Michele Penza

Giorgio Sberveglieri

Wojtek Wlodarski

Yongxiang Li

Nanomaterials for Chemical Sensing Technologies

Jie-Ying Liao

James Q. Yin

Jia-Chang Yue

A Novel Biosensor to Detect MicroRNAs Rapidly

Methane is an important gas for domestic and industrial applications and its source is mainly coalmines. Since methane is extremely inflammable in the coalmine atmosphere, it is essential to develop a reliable and relatively inexpensive chemical gas sensor to detect this inflammable gas below its explosion amount in air. The metal oxides have been proved to be potential materials for the development of commercial gas sensors. The functional properties of the metal oxide-based gas sensors can be improved not only by tailoring the crystal size of metal oxides but also by incorporating the noble metal catalyst on nanocrystalline metal oxide matrix. It was observed that the surface modification of nanocrystalline metal oxide thin films by noble metal sensitizers and the use of a noble metal catalytic contact as electrode reduce the operating temperatures appreciably and improve the sensing properties. This review article concentrates on the nanocrystalline metal oxide methane sensors and the role of noble metals on the sensing properties.

S. Basu

P. K. Basu

Nanocrystalline Metal Oxides for Methane Sensors: Role of Noble Metals

This work reviews physicochemical models on the operation and the response of potentiometric oxygen gas sensors based on ion-conducting electrolytes. The aim for describing the electric response and some properties like response time, ionic conductivity, catalytic activity, or gas selectivity of these devices has led to the development of some models in the last decades. These models have provided information on relations between the response of the sensors, their design and fabrications process, and some morphological properties, like grain size of the electrolyte, diffusion on protective layers, or density of three-phase boundary points in the measuring electrodes. Current trends on improving catalysis, gas selectivity, and activation energy for ion conducting by using nanomaterials are described as well.

Carlos López-Gándara

Francisco M. Ramos

Albert Cirera

YSZ-Based Oxygen Sensors and the Use of Nanomaterials: A Review from Classical Models to Current Trends


This work has explored the development of impedimetric immunosensors based on magnetic iron nanoparticles (IrNP) functionalized with streptavidin to which a biotinylated FAB part of the antibody has been bound using a biotin-streptavidin interaction. SPR analysis shows a deviation on the measured (angle) during antigen-antibody recognition whereas label free detection using by EIS allows us to monitor variation of polarization resistance. Before detection, layers were analyzed by FTIR and AFM. 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Imen Hafaid

Asma Gallouz

Walid Mohamed Hassen

Adnane Abdelghani

Zina Sassi

Francois Bessueille

Nicole Jaffrezic-Renault

Sensitivity Improvement of an Impedimetric Immunosensor Using Functionalized Iron Oxide Nanoparticles

Nanocrystalline-nanoporous ZnO thin films were prepared by an electrochemical anodization method, and the films were tested as methane sensors. It was found that Pd-Ag catalytic contacts showed better sensing performance compared to other noble metal contacts like Pt and Rh. The methane sensing temperature could be reduced to as low as <svg style="vertical-align:-0.17555pt;width:38.450001px;" id="M1" height="11.0375" version="1.1" viewBox="0 0 38.450001 11.0375" width="38.450001"  xmlns="http://www.w3.org/2000/svg">
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				<tspan style="font-size: 12.50px; " x="0" y="0">C</tspan>
			</text>

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	</g>
</svg> by sensitizing nanocrystalline ZnO thin films with Pd, deposited by chemical method. The sensing mechanism has been discussed briefly.

N. Saha

S. K. Jana

H. Saha

A. Lloyd Spetz

Schottky Junction Methane Sensors Using Electrochemically Grown Nanocrystalline-Nanoporous ZnO Thin Films

Surface acoustic wave (SAW) devices are considered to be very promising in providing a high-performance sensing platform with wireless and remote operational capabilities. In this review, the basic principles of SAW devices and Love-mode SAW-based biosensors are discussed first to illustrate the need for surface enhancement for the active area of a SAW sensor. Then some of the recent efforts made to incorporate nanostructures into SAW sensors are summarized. After that, a computational approach to elucidate the underlying mechanism for the operations of a Love-mode SAW biosensor with nanostructured active surface is discussed. Finally, a modeling example for a Love-mode SAW sensor with skyscraper nanopillars added to in its active surface along with some selected results is presented.

