This highlight review describes our contribution to the field of biomimetic and technomimetic molecular machines specially designed to be studied as single molecules on surfaces. Prototypes of molecular wheels, vehicles, gears and motors will be described from their design to the study of their controlled motions using ultra-high-vacuum low-temperature scanning tunneling microscopes (UHV-LT-STM).
Functional graphene quantum dots (IL-GQDs) are synthesized by electrochemical exfoliation in a one-pot process. Ionic liquid in the mixed solution (water/acetonitrile) is used as the electrolyte, which can be bonded to the surface of GQDs. The method just needs a very low concentration of ionic liquid. Fluorescent spectra indicate that the maximum emission intensity is achieved at 465 nm. Further, the obtained IL-GQDs exhibit selective fluorescence quenching towards Cu(II) ion, with a detection limit of ppb level.
A glucopyranosyltriazole unit covalently bonded to a uridine nucleoside was synthesized and its gelation properties evaluated in ionic liquids. The ionogels were thermally stable; no melting occurred up to 111°C at 5 wt % concentration. Moreover, ionogel formed by gelator at 3 wt % concentration in [BMIM][TFSA] was found to retain the high conducting performances of the ionic liquid.
A novel bisurea compound showed columnar liquid crystal phases possessing a new functionality, polarity-adjustability. Its molecular packing structures were analyzed by X-ray diffraction (XRD), and its polarity switching behavior and magnitude of the polarity were examined by electro-optic and second harmonic generation (SHG) experiments, respectively. As a result, it was revealed that the macroscopic polarity gradually increased with every ON/OFF cycle in SHG experiment applying an electric field. This strongly suggests that the anti-parallel hydrogen bonding network in each of the columns is reconstructed to syn-parallel by applying the electric field intermittently. Furthermore, it was confirmed that the reconstructed network mostly remained even once the temperature was raised to its isotropic state.
Synchrotron μ-XRF and autoradiography complementally revealed the different behavior of arsenic and phosphorus in Pteris vittata L. at a high spatial resolution in its living state. We found that P. vittata develops several sequestration mechanisms for As from important biological functions at different growth stages. Some of them relate to the activities in the roots of the sporophyte and the reproduction on the gametophyte.
Three kinds of cyclic tri-β-peptides having different numbers of benzyl ester groups are synthesized. The cyclic peptides formed peptide nanotube bundles showing different surface potentials, piezoelectricity, and electrical conductivity, which are explained by the number of the benzyl ester groups and the rotational symmetry of the cyclic peptides.
The possible configurations of apo-form medaka fish taste receptor type 1, which is a heterodimer consisting of two types of monomers, were studied by a 1-µs molecular dynamics (MD) simulation. The simulation sampled a variety of metastable states of each monomer in the apo form. It was found that representative metastable states of each monomer can be essential configurations for regulating the taste recognition upon ligand binding.
Herein, the synthesis and physical properties of a monovalent [Ni(dmit)2]− salt (dmit2− = 2-thioxo-1,3-dithiole-4,5-dithiolate) containing a supramolecular cation composed of Na+ ions, dibenzocrown-6 molecules, and CH3CN molecules, has been reported. The desorption/adsorption of CH3CN molecules (organic solvent molecules) from/on the [Ni(dmit)2]− salt occurred while maintaining the crystalline state and could be utilized to switch the magnetic properties of the salt.
A novel short process was firstly proposed for the synthesis of nanostructured flower-like metallic Zn from Zn-containing electric arc furnace dust leaching solution. The effects of metal ions coexisting in leachate on the electrodeposition of Zn was investigated. Results indicated that flower-like Zn with a large specific surface area was achieved in the presence of other cations, and the current efficiency reached about 79%. This study may develop a simple way for the direct electrodeposition of metallic Zn from Zn-containing solution with multiple impurity ions.
A one-pot, highly diastereoselective synthesis of chroman derivatives with three contiguous stereogenic centers is described. In this reaction, three transformations (iminium formation/Morita-Baylis-Hillman reaction/oxa-Michael reaction) occurred successively to afford multisubstituted chroman derivatives in moderate chemical yields with excellent diastereoselectivities (d.r. = >20:1:1:1).
