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A novel combined setup of a gas aggregation source and a secondary radio frequency discharge is used to generate, confine, and coat nanoparticles. The approach is demonstrated by generating Ag@SiO2 nanoparticles with a well-defined surface coating.

Polymer–metal composite films with nanostructured metal and/or polymer interfaces show a significant perspective for optoelectronic applications, for example, as sensors or in organic photovoltaics...

Copper (Cu) as an excellent electrical conductor and the amphiphilic diblock copolymer polystyrene-block-poly(ethylene oxide) (PS-b-PEO) as a polymer electrolyte and ionic conductor can be combined with an active material in composite electrodes for polymer lithium-ion batteries (LIBs). As interfaces are a key issue in LIBs, sputter deposition of Cu contacts on PS-b-PEO thin films with high PEO fraction is investigated with in situ grazing-incidence small-angle X-ray scattering (GISAXS) to follow the formation of the Cu layer in real-time. We observe a hierarchical morphology of Cu clusters building larger Cu agglomerates. Two characteristic distances corresponding to the PS-b-PEO microphase separation and the Cu clusters are determined. A selective agglomeration of Cu clusters on the PS domains explains the origin of the persisting hierarchical morphology of the Cu layer even after a complete surface coverage is reached. The spheroidal shape of the Cu clusters growing within the first few nanometers of sputter deposition causes a highly porous Cu-polymer interface. Four growth stages are distinguished corresponding to different kinetics of the cluster growth of Cu on PS-b-PEO thin films: (I) nucleation, (II) diffusion-driven growth, (III) adsorption-driven growth, and (IV) grain growth of Cu clusters. Percolation is reached at an effective Cu layer thickness of 5.75 nm.

Hierarchical, conductive, porous, three-dimensional (3D) carbon networks based on carbon nanotubes are used as a scaffold material for the incorporation of sulfur in the vapor phase to produce carbon nanotube tube/sulfur (CNTT/S) composites for application in lithium ion batteries (LIBs) as a cathode material. The high conductivity of the carbon nanotube-based scaffold material, in combination with vapor infiltration of sulfur, allows for improved utilization of insulating sulfur as the active material in the cathode. When sulfur is evenly distributed throughout the network via vapor infiltration, the carbon scaffold material confines the sulfur, allowing the sulfur to become electrochemically active in the context of an LIB. The electrochemical performance of the sulfur cathode was further investigated as a function of the temperature used for the vapor infiltration of sulfur into the carbon scaffolds (155, 175, and 200 °C) in order to determine the ideal infiltration temperature to maximize sulfur loading and minimize the polysulfide shuttle effect. In addition, the nature of the incorporation of sulfur at the interfaces within the 3D carbon network at the different vapor infiltration temperatures will be investigated via Raman, scanning electron microscopy/energy dispersive X-ray, and X-ray photoelectron spectroscopy. The resulting CNTT/S composites, infiltrated at each temperature, were incorporated into a half-cell using Li metal as a counter electrode and a 0.7 M LiTFSI electrolyte in ether solvents and characterized electrochemically using cyclic voltammetry measurements. The results indicate that the CNTT matrix infiltrated with sulfur at the highest temperature (200 °C) had improved incorporation of sulfur into the carbon network, the best electrochemical performance, and the highest sulfur loading, 8.4 mg/cm2, compared to the CNTT matrices infiltrated at 155 and 175 °C, with sulfur loadings of 4.8 and 6.3 mg/cm2, respectively.

Organic gradient materials are an inherent part of many functional structures in the natural world. Synthetic organic materials, like polymers, are thus the perfect choice to artificially recreate these structures for functional purposes. This work reports on new high-quality gradient copolymer films via large-area deposition from the vapor phase and circumvents thus problems related to current wet chemistry approaches. It enables furthermore for the first time the transfer of this gradient approach to the nanoscale, introducing a new class of organic gradient nanomaterials. This facilitates completely new organic gradient functionality on the nanoscale, not achievable with materials currently in use. Fully functional gradient films of 21 nm have been synthesized, which open up new pathways for many application fields. Their versatility is demonstrated by some application examples ranging from every day life (adhesion of PTFE in frypans) to advanced subwavelength devices on large-area substrates as well as complex geometries.

ACS applied nano materials 5(3), 3832 - 3842 (2022). doi:10.1021/acsanm.1c04473, Tailoring of plasmon resonances is essential for applications in anti-counterfeiting. This is readily achieved by tuning the composition of alloyed metal clusters; in the most simple case binary alloys. Yet, one challenge is the correlation of cluster morphology and composition with the changing optoelectronic properties. Hitherto, the early stages of metal alloy nanocluster formation in immiscible binary systems like silver and copper has been accessible by molecular dynamics simulations and transmission electron microscopy. Here, we investigate in real-time the formation of supported silver, copper and silver-copper-alloy nanoclusters during sputter deposition on poly(methyl methacrylate) by combining in situ surface sensitive X-ray scattering with optical spectroscopy. While following the transient growth morphologies, we quantify the early stages of phase separation at the nanoscale, follow the shifts of surface plasmon resonances and quantify the growth kinetics of the nanogranular layers at different thresholds. We are able to extract the influence of scaling effects on the nucleation and phase selection. The internal structure of the alloy cluster shows a copper-rich core/silver-rich shell structure, since the copper core yields a lower mobility and higher crystallization tendency than the silver fraction. We compare our results to molecular dynamics simulation and transmission electron microscopy data. This demonstrates a route to tailor accurately the plasmon resonances of nanosized, polymer supported clusters which is a crucial prerequisite for anti-counterfeiting., Published by ACS Publications, Washington, DC

