SrGa(0.7)Co(0.3)O(3-δ) perovskite-cobalt oxide-metal nanocomposite films: magnetic and optical properties.

Two-phase nanocomposite films consisting of metallic Co nanoparticles below 50 nm diameter in a perovskite matrix were grown by pulsed laser deposition onto (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) and silicon substrates from a target of SrGa0.73Co0.27O3. The particles made up about 6% by volume of the film and were present within the film and at the substrate interface. The saturation magnetization of the film was up to 85 emu cm(-3) at 80 nm thickness and the Faraday rotation (FR) tracked the out-of-plane hysteresis loop, reaching 3000 deg cm(-1) at 10 kOe for 1550 nm wavelength. The magneto-optical figure of merit defined as FR divided by optical absorption was 0.04-0.06 deg dB(-1) due to the high optical absorption of the Co particles.

Plasmonic Ag/Cu/PEG nanofluids prepared when solids meet liquids in the gas phase.

Since the time of Faraday's experiments, the optical response of plasmonic nanofluids has been tailored by the shape, size, concentration, and material of nanoparticles (NPs), or by mixing different types of NPs. To date, water-based liquids have been the most extensively investigated host media, while polymers, such as poly(ethylene glycol) (PEG), have frequently been added to introduce repulsive steric interactions and protect NPs from agglomeration. Here, we introduce an inverse system of non-aqueous nanofluids, in which Ag and Cu NPs are dispersed in PEG (400 g mol-1), with no solvents or chemicals involved. Our single-step approach comprises the synthesis of metal NPs in the gas phase using sputtering-based gas aggregation cluster sources, gas flow transport of NPs, and their deposition (optionally simultaneous) on the PEG surface. Using computational fluid dynamics simulations, we show that NPs diffuse into PEG at an average velocity of the diffusion front of the order of µm s-1, which is sufficient for efficient loading of the entire polymer bulk. We synthesize yellow Ag/PEG, green Cu/PEG, and blue Ag/Cu/PEG nanofluids, in which the color is given by the position of the plasmon resonance. NPs are prone to partial agglomeration and sedimentation, with a slower kinetics for Cu. Density functional theory calculations combined with UV-vis data and zeta-potential measurements prove that the surface oxidation to Cu2O and stronger electrostatic repulsion are responsible for the higher stability of Cu NPs. Adopting the De Gennes formalism, we estimate that PEG molecules adsorb on the NP surface in mushroom coordination, with the thickness of the adsorbed layer L < 1.4 nm, grafting density σ < 0.20, and the average distance between the grafted chains D > 0.8 nm. Such values provide sufficient steric barriers to retard, but not completely prevent, agglomeration. Overall, our approach offers an excellent platform for fundamental research on non-aqueous nanofluids, with metal-polymer and metal-metal interactions unperturbed by the presence of solvents or chemical residues.

Substrate-independent approach for the generation of functional protein resistant surfaces.

A new route for coating various substrates with antifouling polymer layers was developed. It consisted in deposition of an amino-rich adhesion layer by means of RF magnetron sputtering of Nylon 6,6 followed by the well-controlled, surface-initiated atom transfer radical polymerization of antifouling polymer brushes initiated by bromoisobutyrate covalently attached to amino groups present in the adhesion layer. Polymer brushes of hydroxy- and methoxy-capped oligoethyleneglycol methacrylate and carboxybetaine acrylamide were grafted from bromoisobutyrate initiator attached to a 15 nm thick amino-rich adhesion layer deposited on gold, silicon, polypropylene, and titanium-aluminum-vanadium alloy surfaces. Well-controlled polymerization kinetics made it possible to control the thickness of the brushes at a nanometer scale. Zero fouling from single protein solutions and a reduction of more than 90% in the fouling from blood plasma observed on the uncoated surfaces was achieved. The feasibility of functionalization with bioactive compounds was tested by covalent attachment of streptavidin onto poly(oligoethylene glycol methacrylate) brush and subsequent immobilization of model antibodies and oligonucleotides. The procedure is nondestructive and does not require any chemical preactivation or the presence of reactive groups on the substrate surface. Contrary to current antifouling modifications, the developed coating can be built on various classes of substrates and preserves its antifouling properties even in undiluted blood plasma. The new technique might be used for fabrication of biotechnological and biomedical devices with tailor-made functions that will not be impaired by fouling from ambient biological media.

Mechanical time-of-flight filter based on slotted disks and helical rotor for measurement of velocities of nanoparticles.

