Current Analytical Chemistry

ISSN: 1573-4110

Current Analytical Chemistry
Volume 4, Number 4, October 2008

Contents

Fiber Optic Chemical and Biological Sensors: Perspectives and Challenges Approaching the Nano-Era
Guest Editor: Andrea Cusano, Antonello Cutolo and Michele Giordano



Editorial: Pp. 271-272


New Trends in Fiber-Optic Chemical and Biological Sensors Pp. 273-295
Guillermo Orellana and David Haigh
[Abstract]


Integrated Development of Chemoptical Fiber Nanosensors Pp. 296-315
Andrea Cusano, Michele Giordano, Antonello Cutolo, Marco Pisco and Marco Consales
[Abstract]


Molecularly Imprinted Polymers as Selective Recognition Elements in Optical Sensing Pp. 316-340
María C. Moreno-Bondi, Fernando Navarro-Villoslada, Elena Benito-Peña and Javier L. Urraca
[Abstract]


Fiber-Optic Chemical Nanosensors by Electrostatic Molecular Self-Assembly Pp. 241-355
Ignacio Del Villar, Ignacio R. Matias and Francisco J. Arregui
[Abstract]


Real-Time Monitoring of Siloxane Monolayer Film Formation on Silica Using a Fiber Bragg Grating Pp. 356-361
Christopher J. Stanford, Mario Dagenais, Ju-Hee Park and Philip DeShong
[Abstract]


High Coupling Efficiency in 2D Guided-Wave Photonic Band Gap Extended Microcavities for Sensing Applications Pp. 362-370
Caterina Ciminelli, Richard M. De La Rue and Mario N. Armenise
[Abstract]


Scattered Colorimetry and Multivariate Data Processing as an Objective Tool for Liquid Classification and Mapping Pp. 371-377
Leonardo Ciaccheri and Anna G. Magnani
[Abstract]


Fiber Optic Sensors for Biomedical Applications Pp. 378-390
Francesco Baldini, Ambra Giannetti, Andrea A. Mencaglia and Cosimo Trono
[Abstract]


Chemical Sensor Networks for Gas Detection and Environmental Monitoring Pp. 391-402
Kevin Duffin, Walter Johnstone, Andrew McGettrick, Dave Moodie, George Stewart, Graham Thursby and Brian Culshaw
[Abstract]




Abstracts


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Editorial:Fiber Optic Chemical and Biological Sensors: Perspectives and Challenges Approaching the Nano-Era

Fiber optic sensors emerged from the low loss fiber optic technology developed in the 70’s and incredibly increased their growth in both research and applications over the last two decades. Cost effectiveness of fiber optic sensors comes out from the rapid developments in telecommunications optics, cost reduction in laser diodes and optical fibers. Actually primary fiber optic sensors markets are oil wells, security, smart structures and seismic detection in oil industry with a market grew of about 90% in 2005 achieving revenue of about 130 million $. Today, market opportunities for sensors are developing and expanding due to the increase of environmental global modifications, homeland security needs and elderly population. Fiber optic based technology can respond to these needs due to the inherent networking efficiency, the optimal cost/performance ratio and the demonstrated ease of integration of optical fibers with sensitive materials for physical, chemical and biochemical sensors.

A wide choice of discrete and distributed fiber optic sensors are commercial available based on well assessed optical transduction schemes such as Fabry Perot cavities and Fiber Bragg Gratings or Raman and Brillouin scattering techniques that cover most of the relevant applications in physical sensing (temperature, strain, stress, vibration). Moreover applications in chemical, biological, environmental and medical fields requires a new generation of devices which principle of operation relies on the sensing functions added by specific designed coating materials. In fact fiber optic sensing technology still continues to be the subject of significant basic research effort not only investigating novel phenomena that can be utilized in sensing but also addressing the integration of novel materials and nano/micro technology in the optical sensor design. In particular, the ongoing interest is stimulated by an ever increasing portfolio of technologies through which light may be caused to interact with chemical or biological conditions which surround it and, in recent years, materials nano/micro technology has provided new opportunities for chemical and biological applications. This issue will contribute toward encapsulating recent exciting developments in the integration of new transduction mechanisms and novel materials whilst in parallel covering the continually expanding world of field trials and application assessments, with special attention to explore new perspectives and outline technological challenges.

