Organic framework engineering in mesoporous Nb2O5 thin films used as an active medium for organic vapors sensing

Georgiev, Rosen; Christova, Darinka; Georgieva, Biliana; Babeva, Tsvetanka

doi:10.1117/12.2322527

Cited by 3 publications

(6 citation statements)

References 15 publications

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“…Owing to condensation of vapors in the pores, the effective refractive index increases with 0.0444. It is interesting to note that these values are very close to Δ n values of 0.048 obtained for mesoporous Nb 2 O 5 thin films exposed to acetone vapors reported in [ 33 ]. The porosity of the latter is about 50% and was generated using a commercial organic template [ 33 ].…”

Section: Resultssupporting

confidence: 87%

Acetone-Sensitive Thin Films Comprising Coal Fly Ash Na-X Zeolites and Sol–Gel Nb2O5 Matrix

et al. 2021

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In this study, thin composite films of a sol–gel Nb2O5 matrix doped with coal fly ash Na-X zeolites were deposited by the spin-coating method. Fly ash of lignite coal collected from the electrostatic precipitators of one of the biggest TPPs in Bulgaria was used as a raw material for obtaining zeolites. Zeolite Na-X was synthesized by ultrasonic-assisted double stage fusion-hydrothermal alkaline conversion of coal fly ash. In order to improve the optical quality and sensing properties of the deposited thin films, synthesized zeolites were wet-milled for 60, 120, and 540 s prior to film deposition. The surface morphology of zeolite powders was studied both by scanning electron microscopy and transmission electron microscopy, while their porosity was investigated by N2-physisorption. Refractive index, extinction coefficient, and thickness of the films were determined through fitting of their reflectance spectra. The sensing ability of thin films towards acetone vapors was tested by measuring the reflectance spectra prior to and during exposure to the analyte, and the change in the reflection coefficient ∆R of the films was calculated. The influence of milling time of zeolites on the sensing and optical properties of the films was assumed and confirmed.

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Section: Resultssupporting

confidence: 87%

Acetone-Sensitive Thin Films Comprising Coal Fly Ash Na-X Zeolites and Sol–Gel Nb2O5 Matrix

et al. 2021

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“…In this case, the calculated value for ∆n Ac is 0.04. That is in excellent agreement with previously obtained values concerning the refractive index response of single films [14].…”

Section: Sensing Of Acetone Vaporssupporting

confidence: 93%

“…The change of transmittance ΔTmax is 10.9% for mp-niobia-PE6200 containing stack, and 6.3% for the stack including porous films templated with PE6800. This means that the change in the effective refractive index of mp-niobia-PE6200 is higher compared to mp-niobia-PE6800, which is in accordance with the results obtained for sensing response of single porous films (∆nAc is 0.028 [18] and 0.035 [14] for PE6800 and PE6200 templated stacks). The comparison between Figure 5a,b shows that the stop band of stack including mp-niobia-PE6200 films is wider as compared to that in PE6800 templated stack indicating higher optical contrast in the first case.…”

Section: Sensing Of Acetone Vaporssupporting

confidence: 90%

“…The impact of different pore morphology on refractive index of porous films is well seen in Figure 2: the smaller refractive index and higher porosity is achieved in the case of spherical pores (porous film templated with PE6800). Although the free volume fraction in PE6800-templated films is higher as compared to this in PE6200 templated films (50% and 35%, respectively), the change in refractive index Δn of single films due to exposure to acetone vapors is slightly higher in PE6200 templated films (0.035) [14] as compared to Δn for PE6800-templated one (0.028) [18]. This means that absorption, penetration, and condensation of vapors are more effective when pores are arranged in rows than when they are randomly scattered in the film.…”

Section: Optical and Sensing Properties Of Single Filmsmentioning

confidence: 85%

“…Nb 2 O 5 is well a studied material with wide application in energy storage [10,11] and optoelectronics [12] due to its chemical resistivity, high refractive index value, and aging durability. Previously, our group has studied the optical parameters of mesoporous Nb 2 O 5 thin films mesostructured with different organic templates and concentrations in order to achieve reproducible film parameters [13,14]. A single layer reaction has been quantified when exposed to acetone vapors and Bragg stack of one material in two different forms (dense and porous) has been successfully deposited and used as a sensing medium for VOC's detection using reflectance measurements.…”

Section: Introductionmentioning

confidence: 99%

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Optical Detection of VOC Vapors Using Nb2O5 Bragg Stack in Transmission Mode

et al. 2021

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In this study, an emphasis is put on vapor-sensitive Bragg stacks as an important class of optical sensors. All-niobia Bragg stacks were deposited by spin-coating of sol-gel Nb2O5 thin films alternated with mesoporous layers after proper design through optimization of operating wavelength and number of layers in the stack. Mesoporous Nb2O5 films with different morphology and identical structure were obtained using organic templates (Pluronics PE6200 and PE6800) and subsequent annealing. Transmittance measurements were performed as a detection method that offers technological simplicity and accuracy. It was demonstrated that stacks including PE6200 templated films exhibit higher sensitivity than stacks templated with PE6800. It was assumed and verified by computer-aided modelling of experimental data that mesoporous films prepared with addition of PE6200, although less porous, were more stable compared to those templated with PE6800, and did not collapse during the thermal treatment of the stacks. Furthermore, the reproducibility of optical response was studied by sorption and desorption cycles of acetone vapors. The suitability of all-niobia Bragg stacks for optical sensing of VOCs was discussed.

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