Beatrice Fraboni | AICCON - Associazione Italiana per la Promozione della Cultura della Cooperazione e del Non Profit (original) (raw)
Papers by Beatrice Fraboni
Methylammonium lead tribromide (MAPbBr 3) perovskite single crystals demonstrate to be excellent ... more Methylammonium lead tribromide (MAPbBr 3) perovskite single crystals demonstrate to be excellent direct X-ray and gamma-ray detectors with outstanding sensitivity and low limit of detection. Despite this, thorough studies on the photophysical effects of exposure to high doses of ionizing radiation on this material are still lacking. In this work, we present our findings regarding the effects of controlled X-ray irradiation on the optoelectronic properties of MAPbBr 3 single crystals. Irradiation is carried out in air with an imaging X-ray tube, simulating real-life application in a medical facility. By means of surface photovoltage spectroscopy, we find that X-ray exposure quenches free excitons in the material and introduces new bound excitonic species. Despite this drastic effect, the crystals recover after 1 week of storage in dark and low humidity conditions. By means of X-ray photoelectron spectroscopy, we find that the origin of the new bound excitonic species is the formation of bromine vacancies, leading to local changes in the dielectric response of the material. The recovery effect is attributed to vacancy filling by atmospheric oxygen and water.
Advanced Electronic Materials
Electrochemistry Communications
Advanced Functional Materials
Scientific Reports
The development of wearable sensors, in particular fully-textile ones, is one of the most interes... more The development of wearable sensors, in particular fully-textile ones, is one of the most interesting open challenges in bioelectronics. Several and significant steps forward have been taken in the last decade in order to achieve a compact, lightweight, cost-effective, and easy to wear platform for healthcare and sport activities real-time monitoring. We have developed a fully textile, multi-thread biosensing platform that can detect different bioanalytes simultaneously without interference, and, as an example, we propose it for testing chloride ions (Cl−) concentration and pH level. The textile sensors are simple threads, based on natural and synthetic fibers, coated with the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) and properly functionalized with either a nano-composite material or a chemical sensitive dye to obtain Cl−and pH selective sensing functionality, respectively. The single-thread sensors show excellent sensitivity, reproduc...
Nature Energy
Bifacial monolithic perovskite/silicon tandem solar cells exploit albedo-the diffuse reflected li... more Bifacial monolithic perovskite/silicon tandem solar cells exploit albedo-the diffuse reflected light from the environment-to increase their performance above that of monofacial perovskite/silicon tandems. Here we report bifacial tandems with certified power conversion efficiencies >25% under monofacial AM1.5G 1 sun illumination that reach power-generation densities as high as ~26 mW cm-2 under outdoor testing. We investigated the perovskite bandgap required to attain optimized current matching under a variety of realistic illumination and albedo conditions. We then compared the properties of these bifacial tandems exposed to different albedos and provide energy yield calculations for two locations with different environmental conditions. Finally, we present a comparison of outdoor test fields of monofacial and bifacial perovskite/silicon tandems to demonstrate the added value of tandem bifaciality for locations with albedos of practical relevance.
APL Materials
Dissolved oxygen in cell culture media represents an interesting parameter worth monitoring, espe... more Dissolved oxygen in cell culture media represents an interesting parameter worth monitoring, especially at very low concentrations. Indeed, cells grow faster and live longer in hypoxic conditions, and recent studies relate stronger tumor malignancy, recurrence, and progression with reduced oxygen levels. Standard techniques for dissolved oxygen evaluation rely either on optical investigations or on electrochemical methods. The former requires complex protocols and expensive instrumentations, while for the latter, the presence of a silver/silver chloride electrode hinders the device miniaturization and induces cytotoxic effects. In this work, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (Pedot:Pss)-based Organic Electrochemical Transistors (OECTs) are presented as dissolved oxygen sensors. The catalytic activity of the Pedot chains is exploited for the transduction since oxygen reduction reactions, occurring at the polymer/electrolyte interface, induce Pedot:Pss to switch from the less conductive neutral state (off) to the more conductive oxidized one (on). This transient-doping effect enhances OECT current output, which presents a high signal to noise ratio (i.e., >10 2-10 3). The transistor architecture allows for high output/input signal power amplification (i.e., >15 dB-22 dB) and excellent sensitivities [328 ± 11 mV/dec and −0.38 ± 0.02 mA/dec for transfer and I ds (t), respectively], together with a low detection limit (0.9 μM, which represents the 0.07% of oxygen partial pressure). Finally, the here reported OECT sensors are demonstrated to work also in a real-life complex biological environment. This work paves the way for reliable, real-time oxygen monitoring in in vitro cell cultures for various relevant applications, such as investigating the influence of hypoxia conditions on cell lines or tumors.
