Tito Busani

Nondestructive characterization and enzyme cleaning of painted surfaces: assessment from the macro to nano level.

This work establishes a multiscale and multitechnique nondestructive approach as valid methodology for monitoring surface properties and evaluating the effectiveness of enzymatic removal of varnishes from paintings/polychrome artefacts. Mock-up samples (documented reconstructions of oil, tempera, and gilded layers on canvas and wooden supports) were covered with different proteinaceous varnishes (egg white, animal and fish glue, casein) and then characterized before and after the removal of these coatings with enzyme-based solutions. The varnish was cleaned in several steps (two dry swabs and two wet swabs) with a clearance step for removing the residues from proteinaceous varnish or from enzyme solution. Microscopy [stereomicroscopy (SM), optical microscopy (OM), atomic force microscopy (AFM), and scanning electron microscopy (SEM)] and colorimetric (CIE L*a*b* system) techniques were used for characterization of the reconstruction surfaces at different scales (macro-scale by SM and OM; micro-scale by SEM and nano-scale by AFM). These techniques were also used to monitor the cleaning treatment. Although results presented in this work were obtained for the specific treatment of enzyme removal, the methodology could be extended to other types of materials and cleaning. Further experiments on real works of art are needed for a complete validation of the methodology.

Assessment of green cleaning effectiveness on polychrome surfaces by MALDI‐TOF mass spectrometry and microscopic imaging

This article proposes an innovative methodology which employs nondestructive techniques to assess the effectiveness of new formulations based on ionic liquids, as alternative solvents for enzymes (proteases), for the removal of proteinaceous materials from painted surfaces during restoration treatments. Ionic liquids (ILs), also known as “designer” solvents, because of their peculiar properties which can be adjusted by selecting different cation‐anion combinations, are potentially green solvents due totheir low vapour pressure. In this study, two ionic liquids were selected: IL1 (1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIM][BF4])) and IL2 (1‐ethyl‐3‐methylimidazolium ethylsulphate ([EMIM][EtSO4])). New formulations were prepared with these ILs and two different proteases (E): one acid (E1—pepsin) and one alkaline (E2—obtained from Aspergillus sojae). These formulations were tested on tempera and oil mock‐up samples, prepared in accordance with historically documented recipes, and covered with two different types of protein‐based varnishes (egg white and isinglass—fish glue). A noninvasive multiscale imaging methodology was applied before and after the treatment to evaluate the cleanings effectiveness. Different microscopic techniques—optical microscopy (OM) with visible and fluorescent light, scanning electron microscopy (SEM) and atomic force microscopy (AFM)—together with Matrix‐Assisted Laser Desorption/Ionization—Time of Flight Mass Spectrometry (MALDI‐TOF MS) were applied on areas cleaned with the new formulations (IL + E) and reference areas cleaned only with the commercial enzyme formulations (gels). MALDI‐TOF proved particularly very useful for comparing the diversity and abundance of peptides released by using different enzymatic systems. Microsc. Res. Tech. 77:574–585, 2014.

Demonstration of 99% capacity retention in Li/S batteries with a porous hollow carbon cap nanofiber–graphene structure through a semi-empirical capacity fading model

Lithium/sulfur batteries are a promising candidate for energy storage as they are capable of providing higher energy density in comparison to conventional Li-ion batteries. Here a rigorous numerical model is developed to predict the capacity retention of Li/S batteries discharged at different rates by taking into account the polysulfide (PS) shuttling effect for various nanostructured cathodes. In a numerical model, capacity fading of the cell is considered to be affected by the concentration of sulfur dissolved into the electrolyte and deposited on the anode as a Solid Electrolyte Interphase (SEI) layer. Our approach considers SEI layer formation as the main factor that dominates capacity fading over initial cycles (50 cycles). Equivalent Porosity (EP) is determined for various nanostructures and the model asset structures with smaller EP result in smoother capacity fading over cycling performance. The mean value of percentage error between simulation results and experimental capacity in all analyzed structures is less than 5%, except for mesoporous carbon at high discharge rates (1C). Using simulation results we propose Porous Hollow Carbon cap Nanofiber–Graphene (PHCN–G) as a highly efficient nanostructured cathode with a minimum shuttling effect and >99% capacity retention for long-cycling lifetime batteries.

Characterization of surface defects on Be-implanted GaSb

Characteristics of ion implantation induced damage in GaSb, and its removal by rapid thermal annealing, are investigated by cross-sectional transmission electron microscopy. Rapid thermal annealing (RTA) has been implemented on implanted GaSb for various temperatures and durations with the semiconductor capped, which avoids Sb out-diffusion and Ga agglomeration during the process. The RTA damage induced in the GaSb wafer was studied by scanning electron microscopy and energy dispersive x-ray spectroscopy. The results of the microscopy study were then used to optimize the RTA recipe and the Si3N4 capping layer thickness to achieve doping activation while minimizing crystalline damage. Results indicate a lattice quality that is close to pristine GaSb for samples annealed at 600 °C for 10 s using 260 nm thick Si3N4 capping layer. Secondary ion mass spectrometry measurement indicates that the implanted Be does not migrate in the GaSb at the used annealing temperature. Finally, electrical characteristics of di...

