2008 KAVLI PRIZE LAUREATES IN NANOSCIENCE

THE 2008 KAVLI PRIZE IN NANOSCIENCE is awarded to Louis Brus and Sumio Iijima "for their large impact in the development of the nanoscience field of the zero and one-dimensional nanostructures in physics, chemistry, and biology." When the electronic motion in a solid is confined to zero or one dimension on the nanometer scale, its functional properties can be dramatically altered. This makes nanostructures a subject of both fundamental and practical interest. On this scale, corresponding to the dimension of a few atoms, quantum effects change and lead to unexpected and technically interesting properties. Among the many structures investigated in the last few decades, carbon nanotubes and colloidal nanoparticles have proven to be promising quantum structures in physics, chemistry, and biology, and are actively explored in many research laboratories worldwide. Louis Brus created the interdisciplinary field of colloidal semiconductor nanocrystals, through original discovery, theoretical modelling, chemical synthesis of purified samples, and by studying the spectroscopy of individual nanocrystals. His research, leadership, and mentoring have played a leading role in opening world-wide interest in colloidal nanomaterials with controlled size-dependent properties. The results of his studies have led to a surge of activities by many researchers in the field in the areas of synthesis and the application of these colloidal nanoparticles in many areas of chemistry, biology, and medicine, a few examples of which are discussed below. Colloidal semiconductor nanocrystals, commonly called quantum dots (QD), have a number of properties such as the dependence of their fluorescence wavelength on size and their long-time stability. This makes them suitable for fluorescence based dynamic studies of molecular interactions and reactions in biological systems. There is considerable interest among researchers due to the recent developments in binding colloidal nanocrystals to tumor-targeting antibodies or as drug delivery agent for targeting, imaging, and treating tumor cells. Present efforts are focused on exploring the multiplexing capabilities of the QDs for the simultaneous detection of multiple cancer biomarkers in blood assays and cancer tissue biopsies. These advances in the QD technology have unravelled a great deal of information about the molecular events in tumor cells. In the solar energy field, photovoltaic cells using QD-polymer composite may offer advantages such as mechanical flexibility, low cost, and hopefully increased efficiency. Success in making proof-of-concept quantum dot displays has been achieved. They are useful because they emit light in very specific spectral distributions that can be selected in a display which can more accurately render the colours that the human eye can perceive. Sumio Iijima prepared a new type of finite carbon structure consisting of needle-like tubes using an arc-discharge evaporation method. He also did careful electron microscopic analysis of the structure that revealed that each needle comprises coaxial tubes of graphitic sheets, ranging in number from 2 up to about 50. On each tube, the carbon-atom hexagons are arranged in a helical fashion about the needle axis. The helical pitch varies from needle to needle and from tube to tube within a single needle. From this detailed structural analysis, he has pointed out to many future applications of these nanotubes. They have interesting mechanical, electrical, and thermal properties. They are much stronger than steel at one sixth of the weight. For these reasons, they are used in the re-enforcement of mechanical strength of composite materials ranging from everyday items like clothes and sports gear to construction materials such as cement. The electrical and thermal properties of nanotubes change with their diameter and are sensitive to the way the nanotube is formed. Depending on their atomic structure, they can have semiconducting or metallic properties. For this reason, they have potential use as electronic components such as diodes and transistors, wires, transparent and conductive films; electrodes for super-capacitors; field emitters for displays; and sensor applications. The functionality of nanotubes can be expanded by filling them with active atoms and molecules for various future uses. Colloidal semiconductor nanocrystals and carbon nanotubes will thus play a key role in the future various applications of nanoscience in the fields of energy, environment, electronics, chemistry, composite materials, and bio-medicine. In 2007, Sumio Iijima received the International Balzan Prize for Nanoscience.