Polyvinylalcohol Composite Filled with Carbon Dots Produced by Laser Ablation in Liquids.

Carbon dots (CDs), owing to their excellent photoluminescent features, have been extensively studied for physics preparation methods and for biomedical and optoelectronic device applications. The assessment of the applicability of CDs in the production of luminescent polymeric composites used in LEDs, displays, sensors, and wearable devices is being pursued. The present study reports on an original, environmentally friendly, and low-cost route for the production of carbon dots with an average size of 4 nm by laser ablation in liquid. Jointly, to prove the significance of the study for a wide range of applications, a free-standing flexible polyvinyl alcohol (PVA) composite containing photoluminescent carbon dots was manufactured. CDs were prepared using targets of porose charcoal with a density of 0.271 g/cm3 placed in phosphate-buffered saline (PBS) liquid solution and irradiated for 30 min by pulsed IR diode laser. The optical properties of the obtained suspension containing carbon dots were studied with UV-ViS and FTIR spectroscopies. The photoluminescence of the produced carbon dots was confirmed by the emission peak at 480 nm in the luminescence spectrum. A narrow luminescence band with a full width at half-maximum (FWHM) of less than 40 nm could be an asset in spectral emission analysis in different applications. Atomic force microscopy confirms the feasibility of manufacturing CDs in clean and biocompatible environments, paving the way for an easier and faster production route, crucial for their wider applicability.

Mask-Assisted Deposition of Ti on Cyclic Olefin Copolymer Foil by Pulsed Laser Deposition.

Cyclic olefin copolymer (COC) is a novel type of thermoplastic polymer gaining the attention of the scientific community in electronic, optoelectronic, biomedicine and packaging applications. Despite the benefits in the use of COC such as undoubted optical transparency, chemical stability, a good water-vapor barrier and biocompatibility, its original hydrophobicity restricts its wider applicability and optimization of its performances. Presently, we report on the optical and morphological properties of the films of COC covered with Ti in selected areas. The layer of Ti on COC was deposited by pulsed lased deposition processing. The Ti/COC film was characterized by UV-Vis spectroscopy indicating that its transmittance in the visible region decreased by about 20% with respect to the pristine polymer. The quality of the deposited Ti was assessed with the morphology by scanning electron (SEM) and atomic force microscopies (AFM). The modification of the wettability was observed by the sessile drop method indicating a reduction of the native hydrophilicity.

SiC Measurements of Electron Energy by fs Laser Irradiation of Thin Foils.

SiC detectors based on a Schottky junction represent useful devices to characterize fast laser-generated plasmas. High-intensity fs lasers have been used to irradiate thin foils and to characterize the produced accelerated electrons and ions in the target normal sheath acceleration (TNSA) regime, detecting their emission in the forward direction and at different angles with respect to the normal to the target surface. The electrons' energies have been measured using relativistic relationships applied to their velocity measured by SiC detectors in the time-of-flight (TOF) approach. In view of their high energy resolution, high energy gap, low leakage current, and high response velocity, SiC detectors reveal UV and X-rays, electrons, and ions emitted from the generated laser plasma. The electron and ion emissions can be characterized by energy through the measure of the particle velocities with a limitation at electron relativistic energies since they proceed at a velocity near that of the speed of light and overlap the plasma photon detection. The crucial discrimination between electrons and protons, which are the fastest ions emitted from the plasma, can be well resolved using SiC diodes. Such detectors enable the monitoring of the high ion acceleration obtained using high laser contrast and the absence of ion acceleration using low laser contrast, as presented and discussed.

Ultra-High Molecular Weight Polyethylene Modifications Produced by Carbon Nanotubes and Fe2O3 Nanoparticles.

Thin sheets of ultra-high molecular weight polyethylene (UHMWPE), both in pristine form and containing carbon nanotubes (CNTs) or Fe2O3 nanoparticles (NPs) at different concentrations, were prepared. The CNT and Fe2O3 NP weight percentages used ranged from 0.01% to 1%. The presence of CNTs and Fe2O3 NPs in UHMWPE was confirmed by transmission and scanning electron microscopy and by energy dispersive X-ray spectroscopy analysis (EDS). The effects of the embedded nanostructures on the UHMWPE samples were studied using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and UV-Vis absorption spectroscopy. The ATR-FTIR spectra show the characteristic features of the UHMWPE, CNTs, and Fe2O3. Concerning the optical properties, regardless of the type of embedded nanostructures, an increase in the optical absorption was observed. The allowed direct optical energy gap value was determined from the optical absorption spectra: in both cases, it decreases with increasing CNT or Fe2O3 NP concentrations. The obtained results will be presented and discussed.

