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Polydimethylsiloxane (PDMS) has been irradiated by a ns pulsed IR laser in vacuum and the radiation effects induced by the coherent radiation, above a threshold fluence, produce a non-equilibrium plasma and material ablation. The laser absorption can be enhanced using gold nanoparticles (AuNPs) embedded in the polymer. The laser-generated plasma has been characterized, whereas the ion emission from both the virgin PDMS and the PDMS + AuNPs sheets has been analysed both in mass and energy. Morphological investigations, optical spectroscopy and compositional analyses have been performed. The adopted laser treatment can be employed to modify the properties of PDMS with and without AuNPs inducing a local enrichment of microcrystalline silicon in both cases.

The properties of graphene oxide foils were modified by excimer laser irradiation at different fluences and times. The irradiations were performed in air and in vacuum using a pulsed UV laser operating at 248-nm wavelength and 23-ns pulse duration. Measurements of ablation yield, microscope surface morphology and Raman spectroscopy were performed. The residual surface shows a significant oxygen reduction due to the removing of functional oxygen groups, a thickness reduction due to the removal of graphene layers depending on the used laser shots and a presence of defects in the graphene sheets as evident by the Raman spectroscopy investigation.

The laser spallation effect due to intense shockwaves caused by a brief and intense laser pulse irradiating a target surface, 2 mm thick, has been investigated for silver and other materials. For 300 ps IR laser pulse, at intensities of the order of 10(16) W/cm(2), the shockwave may produce deformations of the back-face in ductile materials, such as Ag, Cu and Al. In heavy materials with high tensile strength, such as Ta, the shockwave produces cracks in the bottom of the laser crater but not deformation in the back-face, while in brittle materials, such as monocrystalline Ge, it produces only superficial cracks and flaking, but not deformation and spallation of the back-face. In thick polymeric materials, such as high-density polyethylene, the ablated crater shape is well defined and the shockwave is strongly damped, and no deformation has been observed in the back-face. The laser ablation yield and the ion acceleration in the backward direction have been measured by mass lost and time-of-flight measurements. SEM microscopy of the different irradiated targets, showing details of the crater size, edges, flaking and deformation in the back-face, useful for a discussion on the shockwave propagation and shock pressure calculation, is presented.

Spherical gold nanoparticles (NPs), 10 nm in diameter, have been dispersed in a type of polydimethylsiloxane, whose polymerisation requires accurate temperature control. At the temperature of 100°C, the polymerisation of the polydimethylsiloxane matrix is completed in 15 min, whereas at room temperature (∼20°C), it takes about 24–48 h. Gold NPs were incorporated into polydimethylsiloxane after which the resulting nanocomposites were placed in an oven preheated to 100°C for different curing times. Both porous and bulk nanocomposites were obtained using a bottom-up approach. Polydimethylsiloxane (PDMS) nanocomposites with the weight-percentage concentration of 0.2% of Au NPs were cured for 15, 30 and 45 min. Different curing times have affected the Au-NP properties. The network of porous PDMS nanocomposite promotes a uniform anchoring of the gold NPs. The porous PDMS nanocomposite samples, prepared using the sugar-template method, have been compared with the bulk counterpart to obtain a full characterisation of the material. The dependence of the morphological and electrical properties of gold NPs on their size has been studied by atomic-force microscopy and two-point-probe electrical-conductivity measurement. The optical performance of the bulk PDMS nanocomposites has been analysed by ultraviolet–visible (UV–vis) spectroscopy in the transmission mode. An enhancement of the absorption was observed after the increase of both the nanocomposite-curing time and the percentage of the Au NPs used as fillers. The fabricated nanocomposite can be used to manufacture optical-sensing devices, switches in optoelectronics and optical waveguides.

A compressible capacitive mechanical pressure sensor has been developed. Porous polydimethylsiloxane (p-PDMS) has been chosen as dielectric insulator because of its dielectric constant value. Gold nanoparticles have been embedded in p-PDMS to change the dielectric properties and to tune its elasticity. p-PDMS and its nanocomposite have been synthesized using the sugar leaching process. The p-PDMS physical characterization, with and without the gold nanoparticles, has been conducted to investigate its elastic response to compressive stresses as a function of both the polymer preparation thermal treatment and the gold nanoparticle concentration. A sensor operating in a low-pressure range between about 100 Pa and 10 kPa with a strain ranging between about 5% and 95% has been realized. Dielectric constant and electrical resistivity measurements have been performed using samples with a starting volume of the order of 1 cm3. The relationship between the dielectric constant, the electrical resistivity and the compressive stress/strain has been also deduced. The described sensor is flexible, biocompatible, water equivalent and can have applications in biomedicine (orthopedic, dentistry), engineering (stress–strain measurements, robotics), and microelectronics (microbalances, stress test on electronic devices).

