-ABEI, after further treatments. All binding energies (BEs) were calibrated with respect to the C 1s BE at 284.6 ev. As shown in Figure S1a, compared with TiO 2 nanoparticles, the survey of TiO 2 -TCPP nanocomposites showed the presence of N1s originating from TCPP, indicating that TCPP was successfully functionalized on the surface of TiO 2 nanoparticles. In Figure S1b, the Ti 2p XP spectrum of TiO 2 nanoparticles consisted of two peaks assigned to the Ti 2p 1/2 at 464.42 ev and Ti 2p 3/2 at 458.67 ev. Compared with these peaks, the Ti 2p 1/2 and Ti 2p 3/2 peaks of TiO 2 -TCPP and TiO 2 -TCPP-ABEI shifted to lower binding energies by 0.2-0.4 ev after the modification of TCPP molecules. These changes were attributed to the coordination of Ti atom as the acceptor with oxygen atom in TiO 2 -TCPP nanocomposites as an electron donor, confirming the dentate binding of TiO 2 nanoparticles with the carboxyl groups of TCPP. 1 Figure S1. The survey spectra (a) and Ti 2p X-ray photoelectron spectra (b) of TiO 2, TiO 2 -TCPP and TiO 2 -TCPP-ABEI nanoparticles. S6
2.1.2 FT-IR spectra FT-IR spectroscopy studies were carried out on TiO 2, TiO 2 -TCPP and TiO 2 -TCPP-ABEI. Figure S2a shows the FT-IR spectrum of TiO 2 nanoparticles. A broad band was displayed at 3440 cm 1, which might be attributed to hydroxyl groups on the surface of TiO 2 nanoparticles. The adsorption band at 1630 cm 1 was due to the presence of moisture in the sample. The intense broad band in the vicinity of 400 800 cm 1 was due to Ti-O vibration. Figure S2b shows the FT-IR spectrum of TiO 2 -TCPP nanocomposites. The broad band at 3440 cm 1 observed in the case of free TiO 2 nanoparticles now clearly enhanced. Moreover, an additional peak at 1400 cm -1 could be observed due to the B 3u vibration of TCPP. These results suggested that TCPP was successfully assembled on TiO 2 nanoparticles through the dehydrated coupling of carboxyl group of TCPP with surface hydroxyl group of TiO 2. Figure S2c shows the FT-IR spectrum of TiO 2 -TCPP-ABEI nanoluminophores. Compared with the FT-IR spectrum of TCPP-TiO 2 nanocomposites, the absorption band at 1247 cm -1 was attributed to the -NH 2 deformation (δ NH2 ) of the amide group. The amide group was formed when the carboxyl acid group of TCPP reacted with the amino group on ABEI. These results demonstrated the existence of ABEI on the surface of TCPP-TiO 2. S7
Figure S2. FT-IR spectra of (a) TiO 2, (b) TiO 2 -TCPP and (c) TiO 2 -TCPP-ABEI nanoparticles. S8
2.1.3 XRD Studies The XRD patterns of TiO 2, TiO 2 -TCPP and TiO 2 -TCPP-ABEI nanoparticles are presented in Figure S3. The diffraction peaks of TiO 2 -TCPP-ABEI nanoluminophores at 2θ = 25.32, 37.75, 47.95, 54.13, 62.72, 70.05 and 75.78 were assigned to the anatase phase of TiO 2 nanoparticles. The result demonstrated that the major crystalline phase of the TiO 2 nanoparticles were pure anatase (JCPDS 21-1272). Furthermore, XRD data showed that the crystalline characteristics of the TiO 2 nanoparticles remain unchanged before and after the reactions. 2 Figure S3. X-ray diffraction spectra of (a) TiO 2, (b) TiO 2 -TCPP and (c) TiO 2 -TCPP-ABEI nanoparticles. S9
2.2 Effect of ph Figure S4. Effect of ph on ECL intensities of ECL-1, ECL-2 and ECL-3. 2.3 Stability of TiO 2 -TCPP-ABEI Nanoluminophores Figure S5. Stability of TiO 2 -TCPP-ABEI nanoluminophores in the 1st, 3rd, 5th and 50th day after synthesis. S10
2.4 A Comparison of ECL Spectra Figure S6. ECL spectra of (a) ABEI moiety in TiO 2 -TCPP-ABEI (black line) and pure ABEI (red line), (b) TCPP moiety in TiO 2 -TCPP-ABEI (black line) and pure TCPP (red line), (c) TiO 2 moiety in TiO 2 -TCPP-ABEI (black line) and pure TiO 2 (red line) using H 2 O 2 and K 2 S 2 O 8 as coreactant in 0.2 M BR buffer (ph 12). 2.5 A comparison of FL Spectra Figure S7. FL spectra of (a) TiO 2 nanoparticles (black line), ABEI (orange line), TiO 2 -TCPP nanoparticles (blue line) and TiO 2 -TCPP-ABEI nanoparticles (red line). The FL spectra was acquired at an excitation wavelength of 275 nm. (b) TiO 2 -TCPP-ABEI nanoparticles. The FL spectrum was acquired at an excitation wavelength of 460 nm. S11
2.6 Stacked ECL spectra of ECL-1, ECL-2 and ECL-3 Figure S8. Stacked ECL spectra of various ECL-1, ECL-2 and ECL-3 in different potential windows extracted from Figure 2. (a) ECL-1 : from 1.30 to 0.85 V, (b) ECL-1 : from 0.85 to 0.50 V, (c) ECL-2 : from -1.80 to -1.50 V, (d) ECL-2 : from -1.50 to -1.20 V, (e) ECL-3: ECL-3 : from -1.75 to -1.65 V, (f) ECL-3 : from -1.65 to -1.50 V. S12
2.7 A Comparison of Cyclic Voltammograms Figure S9. CVs of TiO 2 -TCPP-ABEI (black line) and TiO 2 -TCPP (red line) modified FTO electrode using H 2 O 2 and K 2 S 2 O 8 as dual coreactants in 0.2 M BR buffer (ph 12). Inset shows the enlarged cvp1. 2.8 Partial Enlarged View of 3D ECL Spectrum Figure S10. Partial enlarged view of 3D ECL spectrum of TiO 2 -TCPP-ABEI nanoluminophores using H 2 O 2 and K 2 S 2 O 8 as dual coreactants in the potential range of 0.55 to 1.50 V at the wavelength from 620 to 800 nm. S13
2.9 A Comparison of UV-Vis and FL Spectra with ECL Spectra Figure S11. A comparison of ECL emission spectra with UV-vis absorption spectrum and FL spectra. (a) ECL emission spectrum of ABEI (red line) and UV-vis absorption spectrum of TCPP (black line). (b) FL spectra of TCPP (blue line), TiO 2 -TCPP nanocomposites (green line) and TiO 2 -TCPP-ABEI nanoluminophores (yellow line) in 0.01 M NaOH, and ECL emission spectrum of TiO 2 -TCPP-ABEI nanoluminophores (red line) at 675 and 739 nm on the positive scan using H 2 O 2 and K 2 S 2 O 8 as coreactants in 0.2 M BR buffer (ph 12). The FL spectra was acquired at an excitation wavelength of 460 nm. 3. References (1) Li, D.; Dong, W. J.; Sun, S. M.; Shi, Z.; Feng, S. H. J Phys Chem C 2008, 112, 14878. (2) Rahimi, R.; Moghaddas, M. M.; Zargari, S. J Sol-Gel Sci Techn 2013, 65, 420. S14