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Radiation-induced color centers locally produced in lithium fluoride (LiF) are successfully used for radiation detectors. LiF detectors for extreme ultraviolet radiation, soft and hard X-rays, based on photoluminescence from aggregate electronic defects, are currently under development for imaging applications with laboratory radiation sources, as well as large-scale facilities. Among the peculiarities of LiF-based detectors, noteworthy ones are their very high intrinsic spatial resolution across a large field of view, wide dynamic range, and versatility. LiF crystals irradiated with a monochromatic 8 keV X-ray beam at KIT synchrotron light source (Karlsruhe, Germany) and with the broadband white beam spectrum of the synchrotron bending magnet have been investigated by optical spectroscopy, laser scanning confocal microscopy in fluorescence mode, and confocal Raman micro-spectroscopy. The 3D reconstruction of the distributions of the color centers induced by the X-rays has been performed with both confocal techniques. The combination of the LiF crystal capability to register volumetric X-ray mapping with the optical sectioning operations of the confocal techniques has allowed performing 3D reconstructions of the X-ray colored volumes and it could provide advanced tools for 3D X-ray detection.

Nanocomposite films with high electrical conductivity and UV sensitivity were prepared by integration of DNA-modified graphene nanoplatelets (GNPs) with a polymer matrix made of poly(3,4-ethylenedioxythio-phene):poly(styrenesulfonate) (PEDOT:PSS). The exceptional electrical properties and mechanical strength of graphene were used to enhance the PEDOT:PSS properties and stability, whereas DNA molecules are sensitive to UV and have an exfoliating effect on the GNPs in aqueous solution. GNP-DNA/PEDOT:PSS films were exposed to radiation in the energetic UV-C band (254 nm), and their properties investigated before and after irradiation. Several techniques, including scanning electron microscopy, optical contact angle, electrical impedance and Raman spectroscopies, were used to characterize the nanocomposites and to investigate their sensitivity to UV. In particular, Raman microscopy mapping was used to analyze the chemical structure of the films and its modification at molecular level upon exposure to UV-C radiation. Results of these investigations are useful for the application of the GNP-DNA/PEDOT:PSS films in ultra-small and lightweight UV sensor devices for use in space environment, for example during extravehicular activities (EVA), or for industrial settings on Earth that are characterized by high levels of UV-C radiation.

The toughness mechanisms of epoxy-based nanocomposites reinforced by double-walled carbon nanotubes (DWCNT) are investigated using Raman microscopy mapping. Maps of the residual strain of the carbon nanotubes were generated for the fracture surfaces obtained after tensile loading. By imaging through different microscope objectives, Raman mapping allowed to determine the distribution of the nanotube residual strain, indicating tension or compression, in different sampling volumes near the fracture surface. The G′ band with its high sensitivity to nanotube diameter variations, and not overlapping with the characteristic epoxy Raman lines, was selected for the mapping. Results provide a quantitative analysis of the nanotube bridging and pull-out mechanisms identified by scanning electron microscopy (SEM) inspection of the fracture surfaces.

The main characteristics of the ENEA Discharge Produced Plasma (DPP) Extreme Ultraviolet (EUV) source are presented together with results of irradiations of various materials. The DPP EUV source, based on a Xe-plasma heated up to a temperature of 30 ÷ 40 eV, emits more than 30 mJ/sr/shot at 10 Hz rep. rate in the 10 ÷ 18 nm wavelength spectral range. The DPP is equipped with a debris mitigation system to protect particularly delicate components needed for patterning applications. The ENEA source has been successfully utilized for sub-micrometer pattern generation on photonic materials and on specifically designed chemically amplified resists. Details down to 100 nm have been replicated on such photoresists by our laboratory-scale apparatus for contact EUV lithography. Preliminary EUV irradiations of graphene films aimed at modifying its properties have been also performed. © 2019 SPIE.

The integration of surface sensing elements providing an in situ monitoring of the UV-induced degradation effects in composite materials and structures is crucial for their applications in hostile environments characterized by high levels of radiation, such as space. In this work, the electrical response of a novel UV-sensitive nanocomposite film was investigated using electrical resistance tomography (ERT). The conductivity changes measured at the irradiated surfaces were compared with results from morphology analysis by scanning electron microscopy (SEM) and surface analytical techniques, such as Raman microscopy. Highly conductive and UV-sensitive nanocomposite coatings were prepared by embedding the graphene and deoxyribonucleic acid (DNA) component in a poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) matrix. The coatings were deposited onto carbon-reinforced laminated structures fabricated by resin transfer molding process using an aerospace-grade epoxy resin. Two different irradiation conditions were tested by exposing the nanocomposite surfaces to UV-C irradiances of 2.6 and 4.0 mW/cm2. Results show that the ERT technique has great potential for the in situ health monitoring of carbon-based materials and structures for aerospace applications, which are subject to degradation by UV-C radiation: it allows mapping of the conductivity changes occurring at the surface of the graphene/DNA/PEDOT:PSS coatings during irradiation.

