A layered cesium titanate (Cs2Ti5O11) and a layered sodium titanate (Na2Ti3O7) were used to concentrate Cd(II) ion from aqueous solution. The reaction of aqueous solutions of cadmium(II) acetate with the cesium titanate was examined at room temperature under varied pH. An H type adsorption isotherm was obtained, indicating strong interactions between Cd(II) and the titanate. For the reaction of the sodium titanate with aqueous solutions of cadmium(II) acetate, the formation of cadmium carbonate was observed in addition to the ion exchange of Na2Ti3O7 with Cd(II). The maximum amounts of the collected Cd(II) were 1.28 mmol/g Cs2Ti5O11 and 1.16 mmol/g Na2Ti3O7, which were superior to the values (0.08–0.39 mmol/g adsorbent) reported for other inorganic ion exchangers such as clay minerals and zeolites.
It is commonly known that flexible structures and movable substituents are unfavorable for realizing intense luminescence with organic dyes. On the other hand, we show in this short review that excitation-driven boron complexes are promising platforms for obtaining stimuli-responsive luminescent materials with high sensitivity. Initially, we explained transformation of the valence of boron in heterofluorene from four to three-coordinate state through excitation-driven bond cleavage at the boron dative bond. The mechanism and stimuli-responsive luminescence with high sensitivity are illustrated. The next topic regards rational design of aggregation-induced emission (AIE)-active molecules, which are able to provide enhanced emission by aggregation. By employing theoretical calculations, it was possible to find a series of novel AIE-active skeletons from scratch. Stimuli-responsive luminescent chromism was also observed from the resulting molecules. The final topic is concerned with aryl–o-carborane dyads. It was recently found that rotation of the o-carborane unit proceeds triggered by photo-excitation. By regulating rotation behaviors, not only solid-state luminescence but also dual emission were obtained. The concept and several examples to offer applications of this new class of boron complexes are reviewed.
Recent years have marked substantial research interest in the design and development of photocatalyst materials for the conversion of solar to chemical energy. In this brief account, we present some of the recent research on silver-based plasmonic nanocatalysts supported on silica for their preparative techniques, characterization and efficient catalysis under visible light irradiation conditions. Ag nanoparticles (NPs) which can be prepared with different color and morphology, are explored for possible enhancement effects in catalytic performance activities under visible light irradiation. A number of combinations of Ag with other catalytically active metal NPs is studied for exploring the plasmonic enhancement activities. Ag NPs combined with single site Ti-oxide moiety is studied for the enhanced hydrogen production activity attributing to the Ag plasmonic effect under UV-vis light irradiation. The account is further elaborated by citing some recently reported works, plausible mechanism of enhancements, conclusions and outlook. We expect that the present account will provide insights into the design and investigation of catalytic performances in the visible light driven plasmon-mediated chemical reactions.
The field of chirality has seen a strong rejuvenation due to the observation of nanoscale chirality in plasmonic nanoparticles. This account presents recent advances in the field of plasmonic chirality. The various top-down and bottom-up methods adopted for the synthesis of optically active plasmonic nanomaterials are briefly discussed. After achieving significant progress in the synthesis and mechanistic understanding of chirality at the nanoscale, the major focus of researchers is currently set on finding suitable applications for the synthesized nanomaterials. While different applications such as circular polarizers, chiral sensing and catalysis have been proposed, we propose that plasmon-enhanced chiral signals have great potential for use in the detection and therapy of diseases. We therefore introduce recent developments in the use of chiral plasmonic responses in the biomedical field.
Two-dimensional metal oxide nanosheets are versatile materials for constructing artificial photosynthetic systems that can carry out photocatalytic processes such as water splitting and CO2 fixation. Nanosheets are anisotropic single-crystals that have thicknesses of 1–2 nm and lateral dimensions ranging from several hundreds of nanometers to a few micrometers. This structural feature is advantageous for use as heterogeneous photocatalysts, because the diffusion length of photogenerated electron/hole pairs to the surface can be shortened, with less probability of electron/hole recombination. In this Account, recent progress on the development of metal oxide nanosheets and related materials for applications in photocatalytic water splitting and CO2 fixation made by the authors' groups is described.
