Supporting Information

Transcription

1 Supporting Information White Upconversion Luminescence Nanocrystals for the Simultaneous and Selective Detection of 2,4,6,-trinitrotoluene and 2,4,6-trinitrophenol Yingxin Ma, Sheng Huang, Mingliang Deng, Leyu Wang,* State Key Laboratory of Chemical Resource Engineering, Beijing Key Laboratory of Environmentally Harmful Chemical Analysis, Beijing University of Chemical Technology, Beijing , P. R. China. Fax and Tel: EXPERIMENTAL SECTION Synthesis of UCNPs. The NaYF 4 upconversion nanoparticles (UCNPs) were synthesized via the solvothermal technology developed previously by our group with some modification. In order to get the white upconversion luminescence, Yb 3+, Er 3+, and Tm 3+ ions were co-doped in the NaYF 4 matrixes. In brief, into a three-necked flask, 8 ml of octadecene, 7 ml of oleic acid, and 0.35g of sodium stearate were mixed and heated to 80 C under stirring. Then 1.0 mmol of the rare-earth oleate solution (4 ml, Y:Yb:Er:Tm = 40:59.6:0.2:0.2 ) and 1.4 ml of HF oleylamine solution were successively injected into the flask, and the solution was kept at 80 C for 20 min. Then the mixed solution was heated to 180 C and kept for 10 min before it was heated to 310 C. The NaYF 4 :Yb/Er/Tm UCNPs were obtained after the solution being treated at 310 ºC for 60 min. Finally, the solution was cooled down to room temperature and washed three times with ethanol and cyclohexane. The β-nayf 4 UCNPs were collected and dispersed into chloroform to get a stock solution. By varying the ratio (Y 3+ /Yb 3+ /Er 3+ ) of the dopants, the UC emission color can be changed. Preparation of PSI OAm. Polysuccinimide (PSI) (1.6 g) was dissolved in N, N-Dimethylformamide (DMF) (32 ml) at 60 ºC under magnetic stirring followed by the addition of oleylamine (1.63 ml). The mixture solution was treated at 100 ºC for 5 h before cooling to room temperature. Then 80 ml of methanol was added to precipitate the product (PSI OAm ). Finally, the PSI OAm was redispersed into 1

2 8 ml of chloroform with concentration of 190 mg/ml after centrifugation and then evaporating the trace amount of residual methanol. Scheme S1. Scheme for the charge-transfer interaction between UCNPs and TNT, and the chemical structure of PSI NH. Figure S1. UC emission (a) spectrum of NaYF NH colloidal solution (2.55 mg/ml) and absorption spectra (b) of TNT, TNP, DNT and NB (2.0 μg/ml) in the presence of NaYF NH (2.55 mg) at ph 12, respectively. Insets of (b) are the chemical structures of the nitroaromatics. 2

3 Figure S2. TGA of the UCNPs coating with PSI OAM. Figure S3. Effects of cyclohexane (a1 a3) and toluene (b1 b3) on the NaYF 4 UCNPs luminescence at 363 nm and 546 nm. UCNPs (2.55 mg/ml) 3

4 Figure S4. The digital photos of the UCNPs solution in the presence of different concentration of TNT or TNP (0, 1.5, 3 and 4.5 μg/ml) under the irradiation of 980 nm diode laser. To investigate the luminescence quenching mechanism, the absorption spectra of TNT, TNP, DNT and NB with the addition of a given concentration of NaYF NH were carried out at ph 12, respectively. The upconverting luminescence spectrum of the NaYF NH colloidal solution was depicted in Figure S1a. It is clear that these UCNPs can emit the white luminescence with multiple emission peaks at 349 (Tm 3+ : 1 D 2 3 H 6 ), 363 (Tm 3+ : 1 D 2 3 H 6 ; Er 3+ : 2 G 9/2 4 I 15/2 ), 412 (Er 3+ : 4 H 9/2 4 I 15/2 ), 455 (Tm 3+ : 1 D 2 3 F 4 ; Er 3+ : 4 F 5/2 4 I 15/2 ), 479 (Tm 3+ : 1 G 4 3 H 6 ; Er 3+ : 4 F 7/2 4 I 15/2 ), 546 (Er 3+ : 4 S 3/2 4 I 15/2 ), and 661 (Er 3+ : 4 F 9/2 4 I 15/2 ; Tm 3+ : 1 G 4 3 F 4 ) nm, respectively. As shown in Figure S1b, TNP has a strong absorption at 363 nm and no absorption can be observed over 500 nm. As a result, the 365 nm instead of 546 nm UC luminescence was dramatically quenched by TNP. Meanwhile, TNT has a wide but weak absorption from 350 to 600 nm and thus both the 363 and 546 nm luminescence were quenched by TNT. In the cases of DNT and NB, no absorption was observed above 350 nm and thus DNT and NB could not quench the UC luminescence. To illustrate the good selectivity of the newly developed method, effects of cyclohexane and toluene on the NaYF 4 UCNPs luminescence were further investigated and the results were shown in Figure S3. And cyclohexane and toluene also have no influence on the luminescence of UCNPs. Meanwhile, visual detection is rapid and simple, and the luminescence efficiency of UCNPs in the presence of various TNT or TNP (0, 1.5, 3 and 4.5 μg/ml) has been shown in Figure S4. To further check the selectivity and applicability of this simultaneous luminescence quenching method, the mixed aqueous solution of these four nitroaromatics were analyzed via this strategy. These four nitroaromatics with pretty similar chemical structures were mixed together beforehand with a known concentration (2.0 μg/ml), and a recovery study was carried out. As can be seen in Table S1, the recovery is very satisfactory and a good selectivity is observed. And we also analyzed trace TNT and TNP in real water samples which were got from Beijing, Tianjin and Shijiazhuang. 4

5 TNT and TNP with a known concentration (2.0 μg/ml) were mixed together before adding to the water samples, and the recovery was checked. As shown in Table S2, the high selectivity can also been achieved from the recovery. These results further suggest that the developed method can be used for the simultaneous and selective detection of TNT and TNP in mixture aqueous samples. Table S1. Detection of TNT and TNP in Mixed-Water Samples a Concentration (μg/ml) sample taken found TNT found TNP recovery (%) (mean, n = 6) (mean, n = 6) TNT ± ± 1.37 TNP ± ± 1.23 TNT/TNP 2.0/ ± ± ± 1.41 TNT/TNP/DNT/NB 2.0/2.0/2.0/ ± ± ± 1.45 a n is the repetitive measurement number. Table S2. Analytical Results for the Determination of Trace TNT and TNP in Real Water Samples sample taken TNT/TNP found TNT/TNP (mean, recovery (%) (μg/ml) n = 6) (μg/ml) 1 2.0/ ± 0.06/1.93 ± ± / ± 0.05/1.96 ± ± / ± 0.04/2.01 ± ±