Metal top electrodes such as gold are widely used in organic solar cells. The active layer can be optimized by modifications of the polymer band gap via side-chain engineering, and low band gap polymers based on benzodithiophene units such as PTB7 and PTB7-Th are successfully used. The growth of gold contacts on PTB7 and PTB7-Th films is investigated with in situ grazing incidence small-angle X-ray scattering (GISAXS) and grazing incidence wide-angle X-ray scattering (GIWAXS) during the sputter deposition of gold. From GIWAXS, the crystal structure of the gold film is determined. Independent of the type of side chain, gold crystals form in the very early stages and improve in quality during the sputter deposition until the late stages. From GISAXS, the nanoscale structure is determined. Differences in terms of gold cluster size and growth phase limits for the two polymers are caused by the side-chain modification and result in a different surface coverage in the early phases. The changes in the diffusion and coalescence behavior of the forming gold nanoparticles cause differences in the morphology of the gold contact in the fully percolated regime, which is attributed to the different amount of thiophene rings of the side chains acting as nucleation sites.

Objectives The aim of the study was to evaluate the influence of contamination and different cleaning methods on the tensile bond strength with a phosphate monomer containing luting resin to zirconia ceramic. Methods After the contamination with saliva or silicone disclosing agent, 228 polished and airborne-particle abraded zirconia discs were ultrasonically cleaned with 99% isopropanol. In a second step, the specimens were either treated with argon-oxygen plasma, air plasma, enzymatic cleaning agent or did not undergo an additional cleaning process. Uncontaminated zirconia specimens were used as the control group. X-ray photoelectron spectroscopy (XPS) was used for chemical analysis of the bonding surfaces of specimens. Plexiglas tubes filled with composite resin were bonded to zirconia specimens with a phosphate monomer containing luting resin. Tensile bond strength (TBS) was tested after 3 days or 150 days water storage with 37,500 thermal cycles. Results XPS revealed a decrease of the carbon/oxygen ratio after plasma treatment and an increase after treatment with an enzymatic cleaning agent in all groups. All contaminated specimens showed high and durable TBS after cleaning with a combination of isopropanol and a non-thermal atmospheric plasma. After the cleaning with enzymatic cleaning agent the TBS was significantly reduced in all groups after 150 days thermal cycling. Significance The combination of isopropanol and plasma cleaning was effective in removing salvia and disclosing agent contamination. Enzymatic clearing agent was not able to remove contamination effectively and had a negative impact on the TBS of non-contaminated specimens.

This study aims at deposition and characterization of antibacterial, hydrophobic and semitransparent metal/plasma polymer nanocomposite coating, containing Ag nanoparticles, onto cotton fabrics intended to be used in medical applications. The nano composite coatings were obtained via a simple, one step and ecofriendly plasma based co-deposition approach where silver was magnetron sputtered simultaneously with plasma polymerization of hexamethyldisiloxane (HMDSO) monomer. The nanocomposite thin films containing different concentration of silver were deposited either by varying silver sputter rate or thickness of the plasma polymer matrix to obtain a good balance between optical properties of the coated fabric and its long term antibacterial performance. The obtained coatings were investigated in detail with respect to their composition, morphology, optical properties, nanoparticle size distribution, silver ion release efficiency, antibacterial performance, water contact angle and washing stability of the coating. The thickness of the plasma matrix was found to be more important in controlling the release of silver ions as well as affecting the optical properties of the coating. The water contact angle on the coated fabric was up to 145°, close to super hydrophobicity. The coating showed effective antibacterial efficacy against Staphylococcus epidermidis (a Gram positive bacterium) which was present even when fabric was subjected to 10 repeated washing cycles indicating good washing stability of the coating.

Copper (Cu) as an excellent electrical conductor and the amphiphilic diblock copolymer polystyrene-block-poly(ethylene oxide) (PS-b-PEO) as a polymer electrolyte and ionic conductor can be combined with an active material in composite electrodes for polymer lithium-ion batteries (LIBs). As interfaces are a key issue in LIBs, sputter deposition of Cu contacts on PS-b-PEO thin films with high PEO fraction is investigated with in situ grazing-incidence small-angle X-ray scattering (GISAXS) to follow the formation of the Cu layer in real-time. We observe a hierarchical morphology of Cu clusters building larger Cu agglomerates. Two characteristic distances corresponding to the PS-b-PEO microphase separation and the Cu clusters are determined. A selective agglomeration of Cu clusters on the PS domains explains the origin of the persisting hierarchical morphology of the Cu layer even after a complete surface coverage is reached. The spheroidal shape of the Cu clusters growing within the first few nanometers of sputter deposition causes a highly porous Cu-polymer interface. Four growth stages are distinguished corresponding to different kinetics of the cluster growth of Cu on PS-b-PEO thin films: (I) nucleation, (II) diffusion-driven growth, (III) adsorption-driven growth, and (IV) grain growth of Cu clusters. Percolation is reached at an effective Cu layer thickness of 5.75 nm.

