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Materials that intrinsically exhibit localized surface plasmon resonance (LSPR) in the visible region have been predominantly researched on nanoparticles (NPs) composed of coinage metals, namely Au, Ag, and Cu. Here, as a coinage metal-free intermetallic NPs, colloidal PtIn 2 NPs with a C1 (CaF 2 -type) crystal structure are synthesized by the liquid phase method, which evidently exhibit LSPR at wavelengths similar to face-centered cubic (fcc)-Au NPs. Computational simulations pointed out differences in the electronic structure and photo-excited electron dynamics between C1-PtIn 2 and fcc-Au NPs; reduces interband transition and stronger screening with smaller number of bound d-electrons compare with fcc-Au are unique origins of the visible plasmonic nature of C1-PtIn 2 NPs. These results strongly indicate that the intermetallic NPs are expected to address the development of alternative plasmonic materials by tuning their crystal structure and composition., (© 2024 The Authors. Advanced Science published by Wiley-VCH GmbH.)

Nitrobenzene (NB) is a highly toxic chemical and a cause for concern to human health and the environment. Hence, it is worth designing new efficient and robust sensing platforms for NB. In this study, we present three newly synthesized luminescent silver cluster-based coordination polymers, {[Ag 10 (StBu) 6 (CF 3 COO) 4 (hpbt)] (DMAc) 2 (CH 3 CN) 2 } n (hpbt=N,N,N',N'N",N"-hexa(pyridine-4-yl)benzene-1,3,5-triamine), [Ag 12 (StBu) 6 (CF 3 COO) 6 (bpva) 3 ] n (bpva=9,10-Bis(2-(pyridin-4-yl)vinyl)anthracene), and {[Ag 12 (StBu) 6 (CF 3 COO) 6 (bpb)(DMAc) 2 (H 2 O) 2 ] (DMAc) 2 } n (bpb=1,4-Bis(4-pyridyl)benzene) composed of Ag 10 , Ag 12 and Ag 12 cluster cores, respectively, connected by multidentate pyridine linkers. In addition, two new luminescent polymorphic silver(I)-based coordination polymers, [Ag(CF 3 COO)(dpa)] n (dpa=9,10-di(4-pyridyl)anthracene) referred to as Agdpa (H) and Agdpa (R), where H and R denote hexagon- and rod-like crystal shapes, respectively, have been prepared. The coordination polymers exhibit highly sensitive luminescence quenching effects to NB, attributed to the π-π stacking interactions between the polymers and NB as well as the electron-withdrawing character of NB., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

For the realization of a next-generation energy society, further improvement in the activity of water-splitting photocatalysts is essential. Platinum (Pt) is predicted to be the most effective cocatalyst for hydrogen evolution from water. However, when the number of active sites is increased by decreasing the particle size, the Pt cocatalyst is easily oxidized and thereby loses its activity. In this study, a method to load ultrafine, monodisperse, metallic Pt nanoclusters (NCs) on graphitic carbon nitride is developed, which is a promising visible-light-driven photocatalyst. In this photocatalyst, a part of the surface of the Pt NCs is protected by sulfur atoms, preventing oxidation. Consequently, the hydrogen-evolution activity per loading weight of Pt cocatalyst is significantly improved, 53 times, compared with that of a Pt-cocatalyst loaded photocatalyst by the conventional method. The developed method is also effective to enhance the overall water-splitting activity of other advanced photocatalysts such as SrTiO 3 and BaLa 4 Ti 4 O 15 ., (© 2023 The Authors. Small published by Wiley-VCH GmbH.)

