Departamento de Química, Faculdade de Ciências da Universidade do Porto, Centro de Investigação em Química, Rua Campo Alegre 687, 4169-007 Porto, Portugal.
Talanta. 2010 Mar 15;80(5):1932-8. doi: 10.1016/j.talanta.2009.10.048. Epub 2009 Oct 29.
CdTe quantum dots (QDs), capped with mercaptopropionic acid (MPA), were synthesized and the variation of their fluorescence properties (steady state and lifetime) with pH was assessed in solution and when immobilized in a sol-gel host. Three different sizes of CdTe QDs with excited state lifetimes ranging from 42 to 48 ns and with emission maximum at 540 nm (QD(540)), 580 nm (QD(580)) and 625 nm (QD(625)) were selected. The solution pH affects the maximum emission wavelength (shifts to higher wavelengths of 23, 24 and 27 nm for QD(540), QD(580) and QD(625), respectively), the excited state lifetime and the fluorescence intensity in a reversible way. Linearization of the maximum emission wavelength variation with the pH allows the estimation of an apparent ionization constant (pK(a)) for each QD: 6.5+/-0.1 (QD(540)), 6.1+/-0.5 (QD(580)) and 5.4+/-0.3 (QD(625)). The variation of the QDs fluorescence properties was further explored using confocal laser scanning microscopy allowing the implementation of a new calibration method for pH imaging in solution. QDs were successfully immobilized on the tip of an optical fiber by dip-coating using sol-gel procedure. The immobilized QDs showed a similar pH behaviour to the one observed in solution and an apparent lifetime of 80, 68 and 99 ns, respectively. The proposed QDs based methodology can be successfully used to monitor pH using wavelength encoded data in imaging and fiber optic sensing applications.
CdTe 量子点（QDs）被巯基丙酸（MPA）封端，其荧光性质（稳态和寿命）在溶液中和固定在溶胶-凝胶基质中时随 pH 的变化情况进行了评估。选择了三种不同尺寸的 CdTe QD，激发态寿命为 42 至 48 ns，发射最大值为 540 nm（QD(540)）、580 nm（QD(580)）和 625 nm（QD(625)）。溶液 pH 以可逆的方式影响最大发射波长（分别向较高波长 23、24 和 27 nm 移动）、激发态寿命和荧光强度。最大发射波长随 pH 的变化线性化允许估计每个 QD 的表观离解常数（pK(a)）：6.5+/-0.1（QD(540)）、6.1+/-0.5（QD(580)）和 5.4+/-0.3（QD(625)）。通过共焦激光扫描显微镜进一步探索了 QD 荧光性质的变化，允许在溶液中实现 pH 成像的新校准方法。通过溶胶-凝胶程序通过浸涂将 QD 成功固定在光纤的尖端。固定化的 QD 表现出与溶液中观察到的相似的 pH 行为，分别具有 80、68 和 99 ns 的表观寿命。基于 QD 的提出的方法可以成功地用于使用波长编码数据在成像和光纤传感应用中监测 pH。
