In this work, different lanthanides (Tm³⁺, Er³⁺; Yb³⁺, Ho³⁺, Nd³⁺) were doped into NaYF₄ via a high-temperature coprecipitation method, and followed by SiO₂ coating to improve the water dispersibility, resulting in NaYF₄:Tm³⁺, Er³⁺@NaYF₄@SiO₂ and NaYF₄:Yb³⁺, Ho³⁺@NaYF₄:Nd³⁺@SiO₂ nanoparticles (NPs). The two NPs both exhibited the temperature-dependent second near-infrared (NIR-II) downshifting luminescence over the physiological range. The luminescence ratio of Tm³⁺ emission at 1460 nm to Er³⁺ emission at 1525 nm (Tm³⁺:³H₄ → ³F₄; Er³⁺:⁴I_13/2 → ⁴I_13/2) varies with temperature increase, as well as Yb³⁺ emission at 980 nm and Ho³⁺ emission at 1150 nm (Yb³⁺:²F_5/2 → ²F_7/2; Ho³⁺:⁵I₆ → ⁵I₈). The highest relative sensitivity of NaYF₄:Tm³⁺, Er³⁺@NaYF₄@SiO₂ and NaYF₄:Yb³⁺, Ho³⁺@NaYF₄:Nd³⁺@SiO₂ aqueous suspension is 0.36% K⁻¹ (at 298 K) and 0.76% K⁻¹ (at 343 K), respectively. The biological tests prove the good biocompatibility and low toxicity of the water-soluble NPs. In vitro tissue penetration experiments verify a much better penetration ability of the synthesized NaYF₄:Tm³⁺, Er³⁺@NaYF₄@SiO₂ compared with NaYF₄:Yb³⁺, Ho³⁺@NaYF₄:Nd³⁺@SiO₂ NPs. The excellent physiological luminescent thermometry with favor wave penetration depth provides a promising platform in deep tissue temperature measurement, which is very important in vivo biosensing.

Au-Cu bimetallic thin films with controlled composition were fabricated by magnetron sputtering co-deposition, and their performance for the electrocatalytic reduction of CO ₂ was investigated. The uniform planar morphology served as a platform to evaluate the electronic effect isolated from morphological effects while minimizing geometric contributions. The catalytic selectivity and activity of Au-Cu alloys was found to be correlated with the variation of electronic structure that was varied with tunable composition. Notably, the d-band center gradually shifted away from the Fermi level with increasing Au atomic ratio, leading to a weakened binding energy ofCO, which is consistent with low CO coverage observed in CO stripping experiments. The decrease in theCO binding strength results in the enhanced catalytic activity for CO formation with the increase in Au content. In addition, it was observed that copper oxide/hydroxide species are less stable on Au-Cu surfaces compared to those on the pure Cu surface, where the surface oxophilicity could be critical to tuning the binding strength ofOCHO. These results imply that the altered electronic structure could explain the decreased formation of HCOO ^- on the Au-Cu alloys. In general, the formation of CO and HCOO ^- as main CO ₂ reduction products on planar Au-Cu alloys followed the shift of the d-band center, which indicates that the electronic effect is the major governing factor for the electrocatalytic activity of CO ₂ reduction on Au-Cu bimetallic thin films.

In this work, the highly selective and stable electrocatalytic reduction of CO₂ to CO on nanostructured Ag electrocatalysts is presented. The Ag electrocatalysts are synthesized by the electroreduction of Ag₂CO₃ formed by in situ anodic-etching of Ag foil in a KHCO₃ electrolyte. After 3 min of this etching treatment, the Ag₂CO₃-derived nanostructured Ag electrocatalysts are capable of producing CO with up to 92% Faradaic efficiency at an overpotential as low as 290 mV, which surpasses all of the reported Ag catalysts at identical conditions to date. In addition, the anodic-etched Ag retained ∼90% catalytic selectivity in the electroreduction of CO₂ to CO for more than 100 h. The Ag₂CO₃-derived Ag is able to facilitate the activation of CO₂ via reduction of the activation energy barrier of the initial electron transfer and provide an increased number of active sites, resulting in the dramatically improved catalytic activity for the reduction of CO₂ to CO.