Suppressing the amount of carbon dioxide in the atmosphere is an essential measure toward addressing global warming. Specifically, the photocatalytic CO 2 reduction reaction (CRR) is an effective strategy because it affords the conversion of CO 2 into useful carbon feedstocks by using sunlight and water. However, the practical application of photocatalyst-promoting CRR (CRR photocatalysts) requires significant improvement of their conversion efficiency. Accordingly, extensive research is being conducted toward improving semiconductor photocatalysts, as well as cocatalysts that are loaded as active sites on the photocatalysts. In this review, we summarize recent research and development trends in the improvement of cocatalysts, which have a significant impact on the catalytic activity and selectivity of photocatalytic CRR. We expect that the advanced knowledge provided on the improvement of cocatalysts for CRR in this review will serve as a general guideline to accelerate the development of highly efficient CRR photocatalysts., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Monolayer protected Au nanocluster catalysts are known to undergo structural changes during catalytic reactions, including dissociation and migration of ligands onto the support, which strongly affects their activity and stability. To better understand how the nature of ligands influences the catalytic activity of such catalysts, three types of ceria supported Au nanoclusters with different kinds of ligands (thiolates, phosphines and a mixture thereof) have been studied, employing CO oxidation as model reaction. The thiolate-protected Au 25 /CeO 2 showed significantly higher CO conversion after activation at 250 °C than the cluster catalysts possessing phosphine ligands. Temperature programmed oxidation and in situ infrared spectroscopy revealed that while the phosphine ligands seemed to decompose and free Au surface was exposed, temperatures higher than 250 °C are required to efficiently remove them from the whole catalyst system. Moreover, the presence of residues on the support seemed to have much greater influence on the reactivity than the gold particle size., Competing Interests: The authors declare no conflict of interest., (© 2022 The Authors. ChemCatChem published by Wiley-VCH GmbH.)

Recently, the creation of new heterogeneous catalysts using the unique electronic/geometric structures of small metal nanoclusters (NCs) has received considerable attention. However, to achieve this, it is extremely important to establish methods to remove the ligands from ligand-protected metal NCs while preventing the aggregation of metal NCs. In this study, the ligand-desorption process during calcination was followed for metal-oxide-supported 2-phenylethanethiolate-protected gold (Au) 25-atom metal NCs using five experimental techniques. The results clearly demonstrate that the ligand-desorption process consists of ligand dissociation on the surface of the metal NCs, adsorption of the generated compounds on the support and desorption of the compounds from the support, and the temperatures at which these processes occurred were elucidated. Based on the obtained knowledge, we established a method to form a metal-oxide layer on the surface of Au NCs while preventing their aggregation, thereby succeeding in creating a water-splitting photocatalyst with high activity and stability., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Metal nanoclusters (NCs), which are composed of about 250 or fewer metal atoms, possess great potential as novel functional materials. Fundamental research on metal NCs gradually started in the 1960s, and since 2000, thiolate (SR)-protected metal NCs have been the main metal NCs actively studied. The precise and systematic isolation of SR-protected metal NCs has been achieved in 2005. Since then, research on SR-protected metal NCs for both basic science and practical application has rapidly expanded. This review describes this recent progress in the field of SR-protected metal NCs in three areas: synthesis, understanding, and application. Specifically, the recent study of alloy NCs and connected structures composed of NCs is highlighted in the "synthesis" section, recent knowledge on the reactivity of NCs in solution is highlighted in the "understanding" section, and the applications of NCs in the energy and environmental field are highlighted in the "application" section. This review provides insight on the current state of research on SR-protected metal NCs and discusses the challenges to be overcome for further development in this field as well as the possibilities that these materials can contribute to solving the problems facing modern society., (© 2021 Wiley-VCH GmbH.)

