1,720,954 research outputs found
Generalized hydrodynamics of reaction-diffusion systems and dissipative structures
No full textGeneralized hydrodynamics (GH) are derived and used to describe a reaction-diffusion system. The derived GH equations are hyperbolic and are shown to be more general and more suitable than the conventional parabolic reaction-diffusion equations, especially in small geometries. These equations are applied to the study of dissipative structures in glycolysis and are solved numerically using the finite-element method. The solution exhibits a multitude of wave and Turing patterns. The time evolution of the calortropy production for the obtained pattern seems to correlate with the increasing complexity of the system.AlGhoul M, 1996, PHYSICA D, V97, P531, DOI 10.1016-0167-2789(96)00008-5; AlGhoul M, 1996, J PHYS CHEM-US, V100, P18900, DOI 10.1021-jp960865s; Al-Ghoul M, 2001, J PHYS CHEM A, V105, P8053, DOI 10.1021-jp011158o; AlGhoul M, 1996, PHYSICA D, V90, P119, DOI 10.1016-0167-2789(95)00231-6; DAWSON SP, 1994, J CHEM PHYS, V100, P5211, DOI 10.1063-1.467185; DAWSON SP, 1993, J CHEM PHYS, V98, P1514; DEWEL G, 1983, P NATL ACAD SCI USA, V80, P6429, DOI 10.1073-pnas.80.20.6429; ELKHOURY J, 2002, THESIS U FRANCOPHONI; Eu B. C., 1998, NONEQUILIBRIUM STAT; Eu B.C., 2002, GEN THERMODYNAMICS; Glansdorff P., 1971, THERMODYNAMIC THEORY; Goldbeter A., 1996, BIOCH OSCILLATIONS C; Hairer E., 1996, SOLVING ORDINARY DIF; HODGKIN AL, 1952, J PHYSIOL-LONDON, V117, P500; Kapral R., 1994, CHEM WAVES PATTERNS; KAPRAL R, 1991, PHYS REV LETT, V66, P2539, DOI 10.1103-PhysRevLett.66.2539; Kindzelskii AL, 2002, P NATL ACAD SCI USA, V99, P9207, DOI 10.1073-pnas.132630999; Lucquin B., 1998, INTRO SCI COMPUTING; Muller I., 1993, EXTENDED THERMODYNAM; Murray J. D., 1989, MATH BIOL; Nicolis G, 1977, SELF ORG NONEQUILIBR; Nicolis Gregoire, 1989, EXPLORING COMPLEXITY; Petty HR, 2000, PHYS REV LETT, V84, P2754, DOI 10.1103-PhysRevLett.84.2754; Petty HR, 2000, J PHYS CHEM B, V104, P10952, DOI 10.1021-jp00255lh; Prigogine I., 1961, THERMODYNAMICS IRREV; RICHTER PH, 1981, PROG THEOR PHYS, V66, P385, DOI 10.1143-PTP.66.385; SAAD Y, 2003, PARMS V 1 0; SAAD Y, 1999, PSPARSLIB V 3 0; Scott S. K., 1994, OSCILLATIONS WAVES C; Segel L.A., 1984, MODELLING DYNAMIC PH; Winfree A T, 1980, GEOMETRY BIOL TIME; WOOD PM, 1985, J CHEM PHYS, V82, P1924, DOI 10.1063-1.44837613
Superdiffusive cusp-like waves in the mercuric iodide precipitate system and their transition to regular reaction bands
No full textWe report a two-dimensional (2D) reaction-diffusion system that exhibits a superdiffusive propagating wave with anomalous cusp-like contours. This wave results from a leading precipitation reaction (wavefront) and a trailing redissolution (waveback) between initially separated mercuric chloride and potassium iodide to produce mercuric iodide precipitate (HgI2) in a thin sheet of a solid hydrogel (agar) medium. The propagation dynamics is accompanied by continuous polymorphic transformations between the metastable yellow crystals and the stable red crystals of HgI2. We study the dynamics of wavefront and waveback propagation that reveals interesting anomalous superdiffusive behavior without the influence of external enhancement. We find that a transition from superdiffusive to subdiffusive dynamics occurs as a function of outer iodide concentration. Inner mercuric