Vera La Ferrara | ENEA, Italian National Agency for New Technologies, Energy and Sustainable Economic Development (original) (raw)

Papers by Vera La Ferrara

Fibers

The combination of responsive microgels and Lab-on-Fiber devices represents a valuable technologi... more The combination of responsive microgels and Lab-on-Fiber devices represents a valuable technological tool for developing advanced optrodes, especially useful for biomedical applications. Recently, we have reported on a fabrication method, based on the dip coating technique, for creating a microgels monolayer in a controlled fashion onto the fiber tip. In the wake of these results, with a view towards industrial applications, here we carefully analyze, by means of both morphological and optical characterizations, the effect of each fabrication step (fiber dipping, rinsing, and drying) on the microgels film properties. Interestingly, we demonstrate that it is possible to significantly reduce the duration (from 960 min to 31 min) and the complexity of the fabrication procedure, without compromising the quality of the microgels film at all. Repeatability studies are carried out to confirm the validity of the optimized deposition procedure. Moreover, the new procedure is successfully app...

Sensors

Integrating multi-responsive polymers such as microgels onto optical fiber tips, in a controlled ... more Integrating multi-responsive polymers such as microgels onto optical fiber tips, in a controlled fashion, enables unprecedented functionalities to Lab-on-fiber optrodes. The creation of a uniform microgel monolayer with a specific coverage factor is crucial for enhancing the probes responsivity to a pre-defined target parameter. Here we report a reliable fabrication strategy, based on the dip coating technique, for the controlled realization of microgel monolayer onto unconventional substrates, such as the optical fiber tip. The latter was previously covered by a plasmonic nanostructure to make it sensitive to superficial environment changes. Microgels have been prepared using specific Poly(N-isopropylacrylamide)-based monomers that enable bulky size changes in response to both temperature and pH variations. The formation of the microgel monolayer is efficiently controlled through the selection of suitable operating pH, temperature and concentration of particle dispersions used during the dipping procedure. The effect of each parameter has been evaluated, and the validity of our procedure is confirmed by means of both morphological and optical characterizations. We demonstrate that when the coverage factor exceeds 90%, the probe responsivity to microgels swelling/collapsing is significantly improved. Our study opens new paradigms for the development of engineered microgels assisted Lab-on-Fiber probes for biochemical applications.

Light: Science & Applications

We report on the first demonstration of a proof-of-principle optical fiber 'meta-tip&... more We report on the first demonstration of a proof-of-principle optical fiber 'meta-tip', which integrates a phase-gradient plasmonic metasurface on the fiber tip. For illustration and validation purposes, we present numerical and experimental results pertaining to various prototypes implementing generalized forms of the Snell's transmission/reflection laws at near-infrared wavelengths. In particular, we demonstrate several examples of beam steering and coupling with surface waves, in fairly good agreement with theory. Our results constitute a first step toward the integration of unprecedented (metasurface-enabled) light-manipulation capabilities in optical-fiber technology. By further enriching the emergent 'lab-on-fiber' framework, this may pave the way for the widespread diffusion of optical metasurfaces in real-world applications to communications, signal processing, imaging and sensing.

Materials Research Express

Environmental Science and Pollution Research, 2017

The wide use of ZnO nanoparticles in a number of products implies an increasing release into the ... more The wide use of ZnO nanoparticles in a number of products implies an increasing release into the marine environment, resulting in the need to evaluate the potential effects upon organisms, and particularly phytoplankton, being at the base of the throphic chain. To this aim, dose-response curves for the green alga Tetraselmis suecica and the diatom Phaeodactylum tricornutum derived from the exposure to nano ZnO (100 nm) were evaluated and compared with those obtained for bulk ZnO (200 nm) and ionic zinc. The toxic effects to both algae species were reported as no observable effect concentration (NOEC) of growth inhibition and as 1, 10, and 50% effect concentrations (EC1, EC10, and EC50). The toxicity decreased in the order nano ZnO > Zn(2+) > bulk ZnO. EC50 values for nano ZnO were 3.91 [3.66-4.14] mg Zn/L towards the green microalgae and 1.09 [0.96-1.57] mg Zn/L towards the diatom, indicating a higher sensitivity of P. tricornutum. The observed diverse effects can be ascribed to the interaction occurring between different algae and ZnO particles. Due to algae motility, ZnO particles were intercepted in different phases of aggregation and sedimentation processes, while algae morphology and size can influence the level of entrapment by NP aggregates.This underlines the need to take into account the peculiarity of the biological system in the assessment of NP toxicity.

