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Biofilms are key bacterial communities in genetic and adaptive resistance to antibiotics as well as disease control strategies. The mature high-coverage biofilm formations of the Vibrio campbellii strains (wild type BB120 and isogenic derivatives JAF633, KM387, and JMH603) are studied here through the unstraightforward digital processing of morphologically complex images without segmentation or the unrealistic simplifications used to artificially simulate low-density formations. The main results concern the specific mutant- and coverage-dependent short-range orientational correlation as well as the coherent development of biofilm growth pathways over the subdomains of the image. These findings are demonstrated to be unthinkable based only on a visual inspection of the samples or on methods such as Voronoi tessellation or correlation analyses. The presented approach is general, relies on measured rather than simulated low-density formations, and could be employed in the development of a highly efficient screening method for drugs or innovative materials.

Neutron applications and detection are of paramount importance in industry, medicine, scientific research, homeland security, production of extreme UV optics and so on. Neutron detection requires a converter element that, as a result of its interaction with neutrons, produces reaction products (mainly charged particles) whose detection can be correlated with the neutron flux. Reduced availability and increased cost of the most used converter element, 3He, have triggered research efforts for alternative materials, proper deposition methods and new detector architectures. 10B converter is a valid alternative to 3He thanks to its high thermal neutron cross section and relatively high Q value. In this paper we report on the room temperature Pulsed Laser Deposition (PLD) of high quality and uniform 10B films with the expected density, different thickness values (0.5, 1.0, 1.2, 1.5 and 2.0 μm) and uniform thickness over a circular area of about 30 mm in diameter. Additionally, they are adherent to the substrate with a negligible presence of contaminants. The conversion properties of such 10B coatings coupled to a Si solid state detector are studied upon exposure to a neutron flux from an Am-Be neutron source (2.2·106 n/s). The experimental results, compared with spectra simulated by using a GEANT4 code, present a good agreement and efficiencies of the order of a few percent.

All-inorganic perovskites are widely investigated as a new generation of materials thanks to their superior optoelectronic properties and better stability than hybrid organic–inorganic perovskites. In particular, cesium lead bromide (CsPbBr3) exhibits advantageous properties for numerous applicative fields (photovoltaics, light-emitting diodes, photodetectors, lasing, field effect transistors, and ionizing radiation detectors). The performance of CsPbBr3 being critically dependent on the deposition technique, proper understanding and optimization of the fabrication process are demanding. Despite the well-known potentiality of the Pulsed Laser Deposition (PLD) technique in depositing films with complex stoichiometry, a very limited number of literature studies report on the successful deposition of CsPbBr3 films by PLD. Recently, the authors disclosed the impact of the uneven masses of Cs, Pb, and Br on the film stoichiometry and guidelines to recover the desired composition. Herein, we exploit stoichiometric mechano-chemically synthesized targets to deposit, by nanosecond-PLD (λ = 248 nm, τ = 20 ns, room temperature, fluence of 1 J/cm2), CsPbBr3 films to be studied following time aging, thermal heating and exposure to high relative humidity. Even in the presence of the characteristic absorption peak at ~ 520 nm, the freshly deposited film shows no photoluminescence. Photoluminescence is switched on by thermal annealing (at 250 and 350 °C) or after a few days (at least 15) of exposure to air and it persists over time. Films present interesting morphology evolution and oxygen adsorption following heating.

All-inorganic cesium lead bromine (CsPbBr3) perovskites have gained a tremendous potential in optoelectronics due to interesting photophysical properties and much better stability than the hybrid counterparts. Although pulsed laser deposition (PLD) is a promising alternative to solvent-based and/or thermal deposition approaches due to its versatility in depositing multi-elemental materials, deep understanding of the implications of both target composition and PLD mechanisms on the properties of CsPbBr3 films is still missing. In this paper, we deal with thermally assisted preparation of mechano-chemically synthesized CsPbBr3 ablation targets to grow CsPbBr3 films by PLD at the fluence 2 J/cm2. We study both Cs rich- and stoichiometric PbBr2-CsBr mixture-based ablation targets and point out compositional deviations of the associated films resulting from the mass distribution of the PLD-generated plasma plume. Contrary to the conventional meaning that PLD guarantees congruent elemental transfer from the target to the substrate, our study demonstrates cation off-stoichiometry of PLD-grown CsPbBr3 films depending on composition and thermal treatment of the ablation target. The implications of the observed enrichment in the heavier element (Pb) and deficiency in the lighter element (Br) of the PLD-grown films are discussed in terms of optical response and with the perspective of providing operative guidelines and future PLD-deposition strategies of inorganic perovskites.

