We investigated the creation of SERS-active hierarchical substrates based on self-assembled nanospheres (HSNs). We demonstrate how the “hierarchical” approach could be systematically exploited to extend the SERS hotspots into the third dimension, by enhancing the hot-spots spatial density and intensity. The proposed hierarchical substrates take advantage of the single layer hexagonal closed packed array nanospheres (CPA). An additional layer of upper nanospheres to obtain dense and intense hot spots pattern is employed. To predict the SERS performance and to identify the promising architectures, a numerical analysis is carried out, offering design criteria, an overview of the operating mechanisms and conditions that affect the SERS behavior of substrates. We fabricated HSNs by using a self-assembling approach and the preliminary results reported. The results highlight that HSNs can be used as cost-effective SERS substrates with better performance than simpler single-layer CPA configurations.
The ability to make an accurate diagnosis at the time of treatment is crucial for many diseases. However, current standard diagnostic procedures can only be performed in specialised healthcare facilities. To bring diagnostic methods from a specialised laboratory to the point of treatment, many alternative methods have been proposed. One of them is surfaceenhanced Raman scattering (SERS), which offers advantageous features such as high sensitivity in biotarget detection and higher accuracy. Here, we have developed an advanced SERS platform for the ultrasensitive, rapid and highly specific identification of tumour biomarkers in liquid biopsies. Our particular focus is on the detection of Thyroglobulin (Tg), the most important tumour biomarker for the diagnosis and prognosis of thyroid cancer. Specifically, SERS-active substrates fabricated by nanosphere lithography on chip or on tips of optical fiber (OF) were functionalized with Tg Capture antibodies. Gold nanoparticles were functionalized with Detection antibodies and conjugated with a Raman reporter. The sandwich assay platform was validated in the planar configuration and a detection limit of only 7 pg/ml was successfully achieved. The same approach has been successfully demonstrated on washout fluids from fine needle aspiration biopsies of cancer patients. Finally, the functionalization strategy was translated to the LOF-SERS platform and successfully used to detect Tg concentration. The proposed SERS-assisted immunoassay platform has proven to be highly versatile and can be used with both microfluidic chip POC devices and SERS-OF-based optrodes to perform sensitive, specific and rapid ex vivo assays for Tg detection in liquid intraoperative biopsies.
In this work, we propose a novel immunoassay platform for the detection of human Thyroglobulin (Tg) to be integrated with fine-needle aspiration biopsy for early identification of lymph node metastases in thyroid cancer patients. The sensing platform detects Tg (a well-known biomarker for the classification of metastatic lymph nodes related to thyroid cancer) by a sandwich immunoassay involving a self-assembled surface-enhanced Raman scattering (SERS) substrate assisted and empowered by functionalized gold nanoparticles enabling additional Raman signal amplification and improved molecular specificity. The sandwich assay platform was preliminary validated in a planar configuration and a detection limit as low as 7 pg/mL was successfully achieved. The sandwich assay was successfully demonstrated on washout fluids of fine needle aspiration biopsies from cancer patients and confirmed the high specificity of the proposed methodology when complex biological matrices are considered. Finally, optical fiber SERS optrodes were fabricated and successfully used to detect Tg concentration by applying the same bio-recognition strategy. This opens the possibility of transferring the Tg detection approach to the optical fiber tip to develop point-of-care platforms that can be directly integrated into fine needle aspiration biopsies.
We report on the development and field test of fiber optic hydrophones (FOHs). In details, we focused on the development of acoustic hydrophones for towed arrays applications and seismic hydrophones for seismological monitoring applications. In both cases, the sensing configuration is based on a Michelson interferometer where a fiber coil is wrapped around a compliant mandrel acting as a sensitive element. For the first application, acoustic hydrophones were characterized in an instrumented tank at Leonardo Finmeccanica premises. The hydrophone exhibited a responsivity of about 19 nm/Pa in the frequency range 3÷10 kHz with a resolution down to 300μPa /√Hz. The same FOHs were used as a basic building block to develop a towed array with five elements. By using the same enabling technology, but tailoring the physical and geometrical properties of hydrophones, we developed seismic hydrophones. The sensing system was integrated in the seismologic monitoring system and installed at Campi-Flegrei caldera. During the field trials, we detected several earthquakes occurred in the area and compared the results with a reference piezoelectric hydrophone. The seismic sequence was used to retrieve the sensor responsivity in the frequency range 1-80Hz. The sensing system exhibited a responsivity of about 300nm/Pa and an average noise floor level down to 100μPa/√Hz. The reported field trials demonstrated the capability of FOHs to operate in relevant environments and realistic scenarios.
