Materials Science: State of the Art 2010

Abstract

Each week, Advanced Materials brings you a Review of a cutting-edge topic in materials science, accompanied by a number of short Communications. This issue, however, is different. For the first time, we have selected eight review articles written by leaders in their respective fields to survey what we believe to be the state of the art in materials science in early 2010. From molecular electronics to biomaterials, solar cells to inorganic structures, we hope these reviews will provide an overview of some of the most exciting advances being made in materials science as we enter the second decade of the 20th century. As featured on the cover of this issue, Wenping Hu and Daoben Zhu (Insitute of Chemistry, Chinese Academy of Sciences) review ten years of progress in the development of nanogap electrodes. Electrodes with a nanometer gap can be used for the study of nanometer- and molecular-scale phenomena. Single-molecule transistors, carbon nanotube electrodes, DNA nanowires, and more have all been studied using this technique, and the authors predict a bright future for the field as challenges in reliable electrode manufacture and determining the number of molecules between a nanogap are met and overcome. A major theme in molecular electronics has been the study of single-molecule junctions. While this facilitates theoretical modeling, researchers have faced issues with reproducibility. Ayelet Vilan and David Cahen of the Weizmann Institute of Science and Antoine Kahn of Princeton review ensemble molecular junctions. The study of large, two-dimensional molecular monolayers on silicon has resulted in high-quality, reproducible systems for the study of charge transport mechanisms and energy levels in such hybrid systems. High-efficiency intermediate band solar cells are reviewed by Antonio Luque and Antonio Martí (Universidad Politécnica de Madrid). Since the first report of the concept more than a decade ago, their maximum theoretical efficiency of 63% has proven a tempting target, and work on systems based on quantum dots and on IB alloys have been pursued. Significant progress has been made, and further work on improving the efficiency might lead to low-cost, high-efficiency thin photovoltaics. David Kaplan (Tufts) examines the state of the art in bio-microfluidics: the application of biomaterials and bioinspired design to microfluidics. Biopolymers such as silk or fibroin can replace polydimethylsiloxane and be functionalized with bioactive or stimuli-responsive components. In the future, a bio-microfluidic system might be designed to interface with existing vasculature, disintegrating over time to be replaced with native tissue, resulting in engineered tissue with enhanced transport properties during its development. The incorporation of stem cells into strategies for tissue engineering requires better understanding of the interactions of stem cells with their synthetic environment. To this end, Jason Burdick (University of Pennsylvania) reviews how materials influence stem cell differentiation. The material structure, the chemistry, and the presentation and delivery of differentiation factors influence the differentiation of mensenchymal stem cells, as can control of the cell morphology and the mechanical properties and interactions of the surrounding matrix. Stem cells are sensitive to their microenviroments, and rationally controlling many different variables in a tissue engineering scaffold will be critical for complex regenerative medicine challenges. Rainer Haag and co-workers comprehensively discuss recent progress in developing dendritic polyglycols for biomedical applications. The well-defined structure, monodispersity, and tunable surface functionality of dendrimers, coupled with the non-recognition of polyols by the immune system, make these structures interesting targets for development of nanomedical applications. Metal oxides present a stunningly broad range of structural, electronic, optical, and magnetic properties, making them critical for technological applications as well as presenting fundamental materials science issues. In his review, Scott Chambers (Pacific Northwest National Laboratory) discusses crystalline oxide film growth and, in particular, examines doped transition metal oxides and complex oxides, giving examples where fundamental understanding of the properties has elucidated structure-function relationships. Finally, while applications of ionic liquids for solvent extraction and organic catalysis are well know, the use of ionic liquids for inorganic material synthesis is less than a decade old. As featured on the inside cover of this issue, Sheng Dai (Oak Ridge National Laboratory) and co-workers review progress in ionic liquid mediated synthesis of metal and non-metal nanoparticles, porous silica, metal oxides, metal chalcogenides, porous frameworks, and materials functionalized with ionic liquids.