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Bi2S3 has gained considerable attention as a semiconductor for its versatile functional properties, finding application across various fields, and liquid phase exfoliation (LPE) serves as a straightforward method to produce it in nano-form. Till now, the commonly used solvent for LPE has been N-Methyl-2-pyrrolidone, which is expensive, toxic and has a high boiling point. These limitations drive the search for more sustainable alternatives, with water being a promising option. Nonetheless, surfactants are necessary for LPE in water due to the hydrophobic nature of Bi2S3, and organic molecules with amphoteric characteristics are identified as suitable surfactants. However, systematic studies on the use of ionic surfactants in the LPE of Bi2S3 have remained scarce until now. In this work, we used sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS) and sodium hexadecyl sulfonate (SHS) as representative species and we present a comprehensive investigation into their effects on the LPE of Bi2S3. Through characterizations of the resulting products, we find that all surfactants effectively exfoliate Bi2S3 into few-layer species. Notably, SDBS demonstrates superior stabilization of the 2D layers compared to the other surfactants, while SHS becomes the most promising surfactant for obtaining products with high yield. Moreover, the resulting nano-inks are used for fabricating films using spray-coating, reaching a fine tuning of band gap by controlling the number of cycles, and paving the way for the utilization of 2D Bi2S3 in optoelectronic devices. [ABSTRACT FROM AUTHOR]

The need to develop clean-energy storage systems, harvesting technologies, and new functional materials are but a few of the many contemporary challenges in the domain of science today. To address these challenges, problem solving has become a key skill of the 21st century. It is generally documented, however, that experts and students differ in terms of their problem-solving skills. Experts in a domain are fluent in the use of different resources to solve domain-specific problems, whereas students stumble when using formulas, devices, or measurement methods. In most cases, the students are not aware if and why the resources are appropriate to solve the given problem. To acquire expertise in a domain, it is necessary to become fluent in the domain-specific resources. This means being aware of various resources and how they can be used reflectively in problem solving. In this study, we investigated how students' awareness of various domain-specific resources developed within minimally guided, authentic research projects in an undergraduate materials chemistry course that focuses on crystal structures and its characterisation. By monitoring participants' problem solving through audio-diaries and in-depth qualitative interview data, we examined to what extent their awareness of domain-specific resources developed. We further characterised productive moments of failure and uncertainty during students' problem-solving processes that influenced their awareness. Thick descriptions of these moments facilitate understanding of how students' awareness develops in a minimally guided, authentic learning environment and how students can become fluent in a given domain.

Acquiring a basic understanding about the composition of crystal structures and the resulting structure-property relationship is central for chemists and material chemists, enabling the prediction of desired properties and the solution of a wide range of current challenges in sciences, e.g., the development of clean-energy storage. For a deeper understanding of physical and chemical properties of crystals, it is necessary to focus on different global and local structural features that characterize the composition of several atoms or ions as well as the direct environment of single atoms or ions. To improve students' mental visualization of both global and local features of the three-dimensional order of crystal structures, we developed and implemented a modeling activity with new transparent models. During the activity, students construct and compare models of common crystal structures, like sodium chloride and zinc blend. The usage of clear plastic balls, in particular, allows students to focus on global features such as packing arrangement and lattice structure, as well as on local ones, like coordination number, site occupation, and polyhedral connectivity. The latter features have been difficult to realize so far. We used a design-based research approach to improve the activity and the instructional material, provided herein, through several rounds of evaluation in a course for undergraduate students in materials chemistry. A detailed qualitative analysis of students' discourse during the activity revealed that students were engaged in various content-related interactions with the models and that it is beneficial to combine a student-centered construction of the models with a subsequent comparison phase.

