Search

Chemical solution deposition (CSD) approach was introduced in this work to simplify and to optimize the trifluoracetic based M TiO 3 ( M TO, M = Ca, Sr, and Ba) precursor solution, leading to the high shelf-life and the purity. Growing these M TO solutions on (100) LaAlO 3 single-crystal substrates yields (h00) oriented and dense M TO buffer layers. Whereas it is clear that the roughness of M TO films and the lattice mismatch between M TO buffer layer and superconducting YBa 2 Cu 3 O 7-δ film is crucial for the film formation.

Vascular corrosion casting is a method used to visualize the three dimensional anatomy and branching pattern of blood vessels, guiding insight into health and cardiovascular disease pathogenesis and progression. A polymer resin is injected in the vascular system and, after curing, the surrounding tissue is removed. This corrosion process often deforms or even fractures the fragile cast, resulting in an overall loss of information. Here, we propose a method that does not require corrosion of the tissue, based on in-situ high-resolution computed tomography (micro-CT) scans. Since there is a lack of CT contrast between the polymer cast and the animals’ surrounding soft tissue, we introduce hafnium oxide nanocrystals (HfO2 NCs) as CT contrast agents into the resin. The NCs dramatically improve the overall CT contrast of the cast and allow for straightforward segmentation in the CT scans. We designed the NC surface chemistry to ensure colloidal stability of the NCs in the casting resin, resulting in a homogeneous dispersion that remains stable during casting and curing. Using only 5 m% of HfO2 NCs, high-quality casts of both zebrafish and mouse models could be segmented using CT imaging software, allowing us to differentiate even μm scale details, without having to alter the resin injection method or affecting the resin’s mechanical properties. Our new method of virtual dissection by visualizing casts in-situ using contrast enhanced CT imaging greatly expands the application potential of the technique.

In the surgical treatment of breast cancer the primary tumour is removed together with the so-called sentinel lymph nodes (SLNs), the lymph nodes that have the highest probability of being invaded by cancer cells. The current clinical standard to identify SLNs uses a combination of 99mTc labelled nanocolloids and blue dyes. This workflow comes with downsides such as inflexible procedures, exposure to radioactivity, allergic side-reactions and long-lasting skin discoloration. Here, we develop a dual-modality imaging probe as alternative to the current standard and demonstrate the in vivo detection of SLNs in mice using X-ray computed tomography and near-infrared fluorescence. We synthesize and stabilize hafnium oxide nanocrystals in physiological buffer and attach IRDye 800CW to the surface. The SLN is selectively detected via both imaging modalities 15-30 minutes post-injection of the probe. Moreover, a comparison between the probe and 99mTc nanocolloids reveals similar lymphatic drainage while utilizing faster, cheaper and more readily available imaging infrastructure, which could facilitate clinical integration.

Bi-doped CaO–Al2O3–SiO2 glass microspheres with Ca2Al2SiO7 (gehlenite) composition were prepared by combination of solid-state reaction and flame synthesis. The concentration of Bi was 0.0, 0.5, 1 and 3 mol%. The chemical composition of prepared glass microspheres was determined by X-ray fluorescence (XRF). The structural and magnetic properties of prepared glass microspheres and their polycrystalline analogues were studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Raman spectroscopy and SQUID magnetometry. The closer inspection of glass microspheres surface by SEM confirmed smooth surface and revealed no features indicating presence of crystalline phases. All Bi-doped microspheres are X-ray amorphous, however in case of undoped microspheres XRD detected traces of crystalline gehlenite. XRD analysis of samples crystallized at 1273 K for 10 h revealed the presence of gehlenite as the main crystalline phase. The presence of gehlenite in crystallized samples were also confirmed by Raman spectroscopy. All samples (glass microspheres and their crystalline analogues) showed diamagnetic or weak ferromagnetic behavior at room temperature, whereas paramagnetic or weak ferromagnetic behavior was observed at 2 K.

Electrochemical treatments in (waste)water management show high potential in the global water resource crisis, but are often limited by the ion-exchange membrane (IEM) performance. Low chemical resistance and fouling are major issues in the development of next-generation IEMs. Sulfonated silica-based nanofiber cation-exchange membranes (CEMs) offer a promising solution to these issues due to their superior chemical resistance and self-cleaning properties. Via the direct electrospinning of a sol–gel solution starting from tetraethyl orthosilicate (TEOS) and 3-mercaptopropyl triethoxysilane (MPTES), nanofiber membranes with an ion-exchange capacity (IEC) of 1.3 mmol g−1 can be produced without the need of an additional matrix. The produced nanofiber CEM performs excellent in lab-scale electrochemical tests, with a resistance of 3.2 ± 0.4 *10-3 Ω m2 and a Coulombic efficiency of ± 70 % for the transport of Na+ using a current density of either 128 or 256 A/m−2. Furthermore, the nanofiber CEM shows outstanding resistance against strong acidic solutions and chlorine. After fouling of the membrane with CaCO3, the nanofiber CEM shows self-cleaning properties, eliminating the need for an additional cleaning step during usage. These results illustrate the excellent performance of the silica-based nanofiber CEM for industrial water treatment applications.

The self out-of-plane oriented La2O2CO3 thin film can be used as an integration tool to obtain fiber textured ferroelectric thin film stacks.