GaN nanowire tips for nanoscale atomic force microscopy

Imaging of high-aspect-ratio nanostructures with sharp edges and straight walls in nanoscale metrology by atomic force microscopy (AFM) has been challenging due to the mechanical properties and conical geometry of the majority of available commercial tips. Here we report on the fabrication of GaN probes for nanoscale metrology of high-aspect-ratio structures to enhance the resolution of AFM imaging and improve the durability of AFM tips. GaN nanowires were fabricated using bottom-up and top-down techniques and bonded to Si cantilevers to scan vertical trenches on Si substrates. Over several scans, the GaN probes demonstrated excellent durability while scanning uneven structures and showed resolution enhancements in topography images, independent of scan direction, compared to commercial Si tips.

Classical continuum theory limits to determine the size-dependency of mechanical properties of GaN NWs

We used the stable strain gradient theory including acceleration gradients to investigate the classical and nonclassical mechanical properties of gallium nitride (GaN) nanowires (NWs). We predicted the static length scales, Youngs modulus, and shear modulus of the GaN NWs from the experimental data. Combining these results with atomic simulations, we also found the dynamic length scale of the GaN NWs. Youngs modulus, shear modulus, static, and dynamic length scales were found to be 318 GPa, 131 GPa, 8 nm, and 8.9 nm, respectively, usable for demonstrating the static and dynamic behaviors of GaN NWs having diameters from a few nm to bulk dimensions. Furthermore, the experimental data were analyzed with classical continuum theory (CCT) and compared with the available literature to illustrate the size-dependency of the mechanical properties of GaN NWs. This practice resolves the previous published discrepancies that happened due to the limitations of CCT used for determining the mechanical properties of Ga...

Scatterometry for nanoimprint lithography

Angular scatterometry is used to characterize the nanostructure parameters of two samples: a high dielectric contrast ∼100-nm period Al wire-grid polarizer (WGP), and a low dielectric contrast ∼130-nm period photoresist grating on a flexible polycarbonate substrate; both fabricated by nanoimprint lithography. The zero-order diffraction (reflection) is monitored for a large incident angle range from 8° to 80°. For the WGP, four wavelengths (244-, 405-, 633-, and 982-nm) are used to study the dependence of the scatterometry parametric determination as a function of the sample pitch to wavelength ratio (p/λ: 0.41–0.1). A 4-nm thick native Al2O3 layer was added to the scatterometry simulation and dramatically improved the cross-correlations between results at the different wavelengths. For the photoresist samples, the scatterometry results at 405 nm are compared with atomic force microscopy measurements and the master grating structure. The scatterometry results are sensitive to inhomogeneity of the sample an...

New generation of biomorph integrated with TCO and thermoelectric to enhance efficiency in wide solar spectrum solar cell

A Novel Bio-Organic material, named Cooperative Binary Ionic (CBI) solid, based on chlorophyll type nano structures were self assembled onto ZnO and Bi2Te3 Nano Wires (NWs) as an active layer of a new concept of thermoelectric-organic solar cell. The quality of the organic coating is extremely good and controlled in the range of 0.5-10 nm. 5nm of the CBI onto the ZnO NWs showed a photo efficiency of 3% at 0.2 suns illumination while the thermoelectric current of the Bi2Te3 NWs increased by 1% at 1 sun. Optoelectronic and structural properties of the CBI and the integrated device are discussed.

Beryllium implant activation and damage recovery study in n-type GaSb

Damage induced by the implantation of beryllium in n-type GaSb and its removal by Rapid Thermal Annealing (RTA) are studied in detail by Atomic Force Microscopy (AFM), Cross Sectional Transmission Electron Microscopy (XTEM) and Energy Dispersive X-ray Spectroscopy (EDS). RTA has been implemented with different times and temperatures in order to optimize ion activation and to avoid Sb outdiffusion during the process. Results indicate a lattice quality that is close to pristine GaSb for samples annealed at 600 °C for 10s using a thick Si3N4 capping layer. Electrical response of the implanted diodes is measured and characterized as function of different annealing conditions.

Insufficiency of the Young’s modulus for illustrating the mechanical behavior of GaN nanowires

We use a non-classical modified couple stress theory including the acceleration gradients (MCST-AG), to precisely demonstrate the size dependency of the mechanical properties of gallium nitride (GaN) nanowires (NWs). The fundamental elastic constants, Youngs modulus and length scales of the GaN NWs were estimated both experimentally, using a novel experimental technique applied to atomic force microscopy, and theoretically, using atomic simulations. The Youngs modulus, static and the dynamic length scales, calculated with the MCST-AG, were found to be 323 GPa, 13 and 14.5 nm, respectively, for GaN NWs from a few nanometers radii to bulk radii. Analyzing the experimental data using the classical continuum theory shows an improvement in the experimental results by introducing smaller error. Using the length scales determined in MCST-AG, we explain the inconsistency of the Youngs moduli reported in recent literature, and we prove the insufficiency of the Youngs modulus for predicting the mechanical behavior of GaN NWs.