Analyte Detection with Cu-BTC Metal鈥揙rganic Framework Thin Films by Means of Mass-Sensitive and Work-Function-Based Readout
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- 作者：Polina Davydovskaya ; Annekatrin Ranft ; Bettina V. Lotsch ; Roland Pohle
- 刊名：Analytical Chemistry
- 出版年：2014
- 出版时间：July 15, 2014
- 年：2014
- 卷：86
- 期：14
- 页码：6948-6958
- 全文大小：813K
- ISSN：1520-6882
文摘
Metal鈥搊rganic 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鈥攁lso known as HKUST-1鈥攊s 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鈥揼uest 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鈥揅3) 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.