Synthesis and Structural Analysis of an Emissive Colloidal Argyrodite Nanocrystal: Canfieldite AgSnS.

We resolve a phase identification controversy in the Ag-Sn-S material system by unraveling the polymorphic structure of nanocrystals within the argyrodite material family. Argyrodites are a class of superionic materials used in their bulk form for applications in solid-state batteries and thermoelectrics, where their advantageous properties relate to their polymorphism. However, despite their well-studied bulk applications, the limited exploration at the nanoscale has left considerable potential for the discovery of emerging properties due to size effects.

Improving the Stability of Colloidal CsPbBr Nanocrystals with an Alkylphosphonium Bromide as Surface Ligand Pair.

In this study, we synthesized a phosphonium-based ligand, trimethyl(tetradecyl)phosphonium bromide (TTP-Br), and employed it in the postsynthesis surface treatment of Cs-oleate-capped CsPbBr nanocrystals (NCs). The photoluminescence quantum yield (PLQY) of the NCs increased from ∼60% to more than 90% as a consequence of replacing Cs-oleate with TTP-Br ligand pairs. Density functional theory calculations revealed that TTP ions bind to the NC surface by occupying Cs surface sites and orienting one of their P-CH bonds perpendicular to the surface, akin to quaternary ammonium passivation.

Synthesis, Growth Mechanism, and Photocatalytic Properties of Metallic-Bi/BiSBr Nano-Bell Heterostructures.

We report the synthesis of bell-shaped Bi/BiSBr metal/semiconductor heterostructures as a photocatalyst based on nontoxic and Earth-abundant elements. Their unique morphology arises from a multistep growth process, involving (1) the nucleation of BiSBr nanorods, (2) the reduction of a metallic-Bi domain on their surface induced by -didodecylmethylamine, and (3) the heterostructure accretion by a localized reaction at the Bi/BiSBr interface promoted by Ostwald ripening. These heterostructures display remarkable stability in polar solvents, remaining almost unaffected by prolonged exposure to isopropanol and water, and exhibit high photocatalytic efficiency for the degradation of organic dyes (i.

Optical properties of NIR photoluminescent PbS nanocrystal-based three-dimensional networks.

The assembly of nanocrystals (NCs) into three-dimensional network structures is a recently established strategy to produce macroscopic materials with nanoscopic properties. These networks can be formed by the controlled destabilization of NC colloids and subsequent supercritical drying to obtain NC-based aerogels. Even though this strategy has been used for many different semiconductor NCs, the emission of NC-based aerogels is limited to the ultraviolet and visible and no near-infrared (NIR) emitting NC-based aerogels have been investigated in literature until now.

Morphological Control Over Gel Structures of Mixed Semiconductor-Metal Nanoparticle Gel Networks with Multivalent Cations.

In this work, the influence of two different types of cations on the gel formation and structure of mixed gel networks comprised of semiconductor (namely CdSe/CdS nanorods NR) and Au nanoparticles (NP) as well as on the respective monocomponent gels is investigated. Heteroassemblies built from colloidal building blocks are usually prepared by ligand removal or cross-linking, thus, both the surface chemistry and the destabilising agent play an essential role in the gelation process. Due to the diversity of the composition, morphology, and optical properties of the nanoparticles, a versatile route to fabricate functional heteroassemblies is of great demand.

Influencing the coupling between network building blocks in CdSe/CdS dot/rod aerogels by partial cation exchange.

The assembly of CdSe/CdS dot/rod nanocrystals (NCs) with variable length of ZnS tips into aerogel networks is presented. To this end, a partial region selective cation exchange procedure is performed replacing Cd by Zn starting at the NC tip. The produced aerogel networks are investigated structurally and optically.

BN-Substitution in Dithienylpyrenes Prevents Excimer Formation in Solution and in the Solid State.

Boron-nitrogen substitutions in polycyclic aromatic hydrocarbons (PAHs) have a strong impact on the optical properties of the molecules due to a significantly more heterogeneous electron distribution. However, besides these single-molecule properties, the observed optical properties of PAHs critically depend on the degree of intermolecular interactions such as π-π-stacking, dipolar interactions, or the formation of dimers in the excited state. Pyrene is the most prominent example showing the latter as it exhibits a broadened and strongly bathochromically shifted emission band at high concentrations in solution compared to the respective monomers.

