Giuseppe Maruccio - Academia.edu (original) (raw)
Papers by Giuseppe Maruccio
Materials Science and Engineering: C, 2017
Authors aimed to provide a magnetic responsiveness to bone-mimicking nano-hydroxyapatite (n-HA). ... more Authors aimed to provide a magnetic responsiveness to bone-mimicking nano-hydroxyapatite (n-HA). For this purpose, dextran-grafted iron oxide nanoarchitectures (DM) were synthesized by a green friendly and scalable alkaline co-precipitation method at room temperature and used to functionalize n-HA crystals. Different amounts of DM hybrid structures were added into the nanocomposites (DM/n-HA 1:1, 2:1 and 3:1weight ratio) which were investigated through extensive physicochemical (XRD, ICP, TGA and Zetapotential), microstructural (TEM and DLS), magnetic (VSM) and biological analyses (MTT proliferation assay). X-ray diffraction patterns have confirmed the n-HA formation in the presence of DM as a co-reagent. Furthermore, the addition of DM during the synthesis does not affect the primary crystallite domains of DM/n-HA nanocomposites. DM/n-HAs have shown a rising of the magnetic moment values by increasing DM content up to 2:1 ratio. However, the magnetic moment value recorded in the DM/n-HA 3:1 do not further increases showing a saturation behavior. The cytocompatibility of the DM/n-HA was evaluated with respect to the MG63 osteoblast-like cell line. Proliferation assays revealed that viability, carried out in the absence of external magnetic field, was not affected by the amount of DM employed. Interestingly, assays also suggested that the DM/n-HA nanocomposites exhibit a possible shielding effect with respect to the antiproliferative activity induced by the DM particles alone.
Materials Research Express, 2015
ABSTRACT Increasing the ease and the rapidity of processing in micro and nanotechnology is an ong... more ABSTRACT Increasing the ease and the rapidity of processing in micro and nanotechnology is an ongoing task, which is pursued in both the academic environment for investigation of novel systems and in industry for fabrication of complex circuits on a large scale. In the field of nanoelectronics, the major challenge is to demonstrate a feasible method for device implementation based on individual nanosize objects, such as nanowires, nanotubes and nanocrystals. However, integrating these small objects in a macroscopic circuit is a difficult task. So far, nanostructures have been wired by highly sophisticated techniques not suitable for large-scale integration in macroscopic circuits, such as electron-beam lithography or focused ion-beam deposition. Here we present a 'one-pot' and rapid approach to electrically interconnect individual nanowires from random spatial distribution, with high spatial and positioning resolution and a remarkable reduction in overall fabrication time with respect to the other expensive and laborious techniques. The reliability of such technique is demonstrated by implementing a single semiconductor nanowire device
Nanostructure Science and Technology, 2009
Page 1. 5 Nanoelectronic Devices Based on Proteins Giuseppe Maruccio and Alessandro Bramanti 1 PR... more Page 1. 5 Nanoelectronic Devices Based on Proteins Giuseppe Maruccio and Alessandro Bramanti 1 PROTEINS IN NANOELECTRONICS Acquiring the capability of handling and assembling structures at the molecular scale ...
Nanofabrication, 2011
of Chemistry). 2.2 Top-down processes The top-down approach in building integrated circuits (ICs)... more of Chemistry). 2.2 Top-down processes The top-down approach in building integrated circuits (ICs) usually involves some form of lithography to define the required pattern of features. Many other kinds of processes are required to build an IC, such as ion-implantation, metal evaporation and etching, which are used in several nanoscale devices too; however, here we will concentrate on the problems of lithography, since that is the side of technology directly related to resolution and, consequently, most innovative (and troublesome) in nanodevices. According to a common distinction, we will classify lithographic methods into hard and soft, where the former (often referred to simply as "lithography") are the improved version of those already employed for present ICs, whereas the latter have been purposely developed for nanoscale fabrication (in particular when dealing with fragile molecules). 2.2.1 (Hard) lithography By 'hard lithography' we mean all those techniques using resist layers and optical masks, derived from standard photolithography. The core-idea is to expose a sensitive material (the 'resist') to an activating agent (light or a particle beam) in order to harden (or soften) it in targeted areas. Subsequently, a developer solution will wash away the soft parts of the resist layer selectively, while the remaining hard parts mask the sample for subsequent processing (see the schematic in Figure 2a). Commonly, either the material is etched where unmasked by the layer (and the remaining resist is taken away after the etching); or a new layer of material is grown (e.g. metal by evaporation) so that it builds up upon the patterned resist, where this is present, or upon the underlying material in the resist's voids; finally, the hardened resist will be removed, carrying away the material grown atop (lift-off) and leaving the material inside the patterned voids untouched.