Asia Pacific Optical Sensors Conference, 2016

Journal of Non Crystalline Solids, Jun 1, 2004

In this work we present an investigation of the electrical behavior of an innovative gas sensor b... more In this work we present an investigation of the electrical behavior of an innovative gas sensor based on a heterojunction between porous silicon and hydrogenated amorphous silicon. P-type porous silicon, usually obtained by an electrochemical etching of monocrystalline silicon substrate, can be used as active layer in sensors because of its high surface to volume ratio and high reactivity. A thin layer of n-type amorphous silicon, deposited by plasma enhanced chemical vapor deposition technique on the nanoporous phase structure, still maintains photoluminescence properties as well as gas sensitivity and effective recovery after gas exposure. We found higher sensitivity at higher reverse bias conditions. A detailed investigation of this phenomenon, for different gas concentrations, is presented.

In this paper we present an innovative diode based on the heterojunction between amorphous silico... more In this paper we present an innovative diode based on the heterojunction between amorphous silicon and porous silicon grown on crystalline silicon. The device architecture gives several advantages. Deposition of amorphous silicon on porous material realises high performance junction at temperature less than 250°C and it passives the porous layer against the natural oxidation due to ageing in the environment. Porous technology allows to obtain a controlled textured silicon surface independently from crystalline silicon orientation just to give the opportunity to reduce surface reflectivity and the blue shift of the absorption spectra in solar cell application. Solar cells were characterised by I-V dark/light and quantum yield measurements. Under standard AM 1.5 light we obtained photovoltaic conversion efficiency greater than 10%. Change in photoluminescence in different gas environments showed for gas sensor applications give rise encouraging results. In dark condition we found the typical diode behaviour.

J Porous Mat, 2000

ABSTRACT In this paper we report the sensitivity of porous silicon photoluminescence (PL) to dilu... more ABSTRACT In this paper we report the sensitivity of porous silicon photoluminescence (PL) to diluted mixtures of methane and carbon monoxide in synthetic air. We also investigate the separate effect of synthetic air, purified nitrogen and relative humidity on both photoluminescence and conductance (G). Porous silicon samples have been prepared from n-type silicon substrates. We find that PL intensity and G decrease in synthetic air with respect to their values in N(2). Presence of carbon monoxide reduces the PL intensity while methane provokes the opposite behaviour. The dependence of the PL spectra on methane and carbon monoxide concentrations has been investigated. The observed effects can be related to gas induced modifications in porous surface and suggest that porous silicon can be employed in gas sensor technology.

Physica Status Solidi, 2000

In this work we studied the compatibility of amorphous thin film technology with the porous silic... more In this work we studied the compatibility of amorphous thin film technology with the porous silicon in case of large area applications like gas sensors. We found that thin amorphous silicon layer growth on porous silicon substrates preserves the room temperature photoluminescence of porous material. Also amorphous±porous silicon heterojunction shows a good rectifying behaviour. Those properties, correlated with the porous silicon sensitivity to the gas environments, can be effectively used to realise heterojunction diodes whose current voltage characteristics are modified by the gas reactivity on the porous surface. Sensitivity of those devices and response time to different gas exposure have been investigated.

Lecture Notes in Electrical Engineering, 2009

In this work, we present a novel architecture for nanodevice manufacturing, combining an electroc... more In this work, we present a novel architecture for nanodevice manufacturing, combining an electrochemical process, such as dielectrophoresis, with focused ion beam apparatus. This approach simplifies the growth–pattern fabrication and simultaneously demonstrate the possibility to produce single nanowires of different materials with fully controlled dimensions, position, alignment and electrical contacting. Focused Ion Beam is used to deposit platinum microelectrodes on silicon/silicon nitride substrate. Dielectrophoresis is employed for assembling the single nanowire and precisely positioning it between the nanocontacts. Single nanowire based devices are tested as chemical sensors confirming the reliability of this innovative technology.

