Supporting Information

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1 Supporting Information Chemically Modulated Carbon Nitride Nanosheets for Highly Selective Electrochemiluminescent Detection of Multiple Metal-ions Zhixin Zhou, Qiuwei Shang, Yanfei Shen, Linqun Zhang, Yuye Zhang, Yanqin Lv, Ying Li, Songqin Liu, and Yuanjian Zhang* Jiangsu Province Hi-Tech Key Laboratory for Bio-Medical Research, Jiangsu Optoelectronic Functional Materials and Engineering Laboratory, School of Chemistry and Chemical Engineering, Southeast University, Nanjing , China Medical School, Southeast University, Nanjing 219, China address: S1

2 2 CN-4 CN-45 CN-5 CN-55 CN-6 CN θ (degree) -NH 2 CN-4 CN-45 CN-5 CN-55 CN-6 CN Wavenumber (cm -1 ) Figure S1. XRD (a) and FT-IR of CN-T (T=4, 45, 5, 55, 6 and 65). All patterns of as-obtained CN prepared at different temperatures exhibited a (2) peak at ca. 27 o (2θ), corresponding to the interlayer distance. 1 Interestingly, this peak gradually shifted to a larger diffraction angle and became narrower with the increase of the synthesis temperature, indicating that the CN synthesized at a higher temperature had a denser stacking which may lead to a stronger interlayer electron coupling. 2-4 Meanwhile, the peak at 13. o (2θ), corresponding to approximate dimension of the tri-s-triazine unit, gradually became weaker and broader due to the increase of distortion of planar structure. 3 The chemical structure of various CN was studied by Fourier transform infrared spectra (FT-IR, Figure S1b) spectroscopy and elemental analysis (EA, Table S1). Although all sample showed that the peaks around 8 cm -1 originated from the triazine ring breathing mode, the peaks at and 3-35 cm -1 were distinctive, indicating that the chemical structure of CN polymerized at different temperature was different. The chemical structure of the as-prepared CN was further confirmed by elemental analysis shown in Table S1. The C/N molar ratio increased with the increase of temperature. Therefore, by modulating the synthesis temperature from 4 to 65 o C, the chemical structure and condensation degree of CN can be facilely manipulated, which would greatly favor the further liquid-exfoliation of carbon nitride nanosheets with tunable chemcial structures. S2

3 2 4 o C 2 5 o C 3 65 o C 2 % 1 % 1 % 1 Size (nm) Size (nm) Size (nm) Figure S2. Size distribution of CNNS-4 (a), CNNS-5 and CNNS-65 evaluated by DLS, except for CNNS-4 which was evaluated from TEM measuring by more than 2 individual sheets due to the inapplicability of DLS. The average equivalent size of CNNS-4, CNNS-5 and CNNS-65 was ca. 4 nm, 6 nm and 3 nm, respectively. Figure S3. Tyndall effect of the aqueous dispersion of carbon nitride nanosheets CNNS-T (from left to right, T = 4, 45, 5, 55, 6 and 65). S3

4 Nomarlized PL Time (s) CNNS-4 CNNS-45 CNNS-5 CNNS-55 CNNS-55 CNNS-6 PL Intensity (a.u.) M.5 M.1 M.3 M.5 M.8 M 1 M PL Intensity (a.u.) ph=1 ph=3 ph=5 ph=7 ph=9 ph=11 ph=13 (d) PL Intensity (a.u.) ph Figure S4. (a) Photobleaching properties of the CNNS-T (T = 4, 45, 5, 55, 6 and 65) exfoliated from CN-T under continuous excitation at 3 nm. Effects of ion concentration on fluorescent intensity of CNNS-55. (c-d) Effects of ph on photoluminescent intensity of the CNNS-55. Normarlized PL (a.u.) CNNS-4 CNNS-65 CNNS-5 S-CNNS Figure S5. PL spectra of CN-4, CN-5, CN-65 and S-CN-55. S4

