Application of a cubic-like mesoporous silica film to a surface photovoltage gas sensing system

doi:10.1016/S1387-1811(02)00387-6

Microporous and Mesoporous Materials

Volume 54, Issue 3, 22 July 2002, Pages 269-276

https://doi.org/10.1016/S1387-1811(02)00387-6 Get rights and content

Abstract

A self-ordered cubic-like mesoporous silica film has been successfully fabricated in a metal–insulator–semiconductor (=Au/SiO₂ (cubic-like meso)/Si₃N₄/SiO₂/Si) device based on the surface photovoltage (SPV) system and applied to an NO gas sensor. The self-ordered cubic-like mesoporous silica film is synthesized by using as a template in spin coating a nonionic poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO₁₀₀–PPO₆₅–PEO₁₀₀) type triblock copolymer surfactant. The sensing characteristics of the self-ordered cubic-like mesoporous SPV system have been investigated by repeated exposure to 100 ppm NO gas and standard air, as well as observation of the alternating (photo) current, which resulted from the physical adsorption and chemical interactions between detected NO gas and the self-ordered cubic-like mesoporous film. In sensing NO gas, this cubic-like mesoporous SPV system exhibits a response nearly five times larger than that of a simple SPV sensor without mesoporous silica film. Even at room temperature, this mesoporous SPV system exhibits a recoverable response. These results can be explained by the characteristics of the cubic-like mesoporous silica film including large surface area and a bi-continuous mesopore structure. This kind of mesoporous film has a great potential for application to highly sensitive and responsive gas sensors.

Introduction

Nitrogen oxides (NO_x) generated by combustion are harmful to one's health, and their concentrations in the environment have been regulated. Therefore, a highly sensitive, highly responsive, and portable device for monitoring these gases are urgently required [1], [2], [3], [4], [5], [6], [7], [8].

The surface photovoltage (SPV) semiconductor characterization technique [1], [9] has a great potential for satisfying the requirements of such gas sensors. The basic principle of this characterization technique is based on the semiconductor surface voltage properties of the metal–insulator–semiconductor (MIS) structure [9]. By measuring semiconductor photocurrent, this SPV system sensitively detects the variation in surface voltage, which is induced by physical adsorption of the target gases and depends mainly on the interactions between the target gases and the surface of the sensitive layer [1]. Therefore, the enhancement of the sensor performance requires a refinement of the metal and insulator layer of the MIS. Especially, the capacitance of the insulator layer depends on the gas adsorption performance, and the improvement of gas adsorption performance leads directly to the enhancement of SPV gas sensor characteristics.

The large surface area created by mesoporous materials [10], [11], [12], [13], [14] enables an improvement in the gas adsorption properties of SPV devices. In particular, during the past decade, these mesoporous materials have continued to progress through innovative synthesis methods [10], [11], [12], [13] which incorporate the surfactant self-assembly template system into the sol–gel synthesis method [10], [11], [12], [13]. The innovative mesoporous materials produced by the method have uniform pore size, pore channel alignment in two or three dimensions, and large surface area [10], [11], [12], [13]. Furthermore, this sol–gel synthesis method can be applied to the production of films [15], [16], [17], [18], [19], [20].

Large surface area and bi-continuous mesopores make a mesoporous silica film, the best candidate for the gas adsorption insulator layer of the SPV gas sensor. This paper reports, for the first time, a possible application of a self-ordered cubic-like mesoporous silica film to an NO gas sensor, the film being synthesized by the spin coating method and by the use of nonionic poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO₁₀₀–PPO₆₅–PEO₁₀₀) type triblock copolymer surfactant as a structure-directing agent. The NO gas sensor is based on the SPV characterization system. The mesoporous silica film is assembled as an insulator gas adsorption layer of the MIS structure. The properties, efficacy, and potential performance of the SPV NO gas sensor incorporating the cubic-like mesoporous film are examined.

Section snippets

Synthesis of mesoporous silica film

SBA-16-type mesoporous silica film was adopted as the gas adsorption insulator layer, because its three-dimensional structure provides open pores on its top surface as shown in Fig. 1 [19], [20]. This kind of thick film was produced by the dip coating method [19], and has a cubic structure and a thickness larger than 1 μm. Furthermore, for attaining gas accessibility into mesopores and capacitance for SPV measurement, thin film rather than thick film is desired. Therefore, we modify the dip

Film structure

Fig. 4 shows The X-ray diffraction (Material Analysis and Characterization Science Co., Ltd.: XRD, M03XHF22) pattern and transmission electron micrograph (HITACHI, Ltd.: TEM, HF-2000) images of SBA-16 mesoporous silica. Fig. 4(b) shows the XRD pattern of SBA-16 mesoporous silica powder. Six well-resolved peaks are observed in this figure. These peaks have a d spacing ratio of 1:1/√2:1/2:1/√6:1/√10:1/√12:1/√14 and can be indexed as (1 1 0), (2 0 0), (2 1 1), (3 1 0), (2 2 2) and (3 2 1) reflections

