Nitrogen-doped carbon quantum dots via a facile reflux assisted polymerization of N-Methyl-Pyrrolidone for hydrogen evolution reaction

Molecular Dipoles as a Surface Flattening and Interface Stabilizing Agent for Lithium-Metal Batteries

Reaching the border of the capable energy limit in existing battery technology has turned research attention away from the rebirth of unstable Li-metal anode chemistry in order to achieve exceptional performance. Strict regulation of the dendritic Li surface reaction, which results in a short circuit and safety issues, should be achieved to realize Li-metal batteries. Herein, this study reports a surface-flattening and interface product stabilizing agent employing methyl pyrrolidone (MP) molecular dipoles in the electrolyte for cyclable Li-metal batteries. The excellent stability of the Li-metal electrode over 600 cycles at a high current density of 5 mA cm-2 has been demonstrated using an optimal concentration of the MP additive. This study has identified the flattening surface reconstruction and crystal rearrangement behavior along the stable (110) plane assisted by the MP molecular dipoles. The stabilization of the Li-metal anodes using molecular dipole agents has helped develop next-generation energy storage devices using Li-metal anodes, such as Li-air, Li-S, and semi-solid-state batteries.

Polydopamine-Derived Carbon Catalysts with Optimized Structure-Activity Design towards Electrochemical CO2 Reduction to CO

Electrochemical reduction of CO2 into chemical feedstocks has been regarded as an attractive way to reconstruct the carbon cycle. In this work, nitrogen-doped carbon was prepared by high temperature pyrolysis using polydopamine (PDA) microspheres as precursors. The effects of doped nitrogen units, surface hydrophilicity and pore structures of the N-Carbon catalysts on the CO2 reduction reaction (CO2 RR) activities were systematically investigated. It was demonstrated that the competition between the hydrogen evolution reaction (HER) and the CO2 RR under reduction potentials was modified by the nature of surface hydrophilicity/hydrophobicity and the doped nitrogen units. The CO2 RR activities were further optimized via the pore structures regulation. Results showed that pore structure with size below 1 nm was favorable for CO2 RR and the developed N-Carbon catalysts with optimized nitrogen units, hydrophilicity, and pore structure achieved a high CO2 to CO Faradaic efficiency of 95 % in the H-cell.

Emerging Trends of Carbon-Based Quantum Dots: Nanoarchitectonics and Applications

Carbon-based quantum dots (QDs) have emerged as a fascinating class of advanced materials with a unique combination of optoelectronic, biocompatible, and catalytic characteristics, apt for a plethora of applications ranging from electronic to photoelectrochemical devices. Recent research works have established carbon-based QDs for those frontline applications through improvements in materials design, processing, and device stability. This review broadly presents the recent progress in the synthesis of carbon-based QDs, including carbon QDs, graphene QDs, graphitic carbon nitride QDs and their heterostructures, as well as their salient applications. The synthesis methods of carbon-based QDs are first introduced, followed by an extensive discussion of the dependence of the device performance on the intrinsic properties and nanostructures of carbon-based QDs, aiming to present the general strategies for device designing with optimal performance. Furthermore, diverse applications of carbon-based QDs are presented, with an emphasis on the relationship between band alignment, charge transfer, and performance improvement. Among the applications discussed in this review, much focus is given to photo and electrocatalytic, energy storage and conversion, and bioapplications, which pose a grand challenge for rational materials and device designs. Finally, a summary is presented, and existing challenges and future directions are elaborated.

Green-emission nitrogen-doped carbon quantum dots from alkaline N-methyl-2-pyrrolidinone for determination of β-galactosidase and its inhibitors

A new fluorescence method was established for sensitive detection of β-galactosidase (β-gal) activity in spiked human serum and screening of inhibitor. Nitrogen-doped carbon quantum dots (N-CQDs) were prepared by solvothermal polymerization of N-methyl-2-pyrrolidinone in an alkaline condition. The colloidal N-CQDs exhibit good water solubility, stability, and emit bright green fluorescence with a maximum emission peak at 528 nm upon excitation at 420 nm. β-gal specifically catalyzes the decomposition of its substrate P-nitrophenyl-β-D-galactopyranoside into 4-nitrophenol, whose absorption spectrum overlaps well with the excitation spectrum of the N-CQDs. As a result, the fluorescence of the N-CQDs is remarkably quenched by 4-nitrophenol via an inner filter effect. The sensing platform presents a linear response range for β-gal activity from 0.05 to 3.0 U·L^-1 with a low limit of detection of 0.023 U·L^-1. An acceptable precision is obtained with a relative standard deviation (RSD) of 3.1% for 1.0 U·L^-1 β-gal (n = 11). The method was applied to determine β-gal in spiked human serums with recoveries in the range  96.3-104.7%. The method was employed to evaluate inhibitor screening with D-galactal and chloroquine diphosphate as models.