Small, 2007
Molecular electronics [1] is aimed at demonstrating suitable alternatives to silicon-based nanoel... more Molecular electronics [1] is aimed at demonstrating suitable alternatives to silicon-based nanoelectronics for building complex and functional devices. One of the end goals is to use single molecules as active elements in electronic nanodevices, whereas the main challenges are the interconnection of the molecules and the fabrication of electrical contacts to the outside. In recent years, proteins have attracted much interest as active materials because of their electrontransfer (ET) capabilities (crucial for a number of vital processes such as photosynthesis, respiration, and energy conversion). These pivotal reactions usually take place inside a single protein (intramolecular ET) or between two or a few proteins (intermolecular ET). Therefore, it is crucial to develop reliable methods to interconnect and probe transport in single/few proteins in order to investigate the basic mechanisms underlying ET. This kind of information is not directly accessible by conventional techniques such as spectroscopic and electrochemical methods, which provide average figures over statistical ensembles. Up to now, such studies could only be performed by means of scanning probe methods (SPMs), [2-4] but never in device geometry, due to severe difficulties in the fabrication of devices with single molecules as active components. The physical limitations of optical lithography have prompted the development of alternative, top-down techniques for patterning below the 100-nm scale, but in most cases these do not match the advantages of photolithography in its low cost and high throughput (with the notable exception of nanoimprint lithography [5]). Most of these alternative methods (including mechanical break junctions, electron-beam lithography, electromigration, electrodeposition, etc.) are appropriate for contacting only single devices. Thus, despite the proof-of-concept for individual components, [6-11] the economical fabrication of more complex molecular circuits on a large scale remains a challenge. Recently, Krahne et al. [12] have succeeded in the fabrication of a network of nanojunctions defined only by optical lithography and wet etching of an AlGaAs/GaAs quantumwell (QW) structure (an important step towards low-cost mass production). The gap size is determined by the thickness of the quantum well and of the deposited metal layer with subnanometer precision. This approach enabled the authors to investigate transport through single Au nanoclusters at T = 4 K. However, the main drawback of this technique lies in the relatively large bulk leakage currents through the semiconductor substrate at ambient conditions, which limit the use of the nanojunctions to cryogenic temperatures in the dark and highly conductive nano-objects. In this Communication, we report on i) a significant improvement of this method and ii) the fabrication and characterization of a new class of nanodevices based on few/single proteins that operate at room temperature. Transport in molecular tunnel junctions based on the blue-copper protein Azurin is investigated for the first time at the single-molecule level in device geometry. We observe features characteristic of transport through molecules, such as negative differential resistance (NDR) in the current-voltage characteristics and identify the mechanism and the protein sites responsible (despite recent reports based on SPMs, the NDR phenomenon is little understood on the molecular scale [13]). The nanojunction fabrication started with an AlGaAs/ GaAs (20 nm thick) quantum-well structure grown by metal-organic chemical vapor deposition (MOCVD) (Al concentration between 35 % to 90 %). Mesa structures were defined by optical lithography and wet etching. Next, selective wet etching (using citric acid) was employed to remove a few tens of nanometers of the GaAs layer from the sloped edges of the mesa structure (Figure 1 a). To reduce bulk leakage currents, we employed a selective oxidation technique, carried out after the selective etching and the removal of the GaAs cap layer, which allows the conversion of the Al-rich layers into a stable native oxide (Figure 1 b). This relies on a continuous flow of water steam carried by nitrogen gas that bubbles through deionized water. The oxidation is carried out at a controlled temperature in a home-made oven. After oxidation, the electrodes were defined by optical lithography and evaporation of a 15-nm-thick film of Ti/ Pt. The gap is determined by: 1) the thickness of the GaAs QW, 2) the thickness of the deposited metal layer, and 3) the surface roughness of the etched AlGaAs/GaAs interface. Figure 1 c shows that the resulting gap between elec-A C H T U N G T R E N N U N G trodes is only a few nanometers across; no significant changes in interface roughness are observed after oxidation. In such nanogaps, molecules/nanoparticles can be positioned between the electrodes by electrostatic trapping or by specific immobilization procedures. Since only photolithography is used to define the electrode pattern, the improved mesa-gap technique reported here enables the simultaneous, economic fabrication of large arrays of nanodevices working at ambient conditions. We emphasize that all the described processes are carried out at wafer scale, which is crucial for
Small, 2009
Despite all these studies, however, the influence of the coupling of NCs with the environment on ... more Despite all these studies, however, the influence of the coupling of NCs with the environment on the WFs could not be probed directly so far. Although STS is able to provide spectacular images of WFs of isolated nano-objects (such as QDs,1719 carbon nanotubes,20, 21 and even ...
