Photoactivated Processes on the Surface of Metal Oxides and Gas Sensitivity to Oxygen

Чижов, А. С.; Kutukov, Pavel; Astafiev, Artyom A.; Rumyantseva, M. N.

doi:10.3390/s23031055

Cited by 3 publications

(5 citation statements)

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“…In a previous work [ 12 ], we developed a model according to which, under UV irradiation, the surface of ZnO was enriched with oxygen vacancies through the photolysis of the surface layers. The generated oxygen vacancies acted as adsorption sites for oxygen molecules, which then underwent dissociation with the healing of the surface vacancies.…”

Section: Resultsmentioning

confidence: 99%

“…Figure 2 shows the powder diffraction patterns of the intermediate precipitates and ZnO synthesized at 300 • C. According to the obtained data, ZnO-prec(1) was a twophase sample, consisting of the main phase of orthorhombic zinc ammine carbonate ZnNH 3 CO 3 , a space group Pna2 1 (01-077-5096 card, PDF4), and a small amount of ZnO with a wurtzite structure (card 36-1451, PDF2). The refined unit cell parameters of the synthesized ZnNH 3 CO 3 were a = 9.1488 (11), b = 7.6000 (12), and c = 5.4983 (7). The ZnO-prec( 2) sample was single-phase monoclinic hydrozincite Zn 5 (CO 3 ) 2 (OH) 6 , with a space group C2/m (card 19-1458, PDF2), with refined cell parameters a = 13.6127( 19), b = 6.3301 (12), c = 5.3788 (5), and β = 95.06 (2).…”

Section: Phase Compositionmentioning

confidence: 99%

“…The refined unit cell parameters of the synthesized ZnNH 3 CO 3 were a = 9.1488 (11), b = 7.6000 (12), and c = 5.4983 (7). The ZnO-prec( 2) sample was single-phase monoclinic hydrozincite Zn 5 (CO 3 ) 2 (OH) 6 , with a space group C2/m (card 19-1458, PDF2), with refined cell parameters a = 13.6127( 19), b = 6.3301 (12), c = 5.3788 (5), and β = 95.06 (2). The annealing of the monoclinic HZ phase led to the formation of a single-phase sample of hexagonal ZnO, space group P6 3 mc (card 36-1451, PDF2).…”

Section: Phase Compositionmentioning

confidence: 99%

“…Moreover, defect engineering methods have been widely developed for ZnO that increase its reactivity by introducing additional surface oxygen vacancies during synthesis or physical treatment [ 10 , 11 ]. Compared with other metal oxides used as materials for gas sensors (SnO 2 , In 2 O 3 ), ZnO has photocatalytic properties, which, for example, were demonstrated using photoactivated isotopic oxygen exchange [ 12 ]. Due to its nontoxicity, environmental stability, ecofriendliness, abundance, and low cost, ZnO can be considered as a material for wide practical applications.…”

Section: Introductionmentioning

confidence: 99%

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Highly Active Nanocrystalline ZnO and Its Photo-Oxidative Properties towards Acetone Vapor

et al. 2023

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Zinc oxide is one of the well-known photocatalysts, the potential applications of which are of great importance in photoactivated gas sensing, water and air purification, photocatalytic synthesis, among others. However, the photocatalytic performance of ZnO strongly depends on its morphology, composition of impurities, defect structure, and other parameters. In this paper, we present a route for the synthesis of highly active nanocrystalline ZnO using commercial ZnO micropowder and ammonium bicarbonate as starting precursors in aqueous solutions under mild conditions. As an intermediate product, hydrozincite is formed with a unique morphology of nanoplates with a thickness of about 14–15 nm, the thermal decomposition of which leads to the formation of uniform ZnO nanocrystals with an average size of 10–16 nm. The synthesized highly active ZnO powder has a mesoporous structure with a BET surface area of 79.5 ± 4.0 m2/g, an average pore size of 20 ± 2 nm, and a cumulative pore volume of 0.507 ± 0.051 cm3/g. The defect-related PL of the synthesized ZnO is represented by a broad band with a maximum at 575 nm. The crystal structure, Raman spectra, morphology, atomic charge state, and optical and photoluminescence properties of the synthesized compounds are also discussed. The photo-oxidation of acetone vapor over ZnO is studied by in situ mass spectrometry at room temperature and UV irradiation (λmax = 365 nm). The main products of the acetone photo-oxidation reaction, water and carbon dioxide, are detected by mass spectrometry, and the kinetics of their release under irradiation are studied. The effect of morphology and microstructure on the photo-oxidative activity of ZnO samples is demonstrated.