An important challenge in the valorization of CO2 and H2 into fuels is the development of a stable, reusable and easy to handle heterogeneous catalyst. Here, a silica nanofibrous membrane is investigated as carrier for Ru nanoparticles, themselves encapsulated inside the metal organic framework (MOF) Cr-MIL-101. The catalytic membrane is investigated for the Sabatier methanation reaction. The direct electrospinning of a tetraorthosilicate (TEOS) sol results in a highly thermal resistant silica nanofibrous structure (up to 1100 °C) with pores between the fibers in the µm-range, allowing a high gas throughput with low pressure requirements. A straightforward dip-coating procedure of the carrier was used to obtain a Ru@MIL-101 functionalized silica nanofibrous veil, avoiding Ru clustering. The obtained catalytic membrane exhibited an apparent turnover frequency of 3257 h-1 at 250 °C. This system therefore paves the way towards structured reactors for efficient CO2 hydrogenation processes.

We recently introduced monoalkyl phosphinic acids as a ligand class for nanocrystal synthesis. Their metal salts have interesting reactivity differences with respect to metal carboxylates and phosphonates, and provide cleaner work-up compared to phosphonates. However, there is little known about the surface chemistry of nanocrystals with monoalkyl phosphinate ligands. Here, we probe the relative binding affinity of monoalkyl phosphinate ligands with respect to other X-type ligands. We perform competitive ligand exchange reactions with carboxylate and phosphonate ligands at the surface of HfO2, CdSe, and ZnS nanocrystals. We monitor the ligand shell composition by solution 1H and 31P NMR spectroscopy. Using a monoalkyl phosphinic acid with an ether functionality, we gain an additional NMR signature, apart from the typical alkene resonance in oleic acid and oleylphosphonic acid. We find that carboxylate ligands are easily exchanged upon exposure to monoalkyl phosphinic acids, whereas an equilibrium is reached between monoalkyl phosphinates and phosphonates, slightly in the favour of phosphonate (K = 2). Phosphinic acids have thus an intermediate binding affinity between carboxylic acids and phosphonic acids for all nanocrystals studied. These results enable the sophisticated use of monoalkyl phosphinic acids for nanocrystal synthesis and for post-synthetic surface engineering.

Metal oxo clusters of the type \ce{M6O4(OH)4(RCOO)12} (M = Zr of Hf) are valuable building blocks for material science. Here, we develop them as smallest conceivable nanocrystal prototypes. We synthesize a series of zirconium and hafnium oxo clusters with ligands that are typically used to stabilize oxide nanocrystals (fatty acids with long and/or branched chains). In contrast to previously reported discrete oxo clusters with short/rigid carboxylates (e.g., acetate, benzoate), the fatty acid capped oxo clusters have a high solubility but do not crystallize, precluding traditional purification and single-crystal XRD analysis of clusters. We thus develop alternative purification strategies and structural analysis tools. We use X-ray total scattering and Pair Distribution Function (PDF) analysis as our main tool to elucidate the structure of the cluster core. In contrast to traditional PDF analysis of larger clusters and nanocrystals, we show that the structure models need to include the carboxylate binding groups to obtain excellent refinements. Our methodology is able to pick up the correct structure from a series of possible structure models (\textbf{Zr4}, \textbf{Zr6}, \textbf{Zr12}). Further supporting evidence for the cluster composition (including their ligand shell) is provided by nuclear magnetic resonance (NMR), infrared spectroscopy (FTIR), thermogravimetry analysis (TGA) and mass spectrometry (MS). We find that the ligands have multiple binding modes and that hydrogen bonded carboxylic acid is an intrinsic part of the oxo cluster. Using our analytical tools, we elucidate the conversion from \textbf{Zr6} monomer to \textbf{Zr12} dimer (and vice versa), induced by carboxylate ligand exchange. Finally, we compared the catalytic performance of \textbf{Zr12}-oleate clusters with oleate capped, 3-5 nm zirconium oxide nanocrystals in the esterification of oleic acid with ethanol. The oxo clusters are much more catalytically active, due to their higher surface area. Since the oxo clusters are the limit of downscaling oxide nanocrystals, we thus propose them here as appealing catalytic materials, or at least as atomically precise model systems. In addition, our analytical (PDF) methodology is generally applicable and expected to find use in other areas of clusters as well, and will be especially valuable for clusters with weakly scattering core atoms.

The Ni-doped Ca2Al2SiO7 glass systems were prepared by flame synthesis. Solid-state reaction was used to prepare the powder precursors. The concentration of Ni was 0.5, 1 and 3 mol%. Polydisperse systems were prepared with diameters between 5 and 140 μm. Detailed examination of morphology of the glass microbeads by SEM revealed no features indicating the presence of crystalline phases. However, X-ray diffraction analysis showed that the samples GNi0.5 (0.5 mol% of Ni) and GNi1.0 (1.0 mol% of Ni) contained traces of crystalline gehlenite. HT-XRD was used to determine the temperature dependence of phase composition. For all prepared compositions, only one crystalline phase (Ca2Al2SiO7) was observed. DSC measurements in the temperature range 30–1200 °C at five different heating rates were carried out to study the thermal behavior. The DSC curves of all glasses contained one exothermic peak, which was attributed to crystallization of the gehlenite. The maximum of the peak decreased with increasing Ni content in the microspheres. The kinetic parameters (frequency factor A, apparent activation energy Eapp and the Avrami coefficient m) of the crystallization were determined using the Johnson–Mehl–Avrami–Kolgomorov model. In case of GNi0.5 and GNi1.0 glasses, the nucleation’s rate had linear temperature dependence, the crystal growth interface is controlled by chemical boundary and the crystal growth is one-dimensional. The rate of nucleation is linear, the crystal interface growth is controlled by diffusion and one-dimensional crystal growth prevails in crystallization of the GNi3.0 (3.0 mol% of Ni).