Physical Review B, 2008
The assessment of the presence and the origin of an intrinsic internal electric field in novel co... more The assessment of the presence and the origin of an intrinsic internal electric field in novel colloidal CdSe/CdS nanoheterostructures is of fundamental importance in order to understand their optical properties, due to both their impact on the basic research fields, and their potential in technological applications. To this aim, a deep study of the carrier dynamics in spherical ͑quantum dots͒ and rod-shaped ͑nanorods͒ colloidal seeded grown CdSe/CdS nanocrystals via time-resolved photoluminescence spectroscopy has been carried out in this report. A transient, power-dependent redshift of the spectra is observed. An optical nonlinearity is also found by continuous-wave photoluminescence measurements on ensemble and single nanostructures, which is attributed to a photoinduced screening of an internal field. This internal field could originate from the intrinsic piezoelectric polarization, which is a typical effect in strained heterostructures with a lattice mismatch greater than 3.9%. Our theoretical calculations support the experimental results.
Nature Nanotechnology, 2012
Nanotechnology, 2009
Astrocytes have a key role in the pathogenesis of several diseases including multiple sclerosis a... more Astrocytes have a key role in the pathogenesis of several diseases including multiple sclerosis and were proposed as the designed target for immunotherapy. In this study we used atomic force microscopy (AFM) and proteomics methods to analyse and correlate the modifications induced in the viscoleastic properties of astrocytes to the changes induced in protein expression after interferon-β (IFN-β) treatment. Our results indicated that IFN-β treatment resulted in a significant decrease in the Young's modulus, a measure of cell elasticity, in comparison with control cells. The molecular mechanisms that trigger these changes were investigated by 2DE (two-dimensional electrophoresis) and confocal analyses and confirmed by western blotting. Altered proteins were found to be involved in cytoskeleton organization and other important physiological processes.
Nanotechnology, 2012
Ligand exchange reaction with pyridine is the standard procedure for the integration of colloidal... more Ligand exchange reaction with pyridine is the standard procedure for the integration of colloidal semiconductor nanocrystals (NCs) in photovoltaic devices; however for big sized and irregularly shaped branched nanocrystals, such as CdSe@CdTe tetrapods, this procedure can lead to a considerable waste of materials and the aggregation of NCs in the colloidal solution, therefore resulting in the formation of an inhomogeneous film and low device performances. Here, we report on alternative post-deposition treatments with carboxylic acids on films of CdSe@CdTe tetrapod shaped NCs. This approach guarantees the removal of the insulating surfactant, necessary to obtain a good charge transport among NCs, while preserving the film integrity. We perform a complete characterization of the nanocrystalline films treated with different carboxylic acids and demonstrate the successful integration of such films in photovoltaic devices, showing a doubled efficiency with respect to the standard ligand exchange procedure. Our approach represents a general route towards the development of NC based devices with improved performances and minimized waste of material.
Nano Letters, 2007
We investigate correlation effects in the regime of a few electrons in uncapped InAs quantum dots... more We investigate correlation effects in the regime of a few electrons in uncapped InAs quantum dots by tunneling spectroscopy and wave function (WF) mapping at high tunneling currents where electron-electron interactions become relevant. Four clearly resolved states are found, whose approximate symmetries are roughly s and p, in order of increasing energy. Because the major axes of the p-like states coincide, the WF sequence is inconsistent with the imaging of independent-electron orbitals. The results are explained in terms of many-body tunneling theory, by comparing measured maps with those calculated by taking correlation effects into account.
Microelectronic Engineering, 2007
We demonstrate a method for the simultaneous fabrication (without the need of expensive e-beam sy... more We demonstrate a method for the simultaneous fabrication (without the need of expensive e-beam systems) of large arrays of nanodevices working at room temperature. The electrode gap is defined by a selective wet-etching of a AlGaAs/GaAs quantum well structure and controlled with nanometer precision. A selective oxidation of the Al rich barrier reduces the bulk leakage current by six orders of magnitude and extends the applicability of the produced devices to room temperature functionality. As a demonstration, we employ here these nanojunctions to investigate transport in molecular tunnel-junctions based on individual Azurins, a blue copper protein, under ambient conditions. This approach opens the way to the fabrication of complex circuits consisting of different nanodevices.
Microelectronic Engineering, 2009
We report the development of EIS cell chips able to monitor cell growth and adhesion. They are ma... more We report the development of EIS cell chips able to monitor cell growth and adhesion. They are made of transparent or semitransparent materials to allow complementary analysis of cell behaviour during the measurements through optical microscopy. Our approach is cheap both in fabrication and usage, it is not invasive for cells and it does not require any additional reagent. Our devices are particular suitable to count cells or to evaluate cell morphology and changes as a consequence of different treatments.
