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Design Processes via Manipulation of Nanoparticles and Their Suitability for...
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Design Processes via Manipulation of Nanoparticles and Their Suitability for Gas Sensors

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Materials Processes".

Deadline for manuscript submissions: closed (15 May 2024) | Viewed by 12434

Special Issue Editors

Dr. Gugu Hlengiwe Mhlongo

E-Mail Website
Guest Editor
Council for Scientific and Industrial Research (CSIR), Pretoria 0001, South Africa
Interests: rare earth activated nanophosphors (i.e., down- and upconversion); solid state lighting; magnetic (EPR, VSM) properties; luminescence properties, i.e., photoluminescence; cathodoluminescence; functional nanomaterials and their synthesis and characterization; gas nanosensors for food safety and air quality monitoring; fabrication and testing of gas nanosensors; defect structure control
Dr. Dimitra Papadaki

E-Mail Website
Guest Editor
Group of Building Environmental Studies, Physics Department, National and Kapodistrian University of Athens, 157 84 Athens, Greece
Interests: environmental sciences; energy efficiency; built environment; life cycle analysis; circularity; sustainability
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Innovative developments in the nanotechnology field have helped nanomaterials to attain unique chemical and physical properties that are completely different from those of the bulk, e.g., quantization of electronic states leading to sensitive size-dependent effects (magnetic, etc.), optical properties, and high surface-to-volume ratio, all of which are known to play a key role in modifying the thermal and chemical properties of materials. Thus, nanoparticles are considered most appropriate for various specialist applications, such as gas sensing. Additionally, nanoparticles have a high surface area and surface-to-volume ratio because of their small particle size, and this provides an additional active site for electron transport, while enhanced defects lead to enhanced surface activity. Therefore, taking advantage of these unique properties enables the fabrication of extremely sensitive and stable gas sensors displaying rapid response–recovery times, and low power consumption. These properties are most crucial for sensor performance characteristics and must be considered when designing nanoparticles suitable for gas sensing. In fact, numerous approaches have been used to produce and stabilize metal nano-enabled particles in organic and aqueous media. In most cases, top–down approaches do not enable the fabrication of the anticipated particle size and shape, whereas bottom-up approaches produce nanostructures from atoms, molecules, and even atom clusters utilizing both the physical and chemical deposition methods.

This Special Issue aims to gather papers that provide more insight into the right nanoparticle design and processing approaches to produce nanoparticles that display the unique properties suitable for gas sensing applications. More specifically, the aim is to attract papers describing detailed research studies pertaining to the manipulation and control of these nanoparticles via processing approaches followed by their characterization, modeling, as well as testing to understand their suitability for gas sensing applications.

Dr. Gugu Hlengiwe Mhlongo
Dr. Dimitra Papadaki
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • nanotechnology
  • nanoparticles
  • processing approaches
  • grain size control
  • surface area
  • defects
  • sensor characteristics

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Published Papers (5 papers)

