NANOSTRUCTURED PHOTONIC SENSORS

3D Digital Design and Development participation in the Nanophos project lead to the development of 3 basic systems, which will have use in research and industrial arenas these are: - Project management database, which allows the tracking of large research projects, which involve a number of partners in different countries. This ties up all project workplane, deliverables and partners interaction and results. - Automatic Gas Test Chamber Control System this allows the implementation of operating various control valves, gas mass flow controllers, using recipe approach and various hardware calibration parameters. The software allows the user to set up a full test cycle for a given test, these may be stored and used or edited. Safety consideration was implemented in the overall design and execution of the system. The system supports real time data logging and display to assist the operator to monitor the progress of the current test. - Stand alone electronic platform for testing the Nanophos sensors in free space and waveguide configuration. The free space system provided fully ratiometric measurement system, which automatically compensate for the laser excitation sensors and any environmental variation. Various tests were carried to confirm the system performance under industrial operation. The overall results confirm the success of this approach. Basic tests over a distance of few meters were demonstrated at NHRF facilities in Athens. The system design was based on the use of inexpensive off the shelf electronic optical components.

Nanoparticle (NP) layers sensitive to organic vapors were prepared using tetraoctyammonium bromide-stabilized Au NPs. Sensitivity to specific analytes was achieved using two approaches: - Composite Au NPs - polymer layer; transmission localized surface plasmon resonance (T-LSPR) spectroscopy of Au NPs - polystyrene layers showed specific sensitivity to vapors of good solvents of the polymer. - Modification of the Au NPs' stabilizing shell with an additional ligand; the stabilizing shell of Au NPs was modified with organic ligands bearing bishydroxamic acid groups. Multilayers of functionalized Au NPs were constructed via coordination binding of Zr(IV) with bishydroxamatic acid ligands. T-LSPR spectroscopy of coordination-bound Au NP multilayers showed specific changes after exposure to vapors of organic solvents in which the functional ligands show high solubility. Coordination binding of Au NPs presents a general scheme allowing incorporation of molecules and functional groups with specific sensitivity to target vapor analytes.

FORTH/ICE-HT has installed and operates three experimental work stations (i.e. Optical Kerr effect and Z-scan stations operating with a 35 ps laser at 532 and 1064 nm, and an optical limiting station operating with an 8 ns, at 532 and 1064 nm) in order to characterize the nonlinear optical properties of the materials produced within the consortium and test them for their sensing properties. The experimental capabilities and techniques are appropriate for studies of solutions, suspensions and films on glass, quartz or other transparent substrates. FORTH/ICE-HT has performed complete characterizations of the nonlinear optical properties properties of all delivered films of pure metals, metal oxides, fullerene composites, and also of pure metals and metal oxides nanoparticles incorporated in polymeric matrices. Best results were obtained for gold (Au) continuous films, gold ultrathin nano-islands and fullerene dopped polymers. Two publications summarising these results are under preparation and will be submitted soon by FORTH and NHRF and FORTH and IET respectively. In particular, it was found that the Au ultrathin nano-islands on quartz substrates were exhibiting significant variation of their nonlinear optical properties upon exposure to agents like benzene. It is the first time that such an action is observed experimentally. In addition, the influence of functional parameters like e.g. the size of the Au nano-islands, the pre- or post-treatment, the wavelength of excitation, etc. on the nonlinear optical response of these Au nanostructures have been studied.

Development of a specific facility based on the prism coupler which allows the detection, in guided wave configuration, of refraction index variations of thin films when exposed to HC gases (refractive index variations as low as 10-6 are detected). An optical set-up based on the prism coupler technique (m-lines) for measuring the sensitivity of thin films to gases (especially butane, propane and ozone) has been developed by CR9 IF. The m-line set-up allows measurement of both static and dynamic optical properties in guided-wave configuration. By looking at the m-line (dark line) shape obtained in the laser beam reflected on the prism base when a guided wave is coupled in a thin film pressed on the prism base, one is able to deduce static qualitative optical properties of the film: mainly roughness and optical absorption. Indeed, large and distorted m-line shapes correspond to thin films exhibiting high optical absorption and high diffusion due to roughness. This type of films cannot be used for gas testing because the detection process of the gas is based on the m-line shift during gas exposure. Thus, thin, non-distorted and well-contrasted m-lines are necessary. By looking, at the m-line angular shift during gas exposure, the refractive index variation, that is the optical sensitivity of the thin-film to the gas, can be measured quite easily and with good reproducibility.