Materials Science and Engineering: C, 2008
We report a widely applicable and highly controlled approach, based on electron beam lithography ... more We report a widely applicable and highly controlled approach, based on electron beam lithography (EBL), to interconnect single nano-objects, previously immobilized onto solid surfaces, and to investigate the transport properties at the level of single nanostructures. In particular, a threestep EBL-procedure was used for this purpose by patterning two planar contacts on the sides of an individual nano-object. To demonstrate this approach, we use two different kinds of active elements: a semiconductor nanocrystal (tetrapod) and a thin triangular gold nanoprism (NT).
Lab on a Chip, 2013
Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and lethal cancers in Europ... more Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and lethal cancers in Europe and the United States. It has a very low 5 years-survival rate and its diagnosis is often late and imprecise due to the lack of specificity of currently used markers for PDAC. As previously demonstrated PDAC patients' sera may contain autoantibodies towards phosphorylated a-enolase (ENOA), which in combination with other standard markers can increase specificity in diagnosis of PDAC. In this context we realized a microfluidic platform with integrated EIS biosensors. We achieved a specific antibodies detection by immobilizing onto electrodes peptides corresponding to a portion of ENOA. Phosphorylation of peptides was found to influence the recognition of antibodies in PDAC patients' sera detected by the developed biochip thus validating the EIS technique as a strong tool for quick, cost-saving and label-free analysis of serum samples. Biochip results are in agreement with those from traditional techniques, such as ELISA and western blot, but measurements are much more sensitive and specific, increasing the possibility of PDAC diagnosis. In addition this approach is faster and more reproducible compared to traditional techniques making the developed biochips ideal for a quick, cost-saving and label-free analysis of serum samples.
Journal of Physics: Conference Series, 2011
Page 1. LSMO growing opportunities by PLD and applications in spintronics This article has been... more Page 1. LSMO growing opportunities by PLD and applications in spintronics This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2011 J. Phys.: Conf. Ser. 292 012003 (http://iopscience.iop.org/1742-6596/292/1/012003) ...
Journal of Physics: Conference Series, 2011
... Phys. Lett. 80 2398-400 [44] Qing Q, Chen F, Li P, Tang W, Wu Z and Liu Z 2005 Angewandte Che... more ... Phys. Lett. 80 2398-400 [44] Qing Q, Chen F, Li P, Tang W, Wu Z and Liu Z 2005 Angewandte Chemie International Edition 44 7771-5 [45] Jemmy S and et al. 2010 ... Lett. 6 441-4 [53] Xiang C, Kim JY and Penner RM 2009 Nano Lett. ...
Japanese Journal of Applied Physics, 2005
The metalloprotein azurin, used in biomolecular electronics, is investigated with respect to its ... more The metalloprotein azurin, used in biomolecular electronics, is investigated with respect to its resilience to high electric fields and ambient conditions, which are crucial reliability issues. Concerning the effect of electric fields, two models of different complexity agree indicating an unexpectedly high robustness. Experiments in device-like conditions confirm that no structural modifications occur, according to fluorescence spectra, even after a 40-min exposure to tens of MV/m. Ageing is then investigated experimentally, at ambient conditions and without field, over several days. Only a small conformational rearrangement is observed in the first tens of hours, followed by an equilibrium state.
Nanoscale, Jan 7, 2012
Quantum-dot Cellular Automata (QCA) exploit quantum confinement, tunneling and electrostatic inte... more Quantum-dot Cellular Automata (QCA) exploit quantum confinement, tunneling and electrostatic interaction for transistorless digital computing. Implementation at the molecular scale requires carefully tailored units which must obey several structural and functional constraints, ranging from the capability to confine charge efficiently on different 'quantum-dot centers'-in order to sharply encode the Boolean states-up to the possibility of having their state blanked out upon application of an external signal. In addition, the molecular units must preserve their geometry in the solid state, to interact electrostatically in a controlled way. Here, we present a novel class of organometallic molecules, 6-3,6-bis(1-ethylferrocen)-9H-carbazol-9-yl-6-hexan-1-thiols, which are engineered to satisfy all such crucial requirements at once, as confirmed by electrochemistry and scanning tunneling microscopy measurements, and first principles density functional calculations.
Nanoscale, Jan 7, 2012
We report on the fabrication and single electron tunneling behaviour of large scale arrays of nan... more We report on the fabrication and single electron tunneling behaviour of large scale arrays of nanogap electrodes bridged by bisferrocene-gold nanoparticle hybrids (BFc-AuNP). Coulomb staircase was observed in the low temperature current-voltage curves measured on the junctions with asymmetric tunnel barriers. On the other hand, junctions with symmetric tunneling barrier exhibited mere nonlinear current voltage characteristics without discrete staircase. The experimental results agreed well with simulations based on the orthodox theory. The junction resistance showed thermally activated conduction behaviour at higher temperature. The overall voltage and temperature dependent results show that the transport behaviour of the large arrays of single particle devices obtained by a facile optical lithography and chemical etching process corresponds with the behaviour of single particle devices fabricated by other techniques like e-beam lithography and mechanical breaking methods.
