1,721,010 research outputs found
Functional nanocomposites based on graphene/DNA interface: Towards a bio-inspired sensing of UV radiation effects
Full text linkUltraviolet (UV) radiation naturally characterizes the Earth environment and the outer space, representing one of the most hazardous agents for human health and for the useful lifetime of organic materials. The possibility to develop a UV-detecting system able to ensure a good sensitivity and stability during measurements, and possessing at the same time low weight and real-time response, represents a fascinating challenge towards new technological advances in the field of radiation sensitive materials. This thesis is focused on the design, preparation and testing of bio-inspired UV sensitive nanocomposites based on graphene/DNA interface. The sensing principle of such nanocomposites relies on the highly conductive nature of graphene combined with the chemical sensitivity of DNA strands to UV radiation, particularly in the UV-C band (100 nm to 280 nm). The engineering of these bio-hybrid nanomaterials in the form of thin films or miniaturized materials would be desirable to overcome traditional problems that affect space mission equipment, such as onboard encumbrance, or that can limit their use on terrestrial environments involving a daily use of UV radiation, such as sterilization plants. To this aim, the UV sensitive graphene/DNA filler was integrated in different polymer matrices based on poly(3,4-ethylenedioxythio-phene):poly(styrenesulfonate) (PEDOT:PSS) or polydimethylsiloxane (PDMS), obtaining stiff and flexible UV sensitive materials, respectively. The UV response was investigated using several techniques, including electrical impedance spectroscopy, Raman microscopy, optical contact angle, electrical tomography resistance. In addition, differential scanning calorimetry was used to analyze the curing behavior of the PDMS-based prepolymers and the thermal stability of the related nanocomposites. Results revealed that the bio-hybrid nanocomposites with graphene/DNA filler show a specific UV response, in particular in terms of electrical conductivity variations, and therefore these materials have the potential to be applied in UV monitoring systems, with the additional advantages of real-time response, low weight/mass and reduced siz
Conductive and flexible materials containing graphene-DNA hybrids for cell culture applications
No full textMultifunctional materials designed by integrating a nano-hybrid component with bioactive and electrically conductive properties in a polymeric support matrix have many attractive features for applications in the biomedical and biotechnology fields. For example, it is well known that cells sense the stiffness of their microenvironment, and they can regulate their shape and proliferation according to the rigidity of the underlying substrate. Moreover, flexible substrates that are also electrically conductive can be an ideal tool in applications involving electro-responsive cells, such as the neuronal cells.
In previous work from our group it was established that nanostructured films made by DNA-solubilized carbon nanotubes, retain their electrical conductivity, as indicated by atomic force microscopy experiments combined with electrical measurements on the nanoscale level. Here, we use a similar procedure to solubilize graphene nanoplatelets in DNA solutions and then embed the self-assembled hybrid in a flexible polymer matrix based on silicone polymers
Recent trends in graphene/polymer nanocomposites for sensing devices: synthesis and applications in environmental and human health monitoring
Full text linkGraphene-based nanocomposites are largely explored for the development of sensing devices due to the excellent electrical and mechanical properties of graphene. These properties, in addition to its large specific surface area, make graphene attractive for a wide range of chemical functionalization and immobilization of (bio)molecules. Several techniques based on both top-down and bottom-up approaches are available for the fabrication of graphene fillers in pristine and functionalized forms. These fillers can be further modified to enhance their integration with polymeric matrices and substrates and to tailor the sensing efficiency of the overall nanocomposite material. In this review article, we summarize recent trends in the design and fabrication of graphene/polymer nanocomposites (GPNs) with sensing properties that can be successfully applied in environmental and human health monitoring. Functional GPNs with sensing ability towards gas molecules, humidity, and ultraviolet radiation can be generated using graphene nanosheets decorated with metallic or metal oxide nanoparticles. These nanocomposites were shown to be effective in the detection of ammonia, benzene/toluene gases, and water vapor in the environment. In addition, biological analytes with broad implications for human health, such as nucleic bases or viral genes, can also be detected using sensitive, graphene-based polymer nanocomposites. Here, the role of the biomolecules that are immobilized on the graphene nanomaterial as target for sensing is reviewed
