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采用巯基丙酸(MPA)做稳定剂,在碱性介质中合成水溶性好、半峰宽窄、颗粒分散均匀的碲化镉(CdTe)量子点。在双硫腙存在的情况下,根据CdTe量子点荧光强度的恢复程度与铅离子浓度成正比的现象,建立了基于CdTe量子点荧光开关测定铅离子的新方法。在比色管中加入1mL 2.5×10-4 mol/L CdTe量子点溶液(浓度以Cd~(2+)计)、适量pH 10.0的硼砂缓冲溶液、1mL 90μmol/L的双硫腙乙醇溶液,充分反应5min后,加入不同浓度梯度的Pb~(2+)标准溶液,用pH 10.0的硼砂缓冲溶液定容至5mL后放置5min,于激发波长/荧光发射波长(λex/λem)为400nm/600nm测定体系的相对荧光强度。结果发现,铅离子浓度在2.0×10-6~9.0×10-5 mol/L范围内与其对应的相对荧光强度具有良好的线性关系,相关系数r=0.997 6,方法检出限为3.3×10~(-7) mol/L。采用实验方法对土壤和湖水样品中的铅进行测定,结果与原子吸收光谱法(AAS)基本一致,相对标准偏差(RSD,n=6)为0.99%~1.0%,回收率为95%~105%。
Using mercaptopropionic acid (MPA) as a stabilizer, CdTe quantum dots with good water solubility, half width at peak width and uniform particle dispersion were synthesized in alkaline medium. In the presence of dithizone, a new method for the determination of lead ions based on CdTe quantum dot fluorescence switch was established based on the fact that the degree of recovery of fluorescence intensity of CdTe quantum dots is proportional to the concentration of lead ion. Add 1mL 2.5 × 10-4mol / L CdTe quantum dot solution (Cd 2+ concentration), appropriate amount of borax buffer solution of pH 10.0, 1mL 90μmol / L of dithizone ethanol solution, After reaction for 5min, the Pb 2+ standard solution with different concentration gradient was added. The solution was kept at 5mL with borax buffer solution of pH 10.0 for 5min. The excitation / emission wavelength (λex / λem) was 400nm / 600nm The relative fluorescence intensity of the system was measured. The results showed that there was a good linear relationship between the relative fluorescence intensity and the relative fluorescence intensity in the range of 2.0 × 10-6 ~ 9.0 × 10-5 mol / L with the correlation coefficient r = 0.997 6 and the detection limit of 3.3 × 10 ~ (-7) mol / L. The results of determination of lead in soil and lake samples by experimental methods are basically the same as those of AAS, with relative standard deviations (RSD, n = 6) of 0.99% -1.0% and recoveries of 95% -105 %.