R. Cava et al. /Progress in Solid State Chemistry 30(2002)1-101 Isolated Chains Sheets Frameworks Clusters 57 53 3 Fig. 2. The structural hierarchy of uranyl minerals based on polymerization of cation polyhedra of higher bond-valence(from Burns, 1999[32] Reprinted by permission of the Mineralogical Society of America, USA). ery different often have the same underlying sheet anion topology. This approach is indispensable when dealing with complex sheets, as it provides the means to relate such sheets to simpler topologies. Most sheet anion topologies from uranyl com- ounds can be constructed as stacking sequences of five different chains of polygons Typically, only one or two chain types are needed to construct a given topology 32], and this approach permits comparison of anion topologies. For example unusually complex sheets of uranyl polyhedra have been found in the structures of the Pb uranyl oxide hydrates vandendriesscheite and wolsendorfite 32, 33, with primitive repeat distances of 41 and 56 A, respectively(Fig 3). Analysis of the sheet anion topologies using the chain stacking sequence approach reveals that both of these sheets are built of modules of simpler sheets(Fig. 4). In this regard, complex uranyl mineral structures are similar to some other mineral structures such as sulpho- salts and complex sulfides Recent structural studies of uranyl minerals provide the foundation for devele ment of an understanding of bonding and structural topologies. Bonding potential △A个A入 n Fig 3. The sheet of uranyl polyhedra in the structure of wolsendorfite(from Burns, 1999[32] Reprinted by permission of the Mineralogical Society of America, USA)
16 R.J. Cava et al. / Progress in Solid State Chemistry 30 (2002) 1–101 Fig. 2. The structural hierarchy of uranyl minerals based on polymerization of cation polyhedra of higher bond-valence (from Burns, 1999[32] Reprinted by permission of the Mineralogical Society of America, USA). very different often have the same underlying sheet anion topology. This approach is indispensable when dealing with complex sheets, as it provides the means to relate such sheets to simpler topologies. Most sheet anion topologies from uranyl compounds can be constructed as stacking sequences of five different chains of polygons. Typically, only one or two chain types are needed to construct a given topology [32], and this approach permits comparison of anion topologies. For example, unusually complex sheets of uranyl polyhedra have been found in the structures of the Pb uranyl oxide hydrates vandendriesscheite and wo¨lsendorfite [32,33], with primitive repeat distances of 41 and 56 A˚ , respectively (Fig. 3). Analysis of the sheet anion topologies using the chain stacking sequence approach reveals that both of these sheets are built of modules of simpler sheets (Fig. 4). In this regard, complex uranyl mineral structures are similar to some other mineral structures such as sulphosalts and complex sulfides. Recent structural studies of uranyl minerals provide the foundation for development of an understanding of bonding and structural topologies. Bonding potentials Fig. 3. The sheet of uranyl polyhedra in the structure of wo¨lsendorfite (from Burns, 1999[32] Reprinted by permission of the Mineralogical Society of America, USA)
R. Cava et al. Progress in Solid State Chemistry 30(2002)1-101 鑫 圣￥至 Fig 4. Development of the wolsendorfite sheet anion topology as a stacking sequence of chains. This approach demonstrates that the wolsendorfite anion topology is composed of modules of the simpler a- U3Os and B-U3Os anion topologies( Reprinted by permission of the Mineralogical Society of America, for uranyl polyhedra should be established, perhaps using quantum mechanical simu- lations, although this approach is especially demanding because of relativistic effects involving core electrons on the U atoms. Such potentials may then be used for static energy minimizations and molecular dynamic simulations of uranyl minerals, includ- ing crystal surfaces. The relationships between the structural units and interstitial components also need to be modeled, and the role of interstitial components as struc- ure directing agents should be addressed. An understanding of the energetics of complex sheets of uranyl polyhedra is needed, and may provide the basis for develop- ment of a method to predict thermodynamic properties of uranyl minerals on the basis of structural connectivity X-ray absorption spectroscopy(XAS) permits the probing of oxidation states and local coordination environments about U in minerals [34. Further development of this approach is warranted in the area of analysis of extended X-ray absorption fine structure(EXAFS)Spectra for U6. The situation is complex owing to the occurrence of U6+ in three different coordination environments, and the sharing of uranyl poly hedral elements with a diverse range of oxyanions, including silicate, phosphate arsenate, carbonate, vanadate, and sulfate. The spectra of Ue+ associated with mineral and bacteria surfaces can also be difficult to interpret [35, 36]. Studies of the EXAFS spectra of several model compounds containing different coordination environments about U+, and multiple U valence states, will substantially improve the applicability of this technique to complex natural specimens Recent advances in characterization of the structures and chemistries of uranyl minerals provide the foundation for studies of their thermodynamics. However, there
