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. To demonstrate the feasibility of cation exchange on such macroscopic nanomaterials, the cation exchange on CdSe/CdS core/shell and CdS nanorod based lyogels to Cu2-xSe/Cu2-xS and Cu2-xS and the reversible exchange back to CdSe/CdS and CdS lyogels is presented. These copper-based lyogels can also be used as an intermediate state on the way to other metal chalcogenide-based macroscopic structures. By reversed cation exchange back to cadmium an additional proof is given, that the crystal structures remain unchanged. It is shown that cation exchange reactions can also be transferred to macroscopic objects like aerogels or lyogels. This procedure additionally allows the access of aerogels which cannot be synthesized via direct destabilization of the respective colloidal solutions.

Inside/Outside: Post-Synthetic Modification of the Zr-Benzophenonedicarboxylate Metal-Organic Framework.

The Zr-based metal-organic framework, Zr-bzpdc-MOF, contains the photoreactive linker molecule benzophenone-4,4'-dicarboxylate (bzpdc) which imparts the possibility for photochemical post-synthetic modification. Upon irradiation with UV light, the keto group of the benzophenone moiety will react with nearly every C-H bond-containing molecule. Within this paper, we further explore the photochemical reactivity of the Zr-bzpdc-MOF, especially with regard to which restrictions govern internal versus external reactions. We show that apart from reactions with C-H bond-containing molecules, the MOF reacts also with water. By studying the reactivity versus linear alcohols we find a clear delineation in that shorter alcohol molecules (up to butanol as a borderline case) react with photoexcited keto groups throughout the whole crystals whereas longer ones react only with surface-standing keto groups. In addition, we show that with the alkanes n-butane to n-octane, the reaction is restricted to the outer surface. We hypothesize that the reactivity of the Zr-bzpdc-MOF versus different reagents depends on the accessibility of the pore system which in turn depends mainly on the size of the reagents and on their polarity. The possibility to direct the post-synthetic modification of the Zr-bzpdc-MOF (selective modification of the whole pore system versus surface modification) gives additional degrees of freedom in the design of this metal-organic framework for shaping and for applications.

Solvent-assisted linker exchange as a tool for the design of mixed-linker MIL-140D structured MOFs for highly selective detection of gaseous H2S.

A MIL-140D-sdc framework has been used as a highly stable backbone for the introduction of 4,4'-azobenzene dicarboxylic acid (H2 abdc) via solvent-assisted ligand exchange (SALE). The implemented azo groups can serve as coordination sites for copper ions. These can exchange ligands with different gases, but show a high selectivity against H2S, which makes this material promising for potential sensor applications.

A Low-Temperature Approach for the Phase-Pure Synthesis of MIL-140 Structured Metal-Organic Frameworks.

In a systematic investigation, the synthesis of metal-organic frameworks (MOFs) with MIL-140 structure was studied. The precursors of this family of MOFs are the same as for the formation of the well-known UiO-type MOFs although the synthesis temperature for MIL-140 is significantly higher. This study is focused on the formation of Zr-based MIL-140 MOFs with terephthalic acid (H2 bdc), biphenyl-4,4'-dicarboxylic acid (H2 bpdc), and 4,4'-stilbenedicarboxylic acid (H2 sdc) and the introduction of synthesis field diagrams to discover parameters for phase-pure products. In this context, a MIL-140 network with H2 sdc as linker molecule is first reported. Additionally, an important aspect is the reduction of the synthesis temperature to make MIL-140 MOFs more accessible even though linkers with a more delicate nature are used. The solvothermal syntheses were conducted in highly concentrated reaction mixtures whereby a targeted synthesis to yield the MIL-140 phase is possible. Furthermore, the effect of the often-used modulator approach is examined for these systems. Finally, the characteristics of the synthesized MOFs are compared with physisorption measurements, thermogravimetric analyses, and scanning electron microscopy.

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. By analyzing the local elemental distribution, the shells can be shown to be homogeneous over the macroscopic network monolith. The shell network can be used to considerably reinforce the mechanical strength of the final core-shell network structure.

Continuous improvement process: ortho-geriatric co-management of proximal femoral fractures.

OBJECTIVE: The objective of the current study was to evaluate the effect of a quality management system on treatment and care delivery of proximal femoral fractures. Specifically, our hypothesis was that the "plan-do-check-act (PDCA)" philosophy of the ISO 9001 quality management system results in a continuous improvement process. METHODS: 1015 proximal femoral fractures were prospectively included into a hip fracture database over a 5-year period, after a restructuring process with implementation of clinical pathways and standard operation procedures. A close and structured ortho-geriatric co-management (certified ortho-geriatric center) was the basis for treatment. ISO 9001 certification was granted for the first time in 2012. Procedural and patient outcome parameters were analyzed by year and evaluated statistically using SPSS 25.0. RESULTS: In both categories (procedural and outcome) significant changes could be detected during the 5-year period, e.g., significant reduction of time to surgery for the first 2 years, improvement in discharge management, and reduction of surgical complications. However, no significant changes could be demonstrated for mortality or internal complications such as pneumonia, urinary tract infections, or postoperative delirium. However, the incidence of the latter was already on a very low level at the onset of the quality improvement process. CONCLUSION: We could show a relevant and continuous improvement of several quality indicators during a 5-year period after implementation of a quality management system based on the PDCA philosophy for the treatment of proximal femoral fractures in elderly patients. However, other parameters (internal complications, cost-effectiveness, etc.) need our close attention in the future.