ACS nano 16(5), 7361 - 7372 (2022). doi:10.1021/acsnano.1c08966, Ligands play a crucial role in the synthesis of colloidal nanocrystals. Nevertheless, only a handful molecules are currently used, oleic acid being the most typical example. Here, we show that monoalkyl phosphinic acids are another interesting ligand class, forming metal complexes with a reactivity that is intermediate between the traditional carboxylates and phosphonates. We first present the synthesis of n-hexyl, 2-ethylhexyl, n-tetradecyl, n-octadecyl, and oleylphosphinic acid. These compounds are suitable ligands for high-temperature nanocrystal synthesis (240–300 °C) since, in contrast to phosphonic acids, they do not form anhydride oligomers. Consequently, CdSe quantum dots synthesized with octadecylphosphinic acid are conveniently purified, and their UV–vis spectrum is free from background scattering. The CdSe nanocrystals have a low polydispersity and a photoluminescence quantum yield up to 18% (without shell). Furthermore, we could synthesize CdSe and CdS nanorods using phosphinic acid ligands with high shape purity. We conclude that the reactivity toward TOP-S and TOP-Se precursors decreases in the following series: cadmium carboxylate > cadmium phosphinate > cadmium phosphonate. By introducing a third and intermediate class of surfactants, we enhance the versatility of surfactant-assisted syntheses., Published by Soc., Washington, DC

Chemical science 14(3), 573 - 585 (2022). doi:10.1039/D2SC05037D, Metal oxo clusters of the type M$_6$O$_4$(OH)$_4$(OOCR)$_{12}$ (M = Zr or Hf) are valuable building blocks for materials science. Here, we synthesize a series of zirconium and hafnium oxo clusters with ligands that are typically used to stabilize oxide nanocrystals (fatty acids with long and/or branched chains). The fatty acid capped oxo clusters have a high solubility but do not crystallize, precluding traditional purification and single-crystal XRD analysis. We thus develop alternative purification strategies and we use X-ray total scattering and Pair Distribution Function (PDF) analysis as our main method to elucidate the structure of the cluster core. We identify the correct structure from a series of possible clusters (Zr3, Zr4, Zr6, Zr12, Zr10, and Zr26). Excellent refinements are only obtained when the ligands are part of the structure model. Further evidence for the cluster composition is provided by nuclear magnetic resonance (NMR), infrared spectroscopy (FTIR), thermogravimetry analysis (TGA), and mass spectrometry (MS). We find that hydrogen bonded carboxylic acid is an intrinsic part of the oxo cluster. Using our analytical tools, we elucidate the conversion from a Zr6 monomer to a Zr12 dimer (and vice versa), induced by carboxylate ligand exchange. Finally, we compare the catalytic performance of Zr12-oleate clusters with oleate capped, 5.5 nm zirconium oxide nanocrystals in the esterification of oleic acid with ethanol. The oxo clusters present a five times higher reaction rate, due to their higher surface area. Since the oxo clusters are the lower limit of downscaling oxide nanocrystals, we present them as appealing catalytic materials, and as atomically precise model systems. In addition, the lessons learned regarding PDF analysis are applicable to other areas of cluster science as well, from semiconductor and metal clusters, to polyoxometalates., Published by RSC, Cambridge

Iron oxide and hafnium oxide nanocrystals are two of the few successful examples of inorganic nanocrystals used in a clinical setting. Although crucial to their application, their aqueous surface chemistry is not fully understood. The literature contains conflicting reports regarding the optimum binding group. To alleviate these inconsistencies, we set out to systematically investigate the interaction of carboxylic acids, phosphonic acids and catechols to metal oxide nanocrystals in polar media. Using Nuclear Magnetic Resonance spectroscopy and Dynamic Light Scattering, we map out the pH-dependent binding affinity of the ligands towards hafnium oxide nanocrystals (an NMR compatible model system). Carboxylic acids easily desorb in water from the surface and only provide limited colloidal stability from pH 2 – 6. Phosphonic acids on the other hand provide colloidal stability over a broader pH range but also feature a pH-dependent desorption from the surface. They are most suited for acidic to neutral environments (pH < 8). Finally, nitrocatechol derivatives provide a tightly bound ligand shell and colloidal stability at physiological and basic pH (6-10). While dynamically bound ligands (carboxylates and phosphonates) do not provide colloidal stability in phosphate buffered saline, the tightly bound nitrocatechols provide long term stability. We thus shed light on the complex ligand binding dynamics on metal oxide nanocrystals in aqueous environments. Finally, we provide a practical colloidal stability map, guiding researchers to rationally design ligands for their desired application.

