Co-reporter:Qingpu Wang, Megan R. Bentley, and Oliver Steinbock
The Journal of Physical Chemistry C July 6, 2017 Volume 121(Issue 26) pp:14120-14120
Publication Date(Web):June 9, 2017
DOI:10.1021/acs.jpcc.7b02778
Inorganic precipitate membranes play an important role in chemobrionics and origin of life research. They can involve a range of catalytic materials, affect crystal habits, and show complex permeabilities. We produce such membranes in a microfluidic device at the reactive interface between laminar streams of hydroxide and Co(II) solutions. The resulting linear membranes show striking color bands that, over time, expand in the direction of the Co(II) solution. The cumulative layer thicknesses (here up to 600 μm) obey square root laws, indicating diffusion control. The effective diffusion coefficients are proportional to the hydroxide concentration, but the membrane growth slows down with increasing concentrations of Co(II). On the basis of spatially resolved Raman spectra and other techniques, we present chemical assignments of the involved materials. Electron microscopy reveals that the important constituent β-Co(OH)2 crystallizes as thin hexagonal microplatelets. Under drying, the membrane curls into spirals, revealing mechanical differences between the layers.
Co-reporter:Elias Nakouzi, Pamela Knoll and Oliver Steinbock
Chemical Communications 2016 vol. 52(Issue 10) pp:2107-2110
Publication Date(Web):14 Dec 2015
DOI:10.1039/C5CC09295G
Biomorphs are life-like microstructures of selfassembled barium carbonate nanorods and silica. In a departure from established approaches, we produce biomorphs in CO2- and gradient-free solutions. Our study reveals novel structural motifs for solution-grown biomorphs, reduces pH transients, and expands the upper pH limit for biomorph formation to over 12 where silica is essentially soluble.
Co-reporter:Elias Nakouzi, Pamela Knoll, Kenzie B. Hendrix and Oliver Steinbock
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 33) pp:23044-23052
Publication Date(Web):26 Jul 2016
DOI:10.1039/C6CP04153A
Biomorphs are complex, life-like structures that emerge from the precipitation of barium carbonate and amorphous silica in alkaline media. Despite their inorganic nature, these microstructures have non-crystallographic morphologies such as helices and cardioid sheets. At the nanoscale, biomorphs arrange thousands of crystalline nanorods as hierarchical assemblies that resemble natural biominerals suggesting novel approaches towards the production of biomimetic materials. We report the synthesis of silica–carbonate biomorphs in single-phase, gradient-free solutions that differ markedly from the typical solution–gas or gel–solution setups. Our experimental approach significantly increases the duration of biomorph growth and hence assembles networks in which individual helices extend to several millimeters. These unusually long biomorphs allow the first quantitative measurements of mesoscopic parameters such as the helix wavelength, period, width, and linear as well as tangential growth velocities. We find that the latter quantities are system-specific and tightly conserved during many hours of growth. Moreover, the average double helix wavelength of (19 ± 3) μm and width of (9.6 ± 0.8) μm vary by less than 12% when the initial carbonate concentration is changed by three orders of magnitude. We also delineate the single helix growth mechanism and report the occurrence of ribbon-like structures and highly regular “superhelices”. Our experiments clearly demonstrate the robustness and consistency of biomorph growth under stable chemical conditions.
Co-reporter:Megan R. Bentley, Bruno C. Batista, and Oliver Steinbock
The Journal of Physical Chemistry A 2016 Volume 120(Issue 25) pp:4294-4301
Publication Date(Web):June 7, 2016
DOI:10.1021/acs.jpca.6b03859
The dissolution of metal salts in silicate solution can result in the growth of hollow precipitate tubes. These “chemical gardens” are a model of self-organization far from the equilibrium and create permanent macroscopic structures. The reproducibility of the growth process is greatly improved if the solid salt seed is replaced by a salt solution that is steadily injected by a pump; however, this modification of the original experiment eliminates the membrane-based osmotic pump at the base of conventional chemical gardens and does not allow for analyses in terms of the involved pressure. Here we describe a new experimental method that delivers the salt solution according to a controlled hydrostatic pressure. In one form of the experiment, this pressure slowly decreases as zinc sulfate solution flows into the silicate-containing reaction vessel, whereas a second version holds the respective solution heights constant. In addition to three known growth regimes (jetting, popping, budding), we observe single tubes that fill the vessel in a horizontally undulating but vertically layered fashion (crowding). The resulting, dried product has a cylindrical shape, very low density, and one continuous connection from top to bottom. We also present phase diagrams of these growth modes and show that the flow characteristics of our experiments follow a reaction-independent Hagen–Poiseuille equation.
