Designing nanoscale components and units into functional defined systems and materials has recently received attention as a nanoarchitectonics approach. In particular, exploration of nanoarchitectonics in two-dimensions (2D) has made great progress these days. Basically, 2D nanomaterials are a center of interest owing to the large surface areas suitable for a variety of surface active applications. The increasing demands for alternative energy generation have significantly promoted the rational design and fabrication of a variety of 2D nanomaterials since the discovery of graphene. In 2D nanomaterials, the charge carriers are confined along the thickness while being allowed to move along the plane. Owing to the large planar area, 2D nanomaterials are highly sensitive to external stimuli, a characteristic suitable for a variety of surface active applications including electrochemistry. Because of the unique structures and multifunctionalities, 2D nanomaterials have stimulated great interest in the field of energy conversion and storage. This review highlights recent progress in the synthesis of a variety of 2D nanomaterials and their applications in energy conversion and storage. Finally, opportunities and some critical challenges in these fields are addressed.
Strategies for electrophilic activation by neighboring atoms should contribute to the development of novel catalytic performance in organic reactions. Neighboring electron-withdrawing Lewis acidic atoms can change the character of molecular catalysts, which might be more electrophilic toward inactive electron-rich molecules. In this context, the development of carbene intermediates, diborylmethane derivatives, and multinuclear catalysts has realized efficient transformations. The use of cyclopropenes can generate electrophilic carbenoid intermediates in the presence of a Ag-catalyst, the reaction of which with an organozinc reagent gives allylzinc intermediates. The subsequent allylation reaction of other electrophiles takes place in situ as a 3-components coupling reaction. The novel reactivity of diborylmethane derivatives shows the generation of borate intermediates under ambient conditions, which can take part in the Suzuki–Miyaura cross-coupling reaction. The mono-coupling reaction occurs exclusively without di-coupling reaction to give alkylboronates. The stereoselective synthesis of tetrasubstituted alkenylboronates was successful via the deprotonation of diborylalkanes, subsequent nucleophilic attack to ketones, and syn-elimination. The development of multinuclear catalysts using phosphorous ligands bearing protic moieties has realized efficient stereoselective 1,4-addition reaction of organozinc and organoaluminum reagents, where the creation of chiral quaternary stereogenic centers using acyclic enones is notable.
In biological studies, phospholipid poly(ethylene glycol) (PLPEG) is used to disperse nanocarbons, which effectively reduces the macrophage uptake of nanocarbons. Single-walled carbon nanohorn (CNH), a type of nanocarbon, was dispersed with PLPEG in this study, and the effect of PLPEG quantity on the cytotoxicity of PLPEG-CNH in RAW264.7 mouse macrophages was revealed. The results were compared with the macrophage uptake quantity of PLPEG-CNH or agglomeration size of PLPEG-CNH. It is concluded that the optimum PLPEG:CNH weight ratio was 0.5:1 and 1:1. At the higher or lower ratios, the PLPEG-CNH toxicity and the macrophage uptake quantity increased and large agglomerates appeared. These tendencies at the lower PLPEG:CNH ratio were caused by the CNHs surfaces not being sufficiently well covered by PLPEG. The tendency at the higher PLPEG:CNH ratio was curious, for which we deduced that PLPEG adsorbed on CNHs was detached to form micelles, leading to the reappearance of the CNHs not well covered with PLPEG.
The structure and electronic features of neutral and positively charged pyrene and perylene derivatives were explored. The radical cation of 1,3,6,8-tetraarylpyrene 1 was examined by ESR, UV–vis–NIR spectroscopy and theoretical calculations. The addition of 2 equiv of oxidant to 1 resulted in the formation of dication 12+. The single-crystal X-ray structure of 12+ proved that the aromatic part relocates from biphenyl unit to naphthyl unit upon 2e− oxidation of 1. We have also investigated the oxidation processes of 3,9-diarylperylene 2 and 3,10-diarylperylene 3. The radical cations of 2•+ and 3•+ showed ESR signals and the spin densities were proven to delocalize at 3,4,9,10-positions. In the case of doubly charged 3,9-diarylperylene, we could find the anthracene structure in the core, while the phenanthrene skeleton appeared in two-electron oxidized 3,10-diarylperylene. Finally we validated this phenomenon to apply for the higher analogue terrylene, discovering its large aromaticity relocation upon the 2e− oxidation.