ACS applied materials & interfaces 13(47), 56663 - 56673 (2021). doi:10.1021/acsami.1c18324, Large-scale fabrication of metal cluster layers for usage in sensor applications and photovoltaics is a huge challenge. Physical vapor deposition offers large-scale fabrication of metal cluster layers on templates and polymer surfaces. In the case of aluminum (Al), only little is known about the formation and interaction of Al clusters during sputter deposition. Complex polymer surface morphologies can tailor the deposited Al cluster layer. Here, a poly(methyl methacrylate)-block-poly(3-hexylthiophen-2,5-diyl) (PMMA-b-P3HT) diblock copolymer template is used to investigate the nanostructure formation of Al cluster layers on the different polymer domains and to compare it with the respective homopolymers PMMA and P3HT. The optical properties relevant for sensor applications are monitored with ultraviolet-visible (UV-vis) measurements during the sputter deposition. The formation of Al clusters is followed in situ with grazing-incidence small-angle X-ray scattering (GISAXS), and the chemical interaction is revealed by X-ray photoelectron spectroscopy (XPS). Furthermore, atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) yield topographical information about selective wetting of Al on the P3HT domains and embedding in the PMMA domains in the early stages, followed by four distinct growth stages describing the Al nanostructure formation., Published by Soc., Washington, DC

Ultra-thin metal layers on polymer thin films attract tremendous research interest for advanced flexible optoelectronic applications, including organic photovoltaics, light emitting diodes and sensors. To realize the large-scale production of such metal–polymer hybrid materials, high rate sputter deposition is of particular interest. Here, we witness the birth of a metal–polymer hybrid material by quantifying in situ with unprecedented time-resolution of 0.5 ms the temporal evolution of interfacial morphology during the rapid formation of ultra-thin gold layers on thin polystyrene films. We monitor average non-equilibrium cluster geometries, transient interface morphologies and the effective near-surface gold diffusion. At 1 s sputter deposition, the polymer matrix has already been enriched with 1% gold and an intermixing layer has formed with a depth of over 3.5 nm. Furthermore, we experimentally observe unexpected changes in aspect ratios of ultra-small gold clusters growing in the vicinity of polymer chains. For the first time, this approach enables four-dimensional insights at atomic scales during the gold growth under non-equilibrium conditions.

To evaluate the influence of different cleaning methods on the resin bond strength to contaminated translucent 3Y-TZP ceramic.A total of 133 airborne-particle abraded (0.1 MPa) zirconia specimens were divided into 7 groups. Uncontaminated zirconia specimens were either not cleaned (UN) or cleaned with cleaning paste (Ivoclean) (UP1). After contamination by saliva and blood immersion, zirconia specimens were cleaned using either distilled water rinsing (CW), 99% isopropanol in an ultrasonic bath (CI), cleaning paste according to manufacturer's instructions (CP1), cleaning paste with additional rubbing (CP2), or additional airborne-particle abrasion at 0.1 MPa (CA). Three specimens from each group were examined by x-ray photoelectron spectroscopy (XPS). For each group, sixteen Plexiglas tubes filled with composite resin (Clearfil FII, Kuraray Noritake) were bonded to the zirconia specimens using a primer (Clearfil Ceramic Primer Plus, Kuraray Noritake) and luting composite (Panavia V5, Kuraray Noritake). Before measuring tensile bond strength, specimens were stored in distilled water for 3 or 150 days plus 37,500 thermal cycles.After 3 days, no group showed significantly different TBS compared to the control group UN (p0.05). However, groups CW and CI showed significantly lower TBS than all other groups after 150 days (p ≤ 0.05). XPS analysis revealed more organic residue on zirconia surfaces of groups CW and CI than on the other groups.Cleaning with the cleaning paste and airborne-particle abrasion were effective in removing saliva and blood contamination and enhancing bond strength.

Au nanoparticle (NP) decorated heterogeneous TiO2 catalysts are known to be effective in the degradation of various organic pollutants. The photocatalytic performance of such Au-TiO2 structures remarkably depends on the size, morphology, and surface coverage of the Au NPs decorating TiO2. Here we propose an effective way of preparing a highly active Au nanocluster (NC) decorated TiO2 thin film by a novel photodeposition method. By altering the solvent type as well as the illumination time, we achieved well-controlled surface coverage of TiO2 by Au NCs, which directly influences the photocatalytic performance. Here the Au NCs coverage affects both the electron store capacity and the optical absorption of the hybrid Au-TiO2 system. At low surface coverage, 19.2-29.5%, the Au NCs seem to enhance significantly the optical adsorption of TiO2 at UV wavelengths which therefore leads to a higher photocatalytic performance.

Au nanoparticle (NP) decorated heterogeneous TiO

The massive application requests for high-performance sensors indicate on the importance of precise controlling of the semiconducting oxide characteristics. The sensor longevity needed for the remote areas in harsh environments is mandatory and can benefit greatly from self-cleaning abilities. To serve this demand, we present in our work ultra-thin TiO2 films deposited with different thicknesses down to 15 nm on glass substrates using atomic layer deposition (ALD). The morphological, chemical, topographic, electronic and chemical properties of the fabricated films were investigated in detail, showing the presence of the anatase phase. As it is known by the literature, the UV and gas sensing properties are highly dependent on the thickness of the films, however fully reversible and capable of long term detection. Thinner films (15 nm) showed higher UV and gas sensing performances than thicker films (45 nm), which was related to the film thickness comparable to the Debye length. Further improvement in the UV sensing properties was achieved by surface functionalization of TiO2 films with Au nanoparticles. The UV response increased by about one order of magnitude after the surface functionalization with Au nanoclusters/nanoparticles. All TiO2 ultra-thin films demonstrated good selectivity to hydrogen gas, independent of the thickness. The samples with 15 nm thickness showed a response of ~ 600% to 100 ppm of H2 at 250 °C operating temperature. The presented study demonstrates the importance of the film thickness and surface functionalization with noble metals nanoclusters for sensing applications of ultra-thin TiO2 layers. Such ultra-thin films could be used for the development of a series of integrated detectors and chemical field effect transistors (chemFETs) directly on highly complex chips.