Tungsten Nanoparticles Accelerate Polysulfides Conversion: A Viable Route toward Stable Room-Temperature Sodium-Sulfur Batteries.

Room-temperature sodium-sulfur (RT Na-S) batteries are arousing great interest in recent years. Their practical applications, however, are hindered by several intrinsic problems, such as the sluggish kinetic, shuttle effect, and the incomplete conversion of sodium polysulfides (NaPSs). Here a sulfur host material that is based on tungsten nanoparticles embedded in nitrogen-doped graphene is reported.

Versatile Route for Multifunctional Aerogels Including Flaxseed Mucilage and Nanocrystals.

Preparation of low density monolithic and free-standing organic-inorganic hybrid aerogels of various properties is demonstrated using green chemistry from a biosafe natural source (flaxseed mucilage) and freeze-casting and subsequent freeze drying. Bio-aerogels, luminescent aerogels, and magneto-responsive aerogels are obtained by combination of the flaxseed mucilage with different types of nanoparticles. Moreover, the aerogels are investigated as possible drug release systems using curcumin as a model.

Noble-Metal Nanorod Cryoaerogels with Electrocatalytically Active Surface Sites.

Noble-metal-based electrocatalysts usually contain small nanoparticle building blocks to ensure a high specific surface area as the scene for the surface processes. Here, we show that relatively large noble-metal nanorods are also promising candidates to build up functional macrostructures with prominent electrocatalytic activity. After optimizing and upscaling the syntheses of gold nanorods and gold bipyramid-templated silver nanorods, cryoaerogels are fabricated on a conductive substrate flash freezing and subsequent freeze drying.

Temperature and Composition Dependent Optical Properties of CdSe/CdS Dot/Rod-Based Aerogel Networks.

Employing nanocrystals (NCs) as building blocks of porous aerogel network structures allows the conversion of NC materials into macroscopic solid structures while conserving their unique nanoscopic properties. Understanding the interplay of the network formation and its influence on these properties like size-dependent emission is a key to apply techniques for the fabrication of novel nanocrystal aerogels. In this work, CdSe/CdS dot/rod NCs possessing two different CdSe core sizes were synthesized and converted into porous aerogel network structures.

Substitution Effect on 2-(Oxazolinyl)-phenols and 1,2,5-ChalcogenadiazoleAnnulated Derivatives: Emission-Color-Tunable, Minimalistic Excited-State Intramolecular Proton Transfer (ESIPT)-Based Luminophores.

Minimalistic 2-(oxazolinyl)-phenols substituted with different electron-donating and -withdrawing groups as well as 1,2,5-chalcogenadiazole-annulated derivatives thereof were synthesized and investigated in regard to their emission behavior in solution as well as in the solid state. Depending on the nature of the incorporated substituent and its position, emission efficiencies were increased or diminished, resulting in AIE or ACQ characteristics. Single-crystal analysis revealed J- and H-type packing motifs and a so-far undescribed isolation of ESIPT-based fluorophores in the keto form.

Monodisperse Molybdenum Nanoparticles as Highly Efficient Electrocatalysts for Li-S Batteries.

Lithium-sulfur (Li-S) batteries have attracted widespread attention due to their high theoretical energy density. However, their practical application is still hindered by the shuttle effect and the sluggish conversion of lithium polysulfides (LiPSs). Herein, monodisperse molybdenum (Mo) nanoparticles embedded onto nitrogen-doped graphene (Mo@N-G) were developed and used as a highly efficient electrocatalyst to enhance LiPS conversion.

π-Conjugated stannole copolymers synthesised by a tin-selective Stille cross-coupling reaction.

The synthesis of four well-defined conjugated polymers containing unusual heterocycle units in the main chain, namely stannole units as building blocks, is reported. The stannole-thiophenyl copolymers were generated by tin-selective Stille coupling reactions in nearly quantitative yields of 94% to 98%. NMR data show that the tin atoms in the rings remain unaffected.

L.-Mediated Green Synthesis of Silver Nanoparticles Exhibiting Antioxidant and Anticancer Activities.

This contribution focuses on the green synthesis of silver nanoparticles (AgNPs) with a size < 100 nm for potential medical applications by using silver nitrate solution and L. (St John's wort) aqueous extracts. Various synthesis methods were used and compared with regard to their yield and quality of obtained AgNPs.