The INFN-CIMA project deals with the employment of graphene, graphene oxide (GO) and reduced graphene oxide (rGO) for applications in Nuclear Physics. In particular, the project aim is that to use ...

Pulsed IR lasers were employed to irradiate high boiling elements, such as C, Mo, Ta, W and Re, in high vacuum. The ablation yield, given in terms of removed mass per pulse, was investigated using ...

The present work has the purpose to evaluate experimentally the ablation threshold fluences of copper, silver, and their alloys in order to induce a safety laser cleaning of the metal artifacts avoiding damages to the bulk. We used two different pulsed lasers: a KrF excimer laser operating at 248 nm, 23 ns pulse duration and a Nd:YAG laser operating at 532 nm (second harmonic), 3 ns pulse. Preliminary experimental results about the laser cleaning of bronze coins will be reported. The laser cleaning consists on the reduction of the chlorine concentration from the surface of the coins. The laser cleaning, carried out by the KrF laser, provides a safe way of removing the chlorine concentration as the Energy Dispersive X-Ray Fluorescence analyses will demonstrate.

2.0 MeV proton beam accelerated at Tandetron is extracted in air through a thin film and allowed to scatter to irradiate the cell culture attached to the polymeric base of a biological flask. The irradiated cells were human medulloblastoma cell line Daoy treated with and without 5 nm sized spherical gold nanoparticles. Proton doses from 0.5 to 1.5 Gy have been employed to irradiate the cultures and to investigate the role of the radiotherapy performed with and without the use of the gold nanoparticles. Results indicated that cell survival is significantly reduced to about 50% when the nanoparticles at a concentration of about 6 × 1013 particles/ml are employed.

Reduced graphene oxide (rGO) is a two-dimensional material, which is attracting increasing attention due to its special properties. It can be obtained by laser or ion beam irradiations of pristine ...

Gold nanoparticles were prepared by laser ablation in water and then characterized through physical analyses, in the perspective to be employed for different applications in the fields of P...

Ion irradiation reduces oxidized graphene but causes morphological and structural changes in individual sheets. Graphene oxide (GO) films were irradiated under vacuum with ion beams having different atomic numbers and energies in the range (2–16) MeV. The structural and morphological changes undergone by the individual sheets of reduced graphene oxide (rGO) were analyzed by transmission electron microscopy and Raman spectroscopy. In particular, the electron diffraction highlights the deformations of the sheets through the deformation of the diffraction spots. A quantitative structural evaluation of such features was carried out using a new method based on the analysis of the radial and azimuth profiles extracted from the electron diffraction pattern. The spots deformation involves both the direction normal to the reciprocal lattice vectors and the parallel one. The former deformation is related to the non-planarity of the surface, the latter to the rearrangement of the deformed lattice. Experimental evidence indicates that there are many different orientations present within the electron beam with a diameter of less than one micron and that the surface normal of the sheet must vary in all directions. This is the result of a microscopic roughness inside the sheets. The progressive deformation of the spots depends on the absorbed ion dose. The morphological analysis, carried out at high resolution on rGO sheets, confirms structural results: the rGO sheets take on a static not flat but rippled configuration. Accentuated ripples are dose dependent.

Advanced targets based on thin foils of graphene oxide (GO) covered by metallic layers show many advantages with respect to others because permit high proton and light ion acceleration using high intensity pulsed lasers in Target-Normal Sheath-Acceleration (TNSA) regime. GO foils contain parallel micrometric graphene sheets, have low density, show high penetration, and low scattering by energetic electrons accelerated by laser, inducing electron channelling effects. They contain high concentrations of hydrogen, water, and functional oxygen groups, can be realized as thin films with high mechanical resistance, and show high photon absorbance for laser beams. In this work, we present experimental results obtained by our research group using thin GO targets covered by thin gold films, prepared in our laboratories. Advanced targets have been irradiated in TNSA regime with 40 fs laser pulses at the intensity of the order of 10(19) W/cm(2), using a laser spot of about 10 microns diameter, permitting to accelerate ions at energies of the order of 6 MeV per charge state. The electric field of ion acceleration can be increased by optimizing the irradiation conditions and the GO and Au film thicknesses. The novel findings of this work concern the high forward ion acceleration obtained using thin targets containing GO which induces the effect of electron channelling and production of high-density forward plasma. The plasma diagnostics are developed with fast SiC semiconductor detectors connected in time-of-flight (TOF) configuration. The fast semiconductor detector response permits to optimize the ion acceleration conditions by changing the distance of the laser focus with respect to the target surface, the incidence angle and the laser parameters.