A novel generation of fiber optic devices for chemical and biological sensing is approaching based on the concurrent addressing of the issues related to the different aspects of their global design, such as: dielectric properties definition and optical modeling, materials identification, functionalization and activation, novel optical transduction principle development.

Up to now, great effort has been carried out by the scientific community to develop photonic devices, however, the weak integration of competencies required to address this challenge, intrinsically multidisciplinary, limits the capability to achieve high performances devices. A highly integrated approach involving continuous interactions of different backgrounds aimed to optimize each single aspect with a continuous feed-back, would enable the definition of an overall and global design concept.

This special issue presents relevant developments in the field of fiber optic chemical and biological nano/micro sensors starting from a last five years review presented in chapter 1 including gas optodes (oxygen, hydrogen, carbon dioxide and ammonia), humidity sensors, monitors for pH, cations and anions, sensors for organic compounds. Also, biosensors based on enzymes, antibodies, nucleic acids and whole microorganisms are described to illustrate the state-of-the-art in this active area.

Chapter 2 illustrates advanced interdisciplinary approaches to in-fibre chemical sensing where nano structured materials (nanocristalline polymers, carbon nanotubes and microstructured metallic oxides) and innovative optical transducers schemes (near field optical transducers, photonic bandgap fibers and nano-coated long period gratings) are concurrently developed.

Addressing molecular recognition through the mimic of biological receptors is the theme of chapter 3 where the development of optical biosensors based on molecularly imprinted polymers is reviewed and recent innovations presented with special emphasis on their analytical applications.

Chapter 4 explores the potentiality of nanostructured coatings fabricated by means of the layer-by-layer electrostatic-self assembly (ESA) to develop novel fiber optic refractometers, pH sensors, chemical sensors and biosensors at nano scale.

Development of novel optical transduction schemes is the subject of chapter 5 where modifications of fiber Bragg gratings are used to develop advanced surface sensitive chemical or biological sensors for specific applications.

Remarkable advancements in the field of bio-detection is provided in chapter 6 dealing with the use of photonic crystals to enable the design and fabrication of high-sensitivity and compact novel optical sensors. The unique characteristics and versatility of this new technology are analysed to tailor the sensing performances of this new class of devices.

In chapter 7, several application oriented examples are presented to outline the relevance of the features extraction and data processing techniques in the development of efficient sensors system for in field practices.

Applications of optical sensors in medicine is discussed in chapter 8 where the issue of the clinical validation and the special qualifications and approvals requested for biomedical sensors is addressed.

Chapter 9 discusses the enormous potentiality of direct spectroscopic methods in chemical sensing illustrating the exploitation of tunable diode laser spectroscopy in the near infrared range for environmental monitoring.

This special issue is thus aimed to provide multidisciplinary knowledge that is of novel trend in the active area of chemical, biological and environmental monitoring applications at the edge of the Nano-era.

The authors, chosen from a list of multidisciplinary international team of researchers, are experts in their fields and are authoritative in respect of their contribution. The Editors would like to express their sincere appreciation and gratitude to all authors for their efforts in preparing high quality contributions as chapters for this special issue.


Aims and Scope

Fiber optic sensing technology continues to be the subject of significant research endeavour investigating both the phenomena which can be utilized in sensing and the applications of techniques established within the laboratory. The ongoing interest is stimulated at the basic level by an ever increasing portfolio of technologies through which light may be caused to interact with chemical or biological conditions which surround it. In parallel the applications oriented research, in bioscience area has specifically highlighted one or more of the unique benefits which fiber sensor technology offer. In addition, sensor technologies and nanotechnology have come together, in recent years, to provide new opportunities using nanometer-scale structures for chemical and biological applications. There is considerable promise in the use of such ultra-small fiber optic devices for sensing. For example, it is possible that some phenomena hitherto below detection levels might now be sensed by nanostructures. Fiber Optic Chemical Nanosensors or Bio-nanosensors may be able to provide sensitivity down to the single molecule level. On the other hand, additional difficulties may well present themselves, including the fundamental challenge of the integration of physical structures and devices on the nanometer scale, as well as their integration into the micro-scale world.

This special issue will contribute toward encapsulating recent exciting developments in the incorporation of new transduction mechanisms, novel materials and integration methods whilst in parallel covering the continually expanding world of field trials and application assessments, with special attention to explore new perspectives and outline technological challenges.