A basic platform was designed for proving excitation to the semiconductor laser light source with integrated laser power monitoring. The system provide a fully ratiometric solution for compensation for changes in the operational environment. The system employs standard off shelf electronic components. The platform may be used as the electronic processing end for the range of Nanophos sensors. The platform may be offered as a separate component for other originations who may be interesting in the production and manufacture of any of the Nanophos gas, temperature or relative humidity sensors.

Thin film devices comprising ceramic matrix and embedded metal chloride nanoparticles, which produce specific chemioptical functionalities due to reversible complexation effects. The optical nanocomposites are produced by in-situ chemical synthesis in the matrix to form well-dispersed and sized nanoparticles in the matrix. Special links with the matrix constituents offer greater possibilities. Specific examples include sensors such as silica/cobalt chloride for humidity detection and silica / nickel chloride for ammonia detection.

Integrated photonic free-space point sensor system capable of monitoring physical and chemical parameters at a point in a remote space by interrogating a sensor element by use of light beams. The system comprises optics and electronics platform with transmitter, sensor head and receiver units optically coupled and also data acquisition and processing at the base station. The integrated system enables remote monitoring by interrogating a powerless element located at the remote point. At this point negligible power dissipation occurs. The system has the potential of using multi-sensor platform for simultaneously monitoring several parameters. Remote operation is assisted by use of special atmosphere compensating optics and methods. The photonic system thus offers unique advantages since it provides multisensor operations on a frame of many remote points in space thus producing extended sensory networks at low cost. Application specific systems can be available with relevant platforms designed to conform to individual needs.

By Chitta Ranjan Patra and Aharon Gedanken, NEW JOURNAL OF CHEMISTRY 28 (8): 1060-1065 2004. Since much of the consortium activity was concentrated on metallic oxide nanoparticles being the substrates for the sensing of gases, we have tried to synthesize this materials in small scale. The method by which they were synthesized is microwave dielectric heating. Semiconducting nanoparticles of indium and thallium oxides (In2O3 and Tl2O3) have been successfully synthesized in high yield (>95%) by microwave irradiation. The oxides are synthesized in a simple domestic microwave oven (DMO) by adding an aqueous ammonia solution to the aqueous solutions of indium chloride (InCl3) and thallium chloride (TlCl3), respectively. The particles are of uniform size, being about 16 nm and 24 nm for Tl2O3 and In2O3, respectively

Evaporated gold island films have been the subject of studies dealing with a variety of spectroscopic and sensing applications. Development of these and other applications requires film stability as well as tunability of the morphology and optical properties of the island films. In the present work ultrathin, island-type gold films were prepared by evaporation of 1.0 to 15.0 nm (nominal thickness) gold at a rate of 0.005-0.012 nm s-1 onto glass substrates modified with 3-mercaptopropyl trimethoxysilane (MPTS), the latter used to improve the Au adhesion to the glass. The morphology of the films, either unannealed or annealed (20 h at 200 oC), was studied using atomic force microscopy (AFM) and high-resolution scanning electron microscopy (HR-SEM). The information provided by the two imaging techniques is complementary, giving a good estimate of the shape of the islands and its variation with film thickness and annealing. The optical properties of the films were examined using transmission UV-vis spectroscopy, showing a strong dependence of the localized Au surface plasmon (SP) band on the morphology of the island films. The imaging and spectroscopy indicate a gradual transition from isolated islands to a continuous film upon increasing the Au thickness.