R.J. Cava et al. / Progress in Solid State Chemistry 30 (2002) 1–101 17 Fig. 4. Development of the wo¨lsendorfite sheet anion topology as a stacking sequence of chains. This approach demonstrates that the wo¨lsendorfite anion topology is composed of modules of the simpler aU3O8 and b-U3O8 anion topologies (Reprinted by permission of the Mineralogical Society of America, USA). for uranyl polyhedra should be established, perhaps using quantum mechanical simulations, although this approach is especially demanding because of relativistic effects involving core electrons on the U atoms. Such potentials may then be used for static energy minimizations and molecular dynamic simulations of uranyl minerals, including crystal surfaces. The relationships between the structural units and interstitial components also need to be modeled, and the role of interstitial components as structure directing agents should be addressed. An understanding of the energetics of complex sheets of uranyl polyhedra is needed, and may provide the basis for development of a method to predict thermodynamic properties of uranyl minerals on the basis of structural connectivity. X-ray absorption spectroscopy (XAS) permits the probing of oxidation states and local coordination environments about U in minerals [34]. Further development of this approach is warranted in the area of analysis of extended X-ray absorption fine structure (EXAFS) spectra for U6+ . The situation is complex owing to the occurrence of U6+ in three different coordination environments, and the sharing of uranyl polyhedral elements with a diverse range of oxyanions, including silicate, phosphate, arsenate, carbonate, vanadate, and sulfate. The spectra of U6+ associated with mineral and bacteria surfaces can also be difficult to interpret [35,36]. Studies of the EXAFS spectra of several model compounds containing different coordination environments about U6+ , and multiple U valence states, will substantially improve the applicability of this technique to complex natural specimens. Recent advances in characterization of the structures and chemistries of uranyl minerals provide the foundation for studies of their thermodynamics. However, there
R. Cava et al. /Progress in Solid State Chemistry 30(2002)1-101 is a dearth of material and much of what is available are natural intergrowths of phases. Calorimetric studies of carefully characterized synthetic and natural uranyl compounds will further establish the thermodynamic properties of these minerals and should provide the underpinning for development of methods of prediction of thermodynamic parameters based upon structural connectivity 2.5. Conclusions technological, social, and political issues. Impending real or manipulated shortages of such materials(water, oil, chromium, to name some) are important political driv ers. The transport, refining, use, and eventual disposal of these ores and their techno- logical products pose equally important social environmental questions. The nuclear fuel cycle, for example, must consider the cradle-to-grave(ore body to nuclear reac tor to repository) handling of uranium. Solid state chemical issues(the chemical reactions involved) must be considered in the context of geological processes (transport of contaminants by groundwater, long term climate change, volcanism) Many minerals are crystalline silicates and aluminosilicates, and amorphous and glassy silicates(e.g. obsidian glass)are also found in nature. Thus there is strong overlap of the science of Earth materials with fields such as glass, zeolites, and cements. Certain binary oxides, notably those of Si, Al, Fe, Mn, and Ti are important in both technology and nature. There are commonalities between sulfide minerals and semiconductors. Equally importantly, many processes-crystallization, melting, dissolution, diffusion, surface reaction, catalysis-are common to Earth and materials science. Geological reactions are governed by surfaces, interfaces, and nanoparticles The emerging field of nanogeoscience further links solid state chemistry and Earth science. We therefore believe that the potential benefit derived from fostering increased interactions between these fields is very great 3. Biology Christopher gorman, Milan Mrksich, Uli Wiesner 3.1. Introduction The study and exploitation of biological processes has not yet had substantial overlap with the field of solid state chemistry. However, given recent developments there is substantial reason to believe that this will be an area of tremendous future growth. The earliest manifestation of this research-bio-inorganic chemistry-sought to understand the function of metal clusters in enzymes and electron transfer proteins This field has matured considerably. However, it still begs more fundamental under- ore rtantly, this body of work suggests new opportunities such as mimic of functions of cluster-containing proteins in, for example, energy transduction
18 R.J. Cava et al. / Progress in Solid State Chemistry 30 (2002) 1–101 is a dearth of material and much of what is available are natural intergrowths of phases. Calorimetric studies of carefully characterized synthetic and natural uranyl compounds will further establish the thermodynamic properties of these minerals, and should provide the underpinning for development of methods of prediction of thermodynamic parameters based upon structural connectivity. 