Guigen Zhang

Nanostructure-Enhanced Surface Acoustic Waves Biosensor and Its Computational Modeling

A deep analysis of conductance in nanostructured <svg style="vertical-align:-3.13504pt;width:34px;" id="M2" height="14.6" version="1.1" viewBox="0 0 34 14.6" width="34"  xmlns="http://www.w3.org/2000/svg">
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</svg> thick films has been performed. A model for field-assisted thermionic barrier crossing is being proposed to explain the film conductivity. The model has been applied to explain the behavior of resistance in vacuum of two sets of nanostructured thick-films with grains having two well-distinct characteristic radii (<svg style="vertical-align:-0.17555pt;width:46.712502px;" id="M3" height="11.1" version="1.1" viewBox="0 0 46.712502 11.1" width="46.712502"  xmlns="http://www.w3.org/2000/svg">
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				<tspan style="font-size: 12.50px; " x="0" y="0">𝑅</tspan>
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</svg>&#x2009;nm). In the first case the grain radius is shorter than the depletion region width, a limit at which overlapping of barriers takes place, and in the second case it is longer. The behavior of resistance in the presence of dry air has been explained through the mechanism of barrier modulation through gas chemisorption.

C. Malag&#249;

M. C. Carotta

G. Martinelli

M. A. Ponce

M. S. Castro

C. M. Aldao

Field-Assisted and Thermionic Contributions to Conductance in <svg style="vertical-align:-3.27605pt" height="15.5125" version="1.1" viewBox="0 0 36.650002 15.5125" width="36.650002" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,11.363)"><path id="x53" d="M409 504l-29 -5q-16 60 -44.5 96t-86.5 36q-54 0 -82.5 -32t-28.5 -77q0 -51 30.5 -82.5t96.5 -65.5l35.5 -18t33 -19.5t33.5 -23.5l27 -25.5t24.5 -32t13.5 -36.5t6 -45q0 -80 -62 -134.5t-160 -54.5q-47 0 -98 15q-22 7 -50 21q-8 23 -27 155l30 7q7 -27 18 -52&#xA;t30 -51.5t49 -42.5t67 -16q56 0 88 32.5t32 87.5q0 51 -31.5 82t-98.5 67q-80 44 -110 73q-55 53 -55 124q0 75 56 126.5t150 51.5q53 0 126 -23z" /></g><g transform="matrix(.017,-0,0,-.017,8.018,11.363)"><path id="x6E" d="M524 0h-209v26q44 5 55 18t11 65v167q0 114 -91 114q-50 0 -109 -51v-235q0 -50 10 -61.5t55 -16.5v-26h-217v26q51 5 62 17t11 61v206q0 47 -9.5 58.5t-50.5 19.5v23q82 15 139 40v-79l67 47q47 30 83 30q60 0 94.5 -40t34.5 -112v-193q0 -50 10 -61.5t54 -16.5v-26z&#xA;" /></g><g transform="matrix(.017,-0,0,-.017,17.316,11.363)"><path id="x4F" d="M381 665q131 0 226.5 -93t95.5 -239q0 -158 -96 -253t-238 -95q-137 0 -231 95t-94 238q0 142 92.5 244.5t244.5 102.5zM359 629q-89 0 -151 -74.5t-62 -208.5q0 -141 69 -233t175 -92q90 0 150.5 74t60.5 211q0 152 -69 237.5t-173 85.5z" /></g><g transform="matrix(.012,-0,0,-.012,30.012,15.45)"><path id="x1D7D0" d="M453 211h25l-46 -211h-415v23q97 102 151 166q42 49 81 110q51 78 51 148q0 56 -31.5 91.5t-87.5 35.5q-77 0 -122 -90h-28q67 204 223 204q82 0 132 -49.5t50 -133.5q0 -110 -114 -218l-162 -154h140q82 0 107 13q27 13 46 65z" /></g></svg> Thick-Films