Medical Physics
PURPOSE The development of novel detectors for dosimetry in advanced radiotherapy modalities requ... more PURPOSE The development of novel detectors for dosimetry in advanced radiotherapy modalities requires materials that have a water-equivalent response to ionizing radiation such that characterization of radiation beams can be performed without the need for complex calibration procedures and correction factors. Organic semiconductors are potentially an ideal technology in fabricating devices for dosimetry due to tissue-equivalence, mechanical flexibility and relatively cheap manufacturing cost. The response of a commercial organic photodetector (OPD), coupled to a plastic scintillator, to ionizing radiation from a linear accelerator and orthovoltage x-ray tube has been characterized to assess its potential as a dosimeter for radiotherapy. The radiation hardness of the OPD has also been investigated to demonstrate its longevity for such applications. METHODS Radiation hardness measurements were achieved by observing the response of the OPD to the visible spectrum and 70 keV x-rays after pre-exposure to 40 kGy of ionizing radiation. The response of a pre-irradiated OPD to 6 MV photons from a linear accelerator in reference conditions was compared to a non-irradiated OPD with respect to direct and indirect (RP400 plastic scintillator) detection mechanisms. Dose-rate dependence of the OPD was measured by varying the surface-to-source distance between 90 cm and 300 cm. Energy dependence was characterized from 29.5 keV to 129 keV with an x-ray tube. The percentage depth dose (PDD) curves were measured from 0.5 cm to 20 cm and compared to an ionization chamber. RESULTS The OPD sensitivity to visible light showed substantial degradation of the broad 450nm to 600 nm peak from the donor after irradiation to 40 kGy. After irradiation, the spectral shape has a dominant absorbance peak at 370 nm, as the acceptor better withstood radiation damage. Its response to x-rays stabilized to 30% after 35 kGy, with a 0.5% difference between 770 Gy increments. The OPD exhibited reproducible detection of ionizing radiation when coupled with a scintillator. Indirect detection showed a linear response from 25 cGy to 500 cGy and constant response to dose-rates from 0.31 Gy/pulse to 3.4 x10-4 Gy/pulse. However, without the scintillator, response increased by 100% at low dose rates. Energy independence between 100 keV and 1.2 MeV advocates their use as a dosimeter without beam correction factors. A dependence on the scintillator thickness used during a comparison of the PDD to the ionizing chamber was identified. A 1 mm thick scintillator coupled with the OPD demonstrated the best agreement of ±3%. CONCLUSIONS The response of OPDs to ionizing radiation has been characterized, showing promising use as a dosimeter when coupled with a plastic scintillator. The mechanisms of charge transport and trapping within organic materials varies for visible and ionizing radiation, due to differing properties for direct and indirect detection mechanisms and observing a substantial decrease of sensitivity to the visible spectrum after 40 kGy. This study proved that OPDs produce a stable response to 6 MV photons, and with a deeper understanding of the charge transport mechanisms due to exposure to ionizing radiation, they are promising candidates as the first flexible, water-equivalent, real-time dosimeter.