Compositional and Structural Modifications by Ion Beam in Graphene Oxide for Radiation Detection Studies.

In the present study, graphene oxide foils 10 µm thick have been irradiated in vacuum using same charge state (one charge state) ions, such as protons, helium and oxygen ions, at the same energies (3 MeV) and fluences (from 5 × 1011 ion/cm2 to 5 × 1014 ion/cm2). The structural changes generated by the ion energy deposition and investigated by X-ray diffraction have suggested the generation of new phases, as reduced GO, GO quantum dots and graphitic nanofibers, carbon nanotubes, amorphous carbon and stacked-cup carbon nanofibers. Further analyses, based on Rutherford Backscattering Spectrometry and Elastic Recoil Detection Analysis, have indicated a reduction of GO connected to the atomic number of implanted ions. The morphological changes in the ion irradiated GO foils have been monitored by Transmission Electron, Atomic Force and Scanning Electron microscopies. The present study aims to better structurally, compositionally and morphologically characterize the GO foils irradiated by different ions at the same conditions and at very low ion fluencies to validate the use of GO for radiation detection and propose it as a promising dosimeter. It has been observed that GO quantum dots are produced on the GO foil when it is irradiated by proton, helium and oxygen ions and their number increases with the atomic number of beam gaseous ion.

Synthesis of Porous Polydimethylsiloxane Gold Nanoparticles Composites by a Single Step Laser Ablation Process.

Typically, polymeric composites containing nanoparticles are realized by incorporating pre-made nanoparticles into a polymer matrix by using blending solvent or by the reduction of metal salt dispersed in the polymeric matrix. Generally, the production of pre-made Au NPs occurs in liquids with two-step processes: producing the gold nanoparticles first and then adding them to the liquid polymer. A reproducible method to synthetize Au nanoparticles (NPs) into polydimethylsiloxane (PDMS) without any external reducing or stabilizing agent is a challenge. In this paper, a single-step method is proposed to synthetize nanoparticles (NPs) and at the same time to realize reproducible porous and bulk composites using laser ablation in liquid. With this single-step process, the gold nanoparticles are therefore produced directly in the liquid polymer. The optical properties of the suspensions of AuNPs in distilled water and in the curing agent have been analyzed by the UV-VIS spectroscopy, employed in the transmission mode, and compared with those of the pure curing agent. The electrical dc conductivity of the porous PDMS/Au NPs nanocomposites has been evaluated by the I-V characteristics. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis have monitored the composition and morphology of the so-obtained composites and the size of the fabricated Au nanoparticles. Atomic force microscopy (AFM) has been used to determine the roughness of the bulk PDMS and its Au NP composites.

Role of Phage Capsid in the Resistance to UV-C Radiations.

The conformational variation of the viral capsid structure plays an essential role both for the environmental resistance and acid nuclear release during cellular infection. The aim of this study was to evaluate how capsid rearrangement in engineered phages of M13 protects viral DNA and peptide bonds from damage induced by UV-C radiation. From in silico 3D modelling analysis, two M13 engineered phage clones, namely P9b and 12III1, were chosen for (i) chemical features of amino acids sequences, (ii) rearrangements in the secondary structure of their pVIII proteins and (iii) in turn the interactions involved in phage capsid. Then, their resistance to UV-C radiation and hydrogen peroxide (H2O2) was compared to M13 wild-type vector (pC89) without peptide insert. Results showed that both the phage clones acquired an advantage against direct radiation damage, due to a reorganization of interactions in the capsid for an increase of H-bond and steric interactions. However, only P9b had an increase in resistance against H2O2. These results could help to understand the molecular mechanisms involved in the stability of new virus variants, also providing quick and necessary information to develop effective protocols in the virus inactivation for human activities, such as safety foods and animal-derived materials.

Laser Annealing of P and Al Implanted 4H-SiC Epitaxial Layers.