2.5. Conclusions Many materials are important both in the Earth and in technological applications. The distribution, discovery and mining of ores and other raw materials pose critical technological, social, and political issues. Impending real or manipulated shortages of such materials (water, oil, chromium, to name some) are important political drivers. The transport, refining, use, and eventual disposal of these ores and their technological products pose equally important social environmental questions. The nuclear fuel cycle, for example, must consider the cradle-to-grave (ore body to nuclear reactor to repository) handling of uranium. Solid state chemical issues (the chemical reactions involved) must be considered in the context of geological processes (transport of contaminants by groundwater, long term climate change, volcanism). Many minerals are crystalline silicates and aluminosilicates, and amorphous and glassy silicates (e.g. obsidian glass) are also found in nature. Thus there is strong overlap of the science of Earth materials with fields such as glass, zeolites, and cements. Certain binary oxides, notably those of Si, Al, Fe, Mn, and Ti are important in both technology and nature. There are commonalities between sulfide minerals and semiconductors. Equally importantly, many processes—crystallization, melting, dissolution, diffusion, surface reaction, catalysis—are common to Earth and materials science. Geological reactions are governed by surfaces, interfaces, and nanoparticles. The emerging field of nanogeoscience further links solid state chemistry and Earth science. We therefore believe that the potential benefit derived from fostering increased interactions between these fields is very great. 3. Biology Christopher Gorman, Milan Mrksich, Uli Wiesner 3.1. Introduction The study and exploitation of biological processes has not yet had substantial overlap with the field of solid state chemistry. However, given recent developments, there is substantial reason to believe that this will be an area of tremendous future growth. The earliest manifestation of this research—bio-inorganic chemistry—sought to understand the function of metal clusters in enzymes and electron transfer proteins. This field has matured considerably. However, it still begs more fundamental understanding. More importantly, this body of work suggests new opportunities such as mimic of functions of cluster-containing proteins in, for example, energy transduction
R. Cava et al. /Progress in Solid State Chemistry 30(2002)1-101 and catalysis In parallel, use of metallic surfaces to conjugate proteins and oligonu cleotides has resulted in new opportunities for bio-assays, preparation of bio-inspired devices and fundamental studies of biomolecular function. It is obvious that conju- gation of biomolecules to a wider variety of surfaces can lead to new functions and new opportunities for hybrid devices. These could include solid-state semiconducting materials and the walls of zeolitic channels. This work also extends to the interaction of materials with whole cells-control of their growth and proliferation can be effected using simple surfaces. Perhaps solid-state materials can further the eff to couple electronic, electromagnetic and mechanical stimulations to cells and ulti- mately to tissues 3. 2. The relevance of biology to solid state chemistry Biology shares important relevance with solid state chemistry in two ways: first, lessons from living systems offer new strategies for designing and preparing solid state materials, and secondly, the development of technologies based on biological components(e.g, sensors) require solid state components with specific properties In the first example, organisms produce a variety of materials that parallel synthetic solid state materials, including single crystalline magnetic nanorods and structural scaffolds based on composites of minerals and proteins. These materials are assembled by self-assembly and protein-mediated pathways (in water and at room temperature) which suggest new strategies for preparing synthetic materials. In the second example, many biosensing technologies require that biological components (proteins, nucleic acids, cells, etc. ) be joined to a substrate that can transduce biologi- cal activities into electrical signals. There is still a need for solid-state materials that have tailored electrical, optical, mechanical and magnetic properties to realize new biosensor designs 3.3. Current federal programs and support The attendees of the workshop discussed the state of current federal support for biological opportunities in solid-state materials. While firm data for federal funding of this area was not available, what follows is a community perspective of the fund ing portfolio. Research activity in this area has largely been supported by spec programs and as minor components of traditional programs. Existing programs, larg- ely funded by the NSF, do not have sufficient budget fiexibility to explore biologi- ally oriented approaches in solid-state materials. The nih has a growing interest in developing technologies that in part rely on solid-state materials-largely focused through the beCon consortium-but this agency has yet to implement programs A number of special programs, largely within the DoD, have focused on applied aspects of solid-state materials for biotechnologies. While these programs have been important to demonstrating the promise of this emerging field, they are non-recurrent and therefore must be replaced with stable and renewable sources of support
R.J. Cava et al. / Progress in Solid State Chemistry 30 (2002) 1–101 19 and catalysis. In parallel, use of metallic surfaces to conjugate proteins and oligonucleotides has resulted in new opportunities for bio-assays, preparation of bio-inspired devices and fundamental studies of biomolecular function. It is obvious that conjugation of biomolecules to a wider variety of surfaces can lead to new functions and new opportunities for hybrid devices. These could include solid-state semiconducting materials and the walls of zeolitic channels. This work also extends to the interaction of materials with whole cells—control of their growth and proliferation can be effected using simple surfaces. Perhaps solid-state materials can further the efforts to couple electronic, electromagnetic and mechanical stimulations to cells and ultimately to tissues. 