Materials Science and Engineering: C, 2017
Authors aimed to provide a magnetic responsiveness to bone-mimicking nano-hydroxyapatite (n-HA). ... more Authors aimed to provide a magnetic responsiveness to bone-mimicking nano-hydroxyapatite (n-HA). For this purpose, dextran-grafted iron oxide nanoarchitectures (DM) were synthesized by a green friendly and scalable alkaline co-precipitation method at room temperature and used to functionalize n-HA crystals. Different amounts of DM hybrid structures were added into the nanocomposites (DM/n-HA 1:1, 2:1 and 3:1weight ratio) which were investigated through extensive physicochemical (XRD, ICP, TGA and Zetapotential), microstructural (TEM and DLS), magnetic (VSM) and biological analyses (MTT proliferation assay). X-ray diffraction patterns have confirmed the n-HA formation in the presence of DM as a co-reagent. Furthermore, the addition of DM during the synthesis does not affect the primary crystallite domains of DM/n-HA nanocomposites. DM/n-HAs have shown a rising of the magnetic moment values by increasing DM content up to 2:1 ratio. However, the magnetic moment value recorded in the DM/n-HA 3:1 do not further increases showing a saturation behavior. The cytocompatibility of the DM/n-HA was evaluated with respect to the MG63 osteoblast-like cell line. Proliferation assays revealed that viability, carried out in the absence of external magnetic field, was not affected by the amount of DM employed. Interestingly, assays also suggested that the DM/n-HA nanocomposites exhibit a possible shielding effect with respect to the antiproliferative activity induced by the DM particles alone.
Materials Research Express, 2015
ABSTRACT Increasing the ease and the rapidity of processing in micro and nanotechnology is an ong... more ABSTRACT Increasing the ease and the rapidity of processing in micro and nanotechnology is an ongoing task, which is pursued in both the academic environment for investigation of novel systems and in industry for fabrication of complex circuits on a large scale. In the field of nanoelectronics, the major challenge is to demonstrate a feasible method for device implementation based on individual nanosize objects, such as nanowires, nanotubes and nanocrystals. However, integrating these small objects in a macroscopic circuit is a difficult task. So far, nanostructures have been wired by highly sophisticated techniques not suitable for large-scale integration in macroscopic circuits, such as electron-beam lithography or focused ion-beam deposition. Here we present a 'one-pot' and rapid approach to electrically interconnect individual nanowires from random spatial distribution, with high spatial and positioning resolution and a remarkable reduction in overall fabrication time with respect to the other expensive and laborious techniques. The reliability of such technique is demonstrated by implementing a single semiconductor nanowire device
Nanostructure Science and Technology, 2009
Page 1. 5 Nanoelectronic Devices Based on Proteins Giuseppe Maruccio and Alessandro Bramanti 1 PR... more Page 1. 5 Nanoelectronic Devices Based on Proteins Giuseppe Maruccio and Alessandro Bramanti 1 PROTEINS IN NANOELECTRONICS Acquiring the capability of handling and assembling structures at the molecular scale ...
Nanofabrication, 2011
of Chemistry). 2.2 Top-down processes The top-down approach in building integrated circuits (ICs)... more of Chemistry). 2.2 Top-down processes The top-down approach in building integrated circuits (ICs) usually involves some form of lithography to define the required pattern of features. Many other kinds of processes are required to build an IC, such as ion-implantation, metal evaporation and etching, which are used in several nanoscale devices too; however, here we will concentrate on the problems of lithography, since that is the side of technology directly related to resolution and, consequently, most innovative (and troublesome) in nanodevices. According to a common distinction, we will classify lithographic methods into hard and soft, where the former (often referred to simply as "lithography") are the improved version of those already employed for present ICs, whereas the latter have been purposely developed for nanoscale fabrication (in particular when dealing with fragile molecules). 2.2.1 (Hard) lithography By 'hard lithography' we mean all those techniques using resist layers and optical masks, derived from standard photolithography. The core-idea is to expose a sensitive material (the 'resist') to an activating agent (light or a particle beam) in order to harden (or soften) it in targeted areas. Subsequently, a developer solution will wash away the soft parts of the resist layer selectively, while the remaining hard parts mask the sample for subsequent processing (see the schematic in Figure 2a). Commonly, either the material is etched where unmasked by the layer (and the remaining resist is taken away after the etching); or a new layer of material is grown (e.g. metal by evaporation) so that it builds up upon the patterned resist, where this is present, or upon the underlying material in the resist's voids; finally, the hardened resist will be removed, carrying away the material grown atop (lift-off) and leaving the material inside the patterned voids untouched.
