Enhancing the Electron Transport, Quantum Yield, and Catalytic Performance of Carbonized Polymer Dots via MnO Bridges

Abstract

Carbonized polymer dots (CPDs) have received tremendous attention during the last decade due to their excellent fluorescent properties and catalytic performance. Doping CPDs with transition metal atoms accelerates the local electron flow in CPDs and improves the fluorescent properties and catalytic performance of the CPDs. However, the binding sites and the formation mechanisms of the transition‐metal‐atom‐doped CPDs remain inconclusive. In this work, Mn2+‐ion–doped CPDs (Mn‐CPDs) are synthesized by the hydrothermal method. The Mn2+ ions form MnO bonds that bridge the sp2 domains of carbon cores and increases the effective sp2 domains in the Mn‐CPDs, which redshifts the fluorescence emission peak of the Mn‐CPDs slightly. The Mn2+ ions form covalent bonds in the CPDs and remedy the oxygen vacancies of the CPDs, which cuts off the non‐radiative–recombination process of the Mn‐CPDs and increases the quantum yield of the Mn‐CPDs to 70%. Furthermore, the MnO bonds accelerate the electron flow between adjacent sp2 domains and enhances the electron transport in the Mn‐CPDs. Thus, the Mn‐CPDs demonstrate excellent catalytic performance to activate hydrogen peroxide (H2O2) and produce hydroxyl radicals (•OH) to degrade methylene blue (MB) and rhodamine B (RhB).

Unraveling the Structure Transition and Peroxidase Mimic Activity of Copper Sites over Atomically Dispersed Copper‐Doped Carbonized Polymer Dots

“…These studies show that the doping concentration of Cu 2+ markedly influenced the number of functional groups on Glu−Cu−CPDs. Based on the above‐mentioned analyses, we further refined the formation mechanism of TMA‐doped CPDs in the process of hydrothermal cross‐linking polymerization [6, 7, 17] . As shown in Figure 4d, Cu 2+ ions chelate with O=C−O− and −NH 2 groups of Glu to form Cu−Glu complexes in the initial stage.…”

“…Figure 1g illustrates the high-resolution C 1s spectrum of GluÀ CuÀ CPDs, which consists of three peaks corresponding to CÀ C/C=C, CÀ N, and C=O/C=N at 284.8, 285.7, and 288.1 eV, respectively. [28] In addition, the high-resolution N 1s spectrum for GluÀ CuÀ CPDs (Figure 1h) was fitted with three components assigned to graphitic-N, pyrrolic-N, pyridinic-N. [17] The binding energy (BE) of pyridinic-N for PÀ CPDs locates at 398.2 eV (Figure S5), whereas it shifts to higher BE (398.6 eV) for GluÀ CuÀ CPDs, indicating the coordination between Cu and N atoms. [29] For the Cu 2p spectrum in Figure 1i, the peaks at 932.78 and 952.7 eV are assigned to Cu 2p 3/2 and Cu 2p 1/2 , respectively.…”

“…They determined the presence of MnÀ O bonds in MnÀ CPDs, but the specific binding sites of Mn atoms in MnÀ CPDs were not investigated. [17] As carbon chains are essentially the main matrix for TMA-doped CPDs, the functional groups also affect their properties. For example, the fluorescence emission of CPDs can be modified by hydroxy (À OH), epoxy (CÀ OÀ C), and carbonyl (À C=O) groups.…”

Unraveling the Structure Transition and Peroxidase Mimic Activity of Copper Sites over Atomically Dispersed Copper‐Doped Carbonized Polymer Dots

“…Chemie polymerization. [6,7,17] As shown in Figure 4d, Cu 2 + ions chelate with O=CÀ OÀ and À NH 2 groups of Glu to form CuÀ Glu complexes in the initial stage. The high temperature leads to dehydration and polymerization so that densely cross-linked polymer chains are generated.…”

“…Chen and co‐workers prepared Mn−CPDs by using manganese citrate with Mn‐O 4 structures as precursors. They determined the presence of Mn−O bonds in Mn−CPDs, but the specific binding sites of Mn atoms in Mn−CPDs were not investigated [17] . As carbon chains are essentially the main matrix for TMA‐doped CPDs, the functional groups also affect their properties.…”