1. |
- Ali Malik, Muhammad, et al.
(author)
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Imaging fingerprinting of excitation emission matrices
- 2009
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In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 635:2, s. 196-201
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Journal article (peer-reviewed)abstract
- The spectral fingerprinting of the excitation emission matrix (EEM) of fluorescent substances is demonstrated using polychromatic light sources and tri-chromatic image detectors. A model of the measured fingerprints explaining their features and classification performance, based on the polychromatic excitation of the indicators is proposed.Substantial amount of spectral information is retained in the fingerprints as corroborated by multivariate analysis and experimental conditions that favor such situation are identified.In average, for five different substances, the model shows a fitting goodness measured by the Pearsons r coefficient and the root mean square deviation of 0.8541 and 0.0247 respectively, while principal component classification patterns satisfactorily compare with the EEM spectroscopy classification and respectively explain 96% and 93% of the information in the fist two principal components.The measurements can be performed using regular computer screens as illumination and web cameras as detectors, which constitute ubiquitous and affordable platforms compatible with distributed evaluations, in contrast to regular instrumentation for EEM measurements.
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2. |
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3. |
- Alimelli, Adriano, et al.
(author)
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Fish freshness detection by a computer screen photoassisted based gas sensor array
- 2007
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In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 582:2, s. 320-328
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Journal article (peer-reviewed)abstract
- In the last years a large number of different measurement methodologies were applied to measure the freshness of fishes. Among them the connection between freshness and headspace composition has been considered by gas chromatographic analysis and from the last two decades by a number of sensors and biosensors aimed at measuring some characteristic indicators (usually amines). More recently also the so-called artificial olfaction systems gathering together many non-specific sensors have shown a certain capability to transduce the global composition of the fish headspace capturing the differences between fresh and spoiled products. One of the main objectives related to the introduction of sensor systems with respect to the analytical methods is the claimed possibility to distribute the freshness control since sensors are expected to be "portable" and "simple". In spite of these objectives, until now sensor systems did not result in any tool that may be broadly distributed. In this paper, we present a chemical sensor array where the optical features of layers of chemicals, sensitive to volatile compounds typical of spoilage processes in fish, are interrogated by a very simple platform based on a computer screen and a web cam. An array of metalloporphyrins is here used to classify fillets of thawed fishes according to their storage days and to monitor the spoilage in filleted anchovies for a time of 8 h. Results indicate a complete identification of the storage days of thawed fillets and a determination of the storage time of anchovies held at room temperature with a root mean square error of validation of about 30 min. The optical system produces a sort of spectral fingerprint containing information about both the absorbance and the emission of the sensitive layer. The system here illustrated, based on computer peripherals, can be easily scaled to any device endowed with a programmable screen and a camera such as cellular phones offering for the first time the possibility to fulfil the sensor expectation of diffused and efficient analytical capabilities. © 2006 Elsevier B.V. All rights reserved.
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4. |
- Bazzicalupi, Carla, et al.
(author)
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Multimodal Use of New Coumarin-Based Fluorescent Chemosensors: Towards Highly Selective Optical Sensors for Hg2+ Probing
- 2013
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In: Chemistry - A European Journal. - : Wiley-VCH Verlag. - 0947-6539 .- 1521-3765. ; 19:43, s. 14639-14653
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Journal article (peer-reviewed)abstract
- Despite several types of fluorescent sensing molecules have been proposed and examined to signal Hg2+ ion binding, the development of fluorescence-based devices for in-field Hg2+ detection and screening in environmental and industrial samples is still a challenging task. Herein, we report the synthesis and characterization of three new coumarin-based fluorescent chemosensors featuring mixed thia/aza macrocyclic framework as receptors units, that is, ligands L1-L3. These probes revealed an OFF-ON selective response to the presence of Hg2+ ions in MeCN/H2O 4:1 (v/v), which allowed imaging of this metal ion in Cos-7 cells in vitro. Once included in silica core-polyethylene glycol (PEG) shell nanoparticles or supported on polyvinyl chloride (PVC)-based polymeric membranes, ligands L1-L3 can also selectively sense Hg2+ ions in pure water. In particular we have developed an optical sensing array tacking advantage of the fluorescent properties of ligand L3 and based on the computer screen photo assisted technique (CSPT). In the device ligand L3 is dispersed into PVC membranes and it quantitatively responds to Hg2+ ions in natural water samples.