At present graphene is the most exciting star in the materials science but graphene oxide, GO, that is its low-cost precursor attracts researchers from various fields because it is very easily produced at low cost. GO is an electrical insulator than can be transformed into graphene through the 'reduction' process. The oxygen functional groups it contains can be removed by various ways, also using lasers, ion beams and the intercalation process. The intensive research on graphene has allowed the rediscovery of various graphite-like layered materials with composition other than carbon, but properties are not yet fully known and with interesting possible applications. Among them, manganese thiophosphate, MnPS3, is a layered inorganic host matrix for making, through the intercalation-exfoliation-restacking technique, multi-functional hybrid thin films that can find application as optical switches, transparent coatings, in catalysis and photocatalysis, as lubricants, to create new multilayer structures, as dielectric substrates for graphene-based electronics and so on. If exfoliated at few layers, MnPS3 allows to realize good ultraviolet photodetectors with a gate tunable photoresponsivity and high photo gain. Recent progress in these graphene-like materials will be presented and discussed together with measurements based on the use of lasers, ion beams and intercalation emphasizing their potential applications.

Light trapping and luminescence have been observed in polydimethylsiloxane (PDMS) foils containing about 0.1-0.2 wt% gold nanoparticles (AuNPs). The so-prepared PDMSs have been physically characterized using SEM microscopy, UV-Vis, FTIR and Raman spectroscopies. The used AuNPs have been controlled by means of the surface plasmon resonance absorption spectra. In the AuNPs-PDMS foils, a luminescence peak at about 425 nm has been induced by an exciting light at 280 nm. The light injection with an optical fiber is trapped inside the polymer-containing NPs and illuminates all the polymer volume. The measurements of scattered light show an increment in the light intensity due to the presence of AuNPs and air bubbles inducing diffractions, reflections and Mie scattering. Further investigations have been conducted irradiating the PDMS with AuNPs in vacuum with 2.9 MeV proton beams producing luminescence in the blue region. The mechanisms of light trapping and luminescence and the possible applications of the prepared material are presented and discussed.

mu Raman spectra of graphene oxide (GO) and reduced graphene oxide (rGO) foils, subjected to 2 divided by 3 MeV proton beam irradiations in vacuum at low and high fluence, have been investigated. The spectra detailed analysis indicates that the characteristic D and G peaks yields ratio, the area of the D" peak, located between D and G, the G peak full width at half maximum, the C-H band area and full width at half maximum are functions of the absorbed dose. The D and the D" peaks presence is indicative of the disorder generated in the target by the ion beam. All these observations suggest some useful indexes to read the proton absorbed dose by the irradiated rGO foils. Therefore, these GO based foils can be employed as dosimeters for proton beams in a large range of absorbed dose, from about 100 Gy up to about 114 MGy, within which Raman signals respond linearly.

Graphene-based materials have peculiar optical, electrical, mechanical and chemical properties, which make them useful for making thin films and thick sheets suitable for different needs. Matter physics, nuclear physics, microelectronics, biomedicine, engineering, agriculture and cultural heritage just represent some of the sectors in which these materials can be successfully used. The advancements allow us to go from a given graphene-based material to another transforming, for example, the insulator graphene oxide to electrically and thermally conductive reduced graphene oxide. Thanks to the interesting properties possessed by graphene-based materials, it is possible to realize gas sensors, dosimeters for ionizing radiation, light detectors, electronic devices, membranes for gases and desalination, biocompatible surfaces, medical protheses and thin coating films to preserve underlying layers. Different analysis techniques are presented to control the physical modifications of reduced graphene oxide (rGO) due to the different treatments for the pristine one. The paper reports the possibility to realize GO micro-dosimeters for ionizing radiations, sensors for air humidity and other gases, field effect transistors as the detector of visible and UV radiations, GO and rGO membranes realization for different gases, source ion strippers to enhance the charge state of different ions to be accelerated. Some of these aspects and possible applications will be presented and discussed with measurements carried out in our laboratories.

The pulsed laser cleaning (PLC) technique employing different laser wavelengths, with a ns pulse duration, is presented. Such a technique can be applied to the preservation of cultural heritage artworks on different materials, like metals, ceramics and glasses to clean the surfaces of debris accumulated over the years, to remove the oxidation layers, the dust, the organic materials and other unwanted layers, restoring their original composition and shape. PLC should be preceded by surface analyses to control the state of the surface before and during the cleaning process, which has to be carefully controlled, in order to stop the cleaning before to damage the underlying original surface. PLC examples, applied to metals, terracotta and glazy ceramics, are presented and discussed using IR, visible and UV pulsed laser irradiations at low intensity.