Frontiers in Physics
The aim of this study is to assess direct X-ray detectors based on organic thin films, fabricated... more The aim of this study is to assess direct X-ray detectors based on organic thin films, fabricated onto flexible plastic substrates, and operating at ultra-low bias (<1 V), for different medical applications. With this purpose, flexible fully organic pixelated X-ray detectors have been tested at the imaging beamline SYRMEP (SYnchrotron Radiation for MEdical Physics) at the Italian synchrotron Elettra, Trieste. The detectors' performance has been assessed for potential employment both as reliable wearable personal dosimeters for patients and as flexible X-ray medical imaging systems. A spatial resolution of 1.4 lp mm −1 with a contrast of 0.37 has been evaluated. Finally, we validate the detector using X-ray doses and energies typically employed for actual medical radiography, and using X-ray beam pulses provided by a commercial dental radiography system, recording a sensitivity of 1.6 × 10 5 µC Gy −1 cm −3 with a linear response with increasing of the dose rates and a reliable signal to 100 ms X-rays pulses.
Flexible and Printed Electronics
Stem cell osteogenic differentiation is a complex process, associated with a number of events suc... more Stem cell osteogenic differentiation is a complex process, associated with a number of events such as the secretion of collagen type I, osteopontin, osteonectin, osteocalcin and Bone Morphogenic Protein 2 (BMP-2). These molecules can be used as markers to monitor stem cell fate while studying the effects of a specific osteogenic differentiation treatment (e.g. electrical stimulation). Currently available techniques, such as the evaluation of the expression levels of specific genes and end-point biochemical assays, do not allow real-time monitoring of cellular processes, therefore overlooking potentially interesting information. This study explores a promising functionalization strategy towards on-line electrical monitoring of stem cell osteogenic differentiation process, using an organic electrochemical transistor (OECT) to detect cytokines of interest, secreted by cells during the osteogenic differentiation process, such as BMP-2. In this work, antibodies against BMP-2 were anchored on the poly(3,4-ethylenedioxythiophene):polystyrene (PEDOT:PSS) sulfonate gate electrode of an OECT. The biofunctionalization process was evaluated using multiple techniques such as Atomic Force Microscopy, Electrochemical Raman Spectroscopy, Quartz crystal microbalance. Electrode properties were assessed by running chronoamperometric studies, as well as by characterizing the PEDOT:PSS thin film resistance to ion flow by electrochemical impedance spectroscopy and OECT performance using transient (AC) measurements. Finally, a proof-of-concept, biosensor measurement was performed to test our functionalization strategy for sensing, proving that the antibody-functionalized OECTs were able to detect recombinant BMP-2 at levels that are comparable to those used for in vitro stimulation of bone regeneration via soluble osteoinductive factors.
Small
A comprehensive understanding of electrochemical and physical phenomena originating the response ... more A comprehensive understanding of electrochemical and physical phenomena originating the response of electrolyte-gated transistors is crucial for improved handling and design of these devices. However, the lack of suitable tools for direct investigation of microscale effects has hindered the possibility to bridge the gap between experiments and theoretical models. In this contribution, a scanning probe setup is used to explore the operation mechanisms of organic electrochemical transistors by probing the local electrochemical potential of the organic film composing the device channel. Moreover, an interpretative model is developed in order to highlight the meaning of electrochemical doping and to show how the experimental data can give direct access to fundamental device parameters, such as local charge carrier concentration and mobility. This approach is versatile and provides insight into the organic semiconductor/electrolyte interface and useful information for materials characterization, device scaling, and sensing optimization.