Carbon dioxide (CO2)-laser processing of glasses is a versatile maskless writing technique to engrave micro-structures with flexible control on shape and size. In this study, we present the fabrication of hundreds of microns quartz micro-channels and micro-holes by pulsed CO2-laser ablation with a focus on the great potential of the technique in microfluidics and biomedical applications. After discussing the impact of the laser processing parameters on the design process, we illustrate specific applications. First, we demonstrate the use of a serpentine microfluidic reactor prepared by combining CO2-laser ablation and post-ablation wet etching to remove surface features stemming from laser-texturing that are undesirable for channel sealing. Then, cyclic olefin copolymer micro-pillars are fabricated using laser-processed micro-holes as molds with high detail replication. The hundreds of microns conical and square pyramidal shaped pillars are used as templates to drive 3D cell assembly. Human Umbilical Vein Endothelial Cells are found to assemble in a compact and wrapping way around the micro-pillars forming a tight junction network. These applications are interesting for both Lab-on-a-Chip and Organ-on-a-Chip devices.

Carbon dioxide (CO2)-laser processing of glasses is a versatile maskless writing technique to engrave micro-structures with flexible control on shape and size. In this study, we present the fabrication of hundreds of microns quartz micro-channels and micro-holes by pulsed CO2-laser ablation with a focus on the great potential of the technique in microfluidics and biomedical applications. After discussing the impact of the laser processing parameters on the design process, we illustrate specific applications. First, we demonstrate the use of a serpentine microfluidic reactor prepared by combining CO2-laser ablation and post-ablation wet etching to remove surface features stemming from laser-texturing that are undesirable for channel sealing. Then, cyclic olefin copolymer micro-pillars are fabricated using laser-processed micro-holes as molds with high detail replication. The hundreds of microns conical and square pyramidal shaped pillars are used as templates to drive 3D cell assembly. Human Umbilical Vein Endothelial Cells are found to assemble in a compact and wrapping way around the micro-pillars forming a tight junction network. These applications are interesting for both Lab-on-a-Chip and Organ-on-a-Chip devices., Graphical abstract Image 1, Highlights • Carbon dioxide-laser ablation was used for fast prototyping of quartz. • Serpentine microfluidic reactors were prepared after post-ablation wet etching. • Polymeric micro-pillars were fabricated using quartz micro-holes as molds. • Micro-pillars were used as templates to drive 3D assembly of Endothelial Cells. • Cells organize in a vessel-like configuration forming tight junctions.

Deposition of Au nanoparticles (NPs) through UV ultra-short-pulse laser ablation in vacuum is a methodology suitable for obtaining high purity supported plasmonic NPs with a superb adherence to both planar and patterned substrates. Furthermore, the peculiarity that upon sub-picosecond laser irradiation NPs form directly within the target leads to narrow and controlled size-distribution. While extensive literature theoretically models phase changes and pressure relaxation of metal targets under sub-picosecond irradiation, the evolution of the nanostructured deposit through different ablation regimes is poorly documented experimentally. In this paper, besides modeling the temporal evolution of electron and lattice temperature following sub-picosecond laser pulse irradiation of Au bulk at the threshold ablation fluence (0.1 J/cm2), we report an accurate statistical, morphological and structural characterization of the AuNP distributions as a function of the laser fluence tuned from 0.1 to 3 J/cm2 to drive the target through two ablation regimes. The occurrence of photomechanical spallation and phase explosion at low and high fluence, respectively, is correlated with the evolution of the NP deposits, which are discussed by providing a physical insight in the interplay between fluence-driven ablation regimes of the target, arrangement kinetics of the deposited species (NPs and vapour species) and (crystalline or amorphous) phase of the NPs. This knowledge is key for controlling the surface plasmon resonance response of AuNPs depending on the designed application.

The present generation of Micro-Pattern Gaseous Detectors (MPGDs) are radiation hard detectors, capable of detecting efficiently particle rates of several MHz/cm$^2$ , while exhibiting good spatial resolution ($\leq$ 50 $\mu$m) and modest time resolution of 5-10 ns, which satisfies the current generation of experiments (High Luminosity LHC upgrades of CMS and ATLAS) but it is not sufficient for bunch crossing identification of fast timing systems at FCC- hh. Thanks to the application of thin resistive films such as Diamond-Like Carbon (DLC) a new detector concept was conceived: Fast Timing MPGD (FTM). In the FTM the drift volume of the detector has been divided in several layers each with their own amplification structure. The use of resistive electrodes makes the entire structure transparent for electrical signals. After some first initial encouraging results, progress has been slowed down due to problems with the wet-etching of DLC-coated polyimide foils. To solve these problems a more in-depth knowledge of the internal stress of the DLC together with the DLC-polyimide adhesion is required. We will report on the production of DLC films produced in Italy with Ion Beam Sputtering and Pulsed Laser Deposition, where we are searching to improve the adhesion of the thin DLC films, combined with a very high uniformity of the resistivity values., Comment: MPGD2019 proceedings, presented by Piet Verwilligen

