Chi-Man Lawrence Wu

The modulation of the coordination environment of single atom catalysts (SACs) plays a vital role in promoting CO₂ reduction reaction (CO₂RR). Herein, N or B doped Fe‐embedded graphyne (Fe‐GY), Fe‐nXGYm (n = 1, 2, 3; X = N, B; m = 1, 2, 3), are employed as probes to reveal the effect of the coordination environment engineering on CO₂RR performance via heteroatom doping in SACs. The results show that the doping position and number of N or B in Fe‐GY significantly affects catalyst activity and CO₂RR product selectivity. In comparison, Fe‐1NGY exhibits high‐performance CO₂RR to CH₄ with a low limiting potential of −0.17 V, and Fe‐2NGY3 is demonstrated as an excellent CO₂RR electrocatalyst for producing HCOOH with a low limiting potential of −0.16 V. With applied potential, Fe‐GY, Fe‐1NGY, and Fe‐2NGY3 exhibit significant advantages in CO₂RR to CH₄ while hydrogen evolution reaction is inhibited. The intrinsic essence analysis illustrates that heteroatom doping modulates the electronic structure of active sites and regulates the adsorption strength of the intermediates, thereby rendering a favorable coordination environment for CO₂RR. This work highlights Fe‐nXGYm as outstanding SACs for CO₂RR, and provides an in‐depth insight into the intrinsic essence of the promotion effect from heteroatom doping.

A nanostructure of self‐assembly silver nanoparticles decorated on gold nanoislands (SAM Ag@AuNIs) is proposed in this article as a sensitive sensing medium for localized surface plasmon resonance (LSPR) biosensing applications. A wide tunable plasmonic sensing range from 472 to 552 nm is found by adjusting the Au–Ag atomic ratio. Biotin is employed as an indicator to investigate the potential biosensing applicability and site‐specific bioactivity of the SAM Ag@AuNIs. In virtue of a white light common‐path sensing system, direct adsorption of biotin on the SAM Ag@AuNIs is measured in label‐free manner with detection limit (LOD) of 2.9 pg mL⁻¹ (11.87 × 10⁻¹² m). It is 10⁵‐fold better than that of TiN film, which is previously reported to provide excellent LSPR LOD after functionalization with biotin. The experimental and computational results indicate that the biotin molecule can selectively immobilize onto the Ag nanoparticles (AgNPs) surface through S–Ag bonding, resulting in site‐specific functionalization. Meanwhile, the geometry of AgNPs/AuNIs provided a coupling effect that helps to improve the sensitivity. Here, AgNPs are, for the first time, reported to be directly functionalized with biotin. The SAM Ag@AuNIs can serve as a desirable plasmonic medium in the biosensing community based on the exceptionally good LOD of biotin.

The thermoelectric (TE) performance of pristine Bi₂Se₃ is inferior to that of Bi₂Te₃. Therefore, the study on Bi₂Se₃ has faced a decline. The lower performance is due to the low power factor and high thermal conductivity. In recent years, single aliovalent doping has been adopted to improve the TE performance of Bi₂Se₃. Here, we adopt an isovalent co-doping approach using indium and antimony to create a manifold enhancement in the TE performance of Bi₂Se₃ via the creation of neutral impurities and deep defect states (DDSs). A high figure of merit (ZT = 0.47) is obtained at 473 K for a doping concentration of 0.1 at. %. The TE performance obtained for Bi_2–xIn_xSb_2x/3Se₃, x = 0.1 at. %, is comparable to that obtained in several reports for pristine Bi₂Te₃. Our density functional theory calculation reveals an underlying DDS located at ∼15 eV below the Fermi level. This leads to enhanced electronic properties via density of states optimization induced by the co-doping. The isovalent doping is expected to create neutral impurities, which causes less scattering to conduction electrons while absorbing phonon vibration, thus improving the TE performance.

First-row transition metal embedded pyrazine-based graphynes (TM-pyGYs), especially Mn/Fe/Co/Ni-pyGYs are promising single atom catalysts for the CO ₂ reduction reaction.