The contribution of the IET to the project was the development of the technology of optical metal/oxide multilayer sensors for the detection of environmentally important gases. Process sequence towards the fabrication of micrometer- and submicrometer-size grating-based structures involves deposition of metal/oxide multilayers, photolithography and etching. Metal/oxide multilayer structures composed of metal films with thicknesses varying from 2 nm to 100 nm and 150-800 nm thick metal oxide layers were deposited by magnetron sputtering. Metals such as Pt, Pd, Ru, Au or Zn and oxides such as SnO2 or ZnO were deposited from metallic targets via Ar or reactive Ar/O2 sputtering, respectively. Depositions were performed in a multitarget sputtering system without breaking vacuum. To achieve highly anisotropic etch profiles and smooth side-walls, sputter Ar-ion etching of metal/oxide multilayer structures was elaborated. Since the conventional photoresist masks were not sufficiently selective during dry etching, appropriate hard metal (Ti, Cr, Ni or Al) or SiO2/metal/SiO2 trilevel mask were developed and successfully applied. The patterns were defined first in the hard mask and next transferred to the metal/oxide multilayers. Finally, the mask was removed with a selective etch revealing the underlying diffractive structure. An alternative approach, designed to pattern metal/oxide multilayers with difficult to etch refractory metals, involved lift-off lithography and deposition of metal/oxide multilayers. Due to the fact that for lift-off lithography the substrates are covered with resist layers, deposition parameters were optimised to avoid unintentional heating during sputtering. The achievements of this project should allow the development of more complex elements as well as other oxide-based devices.

Instrumentation facility for photonic sensor testing comprising vacuum and gas handling equipment, computer control operation, photonics platform, electronic data acquisition and analysis systems and peripherals. Testing at a wide range of gas concentrations by control of pressures and use of ultra low differential pressure mass flow controllers. Interconnected chambers for free space photonic sensors and waveguide sensors, the latter by use of fully fiberised platform. Use of calibrated direct power monitors and also lock-in techniques. Capacity for testing electrochemical sensors in the like gas environment conditions.

Integration of an optical sensor head based on the grating coupler and m-line shift measurement allowing butane or propane detection in the range of 100 to 1000 ppm. CR9 IF performed the integration of a sensor head for the detection of HC gases. The basic idea was to use a grating coupler allowing light to be coupled into a waveguide, this waveguide being covered by the gas sensitive layer. When exposed to HC gases, the refractive index of the sensitive layer is slightly modified which results in a modification of the propagation conditions of light into the waveguide. This modification is detected by measuring, in the beam transmitted through the grating coupler, the angular shift of the m-line (mode line) corresponding to the light guided into the waveguide. A polymer thin film (PHMS film) developed by Thales TRT has been selected to be deposited on top of the grating coupler and tested into the integrated sensor head. A software application, under Labview environment, has been specifically developed to perform data acquisition and processing. 1000 ppm of propane or butane diluted in nitrogen or dry air has been detected by the grating coupler sensor head. It has also been demonstrated that the PHMS film can be used to optically detect HC gases down to 100 ppm. Furthermore, this polymer is not sensitive to perturbations by other gases such as ozone.

Methodologies for the synthesis of hybrid nanocomposites comprising polymer matrix and inorganic nanoparticles, the latter synthesised in-situ by chemistry. The nanocomposites exhibit optical properties and chemi-optical sensing functionality. Materials are based on mono-disperse well-characterised polymers, and metal, oxide or chloride or other nanoparticles. In contrast to the simple mixture of commercial compounds, the system provides excellent control of nanoparticle size as well as well-linked organic-inorganic constituents, according to the design. Photonic sensor technology is a prime sector of interest but other applications are also provided by same means. Low cost processing for the materials synthesis and thin or thick film deposition by casting, spin coating, spraying and the like.

Thin film optical devices comprising monodisperse polymer matrix of well defined properties and metal nanoparticles of controlled size produced by in-situ synthesis and capable of providing chemical sensor functionalities for monitoring chemical agents. Low cost mass production fabrication methods. Integration to produce photonic devices.

Photonic sensor head for humidity (H2O- RH) sensing operations by use of the free space point sensor, remote interrogation system. The head comprises a nanocomposite material such as for example silica or a hybrid polymer based -cobalt chloride nanocomposite system as well as transmissive or retro-reflecting units for respective use. The head operates in a diffractive mode by utilising own diffractive properties or by means of diffractive element etched on the material or the substrate to allow interrogation by use of light beam. The sensor head is used either as a single unit or in a multi-parametric unit for combined operations.