Gafchromic HD-V2 films are employed to study the response to light ions useful in radiotherapy, such as protons, helium and carbon beams. The effects induced by the ions at an energy within about 300 keV and 16 MeV were investigated in terms of optical absorbance measurements in the irradiated active region of the film. The employed ion doses range between 0.4 Gy and 12 kGy. The results show that the net optical density increases almost exponentially with the absorbed dose and that it becomes saturated after prolonged dose higher than 1 kGy. The optical density produced in the film was measured by light transmission measurements at 700 nm wavelength, at which is observed the highest gafchromic sensitivity. Calibration curves of optical density versus exposure dose and type of ion are given. The dependence on the ion stopping power was presented and discussed.

The graphene oxide (GO) reduction by ionizing radiation is proportional to the absorbed dose due to the energy release which produces ionizations, deexcitations, chemical bonding breaking, radical formation and recombination, oxygen functional groups and water desorption. Thanks to this, GO can be employed as a dosimeter whose dose can be measured using different analysis techniques, such as Raman spectroscopy, X-ray diffraction (XRD) and Energy Dispersive X-ray (EDX) analysis based on the characteristic X-ray emission, X-ray photoelectron spectroscopy (XPS). To evaluate the GO reduction as a function of the Linear Energy Transfer (LET) of the used radiation, measurements have been performed with XPS and EDX to deduce the C/O atomic ratio versus the X-rays, electron and ion beam energy loss. Results indicate that a linear dependence on LET occurs, as will be presented and discussed.

Proton acceleration can be induced by non-equilibrium plasma developed by high-intensity laser pulses, at 1016 W/cm2, irradiating different types of thin polyethylene targets. The process of proton acceleration and directive yield emission was investigated, optimizing the laser parameters, the irradiation conditions, and the target properties. The use of 600 J pulse energy, a laser focalization inducing self-focusing effects and advanced targets with embedded nanoparticles and optimal thicknesses, has permitted to accelerate forward protons up to the energies of about 6 MeV and amount of the order of 1015 H+/pulse. High proton energy is obtained using thin foils enriched with gold nanoparticles, whereas high proton yield is obtained using targets with a thickness of about 10 μm. The plasma diagnostics using SiC semiconductor detectors in time-of-flight configuration was fundamental to monitor the optimal conditions to improve the plasma processes concerning the ion acceleration and the X-ray and relativistic electron emission.

A Nd:YAG laser operating at 1064 nm was used to irradiate, at different intensities, graphene oxide foils placed in vacuum and in air. The laser irradiated GO foils were analysed successively by using different techniques such as 2.0 MeV alpha particle Rutherford backscattering spectrometry, X-ray photoemission spectroscopy and SEM-EDX. In particular, in vacuum irradiated graphene oxide samples the oxygen reduction has been observed with increment of the carbon content. In air irradiated GO samples an increase in oxygen has instead been highlighted. Furthermore thermal and chemical effects are induced by the photon irradiation. Results will be presented and discussed.

Different ion beams, from protons up to gold ions, with energy from 2 MeV up to 16 MeV, have been employed to irradiate graphene oxide (GO) foils in vacuum. The ion energy deposition reduces GO releasing functional oxygen groups. The effect of radiating ions – GO foils interaction has been investigated by Raman spectroscopy, X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). All the performed analyses show that both reduction and damaging depend on the fluence, the energy and the type of radiating ions. In the regime of electron stopping power the reduction is linearly dependent on the absorbed dose, while in the regime of nuclear stopping power an intense damage is produced in GO, altering the Raman spectrum and producing defects and amorphization of the material. The achieved goal was to quantify the GO's response to ionizing radiation with the aim of using the GO foil as a dosimeter for high energy ion beams.

Proton acceleration using high-intensity laser pulses, at 1016 W/cm2 was studied irradiating different types of thin metal and plastic targets having 1-micron thickness. The maximization of the proton energy process was investigated optimizing the laser parameters, the irradiation conditions and the target properties. Employing 600–700 J laser pulse energy, a focalization inducing self-focusing effects and using targets with optimized thickness, it was possible to accelerate protons up to energies of above 8 MeV. The time-of-flight diagnostics has allowed to monitor the plasma properties and to control the ion acceleration process.

