We report a confined proton transportation in the CeO 2 /CeO 2−δ core−shell structure to build up proton shuttles, leading to a super proton conductivity of 0.16 S cm −1 for the electrolyte and advanced fuel cell performance, 697 mW cm −2 at 520 °C. The semiconductor nature of the CeO 2 (i-type) core and the CeO 2−δ (n-type) shell reveals a unique proton transport mechanism based on the charged layers formed at the interface of the CeO 2−δ /CeO 2 heterostructure. Two key factors of this structure confine proton transport to the particle surface. The first is the high concentration of oxygen vacancies in the surface layer, which benefits proton conduction. The second is a depletion region created by the core−shell interface that allows proton migration only on the surface layer rather than into the bulk CeO 2 . The constrained surface region of the CeO 2−δ builds up continuous proton shuttles. This work presents a new methodology and understanding for proton transport in general oxides and a new generation proton ceramic fuel cells.

pH-Responsive polymers have great potential in biomedical applications, including the selective delivery of preloaded drugs to tissues with low pH values. These polymers usually contain acid-labile linkages such as esters and acetals/ketals. However, these linkages are only mildly pH-responsive with relatively long half-lives (t1/2 ). Orthoester linkages are more acid-labile, but current methods suffer from synthetic challenges and are limited to the availability of monomers. To address these limitations, a sugar poly(orthoester) was synthesized as a highly pH-responsive polymer. The synthesis was achieved by using 2,3,4-tri-O-acetyl-α-D-glucopyranosyl bromide as a difunctional AB monomer and tetra-n-butylammonium iodide (TBAI) as an effective promoter. Under optimal conditions, polymers with molecular weights of 6.9 kDa were synthesized in a polycondensation manner. The synthesized glucose poly(orthoester), wherein all sugar units were connected through orthoester linkages, was highly pH-responsive with a half-life of 0.9, 0.6, and 0.2 hours at pH 6, 5, and 4, respectively.

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A sugar poly(orthoester)-based drug delivery system was constructed to achieve acidity-enhanced drug delivery and cell killing.

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