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5. |
- Di Natale, Corrado, et al.
(author)
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Evaluation of the performance of sensors based on optical imaging of a chemically sensitive layer
- 2010
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In: ANALYTICAL AND BIOANALYTICAL CHEMISTRY. - : Springer Science Business Media. - 1618-2642 .- 1618-2650. ; 397:2, s. 613-621
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Journal article (peer-reviewed)abstract
- Interest in the use of the optical properties of chemical indicators is growing steadily. Among the optical methods that can be used to capture changes in sensing layers, those producing images of large-area devices are particularly interesting for chemical sensor array development. Until now, few studies addressed the characterization of image sensors from the point of view of their chemical sensor application. In this paper, a method to evaluate such performance is proposed. It is based on the simultaneous measurement of absorption events in a metalloporphyrin layer with an image sensor and a quartz microbalance (QMB). Exploiting the well-known behaviour of QMB, comparison of signals enables estimation of the minimum amount of absorbed molecules that the image sensor can detect. Results indicate that at the single pixel level a standard image sensor (for example a webcam) can easily detect femtomoles of absorbed molecules. It should therefore be possible to design sensor arrays in which the pixels of images of large-area sensing layers are regarded as individual chemical sensors providing a ready and simple method for large sensor array development.
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6. |
- Di Natale, Corrado, et al.
(author)
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Investigation of quartz microbalance and ChemFET transduction of molecular recognition events in a metalloporphyrin film
- 2009
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In: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005. ; 135:2, s. 560-567
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Journal article (peer-reviewed)abstract
- Progresses of synthetic chemistry methodologies have allowed the preparation of a great variety of artificial receptors that are particularly appealing for chemical sensor development. In this paper, we investigate and compare the properties of gas sensors based on two types of devices, quartz microbalances (QMBs) and field effect transistors (FETs), which give the means to exploit the molecular recognition events occurring in non-conductive sensing layers formed by a thiol-modified cobalt tetraphenylporphyrin (CoTPPSH). Since QMB is sensitive to mass and FET is sensitive to electric dipoles, the resulting sensors are expected to exhibit different sensitivities and selectivities, although both based on the same sensing layer. In particular we show that the high sensitivity of CoTPPSH-coated FETs towards CO and NO is a consequence of the significant CoTPPSH electric dipole change after the gas coordination to the metal centre.
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7. |
- Di Natale, Corrado, et al.
(author)
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Investigation of the selectivity properties of metalloporphyrines self-assembled-monolayers on QMB and FET transducers
- 2006
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In: Proc Eurosensors XX.
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Conference paper (peer-reviewed)abstract
- Progresses of synthetic chemistry methodologies have allowed the preparation of a great variety of artificial receptors that are particularly appealing for chemical sensor development. In this paper, we investigate and compare the properties of gas sensors based on two types of devices, quartz microbalances (QMBs) and field effect transistors (FETs), which give the means to exploit the molecular recognition events occurring in non-conductive sensing layers formed by a thiol-modified cobalt tetraphenylporphyrin (CoTPPSH). Since QMB is sensitive to mass and FET is sensitive to electric dipoles, the resulting sensors are expected to exhibit different sensitivities and selectivities, although both based on the same sensing layer. In particular we show that the high sensitivity of CoTPPSH-coated FETs towards CO and NO is a consequence of the significant CoTPPSH electric dipole change after the gas coordination to the metal centre.
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8. |
- Di Natale, Corrado, et al.