CH 3 NH 3 PbI 3 layers have been prepared by two-step procedure (spin coating and dipping) on fla... more CH 3 NH 3 PbI 3 layers have been prepared by two-step procedure (spin coating and dipping) on flat substrates under open-air conditions and high relative humidity. The films have been characterized by means of scanning electron microscopy, absorption coefficient and x-ray diffraction when varying spinning rate, washing procedure and dipping time. In particular a novel washing procedure has been developed to improve the film uniformity. Hole transport material free solar cells have been realized on flat substrates. The devices have been characterized by measuring the current density-voltage J(V) characteristics under AM1.5g illumination and the external quantum efficiency (EQE). Preliminary results are discussed.

Un ni iv ve er rs si it tá á d di i B Br re es sc ci ia a, , I It ta aly Editors for North Americ... more Un ni iv ve er rs si it tá á d di i B Br re es sc ci ia a, , I It ta aly Editors for North America Datskos, Panos G., O Oa ak k R Ri id dg ge e N Na at ti io on na al l L La ab bo or ra at to or ry y, , U US

Il Nuovo Cimento D, 1996

In this paper we report on the frequency dependence of the AC conductivity of porous silicon in t... more In this paper we report on the frequency dependence of the AC conductivity of porous silicon in the range 10 Hz-100 kHz. Two types of testing devices have been fabricated on three different series of samples formed electrochemically using as a starting material p-type, n-type and n +-type silicon substrates. For frequencies less than 20-40 kHz the conductivity is found to follow a sublinear frequency dependence. This behaviour is typical of a carrier transport mechanism determined by an anomalous diffusion process. At higher frequencies we find that surface states influence the transport mechanism. This suggests a double-channel transport mechanism: one related to porous-silicon ,~volume, properties and the other more connected to the ,~surface-itself.

Lecture Notes in Nanoscale Science and Technology, 2013

Fibers

The combination of responsive microgels and Lab-on-Fiber devices represents a valuable technologi... more The combination of responsive microgels and Lab-on-Fiber devices represents a valuable technological tool for developing advanced optrodes, especially useful for biomedical applications. Recently, we have reported on a fabrication method, based on the dip coating technique, for creating a microgels monolayer in a controlled fashion onto the fiber tip. In the wake of these results, with a view towards industrial applications, here we carefully analyze, by means of both morphological and optical characterizations, the effect of each fabrication step (fiber dipping, rinsing, and drying) on the microgels film properties. Interestingly, we demonstrate that it is possible to significantly reduce the duration (from 960 min to 31 min) and the complexity of the fabrication procedure, without compromising the quality of the microgels film at all. Repeatability studies are carried out to confirm the validity of the optimized deposition procedure. Moreover, the new procedure is successfully app...

Sensors

Integrating multi-responsive polymers such as microgels onto optical fiber tips, in a controlled ... more Integrating multi-responsive polymers such as microgels onto optical fiber tips, in a controlled fashion, enables unprecedented functionalities to Lab-on-fiber optrodes. The creation of a uniform microgel monolayer with a specific coverage factor is crucial for enhancing the probes responsivity to a pre-defined target parameter. Here we report a reliable fabrication strategy, based on the dip coating technique, for the controlled realization of microgel monolayer onto unconventional substrates, such as the optical fiber tip. The latter was previously covered by a plasmonic nanostructure to make it sensitive to superficial environment changes. Microgels have been prepared using specific Poly(N-isopropylacrylamide)-based monomers that enable bulky size changes in response to both temperature and pH variations. The formation of the microgel monolayer is efficiently controlled through the selection of suitable operating pH, temperature and concentration of particle dispersions used during the dipping procedure. The effect of each parameter has been evaluated, and the validity of our procedure is confirmed by means of both morphological and optical characterizations. We demonstrate that when the coverage factor exceeds 90%, the probe responsivity to microgels swelling/collapsing is significantly improved. Our study opens new paradigms for the development of engineered microgels assisted Lab-on-Fiber probes for biochemical applications.

