Leitão João M M, Gonçalves Helena, Mendonça Conceição, da Silva Joaquim C G Esteves
Laboratório de Métodos Instrumentais de Análise, Faculdade de Farmácia da Universidade de Coimbra, Centro de Estudos Farmacêuticos, 3000-432 Coimbra, Portugal.
Anal Chim Acta. 2008 Nov 3;628(2):143-54. doi: 10.1016/j.aca.2008.09.020. Epub 2008 Sep 16.
The effect of the pH (from 3 to 10) on the excitation emission matrices (EEMs) of fluorescence of CdTe quantum dots (QDs), capped with mercaptopropionic acid (MPA), were analyzed by multiway decomposition methods of parallel factor analysis (PARAFAC), a variant of the parallel factor analysis method (PARAFAC2) and multivariate curve resolution alternating least squares (MCR-ALS). Three different sized CdTe QDs with emission maximum at 555 nm (QDa), 594 nm (QDb) and 628 nm (QDc) were selected for analysis. The three-way data structures composed of sets of EEMs obtained as function of the pH (EEMs, pH) do not have a trilinear structure. A marked deviation to the trilinearity is observed in the emission wavelength order--the emission spectra suffers wavelength shift as the pH is varied. The pH-induced variation of the fluorescence properties of QDs is described with only one-component PARAFAC2 or MCR-ALS models--other components are necessary to model scattering and/or other background signals in (EEMs, pH) data structures. Bigger sized QDs are more suitable tools for analytical methodologies because they show higher Stokes shifts (resulting in simpler models) and higher pH range sensitivity. The pH dependence of the maximum wavelength of the emission spectra is particularly suitable for the development of QDs/EEMs wavelength-encoded pH sensor bioimaging or biological label methodologies when coupled to multiway chemometric decomposition.
采用平行因子分析（PARAFAC）、平行因子分析方法的一种变体（PARAFAC2）以及多元曲线分辨交替最小二乘法（MCR-ALS）等多向分解方法，分析了pH值（3至10）对巯基丙酸（MPA）包覆的碲化镉量子点（QDs）荧光激发发射矩阵（EEMs）的影响。选择了三种不同尺寸、发射峰分别位于555 nm（QDa）、594 nm（QDb）和628 nm（QDc）的碲化镉量子点进行分析。由作为pH值函数获得的EEMs集组成的三维数据结构（EEMs，pH）不具有三线性结构。在发射波长顺序上观察到明显偏离三线性——随着pH值变化，发射光谱会发生波长偏移。量子点荧光性质的pH诱导变化仅用单组分PARAFAC2或MCR-ALS模型来描述——需要其他组分来模拟（EEMs，pH）数据结构中的散射和/或其他背景信号。尺寸较大的量子点是更适合分析方法的工具，因为它们表现出更高的斯托克斯位移（从而得到更简单的模型）和更高的pH范围灵敏度。当与多向化学计量分解相结合时，发射光谱最大波长的pH依赖性特别适用于开发量子点/EEMs波长编码的pH传感器生物成像或生物标记方法。