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Research

14 pages, 5033 KiB  
Article
Evanescent-Field Excited Surface Plasmon-Enhanced U-Bent Fiber Probes Coated with Au and ZnO Nanoparticles for Humidity Detection
by Elnaz Afsharipour, Kirtiman Deo Malviya, Mohammadreza Montazeri, Ebrahim Mortazy, Ramin Soltanzadeh, Alireza Hassani, Federico Rosei and Mohamed Chaker
Processes 2023, 11(2), 642; https://doi.org/10.3390/pr11020642 - 20 Feb 2023
Cited by 8 | Viewed by 2016
Abstract
We report the design, fabrication, and testing of a humidity sensor based on an optical fiber-based evanescent wave probe. The fiber was bent into a U-shape and de-cladded at the location of the bending. The de-cladded section was coated either with Au or [...] Read more.
We report the design, fabrication, and testing of a humidity sensor based on an optical fiber-based evanescent wave probe. The fiber was bent into a U-shape and de-cladded at the location of the bending. The de-cladded section was coated either with Au or with ZnO nanoparticles. Humidity is detected based on the interaction in the surface plasmon resonance of the Au/ZnO nanoparticles excited by an evanescent wave of light passing through the optical fiber. The response of the U-bent fibers to humidity was investigated using a specifically designed low-voltage portable interrogation box. We found that the fibers coated with ZnO nanoparticles were able to detect a minimum 0.1% change in humidity with an average sensitivity of 143 µV/%RH and 95% linearity over the 10% to 80% humidity range. In comparison, samples coated with Au and Au + ZnO nanoparticles demonstrated a minimum change detection of 0.3% RH and 2% RH respectively. The response and recovery time of the sensor were measured to be 3 s and 4 s, respectively, for a 60% change in humidity from 20% to 80%. The entire measurement system was operated by consuming an electrical power of 1.62 W at an input voltage of 12 Vdc. Full article
(This article belongs to the Special Issue Design Processes via Manipulation of Nanoparticles and Their Suitability for Gas Sensors)
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12 pages, 3047 KiB  
Article
Adsorption of NH3 and NO2 Molecules on Sn-Doped and Undoped ZnO (101) Surfaces Using Density Functional Theory
by Ratshilumela S. Dima, David Magolego Tshwane, Katekani Shingange, Rosinah Modiba, Nnditshedzeni E. Maluta and Rapela R. Maphanga
Processes 2022, 10(10), 2027; https://doi.org/10.3390/pr10102027 - 7 Oct 2022
Cited by 2 | Viewed by 2185
Abstract
The adsorption and interaction mechanisms of gaseous molecules on ZnO surfaces have received considerable attention because of their technological applications in gas sensing. The adsorption behavior of NH3 and NO2 molecules on undoped and Sn-doped ZnO (101) surfaces was investigated using [...] Read more.
The adsorption and interaction mechanisms of gaseous molecules on ZnO surfaces have received considerable attention because of their technological applications in gas sensing. The adsorption behavior of NH3 and NO2 molecules on undoped and Sn-doped ZnO (101) surfaces was investigated using density functional theory. The current findings revealed that both molecules adsorb via chemisorption rather than physisorption, with all the adsorption energy values found to be negative. The calculated adsorption energy revealed that the adsorption of the NH3 molecule on the bare ZnO surface is more energetically favorable than the adsorption of the NO2 molecule. However, a stable adsorption configuration was discovered for the NO2 molecule on the surface of the Sn-doped ZnO surface. Furthermore, the adsorption on the undoped surface increased the work function, while the adsorption on the doped surface decreased. The charge density redistribution showed charge accumulation and depletion on both adsorbent and adsorbate. In addition, the density of states and band structures were studied to investigate the electronic behavior of NH3 and NO2 molecules adsorbed on undoped and Sn-doped ZnO (101) surfaces. Full article
(This article belongs to the Special Issue Design Processes via Manipulation of Nanoparticles and Their Suitability for Gas Sensors)
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14 pages, 8224 KiB  
Article
Enhanced Propanol Response Behavior of ZnFe2O4 NP-Based Active Sensing Layer Induced by Film Thickness Optimization
by Murendeni I. Nemufulwi, Hendrik C. Swart and Gugu H. Mhlongo
Processes 2021, 9(10), 1791; https://doi.org/10.3390/pr9101791 - 9 Oct 2021
Cited by 6 | Viewed by 2449
Abstract
Development of gas sensors displaying improved sensing characteristics including sensitivity, selectivity, and stability is now possible owing to tunable surface chemistry of the sensitive layers as well as favorable transport properties. Herein, zinc ferrite (ZnFe2O4) nanoparticles (NPs) were produced [...] Read more.