In this work, we propose new Lab-on-Fiber SERS optrodes, realized directly on the optical fiber tip with different SERS active substrates, to detect biological targets of different sizes (bovine serum albumin and red blood cells membrane).
Surface-enhanced Raman scattering (SERS) has established itself as powerful tool for molecular sensing in biology and medicine. The integration of SERS systems with optical fiber is a challenging but potentially very rewarding endeavour. However, efforts to transfer the technology from the laboratory to the clinic have been frustrated by the lack of robust stable and sensitive substrates on the fiber tip, as well as the complexity of interfacing between sample and the substrate itself. Here, we propose the Lab-on-Fiber SERS optrodes, realized on the optical fiber tip by nanosphere lithography. Three types of highly ordered and reproducible SERS-active substrates have been realized: close-packed array (CPA); CPA after sphere removal (SR) and sparse array (SA) of polystyrene nanospheres, covered by a gold thin layer. To optimize the SERS probes, we compared the SERS performances in terms of Enhancement Factor (EF) and reproducibility pertaining to different patterns with different nanosphere diameters and gold thicknesses using the biphenyl-4-thiol (BPT), as target molecule. Moreover, we analysed and compared the SERS spectra of two representative biological probes, bovine serum albumin (BSA, medium molecule) and red blood cells (RBCs), in order to correlate the SERS response to the morphology and hysteric hindrance of the biological target. The SERS analysis indicated that the CPA substrate amplifies the BPT Raman intensity twice as well as the SR and SA substrates, while BSA and RBCs, with the CPA substrate, provide signals comparable to those of SR and SA substrates. Finally, we have optimized a Raman system for SERS optrode operation with efficient lighting and collection via optical fiber.
We report on our activities related to the development of surface enhanced Raman scattering (SERS) probes realized onto the optical fiber tip (OFT) through nanosphere lithography. In the first stage of our research, we adapted the nanosphere lithography to operate on the optical fiber tip, by assessing the process and demonstrating either the potentiality or the repeatability of the proposed nanopatterning approach. Successively, we investigated the ability of the manufactured structures on the fiber tip to act as SERS probes by measuring the SERS spectra in presence of a Biphenyl Thiol (BPT) monolayer. Firstly, we focused the attention on the samples shaped as closed packed array of nanospheres covered by gold. The analysis allowed us to identify the most promising SERS platform, exhibiting an Enhancement Factor (EF) of 4×105 and a SERS measurements variability lower than 10%. We addressed also the limitations related to the use of the same optical fiber for both illumination and light collection by selecting a commercial optical fiber exhibiting a suitable trade-off in terms of high excitation/collection efficiency and low silica background. Current activities are devoted to the investigation of other nanopatterns on the optical fiber tip (namely, Sparse Array of metallodielectric spheres) and the analysis of the probes response against different molecules.
In this paper, we developed Lab On Fiber (LOF) accelerometers based on micro-opto-mechanical cavities on the optical fiber tip. We designed the mechanical structures with different performances features specialized for target applications. In particular, a LOF accelerometer was designed for seismic surveillance applications. The sensor response was first characterized in laboratory, exhibiting a resolution down to 0.44μg/√Hz over a 3 dB frequency band of 60 Hz. To demonstrate the sensor capability to operate in a realistic seismic surveillance system, the developed sensors were continuously used in combination with a commercial seismic sensing network. During the field trial, the LOF sensor registered the ground acceleration associated with the seismic sequence that struck central Italy on October 30, 2016. Overall, the comparison, with traditional sensors incorporated into the geophysical network, demonstrated that the LOF sensors exhibit competitive performance with commercial seismic accelerometers. Ongoing activities are devoted to the design and realization of LOF accelerometers, based either on cantilever structures or on membranes, featuring different mechanical features and thus leading to different performances of the final accelerometer, by retaining the same principle of operation.
This paper reports on the assessment of a simple and economical self-assembly methodology to obtain reproducible substrates onto the optical fiber tip for surface-enhanced Raman spectroscopy (SERS) applications. The method relies on the use of the nanosphere lithography of the optical fiber end facet. A careful analysis has been carried out to investigate the capability of the proposed procedure to realize repeatable pattern on the optical fiber tip. Finally, we demonstrate the effective application of the patterned OFTs as SERS nanoprobes.