Novel graphene-based nanocomposite films for monitoring UV radiation effects on space structures
No full textA new hybrid nanocomposite material was developed to monitor the effects of UV-C radiation on space-grade structures. Ultraviolet radiation represents one of the most critical limitations for human space exploration and survival. In particular, the UV-C band with shorter wavelengths (100-280 nm) can severely damage materials and life in space. Ultraviolet sensing films were realized using graphene nanoplatelets (GNPs) as signal transducer and DNA as biological sensitive component. Hybrid GNP/DNA nanoparticles were dispersed into a conductive polymer matrix of poly (3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) to improve the adhesion of the sensing film on space-grade structures based on epoxy resins
Smart nanomaterial-based hybrid films for sensing UV radiation damage in space environment
No full textIn our work we investigate the fabrication and properties of ultraviolet-sensing films based on hybrid nanomaterials containing highly conductive graphene nanoplatelets (GNP) and DNA as biological UV-sensitive element. Using sonication processes in suitable solvents, the sensor components are assembled into non-covalent complexes which are then embedded in a polymer matrix to improve the film adhesion on several types of space-grade materials and structures. DNA strands are used for the assembly of the nanomaterial-based sensors due to the real-time sensitivity of nucleic acids to UV exposure, in particular to the most energetic UV-C band. At the same time, DNA molecules are efficient solubilizing agents for the highly hydrophobic graphene nanoparticles, ensuring a good stability of the GNP dispersions without modifying the electrical and chemical properties of the nanoparticles. Several techniques (electrical impedance spectroscopy, electrical resistance tomography, SEM microscopy, optical contact angle for surface wettability) are used for the characterization of the hybrid films before and after UV-C irradiation. We show that these nanomaterial sensing films are potentially useful to monitor the effects of UV radiation exposure in real time. Possible applications include monitoring the effects of solar UV radiation in space environment, where the UV-C component adversely affects performance of spacecraft components and represents a critical risk for human extra-vehicular activities (EVA). In this context, the use of miniaturized and light-weight sensor devices is an essential requirement for the mission outcome
The effect of crosslinking density on the dynamic behavior of thermo‐responsive poly(N‐isopropylacrylamide) hydrogels
No full textStimuli-responsive hydrogels are of great interest in many biomedical applications, from drug delivery to tissue engineering. In this work, thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) hydrogels are prepared by adding different amounts of crosslinking agent (N,N′-methylenebisacrylamide, BIS) in a two-step-freezing polymerization method, which is simple and potentially able to reduce fabrication times and costs. The hydrogel swelling behavior and the temporal evolution of the volume variation in response to temperature changes are investigated. Results demonstrate how the thermo-responsive behavior of these materials is related to the content of the BIS crosslinking agent, which is helpful to guide the synthesis of dynamic hydrogels with tunable functional properties
Ultraviolet-sensing surfaces based on hybrid nanocomposites for radiation monitoring systems
No full textSolar ultraviolet (UV) radiation, especially the most energetic UV-C band, is one of the major variables that negatively affects materials performance in space environment. Our work is focused on the design and fabrication of novel nanocomposite films that combine highly conductive graphene nanoplatelets and biological UV-sensitive molecules, which can be used to measure the effects of ultraviolet radiation exposure in real time. UV sensor films were deposited on samples made of space-grade reinforced composites, which are generally used in spacecraft components and structures, and the variation of their electrical properties upon UV-C irradiation was investigated
Raman microscopy analysis of graphene-based nanocomposite materials under UV-C exposure