Solid-state neutron detectors exploit nuclear interactions producing energetic charged particles within a converter layer embedding nuclei with high neutron capture cross section and with thickness compatible with the charged particle range. Recently, boron-10 (10B) is being considered as a valid alternative to the expensive and decreasingly available 3He gas thanks to its large neutron absorption cross section and high-energy reaction products. Minimized amounts of impurities, films with optimal and well-controlled thickness, good uniformity over large areas and good adhesion to the substrates are essential to achieve efficient neutron detection performance. In this study, we present well-adherent 1-µm-thick 10B-enriched boron coatings, deposited over a large area by off-axis pulsed laser deposition (PLD) using a nanosecond Nd-YAG laser beam operating at 1064 nm and high fluence (~ 10 J/cm2), onto 1-mm-thick Al substrate as well as smooth and rough C substrates. By combining plasma plume divergence and peaked profile under off-axis deposition geometry, uniform10B films were obtained over an area of a 3.4 × 3.4 cm2. We discuss the morphological characteristics of our deposits as related to the mechanisms of nanosecond laser ablation and present energy dispersive spectroscopy (EDS) elemental analysis of the film, paying attention to the different surface features. Negligible presence of O, N and C contaminants was achieved by controlled vacuum conditions. Moreover, we present encouraging neutron detection performances of our film deposited onto Al.

Optically thin perforated gold films, fabricated using template colloidal masks self-assembled by following an elsewhere described simplified colloidal lithography protocol, are presented and discussed with the aim to develop a theory of short-range ordered nanoholes without straightforwardly extending concepts strictly related to periodic nanoholes. By Scanning Electron Microscopy (SEM) analysis of the evolution of nanohole short-range ordering and spatial coordination geometry under increasing interhole average spacing (dNN), unprecedented differences in the spectroscopic response are pointed out with respect to periodic systems. First, the dependence of the wavelength of a propagating plasmon mode on dNN is demonstrated to deviate from the linear relationship predicted by the grating-coupling picture developed for periodic arrays. Second, dNN cannot be straightforwardly interpreted as the counterpart of the lattice constant of periodic nanoholes, which demands to introduce a conceptually more rigorous periodicity-like length-scale. Once the impact of these findings on setting the operating parameters of a nanohole distribution is demonstrated, they are related, experimentally and by using a theoretical model developed by the authors, to the changes of the local coordination geometry (from quasi-hexagonal to quasi-square packing through mixed hexagonal–square coordination) induced by varying dNN over a wide interval. Autocorrelation analysis of SEM images is exploited to estimate a short-range periodicity-like length-scale, as a conceptual advance for laying the foundation of the concept of short-range ordered nanohole lattices and for deeper insight into the spectral response. As discussion is based on realistic, rather than simulated, evolution of colloidal arrangements, the formulated interpretative model accounts for realistic effects impacting transmission resonances.

Polystyrene colloids adsorbed onto a poly(diallyldimethylammonium chloride) (PDDA) monolayer is the model-system exploited to present and discuss both theoretical assessment and extended practical roadmap of the monolayer colloidal lithography (MNL-CL) protocol, recently developed by the authors to efficiently simplify and speed-up the deposition of template colloidal masks. Advantages of the MNL-CL protocol are demonstrated, in terms of ordering and coverage optimization of colloid arrangements, over the entire coverage range of its application, that is even under the commonly disregarded unsaturated adsorption conditions. A conceptual model is presented predicting an interparticle threshold spacing below which the impact of the polyelectrolyte binding surface on colloidal arrangement, degree of ordering and coverage may be observed. This discussion discloses the key interplay between the critical working parameters (mainly deposition times of PDDA and colloids as well as salt-induced screening of the intercolloid repulsion) allowing optimal design of colloidal arrangements in terms of order, homogeneity and coverage. In this respect, the occurrence of correlated disorder with respect to disordered arrangements is rigorously characterized by quoting a periodicity-like length associated to the real colloidal distributions. Finally, we perform optical and sensing characterization of metal nanohole distributions with tailored short-range ordering fabricated by the MNL-CL protocol.

