Kan Wang

Bio: Kan Wang is an academic researcher from University of Science and Technology of China. The author has contributed to research in topics: Hydrothermal carbonization & Electrospinning. The author has an hindex of 4, co-authored 4 publications receiving 2085 citations.

Engineering Carbon Materials from the Hydrothermal Carbonization Process of Biomass

Abstract: Energy shortage, environmental crisis, and developing customer demands have driven people to find facile, low-cost, environmentally friendly, and nontoxic routes to produce novel functional materials that can be commercialized in the near future. Amongst various techniques, the hydrothermal carbonization (HTC) process of biomass (either of isolated carbohydrates or crude plants) is a promising candidate for the synthesis of novel carbon-based materials with a wide variety of potential applications. In this Review, we will discuss various synthetic routes towards such novel carbon-based materials or composites via the HTC process of biomass. Furthermore, factors that influence the carbonization process will be analyzed and the special chemical/physical properties of the final products will be discussed. Despite the lack of a clear mechanism, these novel carbonaceous materials have already shown promising applications in many fields such as carbon fixation, water purification, fuel cell catalysis, energy storage, CO(2) sequestration, bioimaging, drug delivery, and gas sensors. Some of the most promising examples will also be discussed here, demonstrating that the HTC process can rationally design a rich family of carbonaceous and hybrid functional carbon materials with important applications in a sustainable fashion.

Large-scale synthesis of flexible free-standing SERS substrates with high sensitivity: electrospun PVA nanofibers embedded with controlled alignment of silver nanoparticles.

Abstract: A new and facile way to synthesize a free-standing and flexible surface-enhanced Raman scattering (SERS) substrate has been successfully developed, where high SERS-active Ag dimers or aligned aggregates are assembled within poly(vinyl alcohol) (PVA) nanofibers with chain-like arrays via electrospinning technique. The aggregation state of the obtained Ag nanoparticle dimers or larger, which are formed in a concentrated PVA solution, makes a significant contribution to the high sensitivity of SERS to 4-mercaptobenzoic acid (4-MBA) molecules with an enhancement factor (EF) of 109. The superiority of enhancement ability of this Ag/PVA nanofiber mat is also shown in the comparison to other substrates. Furthermore, the Ag/PVA nanofiber mat would keep a good reproducibility under a low concentration of 4-MBA molecule (10−6 M) detection with the average RSD values of the major Raman peak less than 0.07. The temporal stability of the substrate has also been demonstrated. This disposable, easy handled, flexible fre...

Microwave-assisted rapid facile "Green" synthesis of uniform silver nanoparticles: Self-assembly into multilayered films and their optical properties

Abstract: We report an environmentally benign process for the synthesis of nearly monodisperse silver nanoparticles in large quantities via a microwave-assisted “green” chemistry method in an aqueous system, using basic amino acids, such as l-lysine or l-arginine, as reducing agents and soluble starch as a protecting agent. The presence of amino acids with basicity such as l-lysine or l-arginine, having two amino groups in each molecule, is indispensable for the synthesis of uniform silver nanoparticles. The current synthetic process can be readily applied to large-scale production, for example, a reaction yielding 0.1 g of nearly monodisperse silver nanoparticles can be performed in a 80 mL microwave sealed vessel. This combination of solvent, renewable reactants, and microwave irradiation seem to make it clear that green chemical synthesis of metal nanoparticles with well-controlled shapes, sizes, and structures has practical potential. Self-assembly of starch-capped silver nanoparticles results in multilayered m...

Functional carbonaceous materials from hydrothermal carbonization of biomass: an effective chemical process

Abstract: Recently, much attention has been attracted to the use of biomass to produce functional carbonaceous materials from the viewpoint of economic, environmental and societal issues. Among different techniques, the hydrothermal carbonization (HTC) process, a traditional but recently revived method, presents superior characteristics that make it a promising route of wide potential application. This perspective gives an overview of the latest advances in the HTC process of functional carbonaceous materials from biomass. First, we discuss the preparation of carbonaceous materials synthesized by the use of either highly directed or catalyst/template-assisted methods, from crude plant materials and carbohydrates respectively. These carbonaceous materials not only have special morphologies, such as nanospheres, nanocables, nanofibers, submicrocables, submicrotubes and porous structures, but also contain rich functional groups which can greatly improve hydrophilicity and chemical reactivity. Further, a general look is cast on the applications of this kind of carbonaceous materials in environmental, catalytic and electrical areas. Recent advances have demonstrated that the HTC process from biomass can provide promising methods for the rational design of a rich family of carbonaceous and hybrid functional carbon materials with important applications.