Light: Science & Applications

We report on the first demonstration of a proof-of-principle optical fiber 'meta-tip&... more We report on the first demonstration of a proof-of-principle optical fiber 'meta-tip', which integrates a phase-gradient plasmonic metasurface on the fiber tip. For illustration and validation purposes, we present numerical and experimental results pertaining to various prototypes implementing generalized forms of the Snell's transmission/reflection laws at near-infrared wavelengths. In particular, we demonstrate several examples of beam steering and coupling with surface waves, in fairly good agreement with theory. Our results constitute a first step toward the integration of unprecedented (metasurface-enabled) light-manipulation capabilities in optical-fiber technology. By further enriching the emergent 'lab-on-fiber' framework, this may pave the way for the widespread diffusion of optical metasurfaces in real-world applications to communications, signal processing, imaging and sensing.

Materials Research Express

Environmental Science and Pollution Research, 2017

The wide use of ZnO nanoparticles in a number of products implies an increasing release into the ... more The wide use of ZnO nanoparticles in a number of products implies an increasing release into the marine environment, resulting in the need to evaluate the potential effects upon organisms, and particularly phytoplankton, being at the base of the throphic chain. To this aim, dose-response curves for the green alga Tetraselmis suecica and the diatom Phaeodactylum tricornutum derived from the exposure to nano ZnO (100 nm) were evaluated and compared with those obtained for bulk ZnO (200 nm) and ionic zinc. The toxic effects to both algae species were reported as no observable effect concentration (NOEC) of growth inhibition and as 1, 10, and 50% effect concentrations (EC1, EC10, and EC50). The toxicity decreased in the order nano ZnO > Zn(2+) > bulk ZnO. EC50 values for nano ZnO were 3.91 [3.66-4.14] mg Zn/L towards the green microalgae and 1.09 [0.96-1.57] mg Zn/L towards the diatom, indicating a higher sensitivity of P. tricornutum. The observed diverse effects can be ascribed to the interaction occurring between different algae and ZnO particles. Due to algae motility, ZnO particles were intercepted in different phases of aggregation and sedimentation processes, while algae morphology and size can influence the level of entrapment by NP aggregates.This underlines the need to take into account the peculiarity of the biological system in the assessment of NP toxicity.

Asia Pacific Optical Sensors Conference, 2016

Journal of Non Crystalline Solids, Jun 1, 2004

In this work we present an investigation of the electrical behavior of an innovative gas sensor b... more In this work we present an investigation of the electrical behavior of an innovative gas sensor based on a heterojunction between porous silicon and hydrogenated amorphous silicon. P-type porous silicon, usually obtained by an electrochemical etching of monocrystalline silicon substrate, can be used as active layer in sensors because of its high surface to volume ratio and high reactivity. A thin layer of n-type amorphous silicon, deposited by plasma enhanced chemical vapor deposition technique on the nanoporous phase structure, still maintains photoluminescence properties as well as gas sensitivity and effective recovery after gas exposure. We found higher sensitivity at higher reverse bias conditions. A detailed investigation of this phenomenon, for different gas concentrations, is presented.

In this paper we present an innovative diode based on the heterojunction between amorphous silico... more In this paper we present an innovative diode based on the heterojunction between amorphous silicon and porous silicon grown on crystalline silicon. The device architecture gives several advantages. Deposition of amorphous silicon on porous material realises high performance junction at temperature less than 250°C and it passives the porous layer against the natural oxidation due to ageing in the environment. Porous technology allows to obtain a controlled textured silicon surface independently from crystalline silicon orientation just to give the opportunity to reduce surface reflectivity and the blue shift of the absorption spectra in solar cell application. Solar cells were characterised by I-V dark/light and quantum yield measurements. Under standard AM 1.5 light we obtained photovoltaic conversion efficiency greater than 10%. Change in photoluminescence in different gas environments showed for gas sensor applications give rise encouraging results. In dark condition we found the typical diode behaviour.

