Zhifeng Ren

Bio: Zhifeng Ren is an academic researcher from Texas Center for Superconductivity. The author has contributed to research in topics: Thermoelectric effect & Thermoelectric materials. The author has an hindex of 122, co-authored 695 publications receiving 71212 citations. Previous affiliations of Zhifeng Ren include Massachusetts Institute of Technology & University of Cincinnati.

Randomly Textured Absorber for Omnidirectional Light Absorption

Abstract: Realizing light manipulation with respect to both frequency and angular selectivity is of great significance for sunlight‐to‐heat conversion, but developing a facile and scalable method to enhance light absorption at oblique incidence remains a major challenge. Here a randomly textured absorber is theoretically designed and experimentally achieved by depositing a Ti‐SiO2 cermet‐based quasi‐optical cavity structure absorber onto a structured stainless‐steel substrate to realize omnidirectional absorption‐enhanced light absorption over a wide incidence‐angle range up to 75°. A strategy is employed of combined chemical etching and sputtering that is suitable for large‐scale production to prepare the randomly textured absorber, which exhibits a near‐complete absorption of 98% at near‐normal incidence. It also shows a remarkable angular absorption of higher than 85% at an oblique incidence angle of 75°, surpassing previously reported absorbers. The absorber's superior angular absorption is ascribed to multiscale scattering on its randomly textured surface and resonance absorption in its quasi‐optical cavity structure. In addition, the randomly textured absorber demonstrates good hydrophobicity, which is beneficial for practical photothermal applications. This appealing strategy highlights a new route for fabricating other omnidirectional absorbers.

SYSTEMS AND METHODS FOR THE SYNTHESIS OF HIGH THERMOELECTRIC PERFORMANCE DOPED-SnTe MATERIALS

Abstract: A thermoelectric composition comprising tin (Sn), tellurium (Te) and at least one dopant that comprises a peak dimensionless figure of merit ( ZT ) of 1.1 and a Seebeck coefficient of at least 50 µV/K and a method of manufacturing the thermoelectric composition. A plurality of components are disposed in a ball-milling vessel, wherein the plurality of components comprise tin (Sn), tellurium (Te), and at least one dopant such as indium (In). The components are subsequently mechanically and thermally processed, for example, by hot-pressing. In response to the mechanical-thermally processing, a thermoelectric composition is formed, wherein the thermoelectric composition comprises a dimensionless figure of merit ( ZT ) of the thermoelectric composition is at least 0.8, and wherein a Seebeck coefficient of the thermoelectric composition is at least 50 µV/K at any temperature.

Carbon Nanotubes Based Nanoelectrode Arrays: Fabrication, Evaluation, and Sensing Applications

Abstract: The fabrication, electrochemical characterization, and applications of low-site density carbon nanotubes based nanoelectrode arrays (CNT-NEAs) are reported in this work. Spin-coating of an epoxy resin provides a new way to create the electrode passivation layer that effectively reduces the current leakage and eliminates the electrode capacitance by sealing the side-wall of CNTs. The CNT-NEAs fabricated in our work effectively use the open ends of CNTs for electrochemical sensing. The open ends of the CNTs have fast electron transfer rates similar to a graphite edge-plane electrode, while the side-walls present very slow electron transfer rates similar to the graphitic basal plane. Cyclic voltammetry showed the sigmoidal shape curves with low capacitive current and scan-rate-independent limiting current. The CNT-NEAs were used successfully for voltammetric detection of trace concentrations of lead (II) at ppb level. The successful development of a glucose biosensor based on CNT-NEAs for the selective detection of glucose is also described. Glucose oxidase was covalently immobilized on the CNTs tips via carbodiimide chemistry by forming amide linkages between the amine residues and carboxylic acid groups on the open ends of CNTs. The biosensor effectively performs selective electrochemical detections of glucose in the presence of common interferences. The CNT-NEAs provide anmore » excellent platform for ultra sensitive electrochemical sensors for chemical and biological sensing.« less

Cerium Doped Bismuth Antimony

Abstract: Bismuth-Antimony alloys have been shown to have high ZT values below room temperature, especially for single crystals. For polycrystalline samples, impurity doping and magnetic field have proven to be powerful tools in the search for understanding and improving thermoelectric performance. Nanopolycrystalline Bi0.88Sb0.12 doped with 0.05, 0.5 and 3 % Ce were prepared by ball milling and dc hot pressing techniques. Electrical resistivity, Seebeck coefficient, thermal conductivity, carrier concentration, mobility, and magnetization are measured in a temperature range of 5-350 K and in magnetic fields up to 9 Tesla. The effects of Ce doping on the thermoelectric properties of Bi0.88Sb0.12 in zero magnetic field are discussed.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Carbon Nanotubes--the Route Toward Applications

Abstract: Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects. Some of these applications are now realized in products. Others are demonstrated in early to advanced devices, and one, hydrogen storage, is clouded by controversy. Nanotube cost, polydispersity in nanotube type, and limitations in processing and assembly methods are important barriers for some applications of single-walled nanotubes.