An ns Nd:YAG pulsed laser was used to deposit thin films in a vacuum and to generate nanoparticles in the water of Ni, Ti, and NiTi alloys. Laser ablation was measured in terms of removing mass per laser pulse. The laser-generated plasma in vacuum was characterized in terms of temperature and energy of emitted particles. The ablation in water produces nanoparticles with dimensions of the order of 25 nm and solutions with concentrations of the order of some mg/ml. The NiTi alloy stoichiometry is well reported in the deposited thin film and in the composition of the produced nanoparticles.

A laptop neutron source suited for the most demanding field or laboratory applications is presented. It is based on laser ablation of CD2 primary targets, plasma acceleration of the D+ ions, and their irradiation of secondary CD2 targets. The deuterium–deuterium (D-D) fusion reaction is induced in the secondary target, according to the values of fusion cross-section versus deuteron energy, which show a significant probability also at relatively low ion energies. The experiments were completed in the PALS laboratory, Prague, detecting monoenergetic neutrons at 2.45 MeV with an emission flux of about 109 neutrons per laser shot. Other experiments demonstrating the possibility to induce D-D events were performed at IPPLM, Warsaw, and at INFN-LNS, Catania, where the deuterons were accelerated at about 4 MeV and 50 keV, respectively. In the last case, a low laser intensity and a post-ion acceleration system were employed. A special interaction chamber, under vacuum, is proposed to develop a new source of monochromatic neutrons or thermalized distribution of neutrons.

Measurements of nitrogen diffusion coefficient in graphene oxide (GO) and reduced graphene oxide (rGO) have been performed at different temperatures ranging between 21 °C and 101 °C. GO and rGO foils have been prepared as thin foils with 15 μm in thickness, total surface of about 5 cm2 and active diffusion surface of about 20 mm2. The rGO foils have been obtained by thermal annealing at 170 °C for 30 min in air. The measured room temperature diffusion coefficients, of 3.43 × 10−4 cm2/s for GO and 5.1 × 10−4 cm2/s for rGO, and, at 101 °C, of 5.22 × 10−4 cm2/s for GO and 10.7 × 10−4 cm2/s for rGO, have been obtained with a simple experimental set-up measuring the gas pressure gradient applied to the two faces of the thin foils versus the time. The rGO foils show a significant increasing of the diffusion coefficients with respect to the pristine GO due to the removing of water and some functional oxygen groups which determines the aperture of nanochannels through which the N2 gas diffuses. The thermal activation energy of nitrogen diffusion is evaluated for the two investigated materials. The experimental apparatus to measure the diffusion coefficients, the obtained results, their correlation with the graphene sheets structure and the comparison with the literature data are presented and discussed.

Different ion beams, with energy from 2 MeV up to 16 MeV at different atomic number, have been employed to irradiate graphene oxide (GO) foils in vacuum. Due to effects of electron and nuclear ion stopping powers, the ion energy deposition reduces the irradiated GO foils and structurally modifies them. The ion bombarded GO foils X-ray diffraction (XRD) investigations have permitted to shed light on the different structural phases induced by the ion energy deposition. The changes in the GO foils pristine structure shift the diffraction main peak towards larger angles and produce new diffraction peaks indicating the presence of new phases, such as reduced GO (rGO), carbon nanotubes (CNT), amorphous carbon (a-C), onion like carbon (OLC) and probably new carbon allotropes. The obtained results indicate that the inner structure of the GO foils becomes more and more compact and dense with the absorbed dose, suggesting that the removal of the functional oxygen groups leads to a near graphite structure with a significant increase of the material mass density. The different structural phase modifications induced by the different ion beams as a function of the stopping power, fluence and dose will be presented and discussed in detail.

fs pulsed lasers at an intensity of the order of 1018 W/cm2, with a contrast of 10−5, were employed to irradiate thin foils to study the target-normal-sheath-acceleration (TNSA) regime. The forward ion acceleration was investigated using 1/11 µm thickness foils composed of a metallic sheet on which a thin reduced graphene oxide film with 10 nm thickness was deposited by single or both faces. The forward-accelerated ions were detected using SiC semiconductors connected in time-of-flight configuration. The use of intense and long pre-pulse generating the low contrast does not permit to accelerate protons above 1 MeV because it produces a pre-plasma destroying the foil, and the successive main laser pulse interacts with the expanding plasma and not with the overdense solid surface. Experimental results demonstrated that the maximum proton energies of about 700 keV and of 4.2 MeV carbon ions and higher were obtained under the condition of the optimal acceleration procedure. The measurements of ion energy and charge states confirm that the acceleration per charge state is measurable from the proton energy, confirming the Coulomb–Boltzmann-shifted theoretical model. However, heavy ions cannot be accelerated due to their mass and low velocity, which does not permit them to be subjected to the fast and high developed electric field driving the light-ion acceleration. The ion acceleration can be optimized based on the laser focal positioning and on the foil thickness, composition, and structure, as it will be presented and discussed.

