A High Efficiency, Low Resistance Antibacterial Filter Formed by Dopamine-Mediated In Situ Deposition of Silver onto Glass Fibers.

The coating of filter media with silver is typically achieved by chemical deposition and aerosol processes. Whilst useful, such approaches struggle to provide uniform coating and are prone to blockage. To address these issues, an in situ method for coating glass fibers is presented via the dopamine-mediated electroless metallization method, yielding filters with low air resistance and excellent antibacterial performance. It is found that the filtration efficiency of the filters is between 94 and 97% and much higher than that of silver-coated filters produced using conventional dipping methods (85%). Additionally, measured pressure drops ranged between 100 and 150 Pa, which are lower than those associated with dipped filters (171.1 Pa). Survival rates of Escherichia coli and Bacillus subtilis bacteria exposed to the filters decreased to 0 and 15.7%±1.49, respectively after 2 h, with no bacteria surviving after 6 h. In contrast, survival rates of E. coli and B. subtilis bacteria on the uncoated filters are 92.5% and 89.5% after 6 h. Taken together, these results confirm that the in situ deposition of silver onto fiber surfaces effectively reduces pore clogging, yielding low air resistance filters that can be applied for microbial filtration and inhibition in a range of environments.

Precursor- and waste-free synthesis of spark-ablated nanoparticles with enhanced photocatalytic activity and stability towards airborne organic pollutant degradation.

Photocatalyst synthesis typically involves multiple steps, expensive precursors, and solvents. In contrast, spark ablation offers a simple process of electrical discharges in a gap between two electrodes made from a desirable material. This enables a precursor- and waste-free generation of pure metal oxide nanoparticles or mixtures of various compositions. This study presents a two-step method for the production of photocatalytic filters with deposited airborne MnOx, TiO2, and ZnO nanoparticles using spark ablation and calcination processes. The resulting MnOx and TiO2 filters demonstrated almost twice the activity with outstanding performance stability, as compared to sol-gel MnO2 and commercial TiO2. The introduced method is not only simple, precursor- and waste-free, and leads to superior performance for the case studied, but it also has future potential due to its versatility. It can easily produce mixed and doped materials with further improved properties, making it an interesting avenue for future research.

Operando Electrochemical Liquid Cell Scanning Transmission Electron Microscopy Investigation of the Growth and Evolution of the Mosaic Solid Electrolyte Interphase for Lithium-Ion Batteries.

The solid electrolyte interphase (SEI) is a key component of a lithium-ion battery forming during the first few dischage/charge cycles at the interface between the anode and the electrolyte. The SEI passivates the anode-electrolyte interface by inhibiting further electrolyte decomposition, extending the battery's cycle life. Insights into SEI growth and evolution in terms of structure and composition remain difficult to access. To unravel the formation of the SEI layer during the first cycles, operando electrochemical liquid cell scanning transmission electron microscopy (ec-LC-STEM) is employed to monitor in real time the nanoscale processes that occur at the anode-electrolyte interface in their native electrolyte environment. The results show that the formation of the SEI layer is not a one-step process but comprises multiple steps. The growth of the SEI is initiated at low potential during the first charge by decomposition of the electrolyte leading to the nucleation of inorganic nanoparticles. Thereafter, the growth continues during subsequent cycles by forming an island-like layer. Eventually, a dense layer is formed with a mosaic structure composed of larger inorganic patches embedded in a matrix of organic compounds. While the mosaic model for the structure of the SEI is generally accepted, our observations document in detail how the complex structure of the SEI is built up during discharge/charge cycling.

Controlling lipid crystallization across multiple length scales by directed shear flow.