(author)
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Multi-transduction of molecular recognition events in metalloporphyrin layers
- 2009
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In: Journal of Porphyrins and Phthalocyanines. - 1088-4246 .- 1099-1409. ; 13:11, s. 1123-1128
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Journal article (peer-reviewed)abstract
- Besides the design and synthesis of appropriate molecular recognition systems, the development of chemical sensors requires a careful selection of the transducer to allow conversion of the chemical interaction into an exploitable electric signal. Metalloporphyrins, which are characterized by manifold of interactions of different strength and selectivity, provide a good example of the complexity of such an issue. In this paper, an example of the different ways to capture interactions occurring in a metalloporphyrin layer is presented. In particular, the properties of mass ( quartz microbalance) and surface potential transducers (field effect transistor) are illustrated. Results suggest that field effect transistors are more suitable to preserve the interactions magnitude scale than to maintain the original selectivity of the molecular recognition system.
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9. |
- Dini, Francesca, et al.
(author)
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Chemical sensitivity of self-assembled porphyrin nano-aggregates
- 2009
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In: NANOTECHNOLOGY. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 20:5, s. 055502-
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Journal article (peer-reviewed)abstract
- Nanostructured molecular assemblies may provide additional sensing properties not found in other arrangements of the same basic constituents. Among three-dimensional structures, nanotubes are particularly appealing for applications as chemical sensors, because of the potential inclusion of different guests inside the cavity or the induced modification of the skeletal interaction after analyte binding. Porphyrins are a class of compounds characterized by brilliant sensing properties, appearing also in non-ordered solid-state aggregates. In recent years, it was reported that aggregation of oppositely charged porphyrins led to the formation of self-assembled nanotubes and in this paper their sensing properties, both in solution and in the solid state, have been investigated. The interactions of porphyrin nanotubes with guest molecules have been monitored by following the changes in their UV-vis spectra. The results obtained have been exploited to build up a sensing platform based on a computer screen as a light source and a digital camera as detector. Porphyrin nanostructures exhibited an enhanced sensitivity to different compounds with respect to those shown by single porphyrin subunits. The reason for the increased sensitivity may be likely found in an additional sensing mechanism related to the modulation of the strength of the forces that keep the supramolecular ensemble together.
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10. |
- Dini, Francesca, et al.
(author)
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Combining porphyrins and pH indicators for analyte detection
- 2015
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In: Analytical and Bioanalytical Chemistry. - : Springer. - 1618-2642 .- 1618-2650. ; 407:14, s. 3975-3984
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Journal article (peer-reviewed)abstract
- High sensitivity and cross-selectivity are mandatory properties for sensor arrays. Although metalloporphyrins and pH indicators are among the most common and appropriate choices for the preparation of optical sensor arrays, the sensitivity spectrum of these dyes is limited to those analytes able to induce an optical response. To extend the receptive field of optical sensors, we explore the design of composite materials, where the molecular interaction among the subunits enriches their sensing working mechanisms. We demonstrate that blends of single metalloporphyrins and pH indicators, tested with a transduction apparatus based on ubiquitous and easily available hardware, can be endowed with sensing properties wider than those of single constituents, enabling the recognition of a broad range of volatiles.
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11. |
- Dini, Francesca, et al.
(author)
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Computer screen assisted digital photography
- 2013
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In: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 179:SI, s. 46-53
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Journal article (peer-reviewed)abstract
- The computer screen photo-assisted techniques (CSPT) have been developed during the last 10 years through an extensive collaboration between University of Rome "Tor Vergata" and Linkoping University in Sweden. CSPT has thus evolved into a concept we now call computer screen assisted digital photography, yielding detailed information about the interaction between color indicators and (volatile) analytes. In the present paper, we give a brief summary of the CSPT concept and its connection to digital photography. We concentrate, however, on the most recent results, which were obtained by using most of the degrees of freedom offered by a computer screen as a light source and a digital (web) camera as a detector. Thus, we describe in detail recent experiments on cotton yarns impregnated with color indicators for volatile organic molecules. The interaction between the color indicators and molecules, like trimethylamine, was investigated by CSPT in high dynamic imaging together with a background noise limiting algorithm. It is shown that the simultaneous use of the last two additions to the CSPT concept considerably enhances the chemical sensing ability of CSPT. It is concluded that the collaboration between Rome and Linkoping has generated a useful platform for further developments of chemical analysis with a ubiquitous instrumentation, a (computer) screen and a web camera. This technique is aimed at facilitating the assembly of opto-chemical sensors with evident benefits in the reduction of cost of sensor systems and in an increased integrability with the existent telecommunication infrastructures.
