posted on 2024-02-28, 10:29authored byLiwei Hou, Xinyue Xu, Zhoujun Zhong, Fengchun Tian, Li Wang, Yi Xu
The
demand for the detection of ultralow concentrations of ammonia
gas is growing. A bimetallic metal–organic framework (MOF)
comprising Prussian blue analogs (PBAs) was used to achieve highly
sensitive and stable detection of ammonia gas at room temperature
in this study. First, PB was enriched by using ammonia for improved
gas sensing properties. Second, a sensitive membrane with more vacancies
was formed by partially replacing Fe3+ with Cu2+ through a cation-exchange strategy. Finally, a capacitive sensor
was developed for ultralow-concentration ammonia detection using a
Cu–Fe PBA sensitive membrane and interdigitated electrodes
(IDEs). To investigate the adsorption efficiency of the designed composite
sensitive film for ammonia, PBAs nanoparticles were deposited on a
quartz microcrystal balance (QCM) via cyclic voltammetry and a hydrothermal
method. Approximately 10 ppm of ammonia was adsorbed under 1 atm by
the Cu–Fe PBA film prepared using a reaction time of 36 h,
and the adsorption efficiency was measured to be 2.2 mmol g–1 using the QCM frequency response. The Cu–Fe PBAs were also
tested using scanning electron microscopy, transmission electron microscopy,
X-ray diffraction, and Brunauer–Emmett–Teller theory.
The introduction of Cu2+ ions significantly increased the
specific surface area of Cu–Fe PBAs MOF, and the number of
adsorption sites for ammonia also increased; however, its skeleton
structure remained similar to that of PB. Then, the capacitive sensor
based on Cu–Fe PBA sensitive membrane and IDE was fabricated
and the gas sensing detection device was established for ammonia detection.
Overall, the developed capacitive sensor exhibits a linear response
of 75–1000 ppb and a detection limit of 3.8 ppb for ultralow
ammonia concentrations, which makes it superior to traditional detection
methods and thus allows excellent application prospects.