Nd-sensitized upconversion nanoparticles are among the most promising emerging fluorescent nanotransducers. They are activated by 808 nm irradiation, which features merits such as limited tissue overheating and deeper penetration depth, and hence are attractive for diagnostic and therapeutic applications. Recent studies indicate that ultrasmall nanoparticles (<10 nm) are potentially more suitable for clinical application due to their favorable biodistribution and safety profiles. However, upconversion nanoparticles in the sub-10 nm range suffer from poor luminescence due to their ultrasmall size and greater proportion of lattice defects. To reconcile these opposing traits, we adopt a combinatorial strategy of energy migration manipulation and crystal lattice modification, creating ultrasmall-superbright Nd-sensitized nanoparticles with 2 orders of magnitude enhancement in upconversion luminescence. Specifically, we configure a sandwich-type nanostructure with a Yb-enriched intermediate layer [Nd]-[Yb-Yb]-[Yb-Tm] to form a positively reinforced energy migration system, while introducing Ca into the crystal lattice to reduce lattice defects. Furthermore, we apply the nanoparticles to 808 nm light-mediated drug release. The results indicate time-dependent cancer cells killing and better antitumor activities. These ultrasmall-superbright dots have unraveled more opportunities in upconversion photomedicine with the promise of potentially safer and more effective therapy.

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Rechargeable Zn–air battery is a promising alternative to the widely used lithium–ion battery. Its practical use, however, is hindered by low power density, unsatisfactory energy efficiency, poor durability, and unstable voltage output. Here, we demonstrate a bifunctional catalyst for oxygen evolution and oxygen reduction reactions based on 3D MXene coupled with nitrogen-doped cobalt selenide nanocrystals (N-CoSe2/3D Ti3C2T x ). Combining experimental characterizations and density functional theory (DFT), the excellent performance is ascribed to enhanced intrinsic activity of CoSe2 due to electron transfer from MXene, N doping which lowers the reaction energy barriers, and 3D MXene architecture which provides large specific surface area, high porosity, and good conductivity. Moreover, Zn–air battery equipped with the developed N-CoSe2/3D MXene as the air cathode exhibits better power/energy densities and long-lasting cycling life (over 500 cycles) compared with that of mixed Pt/C and RuO2.

Near-infrared (NIR) light penetrates tissue deeply, but its application to motor behavior stimulation has been limited by the lack of known genetic NIR light-responsive sensors. We designed and synthesized a Yb 3+ /Er 3+ /Ca 2+ -based lanthanide-doped upconversion nanoparticle (UCNP) that effectively converts 808 nm NIR light to green light emission. This UCNP is compatible with Chrimson, a cation channel activated by green light; as such, it can be used in the optogenetic manipulation of the motor behaviors of Caenorhabditis elegans. We show that this UCNP effectively activates Chrimson-expressing, inhibitory GABAergic motor neurons, leading to reduced action potential firing in the body wall muscle and resulting in locomotion inhibition. The UCNP also activates the excitatory glutamatergic DVC interneuron, leading to potentiated muscle action potential bursts and active reversal locomotion. Moreover, this UCNP exhibits negligible toxicity in neural development, growth, and reproduction, and the NIR energy required to elicit these behavioral and physiological responses does not activate the animal's temperature response. This study shows that UCNP provides a useful integrated optogenetic toolset, which may have wide applications in other experimental systems.

A judicious layer-by-layer assembly strategy has been developed to rationally integrate graphene quantum dots with metal nanocrystals for multifarious catalysis.