Metal nanoclusters (NCs) have a particle size of about one nanometer, which makes them the smallest unit that can give a function to a substance. In addition, metal NCs possess physical and chemical properties that are different from those of the corresponding bulk metals. Metal NCs with such characteristics are expected to be important for use in nanotechnology. Research on the precise synthesis of metal NCs and elucidation of their physical/chemical properties and functions is being actively conducted. When metal NCs are alloyed, it is possible to obtain further various electronic and geometrical structures and functions. Thus, research on alloy NCs has become a hot topic in the study of metal NCs and the number of publications on alloy NCs has increased explosively in recent years. Such publications have provided much insight into the effects of alloying on the electronic structure and function of metal NCs. However, the rapid increase in knowledge has made it difficult for researchers (especially those new to the field) to grasp all of it. Therefore, in this review, we summarize the reported chemical composition, geometrical structure, electronic structure, and physical and chemical properties of Au n-x M x (SR) m , Ag n-x M x (SR) m , Au n-x M x (PR 3 ) l (SR) m , and Ag n-x M x (PR 3 ) l (SR) m (Au=gold, Ag=silver, M=heteroatom, PR 3 =phosphine, and SR=thiolate) NCs. This review is expected to help researchers understand the characteristics of alloy NCs and lead to clear design guidelines to develop new alloy NCs with intended functions., (© 2020 Wiley-VCH GmbH.)

Invited for the cover of this issue is the group of Yuichi Negishi at Tokyo University of Science. The image depicts the alloy nanoclusters reported in this review. Read the full text of the article at 10.1002/chem.202001877., (© 2020 Wiley-VCH GmbH.)

The activity of many water-splitting photocatalysts could be improved by the use of Rh III -Cr III mixed oxide (Rh 2-x Cr x O 3 ) particles as cocatalysts. Although further improvement of water-splitting activity could be achieved if the size of the Rh 2-x Cr x O 3 particles was decreased further, it is difficult to load ultrafine (<2 nm) Rh 2-x Cr x O 3 particles onto a photocatalyst by using conventional loading methods. In this study, a new loading method was successfully established and was used to load Rh 2-x Cr x O 3 particles with a size of approximately 1.3 nm and a narrow size distribution onto a BaLa 4 Ti 4 O 15 photocatalyst. The obtained photocatalyst exhibited an apparent quantum yield of 16 %, which is the highest achieved for BaLa 4 Ti 4 O 15 to date. Thus, the developed loading technique of Rh 2-x Cr x O 3 particles is extremely effective at improving the activity of the water-splitting photocatalyst BaLa 4 Ti 4 O 15 . This method is expected to be extended to other advanced water-splitting photocatalysts to achieve higher quantum yields., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Bcl6, a sequence-specific transcriptional repressor, is important for generation and maintenance of memory CD8(+) T cells. Although memory CD8(+) T cells are generated from effector CD8(+) T cells, a role for Bcl6 in effector CD8(+) T cells is largely unknown. We show here that Bcl6 expression was transiently induced in activated CD8(+) T cells and continuously up-regulated in effector CD8(+) T cells. The amount of granzyme B mRNA among effector molecules produced by effector CD8(+) T cells inversely correlated with the amount of Bcl6 mRNA in CD8(+) T cells. Overexpression of Bcl6 in CD8(+) T cells resulted in lower killing activity at their effector phase, supporting the reduction of granzyme B expression in effector CD8(+) T cells by Bcl6. We identified a putative Bcl6-binding DNA sequence in the promoter region of the granzyme B gene. Binding of Bcl6 to the Bcl6-binding sequence was detected in naive CD8(+) T cells but not in activated CD8(+) T cells by chromatin immunoprecipitation assay. Furthermore, the Bcl6-binding sequence was required for Bcl6 to repress the luciferase reporter gene expression controlled by the granzyme B promoter. Thus, the granzyme B gene is a molecular target of Bcl6 in effector CD8(+) T cells.

