Pulsed Laser Evaporation Research Articles

New bio-active, antimicrobial and adherent coatings of nanostructured carbon double-reinforced with silver and silicon by Matrix-Assisted Pulsed Laser Evaporation for medical applications

We report on Matrix-Assisted Pulsed Laser Evaporation (MAPLE) deposition of Carbon thin films, simple or reinforced with intended concentrations of Ag and Si. A KrF∗ (λ = 248 nm, τFWHM ≤ 25 ns, ν = 10 Hz) excimer laser was used for irradiation. The effect of a post-deposition thermal treatment in vacuum was studied. Besides detailed morphological, compositional, structural and pull-out adherence characterizations, the potential of the carbonaceous films for medical applications was investigated in vitro by anti-biofilm and cytocompatibility assays. The microscopic images evidenced no delaminations. Micro-Raman spectroscopy revealed a graphitization tendency depending on preparation conditions, thermal treatment and reinforcing agents’ presence. Adherence values improved considerably after thermal treatment. In vitro biological evaluation showed that the films containing ∼1.85 at.% Ag were non-cytotoxic for MG63 cells, while eliciting a limited antimicrobial activity. The increase of Ag content to 3.6 at.% results in a significant enhancement of antimicrobial activity, whilst maintaining the cytotoxic action and adherence characteristics at acceptable levels.We propose a new class of metamaterials based on C reinforced with Ag and Si obtained by MAPLE for medical applications, i.e. the prevention and treatment of various infections associated with biofilms developed on implants and other medical equipments.

Molecular weight dependent structure and charge transport in MAPLE‐deposited poly(3‐hexylthiophene) thin films

ABSTRACTIn this work, poly(3‐hexylthiophene) (P3HT) films prepared using the matrix‐assisted pulsed laser evaporation (MAPLE) technique are shown to possess morphological structures that are dependent on molecular weight (MW). Specifically, the structures of low MW samples of MAPLE‐deposited film are composed of crystallites/aggregates embedded within highly disordered environments, whereas those of high MW samples are composed of aggregated domains connected by long polymer chains. Additionally, the crystallite size along the side‐chain (100) direction decreases, whereas the conjugation length increases with increasing molecular weight. This is qualitatively similar to the structure of spin‐cast films, though the MAPLE‐deposited films are more disordered. In‐plane carrier mobilities in the MAPLE‐deposited samples increase with MW, consistent with the notion that longer chains bridge adjacent aggregated domains thereby facilitating more effective charge transport. The carrier mobilities in the MAPLE‐deposited simples are consistently lower than those in the solvent‐cast samples for all molecular weights, consistent with the shorter conjugation length in samples prepared by this deposition technique. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 652–662

Tuning Morphology and Melting Temperature in Polyethylene Films by MAPLE

The control of structure and thermal stability in semicrystalline polymer films remains an important challenge in applications ranging from solar energy devices to packaging films. Here, we demonstrate the ability to dramatically alter the morphology and melting temperature (Tm) of low-molecular-weight linear polyethylene (PE) by employing an innovative vapor-assisted deposition process termed matrix assisted pulsed laser evaporation (MAPLE). We report the ability to tune Tm of PE films by 20 °C by simply adjusting the deposition temperature during MAPLE processing. This unique capability stems from the ability of MAPLE to exploit confined crystallization during thin film growth. In addition, we demonstrate the ability to exploit MAPLE to design PE films that exhibit the same Tm as their melt-crystallized analogues but have an ∼25% higher degree of crystallinity. Our investigation offers new insights into how confinement effects in polymer crystallization can be utilized in the emerging field of polymer f...

