Special Issue "Nanomaterials for Gas Sensors Applications"

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Nanoelectronics, Nanosensors and Devices".

Deadline for manuscript submissions: closed (10 July 2021).

Special Issue Editor

Prof. Dr. Giuseppe Cappelletti
E-Mail Website
Guest Editor
Dipartimento di Chimica, Universita' degli Studi Di Milano, via Golgi 19, 20133 Milano, Italy
Interests: surface modification and functionalization; wettability; nanomaterials; thin layer; cultural heritage protection; colloids and interfaces; photocatalysis and VOC sensing; advanced oxidation processes for environmental remediation; formulation technol-ogy
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Special Issue Information

Dear Colleagues,


Solid state gas sensors have been deeply investigated in recent decades, especially for environmental monitoring, process safety control, and, more recently, for the medical diagnosis of human diseases from breath analysis. The miniaturization and integration of such sensors in microsystems has led to low-cost, portable devices that are capable of selectively recognizing specific analytes. In this context, semiconductor nanomaterials have attracted great attention thanks to their unique physicochemical properties. However, there are still some drawbacks to their use, concerning the sensitive and selective sensing of volatile organic compounds (VOCs), particularly at room temperature. Hence, innovative metal oxide-based composites have recently been proposed, resulting in very promising sensing materials.


This Special Issue of Nanomaterials will attempt to cover the recent developments in gas sensors based on metal oxide semiconductor nanomaterials, showing highly sensitive and selective responses mainly towards volatile organic compounds.

Prof. Dr. Giuseppe Cappelletti
Guest Editor

Manuscript Submission Information

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Keywords

  • nanomaterials
  • gas sensor
  • volatile organic compounds
  • breath analysis
  • oxides semiconductors
  • point-of-care devices
  • sensitivity
  • selectivity

Published Papers (5 papers)

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Research

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Article
Low Temperature HCHO Detection by SnO2/TiO2@Au and SnO2/TiO2@Pt: Understanding by In-Situ DRIFT Spectroscopy
Nanomaterials 2021, 11(8), 2049; https://doi.org/10.3390/nano11082049 - 11 Aug 2021
Viewed by 696
Abstract
In this work we analyze the effectiveness of decoration of nanocrystalline SnO2/TiO2 composites with gold nanoparticles (Au NPs) and platinum nanoparticles (Pt NPs) in enhancing gas sensor properties in low-temperature HCHO detection. Nanocrystalline SnO2/TiO2 composites were synthesized [...] Read more.
In this work we analyze the effectiveness of decoration of nanocrystalline SnO2/TiO2 composites with gold nanoparticles (Au NPs) and platinum nanoparticles (Pt NPs) in enhancing gas sensor properties in low-temperature HCHO detection. Nanocrystalline SnO2/TiO2 composites were synthesized by a chemical precipitation method with following modification with Pt and Au NPs by the impregnation method. The nanocomposites were characterized by TEM, XRD, Raman and FTIR spectroscopy, DRIFTS, XPS, TPR-H2 methods. In HCHO detection, the modification of SnO2 with TiO2 leads to a shift in the optimal temperature from 150 to 100 °C. Further modification of SnO2/TiO2 nanocomposites with Au NPs increases the sensor signal at T = 100 °C, while modification with Pt NPs gives rise to the appearance of sensor responses at T = 25 °C and 50 °C. At 200 °C nanocomposites exhibited high selectivity toward formaldehyde within the sub-ppm concentration range among different VOCs. The influence of Pt and Au NPs on surface reactivity of SnO2/TiO2 composite and enhancement of the sensor response toward HCHO was studied by DRIFT spectroscopy and explained by the chemical and electronic sensitization mechanisms. Full article
(This article belongs to the Special Issue Nanomaterials for Gas Sensors Applications)
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Article
Morphology of Ga2O3 Nanowires and Their Sensitivity to Volatile Organic Compounds
Nanomaterials 2021, 11(2), 456; https://doi.org/10.3390/nano11020456 - 11 Feb 2021
Cited by 3 | Viewed by 821
Abstract
Gas sensitive structures made of nanowires exhibit extremally large specific surface area, and a great number of chemically active centres that can react with the ambient atmosphere. This makes the use of nanomaterials promising for super sensitive gas sensor applications. Monoclinic β-Ga2 [...] Read more.
Gas sensitive structures made of nanowires exhibit extremally large specific surface area, and a great number of chemically active centres that can react with the ambient atmosphere. This makes the use of nanomaterials promising for super sensitive gas sensor applications. Monoclinic β-Ga2O3 nanowires (NWs) were synthesized from metallic gallium at atmospheric pressure in the presence of nitrogen and water vapor. The nanowires were grown directly on interdigitated gold electrodes screen printed on Al2O3 substrates, which constituted the gas sensor structure. The observations made with transmission electron microscope (TEM) have shown that the nanowires are monocrystalline and their diameters vary from 80 to 300 nm with the average value of approximately 170 nm. Au droplets were found to be anchored at the tips of the nanowires which may indicate that the nanowires followed the Vapor–Liquid–Solid (VLS) mechanism of growth. The conductivity of β-Ga2O3 NWs increases in the presence of volatile organic compounds (VOC) even in the temperature below 600 °C. The gas sensor based on the synthesized β-Ga2O3 NWs shows peak sensitivity to 100 ppm of ethanol of 75.1 at 760 °C, while peak sensitivity to 100 ppm of acetone is 27.5 at 690 °C. Full article
(This article belongs to the Special Issue Nanomaterials for Gas Sensors Applications)
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Article
Enhanced Stability and Amplified Signal Output of Single-Wall Carbon Nanotube-Based NH3-Sensitive Electrode after Dual Plasma Treatment
Nanomaterials 2020, 10(6), 1026; https://doi.org/10.3390/nano10061026 - 27 May 2020
Cited by 1 | Viewed by 765
Abstract
Pristine nanomaterials are normally prepared using finely controlled fabrication processes. Because no imperfect nanostructure remains, they cannot be used directly as electrode substrates of functional devices. This is because perfectly organized nanostructures or nanomaterials commonly require posttreatment to generate intentionally, the kinds of [...] Read more.
Pristine nanomaterials are normally prepared using finely controlled fabrication processes. Because no imperfect nanostructure remains, they cannot be used directly as electrode substrates of functional devices. This is because perfectly organized nanostructures or nanomaterials commonly require posttreatment to generate intentionally, the kinds of desirable defects inside or on their surfaces that enable effective functionalization. Plasma treatment is an easier, simpler and more widely used way (relative to other methods) to modify a variety of nanomaterials, although plasma-functionalized nano surfaces commonly have a short lifetime. We present herein a dual plasma treatment (DPT) that significantly enhances the degree and lifetime of plasma-induced surface functional groups on single-walled carbon nanotubes (SWCNTs). The DPT process consists of two individually optimized oxygen–plasma treatments. The DPT-modified SWCNT functioned as a sensing material for ammonia gas for more than a month. It also provided more than three times the degree of functionality for amplified signal output than with a single-plasma-treated SWCNT electrode. Full article
(This article belongs to the Special Issue Nanomaterials for Gas Sensors Applications)
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Article
Exploring SnxTi1−xO2 Solid Solutions Grown onto Graphene Oxide (GO) as Selective Toluene Gas Sensors
Nanomaterials 2020, 10(4), 761; https://doi.org/10.3390/nano10040761 - 15 Apr 2020
Cited by 7 | Viewed by 950
Abstract
The major drawback of oxide-based sensors is the lack of selectivity. In this context, SnxTi1−xO2/graphene oxide (GO)-based materials were synthesized via a simple hydrothermal route, varying the titanium content in the tin dioxide matrix. Then, toluene and [...] Read more.
The major drawback of oxide-based sensors is the lack of selectivity. In this context, SnxTi1−xO2/graphene oxide (GO)-based materials were synthesized via a simple hydrothermal route, varying the titanium content in the tin dioxide matrix. Then, toluene and acetone gas sensing performances of the as-prepared sensors were systematically investigated. Specifically, by using 32:1 SnO2/GO and 32:1 TiO2/GO, a greater selectivity towards acetone analyte, also at room temperature, was obtained even at ppb level. However, solid solutions possessing a higher content of tin relative to titanium (as 32:1 Sn0.55Ti0.45O2/GO) exhibited higher selectivity towards bigger and non-polar molecules (such as toluene) at 350 °C, rather than acetone. A deep experimental investigation of structural (XRPD and Raman), morphological (SEM, TEM, BET surface area and pores volume) and surface (XPS analyses) properties allowed us to give a feasible explanation of the different selectivity. Moreover, by exploiting the UV light, the lowest operating temperature to obtain a significant and reliable signal was 250 °C, keeping the greater selectivity to the toluene analyte. Hence, the feasibility of tuning the chemical selectivity by engineering the relative amount of SnO2 and TiO2 is a promising feature that may guide the future development of miniaturized chemoresistors. Full article
(This article belongs to the Special Issue Nanomaterials for Gas Sensors Applications)
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Review

