Carbon‐based heteroatom‐coordinated single‐atom catalysts (SACs) are promising candidates for energy‐related electrocatalysts because of their low‐cost, tunable catalytic activity/selectivity, and relatively homogeneous morphologies. Unique interactions between single metal sites and their surrounding coordination environments play a significant role in modulating the electronic structure of the metal centers, leading to unusual scaling relationships, new reaction mechanisms, and improved catalytic performance. This review summarizes recent advancements in engineering of the local coordination environment of SACs for improved electrocatalytic performance for several crucial energy‐convention electrochemical reactions: oxygen reduction reaction, hydrogen evolution reaction, oxygen evolution reaction, CO2 reduction reaction, and nitrogen reduction reaction. Various engineering strategies including heteroatom‐doping, changing the location of SACs on their support, introducing external ligands, and constructing dual metal sites are comprehensively discussed. The controllable synthetic methods and the activity enhancement mechanism of state‐of‐the‐art SACs are also highlighted. Recent achievements in the electronic modification of SACs will provide an understanding of the structure–activity relationship for the rational design of advanced electrocatalysts.
The electrochemical CO 2 reduction reaction (CO 2 RR) is a promising strategy to achieve electrical-to-chemical energy storage while closing the global carbon cycle. The carbon-supported single-atom catalysts (SACs) have great potential for electrochemical CO 2 RR due to their high efficiency and low cost. The metal centers' performance is related to the local coordination environment and the long-range electronic intercalation from the carbon substrates. This review summarizes the recent progress on the synthesis of carbon-supported SACs and their application toward electrocatalytic CO 2 reduction to CO and other C 1 and C 2 products. Several SACs are involved, including MN x catalysts, heterogeneous molecular catalysts, and the covalent organic framework (COF) based SACs. The controllable synthesis methods for anchoring single-atom sites on different carbon supports are introduced, focusing on the influence that precursors and synthetic conditions have on the final structure of SACs. For the CO 2 RR performance, the intrinsic activity difference of various metal centers and the corresponding activity enhancement strategies via the modulation of the metal centers' electronic structure are systematically summarized, which may help promote the rational design of active and selective SACs for CO 2 reduction to CO and beyond.
Two-photon excitation (TPE) with near-infrared (NIR) photons as the excitation source have the unique properties of lower tissue autofluorescence and self-absorption, reduced photodamage and photobleaching, higher spatial resolution, and deeper penetration depth (>500 μm). Carbon nanomaterials, for example, graphene oxide (GO), have the advantages of good biocompatibility, efficient transporters into cells, protecting the carried DNA or peptides from enzymatic cleavage, and super fluorescence quenching efficiency. By combination of the nanostructured carbon materials with the TPE technique, herein we have designed an aptamer-two-photon dye (TPdye)/GO TPE fluorescent nanosensing conjugate for molecular probing in biological fluids, living cells, and zebrafish. This approach takes advantage of the exceptional quenching capability of GO for the proximate TP dyes and the higher affinity of single-stranded DNA on GO than the aptamer-target complex. Successful in vitro and in vivo detection of ATP was demonstrated with this sensing strategy. Our results reveal that the GO/Aptamer-TPdye system not only is a robust, sensitive, and selective sensor for quantitative detection of ATP in the complex biological environment but also can be efficiently delivered into live cells or tissues and act as a "signal-on" in vivo sensor for specific, high-contrast imaging of target biomolecules. Our design provides a methodology model scheme for development of future carbon nanomaterial-based two-photon fluorescent probes for in vitro or in vivo determination of biological or biologically relevant species.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.