The ablation of a metal target at laser energy densities in the range of 1–10 TW/cm2 leads to the generation of nanoparticles (NP) of the ablated material. This aspect is of particular interest if the immobilization of NPs on three-dimensional (3D) substrates is necessary as for example in sensing applications. In this work the deposition of Au NP by irradiation of a Au bulk target with a sub-picosecond laser beam (500 fs; 248 nm; 10 Hz) on 2D (silica and Si(100)) and 3D substrates (silica nanowire forests) is reported for different number of laser pulses (500, 1000, 1500, 2000, 2500). A uniform coverage of small Au NPs (with a diameter of few nm) on both kinds of substrates has been obtained using a suitable number of laser pulses. The presence of spherical droplets, with a diameter ranging from tens of nm up to few μm was also detected on the substrate surface and their presence can be explained by the weak electron-phonon coupling of Au. The optical characterization of the samples on 2D and 3D substrates evidenced the surface plasmon resonance peak characteristic of the Au NPs although further improvements of the size-distribution are necessary for future applications in sensing devices.

We present an experimental method for measuring “realistically” the swelling ratio in terms of weight (SR W ) of PDMS, where “realistically” means without the underestimation involved by the standard protocol (weight-measurements in open environment with time-delay incompatible with fast solvent evaporation rate). Comparison with the literature demonstrates that misleading conclusions can result under application of the standard protocol to very volatile solvents. To discuss this point, we develop a mathematical expression of SR W including solvent properties and the effective amount of sorbed solvent determining a weight gain, consider two solvents with different volatility that severely swell PDMS (i.e., toluene and dichloromethane), check that the results of our measurements are consistent with theoretical predictions, demonstrate that our protocol rules out any dependence of SR W on the solvent volatility and its reliability to measure and compare SR W values of PDMS (or any swelling polymer/soft material) in the case of solvents with very different volatility.

Unconventional lithography (such as nanosphere lithography (NSL) and colloidal lithography (CL)) is an attractive alternative to sequential and very expensive conventional lithography for the low-cost fabrication of large-area nano-optical devices. Among these, nanohole (NH) arrays are widely studied in nanoplasmonics as transducers for sensing applications. In this work, both NSL and CL are implemented to fabricate two-dimensional distributions of gold NHs. In the case of NSL, highly ordered arrays of gold NHs distributed in a hexagonal lattice onto glass substrates were fabricated by a simple and reproducible approach based on the self-assembling of close-packed 500 nm diameter polystyrene particles at an air/water interface. After the transfer onto a solid substrate, the colloidal masks were processed to reduce the colloidal size in a controllable way. In parallel, CL was implemented with short-range ordered gold NH arrays onto glass substrates that were fabricated by electrostatically-driven self-assembly of negatively charged colloids onto a polydiallyldimethylammonium (PDDA) monolayer. These distributions were optimized as a function of the colloidal adsorption time. For both approaches, controllable and reproducible procedures are presented and discussed. The optical responses of the NH structures are related to the short-range ordering level, and their good performances as refractive index transducers are demonstrated.

Colloidal lithography is widely used as a low cost and large-area deposition approach, alternative to the conventional small-area expensive lithographic techniques, for the fabrication of short-range ordered sub-wavelength metallic nanostructures. This paper contributes to the understanding of the impact of the fabrication protocol of a colloidal mask on the optical and sensing properties of short range-ordered nanohole (NH) distributions fabricated by colloidal lithography in optically thin (20 nm thick) gold films. We consider polystyrene nanospheres (PS-NSPs) with a nominal diameter of 80 nm, electrostatically adsorbed from a salt-free colloidal solution onto a polydiallyldimethylammonium (PDDA) countercharged monolayer. By avoiding the conventional polyelectrolyte multilayer and based on the interplay between the deposition times of both PDDA and PS-NSPs, we demonstrate effective simplification of the commonly applied deposition protocol and effective tuning of the NH-to-NH spacing (d NN ) with negligible agglomeration. Comparison with NH samples prepared by salt-containing colloidal solutions points out the negative impact of salt addition on the optical properties. The effective tuning of d NN obtained by our protocol demonstrates highly correlated disorder under unsaturated adsorption and allows a discussion on the analogies of the optical response between long- and short- range ordered NH systems, which is a still debated topic. By Fast Fourier Transform of autocorrelation images of scanning electron microscopy micrographs we demonstrate quantitatively, rather than in principle, the correspondence between an inherent ordering length-scale and d NN . As optical transducers for detecting refractive index changes, our samples exhibit significant bulk sensitivity (∼309 nm RIU -1 ) in the framework of short range ordered NH systems.