This work describes the development of a new method for ion implantation induced crystal damage recovery using multiple XeCl (308 nm) laser pulses with a duration of 30 ns. Experimental activity was carried on single phosphorus (P) as well as double phosphorus and aluminum (Al) implanted 4H-SiC epitaxial layers. Samples were then characterized through micro-Raman spectroscopy, Photoluminescence (PL) and Transmission Electron Microscopy (TEM) and results were compared with those coming from P implanted thermally annealed samples at 1650-1700-1750 °C for 1 h as well as P and Al implanted samples annealed at 1650 °C for 30 min. The activity outcome shows that laser annealing allows to achieve full crystal recovery in the energy density range between 0.50 and 0.60 J/cm2. Moreover, laser treated crystal shows an almost stress-free lattice with respect to thermally annealed samples that are characterized by high point and extended defects concentration. Laser annealing process, instead, allows to strongly reduce carbon vacancy (VC) concentration in the implanted area and to avoid intra-bandgap carrier recombination centres. Implanted area was almost preserved, except for some surface oxidation processes due to oxygen leakage inside the testing chamber. However, the results of this experimental activity gives way to laser annealing process viability for damage recovery and dopant activation inside the implanted area.

Study of gold nanoparticles for mammography diagnostic and radiotherapy improvements.

AIM: A study on the possibility to use gold nanoparticles in mammography, both for a better image diagnostics and radiotherapy, is presented and discussed. We evaluate quantitatively the increment of dose released to the tumor enriched with Au-NPs with respect to the near healthy tissues, finding that for X-rays the increase can reach two orders of greater intensity. BACKGROUND: Gold nanoparticles continue to be investigated for their potential to improve existing therapies and to develop novel therapies. They are simple to obtain, can be functionalized with different chemical approaches, are stable, non-toxic, non-immunogenic and have high permeability and retention effects in the tumor cells. The possibility to use these for breast calcified tumors to be better treated by radiotherapy is presented as a possible method to destroy the tumor. MATERIALS AND METHODS: The nanoparticles can be generated in water using the top-down method, should have a size of the order of 10-20 nm and be treated to avoid their coalescence. Under diagnostic X-ray monitoring, the solution containing nanoparticles can be injected locally inside the tumor site avoiding injection in healthy tissues. The concentrations that can be used should be of the order of 10 mg/ml or higher. RESULTS: An enhancement of the computerized tomography diagnostics using 80-150 keV energy is expected, due to the higher mass X-ray coefficient attenuation with respect to other contrast media. Due to the increment of the effective atomic number of the biological tissue containing the gold nanoparticles, also an improvement of the radiotherapy effect using about 30 keV X-ray energy is expected, due to the higher photoelectric cross sections involved. CONCLUSIONS: The study carried out represents a feasibility proposal for the use of Au-nanoparticles for mammographic molecular imaging aimed at radiotherapy of tumor nodules but no clinical results are presented.

Gold Nanoparticles by Laser Ablation for X-Ray Imaging and Protontherapy Improvements.

BACKGROUND: Gold nanoparticles, 5-20 nm in diameter, were generated with a pulsed Nd: YAG laser at 1010 W/cm2 at solution concentrations ranging between 1-100 mg/ml. The incremental X-ray contrast imaging using gold nanoparticles was investigated and measured. The study was performed with the aim to enhance the massive absorption coefficient of X-ray radiation in the tumor for medical image quality and to improve traditional X-ray radiotherapy or proton therapy. A simulation of proton therapy improvement was conducted using a human ocular melanoma model, placed 3 cm behind the eye lens, and testing 60 MeV protons. Calculations suggest that the local injection of a solution containing Au-NPs may increase the proton energy released in the tumor above 50%, with the dose in the surrounding tissues leading to an increased probability of tissue healing. A discussion on recent patents in the ambit of the preparation and use of Au nanoparticles in medical imaging and therapy is presented. METHODS: Au nanoparticles were characterized using optical absorbance, X-ray fluorescence, SEM, and TEM microscopies. Biocompatible nanoparticle solutions were injected intravenously into tail veins of mice followed by X-ray imaging using 20-45 keV photons to evaluate the uptake and the clearance by different organs of the nanoparticles. RESULTS: Diagnostic X-ray images of mice in which the Au-NPs were injected showed high spatial resolution contrast of different organs having high up-take. A calculation of the dose released by X-rays, electrons and protons to the tumor site demonstrates that an increment of the order of 50% can be obtained using adapt solution concentration. CONCLUSION: The use of Au-NPs in biocompatible solutions injected in living organism permits their blood transport up to different organs. The NPs can be employed as contrast medium to enhance the medical image resolution and to prepare the cancer tissues to be exposed to ionization radiations in order to enhance the dose released to the tumor cells. This effect permits to reduce the total dose given to the patient and to increase the dose released to the tumor cells with respect to healthy ones.

Gold nanoparticles enhancing protontherapy efficiency.

