Zheng Li

Bio: Zheng Li is an academic researcher from Hunan University. The author has contributed to research in topics: Mesoporous material & Quantum dot. The author has an hindex of 19, co-authored 32 publications receiving 3128 citations. Previous affiliations of Zheng Li include Argonne National Laboratory & University of Arkansas.

Ordered Mesoporous Polymers and Homologous Carbon Frameworks: Amphiphilic Surfactant Templating and Direct Transformation

Abstract: Organic porous materials—a class of advanced materials— possess enormous potential for many high-tech applications, such as bioreactors, dielectrics, sensors, microelectrophoresis, thermal insulation, and catalysts. In general, they can be prepared by phase separation, and a hard templating approach, such as those employing colloidal particles. Phase separation can be derived from organic– organic phases, while the pore structures can be formed after etching, or by dissolving one block (A) from the assembled block copolymer (A–B). However, most of the resulting porous polymer structures are disordered with wide pore size distributions because of the contraction and swelling from changes in volume, as well as the structured defects formed during template removal. Large porosities have rarely been reported. Furthermore, the resistance of the pore structure to heat and solvents is rather low because the materials are formed by weak van der Waals forces and physical twists between polymer chains, which means that the framework is not connected by covalent bonds. Recently, a procedure for cross-linking lyotropic liquid crystals (LLC) in water was introduced to prepare periodic porous organic mesostructures. Unfortunately, polymerization only occurs between nearest neighboring head groups, and the mesostructured channels are fully occupied with solution. Therefore, it is not surprising that porosity has yet to be reported. Carbon materials, including nanotubes and fullerenes, have attracted considerable attention because of their remarkable properties. The traditional carbonization process for active carbon and related materials can only generate

Size/shape-controlled synthesis of colloidal CdSe quantum disks: ligand and temperature effects.

Abstract: Size/shape-controlled colloidal CdSe quantum disks with zinc-blende (cubic) crystal structure were synthesized using air-stable and generic starting materials. The colloidal CdSe quantum disks were approximately square, and their lateral dimensions were varied between 20 and 100 nm with the thickness controlled between 1 and 3 nm, which resulted in sharp and blue-shifted UV−vis and PL peaks due to one-dimensional quantum confinement. The quantum disks were grown with either ⟨001⟩ or ⟨111⟩ direction, polar directions in the single crystalline disks, as the short axis, and both basal planes were terminated with Cd ions. These surface Cd ions were passivated with negatively charged fatty acid ligands to neutralize the net positive charges caused by the excess monolayer of Cd ions. The coordination of the Cd ions and carboxylate groups further enabled the close-packing monolayer of fatty acid ligands on each basal plane. The close packing of the hydrocarbon chains of fatty acids dictated the up temperature li...

Nucleation kinetics vs chemical kinetics in the initial formation of semiconductor nanocrystals.

Abstract: The initial formation of semiconductor nanocrystals/nanoclusters, that is, nucleation in the classic literature, was examined both theoretically and experimentally. An experimental method based on determining the initial reaction rate for the formation of nanocrystals/nanoclusters with fixed size and size distribution was developed using InP and CdS nanocrystals/nanoclusters systems, especially the InP one. This experimental strategy relies on the size-dependent absorption spectra of these semiconductor nanoparticles as quantitative probes. The experimental results along with theoretical analysis indicate that the classic nucleation model was unlikely relevant for such crystallization systems, whose bulk crystal solubility in a solution is extremely low. Instead, the formation process was found to match a reaction-controlled kinetics model. The results further imply that understanding of crystallization and development of controlled synthesis of high quality colloidal nanocrystals are both closely related to identifying the molecular mechanism and chemical kinetics.

A review of electrode materials for electrochemical supercapacitors

Abstract: In this critical review, metal oxides-based materials for electrochemical supercapacitor (ES) electrodes are reviewed in detail together with a brief review of carbon materials and conducting polymers. Their advantages, disadvantages, and performance in ES electrodes are discussed through extensive analysis of the literature, and new trends in material development are also reviewed. Two important future research directions are indicated and summarized, based on results published in the literature: the development of composite and nanostructured ES materials to overcome the major challenge posed by the low energy density of ES (476 references).

Carbon-based materials as supercapacitor electrodes

Abstract: This tutorial review provides a brief summary of recent research progress on carbon-based electrode materials for supercapacitors, as well as the importance of electrolytes in the development of supercapacitor technology. The basic principles of supercapacitors, the characteristics and performances of various nanostructured carbon-based electrode materials are discussed. Aqueous and non-aqueous electrolyte solutions used in supercapacitors are compared. The trend on future development of high-power and high-energy supercapacitors is analyzed.

Advanced Materials for Energy Storage

Abstract: [Liu, Chang; Li, Feng; Ma, Lai-Peng; Cheng, Hui-Ming] Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, Shenyang 110016, Peoples R China.;Cheng, HM (reprint author), Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, 72 Wenhua Rd, Shenyang 110016, Peoples R China;cheng@imr.ac.cn

Recent Advances in Ultrathin Two-Dimensional Nanomaterials

Abstract: Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

Polymeric Graphitic Carbon Nitride as a Heterogeneous Organocatalyst: From Photochemistry to Multipurpose Catalysis to Sustainable Chemistry

Abstract: Polymeric graphitic carbon nitride materials (for simplicity: g-C(3)N(4)) have attracted much attention in recent years because of their similarity to graphene. They are composed of C, N, and some minor H content only. In contrast to graphenes, g-C(3)N(4) is a medium-bandgap semiconductor and in that role an effective photocatalyst and chemical catalyst for a broad variety of reactions. In this Review, we describe the "polymer chemistry" of this structure, how band positions and bandgap can be varied by doping and copolymerization, and how the organic solid can be textured to make it an effective heterogenous catalyst. g-C(3)N(4) and its modifications have a high thermal and chemical stability and can catalyze a number of "dream reactions", such as photochemical splitting of water, mild and selective oxidation reactions, and--as a coactive catalytic support--superactive hydrogenation reactions. As carbon nitride is metal-free as such, it also tolerates functional groups and is therefore suited for multipurpose applications in biomass conversion and sustainable chemistry.