Güntner A T, Pineau N J, Chie D, Krumeich F, Pratsinis S E
Particle Technology Laboratory, Institute of Process Engineering, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, Zurich 8092, Switzerland.
J Mater Chem B. 2016 Aug 28;4(32):5358-5366. doi: 10.1039/c6tb01335j. Epub 2016 Jul 21.
Exhaled isoprene could enable non-invasive monitoring of cholesterol-lowering therapies. Here, we report an isoprene-selective sensor at high relative humidity (RH) for the first time (to our knowledge). It is made of nanostructured, chemo-resistive Ti-doped ZnO particles (10-20 nm crystal size) produced by flame spray pyrolysis (FSP) and directly deposited in one step onto compact sensor substrates forming highly porous films. The constituent particles consist of stable Ti-doped ZnO solid solutions for Ti levels up to 10 mol% apparently by substitutional incorporation of Ti into the ZnO wurtzite lattice and dominant presence at the particle surface. These Ti point defects strongly enhance the isoprene sensitivity (>15 times higher than pure ZnO) and turn ZnO isoprene-selective, while also improving its thermal stability. In situ infrared spectroscopy confirms that Ti intensifies the surface interaction of Ti-doped ZnO with isoprene by providing additional sites for chemisorbed hydroxyl species. In fact, at an optimal Ti content of 2.5 mol%, this sensor shows superior isoprene responses compared to acetone, NH and ethanol at 90% RH. Most notably, breath-relevant isoprene concentrations can be detected accurately down to 5 ppb with high (>10) signal-to-noise ratio. As a result, an inexpensive isoprene detector has been developed that could be easily incorporated into a portable breath analyzer for non-invasive monitoring of metabolic disorders (e.g. cholesterol).
呼出的异戊二烯可实现对降胆固醇疗法的无创监测。在此，我们首次（据我们所知）报道了一种用于高相对湿度（RH）环境的异戊二烯选择性传感器。它由通过火焰喷雾热解（FSP）制备的纳米结构化学电阻式掺钛ZnO颗粒（晶体尺寸为10 - 20纳米）制成，并通过一步直接沉积在紧凑的传感器基板上，形成高度多孔的薄膜。对于高达10 mol%的钛含量，组成颗粒由稳定的掺钛ZnO固溶体组成，显然是通过钛替代掺入ZnO纤锌矿晶格并主要存在于颗粒表面。这些钛点缺陷极大地提高了对异戊二烯的灵敏度（比纯ZnO高15倍以上），使ZnO具有异戊二烯选择性，同时还提高了其热稳定性。原位红外光谱证实，钛通过为化学吸附的羟基物种提供额外位点，增强了掺钛ZnO与异戊二烯的表面相互作用。事实上，在最佳钛含量为2.5 mol%时，该传感器在90% RH下对异戊二烯的响应优于丙酮、NH₃和乙醇。最值得注意的是，与呼吸相关的低至5 ppb的异戊二烯浓度能够以高（>10）信噪比被准确检测到。因此，已开发出一种廉价的异戊二烯探测器，它可以很容易地集成到便携式呼吸分析仪中，用于对代谢紊乱（如胆固醇）进行无创监测。