A mechanical time-of-flight filter intended for measurement of velocities of nanoparticles exiting a gas aggregation source has been developed. Several configurations maximizing simplicity, throughput or resolution are suggested and investigated both theoretically and experimentally. It is shown that the data measured using such filters may be easily converted to the real velocity distribution with high precision. Furthermore, it is shown that properly designed filters allow for the monitoring of the velocity of nanoparticles even at the conditions with extremely low intensity of the nanoparticle beam.

Structure of Plasma (re)Polymerized Polylactic Acid Films Fabricated by Plasma-Assisted Vapour Thermal Deposition.

Plasma polymer films typically consist of very short fragments of the precursor molecules. That rather limits the applicability of most plasma polymerisation/plasma-enhanced chemical vapour deposition (PECVD) processes in cases where retention of longer molecular structures is desirable. Plasma-assisted vapour thermal deposition (PAVTD) circumvents this limitation by using a classical bulk polymer as a high molecular weight "precursor". As a model polymer in this study, polylactic acid (PLA) has been used. The resulting PLA-like films were characterised mostly by X-ray photoelectron spectroscopy (XPS) and nuclear magnetic resonance (NMR) spectroscopy. The molecular structure of the films was found to be tunable in a broad range: from the structures very similar to bulk PLA polymer to structures that are more typical for films prepared using PECVD. In all cases, PLA-like groups are at least partially preserved. A simplified model of the PAVTD process chemistry was proposed and found to describe well the observed composition of the films. The structure of the PLA-like films demonstrates the ability of plasma-assisted vapour thermal deposition to bridge the typical gap between the classical and plasma polymers.

Degradable Poly(ethylene oxide)-Like Plasma Polymer Films Used for the Controlled Release of Nisin.

Poly(ethylene oxide) (PEO)-like thin films were successfully prepared by plasma-assisted vapor thermal deposition (PAVTD). PEO powders with a molar weight (Mw) between 1500 g/mol and 600,000 g/mol were used as bulk precursors. The effect of Mw on the structural and surface properties was analyzed for PEO films prepared at a lower plasma power. Fourier transform (FTIR-ATR) spectroscopy showed that the molecular structure was well preserved regardless of the Mw of the precursors. The stronger impact of the process conditions (the presence/absence of plasma) was proved. Molecular weight polydispersity, as well as wettability, increased in the samples prepared at 5 W. The influence of deposition plasma power (0-30 W) on solubility and permeation properties was evaluated for a bulk precursor of Mw 1500 g/mol. The rate of thickness loss after immersion in water was found to be tunable in this way, with the films prepared at the highest plasma power showing higher stability. The effect of plasma power deposition conditions was also shown during the permeability study. Prepared PEO films were used as a cover, and permeation layers for biologically active nisin molecule and a controlled release of this bacteriocin into water was achieved.

Plasma Polymerization of Acrylic Acid for the Tunable Synthesis of Glassy and Carboxylated Nanoparticles.

Polymer nanoparticles (NPs) can be highly attractive in numerous applications, including biomedicine, where the use of inorganic matter may be detrimental for living tissues. In conventional wet chemistry, polymerization and functionalization of NPs with specific chemical groups involves complex and often numerous reactions. Here, we report on a solvent-free, single-step, low-temperature plasma-based synthesis of carboxylated NPs produced by the polymerization of acrylic acid under the conditions of a glow discharge. In a monomer-deficient regime, the strong fragmentation of monomer molecules by electron impact results in the formation of 15 nm-sized NPs with <1% retention of the carboxyl groups. In an energy-deficient regime, larger 90 nm-sized NPs are formed with better retention of carboxyl groups that reaches 16%. All types of NPs exhibit a glass transition above room temperature, which makes them highly stable in an aqueous environment with no dissolution or swelling. The NPs are also found to degrade thermally when heated above 150 °C, with a decrease in the mean NP size but with retention of the chemical composition. Thus, plasma polymerization proves to be a versatile approach for the production of polymer NPs with a tunable size distribution, chemical composition, and physical properties.

Vacuum thermal degradation of poly(ethylene oxide).

Thermal degradation of poly(ethylene oxide) (PEO) was studied under vacuum conditions. PEO macromolecules degrade predominantly by random chain scission of a backbone with elimination of oligomer fragments. The reactions include the mechanism of radical termination by disproportionation. The eliminated fragments form thin film deposits which have chemical composition close to the original PEO. Activation of the evaporated flux with a glow discharge leads to further fragmentation and recombination of the released species and can be used to tune the properties of the resulting thin films.

Magnetron-sputtered copper nanoparticles: lost in gas aggregation and found by in situ X-ray scattering.