The synthesis and single-crystal X-ray structures of three

Surfactants play a crucial role in the synthesis of colloidal nanocrystals. Nevertheless, only a handful molecules are currently used, oleic acid being the most typical example. Here, we show that mono-alkyl phosphinic acids are an interesting surfactant class with a reactivity that is intermediate between carboxylic acids and phosphonic acids. We first present the synthesis of n-hexyl, 2-ethylhexyl, n-tetradecyl, n-octadecyl, and oleyl phosphinic acid. These compounds are suitable surfactants during high-temperature nanocrystal synthesis (240-300°C). In contrast to phosphonic acids, they do not form poly anhydride gels. Consequently, CdSe quantum dots synthesized with octadecylphosphinic acid are conveniently purified, and are free from background scattering in UV-Vis. The CdSe nanocrystals have a very low polydispersity and a photoluminescence quantum yield up to 18%, without additional shell. Furthermore, we could synthesize CdSe and CdS nanorods using phosphinic acid ligands and found a remarkable purity (i.e. without tetrapod impurities). We conclude that the reactivity towards TOP-S and TOP-Se precursors decreases in the series: cadmium carboxylate > cadmium phosphinate > cadmium phosphonate. By introducing a third and intermediate class of surfactants, we enhance the versatility of surfactant-assisted syntheses.

In this paper, a novel synthesis for a chemical precursor for nanocrystalline VO2 coatings is elaborated. The compatibility of the precursor towards the substrate is optimized for spin coating. This is done by subjecting multiple solvents to contact angle measurements. A suitable thermal treatment is developed to densify the coating and to induce crystallization. Afterwards the microstructure of the coating is investigated using X-Ray diffraction, electron microscopy and ellipsometry techniques. To assess the thermochromic properties of the fabricated device, optical transmission experiments were conducted both at room temperature and at elevated temperature. A correlation between these thermochromic properties and coating thickness was investigated in order to obtain an optimized thermochromic device, where both high visual transparency and prominent thermochromic switching abilities are aimed for. In this work, an optimal coating thickness is proposed for a thermochromic coating with high switching ability and solar modulation.

Monometallic cerium layered double hydroxides (Ce-LDH) supports were successfully synthesized by a homogeneous alkalization route driven by hexamethylenetetramine (HMT). The formation of the Ce-LDH was confirmed and its structural and compositional properties studied by XRD, SEM, XPS, iodometric analyses and TGA. HT-XRD, N2-sorption and XRF analyses revealed that by increasing the calcination temperature from 200 to 800 &deg, C, the Ce-LDH material transforms to ceria (CeO2) in four distinct phases, i.e., the loss of intramolecular water, dehydroxylation, removal of nitrate groups and removal of sulfate groups. When loaded with 2.5 wt% palladium (Pd) and 2.5 wt% nickel (Ni) and calcined at 500 &deg, C, the PdNi-Ce-LDH-derived catalysts strongly outperform the PdNi-CeO2 benchmark catalyst in terms of conversion as well as selectivity for the hydrogenolysis of benzyl phenyl ether (BPE), a model compound for the &alpha, O-4 ether linkage in lignin. The PdNi-Ce-LDH catalysts showed full selectivity towards phenol and toluene while the PdNi-CeO2 catalysts showed additional oxidation of toluene to benzoic acid. The highest BPE conversion was observed with the PdNi-Ce-LDH catalyst calcined at 600 &deg, C, which could be related to an optimum in morphological and compositional characteristics of the support.

In view of today's challenges in clean water depletion and wastewater management, electrochemical water treatment processes are increasingly applied for e.g. desalination of brackish water, recovery of resources and energy production from waste streams, and disinfection of wastewater. These electrochemical processes typically make use of an ion-exchange membrane in between the anode and cathode. The choice of material for this membrane is crucial for the performance of the cell and often its performance is the key bottleneck. Over the last decade, research has been focused on the production of ion-exchange nanofibers as membrane material due to their outstanding ionic properties as a result of their specific morphology. Nanofiber membranes are known to have a large specific surface area, flexibility, high porosity and interconnected pores. Different strategies are applied for the production and structural design of these ion-exchange nanofiber membranes, which are discussed in this review. Nanofibers with an ion-exchange functionality can be produced by either pre-or postfunctionalization methods, combined with electrospinning. Depending on the application, these nanofiber mats can be used as such, or further membrane processing is possible to improve the dimensional stability, typically by adding a pore-filling matrix in between the nanofibers. Eventually, the current state of research on ion-exchange nanofibers in electrochemical separation and degradation applications is discussed. The many examples highlighted in this review prove the potential of nanofibers as ion-exchangers and provide insights for future research in this area.

To increase the recycling potential of concrete, Completely Recyclable Concrete (CRC) has been developed to be used as a raw material for cement clinker production. Sulfates may penetrate CRC structures in time and their presence could affect the clinkering process of the eventually obtained CRC rubble. Therefore, the effect of CaSO 4 additions on the final CRC clinker mineralogy has been investigated using XRD/Rietveld and SEM/EDX. An increasing sulfate content was found to stimulate the formation of sulfates that incorporate CaO, i.e. calcium langbeinite and anhydrite. Moreover, belite tends to be stabilized at the expense of alite with more SO 3 present.