Photonic sensor head for alcohols sensing operations by use of the free space point sensor, remote interrogation system. The head comprises a nanocomposite material such as for example poly(2-vinilpyridine) (P2VP) as well as transmissive or retro-reflecting units for respective use. The head operates in a diffractive mode by utilising own diffractive properties or by means of diffractive element etched on the material or the substrate to allow interrogation by use of light beam. The sensor head is used either as a single unit or in a multi-parametric unit for combined operations.

3D developed a simple elctronic interface for monitoring relative humidity using Nanophos sensors in free space. Special electronic system was designed to provide fully ratiometric measurement. The results compared well with standard semiconductor sensor.Areas of application are in power stations, power distribution and sub-stations. The interface electronic is operated remotely from the Nanophos relative humidity sensor.

An optical sensor interrogation platform comprising one transmitter unit, one sensor head with retro-reflecting capability incorporating the active sensor element and a receiver optics unit. The system comprises laser beam collimators and expanders according to the application and interrogation optical path length. Platforms comprise opto-mechanical mounts for optics, source(s) and receiver(s). If natural obstacles obscure the optical path, the use of a fiber optic link is provided. They comprise at least one additional system for providing a normalisation optical reference independent of the sensing operation, by use of a multiplexed wavelength(s) and / or polarisation modulation or separate neighbouring beams, or there are provided means for interrogation by optical imaging. The system is accepting one or more active sensor materials in an interchangeable fashion. In another embodiment a plurality of sensor heads is provided with multiple sensing operations via wavelength multiplexing. Special adaptive or holographic optics and the like to compensate for atmospheric effects are used as appropriate. The system is used in conjunction with active sensor materials and an electronics platform, to produce a photonic sensor system for multiple applications in environmental and industrial monitoring and control, with extended use in health sciences and other sectors.

WP2.5-SnO2 nanostructured films deposited by pulsed laser ablation deposition It was found that the O2 background pressure, target-substrate distance and the substrate temperature are three critical parameters for the deposition of SnO2 films with the suited catalytic nanoarchitecture. It was also observed that the growth of the nanoparticles up to sizes of some nanometers takes place in the gas phase during the expansion of the plasma. Yet, it was shown that for gas sensing applications, nanostructured thin films with high surface roughness are more suitable, and the smaller are the nanoparticles, the higher is the sensitivity. Finally, the optimum deposition parameters, which allow us the preparation of high quality samples, have been established. WP6.3- Testing systems An upgraded version of a full testing facility has been designed and built by the present partner (UNILE-CR10). This version of gas sensing system, installed and operating in NHRF of Athens, was built on the base of experience got with previous systems built and installed in the University of Lecce. The new system is able of handling gases such as HC, CO, O2, O3, alcohols etc. This system has been interfaced with electronics and processing systems. Publications of two papers in international scientific journals. UNILE-CR10 has managed the deposition of nanostructured SnO2 specimens with well-defined properties in terms of morphology, structure and composition. Deliverable: published papers. Months 12 Presentation at the Conference: Sensors & their Applications. Liverpool September 2007. Presentation in September 2007. Deliverable publication on Proceedings of the Conference. Months 12 Thesis of Laurea at University. A thesis of Laurea will be discussed to the Physics Department of University of Lecce. Deliverable: Thesis of Laurea. Months 3 Bilateral agreement with a Romanian research group. A Romania-Italian bilateral project has been financed by the Italian Ministry of Foreign Affairs to develop gas sensor systems. Deliverable: submitted papers. Months 24 Collaborations with other groups are foreseen in the field of R&D, INFO and CONS.