Andrea Cusano / Antonello Cutolo
Guest Editors
Optoelectronic Division
Engineering Department
University of Sannio
Italy

and

Michele Giordano
Institute for Composite and
Biomedical Materials
CNR, Napoli
Italy


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New Trends in Fiber-Optic Chemical and Biological Sensors
Guillermo Orellana and David Haigh

The most relevant contributions in the field of fiber-optic chemical sensors and biosensors in the last five years are reviewed. Gas optodes (including oxygen, hydrogen, carbon dioxide and ammonia), humidity sensors, monitors for pH, cations and anions, and sensors for organic compounds constitute the different sections. Optical fiber biosensors based on enzymes, antibodies, nucleic acids and whole microorganisms serve to illustrate the state-of-the-art in this active area. Selected examples of absorbance-based, luminescent, evanescent wave, Fabry-Perot, chemiluminescent and surface plasmon resonance-based sensors and biosensors, among other techniques used for interrogate the sensitive part of the devices, are described.


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Integrated Development of Chemoptical Fiber Nanosensors
Andrea Cusano, Michele Giordano, Antonello Cutolo, Marco Pisco and Marco Consales

The development of fiber optic chemical sensors based on the integrated design of novel sensitive nano-coatings combined with advanced sensing configurations is reported in the present study. Different sensitive coating materials have been exploited togheter with their deposition techniques, i.e nano-porous polymers deposited by using dip coating, carbon nanotubes deposited by Langmuir-Blodgett method and metal oxides, prepared by electrostatic spray pyrolysis. In accordance to the chemo-optical properties of these materials novel sensing schemes based on nano-coated Long Period Fiber Gratings, modified Fabry-Perot interferometers involving near field effect and photonic bandgap modification in Hollow-core Optical Fibers, have been proposed, respectively, to provide the best sensing performance. Experimental results reveal the potentiality of the integated approach that simultaneously accounts for the selection of the coating materials and of the fiber optic sensing scheme in developing optical devices for a wide range of applications related to the environmental monitoring either in air and water environments.


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Molecularly Imprinted Polymers as Selective Recognition Elements in Optical Sensing
María C. Moreno-Bondi, Fernando Navarro-Villoslada, Elena Benito-Peña and Javier L. Urraca

Molecular imprinted polymers (MIPs) are molecular recognition elements that can be tailored towards a wide variety of target molecules. These human-made materials are relatively easy to prepare and have found a broad application as substitutes of antibodies or enzymes. They have been successfully applied to the development of chromatographic or solid phase extraction methods and have attracted a great interest for the development of electrochemical, piezoelectrical or optical sensors. In parallel with the classification of biosensors, MIP-based devices can work according to two different detection schemes: affinity sensors (“plastic-bodies”) and catalytic sensors (“plastic-enzymes”). These devices can be interrogated using different optical techniques, such as fluorescence, light absorption (UV-Vis, Infrared) spectroscopy, chemiluminescence, surface plasmon resonance, or Raman scattering. This paper reviews the main developments and applications of MIPs in the area of optical sensors with special emphasis on their analytical applications.


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Fiber-Optic Chemical Nanosensors by Electrostatic Molecular Self-Assembly
Ignacio Del Villar, Ignacio R. Matias and Francisco J. Arregui

A review of optical fiber sensors based on nanostructured coatings fabricated by means of the layer-by-layer electrostatic-self assembly (ESA) method is presented here. The modification of the optical properties of these sensing coatings by the target parameter can induce changes in the reflected or transmitted spectrum. This property can be exploited for the development of refractometers, pH sensors, chemical sensors, biosensors and other applications. In addition to the experiments performed, the theory of some of these phenomena have been also studied in order to understand the behavior of the sensors and to improve their sensing characteristics.


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Real-Time Monitoring of Siloxane Monolayer Film Formation on Silica Using a Fiber Bragg Grating
Christopher J. Stanford, Mario Dagenais, Ju-Hee Park and Philip DeShong

We present a series of experiments to study the silanization of the silica surface of a fiber Bragg grating biosensor. A simple 4-layer attachment model is developed to describe the bonding of 3-aminopropyl triethoxysilane (APTES) or 3-aminopropylethoxydimethylsilane (APMDS) to the silica surface when both APTES and APMDS are dissolved in water or in pure ethanol. An adsorbed water layer is created during the attachment of APTES and APMDS and is necessary to explain the results in water and in ethanol. It is found that a monolayer of APMDS attaches to the silica surface when APMDS is diluted in either water or ethanol. In the case of APTES, it is found that a 1-2 and 5 APTES layers attach to the glass surface when APTES is diluted in water and in ethanol, respectively.