Co-reporter:Elias Nakouzi
Science Advances 2016 Vol 2(8) pp:e1601144
Publication Date(Web):19 Aug 2016
DOI:10.1126/sciadv.1601144
Self-organized precipitation structures might hold the key to a new microengineering paradigm that grows materials biomimetically.
Co-reporter:Laura M. Barge, Silvana S. S. Cardoso, Julyan H. E. Cartwright, Geoffrey J. T. Cooper, Leroy Cronin, Anne De Wit, Ivria J. Doloboff, Bruno Escribano, Raymond E. Goldstein, Florence Haudin, David E. H. Jones, Alan L. Mackay, Jerzy Maselko, Jason J. Pagano, J. Pantaleone, Michael J. Russell, C. Ignacio Sainz-Díaz, Oliver Steinbock, David A. Stone, Yoshifumi Tanimoto, and Noreen L. Thomas
Chemical Reviews 2015 Volume 115(Issue 16) pp:8652
Publication Date(Web):July 15, 2015
DOI:10.1021/acs.chemrev.5b00014
Co-reporter:Bruno C. Batista and Oliver Steinbock
Chemical Communications 2015 vol. 51(Issue 65) pp:12962-12965
Publication Date(Web):09 Jul 2015
DOI:10.1039/C5CC04724B
Contrary to common belief, hollow precipitation tubes form in the absence of silicate if sodium hydroxide solution is injected into solutions of various metal ions. In many cases, the growth speed has a power law dependence on the flow rate. For vanadyl, we observe damped oscillations in the tube height.
Co-reporter:Dr. Bruno C. Batista;Patrick Cruz ; Dr. Oliver Steinbock
ChemPhysChem 2015 Volume 16( Issue 11) pp:2299-2303
Publication Date(Web):
DOI:10.1002/cphc.201500368
Abstract
Propagating reaction fronts allow the formation of materials in self-sustained, steep concentration gradients, which would otherwise rapidly decay. These conditions can result in macroscopic, noncrystallographic structures, such as tubes with large aspect ratios. For hollow silica/Zn(OH)2 tubes, we report the inclusion of diverse mesoscopic building blocks ranging from polymer beads to biological cells. For agarose beads, we observe spontaneous alignment along vertical tracks; the nearly periodic spacing of the beads along these tracks follows a log-normal distribution. We interpret this patterning in terms of hydrodynamic recruitment and discuss similarities to the adhesion dynamics of leukocytes in blood vessels. For diatoms and other cells, we observe novel surface textures, and yeast tagged with a green fluorescent protein shows strong fluorescence activity after trapping. The inclusion of these guest units should improve the possibilities for the application of these tubes in microfluidics and biotechnology.
Co-reporter:Elias Nakouzi
The Journal of Physical Chemistry C 2015 Volume 119(Issue 27) pp:15749-15754
Publication Date(Web):June 8, 2015
DOI:10.1021/acs.jpcc.5b04411
The coprecipitation of barium carbonate and silica spontaneously creates complex micrometer-scale objects such as sheets and helices. These structures consist of densely packed crystalline nanorods that in the case of sheets align in radial direction. We report the existence of an additional level of self-organization that creates oscillatory height variations in biomorph sheets. These topographic features take the form of either concentric rings or disordered, patchy patterns and form immediately in the wake of the crystallization front. Their wavelength varies around 6.5 μm and shows no pronounced dependence on the reactant concentrations. Atomic force microscopy reveals height variations of up to 500 nm which equal 45% of the average sheet thickness. These undulations are accompanied by a systematic out-of-plane displacement of the nanorods. Our results are discussed in the context of an earlier hypothesis that predicts pH oscillations near the crystallization front.
