Method for detecting Ni(II) based on up-conversion fluorescence inner filter effect

[0043] 1) Preparation of NaYF by thermal decomposition method 4 : Yb, Tm nanocrystals (OA-UCNPs): 0.8mmol of rare earth stearate (wherein Y:Yb:Tm molar ratio is 79.5:20:0.5), 28mmol of NaF, 12mmol of oleic acid (OA), 8mmol of octadecanoate Diene (ODE) was added in the 100mL three-necked flask;

[0044] The system was placed in an argon atmosphere and heated to 140° C. for 30 min to obtain anhydrous and oxygen-free reaction conditions. Then heat up rapidly, keep the temperature between 312-314°C, continue to react for 45min and then cool to room temperature naturally, centrifuge the reaction product at a speed of 11000rpm for 3min, remove the supernatant, add ethanol to make the product settle, and wash with cyclohexane and distilled water Wash and centrifuge several times until there is no organic oil and NaF components, transfer to an oven for vacuum drying at 70°C for later use, and obtain β-phase NaYF 4 : Yb, Tm nanocrystals (OA-UCNPs, OA is oleic acid).

[0045] TEM and XR

[0056] Same as Example 1, the difference is that the Ni(II) aqueous solution of different concentrations in step 4) is replaced, so that the final concentrations of the composition in the mixture are respectively: 35 μM Ni(II), 350 μM Fe(II), 350 μM Fe( III), 350 μM Cd(II), 350 μM Cr(III), 350 μM Cu(II), 350 μM Ag(I), 350 μM Mg(II), 350 μM Zn(II), 350 μM Ca(II), 350 μM Na(I) , 350μM K(I), carry out selectivity test, the result is as follows Figure 9 shown.

[0057] from Figure 9 It can be seen that Ni(II) can greatly quench the fluorescence of UCNPs compared with other metal ions, F 0 / F(F 0 Indicates the initial fluorescence intensity of the solution without Ni(II), and F indicates the fluorescence intensity of the solution after adding Ni(II)), the ratio of which is the largest. It shows that the method for detecting Ni(II) based on the up-conversion fluorescence inner filter effect designed by the present invention has better selectivity (shown in black bars). The ant