Massimo Filograno, Marco Pisco, Angelo Catalano, Ernesto Forte, Marco Aiello, Andrea Soricelli, Daniele Davino, Ciro Visone, Antonello Cutolo, Andrea Cusano
In this paper, we report a fiber-optic triaxial magnetic field sensor, based on Fiber Bragg Gratings (FBGs) integrated with giant magnetostrictive material, the Terfenol-D. The realized sensor has been designed and engineered for Magnetic Resonance Imaging (MRI) applications. A full magneto-optical characterization of the triaxial sensing probe has been carried out, providing the complex relationship among the FBGs wavelength shift and the applied magnetostatic field vector. Finally, the developed fiber optic sensors have been arranged in a sensor network composed of 20 triaxial sensors for mapping the magnetic field distribution in a MRI-room at a diagnostic center in Naples (SDN), equipped with Positron emission tomography/magnetic resonance (PET/MR) instrumentation. Experimental results reveal that the proposed sensor network can be efficiently used in MRI centers for performing quality assurance tests, paving the way for novel integrated tools to measure the magnetic dose accumulated day by day by MRI operators.
In this work, we report a straightforward and cost-effective fabrication route for the development of nano-patterned optical fiber tips. The technique is based on self-assembling polystyrene microspheres at the air/water interface and on their successive transferring on the fiber tip of single mode optical fiber. By applying to the fiber further treatments like particle size reduction, metal coating and sphere removal, different periodic structures have been conveniently realized. The morphological analysis reveals indeed the successful creation on the optical fiber tip of regular metallic-dielectric spheres’ arrays as well as metallic patterns with dimensional features down to a submicron scale. Finally, as proof of concept, we demonstrated the capability of the realized patterns to work as efficient Surface Enhanced Raman Spectroscopy (SERS) fiber probes.
In this work, we report a fabrication route for self-assembling periodic patterns on optical fiber tips. The technique is based on self-assembling polystyrene microspheres at the air/water interface and on successive transferring of the monolayer colloidal crystal on the fiber tip. By applying to the fiber further treatments like particle size reduction, metal coating and sphere removal, different periodic structures are conveniently realized. The results obtained indicate that self-assembly technique affords opportunity to create on the optical fiber tip dielectric and metallic-dielectric spheres’ arrays with a feature size down to a submicron scale or metallic patterns with a few hundred nanometers at low fabrication costs.
We present recent results on the fabrication of metallo-dielectric structures on the optical fiber tip by using a self-assembly technique. Our studies aim to attain advanced nanostructured sensors by exploiting easy and low cost fabrication processes suitable to be employed in massive production of technologically advanced devices in the roadmap of the Lab on Fiber Technology. The pursued approach basically consists in the preliminary preparation of a patterned polymeric film by the breath figure technique, directly on the optical fiber tip, and in the successive metal deposition by evaporation. The experimental results demonstrate the successful creation of a metallo-dielectric honeycomb pattern on the optical fiber tip. The experimental spectral features are in good agreement with the numerical analysis, elucidating the photonic and plasmonic interactions occurring in the Lab onto the optical fiber tip. The sensing properties of the optical fiber probes have been successfully explored in terms of sensitivity to the surrounding refractive index changes demonstrating their potentialities for chemical and biological sensing applications.
The “Lab on Fiber” technology has been recently proposed as a valuable route for the realization of novel and highly
functionalized technological platforms completely integrated in a single optical fiber in communication and sensing
applications. As a follow up of the proposed technological approach, here, we present recent results on the fabrication of metallo-dielectric structures on the optical fiber tip by using a self-assembly technique. Our studies aim to attain advanced nanostructured sensors by exploiting easy and low cost fabrication processes suitable to be employed in massive production of technologically advanced devices. The pursued approach basically consists in the preliminary preparation of a patterned polymeric film by the breath figure technique, directly on the optical fiber tip, and in the successive metal deposition by evaporation. The experimental results demonstrate the successful creation of a metallodielectric honeycomb pattern on the optical fiber tip. The experimental spectral features are in good agreement with the numerical analysis, elucidating the photonic and plasmonic interactions occurring in the Lab onto the optical fiber tip. The sensing properties of the optical fiber probes have been successfully explored in terms of sensitivity to the surrounding refractive index changes demonstrating their potentialities for chemical and biological sensing applications.