We present a facile method, combining sputtering and gas aggregation techniques, to prepare a photocatalytic TiO2 thin film decorated with stable aluminum plasmonic nanoparticles (Al NPs) to reveal the localized surface plasmon resonance (LSPR) effect on TiO2 photocatalysis under UV irradiation. We demonstrate for the first time the negative and positive influences of LSPR on UV photocatalysis by irradiating Al NPs/TiO2 hybrid structures at two different UV wavelengths: both at and above the plasmonic absorption of Al NPs. These findings open the door to design low-cost Al/TiO2 photocatalytic hybrid surfaces that function in a broad spectral range from deep-ultraviolet to visible wavelengths.

While there is continuous progress in development of new photocatalytic thin films and coatings, the lack of a reliable and standard procedure for measuring the photocatalytic performance of such active surfaces makes it difficult to compare results between research groups and different measurement setups. Here, a comparative study was carried out to demonstrate the high photocatalytic activity of sputter-deposited TiO2 film with self-organized nanocrack networks by using two different analytical approaches: (i) bleaching of a thin Methylene Blue (MB) solid layer on photocatalytic TiO2 thin film (in-air) and (ii) the decolorization of a MB aqueous solution in the presence of TiO2 thin film (in-solution). While the decolorization of aqueous MB solution provides an indirect observation of the photocatalytic effect imposed by the TiO2 film, the use of a solid MB layer as an indicator allows monitoring of photocatalytic reactions at the solid-air interface directly. We showed the applicability of this approach as a complementary and a fast analysis method to reveal the photocatalytic efficiency of thin films by comparing it with the state of the art inks (based on MB and other similar organic dyes) used as photocatalysis indicator.

Detection and differentiation of volatile organic compounds (VOC) is highly important since these gaseous pollutants degrade the air quality and represent, even in small amounts, a threat to human health. In this work, a simple and cost-effective method to synthesize a multilayered (CuO-Cu2O)/ZnO:Al nanostructured film forming non-planar heterojunctions for efficient detection of volatile organic compound vapors is presented. While the ZnO:Al layer with different contents of Al (∼0.1 and 0.2 at%) was deposited on a glass substrate via a synthesis from chemical solutions (SCS, at a temperature

Multifunctional polymer surfaces exhibiting both hydrophilic and hydrophobic functionality were created using self-organized plasma “streamer” microdischarges occurring in atmospheric pressure dielectric barrier discharges (DBD) operating with argon and air. Surface chemistry and wettability change of polymethylmethacrylate (PMMA) were found to spatially correlate with self-organized streamer patterns. Gas atmosphere was found to play a significant role on streamer density, pattern stability, and lateral contrast of plasma-induced physicochemical property changes across the surface. Stable streamer patterns, with each streamer surrounded by a glowlike discharge, were obtained in argon; discharges in air had more transient and chaotic streamers that were surrounded by dark “plasma free”-like zones. Air plasma streamer treatment of PMMA resulted in hybrid hydrophilic/phobic surfaces with water contact angles (WCA) ranging from 30° to 100° (PMMA WCA = 75°), depending on processing conditions and location. WCA and XPS mapping after treatment revealed that surface chemistry is preferentially modified near streamers, and moreover, that streamer exposure in air locally renders the surface more hydrophilic, surrounded by regions that are more hydrophobic. Overall, this work demonstrates that self-organized streamers in DBD plasmas could be used for scalable and localized modification of surfaces.

Dielectric insulators with patterned topographic relief were used in dielectric barrier discharge (DBD) plasmas operating at atmospheric pressure to spatially define the formation of filamentary microdischarges (“plasma streamers”). Precise localization of microdischarge streamers is demonstrated with concomitant treatment patterns on surfaces, enabling localized etching, surface micro-texturing, and chemically and structurally induced wettability modification without the use of lithographic masks on the sample. Proof-of-concept examples include generation of arbitrary streamer patterns (lines, arrays, and letters), anisotropic etching of PMMA films, and spatial patterning of Teflon to be hydrophilic. The approach herein allows user-defined patterning of DBD streamers for subsequent modification and treatment of surfaces (e.g., roughness, wettability, etc.), materials deposition, or etching.

The reproducible low-cost fabrication of functional polymer-metal interfaces via self-assembly is of crucial importance in organic electronics and organic photovoltaics. In particular, submonolayer and nanogranular systems expose highly interesting electrical, plasmonic, and catalytic properties. The exploitation of their great potential requires tailoring of the structure on the nanometer scale and below. To obtain full control over the complex nanostructural evolution at the polymer-metal interface, we monitor the evolution of the metallic layer morphology with in situ time-resolved grazing-incidence small-angle X-ray scattering during sputter deposition. We identify the impact of different deposition rates on the growth regimes: the deposition rate affects primarily the nucleation process and the adsorption-mediated growth, whereas rather small effects on diffusion-mediated growth processes are observed. Only at higher rates are initial particle densities higher due to an increasing influence of random nucleation, and an earlier onset of thin film percolation occurs. The obtained results are discussed to identify optimized morphological parameters of the gold cluster ensemble relevant for various applications as a function of the effective layer thickness and deposition rate. Our study opens up new opportunities to improve the fabrication of tailored metal-polymer nanostructures for plasmonic-enhanced applications such as organic photovoltaics and sensors.