3.2. The relevance of biology to solid state chemistry Biology shares important relevance with solid state chemistry in two ways: first, lessons from living systems offer new strategies for designing and preparing solid state materials, and secondly, the development of technologies based on biological components (e.g., sensors) require solid state components with specific properties. In the first example, organisms produce a variety of materials that parallel synthetic solid state materials, including single crystalline magnetic nanorods and structural scaffolds based on composites of minerals and proteins. These materials are assembled by self-assembly and protein-mediated pathways (in water and at room temperature) which suggest new strategies for preparing synthetic materials. In the second example, many biosensing technologies require that biological components (proteins, nucleic acids, cells, etc.) be joined to a substrate that can transduce biological activities into electrical signals. There is still a need for solid-state materials that have tailored electrical, optical, mechanical and magnetic properties to realize new biosensor designs. 3.3. Current federal programs and support The attendees of the workshop discussed the state of current federal support for biological opportunities in solid-state materials. While firm data for federal funding of this area was not available, what follows is a community perspective of the funding portfolio. Research activity in this area has largely been supported by special programs and as minor components of traditional programs. Existing programs, largely funded by the NSF, do not have sufficient budget flexibility to explore biologically oriented approaches in solid-state materials. The NIH has a growing interest in developing technologies that in part rely on solid-state materials—largely focused through the BECON consortium—but this agency has yet to implement programs. A number of special programs, largely within the DoD, have focused on applied aspects of solid-state materials for biotechnologies. While these programs have been important to demonstrating the promise of this emerging field, they are non-recurrent and therefore must be replaced with stable and renewable sources of support
R. Cava et al. /Progress in Solid State Chemistry 30(2002)1-101 3.4. Breakdown of scientific opportunities 3.4.1. What does biology bring to solid-state chemistry? he control of the shape and the size of inorganic materials is an important feature of natural growth phenomena. For biological systems both are the result of long evolutionary optimisation processes and are intimately related to specific functions 37]. In biomineralization, complex morphologies on different length scales are usu ally obtained through cooperative self-assembly of organic and inorganic species 38, 39 In spite of the considerable success in understanding the mechanisms of self-assembly, it remains a challenge for solid-state chemists and material scientists to mimic such natural pathways and develop simple and efficient routes to advanced materials. In Fig. 5 is a picture of single cellular organisms that use inorganic sub- stances as building material for complex shell structures [40]. Organic molecules serve as structure directing agents for the generation of these shells. Structure direc tion is exerted on both crystalline(e.g, CaCO, )as well as ag at Fig. 5. First of all, structure formation down to the nanometer regime is realized in these shell structur Second, inorganic materials in the vicinity of cell surfaces have survived billions of years of evolution indicating that these materials have a lot to offer when it comes down to, e.g., issues of biocompatibility In natural growth phenomena proteins play a key role. While in the biological sciences a lot of effort is devoted to the detailed understanding of their functions on the materials science side structural protein concepts are more and more integrated Fig. 5. Single cellular organisms with complex shell structures from inorganic materials(40)Reprinted
20 R.J. Cava et al. / Progress in Solid State Chemistry 30 (2002) 1–101 3.4. Breakdown of scientific opportunities 3.4.1. What does biology bring to solid-state chemistry? The control of the shape and the size of inorganic materials is an important feature of natural growth phenomena. For biological systems both are the result of long evolutionary optimisation processes and are intimately related to specific functions [37]. In biomineralization, complex morphologies on different length scales are usually obtained through cooperative self-assembly of organic and inorganic species [38,39]. In spite of the considerable success in understanding the mechanisms of self-assembly, it remains a challenge for solid-state chemists and material scientists to mimic such natural pathways and develop simple and efficient routes to advanced materials. In Fig. 5 is a picture of single cellular organisms that use inorganic substances as building material for complex shell structures [40]. Organic molecules serve as structure directing agents for the generation of these shells. Structure direction is exerted on both crystalline (e.g., CaCO3) as well as amorphous (e.g., SiO2) inorganic materials. Several lessons can be learned from looking at Fig. 5. First of all, structure formation down to the nanometer regime is realized in these shell structures. Second, inorganic materials in the vicinity of cell surfaces have survived billions of years of evolution indicating that these materials have a lot to offer when it comes down to, e.g., issues of biocompatibility. In natural growth phenomena proteins play a key role. While in the biological sciences a lot of effort is devoted to the detailed understanding of their functions, on the materials science side structural protein concepts are more and more integrated Fig. 5. Single cellular organisms with complex shell structures from inorganic materials[40] Reprinted by permission of Wiley-VCH, UK)