The crystallization behavior of lipids is relevant in many fields such as adipose tissue formation and regeneration, forensic investigations and food production. Using a lipid model system composed of triacylglycerols, we study the formation of crystalline structures under laminar shear flows across various length scales by polarized light-, scanning electron-, and atomic force microscopy, as well as laser diffraction spectroscopy. The shear rate during crystallization γ̇cryst influences the acyl-chain length structure and promotes domain growth into the flow direction thereby transforming the crystallites from oblate into prolate particles. Concentration dependent aggregation of crystallites into clusters is the rate limiting step for floc and floc network formation. At high γ̇cryst, fast crystallite cluster formation at smaller equilibrium diameters is promoted. The high crystallite cluster concentration induces their aggregation into flocs which form weak networks. At low γ̇cryst, floc generation is limited by the low amount of crystallite clusters leading to slow growth of larger flocs and forming of strong networks. The findings in this work have potential implications ranging from the design of injectable soft tissue fillers for adipose tissue regeneration, to the crystalline network formation in microorganism derived lipids, up to a more energy-efficient production of chocolate confectionery.

Effect of the Coupling Agent (3-Aminopropyl) Triethoxysilane on the Structure and Fire Behavior of Solvent-Free One-Pot Synthesized Silica-Epoxy Nanocomposites.

Uniformly distributed silica/epoxy nanocomposites (2 and 6 wt.% silica content) were obtained through a "solvent-free one-pot" process. The inorganic phases were obtained through "in situ" sol-gel chemistry from two precursors, tetraethyl orthosilicate (TEOS) and (3-aminopropyl)-triethoxysilane (APTES). APTES acts as a coupling agent. Surprisingly when changing TEOS/APTES molar ratio (from 2.32 to 1.25), two opposite trends of glass transformation temperature (Tg) were observed for silica loading, i.e., at lower content, a decreased Tg (for 2 wt.% silica) and at higher content an increased Tg (for 6 wt.% silica) was observed. High-Resolution Transmission Electron Microscopy (HRTEM) showed the formation of multi-sheet silica-based nanoparticles with decreasing size at a lower TEOS/APTES molar ratio. Based on a recently proposed mechanism, the experimental results can be explained by the formation of a co-continuous hybrid network due to reorganization of the epoxy matrix around two different "in situ" sol-gel derived silicatic phases, i.e., micelles formed mainly by APTES and multi-sheet silica nanoparticles. Moreover, the concentration of APTES affected the size distribution of the multi-sheet silica-based nanoparticles, leading to the formation of structures that became smaller at a higher content. Flammability and forced-combustion tests proved that the nanocomposites exhibited excellent fire retardancy.

Solvent-Free One-Pot Synthesis of Epoxy Nanocomposites Containing Mg(OH)2 Nanocrystal-Nanoparticle Formation Mechanism.

Epoxy nanocomposites containing Mg(OH)2 nanocrystals (MgNCs, 5.3 wt %) were produced via an eco-friendly "solvent-free one-pot" process. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and thermogravimetric analysis (TGA) confirm the presence of well-dispersed MgNCs. HRTEM reveals the presence also of multisheet-silica-based nanoparticles and a tendency of MgNCs to intergrow, leading to complex nanometric structures with an intersheet size of ∼0.43 nm, which is in agreement with the lattice spacing of the Mg(OH)2 (001) planes. The synthesis of MgNCs was designed on the basis of a mechanism initially proposed for the preparation of multisheet-silica-based/epoxy nanocomposites. The successful "in situ" generation of MgNCs in the epoxy via a "solvent-free one-pot" process confirms the validity of the earlier disclosed mechanism and thus opens up possibilities of new NCs with different fillers and polymer matrix. The condition would be the availability of a nanoparticle precursor soluble in the hydrophobic resin, giving the desired phase through hydrolysis and polycondensation.

Biomimetic Light-Driven Aerogel Passive Pump for Volatile Organic Pollutant Removal.

Inspired by the solar-light-driven oxygen transportation in aquatic plants, a biomimetic sustainable light-driven aerogel pump with a surface layer containing black manganese oxide (MnO2 ) as an optical absorber is developed. The flow intensity of the pumped air is controlled by the pore structure of nanofilbrillated cellulose, urea-modified chitosan, or polymethylsilsesquioxane (PMSQ) aerogels. The MnO2 -induced photothermal conversion drives both the passive gas flow and the catalytic degradation of volatile organic pollutants. All investigated aerogels demonstrate superior pumping compared to benchmarked Knudsen pump systems, but the inorganic PMSQ aerogels provide the highest flexibility in terms of the input power and photothermal degradation activity. Aerogel light-driven multifunctional gas pumps offer a broad future application potential for gas-sensing devices, air-quality mapping, and air quality control systems.

