Despite the contribution of changes in pancreatic β‐cell mass to the development of all forms of diabetes mellitus, few robust approaches currently exist to monitor these changes prospectively in vivo. Although magnetic‐resonance imaging (MRI) provides a potentially useful technique, targeting MRI‐active probes to the β cell has proved challenging. Zinc ions are highly concentrated in the secretory granule, but they are relatively less abundant in the exocrine pancreas and in other tissues. We have therefore developed functional dual‐modal probes based on transition‐metal chelates capable of binding zinc. The first of these, Gd ?1 , binds ZnII directly by means of an amidoquinoline moiety (AQA), thus causing a large ratiometric Stokes shift in the fluorescence from λem=410 to 500 nm with an increase in relaxivity from r1=4.2 up to 4.9 mM ?1 s?1. The probe is efficiently accumulated into secretory granules in β‐cell‐derived lines and isolated islets, but more poorly by non‐endocrine cells, and leads to a reduction in T1 in human islets. In vivo murine studies of Gd ?1 have shown accumulation of the probe in the pancreas with increased signal intensity over 140 minutes. 相似文献
Fluorenes are a commonly encountered structural motif in materials science, pharmaceutical chemistry, and organic synthesis. Among various strategies towards the synthesis of this unique structure, transition metal‐catalyzed functionalization has emerged as one of the most efficient methods. This Minireview presents an overview of the recent advances in this emerging area by highlighting the reactions’ specificity and applicability and, where possible, provides a mechanistic rationale. 相似文献
By carefully selecting an existing synthetic strategy and suitable coordination subunits, constructing desired coordination geometries is no longer that difficult to accomplish. Herein, a new strategy to construct a series of unprecedented structures by using conjugated Cp*Rh‐based complex BN‐OTf (Cp*=η5‐C5Me5) as the building block is proposed. DFT calculations revealed extensive delocalized π bonds in the subunit. With BN‐OTf , rectangular macrocycles TN‐bpy and TN‐bpe were controllably synthesized. Single‐crystal XRD studies confirmed one‐dimensional stacking channels for the tetranuclear structure. Notably, the starting ligand imidazole‐4,5‐dicarboxylate was found to act not only as a tetradentate but also as a hexadentate ligand that can coordinate to further metal ions. Subsequently, [4 Rh+1 M] heterometallic complexes HMZ (M=Cu and Zn) were accessed by chelating borderline hard/soft Lewis acids. With TN‐Linker or HMZ , two routes resulted in the [8 Rh+2 M] heterometallic cages HMC (M=Cu and Zn) with excellent crystallinity and stability. Surprisingly, when BN‐OTf bonded to rhodium itself, triangular prisms TP‐Linker were obtained with high solubility after being linked by bipyridine linkers. Both the X‐ray structure and 1H NMR spectrum confirmed the novel isomerization of the triangular structures. All of the compounds were obtained in high yields and were fully characterized by 1H NMR spectroscopy, elemental analysis, IR spectroscopy, and in most cases single‐crystal X‐ray structure determination. 相似文献
Well‐defined AbBA triblock bottlebrush with poly(N,N‐dimethyl acrylamide) (PAm) as A block and polyacrylate, densely grafted with poly(tert‐butyl acrylate)‐block‐polystyrene (PBA‐b‐PS), as brush bB block is prepared by controlled radical polymerization and click chemistry. The triblock copolymer with a composition of PAm200‐b‐b(PBA14‐b‐PS47)167‐b‐PAm200 is obtained and is further transformed into PAm200‐b‐b(PAA14‐b‐PS47)167‐b‐PAm200 by hydrolysis of the PBA segment into poly(acrylic acid) (PAA). In a mixture of N,N‐dimethylformamide (DMF) and methanol, a poor solvent of bB block, PAm200‐b‐b(PAA14‐b‐PS47)167‐b‐PAm200 self‐assembled into disk‐like platelets, which have an internal lamellar structure by further microphase‐separation of PAA‐b‐PS branches in 2D. Moreover, Ag nanoparticles are aligned by PAA segments along the disk to form a pattern.
Recent advances in the applications of transition metal chalcogenides/graphene (TMC/graphene) nanocomposites in future energy storage and conversion are reviewed. The synthesis processes and structures of TMC/graphene, workingpriciple of evergy energy device, and the electrochemical performances are summarized. 相似文献
A novel SrTiO3/BiPO4 heterostructure with different amounts of SrTiO3 have been successfully prepared through the hydrothermal process. The photocatalysts were characterized by X-ray powder diffraction, UV–Vis diffuse reflectance spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The photocatalytic performance was evaluated by degrading the methylene blue dye solution under UV light. Results showed that the samples displayed excellent photocatalytic degradation efficiency due to the highly efficient suppression of the recombination of electron–hole pairs. A possible mechanism of SrTiO3/BiPO4 heterojunctions was discussed. The research indicated that the as-prepared SrTiO3/BiPO4 heterogeneous photocatalyst can be used as an effective material for degrading industrial organic wastewater. 相似文献