5 ECL Intensity (a.u.) Cathode ECL ECL Intensity (a.u.) Time (s) ECL Intensity (a.u.) CNNS-4+Cu Potential (V) Time (s) CNNS-65+Cd 2+ ECL Intensity (a.u.) Anodic ECL Time (s) Time (s) Figure S6. Cathode (up) and anodic (bottom) ECL-potential curves of CNNS-5 (a). Inset: the stability of cathode (up) and anodic (bottom) ECL curves of CNNS-5 under ten continuous cycles of cyclic voltammetry scan. The ECL intensity change of CNNS-4 and CNNS-65 after adding the Cu 2+ and Cd 2+, respectively, with time. S5

6 Cu Ni Cd Figure S7. UV-vis absorption spectra of Cu 2+ (a), Ni 2+ and Cd 2+ (d) in aqueous solution. S6

7 2 1 CNNS-65-ECL CNNS-65 CNNS-65+Ni 2+ ECL intensity (a.u.) CNNS-ECL CNNS-4 CNNS-4-Ni 2+ ECL intensity (a.u.) CNNS-65-ECL CNNS-65 CNNS-65+Cd 2+ ECL intensity (a.u.) (d) Intensity (a.u.) CNNS-65 CNNS-65+Cd Time (ns) Figure S8. UV-vis absorption spectra in the absence and presence of Ni 2+ and ECL emission spectra of CNNS-65 (a) and CNNS-4. UV-vis absorption spectra in the absence and presence of Cd 2+ and ECL emission spectra of CNNS-65. Time-resolved PL spectra of CNNS-65 in the absence and presence of Cd 2+ (d). S7

8 N Si CNNS-4+Cu 2+ Intensity (a.u.) C O Cu Cl KeV CNNS-5+Ni 2+ N Si Intensity (a.u.) C O Ni KeV CNNS-65+Cd 2+ Intensity (a.u.) C N Si O Cl Cd KeV Figure S9. EDX spectra of CNNS-4+Cu 2+, CNNS-5+Ni 2+ and CNNS-65+Cd 2+. The atomic ratios of Cu 2+, Ni 2+, and Cd 2+ in them were 2.7 %,.6% and.6%, respectively. S8

9 .8.4 (αhν) CNNS-4 CNNS-5 CNNS Energy (ev) Intensity (a.u.) CNNS-4 CNNS-5 CNNS ev 2.85 ev ev Binding Energy (ev) Figure S1. (a) UV-Vis absorption spectra of the CNNS-4, CNNS-5, and CNNS-65. Inset: (αhν) 2 versus hυ curve of CNNS-4, CNNS-5, and CNNS-65. The horizontal black line marks the baseline; the other lines are the tangents of the curves. The intersection value is the band gap. XPS VB spectra of the CNNS-4, CNNS-5, and CNNS-65; Scheme of relative CB and VB positions for the CNNS-4, CNNS-5, and CNNS-65. CB: conduction band; VB: valence band. S9

10 Scheme S1. The proposed copolymerization process of urea with ATCN at 55 o C for S-CN-55. Table S1. Elemental analysis of as-prepared bulk CN-T (T= 4, 5 and 65) Sample C a N a H a C/N b CN CN CN a wt.%; b molar ratio S1

11 Reference: (1) Martin, D. J.; Qiu, K. P.; Shevlin, S. A.; Handoko, A. D.; Chen, X. W.; Guo, Z. X.; Tang, J. W. Angew. Chem. Int. Ed. 214, 53, 924. (2) Tyborski, T.; Merschjann, C.; Orthmann, S.; Yang, F.; Lux-Steiner, M. C.; Schedel-Niedrig, T. J. Phys-condens. Mat. 213, 25. (3) Zhang, H. Y.; Yu, A. C. J. Phys. Chem. C 214, 118, (4) Du, A. J.; Sanvito, S.; Li, Z.; Wang, D. W.; Jiao, Y.; Liao, T.; Sun, Q.; Ng, Y. H.; Zhu, Z. H.; Amal, R.; Smith, S. C. J. Am. Chem. Soc. 212, 134, S11