Chemical solution deposition (CSD) of YBa2Cu3O7−δ (YBCO) nanocomposites from colloidal precursor solutions containing double metal oxide preformed nanocrystals is a promising, cost effective and reproducible approach to produce superconducting films with high critical current density (Jc) and enhanced pinning. Here, the influence of the preformed nanocrystal composition on the microstructure and superconducting properties of the YBCO nanocomposite films is studied, with a focus on establishing a simple and scalable process to grow nanocomposites that can be transferred to grow nano-added coated conductors. Colloidal stable BaZrO3, BaHfO3, BaTiO3 and SrZrO3 nanocrystals (3-6 nm in diameter) were synthesized and added to an environment-friendly low-fluorine YBCO precursor solution. High-quality superconducting layers were grown on LaAlO3 single-crystal substrates from these four nanocomposite precursor solutions in a single deposition process, without the need of a seed layer, yielding Jc of 4-5 MA/cm² at 77 K in self-field. The different YBCO microstructures produced by the four types of nanocrystals and the resulting microstrain of the films are compared and related with the magnetic-field and angular dependence of Jc. We demonstrate the BaHfO3-containing nanocomposite as the best-performing with a homogeneous distribution of nanoparticles with 7 nm in average diameter and a high density of stacking faults, which leads to some of the best superconducting properties ever achieved via low-fluorine CSD. The Jc exhibits a much smoother decay in applied magnetic fields and a much more isotropic behaviour for non-parallel magnetic fields, and the pinning force is increased by a factor of 3.5 at 77 K and 1 T with respect to the pristine film.

We demonstrate the synthesis of copper nanocolloids by the thermal decomposition of copper formate in oleylamine under ambient conditions. By progressively increasing the loading of copper formate in the reaction mixture and imposing sufficiently high conversion rates, we demonstrate the formation of nanocrystals that are more than 97% pure copper without using an inert atmosphere. We attribute this result to the excess of copper formate relative to initially dissolved oxygen, and to the suppression of oxygen influx in the reactor. By adjusting the precursor and ligand concentrations, we obtain copper nanocrystals with sizes ranging from 10 to 200 nm. In view of applications, we show that the reaction can be upscaled to a 1 L reaction volume to produce over 50 g of copper nanocrystals. Moreover, we formulate a conductive ink based on the copper nanocolloids obtained here with which we printed copper films exhibiting a resistivity of 23 mu Omega cm after thermal sintering under N-2. We conclude that the approach presented here constitutes a next step toward the cost-effective production of metallic copper nanocrystals for printed electronics.

A new series of bimetallic COMOC-2(V)/DUT-5(Al) frameworks are developed and fully characterized. Electron paramagnetic resonance and transmission electron microscopy confirm the homogeneous dispersion of Al/V in the entire framework. The study of the flexibility by means of CO2 pressure dependent XRPD and high pressure sorption reveals the co-existence of two different large pore phases and a narrow pore phase in the entire pressure regime.

A method to obtain photocatalytically active thin films of anatase nanocrystals on polymer substrates was explored. Anatase nanocrystals were synthesized by a fast hydrolysis synthesis in an apolar solvent and characterized with regard to their crystallinity, size, and dispersibility and the stability of the resulting suspensions. The stable titania nanocrystal suspensions were further processed for their use in polar solvents using ligand exchange. Oleic acid was exchanged for 3-aminopropyltriethoxysilane (APTES), resulting in aqueous suspensions of charge-stabilized nanocrystals. These were adapted for use as coating suspensions for surface-treated PMMA substrates in order to obtain thin films containing anatase nanocrystals covalently coupled to the surface of the PMMA substrates. Thereby, the ligand exchange was beneficial for increasing the compatibility and durability of the inorganic/organic composite, by the formation of a covalent amide bond between the silane ligands on the nanocrystals and the carboxylic acid groups on the polymer substrate. The surface morphology, transparency, and photocatalytic activity toward the degradation of organic pollutants of the coatings, obtained through dip-coating, were evaluated.

In this work, we present preparation and stabilization methods for highly crystalline TiO2 nanoparticle suspensions for the successful deposition of transparent, photocatalytically active TiO2 thin films toward the degradation of organic pollutants by a low temperature deposition method. A proof-of-concept is provided wherein stable, aqueous TiO2 suspensions are deposited on glass substrates. Even if the processing temperature is lowered to 150-200 °C, the subsequent heat treatment provides transparent and photocatalytically active titania thin layers. Because all precursor solutions are water-based, this method provides an energy-efficient, sustainable, and environmentally friendly synthesis route. The high load in crystalline titania particles obtained after microwave heating opens up the possibility to produce thin coatings by low temperature processing, as a conventional crystallization procedure is in this case superfluous. The impact of the precursor chemistry in Ti(4+)-peroxo solutions, containing imino-diacetic acid as a complexing ligand and different bases to promote complexation was studied as a function of pH, reaction time and temperature. The nanocrystal formation was followed in terms of colloidal stability, crystallinity and particle size. Combined data from Raman and infrared spectroscopy, confirmed that stable titanium precursors could be obtained at pH levels ranging from 2 to 11. A maximum amount of 50.7% crystallinity was achieved, which is one of the highest reported amounts of anatase nanoparticles that are suspendable in stable aqueous titania suspensions. Decoloring of methylene blue solutions by precipitated nanosized powders from the TiO2 suspensions proves their photocatalytic properties toward degradation of organic materials, a key requisite for further processing. This synthesis method proves that the deposition of highly crystalline anatase suspensions is a valid route for the production of photocatalytically active, transparent films on heat-sensitive substrates such as polymers.