The self-assembly of double-stranded DNA (dsDNA) segments on two variations of graphene surfaces having nano-platelets with different lateral sizes and thicknesses was investigated using surface-enhanced Raman spectroscopy (SERS) and electrical impedance spectroscopy (EIS) techniques. Due to the strong local field-enhancement, the SERS signals from functional molecules bound to the graphene edges and from DNA moieties were recorded. Relative intensities of specific Raman modes were used as contrast parameters to build Raman signal intensity maps. The observed variation in the SERS signal intensity was related to the different configuration (tilted or flattened) in which dsDNA segments are assembled on the carbon surface, depending on the graphene platelet size. EIS was used to characterize the conductive properties of nano-structured films containing pristine or DNA-functionalized graphene nano-platelets. Results from the EIS analysis supported the SERS findings and confirmed that SERS mapping is a reliable method for a rapid monitoring of the procedures used to interface DNA with graphene surfaces. The present study, linking DNA anchoring morphology to the conductive properties of nano-structured hybrid films, contribute to define a new approach in the optimization of biosensor design. © 2016 Elsevier Ltd

In this work, we combined AFM, FE-SEM and Raman spectroscopy to study the commercially available CVD grown graphene on Cu and Si substrate. SEM and AFM provide topographic information, show a network of out of plane deformations, 'wrinkles', whereas Raman spectroscopy which can give information on structural properties of the graphene films, such as the number of layers and level of disorder, by observing the peaks, indicates a I2D/IG ratio smaller than the value expected for mono-layer graphene. © 2018 Author(s).

Multi-walled nanotube (MWNT) functionalisation was investigated by surface-enhanced Raman spectroscopy (SERS). The MWNTs were deposited as dilute dispersions on SERS-active substrates. We used nano-structured gold surfaces with various morphologies for our measurements. The surface enhancement effect was used to amplify the Raman signal from functional molecules bound to the nanotube walls. The recorded spectral features allowed for discrimination between the differently functionalised MWNTs. Although the present study is limited to a few examples, our measurements indicate the higher specificity obtained by the SERS approach and its possible use for a systematic study of functionalisation effects on MWNT structures. © the Owner Societies 2015.

Recent advances in nanotechnology and nanostructured materials offer the possibility to improve the mechanical properties of composite structures in terms of toughness and stiffness. In particular, in aerospace applications research efforts are focused on the design of advanced composite materials reinforced with carbon nanotubes (CNTs) that combine weight saving with multifunctional properties, including thermal, mechanical and electromagnetic ones. It is well known that carbon nanoparticles enhance the fracture strength, the modulus, and the yield strength of a polymer matrix through different mechanisms. However, despite the large amount of investigations on CNT-based composites and their relevant properties, there is a lack of understanding of the mechanisms leading to the failure of these materials under impact or static loads, which limits their use in practical applications. In this work, we present an experimental investigation of the fracture mechanisms of aerospace grade epoxy composites reinforced with multi-walled CNTs bridging the mechanical characterization with non-destructive methods, such as optical spectroscopy and electron microscopy. Our results show that it is possible to link the failure mechanisms of the nanostructured composite at the interface between the CNT and the epoxy matrix, namely cracking, pull-out and telescopic failure, with the molecular fingerprint of the carbon structure at the fracture surface after mechanical testing. © 2014 The Authors. Published by Elsevier Ltd.

We report the results of Raman measurements on some common military explosives and explosives precursors deposited on clothing fabrics, both synthetic and natural, in concentration comparable to those obtained from a single fingerprint or mixed with similar harmless substances to detect illegal compounds for smuggling activities. Raman spectra were obtained using an integrated portable Raman system equipped with an optical microscope and a 785-nm laser in an analysis of

In this work we report the results of RS measurements on some common military explosives and some of the most common explosives precursors deposited on clothing fabrics, both synthetic and natural, such as polyester, leather and denim cotton at concentration comparable to those obtained from a single fingerprint. RS Spectra were obtained using an integrated portable Raman system equipped with an optical microscope, focusing the light of a solid state GaAlAs laser emitting at 785 nm. A maximum exposure time of 10 s was used, focusing the beam in a 45 μm diameter spot on the sample. The substances were deposited starting from commercial solutions with a Micropipetting Nano-Plotter, ideal for generating high-quality spots by non-contact dispensing of sub-nanoliter volumes of liquids, in order to simulate a homogeneous stain on the fabric surface. Images acquired with a Confocal Laser Scanning Microscope provided further details of the deposition process showing single particles of micrometric volume trapped or deposited on the underlying tissues. The spectral features of each substance was clearly identified and discriminated from those belonging to the substrate fabric or from the surrounding fluorescence. Our results show that the application of RS using a microscope-based apparatus can provide interpretable Raman spectra in a fast, in-situ analysis, directly from explosive particles of some μm3 as the ones that it could be found in a single fingerprint, despite the contribution of the substrate, leaving the sample completely unaltered for further, more specific and propaedeutic laboratory analysis. The same approach can be envisaged for the detection of other illicit substances like drugs. © 2013 SPIE.

Single-walled carbon nanotubes (SWCN) have been produced treating nanosized graphitic powders with atomic hydrogen fluxes in a purpose-designed reactor. The Fe-catalyzed synthesis process yielded rather dense networks of nanotubes forming continuous layers adherent to the substrates. Raman spectroscopy in the 140–250 cm −1 region, high-resolution transmission electron microscopy and reflection electron diffraction in selected area configuration have been used to define the structural details of the nanotubes. The analysis evidenced a nanotubes population belonging prevalently to the ( n ,0) achiral symmetry subclass. This new experimental approach for SWCNs growth provides promising conditions for maximizing yields and generating selected tubular configurations.