Sensors and Actuators B: Chemical
Abstract The development of portable and wearable sensors is of high importance in several fields... more Abstract The development of portable and wearable sensors is of high importance in several fields such as point-of-care medical applications and environmental monitoring. Here we design, synthesize and exploit a new composite material based on Ag/AgCl nanoparticles and PEDOT:PSS (poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate)) to fabricate a novel kind of sensor inspired by the organic electrochemical transistor (OECT). We are able to integrate an Ag/AgCl gate electrode into the semiconducting polymer in the form of NPs. As a consequence, our sensor combines an intrinsically amplified response with a simple two terminal electrical connection. Electrostatic Force Microscopy and Electrochemical Impedance Spectroscopy demonstrate the electronic coupling between the electrochemically active nanoparticles and the ionic charge gated semiconducting polymer, allowing to explain the sensor amplified transduction. The analytical signal is the current that flows in the composite polymer and its variation is directly proportional to the logarithm of Cl− concentration in the range 10−4 to 1 M, with a limit of detection of 0.5 10−4 M. Moreover, the device exhibits a shorter response time than the one of a conventional OECT endowed with an Ag/AgCl gate electrode. The sensor was used for in-situ detection of salinity in water and a textile device was obtained by depositing the composite material directly onto a cotton yarn for real-time sweat monitoring.
Advanced Materials Technologies
Advanced Materials Technologies
Science advances, 2018
Distributed x-ray radiation dosimetry is crucial in diverse security areas with significant envir... more Distributed x-ray radiation dosimetry is crucial in diverse security areas with significant environmental and human impacts such as nuclear waste management, radiotherapy, or radioprotection devices. We present a fast, real-time dosimetry detection system based on flexible oxide thin-film transistors that show a quantitative shift in threshold voltage of up to 3.4 V/gray upon exposure to ionizing radiation. The transistors use indium-gallium-zinc-oxide as a semiconductor and a multilayer dielectric based on silicon oxide and tantalum oxide. Our measurements demonstrate that the threshold voltage shift is caused by the accumulation of positive ionization charge in the dielectric layer due to high-energy photon absorption in the high- dielectric. The high mobility combined with a steep subthreshold slope of the transistor allows for fast, reliable, and ultralow-power readout of the deposited radiation dose. The order-of-magnitude variation in transistor channel impedance upon exposure...
Advanced Electronic Materials
A novel organic transistor-based sensor for direct X-ray detection is proposed. The device operat... more A novel organic transistor-based sensor for direct X-ray detection is proposed. The device operates at low voltages (≤3 V) and is entirely fabricated on flexible, plastic substrates with techniques that can be easily upscaled to an industrial scale. It is claimed that flexible, low voltage organic transistors have never been employed as direct ionizing radiation detectors, as two terminal photodetectors are typically considered for this application. It is demonstrated that, differently from two-terminal photodetectors, X-ray detection ability of the proposed sensor can be tuned acting on the transistor polarization conditions. Thanks to such a peculiar feature of the device, outstanding values of sensitivity are observed (up to 1200 nC Gy−1), much larger than the ones reported for two terminal direct organic photodetectors. It is notable that, the reported performances have been obtained using as sensing layer a standard, commercially available organic semiconductor: a complete explanation of the mechanism behind the detection ability is thoroughly discussed. The device functionality is perfectly maintained even after the exposure to high X-ray doses (160 Gy), thus demonstrating the significant radiation hardness of the detector.
ACS Applied Materials & Interfaces
Organic electronic devices fabricated on flexible substrates are promising candidates for applica... more Organic electronic devices fabricated on flexible substrates are promising candidates for applications in environments where flexible, lightweight, and radiation hard materials are required. In this work, device parameters such as threshold voltage, charge mobility, and trap density of 13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene)-based organic thin-film transistors (OTFTs) have been monitored for performing electrical measurements before and after irradiation by high-energy protons. The observed reduction of charge carrier mobility following irradiation can be only partially ascribed to the increased trap density. Indeed, we used other techniques to identify additional effects induced by proton irradiation in such devices. Atomic force microscopy reveals morphological defects occurring in the organic dielectric layer induced by the impinging protons, which, in turn, induce a strain on the TIPS-pentacene crystallites lying above. The effects of this strain are investigated by density functional theory simulations of two model structures, which describe the TIPS-pentacene crystalline films at equilibrium and under strain. The two different density of states distributions in the valence band have been correlated with the photocurrent spectra acquired before and after proton irradiation. We conclude that the degradation of the dielectric layer and the organic semiconductor sensitivity to strain are the two main phenomena responsible for the reduction of OTFT mobility after proton irradiation.