Nine compositional series of 15(Na2O, K2O)center dot 10(CaO, ZnO)center dot 75(ZrO2, SiO2) glass-forming melts were studied, all with the ZrO2 content of 0, 1, 3, 5 and 7 mol.%. The investigated glass compositions were obtained by equimolar substitutions ZrO2 / SiO2, ZnO / CaO and K2O / Na2O. Surface tension of studied glassforming melts was de-termined by the sessile and pendant drop profile numerical analysis in the temperature range (1250 1500) degrees C. The experimental values of melt density were used. The linear temperature dependence of surface tension was observed for all samples with only small differences between values obtained from sessile and pendant drop profiles. The Shakhmatkin and Vedishcheva thermodynamic model (TDM) was evaluated for each glass melt at temperature of 1400 degrees C. The total number of 36 components was considered in TDM. Only 26 components were present with non-negligible equilibrium amount. The surface tension was described by the multilinear function of equilibrium amounts of statistically independent non-negligible components of the TDM. The surface active components were identified by negative values of their coefficients. Such way the N3S8 and C2ZrS4 were identified as "strongly" surface active and NCS5 and KS4 as probably surface active. Regarding the oxide compositional point of view, the surface tension was mostly influenced by ZnO (increase with the addition of the oxide) and by K2O (decrease with the addition of the oxide).

A challenge for the photodegradation of (organic) micro-pollutants in waste water treatment is the mechanistic and kinetic understanding beyond the degradation of the initial (parent) harmful product, e.g. the phenylurea herbicide isoproturon (IPU). By combining liquid chromatography-mass spectrometry and kinetic Monte Carlo modeling, we demonstrate that upon optimizing the dip-coating conditions (0.34 mol L (-1) TiO2 solution at a coating speed of 160 mm min( -1)) for the functionalization of a superhydrophilic electrospun silica nanofibrous membrane (i) hydroxylation is a dominant reaction pathway and (ii) once IPU reacts on the surface of the TiO(2 )nanoparticles, further hydroxylation occurs sufficiently fast, with complete IPU removal under the detection limit (5-10 mg Lsolution(-1)) as a result of UV irradiation within 8 h. As hydroxylation is dominant, degradation intermediates with a higher water solubility are formed and therefore a decreased toxicity is obtained upon reintroducing the treated solution into the environment. This is confirmed by respirometry, with an increase in the oxygen uptake rate of an activated sludge from 5.9 mg O(2 )g(activated) ( -1)(sludge) h (-1 )for an untreated 10 mg L-1 IPU solution to 8.2 mg O-2 g(activated sludge) (-1) h( -1) for a solution irradiated for 8 h, in line with a blank solution.

Although already some mesoporous (2–50 nm) sol–gel TiO2 synthesis strategies exist, no pore size control beyond the 12 nm range is possible without using specialized organic structure-directing agents synthetized via controlled anionic/radical polymerizations. Here, we present the use of reversible addition–fragmentation chain transfer (RAFT) polymerization as a straightforward and industrial applicable alternative to the existing controlled polymerization methods for structure-directing agent synthesis. Poly(N,N-dimethylacrylamide)-block-polystyrene (PDMA-b-PS) block copolymer, synthesized via RAFT, was chosen as structure-directing agent for the formation of the mesoporous TiO2. Crack-free thin layers TiO2 with tunable pores from 8 to 45 nm could be acquired. For the first time, in a detailed and systematic approach, the influence of the block size and dispersity of the block copolymer is experimentally screened for their influence on the final meso-TiO2 layers. As expected, the mesoporous TiO2 pore sizes showed a clear correlation to the polystyrene block size and the dispersity of the PDMA-b-PS block copolymer. Surprisingly, the dispersity of the polymer was shown not to be affecting the standard deviation of the pores. As a consequence, RAFT could be seen as a viable alternative to the aforementioned controlled polymerization reactions for the synthesis of structure-directing agents enabling the formation of mesoporous pore size-controlled TiO2. To examine the photocatalytic activity of the mesoporous TiO2 thin layers, the degradation of acetaldehyde, a known indoor pollutant, was studied. Even after 3 years of aging, the TiO2 thin layer retained most of its activity.

The thickness characterization of transparent protective coatings on functional, transparent materials is often problematic. In this paper, a toolbox to determine the thicknesses of a transparent coating on functional window films is presented. The toolbox consists of a combination of secondary ion mass spectrometry and profilometry and can be transferred to other transparent polymeric materials. A coating was deposited on designed model samples, which were characterized with cross-sectional views in transmission and in scanning/transmission electron microscopy and ellipsometry. The toolbox was then used to assess the thicknesses of the protective coatings on the pilot-scale window films. This coating was synthesized using straightforward sol-gel alkoxide chemistry. The kinetics of the condensation are studied in order to obtain a precursor that allows fast drying and complete condensation after simple heat treatment. The shelf life of this precursor solution was investigated in order to verify its accordance to industrial requirements. Deposition was performed successfully at low temperatures below 100 &deg, C, which makes deposition on polymeric foils possible. By using roll-to-roll coating, the findings of this paper are easily transferrable to industrial scale. The coating was tested for scratch resistance and adhesion. Values for the emissivity (&epsilon, ) of the films were recorded to justify the use of the films obtained as infrared reflective window films. In this work, it is shown that the toolbox measures similar thicknesses to those measured by electron microscopy and can be used to set a required thickness for protective coatings.

