Lifeng Chi

Bio: Lifeng Chi is an academic researcher from Soochow University (Suzhou). The author has contributed to research in topics: Monolayer & Scanning tunneling microscope. The author has an hindex of 63, co-authored 461 publications receiving 14971 citations. Previous affiliations of Lifeng Chi include Jilin University & Imperial College London.

High- k Gate Dielectrics for Emerging Flexible and Stretchable Electronics

Abstract: Recent advances in flexible and stretchable electronics (FSE), a technology diverging from the conventional rigid silicon technology, have stimulated fundamental scientific and technological research efforts. FSE aims at enabling disruptive applications such as flexible displays, wearable sensors, printed RFID tags on packaging, electronics on skin/organs, and Internet-of-things as well as possibly reducing the cost of electronic device fabrication. Thus, the key materials components of electronics, the semiconductor, the dielectric, and the conductor as well as the passive (substrate, planarization, passivation, and encapsulation layers) must exhibit electrical performance and mechanical properties compatible with FSE components and products. In this review, we summarize and analyze recent advances in materials concepts as well as in thin-film fabrication techniques for high-k (or high-capacitance) gate dielectrics when integrated with FSE-compatible semiconductors such as organics, metal oxides, quantum...

Transparent superhydrophobic/superhydrophilic TiO2-based coatings for self-cleaning and anti-fogging

Abstract: A stable titanate nanobelt (TNB) particle suspension was prepared by a hydrogen-bond-driven assembly of pre-hydrolysed fluoroalkylsilane (FAS) on its surface. A one-step electrophoretic deposition was applied to fabricate a transparent cross-aligned superhydrophobic TNB/FAS film on a conducting glass substrate. By controlling the deposition time, we have shown the transition between a “sticky” hydrophobic state (high contact angle with strong adhesion) and a “sliding” superhydrophobic state (high contact angle with weak adhesion). The optical transmittance can reach as high as 80% throughout most of the visible light region of the spectrum. These coatings have also displayed high chemical stability and self-cleaning ability. Upon heating the hydrophobic coatings at 500 °C, the TNB coating transforms into a porous TiO2(B) structure with superhydrophilic behavior and could be used for anti-fogging applications. With this TiO2-based system, we have demonstrated three different wetting states: superhydrophobicity with weak adhesion, high hydrophobicity with strong adhesion, and superhydrophilicity with immediate water spreading. Moreover, this work has also demonstrated superhydrophobic TNB/FAS films with high chemical stability and good self-cleaning performance and superhydrophilic pore-like TiO2(B) films with rapid water spreading and excellent anti-fogging ability.

Nanoscopic channel lattices with controlled anisotropic wetting

Abstract: Engineered microscopic surface structures allow local control of physical surface properties such as adhesion, friction and wettability. These properties are related both to molecular interactions and the surface topology1,2—for example, selective adsorption and molecular recognition capabilities3 require controlled anisotropy in the surface properties. Chemistry with extremely small amounts of material has become possible using liquid-guiding channels of sub-micrometre dimensions4,5,6. Laterally structured surfaces with differing wettabilities may be produced using various techniques, such as microcontact printing7,8,9, micromachining10, photolithography11,12 and vapour deposition13. Another strategy14 for introducing anisotropic texture is based on the use of the intrinsic material properties of stretched ultrathin polymer coatings. Here we present a fast and simple method to generate extended patterned surfaces with controlled wetting properties on the nanometre scale, without any lithographic processes. The technique utilizes wetting instabilities that occur when monomolecular layers are transferred onto a solid substrate. The modified surfaces can be used as templates for patterning a wide variety of molecules and nanoclusters into approximately parallel channels, with a spatial density of up to 20,000 cm-1.We demonstrate the transport properties of these channels for attolitre quantities of liquid.

A new approach for the fabrication of an alternating multilayer film of poly(4-vinylpyridine) and poly(acrylic acid) based on hydrogen bonding

Abstract: A new approach for the fabrication of a multilayer film assembly is explored, which is based on the alternating assembling of poly(4-vinylpyridine) and poly(acrylic acid) via hydrogen bonding. The homogeneous multilayer films were characterized by UV-Vis, X-ray diffraction and atomic force microscopy (AFM) measurements. The nature of interaction between the two polymers is identified as hydrogen bonding by IR spectroscopy.