Fine manipulation of fluid flows at the microscale has a tremendous impact on mass transport phenomena of chemical and biological processes inside microfluidic platforms. Fluid mixing in the laminar flow regime at low Reynolds is poorly effective due to the inherently slow diffusive mechanism. As a strategy to enhance mixing and prompt mass transport, here, we focus on polyelectrolyte multilayer capsules (PMCs) embodying a catalytic polyoxometalate as microobjects to create elastic turbulence and as micromotors to generate chaotic flows by fuel-fed propulsions. The effects of the elastic turbolence and of the artificial propulsion on some basic flow parameters, such as pressure and volumetric flow rate are studied by a microfluidic set-up including pressure and flow sensors. Numerical-handling and physical models of the experimental data are presented and discussed to explain the measured dependence of the pressure drop on the flow rate in presence of the PMCs. As a practical outcome of the study, a strong decrease of the mixing time in a serpentine microreactor is demonstrated. Unlike our previous reports dealing with capillarity flow studies, the present paper relies on hydrodynamic pumping experiments, that allows us to both develop a theoretical model for the understanding of the involved phenomena and demonstrate a successfully microfluidic mixing application. All of this is relevant in the perspective of developing microobject based methods to overcome microscale processes purely dominated by diffusion with potential improvements of mass trasport in microfluidic platforms., In Press, Corrected Proof

Boron carbide (B4C) has outstanding properties making it particularly interesting in the field of neutron detection. In this study we exploit nanosecond pulsed laser deposition (PLD) for the synthesis of B-enriched films with micrometer-scale thickness for future realization of a neutron converter layer. B-enriched B4C layers were deposited by PLD at room temperature under different wavelength conditions (λP = 266, 248,193 nm), fluence (from 2 to 10 J/cm2) and substrate (silica, Si (100), kapton (polyamide), PMMA and AZ 1512 resist). The measured elemental composition of boron (B), carbon (C) and oxygen (O) as well as the structural properties of the deposited films highlighted: i) wavelength- and fluence-dependent B sub-stoichiometry with respect to the ablated target, ii) formation of polycrystalline grains despite the room temperature growth in the case of λP = 266 nm, and iii) deposition rates higher for λP = 266 than for the other investigated wavelengths. The film deposited at a wavelength of λP = 266 nm and F = 2 J/cm2 yielded the best B/C ratio, negligible O-contaminations, and a very smooth surface with low density of surface particulates. Moreover, the possibility of depositing well adherent films on soft substrates with thicknesses > 1 μm is demonstrated, due to ability to accommodate tensile stress at the substrate-B4C film interface.

The production of reproducible batches of liposomes suitable for parenteral administration is a time-consuming, multi-step process requiring extensive workable area. Microfluidic Hydrodynamic Focusing (MHF) chips allow one-pot synthesis of injectable size liposomes, although the use of low height-to-width aspect ratio (AR) microreactors limits the production rates. Herein, aiming at scaling up liposome production, while avoiding lithographic methods and clean room facilities, easy-fabrication glass MHF large channel (MHF-LC) chips of AR = 1, 3 with T-shaped and coaxial injection geometries are demonstrated. Narrowly distributed unilamellar nanoliposomes (unprecedented minimum average diameters 85 nm and polydispersity index of 0.13) with the formulation of a known pharmaceutical product (i.e., DOXIL®(CAELYX®)) are synthesized at production rates 15–20 times larger than T-MHF chips. The dependence of liposome size on the Reynolds numbers (in the range of 5–50) in the coaxial configuration is discussed as due to viscosity-induced mixing dynamics at the water–ethanol interface.

In this study, we examine at both experimental and fundamental levels, the experimental evidence of nanoparticle formation in transmission electron microscopy (TEM) metal grids annealed at temperatures lower than the melting point of the corresponding metal bulk material. Our experimental investigation considers the most thermally unstable TEM grids (i.e. Cu-grids) and inspects the possible sources and mechanisms of contamination of thin films, conventionally deposited on carbon-coated Cu-grids. The investigations are supported by morphological–compositional analyses performed in different regions of the TEM sample. Then, a general model is formulated and discussed in order to explain the grid thermal instability, based on the critical role of edge-melting (i.e. melting initiated at edges and corners of the grid bars), the enhanced rate of evaporation from a liquid surface and the polycristallinity of the grid bars. Hence, we totally disregard conventional arguments such as bulk evaporation and metal vapor pressure and, in order to emphasize and clarify the alternative point of view of our model, we also overview the nano-scale melting phenomenology relevant to our discussion and survey the discrepancies reported in the literature.

In this paper, an unprecedented inspection of the effects of thermal aging on swelling and wettability of PDMS as a function of the interplay between temperature (from 100 to 180 °C) and duration (from 20 min to 24 h) of the treatment is presented. Dichloromethane was used as sample swelling solvent and the swollen weight was measured by a method properly designed to avoid underestimation related to the volatility of the solvent. This study: i) provides practical guidelines for performing optimal thermal aging treatments of PDMS against swelling (for example, in microfluidic platforms to synthesize cancer tracers), and ii) contributes to the fundamental understanding of the swelling process of soft matter systems. An interpretative model has been developed of the observed swelling regimes based on heating-promoted crosslinking and chain reorganization (inter-chain mobility) at short-lasting heating timescales and conformational changes (intra-chains transitions) at long-lasting heating timescales.