Methylammonium lead tribromide (MAPbBr 3) perovskite single crystals demonstrate to be excellent ... more Methylammonium lead tribromide (MAPbBr 3) perovskite single crystals demonstrate to be excellent direct X-ray and gamma-ray detectors with outstanding sensitivity and low limit of detection. Despite this, thorough studies on the photophysical effects of exposure to high doses of ionizing radiation on this material are still lacking. In this work, we present our findings regarding the effects of controlled X-ray irradiation on the optoelectronic properties of MAPbBr 3 single crystals. Irradiation is carried out in air with an imaging X-ray tube, simulating real-life application in a medical facility. By means of surface photovoltage spectroscopy, we find that X-ray exposure quenches free excitons in the material and introduces new bound excitonic species. Despite this drastic effect, the crystals recover after 1 week of storage in dark and low humidity conditions. By means of X-ray photoelectron spectroscopy, we find that the origin of the new bound excitonic species is the formation of bromine vacancies, leading to local changes in the dielectric response of the material. The recovery effect is attributed to vacancy filling by atmospheric oxygen and water.
Advanced Electronic Materials
Electrochemistry Communications
Advanced Functional Materials
Scientific Reports
The development of wearable sensors, in particular fully-textile ones, is one of the most interes... more The development of wearable sensors, in particular fully-textile ones, is one of the most interesting open challenges in bioelectronics. Several and significant steps forward have been taken in the last decade in order to achieve a compact, lightweight, cost-effective, and easy to wear platform for healthcare and sport activities real-time monitoring. We have developed a fully textile, multi-thread biosensing platform that can detect different bioanalytes simultaneously without interference, and, as an example, we propose it for testing chloride ions (Cl−) concentration and pH level. The textile sensors are simple threads, based on natural and synthetic fibers, coated with the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) and properly functionalized with either a nano-composite material or a chemical sensitive dye to obtain Cl−and pH selective sensing functionality, respectively. The single-thread sensors show excellent sensitivity, reproduc...
Nature Energy
Bifacial monolithic perovskite/silicon tandem solar cells exploit albedo-the diffuse reflected li... more Bifacial monolithic perovskite/silicon tandem solar cells exploit albedo-the diffuse reflected light from the environment-to increase their performance above that of monofacial perovskite/silicon tandems. Here we report bifacial tandems with certified power conversion efficiencies >25% under monofacial AM1.5G 1 sun illumination that reach power-generation densities as high as ~26 mW cm-2 under outdoor testing. We investigated the perovskite bandgap required to attain optimized current matching under a variety of realistic illumination and albedo conditions. We then compared the properties of these bifacial tandems exposed to different albedos and provide energy yield calculations for two locations with different environmental conditions. Finally, we present a comparison of outdoor test fields of monofacial and bifacial perovskite/silicon tandems to demonstrate the added value of tandem bifaciality for locations with albedos of practical relevance.
APL Materials
Dissolved oxygen in cell culture media represents an interesting parameter worth monitoring, espe... more Dissolved oxygen in cell culture media represents an interesting parameter worth monitoring, especially at very low concentrations. Indeed, cells grow faster and live longer in hypoxic conditions, and recent studies relate stronger tumor malignancy, recurrence, and progression with reduced oxygen levels. Standard techniques for dissolved oxygen evaluation rely either on optical investigations or on electrochemical methods. The former requires complex protocols and expensive instrumentations, while for the latter, the presence of a silver/silver chloride electrode hinders the device miniaturization and induces cytotoxic effects. In this work, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (Pedot:Pss)-based Organic Electrochemical Transistors (OECTs) are presented as dissolved oxygen sensors. The catalytic activity of the Pedot chains is exploited for the transduction since oxygen reduction reactions, occurring at the polymer/electrolyte interface, induce Pedot:Pss to switch from the less conductive neutral state (off) to the more conductive oxidized one (on). This transient-doping effect enhances OECT current output, which presents a high signal to noise ratio (i.e., >10 2-10 3). The transistor architecture allows for high output/input signal power amplification (i.e., >15 dB-22 dB) and excellent sensitivities [328 ± 11 mV/dec and −0.38 ± 0.02 mA/dec for transfer and I ds (t), respectively], together with a low detection limit (0.9 μM, which represents the 0.07% of oxygen partial pressure). Finally, the here reported OECT sensors are demonstrated to work also in a real-life complex biological environment. This work paves the way for reliable, real-time oxygen monitoring in in vitro cell cultures for various relevant applications, such as investigating the influence of hypoxia conditions on cell lines or tumors.
