Professor C. N. R. Rao on his 75th birthday

It gives us enormous pleasure to write this Editorial for the issue of Journal of Materials Chemistry to mark the 75th birthday of Professor C. N. R. Rao. Ram, as he is known to his many friends, is one of the world's leading chemists. His contributions to the field of solid-state and materials chemistry are remarkable for their originality, enormous diversity, and extraordinary prolificacy (over 1400 papers and 40 books in a career spanning over 50 years). Not surprisingly, he has a very impressive citation record (over 35 000 citations and an h-index of 84), especially for the work that he has done in the last decade. His early interests lay in the area of spectroscopy, where he did pioneering IR and NMR studies on hydrogen bonding in model systems. He later transitioned to surface chemistry, particularly the use of photoelectron spectroscopy, where his work also had a major influence. However, his impact has undoubtedly been most dramatic in some of the more recent developments in the materials chemistry of oxides and nanomaterials. For example, his extensive contributions to our understanding of the metal to semiconductor transition and the relationship between magnetism and electronic properties in transition metal oxides include early work on the electronic structure of the parent compound of the high T_c superconductors, La₂CuO₄. His experience with metal cuprates placed him in a strong position to make early and highly significant contributions in the high T_c area in 1986. For example, he was one of the first to recognize that the chemical composition of yttrium barium cuprate, which was the first material with a T_c in excess of the boiling point of liquid nitrogen, was YBa₂Cu₃O₇. This is all the more remarkable, given that thousands of solid-state chemists and physicists, in the world's best-equipped laboratories, were working intensively on this material.

More recently, Ram's experience with oxide ceramics enabled him to become a major player in another exciting area of modern materials science—colossal magnetoresistance in lanthanum manganates and related materials. His group has made substantial contributions in this area during the last 15 years, in particular concerning the influence of cation size on the diverse electronic and magnetic properties of these materials. This work has led naturally into equally important contributions in the closely related areas of charge ordering, where he has elucidated the factors that control the delicate balance between charge ordering, orbital ordering and ferromagnetism, as well as multiferroics and phase separation.

Ram's impact has extended to other competitive areas of materials chemistry, including the structure of liquids and the chemistry of fullerenes. His contributions in these areas have shared a common thread—the complementary use of both spectroscopic methods and Monte Carlo simulations to study phase transitions (which have also been a life-long interest and the subject of one of his many books). As a measure of his standing in the fullerene area at the height of their popularity, it is worth noting that Ram was chosen as one of three guest editors for a special Fullerenes issue of the Bulletin of the Materials Research Society in 1994. He has more recently focused his attention on nanotubes and nanowires, where, in addition to working on carbon systems, his knowledge of oxides enabled him to make the first nanotubes based upon oxide ceramics. The nanotube and nanowire theme has continued to fascinate him. For example, in 2001 he developed an ingenious and simple method for synthesizing nanotubes based upon transition metal sulfides, and he has also discovered novel ways of synthesizing a host of oxide and nitride nanowires. Very recently, he has discovered a simple arc-discharge strategy for the controlled synthesis of graphene samples that are two to four layers thick.

During the last decade, Ram has also become heavily involved in research on open-framework materials, particularly phosphates, sulfates and carboxylates, and he has enjoyed a very stimulating and productive collaboration with one of the authors of this Editorial (A. K. C.) in this area. Ram's own group has focused very much on the difficult question of how such materials form from smaller units that are present in solution under hydrothermal conditions, and he has recently written a terrific Chemical Review on this area, with specific emphasis on phosphates.

It is important to remember that Ram Rao's monumental achievements have been accomplished in less than the most favorable of circumstances. It is also important on this occasion to celebrate his substantial contributions to science and society in the broader sense, including his work as President of the International Union of Pure and Applied Chemistry (IUPAC) and especially his dynamic and most effective Presidency of the Academy of Sciences for the Developing World (TWAS). Nor should we forget his impressive track record as a builder of institutions and as a tireless educator of both young and old.

Ram Rao's extraordinary achievements, as well as his drive and passion to create heretofore unknown materials with unique properties, have been, and continue to be, an inspiration to generations of scientists, worldwide. His accomplishments have been recognized by his peers through election to virtually every national academy in both the developed and the developing world and by an enormous number of national and international awards. Additionally, he has served on the Advisory Board of Journal of Materials Chemistry since its launch in 1991.

In this issue, articles authored by many who have been closely associated with Ram are featured. Ram, on behalf of your many friends and colleagues around the world, we are delighted to wish you a very happy 75th birthday. We hope that you will enjoy many more years of excellent health, creative science, and great happiness with your dear wife, and companion, Indu.

Tony Cheetham, Mike Klein and Swapan Pati.

---