Despite tremendous efforts toward fabrication of three-dimensional macrostructures of two-dimensional (2D) materials, the existing approaches still lack sufficient control over microscopic (morphology, porosity, pore size) and macroscopic (shape, size) properties of the resulting structures. In this work, a facile fabrication method for the wet-chemical assembly of carbon 2D nanomaterials into macroscopic networks of interconnected, hollow microtubes is introduced. As demonstrated for electrochemically exfoliated graphene, graphene oxide, and reduced graphene oxide, the approach allows for the preparation of highly porous (> 99.9%) and lightweight (-3) aeromaterials with tailored porosity and pore size as well as tailorable shape and size. The unique tubelike morphology with high aspect ratio enables ultralow-percolation-threshold graphene composites (0.03 S m-1, 0.05 vol%) which even outperform most of the carbon nanotube-based composites, as well as highly conductive aeronetworks (8 S m-1, 4 mg cm-3). On top of that, long-term compression cycling of the aeronetworks demonstrates remarkable mechanical stability over 10;000 cycles, even though no chemical cross-linking is employed. The developed strategy could pave the way for fabrication of various macrostructures of 2D nanomaterials with defined shape, size, as well as micro- and nanostructure, crucial for numerous applications such as batteries, supercapacitors, and filters.

TiO2 thin films are used extensively for a broad range of applications including environmental remediation, self-cleaning technologies (windows, building exteriors, and textiles), water splitting, antibacterial, and biomedical surfaces. While a broad range of methods such as wet-chemical synthesis techniques, chemical vapor deposition (CVD), and physical vapor deposition (PVD) have been developed for preparation of TiO2 thin films, PVD techniques allow a good control of the homogeneity and thickness as well as provide a good film adhesion. On the other hand, the choice of the PVD technique enormously influences the photocatalytic performance of the TiO2 layer to be deposited. Three important parameters play an important role on the photocatalytic performance of TiO2 thin films: first, the different pathways in crystallization (nucleation and growth); second, anatase/rutile formation; and third, surface area at the interface to the reactants. This study aims to provide a review regarding some strategies developed by our research group in recent years to improve the photocatalytic performance of TiO2 thin films. An innovative approach, which uses thermally induced nanocrack networks as an effective tool to enhance the photocatalytic performance of sputter deposited TiO2 thin films, is presented. Plasmonic and non-plasmonic enhancement of photocatalytic performance by decorating TiO2 thin films with metallic nanostructures are also briefly discussed by case studies. In addition to remediation applications, a new approach, which utilizes highly active photocatalytic TiO2 thin film for micro- and nanostructuring, is also presented.

In this research, the low-temperature single-step electrochemical deposition of arrayed ZnO nanowires (NWs) decorated by Au nanoparticles (NPs) with diameters ranging between 10 and 100 nm is successfully demonstrated for the first time. The AuNPs and ZnO NWs were grown simultaneously in the same growth solution in consideration of the HAuCl4 concentration. Optical, structural, and chemical characterizations were analyzed in detail, proving high crystallinity of the NWs as well as the distribution of Au NPs on the surface of zinc oxide NWs demonstrated by transmission electron microscopy. Individual Au NPs-functionalized ZnO NWs (Au-NP/ZnO-NWs) were incorporated into sensor nanodevices using an focused ion bean/scanning electron microscopy (FIB/SEM) scientific instrument. The gas-sensing investigations demonstrated excellent selectivity to hydrogen gas at room temperature (RT) with a gas response, Igas/Iair, as high as 7.5–100 ppm for Au-NP/ZnO-NWs, possessing a AuNP surface coverage of ∼6.4%. The concent...

Tailoring the optical and electronic properties of nanostructured polymer-metal composites demonstrates great potential for efficient fabrication of modern organic optical and electronic devices such as flexible sensors, transistors, diodes, or photovoltaics. Self-assembled polymer-metal nanocomposites offer an excellent perspective for creating hierarchical nanostructures on macroscopic scales by simple bottom-up processes. We investigate the growth processes of nanogranular silver (Ag) layers on diblock copolymer thin film templates during sputter deposition. The Ag growth is strongly driven by self-assembly and selective wetting on the lamella structure of polystyrene

In this paper, the effect of the thickness of nano-structured TiO2 thin films (12–40 nm) and successive deposition of different noble metal nanoparticles on the performances of propanol vapor and H2 gas sensors was investigated. The obtained titania thin films were integrated into a device for UV, gas, and gas/vapor sensing studies at different operating temperatures. Qualitative analysis revealed that the sensor selectivity and its response could be altered by film thickness and type of noble metal nanoparticles. The results indicate that the sensor with 40 nm TiO2 film has the highest response to H2 gas (˜ 650%). The fastest response time and the most rapid recovery however were achieved by the sensors made of 12 nm sprayed TiO2 ultra-thin films, which also offered the highest selectivity to H2 gas. The best UV detection performances were demonstrated by films functionalized with Au nanoparticles (the IUV/Idark ≈ 80). The structural, chemical, electrical, UV, and gas sensing properties of such films were investigated using SEM, AFM, Raman spectroscopy, electrical characterization, and sensing experiments. It has been clearly demonstrated that films are nanostructured and have mixed phases that contain mostly anatase (annealed at 450 °C) and small amounts of rutile after thermal annealing at higher temperatures (more than 600 °C), as improved materials for sensor applications. Our combined study analyzes the relationship between thickness, electrical properties and the gas/vapor sensing performance of such thin film based TiO2 gas sensors as well as the effect of different types of noble metal nanoparticles (Au, Ag, Ag-Au and Ag-Pt) deposited on the surface. The enhanced response was attributed to the involvement of noble nanoalloy or nanoparticle interface to titania forming nano-junctions in the gas sensing mechanism. Highly selective and sensitive sensors towards specific gas or vapor molecules are essential for environmental monitoring, and for health and safety issues.