Cesium, in particular radioactive Cs 137 is currently a significant environmental problem in Japan following the incident at the Fukushima-Daiichi nuclear power plant caused by the Great East Japan earthquake. Although radioscopes and gamma ray cameras have been developing to visualize radioactive species or contamination, it is not necessarily a simple matter to locate sources of contamination under high levels of background radiation. However, supramolecular approaches for environmental sensing of analyses are useful in the design of high-resolution molecular sensors. Here, we have developed an optical imaging technique for cesium ions involving an optode system in environmental water. An optode membrane was prepared incorporating a calixarene derivative, which showed excellent selectivity toward cesium ions in aqueous solutions, even in water supplied for domestic use or seawater. Furthermore, this membrane was fabricated using nanoparticles with a diameter of ca. 100 nm. The nano-optode also gave an excellent response to cesium ions. Therefore, this optode provides a higher spatial resolution than existing radioscopes and gamma ray cameras under high level radioactive environments.
Crystal structures of eight derivatives of bis(diphenylglyoximato)–nickel(II), bearing four alkoxy chains of different lengths, were determined by single-crystal X-ray crystallography. Sequential transition of packing structures by chain elongation was observed. The packing structures were typically one-dimensional columnar structure comprising metal wires, herringbone structures, quasi-layered structures and layered structures having an interdigitation of alkyl moieties in the alkoxy chains. Each structural characteristic depends on odd–even effect and alkoxy chain interactions. Additionally, the gauche conformation of the alkoxy chains contributes to filling the empty spaces of the structures, placing out of the molecular plane packing, and forming a clip structure of the alkoxy chains.
The coupling reactions of 3-phenylpropanoic acid and N-carboxybenzyl α-amino acids with unprotected α-amino acids containing hydrophilic side chains such as aliphatic alcohol, aromatic alcohol, thiol, carboxylic acid, and amide afforded the corresponding amides in 66–96% yield without racemization via the corresponding mixed carbonic carboxylic anhydrides under basic conditions through an ecological green synthetic method.
The synthesis and characterization of thermally stable monosubstituted thiophene 1-oxide and 1-imides stabilized by EMind (1,1,7,7-tetraethyl-3,3,5,5-tetramethyl-s-hydrindacen-4-yl) group on the 3-position are described. In addition to the molecular structures determined by X-ray crystallography, inversion barriers at the three-coordinated sulfur atoms have been determined by a coalescence method using diastereotopic C-3 and C-5 indacene carbon atoms as a 13C NMR probe.
Colloidal mesoporous silica nanoparticles (CMS) are useful as carriers for imaging probes because of their unique features. A simple method for the pore clogging of CMS has been proved by the addition of tetraethoxysilane under weakly basic conditions. The pore clogging of CMS is useful for encapsulation of thermoresponsive dyes.
We have investigated concentration-dependent fluorescence color tuning of BF2AVB in a poly(methyl methacrylate) film. BF2AVB exhibits a color change from purple-blue to orange via green, and then crystals segregate from the polymer matrix. We analyzed the fluorescence and fluorescence excitation spectral change as a function of the BF2AVB concentration in the film. We also obtained fluorescence microscope images to confirm the miscibility and crystallization properties in the films. This originates from the aggregated state formed in the polymer matrix depending on the stacking structure of the parallel (B-phase), antiparallel (G-phase), and amorphous states. The emissive species change with increasing BF2AVB concentration. The polymer matrix isolation method enables not only directly visualization of the dynamics of the crystal formation process and Ostwald’s rule of stages by fluorescence changes, but it also enables device fabrication, such as fabrication of organic light-emitting diodes and luminescent solar concentrators.
Here, we demonstrated that actin filaments mediate axonal transport in dorsal root ganglia (DRG) neurons using fluorescence single-particle tracking. We employed a compartmentalized microfluidic cell culturing chamber that allows depolymerization of actin filaments within an axonal segment. We observed that local actin depolymerization results in a two-fold increase in the average pausing duration, whereas the microtubule-dependent instantaneous transport speed is not perturbed. Collectively, our data reveal an important role of actin filaments in assisting microtubule-dependent long-range NGF axonal transport in DRG neurons.
Noble metal nanoparticles always show bond length contraction with the decrease in particle size. PVP-protected small Pd metal nanoparticles (MNPs) were reported to have the unique characteristic of expanding Pd-Pd bond lengths with decreases in particle size. To investigate the origin of this phenomenon in more detail, this work examined Pd MNPs supported on SiO2 (Pd MNPs/SiO2) via extended X-ray absorption fine structure (EXAFS) analysis, where the SiO2 support was used to stabilize the MNPs to prevent unexpected aggregation at higher temperatures. EXAFS data showed that each sample had a face-centered cubic (fcc) structure and that the smallest particles had the longest Pd-Pd bonds. Temperature dependent EXAFS measurements also revealed significant static disorder in the bond-elongated Pd MNPs/SiO2 samples. The XAFS spectral features of these bond-elongated Pd MNPs on SiO2 are in good agreement with those for palladium carbide, and we conclude that the lattice expansion in Pd MNPs can be attributed to the formation of palladium carbide.