Conclusions

A spin-coated film composed of cubic-like mesoporous silica SBA-16 has been successfully fabricated and incorporated into a SPV gas sensor system. The sensing properties for NO gas (100 ppm) have been investigated by the CB curve. The large bias shift in the CB curve and the well-reproducible responses observed in the measurement can be explained by changes in dielectric constant and charge in the cubic-like mesoporous silica layer. The changes in dielectric constant and charge are due to the

Acknowledgements

This work was funded in part by a grant from New Energy and Industrial Technology Development Organization (NEDO).

References (21)

W. Zhang et al.
Sensors Actuators B
(1998)
N. Miura et al.
Sensors Actuators B
(1993)
M.J. Tierney et al.
Sensors Actuators B
(1993)
M. Akiyama et al.
Sensors Actuators B
(1993)
G. Sberveglieri et al.
Sensors Actuators B
(1995)
C. Cantalini et al.
Sensors Actuators B
(1996)
L.E. Depero et al.
Sensors Actuators B
(1996)
L. Boarino et al.
Sensors Actuators B
(2000)
K.S.W. Sing
Coll. Surf.
(1989)
D.K. Schroder
Meas. Sci. Technol.
(2001)

There are more references available in the full text version of this article.

Cited by (73)

Silica mesoporous thin films as containers for benzotriazole for corrosion protection of 2024 aluminium alloys
2015, Applied Surface Science
Citation Excerpt :
Mesoporous thin films are very attractive for numerous applications involving the controlled immobilization or release of guest molecules such as Dye Sensitized Solar Cells (DSSC) [1–5], drug delivery [6–8], gas sensors [9–11] etc.
This work contributes to the development of a new environmentally friendly alternative pretreatment for 2024 aluminium alloys to replace hexavalent chromium based conversion layers in the aeronautical field. A silica mesoporous thin film, synthesized through the evaporation induced self-assembly process, was doped with benzotriazole to obtain active corrosion protection. Inhibitor loading contents were correlated with pore characteristics. The release kinetics was studied as function of pH. The application of the doped mesoporous film on 2024 aluminium alloy revealed a slowing down of corrosion processes, demonstrating its potential as an active inhibitor storage layer.
Rayleigh surface acoustic wave sensor for ppb-level nitric oxide gas sensing
2014, Sensors and Actuators, A: Physical
A copper ion-doped polyaniline/tin oxide nanocomposited film, Cu²⁺/PANI/SnO₂, was investigated on a Rayleigh surface acoustic wave device for nitric oxide (NO) gas sensing at room temperature. The surface morphology, chemical structures and the electric properties were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Hall Effect measurement, respectively. Copper ion-doped sensing film, Cu²⁺/PANI/SnO₂, exhibited high NO gas sensitivity, repeatability and long-term stability. Moreover, it showed an estimated detection limit of 5 ppb. The sensor exhibited distinctive selectivity towards NO gas with no significant response to NO₂, CO₂ and O₂ gases.
Acid functionalized mesoporous PAN monolith as reusable heterogeneous organocatalyst
2014, Microporous and Mesoporous Materials
A polyacrylonitrile (PAN) monolith has been functionalized by hydrolysis of the surface nitrile into carboxylic acid groups. This mesoporous acid functionalized polyacrylonitrile monolith (AFPM) has been characterized by Fourier transform infrared spectroscopy (FT IR), chemical analysis, solid state MAS NMR spectroscopy, elemental mapping, field-emission scanning electron microscopy and N₂ adsorption–desorption study. N₂ sorption analysis revealed high surface areas (130–138 m² g⁻¹) and narrow pore size distributions (1.6–5.3 nm) along with macropore for different samples. FT IR, elemental mapping and MAS NMR results revealed the presence of both nitrile and acid group in the same monolith which supports the hydrolysis of surface nitrile groups during the hydrolysis. The acid functionalized monolith can serve as a reusable heterogeneous organocatalyst as demonstrated in its successful application to the synthesis of xanthene in room temperature.
Synthesis of mesoporous silica (SBA-16) nanoparticles using silica extracted from stem cane ash and its application in electrocatalytic oxidation of methanol
2013, International Journal of Hydrogen Energy
Citation Excerpt :
Mesoporous material is a kind of porous materials with regular and tunable pore from 2 to 50 nm [14]. Since its discovery, mesoporous material has been used widely in different research area such as catalysis [15,16], sensing [17,18] and energy storage [19]. These materials have attracted the attention of material scientists due to their high surface area (∼1000 m2/g) and narrow pore size distribution with long range ordering.
