Growth, Transport and Functionalization of Noble Metal Nanoparticles Inside and Outside a Gas Aggregation Cluster Source: Uncovered by in-situ Diagnostics

The Haberland type gas aggregation cluster source (HGAS), which was invented in 1992 by Haberland et al., provides the opportunity to synthesize different types of NPs and tailor their properties by adjusting the operating parameters of the HGAS. Although nowadays the HGAS is used by many groups for the synthesis of NPs, the processes inside the HGAS are not fully understood until today. Therefore, the aim of this dissertation is to increase the understanding of the ongoing processes inside the HGAS, because this opens the way for new fields of applications. In order to gain a better understanding of the HGAS, in‑situ diagnostics with a good spatial and temporal resolution are essential. Five different in-situ methods were used, which together contribute to a better understanding of growth, transport and functionalization of NPs inside a HGAS. By combining different in-situ methods it was possible to investigate dynamic processes in a HGAS and thereby gain new insights into growth, transport and trapping of NPs. Furthermore, the reliability of the multicomponent target approach could be enhanced, which makes it an excellent tool for the fabrication of alloy NPs with tailored composition. Finally, a new approach for the production of core-shell NPs in the gas phase was developed, which is expected to open up new applications for core-shell NPs because of its outstanding flexibility in terms of material combinations and reliability

In Situ Laser Light Scattering for Temporally and Locally Resolved Studies on Nanoparticle Trapping in a Gas Aggregation Source

Gas phase synthesis of nanoparticles (NPs) via magnetron sputtering in a gas aggregation source (GAS) has become a well-established method since its conceptualization three decades ago. NP formation is commonly described in terms of nucleation, growth, and transport alongside the gas stream. However, the NP formation and transport involve complex non-equilibrium processes, which are still the subject of investigation. The development of in situ investigation techniques such as UV–Vis spectroscopy and small angle X-ray scattering enabled further insights into the dynamic processes inside the GAS and have recently revealed NP trapping at different distances from the magnetron source. The main drawback of these techniques is their limited spatial resolution. To understand the spatio-temporal behavior of NP trapping, an in situ laser light scattering technique is applied in this study. By this approach, silver NPs are made visible inside the GAS with good spatial and temporal resolution. It is found that the argon gas pressure, as well as different gas inlet configurations, have a strong impact on the trapping behavior of NPs inside the GAS. The different gas inlet configurations not only affect the trapping of NPs, but also the size distribution and deposition rate of NPs

Enhancing composition control of alloy nanoparticles from gas aggregation source by in operando optical emission spectroscopy

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

On the plasma permeability of highly porous ceramic framework materials using polymers as marker materials

Highly porous framework materials are of large interest due to their broad potential for application, for example, as sensors or catalysts. A new approach is presented to investigate, how deep plasma species can penetrate such materials. For this purpose, a polymer (ethylene propylene diene monomere rubber) is used as marker material and covered with the porous material during plasma exposure. Water contact-angle and X-ray photoelectron spectroscopy measurements are used to identify changes in the polymer surface, originating from the interaction of plasma species with the polymer. The method is demonstrated by studying the plasma permeability of tetrapodal zinc oxide framework materials with a porosity of about 90% in an oxygen low-pressure capacitively coupled plasma. Significant differences in the penetration depth ranging from roughly 1.6–4 mm are found for different densities of the material and different treatment conditions

Improved Long‐Term Stability and Reduced Humidity Effect in Gas Sensing: SiO 2 Ultra‐Thin Layered ZnO Columnar Films

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

Co‐sputtering of A Thin Film Broadband Absorber Based on Self‐Organized Plasmonic Cu Nanoparticles

The efficient conversion of solar energy to heat is a prime challenge for solar thermal absorbers, and various material classes and device concepts are discussed. One exciting class of solar thermal absorbers are plasmonic broadband absorbers that rely on light absorption thanks to plasmonic resonances sustained in metallic nanoparticles. This work focuses on Cu/Al$_2$O$_3$ plasmonic absorbers, which consist of a thin film stack of a metallic Cu-mirror, a dielectric Al$_2$O$_3$ spacer, and an Al$_2$O$_3$/Cu-nanoparticle nanocomposite. This work explores two preparation routes for the Al$_2$O$_3$/Cu-nanoparticle nanocomposite, which rely on the self-organization of Cu nanoparticles from sputtered atoms, either in the gas phase (i.e., via gas aggregation source) or on the thin film surface (i.e., via simultaneous co-sputtering). While in either case, Cu-Al$_2$O$_3$-Al$_2$O$_3$/Cu absorbers with a low reflectivity over a broad wavelength regime are obtained, the simultaneous co-sputtering approach enabled better control over the film roughness and showed excellent agreement with dedicated simulations of the optical properties of the plasmonic absorber using a multi-scale modeling approach. Upon variation of the thickness and filling factor of the Al$_2$O$_3$/Cu nanocomposite layer, the optical properties of the plasmonic absorbers are tailored, reaching an integrated reflectance down to 0.17 (from 250 to 1600 nm)