The huge and impossible to list number of publications dealing with luminescent materials demonstrates widespread interest at both fundamental and technological level in their spectroscopic properties and applications. Moreover consequences, opportunities and challenges of spatial confinement have prompted worldwide interest in nanoscale-sized luminescent materials, termed nanophosphors (n-PSPs) as a valid alternative to fluorophores and semiconductor quantum dots.

Deposition is a manufacturing process in which a precursor material is delivered to a surface on which it reorganizes by interplay between thermodynamics and kinetics. The evolution of the microstructure of the deposit (layers with thicknesses between a few atomic layers and several micrometers [films] or nanostructure distributions or nanostructured films) is highly dependent on the physical conditions (i.e., the deposition technique and parameters) under which deposition takes place, apart from the choice of materials. Understanding the mechanisms underlying the structural and morphological evolution of a growing deposit is essential to being able to tailor the properties and performances of functional materials at the atomic scale depending on the deposition approach. In this chapter a comprehensive overview to the classical theory of growth will be given, with a focus on the importance of kinetic factors and processes as well as the growth manipulations enabled by a prototypal far-from-equilibrium deposition technique, such as pulsed laser deposition

The formation of Pd nanoparticles (NPs) by matrix-assisted pulsed laser evaporation (MAPLE) of a palladium acetate solution has been studied as a function of the carrier solvent, laser-pulse number, metal precursor concentration and post-deposition thermal heating. Structural and compositional analyses demonstrate that: (i) the conventional MAPLE process can induce self-reduction of the metal salt precursor, thereby leading to the formation of metallic Pd(0) NPs; (ii) the solvent critically determines the size, morphology, and size distribution of the resulting NPs; and (iii) the cumulative effects of laser-pulse number and solute concentration are less influential than the type of solvent used. For diethyl ether-derived samples, a bimodal distribution of NP sizes spanning from ∼1 nm up to 20 nm was obtained. Conversely, by using acetone, a mono-modal distribution of sizes in the ∼1 nm–6 nm range (mean diameter of 1.5±0.7 nm) and a more uniform and densepacked surface coverage (NP coverage was twice as dense as the one obtained with diethyl ether) resulted in. These observations point out that solvents with low dynamical viscosity coefficients and high volatility favor the formation of larger and more broadly dispersed NPs. A general theoretical picture has been proposed to describe the NP formation pathways on account of the solvent properties and the mechanisms underlying the MAPLE process enabled by the technique.

The properties of phosphor materials in nanoscale form, usually termed “nanophosphors”, present particular aspects that are worthy of extensive investigations at both fundamental and applicative level. Nanophosphors are mainly represented by compounds doped with rare earths, whose 4f optically active electrons are protected from static and dynamic perturbations by the 5s and 5p subshells. In this paper we first review the spectroscopy of rare earth ions and the properties of bulk phosphors (physical mechanisms underlying luminescence processes, thermal line broadening and line shift) and then consider the corresponding scenario at the nanoscale and discuss the role that spectroscopy may play in the investigation of nanophosphors. The paper aims at giving a background to a reader new to the spectroscopy of nanophosphors and useful points of discussion as well as guidelines for further studies.

The term “nanosystem” refers to a system with at least one spatial dimension scaled down to the nanometer-scale (

6-[F-18]fluoro-3,4-dihydroxyphenylalanine ([F-18]F-DOPA) is a diagnostic positron emission tomography agent, widely used in imaging the loss of dopaminergic neurons in Parkinson's disease and, recently, to detect, stage and restage neuroendocrine tumors and to search for recurrence of viable glioma tissue. In this paper, we establish a protocol of thermal aging (i.e., heating timescales of the order of 24 hand temperatures higher than 120 degrees C) against the swelling and morphological surface degradation (inspected by microscope imaging) of poly(dimethylsiloxane) (PDMS) by dichloromethane (DCM) and hydriodic acid (HI), that are chemicals involved in the microfluidic synthesis of [F-18]F-DOPA. Swelling tests on PDMS channels heated at 150 degrees C (for 24 and 48h) and 180 degrees C (for 24h) confirm a percentage change of the channel dimension as low as 2-8% after loading with DCM. Also, X-ray photoelectron spectroscopy analysis is presented to illustrate changes of surface chemistry following treatments with DCM, HI and an aqueous solution containing F-19-fluoride as one of the products (impurities) in the [F-18]F-DOPA synthesis. Rinsing with distilled water was demonstrate to allow removal of any chemical contamination from the PDMS surface treated with HI and a [F-18]-fluoride-based solution, which is critical to synthesize high-purity (>= 98%) [F-18]F-DOPA to be clinically used. (C) 2017 Elsevier B.V. All rights reserved.