Radiochromic films (RCF), also called GafChromic™ films, represent a performant material for accurate quantitative radiation dosimetry. Their compositions allow high dose sensitivity and fewer envi...

A pulsed ns IR laser at about 1010 W/cm2 intensity is employed to irradiate a Cu target placed in a vacuum and in nitrogen gas. The produced plasma is characterized in terms of emitted ions and photons as a function of the nitrogen pressure in the chamber. The mechanisms of ion gas interactions are investigated in terms of Cu ion energy loss and X-ray attenuation using an ion collector and a SiC detector. A fast CCD camera in the visible region has produced the collision images of the ions with the nitrogen molecules. A plasma temperature of about 44 eV, an emission of soft X-rays up to about 100 eV, an ablation yield of about 2.4 × 1015 atoms/pulse, a maximum Cu ion acceleration of 1.4 keV and a maximum ionization up to Cu9+ were measured in high vacuum.

Thin foils of graphene oxide (GO) are irradiated by a fs titanium sapphire laser at an intensity of about 1019 W/cm2 in high vacuum. The produced plasma in the forward direction accelerates ions in a regime of target-normal-sheath-acceleration, thanks to the relativistic electron emission from the target surface and to their emission from the rear foil surface, generating a high electric field pulse with the positive target. The ion acceleration is measured mainly using SiC detectors in the time-of-flight configuration. Adding gold as nanoparticles or as a thin coverage film, the ion acceleration is enhanced as a result of a higher plasma electron density. The optimal acceleration is reached by varying the GO thickness, the Au nanoparticle concentration, the thin Au film thickness, and the irradiation conditions. Particularly important is the laser focal position with respect to the target surface, which is responsible for different acceleration values. In the used experimental conditions, a maximum proton energy of 2.6 MeV was obtained and the best modality to add Au atoms to the target is discussed.

A new type of ion dosimeter based on graphene oxide (GO) foils is presented and discussed. GO is biocompatible, stable, tissue equivalent and has special chemical and physical properties. The ion i...

The oxygen content in graphene oxide (GO) can be reduced by the ion beam irradiation in high vacuum conditions. The reduction changes the C/O atomic ratio that increases with the absorbed ion dose. Moreover, as the level of reduction increases, the surface flattens and the material becomes denser. At high absorbed doses, greater than about 100 MGy, the material is affected by the high energy deposited with damage radiation effects which make the C/O ratio not proportional to the dose. At low doses, less than about 100 MGy, the C/O atomic ratio shows an optimal linearity with the ion dose and is independent of the ion stopping power, thus assuming the characteristics of a good biocompatible water-tissue equivalent dosimeter. The aim of the work was that to explore the possibility to use GO as ionizing radiation dosimeter for energetic ion beams by the measure of the compositional C/O atomic ratio.

A hybrid film consisting of graphene oxide covered with poly(dimethylsiloxane) was prepared via spin coater and followed by thermal annealing to improve the bond strength of the polymerized systems. Direct patterning on both graphene oxide and hybrid graphene oxide–poly(dimethylsiloxane) foils by ion microbeam was performed to induce localized reduction in the ion irradiated material. It is well established that the ion irradiation of graphene oxide induces modifications in its electrical, mechanical, and optical properties and disorder in the carbon crystal structure and defect production. The presence of poly(dimethylsiloxane) can be useful as it confers flexibility to the produced pattern and oxygen permeability from the graphene oxide surface. Rutherford backscattered spectroscopy and elastic recoil detection analysis were performed to evaluate the compositional changes in the composite. Atomic force microscopy studied the pattern fidelity. The electrical conductivity of the hybrid material was used to evaluate the changes induced during the proton irradiation of the material.

