The body-centered cubic structure of methyllithium tetramer crystal: staggered methyl conformation by electrostatic stabilization via intratetramer multipolarization

The methyllithium tetramer (CH3Li)4 structure in the bcc crystal has been theoretically optimized with the use of density functional theory calculations under the periodic boundary condition. The X-ray structure shows that the methyl-group conformation in tetramer in crystal takes the staggered form rather than the eclipsed form that is taken in the isolated tetramer, i.e., the crystal packing effect, and this has been reproduced for the first time. It is concluded that the staggered form is advantageous in crystal, as a whole, due to the larger electrostatic stabilization via the induced intratetramer multipolarization, although it should cause, simultaneously, smaller destabilization in intratetramer electronic energy.     

Electrochemical evaluation of alternating duplex-triplex conversion effect on the anthraquinone-photoinjected hole transport through DNA duplex immobilized on a gold electrode

Amperometry was employed to characterize the anthraquinone (AQ)-photoinjected hole transport through a 20-mer oligodeoxynucleotide (ODN) duplex, as immobilized on the surface of a gold electrode, and its triplex forms converted by association with several third oligopyrimidine (OPD) short strands. While the cathodic photocurrent was observed upon irradiation at 365 nm of the AQ photosensitizer linked to the end of DNA duplex, a marked lowering of the current density was identified to occur by the triplex formation of a duplex with a given third OPD short strand. The photocurrent through the DNA duplex showed a reversible fall-rise response concomitant with alternating association-dissociation cycle of the OPD short-strand, as regulated by temperature change around the corresponding melting temperature of the DNA triplex. Both the switched photoirradiation and the thermally alternating duplex-triplex conversion could provide tools of regulating the DNA hole transport.     

Self-condensed nanoparticles of oligofluorenes with water-soluble side chains

Self-condensation of the amphiphilic fluorene trimer occurs in the solvent mixture, giving pure "green" fluorescent nanoparticles with controlled radii of 20-100 nm. The origin of the green fluorescence is attributed to the excimer emission via excitation of aggregated dimer structures in the nanoparticles rather than the keto-defects. The present study also suggests the possibility of spectral tuning of emissions from oligofluorene aggregates.     

Nanographenes: Ultrastable,Switchable, and Bright Probes for Super‐Resolution Microscopy

Super‐resolution fluorescence microscopy has enabled important breakthroughs in biology and materials science. Implementations such as single‐molecule localization microscopy (SMLM) and minimal emission fluxes (MINFLUX) microscopy in the localization mode exploit fluorophores that blink, i.e., switch on and off, stochastically. Here, we introduce nanographenes, namely large polycyclic aromatic hydrocarbons that can also be regarded as atomically precise graphene quantum dots, as a new class of fluorophores for super‐resolution fluorescence microscopy. Nanographenes exhibit outstanding photophysical properties: intrinsic blinking even in air, excellent fluorescence recovery, and stability over several months. As a proof of concept for super‐resolution applications, we use nanographenes in SMLM to generate 3D super‐resolution images of silica nanocracks. Our findings open the door for the widespread application of nanographenes in super‐resolution fluorescence microscopy.     

Synthesis of Sm-doped TiO2 nanotubes and analysis of their methylene blue-removal properties under dark and UV-irradiated conditions

TiO₂ nanotubes (TNTs) have received much attention over the past decade because of their unique nanostructure and physicochemical properties; in particular, TNTs can be applied in photocatalysis. In this study, degradation of methylene blue (MB) by samarium (Sm)-doped TNTs synthesized by a soft chemical process was investigated. Transmission electron microscopy revealed TNTs had diameters of approximately 10 nm and lengths of several hundreds of nanometers. MB degradation with and without ultraviolet irradiation revealed that all Sm-doped TNTs could adsorb organic molecules and were photocatalytically active. MB adsorption by Sm-doped TNT was better than by undoped TNT. Adsorption isotherm analysis showed that amounts of MB adsorbed increased on increasing the amount of Sm dopant. Introduction of Sm³⁺ as dopant was important for formation of oxygen vacancies in the TNTs, which enhanced molecular adsorption but did not contribute to photoreactivity because of charge state and carrier recombinations in Sm-doped TNTs.     

Structural isomers in a 2-(5-bromo-2-pyridylazo)-5diethylaminophenolatochloropalladium(II) crystal.

Crystal structure of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenolatochloropalladium(II) (PdLCl) has been determined by X-ray diffraction. A crystal of PdLCl was constructed by two structural isomers of PdLCl molecules, which were particularly different in the positions of the carbon atoms at the diethylamino group, having cis-like or trans-like conformation for the carbon atoms. The molecules of PdLCl in the crystal were warped by a steric hindrance of the diethylamino group.     

Facile synthesis of hydroxymethylcytosine-containing oligonucleotides and their reactivity upon osmium oxidation

DNA strands containing a 5-hydroxymethylcytosine ((hm)C), which have recently been found in neuron cells and embryonic stem cells, were synthesized through a facile synthetic technique. The (hm)C-containing strands were efficiently oxidized at (hm)C using an osmium oxidation assay. The (hm)C was oxidized as easily as 5-methylcytosine, which can be distinguished from unmethylated cytosine.     

Production of an ordered (B2) CuPd nanoalloy by low-temperature annealing under hydrogen atmosphere

CuPd (1/1) nanoalloys composed of disordered body-centered-cubic crystals (crystal size = 1.6 nm) were prepared by synchronous reduction of Cu and Pd precursor ions with NaBH(4). In situ XRD measurement revealed that Cu and Pd atoms in the CuPd nanoalloys are arranged into an ordered B2 structure under exposure to H(2) (5 kPa) at 373 K. Ordering of Cu and Pd atoms over a longer distance (up to 3.6 nm) was achieved by annealing the nanoalloys for a longer time under a H(2) atmosphere.     

Synthesis and characterization of Au102(p-MBA)44 nanoparticles

The synthesis of Au(102)(p-MBA)(44) nanoparticles on a preparative scale in high yield is described. Various analytical methods are shown to give results consistent with the composition and known structure of the particles, showing the preparation is essentially homogeneous, and attesting to the validity of the methods as well. Derivatization of the particles with proteins and DNA is demonstrated, and conditions are described for imaging individual particles by cryo-EM at low electron dose, close to focus, conditions optimal for recording high-resolution details.