J Porous Mat, 2000

ABSTRACT In this paper we report the sensitivity of porous silicon photoluminescence (PL) to dilu... more ABSTRACT In this paper we report the sensitivity of porous silicon photoluminescence (PL) to diluted mixtures of methane and carbon monoxide in synthetic air. We also investigate the separate effect of synthetic air, purified nitrogen and relative humidity on both photoluminescence and conductance (G). Porous silicon samples have been prepared from n-type silicon substrates. We find that PL intensity and G decrease in synthetic air with respect to their values in N(2). Presence of carbon monoxide reduces the PL intensity while methane provokes the opposite behaviour. The dependence of the PL spectra on methane and carbon monoxide concentrations has been investigated. The observed effects can be related to gas induced modifications in porous surface and suggest that porous silicon can be employed in gas sensor technology.

Physica Status Solidi, 2000

In this work we studied the compatibility of amorphous thin film technology with the porous silic... more In this work we studied the compatibility of amorphous thin film technology with the porous silicon in case of large area applications like gas sensors. We found that thin amorphous silicon layer growth on porous silicon substrates preserves the room temperature photoluminescence of porous material. Also amorphous±porous silicon heterojunction shows a good rectifying behaviour. Those properties, correlated with the porous silicon sensitivity to the gas environments, can be effectively used to realise heterojunction diodes whose current voltage characteristics are modified by the gas reactivity on the porous surface. Sensitivity of those devices and response time to different gas exposure have been investigated.

Lecture Notes in Electrical Engineering, 2009

In this work, we present a novel architecture for nanodevice manufacturing, combining an electroc... more In this work, we present a novel architecture for nanodevice manufacturing, combining an electrochemical process, such as dielectrophoresis, with focused ion beam apparatus. This approach simplifies the growth–pattern fabrication and simultaneously demonstrate the possibility to produce single nanowires of different materials with fully controlled dimensions, position, alignment and electrical contacting. Focused Ion Beam is used to deposit platinum microelectrodes on silicon/silicon nitride substrate. Dielectrophoresis is employed for assembling the single nanowire and precisely positioning it between the nanocontacts. Single nanowire based devices are tested as chemical sensors confirming the reliability of this innovative technology.

CH 3 NH 3 PbI 3 layers have been prepared by two-step procedure (spin coating and dipping) on fla... more CH 3 NH 3 PbI 3 layers have been prepared by two-step procedure (spin coating and dipping) on flat substrates under open-air conditions and high relative humidity. The films have been characterized by means of scanning electron microscopy, absorption coefficient and x-ray diffraction when varying spinning rate, washing procedure and dipping time. In particular a novel washing procedure has been developed to improve the film uniformity. Hole transport material free solar cells have been realized on flat substrates. The devices have been characterized by measuring the current density-voltage J(V) characteristics under AM1.5g illumination and the external quantum efficiency (EQE). Preliminary results are discussed.

Un ni iv ve er rs si it tá á d di i B Br re es sc ci ia a, , I It ta aly Editors for North Americ... more Un ni iv ve er rs si it tá á d di i B Br re es sc ci ia a, , I It ta aly Editors for North America Datskos, Panos G., O Oa ak k R Ri id dg ge e N Na at ti io on na al l L La ab bo or ra at to or ry y, , U US

Il Nuovo Cimento D, 1996

In this paper we report on the frequency dependence of the AC conductivity of porous silicon in t... more In this paper we report on the frequency dependence of the AC conductivity of porous silicon in the range 10 Hz-100 kHz. Two types of testing devices have been fabricated on three different series of samples formed electrochemically using as a starting material p-type, n-type and n +-type silicon substrates. For frequencies less than 20-40 kHz the conductivity is found to follow a sublinear frequency dependence. This behaviour is typical of a carrier transport mechanism determined by an anomalous diffusion process. At higher frequencies we find that surface states influence the transport mechanism. This suggests a double-channel transport mechanism: one related to porous-silicon ,~volume, properties and the other more connected to the ,~surface-itself.

Lecture Notes in Nanoscale Science and Technology, 2013