In the present study, we report on a simple optical method based on thin film interferometry for the swelling evaluation in polymer nanocomposite layers used for gas sensing applications. We show that white light interferometry can be profitably applied to characterize scattering materials such as polymer/carbon black nanocomposites. A properly adjusted experimental setup was implemented to monitor the swelling behavior of the sensitive films in real device operating conditions.
In particular, the behavior of poly(2-hydroxyethyl methacrylate) (PHEMA) and of carbon black/PHEMA nanocomposite layers, used for volatile organic compounds (VOCs) detection, was investigated and measured under ethanol vapors exposure (max 1%). The method is very sensitive and the swelling in the range of only few nanometers can be measured. Interestingly, we have found that the nanocomposite undergoes a more pronounced swelling process with respect to pristine polymer. Ethanol diffusion coefficients in the nanocomposite were evaluated.

Anna De Girolamo Del Mauro

Angelica Immacolata Grimaldi

Vera La Ferrara

Ettore Massera

Maria Lucia Miglietta

Tiziana Polichetti

Girolamo Di Francia

A Simple Optical Model for the Swelling Evaluation in Polymer Nanocomposites

The fabrication process and the growth mechanism of titanium/titania nanotubes prepared by anodization process is reviewed, and their applications in the fields of dye sensitized solar cells, photocatalysts, electrochromic devices, gas sensors, and biomaterials are presented. The anodization of Ti thin films on different substrates and the growth process of anodic titanium oxide are described using the current-time curves. Special attention is paid on the influences of the initial film smoothness on the resulted nanoporous morphologies. The &#x201c;threshold barrier layer thickness model&#x201d; is used to discuss the growth mechanism. As a case study for gas sensing, anodized highly ordered  <svg     style="vertical-align:-3.27605pt;width:32.512501px;" id="M2" height="15.675" version="1.1" viewBox="0 0 32.512501 15.675" width="32.512501"  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg">
	
		
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			<g transform="matrix(.012,-0,0,-.012,26.125,15.613)"><path id="x32" d="M412 140l28 -9q0 -2 -35 -131h-373v23q112 112 161 170q59 70 92 127t33 115q0 63 -31 98t-86 35q-75 0 -137 -93l-22 20l57 81q55 59 135 59q69 0 118.5 -46.5t49.5 -122.5q0 -62 -29.5 -114t-102.5 -130l-141 -149h186q42 0 58.5 10.5t38.5 56.5z" /></g>

		
	
</svg> nanotube arrays and nanoporous thin films that show porous surface with an average diameter of 25&#x2009;nm and interpore distance of 40&#x2009;nm were prepared. Gas sensors based on such nanotube arrays and nanoporous thin films were fabricated, and their sensing properties were investigated. Excellent <svg     style="vertical-align:-3.27605pt;width:19.475px;" id="M3" height="15.25" version="1.1" viewBox="0 0 19.475 15.25" width="19.475"  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg">
	
		
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			<g transform="matrix(.012,-0,0,-.012,13.087,15.187)"><use xlink:href="#x32"/></g>

		
	
</svg> gas sensing properties were obtained for sensors prepared from these highly ordered <svg     style="vertical-align:-3.27605pt;width:32.512501px;" id="M4" height="15.675" version="1.1" viewBox="0 0 32.512501 15.675" width="32.512501"  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg">
	
		
			<g transform="matrix(.017,-0,0,-.017,.062,11.537)"><use xlink:href="#x54"/></g><g transform="matrix(.017,-0,0,-.017,8.868,11.537)"><use xlink:href="#x69"/></g><g transform="matrix(.017,-0,0,-.017,13.424,11.537)"><use xlink:href="#x4F"/></g>

			<g transform="matrix(.012,-0,0,-.012,26.125,15.613)"><use xlink:href="#x32"/></g>

		
	
</svg> nanotube arrays, which present stable response even at a low operating temperature of <svg     style="vertical-align:-0.20474pt;width:32.787498px;" id="M5" height="13.1875" version="1.1" viewBox="0 0 32.787498 13.1875" width="32.787498"  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg">
	
