1,721,053 research outputs found
Novel hybrid nanocomposites based on graphene derivatives and colloidal nanoparticles for sensing applications
Full text linkThe research activity of this PhD course reports on the synthesis and chemical physical characterization of a novel hybrid nanocomposite formed of Histidine (His) functionalized Reduced Graphene Oxide (RGO) sheets, decorated with Ag nanowires (NWs) (His-RGO/Ag NWs), and its applications in sensors devices.
Graphene is among the carbonaceous nanostructures, one of the most interesting for its high specific surface area, high conductivity, high electrocatalytic activity, SERS activity, high Young’s modulus and mechanical strength, high thermal and electrical conductivity, all amiable properties that have been exploited in electrochemical and SERS sensors, devices for energy conversion and storage, Field-Effect Transistors (FETs), touch panels, and membranes. On the other hand, Ag NWs show interesting plasmonic properties, high electric and thermal conductivity, optical transparency and good mechanical flexibility, properties that have been exploited in Surface Enhanced Raman Scattering (SERS), electrochemical, pressure and temperature sensors, transparent heaters, electrodes for solar cells and touch screen panels.
Our interest in developing hybrid nanocomposites formed of graphene and Ag NWs, relays on the possibility to merge their outstanding properties, resulting in materials with novel properties or with enhanced the functionalities of the pristine components. In particular, nanocomposites based on inorganic nanoparticles and graphene derivatives found wide applications in the aerospace industry for the manufacturing of composites having high Young’s modulus to integrate in vehicles, advanced thermoregulatory textiles for manufacturing sophisticated clothes for individual thermal comfort in extreme thermal conditions, components for energy storage as battery and supercapacitors, electromagnetic shielding materials, sensors for monitoring atmosphere conditions, temperature and pressure and individual physiological parameters.
In the frame of this research project, the hybrid nanocomposite has been synthesized starting from the exfoliation of RGO sheets with His in water. The amino acid intercalates among the RGO multilayers, anchors onto the RGO basal plane by π-π interactions and grafts it by -COOH and -NH2 groups allowing its exfoliation. The use of His prevented the use of the toxic organic solvents that are typically used in the exfoliation of RGO, because its binding to the RGO scaffold allows RGO dispersion in aqueous solutions. Then, the Ag NWs were synthesized in situ onto the RGO basal plane by the polyol approach, using AgNO3 as precursor, ethylene glycol (EG) as solvent and reducing agent, and polyvinylpyrrolidone (PVP) as capping and steric stabilizing agent. The synthesized NWs anchor RGO basal plane binding, by coordination, the -COOH groups of His, and RGO behaves as support and protective coating layer, avoiding NWs aggregation and oxidation thanks to its gas and moisture barrier properties. The synthesis of the His-RGO/Ag NWs has been optimized by using PVP of 360 kDa, and ca. 3.4 ± 0.9 μm long and 0.06 ± 0.01 μm thick Ag NWs, with aspect ratio of 57, were achieved. The synthesized nanocomposite His-RGO/Ag NWs have been tested for the electrochemical detection of the pesticide carbofuran and for the SERS detection of probe molecules. Such a study has been conceived to test and validate, as a proof-of-concept demonstration, the potentialities of the novel engineered nanocomposite material, opening perspectives to its leveraging in sensors having applications closer to those related to aerospace industry.
Electrochemical sensors
When integrated on screen-printed carbon electrodes (SPCEs) and further modified by the electropolymerization of the polymer PEDOT:PSS, the achieved SPCE/His-RGO/Ag NW/PEDOT:PSS electrodes have shown an increased conductivity, a higher heterogeneous charge transfer constant and an higher electrocatalytic activity, favoring oxidation of carbofuran at the electrode surface. Thus, the fabricated SPCEs/His-RGO/Ag NW/PEDOT:PSS electrodes have shown a high sensitivity in the detection of carbofuran, with a limit of detection of 17.3 nM, that is lower than the U.S. EPA recommended concentration in drinking water with a relatively good %RSD of selectivity, repeatability, reproducibility and storage stability. This improved sensitivity is due to the electrocatalytic properties of Ag NWs and the high conductivity of both the nanocomposite and the electropolymerized PEDOT:PSS film, opening the venue to the application of the fabricated electrode in the detection of other molecules of environment interest.
