Thermal treatment of a mixture of triphenylphosphine and zeolite Y resulted in inclusion of the former into the zeolite supercage (SC), with up to 1.5 molecules per SC. The included molecules were strongly bound by zeolite Y, with desorption observed at higher temperature compared with those of unloaded triphenylphosphine. Calculations using molecular dynamics and density functional theory revealed that each of the three phenyl groups of triphenylphosphine was inserted into the 12-membered rings of zeolite Y, thus forming inclusion compounds. By utilizing the phenomenon observed in triphenylphosphine and zeolite Y, Pd complex bearing triphenylphosphine ligand was tired to anchor on the external surface of zeolite β. We found that bis(triphenylphosphine)palladium(II) dichloride (Pd(PPh3)2Cl2) was anchored on zeolite β almost intact just by stirring the solution of the Pd complex in the presence of zeolite β. The obtained catalyst exhibited a much higher activity in Tsuji-Trost reaction compared to that of the pristine Pd(PPh3)2Cl2 or Pd supported on γ-Al2O3, MgO and TiO2. Repeated use of the Pd complexloaded zeolite β was possible in the reaction.
Although aberration-corrected scanning transmission electron microscope (STEM) enables the atomic-scale visualization of ultrathin 2D materials such as graphene, imaging of electron-beam sensitive 2D materials with structural complexity is an intricate problem. Here, we demonstrate the first atomic-scale imaging of a free-standing (without any surfactants or matrices) monolayer clay mineral nanosheet by annular dark field (ADF) imaging on aberration-corrected scanning transmission electron microscope (STEM) The monolayer Mt nanosheet was stably observed at the atomic scale, while typical bulk clay minerals are highly sensitive to an electron beam irradiation during the electron micrography.
Effective control of drug release from nanodrugs is one of the most important factors to determine the drug efficacy. In this paper, prodrugs of anticancer agent SN-38 was synthesized with various substituent groups and fabricated their nanoparticles called “nano-prodrugs (NPs)”. The hydrophobicity of the prodrug molecules was critically depended on drug release from NPs. In view of this knowledge and the dispersion stability, SN-38 NPs linked with cholesterol (SN-38-chol NPs) were selected to be the optimal candidate. The in vivo pharmacological effect of SN-38-chol NPs were about 10 times more effective than irinotecan, which is a clinically used SN-38 prodrug. In addition, it was found that SN-38-chol NPs showed low side effects. The nano-prodrugs will have different applications as a next-generation drug treatment.
Tantalum is known to form bulk nitrides in the oxidation states of either +5 (Ta3N5) or +3 (TaN), whereas vanadium and niobium form nitrides only in the oxidation state of +3 (VN and NbN). Gas-phase free clusters provide us with an ideal approach to investigate the origin of nitride composition of group 5 metals. Here we present nitridation pathways of free tantalum cluster cations, Tan + (n = 1–10), reacting with ammonia molecules. TanNmH+ and TanNm + are produced through successive reaction with NH3 molecules; a pure nitride and three H2 molecules are formed every other NH3 molecules. The nitridation occurs successively until the oxidation number of tantalum atoms reaches +5. This is in contrast to other group 5 elements, i.e., vanadium and niobium, which have been reported to produce nitrides with lower oxidation states. The present results on small gas-phase metal-nitride clusters show correlation with their bulk properties. Along with DFT calculations, these findings reveal that the electronegativity of the metal plays a key role in determining the composition of group 5 metal nitrides.
Research on alloy nanoclusters (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. Among them, thiolate (SR)-protected Au25−xMx alloy NCs (Au25−xMx(SR)18; M = heteroatom) are the most studied alloy NCs. However, the Cu-substitution site in [Au25−xCux(SR)18] − has not been determined by single crystal X-ray diffraction (SC-XRD) analysis. In this study, we have found the suitable crystallization conditions for [Au25−xCux(PET)18] − (PET = phenylethanethiolate) and thereby determined the preferential Cu-substitution site in [Au25−xCux(PET)18] − by SC-XRD. The results demonstrated that Cu preferentially substitute with Au in the staple regardless of the synthesis method.
ZnxFe2O4 (x = 0.2, 0.4, 0.6, 0.8) nanoparticles(NPs) encapsulated with amorphous SiO2 were prepared by our original wet chemical method. The crystal structure of the samples in amorphous SiO2 were estimated by X-ray diffraction. Particle sizes were controlled about 4.5 nm by adjusting the annealing temperature. From the result of magnetization measurement for our samples in a AC magnetic field, the maximum value imaginary part of AC susceptibility (χ”) in a sample of x = 0.2 exhibited the largest value at room temperature with a peak around 15 kHz. T2 relaxation curves were measured by the spin echo method. As a result, the highest relaxation rate R2 was observed with the sample of x = 0.2. In order to confirm self-heating effect, the rise in temperature at field was observed in a 145 Oe, 15 kHz AC magnetic field for our samples. The highest temperature increase was found with the sample of x = 0.2 as expected by AC magnetic measurements. The samples of x = 0.2 would be effective as an agent for hyperthermia treatment. We conclude that the Zn0.2 Fe2.8O4 samples would be effective as an agent for magnetic hyperthermia and MRI contrast.