The suitability of graphene oxide (GO) foils as radiation sensitive materials for soft X-ray irradiation is investigated by means of X-ray photoelectron spectroscopy (XPS). In particular GO micrometric foils have been irradiated by soft X-rays at a 1486.6 eV energy at high flux (>1012 photons/cm2s) in ultra-high vacuum. The XPS analysis of the carbon-carbon (CC) and the carbon-oxygen links (CO) characterizes the composition of the first layers of the GO foils. The CC/CO ratio of the high-resolution C1s XPS spectrum is used as dosimetric index. The incident X-ray photons, proportionally to their fluence, partially reduce GO foils decreasing the amount of oxygen groups chemically bonded to carbon network. This decrease causes an increase on the CC/CO ratio that is correlated to the irradiation time, i.e. to the dose absorbed by the GO foil, showing a linear increment with the dose. Our preliminary investigations indicate that GO can be employed to realize a thin foil dosimeter giving a linear response to the absorbed dose in the (275.76 kGy ÷ 8.02 MGy) range. The absorbed dose can be also evaluated by measuring the C/O ratio from the C1s and O1s XPS spectra analysis or with different techniques, as discussed in the paper.

Non-equilibrium plasma was obtained by irradiating Al foils in vacuum with a femtosecond (fs) laser at intensities of the order of 1018 W/cm2. Protons and other light ions were accelerated in the forward direction by using the target-normal-sheath acceleration regime. Time-of-flight technique was employed to measure the ions' kinetic energy using SiC detectors placed at known distances and angles. The ion acceleration was monitored under different conditions of laser focal position, laser pulse energy, and laser contrast. The target was irradiated using different thicknesses and anti-reflecting graphene films. By optimizing the laser parameters, irradiation conditions, and target properties, it was possible to accelerate up to 2.3 MeV per charge state, as will be presented and discussed.

Two well-established electrical insulators, graphene oxide and poly(methylmethacrylate) (PMMA) have been selectively exposed to controlled energy and fluence of ions. Ion micro beam has been propos...

The nonequilibrium plasma generated by nanosecond laser pulse is characterized using a SiC detector connected in time-of-flight configuration to measure the radiations emitted from the plasma. Different metallic targets were irradiated by the pulsed laser at an intensity of 1010 W/cm2 and 200 mJ pulse energy. The SiC allows detecting ultraviolet radiations and soft X-rays, electrons, and ions. The obtained plasma has a temperature of the order of tens to hundreds eV depending on the atomic number of the irradiated target and ion accelerations of the order of 100 eV per charge state.

A ns Nd:YAG pulsed laser has been employed to produce plasma from the interaction with a dense target, generating continuum and UV and soft x-ray emission depending on the laser parameters and target properties. The laser hits solid and gaseous targets producing plasma in high vacuum, which was investigated by employing a silicon carbide detector. The two different interaction mechanisms were studied, as well as their dependence on the atomic number. The photon emission from laser-generated plasma produced by solid targets, such as boron nitride (BN) and other elements (Al, Cu, Sn and Ta) and compounds such as polyethylene, has been compared with that coming from plasma produced by irradiating different gas-puff targets based on N2 and other gases (Ar, Xe, Kr, SF6). The experimental results demonstrated that the yields are comparable and, in both cases, increase proportionally to the target atomic number. The obtained results, focusing the attention on the advantages and drawbacks of the employed targets, are presented and discussed.

Bronze coins coming from the area of the Mediterranean basin, dated back the II–X Cent. A.D., were analyzed using different physical analytical techniques. Characteristic X-ray fluorescence was used with electrons and photons, in order to investigate the elemental composition of both the surface layers and bulk. Moreover, the quadrupole mass spectrometry coupled to laser ablation (LAMQS technique) in high vacuum was used to analyse typical material compounds from surface contamination. Mass spectrometry, at high resolution and sensitivity, extended up to 300 amu, allowed measuring the 208Pb/206Pb and 207Pb/206Pb isotopic ratios into the coins. Quantitative relative analyses of these isotopic ratios identify the coin composition such as a “fingerprint” depending on the mineral used to extract the lead. Isotopic ratios in coins can be compared to those of the possible minerals used to produce the bronze alloy. A comparison between the measured isotope ratios in the analyzed coins and the literature database, related to the mineral containing Pb as a function of its geological and geophysical extraction mine, is presented. The analysis, restricted to old coins and the mines of the Mediterranean basin, indicates a possible correlation between the coin compositions and the possible geological sites of the extracted mineral.

Measurements of electrical conductivity were carried out at temperatures ranging between 77 K and 450 K on high vacuum thermal reduced graphene oxide (rGO) films. The investigated samples were characterized in composition and structure before being analyzed in terms of electrical conduction. Their electrical conductivity was also measured in air at room temperature. Measurements have demonstrated that at first graphene oxide (GO) was not stable both in air and vacuum. It stabilized after having been subjected to 7 thermal cycles under high vacuum conditions, about 10−7 torr, up to a Tmax of 450 K. At room temperature the initial GO material had a very low conductivity, of the order of 10−10 Ω−1 x cm−1, which increased to about 2.5 Ω−1x cm−1 when it was thermal stabilized in rGO. The stabilization process, induced by the high vacuum heating procedure, seems due to a good reduction of GO, which gives rise to such expansion of the conjugated π-electron system that a band-like transport with small thermal activation energies (Ea = 10–50 meV) occurs. The performed electrical conductivity measurements are presented and discussed.

