The properties of metal nanoclusters depend on both their structures and electronic states. However, in contrast to the significant advances achieved in the synthesis of structurally well-defined metal nanoclusters, systematic control of their electronic states is still challenging. In particular, stimuli-responsive and reversible control of the electronic states of metal nanoclusters is attractive from the viewpoint of their practical applications. Recently, we developed a synthesis method for atomically precise Ag nanoclusters using polyoxometalates (POMs) as inorganic ligands. Herein, we exploited the acid/base nature of POMs to reversibly change the electronic states of an atomically precise {Ag27} nanocluster via protonation/deprotonation of the surrounding POM ligands. We succeeded in systematically controlling the electronic states of the {Ag27} nanocluster by adding an acid or a base (0–6 equivalents), which was accompanied by drastic changes in the ultraviolet-visible absorption spectra of the nanocluster solutions. These results demonstrate the great potential of Ag nanoclusters for unprecedented applications in various fields such as sensing, biolabeling, electronics, and catalysis.The electronic states of Ag nanoclusters were reversibly controlled driven by protonation/deprotonation of polyoxometalate ligands.相似文献
The change in polymer distribution during depolymerization in which monomer molecules are severed one by one from the chain ends, is considered. Assuming irreversible depolymerization and equal reactivity of all the chain ends, a general formula to calculate the MWD is proposed. After the removal of monomers severed from the chains, the MWDs of depolymerized polymers always approach the most probable distribution whose PDI is practically equal to 2. It may appear to be counterintuitive, but the average MWs of polymers may increase during chain scission when the initial distribution is broader than the most probable (PDI > 2). The interpretation of the MWD data of polymers during depolymerization, such as those obtained by GPC, are not straightforward especially for the initial broad MWDs.
Some 2‐isopropenyl‐2,3‐dihydronaphtho[2,3‐b]furan‐4,9‐diones la‐f,b',f were prepared by one‐step cyclizations of 2‐hydroxy‐1,4‐naphthoquinones 2a‐f with 1,4‐dibromo‐2‐methyl‐2‐butene ( 3 ). 相似文献
To understand the fundamental aspects of the polycondensation reaction of hydrolyzed tetraethoxysilane (TEOS) and silanol‐terminated poly(dimethylsiloxane) (PDMS), we modeled the reaction system as a step‐growth polymerization of A4 and polydisperse A2, assuming the reactivities of all functional groups are equal. The analytical solution for the weight‐average molecular weight is developed, and in addition, a Monte Carlo simulation is conducted to investigate the detailed structural development. It was found that as long as the molecular weight of PDMS is much larger than TEOS, the apparent behavior is significantly different from usual gelling systems. The gel point is relatively insensitive to the weight fraction of crosslinker (TEOS), the polydispersity index may decrease during polymerization before the rapid increase to infinity, and the molecular weight distribution profile may not show a significant broadening toward gelation. Even though the present model assumes a complete random reaction process among functional groups, formation of a heterogeneous structure in which a tight core consisting of TEOS‐based molecules is surrounded by soft PDMS chains was observed in the Monte Carlo simulation. 相似文献
In our previous paper, we reported that amphiphilic Ir complex–peptide hybrids (IPHs) containing basic peptides such as KK(K)GG (K: lysine, G: glycine) (e.g., ASb-2) exhibited potent anticancer activity against Jurkat cells, with the dead cells showing a strong green emission. Our initial mechanistic studies of this cell death suggest that IPHs would bind to the calcium (Ca2+)–calmodulin (CaM) complex and induce an overload of intracellular Ca2+, resulting in the induction of non-apoptotic programmed cell death. In this work, we conduct a detailed mechanistic study of cell death induced by ASb-2, a typical example of IPHs, and describe how ASb-2 induces paraptotic programmed cell death in a manner similar to that of celastrol, a naturally occurring triterpenoid that is known to function as a paraptosis inducer in cancer cells. It is suggested that ASb-2 (50 µM) induces ER stress and decreases the mitochondrial membrane potential (ΔΨm), thus triggering intracellular signaling pathways and resulting in cytoplasmic vacuolization in Jurkat cells (which is a typical phenomenon of paraptosis), while the change in ΔΨm values is negligibly induced by celastrol and curcumin. Other experimental data imply that both ASb-2 and celastrol induce paraptotic cell death in Jurkat cells, but this induction occurs via different signaling pathways. 相似文献