SERS sensors
When deposited by drop-casting onto hydrophobic paper substrates, the nanocomposite has been tested in the SERS detection of model molecules having a different chemical structure, namely 1-naphthalenethiol (1-Nat), rhodamine 6G (R6G), and benzo[a]pyrene), against paper substrates modified by neat Ag NWs based samples. The study reveals that 1-Nat, possessing a high affinity for silver, exhibits strong SERS signals on both His-RGO/Ag NWs and the neat Ag NWs substrates. Meanwhile, R6G generates even more intense SERS peaks compared to 1-Nat on both substrates due to its high affinity with silver and its interaction with RGO. Both molecules 1-Nat and R6G reach a limit of detection (LOD) of 10−7 M on both His-RGO/Ag NWs and Ag NWs substrates. In contrast, benzo[a]pyrene produced no detectable SERS signal. This absence of response was attributed to the absence of functional groups in benzo[a]pyrene having chemical affinity for silver and to the reduced number of aromatic rings in the molecule's structure that undergoes weak aromatic π- π stacking interactions.
The developed hybrid nanocomposite materials designed for the detection of pollutant molecules hold significant potential in the aerospace sector, which increasingly relies on advanced sensing technologies to enhance operational safety, environmental compliance, and crew health in complex environments. Monitoring air quality in aircraft cabins and space vehicles is crucial due to the potential accumulation of toxic chemicals, which may arise from system-related emissions, prolonged closed-loop life support, and even contaminants like pesticides in agricultural aviation settings. Detecting and managing these pollutants in real-time requires sensor technologies that are both highly sensitive and robust under challenging aerospace conditions
Graphene-Based nanostructures and colloidal silver coatings for flexible cellulose substrates
Full text linkGrowing global critical concerns around public health and environmental protection demand for more even more effective and innovative technologies to mitigate these issues. Specifically, the rise of antibiotic-resistant bacteria and emerging microbial threats highlight the need for advanced antimicrobial solutions, while the widespread environmental presence of pharmaceutical contaminants introduces new monitoring challenges. To address these objectives, the scientific community is prioritizing zero-impact approaches in materials engineering, guided by sustainable and green chemistry principles. These adaptable and functional solutions are designed to perform effectively across diverse applications, aligning with Industry 4.0’s commitment to environmentally responsible and high-performance manufacturing.
In this frame, the research activity of this PhD thesis focuses on developing innovative sustainable nanostructured and, as far as possible, Eco friend materials with multifunctional capabilities for fulfilling health and environmental concerns.
This work introduces a novel hybrid nanocomposite based on Reduced Graphene Oxide (RGO), functionalized with the biocompatible amino acid histidine, and decorated with silver (Ag) nanostructures. By leveraging in situ and ex situ colloidal synthesis methods, and finely adjusting synthesis parameters, this research achieves a nanocomposite material, whose properties—including antimicrobial efficacy, thermal conductivity and SERS plasmonic properties—can be accurately tuned by controlling size and shape of the Ag nanostructures (nanoparticles - NPs - and nanowires – NWs -). Remarkably, these processes allow for solution-based integration of these nanocomposites into cellulose-based substrates like paper and cotton textiles.
The development and application of the engineered nanocomposites is explored across three key fields: 1) antimicrobial coatings for textile, aimed at combating bacterial resistance, 2) flexible paper sensors for real-time monitoring of pharmaceuticals and pollutants in both environmental and biomedical settings, and 3) thermally conductive coatings for cotton fabrics, evaluating their suitability for use in wearable and flexible devices. Together, these applications highlight the versatile potential of nanocomposites in advancing sustainable, high-performance solutions for health and environmental challenges.
The materials developed in this study highlight the integration embody of nanotechnology and sustainable chemistry, demonstrating how nanoscale modifications of structural and functional properties can greatly enhance versatility and performance. This approach not only advances adaptable, high-performing solutions but also emphasizes the critical role of nanoscience in fostering safer and more sustainable technologies, aligning with the United Nations Sustainable Development Goals (SDGs), particularly SDG 3 (Good Health and Well-being), SDG 6 (Clean Water and Sanitation), and SDG 12 (Responsible Consumption and Production). By addressing key health and environmental challenges, this research contributes to a safer, more sustainable technological landscape, supporting societal goals for resilience, well-being, sustainability, and public well-being
(Photo)Electrochemically Active Functional Hybrids of Multilayer CVD Graphene Decorated with Colloidal TiO2 Nanocrystals
No full textA direct and facile solution-based procedure has been implemented for manufacturing optically transparent and UV-light photoactive hybrids based on graphene (from one to 5 layers), grown by Chemical Vapor Deposition (CVD) and decorated with TiO2 nanocrystals (NC) surface functionalized with 1-pyrene butyric acid (PBA). PBA functionalization was obtained by a capping exchange procedure onto pre-synthesized organic-capped NCs [1].