FORTH/ICE-HT has significant expertise in the production of novel carbon nanostructures and has developed methods based on the synthesis of carbon nanostructures with catalytic chemical vapor deposition (CCVD or CVD) of different carbon sources on substrates of metal oxides impregnated with metal catalysts. FORTH/ICE-HT can produce and deliver to potential partners high purity multi-wall and single-wall nanotubes in quantities ranging from milligrams to several hundreds of grams. In addition to nanotubes, FORTH/ICE-HT also can offer R&D services on the process engineering of systems in which nanotubes and other nanomaterials are produced or employed. Furthermore, FORTH/ICE-HT can provide both scientific and technological know-how on: - Surface modification and tailoring of the chemical functionality of carbon nanotubes towards polymer matrix structures. - Characterization of the nanotubes size distribution and dispersion capability and determine the tensile strength of nanocomposites and the orientation of the nanotubes within the nanocomposite. - Development and characterization of CCVD nanostructured materials based on aluminium oxide and carbon.

Photonic sensor head for ammonia sensing operations by use of the free space point sensor, remote interrogation system. The head comprises a nanocomposite material such as for example silica-nickel chloride system or a hybrid polymer based nanocomposite as well as transmissive or retro-reflecting units for respective use. The head operates in a diffractive mode by utilising own diffractive properties or by means of diffractive element etched on the material or the substrate to allow interrogation by use of light beam. The sensor head is used either as a single unit or in a multi-parametric unit for combined operations.

We have developed a preparative scheme for controlled modification of gold nanoparticles (NPs) by using reversible binding to a polymeric solid support, potentially useful for immobilization of specific receptors for target analytes. Reversible binding of Au nanoparticles (NPs) to a polymeric solid support was demonstrated by using boronic-derivatized resins and the specific reaction of diol molecules with boronic acid. The versatility of boronic acid chemistry offers a powerful tool for NP manipulation, while the polymer support provides the preparative element. In the present case the boronic acid/diol chemistry was exploited for controlled transfer of linker molecules from the resin to the capping layer of the NPs, to obtain free, linker-modified Au NPs. The reversibility of boronic acid chemistry was used for rebinding linker-bearing NPs to a boronic resin by means of the diol linker molecule, thereby establishing 1) the presence of linker molecules on the modified NPs, and 2) an effective affinity separation scheme. This enabled selective extraction and separation of NPs from a mixed solution, as well as convenient NP recovery. The preparative schemes presented here may be useful in various aspects of NP technology. These include specialized NP modification, controlled NP release, NP separation and purification, chemical reactions on immobilized NPs, and others.

ZnO thin films were coated on SiO2 (001) substrates by PLD using an excimer KrF* laser source (248 nm, 7 ns, 2 Hz), operated at a laser fluence of 2.6 J/cm2 for a 5-cm target-substrate distance. Prior to any deposition, the chamber was evacuated down to a residual pressure of 10^-4 Pa. Meanwhile, the chamber walls were heated up in order to facilitate the desorption of water vapors and other contaminants. The 99.9% pure commercial ZnO raw powder was pressed at 20 MPa into pellets of 13 mm diameter and 2 mm thickness which were sintered in air at 1100º C for 8 h. Prior to each deposition, the target surface was cleaned by applying 5,000 laser pulses. In order to prevent the deposition of material ablated from the first layers of the target, a region, which can contain contaminants, a shutter was interposed between the target and the substrate. For avoiding the drilling effect and for ensuring surface cleanliness and uniform surface usage, the target was submitted to a rotational movement at a frequency of 0.04 Hz while translated on orthogonal directions. The coatings were grown by applying 30,000 subsequent laser pulses on the undoped ZnO or Au (0.5% wt.) doped ZnO targets, respectively. The depositions were performed in a uniform dynamic oxygen flow of 10 Pa monitored by an MKS 50 controller. Au nanoclusters were deposited in a second PLD step starting from an Au target, in vacuum (10-4 Pa) at room temperature. In this case, to avoid uncontrolled contamination exposure to ambient air and to minimize processing time, a multi-target carousel holding both the ZnO and Au targets, was mounted inside the chamber. After completing the deposition of ZnO structures, the ZnO target was simply shifted and replaced by rotation by the Au target, without opening the chamber or performing other supplementary operation. Highly c-axis oriented ZnO films were grown on (001) SiO2 substrate by pulsed laser deposition. All deposited thin films surfaces are smooth and uniform, which constitute a major advantage when using the m-line detection technique. The optical refractive index and extinction coefficient were very close to those of the reported reference data for ZnO thin films. The transmission of the films measured in the range 200-1400 nm had an average value of about 85%. The good optical properties stand for the basic requirements, which allow the implementation of the obtained thin films in future optical gas sensors. Butane concentrations down to 100 ppm were detected. Moreover, we observed that nanostructure doping with noble metal nanoparticles resulted in a slight decrease of the detection sensitivity, which was probably due to enhanced light diffusion, scattering, and/or absorption.