In this work, we report the preliminary results on the fabrication of metallo-dielectric nanostructures on the optical fiber
tip by using a simple and low cost self-assembly approach. The fabrication process relies on the breath figure technique
here adapted to operate on unconventional substrates as the case of single mode optical fibers. The experimental results
demonstrate the successful creation of a honeycomb pattern on the optical fiber tip and the feasibility of the proposed
approach in the roadmap of "Lab on fiber" technology development. Further work is currently running aimed to the
assessment the presented fabrication procedures in order to attain advanced optical fiber sensing probes with high
fabrication throughput by exploiting a low cost technology.
PART ONE:
The "Lab on Fiber" concept envisions novel and highly functionalized technological platforms completely
integrated in a single optical fiber that would allow the development of advanced devices, components and sub-systems
to be incorporated in modern optical systems for communication and sensing applications. The realization of integrated
optical fiber devices requires that several structures and materials at nano and micro scale are constructed, embedded and
connected all together to provide the necessary physical connections and light-matter interactions.
This paper reviews the strategies, the main achievements and related devices in the "Lab on Fiber" roadmap
discussing perspectives and challenges that lie ahead.
PART TWO:
After having reviewed, in the previous part, the main results achieved in the "Lab o Fiber" roadmap through the
development of several wavelength-scale devices and components based on the lab on fiber concept, here we focus the
attention on new trends involving innovative nano-fabrication strategies enabling to exploit further intriguing photonic
and/or plasmonic phenomena at the forefront of optical research.
Novel complex fabrication techniques of "Lab-on-fiber" device at the nanoscale are here presented and discussed,
from advanced multi material stacks and drawing technique up to the use of nanotechnologies, including standard
lithographic tools as well as new nano-imprinting approaches.
In particular, for the first time, we report some preliminary results obtained by our multidisciplinary research group
concerning the design and fabrication of a 2D hybrid metallo-dielectric photonic crystal (PC) nanostructure, directly
realized by innovatively applying the electron beam lithography technique on the cleaved end of standard single mode
optical fibers.
In this work, we report the first evidence of the resonant behavior of underwater acoustic sensors constituted by a Fiber
Bragg Grating (FBG) coated by a ring shaped overlay. The complex opto-acousto-mechanical interaction among an
incident acoustic wave travelling in water, the optical fiber surrounded by the ring shaped coating and the FBG inscribed
in an optical fiber is numerically analyzed by means of a commercial multiphysics software (COMSOLtm) implementing
the finite element method. The numerical analysis has been performed in the frequency range 0.5-30 kHz, typically used
in sonar applications. The retrieved numerical results, describing the opto-acoustic response of the optical hydrophone,
highlighted that the coating is able to notably improve the sensitivity of the hydrophone, in the whole investigated
frequency range, when compared to a FBG without coating. Furthermore, the hydrophone sensitivity versus the
frequency presents characteristic resonances, which strongly improve the hydrophone opto-acoustic sensitivity with
respect to the sensitivity background far from the resonances. As ascertained by means of a three-dimensional modal
analysis of the hydrophone, the composite cylindrical structure of the sensor acts as an acoustic resonator accorded to the
frequencies of the longitudinal vibration modes of the composite structure. In order to provide a full description of the
sensor performances, we carried out also a parametric analysis by varying the geometrical and mechanical properties of
the coating. The numerical results, besides outlining the resonant behavior of the coated FBG, also provided a tool for
the design and optimization of the sensor performances which in turn can be tailored for specific Sonar applications.
Here, we report on recent experimental results obtained with Fiber Bragg Grating (FBG) hydrophones for underwater
sound pressure detection. Investigated optical hydrophones consist of FBGs coated with ring shaped polymers of
different size. Coating material has been selected to provide mechanical amplification through a low elastic modulus
combined with acoustic impedance matching. Underwater acoustic measurements carried out in the range 4-35KHz
reveal a resonant behaviour depending on the coating size. This behaviour is consistent with numerical analysis
performed using finite element method and presented in part I. In addition, good linearity was observed versus local
sound pressure demonstrating a minimum detectable sound pressure of few Pascal.
A novel interrogation scheme for Tilted Fiber Bragg Gratings (TFBGs) sensors is here proposed based on single
wavelength time delay measurements. To this aim, the group delay of a weakly tilted TFBG has been characterized by
direct time domain measurement. The experimental characterization shows the capability of TFBGs to enable
superluminal and subluminal propagation of an optical pulse in optical fibers. The sharp group delay features of the
TFBGs are exploited for refractometric applications to detect the SRI variations by single wavelength time delay
measurements. The obtained preliminary results demonstrate the possibility to detect SRI changes by means of single
wavelength time delay measurements with a sensitivity enhanced in the range 1.33-1.40 with respect to previously
reported interrogation techniques.