Poly(dimethylsiloxane) (PDMS) is widely used in integrated microfluidics and biomedical platforms due to its many advantageous properties. However, the use of common organic solvents in synthesis and diagnostic protocols performed in PDMS-based devices has prompted the search for treatments of PDMS able to avoid the undesirable consequences of the PDMS swelling. Due to the solvent volatility, systematic underestimation of the weight-gain can result from standard measurements of swollen weight in open environment and affected by time-delay comparable to the solvent evaporation rate. In this study, we consider dichloromethane (DCM) as an example-solvent that swells PDMS and consider: i) an experimental procedure properly designed for measuring the swollen weight of PDMS with control on the weight loss due to the solvent volatility, and ii) post-curing thermal aging of PDMS for effectively improving its chemical resistance against swelling and removing its morphology degradation upon chemical treatment. Based on X-ray spectroscopy (XPS) analysis and microscope imaging we explore the surface chemistry and morphological degradation of PDMS treated by DCM and show the temporal evolution of the swelling ratio of PDMS thermally aged up to 150°C for 24 hours.

Even if it has been recently assessed that sub-picosecond ablation is not a “melting-free” process, a systematic investigation of the issue of droplets is still lacking. In this paper we discuss the effects of fluence (F = 0.3, 1, 3 J/cm 2 ), target-substrate distance (d TS = 5, 6, 7, 8, 9 cm) and number of laser pulses per site (N p/s = 2, 12, 22, 36, 96) on the morphology in terms of droplets and plasmonic response of gold nanoparticles deposited by sub-picosecond pulsed laser ablation. Among metals, gold is an ideal candidate to study the occurrence of droplets due to its low electron-phonon coupling that favors the appearance of heat affected zones. Our findings demonstrate that N p/s affects the production of large droplets more intensely than F and d TS . In fact, increasing N p/s produced much larger droplets than the ones obtained by tuning the fluence and an increment in the droplet density of 10 times. On the other hand, while the maximum density of small droplets (average diameter ≤ 0.15 μm) occurs at F = 1 J/cm 2 (with respect to 0.3 J/cm 2 and 3 J/cm 2 ), the total droplet density exhibits a minimum at such fluence.

We report the production of a broad band (ranging from 400 to 900 nm) white light following the monochromatic infrared light (803.5 and 975 nm) excitation of both nominally un-doped and Nd 3+ -doped Y 2 O 3 nano-powders, even up to 20% of Nd 3+ content. Experimental results indicate that such emission feature is a nano-scale phenomenon, cannot be ascribed to an overlap of sharp emission bands in the un-doped case and, even if assisted by the Nd 34 presence, is a host matrix-related process. The measured white light emission is strongly dependent on either environment pressure (a pressure threshold occurs) or pumping power. The rising patterns of the white light emission were found to increase faster for either increasing Nd 3+ content and pumping power or decreasing particle size. Notably, high correlated color temperature (2756 K), color rendering index (99), and efficiency (864 lx/W) values were measured for the un-doped sample under 803.5 nm exciting wavelength.

Synthetic garnet nanopowders of Y 3 Al 5 O 12 (YAG) and Gd 3 Ga 5 O 12 (GGG) were produced, and the occurrence of a broadband bright visible emission by nominally undoped YAG and GGG and Cr 3+ doped GGG, depending on the environment pressure, as well as exciting on the pumping power, was demonstrated. The results indicate that high-intensity infrared laser irradiation in samples not only leads to heating (melting effects) but also produces visible broadband emission. Low pressure of the powders' environment favors the white light emission by lowering the threshold pumping power. A hypothesis on the nature of the emission is presented.

To study the role of the solvent and of the laser fluence in the matrix-assisted pulsed laser evaporation (MAPLE) process, we used a soft polymer (polydimethylsiloxane— PDMS) as ‘‘sensing surface’’ and toluene as solvent. Thin films of the PDMS polymer were placed in the position of the growing film, while a frozen toluene target was irradiated with an ArF laser at the conventional fluences used in MAPLE depositions (60–250 mJ/cm2). Apart the absence of solute, the MAPLE typical experimental conditions for the deposition of thin organic layers were tested. The effects on the PDMS films of the toluene target ablation, at different fluences, were studied using atomic force microscopy and contact angles measurements. The results were compared with the effects produced on similar PDMS films by four different treatments (exposure to a drop of the solvent, to saturated toluene vapors and to plasma sources of two different powers). From this comparative study, it appears that depending on the MAPLE experimental conditions: (1) the MAPLE process may be ‘‘semidry’’ rather than purely dry (namely the solvent is likely to be present in the deposition environment near the growing film), (2) the solvent, if sufficiently volatile, is in form of vapor molecules (neutral, ionized and probably dissociated) rather than in liquid phase near the substrate and (3) at relatively high laser fluences ([150 mJ/cm2), the formation of an intense plasma plume results which can damage/affect a soft substrate as well as a growing polymer film.

