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Purpose: To evaluate the influence of different cleaning methods on the resin bond strength to contaminated translucent 3Y-TZP ceramic. Materials and Methods: 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. Results: After 3 days, no group showed significantly different TBS compared to the control group UN (p > 0.05). 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. Conclusion: Cleaning with the cleaning paste and airborne-particle abrasion were effective in removing saliva and blood contamination and enhancing bond strength. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the influence of contamination and plasma treatment on the bond strength of resin to zirconia ceramic. Materials and Methods: After immersion in saliva or the use of a silicone disclosing agent, polished and airborneparticle 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. Results: 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. Conclusion: Plasma treatment was effective in removing salivary contamination but not silicone disclosing agent residue from the bonding surface of zirconia. [ABSTRACT FROM AUTHOR]

Tailoring of plasmon resonances is essential for applications in anticounterfeiting. This is readily achieved by tuning the composition of alloyed metal clusters; in the simplest case, binary alloys are used. 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 such as silver and copper have been accessible by molecular dynamics (MD) simulations and transmission electron microscopy (TEM). 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 because the copper core yields a lower mobility and higher crystallization tendency than the silver fraction. We compare our results to MD simulation and TEM data. This demonstrates a route to tailor accurately the plasmon resonances of nanosized, polymer-supported clusters which is a crucial prerequisite for anticounterfeiting. [ABSTRACT FROM AUTHOR]

In this study, in situ UV–Vis spectroscopy is used to investigate the growth and transport of nanoparticles inside a gas aggregation source (GAS) dependent on the Ar gas flow and operating pressure. It was found that the nanoparticles were becoming trapped at different positions inside the GAS dependent on the gas flow. Moreover, in situ UV–Vis spectroscopy suggested the presence of large nanoparticles inside the GAS, which were not observed outside. Computational fluid dynamic simulations were performed to study the velocity distribution inside the GAS. Three distinct areas were identified, where nanoparticles can become trapped or lost. The gas flow velocity distribution was found to strongly impact the transport of nanoparticles. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Hierarchical colloid-based lithography and two-step plasma etching involving mask reduction were used to probe and tune the wettability landscape of Si and GaN surfaces from the hydrophilic to superhydrophobic limits over cm length scales. Hydrophobicity, due to the classical Cassie–Baxter (CB) wetting effect, was observed on Si with surface pillars having pitches below 1 μm. Additional tuning of plasma processing conditions at this critical transition provided additional increases in hydrophobicity and led to a highly repellent, lotus leaf effect. Superhydrophobic surfaces were created within the CB wetting state by varying the extent and duration of plasma-based mask reduction and pattern transfer, achieving a maximum contact angle of 157°. Additional submicrometer topography (310 nm spacing) was added to a nominally Wenzel-impregnated, hydrophilic Si micropillar surface (a diameter of 6 μm) with a second lithography cycle, rendering the surface hydrophobic and robust to aging in ambient conditions. An increase in the contact angle with added hierarchy (46°–88°) was also observed for GaN surfaces, albeit diminished compared to Si owing to the relatively lower initial GaN-water contact angle. Overall, this approach has demonstrated a significant degree of wetting tunability in multiple semiconductor systems using colloidal-based nano- and micro-patterning. [ABSTRACT FROM AUTHOR]

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 (OPVs). The polymer components used in these devices are mostly nanostructured conductive polymers with conjugated π-electron systems. Enhanced OPV's power conversion efficiencies or sensor sensitivity can be achieved by selective metal deposition on or into polymer templates. In this study, we exploit time-resolved grazing-incidence X-ray scattering to observe the metal–polymer interface formation and the cluster crystallite size in situ during silver (Ag) sputter deposition on a poly-(3-hexylthiophene-2,5-diyl)-b-poly-(methyl methacrylate) (PMMA-b-P3HT) template. We compare the arising nanoscale morphologies with electronic properties, determine Ag growth regimes, and quantify the selective Ag growth for the diblock copolymer (DBC) template using the corresponding homopolymer thin films (P3HT and PMMA) as a reference. Hence, we are able to describe the influence of the respective polymer blocks and substrate effects on the Ag cluster percolation: the percolation threshold is correlated with the insulator-to-metal transition measured in situ with resistance measurements during the sputter deposition. The Ag cluster percolation on PMMA-b-P3HT starts already on the network of the hexagonal P3HT domain before a complete metal film covers the polymer surface, which is complemented by microscopic measurements. In general, this study demonstrates a possible method for the selective Ag growth as a scaffold for electrode preparation in nanoelectronics and for energy harvesting applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Kinetic aspects of the synthesis of Ag nanoparticles (NPs) by magnetron sputtering are studied by in situ and time‐resolved small angle X‐ray scattering (SAXS). Part of the NPs are found to become confined within a capture zone at 1–10 mm from the surface of the target and circumscribed by the plasma ring. Three regimes of the NP growth are identified: 1) early growth at which the average NP diameter rapidly increases to 90 nm; 2) cycling instabilities at which the SAXS signal periodically fluctuates either due to expelling of large NPs from the capture zone or due to the axial rotation of the NP cloud; and 3) steady‐state synthesis at which stable synthesis of the NPs is achieved. The NP confinement within the capture zone is driven by the balance of forces, the electrostatic force being dominant. On reaching the critical size, large NPs acquire an excessive charge and become expelled from the capture zone via the electrostatic interactions. As a result, significant NP deposits are formed on the inner walls of the aggregation chamber as well as in the central area of the target. [ABSTRACT FROM AUTHOR]