The insertion of gold nanoparticles in biological liquids, tissues and organs permits to increase the equivalent atomic number of the medium that, if used as target to be irradiated by ionizing radiation, permits an increment of the absorbed dose. No toxic nanoparticles, such as the Au, can be injected in the cancer tissues at different concentrations before using a localized treatment that uses energetic proton beams for radiotherapy. Due to the high density and atomic number of the used gold nanoparticles, the absorbed radiation dose can be increased to about a factor six per cent using relatively low concentration of nanoparticles injectable as solution in the tumor tissue. This means to reduce the exposition to ionizing radiation or to increase the dose to the tumor site. Simulation programs of proton energy loss in tissues, using SRIM Code, are employed to evaluate the Bragg peak enhancing in presence of Au nanoparticles, so it will be presented and discussed. Some research findings and patents in the gold nanoparticle preparation and application to Medicine are reviewed in the present paper.

Radiotherapy Improvements by Using Au Nanoparticles.

Au nanoparticles can be prepared inside biological solutions and incorporated in special molecules for their transport through blood, drugs and proteins up to the tumour sites or directly injected in their volume when it is possible. The Au nanoparticles are biocompatible and can be accepted locally in the organism also at relatively high concentrations. The use of Au nanoparticles injected in the tumour site enhances significantly the effective atomic number of the medium, depending on the used concentration, and consequently the proton and electron energy loss and the X-ray absorption coefficient determining an increment of the local absorbed dose during radiotherapy. Traditional radiotherapy using electrons, X-rays and gamma rays, and innovative protontherapy can benefit the increment of the effective atomic number of the tissue in the presence of Au-nanoparticles embedded in the tumour volume with an adaptive up-take procedure. This method decreases the dose released to the healthy tissues permitting a better cantering of the irradiated targets and shielding the healthy tissue placed behind the tumour. The presented theoretical study approach permits to evaluate an enhancement of the radiotherapy dose of the order of 1 % using 60 MeV protons, of the order of 10% using 6 MeV electrons and of the order of 100 % using 100 keV X-ray photons. Here, we also disccused for patents relaed to the topic.

Ion acceleration and D-D nuclear fusion in laser-generated plasma from advanced deuterated polyethylene.

Deuterated polyethylene targets have been irradiated by means of a 1016 W/cm2 laser using 600 J pulse energy, 1315 nm wavelength, 300 ps pulse duration and 70 micron spot diameter. The plasma parameters were measured using on-line diagnostics based on ion collectors, SiC detectors and plastic scintillators, all employed in time-of-flight configuration. In addition, a Thomson parabola spectrometer, an X-ray streak camera, and calibrated neutron dosimeter bubble detectors were employed. Characteristic protons and neutrons at maximum energies of 3.0 MeV and 2.45 MeV, respectively, were detected, confirming that energy spectra of reaction products coming from deuterium-deuterium nuclear fusion occur. In thick advanced targets a fusion rate of the order of 2 × 108 fusions per laser shot was calculated.

Monte Carlo study of the dose enhancement effect of gold nanoparticles during X-ray therapies and evaluation of the anti-angiogenic effect on tumour capillary vessels.

Gold nanoparticles (GNPs) are a promising radiosensitizer agent in radiotherapy. Through a simulation performed with the Geant4 Monte Carlo code, we evaluated the dose enhancement effect of GNPs during therapies with an x-ray tube operating at 150 kV (E = 55 keV and E(max) = 150 keV) and we studied the impact of GNP diffusion out of the tumour vessels, in terms of antiangiogenic and cytotoxic effects. Firstly, a single x-ray beam was assumed to irradiate a parallelepiped volume of soft tissue, in which a GNP-doped "target" volume was placed at different depths. Average dose enhancement factors (DEF) in presence of GNPs were obtained as a function of the target depth and GNP concentration, uniformly distributed; values ranging between 1.6 for 10 mg Au/g at 0 cm and 7.2 for 200 mg Au/g at 5 cm were determined. Furtherly, a second geometry was adopted, in which a blood capillary vessel (10 µm thick and 10 µm of inner radius) was placed at the centre of a cubic volume of soft tissue; doses and DEFs to the capillary endothelium as well as to the surrounding viable tumour were evaluated, for different models of GNP diffusion. Our results indicate that the radial DEF profiles around the vessel are in close relationship with the radial profiles of GNP concentration assumed, except for at sharp gradients of concentration. DEFs at the endothelium ranged from 1.6 to 6.5, for GNP concentrations in the blood of 10 and 200 mg/ml, respectively. These data can be helpful for the development of new and more specific GNP-based radiosensitizers of potential interest in radiotherapy, exploiting the combined benefit of anti-angiogenic and cytotoxic dose enhancement effects.