From chemical gardens to chemobrionics , , , Laura M. Barge,⇤ † Silvana S. S. Cardoso,⇤ ‡ Julyan H. E. Cartwright,⇤ ¶ , , , Geoffrey J. T. Cooper,⇤ § Leroy Cronin,⇤ § Anne De Wit,⇤ k Ivria J. , , ,# Doloboff,⇤ † Bruno Escribano,⇤ ? Raymond E. Goldstein,⇤ Florence , ,@ , , Haudin,⇤ k David E. H. Jones,⇤ Alan L. Mackay,⇤ 4 Jerzy Maselko,⇤ r , , , Jason J. Pagano,⇤ †† J. Pantaleone,⇤ ‡‡ Michael J. Russell,⇤ † C. Ignacio , , , Sainz-D´ıaz,⇤ ¶ Oliver Steinbock,⇤ ¶¶ David A. Stone,⇤ §§ Yoshifumi , , Tanimoto,⇤ kk and Noreen L. Thomas⇤ ?? Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA † Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge ‡ CB2 3RA, UK Instituto Andaluz de Ciencias de la Tierra, CSIC–Universidad de Granada, E-18100 Armilla, ¶ Granada, Spain WestCHEM School of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK § Nonlinear Physical Chemistry Unit, CP231, Universite´ libre de Bruxelles (ULB), B-1050 k Brussels, Belgium Basque Center for Applied Mathematics, E-48009 Bilbao, Spain ? #Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, UK @Department of Chemistry, University of Newcastle upon Tyne NE1 7RU, UK Birkbeck College, University of London, Malet Street, London WC1E 7HX, UK 4 Department of Chemistry, University of Alaska, Anchorage, Alaska 99508, USA r Department of Chemistry, Saginaw Valley State University, University Center, Michigan †† 48710-0001, USA Department of Physics, University of Alaska, Anchorage, Alaska 99508, USA ‡‡ Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida ¶¶ 32306-4390, USA Iron Shell LLC, Tucson, Arizona 85717, USA §§ Faculty of Pharmacy, Osaka Ohtani University, Tondabayashi 548-8540, Japan kk Department of Materials, Loughborough University, Loughborough LE11 3TU, UK ?? E-mail: [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; fl[email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected] 1 This is version 4.3 of May 29, 2015. 8 Chemical Gardens in Nature and Impli- cations for the Origin of Life 54 8.1 Hydrothermal vents: A natural Contents chemical garden as a hatchery of life . 55 1 Introduction 2 8.2 A reconsideration as to what con- stitutes prebiotic molecules . 58 2 History 4 8.3 Towards the origin of life . 59 2.1 17th–18th centuries . 4 8.4 Brinicles: chemical gardens in sea 2.2 The 19th and early 20th centuries . 5 ice . 60 2.3 The mid 20th century . 7 9 Intellectual Challenges and Research 3 An Inventory of Experimental Methods 10 Opportunities 62 3.1 Seed growth . 10 9.1 How can we make experimen- 3.2 Injection growth . 13 tal, computational, and theoretical 3.3 Bubble guidance . 15 progress in this field? . 62 3.4 Membrane growth . 17 9.2 What are the most important re- 3.5 Growth in gels . 18 search questions in chemobrionics 3.6 Varying gravity . 18 today? . 63 3.7 Growth in quasi two dimensions . 20 9.3 What are the possibilities for tech- 4 Materials Characterization 23 nological applications? . 63 4.1 Morphology . 23 9.4 Coda . 65 4.2 Composition, porosity, and post- Biographies 65 synthetic changes . 27 References 70 5 Energetic Phenomena 28 5.1 Electrochemical properties and fuel cells . 28 1 Introduction 5.2 Magnetic properties . 31 5.3 Chemical motors . 33 Chemical gardens are perhaps the best exam- ple in chemistry of a self-organizing nonequi- 6 Mathematical Modeling 35 librium process that creates complex structures. 6.1 Tube width . 37 Many different chemical systems and materials 6.2 Tube pressure . 38 can form these self-assembling structures, which 6.3 Osmotic growth . 39 span at least eight orders of magnitude in size, 6.4 Relaxation oscillations . 40 from nanometers to meters. Key to this marvel is 6.5 Fracture dynamics . 41 the self-propagation under fluid advection of re- 6.6 Spirals in two dimensions . 42 action zones forming semipermeable precipitation 6.7 Templating by a fluid jet . 44 membranes that maintain steep concentration gra- dients, with osmosis and buoyancy as the driv- 7 Applications: From Corrosion and Ce- ing forces for fluid flow. Chemical gardens have ment to Materials Science and Techno- been studied from the alchemists onwards, but logically Relevant Products 45 now in the 21st century we are beginning to un- 7.1 Corrosion tubes . 45 derstand how they can lead us to a new domain of 7.2 Cement hydration . 49 self-organized structures of semipermeable mem- 7.3 Chemical grouting in soils . 50 branes and amorphous as well as polycrystalline 7.4 Polyoxometalates: synthetic mi- solids produced at the interface of chemistry, fluid crotubes . 51 dynamics, and materials science. We propose to call this emerging field chemobrionics. 