Chemical surface functionalization of carbon nanodots (CNDs) offers a valuable opportunity to tailor multifunctionality in these nanocarbons, by engineering the composition of their molecular surface. Therefore, it is important to elucidate the type and amount of CNDs surface functionalization to be able to design their properties accurately. CNDs are often functionalized through amide coupling without validating the degree of surface functionalization. As a measure of surface functionalization, the amounts of primary amines via Kaiser test (KT) or imine reactions of the bare CNDs is often considered. However, this may lead to overestimating the degree of surface functionalization obtained by the pure amide coupling due to different reaction mechanisms and involved intermediates. Herein, four different CNDs prepared by microwave‐assisted synthesis from arginine or citric acid with varying amounts of ethylenediamine are presented. We resorted to combining physicochemical methods to provide elemental, structural, and optical information. By that, we developed a method to quantify the degree of surface functionalization by amide coupling and show that the surface functionalization is lower than anticipated. Comparing experimental optical features of the CNDs with different computed model systems enables us to provide a more advanced vision of structure‐property relationships in these still elusive nanocarbons. [ABSTRACT FROM AUTHOR]

Supercapacitors (SCs) are considered a promising alternative to batteries to power up portable and wearable devices. Among different categories of materials for SCs, carbon nanofibers (CNFs) are particularly appealing for their electrochemical, morphological, and mechanical properties, coupled with the ease of synthesis. Electrospinning is a simple and low‐cost technique to prepare the polymer‐based precursors for CNFs, allowing to obtain fibers with a tunable morphology and a diameter in the nanometer range. However, even if electrospun CNFs were intensely studied over the years, in the literature there is a lack of information regarding the optimization of the thermal treatment to prepare bare CNFs with high specific capacitance (Cs). Herein, a systematic study on the optimization of the stabilization and carbonization temperatures for electrospun CNFs prepared from polyacrylonirtile is reported, achieving a maximum Cs of 49 F g−1 at 0.5 A g−1 in a symmetrical SC device based on 1 m H2SO4 electrolyte. Aspects related to the specific surface area, nitrogen doping, and carbon microstructure are examined concerning the different thermal treatments, allowing to define structure–property–function relationships in these capacitive nanoarchitectures. [ABSTRACT FROM AUTHOR]

Organocatalysis via the enamine mechanism developed to one of the most relevant tools in carbonyl chemistry and is widely used in asymmetric organic synthesis. In this work, a strategy is presented to conveniently immobilize a peptide‐based catalyst on silica supports for use in continuous flow catalysis reactions. A set of different porous silica supports is investigated spanning from mesoporous silica particles with defined pore sizes suitable for packed bed column reactors to silica monoliths with hierarchical meso‐macropore spaces. While the silica supports are functionalized with norbornene entities, the peptide‐based organocatalyst is modified with a tetrazine moiety, enabling the immobilization via inverse electron‐demand Diels‐Alder (IEDDA) reaction. The ligation results in catalyst loadings up to 0.2 mmol g‐1, without compromising the mesopore network. The catalytic activity of the materials is proven by the asymmetric C−C coupling reaction of n‐butanal to ß‐nitrostyrene proceeding in high yield and enantioselectivity in both batch and continuous flow setups. [ABSTRACT FROM AUTHOR]

A rational synthetic approach is introduced to enable hydrogen insertion into oxides by forming a solid solution of a reducible oxide with a less reducible oxide as exemplified with RuO2 and TiO2 (Ru_x, a mixture of x% RuO2 with (100−x)% TiO2). Hydrogen exposure at 250 °C to Ru_x (Ru_x_250R) results in substantial hydrogen incorporation accompanied by lattice strain that in turn induces pronounced activity variations. Here, we demonstrate that hydrogen incorporation in mixed oxides promotes the oxidation catalysis of propane combustion with Ru_60_250R being the catalytically most active catalyst. [ABSTRACT FROM AUTHOR]

