Preparation of raspberry-like nanocapsules by the combination of Pickering emulsification and solvent displacement technique

Well-defined raspberry-like nanocapsules were prepared by the combination of Pickering emulsification and solvent displacement technique by using silica particles as stabilizer and hexadecane (HD) as soft template. The formation of the capsule morphology is caused by the phase separation of poly(styrene-co-4-vinyl pyridine) (poly(St-co-4-VP)) in the droplets due to the diffusion of good solvent for the (co)polymer to the aqueous continuous phase. The size of capsules was successfully reduced from tens of micrometers in the dispersion by simply stirring to the nanorange by the employment of sonication and Ostwald ripening. The formation of silica-particles-armored nanocapsules was confirmed by transmission electron microscopy (TEM), high-resolution scanning electron microscopy (HRSEM), dynamic light scattering (DLS), and zeta potential measurement. The colloidal stability and particle properties, including size and morphology, depend on the amount of HD, and copolymers, the sonication time, the dispersion pH value, the type of solvent, and the copolymer composition.     

THz Detection of Biomolecules in Aqueous Environments—Status and Perspectives for Analysis Under Physiological Conditions and Clinical use

Bioanalytical THz sensing techniques have proven to be an interesting and viable tool for the label-free detection and analysis of biomolecules. However, a major challenge for THz bioanalytics is to perform investigations in the native aqueous environments of the analytes. This review recapitulates the status and future requirements for establishing THz biosensing as a complementary toolbox in the repertoire of standard bioanalytic methods. The potential use in medical research and clinical diagnosis is discussed. Under these considerations, this article presents a comprehensive categorization of biochemically relevant analytes that have been investigated by THz sensing techniques in aqueous media. The detectable concentration levels of ions, carbohydrates, (poly-)nucleotides, active agents, proteins and different biomacromolecules from THz experiments are compared to characteristic physiological concentrations and lower detection limits of state-of-the-art bioanalytical methods. Finally, recent experimental developments and achievements are discussed, which potentially pave the way for THz analysis of biomolecules under clinically relevant conditions.

     

Irreversible Structural Changes of Copper Hexacyanoferrate Used as a Cathode in Zn-Ion Batteries

The structural changes of copper hexacyanoferrate (CuHCF), a Prussian blue analogue, which occur when used as a cathode in an aqueous Zn-ion battery, are investigated using electron microscopy techniques. The evolution of Zn_xCu_1−xHCF phases possessing wire and cubic morphologies from initial CuHCF nanoparticles are monitored after hundreds of cycles. Irreversible introduction of Zn ions to CuHCF is revealed locally using scanning transmission electron microscopy. A substitution mechanism is proposed to explain the increasing Zn content within the cathode material while simultaneously the Cu content is lowered during Zn-ion battery cycling. The present study demonstrates that the irreversible introduction of Zn ions is responsible for the decreasing Zn ion capacity of the CuHCF cathode in high electrolyte concentration.     

Persistent Room Temperature Phosphorescence from Triarylboranes: A Combined Experimental and Theoretical Study

Achieving highly efficient phosphorescence in purely organic luminophors at room temperature remains a major challenge due to slow intersystem crossing (ISC) rates in combination with effective non‐radiative processes in those systems. Most room temperature phosphorescent (RTP) organic materials have O‐ or N‐lone pairs leading to low lying (n, π*) and (π, π*) excited states which accelerate k_isc through El‐Sayed's rule. Herein, we report the first persistent RTP with lifetimes up to 0.5 s from simple triarylboranes which have no lone pairs. RTP is only observed in the crystalline state and in highly doped PMMA films which are indicative of aggregation induced emission (AIE). Detailed crystal structure analysis suggested that intermolecular interactions are important for efficient RTP. Furthermore, photophysical studies of the isolated molecules in a frozen glass, in combination with DFT/MRCI calculations, show that (σ, B p)→(π, B p) transitions accelerate the ISC process. This work provides a new approach for the design of RTP materials without (n, π*) transitions.     

Enantioselective Catalytic [4+1]-Cyclization of ortho-Hydroxy-para-Quinone Methides with Allenoates

The first highly asymmetric catalytic synthesis of densely functionalized dihydrobenzofurans is reported, which starts from ortho-hydroxy-containing para-quinone methides. The reaction relies on an unprecedented formal [4+1]-annulation of these quinone methides with allenoates in the presence of a commercially available chiral phosphine catalyst. The chiral dihydrobenzofurans were obtained as single diastereomers in yields up to 90 % and with enantiomeric ratios up to 95:5.     

Solid State Metathesis Reactions in Various Applications

Solid state metathesis reactions have been studied in fused silica tubes, by differential thermal analysis, and by X‐ray powder diffraction. A selection of reactions between metal (La, Nb, and Ni) chlorides and lithium nitride or lithium acetylide were investigated to get more insight into reaction pathways and intermediate reaction stages that may be adopted on course of the formation of metal nitrides or carbides. Intermediate compounds are considered to be important because they can control the reactivity of a system. Such compounds were traced by changing the molar ratios of reaction partners away from the salt‐balanced binary metal nitride or carbide target compositions. New preparative perspectives are discovered when metal chlorides were reacted with lithium nitridoborate or lithium cyanamide. Due to their reductive nature towards several d‐block metal chlorides, (BN₂)^3‐ and (CN₂)^2‐ react to form metals or metal nitrides plus X‐ray amorphous BN, and probably C₃N₄. With lanthanum chloride they can react to form nitridoborates and nitridocarbonates. The metathesis reaction between lithium cyanamide and cyanuric chloride (C₃N₃Cl₃) instead of metal chloride was studied for the synthesis of C₃N₄.     

Synthese und Charakterisierung von Fluorenylgallaten und Fluorenylindaten

Synthesis and Characterization of Fluorenyl Gallates and Fluorenyl Indates GaCl₃ reacts with Fluorenyllithium (LiFl) in the ratio 1:4 in Et₂O to [Li(THF)₄][GaFl₄] ( 1 ). The addition of DME (1,2-dimethoxyethane) to solutions of 1 in THF leads to [Li(DME)₃][GaFl₄] ( 2 ) under replacement of THF molecules by DME molecules in the coordination sphere of the Li⁺ ions. Treatment of InCl with LiFl in Et₂O and recrystallization from THF gives [Li(THF)₄][ClInFl₃] ( 3 ), which is formed by an disproportionation reaction. 3 can also be obtained by the reaction of InCl with FlZnCl/LiCl in Et₂O and recrystallization from THF. 1 and 2 crystallize from THF and THF/DME as [Li(THF)₄][GaFl₄] · THF ( 1 · THF) and [Li(DME)₃][GaFl₄] · THF ( 2 · THF), respectively. Crystalline 3 is isolated from the reaction of InCl and FlZnCl/LiCl, while the reaction mixture of InCl and LiFl gives after recrystallization in THF 3 · 1,5 THF. The gallate ions in 1 and 2 differ mainly in the position of the fluorenyl ligands. The unit cells of 3 and 3 · 1,5 THF contain two crystallographic unique ion pairs of [Li(THF)₄][ClInFl₃].