2 Figure 1: A classical chemical garden formed by the addition of cobalt, copper, iron, nickel, and zinc salts to a sodium silicate solution. The image corresponds to 5.5 3.7 cm. Image courtesy of Bruno Batista. ⇥ For the past four centuries, the amazing pre- ing anions such as silicate, phosphate, carbon- cipitation structures known as chemical (or sil- ate, oxalate, or sulfide. The dissolving seed re- ica, silicate, crystal) gardens have been the sub- leases metal ions that precipitate with the anions ject of fascination, as well as the basis of differ- in the outer solution, forming a gelatinous col- ent philosophical and scientific theories, an inspi- loidal membrane enclosing the seed. There are ration for literature, and the motivation for many many other reaction systems that can form anal- experiments. There is an obvious visual simi- ogous chemical gardens, and many details of their larity between precipitated chemical-garden struc- formation process are specific to the particular sys- tures (Fig. 1) and a variety of biological forms in- tem, but the key universal aspect is the forma- cluding those of plants, fungi, and insects; and in tion of a semipermeable precipitation membrane some ways, the process of formation of chemical of some sort, across which steep concentration gardens from an inorganic “seed” in a reactive so- gradients may be formed and maintained, leading lution is reminiscent of plant growth from a seed to osmotic and buoyancy forces. Of course chem- in water or soil. These biomimetic structures and ical gardens are by no means the only pattern- processes have from the very beginning caused re- forming system in chemistry; Liesegang rings, for searchers to wonder: Do chemical gardens and bi- example, are another long-studied pattern-forming ological structures share any similar processes of system involving chemical precipitation. How- formation; can these inorganic structures teach us ever, Liesegang rings do not involve semiperme- about biological morphogenesis, or is the similar- able membranes and are as such a quite different ity only accidental? Are they related to the origin phenomenon. Thus in this review we shall restrict of life? And, if their precipitation is affected by ourselves to chemical gardens and related systems. chemical and environmental parameters, can the We shall describe chemical gardens in laboratory process be controlled to build complex structures chemistries ranging from silicates to polyoxometa- as biology does, to produce self-organized precip- lates, in applications ranging from corrosion prod- itates as useful materials? ucts to the hydration of Portland cement, and in Classical chemical gardens are the hollow pre- natural settings ranging from hydrothermal vents cipitation structures that form when a metal-salt in the ocean depths to brinicles beneath sea ice. seed is dropped into an aqueous solution contain- The structures formed in chemical-garden ex- 3 periments can be very complex. Experimental with diffusion and fluid motion. We therefore sug- and theoretical studies of chemical-garden sys- gest a new overall name for this emerging field tems have accelerated from the end of the 20th that intersects with chemistry, physics, biology, century with the development of nonlinear dy- and materials science: Chemobrionics. namics, the study of complex systems, the un- derstanding of pattern formation in chemical and physical systems, and the development of more 2 History advanced experimental and analytical techniques. Many aspects of the chemical-garden system, such 2.1 17th–18th centuries as electrochemical and magnetic properties, have In 1646 Johann Glauber published Furni Novi recently been and are being characterized; and it Philosophici (New Philosophical Furnaces), a has been observed that in certain systems, self- textbook of the new science of chemistry.1 In it, assembling chemical engines, or motors, can spon- among many other experimental techniques, he taneously emerge. The increased understanding discussed of the chemical-garden formation process in the past several decades has also enabled researchers “A water [solution] into which when to begin to control it, to produce intentional struc- any metal is put, it begins to grow tures via sophisticated precipitation techniques within twenty four hours time in the that have many potential uses for materials science form of plants and trees, each metal and technology, especially on the nanoscale. according to its inmost colour and Chemical gardens on one hand show us that property, which metalline vegetations complex structures do not have to be biotic in ori- are called philosophical trees, both gin — and thus highlight the dangers of using mor- pleasant to the eye and of good use.” phology as a sign of biological origin — and on the other hand point to a possible way to arrive at He provides this first detailed description of how a proto-cell from an abiotic beginning.