Davydovskaya Polina, Ranft Annekatrin, Lotsch Bettina V, Pohle Roland
Siemens AG, Corporate Technology , Otto-Hahn-Ring 6, 81739 Munich, Germany.
Anal Chem. 2014 Jul 15;86(14):6948-58. doi: 10.1021/ac500759n. Epub 2014 Jul 2.
Metal-organic frameworks (MOFs) constitute a new generation of porous crystalline materials, which have recently come into focus as analyte-specific active elements in thin-film sensor devices. Cu-BTC--also known as HKUST-1--is one of the most theoretically and experimentally investigated members of the MOF family. Its capability to selectively adsorb different gas molecules renders this material a promising candidate for applications in chemical gas and vapor sensing. Here, we explore details of the host-guest interactions between HKUST-1 and various analytes under different environmental conditions and study the vapor adsorption mechanism by mass-sensitive and work-function-based readouts. These complementary transduction mechanisms were successfully applied for the detection of low ppm (2 to 50 ppm) concentrations of different alcohols (methanol, ethanol, 1-propanol, and 2-propanol) adsorbed into Cu-BTC thin films. Evaluation of the results allows for the comparison of the amounts of adsorbed vapors and the contribution of each vapor to the changes of the electronic properties of Cu-BTC. The influence of the length of the alcohol chain (C1-C3) and geometry (1-propanol, 2-propanol) as well as their polarity on the sensing performance was investigated, revealing that in dry air, short chain alcohols are more likely adsorbed than long chain alcohols, whereas in humid air, this preference is changed, and the sensitivity toward alcohols is generally decreased. The adsorption mechanism is revealed to differ for dry and humid atmospheres, changing from a site-specific binding of alcohols to the open metal sites under dry conditions to weak physisorption of the analytes dissolved in surface-adsorbed water reservoirs in humid air, with the signal strength being governed by their relative concentration.
金属有机框架材料（MOFs）是新一代多孔晶体材料，最近作为薄膜传感器设备中分析物特异性活性元素受到关注。Cu-BTC（也称为HKUST-1）是MOF家族中在理论和实验上研究最多的成员之一。其选择性吸附不同气体分子的能力使该材料成为化学气体和蒸汽传感应用的有前途的候选者。在这里，我们探讨了不同环境条件下HKUST-1与各种分析物之间主客体相互作用的细节，并通过基于质量敏感和功函数的读数研究了蒸汽吸附机制。这些互补的转导机制已成功应用于检测吸附在Cu-BTC薄膜中的低ppm（2至50 ppm）浓度的不同醇类（甲醇、乙醇、1-丙醇和2-丙醇）。对结果的评估允许比较吸附蒸汽的量以及每种蒸汽对Cu-BTC电子性质变化的贡献。研究了醇链长度（C1-C3）、几何形状（1-丙醇、2-丙醇）及其极性对传感性能的影响，结果表明，在干燥空气中，短链醇比长链醇更容易吸附，而在潮湿空气中，这种偏好发生变化，对醇类的灵敏度通常会降低。结果表明，干燥和潮湿气氛下的吸附机制不同，从干燥条件下醇类与开放金属位点的位点特异性结合转变为潮湿空气中溶解在表面吸附水库中的分析物的弱物理吸附，信号强度由它们的相对浓度决定。