MAPbI3 Solar Cells with Absorber Deposited by Resonant Infrared Matrix-Assisted Pulsed Laser Evaporation

Resonant infrared, matrix-assisted pulsed laser evaporation (RIR-MAPLE) is a gentle thin-film deposition technique that combines the facile chemical control of solution processing with the growth control of vapor-phase deposition, yet one that has not been widely applied to crystalline organic–inorganic hybrid materials. In this work, we investigate the optoelectronic quality of RIR-MAPLE-deposited CH3NH3PbI3 (MAPbI3) perovskite films and report on the fabrication of perovskite solar cells in which the absorber is deposited by RIR-MAPLE. We find the composition, morphology, and optical properties of these perovskite films to be comparable to those produced by more conventional methods, such as spin coating. The champion device reaches a stabilized power conversion efficiency of over 12%, a high value for perovskite solar cells deposited by a laser ablation process, highlighting the ability of this new technique to produce device-quality films.

Reactive laser synthesis of nitrogen-doped hybrid graphene-based electrodes for energy storage

A reactive inverse matrix assisted pulsed laser evaporation method was used for the fabrication of hybrid graphene-based electrodes for supercapacitors.

Infrared photodissociation spectroscopic and theoretical study of the H<sub>3</sub>C<sub>3</sub>O<sup>+</sup> and D<sub>3</sub>C<sub>3</sub>O<sup>+</sup> acryloyl cations

The carbocations, H3C3O+ and D3C3O+ are produced via pulsed laser vaporization of a graphite target in supersonic expansions of helium seeded with carbon monoxide and acetylene or methane. The infrared spectra are measured via mass-selected infrared photodissociation spectroscopy of their CO-tagged [H3C3O·CO]+ and [D3C3O·CO]+ cation complexes. The geometry of the cation complex is determined by the infrared spectra in conjunction with theoretical calculations. The H3C3O+ and D3C3O+ core cations are determined to be acryloyl cations with 1A ¢ electronic ground state and C s symmetry. The AdNDP bonding analysis indicates that besides the localized two-center-two-electron (2c-2e) C–O, C–C, and C–H σ bonds as well as 2c-2e CO π bonds, there is a delocalized three-center-two-electron (3c-2e) CCC π bond.

Crystallization Mechanism and Charge Carrier Transport in MAPLE-Deposited Conjugated Polymer Thin Films.

Although spin casting and chemical surface reactions are the most common methods used for fabricating functional polymer films onto substrates, they are limited with regard to producing films of certain morphological characteristics on different wetting and nonwetting substrates. The matrix-assisted pulsed laser evaporation (MAPLE) technique offers advantages with regard to producing films of different morphologies on different types of substrates. Here, we provide a quantitative characterization, using X-ray diffraction and optical methods, to elucidate the additive growth mechanism of MAPLE-deposited poly(3-hexylthiophene) (P3HT) films on substrates that have undergone different surface treatments, enabling them to possess different wettabilities. We show that MAPLE-deposited films are composed of crystalline phases, wherein the overall P3HT aggregate size and crystallite coherence length increase with deposition time. A complete pole figure constructed from X-ray diffraction measurements reveals that in these MAPLE-deposited films, there exist two distinct crystallite populations: (i) highly oriented crystals that grow from the flat dielectric substrate and (ii) misoriented crystals that preferentially grow on top of the existing polymer layers. The growth of the highly oriented crystals is highly sensitive to the chemistry of the substrate, whereas the effect of substrate chemistry on misoriented crystal growth is weaker. The use of a self-assembled monolayer to treat the substrate greatly enhances the population and crystallite coherence length at the buried interfaces, particularly during the early stage of deposition. The evolution of the in-plane carrier mobilities during the course of deposition is consistent with the development of highly oriented crystals at the buried interface, suggesting that this interface plays a key role toward determining carrier transport in organic thin-film transistors.

Frozen Microemulsions for MAPLE Immobilization of Lipase.