Medical Physics
PURPOSE The development of novel detectors for dosimetry in advanced radiotherapy modalities requ... more PURPOSE The development of novel detectors for dosimetry in advanced radiotherapy modalities requires materials that have a water-equivalent response to ionizing radiation such that characterization of radiation beams can be performed without the need for complex calibration procedures and correction factors. Organic semiconductors are potentially an ideal technology in fabricating devices for dosimetry due to tissue-equivalence, mechanical flexibility and relatively cheap manufacturing cost. The response of a commercial organic photodetector (OPD), coupled to a plastic scintillator, to ionizing radiation from a linear accelerator and orthovoltage x-ray tube has been characterized to assess its potential as a dosimeter for radiotherapy. The radiation hardness of the OPD has also been investigated to demonstrate its longevity for such applications. METHODS Radiation hardness measurements were achieved by observing the response of the OPD to the visible spectrum and 70 keV x-rays after pre-exposure to 40 kGy of ionizing radiation. The response of a pre-irradiated OPD to 6 MV photons from a linear accelerator in reference conditions was compared to a non-irradiated OPD with respect to direct and indirect (RP400 plastic scintillator) detection mechanisms. Dose-rate dependence of the OPD was measured by varying the surface-to-source distance between 90 cm and 300 cm. Energy dependence was characterized from 29.5 keV to 129 keV with an x-ray tube. The percentage depth dose (PDD) curves were measured from 0.5 cm to 20 cm and compared to an ionization chamber. RESULTS The OPD sensitivity to visible light showed substantial degradation of the broad 450nm to 600 nm peak from the donor after irradiation to 40 kGy. After irradiation, the spectral shape has a dominant absorbance peak at 370 nm, as the acceptor better withstood radiation damage. Its response to x-rays stabilized to 30% after 35 kGy, with a 0.5% difference between 770 Gy increments. The OPD exhibited reproducible detection of ionizing radiation when coupled with a scintillator. Indirect detection showed a linear response from 25 cGy to 500 cGy and constant response to dose-rates from 0.31 Gy/pulse to 3.4 x10-4 Gy/pulse. However, without the scintillator, response increased by 100% at low dose rates. Energy independence between 100 keV and 1.2 MeV advocates their use as a dosimeter without beam correction factors. A dependence on the scintillator thickness used during a comparison of the PDD to the ionizing chamber was identified. A 1 mm thick scintillator coupled with the OPD demonstrated the best agreement of ±3%. CONCLUSIONS The response of OPDs to ionizing radiation has been characterized, showing promising use as a dosimeter when coupled with a plastic scintillator. The mechanisms of charge transport and trapping within organic materials varies for visible and ionizing radiation, due to differing properties for direct and indirect detection mechanisms and observing a substantial decrease of sensitivity to the visible spectrum after 40 kGy. This study proved that OPDs produce a stable response to 6 MV photons, and with a deeper understanding of the charge transport mechanisms due to exposure to ionizing radiation, they are promising candidates as the first flexible, water-equivalent, real-time dosimeter.