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12. |
- Dini, Francesca, et al.
(author)
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Data processing for image-based chemical sensors: unsupervised region of interest selection and background noise compensation
- 2012
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In: Analytical and Bioanalytical Chemistry. - : Springer Verlag (Germany). - 1618-2642 .- 1618-2650. ; 402:2, s. 823-832
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Journal article (peer-reviewed)abstract
- Natural olfaction suggests that numerous replicas of small sensors can achieve large sensitivity. This concept of sensor redundancy can be exploited by use of optical chemical sensors whose use of image sensors enables the simultaneous measurement of several spatially distributed indicators. Digital image sensors split the framed scene into hundreds of thousands of pixels each corresponding to a portion of the sensing layer. The signal from each pixel can be regarded as an independent sensor, which leads to a highly redundant sensor array. Such redundancy can eventually be exploited to increase the signal-to-noise ratio. In this paper we report an algorithm for reduction of the noise of pixel signals. For this purpose, the algorithm processes the output of groups of pixels whose signals share the same time behavior, as is the case for signals related to the same indicator. To define these groups of pixels, unsupervised clustering, based on classification of the indicator colors, is proposed here. This approach to signal processing is tested in experiments on the chemical sensitivity of replicas of eight indicators spotted on to a plastic substrate. Results show that the groups of pixels can be defined independently of the geometrical arrangement of the sensing spots, and substantial improvement of the signal-to-noise ratio is obtained, enabling the detection of volatile compounds at any location on the distributed sensing layer.
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13. |
- Dini, Francesca, et al.
(author)
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Polymer matrices effects on the sensitivity and the selectivity of optical chemical sensors
- 2011
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In: SENSORS AND ACTUATORS B-CHEMICAL. - : Elsevier Science B.V., Amsterdam.. - 0925-4005. ; 154:2, s. 220-225
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Journal article (peer-reviewed)abstract
- Polymers are commonly used in optical chemical sensors as inert supports for indicator dyes keeping the molecules apart to allow for exposure to analytes and to maintain the peculiar optical properties of the sensitive dyes. However, the partitioning properties of polymers may play a significant role in determining the sensitivity of the sensors. Herewith, the properties of a single dye blended with different polymers have been studied through optical absorbance changes elicited by the exposure to organic vapors. Results show that the partitioning properties of polymers modulate the response of the dye and confer a combinatorial selectivity to the system, allowing for the recognition of vapors.
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14. |
- Dini, Francesca, et al.
(author)
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Polymers with embedded chemical indicators as an artificial olfactory mucosa
- 2010
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In: ANALYST. - : Royal Society of Chemistry. - 0003-2654. ; 135:6, s. 1245-1252
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Journal article (peer-reviewed)abstract
- Physiological investigations suggest that the olfactory mucosa probably plays an ancillary role in the recognition of odours introducing a sort of chromatographic separation that, together with the zonal distribution of olfactory receptors, gives place to selective spatio-temporal response patterns. It has been recently suggested that this behaviour may be simulated by chemical sensors embedded in continuous polymer layers. In this paper, in analogy to the biology of olfaction, a simple and compact platform able to separate and detect gases and vapours on the basis of their diffusion properties is proposed. In such a system, broadly selective colour indicators, such as metalloporphyrins, are embedded in continuous layers of polymers with different sorption properties. The exposure to various alcohols and amines shows that the porphyrins are mainly responsible for the recognition of the molecular family, while the occurring spatio-temporal signal patterns make possible the identification of the individual chemical species.
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15. |
- Dini, Francesca, et al.