We synthesized N-benzoyl-protected peptide nucleic acid (PNA) monomers, which are robust under the conditions for deprotecting the 9-fluorenylmethoxycarbonyl (Fmoc) group by piperidine but are removable by aqueous ammonia and hence totally compatible with Fmoc-solid phase synthesis. This new invention expands the range of available nucleobase sequences, allowing us to use acid-sensitive PNA oligomers and purine nucleotides (both of which are difficult to use in the conventional methods) in the preparation of PNA-DNA chimeras to avoid the drawbacks of traditional PNAs.
Into colloidal particles formed from chitosan and DNA, microcrystallines of either H- or J-aggregates of astaxanthin have been selectively incorporated. Which form of the aggregate is produced in the nanoparticles is governed by the composition of ethanol-water solutions used for their preparations. These aqueous colloidal dispersions show large hypsochromic and bathochromic shifts, with respect to the monomeric dye, indicating strong potentials for medical and pharmaceutical applications.
We investigated the effects of addition of oleic acid (OA) on the stability of CsPbBr3 quantum dot (QD) dispersions in toluene during storage and light irradiation. Excess amounts of OA degraded the fluorescent perovskite CsPbBr3 QDs because of promoted crystal growth through dissolution and reprecipitation. In contrast, a suitable amount of OA (0.2 vol %) improved their photostability possibly due to re-adsorption of OA on the exposed CsPbBr3 crystal surface after the photoinduced desorption of OA.
The first transition metal-free catalytic oxidative dearomatizative azidation of arenols has been developed using hypoiodite catalysis with aqueous hydrogen peroxide and trimethylsilyl azide as an oxidant and azide source, respectively, under mild conditions. The corresponding quaternary azides can be obtained in high to excellent yields.
Transient circular dichroism (TR-CD) spectra of (P)- and (M)-hexahelicenes (HHs) in the excited triplet state, (P)- and (M)-3HH*, and their growth and decay behaviors in the µs time domains were recorded for the first time in toluene at room temperature, using an improved Kliger’s method. The TR-CD spectra of (P)- and (M)-3HH* obtained were mirror-imaged, exhibiting strong positive and negative Cotton effect, respectively, of |Δε| = 55 M−1 cm−1 for the lowest-energy band at 660 nm and additional sign-alternating less intense peaks in the higher energy region, the major features of which were well reproduced by the TD-DFT calculations at the UCAM-B3LYP/6-31G(d,p) level.
Aryl(triethyl)silanes were found to cross-couple with aryl chlorides by palladium/copper dual catalysis and XPhos as a crucial ligand. The catalyst system is applicable to a facile oligothiophene synthesis from thienyl(trialkyl)silanes and thienyl chlorides. As the starting silanes are readily accessible by the catalytic C–H silylation, our method provides a protocol for a rapid biaryl synthesis starting with aromatic hydrocarbons straightforwardly.
Iron(II) dichloride coordinated with a phenanthroline-based meridional PNNP ligand [FeCl2(PNNP)] (1) (PNNP = 2,9-bis((diphenylphosphino)methyl)-1,10-phenanthroline) underwent deprotonation upon treatment with tBuONa to afford the corresponding iron(II) complex 2, which bears a deprotonated PNNP ligand with one dearomatized pyridine ring. Single-crystal X-ray diffraction analysis supported the contribution of the charge delocalization both on the ligand and the iron metal in the structure of 2.
In this work, VO2(B) nanorod/MoS2 nanosheet heterostructures with MoS2 nanosheets grown on VO2(B) nanorods have been synthesized by a two-step hydrothermal method. The VO2(B) nanorod/MoS2 nanosheet heterostructure electrodes maintained a high reversible capacity of 694.5 mA h g−1 for 100 cycles at a current density of 100 mA g−1. Furthermore, the electrodes still maintained a high reversible capacity of 403.2 mA h g−1 at a current density of 500 mA g−1 after 60 cycles, which is far superior to that of bare VO2 nanorods.