In recent years, heterogeneous photocatalysis has gained enormous interest due to increasing concerns about environmental pollution. Here we propose a facile approach to synthesize cauliflower-like CeO

Extensive application requests on high-performance gas sensors and photodetectors reveal the importance of controlling semiconducting oxide properties. Sensing properties of ZnO nano- and micro-structures can be tuned and their functional performances can be enhanced more efficiently by metal-doping. Here, we report the synthesis of crystalline Fe-doped ZnO (ZnO:Fe) nanostructured films via a cost-effective and simple synthesis from chemical solutions (SCS) approach followed by rapid thermal annealing (RTA) with excellent potential for the development of multifunctional devices for UV and ethanol (C 2 H 5 OH) vapour sensing. The effects of two types of thermal annealing on the ZnO:Fe morphology, the crystallinity, the electronic and the vibrational properties, the UV radiation and the gas sensing properties are investigated. The experimental results indicate an increase in UV response ( I UV / I DARK ~10 7 ) of as-grown ZnO nanostructured films by Fe-doping, as well as an essential improvement in rise and decay times due to RTA effects at 725 °C for 60 s. In comparison with un-doped samples, ZnO:Fe (0.24 at%) specimens showed a response to ethanol which is enhanced by a factor of two, R air / R gas ~61. It was demonstrated that by using Fe-doping of ZnO it is possible to reduce essentially the response τ r and recovery times τ d of the multifunctional device. The involved gas sensing mechanism is discussed in detail in this paper. The presented results could be of great importance for the application of RTA and doping effects for further enhancement of UV detection and gas sensing performances of the ZnO:Fe nanomaterial-based multifunctional device.

The copper oxides are advanced materials due to their remarkable sensing, optical, electrical, thermal and magnetic performances. Nanostructuring and doping of copper oxides enhance further the possible features of these important and attractive materials for various applications. In this work, we report for the first time on enhanced performances of p-type semiconductor sensors due to Zn-doping in copper oxides and formation of two distinctly different phases of such nanocrystals, namely Cu2O:Zn, CuO:Zn, as well as mixed phases of CuO:Zn/Cu2O:Zn bi-layer structures. Zinc-doping in cuprite and tenorite (ZnxCu1−xOy) nanocrystallite layers has been identified by XPS and indicates that the bilayer CuO:Zn/Cu2O:Zn nano-heterojunction with mixed phases in nano-crystals has been obtained by rapid thermal annealing (RTA) at 525 °C in 60 s. By doping with Zn in copper oxide and forming a nano-heterojunction by RTA for 60 s it was possible to change the sensing properties from the ethanol vapour (pure copper oxide) to hydrogen gas (zinc-doped copper oxide). The gas sensing characteristics in dependence of the zinc-doping level and film thicknesses were evidenced and found a highly efficient nanomaterial based on 3.0 wt% Zn–doped CuO:Zn/Cu2O:Zn nanoscale p–p heterojunction. Relatively fast response and recovery times for hydrogen gas sensors based on ZnxCu1−xOy bi-layers were obtained. The involved gas sensing mechanism of these nanostructures has been proposed and described. The obtained results will be of high interest for the development of p-type semiconductor based gas sensors.

Silver nanoparticle-based antibacterial nanocomposite coatings were fabricated by means of gas aggregation source of Ag nanoparticles and plasma-enhanced chemical vapour deposition of matrix material. Combination of these techniques makes it possible to independently control the amount of Ag nanoparticles in the nanocomposites, as well as properties of matrix material, such as its chemical composition or wettability. This subsequently enables to tune kinetics of silver ion release and hence the antibacterial performance of produced nanocomposites. Based on detail measurements of silver ion release from Ag/plasma polymerized hexamethyldisiloxane and Ag/SiOx nanocomposites, it may be concluded that the release rate is strongly dependent both on matrix material and amount of Ag nanoparticles present in the nanocomposite. These measurements are furthermore accompanied with tests focused on the evaluation of antibacterial potency of produced nanocomposites.