Candida rugosa lipase (CRL) was deposited by matrix assisted pulsed laser evaporation (MAPLE) in order to immobilize the enzyme with a preserved native conformation, which ensures its catalytic functionality. For this purpose, the composition of the MAPLE target was optimized by adding the oil phase pentane to a water solution of the amino acid 3-(3,4-dihydroxyphenyl)-2-methyl-l-alanine (m-DOPA), giving a target formed by a frozen water-lipase-pentane microemulsion. Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM) were used to investigate the structure of MAPLE deposited lipase films. FTIR deconvolution of amide I band indicated a reduction of unfolding and aggregation, i.e., a better preserved lipase secondary structure in the sample deposited from the frozen microemulsion target. AFM images highlighted the absence of big aggregates on the surface of the sample. The functionality of the immobilized enzyme to promote transesterification was determined by thin layer chromatography, resulting in a modified specificity.

Functional Micrococcus lysodeikticus layers deposited by laser technique for the optical sensing of lysozyme

Whole cell optical biosensors, made by immobilizing whole algal, bacterial or mammalian cells on various supports have found applications in several fields, from ecology and ecotoxicity testing to biopharmaceutical production or medical diagnostics. We hereby report the deposition of functional bacterial layers of Micrococcus lysodeikticus (ML) via Matrix-Assisted Pulsed Laser Evaporation (MAPLE) on poly(diallyldimethylamonium) (PDDA)-coated-glass slides and their application as an optical biosensor for the detection of lysozyme in serum. Lysozyme is an enzyme upregulated in inflammatory diseases and ML is an enzymatic substrate for this enzyme. The MAPLE-deposited bacterial interfaces were characterised by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Fourier-Transformed Infrared Spectroscopy (FTIR), Raman and optical microscopy and were compared with control interfaces deposited via layer-by-layer on the same substrate. After MAPLE deposition and coating with graphene oxide (GO), ML-modified interfaces retained their functionality and sensitivity to lysozyme’s lytic action. The optical biosensor detected lysozyme in undiluted serum in the clinically relevant range up to 10μgmL−1, in a fast and simple manner.

Numerical analysis of time-of-flight distributions of neutral particles for pulsed laser ablation of binary substances into vacuum

Direct Monte Carlo simulation of the laser-induced plume expansion under pulsed laser evaporation of binary substances into vacuum has been performed. Analysis of separation of the mixture components has been carried out for a wide range of the problem parameters: the mass ratio, the number of evaporated monolayers, and the initial mixture concentration. Special attention has been paid to examination of the mixture separation and changing the mixture concentration for particles passing through the time-of-flight detector located on the normal to the evaporating surface. Universal dependences of the energy and concentration ratios of species passing through the time-of-flight detector on the number of evaporated monolayers have been obtained. It is shown that these dependences can be used for analysis of any experimental data independently on the concentration ratio. The obtained relations well correlate with known numerical and experimental data on gas phase separation under pulsed evaporation into vacuum. The obtained results allow to completely determine the conditions at the evaporating surface (the surface temperature, the number of evaporated monolayers, and the initial mixture composition) from experimentally measured time-of-flight distributions of neutral particles.

Organic/hybrid thin films deposited by matrix-assisted pulsed laser evaporation (MAPLE)

Some of the most exciting materials research in the 21st century attempts to resolve the challenge of simulating, synthesizing, and characterizing new materials with unique properties designed from first principles. Achievements in such development for organic and organic-inorganic hybrid materials make them important options for electronic and/or photonic devices because they can impart multi-functionality, flexibility, transparency, and sustainability to emerging systems, such as wearable electronics. Functional organic materials include small molecules, oligomers, and polymers, while hybrid materials include inorganic nanomaterials (such as zero-dimensional quantum dots, one-dimensional carbon nanotubes, or two-dimensional nanosheets) combined with organic matrices. A critically important step to implementing new electronic and photonic devices using such materials is the processing of thin films. While solution-based processing is the most common laboratory technique for organic and hybrid materials, vacuum-based deposition has been critical to the commercialization of organic light emitting diodes based on small molecules, for example. Therefore, it is desirable to explore vacuum-based deposition of organic and hybrid materials that include larger macromolecules, such as polymers. This review article motivates the need for physical vapor deposition of polymeric and hybrid thin films using matrix-assisted pulsed laser evaporation (MAPLE), which is a type of pulsed laser deposition. This review describes the development of variations in the MAPLE technique, discusses the current understanding of laser-target interactions and growth mechanisms for different MAPLE variations, surveys demonstrations of MAPLE-deposited organic and hybrid materials for electronic and photonic devices, and provides a future outlook for the technique.

