We show how the ideas of high-throughput combinatorial synthesis can be translated from organic chemistry to solid-state thin film synthesis. In particular, we describe a combinatorial laser molecular beam epitaxy setup that can synthesize libraries of complex transition-metal oxide lattices and superlattices. As a demonstration of the capabilities of the system, we have analyzed the effects of artifical phase separation in ferromagnetic [(LaMnO3)m/(SrMnO3)m]n superlattices.
We have developed a combinatorial pulsed laser deposition (PLD) combined with in-situ surface analysis techniques such as a scanning tunneling microscope (STM) and a low energy electron diffraction (LEED). Based on an atomically controlled PLD growth of an epitaxial anatase thin film, we have quickly screened transition metals of Ti to Cu deposited on the anatase TiO2(001) surfaces by combinatorial approach. The behavior of transition metals on the anatase could be well understood in terms of the relationship between oxide formation enthalpy and surface diffusivity for each transition metal. Furthermore, after such an intensive screening experiment, we successfully discovered a new surface reconstruction induced by an impurity of Cr diffused into the bulk. The advantage of the combinatorial approach for surface science study is discussed.
We have constructed a high-resolution synchrotron-radiation photoemission spectroscopy system combined with a combinatorial laser molecular-beam epitaxy (laser MBE) thin film growth system, in order to realize high-throughput characterization of surface and interface electronic structures of transition-metal oxide thin films. The combinatorial laser MBE chamber is directly connected to the photoemission chamber so that a fabricated thin-film library can be transferred quickly into the photoemission chamber without breaking ultra high-vacuum. The combinatorial laser MBE system can be used for fabricating combinatorial thin film libraries, i. e. using physical masking during deposition to grow films under different deposition conditions with different compositions or with different thicknesses at different parts of a single substrate. Mapping electronic structures can be performed in a single growth-characterization cycle by scanning the synchrotron radiation beam over the thin film libraries. The capabilities of the system have been demonstrated by in-situ photoemission analysis of (1) the La1−xSrxMnO3 thin-film libraries with different compositions, (2) the La0.6Sr0.4MnO3 thin-film libraries with different growth conditions, and (3) the La0.6Sr0.4FeO3/La0.6Sr0.4MnO3 superlattice libraries with different thicknesses.
A new methodology “Combinatorial Computational Chemistry” was proposed to realize theoretical high-throughput screening of materials. In this review, we introduced our recent successful applications of combinatorial computational chemistry to material design. Especially, we succeeded in the development of huge number of new simulation programs for combinatorial computational chemistry. For example, our SCF-tight-binding quantum chemical molecular dynamics program is very effective to realize high-throughput screening, since it realizes more than 5,000 times acceleration. Furthermore, we succeeded in the development of multi-physics quantum chemical molecular dynamics program based on our SCF-tight-binding theory, which can simulate multi-physics phenomena including chemical reaction, shear, impact, stress, flow, electric field and so on. This new program realizes various process design in addition to material design on the basis of the combinatorial computational chemistry. We emphasized here that our new simulation programs are very powerful tool to realize high-throughput screening for both material and process design, which cannot be accomplished by the traditional first-principles approach.
The advantages of combinatorial catalysis are mainly provided by a high throughput experiment. The technology introduces two methodologies to catalysis developments: one is a stochastic method such as genetic algorism useful for the investigation of large combinatorial space which appears when we treat multiphase materials. The other is a data mining technology such as artificial neural network for withdrawing knowledge from large database. The disadvantage of combinatorial catalysis at present is the poor surface characterization of catalyst library. We have examined the surface analysis of a combinatorial library to realize “Materiomics” in catalysis field. “Materiomics” is the comprehensive research of functional materials whose ultimate goal is the achievement of enough knowledge to design functional materials as we like. Combinatorial methodology is suitable to obtain systematic database useful to understand interactions among multiple chemical species. Our recent results directed to the fusion of surface science and combinatorial catalysis are described.
In order to design an injectable formulation of E5531, a novel synthetic disaccharide analog of novel lipid A, for the treatment of septic shock, a ‘pH-jump method’ was developed. In this method, E5531 was dispersed in 0.003 mol/L NaOH (pH 11.0, above pKa2) at 50oC (above phase transition temperature) and then mixed with a buffer to neutralize the pH to 7.3. E5531 was dispersed as particles, and the size was approximately 20 nm. The structure of the particles was vesicular. After dispersal, the dispersion was sterilized using a filter, filled aseptically into vials, and lyophilized. The size of the particles did not change after lyophilization. The relationship between the physicochemical properties of the particles and the pharmacokinetics in rats after intravenous administration was investigated. The membrane fluidity of the particles was affected by the dispersal methods, the dispersal time in 0.003 N NaOH in the pH-jump method, and the addition of Ca2+ to the solution. The membrane fluidity was correlated with the pharmacokinetics in rats.
For the purpose of avoiding the snow accumulation and ice forming on antennas, super water-repellent materials have been developed. There are many super water-repellent materials proposed so far, but they lack long-running characteristics in the water. Our materials can be applied to antennas and others such as outside structures and hobbies.