In this work, a new catalyst based on modified mesoporous silica SBA-16 is proposed and used for electrochemical oxidation of methanol. Mesoporous silica SBA-16 nanoparticles are synthesized hydrothermally under the acidic medium using SiO₂/F127/BuOH/HCl/H₂O gel. Pure SiO₂ powder is prepared from inexpensive and environmentally friendly silica source of stem cane ash (SCA). The synthesized SBA-16 is characterized using X-ray diffraction, scanning electronic microscopy, transmission electron microscopy, Brumauer–Emmett–Teller (BET) and FT-IR techniques. The synthesized SBA-16 is modified with Ni(II) by dispersion in a 0.1 M nickel chloride solution. A modified carbon paste electrode (CPE) is prepared by mixing of NiSBA-16 to carbon paste (NiSBA-16CPE). The electrocatalytic oxidation of methanol was studied on modified electrode by cyclic voltammetry and chronoamperometry. From cyclic voltammetry, it is observed that the oxidation current is extremely increased by using NiSBA-16CPE compared to the nonmodified CPE. The incorporation of Ni²⁺ into SBA-16 channels provides the active sites for catalysis of methanol oxidation. Also, the rate constant for the catalytic reaction (k) of methanol is obtained.
Development of cholesterol biosensor with high sensitivity using dual-enzyme immobilization into the mesoporous silica materials
2011, Applied Surface Science
Mesoporous silica (MPS) materials with different pore diameters were synthesized by a sol–gel method where organic templates such as cationic surfactant (cetyltrimethylammonium bromide) and triblock co-polymer of (poly(ethylene glycol)–poly(propylene glycol)–poly(ethylene glycol) (Pluronic P123, EO₂₀PO₇₀EO₂₀)), were used. MPS surface was organo-functionalized using a silane coupling reagent (ethyl-, phenyl-, or 3-mercaptpropyltriethoxysilane). Dual-enzyme, cholesterol esterase (10.0 nm × 5.4 nm × 11.0 nm) and cholesterol oxidase (6.8 nm × 8.5 nm × 8.8 nm), was immobilized on MPS materials by physical adsorption. Amount of dual-enzyme immobilized on all MPS materials, having a different pore size (2.7, 6.4, 12.4, 14.7, and 22.6 nm), and organo-functionalized MPS was similar (CE: 1.5 mg/mg silica and CO: 0.01 mg/mg silica). High activity of dual-enzyme was obtained by adjacently immobilizing on MPS materials. Its activity on MPS-2 (pore diameter: 6.4 nm) or MPS-5 (pore diameter: 22.6 nm) showed approximately 60% of native activity. Moreover, dual-enzyme immobilized on MPS with highly hydrophobic organo-functional groups (phenyl- or mercaptopropyl-group) exhibited higher activity than that on no-substituted MPS. Relative activity of dual-enzyme immobilized on organo-functionalized MPS-2 increased from 58% to 93%, under the optimum conditions.
Facile synthesis of ordered mesoporous γ-alumina monoliths via polymerization-based gel-casting
2011, Microporous and Mesoporous Materials
Porous γ-alumina monoliths with hexagonal mesoporous structures were prepared starting from well-ordered mesoporous alumina powders which were firstly synthesized by the self-assembly of aluminum isopropoxide and a triblock copolymer in the presence of nitric acid. The alumina powders were fused together to form alumina monoliths by the integration of polymer gel-casting together with the calcination at different temperatures in air. The powdery and monolithic products were investigated using transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), small-angle X-ray scattering (SAXS), powder wide-angle X-ray diffraction (WA-XRD) and the nitrogen adsorption–desorption isotherm measurements. As results, the as-prepared powdery alumina possesses ordered p6mm hexagonal mesoporosity, high BET surface area and narrow pore-size distribution. After high-temperature calcination, the obtained alumina monoliths still exhibit ordered mesoporosity with hexagonal symmetry, which is very similar to that of the original powdery sample except for the reduced pore volume and specific surface area. The method can be extended to prepare other porous metal oxide monoliths when appropriate powdery metal oxides with a connected pore system are applied.

View all citing articles on Scopus

View full text

Application of a cubic-like mesoporous silica film to a surface photovoltage gas sensing system

Abstract

Introduction

Section snippets

Synthesis of mesoporous silica film

Film structure

Conclusions

Acknowledgements

Sensors Actuators B

Sensors Actuators B

Sensors Actuators B

Sensors Actuators B

Sensors Actuators B

Sensors Actuators B

Sensors Actuators B

Sensors Actuators B

Coll. Surf.

Meas. Sci. Technol.