Development of gas sensors displaying improved sensing characteristics including sensitivity, selectivity, and stability is now possible owing to tunable surface chemistry of the sensitive layers as well as favorable transport properties. Herein, zinc ferrite (ZnFe2O4) nanoparticles (NPs) were produced using a microwave-assisted hydrothermal method. ZnFe2O4 NP sensing layer films with different thicknesses deposited on interdigitated alumina substrates were fabricated at volumes of 1.0, 1.5, 2.0, and 2.5 µL using a simple and inexpensive drop-casting technique. Successful deposition of ZnFe2O4 NP-based active sensing layer films onto alumina substrates was confirmed by X-ray diffraction and atomic force microscope analysis. Top view and cross-section observations from the scanning electron microscope revealed inter-agglomerate pores within the sensing layers. The ZnFe2O4 NP sensing layer produced at a volume of 2 μL exhibited a high response of 33 towards 40 ppm of propanol, as well as rapid response and recovery times of 11 and 59 s, respectively, at an operating temperature of 120 °C. Furthermore, all sensors demonstrated a good response towards propanol and the highest response against ethanol, methanol, carbon dioxide, carbon monoxide, and methane. The results indicate that the developed fabrication strategy is an inexpensive way to enhance sensing response without sacrificing other sensing characteristics. The produced ZnFe2O4 NP-based active sensing layers can be used for the detection of volatile organic compounds in alcoholic beverages for quality check in the food sector. Full article
(This article belongs to the Special Issue Design Processes via Manipulation of Nanoparticles and Their Suitability for Gas Sensors)
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13 pages, 5888 KiB  
Article
Hierarchical Nanoflowers of Colloidal WS2 and Their Potential Gas Sensing Properties for Room Temperature Detection of Ammonia
by Siziwe S. Gqoba, Rafael Rodrigues, Sharon Lerato Mphahlele, Zakhele Ndala, Mildred Airo, Paul Olawale Fadojutimi, Ivo A. Hümmelgen, Ella C. Linganiso, Makwena J. Moloto and Nosipho Moloto
Processes 2021, 9(9), 1491; https://doi.org/10.3390/pr9091491 - 25 Aug 2021
Cited by 5 | Viewed by 2407
Abstract
A one-step colloidal synthesis of hierarchical nanoflowers of WS2 is reported. The nanoflowers were used to fabricate a chemical sensor for the detection of ammonia vapors at room temperature. The gas sensing performance of the WS2 nanoflowers was measured using an [...] Read more.
A one-step colloidal synthesis of hierarchical nanoflowers of WS2 is reported. The nanoflowers were used to fabricate a chemical sensor for the detection of ammonia vapors at room temperature. The gas sensing performance of the WS2 nanoflowers was measured using an in-house custom-made gas chamber. SEM analysis revealed that the nanoflowers were made up of petals and that the nanoflowers self-assembled to form hierarchical structures. Meanwhile, TEM showed the exposed edges of the petals that make up the nanoflower. A band gap of 1.98 eV confirmed a transition from indirect-to-direct band gap as well as a reduction in the number of layers of the WS2 nanoflowers. The formation of WS2 was confirmed by XPS and XRD with traces of the oxide phase, WO3. XPS analysis also confirmed the successful capping of the nanoflowers. The WS2 nanoflowers exhibited a good response and selectivity for ammonia. Full article
(This article belongs to the Special Issue Design Processes via Manipulation of Nanoparticles and Their Suitability for Gas Sensors)
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13 pages, 5876 KiB  
Article
Effect of  Nb5+ and In3+  Ions on Moisture Sensitivity of Electrospun Titanium/Tungsten Oxide Nanostructures: Microstructural Characterization and Electrical Response
by Georgenes M. G. Silva, Victor N. S. Leão, Michel F. G. Pereira, Pedro M. Faia and Evando S. Araújo
Processes 2021, 9(8), 1336; https://doi.org/10.3390/pr9081336 - 30 Jul 2021
Cited by 2 | Viewed by 2262
Abstract
In this work, Nb5+ and In3+ ions were used as dopants in titanium/tungsten oxide nanostructures that are produced by the electrospinning and sintering process, for relative humidity (RH) detection. The microstructural properties were investigated [...] Read more.
In this work, Nb5+ and In3+ ions were used as dopants in titanium/tungsten oxide nanostructures that are produced by the electrospinning and sintering process, for relative humidity (RH) detection. The microstructural properties were investigated by SEM, EDS, XRD, Raman and FTIR techniques. The electrical response characterization of the samples was performed by electrical impedance spectroscopy in the range of 400 Hz to 40 MHz, at 20 °C. The sensors sensitivity to moisture was evaluated in terms of the impedance variations to RH (10–100%). The combined analysis of the microstructural characterization results confirmed the surface interaction between the oxides and the ions incorporation in Ti crystal lattice. All the studied sensors showed a conduction transition from p- to n-type at around 30–40% RH: besides, they also displayed better sensitivity to moisture than those obtained in a previous work using titanium/tungsten combination using a different fabricationn route. The impedance modulus variation up to 1.1 and 1.3 orders of magnitude for the 4 wt % niobium and indium doped samples, respectively. The results are directly associated with the microstructure and alternative preparation process. Full article
(This article belongs to the Special Issue Design Processes via Manipulation of Nanoparticles and Their Suitability for Gas Sensors)
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