Electrospinning and Electrospun Nanofibers: Methods, Materials, and Applications

Abstract: Electrospinning is a versatile and viable technique for generating ultrathin fibers. Remarkable progress has been made with regard to the development of electrospinning methods and engineering of electrospun nanofibers to suit or enable various applications. We aim to provide a comprehensive overview of electrospinning, including the principle, methods, materials, and applications. We begin with a brief introduction to the early history of electrospinning, followed by discussion of its principle and typical apparatus. We then discuss its renaissance over the past two decades as a powerful technology for the production of nanofibers with diversified compositions, structures, and properties. Afterward, we discuss the applications of electrospun nanofibers, including their use as "smart" mats, filtration membranes, catalytic supports, energy harvesting/conversion/storage components, and photonic and electronic devices, as well as biomedical scaffolds. We highlight the most relevant and recent advances related to the applications of electrospun nanofibers by focusing on the most representative examples. We also offer perspectives on the challenges, opportunities, and new directions for future development. At the end, we discuss approaches to the scale-up production of electrospun nanofibers and briefly discuss various types of commercial products based on electrospun nanofibers that have found widespread use in our everyday life.

Carbon quantum dots: synthesis, properties and applications

Abstract: Carbon quantum dots (CQDs, C-dots or CDs), which are generally small carbon nanoparticles (less than 10 nm in size) with various unique properties, have found wide use in more and more fields during the last few years. In this feature article, we describe the recent progress in the field of CQDs, focusing on their synthetic methods, size control, modification strategies, photoelectric properties, luminescent mechanism, and applications in biomedicine, optronics, catalysis and sensor issues.

Synthesis of Nitrogen-Doped Porous Carbon Nanofibers as an Efficient Electrode Material for Supercapacitors

Abstract: Supercapacitors (also known as ultracapacitors) are considered to be the most promising approach to meet the pressing requirements of energy storage. Supercapacitive electrode materials, which are closely related to the high-efficiency storage of energy, have provoked more interest. Herein, we present a high-capacity supercapacitor material based on the nitrogen-doped porous carbon nanofibers synthesized by carbonization of macroscopic-scale carbonaceous nanofibers (CNFs) coated with polypyrrole (CNFs@polypyrrole) at an appropriate temperature. The composite nanofibers exhibit a reversible specific capacitance of 202.0 F g–1 at the current density of 1.0 A g–1 in 6.0 mol L–1 aqueous KOH electrolyte, meanwhile maintaining a high-class capacitance retention capability and a maximum power density of 89.57 kW kg–1. This kind of nitrogen-doped carbon nanofiber represents an alternative promising candidate for an efficient electrode material for supercapacitors.

Doping carbons beyond nitrogen: an overview of advanced heteroatom doped carbons with boron, sulphur and phosphorus for energy applications

Abstract: Heteroatom doped carbon materials represent one of the most prominent families of materials that are used in energy related applications, such as fuel cells, batteries, hydrogen storage or supercapacitors. While doping carbons with nitrogen atoms has experienced great progress throughout the past decades and yielded promising material concepts, also other doping candidates have gained the researchers' interest in the last few years. Boron is already relatively widely studied, and as its electronic situation is contrary to the one of nitrogen, codoping carbons with both heteroatoms can probably create synergistic effects. Sulphur and phosphorus have just recently entered the world of carbon synthesis, but already the first studies published prove their potential, especially as electrocatalysts in the cathodic compartment of fuel cells. Due to their size and their electronegativity being lower than those of carbon, structural distortions and changes of the charge densities are induced in the carbon materials. This article is to give a state of the art update on the most recent developments concerning the advanced heteroatom doping of carbon that goes beyond nitrogen. Doped carbon materials and their applications in energy devices are discussed with respect to their boron-, sulphur- and phosphorus-doping.