Photocatalytic reaction of trans-stilbene on TiO2 particles produces benzaldehyde with high selectivity in acetonitrile-water mixed solvent. Introduction of electron-donating substituents to the benzene rings accelerated the reaction. On the other hand, the rate was decelerated by electron-withdrawing substituents. These results suggest that the reaction proceeds by hydroperoxo or hydroperoxy, which were formed on TiO2 surface by UV irradiation, rather than free OH radicals.
Halloysite is a natural tubular aluminosilicate clay of ca. 50 nm diameter and 0.5–1.5 micrometers in length. The nanoarchitectural modification of halloysite inner/outer surfaces can be achieved through supramolecular and covalent interactions exploiting its different inside/outside chemistry (Al2O3/SiO2). The tubular morphology makes halloysite a prospective nanotemplate for core-shell structured mesoporous catalysts. Catalytic metals can be incorporated on the nanotubes’ outer surface or in the inner lumens with selective metal binding. 2–5 nm diameter Au, Ag, Pt, Pd, Co, Ru, Cu-Ni, Fe2O3, CoxBy, CdS, and CdxZn1−xS particles were templated on halloysite. In this work, CdS and Ru-containing halloysite based nanocatalysts were synthesized via modification with organic ligands and microwave-assisted wetness ion impregnation. The catalytic hydrogenation of benzene and its homologues as well as phenol was performed. The impacts of the core-shell architecture, the metal particle size and seeding density were optimized for high reaction efficiency. An efficient Co-halloysite catalyst was formed using azines as ligands, and it contained 16 wt. % of cobalt with hydrogen evolution rate of 3.0 L/min × g(cat). The mesocatalysts produced are based on a safe and cheap natural clay nanomaterial and may be scaled-up for industrial applications.
Self-assembly is omnipresent in nature. While natural self-assembly systems are complicated in structure, the simplification of natural systems while maintaining their inherent functionalities has proven to be a highly promising route towards artificial nanoarchitectonics with great potential for application. In this review, we summarize our recent works on self-assembling peptide-based nanoarchitectonics, where peptides with a simple molecular structure can modulate the assembly of various species in a flexible and controllable way and efficiently construct nanoarchitectonics with desired functionalities. Our recent findings regarding the applications of self-assembling peptides in the fields of biomimetic photosystems, oriented microtubes for optical waveguiding, and phototherapy are discussed in detail. In addition, the self-assembly mechanism and the effects of peptides on self-assembly are reviewed. This review is expected to provide an understanding of the role of peptides in the assembly of nanoarchitectonics and guidance towards the future design and application of novel functional peptide-modulated self-assembling materials.
The infrared (IR) absorption bands due to peptide bonds (amide bands) have long been used to determine the secondary structure of a peptide and to analyze intra- and intermolecular interactions between amides. In the present study, the dihedral angles of a residue in peptides have also been evaluated using the amide I IR band of two successive residues with isotope labeling. The two successive residues labeled with the 13C and 18O isotopes give the doublet amide I IR band and the intensity ratio (Rint) and the difference in peak position (Δν) of the doublet band were analyzed using GF matrix and ab initio molecular orbital calculations. We obtained the two-dimensional calculation maps of Rint and Δν against the two dihedral angles. The crossing point of the curves of Rint and Δν is the two dihedral angles of the measured residue. The evaluated dihedral angles of the simple peptides are compared with the reported values. We discuss the limitation and the application of the present method to biopolymers from the obtained results.
The dynamic and static nature of each hydrogen bond (HB) in acetic acid dimer (1), acetamide dimer (2a), thio- and seleno-derivatives of 2a (2b and 2c, respectively), and acetic acid–acetamide mixed dimer (3) was elucidated with QTAIM dual functional analysis (QTAIM-DFA). Such multi-HBs will form in 1–3, in close proximity in space, and interact mutually and strongly with each other. Perturbed structures generated using coordinates derived from the compliance force constants (Cij: the method being called CIV) are employed in QTAIM-DFA, for the establishment of the methodology to elucidate the nature of each HB in the multi-HBs. The dynamic nature of interactions with CIV is described as the “intrinsic dynamic nature of interactions”, since the coordinates corresponding to Cij are invariant to the choice of the coordinate system. Each HB in the multi-HBs of 1–3 are predicted to have the nature of CT-MC (molecular complex formation through charge transfer) appear at the regular closed shell region, which are stronger than each HB of the isomers of 1–3. The methodology to elucidate the nature of multi-HBs is well established, which employs the perturbed structures generated with CIV for QTAIM-DFA.