(author)
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Volatile Emissions from Compressed Tissue
- 2013
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In: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 8:7
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Journal article (peer-reviewed)abstract
- Since almost every fifth patient treated in hospital care develops pressure ulcers, early identification of risk is important. A non-invasive method for the elucidation of endogenous biomarkers related to pressure ulcers could be an excellent tool for this purpose. We therefore found it of interest to determine if there is a difference in the emissions of volatiles from compressed and uncompressed tissue. The ultimate goal is to find a non-invasive method to obtain an early warning for the risk of developing pressure ulcers for bed-ridden persons. Chemical analysis of the emissions, collected in compresses, was made with gas-chromatography – mass spectrometry and with a chemical sensor array, the so called electronic nose. It was found that the emissions from healthy and hospitalized persons differed significantly irrespective of the site. Within each group there was a clear difference between the compressed and uncompressed site. Peaks that could be certainly deemed as markers of the compression were, however, not identified. Nonetheless, different compounds connected to the application of local mechanical pressure were found. The results obtained with GC-MS reveal the complexity of VOC composition, thus an array of non-selective chemical sensors seems to be a suitable choice for the analysis of skin emission from compressed tissues; it may represent a practical instrument for bed side diagnostics. Results show that the adopted electronic noses are likely sensitive to the total amount of the emission rather than to its composition. The development of a gas sensor-based device requires then the design of sensor receptors adequate to detect the VOCs bouquet typical of pressure. This preliminary experiment evidences the necessity of studies where each given person is followed for a long time in a ward in order to detect the insurgence of specific VOCs pattern changes signalling the occurrence of ulcers.
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16. |
- Filippini, Daniel, 1968-, et al.
(author)
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Chemical Sensing with Familiar Devices
- 2006
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In: Angewandte Chemie : : a journal of the Gesellschaft Deutscher Chemiker.. International edition. - : Wiley. ; 45:23, s. 3800-3803
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Journal article (peer-reviewed)
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17. |
- Filippini, Daniel, et al.
(author)
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Spectral fingerprinting of porphyrins for distributed chemical sensing
- 2009
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In: JOURNAL OF PORPHYRINS AND PHTHALOCYANINES. - 1088-4246. ; 13:1, s. 77-83
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Journal article (peer-reviewed)abstract
- Recent progress in spectral fingerprinting of fluorescent indicators using distributed instrumentation based on consumer electronic devices is reviewed. In particular, the evaluation of disposable assays using a computer screen photo-assisted technique (CSPT) is discussed. Sample identification and optimization strategies are analyzed as well as the underlying theoretical background for polychromatic spectral fingerprinting.
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18. |
- Guanais Goncalves, Carla, et al.
(author)
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Detection of diverse potential threats in water with an array of optical sensors
- 2016
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In: Sensors and actuators. B, Chemical. - : ELSEVIER SCIENCE SA. - 0925-4005 .- 1873-3077. ; 236, s. 997-1004
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Journal article (peer-reviewed)abstract
- Optical sensor arrays are widely used for sensing the evolution and the identification of complex patterns of chemicals either in air or in water. This popularity stems from the fact that low-cost, ready-to-use optical devices, made available by the current commercial development of electronics commodities, are complemented by a number of low-cost chemical indicators, suitable for a wide range of applications. Among them, pH indicators, and metalloporphyrins make a solid library of molecules that can be adequately assembled for many different tasks. Here, such an array is used for the identification of toxic compounds of different origin that may be released in water distribution systems as a consequence of either accidents or deliberated contaminations. The compounds considered are intermediate products of chemical industry (dimethyl methylphosphonate and cyclohexanone), drugs (5-Fluorouracil and piperazine) and pesticides (imidacloprid and paraoxon). Results show that the sensors are sensitive, but with low selectivity, in the interval from 10(-7) mol L-1 to 10(-4) mol L-1. The sensor signals show a linear correlation with the logarithm of the concentration. Although the limited selectivity of individual sensors, the different sensitivity patterns allow for a clear identification of the compounds, independent of their concentration.(C) 2016 Elsevier B.V. All rights reserved.
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19. |
- Lvova, Larisa, et al.