Co-reporter:Bruno C. Batista
The Journal of Physical Chemistry C 2015 Volume 119(Issue 48) pp:27045-27052
Publication Date(Web):November 10, 2015
DOI:10.1021/acs.jpcc.5b08813
The hollow precipitate tubes in chemical gardens conserve the nonequilibrium conditions present during their formation and are an important example of molecular processes causing complex macroscopic self-organization. We report a greatly simplified experimental model of these structures that is based on the formation of an inorganic membrane in a microfluidic device. Within this device, we induce the precipitation of Mn(OH)2 and other metal hydroxides at the reactive interface of steadily injected NaOH and MnCl2 solutions. The resulting precipitate wall extends along the entire length of the reactor channel and can be positioned at will, and its width increases strictly in the direction of the metal solution. These thickening dynamics obey a square root law. The corresponding effective diffusion coefficient is proportional to [OH–], shows a sigmoidal dependence on [Mn2+], and also depends on the precipitating metal ion. The precipitate wall is permeable to methylene blue and strongly adsorbs methyl orange. Electron and optical microscopy reveals decaying micrometer-sized perturbations and a 40 μm thick gel-like layer on the surface exposed to the Mn2+ solution. The wall growth is also followed by in situ Raman spectroscopy. Potential applications toward materials and origins-of-life research are discussed.
Co-reporter:Elias Nakouzi, Raymond E. Goldstein, and Oliver Steinbock
Langmuir 2015 Volume 31(Issue 14) pp:4145-4150
Publication Date(Web):November 19, 2014
DOI:10.1021/la503562z
Surprisingly, macroscopic objects such as melting ice cubes and growing stalactites approach nonintuitive geometric ideals. Here we investigate the shape of dissolving cylinders in a large volume of water. The cylinders are oriented vertically and consist of amorphous glucose or poly(ethylene glycol). The dissolution causes density differences in the surrounding fluid, which induce gravity-driven convection downward along the object. The resulting concentration gradient shapes the cylinder according to fast dissolution at the tip and slow dissolution at the base. The contour of the object approaches a power law of the form z ∝ R2, where z is the vertical distance from the tip and R is the corresponding radius. We suggest that this paraboloidal shape is the geometric attractor for the dissolution of noncrystalline objects in the presence of gravity.
Co-reporter:Rabih Makki ; Xin Ji ; Hedi Mattoussi
Journal of the American Chemical Society 2014 Volume 136(Issue 17) pp:6463-6469
Publication Date(Web):April 4, 2014
DOI:10.1021/ja501941d
The combination of top-down and bottom-up approaches offers great opportunities for the production of complex materials and devices. We demonstrate this approach by incorporating luminescent CdSe-ZnS nanoparticles into macroscopic tube structures that form as the result of externally controlled self-organization. The 1–2 mm wide hollow tubes consist of silica-supported zinc oxide/hydroxide and are formed by controlled injection of aqueous zinc sulfate into a sodium silicate solution. The primary growth region at the top of the tube is pinned to a robotic arm that moves upward at constant speed. Dispersed within the injected zinc solution are 3.4 nm CdSe-ZnS quantum dots (QDs) capped by DHLA-PEG–OCH3 ligands. Fluorescence measurements of the washed and dried tubes reveal the presence of trapped QDs at an estimated number density of 1010 QDs per millimeter of tube length. The successful inclusion of the nanoparticles is further supported by electron microscopy and energy dispersive X-ray spectroscopy, with the latter suggesting a nearly homogeneous QD distribution across the tube wall. Exposure of the samples to copper sulfate solution induces quenching of about 90% of the tubes’ fluorescence intensity. This quenching shows that the large majority of the QDs is chemically accessible within the microporous, about 15-μm-wide tube wall. We suggest possible applications of such QD-hosting tube systems as convenient sensors in microfluidic and related applications.
Co-reporter:Hua Ke, Zhihui Zhang, and Oliver Steinbock
The Journal of Physical Chemistry A 2014 Volume 118(Issue 34) pp:6819-6826
Publication Date(Web):July 31, 2014
DOI:10.1021/jp5060292
Excitable reaction–diffusion systems form a wealth of dissipative concentration patterns that exist not only in chemical systems but also control or disrupt biological functions. An important example are rotating spiral waves in the autocatalytic Belousov–Zhabotinsky reaction. We show that the viscosity of this system can be increased by the addition of the polymer xanthan gum. In the resulting system, we pin spiral waves to a thin glass rod and then reposition the vortex centers by a linear motion of the heterogeneity. The Stokes flow generated by this motion can be a weak perturbation to the wave pattern and follows a simple, analytical expression. Numerical simulations of a corresponding reaction–diffusion-flow model reproduce the experimental observations and show that the spatial extent of the flow field can vary widely around the characteristic wavelength of the spiral. We find that a sharp spatial decay of the flow pattern corresponds to our experimental observations, whereas more expansive flow fields surprisingly allow the repositioning of spiral tips at speeds faster than the wave velocity.