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Review
VOCs Sensing by Metal Oxides, Conductive Polymers, and Carbon-Based Materials
Nanomaterials 2021, 11(2), 552; https://doi.org/10.3390/nano11020552 - 22 Feb 2021
Cited by 6 | Viewed by 1389
Abstract
This review summarizes the recent research efforts and developments in nanomaterials for sensing volatile organic compounds (VOCs). The discussion focuses on key materials such as metal oxides (e.g., ZnO, SnO2, TiO2 WO3), conductive polymers (e.g., polypyrrole, polythiophene, poly(3,4-ethylenedioxythiophene)), [...] Read more.
This review summarizes the recent research efforts and developments in nanomaterials for sensing volatile organic compounds (VOCs). The discussion focuses on key materials such as metal oxides (e.g., ZnO, SnO2, TiO2 WO3), conductive polymers (e.g., polypyrrole, polythiophene, poly(3,4-ethylenedioxythiophene)), and carbon-based materials (e.g., graphene, graphene oxide, carbon nanotubes), and their mutual combination due to their representativeness in VOCs sensing. Moreover, it delves into the main characteristics and tuning of these materials to achieve enhanced functionality (sensitivity, selectivity, speed of response, and stability). The usual synthesis methods and their advantages towards their integration with microsystems for practical applications are also remarked on. The literature survey shows the most successful systems include structured morphologies, particularly hierarchical structures at the nanometric scale, with intentionally introduced tunable “decorative impurities” or well-defined interfaces forming bilayer structures. These groups of modified or functionalized structures, in which metal oxides are still the main protagonists either as host or guest elements, have proved improvements in VOCs sensing. The work also identifies the need to explore new hybrid material combinations, as well as the convenience of incorporating other transducing principles further than resistive that allow the exploitation of mixed output concepts (e.g., electric, optic, mechanic). Full article
(This article belongs to the Special Issue Nanomaterials for Gas Sensors Applications)
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