Copper oxide nanostructures are fascinating nanomaterials due to their remarkable electrical, optical, thermal, and sensing properties given that their tunability and the stabilization of specific phases are uniquely possible at the nanoscale dimensions. The present study reports on nano-crystalline copper oxide thin films via a simple synthesis from chemical solutions (SCS) followed by two types of thermal annealing, namely rapid thermal annealing (RTA) and conventional thermal annealing (TA). We report on the enhanced ethanol sensing performances of the device structures based on synthesized copper oxide nanocrystals with one and two distinctly different phases, namely Cu2O, CuO, as well as mixed phases CuO/Cu2O. A gradient in phase change of nano-crystals was observed for annealed samples starting from CuO on the top to Cu2O in their central region. RTA effects on the gas response of the CuxOy nano-crystals have been identified as unprecedented selectivity and sensitivity to ethanol vapours at different temperatures. An increase in resistance value of about one order in magnitude was detected for samples treated by conventional-TA at 400 °C for 30 min at optimal operating temperature of 300 °C and RTA at 525 °C for 60 s at lower optimal operating temperature of 275 °C. It has been observed that the response and recovery times for pure copper oxide-based sensors can be significantly improved by Zn-doping, e.g. from ∼4.1 s and ∼10.5 s to about 3.3 s and 7.2 s, respectively. The obtained results were discussed in details and it provide an exciting alternative for fast, sensitive, and selective detection of trace gases, which could be of several benefits in the technologies dealing with public securities and environmental monitoring applications.

The use of multicomponent targets allows the gas‐phase synthesis of a large variety of alloy nanoparticles (NPs) via gas aggregation sources. However, the redeposition of sputtered material impacts the composition of alloy NPs, as demonstrated here for the case of AgAu alloy NPs. To enable NPs with tailored Au fractions, in operando control over the composition of the NPs is in high demand. We suggest the use of optical emission spectroscopy as a versatile diagnostic tool to determine and control the composition of the NPs. A strong correlation between operating pressure, intensity ratio of Ag and Au emission lines, and the obtained NP compositions is observed. This allows precise in operando control of alloy NP composition obtained from multicomponent targets.

Magnetron sputtering and gas aggregation source (GAS) approaches were combined for the preparation of columnar TiO2 structures decorated with PdO nanoparticles (NPs). The totally solvent-free synthesis approach provides good control of surface coverage, size, morphology, and stoichiometry of PdO NPs in comparison to wet chemical synthesis methods. X-ray photoelectron spectroscopy (XPS) analysis showed that the heat treatment led to the formation of a mixed oxide state PdO/PdO2 on the TiO2 layer. A steady equilibrium between PdO (oxidation by free and adsorbed •OH) and PdO2 (reduced by trapped photogenerated electrons) phases under UV irradiation seems to provide an efficient electron-hole pair separation. Such robust PdO–TiO2 thin films have a strong potential for use as photocatalytic and self-cleaning windows or similar out-door technical surfaces.

Crystalline silicon is an ideal anode candidate for lithium ion batteries as it offers a high Li+ ion storage capacity, direct current pathway and is a stable and earth abundant element. In order to match the high theoretical energy density of silicon in lithium ion batteries a suitable cathode material is required. Sulfur based cathodes have a high theoretical storage capacity for application in lithium ion batteries, based on the conversion reaction of the cyclic S8 molecule with lithium to form smaller lithium polysulfides up to Li2S, and are also cheap and earth abundant. One of the major drawbacks of lithium sulfur cathode materials is the tendency of lithium polysulfides to be dissolved by the electrolyte, which causes the polysulfides to migrate away from the cathode, leading to an overall capacity loss. For application of porous silicon in a full cell lithium ion battery with sulfur it is important to understand the impact the presence of lithium polysulfides can have on the functionality of porous silicon as an anode. In this study porous silicon anodes with thicknesses of 6 µm and 12 µm were cycled in a half cell in the presence of varying concentrations of Li2S6 (0 M, 0.017 M and 0.083 M). For the electrolyte with 0.017 M Li2S6 the cycling behavior was comparable, or better, than the electrolyte with no polysulfides. The SEI layer formed on the surface of the porous silicon anodes was investigated ex situ with X-ray photoelectron spectroscopy, Raman spectroscopy and scanning electron microscopy after one, five and ten cycles. It was seen that in the first cycle lithium polysulfides are contained in the SEI and undergo an oxidation reaction to form sulfates over the following cycles. This leads to a more inorganic SEI layer in the presence of polysulfides, especially in the case of the 12 µm porous silicon, and long term cycling stability. The 12 µm porous silicon anode cycled in the presence of 0.083 M Li2S6 showed stable cycling behavior over one hundred cycles, with limited capacity loss and coulombic efficiencies of 96.2 % after one hundred cycles.

This talk will highlight our recent work on the development of atmospheric pressure plasma tools and methods to modify the roughness, surface chemistry, and wettability of dielectric, polymer, and textile surfaces. Dielectric barrier discharges (DBD) at both low (60 Hz) and high frequency (10s kHz, pulsed), along with RF (13.56 MHz) microplasma jets, were used to directly create hydrophobic/philic areas and bio-reactive groups (-COOH, -CFx, -NH2) on surfaces for subsequent immobilization of enzymes and bioactive compounds for sensing, environmental threat detection, and chemical agent destruction. The goal of the work is to provide fundamental understanding of how interfacial properties, namely chemical termination and surface area, roughness geometry and length scale, and incorporation of 2D/3D nanostructures, can impart multi-functionality to different material surfaces. The effect of various plasma operating conditions (e.g., streamer density, frequency, gas atmosphere, power) on wettability contrast, roughness, surface chemistry, and enzyme grafting and viability for different model surfaces will be discussed.

