<p> Supporting Information</p><p> for</p><p>A Highly Selective and Sensitive Fluorescent Chemosensor for Aluminum Ions Based on Schiff Base</p><p>Cunji Gao, Peixian Zang, Weisheng Liu, Yu Tang *</p><p>Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China</p><p>1 Figure S1. H NMR spectrum of the fluorescent sensor H2L in d6-DMSO. 13 Figure S2. C NMR spectrum of the fluorescent sensor H2L in d6-DMSO. Figure S3. Mass spectrum of H2L. 3+ Figure S4. Job’s plot for H2L (forms 1:1 complexes) in EtOH–H2O (3:7, v/v) solution. Total [H2L] + [Al ] = 20 M.</p><p>Figure S5. HR-MS spectrum of L−Al complex. 3+ Figure S6. Fluorescence intensity of H2L versus increasing concentration of lg[Al ]. λex = 420 nm, the concentration of H2L was 5 μM. The fluorescence response fits to a Hill coefficient of 1 (1.0327); It suggest the formation of the L–Al complex is 1:1 in solution.</p><p>Calculation of detection limit [S1,S2] The detection limit was determined from the fluorescence titration data based on a reported method. [S1,S3] According to the result of titrating experiment, the fluorescence intensity data at 468 nm were normalized between the minimum intensity and the maximum intensity. A linear regression curve was then fit to these normalized fluorescence intensity data, and the point at which this line crossed the ordinate axis was considered as the detection limit. Figure S7. Fluorescence intensity of H2L in EtOH–H2O (3:7, v/v) solution, λex =420 nm at each concentration of Al3+ added. The detection limit (LOD) was measured to be 3.60 × 10−6 M.</p><p>3+ Figure S8. Effect of pH on the emission intensity of H2L and its Al complex at 468 nm in ethanol–H2O (3:7,</p><p>3+ v/v): red circle, 50 M H2L; black square, 50 M H2L + 50 M Al .</p><p>Table S1. Association constant and detection limit of reported papers and this work.</p><p>Sensor association constant(M-1) Detection limit (M) References Receptor 2 5.23 ×105 8.87×10-7 [S4] 1 8.32 ×106 3.28×10-6 [S5] L 3.14×105 3.26×10-6 [S6] 1 6.71×104 1.2×10-7 [S7] (R)-1 1.77×104 8.0×10-7 [S8] CB1 Not Given 1.0×10-7 [S9] L 2.12×105 3.0×10-7 [S10] 1 1.23×105 4.9×10-7 [S11] Spiropyran Not Given 5.0×10-7 [S12] 4 8.7×103 Not Given [S13] 5 −6 H2L 1.21 × 10 3.60 × 10 M This work</p><p>References [S1] Shortreed M, Kopelman R, Kuhn M. Hoyland B (1996) Anal Chem 68:1414–1418 [S2] Wang HH, Xue L, Jiang H, (2011) Org Lett 13: 3844–3847 [S3] Wang WH, Rusin O, Xu XY, Kim KK, Escobedo J O, Fakayode SO, Fletcher KA, Lowry M, Schowalter CM, Lawrence CM, Fronczek FR, Warner IM, Strongin RM (2005) J Am Chem Soc 127:15949–15958 [S4] Chen CH, Liao DJ, Wan CF, Wu AT (2013) Analyst 138:2527−2530 [S5] Liu Y W, Chen C H , Wu A T (2012) Analyst 137:5201−5203 [S6] Fu Y, Jiang XJ, Zhu YY, Zhou BJ, Zang SQ, Tang MS, Zhang HY, Maka TCW (2014) Dalton T 43:12624–12632 [S7] Hau FKW, He XM, Lam WH, Yam VWW (2011) Chem Commun 47:8778−8780 [S8] Ma TH, Dong M, Dong YM, Wang YW, Peng Yu (2010) Chem Eur J 16:10313 −10318 [S9] Maity D, Govindaraju T (2010) Inorg Chem 49:7229−7231 [S10] Sahana A, Banerjee A, Das S, Lohar S, Karak D, Sarkar B, Mukhopadhyay SK, Mukherjee AK, Das D, (2011) Org Biomol Chem 9:5523–5529 [S11] Sun X, Wang YW, Peng Yu, (2012) Org Lett 14: 3420–3423 [S12] Ren JQ, Tian H, (2007) Sensors 7:3166-3178 [S13]Othman AB, Lee JW, Huh YD, Abidi R, Kim JS, Vicens J (2007) Tetrahedron 63:10793−10800 </p>