An experimental investigation into the reduced mobilities of lanthanide cations using high-resolution ion mobility mass spectrometry

Reduced mobilities for ground-state electronic configurations of the complete lanthanide series of cations, excluding promethium, have been measured. These values were obtained using an ion mobility mass spectrometer that utilizes a 2m drift tube to generate high-resolution ion mobility data. In all cases, lanthanide cations were generated using pulsed-laser vaporization of either a metal rod or foil target. The mobilities of Eu+, Gd+, Yb+, and Lu+ have been previously examined and these data are also included. All other lanthanide cation mobilities, measured in He, are reported here for the first time. A discussion of the observed trends in the mobilities of the lanthanide series is also provided.

Infrared Spectroscopy of Au(Acetylene)n + Complexes in the Gas Phase

Au(C2H2)n + (n = 1–6) ion–molecule complexes are produced in the gas phase via pulsed laser vaporization in a supersonic expansion of acetylene and argon. Cations are size selected and studied with infrared photodissociation spectroscopy in the C–H stretching region (3000–3500 cm−1). Insight into the structure and bonding of these species is obtained from the number of infrared active bands, their relative intensities and their frequency positions. Density functional theory calculations provide structures for these complexes and predicted spectra are compared to the experiment. The combined data indicate that gold cation has a primary coordination number of two with respect to acetylene binding, and a secondary coordination sphere that is completed with a third ligand. Larger complexes (n = 4–6) are formed by solvation of the Au(C2H2)3 + core ion with acetylene, in a pattern like that seen previously for Cu(C2H2)n + complexes. Small differences in the spectra between corresponding copper and gold cation complexes are explained by theory, but only when relativistic corrections are included for the gold complexes.

Tailored biodegradable triblock copolymer coatings obtained by MAPLE: a parametric study

Biocompatible and biodegradable coatings with controllable and tailored chemical and physical characteristics (i.e. morphology and roughness) are of great interest in bone related research applications. Within this research direction, in this work, a series of novel biodegradable coatings based on triblock copolymers poly(lactide-co-caprolactone)-block-poly(ethylene–glycol)-block-poly(lactide-co-caprolactone) (PLCL–PEG–PLCL) were obtained by matrix-assisted pulsed laser evaporation (MAPLE) and their morphological characteristics and roughness were modulated by varying target composition and laser fluence. The coatings were used for preliminary in vitro testing with MC3T3-E1 pre-osteoblasts. It was found that for a specific range of fluences, the main functional groups in the MAPLE-deposited thin films, as determined by Fourier transform infrared spectroscopy, are similar to the molecular structures of the initial material. Depending on the deposition parameters, significant changes in morphologies, i.e. material accumulation in the form of droplets, wrinkles, or carpet-like structures were revealed by atomic force microscopy (AFM) and scanning electron microscopy. The optimized coating characteristics were further correlated to MC3T3-E1 pre-osteoblasts response. The ability to control the morphology and to maintain unaltered the chemistry of the deposited material through MAPLE is an important step in creating functional bio-interfaces in the field of biomedical research and tissue engineering.