Co-reporter:Bruno C. Batista, Patrick Cruz, and Oliver Steinbock
Langmuir 2014 Volume 30(Issue 30) pp:9123-9129
Publication Date(Web):2017-2-22
DOI:10.1021/la5020175
Many inorganic precipitation reactions self-organize macroscopic tubes known as chemical gardens. We study the nonequilibrium formation of these structures by injecting aqueous sodium sulfide solution into a reservoir of iron(II) chloride solution. Our experiments reveal a distinct, concentration-dependent transition from convective plumes of reaction-induced, colloidal particles to mechanically connected, hollow tubes. The transition concentration (0.1 mol/L) is widely independent of the injection rate and causes a discontinuous change from the radius of the plume stalk to the radius of the tube. In addition, tubes have lower growth speeds than plumes. At the transition concentration, one observes the initial formation of a plume followed by the growth of a mechanically weak tube around a jet of upward-moving precipitation particles. We find that the plumes’ morphology and geometric scaling are similar to that of laminar starting plumes in nonreactive systems. The characterization of dried tubes by X-ray diffraction indicates the presence of greigite and lepidocrocite.
Co-reporter:Oliver Steinbock
PNAS 2014 Volume 111 (Issue 49 ) pp:17346-17347
Publication Date(Web):2014-12-09
DOI:10.1073/pnas.1420475111
Co-reporter:Laszlo Roszol, Rabih Makki and Oliver Steinbock
Chemical Communications 2013 vol. 49(Issue 51) pp:5736-5738
Publication Date(Web):26 Mar 2013
DOI:10.1039/C3CC41516C
Using reaction conditions far from equilibrium, we produce hollow tubes of silica-supported Cu(OH)2. The samples are then processed postsynthetically without compromising the macroscopic tubular structure. We specifically induce an amorphous–crystalline transition and demonstrate the sequential conversion of Cu(OH)2 to CuO, Cu2O, and metallic copper using thermal treatment and wet chemistry.
Co-reporter:Rabih Makki
Journal of the American Chemical Society 2012 Volume 134(Issue 37) pp:15519-15527
Publication Date(Web):August 15, 2012
DOI:10.1021/ja3064843
Materials synthesis far from thermodynamic equilibrium can yield hierarchical order that spans from molecular to macroscopic length scales. Here we report the nonequilibrium formation of millimeter-scale iron oxide–silica tubes in experiments that tightly control the tube radius and growth speed. The experiments involve the hydrodynamic injection of an iron (II,III) solution into a large volume of solution containing sodium silicate and ammonium hydroxide. The forming tubes are pinned to a motorized glass rod that moves at a predetermined speed. X-ray diffraction and electron microscopy, as well as Raman and Mössbauer spectroscopy, reveal magnetite nanoparticles in the range of 5–15 nm. Optical data suggest that the magnetite particles follow first-order nucleation–growth kinetics. The hollow tubes exhibit superparamagnetic behavior at room temperature, with a transition to a blocked state at TB = 95 K for an applied field of 200 Oe. Heat capacity measurements yield evidence for the Verwey transition at 20 K. Finally, we show a remarkable dependence of the tubes’ magnetic properties on the speed of the pinning rod and the injection rate employed during synthesis.
Co-reporter:László Roszol and Oliver Steinbock
Physical Chemistry Chemical Physics 2011 vol. 13(Issue 45) pp:20100-20103
Publication Date(Web):20 Oct 2011
DOI:10.1039/C1CP22556A
We investigate the growth of self-organized tubes formed by injection of metal salt solutions into silicate solution. The wall thickness increases strictly in an inward direction and obeys square root functions suggesting the presence of a traveling reaction-diffusion front in the radial direction. We also demonstrate the construction of multi-layered tubes.