		
			<g transform="matrix(.017,-0,0,-.017,.062,12.875)"><path id="x39" d="M244 635q90 0 143 -72t53 -177q0 -133 -65 -229.5t-171 -139.5q-79 -32 -140 -32l-5 30q109 18 185 91t101 186l-68 -36q-29 -16 -60 -16q-79 0 -129 51.5t-50 130.5q0 80 57 146.5t149 66.5zM228 602q-52 0 -78 -45.5t-26 -98.5q0 -69 36.5 -115.5t97.5 -46.5&#xA;q53 0 90 28q4 31 4 66q0 51 -9.5 95.5t-39 80.5t-75.5 36z" /></g><g transform="matrix(.017,-0,0,-.017,8.222,12.875)"><path id="x30" d="M241 635q53 0 94 -28.5t63.5 -76t33.5 -102.5t11 -116q0 -58 -11 -112.5t-34 -103.5t-63.5 -78.5t-94.5 -29.5t-95 28t-64.5 75t-34.5 102.5t-11 118.5q0 58 11.5 112.5t34.5 103t64.5 78t95.5 29.5zM238 602q-32 0 -55.5 -25t-35.5 -68t-17.5 -91t-5.5 -105&#xA;q0 -76 10 -138.5t37 -107.5t69 -45q32 0 55.5 25t35.5 68.5t17.5 91.5t5.5 105t-5.5 105.5t-18 92t-36 68t-56.5 24.5z" /></g>

			<g transform="matrix(.012,-0,0,-.012,16.375,4.712)"><path id="x2218" d="M326 255q0 -56 -41 -96t-99 -40t-99 40t-41 96t41 96t99 40t99 -40t41 -96zM274 255q0 38 -25.5 65t-62.5 27t-62.5 -27t-25.5 -65t25.5 -65t62.5 -27t62.5 27t25.5 65z" /></g>

			<g transform="matrix(.017,-0,0,-.017,21.412,12.875)"><path id="x43" d="M614 175l29 -10q-33 -109 -57 -154q-121 -26 -184 -26q-90 0 -160.5 29t-112.5 77t-63.5 105.5t-21.5 119.5q0 157 108 253t277 96q36 0 71.5 -5t69 -13.5t36.5 -8.5q15 -102 20 -150l-29 -8q-20 79 -66.5 114t-128.5 35q-119 0 -187.5 -86t-68.5 -207&#xA;q0 -140 73.5 -227.5t188.5 -87.5q73 0 119.5 37.5t86.5 116.5z" /></g>

		
	
</svg>. Based on our experimental results, &#x201c;H-induced <svg     style="vertical-align:-0.20473pt;width:26.137501px;" id="M6" height="16.1" version="1.1" viewBox="0 0 26.137501 16.1" width="26.137501"  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg">
	
		
			<g transform="matrix(.017,-0,0,-.017,.062,15.775)"><use xlink:href="#x4F"/></g>

			<g transform="matrix(.012,-0,0,-.012,12.763,7.613)"><use xlink:href="#x32"/></g><g transform="matrix(.012,-0,0,-.012,18.474,7.613)"><path id="x2212" d="M535 230h-483v50h483v-50z" /></g>

		
	
</svg> desorption&#x201d; mechanism was used for explaining the hydrogen gas sensing mechanism. 

Xiaofeng Yu

Qunbao Yang

Fabrication of <svg style="vertical-align:-3.27605pt" height="15.675" version="1.1" viewBox="0 0 32.75 15.675" width="32.75" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg">
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q2 -89 11 -177z"/>
		</g>
		<g transform="matrix(.017,-0,0,-.017,8.868,11.537)">
			<path id="x69" d="M135 536q-20 0 -35 15.5t-15 35.5q0 22 15 37t36 15t35.5 -15t14.5 -37q0 -21 -15 -36t-36 -15zM252 0h-220v26q48 5 59 17t11 63v206q0 47 -9 58t-54 18v24q78 12 142 39v-345q0 -51 11.5 -63t59.5 -17v-26z"/>
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	</svg> Nanotube Thin Films and Their Gas Sensing Properties

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<p>Chief Editor, Professor Harith Ahmad, is currently the director of the Photonics Research Center, University of Malaya, Malaysia. His current research is in the exploration of various 2D and 3D nanomaterials for optoelectronics applications.</p>


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