Small, 2007
Molecular electronics [1] is aimed at demonstrating suitable alternatives to silicon-based nanoel... more Molecular electronics [1] is aimed at demonstrating suitable alternatives to silicon-based nanoelectronics for building complex and functional devices. One of the end goals is to use single molecules as active elements in electronic nanodevices, whereas the main challenges are the interconnection of the molecules and the fabrication of electrical contacts to the outside. In recent years, proteins have attracted much interest as active materials because of their electrontransfer (ET) capabilities (crucial for a number of vital processes such as photosynthesis, respiration, and energy conversion). These pivotal reactions usually take place inside a single protein (intramolecular ET) or between two or a few proteins (intermolecular ET). Therefore, it is crucial to develop reliable methods to interconnect and probe transport in single/few proteins in order to investigate the basic mechanisms underlying ET. This kind of information is not directly accessible by conventional techniques such as spectroscopic and electrochemical methods, which provide average figures over statistical ensembles. Up to now, such studies could only be performed by means of scanning probe methods (SPMs), [2-4] but never in device geometry, due to severe difficulties in the fabrication of devices with single molecules as active components. The physical limitations of optical lithography have prompted the development of alternative, top-down techniques for patterning below the 100-nm scale, but in most cases these do not match the advantages of photolithography in its low cost and high throughput (with the notable exception of nanoimprint lithography [5]). Most of these alternative methods (including mechanical break junctions, electron-beam lithography, electromigration, electrodeposition, etc.) are appropriate for contacting only single devices. Thus, despite the proof-of-concept for individual components, [6-11] the economical fabrication of more complex molecular circuits on a large scale remains a challenge. Recently, Krahne et al. [12] have succeeded in the fabrication of a network of nanojunctions defined only by optical lithography and wet etching of an AlGaAs/GaAs quantumwell (QW) structure (an important step towards low-cost mass production). The gap size is determined by the thickness of the quantum well and of the deposited metal layer with subnanometer precision. This approach enabled the authors to investigate transport through single Au nanoclusters at T = 4 K. However, the main drawback of this technique lies in the relatively large bulk leakage currents through the semiconductor substrate at ambient conditions, which limit the use of the nanojunctions to cryogenic temperatures in the dark and highly conductive nano-objects. In this Communication, we report on i) a significant improvement of this method and ii) the fabrication and characterization of a new class of nanodevices based on few/single proteins that operate at room temperature. Transport in molecular tunnel junctions based on the blue-copper protein Azurin is investigated for the first time at the single-molecule level in device geometry. We observe features characteristic of transport through molecules, such as negative differential resistance (NDR) in the current-voltage characteristics and identify the mechanism and the protein sites responsible (despite recent reports based on SPMs, the NDR phenomenon is little understood on the molecular scale [13]). The nanojunction fabrication started with an AlGaAs/ GaAs (20 nm thick) quantum-well structure grown by metal-organic chemical vapor deposition (MOCVD) (Al concentration between 35 % to 90 %). Mesa structures were defined by optical lithography and wet etching. Next, selective wet etching (using citric acid) was employed to remove a few tens of nanometers of the GaAs layer from the sloped edges of the mesa structure (Figure 1 a). To reduce bulk leakage currents, we employed a selective oxidation technique, carried out after the selective etching and the removal of the GaAs cap layer, which allows the conversion of the Al-rich layers into a stable native oxide (Figure 1 b). This relies on a continuous flow of water steam carried by nitrogen gas that bubbles through deionized water. The oxidation is carried out at a controlled temperature in a home-made oven. After oxidation, the electrodes were defined by optical lithography and evaporation of a 15-nm-thick film of Ti/ Pt. The gap is determined by: 1) the thickness of the GaAs QW, 2) the thickness of the deposited metal layer, and 3) the surface roughness of the etched AlGaAs/GaAs interface. Figure 1 c shows that the resulting gap between elec-A C H T U N G T R E N N U N G trodes is only a few nanometers across; no significant changes in interface roughness are observed after oxidation. In such nanogaps, molecules/nanoparticles can be positioned between the electrodes by electrostatic trapping or by specific immobilization procedures. Since only photolithography is used to define the electrode pattern, the improved mesa-gap technique reported here enables the simultaneous, economic fabrication of large arrays of nanodevices working at ambient conditions. We emphasize that all the described processes are carried out at wafer scale, which is crucial for
Small, 2009
Despite all these studies, however, the influence of the coupling of NCs with the environment on ... more Despite all these studies, however, the influence of the coupling of NCs with the environment on the WFs could not be probed directly so far. Although STS is able to provide spectacular images of WFs of isolated nano-objects (such as QDs,1719 carbon nanotubes,20, 21 and even ...