In recent years, heterogeneous photocatalysis has gained enormous interest due to increasing concerns about environmental pollution. Here we propose a facile approach to synthesize cauliflower-like CeO 2 -TiO 2 hybrid structures by magnetron reactive sputtering, exhibiting an extremely high photocatalytic activity. While heating and air-quenching of the sputter deposited TiO 2 thin film (first layer) triggered the formation of a nanocrack network, the second heat-treatment led to transformation of the CeO 2 film (second layer) into CeO 2 nanoclusters (NCs). We attribute the resulting high photocatalytic activity to the confined structure of the CeO 2 NCs and the CeO 2 -TiO 2 interface, which allows Ce 3+ /Ce 4+ dynamic shifting. In addition to high photocatalytic activity in an aqueous medium, the prepared CeO 2 -TiO 2 hybrid structures exhibited significant self-cleaning properties in air (non-aqueous).

To evaluate the influence of contamination and plasma treatment on the bond strength of resin to zirconia ceramic.After immersion in saliva or the use of a silicone disclosing agent, polished and airborne-particle abraded zirconia specimens were cleaned either ultrasonically in 99% isopropanol or with nonthermal plasma. Uncontaminated zirconia specimens were used as control. For chemical analysis, specimens of all groups were examined with x-ray photoelectron spectroscopy (XPS). Plexiglas tubes filled with composite resin were bonded to ceramic specimens with a phosphate-monomer-containing luting resin. The influence of contamination and cleaning methods on ceramic bond durability was examined by tensile testing after 3 and 150 days of water storage, with an additional 37,500 thermocycles during the 150-day storage.XPS showed an increase in the amount of oxygen and a decrease in the amount of carbon on the zirconia surface after plasma treatment. After contamination with silicone, XPS revealed a high amount of Si residue on the surface that none of the investigated cleaning processes could completely remove. The tensile bond strength to uncontaminated zirconia ceramic was durable, but was significantly reduced by contamination.Plasma treatment was effective in removing salivary contamination but not silicone disclosing agent residue from the bonding surface of zirconia.

Noble metals and their oxide nano-clusters are considered to be the most promising candidates for fabricating advanced H

Metal clusters and nanoparticles (NPs) have been studied intensively due to their unique chemical, physical, electrical, and optical properties, resulting from their dimensions, which provided host of applications in nanoscience and nanotechnology. Formation of new materials by embedding NPs into various matrices (i.e. formation of nanocomposites) further expands the horizon of possible application of such nanomaterials. In the last few decades, the focus was put on the formation of metallic and metal oxide NPs via a so-called gas aggregation nanoparticle source employing magnetron sputtering (i.e. Haberland concept). In this paper, an overview is given of the recent progress in formation and deposition of NPs by the gas aggregation method. Examples range from noble metals (Ag, Au) through reactive metals (Al, Ti) to Si and the respective oxides. Emphasis is placed on the mechanism of nanoparticle growth and the resulting properties. Moreover, kinetic Monte Carlo simulations were developed to explain the growth mechanism and dynamics of nanoparticle formation depending on the experimental conditions. In addition, the role of trace amounts of reactive gases and of pulsed operation of the plasma on the nucleation process is addressed. Finally, the treatment of the NPs in the plasma environment resulting in nanoparticle charging, morphological and chemical modifications is discussed.

Nanoscale 10(38), 18275 - 18281 (2018). doi:10.1039/C8NR06155F, 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., Published by RSC Publ., Cambridge

Noble metals and their oxide nano-clusters are considered to be the most promising candidates for fabricating advanced H2 gas sensors. Through this work, we propose a novel strategy to grow and modulate the density of PdO/PdO2 nanoparticles uniformly on nanostructured Pd-doped ZnO (ZnO : Pd) films by a one-step solution approach followed by thermal annealing at 650 °C, and thus to detect ppm-level H2 gas in a selective manner. The gas sensing properties of such hybridized materials showed that the PdO-functionalized ZnO samples offer significantly improved H2 gas sensing properties in an operating temperature range of 25–200 °C. The deposition of ZnO : Pd films via a simple synthesis from chemical solutions (SCS) approach with an aqueous bath (at relatively low temperatures, 150 °C, up to 350 °C); however, the PdO/PdO2 mixed phases of the nanocluster-modified surface ZnO : Pd films showed a much better selectivity to H2 gas, even at a lower operating temperature, in the range of 25–150 °C. For such PdO-functionalized ZnO : Pd films, even at room temperature, a gas response of ∼12.7 to 1000 ppm of H2 gas was obtained, without response to any other reducing gases or tested vapors. The large recovery time of the samples at room temperatures (>500 s) can be drastically reduced by applying higher bias voltages. Furthermore, we propose and discuss the gas sensing mechanism for these structures in detail. Our study demonstrates that surface functionalization with PdO/PdO2 mixed phase nanoclusters–nanoparticles (NPs) is much more effective than only the Pd doping of nanostructured ZnO films for selective sensing applications. This approach will pave a new way for the controlled functionalization of PdO/PdO2 nanoclusters on ZnO : Pd surfaces to the exact detection of highly explosive H2 gas under various atmospheres by using solid state gas sensors.

The tuning of wetting over an extreme range, from superhydrophilic to superhydrophobic, was demonstrated on 1D Al/Al2O3 nanostructures. While chaotic and tangled 1D Al/Al2O3 nanostructures exhibited complete wetting, they became water repellent (with a water contact angle (CA) ≥173°) after the infiltration of poly[bis(2,2,2-trifluoroethoxy)phosphazene] (PTFEP) solution. This simple strategy allows the achievement of two extreme wetting regimes, perfect wetting and non-wetting, without altering the nanostructured surface topography. The same surface was also found to exhibit repellency towards artificial blood and hexadecane.