An in-depth characterization by SEM, EDS, AFM, Raman spectroscopy, Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) measurements demonstrated the successful immobilization of the colloidal NCs on the graphene multilayers, which preserves or even enhances the graphene intrinsic structural properties. In particular, we observed an electrical conductivity higher than that measured for bare graphene, which has been accounted for by a p-doping effect of graphene, due to a hole transfer from the nano-objects to graphene, mediated by the short aromatic ligand acting as a charge channel.
The hybrids properties are strongly dependent on the number of layers of CVD graphene. The use of two redox mediator probes [inner-sphere, surface sensitive (K4Fe(CN)6) and outer-sphere, surface insensitive (Ru(NH3)6Cl3)], in a synergistic CV and EIS study, allowed to understand these features from a morphological point of view. The results showed a strong difference between the mono-, the bi- and the other multi-layers, in terms of different diffusional mechanism and redox active sites [2-4].
Moreover, the stacked layers of the pyrene-coated TiO2 NCs are found to increase the electroactivity, the capacitive behavior, as well as the photo-electrical response of graphene, concomitantly maintaining its high charge mobility. The photoelectrical conversion of the hybrid is enhanced of 50% with respect to the bare graphene, with a long recombination lifetime of the photogenerated electron-hole pairs.
For all the above reasons, the photoactive composite has a great potential as an optically transparent component for manufacturing photoanodes to be integrated in solar cells or photodetectors and in FETs or (photo)electrochemical sensors, also exploiting the possibility of photorenovate the sensor surface [5].
References
[1] C. Ingrosso et al., ACS Appl. Mater. & Interfaces, (2015), 7, 4151-4159.
[2] C. Ingrosso et al., J. Mat. Chem. A, (2017), submitted, under review.
[3] D.A.C. Brownson, D.K. Kampouris, C.E. Banks, Chem. Soc. Rev., (2012), 41, 6944-6976.
[4] A. Ambrosi, M. Pumera, J. Phys. Chem. C, (2013), 117, 2053-2058.
[5] V. Pifferi et al., Anal. Bioanal. Chem., (2016), 408 (26), 7339-7349.
Acknowledgements
The authors acknowledge the MIUR National Project PRIN 2012 (prot. 20128ZZS2H)
Post-war Italian collective dwellings: Naples, Rome, Milan
No full texte paper is focused on post-war Italian collective dwellings. e goal is to in- vestigate the private architectures realized in Italy in this period, with particular attention to some the Neapolitan architectures compared with Roman and Mil- anese architectures.
While for the public dwellings the critics is almost compact in identifying it excellence, as regards private housing, its attitude could be described as embar- rassed, preferring, as it were, to turn a blind eye to the work carried out in those years. However, the building with “apartments one on top of the other” of dif- ferent sizes was the task given to the architects in the boom years (1958-1963) as well as that of the maximum exploitation of land for speculative purposes. It has been shown that the model of urban growth in Italy in the 1950s was one of “concentration spontaneity”, devoid in most cases of any level of planning [Ferra- cuti, Marcelloni, 1983], and the buildings in Milan, as well as those in Naples or Rome, were planning solutions to similar demands
(Photo)electrochemical characterization of TiO2 Nanocrystals Decorated CVD Graphene based Hybrid
No full textGraphene (G) is an extraordinary structural material for electroanalytical sensors, due to its excellent electrical conductivity, high surface area and mechanical strength. [1] Its potential application in sensors can be extended by a further functionalization with organic and inorganic materials. Here, a solution-based procedure [2] has been implemented, for manufacturing a UV photoactive hybrid material, based on CVD graphene films decorated with UV-light absorbing 1-pyrene butyric acid surface coated TiO2 NCs. The functional properties of the obtained hybrid have been demonstrated by (photo)electrochemical investigations.
Cyclic voltammetry profiles have been recorded in presence of an outer- and an inner-sphere probe, namely [Ru(NH3)6]Cl3 and K4[Fe(CN)6], respectively in order to study the electron transfer and the structural properties of the prepared hybrid material based working electrodes. The charge recombination behaviour of the systems has been investigated by studying the transient photocurrent decay that occurs immediately after UV-light illumination. Finally, the devices were tested in the electroanalytical detection of dopamine and norepinephrine, showing promising results.
References
[1] K.S. Noselov et al., Nature, 490, (2012), 192-200.
[2] C. Ingrosso et al., ACS Appl. Mater. & Interfaces, 7, (2015), 4151-4159
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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