Deposition of Methylammonium Lead Triiodide by Resonant Infrared Matrix-Assisted Pulsed Laser Evaporation

Resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) was used to deposit the metal-halide perovskite (MHP) CH3NH3PbI3 (methylammonium lead triiodide, or MAPbI), creating phase-pure films. Given the moisture sensitivity of these crystalline, multi-component organic–inorganic hybrid materials, deposition of MAPbI by RIR-MAPLE required a departure from the use of water-based emulsions as deposition targets. Different chemistries were explored to create targets that properly dissolved MAPbI components, were stable under vacuum conditions, and enabled resonant laser energy absorption. Secondary phases and solvent contamination in the resulting films were studied through Fourier transform infrared (FTIR) absorbance and x-ray diffraction (XRD) measurements, suggesting that lingering excess methylammonium iodide (MAI) and low-vapor pressure solvents can distort the microstructure, creating crystalline and amorphous non-perovskite phases. Thermal annealing of films deposited by RIR-MAPLE allowed for excess solvent to be evaporated from films without degrading the MAPbI structure. Further, it was demonstrated that RIR-MAPLE does not require excess MAI to create stoichiometric films with optoelectronic properties, crystal structure, and film morphology comparable to films created using more established spin-coating methods for processing MHPs. This work marks the first time a MAPLE-related technique was used to deposit MHPs.

Electrically responsive microstructured polypyrrole-polyurethane composites for stimulated osteogenesis

In this work, we demonstrate the efficiency of substrate-mediated electrical stimulation of micropatterned polypyrrole/polyurethane (PPy/PU) composites for enhancing the osteogenesis in osteoblast-like cells. The PPy/PU substrates were obtained by dispersing electrically conductive PPy nanograins within a mechanically resistant PU matrix. Spin-coated PPy/PU layers were micropatterned with predefined 3D geometries by ultrashort laser ablation. Then they were conformally coated by Matrix Assisted Pulsed Laser Evaporation, in order to restore their chemical and electrical integrity. The chemical structure of the laser-processed PPy/PU substrates was investigated by 2D and 3D mapping of the laser-processed areas, via Raman microspectroscopy. In vitro studies revealed that the micropatterned PPy/PU substrates facilitated the topological and electrical communication of the seeded osteoblasts. Specifically, we demonstrated the cells attachment on the predefined 3D micropatterns. More importantly, we found evidence about the cells mineralization inside the 3D micropatterns by investigating the calcium deposits by Energy-Dispersive X-Ray Spectroscopy (EDS) and Alizarin Red staining. We found that the substrate-mediated electrical stimulation of the PPy/PU substrates induced a twofold increase of the Ca deposits in the cultured cells.

MAPLE synthesis of reduced graphene oxide/silver nanocomposite electrodes: Influence of target composition and gas ambience

Graphene oxide (GO) and reduced GO films with different amounts of silver nanoparticles (Ag NPs) have been deposited on quartz and silicon substrates by matrix assisted pulsed laser evaporation (MAPLE). The morphology, structure, chemical composition, and optical and electrochemical properties were evaluated by scanning electron microscopy, X-ray photoelectron spectroscopy, ultraviolet–visible spectrophotometry, and cyclic voltammetry measurements. The properties of the films obtained with two types of GO precursors have been compared. A reduction of the amount of oxygen containing groups is observed with the increase of the Ag concentration, which leads to a decrease of the optical band gap. Moreover, the deposition in nitrogen gas ambience leads to the N-doping of rGO material. The films obtained with the highest amount of Ag and with nitrogen doping show potential to be used in energy storage electrodes.

In vitro testing of curcumin based composites coatings as antitumoral systems against osteosarcoma cells

In this work, we propose a new design for biodegradable composite coatings obtained by laser methods, which are aimed at evaluating the effects of active antitumoral elements on osteosarcoma cells. Our approach relies on embedding curcumin, which is a natural polyphenol having antitumoral properties, within biodegradable copolymer coatings (i.e. polyvinyl alcohol-polyethylene glycol − PVA-PEG) by using matrix assisted pulsed laser evaporation (MAPLE). The structural and morphological characteristics of the coatings were tailored by using different solvents (water, ethanol, benzene, dimethylsufoxide) as deposition matrix. The morphological characteristics of the resulting films were investigated by atomic force microscopy (AFM), whereas their chemical composition was characterized by Fourier transform infrared spectroscopy (FTIR). These characteristics were correlated with the degradation behavior by using ellipsometry (SE) and AFM measurements data. The in vitro study of the MG-63 osteosarcoma cell behavior indicates that the developed hybrid coatings significantly decreased osteosarcoma cell viability and proliferation potential. The physico-chemical characteristics of the thin films, along with the preliminary in vitro analyses, suggest that our developed polymeric hybrid coatings represent an efficient way to tackle the design of antitumoral surfaces, with applications in biomedicine.