Co-reporter:Dr. Véronique Pimienta;Dr. Michèle Brost;Dr. Nina Kovalchuk;Stefan Bresch;Dr. Oliver Steinbock
Angewandte Chemie International Edition 2011 Volume 50( Issue 45) pp:10728-10731
Publication Date(Web):
DOI:10.1002/anie.201104261
Co-reporter:Rabih Makki
The Journal of Physical Chemistry C 2011 Volume 115(Issue 34) pp:17046-17053
Publication Date(Web):July 26, 2011
DOI:10.1021/jp2046849
We describe an experiment that establishes control over the growth velocities of macroscopic tubes in the reaction between a polymerizable inorganic anion and a nonalkali metal ion. Our approach is demonstrated for the injection of an acidic cupric sulfate solution into a large volume of a basic sodium silicate solution. The forming tube is pinned to a gas bubble that is held at the end of a hollow glass rod. The tube’s linear growth follows the speed of the glass rod (0.5–11 mm/s), while its radius (0.2–1.6 mm) is self-selected according to the volume conservation of the injected solution. Depending on the experimental conditions, tube growth occurs at either the moving gas bubble or the stationary glass capillary. Oscillatory modulations of the growth velocity provoke the formation of hollow nodules on the outer tube surface. These nodules form after each rapid velocity decrease at exponentially decaying rates and seem to be energetically favored over a sudden isotropic increase in tube radius.
Co-reporter:Sumana Dutta and Oliver Steinbock
The Journal of Physical Chemistry Letters 2011 Volume 2(Issue 9) pp:945-949
Publication Date(Web):April 12, 2011
DOI:10.1021/jz2003183
Three-dimensional scroll waves in excitable reaction−diffusion systems rotate around one-dimensional phase singularities. Although these filaments are dynamic objects, their motion can be arrested if pinned to unexcitable obstacles. We study this vortex pinning for a case in which the topology of the initial filament (circular loop) differs from the topology of the obstacle (double torus). In experiments with the Belousov−Zhabotinsky reaction and numerical simulations, we show that pinning is possible and that it induces periodic rotation patterns. Continuous rotation extends around either one or both halves of the double torus. The latter case is doubly degenerate because waves can move through the two holes in the same or opposite directions. Opposite rotation is organized by a two-armed vortex segment that emits waves at a period approximately two-times larger than the other pinned vortex states.Keywords: autocatalysis; Belousov−Zhabotinsky reaction; reaction−diffusion system; scroll wave; spiral wave; vortex pinning;
Co-reporter:Rabih Makki;Mohammed Al-Humiari;Sumana Dutta Dr.
Angewandte Chemie International Edition 2009 Volume 48( Issue 46) pp:8752-8756
Publication Date(Web):
DOI:10.1002/anie.200903292
Co-reporter:Rabih Makki;Mohammed Al-Humiari;Sumana Dutta Dr.
Angewandte Chemie 2009 Volume 121( Issue 46) pp:8908-8912
Publication Date(Web):
DOI:10.1002/ange.200903292
Co-reporter:JasonJ. Pagano ;Tamás Bánsági Jr. Dr.
Angewandte Chemie 2008 Volume 120( Issue 51) pp:10048-10051
Publication Date(Web):
DOI:10.1002/ange.200803203
Co-reporter:JasonJ. Pagano ;Tamás Bánsági Jr. Dr.
Angewandte Chemie International Edition 2008 Volume 47( Issue 51) pp:9900-9903
Publication Date(Web):
DOI:10.1002/anie.200803203
Co-reporter:Jason J. Pagano, Stephanie Thouvenel-Romans and Oliver Steinbock
Physical Chemistry Chemical Physics 2007 vol. 9(Issue 1) pp:110-116
Publication Date(Web):06 Nov 2006
DOI:10.1039/B612982J
Silica gardens consist of hollow tubular structures that form from salt crystals seeded into silicate solution. We investigate the structure and elemental composition of these tubes in the context of a recently developed experimental model that allows quantitative analyses based on predetermined reactant concentrations and flow rates. In these experiments, cupric sulfate solution is injected into large volumes of waterglass. The walls of the resulting tubular structures have a typical width of 10 µm and are gradient materials. Micro-Raman spectroscopy along with energy dispersive X-ray fluorescence data identify amorphous silica and copper(II) hydroxide as the main compounds within the inner and outer tube surfaces, respectively. Upon heating the blueish precipitates to approximately 150 °C, the material turns black as copper(II) hydroxide decomposes to copper(II) oxide. Moreover, we present high resolution transmission electron micrographs that reveal polycrystalline morphologies.