We have succeeded in the synthesis of dihydropyrazine-fused porphyrin dimers through oxidation of β-aminoporphyrins. The structure of the dimer was revealed by X-ray diffraction analysis, showing its saddle like conformation. Optical and electrochemical analysis was conducted to elucidate the properties of the dimers. The theoretical calculation suggested that the electron-donation from the dihydropyrazine nitrogen atoms to the porphyrin π-plane was weakened due to its distorted conformation.
Supported NiO nanoclusters were prepared by using nickel colloid as a precursor. NiO nanoclusters wer supported on hydrotalcite and the obtained catalyst was applied to oxidative dehydrogenation of alcohols. As a consequence, the prepared catalyst showed the highest activity compared to conventional heterogeneous nickel-based catalysts under clean reaction condition such as molecular O2 as an oxidant and base free conditions. Utilizing nanocluster and support facilitated the high activity for the reaction.
A nanocomposite hydrogel of poly(vinyl alcohol) (PVA) and polystyrene (PS)-poly(N-vinylacetamide) (PNVA) colloid particles was prepared by repeated freezing and thawing. The polymer colloid was synthesized by soap-free emulsion polymerization, and its molecular weight was controlled by varying the initiator concentration. The biologically safe PNVA hydrogen-bonds with PVA to form a network. To prepare a hydrogel with higher mechanical strength, a composite of PVA with uniformly dispersed PS-PNVA particles was prepared. This gel was evaluated in terms of the swelling characteristics and mechanical properties, for its application to biomaterials.
ZnO films were fabricated on polyether sulfone substrates using gas-assisted liquid phase deposition with ethylene glycol (EG) at 60 °C. Water and NH3 vapors diffused from a water/EG/hexamethylenetetramine solution into a Zn(NO3)2/EG solution. This caused heterogeneous nucleation at the solid-liquid interface, which resulted in the formation of ZnO films. The ZnO films had a continuous film structure because of EG adhesion, and they exhibited visible light transmittance greater than 60%.
In this study, a dual frequency liquid crystal (DFLC) consisting of low molecular weight liquid crystals (LCs) was newly prepared, and the electrorheological (ER) properties were investigated. The liquid crystalline properties of the mixture were analyzed by polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD), and the results revealed that the mixture exhibited a smectic A phase. The DFLC mixture showed the ER effects by switching the frequencies, and the change in the viscosity was found to be affected by the given frequencies. Interestingly, the ER effect in the smectic A phase was different from the one observed in the nematic phase.
Uniformly sized nanoparticles 3–5 nm in diameter of Y2O3-stabilized ZrO2 (YSZ) were fabricated by a water-toluene two-phase solvothermal method. The nanoparticles that were covered with oleic acid were highly dispersed in organic media. The size and doping concentration were tuned by adjusting the preparation conditions. The fabrication of YSZ thin films was achieved through hexagonal arrangement by evaporation-induced self-assembly of highly dispersive mono-sized nanoparticles.
A novel MWCNT/UiO-66-NH2 nanocomposite with high porosity and water stability was fabricated through a facile acid-promoted method, which has high adsorption efficiency for ketoprofen (KET) from aqueous solutions. The nanomaterials were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller theory (BET), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), transmiassion electron microscopy (TEM) and Zeta potentials to study their structures and functionalities. The as-developed MWCNT/UiO-66-NH2 nanocomposite exhibited excellent adsorption efficiency (over 93% for 40 mg/L ketoprofen) by combining multi-walled carbon nanotubes (MWCNT) with amination of zirconium-based metal organic frameworks (UiO-66-NH2). The adsorption capacity of MWCNT/UiO-66-NH2 was observed to reach up to 233 mg/g for KET. The improved adsorption capacity of MWCNT/UiO-66-NH2 was due to the anchoring technology, which prevented the aggregation of UiO-66-NH2 nanoparticles and increased the effective adsorption surface of the MWCNT/UiO-66-NH2 nanocomposite. The main factors affecting the adsorption process such as time, pH and ionic strength were investigated in detail. Besides, MWCNT/UiO-66-NH2 nanocomposite could be reproduced without significant degradation by means of simple ethanol washing and reused for continuous adsorption. Herein, MWCNT/UiO-66-NH2 nanocomposite showed great potential for effective removal of ketoprofen from water.