Recommendations from the United European Gastroenterology evidence-based guidelines for the diagnosis and therapy of chronic pancreatitis

In collaboration with United European Gastroenterology, the working group on 'Harmonizing diagnosis and treatment of chronic pancreatitis across Europe' (HaPanEU) developed European guidelines for the management of chronic pancreatitis using an evidence-based approach.Recommendations of multidisciplinary review groups based on systematic literature reviews to answer predefined clinical questions are summarised. Recommendations are graded using the Grading of Recommendations Assessment, Development and Evaluation system.Recommendations covered topics related to the clinical management of chronic pancreatitis: aetiology, diagnosis of chronic pancreatitis with imaging, diagnosis of pancreatic exocrine insufficiency, surgical therapy, medical therapy, endoscopic therapy, treatment of pancreatic pseudocysts, pancreatic pain, nutrition and malnutrition, diabetes mellitus and the natural course of the disease and quality of life.The HaPanEU/United European Gastroenterology guidelines provide evidence-based recommendations concerning key aspects of the medical and surgical management of chronic pancreatitis based on current available evidence. These recommendations should serve as a reference standard for existing management of the disease and as a guide for future clinical research. This article summarises the HaPanEU recommendations and statements

Nanosensors Based on a Single ZnO:Eu Nanowire for Hydrogen Gas Sensing

Fast detection of hydrogen gas leakage or its release in different environments, especially in large electric vehicle batteries, is a major challenge for sensing applications. In this study, the morphological, structural, chemical, optical, and electronic characterizations of ZnO:Eu nanowire arrays are reported and discussed in detail. In particular, the influence of different Eu concentrations during electrochemical deposition was investigated together with the sensing properties and mechanism. Surprisingly, by using only 10 μM Eu ions during deposition, the value of the gas response increased by a factor of nearly 130 compared to an undoped ZnO nanowire and we found an H2gas response of ∼7860 for a single ZnO:Eu nanowire device. Further, the synthesized nanowire sensors were tested with ultraviolet (UV) light and a range of test gases, showing a UV responsiveness of ∼12.8 and a good selectivity to 100 ppm H2gas. A dual-mode nanosensor is shown to detect UV/H2gas simultaneously for selective detection of H2during UV irradiation and its effect on the sensing mechanism. The nanowire sensing approach here demonstrates the feasibility of using such small devices to detect hydrogen leaks in harsh, small-scale environments, for example, stacked battery packs in mobile applications. In addition, the results obtained are supported through density functional theory-based simulations, which highlight the importance of rare earth nanoparticles on the oxide surface for improved sensitivity and selectivity of gas sensors, even at room temperature, thereby allowing, for instance, lower power consumption and denser deployment

United European Gastroenterology evidence-based guidelines for the diagnosis and therapy of chronic pancreatitis (HaPanEU)

Background:There have been substantial improvements in the management of chronic pancreatitis, leading to the publication of several national guidelines during recent years. In collaboration with United European Gastroenterology, the working group on Harmonizing diagnosis and treatment of chronic pancreatitis across Europe' (HaPanEU) developed these European guidelines using an evidence-based approach. Methods: Twelve multidisciplinary review groups performed systematic literature reviews to answer 101 predefined clinical questions. Recommendations were graded using the Grading of Recommendations Assessment, Development and Evaluation system and the answers were assessed by the entire group in a Delphi process online. The review groups presented their recommendations during the 2015 annual meeting of United European Gastroenterology. At this one-day, interactive conference, relevant remarks were voiced and overall agreement on each recommendation was quantified using plenary voting (Test and Evaluation Directorate). After a final round of adjustments based on these comments, a draft version was sent out to external reviewers. Results: The 101 recommendations covered 12 topics related to the clinical management of chronic pancreatitis: aetiology (working party (WP)1), diagnosis of chronic pancreatitis with imaging (WP2 and WP3), diagnosis of pancreatic exocrine insufficiency (WP4), surgery in chronic pancreatitis (WP5), medical therapy (WP6), endoscopic therapy (WP7), treatment of pancreatic pseudocysts (WP8), pancreatic pain (WP9), nutrition and malnutrition (WP10), diabetes mellitus (WP11) and the natural course of the disease and quality of life (WP12). Using the Grading of Recommendations Assessment, Development and Evaluation system, 70 of the 101 (70%) recommendations were rated as strong' and plenary voting revealed strong agreement' for 99 (98%) recommendations. Conclusions:The 2016 HaPanEU/United European Gastroenterology guidelines provide evidence-based recommendations concerning key aspects of the medical and surgical management of chronic pancreatitis based on current available evidence. These recommendations should serve as a reference standard for existing management of the disease and as a guide for future clinical research