We report on recent results obtained with a fiber optic hydrophone based on the intensity modulation of the laser light in
a FBG (Fiber Bragg Grating) under the influence of the sound pressure. In order to control the behavior of the
hydrophone in terms of sensitivity and bandwidth, FBGs have been coated with proper materials, characterized by
different elastic modulus and shapes. In particular, new experiments have been carried out using a cylindrical geometry
with two different coating, showing that the sensitivity is not influenced by the shape but by the transversal dimension
and the material characteristics of the coating.
In the last decade there has been an increasing interest for terahertz technology. The reasons of this increasing interest is
mainly due to its potential use in security applications with particular reference to drug and explosive detection. In this
framework, the appropriate integration of metamaterials with nanotechnologies looks very promising for the construction
of new compact low cost devices. Following this line of argument, we are exploring the possibility to combine the use of
nanocathodes as sources of electron beams with engineered metamaterial layers in order to deliver coherent tunable
terahertz radiation. More exactly, starting from a revised design of microwave sources, we discuss the issues related to
manufacture miniaturized planar devices taking advantage of some appropriate integration of post silicon technologies.
KEYWORDS: Sensors, Near field optics, Particles, Molecules, Optical fibers, Molecular interactions, Near field, Near field scanning optical microscopy, Biological and chemical sensing, Optical coatings
In this work, the surprising sensing performances of opto-chemical sensors based on SnO2 particles layers against
chemical pollutants either in air and water environment, at room temperature, are reported. The Electrostatic Spray
Pyrolysis (ESP) method has been used to deposit the sensing coatings upon the distal end of standard fibers. This
technique allows the fabrication of SnO2 layers composed of micron and sub-micron dimensions able to locally modify
the profile of the optical near-field collected in the close proximity of the fiber tip. Such layers morphology leads to
strong surface interactions between sensing coatings, analyte molecules and the evanescent contribute of the field,
resulting in an excellent sensors sensitivity against chemical pollutants, even at room temperature.
In this work, Hollow-core Optical Fibers (HOF) functionalized with Single Walled Carbon NanoTubes (SWCNTs) are
proposed for volatile organic compounds (VOCs) detection. The sensing probe is composed by a piece of HOF with a
termination coated and partially filled by SWCNTs. The infiltration of the SWCNTs inside the HOF holes has been
accomplished by means of the Langmuir-Blodgett technique. Reflectance and far field transmission characteristics have
been carried out within the HOF bandwidth. Finally the sensing capability of the proposed sensors has been investigated
by exposure in a proper designed test chamber to traces of toluene. The experimental results obtained demonstrate the
success of the SWCNTs partial filling within the HOF holes and the sensor capability to perform VOCs detection with a
good sensitivity and fast response times.
In this work, we report on the investigation of in-fiber photonic devices based on microstructured chirped fiber Bragg
gratings (CFBGs) for sensing applications. The basic device here analyzed consists in a CFBG with single or multiple
defects obtained by a deep and localized stripping of the cladding layer along the grating structure. The effect of each
local thinning along the grating length, properly exploited, basically enables the formation of one pass-band channel
within the pristine grating bandwidth and correspondently in one stop-band out of the pristine grating bandwidth. In
addition, due to spatial encoding in chirped gratings, each channel spectral position exclusively depends on the features
of its own defect (length, depth of the defect and surrounding refractive index) in a well defined location along the
grating. Thus, the spectral properties of each channel are not affected by defects located elsewhere along the grating
structure, enabling the possibility to develop independent multipoint sensors by exploiting a single grating device.
