Although widely need from various applications, the luminescence of Cr³⁺ is easily prone to thermal quenching (TQ), causing remarkable intensity reduction as temperature rises, and posing a significant constraint in applications such as high-power lighting, solid-state lasers, and high-temperature optical sensing. Numerous strategies have been reported to realize anti-thermal quenching luminescence (ATQL) of Cr³⁺. However, researches into anti-thermal quenching upconversion luminescence (ATQUL) of Cr³⁺ are barely seen. Herein, taking advantage of the enhanced luminescence of Yb³⁺ facilitated by the Frenkel defects formed within Sc₂(WO₄)₃ (SWO) matrix upon heating, we have established Yb³⁺→Cr³⁺ cooperative sensitization pathway for upconversion luminescence of Cr³⁺, and achieved ATQUL of Cr³⁺ in SWO:Yb/Cr. Our findings have not only offered novel perspectives for medium to high-temperature applications of Cr³⁺-based phosphors, the design principles are also extendable to other transition metal ions.

Promoting the oxygen reduction reaction (ORR) is critical for commercialization of intermediate-temperature solid oxide fuel cells (IT-SOFCs), where Sr₂Fe_1.5Mo_0.5O_6−δ (SFM) is a promising cathode by working as a mixed ionic and electronic conductor. In this work, doping of In³⁺ greatly increases the oxygen vacancy concentration and the content of adsorbed oxygen species in Sr₂Fe_1.5Mo_0.5−xIn_xO_6−δ (SFMIn_x), and thus effectively promotes the ORR performance. As a typical example, SFMIn_0.1 reduces the polarization resistance (R_p) from 0.089 to 0.046 Ω∙cm² at 800 °C, which is superior to those doped with other metal elements. In addition, SFMIn_0.1 increases the peak power density from 0.92 to 1.47 W∙cm⁻² at 800 °C with humidified H₂ as the fuel, indicating that In³⁺ doping at the Mo site can effectively improve the performance of SOFC cathode material.

We report a high-throughput approach to generating lanthanide-doped upconversion nanoparticle (UCNP) arrays through polymer pen lithography (PPL), where instead of the expensive block co-polymer, two types of polymers are employed with one working as ink carrier, e.g., polyethylene glycol-400 (PEG-400) to facilitate smooth transfer from the tip to the substrate and the other, e.g., polyvinyl pyrrolidone (PVP), as chelator to ensure successful patterning of metal ions. The strong coordination of PVP with rare earth ions (RE³⁺) is the key for weakening the interaction between RE³⁺ ions and the carrier PEG-400 so that the good mobility of ink can be retained. Further experimental results have shown that besides PVP, small molecules with functional groups that can coordinate with RE³⁺ ions, such as oleic acid, can also serve the same role as PVP, which greatly enriches the ink library for PPL. Over 1 cm² area arrays comprising individual UCNP can be reliably generated with characteristic upconversion luminescence. This strategy not only allows reliable production of individual UCNP arrays, it also paves new avenue to the precise synthesis of multifunctional NPs for lasing, imaging, encryption, and anticounterfeiting.

This paper presents a p–n heterojunction photoanode based on a p-type porphyrin metal–organic framework (MOF) thin film and an n-type rutile titanium dioxide nanorod array for photoelectrochemical water splitting. The TiO₂@MOF core–shell nanorod array is formed by coating an 8 nm thick MOF layer on a vertically aligned TiO₂ nanorod array scaffold via a layer-by-layer self-assembly method. This vertically aligned core–shell nanorod array enables a long optical path length but a short path length for extraction of photogenerated minority charge carriers (holes) from TiO₂ to the electrolyte. A p–n junction is formed between TiO₂ and MOF, which improves the extraction of photogenerated electrons and holes out of the TiO₂ nanorods. In addition, the MOF coating significantly improves the efficiency of charge injection at the photoanode/electrolyte interface. Introduction of Co(Ⅲ) into the MOF layer further enhances the charge extraction in the photoanode and improves the charge injection efficiency. As a result, the photoelectrochemical cell with the TiO₂@Co-MOF nanorod array photoanode exhibits a photocurrent density of 2.93 mA/cm² at 1.23 V (vs. RHE), which is ~ 2.7 times the photocurrent achieved with bare TiO₂ nanorod array under irradiation of an unfiltered 300 W Xe lamp with an output power density of 100 mW/cm².

Inexpensive copper nanoparticles are generally thought to possess weak and broad localized surface plasmon resonance (LSPR). The present experimental and theoretical studies show that tailoring the Cu nanoparticle to a cubic shape results in a single intense, narrow, and asymmetric LSPR line shape, which is even superior to round-shaped gold nanoparticles. In this study, the dielectric function of copper is decomposed into an interband transition component and a free-electron component. This allows interband transition-induced plasmon damping to be visualized both spectrally and by surface polarization charges. The results reveal that the LSPR of Cu nanocubes originates from the corner mode as it is spectrally separated from the interband transitions. In addition, the interband transitions lead to severe damping of the local electromagnetic field but the cubic corner LSPR mode survives. Cu nanocubes display an extinction coefficient comparable to the dipole mode of a gold nanosphere with the same volume and show a larger local electromagnetic field enhancement. These results will guide development of inexpensive plasmonic copper-based nanomaterials.