Clast5/Stra13/DEC1 is a member of the helix-loop-helix family of transcriptional repressors. We have previously shown that Clast5 is rapidly down-regulated upon B cell activation and its overexpression inhibits cell cycle progression in B lymphoma cells. In the present study, we show that Clast5 expression is developmentally regulated during B cell differentiation, being expressed at the progenitor B cells, down-regulated at the precursor B cells, elevated in immature and mature resting B lymphocytes, and down-regulated again in germinal center B cells. To investigate the function of Clast5 in regulating lymphocyte development, we have generated transgenic mice expressing Clast5 in B- and T-lineage cells (Clast5-Tg). Clast5-Tg mice grew and bred normally but their spleen and thymus cellularity was reduced compared with control littermates. The development of B cells in the bone marrow and T cells in the thymus was impaired, with the expansion of progenitor B and T cells most strongly affected. The frequency of IL-7-responsive cells in the bone marrow of Clast5-Tg mice was reduced by >80% and their proliferative response to IL-7 was also compromised. Mature B cells from Clast5-Tg mice were hyporesponsive to antigen receptor cross-linking and exhibited mild reduction in the proliferative response to CD40 ligation or lipopolysaccharide stimulation. Moreover, the development of germinal center B cells and antibody production against a T-dependent antigen were reduced in Clast5-Tg mice. These results reveal a critical role for Clast5/Stra13/DEC1 in negatively regulating lymphocyte development and function in vivo.

We have identified a novel subset of early B lineage cells in the mouse bone marrow (BM) by GL7 expression on cell surface. GL7(+)B220(low) BM cells have a large cell size and are CD43(-to low), CD95(-), Sca-1(-), I-A(low), IgM(-) and IgD(-), suggesting that they are large pre-B cells. These BM cells express lambda5 and VpreB but not terminal deoxytransferase (TdT) and Bcl-2, and approximately 50 % of them are in cell cycle. This fraction was not detected in BM cells of Rag-1-deficient and Scid mice, supporting that GL7(+)B220(low) BM cells belong to fraction C' and D according to Hardy's criteria or to an early large pre-B-II fraction according to Melchers-Rolink's criteria. Furthermore, GL7(+)B220(low) BM cells can differentiate into IgM(+) immature B cells in co-culture with stromal cells. These results suggest that B lymphocytes pass through the GL7(+) pre-B cell stage during differentiation in the BM. Thus, GL7 is the critical marker to define the proliferation stage of large pre-B cells.

It was previously shown that in C57BL/6 mice chronic suppression of an idiotypically defined subset of lambda 1 chain-bearing anti-(4-hydroxy-3-nitrophenyl)acetyl (NP) antibodies is achieved by neonatal administration of allogeneic monoclonal anti-idiotope antibodies reactive with this subset, or by NP coupled to mouse immunoglobulin. The present data show that isologous monoclonal anti-idiotope antibodies have the same effect. In contrast, antibodies against constant region determinants of lambda 1, mu or delta immunoglobulin chains failed to induce chronic suppression of the same antibody subset. Furthermore, the effect of the anti-idiotope antibodies was neutralized by idiotypic antibodies of the IgG1 class, injected before or together with the anti-idiotype. These results suggest that the mere complexing of idiotypic molecules on the B cell surface or in the circulation is insufficient for the induction of chronic idiotype suppression. In the present system, induction appears to require the binding of a ligand to idiotype-bearing receptor V regions, expressed on the surface of B (or T?) cells.

The xid gene in mice controls a recessive defect resulting in the absence of a late maturing subset of B cells. Whereas the responsiveness pattern of these mice have been clearly defined in terms of their ability or inability to make antibodies to certain classes of thymus-independent antigens, there are conflicting reports in regard to affinity maturation of the antibody response to thymus-dependent antigens. To resolve this controversial issue, the two major isotypes of the IgG response, namely IgG1 and IgG2a were examined with a highly sensitive radioimmunoassay that measures both the magnitude and affinity of the anti-2,4-dinitrophenyl antibody of each isotype in individual serum samples. It was found that the xid gene reduced the amount but not affinity of the IgG1 antibody produced, whereas it impaired the whole IgG2a responses severely. In fact, mice carrying the defective gene were unable to mount a secondary IgG2a response, measured either quantitatively or qualitatively in terms of increased affinity. To test the possibility that Lyb3, an isogenic B cell-triggering receptor lacking in xid-mutant mice, plays a direct role in the maturation of the immune response, the antibody profile in normal mice immunized eigher with antigen alone or in combination with anti-Lyb3 receptor substantially elevated and accelerated the primary IgG2a response, whereas it had little effect on the IgG1 response.