Co-reporter:Tedric D. Campbell;Ry P. Washington and
Journal of Polymer Science Part A: Polymer Chemistry 2007 Volume 45(Issue 13) pp:2593-2600
Publication Date(Web):14 MAY 2007
DOI:10.1002/pola.22016
We report the synthesis of poly N-(2-hydroxypropyl)methacrylamide ordered arrays of fluid filled channels. The polymerization and crosslinking reactions are carried out under the influence of a constant electric field (60 V/cm). A charged comonomer, immobiline (pK 3.6), and porogen, polyethylene glycol (PEG) are added to the pregel solutions. Scanning electron microscopy reveals that the channels have a typical diameter of 2–25 μm and are oriented parallel to the electric field employed during synthesis. The self-organization of channels occurs around an optimal PEG concentration of 8.6 wt/vol %, whereas significantly higher or lower concentrations yield random, isotropic pore structures. Moreover, tensile strength measurements show that the mechanical stability increases with decreasing concentration of PEG. Rheology experiments reveal that the swelling degree of these superabsorbant hydrogels increases with increasing PEG. Possible applications of these microstructured hydrogels as bidirectional scaffolds for regenerating neurons in the injured spinal cord are discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2593–2600, 2007
Co-reporter:Stephanie Thouvenel-Romans, Jason J. Pagano and Oliver Steinbock
Physical Chemistry Chemical Physics 2005 vol. 7(Issue 13) pp:2610-2615
Publication Date(Web):01 Jun 2005
DOI:10.1039/B504407C
Numerous types of reaction–precipitation systems involve the growth of tubular structures similar to those formed in “silica gardens”. As a model case for this phenomenon, we investigate the rapid growth of hollow tubes in the reaction between sodium silicate and cupric sulfate. The latter solution is injected hydrodynamically at constant flow rates of 1–20 mL h−1 into a large reservoir of waterglass. In this study, the growth is templated and guided by single, buoyant gas bubbles. The resulting tubes can be several decimetres long and have constant radii in the range of 100–600 μm. Systematic measurements show that bubble size governs the tube radius. According to this radius, the system selects its growth velocity following volume conservation of the injected solution. Moreover, scanning electron microscopy reveals intricate ring patterns on the tube walls. We also show evidence for the existence of a minimal and a maximal tube radius. Finally, we report an intriguing collapse of tubes created at high silicate concentrations, which yields twisted ribbon-like structures. Critical radii and tube collapse are discussed in terms of simple competing forces.
Co-reporter:Paul R. Giunta;Ry P. Washington Dr.;Tedric D. Campbell Dr.;A. E. Stiegman Dr.
Angewandte Chemie 2004 Volume 116(Issue 12) pp:
Publication Date(Web):9 MAR 2004
DOI:10.1002/ange.200352813
Silicatmonolithe mit geordneten Bereichen mikrometergroßer Säulen werden in Polyacrylamidgel-Templaten gebildet. Die Herstellung der Template wird durch ein externes elektrisches Feld gesteuert. Der Ansatz führt zur Selbstorganisation säulenförmiger Muster im Templat (links; Balken=10μm), die sich durch Imprägnieren mit Tetramethylorthosilicat und anschließendes Calcinieren in Silicatmonolithe (rechts) übertragen lassen.
Co-reporter:Paul R. Giunta;Ry P. Washington Dr.;Tedric D. Campbell Dr.;A. E. Stiegman Dr.
Angewandte Chemie International Edition 2004 Volume 43(Issue 12) pp:
Publication Date(Web):9 MAR 2004
DOI:10.1002/anie.200352813
Silica monoliths with ordered arrays of micrometer-scale columns were fabricated from polyacrylamide gel templates. The preparation of the template involves the charged comonomer, N-acryloyl glycine, and is controlled by an externally applied electric field. This approach gives rise to the self-organization of columnar density patterns in the template (left; bar=10μm) that are recovered in the silica monoliths upon impregnation with tetramethylorthosilicate and subsequent calcination (right).
Co-reporter:Elias Nakouzi, Pamela Knoll and Oliver Steinbock
Chemical Communications 2016 - vol. 52(Issue 10) pp:NaN2110-2110
Publication Date(Web):2015/12/14
DOI:10.1039/C5CC09295G
Biomorphs are life-like microstructures of selfassembled barium carbonate nanorods and silica. In a departure from established approaches, we produce biomorphs in CO2- and gradient-free solutions. Our study reveals novel structural motifs for solution-grown biomorphs, reduces pH transients, and expands the upper pH limit for biomorph formation to over 12 where silica is essentially soluble.