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High Coupling Efficiency in 2D Guided-Wave Photonic Band Gap Extended Microcavities for Sensing Applications
Caterina Ciminelli, Richard M. De La Rue and Mario N. Armenise

Label-free techniques for sensing are of great interest for identification of molecules on a functional surface. Currently, a growing research activity dealing with optical approaches does contribute to the development of new devices.

A remarkable advance in the field of bio-detection is given by the use of photonic crystals enabling to design and fabricate high-sensitivity and compact novel optical sensors. Many photonic crystal sensors on several different materials have been proposed in literature. However, further improvement of the sensitivity requires an additional research effort on the optimization of both the design and fabrication process.

In this paper we report on the solution of the mode-mismatch occurring at the input and output interfaces of the micro-cavity. Mode-mismatch is responsible for the increase of the scattering and degradation of transmission characteristics of the photonic crystal. Optimization of the sensor design can be achieved by using an appropriate tapering of some hole rows into reflectors.

Numerical results have proved that two physical effects occur simultaneously, i.e. conventional tapering which is dominant at high resonant wavelengths, and resonant conditions of the external cavity, when the radius of the holes in the external row is greater than that of the internal one. This last effect is more clear at low wavelength.


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Scattered Colorimetry and Multivariate Data Processing as an Objective Tool for Liquid Classification and Mapping
Leonardo Ciaccheri and Anna G. Magnani

Scattered colorimetry, that is multi-angle and multi-wavelength absorption spectroscopy performed in the visible spectral range, provides an integrated and global measurement of the color and turbidity of liquids. By a multivariate processing of the spectral data, the liquids can be mapped, classified and compared according to their peculiar characteristics. Details of the instrumentation and data processing are given, and the results achieved by analyzing many different types of liquids such as extra-virgin olive oil, beer, detergent in water and lubricant oil, are presented.


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Fiber Optic Sensors for Biomedical Applications
Francesco Baldini, Ambra Giannetti, Andrea A. Mencaglia and Cosimo Trono

Biomedicine is surely the area where the optical fibre sensors can play an important role. Thanks to their potential miniaturisation and their easy handling they are offering unique performances in invasive or minimally invasive applications. The immunity to electromagnetic interference and the absence of electrical contact make the optical fibres useful also in the case of non invasive applications for the setting of the interrogation optoelectronic unit in a safer location, keeping only the sensing element close to the patient’s bedside. As a matter of fact, there are many optical fibre sensors designed for biomedical applications and described in the literature, but the greater part of them stops at the prototype level, without entering the hospital. The clinical validation, which is the necessary step after the characterisation of the laboratory prototype, is often an insurmountable obstacle due to the requirements of compliance with the European Directives on Medical Devices or with the regulations of the Food and Drug Administration. The strategy followed for the clinical validation in the case of optical fibre sensors developed at the Institute of Applied Physics for the detection of bile-containing refluxes, gastric carbon dioxide and interstitial pH is described. An example for potential non-invasive applications in point of care testing is also given with a novel optical platform for the interrogation of optical biochips.


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Chemical Sensor Networks for Gas Detection and Environmental Monitoring
Kevin Duffin, Walter Johnstone, Andrew McGettrick, Dave Moodie, George Stewart, Graham Thursby and Brian Culshaw

This paper reviews the principles and prospects for optical fibre based measurement techniques for determining gas concentrations. Most of these exploit the precision and versatility of tuneable diode laser spectroscopy in the near infrared. We demonstrate the potential offered by large area multipoint totally passive networks and establish the performance potential which these may offer in hostile environments. These benefits include more than adequate sensitivity for most applications, automatic recalibration of both zero point and scale factor and the ability to precisely determine line shape information and in some cases perform detailed line spectrum analysis to determine concentration, pressure and temperature simultaneously. We also briefly describe the principles and application of photo acoustic spectroscopy and outline the performance improvements which tuneable diode laser systems also offer in this context. These studies have illustrated that, in appropriate niche applications, fibre based gas measurement systems offer substantial long term engineering potential.