Frontiers in Physics
The aim of this study is to assess direct X-ray detectors based on organic thin films, fabricated... more The aim of this study is to assess direct X-ray detectors based on organic thin films, fabricated onto flexible plastic substrates, and operating at ultra-low bias (<1 V), for different medical applications. With this purpose, flexible fully organic pixelated X-ray detectors have been tested at the imaging beamline SYRMEP (SYnchrotron Radiation for MEdical Physics) at the Italian synchrotron Elettra, Trieste. The detectors' performance has been assessed for potential employment both as reliable wearable personal dosimeters for patients and as flexible X-ray medical imaging systems. A spatial resolution of 1.4 lp mm −1 with a contrast of 0.37 has been evaluated. Finally, we validate the detector using X-ray doses and energies typically employed for actual medical radiography, and using X-ray beam pulses provided by a commercial dental radiography system, recording a sensitivity of 1.6 × 10 5 µC Gy −1 cm −3 with a linear response with increasing of the dose rates and a reliable signal to 100 ms X-rays pulses.
Flexible and Printed Electronics
Stem cell osteogenic differentiation is a complex process, associated with a number of events suc... more Stem cell osteogenic differentiation is a complex process, associated with a number of events such as the secretion of collagen type I, osteopontin, osteonectin, osteocalcin and Bone Morphogenic Protein 2 (BMP-2). These molecules can be used as markers to monitor stem cell fate while studying the effects of a specific osteogenic differentiation treatment (e.g. electrical stimulation). Currently available techniques, such as the evaluation of the expression levels of specific genes and end-point biochemical assays, do not allow real-time monitoring of cellular processes, therefore overlooking potentially interesting information. This study explores a promising functionalization strategy towards on-line electrical monitoring of stem cell osteogenic differentiation process, using an organic electrochemical transistor (OECT) to detect cytokines of interest, secreted by cells during the osteogenic differentiation process, such as BMP-2. In this work, antibodies against BMP-2 were anchored on the poly(3,4-ethylenedioxythiophene):polystyrene (PEDOT:PSS) sulfonate gate electrode of an OECT. The biofunctionalization process was evaluated using multiple techniques such as Atomic Force Microscopy, Electrochemical Raman Spectroscopy, Quartz crystal microbalance. Electrode properties were assessed by running chronoamperometric studies, as well as by characterizing the PEDOT:PSS thin film resistance to ion flow by electrochemical impedance spectroscopy and OECT performance using transient (AC) measurements. Finally, a proof-of-concept, biosensor measurement was performed to test our functionalization strategy for sensing, proving that the antibody-functionalized OECTs were able to detect recombinant BMP-2 at levels that are comparable to those used for in vitro stimulation of bone regeneration via soluble osteoinductive factors.
Small
A comprehensive understanding of electrochemical and physical phenomena originating the response ... more A comprehensive understanding of electrochemical and physical phenomena originating the response of electrolyte-gated transistors is crucial for improved handling and design of these devices. However, the lack of suitable tools for direct investigation of microscale effects has hindered the possibility to bridge the gap between experiments and theoretical models. In this contribution, a scanning probe setup is used to explore the operation mechanisms of organic electrochemical transistors by probing the local electrochemical potential of the organic film composing the device channel. Moreover, an interpretative model is developed in order to highlight the meaning of electrochemical doping and to show how the experimental data can give direct access to fundamental device parameters, such as local charge carrier concentration and mobility. This approach is versatile and provides insight into the organic semiconductor/electrolyte interface and useful information for materials characterization, device scaling, and sensing optimization.
Sensors and Actuators B: Chemical
Abstract The development of portable and wearable sensors is of high importance in several fields... more Abstract The development of portable and wearable sensors is of high importance in several fields such as point-of-care medical applications and environmental monitoring. Here we design, synthesize and exploit a new composite material based on Ag/AgCl nanoparticles and PEDOT:PSS (poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate)) to fabricate a novel kind of sensor inspired by the organic electrochemical transistor (OECT). We are able to integrate an Ag/AgCl gate electrode into the semiconducting polymer in the form of NPs. As a consequence, our sensor combines an intrinsically amplified response with a simple two terminal electrical connection. Electrostatic Force Microscopy and Electrochemical Impedance Spectroscopy demonstrate the electronic coupling between the electrochemically active nanoparticles and the ionic charge gated semiconducting polymer, allowing to explain the sensor amplified transduction. The analytical signal is the current that flows in the composite polymer and its variation is directly proportional to the logarithm of Cl− concentration in the range 10−4 to 1 M, with a limit of detection of 0.5 10−4 M. Moreover, the device exhibits a shorter response time than the one of a conventional OECT endowed with an Ag/AgCl gate electrode. The sensor was used for in-situ detection of salinity in water and a textile device was obtained by depositing the composite material directly onto a cotton yarn for real-time sweat monitoring.