Magnetron discharge in a cold buffer gas represents a liquid-free approach to the synthesis of metal nanoparticles (NPs) with tailored structure, chemical composition and size. Despite a large number of metal NPs that were successfully produced by this method, the knowledge of the mechanisms of their nucleation and growth in the discharge is still limited, mainly because of the lack of in situ experimental data. In this work, we present the results of in situ Small Angle X-ray Scattering measurements performed in the vicinity of a Cu magnetron target with Ar used as a buffer gas. Condensation of atomic metal vapours is found to occur mainly at several mm distance from the target plane. The NPs are found to be captured preferentially within a region circumscribed by the magnetron plasma ring. In this capture zone, the NPs grow to the size of 90 nm whereas smaller ones sized 10-20 nm may escape and constitute a NP beam. Time-resolved measurements of the discharge indicate that the electrostatic force acting on the charged NPs may be largely responsible for their capturing nearby the magnetron.

Advances and challenges in the field of plasma polymer nanoparticles.

This contribution reviews plasma polymer nanoparticles produced by gas aggregation cluster sources either via plasma polymerization of volatile monomers or via radio frequency (RF) magnetron sputtering of conventional polymers. The formation of hydrocarbon, fluorocarbon, silicon- and nitrogen-containing plasma polymer nanoparticles as well as core@shell nanoparticles based on plasma polymers is discussed with a focus on the development of novel nanostructured surfaces.

Description of D-glucosamine immobilization kinetics onto poly(lactic acid) surface via a multistep physicochemical approach for preparation of novel active biomaterials.

Poly(lactic acid) (PLA) has shown much success in the preparation of tissue engineering scaffolds as it can be fabricated with a tailored architecture. However, the PLA surface has drawbacks including the lack of biofunctional motifs which are essential for high affinity to biological cells. Therefore, this study describes a multistep physicochemical approach for the immobilization of d-glucosamine (GlcN), a naturally occurring monosaccharide having many biological functions, on the PLA surface aiming at enhancing the cell proliferation activity. In this approach, poly(acrylic acid) (PAAc) spacer arms are first introduced into the PLA surface via plasma post-irradiation grafting technique. Then, covalent coupling or physical adsorption of GlcN with/on the PAAc spacer is carried out. Factors affecting the grafting yield are controlled to produce a suitable spacer for bioimmobilization. X-ray photon spectroscopic (XPS) analyses confirm the immobilization of GlcN on the PLA surface. The XPS results reveal also that increasing the yield of grafted PAAc spacer on the PLA surface increases the amount of covalently immobilized GlcN, but actually inhibits the immobilization process using the physical adsorption method. Contact angle measurements and atomic force microscopy (AFM) show a substantial increase of surface energy and roughness of PLA surface, respectively, upon the multistep modification procedure. The cytocompatibility of the modified surfaces is assessed using a mouse embryonic fibroblast (MEF) cell line. Observation from the cell culture basically demonstrates the potential of GlcN immobilization in improving the cytocompatibility of the PLA surface. Moreover, the covalent immobilization of GlcN seems to produce more cytocompatible surfaces if compared with the physical adsorption method. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3176-3188, 2017.

Microphase-Separated PE/PEO Thin Films Prepared by Plasma-Assisted Vapor Phase Deposition.

Immiscible polymer blends tend to undergo phase separation with the formation of nanoscale architecture which can be used in a variety of applications. Different wet-chemistry techniques already exist to fix the resultant polymeric structure in predictable manner. In this work, an all-dry and plasma-based strategy is proposed to fabricate thin films of microphase-separated polyolefin/polyether blends. This is achieved by directing (-CH2-)100 and (-CH2-CH2-O-)25 oligomer fluxes produced by vacuum thermal decomposition of poly(ethylene) and poly(ethylene oxide) onto silicon substrates through the zone of the glow discharge. The strategy enables mixing of thermodynamically incompatible macromolecules at the molecular level, whereas electron-impact-initiated radicals serve as cross-linkers to arrest the subsequent phase separation at the nanoscale. The mechanism of the phase separation as well as the morphology of the films is found to depend on the ratio between the oligomeric fluxes. For polyolefin-rich mixtures, polyether molecules self-organize by nucleation and growth into spherical domains with average height of 22 nm and average diameter of 170 nm. For equinumerous fluxes and for mixtures with the prevalence of polyethers, spinodal decomposition is detected that results in the formation of bicontinuous structures with the characteristic domain size and spacing ranging between 5 × 10(1) -7 × 10(1) nm and 3 × 10(2)-4 × 10(2) nm, respectively. The method is shown to produce films with tunable wettability and biologically nonfouling properties.