Sensing Nitrogen Mustard Gas Simulant at the ppb Scale via Selective Dual-Site Activation at Au/Mn₃O₄ Interfaces

Abstract

The efficient detection of chemical warfare agents (CWAs), putting at stake human life and global safety, is of paramount importance in the development of reliable sensing devices for safety applications. Herein, we present the fabrication of Mn3O4-based nanocomposites containing noble metal particles for the gas-phase detection of a simulant of vesicant nitrogen mustard, i.e., di­(propylene glycol) monomethyl ether (DPGME). The target materials were fabricated by chemical vapor deposition of manganese oxide on Al2O3 substrates and subsequent functionalization with silver or gold via radio frequency sputtering. The obtained high purity composites, characterized by an intimate metal/oxide contact, yielded an outstanding efficiency in the detection of DPGME. In particular, sensing of the latter analyte with an ultralow detection limit of 0.6 ppb could be performed selectively with respect to other CWA simulants. In addition, the tuneability of selectivity patterns as a function of metal nanoparticle nature paves the way to the development of efficient and selective devices for practical end uses.

Chemical Gas Sensors Studied at SENSOR Lab, Brescia (Italy): From Conventional to Energy-Efficient and Biocompatible Composite Structures

“…Consistently, such an effect can also explain the In the next work, the catalytic effect of Au on the sensing behavior of Fe 2 O 3 was investigated varying the concentration of catalyst material. The gas tests were carried out at 25, 100 and 200 • C [70]. In this case, the Au particles not only affect the sensor response but similarly influences the operating temperature and selectivity of Fe 2 O 3 towards nitrogen dioxide (NO 2 ) ( Figure 6).…”

“…Response to 5 ppm of NO 2 as a function of the sensor working temperature for ε-Fe 2 O 3 and Au/ε-Fe 2 O 3 nanocomposites with different gold contents. Reproduced with permission from[70].…”

Hydrogen Gas Sensing Performances of p-Type Mn3O4 Nanosystems: The Role of Built-in Mn3O4/Ag and Mn3O4/SnO2 Junctions

“…Atomic percentage (at.%; uncertainty = ±2%) values were determined by peak integration using Φ V5.4A sensitivity factors, after a Shirley-type background subtraction. Silver and tin molar fractions were calculated as X M = [(M at.%)/(M at.% + Mn at.%) × 100], with M = Ag, Sn [38,46]. Spectra were fitted with mixed Gaussian-Lorentzian peak shapes using the XPSPEAK program [57].…”

“…Among p-type systems, Mn 3 O 4 has received significant attention due to its low cost, large natural abundance, environmentally friendly character and versatile chemico-physical properties, including the coexistence of mixed valence states [36,37]. Over the last decade, different studies have reported on Mn 3 O 4 -containing gas sensors for various analytes, including CH 3 CH 2 OH, CH 3 COCH 3 , NH 3 and chemical warfare agent simulants [31,[35][36][37][38][39][40][41]. Nonetheless, only two works on Mn 3 O 4 -based gas sensors for molecular hydrogen detection are available in the literature so far [35,42], and the implementation of H 2 sensors endowed with improved sensitivity and selectivity undoubtedly requires additional research efforts [29,35,37,38].…”

“…At variance with our previous studies, which have involved the fabrication of Mn 3 O 4 -based sensors by means of thermally activated chemical vapor deposition (CVD)-based processes [31,38,39,41], in this work a novel two-step plasma-assisted route was adopted for the preparation of the present materials. The fabrication procedure ( Figure 1) involved: (i) the initial plasma assisted-CVD (PA-CVD) on alumina substrates of MnO 2 from Mn(hfa) 2 TMEDA (Hhfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; TMEDA = N,N,N',N'-tetramethylethylenediamine) [51,52], a molecular precursor never utilized so far for PA-CVD processes; (ii) the functionalization with Ag or SnO 2 by means of radio frequency (RF)-sputtering, and (iii) a final thermal treatment in air to trigger the transformation of MnO 2 into Mn 3 O 4 .…”