KEYWORDS: Near field, Sensors, Near field optics, Particles, Tin, Fiber optics sensors, Near field scanning optical microscopy, Optical fibers, Annealing, Metals
In the last decade a huge number of SnO2-based gas sensors have been proposed for environmental monitoring, automotive applications, air conditioning in houses, airplane and aircrafts. However, most of the proposed sensors work at very high temperatures in order to reach high sensitivities. Here, a SnO2-based optical fiber sensor is proposed for the room temperature detection of chemical pollutants in air. Particles layers composed by tin dioxide grains, with wavelength and subwavelength dimensions, resulted very promising because they are able to significantly modify the optical near field profile emerging from the film surface due to local enhancements of the evanescent wave contribute, and thus to improve the sensitivity to surface effects induced by the analyte interaction. The room temperature sensing performances of SnO2-based particles layers towards environmental pollutants have been investigated by the exposure to different concentrations of toluene and xylene vapors as well as gaseous ammonia. They have also been compared with the performances obtained with other optical fiber sensors in the same configuration, but coated with different sensitive materials, such as Single-Walled carbon nanotubes. The preliminary results obtained evidenced the surprising capability of the SnO2-based optical sensor to detect chemical pollutants at ppm level in air at room temperature. Finally, preliminary results on the effects of the processing parameters and post processing thermal annealing on film morphology and optical near field are presented.
In this work, we report on the integration of Hollow-core Optical Fibers (HOF) and Single Walled Carbon NanoTubes (SWCNTs) in order to obtain new functionalized devices by means of the modification of the photonic bandgap (PBG) characterizing the HOF itself. The samples were obtained by coating and partially filling by SWCNTs the termination of HOFs. The infiltration of SWCNTs inside the HOF holes has been accomplished by means of the Langmuir-Blodgett technique. Far field transmission characterizations have been carried out at 1550nm in order to study the influence of the carbon nanotubes within the HOF holes on the HOF PBG. Finally, in light of the sensing features of the SWCNTs, the realized samples have been employed as opto-chemical sensors for volatile organic compounds (VOCs) detection and their sensing capability has been proved by their exposure to VOCs traces. Experimental results demonstrate the success of the SWCNTs partial filling within the HOF holes, the influence of the deposition parameters on the HOF PBG and sensing performances as well as the sensor capability to perform VOCs detection with a good sensitivity and fast response times.
In this work an electrically tunable true time delay line (TTD), useful for phased array antennas, is experimentally demonstrated. The TTD line operates at a single optical wavelength and it is based on a linearly chirped fiber Bragg grating (LCFBG). Continuous TTD is achieved by changing the temperature of the LCFBG. In order to reduce the range of temperatures required for supply high time delay variations, the grating was bonded onto a metallic support and the effect of the thermal apparent strain was considered. The time delay response of the system has been measured with an optical signal modulated with Double Side Band technique at a frequency of 2GHz. The experimental results demonstrate a minimum time delay of 3.1ps employing a temperature controller with a stability of ±0.1°C and a maximum time delay of 96ps over a temperature range of 16-40°C. The time delay-temperature characteristic offers a slope of 3.8ps/°C with a mean deviation from the linearity of 3.5ps. Such a delay line, by operating at a single optical wavelength and by using a simple actuating system, offers many advantages being low cost, compact and reliable. The main limitation to the TTD resolution is the amplitude ripple of the LCFBG and a performance enhancement can be obtained with specifically tailored LCFBG.
In this work, the possibility to detect ppm ammonia concentrations in water environment, at room temperature, by means of Standard Optical Fibers (SOFs) sensors coated by Metal Oxides (MOXs) films has been demonstrated. Electro-spray pyrolisis technique has been used to deposit SnO2 films onto the distal end of single-mode optical fibers. This deposition technique allows the possibility to tailor the fabricated films properties by varying the deposition parameters, such as the metal chloride concentrations, the solution volume and the substrate temperature. The sensor operating principle relies on the measurement of the light intensity reflected by the fiber-sensitive layer interface: the pollutant molecules adsorption within the MOX film causes a change in its complex dielectric function and thus in the fiber-film reflectance. Spectral characterization of the obtained sensing probes has been carried out in the range 400-1750nm. Single wavelength reflectance measurements have been carried out to test the sensor performances for ppm ammonia detection. High sensitivity to the target analyte, response times of approximately 10-20 minutes and a Limit Of Detection as low as sub-ppm has been observed.
In this work, preliminary experimental results on the capability of a Metal Oxides (MOXs) based optical sensor to perform ammonia detection in water environments, at room temperature, are presented. Electro-spray pyrolisis technique has been used to deposit the SnO2 films on the distal end of standard Silica Optical Fibers (SOFs). Reflection spectra of the sensing probes have been measured in the range 1520-1620nm by using a tunable laser and an optical spectrum analyzer. Single wavelength reflectance measurements have been carried out to test the sensing performances for ammonia detection in the range 4-20 ppm. High sensitivity to the target analyte and fast response times have been observed. From the results obtained, a Limit Of Detection (LOD) as low as sub-ppm has been achieved.
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