Physical Review B, 2008
The assessment of the presence and the origin of an intrinsic internal electric field in novel co... more The assessment of the presence and the origin of an intrinsic internal electric field in novel colloidal CdSe/CdS nanoheterostructures is of fundamental importance in order to understand their optical properties, due to both their impact on the basic research fields, and their potential in technological applications. To this aim, a deep study of the carrier dynamics in spherical ͑quantum dots͒ and rod-shaped ͑nanorods͒ colloidal seeded grown CdSe/CdS nanocrystals via time-resolved photoluminescence spectroscopy has been carried out in this report. A transient, power-dependent redshift of the spectra is observed. An optical nonlinearity is also found by continuous-wave photoluminescence measurements on ensemble and single nanostructures, which is attributed to a photoinduced screening of an internal field. This internal field could originate from the intrinsic piezoelectric polarization, which is a typical effect in strained heterostructures with a lattice mismatch greater than 3.9%. Our theoretical calculations support the experimental results.
Nature Nanotechnology, 2012
Nanotechnology, 2009
Astrocytes have a key role in the pathogenesis of several diseases including multiple sclerosis a... more Astrocytes have a key role in the pathogenesis of several diseases including multiple sclerosis and were proposed as the designed target for immunotherapy. In this study we used atomic force microscopy (AFM) and proteomics methods to analyse and correlate the modifications induced in the viscoleastic properties of astrocytes to the changes induced in protein expression after interferon-β (IFN-β) treatment. Our results indicated that IFN-β treatment resulted in a significant decrease in the Young's modulus, a measure of cell elasticity, in comparison with control cells. The molecular mechanisms that trigger these changes were investigated by 2DE (two-dimensional electrophoresis) and confocal analyses and confirmed by western blotting. Altered proteins were found to be involved in cytoskeleton organization and other important physiological processes.
Nanotechnology, 2012
Ligand exchange reaction with pyridine is the standard procedure for the integration of colloidal... more Ligand exchange reaction with pyridine is the standard procedure for the integration of colloidal semiconductor nanocrystals (NCs) in photovoltaic devices; however for big sized and irregularly shaped branched nanocrystals, such as CdSe@CdTe tetrapods, this procedure can lead to a considerable waste of materials and the aggregation of NCs in the colloidal solution, therefore resulting in the formation of an inhomogeneous film and low device performances. Here, we report on alternative post-deposition treatments with carboxylic acids on films of CdSe@CdTe tetrapod shaped NCs. This approach guarantees the removal of the insulating surfactant, necessary to obtain a good charge transport among NCs, while preserving the film integrity. We perform a complete characterization of the nanocrystalline films treated with different carboxylic acids and demonstrate the successful integration of such films in photovoltaic devices, showing a doubled efficiency with respect to the standard ligand exchange procedure. Our approach represents a general route towards the development of NC based devices with improved performances and minimized waste of material.
Nano Letters, 2007
We investigate correlation effects in the regime of a few electrons in uncapped InAs quantum dots... more We investigate correlation effects in the regime of a few electrons in uncapped InAs quantum dots by tunneling spectroscopy and wave function (WF) mapping at high tunneling currents where electron-electron interactions become relevant. Four clearly resolved states are found, whose approximate symmetries are roughly s and p, in order of increasing energy. Because the major axes of the p-like states coincide, the WF sequence is inconsistent with the imaging of independent-electron orbitals. The results are explained in terms of many-body tunneling theory, by comparing measured maps with those calculated by taking correlation effects into account.
Microelectronic Engineering, 2007
We demonstrate a method for the simultaneous fabrication (without the need of expensive e-beam sy... more We demonstrate a method for the simultaneous fabrication (without the need of expensive e-beam systems) of large arrays of nanodevices working at room temperature. The electrode gap is defined by a selective wet-etching of a AlGaAs/GaAs quantum well structure and controlled with nanometer precision. A selective oxidation of the Al rich barrier reduces the bulk leakage current by six orders of magnitude and extends the applicability of the produced devices to room temperature functionality. As a demonstration, we employ here these nanojunctions to investigate transport in molecular tunnel-junctions based on individual Azurins, a blue copper protein, under ambient conditions. This approach opens the way to the fabrication of complex circuits consisting of different nanodevices.
Microelectronic Engineering, 2009
We report the development of EIS cell chips able to monitor cell growth and adhesion. They are ma... more We report the development of EIS cell chips able to monitor cell growth and adhesion. They are made of transparent or semitransparent materials to allow complementary analysis of cell behaviour during the measurements through optical microscopy. Our approach is cheap both in fabrication and usage, it is not invasive for cells and it does not require any additional reagent. Our devices are particular suitable to count cells or to evaluate cell morphology and changes as a consequence of different treatments.
Materials Science and Engineering: C, 2008
We report a widely applicable and highly controlled approach, based on electron beam lithography ... more We report a widely applicable and highly controlled approach, based on electron beam lithography (EBL), to interconnect single nano-objects, previously immobilized onto solid surfaces, and to investigate the transport properties at the level of single nanostructures. In particular, a threestep EBL-procedure was used for this purpose by patterning two planar contacts on the sides of an individual nano-object. To demonstrate this approach, we use two different kinds of active elements: a semiconductor nanocrystal (tetrapod) and a thin triangular gold nanoprism (NT).