Novel perfluoroalkyl gelators without hydrogen bonds–bis(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctyl) isophthalate (1m), bis(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctyl) terephthalate (1p), and tris(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctyl) benzene-1,3,5-tricarboxylate (2)–were synthesized. Their molecular structures were investigated by density functional theory calculations at the B3LYP/cc-pVDZ level. The gelation abilities of 1m, 1p, and 2 were examined and compared to their normal octyl homologues 1m′, 1p′, and 2′. None of the gelators could be gelated in common organic solvents, but gelated well in fluorinated solvents.
The catalytic ability of Fe-iminobipyridine complexes ((BPI)FeBr2, BPI = iminobipyridine) for hydrosilylation of both a non-conjugated diene and a conjugated diene was investigated aiming at the production of organosilane compounds bearing a terminal olefin portion. Steric effects of (BPI)FeBr2 were controlled by the substituents at the terminal pyridine ring (R1), the imino carbon (R2), and the imino nitrogen (Ar) of the BPI ligand. As regards a non-conjugated diene, hydrosilylation of 1,7-octadiene with diphenylsilane (Ph2SiH2) produced a mixture of mono- and di-hydrosilylated compounds. To obtain the mono-hydrosilylated compound preferably in the 1:1 reaction of non-conjugated diene and silane, the substituent effect of the BPI ligand was investigated. As a result, larger steric hindrance of (BPI)FeBr2 based on substituents slowed the hydrosilylation, instead the selectivity of the mono-hydrosilylated compound was substantially improved. The 6′-Me group on a terminal pyridine was most effective. Finally, production of the mono-hydrosilylated compound from 1,7-octadiene and Ph2SiH2 reached 77% yield and 0.94 selectivity. In the case of a conjugated diene, (BPI)FeBr2 with any substituents selectively generated 1,4-hydrosilylated compound in hydrosilylation of 2,3-dimethyl-1,3-butadiene with Ph2SiH2. In this case, higher steric hindrance of (BPI)FeBr2 simply decreased the yield of the product.
This study investigates the effect of the number of oxyethylene (OE) groups on the solubilization and cosolubilization of two polycyclic aromatic hydrocarbons (PAHs) viz, naphthalene and pyrene in the conventional nonionic surfactants of the Brij series viz., Brij30, Brij56, Brij58 and Brij35 using various techniques like UV-visible spectrophotometry, spectrofluorometry, 1H NMR, and time resolved anisotropy measurements. In Brij56, Brij58 and Brij35 surfactant systems with relatively higher number of OE units, the micellar palisade layer is more hydrated than that of the Brij30 micelle which has only 4 OE groups constituting the palisade layer. Hence in these micellar systems the palisade layer being more hydrated is a less preferred choice for the hydrophobic compounds to reside. As a result of this, the two PAHs compete for the same hydrophobic core of the micelle which leads to the decrease in the solubilization of naphthalene as pyrene competes with it successfully because of its more hydrophobic character. In the case of Brij30, as the palisade layer of the micelle is less hydrated, naphthalene resides in the palisade layer whereas pyrene resides in the core because of its higher hydrophobicity. This leads to elimination of the competition between the two PAHs for the same solubilization site.
A hybrid photocatalyst constructed with Ta3N5 and a binuclear ruthenium(II) complex had the ability to reduce CO2 into formate with >99% selectivity under visible light (λ > 480 nm), presenting the first report of a semiconductor material with a 600-nm absorption edge that is operable in a metal-complex/semiconductor photocatalyst.
