Open Access

In this study, the effect of post-synthetic ball milling on the structural and functional properties of as-synthesized nanoparticles of the copper-based metal-organic framework (MOF) HKUST-1 was investigated for the first time. Nanoparticles were synthesized using sodium formate as a capping agent. The crystalline particles were subjected to a controlled ball milling process, which induced significant structural changes. Powder X-ray diffraction (PXRD) revealed a reduction in crystallite size from 91 nm to 21 nm and the introduction of microstrain, partially disrupting the MOF's long-range crystalline order, as evidenced by peak broadening and the diminished intensity of high-angle reflections. Particle morphology pre- and post-milling was further studied with scanning electron microscopy (SEM) imaging, verifying a narrow particle size distribution of ± 22 nm after milling. Fourier-transform infrared spectroscopy (FTIR) indicated protonation of carboxylate groups in the larger pores of the framework, likely due to moisture incorporation during milling. Brunauer-Emmett-Teller (BET) surface area analysis showed a substantial decrease in specific surface area from 521 m²/g to 226 m²/g, suggesting a partial collapse of the porous framework. We discuss the applicability of ball milling as a versatile means of post-synthetic approach to reduce MOF particle sizes, a key element in the preparation of MOF-based thin films using inks or polymers.

Cuprous oxide (Cu2O) and cupric oxide (CuO) particles were synthesized using a wet chemical surfactant free method at different synthesis temperatures from 25 °C to 60 °C. Morphology, size, and chemical composition of the prepared Cu2O particles were analyzed by FESEM, PXRD, and UV-vis. We discovered that the chemical composition of the Cu2O particles remained unaffected by the synthesis temperature. However, morphology and size of the particles showed a strong temperature dependency. This could be attributed to the temperature induced formation of CuO species from the copper hydroxide (Cu(OH)2) precursor which also functions as copper precursor for the Cu2O particle growth. The cupric oxide species was determined to be the main cause for the formation of micrometer sized particles, whereas with the Cu(OH)2 precursor species for the Cu2O particles nanocubes with smaller edge lengths as well as octahedrons were obtained.

Metal-organic frameworks (MOFs), such as Zeolitic Imidazolate Framework-8 (ZIF-8), are increasingly explored for sensing applications. In this field, the formation of uniform thin films is often essential. This study details the deposition and stepwise characterization of covalently bonded ZIF-8 thin films for methane sensing on two types of silica-based substrates: silicon wafers with native oxide and optical fibers. We emphasize practical and accessible methods to verify each step of the deposition process. Surface preparation was tailored to each substrate. Silicon wafer substrates were cleaned using Caro’s acid, while optical fibers were activated via oxygen plasma to account for handling constraints. Both substrate types were subsequently functionalized with a monolayer of isopropyltrimethoxysilane (IPTES) to promote covalent bonding of ZIF-8. Particles of ZIF-8 were deposited using a seeded growth approach. Solvothermal synthesis of ZIF-8 was performed, while simultaneously immersing the substrates in the synthesis solution, promoting the formation of a continuous thin film. The deposition process was characterized at each stage. Free ZIF-8 powder obtained from the synthesis was centrifuged, washed with ethanol and analyzed by attenuated total reflection infrared (ATR-IR) spectroscopy. Silicon wafers enabled contact angle measurements to assess IPTES functionalization, as well as spectroscopic ellipsometry for analysis of the formed ZIF-8 thin film. Scanning electron microscopy (SEM) was used to examine film morphology on both substrate types. To evaluate methane sensitivity, optical fibers coated with ZIF-8 were exposed to vacuum and methane atmospheres, while changes in transmitted optical power were monitored to probe refractive index variations.

Hochschulen für angewandte Wissenschaften (HAW) kommt als regionalen Innovationstreibern eine gesellschaftliche Verantwortung durch ihre Zusammenarbeit mit Unternehmen und Gesellschaft zu. Diese Zusammenarbeit geschieht im Rahmen von Aktivitäten des Wissens- und Technologietransfers. Die Beurteilung des Erfolgs dieser Transferaktivitäten verursacht jedoch regelmäßig Schwierigkeiten, da geeignete Indikatoren zur Erfolgsmessung fehlen. Im Rahmen des vom Bundesministerium für Bildung und Forschung (BMBF) geförderten Verbundforschungsprojektes Transfer_i wurde ein Modell zur Objektivierung und Messung von Forschungsleistung, forschungsbasiertem Transfer sowie dessen Umsetzung am Markt in Form von Innovationen erarbeitet. Mit dem Forschungsprojekt wurden kausale Zusammenhänge für das Gelingen von Transfer identifiziert und daraufhin entsprechende Indikatoren definiert, um auf dieser Basis die Steuerung von Transferprozessen zu ermöglichen. In diesem Beitrag werden zwei im Projekt Transfer_i entwickelte Modelle und Indikatoren vorgestellt, die die Voraussetzungen für einen erfolgreichen Transferprozess abbilden können. Auf dieser Grundlage zeigen wir anhand eines Projekts (MAGGIE) der Ostbayerischen Technischen Hochschule (OTH) Regensburg mit mehreren regionalen Partnern, wie die vorher definierten Modelle und Indikatoren in einem konkreten Anwendungsfall verwendet werden können. Abschließend beschreiben wir die erforderlichen Rahmenbedingungen für die erfolgreiche Umsetzung von Transfer an Hochschulen und wie darauf bezogene Indikatoren effektiv eingeführt werden können.

In this work, a simple two-step method to create tunable self-assembled three-dimensional nanostructure array-like nanoantennas directly on the tip of an optical quartz glass fiber is described. The structures are prepared by using dry etching of the fiber tip. For the etching process, gold nanoparticles fabricated by thermal dewetting technique were used as template. The structures are applied as sensors for label-free analysis of organic substances in ppb range, such as drug residues in liquid solutions. The measurements are carried out by a portable Raman device with an exchangeable sensor head utilizing the SERS-effect. This method allows in situ applications. In order to characterize the SERS cells, para-thiocresol and diclofenac sodium are used as model substances. For optimization of the substrate performance, different thicknesses of the dewetting-layer (6, 9, 12 nm), different etching times for formation of the pillars (6, 8, 10 and 12 min), and different thicknesses of SERS-metallization (25, 50, 75 nm) of gold and silver are compared. In order to show the applicability of the structure on the tip of a fiber, measurements from the upper side and from the underside of the substrate on quartz plates are compared. Reproducible SERS enhancement factors up to 10 7 {10^{7}} were achieved.