The contribution of the ORC to the project was the development of integrated optical sensor devices that showed sensitivity to target agents such as humidity, alcohols and butane. They were based on waveguiding Mach-Zehnder interferometers fabricated via ion-exchange in soda lime glass chips as well as via laser writing in hybrid organic/inorganic chips produced by sol-gel. They were operating on the principle of Mach-Zehnder interferometers and had one reference and one sensor output. After fabrication the chips were coated by an isolation layer of sputtered silica apart from a window on the sensing arm of the interferometers, which limits the spatial extent of the interaction of the guided light with the sample. In other words the interaction of the guided light with the sample was restricted to the region in the window. The whole chips were then coated with thin films materials sensitive to the target agent in order to increase the sensitivity of both the MZIs and the exposed reference waveguide. The thin films were single-mode planar waveguides with a thickness just below the cut-off condition for the TE00 mode. This led to an enhancement of the evanescent field and subsequently to an improvement of the sensitivity so that the high index film practically served as the sensing regions of the chip. The chip design for a 10-mm-long window allowed precise measurement of very small refractive index changes (down to n~10-7) by observing changes at the outputs of the inteferometric pattern. The materials were deposited on the window areas using various techniques such as pulsed laser deposition, reactive sputtering, spin coating, casting and spray coating techniques by the consortium partners. Layers of the following materials were then deposited on the widows: "Active layers of indoleacetic acid (IAA) doped with gold (Au) with thicknesses varying from 400 nm to 3 microns for alcohol detection "SnO2 and ZnO layers layers with a thickness between 25 and 30 nm "Polyethylene oxide for alcohol detection. "Polymethyl [4-hydroxy-4,4bis(trifluoromethyl)butyl] siloxane (PLG) with a thicknens in the range of 5 to 10 nm. In all our achievement was the development of innovative approaches an to produce miniaturized integrated optical devices for sensing of various chemical agents with advanced sensitivity and stability with potential for implementation in various application areas and particularly in industrial environments and security.

Different versions of vacuum systems for gas sensing have been designed and built in the University of Lecce. These systems have been used for preliminary studies of the gas sensing properties of the samples prepared by the consortium. The experience got by these studies lead to define the technical specifications of the final testing chamber.

Butane sensitive elements based on the light waveguide propagation into a thin or periodically structured ZnO films have been produced and tested. High optical quality c-axis oriented ZnO thin films have been grown by pulsed laser deposition on quartz (amorphous or 001) substrates using an excimer XeCl* laser source (308 nm, 20 ns, 2 Hz), operated at a laser fluence of 2 J/cm2 for a 4-cm target-substrate distance. In case of the periodical structured configuration, a holographic grating (period 552 nm and depth h = 235 nm) was produced first on the amorphous quartz substrate by using HeCd laser in a standard holographic configuration and then the ZnO film was deposited. The depth of the groves decreases to about 90 nm, as the period of the grating remains unchanged. A prism coupling or periodical structure was used in order to introduce the light into the planar ZnO waveguide and to ensure an optical detection mechanism. ZnO films are proven to be sensitive to butane (down to 100 ppm diluted in air or N2). The periodically structured ZnO waveguides are sensitive to butane (1000 ppm diluted in air).