The development of alternative deposition techniques of conjugated polymeric compounds is an important step towards the fabrication of low cost multi-layered organic light emitting diodes suitable for display or lighting applications. In this work we show a white light -emitting polymeric hetero-structured diode consisting of three-stacked blue, red and green light emitting polymers. In order to circumvent the issue of selecting orthogonal solvents in solution -deposition approaches, we combine spin-coating with the Matrix Assisted Pulsed Laser Evaporation technique, resulting in the realization of a polymeric multilayered stack. By controlling the carriers and the energy transfer across the three light emitting layers interfaces, as well as the interplay between the deposition parameters, a pure white colour emission with Commission Internationale de l'Éclairage coordinates (X=0.327, Y=0.374) and a Color Rendering Index of 70 have been achieved. Our study represents the first proof of a light emitting diode made by multilayer polymeric thin films emitting white light.

Engineered silver nanoparticles (AgNPs) are among the most used nanomaterials in consumer products, therefore concerns are raised about their potential for adverse effects in humans and environment. Although an increasing number of studies in vitro and in vivo are being reported on the toxicity of AgNPs, most of them suffer from incomplete characterization of AgNPs in the tested biological media. As a consequence, the comparison of toxicological data is troublesome and the toxicity evaluation still remains an open critical issue. The development of a reliable protocol to evaluate interactions of AgNPs with surrounding proteins as well as to assess their colloidal stability is therefore required. In this regard, it is of importance not only to use multiple, easy-to-access and simple techniques but also to understand limitations of each characterization methods. In this work, the morphological and structural behaviour of AgNPs has been studied in two relevant biological media, namely 10 % FBS and MP. Three different techniques (Dynamic Light Scattering, Transmission Electron Microscopy, UV–Vis spectroscopy) were tested for their suitability in detecting AgNPs of three different sizes (10, 40 and 100 nm) coated with either citrate or polyvinylpyrrolidone. Results showed that UV–Vis spectroscopy is the most versatile and informative technique to gain information about interaction between AgNPs and surrounding proteins and to determine their colloidal stability in the tested biological media. These findings are expected to provide useful insights in characterizing AgNPs before performing any further in vitro/in vivo experiment.

We consider the reported emission of white light (WL) in the spectral range from 400 to beyond 900 nm induced by monochromatic infrared light (803.5 and 975 nm) continuous wave excitation of nominally un-doped yttrium oxide (Y 2 O 3 ) nano-powders. Based on the experimental evidence, such an emission feature is a nano-scale phenomenon, resembles very closely the emission from an incandescent lamp (mimicking the sunlight, i.e., the most comfortable light to human eyes) and exhibits very high efficiency (864 lum/W) and nearly theoretical (i.e., 99) color rendering index. At the fundamental level, the origin of this phenomenon is still unexplained. In this paper we address the fundamental questions raised by the reported occurrence of WL emission from Y 2 O 3 nanopowders and attempt an interpretation at a more fundamental level. In particular we focus on the multiphoton-absorption and nonexponential decay patterns of the reported WL emission as starting points to formulate models and interpretations of the experimental occurrences still lacking in the literature. Our discussion invokes the electronic dispersion of Y 2 O 3 and nanoscale effects, which is supported by the experimental evidence according to which the observed warm WL emission is a nanoscale phenomenon with properties that only can be explained by nanoscale physics.

Silica two-dimensional substrates and nanowires (NWs) forests have been successfully decorated with Au nanoparticles (NPs) through laser ablation by using a pulsed ArF excimer laser, for sensor applications. A uniform coverage of both substrate surfaces with NPs has been achieved controlling the number of laser pulses. The annealing of the as-deposited particles resulted in a uniform well-defined distribution of spherical NPs with an increased average diameter up to 25 nm. The deposited samples on silica NWs forest present a very good plasmonic resonance which resulted to be very sensitive to the changes of the environment (ethanol/water solutions with increasing concentration of ethanol) allowing the detection of changes on the second decimal digit of the refractive index, demonstrating its potentiality for further biosensing functionalities.