(author)
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A Ferrocene-Porphyrin Ligand for Multi-Transduction Chemical Sensor Development
- 2013
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In: Sensors. - : MDPI. - 1424-8220. ; 13:5, s. 5841-5856
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Journal article (peer-reviewed)abstract
- 5,10,15,20-Tetraferrocenyl porphyrin, H2TFcP, a simple example of a donor-acceptor system, was tested as ligand for the development of a novel multi-transduction chemical sensors aimed at the determination of transition metal ions. The fluorescence energy transfer between ferrocene donor and porphyrin acceptor sub-units was considered. The simultaneously measured optical and potentiometric responses of solvent polymeric membranes based on H2TFcP permitted the detection of lead ions in sample solutions, in the concentration range from 2.7 × 10−7 to 3.0 × 10−3 M. The detection limit of lead determination was 0.27 μM, low enough to perform the direct analysis of Pb2+ in natural waters.
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20. |
- Lvova, Larisa, et al.
(author)
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Multi-transduction sensing films for Electronic Tongue applications
- 2015
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In: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 207, s. 1076-1086
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Journal article (peer-reviewed)abstract
- In this paper the use of multi-transduction principle for sensing materials development is reviewed. In particular, the application of porphyrin-based films to a multi-transduction Electronic Tongue system for different analytical tasks is presented. The optical response of sensing films was registered by means of Computer Screen Photoassisted Technology (CSPT) that applies familiar devices, such as computer monitor screen and web-camera, as illumination light source and signal detectors. Simultaneously the electrochemical amperometric or potentiometric response of the same sensing material was measured. Data analysis combining both signals significantly improves the performance of the Electronic Tongue, thus opening new frontiers in application of such a system.
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21. |
- Lvova, Larisa, et al.
(author)
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Towards Hyphenated Sensors Development: Design and Application of Porphyrin Electropolymer Materials
- 2012
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In: Electroanalysis. - : Wiley-VCH Verlag Berlin. - 1040-0397 .- 1521-4109. ; 24:4, s. 776-789
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Journal article (peer-reviewed)abstract
- The peculiar properties of porphyrins allow their exploitation as sensing materials in chemical sensors having different transduction principles, or even the intriguing possibility to develop sensors where two different transduction mechanisms are hyphenated in the same substrate. This approach can allow a significant increase in the chemical information obtained from the device and it can boost the performances in terms of selectivity and sensitivity. Our recent achievements in the field of functionalized porphyrins application for the development of the hyphenated optoelectrochemical sensors will be discussed in this contribution.
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22. |
- Macken, Stephen, et al.
(author)
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Towards integrated devices for computer screen photo-assisted multi-parameter sensing
- 2009
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In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 632:1, s. 143-147
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Journal article (peer-reviewed)abstract
- The computer screen photo-assisted technique (CSPT) utilizes consumer electronic devices such as computer screens and web cameras for distributed chemical sensing. Key to this method is the development of small and disposable sensing assays able to aid the CSPT optical detection, and the evaluation of multiple indicators. Here we demonstrate CSPT identification of fluorescent indicators from individual 100 mu m SU-8 (10) pillars covering an area of 4 mm x 4 mm with a density of 47 elements mm-2. The extraction of distinctive spectral fingerprints is aided by the exploitation of a three-band Moire interference that enables the partial Bayer decoding of the CSPT images.
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23. |
- Tortora, Luca, et al.
(author)
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The hyphenated CSPT-potentiometric analytical system : An application for vegetable oil quality control
- 2009
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In: SENSORS AND ACTUATORS B-CHEMICAL. - : Elsevier BV. - 0925-4005. ; 142:2, s. 457-463
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Journal article (peer-reviewed)abstract
- The computer screen photo assisted technique (CSPT) has been used to develop a hyphenated optical-potentiometric sensing at-ray, based on porphyrinoid materials dispersed into PVC membranes. Sensing layers have been deposited onto indium tin oxide (ITO) glass slides, which were exploited as electrodes, for potentiometric measurements, and chromophore spots, to obtain CSPT data. Both measurements were contemporaneously carried out in the hyphenated sensing platform. The performances of the hyphenated sensing array were first tested for the detection of model analytes, characteristics of vegetable oil matrices, and then evaluated in the discrimination of real samples of olive and seed oils. The results obtained demonstrated that the hyphenated system affords a significant improvement of information and oils classification with respect to the individual potentiometric and optical components.
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