Mesoporous carbons were synthesized via both soft and hard template methods and compared to a commercial powder activated carbon (PAC) for the adsorption ability of bisphenol-A (BPA) from an aqueous solution. The commercial PAC had a BET-surface of 1027 m2/g with fine pores of 3 nm and less. The hard templated carbon (CMK-3) material had an even higher BET-surface of 1420 m2/g with an average pore size of 4 nm. The soft templated carbon (SMC) reached a BET-surface of 476 m2/g and a pore size of 7 nm. The maximum observed adsorption capacity (qmax) of CMK-3 was the highest with 474 mg/g, compared to 290 mg/g for PAC and 154 mg/g for SMC. The difference in adsorption capacities was attributed to the specific surface area and hydrophobicity of the adsorbent. The microporous PAC showed the slowest adsorption, while the ordered mesopores of SMC and CMK-3 enhanced the BPA diffusion into the adsorbent. This difference in adsorption kinetics is caused by the increase in pore diameter. However, CMK-3 with an open geometry consisting of interlinked nanorods allows for even faster intraparticle diffusion.

This paper aims to examine the use of fines generated out of recycled aggregates production as an alternative raw material for Portland clinker kilns with enumeration of possible limitations. Different technical set-ups were used to separate these fines from the recycled aggregates. The relationship between the particle size distribution of the generated fines fraction and their chemical composition as well as the relationship between the final filler (

The formation of superconducting nanocomposites from preformed nanocrystals is still not well understood. Here, we examine the case of ZrO2 nanocrystals in a YBa2Cu3O7&minus, x matrix. First we analyzed the preformed ZrO2 nanocrystals via atomic pair distribution function analysis and found that the nanocrystals have a distorted tetragonal crystal structure. Second, we investigated the influence of various surface ligands attached to the ZrO2 nanocrystals on the distribution of metal ions in the pyrolyzed matrix via secondary ion mass spectroscopy technique. The choice of stabilizing ligand is crucial in order to obtain good superconducting nanocomposite films with vortex pinning. Short, carboxylate based ligands lead to poor superconducting properties due to the inhomogeneity of metal content in the pyrolyzed matrix. Counter-intuitively, a phosphonate ligand with long chains does not disturb the growth of YBa2Cu3O7&minus, x. Even more surprisingly, bisphosphonate polymeric ligands provide good colloidal stability in solution but do not prevent coagulation in the final film, resulting in poor pinning. These results thus shed light on the various stages of the superconducting nanocomposite formation.

The metastable titania phase, bronze, has great potential as photo-catalyst or as anode material in Li-ion batteries. Here, we report the first synthesis of colloidally stable, size-tunable TiO2-bronze (TiO2-B) nanocrystals, via a hydrothermal process. By employing Definitive Screening Design, the experimental parameters affecting the size and agglomeration of the nanocrystals are identified. The size is mostly determined by the reaction temperature, resulting in 3 – 8 nm NCs in the range of 130 °C – 180 °C. To avoid irreversible aggregation, short reaction times are desired and in this respect microwave heating proved essential due to its fast heating and cooling rates. The resulting nanocrystals are de-aggregated and stabilized in polar solvents using either positive or negative surface charges. In nonpolar solvents, steric stabilization is provided by long chain amines and carboxylic acids. Furthermore, we study this peculiar post-synthetic surface modification through solution 1H NMR and elemental analysis. Surprisingly, we find ion-pairs of alkylammonium carboxylates bound to the surface, contrasting with earlier reports on carboxylic acid stabilized metal oxide nanocrystals. To rationalize this, a general framework of acid/base chemistry with metal oxide nanocrystals is constructed and discussed.

In this paper, we present an overview as well as current advances in the low-temperature deposition of highly crystalline suspensions of titania nanoparticles on polymers for photocatalytic applications. The presence of preformed titania nanoparticles yields the possibility of producing photocatalytically active coatings at reduced temperatures. Transparent and photocatalytically active TiO2 coatings that degrade organic matter, have been widely applied to bestow self-cleaning properties onto surfaces. This low-temperature deposition method and its transition to polymers would open an entire array of possible self-cleaning applications. During this research, incorporation of a silica buffer layer was applied to improve the compatibility of the inorganic coating on a substrate, such as polymethylmethacrylate (PMMA) and polyphenylsulphone (PPSU). The photocatalytic activity of the obtained coating was analyzed for its photocatalytic abilities by evaluating the color removal of a dye solution (methylene blue, MB) under UV irradiation and compared with commercial Pilkington Activ® self-cleaning glass. Our results indicate that the titania-coated silica-polymer systems yield a higher photocatalytic activity towards the degradation of organic pollutants. This method proves that the deposition of highly crystalline anatase suspensions on silica buffer layers is a viable method to produce photocatalytic coatings on heat-sensitive substrates.

