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.

Density controlled carbon nanotube array electrodes

Abstract: CNT materials comprising aligned carbon nanotubes (CNTs) with pre-determined site densities, catalyst substrate materials for obtaining them and methods for forming aligned CNTs with controllable densities on such catalyst substrate materials are described. The fabrication of films comprising site-density controlled vertically aligned CNT arrays of the invention with variable field emission characteristics, whereby the filed emission properties of the films are controlled by independently varying the length of th CNTs in the aligned array within the film or by independently varying inter-tubule spacing of the CNTs within the array (site density) are disclosed. The fabrication of microelectrode arrays (MEAs) formed utilizing the carbon nanotrube material of the invention is also described.

Thermoelectric Properties of n-type ZrNiPb-Based Half-Heuslers

Abstract: Here we investigate the half-Heusler ZrNiPb as a n-type thermoelectric material. Our results show that the n-type ZrNiPb-based materials can achieve high peak power factors, ∼50 μW cm–1 K–2, by optimally tuning the carrier concentration via Bi doping. By further Sn-alloying in Pb site, we achieve a significant reduction of lattice thermal conductivity while maintaining the power factor almost unchanged and hence noticeably improve the ZT. Our work demonstrates that n-type ZrNiPb-based half-Heuslers are promising thermoelectric materials.

Photovoltaic cell and method of making thereof

Abstract: A photovoltaic cell includes a first electrode, a second electrode, and a photovoltaic material located between and in electrical contact with the first and the second electrodes. The photovoltaic material comprises i) semiconductor nanocrystals having a bang gap that is significantly smaller than peak solar radiation energy to exhibit a multiple exciton effect in response to irradiation by the solar radiation; and/or ii) a first and a second set of semiconductor nanocrystals and the nanocrystals of the first set have a different band gap energy than the nanocrystals of the second set. A width of the photovoltaic material in a direction from the first electrode to the second electrode is less than about 200 nm while a height of the photovoltaic material in a direction substantially perpendicular to the width of the photovoltaic material is at least 1 micron.

Using Block Copolymer Micellar Thin Films as Templates for the Production of Catalysts for Carbon Nanotube Growth

Abstract: We report a novel approach that uses block copolymer micelles as a means to create large area arrays of iron-containing nanoclusters capable of catalyzing the growth of carbon nanotubes (CNTs). The amphiphilic block copolymer poly(styrene-block-acrylic acid) (PS-b-PAA) forms micelles in solution which are capable of self-organizing into ordered structures on surfaces. By spin-coating these solutions onto a variety of substrates, we can create quasi-hexagonal arrays of PAA spheres within a PS matrix. The carboxylic acids groups in the PAA domains can be utilized in an ion-exchange protocol to selectively sequester iron ions, which results in iron-containing nanoclusters that are nearly monodisperse in size (diameter ∼8 nm) and patterned at a density of approximately 1011 particles per cm2. In principle, this route for synthesizing iron-containing nanoclusters offers the capability of controlling the cluster size and spacing by altering the molecular weight of the block copolymer. In this report, we demonst...

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.