Lab on a Chip, 2013
Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and lethal cancers in Europ... more Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and lethal cancers in Europe and the United States. It has a very low 5 years-survival rate and its diagnosis is often late and imprecise due to the lack of specificity of currently used markers for PDAC. As previously demonstrated PDAC patients' sera may contain autoantibodies towards phosphorylated a-enolase (ENOA), which in combination with other standard markers can increase specificity in diagnosis of PDAC. In this context we realized a microfluidic platform with integrated EIS biosensors. We achieved a specific antibodies detection by immobilizing onto electrodes peptides corresponding to a portion of ENOA. Phosphorylation of peptides was found to influence the recognition of antibodies in PDAC patients' sera detected by the developed biochip thus validating the EIS technique as a strong tool for quick, cost-saving and label-free analysis of serum samples. Biochip results are in agreement with those from traditional techniques, such as ELISA and western blot, but measurements are much more sensitive and specific, increasing the possibility of PDAC diagnosis. In addition this approach is faster and more reproducible compared to traditional techniques making the developed biochips ideal for a quick, cost-saving and label-free analysis of serum samples.
Journal of Physics: Conference Series, 2011
Page 1. LSMO growing opportunities by PLD and applications in spintronics This article has been... more Page 1. LSMO growing opportunities by PLD and applications in spintronics This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2011 J. Phys.: Conf. Ser. 292 012003 (http://iopscience.iop.org/1742-6596/292/1/012003) ...
Journal of Physics: Conference Series, 2011
... Phys. Lett. 80 2398-400 [44] Qing Q, Chen F, Li P, Tang W, Wu Z and Liu Z 2005 Angewandte Che... more ... Phys. Lett. 80 2398-400 [44] Qing Q, Chen F, Li P, Tang W, Wu Z and Liu Z 2005 Angewandte Chemie International Edition 44 7771-5 [45] Jemmy S and et al. 2010 ... Lett. 6 441-4 [53] Xiang C, Kim JY and Penner RM 2009 Nano Lett. ...
Japanese Journal of Applied Physics, 2005
The metalloprotein azurin, used in biomolecular electronics, is investigated with respect to its ... more The metalloprotein azurin, used in biomolecular electronics, is investigated with respect to its resilience to high electric fields and ambient conditions, which are crucial reliability issues. Concerning the effect of electric fields, two models of different complexity agree indicating an unexpectedly high robustness. Experiments in device-like conditions confirm that no structural modifications occur, according to fluorescence spectra, even after a 40-min exposure to tens of MV/m. Ageing is then investigated experimentally, at ambient conditions and without field, over several days. Only a small conformational rearrangement is observed in the first tens of hours, followed by an equilibrium state.
Nanoscale, Jan 7, 2012
Quantum-dot Cellular Automata (QCA) exploit quantum confinement, tunneling and electrostatic inte... more Quantum-dot Cellular Automata (QCA) exploit quantum confinement, tunneling and electrostatic interaction for transistorless digital computing. Implementation at the molecular scale requires carefully tailored units which must obey several structural and functional constraints, ranging from the capability to confine charge efficiently on different 'quantum-dot centers'-in order to sharply encode the Boolean states-up to the possibility of having their state blanked out upon application of an external signal. In addition, the molecular units must preserve their geometry in the solid state, to interact electrostatically in a controlled way. Here, we present a novel class of organometallic molecules, 6-3,6-bis(1-ethylferrocen)-9H-carbazol-9-yl-6-hexan-1-thiols, which are engineered to satisfy all such crucial requirements at once, as confirmed by electrochemistry and scanning tunneling microscopy measurements, and first principles density functional calculations.
Nanoscale, Jan 7, 2012
We report on the fabrication and single electron tunneling behaviour of large scale arrays of nan... more We report on the fabrication and single electron tunneling behaviour of large scale arrays of nanogap electrodes bridged by bisferrocene-gold nanoparticle hybrids (BFc-AuNP). Coulomb staircase was observed in the low temperature current-voltage curves measured on the junctions with asymmetric tunnel barriers. On the other hand, junctions with symmetric tunneling barrier exhibited mere nonlinear current voltage characteristics without discrete staircase. The experimental results agreed well with simulations based on the orthodox theory. The junction resistance showed thermally activated conduction behaviour at higher temperature. The overall voltage and temperature dependent results show that the transport behaviour of the large arrays of single particle devices obtained by a facile optical lithography and chemical etching process corresponds with the behaviour of single particle devices fabricated by other techniques like e-beam lithography and mechanical breaking methods.