Fujian Institute of Research on The Structure of Matter

Pyroptosis is an effective strategy for inducing inflammatory responses in 'cold' tumors, boosting the efficacy of immunotherapy. Although biodegradable inorganic nanoparticles (BINPs) show great potential in pyroptosis by releasing ions to break intracellular homeostasis, the limited intracellular ion release efficiency restricts pyroptosis level and subsequent immune activation. Herein, by heterovalent substitution strategy, a series of Na₃ZrF₇:x%Yb³⁺ (NZF:x%Yb, x = 0, 9, and 18) BINPs with tunable intracellular ion release efficiency are synthesized for enhanced pyroptosis and tumor immunotherapy. Specifically, the size of NZF:x%Yb³⁺ gradually decrease with increasing Yb³⁺ -doped and smaller NZF:x%Yb presents a higher degradation rate and cellular uptake ability, enabling improved intracellular ion release efficiency. This leads to drastic intracellular homeostasis stress and abundant ROS generation, thereby provoking enhanced caspase-1-related pyroptosis. Antitumor experiments in triple-negative breast cancer model confirm that the ultra-small NZF:x%Yb (NZF:18%Yb) with the highest intracellular ion release efficiency shown the most effective antitumor ability, and significant inhibition of distal tumor. This study reveals precise control over the size of NZF:x%Yb is especially vital to achieving pyroptosis-induced immunotherapy, which offers a new perspective for the design of BINPs.

KVPO₄F (KVPF) is a novel insertion-type anode for potassium ion batteries. For improving its electrochemical performance, the doping strategy was selected and a series of Fe-doped KVPF materials were synthesized by a facile solid-state sintering method to find out the suitable ratio. After comparation, KVPF sample with 5 % Fe-doped ratio (KVPF/Fe-5) delivers the best performance, e.g. rate capacity (94.3 mA h g^-1 at 500 mA g^-1) and long-term discharge capacity (74.1 mA h g^-1 after 1000 cycles at 200 mA g^-1, 0.03 % capacity decay ratio per cycle), which is mainly attributed to its larger K⁺ diffusion rate. The in-situ X-ray diffraction analysis clarify the two-step K⁺ storage mechanism of KVPF/Fe-5 anode, and the density functional theory calculations verify that Fe-doping can reduce diffusion energy barrier of K⁺ and increase electronic conductivity of KVPF. When used as cathode, KVPF/Fe-5 delivers 51.8 mA h g^-1 at 100 mA g^-1 after cycling 200 cycles. In addition, the symmetric cell by employing KVPF/Fe-5 as anode and cathode simultaneously was also assembled successfully, pointing out a new research direction for potassium-ion batteries.

Platinum (Pt) is the most active catalyst for the oxygen reduction reaction (ORR). However, the scarcity, high cost, and susceptibility to deactivation of Pt constrain its large-scale applications. Transition metal oxide (TMO) materials have emerged as promising alternatives due to their abundant availability and catalytic potential. Herein, we report a dissolution-and-carbonization strategy to synthesize a carbon-supported nitrogen-doped Sc₂O₃ catalyst (N-Sc₂O₃/C). Nitrogen doping significantly enhances the conductivity of the otherwise poor-conductivity Sc₂O₃, transforming it into a superior ORR catalyst. The synthesized N-Sc₂O₃/C exhibits remarkable ORR performance in 0.1 M KOH, achieving a half-wave potential of 0.92 V, which is 55 mV higher than the state-of-the-art commercial Pt/C (0.87 V). Moreover, as a cathode for a zinc-air battery, N-Sc₂O₃/C achieves a peak power density of 150.7 mW cm^-2 and a specific capacity of 766.4 mAh g_Zn^-1. Density functional theory calculations reveal that nitrogen doping induces electron spin polarization within Sc₂O₃, narrowing the bandgap. This enhanced electronic structure improves conductivity and optimizes the adsorption of oxygen intermediates, thereby facilitating the ORR process. Our study demonstrates that nitrogen doping activates the wide-bandgap Sc₂O₃ semiconductor, converting it into a highly efficient ORR electrocatalyst and highlighting the potential of wide-bandgap TMO materials in energy applications.