Non-graphitic carbons (NGCs), such as glass-like carbons, pitch cokes, and activated carbon consist of small graphene layer building stacks arranged in a turbostratic order. Both structure features, including the single graphene sheets as well as the stacks, possess structural disorder, which can be determined using wide-angle X-ray or neutron scattering (WAXS/WANS). Even if WANS data of NGCs have already been extensively reported and evaluated in different studies, there are still open questions with regard to their validation with WAXS, which is usually used for routine characterization. In particular, using WAXS for the damping of the atomic form factor and the limited measured range prevent the analysis of higher-ordered reflections, which are crucial for determining the stack/layer size (La, Lc) and disorder (σ1, σ3) based on the reflection widths. Therefore, in this study, powder WANS was performed on three types of carbon materials (glass-like carbon made out of a phenol-formaldehyde resin (PF-R), a mesophase pitch (MP), and a low softening-point pitch (LSPP)) using a beamline at ILL in Grenoble, providing a small wavelength and thus generating WANS data covering a large range of scattering vectors (0.052 Å−1 < s < 3.76 Å−1). Merging these WANS data with WANS data from previous studies, possessing high resolution in the small s range, on the same materials allowed us to determine both the interlayer and the interlayer structure as accurately as possible. As a main conclusion, we found that the structural disorder of the graphene layers themselves was significantly smaller than previously assumed. [ABSTRACT FROM AUTHOR]

We present a free software script operating in GNU Octave for the refinement of wide-angle X-ray and neutron scattering (WAXS/WANS) data of non-graphitic carbons (NGCs). The refinement script (OctCarb) is based on the evaluation approach of Ruland and Smarsly (2002). As result, up to 14 physically meaningful parameters such as the layer extension La, the stack height Lc, as well as the degree of disorder of the graphenes and their stacking are obtained through a well-established fitting routine. In addition, background scattering based on specific physical phenomena and different correction parameters such as polarization and absorption can be considered. Since the complex mathematical calculations are implemented and performed in the background, with only a few settings to be made, the software was designed to be usable by inexperienced users. As another key feature, Octave and thus OctCarb run on all common operating systems (Windows, MacOS and Linux), and can even be used on high-performance computing clusters (HPCs) to perform multiple calculations at once. In addition to this, the whole refinement can be performed within minutes, and it is possible to tweak and optimize it for special purposes and measuring geometries. These features make OctCarb useful for all scientists dealing with the characterization of NGCs by X-ray or neutron scattering techniques. [ABSTRACT FROM AUTHOR]

Five different rare‐earth‐based nanocrystalline high entropy oxides (HEOs) with fluorite structure and average crystallite sizes between 6 and 8 nm are prepared and their photocatalytic behavior toward azo dye degradation and photoelectrochemical water splitting for hydrogen generation is examined. The cationic site in the fluorite lattice consists of five equimolar elements selected from the group of rare‐earth elements including La, Ce, Pr, Eu, and Gd and second‐row transition metals, Y and Zr. The studied HEOs exhibit bandgaps in the range from 1.91 to 3.0 eV and appropriate valence and conduction bands for water splitting. They reveal high photocatalytic activity that is mostly attributed to the accessibility of more photocatalytic active sites, which provide radicals responsible for the azo dye degradation. The materials successfully produce hydrogen by photocatalytic water splitting, suggesting the potential of HEOs as new photocatalysts. The photocatalytic performances of all studied HEOs outperform the single fluorite oxides or equivalent mixed oxides. The Ce0.2Zr0.2La0.2Pr0.2Y0.2O2 (CZLPY) engender hydrogen in 9.2 µmol mg−1 per hour that is much higher content than for pristine CeO2 material which amounts to 0.8 µmol mg−1 per hour. [ABSTRACT FROM AUTHOR]

Mixed oxide catalysts RuxIr1‐xO2 with varying composition x (x=0, 0.25, 0.5, 0.75, 1.0) supported on CeO2, γ‐Al2O3 or ZrO2 are successfully prepared and tested in the catalytic propane combustion in terms of activity and stability. Pure IrO2 reveals a significantly lower activity than RuxIr1‐xO2 with x≥0.25. For low conversion, pure RuO2 on CeO2 turns out to be the most active catalyst, while at higher conversion, Ru0.75Ir0.25O2 on ZrO2 is found to be more active than RuO2, pointing towards synergism of Ru and Ir sites. Long‐term stability and also the resistance against water poisoning are highest for ZrO2‐supported catalysts. The higher the Ir concentration in the active component RuxIr1‐xO2 the more susceptible is the catalyst to water poisoning. Water poisoning is shown to be reversible, consistent with a blocking of catalytically active sites by water adsorption. [ABSTRACT FROM AUTHOR]