Emission color-tunable oxazol(in)yl-substituted excited-state intramolecular proton transfer (ESIPT)-based luminophores.

Oxazolinyl- and arylchalcogenazolyl-substituted hydroxyfluorenes exhibiting excited-state intramolecular proton transfer (ESIPT) are described as potent and highly modular luminophores. Emission color tuning was achieved by varying the π-expansion and the insertion of different chalcogen atoms.

Control over Structure and Properties in Nanocrystal Aerogels at the Nano-, Micro-, and Macroscale.

The assembly of individual colloidal nanocrystals into macroscopic solvogels and aerogels introduced a new exciting type of material into the class of porous architectures. In these so-called nanocrystal gels, the structure and properties can be controlled and fine-tuned to the smallest details. Recently it was shown that by employing nanocrystal building blocks for such gel materials, the interesting nanoscopic properties can be conserved or even expanded to properties that are available neither in the nanocrystals nor in their respective bulk materials.

A Versatile Route to Assemble Semiconductor Nanoparticles into Functional Aerogels by Means of Trivalent Cations.

3D nanoparticle assemblies offer a unique platform to enhance and extend the functionality and optical/electrical properties of individual nanoparticles. Especially, a self-supported, voluminous, and porous macroscopic material built up from interconnected semiconductor nanoparticles provides new possibilities in the field of sensing, optoelectronics, and photovoltaics. Herein, a method is demonstrated for assembling semiconductor nanoparticle systems containing building blocks possessing different composition, size, shape, and surface ligands.

Reversible cation exchange on macroscopic CdSe/CdS and CdS nanorod based gel networks.

Over the past decades, cation exchange reactions applied to nanoparticles have opened up synthetic pathways to nanocrystals, which were not accessible by other means before. The limitation of cation exchange on the macroscopic scale of bulk materials is given by the limited ion diffusion within the crystal structure. Lyogels or aerogels are macroscopic, highly voluminous, porous materials composed of interconnected nanoscopic building blocks and hence represent a type of bridge between the macroscopic and the nanoscopic world.

Methanol-to-Olefins in a Membrane Reactor with in situ Steam Removal - The Decisive Role of Coking.

The reaction of methanol to light olefins and water (MTO) was studied in a fixed bed tubular membrane reactor using commercial SAPO-34 catalyst. In the fixed bed reactor without membrane support, the MTO reaction collapsed after 3 h time on stream. However, if the reaction by-product steam is in situ extracted from the reactor through a hydrophilic tubular LTA membrane, the reactor produces long-term stable about 60 % ethene and 10 % propene.

Nanocrystal Aerogels with Coupled or Decoupled Building Blocks.

The influence of interparticle contact in nanoparticle-based aerogel network structures is investigated by selectively connecting or isolating the building blocks inside of the network, thereby coupling and decoupling them in regards to their optical and electronic properties. This is achieved by tuning the synthesis sequence and exchanging the point of shell growth and the point of particle assembly, leading to two distinctly different structures as examined by electron microscopy. By thorough examination of the resulting optical properties of the generated structures, the clear correlation between nanoscopic/microscopic structure and macroscopic optical properties is demonstrated.

Patterning of Nanoparticle-Based Aerogels and Xerogels by Inkjet Printing.

Nanoparticle-based voluminous 3D networks with low densities are a unique class of materials and are commonly known as aerogels. Due to the high surface-to-volume ratio, aerogels and xerogels might be suitable materials for applications in different fields, e.g.

Versatile route to core-shell reinforced network nanostructures.

In this work we present the generation of new core-shell network nanostructures of macroscopic dimensionality by a two-step process analogous to the seeded-growth method in colloidal nanoparticle modification. The nanoparticle-based core network is assembled first and in a separate second step it is coated with a continuous metal oxide shell by sol-gel methods. The interparticle contact of the nanoparticles comprising the core network is kept intact throughout the process.

Metal-Organic Framework Co-MOF-74-Based Host-Guest Composites for Resistive Gas Sensing.

Increasing demands in the field of sensing, especially for gas detection applications, require new approaches to chemical sensors. Metal-organic frameworks (MOFs) can play a decisive role owing to their outstanding performances regarding gas selectivity and sensitivity. The tetrathiafulvalene (TTF)-infiltrated MOF, Co-MOF-74, has been prepared following the host-guest concept and evaluated in resistive gas sensing.