Dapeng Yang

Bio: Dapeng Yang is an academic researcher from North China University of Water Conservancy and Electric Power. The author has contributed to research in topics: Excited state & Bond graph. The author has an hindex of 11, co-authored 59 publications receiving 314 citations. Previous affiliations of Dapeng Yang include École centrale de Lille & Petroleum Institute.

Photodegradation of Rhodamine B and Methyl Orange over Boron-Doped g-C3N4 under Visible Light Irradiation

Abstract: Graphitic carbon nitride (g-C3N4) and boron-doped g-C3N4 were prepared by heating melamine and the mixture of melamine and boron oxide, respectively. X-ray diffraction, X-ray photoelectron spectroscopy, and UV−vis spectra were used to describe the properties of as-prepared samples. The electron paramagnetic resonance was used to detect the active species for the photodegradation reaction over g-C3N4. The photodegradation mechanisms for two typical dyes, rhodamine B (Rh B) and methyl orange (MO), are proposed based on our comparison experiments. In the g-C3N4 photocatalysis system, the photodegradation of Rh B and MO is attributed to the direct hole oxidation and overall reaction, respectively; however, for the MO photodegradation the reduction process initiated by photogenerated electrons is a major photocatalytic process compared with the oxidation process induced by photogenerated holes. Boron doping for g-C3N4 can promote photodegradation of Rh B because the boron doping improves the dye adsorption and...

Hydrogen Bonding in the Electronic Excited State

Abstract: Because of its fundamental importance in many branches of science, hydrogen bonding is a subject of intense contemporary research interest. The physical and chemical properties of hydrogen bonds in the ground state have been widely studied both experimentally and theoretically by chemists, physicists, and biologists. However, hydrogen bonding in the electronic excited state, which plays an important role in many photophysical processes and photochemical reactions, has scarcely been investigated.Upon electronic excitation of hydrogen-bonded systems by light, the hydrogen donor and acceptor molecules must reorganize in the electronic excited state because of the significant charge distribution difference between the different electronic states. The electronic excited-state hydrogen-bonding dynamics, which are predominantly determined by the vibrational motions of the hydrogen donor and acceptor groups, generally occur on ultrafast time scales of hundreds of femtoseconds. As a result, state-of-the-art femtos...

Light Generation and Harvesting in a Van der Waals Heterostructure

Abstract: Two-dimensional (2D) materials are a new type of materials under intense study because of their interesting physical properties and wide range of potential applications from nanoelectronics to sensing and photonics. Monolayers of semiconducting transition metal dichalcogenides MoS2 or WSe2 have been proposed as promising channel materials for field-effect transistors. Their high mechanical flexibility, stability, and quality coupled with potentially inexpensive production methods offer potential advantages compared to organic and crystalline bulk semiconductors. Due to quantum mechanical confinement, the band gap in monolayer MoS2 is direct in nature, leading to a strong interaction with light that can be exploited for building phototransistors and ultrasensitive photodetectors. Here, we report on the realization of light-emitting diodes based on vertical heterojunctions composed of n-type monolayer MoS2 and p-type silicon. Careful interface engineering allows us to realize diodes showing rectification and light emission from the entire surface of the heterojunction. Electroluminescence spectra show clear signs of direct excitons related to the optical transitions between the conduction and valence bands. Our p–n diodes can also operate as solar cells, with typical external quantum efficiency exceeding 4%. Our work opens up the way to more sophisticated optoelectronic devices such as lasers and heterostructure solar cells based on hybrids of 2D semiconductors and silicon.

Boron doped graphitic carbon nitride with acid-base duality for cycloaddition of carbon dioxide to epoxide under solvent-free condition

Abstract: The cycloaddition of CO 2 and epoxides to yield cyclic carbonate under solvent-free conditions is an eco-friendly way to utilize CO 2 in environmental science and green chemistry. In this paper, we report that boron doped carbon nitride (BCN) is highly active and selective for such reactions. BCN, especially if supported on mesoporous silica SBA-15 (i.e., B 0.1 CN/SBA-15), shows above 95% conversion and selectivity for cycloaddition of CO 2 and styrene oxide (SO) to yield styrene carbonate (SC), even under solvent-free conditions. That is mainly due to the acid-base duality induced by B doping, which enables the co-activation of CO 2 and epoxide. A mechanism based on acid-base duality is proposed, where CO 2 is activated on the basic >NH sites and SO is on the acidic −B(OH) 2 sites through a hydrogen bonding. The co-activated CO 2 and SO react with each other to yield the SC. Density functional theory (DFT) calculations were conducted to support the mechanism, which show that the co-adsorption of CO 2 and SO on BCN is energetically favorable and the reaction follows the Langmuir-Hinshelwood mechanism. The BCN with acid-base duality provides an option for cheap, green and efficient catalysts for CO 2 utilization.