No full textIn this work, we focused on the investigation of UV-C radiation effects on novel nanomaterials structured with graphene nanoplatelets (GNPs) and DNA. Multifunctional nanocomposites were realized by combining the good electrical conductivity of GNPs with the biocompatibility and UV sensitivity of double-stranded DNA. GNP/DNA nanostructures were prepared by sonication-driven self-assembly in aqueous solution, and then dispersed into a PEDOT:PSS (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)) matrix. The UV-sensitivity of the GNP/DNA/PEDOT:PSS samples was investigated by exposing them to the energetic UV-C band, and investigating their morphology, surface wettability, chemical and electrical properties before and after irradiation using several techniques (scanning electron microscopy, Raman spectroscopy, electrical impedance spectroscopy). In particular, Raman imaging was used as suitable technique to analyze the chemical arrangements and their modifications upon irradiation on selected surface areas. This technique allowed appreciating chemical changes caused by the UV-C interaction with the nanocomposite original structure. Results give information about the potential applications of GNP/DNA/PEDOT:PSS nanomaterials in all environments affected by UV radiations, for example for chemical reactions or sterilization purposes, or where they are naturally present, such as in space. In reference to space environment, the GNP/DNA/PEDOT:PSS nanocomposites were also tested under UV-C while reducing the amount of oxygen reaching the sample surface, in order to separate the effects due to the atmosphere from those of the irradiation
3D printing of radiation shielding polyethylene composites filled with Martian regolith simulant using fused filament fabrication
No full textA highly sought-after objective of Space Agencies is the development of additive manufacturing (AM) technologies and of multifunctional materials, key elements to future exploration and colonization of Moon and Mars. The 3D printing process via fused filament fabrication (FFF) is increasingly viewed as an interesting approach for the in-situ manufacturing of buildings and items using regolith as a feedstock material, enabling the necessary repair and recycling capabilities to ensure crew safety. In this work, we investigate the radiation shielding properties and the FFF 3D printing process of polyethylene-based composites filled with Martian regolith. The on-line tool for the assessment of radiation in space (OLTARIS) software developed by NASA was used to assess the radiation shielding effectiveness of polyethylene (PE)/regolith (RG) composites in the Martian radiation environment. A basalt powder with chemical composition similar to that of Mars soil was used as Martian regolith simulant in the 3D printing process. Differential scanning calorimetry (DSC) was used to determine the melting properties and crystallization degree of PE/RG composites at different RG concentrations, in order to analyze the effect of the simulant on the process parameters of filament extrusion and 3D printing. Low-impact Izod tests were also performed, with all PE/RG composites showing improved impact strength with respect to neat PE. Based on the DSC and Izod tests results, filaments of PE/RG composites were fabricated and used to 3D-print samples for tensile tests and 3-point bending tests. Results demonstrate the radiation shielding effectiveness of PE/RG composites and the capability of 3D-printers based on FFF to successfully manufacture components made of PE/RG composites starting from extruded filaments
Graphene/polymer nano-composites for antibacterial surfaces
No full textGraphene is a material with extraordinary properties: it is 200 times stronger and 100 times more resistant than steel, it is a semiconductor with a zero band gap, it has the highest conductivity of electricity and heat, it is characterized by flexibility, transparency, stability, and high idrophobicity, and it has the highest melting point of any material in vacuum. Therefore, it is not surprising that graphene is increasingly finding wide application in many field. Unfortunately, such outstanding properties are exhibited only by high-quality single-layer graphene, that can be produced only by using sophisticated methods as Chemical Vapour Deposition. To this respect, it is worth to note that several polymer composites containing graphene were developed because the insertion of graphene can change dramatically their properties.
In this framework, we studied the properties of polymer/graphene coatings, developed at DICMA Sapienza, with high graphene content to realise antibacterial surfaces. Antibacterial surfaces can act on the adhesion phases as a non-stick agent against bacteria. Once the bacteria adhere, the surfaces can act on the bacterial inhibition and on the destruction of the membrane, showing a bactericidal behavior. By increasing the concentration of GNP, surface scanning Raman spectroscopy showed that more ordered flakes with gradually larger crystals are inserted in the polymer matrix, while confocal optical microscopy shows an increase in surface roughness. The bacterial cells could be affected by these graphene-based nanocomposite since the surface roughness peaks corresponding to graphene flakes may directly affect bacterial viability by increasing the surface contact area and, consequently, the piercing action of exposed graphene flakes
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