Advanced Materials Technologies
Advanced Materials Technologies
Science advances, 2018
Distributed x-ray radiation dosimetry is crucial in diverse security areas with significant envir... more Distributed x-ray radiation dosimetry is crucial in diverse security areas with significant environmental and human impacts such as nuclear waste management, radiotherapy, or radioprotection devices. We present a fast, real-time dosimetry detection system based on flexible oxide thin-film transistors that show a quantitative shift in threshold voltage of up to 3.4 V/gray upon exposure to ionizing radiation. The transistors use indium-gallium-zinc-oxide as a semiconductor and a multilayer dielectric based on silicon oxide and tantalum oxide. Our measurements demonstrate that the threshold voltage shift is caused by the accumulation of positive ionization charge in the dielectric layer due to high-energy photon absorption in the high- dielectric. The high mobility combined with a steep subthreshold slope of the transistor allows for fast, reliable, and ultralow-power readout of the deposited radiation dose. The order-of-magnitude variation in transistor channel impedance upon exposure...
Advanced Electronic Materials
A novel organic transistor-based sensor for direct X-ray detection is proposed. The device operat... more A novel organic transistor-based sensor for direct X-ray detection is proposed. The device operates at low voltages (≤3 V) and is entirely fabricated on flexible, plastic substrates with techniques that can be easily upscaled to an industrial scale. It is claimed that flexible, low voltage organic transistors have never been employed as direct ionizing radiation detectors, as two terminal photodetectors are typically considered for this application. It is demonstrated that, differently from two-terminal photodetectors, X-ray detection ability of the proposed sensor can be tuned acting on the transistor polarization conditions. Thanks to such a peculiar feature of the device, outstanding values of sensitivity are observed (up to 1200 nC Gy−1), much larger than the ones reported for two terminal direct organic photodetectors. It is notable that, the reported performances have been obtained using as sensing layer a standard, commercially available organic semiconductor: a complete explanation of the mechanism behind the detection ability is thoroughly discussed. The device functionality is perfectly maintained even after the exposure to high X-ray doses (160 Gy), thus demonstrating the significant radiation hardness of the detector.
ACS Applied Materials & Interfaces
Organic electronic devices fabricated on flexible substrates are promising candidates for applica... more Organic electronic devices fabricated on flexible substrates are promising candidates for applications in environments where flexible, lightweight, and radiation hard materials are required. In this work, device parameters such as threshold voltage, charge mobility, and trap density of 13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene)-based organic thin-film transistors (OTFTs) have been monitored for performing electrical measurements before and after irradiation by high-energy protons. The observed reduction of charge carrier mobility following irradiation can be only partially ascribed to the increased trap density. Indeed, we used other techniques to identify additional effects induced by proton irradiation in such devices. Atomic force microscopy reveals morphological defects occurring in the organic dielectric layer induced by the impinging protons, which, in turn, induce a strain on the TIPS-pentacene crystallites lying above. The effects of this strain are investigated by density functional theory simulations of two model structures, which describe the TIPS-pentacene crystalline films at equilibrium and under strain. The two different density of states distributions in the valence band have been correlated with the photocurrent spectra acquired before and after proton irradiation. We conclude that the degradation of the dielectric layer and the organic semiconductor sensitivity to strain are the two main phenomena responsible for the reduction of OTFT mobility after proton irradiation.