Hydrogel-based piezoresistive pH sensors: Investigations using FT-IR attenuated total reflection spectroscopic Imaging
Hydrogel-based piezoresistive pH sensors: Investigations using FT-IR attenuated total reflection spectroscopic Imaging
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DOI：
10.1021/ac702598n
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发表时间：
2008-04-15
影响因子：
7.4
通讯作者：
Arndt, Karl-Friedrich
中科院分区：
文献类型：
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作者：
Sorber, Joerg;Steiner, Gerald;Arndt, Karl-Friedrich
PH响应型聚丙烯酸/聚乙烯醇(PAA/PVA)水凝胶具有很强的溶胀能力，将压阻响应元件作为机电换能器和水凝胶的相变行为作为化学机械换能器相结合的新型传感器的开发成为可能。该传感器由pH响应型PAA/PVA水凝胶和标准压力传感器芯片组成。然而，与时间相关的传感器输出电压只能反映水凝胶的物理膨胀过程，而不能反映相应的化学反应。因此，研究这种水凝胶的溶胀行为对于传感器的优化设计是至关重要的。本文利用傅里叶变换红外(FT-IR)光谱成像技术研究了水凝胶在原位条件下的溶胀行为。特别是，在衰减全反射模式下获得了横向和时间分辨的FT-IR图像，并用主成分分析(PCA)对超过8万个FT-IR光谱的整个数据集进行了评估。第一和第三主成分(PC)表示膨胀过程。在第二个和第四个PC中观察到了羧基内部的分子变化，并被确定为溶胀行为的关键过程。研究发现，分子随时间的变化与电传感器的输出信号相似。FT-IR光谱图像的结果使改进的化学传感器成为可能，并表明原位FT-IR成像是表征化学敏感材料中分子过程的一种强有力的方法。
The strong swelling ability of the pH-responsive poly(acrylic acid)/poly(vinyl alcohol) (PAA/PVA) hydrogel makes the development of a new type of sensor possible, which combines piezoresistive-responsive elements as mechanoelectrical transducers and the phase transition behavior of hydrogels as a chemomechanical transducer. The sensor consists of a pH-responsive PAA/PVA hydrogel and a standard pressure sensor chip. However, a time-dependent sensor output voltage mirrors only the physical swelling process of the hydrogel but not the corresponding chemical reactions. Therefore, an investigation of the swelling behavior of this hydrogel is essential for the optimization of sensor design. In this work, Fourier transform infrared (FT-IR) spectroscopic imaging was used to study the swelling of the hydrogel under in situ conditions. In particular, laterally and time-resolved FT-IR images were obtained in the attenuated total reflection mode and the entire data set of more than 80 000 FT-IR spectra was evaluated by principal component analysis (PCA). The first and third principal components (PCs) indicate the swelling process. Molecular changes within the carboxyl groups were observed in the second and fourth PC and identified as key processes for the swelling behavior. It was found that time-dependent molecular changes are similar to the electrical sensor output signal. The results of the FT-IR spectroscopic images render an improved chemical sensor possible and demonstrate that in situ FT-IR imaging is a powerful method for the characterization of molecular processes within chemical-sensitive materials.