The rheology and foamability of crystal-melt suspensions composed of triacylglycerols.

The rheology of triacylglycerol (TAG) crystal-melt suspensions (CMSs) consisting of anhydrous milk fat (AMF), cocoa butter (CB), and palm kernel oil (PKO) as function of crystallization shear rate cryst and crystal volume fraction ΦSFC is investigated by in-line ultrasound velocity profiling - pressure difference (UVP-PD) rheometry. Measurements up to ΦSFC = 8.8% are presented. Below the percolation threshold Φc, no yield stress τ0 is observed and the viscosity η scales linearly with ΦSFC. Above Φc, a non-linear dependency of both τ0 and η as function of ΦSFC is apparent. For AMF and CB, the increase in cryst leads to a decrease in η and τ0 as function of ΦSFC, whereas for PKO based CMSs the opposite is the case. Scanning electron microscopy (SEM) and polarized light microscopy (PLM) relate these rheological findings to the microstructure of the investigated CMSs by taking the effective aspect ratio aeff and the concept of the effective crystal volume fraction ΦeffSFC into account. Foam formation by dynamically enhanced membrane foaming (DEMF) is performed directly after crystallization and reveals that depending on the CMS rheology and crystallite-, crystallite cluster- and crystal floc microstructure, a wide range of gas volume fractions between 0.05-0.6 are achievable.

Structure and Bottom-up Formation Mechanism of Multisheet Silica-Based Nanoparticles Formed in an Epoxy Matrix through an In Situ Process.

Organic/inorganic hybrid composite materials with the dispersed phases in sizes down to a few tens of nanometers raised very great interest. In this paper, it is shown that silica/epoxy nanocomposites with a silica content of 6 wt % may be obtained with an "in situ" sol-gel procedure starting from two precursors: tetraethyl orthosilicate (TEOS) and 3-aminopropyl-triethoxysilane (APTES). APTES also played the role of a coupling agent. The use of advanced techniques (bright-field high-resolution transmission electron microscopy, HRTEM, and combined small- and wide-angle X-ray scattering (SAXS/WAXS) performed by means of a multirange device Ganesha 300 XL+) allowed us to evidence a multisheet structure of the nanoparticles instead of the gel one typically obtained through a sol-gel route. A mechanism combining in a new manner well-assessed knowledge regarding sol-gel chemistry, emulsion formation, and Ostwald ripening allowed us to give an explanation for the formation of the observed lamellar nanoparticles.

Influence of the Rear Interface on Composition and Photoluminescence Yield of CZTSSe Absorbers: A Case for an Al2O3 Intermediate Layer.

The rear interface of kesterite absorbers with Mo back contact represents one of the possible sources of nonradiative voltage losses (ΔVoc,nrad) because of the reported decomposition reactions, an uncontrolled growth of MoSe2, or a nonoptimal electrical contact with high recombination. Several intermediate layers (IL), such as MoO3, TiN, and ZnO, have been tested to mitigate these issues, and efficiency improvements have been reported. However, the introduction of IL also triggers other effects such as changes in alkali diffusion, altered morphology, and modifications in the absorber composition, all factors that can also influence ΔVoc,nrad. In this study, the different effects are decoupled by designing a special sample that directly compares four rear structures (SLG, SLG/Mo, SLG/Al2O3, and SLG/Mo/Al2O3) with a Na-doped kesterite absorber optimized for a device efficiency >10%. The IL of choice is Al2O3 because of its reported beneficial effect to reduce the surface recombination velocity at the rear interface of solar cell absorbers. Identical annealing conditions and alkali distribution in the kesterite absorber are preserved, as measured by time-of-flight secondary ion mass spectrometry and energy-dispersive X-ray spectroscopy. The lowest ΔVoc,nrad of 290 mV is measured for kesterite grown on Mo, whereas the kesterite absorber on Al2O3 exhibits higher nonradiative losses up to 350 mV. The anticipated field-effect passivation from Al2O3 at the rear interface could not be observed for the kesterite absorbers prepared by the two-step process, further confirmed by an additional experiment with air annealing. Our results suggest that Mo with an in situ formed MoSe2 remains a suitable back contact for high-efficiency kesterite devices.