Metal Clusters and Colloids

Abstract: The properties of solid matter are determined by the “infinite” three-dimensional arrangement of its building blocks. These can consist of single ions, covalently organized units such as “SiO2” in quartz, or individual molecules in a molecular lattice, e.g., I2 in iodine crystals. What does “infinite” mean? How small can a piece of a distinct material become and still be the same material? The optical properties of quartz, the brilliance of diamond, the conductivity of graphite, or the melting point of gold will all change at some point if the number of specific building blocks becomes small enough. In the last decade there has been important progress towards answering these questions and it has been shown that the nature of materials can dramatically change if the borderline of what we call the “solid state” is reached. Nanometer-sized “cutouts” of various solid materials have been made and their properties studied. In all cases the chemical and physical properties deviate considerably from those of the bulk: the rules of classical mechanics are replaced by those of quantum mechanics. A few examples are presented to elucidate this. Fullerenes as well as carbon nanotubes are considered as nature’s fascinating answer to what happens if the size of an element is reduced to the

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Semiempirical GGA-type density functional constructed with a long-range dispersion correction.

Abstract: A new density functional (DF) of the generalized gradient approximation (GGA) type for general chemistry applications termed B97-D is proposed. It is based on Becke's power-series ansatz from 1997 and is explicitly parameterized by including damped atom-pairwise dispersion corrections of the form C(6) x R(-6). A general computational scheme for the parameters used in this correction has been established and parameters for elements up to xenon and a scaling factor for the dispersion part for several common density functionals (BLYP, PBE, TPSS, B3LYP) are reported. The new functional is tested in comparison with other GGAs and the B3LYP hybrid functional on standard thermochemical benchmark sets, for 40 noncovalently bound complexes, including large stacked aromatic molecules and group II element clusters, and for the computation of molecular geometries. Further cross-validation tests were performed for organometallic reactions and other difficult problems for standard functionals. In summary, it is found that B97-D belongs to one of the most accurate general purpose GGAs, reaching, for example for the G97/2 set of heat of formations, a mean absolute deviation of only 3.8 kcal mol(-1). The performance for noncovalently bound systems including many pure van der Waals complexes is exceptionally good, reaching on the average CCSD(T) accuracy. The basic strategy in the development to restrict the density functional description to shorter electron correlation lengths scales and to describe situations with medium to large interatomic distances by damped C(6) x R(-6) terms seems to be very successful, as demonstrated for some notoriously difficult reactions. As an example, for the isomerization of larger branched to linear alkanes, B97-D is the only DF available that yields the right sign for the energy difference. From a practical point of view, the new functional seems to be quite robust and it is thus suggested as an efficient and accurate quantum chemical method for large systems where dispersion forces are of general importance.

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

Abstract: Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

Aggregation-induced emission

Abstract: Luminogenic materials with aggregation-induced emission (AIE) attributes have attracted much interest since the debut of the AIE concept in 2001. In this critical review, recent progress in the area of AIE research is summarized. Typical examples of AIE systems are discussed, from which their structure–property relationships are derived. Through mechanistic decipherment of the photophysical processes, structural design strategies for generating new AIE luminogens are developed. Technological, especially optoelectronic and biological, applications of the AIE systems are exemplified to illustrate how the novel AIE effect can be utilized for high-tech innovations (183 references).

Shape‐Controlled Synthesis of Metal Nanocrystals: Simple Chemistry Meets Complex Physics?

Abstract: Nanocrystals are fundamental to modern science and technology. Mastery over the shape of a nanocrystal enables control of its properties and enhancement of its usefulness for a given application. Our aim is to present a comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals. We begin with a brief introduction to nucleation and growth within the context of metal nanocrystal synthesis, followed by a discussion of the possible shapes that a metal nanocrystal might take under different conditions. We then focus on a variety of experimental parameters that have been explored to manipulate the nucleation and growth of metal nanocrystals in solution-phase syntheses in an effort to generate specific shapes. We then elaborate on these approaches by selecting examples in which there is already reasonable understanding for the observed shape control or at least the protocols have proven to be reproducible and controllable. Finally, we highlight a number of applications that have been enabled and/or enhanced by the shape-controlled synthesis of metal nanocrystals. We conclude this article with personal perspectives on the directions toward which future research in this field might take.