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Section: Resultsmentioning

confidence: 99%

Section: Phase Compositionmentioning

confidence: 99%

Section: Phase Compositionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Highly Active Nanocrystalline ZnO and Its Photo-Oxidative Properties towards Acetone Vapor

et al. 2023

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“…Small hand-held measuring devices equipped with a photoionization detector (PID) and other micro gas sensors (e.g., metal oxide sensors [ 2 ] or electrochemical cells) have been available on the market for years. The latter micro gas sensors detect the presence of gas groups with considerable sensitivity but lack any referenceable gas identification.…”

Section: Introductionmentioning

confidence: 99%

Physical Trace Gas Identification with the Photo Electron Ionization Spectrometer (PEIS)

Doll,

Fuenzalida,

Schütte

et al. 2024

Sensors

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Chemosensor technology for trace gases in the air always aims to identify these compounds and then measure their concentrations. For identification, traceable methods are sparse and relate to large appliances such as mass spectrometers. We present a new method that uses the alternative traceable measurement of the ionization energies of trace gases in a way that can be miniaturized and energetically tuned. We investigate the achievable performance. Since tunable UV sources are not available for photoionization, we take a detour via impact ionization with electrons, which we generate using the photoelectric effect and bring to sharp, defined energies on a nanoscale in the air. Electron impact ionization is thus possible at air pressures of up to 900 hPa. The sensitivity of the process reaches 1 ppm and is equivalent to that of classic PID. With sharpened energy settings, substance identification is currently possible with an accuracy of 30 meV. We can largely explain the experimental observations with the known quantum mechanical models.

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Room Temperature UV-Activated NO2 and NO Detection by ZnO/rGO Composites

et al. 2023

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Nanocomposites, including nanoparticles of semiconductor metal oxide (MO) and reduced graphene oxide (rGO), are of exceptional interest for light-activated gas sensors functioning without thermal heating. In this paper, we discuss the sensor properties of electrospun ZnO nanofibers and ZnO/rGO composites. The materials were characterized by transmission and scanning electron microscopy (TEM, SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and IR spectroscopy (FTIR). The sensor characteristics were studied when detecting reducing gases CO, H2, and NH3 and oxidizing gases NO and NO2 at 25–150 °C in dark conditions and under UV illumination. ZnO nanofibers and ZnO/rGO composites have no sensitivity when detecting CO, NH3, and H2 either in dark conditions or under UV illumination. At T = 25 °C, UV illumination is a necessary condition for the appearance of a sensor response when detecting both NO and NO2. The increased sensitivity of ZnO/rGO composites when detecting nitrogen oxides at T = 25 °C is discussed in terms of the heterojunction formation. Observed at T = 150 °C, opposite trends in the UV illumination influence on the sensor response toward NO and NO2 are due to the participation of chemisorbed oxygen in the processes responsible for the sensor response formation when detecting NO.

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Photoactivated Processes on the Surface of Metal Oxides and Gas Sensitivity to Oxygen

Cited by 3 publications

References 68 publications

Highly Active Nanocrystalline ZnO and Its Photo-Oxidative Properties towards Acetone Vapor

Highly Active Nanocrystalline ZnO and Its Photo-Oxidative Properties towards Acetone Vapor

Physical Trace Gas Identification with the Photo Electron Ionization Spectrometer (PEIS)

Room Temperature UV-Activated NO2 and NO Detection by ZnO/rGO Composites

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