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Ordered porous gold/titanium dioxide (Au/TiO2) hybrid nanostructured films are specifically interesting in large-scale applications using localized surface plasmon resonances (LSPRs) and surface-enhanced Raman scattering (SERS). Deposition of Au nanoparticles via sputter deposition is one of the promising technologies to establish optically active sites at low cost in combination with nanostructured TiO2 films. In this work, we investigate the optical response of sputter-deposited Au/TiO2 nanohybrid thin films with a focus on the plasmonic response and application as molecular sensors. The LSPR peak red shifts with an increasing thickness of deposited Au. The Raman intensity of deposited molecules, probed with rhodamine 6G (R6G), depends on the deposited gold thickness. It has its maximum at an effective Au thickness of 3.4 nm. To elucidate the origin of this behavior, we apply in situ grazing-incidence small-angle X-ray scattering (GISAXS) to investigate the growth kinetics of Au on a TiO2 template during sputter deposition. On the basis of time-resolved GISAXS, the growth characteristics of sputter-deposited Au on a TiO2 template with a final effective Au layer thickness around the percolation threshold is described with the well-known four-stage model of nucleation and cluster formation, diffusion-mediated growth, adsorption-mediated growth, and grain growth. The maximum in SERS intensity is corroborated by the existence and optimal size of hot spots in the narrow space occurring between the sputter-deposited Au clusters, on staying below the percolation threshold. On the basis of the growth laws extracted, we give a guideline for tailoring the ordered porous Au/TiO2 nanohybrid thin films for SERS sensor applications. [ABSTRACT FROM AUTHOR]

Various methods are developed and used to treat oil‐contaminated water, including mechanical separation, chemical treatment, biological treatment, membrane filtration, and sorption. Oil clean‐up via selective sorption of the oil by an engineered surface is the most accepted technique due to its high removal efficiency and low cost. Here, a multifunctional surface providing highly selective oil sorption and clean‐up capability via the photocatalytic decomposition is proposed. This novel surface is named as the "three‐in‐one (3‐in‐1) surface" since it is composed of 1) a highly photocatalytic layer, 2) micro‐ and nanostructures, and 3) a low surface energy layer. First, the TiO2 photocatalytic layer is prepared by magnetron sputtering. Then flowerlike Ag nanoplates are photocatalytically deposited on the sputtered TiO2 layer. Afterward, a low surface energy layer, poly‐1,3,5‐trivinyl‐1,3,5‐trimethylcyclotrisiloxane (p‐V3D3), is over‐coated on Ag/TiO2 surface by initiated chemical vapor deposition (iCVD) while retaining the topographical features of the surface (micro‐ and nanoscale surface structures). The p‐V3D3/Ag/TiO2 surface demonstrates a high selective adsorption to oil whereas simultaneously it shows extreme repellency to water. The p‐V3D3/Ag/TiO2 surface can also be photocatalytically cleaned up and this may find applications in various technology fields including water treatment, microfluidics, self‐cleaning, and water harvesting. [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]

Miniaturized piezoelectric/magnetostrictive contour‐mode resonators are effective magnetometers by exploiting the ΔE effect. With dimensions of ≈100–200 µm across and <1 µm thick, they offer high spatial resolution, portability, low power consumption, and low cost. However, a thorough understanding of the magnetic material behavior in these devices is lacking, hindering performance optimization. This manuscript reports on the strong, nonlinear correlation observed between the frequency response of these sensors and the stress‐induced curvature of the resonator plate. The resonance frequency shift caused by DC magnetic fields drops off rapidly with increasing curvature: about two orders of magnitude separate the highest and lowest frequency shift in otherwise identical devices. Similarly, an inverse correlation with the quality factor is found, suggesting a magnetic loss mechanism. The mechanical and magnetic properties are theoretically analyzed using magnetoelastic finite‐element and magnetic domain‐phase models. The resulting model fits the measurements well and is generally consistent with additional results from magneto‐optical domain imaging. Thus, the origin of the observed behavior is identified and broader implications for the design of nanomagnetoelastic devices are derived. By fabricating a magnetoelectric nanoplate resonator with low curvature, a record‐high DC magnetic field sensitivity of 5 Hz nT–1 is achieved. [ABSTRACT FROM AUTHOR]

The undoped and metal‐doped zinc oxide columnar films (ZnO:Sn, ZnO:Fe, ZnO:Ag, and ZnO:Cu) are covered with an ultra‐thin layer of SiO2 (10–20 nm). The electrical, UV, and volatile organic compounds (VOCs) sensing properties are evaluated under different ambient conditions for ≈7 months to investigate the impact of the top SiO2‐layer on the long‐term stability of samples. The obtained results show a high immunity of sensing properties of SiO2‐coated samples to humidity. Furthermore, gas sensing measurements show that the loss in response after 203 days is significantly lower for coated samples indicating higher stability of sensing performance. For ZnO:Fe the gas response is reduced by about 90% after 203 days, but for SiO2‐coated ZnO:Fe columnar films the gas response is slightly reduced by only 38%. The density functional theory (DFT) calculations show that water species bind strongly with the surface SiO2 layer atoms with a −0.129 e− charge transfer, which is, much higher compared to the interaction with ethanol and acetone. Calculations show strong binding of water species on the SiO2 layer indicating preferential absorption of water molecules on SiO2. The obtained results demonstrate an important role of the top SiO2 ultra‐thin layer in order to produce humidity‐tolerant sensitive devices. [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]