The design and prototype manufacture of Nanophos Sensors demonstrate beyond doubt the feasibility of such devices. With increase in awareness of the effects of pollutant gases and their effect on the EU citizens and environment, new safe, reliable and economical sensors will find wide acceptance in the home and the workspace. The introduction and the expansion of the use of natural gas heating systems in the home and most commercial building requires constant monitoring and alarming of dangerous gases such as carbon monoxide. In addition the ever-increasing use of land-filled sites across the EU, leads to an increase in the discharge of methane gas in the environment which increases the level of pollution and the possible of explosions The current prototype sensors developed during the Nanophos project show promising results which would lead to the possibility of apply to venture capital in order to manufacture second level of prototypes which will be demonstrated on actual prospective clients sites over a medium period to generate high level of confidence in the accuracy, reliability and long term stability. Application will be made for obtaining a patent for the current ideas of the Nanophos sensors during the spring of 2007. The venture capital companies will be approached during the autaum of 2007 with a basic business plan for the production of the second generation prototype sensors which includes temperature sensor, relative humidity and ammonia sensors, should this prove fruitful then further capital may be requested to further develop the MZ sensors and the carbon monoxide sensors. The above work will be carried out in conjunction with NHRF and the University of Lecce

Mach Zehnder interferometric systems comprising a window on one arm, which is coated with hybrid polymer based composite layer in order to provide sensing by means of refractive index variation upon exposure to physical or chemical environment. Method for depositing the hybrid layer. Interrogation by means of light propagation in the waveguide.

Devices comprising diffractive elements fabricated on multilayer metal/metal-oxide structures for interrogating the sensor functionality by means of alterations in the properties of the diffractive element. Diffractive designs include simple linear gratings, computer generated holographic optics and Fresnel optics. Applications in sensing of physical and chemical parameters through the alteration of nanocomposite optical materials refractive properties. Other applications in photonic systems including switching among others.

By Chitta Ranjan Patra, Yitzhak Mastai and Aharon Gedanken, JOURNAL OF NANOPARTICLE RESEARCH 6 (5): 509-518 OCT 2004 Since much of the consortium activity was concentrated on metallic oxide nanoparticles being the substrates for the sensing of gases, we have tried to synthesize this materials in small scale. The method by which they were synthesized is microwave dielectric heating. Submicrometer sized gallium oxide hydroxide (GaO(OH)) and gallium oxide (Ga2O3) rods have been successfully fabricated on a large scale by refluxing an aqueous solution of Ga(NO3)(3) and NH4OH in a simple domestic microwave oven (DMO). The calcined product consists of submicrometer rods with diameters of 0.4 - 0.5 microns and lengths of 5 - 5.5 microns.

Prototype devices based on [metal/metal-oxide/metal] multilayers in which each layer is of nanometric size in order to form a composite with nanoscopic photonic properties. Devices comprise specific designs for large differential interferometric operation for sensor and or light switching applications. Specific examples concern sensor head for remote temperature monitoring. The system is implemented by means of laser sputtering or by means of electric magnetron sputtering. Devices implemented are based on same metal/metal oxide, or on other metal oxide, the latter comprising rare earth or noble metals.

The design and prototype manufacture of Nanophos Sensors demonstrate beyond doubt the feasibility of such devices. With increase in awareness of the effects of pollutant gases and their effect on the EU citizens and environment, new safe, reliable and economical sensors will find wide acceptance in the home and the workspace. The introduction and the expansion of the use of natural gas heating systems in the home and most commercial building requires constant monitoring and alarming of dangerous gases such as carbon monoxide. In addition the ever-increasing use of land-filled sites across the EU, leads to an increase in the discharge of methane gas in the environment which increases the level of pollution and the possible of explosions The current prototype sensors developed during the Nanophos project show promising results which would lead to the possibility of apply to venture capital in order to manufacture second level of prototypes which will be demonstrated on actual prospective clients sites over a medium period to generate high level of confidence in the accuracy, reliability and long term stability.

A photonic sensor head for use in the remote point temperature monitoring system. The sensor head comprises multilayer element with retro-reflecting capability either in the specular reflection mode or by use of reflective diffractive optics. The multilayer element is produced on planar and non-planar surfaces according to specific design. The system is based on metal/metal-oxide technology described herein and is incorporating retro-reflecting operation either integral or externally provided. Available designs can be tuned to cover various temperature ranges with high accuracy. The temperature sensing head becomes an integral part of the free space sensor system either for single or multi parameter use as described herein.