Perspectives of Single-Wall Carbon Nanotube Production in the Arc Discharge Process

<p>Single-wall carbon nanotubes (SWNTs) promise wide applications in many technical fields. As a result purified SWNT material is sold now on the West market at more than $1000 per 1 gram. Thus developing an effective technology for SWNTs production rises to a very important scientific problem. The perspectives of three existing methods providing raw material in the technology of SWNT production have been analyzed. They are i) pulsed laser evaporation of graphite/metal composites, ii) evaporation of graphite electrodes with metal content in the arc discharge process, and iii) catalytic decomposition of the mixture of CO and metal carbonyl catalyst precursor. The observed dynamics of SWNT market points to replacing the laser method of SWNTs production by the arc process. The conclusion has been made that the technology based on the arc process will be the major one for the fabrication of purified SWNTs at least for the next five years. A reliable estimation of a low price limit of SWNTs was derived from a comparison of two technologies based on the arc discharge process: the first one is the production of SWNTs and the second one is the production of a fullerene mixture С<sub>60</sub> + С<sub>70</sub>. The main conclusion was made that the price of purified SWNTs should always be more by 2-3 times the price of fullerene mixture. The parameters of a lab-scale technology for the production of purified SWNTs are listed. A large-scale application of the developed technology is expected to reduce the price of purified SWNTs by approximately ten times. The methods now employed for the characterization of products containing SWNTs are briefly observed. It is concluded that electron microscopy, thermogravimetric analysis, absorption and Raman spectroscopy, measurement of the specific surface aria, optical microscopy – each in separation is not enough for extensive characterization of a sample containing SWNTs, and all these methods should be used together.</p>

Histamine detection using functionalized porphyrin as electrochemical mediator

This study reports on deposition of asymmetrical substituted meso -phenyl porphyrin, 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin (CPTPP) thin films by matrix-assisted pulsed laser evaporation (MAPLE) on screen-printed electrodes, aiming for histamine detection. Raman spectrometry confirmed that CPTPP chemical structure was preserved in MAPLE-deposited thin films at 200 mJ/cm 2 laser fluence. Atomic force microscopy topography revealed that MAPLE-deposited thin films have a better coverage on the working electrode made of carbon compared to the ones obtained by dropcasting. Cyclic voltammetry demonstrated that CPTPP is an appropriate mediator for histamine detection in trichloroacetic acid solution. We proved that MAPLE serves as a soft technique in fabrication of porphyrin thin films and patterns. Cet article traite du dépôt de couches minces, par évaporation laser assistée par matrice (MAPLE), de 5-(4-carboxyphényl)-10,15,20-triphénylporphyrine (CPTPP) substituée asymétriquement. Les couches minces ont été déposées sur des électrodes imprimées, avec comme objectif la détection de l'histamine. La spectroscopie Raman a confirmé que la structure chimique de la CPTPP a été préservée dans les couches minces déposées par MAPLE avec une fluence laser de 200 mJ/cm 2 . La topographie AFM a révélé une meilleure couverture de l'électrode de carbone par MAPLE par rapport au dropcast . La voltamétrie cyclique a démontré que la CPTPP est un médiateur approprié pour la détection de l'histamine dans une solution d'acide trichloracétique. On montre que MAPLE est une technique douce pour la fabrication de couches minces et de motifs de porphyrine.