In this work, a new strategy based on the surface functionalization and doping of semiconducting oxides was proposed for tuning device properties. A considerable increase in the gas sensing ability of Fe-doped ZnO (ZnO:Fe) columnar films grown by chemical deposition is achieved via surface decoration with oxidized silver nanoparticles (AgO/Ag NPs) with a diameter of ∼7–10 nm. AgO/Ag-decorated ZnO:Fe (Ag/ZnO:Fe) samples showed an optimal operating temperature of 300 °C with fast recovery of the signal (∼7 s) and ultra-high sensitivity to ethanol vapor versus CH4 and H2 gases. The results presented demonstrate the potential for a significant increase in sensitivity to ethanol vapors by surface decoration with AgO/Ag NPs (density of ∼0.8 × 109 cm−2) while maintaining extremely high selectivity. Quantum mechanical simulations show that the transition metal oxide clusters modify the surface chemistry of the doped zinc oxide ZnO (101̅0) surface to improve ethanol sensing. Using thermodynamic arguments, we have investigated the substitutional Fe doping of the symmetrically different Zn ions exposed at the surface. The most energetically favorable doped surface was decorated with (AgO)m nanoparticles of different sizes (1 ≤m≤ 6) which were sited at different relative positions to the Fe atom. The simulated work function explains the reactivity trends of the surface models, while the scanning tunneling microscopy images are in agreement with experimental data when the (AgO)m cluster is placed over the dopant. The interface formed between the substrate and the nanoparticle is essential to enable the ethanol conversion into ethanal, suggesting that dehydrogenation plays a key role in the alcohol detection. [ABSTRACT FROM AUTHOR]

Treatment of nanoparticles (NPs) in complex environments, such as plasmas, is of interest for the fabrication of advanced nanomaterials with desired properties and also from a physical point of view. Here, the authors investigate the mutual interaction between silver NPs and a radio frequency (RF) plasma at different conditions by combining a cylindrical hollow electrode with a gas aggregation source. The investigation of the NP deposits and the morphology of the casted films shows that the applied RF discharge significantly changes the path of the NPs as well as the NP size distribution in the beam. Starting from a neutral NP beam, it is observed that most of the NPs leave the plasma region with negative charge(s), yet the fraction of positively charged NPs grows with power. Furthermore, the plasma characteristics are slightly influenced by the NP flux since the passing NPs collect the plasma charge carriers. [ABSTRACT FROM AUTHOR]

For the use of a gas aggregation cluster source a high and stable deposition rate is desired. For many metals, nanoparticle formation is enhanced by admixture of reactive gases. Here, the role of reactive gas admixtures on the nanoparticle deposition rates is investigated for the case of reactive direct current magnetron sputtering of Ti in a gas aggregation chamber. The results show that, at low working gas (argon) pressures, stable cluster deposition at high rates can only be achieved for admixtures with a very narrow oxygen flow range. At higher pressures, stable deposition can be observed only after an intermediate maximum rate has been crossed or a stable deposition rate is not reached at all. For the different sputtering conditions, the partial pressure of oxygen was monitored with a mass spectrometer. The results are explained in terms of the competing roles of oxygen in cluster nucleation as well as in target poisoning. The cluster size distributions for different conditions were characterized by scanning electron microscopy. [ABSTRACT FROM AUTHOR]