Underwater adhesion is crucial to many marine life forms living a sedentary lifestyle. Amongst them, mussel adhesion has been mostly studied, which inspires numerous investigations of 3,4-dihydroxyphenylalanine (DOPA)-based organic adhesives. In contrast, reef-building oysters represent another important "inorganic" strategy of marine molluscs for adhesion by generating biomineralized organic-inorganic adhesives, which is still rarely studied and no synthetic analogues have ever been reported so far. Here, a novel type of oyster-inspired organic-inorganic adhesive based on a biomineralized polyelectrolyte hydrogel is reported, which consists of polyacrylic acid physically cross-linked by very small amorphous calcium carbonate nanoparticles (<3 nm). The mineral-enhanced polyelectrolyte hydrogel adhesive is shown to be injectable, reusable, and optically clear upon curing in air. Moreover, comparable adhesion performance to DOPA-based adhesives is found for the hydrogel adhesive in both dry and wet conditions, which can even be further enhanced by introducing a small amount of second large cross-linker such as negatively charged nanoparticles. The present mineral hydrogel represents a new type of bio-inspired organic-inorganic adhesive that may find a variety of potential applications in adhesive chemistry.

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The evolution from superconducting LiTi2O4-δ to insulating Li4Ti5O12 thin films has been studied by precisely tuning the oxygen pressure in the sample fabrication process. In superconducting LiTi2O4-δ films, with the increase of oxygen pressure, the oxygen vacancies are filled gradually and the c-axis lattice constant decreases. When the oxygen pressure increases to a certain critical value, the c-axis lattice constant becomes stable, which implies that the sample has been completely converted to Li4Ti5O12 phase. The two processes can be manifested by the angular bright-field images of the scanning transmission electron microscopy techniques. The transition temperature (Tch) of magnetoresistance from the positive to the negative shows a nonmonotonic behavior, i.e. first decrease and then increase, with the increase of oxygen pressure. We suggest that the decrease Tch can be attributed to the suppressing of orbital-related state, and the inhomogeneous phase separated regions contribute positive MR and thereby lead to the reverse relation between Tch and oxygen pressure.

Polycrystalline La0.5Sr0.5CoO3 (LSCO) film is prepared on Pt/Ti/SiO2/Si substrates by pulsed laser deposition in order to explore the resistive switching behavior of the Ag/LSCO/Pt structure. It is found that the oxygen stoichiometric LSCO (LSCO-2) structure does not possess distinct rectifying behavior, while the oxygen deficient La0.5Sr0.5CoO3−σ (LSCO-1) structure exhibits very stable bipolar resistive switching behavior, which is attributed to the oxygen vacancies in the LSCO film. The resistance ratio between high resistance state and low resistance state is about 100, which can be maintained up to 200 cycles and 25 h with no observable degradation, indicating that the Ag/LSCO-1/Pt device possesses very good endurance and retention characteristics. Moreover, the current-voltage characteristic of Ag/LSCO-1/Pt heterostructure can be well explained by the space-charge-limited conduction mechanism. The present results provide essential evidence for the analysis of the switching mechanism and evaluation of the memory devices.