| 1. |
- Di Natale, Corrado, et al.
(författare)
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Investigation of quartz microbalance and ChemFET transduction of molecular recognition events in a metalloporphyrin film
- 2009
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005. ; 135:2, s. 560-567
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Dini, Francesca, et al.
(författare)
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Chemical sensitivity of self-assembled porphyrin nano-aggregates
- 2009
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Ingår i: NANOTECHNOLOGY. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 20:5, s. 055502-
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Dini, Francesca, et al.
(författare)
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Combining porphyrins and pH indicators for analyte detection
- 2015
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer. - 1618-2642 .- 1618-2650. ; 407:14, s. 3975-3984
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Dini, Francesca, et al.
(författare)
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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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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Verlag (Germany). - 1618-2642 .- 1618-2650. ; 402:2, s. 823-832
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Tidskriftsartikel (refereegranskat)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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| 5. |
- Dini, Francesca, et al.
(författare)
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Polymer matrices effects on the sensitivity and the selectivity of optical chemical sensors
- 2011
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Ingår i: SENSORS AND ACTUATORS B-CHEMICAL. - : Elsevier Science B.V., Amsterdam.. - 0925-4005. ; 154:2, s. 220-225
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Guanais Goncalves, Carla, et al.
(författare)
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Detection of diverse potential threats in water with an array of optical sensors
- 2016
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Ingår i: Sensors and actuators. B, Chemical. - : ELSEVIER SCIENCE SA. - 0925-4005 .- 1873-3077. ; 236, s. 997-1004
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Tidskriftsartikel (refereegranskat)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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| 7. |
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| 8. |
- Martinelli, L., et al.
(författare)
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Collective Nature of Orbital Excitations in Layered Cuprates in the Absence of Apical Oxygens
- 2024
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 132:6
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the 3d orbital excitations in CaCuO2 (CCO), Nd2CuO4 (NCO), and La2CuO4 (LCO) using high-resolution resonant inelastic x-ray scattering. In LCO they behave as well-localized excitations, similarly to several other cuprates. On the contrary, in CCO and NCO the dxy orbital clearly disperses, pointing to a collective character of this excitation (orbiton) in compounds without apical oxygen. We ascribe the origin of the dispersion as stemming from a substantial next-nearest-neighbor (NNN) orbital superexchange. Such an exchange leads to the liberation of the orbiton from its coupling to magnons, which is associated with the orbiton hopping between nearest neighbor copper sites. Finally, we show that the exceptionally large NNN orbital superexchange can be traced back to the absence of apical oxygens suppressing the charge transfer energy.
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