Determination of arsenic(iii) based on the fluorescence resonance energy transfer between CdTe QDs and Rhodamine 6G

Abstract

1In this paper, a sensitive and selective arsenic (III)(As (III)) detection method based on the fluorescence resonance 2 energy transfer (FRET) system between mercaptopropionic acid (MPA)-capped CdTe quantum dots (QDs) and Rhodamine 3 6G (R6G) was developed. In this system, CdTe QDs acted as energy donors, while R6G acted as energy acceptor. 4Glutathione (GSH) could attach to the surface of CdTe QDs to decrease the efficiency of FRET, As (III) could combine with 5 GSH and remove the GSH from QDs, which could recover the efficiency of FRET. We optimized some important factors 6 which would affect the efficiency of FRET system. Under the optimized experimental conditions, As (III) could be detected 7 based on the fluorescence intensity changes of R6G in the FRET system. There was a good linear relationship between the 8 fluorescence intensity of R6G and the concentration of As (III) in the range of 0.02-2 µmol/L and the detection limit was 9 0.006 µmol/L. The proposed method has been applied to detect As (III) in lake water samples with satisfactory results. 10 11 of As (III) and As (V), but inorganic As (III) is more stable in environment. In particular, in our body, As (V) can be 19 converted to As (III) by some reducing agent, such as vitamin C. Thus, rapid and sensitive analytical methods to detect As 20 (III) in food products and the nature are very urgent to the whole society. There has been some methods for As (III) detection, 21 such as electrocatalytic technique, 14 GC-ICPMS, 15 HPLC-ICP-MS, 16 resonance Rayleigh scattering, 17 and colorimetric 22 detection. 18 Though the above methods can get a low detection limit or a good sensitivity, some of them are not suitable for 23 real time monitoring, because these methods usually depend on large amounts of pretreatment processes and sophisticated 24 a more effectively quenching of the fluorescence intensity of CdTe QDs after adding As (III), the concentration of CdTe QDs 21 was chosen to be 0.65 µmol/L in our study. 22 Effect of the concentration of GSH 23The effect of the concentration of GSH was then studied. As shown in Fig. 3C, the fluorescence intensity of R6G 24 GSH than other substance containing single -SH, -COOH or -NH 2 . 23 So the FRET system could be influenced obviously by 20 the addition of GSH. But GSH can react with As (III): 21As 3+ + 3GSH →As(SG) 3 + 3H + 22Therefore, the GSH capping layer was preferentially removed from the surface of CdTe QDs due to the binding of As 23 (III) and GSH. The remove of GSH consequently gave R6G the chance to recombine with the CdTe QDs, which made the 24

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