High‐Strength Pressure‐Free Bonding Using Cu and Ni‐Sn Nanoparticles

High‐strength pressure‐free bonding is investigated using Cu nanoparticles as an alternative to conventional solders. Focus is placed on the morphology of Ni‐Sn intermetallic nanoparticles, an additive to a paste of Cu nanoparticles, for improvement of sinterability. The shear strength increases from 23.2 (Cu nanoparticles only) to 31.8 MPa, when 10 wt% of the newly synthesized 15‐nm Ni₃Sn₂ nanocubes is mixed with the Cu nanoparticle paste. This is the first example of the use of base metal nanoparticles under pressure‐free conditions to achieve the bonding strength of an ordinary Pb‐free solder (Sn‐Ag‐Cu). The addition of smaller Ni₃Sn₂ nanocubes 8 nm in size or irregularly shaped Ni₃Sn₂ nanoparticles (25.0 MPa) results in a limited increase in shear strength (26.6 MPa), while the addition of micrometer‐sized Ni₃Sn₂ particles results in a decrease in shear strength (21.5 MPa). The effects of the size and shape of the added Ni₃Sn₂ particles on the shear strength are discussed based on SEM observation of the sintered layers.     

Control of the Transition between Ni‐C and Ni‐SIa States by the Redox State of the Proximal Fe?S Cluster in the Catalytic Cycle of [NiFe] Hydrogenase

[NiFe] hydrogenase catalyzes the reversible cleavage of H₂. The electrons produced by the H₂ cleavage pass through three Fe–S clusters in [NiFe] hydrogenase to its redox partner. It has been reported that the Ni‐SI_a, Ni‐C, and Ni‐R states of [NiFe] hydrogenase are involved in the catalytic cycle, although the mechanism and regulation of the transition between the Ni‐C and Ni‐SI_a states remain unrevealed. In this study, the FT‐IR spectra under light irradiation at 138–198 K show that the Ni‐L state of [NiFe] hydrogenase is an intermediate between the transition of the Ni‐C and Ni‐SI_a states. The transition of the Ni‐C state to the Ni‐SI_a state occurred when the proximal [Fe₄S₄]_p^2+/+ cluster was oxidized, but not when it was reduced. These results show that the catalytic cycle of [NiFe] hydrogenase is controlled by the redox state of its [Fe₄S₄]_p^2+/+ cluster, which may function as a gate for the electron flow from the NiFe active site to the redox partner.     

Proton‐Transfer Reaction Dynamics and Energetics in Calcification and Decalcification

CaCO₃‐saturated saline waters at pH values below 8.5 are characterized by two stationary equilibrium states: reversible chemical calcification/decalcification associated with acid dissociation, Ca²⁺+HCO₃^??CaCO₃+H⁺; and reversible static physical precipitation/dissolution, Ca²⁺+CO₃^2??CaCO₃. The former reversible reaction was determined using a strong base and acid titration. The saturation state described by the pH/P_CO2‐independent solubility product, [Ca²⁺][CO₃^2?], may not be observed at pH below 8.5 because [Ca²⁺][CO₃^2?]/([Ca²⁺][HCO₃^?]) ?1. Since proton transfer dynamics controls all reversible acid dissociation reactions in saline waters, the concentrations of calcium ion and dissolved inorganic carbon (DIC) were expressed as a function of dual variables, pH and P_CO2. The negative impact of ocean acidification on marine calcifying organisms was confirmed by applying the experimental culture data of each P_CO2/pH‐dependent coral polyp skeleton weight (Wskel) to the proton transfer idea. The skeleton formation of each coral polyp was performed in microspaces beneath its aboral ectoderm. This resulted in a decalcification of 14 weight %, a normalized CaCO₃ saturation state Λ of 1.3 at P_CO2 ≈400 ppm and pH ≈8.0, and serious decalcification of 45 % and Λ 2.5 at P_CO2 ≈1000 ppm and pH ≈7.8.     