Methods for the tailoring of synthetic photonic materials interfaces by means of diffractive elements, in order to provide the desired light diffraction functionality. Use of the refractive and geometrical parameters determining diffraction for the detection of refractive, and also absorptive, changes of the photonic material. The tailoring of the interface includes optimised linear grating structures tuned at maximum slope of their diffraction efficiency at a wavelength of interest and computer generated holographic structures in the far or near field regime.

Methodologies for the chemical fabrication of nanocomposite materials for sensor and other applications, comprising ceramic matrix and embedded nanoparticles, including metals, oxides, chlorides and other clusters. The methods achieve proper and absolute nanoparticle dispersion in the matrix, together with excellent control of the size, due to the in-situ character of the synthesis, in contrast to the physical mixing of nanomaterials and matrix, in which case agglomeration effects are present, for specific applications. The size of the embedded nanoparticles can be tuned from a few nanometers to hundreds of nanometers by chemical conditions. Processes are low cost and can be conveniently industrialised. Sensors based on refractive chemioptical alterations are formed by thin and thick film casting, spin coating or spaying and the like methods. Other applications of the materials are foreseen.

Nanocomposite devices comprising changeable and reversible light diffraction effects due to their surface morphology, for use in sensor technologies and other applications involving light scattering. The devices are fabricated by in situ synthesis of nanoparticles in polymer or sol gel matrices. The morphology of the structure is amended by exposure to environmental agents with effect to alter the light scattering properties of the structure in a well-determined and reversible manner without detectable fatigue, deterioration or aging effects. Also the refractive index of the system is affected locally and this produces additional modifications. Specific demonstrations include the remote detection of humidity, alcohols and ammonia by use of the relevant low cost systems described here and without further need for structuring the optical interfaces.

3D developed and integrated data logging, monitoring and archiving software for used with the gas testing facility at the NHRF in Athens. Software allows the operator to enter information for the identification of sensor under test such as type. Serial number, manufacture, test chamber conditions such as gas concentration and ambient condition. This data is stored in a database for long-term storage. The software allows real time display of all the test facility operating parameters such as gas flow control valves, mass flow controller settings and actual mass flow, gas chamber pressure, laser diode power level and gas photo-diode output. In addition the software allows repeated test from test recopies database. The software provides full safety consideration for the operator and the test environment. This software package may used by other laboratories or companies which carry out calibration service for most of gas sensors irrespective of the type sensor used.

The contribution of the IET to the project was the development of the fabrication technology of diffractive optical elements (DOE) such holographic elements and Fresnel lenses. Process sequence involves deposition of thin oxide films, photolithography, and etching. Undoped and intentionally doped oxide layers were deposited by reactive magnetron sputtering from metallic and ceramic targets. Additional thermal processing was used to modify oxide microstructure and composition. Dry etching processes of oxide-based structures to achieve highly anisotropic etch profiles and smooth side-walls were elaborated. The DOE features were reactive ion etched (RIE) in BCl3/Ar plasma or sputter Ar+-ion etched. Because of not sufficient selectivity of the photoresist mask during dry etching, appropriate hard metal (Ti, Cr, Ni or Al) or SiO2/metal/SiO2 trilevel masks were developed. The DOE patterns were defined first in the hard mask and next transferred to the oxide-based layers. Finally, the mask was removed with a selective etch revealing the underlying DOE. The achievements of this project should allow the development of more complex DOEs as well as other oxide-based devices.

The influence of several different solvents (i.e. of polar and non-polar nature) on the third order nonlinear optical response of ultrathin Au island films has been investigated in details. For this purpose, several annealed thin Au island type films having different thicknesses were prepared, both uncoated and coated with polyisoprene and were studied. In all cases, their NLO response was measured before and after being exposed to the solvents. The main results can be summarized as following: - A significant enhancement of about 400% of the nonlinear optical response was observed during the first 10 minutes after benzene exposure, followed by a gradual reduction upon time, leading finally to the initial observed nonlinear response of the unexposed film. - Similar experiments performed using chloroform resulted to very small modification of the NLO response. - Acetone exposure resulted in a marked decrease of the OKE signal by about 17%. The results of this investigation are in the preparation phase of a paper, which will be submitted for publication very soon.

Deliverables

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