Incompletely condensed polyhedral oligomeric silsesquioxane (IC-POSS), which has an open-cage structure, exhibits high optical transparency even incorporating 30 wt% of the IC-POSS fillers in a poly(methyl methacrylate) (PMMA) matrix dependent on their substituents. However, real understanding of the substituent-dependent dispersibility of the IC-POSS fillers is unclear. In this work, we studied structure-dependent bulk thermal properties of the IC-POSS derivatives substituting isobutyl, phenyl and cyclohexyl groups at the Si corners and dimethylsilyl, trimethylsilyl, dimethylethylsilyl, dimethylvinylsilyl, dimethylphenylsilyl, and dimethylethylcyclohexyl groups at the opening moieties. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurement revealed that both the substituents at the corners and opening moieties significantly affected the thermal properties of the IC-POSS derivatives. We found volcano-type dependence of the phase transition temperature on the molecular weights of the substituents at the opening moieties in all the tested IC-POSS derivatives. The trimethylsilyl groups and the dimethylphenylsilyl groups at the open moieties showed highest and lowest phase transition temperatures, respectively. Especially, the phenyl groups at the opening moieties lead to low melting point and high thermal stability.
The catalytic function of perovskite oxides has received significant attention because of their structural flexibility and controllable physicochemical properties. In contrast to their catalytic application to gas-phase high-temperature, electrochemical, and photocatalytic reactions, liquid-phase organic reactions with perovskite oxide-based catalysts are still underexplored. Numerous nanosized and porous perovskite oxide catalysts have been synthesized by co-precipitation, sol-gel, solution combustion, and soft/hard templating methods, and these catalyst systems are effective for various types of liquid-phase organic reactions that have been classified into three main groups: (a) cross-coupling reactions, (b) acid/base-catalyzed reactions, and (c) selective oxidation reactions. This review article focuses on the relationships among the structures, the physicochemical properties, and the unique catalytic properties of perovskites in liquid-phase according to groups (a)–(c). In addition, the reaction mechanisms, kinetics, spectroscopy, catalyst stability/recyclability, and heterogeneous nature are comprehensively summarized for some catalytic systems.
In this paper, we summarize recent developments made by our group in direct arylation polycondensation. The direct arylation method under optimal conditions affords a high-molecular-weight polymer with high purity through a simple purification process. The high-quality polymers have been used as active materials for optoelectronic applications and show equivalent or superior performance to the same polymers prepared by conventional methods. The development of facile synthetic protocols could increase their practical applications. Recent developments in C-H/C-H coupling polycondensation are also described.
We describe the design and facile synthesis of a fluorescent alkoxyfuroxan naphthalenediimide (NDI) hybrid nitric oxide (NO) donor molecule which releases NO under spatiotemporal control when irradiated with visible light (420–600 nm). The hybrid also demonstrates cellular uptake made possible by its fluorescence capability. This research consolidates our recent work into visible light absorbing photosensitised furoxan NO release by addressing the limitations of previous designs. Key points of photoinduced nitric oxide donors are highlighted such as water solubility, NO release, cellular uptake, fluorescence, and longer absorption wavelengths.
Single-walled carbon nanotubes (SWCNTs) possess novel conducting properties and high potential as a building block for molecular electronic devices. In this paper, we report accurate ionization potentials, electron affinities and electronegativities for large SWCNTs using our state-of-the-art implementations of reduced-scaling coupled-cluster method (DLPNO-CCSD(T)) using triple zeta basis set.
The NiCo-MOF microflowers are fabricated by a rapid spray method, which are assembled by 2D NiCo-MOF nanosheets with uniform crystal morphology and homogeneous dispersion of Ni and Co. Because of their large exposed active sites and nanoscale thickness, the NiCo-MOF microflowers exhibit good catalytic performance for the reduction of 4-nitrophenol.
This account deals with recent trends and challenges regarding photo(electro)chemical solar fuels produced by CO2 reduction and water splitting.
The CO2 reduction process is limited by product selectivity, catalyst stability, and its complex reaction mechanism. A variety of catalysts—including thermocatalysts, photocatalysts, electrocatalysts, and combinations of photo- and electrocatalysts—have been employed to facilitate selective and durable CO2 reduction. In addition, the roles of the supporting electrolyte, pH, reaction temperature, chemical environment, and catalyst surface chemistry in efficient CO2 reduction have been thoroughly studied in recent years.