Nanofibrous materials produced through electrospinning are characterized by a high porosity, large specific surface area, and high pore interconnectivity and, therefore, show potential for, e.g., separation and filtration. The development of more inert nanofibers with higher thermal and chemical resistance extends the application field to high-end purification. Silica nanofibrous membranes produced by direct electrospinning of a sol–gel solution without a sacrificing carrier, starting from tetraethoxysilane, meet these challenging requirements. After electrospinning the membrane is highly hydrophobic. Storage under dry conditions preserves this property. Oppositely, a superhydrophilic membrane is obtained by storage under high humidity (month scale). This switch is caused by the reaction of ethoxy groups, present due to incomplete hydrolysis of the precursor, with moisture in the air, resulting in an increased amount of silanol groups. This transition can be accelerated to hour scale by applying a heat treatment, with the additional increase in cross-linking density for temperatures above 400 °C, enabling applications that make use of hydrophobic and hydrophilic membranes by tuning the functionalization. It is showcased that upon designing the water repellent or absorbing nature of the silica material, fast gravity-driven membrane separation of heterogeneous azeotropes can be achieved.

In today’s cement and concrete research, mineralogical quantification of (un)hydrated cement samples by X-ray Diffraction/Rietveld analysis becomes more and more important. As the results from XRD/Rietveld analysis are becoming increasingly more accurate, it became a widely used tool to study the hydration of cementitious materials besides other techniques e.g. isothermal calorimetry or thermogravimetric analysis. To quantify amorphous or non-identified phases, an internal standard might be added to estimate these so-called ‘other’ phases. Compared to unhydrated samples which are almost completely crystalline, it has a higher significance in hydrated samples, as certain cement hydrates, such as C-S-H, hydrogarnet, hydrotalcite, AFm, etc., are often poorly crystalline. Within the development of Completely Recyclable Concrete (CRC – a concrete designed for reincarnation within the cement production following the Cradle-to-Cradle Principle) the hydration of the regenerated cement was assessed by XRD/Rietveld analysis. Within this study it was found that the particle size distributions of the sample and the internal standard should not be underestimated within the quantification of the ‘other’ phases.

Although concrete is a durable material, it has a big impact on the environment due to its high production volumes. This impact is mostly related to the consumption of virgin raw materials, the production of waste and the emission of carbon dioxide. To optimize the recycling opportunities of concrete, Completely Recyclable Concrete is designed as a raw material for clinker production, without the need for ingredient adjustments. However, CRC concrete constructions may be exposed to environments rich in chlorides, sulphates and other ions, affecting the clinkering process of CRC rubble. Therefore, it is important to know the effect of these ions on the mineralogy of CRC clinker. In this study the effect of sulphate additions to CRC raw meals on the final clinker mineralogy was studied by XRD/Rietveld analysis. It was found that an increasing sulphate content stimulates the formation of CaO containing sulphates such as calcium langbeinite and anhydrite. Additionally SO3 was found to stabilize belite at the expense of alite.

This paper presents a study of the hydration reactions of a cement regenerated from Completely Recyclable Concrete by thermogravimetric analysis and X-ray powder diffraction/Rietveld analysis. The experimental results for the hydration reactions of the clinker phases in the regenerated cement were compared to a hydration model for OPC. A good agreement between the experimental and modeling results was observed. Therefore in terms of both reaction kinetics and hydration product assemblages the hydration of cement regenerated from CRC is concluded to be very similar to the hydration of OPC.

In this Article, epitaxial thin films of SrTiO3 were prepared on single crystalline (100) LaAlO3 by an aqueous chemical solution deposition method. By using different chelating agents to stabilize the metal ions in water, the impact of the precursor chemistry on the microstructural and crystalline properties of the films was studied. Thorough investigation of the precursor by means of infrared and Raman spectroscopy as well as thermogravimetric analysis revealed that stable precursors can be obtained in which strontium ions can be either free in the solution or stabilized by one of the chelating agents. This stabilization of strontium ions appeared to be essential in order to obtain single phase SrTiO3 films. Precursors in which Sr(2+) remained as free ions showed SrO microcrystal segregation. Precursors in which both metal ions were stabilized gave rise to strongly textured, dense, and terraced SrTiO3 films, allowing subsequent deposition of YBa2Cu3O7-δ with superior superconducting performances.

This paper aims to investigate the use of cellular concrete as an alternative raw material (ARM) for Portland clinker kilns. The possibility to generate a raw material with a stable compositional variation was investigated as well as simulations were carried out to maximise their use in clinker kilns. Based on these simulations, experimental clinkers were produced with dosages that were esteemed as realistic. Because of the presence of important levels of quartz sand in the cellular concrete materials, the energy necessary to grind the alternative raw material in comparison with comparable classic raw materials was investigated as well as the influence of the final particle size distribution of the Cold Clinker Meal (CCM) on the mineralogical composition of the final clinkers. It will be demonstrated that cellular concrete materials can be used as ARM for clinker production although there are some important restrictions that will limit the practical implementation. This investigation will also provide some interesting knowledge on the use of other recycled concrete materials as alternative raw material for Portland clinker production.