The reaction of an oxygen- and sulfur-bridged incomplete cubane-type molybdenum complex [Mo3(µ3-S)(µ-S)2(µ-O)(dtp)3(µ-dtp)(CH3CN)] (3) (dtp, diethyl dithiophosphate) with methyl propiolate (HC≡CCOOCH3, MP) and phenyl acetylene (HC≡CC6H5, PA) yields trinuclear mixed-valence Mo3(IV, V, V) complexes [Mo3(O)2(µ3-S)(µ3-SCH=C(COOCH3)S)(dtp)3(µ-OAc)] (3MP) and [Mo3(O)2(µ3-S)(µ3-SCH=C(C6H5)S)(dtp)3(µ-OAc)] (3PA), respectively, and also dinuclear Mo2(V, V) complexes [Mo2(O)2(µ-S)(µ-SCH=C(COOCH3)S)(dtp)2] (2aMP and 2bMP (a geometrical isomer of 2aMP)) and [Mo2(O)2(µ-S)(µ-SCH=C(C6H5)S)(dtp)2] (2aPA and 2bPA (a geometrical isomer of 2aPA)), respectively. The origin of the geometrical isomerism of the dimers comes from the unsymmetric nature of the acetylene derivatives. All of the structures were determined by X-ray crystallography, which revealed that each complex has two carbon-sulfur (µ-S) bonds arising from the adduct formation reaction between complex 3 and an acetylene derivative MP or PA. 1H NMR spectroscopy has proven that the dinuclear complexes are formed via the trinuclear complexes. The XPS spectra of 3MP show that the peaks of Mo 3d3/2 and Mo 3d5/2 are clearly split into two in the ratio of two to one, respectively, while those of 3 show no splitting, which indicates that 3MP is a mixed-valence complex with Mo3(IV, V, V) oxidation states. Cyclic voltammograms of 3MP and 3PA show chemically reversible one-electron oxidation processes at E1/2 = 0.21 V and E1/2 = 0.15 V vs. Ag/Ag+, respectively, and irreversible reduction peaks at −0.92 V and −1.00 V vs. Ag/Ag+, respectively. The dinuclear complexes, especially 2aPA and 2bPA having phenyl groups, are photosensitive to give their isomeric counter parts.
New amphiphilic transition metal complexes with helical structures self-assembled to form disk-like units in 20 wt % EtOH/water. d–d transition bands in the visible-near IR region were used to probe conformational changes during the assembly process. Self-assembly resulted in dynamic conformational changes and considerable enhancement of circular dichroism (CD) in the d–d transition bands due to steric interaction among neighboring complexes. A copper(II) complex showed the most dramatic CD changes upon self-assembly, including sign inversion of the CD signal. The self-assembled Cu(II) complexes also showed pH-responsive Cotton effects between pH 6 and pH 7 due to deprotonation. The Cotton effects of the Cu(II) complex could be finely tuned by varying the pH and ethanol content of the aqueous solvent.
Herein, a novel imidazolium-functionalized magnetic graphene oxide (GO@magnetite@Im) composite was synthesized and utilized for speciation analysis of Cr(III) and Cr(VI) via determination by electrothermal atomic absorption spectrometry. The nanosorbent was characterized with various techniques. This material is illustrated to represent a viable sorbent for separation and removal of Cr(III) and Cr(VI) ions. GO@magnetite@Im sorbent exhibited selectivity toward Cr(VI) species at pH = 2.0 through electrostatic interaction with imidazolium rings, while Cr(III) and Cr(V) species were sorbed on the active sites of the sorbent at pH = 6.0, simultaneously. No preoxidation or prereduction step was performed. Experimental design methodology was employed to find the best extraction conditions by exploring the affecting parameters on extraction procedure. Under the best optimized extraction conditions the linearity was 4–350 ng L−1 for Cr(VI) and 5–400 ng L−1 for total chromium. Detection limit and relative standard deviation for Cr(VI) were 1.2 ng L−1, and 6.8%, respectively, while these values for total chromium were 1.9 ng L−1 and 8.0%, respectively. The accuracy of the developed method was confirmed by analyzing two certified reference materials. Ultimately, this method was utilized for rapid extraction and speciation analysis of Cr(III) and Cr(VI) in water samples and food samples.
Based on the features of ultrasonic and microwave radiation methods, bovine serum albumin-protected gold nanoclusters have been efficiently synthesized in a novel fashion via ultrasonic-microwave heating. The experimental results show that the mean diameter of Au NCs is about 3.3 nm. In particular, Au NCs are found to reach a high quantum yield of 7.1%. The prepared Au NCs powders are utilized to develop latent fingermarks. With the self-assembly development observation system, fingermarks, even the old fingermarks emit orange-red fluorescence and show clear ridge details. Consequently, developing old fingermarks deposited on different surfaces with Au NCs is an efficient and green method.