Advanced targets based on graphene oxide and gold thin film were irradiated at high laser intensity (1018–1019 W/cm2) with 50-fs laser pulses and high contrast (108) to investigate ion acceleration in the target-normal-sheath-acceleration regime. Time-of-flight technique was employed with SiC semiconductor detectors and ion collectors in order to measure the ion kinetic energy and to control the properties of the generated plasma. It was found that, at the optimized laser focus position with respect to the target, maximum proton acceleration up to about 3 MeV energy and low angular divergence could be generated. The high proton energy is explained as due to the high electrical and thermal conductivity of the reduced graphene oxide structure. Dependence of the maximum proton energy on the target focal position and thickness is presented and discussed.

Reduced graphene oxide (rGO) films can be employed as ion strippers in an accelerator. They show some advantages with respect to the graphite foils, due to their high thermal and electrical conductivity, low density, high mechanical resistance and high stability. Thin graphene oxide (GO) films with a sub-micron thickness have been synthesized and transformed into reduced GO (rGO) by ion beam irradiations. Physical characterizations of the pristine and ion irradiated GO films have been performed. Measurements of stripping efficiency have been carried out by using helium, lithium, carbon and oxygen ion beams. The rGO stripper films demonstrate a significantly high charge production, comparable to that of the graphite films but with the advantage of a longer lifetime.

The laser irradiation of tantalum targets is presented for different pulsed laser intensities ranging from 1010 up to about 1018 W/cm2 and pulse durations from 9 ns up to 40 fs. The results show that the produced non-equilibrium plasma accelerates Ta ions in the backward direction from values of the order of keV up to values of about 5 MeV. In thin foils, the forward plasma, developed behind the target along the direction of incoming laser, at intensities of about 1016 W/cm2 and 300 ps pulse duration, accelerates Ta ions at energies of the order of 4.6 MeV and produces charge states up to about 40+. For fs lasers at intensities of the order of 1018 W/cm2, only proton acceleration occurs up to 2.1 MeV while no Ta ions are accelerated, due to the reduced duration of the electric field and to the too high inertial mass of the Ta ions.

In recent years graphene and its derivatives, have attracted scientific interest due to their unique properties. This study is to explore the quality of synthesized graphene oxide and reduced graphene oxide foils under the irradiation of protons and helium ions of the same energy and current. Fully characterizations by Raman spectroscopy, Rutherford backscattering spectrometry and Elastic recoil detection analysis and the relative results are presented. The effects of parameters, such as type of ions, their current and irradiation time, are studied. The quality of large-scale fabrication of graphene oxide and reduced graphene oxide (rGO) is important for industrial and research applications of these materials. An overview on the changes in the optical property and electron conductivity of graphene oxide and reduced graphene oxide under irradiation by protons, helium and carbon ions are also summarized.

Graphene oxide (GO) is prepared as a self-supporting thin film by a liquid solution of GO. The so-obtained GO films have been characterized in terms of thickness and density. The GO film composition and trace elements have been measured with Rutherford backscattering spectrometry (RBS) and Elastic recoil detection analysis (ERDA), using MeV helium ion beams. The presence of crystalline and amorphous phases has been also investigated with X-ray diffraction (XRD) and the morphology by scanning electron microscopy (SEM). Information about the GO film structure, oxidation degree and thickness has been deduced by means of Fourier transform infrared spectroscopy (FT-IR), Raman and optical spectroscopy (ultraviolet-visible-near infrared spectroscopy, UV-Vis-nIR). In particular, the GO film thickness varies from sub-micrometric values up to micrometric ones. Furthermore, the GO film heating in air up to 60 °C produces oxidation effects as deduced from the interpretation of our data.

The laser ablation of boron-nitride (BN) ceramic was employed for the preparation of thin films in high vacuum and nanoparticles and nanocrystals generated in water. The obtained plasma was investigated using ion detectors to determine the ion velocity, the energy per charge state and the plasma temperature and describing the acceleration mechanism. The kinetics of laser ablation in water and the comparison of different ablation rates in the vacuum and in water, and the possible applications of the BN thin film and nanoparticles are presented and discussed.