Co-reporter:Jason J. Pagano, Stephanie Thouvenel-Romans and Oliver Steinbock
Physical Chemistry Chemical Physics 2007 - vol. 9(Issue 1) pp:NaN116-116
Publication Date(Web):2006/11/06
DOI:10.1039/B612982J
Silica gardens consist of hollow tubular structures that form from salt crystals seeded into silicate solution. We investigate the structure and elemental composition of these tubes in the context of a recently developed experimental model that allows quantitative analyses based on predetermined reactant concentrations and flow rates. In these experiments, cupric sulfate solution is injected into large volumes of waterglass. The walls of the resulting tubular structures have a typical width of 10 µm and are gradient materials. Micro-Raman spectroscopy along with energy dispersive X-ray fluorescence data identify amorphous silica and copper(II) hydroxide as the main compounds within the inner and outer tube surfaces, respectively. Upon heating the blueish precipitates to approximately 150 °C, the material turns black as copper(II) hydroxide decomposes to copper(II) oxide. Moreover, we present high resolution transmission electron micrographs that reveal polycrystalline morphologies.
Co-reporter:Bruno C. Batista and Oliver Steinbock
Chemical Communications 2015 - vol. 51(Issue 65) pp:NaN12965-12965
Publication Date(Web):2015/07/09
DOI:10.1039/C5CC04724B
Contrary to common belief, hollow precipitation tubes form in the absence of silicate if sodium hydroxide solution is injected into solutions of various metal ions. In many cases, the growth speed has a power law dependence on the flow rate. For vanadyl, we observe damped oscillations in the tube height.
Co-reporter:Laszlo Roszol, Rabih Makki and Oliver Steinbock
Chemical Communications 2013 - vol. 49(Issue 51) pp:NaN5738-5738
Publication Date(Web):2013/03/26
DOI:10.1039/C3CC41516C
Using reaction conditions far from equilibrium, we produce hollow tubes of silica-supported Cu(OH)2. The samples are then processed postsynthetically without compromising the macroscopic tubular structure. We specifically induce an amorphous–crystalline transition and demonstrate the sequential conversion of Cu(OH)2 to CuO, Cu2O, and metallic copper using thermal treatment and wet chemistry.
Co-reporter:László Roszol and Oliver Steinbock
Physical Chemistry Chemical Physics 2011 - vol. 13(Issue 45) pp:NaN20103-20103
Publication Date(Web):2011/10/20
DOI:10.1039/C1CP22556A
We investigate the growth of self-organized tubes formed by injection of metal salt solutions into silicate solution. The wall thickness increases strictly in an inward direction and obeys square root functions suggesting the presence of a traveling reaction-diffusion front in the radial direction. We also demonstrate the construction of multi-layered tubes.
Co-reporter:Elias Nakouzi, Pamela Knoll, Kenzie B. Hendrix and Oliver Steinbock
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 33) pp:NaN23052-23052
Publication Date(Web):2016/07/26
DOI:10.1039/C6CP04153A
Biomorphs are complex, life-like structures that emerge from the precipitation of barium carbonate and amorphous silica in alkaline media. Despite their inorganic nature, these microstructures have non-crystallographic morphologies such as helices and cardioid sheets. At the nanoscale, biomorphs arrange thousands of crystalline nanorods as hierarchical assemblies that resemble natural biominerals suggesting novel approaches towards the production of biomimetic materials. We report the synthesis of silica–carbonate biomorphs in single-phase, gradient-free solutions that differ markedly from the typical solution–gas or gel–solution setups. Our experimental approach significantly increases the duration of biomorph growth and hence assembles networks in which individual helices extend to several millimeters. These unusually long biomorphs allow the first quantitative measurements of mesoscopic parameters such as the helix wavelength, period, width, and linear as well as tangential growth velocities. We find that the latter quantities are system-specific and tightly conserved during many hours of growth. Moreover, the average double helix wavelength of (19 ± 3) μm and width of (9.6 ± 0.8) μm vary by less than 12% when the initial carbonate concentration is changed by three orders of magnitude. We also delineate the single helix growth mechanism and report the occurrence of ribbon-like structures and highly regular “superhelices”. Our experiments clearly demonstrate the robustness and consistency of biomorph growth under stable chemical conditions.
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