Effective use of solar light is a significant part of realizing efficient solar-to-hydrogen conversion during the water splitting process, and so the response of photo(electro)systems to visible light is key. To this end, several strategies have been studied in detail, including band engineering of photocatalysts, photocatalytic systems that mimic natural photosynthesis, and the development of photoanodes and their combination with photovoltaic systems.
Here, we summarize recent developments surrounding the CO2-reduction and water-splitting reactions and progress towards achieving artificial photosynthesis.
Metal clusters show novel and size-specific properties due to unique geometric and quantized electronic structures. State-of-the art synthetic methods allow us to control with atomic precision the size and compositions of clusters stabilized with polymers, protected by ligands, and immobilized on supports. The geometric structure is key information for understanding the origin of the specific and novel properties and for rationally designing their functions. Single-crystal X-ray diffraction analysis provides direct and atomic-level structural information on ligand-protected metal clusters that can be crystallized, but cannot be applied to polymer-stabilized and supported clusters even though their size and composition are precisely defined. X-ray absorption spectroscopy (XAS) is a versatile tool for determining the local structure and electronic state of a specific element within the clusters regardless of their environment. In addition to static structures, dynamic changes in electronic and geometric structures can be probed by a time-resolved measurement. Simultaneous measurement of XAS with other spectroscopies provides further insight into the reaction mechanism. This article summarizes our XAS studies on the size and atomic packing of metal clusters, location of dopant in the clusters, interfacial structures between the clusters and the surroundings, thermal properties of the clusters, and structural and electronic dynamics during the reactions.
For the acyclic conjugated polyenes of N ≤ 12 fairly good correlation between the HMO Eπ and topological index Z is demonstrated and analyzed mathematically. By using a much simpler index, mean length of conjugation L, relative stability among the isomers can roughly be anticipated and understood even by beginners of chemistry. The genealogy of the acyclic conjugated polyene family is obtained and interpreted by drawing systematic diagrams growing from ethylene by using the four modes, i.e., elongation, inner and outer branching, and horn growing. The definition and importance of cross-conjugation in organic chemistry is discussed.
Ailment related to pathogenic bacteria and toxins remains a significant threat to the human body. Specifically, pathogenic bacteria are the main source of epidemic diseases and are infectious to human beings owing to their appearance in food, water, and other biological samples. Over the past several years, advanced nanomaterials-based sensing has been considered as an efficient and unique platform for the rapid, selective, ultrasensitive, qualitative, and quantitative detection of single or multiple pathogenic bacteria. Towards this end, various emerging nanomaterials have been purposefully designed and developed to integrate them onto sensor systems for the recognition of pathogenic bacteria. The present review describes a wide range of analytical techniques such as surface-enhanced Raman scattering, electrochemistry (electrochemical and electronic), a field-effect transistor, fluorescence, calorimetry and surface-plasmon resonance etc. which incorporate nano-biosensor technology to develop a pathogenic bacterium based sensor. This review also highlights the progress, trends and strategy utilized toward the identification of harmful bacteria by focusing on the pertinent literature available on the various advanced nanomaterials (such as semiconducting, magnetic, noble metal and carbon-based nanomaterials) incorporating nano-bio sensor platforms.
In this account, we review a blowing strategy for manufacturing cellular solid materials. Solid foams have been important engineering materials since the early 20th century, and are newly explored for versatile functionalities in recent decades. The blowing route is a practicable technique to yield foams, compatible with scalable industry. With rising 2D materials, the blowing protocol has been applied to synthesizing foams built of 2D materials or nanosheets for the past several years. It is worthy outlining the fundamentals of foaming processes, which include geometry, statics, kinetics, and dynamics in foaming, to study topological constraint, equilibrium configuration, nucleation-growth, and structural evolution, respectively. They are essential for controlling the production towards high-quality foams. Recent progress on foams derived via blowing methods is surveyed, covering traditional foams and newly developed inorganic foams. Advanced foams of boron-carbon-nitrogen systems, e.g. carbon foams, 3D graphene foams, carbon nitride foams, boron nitride foams, doped and hybrid foams, are highlighted and elaborated individually. The relationships between structure, property, and functionality in foam structures are additionally discussed, and the constructive applications of foams are investigated.