Senzor de hidrogen ultra-rapid și ultra-sensibil pentru nanofire(Ultra-fast and ultra-sensitive nanowire hydrogen sensor)

O echipă KAIST a realizat un senzor de hidrogen ultra rapid care poate detecta nivelurile de gaze de hidrogen sub 1% în mai puțin de șapte secunde. De asemenea, senzorul poate detecta sute de părți la un milion de niveluri de hidrogen gazos în 60 de secunde la temperatura camerei ( materiale și interfețe aplicate ACS , „Nanowires compozit Pd-Ag compozit pentru răspuns rapid și senzori de hidrogen transparent” ).Profesorul Kim se așteaptă ca senzorul ultra-rapid de hidrogen să poată fi util pentru prevenirea accidentelor de explozie provocate de scurgeri de hidrogen gazos. În plus, se așteaptă ca alte gaze nocive din aer să poată fi detectate cu precizie prin nano-filtrare eficientă prin utilizarea unei varietăți de straturi MOF.

Posted: Sep 29, 2017

Ultra-fast and ultra-sensitive nanowire hydrogen sensor

(Nanowerk News) A KAIST team made an ultra-fast hydrogen sensor that can detect hydrogen gas levels under 1% in less than seven seconds. The sensor also can detect hundreds of parts per million levels of hydrogen gas within 60 seconds at room temperature (ACS Applied Materials and Interfaces, „Hollow Pd-Ag Composite Nanowires for Fast Responding and Transparent Hydrogen Sensors „).
A research group under Professor Il-Doo Kim in the Department of Materials Science and Engineering at KAIST, in collaboration with Professor Reginald M. Penner of the University of California-Irvine, has developed an ultra-fast hydrogen gas detection system based on a palladium (Pd) nanowire array coated with a metal-organic framework (MOF).
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Schematic illustration of a metal-organic framework (MOF). The MOF, consisting of metal ions and organic ligands, is a highly porous material with a ultrahigh surface area. The various structures of MOFs can be synthesized depending on the kinds of metal ions and organic ligands. (Image: KAIST)
Hydrogen has been regarded as an eco-friendly next-generation energy source. However, it is a flammable gas that can explode even with a small spark. For safety, the lower explosion limit for hydrogen gas is 4 vol% so sensors should be able to detect the colorless and odorless hydrogen molecule quickly.
The importance of sensors capable of rapidly detecting colorless and odorless hydrogen gas has been emphasized in recent guidelines issued by the U.S. Department of Energy. According to the guidelines, hydrogen sensors should detect 1 vol% of hydrogen in air in less than 60 seconds for adequate response and recovery times.
Ultra-fast and ultra-sensitive nanowire hydrogen sensor
Representative image of this paper published in ACS Nano on Sept. 26.
To overcome the limitations of Pd-based hydrogen sensors, the research team introduced a MOF layer on top of a Pd nanowire array. Lithographically patterned Pd nanowires were simply overcoated with a Zn-based zeolite imidazole framework (ZIF-8) layer composed of Zn ions and organic ligands. ZIF-8 film is easily coated on Pd nanowires by simple dipping (for 2-6 hours) in a methanol solution including Zn (NO3)2·6H2O and 2-methylimidazole.
As synthesized ZIF-8 is a highly porous material composed of a number of micro-pores of 0.34 nm and 1.16 nm, hydrogen gas with a kinetic diameter of 0.289 nm can easily penetrate inside the ZIF-8 membrane, while large molecules (>0.34 nm) are effectively screened by the MOF filter.
Thus, the ZIF-8 filter on the Pd nanowires allows the predominant penetration of hydrogen molecules, leading to the acceleration of Pd-based H2 sensors with a 20-fold faster recovery and response speed compared to pristine Pd nanowires at room temperature.
Images of Pd nanowire array-based hydrogen sensors, scanning electron microscopy image of a Pd nanowire covered by a metal-organic framework layer, and the hydrogen sensing properties of the sensors
Images of Pd nanowire array-based hydrogen sensors, scanning electron microscopy image of a Pd nanowire covered by a metal-organic framework layer, and the hydrogen sensing properties of the sensors. (Image: KAIST)
Professor Kim expects that the ultra-fast hydrogen sensor can be useful for the prevention of explosion accidents caused by the leakage of hydrogen gas. In addition, he expects that other harmful gases in the air can be accurately detected through effective nano-filtration by using of a variety of MOF layers.
Source: The Korea Advanced Institute of Science and Technology (KAIST)