Surface‐Junction Effects on Interfacial Electron Transfer between Bis(terpyridine)iron(II) and Hydrogen‐Terminated Silicon(111) Electrode

Interfacial electron transfer at bis(tpy)–iron(II) complexes (tpy=2,2′:6′,2′′‐terpyridine) on Si(111) electrodes was investigated by using four types of surface‐anchor terpyridine ligands. Despite the greater distance, electron transfer between the bis(tpy)–iron(II) unit and the electrode is accelerated in surface‐anchor ligands with an additional phenylene group.     

Design of Superhydrophobic Porous Coordination Polymers through the Introduction of External Surface Corrugation by the Use of an Aromatic Hydrocarbon Building Unit

We demonstrate a new approach to superhydrophobic porous coordination polymers by incorporating an anisotropic crystal morphology featuring a predominant surface that is highly corrugated and terminated by aromatic hydrocarbon moieties. The resulting low‐energy surface provides particularly promising hydrophobic properties without the need for postsynthetic modifications or surface processing that would block the porosity of the framework. Consequently, hydrophobic organic molecules and water vapor are able to penetrate the surface and be densely accommodated within the pores, whereas bulk water is repelled as a result of the exterior surface corrugation derived from the aromatic surface groups. This study provides a new strategy for the design and development of superhydrophobic porous materials.     

Exfoliation of Graphite into Graphene in Polar Solvents Mediated by Amphiphilic Hexa‐peri‐hexabenzocoronene

A water‐soluble surfactant consisting of hexa‐peri‐hexabenzocoronene (HBC) as hydrophobic aromatic core and hydrophilic carboxy substituents was synthesized. It exhibited a self‐assembled nanofiber structure in the solid state. Profiting from the π interactions between the large aromatic core of HBC and graphene, the surfactant mediated the exfoliation of graphite into graphene in polar solvents, which was further stabilized by the bulky hydrophilic carboxylic groups. A graphene dispersion with a concentration as high as 1.1 mg L^?1 containing 2–6 multilayer nanosheets was obtained. The lateral size of the graphene sheets was in the range of 100–500 nm based on atomic force microscope (AFM) and transmission electron microscope (TEM) measurements.     

Neuritogenic activity-guided isolation of a free base form manzamine A from a marine sponge, Acanthostrongylophora aff. ingens (Thiele, 1899)

Two manzamine-class alkaloids, manzamine A (1) and 8-hydroxymanzamine (2) were isolated from a Japanese marine sponge Acanthostrongylophora aff. ingens, together with three known alkaloids manzamine E (3), manzamine F (4), and manzamine X (5). The spectral features of 1 and 2 were different from the reported data. Detailed structure analysis using 2D NMR revealed the structure of 1 and 2 as a free base form of hydrochloric salt. These manzamine-class alkaloids showed neuritogenic activity against Neuro 2a cells.     

Influence of crystallite microstrain on surface complexes governing the metastable equilibrium solubility behavior of carbonated apatites

This study was on the influence of the mineral phase crystallite microstrain (CM) on the nature of the surface complex (SC) governing the metastable equilibrium solubility (MES) behavior of carbonated apatites (CAPs) in aqueous acidic media (0.10 M acetate buffers, with and without fluoride, 0.50 M ionic strength maintained with NaCl). The MES behavior of a set of four CAPs (synthesized at 85 degrees C by a precipitation method) of increasing CM and therefore of increasing MES (CAP4 > CAP3 > CAP2 > CAP1) was quantified. The following were the findings. For CAP1 and CAP2, the SCs deduced were Ca10(PO4)6(OH)2 and Ca10(PO4)6F2 for the nonfluoride and the fluoride cases, respectively. For CAP3 and CAP4, the SCs deduced were Ca9.5(PO4)6OH or Ca9.5(HPO4)(PO4)5(OH)2 and NaCa9.5(PO4)6F2 for the nonfluoride and the fluoride cases, respectively. These results together with that from an earlier limited study show that the Ca/P ratio of the SC decreases from 1.67 to 1.58 to 1.50 with increasing CM of the CAPs; this relationship inversely correlates with the chemistry of maturation of aqueously precipitated defective apatites. Also the SCs do not appear to exist as a continuous series and only a few SCs may account for the MES behavior over a wide range of CAP preparations.