Solution Processing and Self-Organization of PbS Quantum Dots Passivated with Formamidinium Lead Iodide (FAPbI3).

Solution-processed lead sulfide quantum dots (PbS QDs) are very attractive as NIR-active semiconductors for the fabrication of cost-efficient optoelectronic devices. To control the thin film carrier transport, as well as stability, surface passivation is of crucial importance. Here, we present the successful surface passivation of PbS QDs by the formamidinium lead iodide (FAPbI3) ligand. An effective procedure for the fabrication of FAPbI3-passivated PbS QDs through a binary-phase ligand exchange protocol in hexane and n-methylformamide is demonstrated. It is shown that this solution-processed ligand exchange drastically changes the photoluminescence intensity, exciton recombination dynamics, and carrier lifetime of the nanocrystals. The solution casting of the ligand-exchanged nanocrystals into thin films results in the periodic ordering of QDs in a square superlattice with close contacts. Planar graphene/QD photodetectors fabricated with PbS QDs passivated with FAPbI3 show substantially increased thermal stability as compared to similar devices using PbS QDs passivated with commonly used methylammonium lead iodide.

In Vitro Endothelialization of Surface-Integrated Nanofiber Networks for Stretchable Blood Interfaces.

Despite major technological advances within the field of cardiovascular engineering, the risk of thromboembolic events on artificial surfaces in contact with blood remains a major challenge and limits the functionality of ventricular assist devices (VADs) during mid- or long-term therapy. Here, a biomimetic blood-material interface is created via a nanofiber-based approach that promotes the endothelialization capability of elastic silicone surfaces for next-generation VADs under elevated hemodynamic loads. A blend fiber membrane made of elastic polyurethane and low-thrombogenic poly(vinylidene fluoride- co-hexafluoropropylene) was partially embedded into the surface of silicone films. These blend membranes resist fundamental irreversible deformation of the internal structure and are stably attached to the surface, while also exhibiting enhanced antithrombotic properties when compared to bare silicone. The composite material supports the formation of a stable monolayer of endothelial cells within a pulsatile flow bioreactor, resembling the physiological in vivo situation in a VAD. The nanofiber surface modification concept thus presents a promising approach for the future design of advanced elastic composite materials that are particularly interesting for applications in contact with blood.

Differentiation of dental restorative materials combining energy-dispersive X-ray fluorescence spectroscopy and post-mortem CT.

Today, post-mortem computed tomography (CT) is routinely used for forensic identification. Mobile energy-dispersive X-ray fluorescence (EDXRF) spectroscopy of a dentition is a method of identification that has the potential to be easier and cheaper than CT, although it cannot be used with every dentition. In challenging cases, combining both techniques could facilitate the process of identification and prove to be advantageous over chemical analyses. Nine dental restorative material brands were analyzed using EDXRF spectroscopy. Their differentiability was assessed by comparing each material's x-ray fluorescence spectrum and then comparing the spectra to previous research investigating differentiability in CT. To verify EDXRF's precision and accuracy, select dental specimens underwent comparative electron beam excited x-ray spectroscopy (EDS) scans, while the impact of the restorative surface area was studied by scanning a row of dental specimens with varying restorative surface areas (n = 10). EDXRF was able to differentiate all 36 possible pairs of dental filling materials; however, dual-energy CT was only able to differentiate 33 out of 36. The EDS scans showed correlating x-ray fluorescence peaks on the x-ray spectra compared to our EDXRF. In addition, the surface area showed no influence on the differentiability of the dental filling materials. EDXRF has the potential to facilitate corpse identification by differentiating and comparing restorative materials, providing more information compared to post-mortem CT alone. Despite not being able to explicitly identify a brand without a control sample or database, its fast and mobile use could accelerate daily routines or mass victim identification processes. To achieve this goal, further development of EDXRF scanners for this application and further studies evaluating the method within a specific routine need to be performed.