concentrations lead to the transition from the anomalous cusp-like to cusp-free regular bands. While gel concentration affects the speed of propagation of the wave, it has no effect on its shape or on its superdiffusive dynamics. Microscopically, we show that the macroscopic wave propagation and polymorphic transformations are accompanied by an Ostwald ripening mechanism in which larger red HgI2 crystals are formed at the expense of smaller yellow HgI2 crystals. © 2014 American Chemical Society.Mansour AA, 2011, PHYS REV E, V84, DOI 10.1103-PhysRevE.84.026107; Al-Ghoul M, 2001, J PHYS CHEM A, V105, P8053, DOI 10.1021-jp011158o; Al-Ghoul M, 2012, J PHYS CHEM A, V116, P4427, DOI 10.1021-jp300163f; Antal T, 1998, J CHEM PHYS, V109, P9479, DOI 10.1063-1.477609; Badr L., 2009, J PHYS CHEM A, V113, P6581; Berenstein I, 2008, PHYS REV E, V78, DOI 10.1103-PhysRevE.78.025101; CORNELL S, 1991, PHYS REV A, V44, P4826, DOI 10.1103-PhysRevA.44.4826; CROSS MC, 1993, REV MOD PHYS, V65, P851, DOI 10.1103-RevModPhys.65.851; DAS I, 1989, J PHYS CHEM-US, V93, P7269, DOI 10.1021-j100357a047; DAS I, 1990, J PHYS CHEM-US, V94, P8968, DOI 10.1021-j100389a023; DAS I, 1991, J PHYS CHEM-US, V95, P3866, DOI 10.1021-j100162a078; Deutsch A., 2005, CELLULAR AUTOMATON M; Fernandez-Garcia G, 2008, EUR PHYS J-SPEC TOP, V165, P169, DOI 10.1140-epjst-e2008-00860-2; FIELD RJ, 1972, J AM CHEM SOC, V94, P8649, DOI 10.1021-ja00780a001; GALFI L, 1988, PHYS REV A, V38, P3151, DOI 10.1103-PhysRevA.38.3151; Greenwell HC, 2006, J CRYST GROWTH, V294, P53, DOI 10.1016-j.jcrysgro.2006.05.048; Grzybowski B., 2009, CHEMISTRY IN MOTION; Hantz P, 2002, PHYS CHEM CHEM PHYS, V4, P1262, DOI 10.1039-b107742b; Hantz P, 2000, J PHYS CHEM B, V104, P4266, DOI 10.1021-jp992456c; Hilal N, 2003, CHEM PHYS LETT, V374, P183, DOI 10.1016-S0009-2614(03)00726-7; Horvat S, 2005, J CHEM PHYS, V123, DOI 10.1063-1.1943409; Hostettler M, 2003, HELV CHIM ACTA, V86, P1410, DOI 10.1002-hlca.200390126; Hostettler M, 2001, CHIMIA, V55, P541; Hostettler M, 2002, ACTA CRYSTALLOGR B, V58, P903, DOI 10.1107-S010876810201618X; Hostettler M, 2005, CR CHIM, V8, P147, DOI 10.1016-j.crci.2004.06.006; JEFFREY GA, 1967, INORG CHEM, V6, P396, DOI 10.1021-ic50048a048; Kapral R., 1995, CHEMICAL WAVES AND P; Kleber W., 1968, KRIST TECH, V3, P65, DOI 10.1002-crat.19680030109; KOO YE, 1990, MOL CRYST LIQ CRYST, V183, P187, DOI 10.1080-15421409008047455; Koza Z, 1996, PHYS REV E, V54, pR1040, DOI 10.1103-PhysRevE.54.R1040; Lagzi I, 2012, LANGMUIR, V28, P3350, DOI 10.1021-la2049025; LARRALDE H, 1992, PHYS REV A, V46, P855, DOI 10.1103-PhysRevA.46.855; Leger C, 1999, J PHYS CHEM B, V103, P5841, DOI 10.1021-jp990486+; Liesegang R, 1896, NATURWISS WOCHENSCHR, V10, P353; Meinhardt H., 2009, THE ALGORITHMIC BEAU; Muller SC, 2003, J PHYS CHEM A, V107, P7997, DOI 10.1021-jp030364o; Murray J. D., 2002, MATHEMATICAL BIOLOGY, V2; NOSZTICZIUS Z, 1991, J PHYS CHEM-US, V95, P6575, DOI 10.1021-j100170a038; Panfilov AV, 2007, P NATL ACAD SCI USA, V104, P7922, DOI 10.1073-pnas.0701895104; Paoletti MS, 2006, PHYS REV LETT, V96, DOI 10.1103-PhysRevLett.96.124101; Sultan R, 1996, J PHYS CHEM-US, V100, P16912, DOI 10.1021-jp960958+; Sultan R, 2001, PHYSICA D, V157, P241, DOI 10.1016-S0167-2789(01)00303-7; Taitelbaum H, 1996, PHYS REV E, V54, P5942, DOI 10.1103-PhysRevE.54.5942; Taylor AF, 2002, PROG REACT KINET MEC, V27, P247; Tinsley MR, 2013, J PHYS CHEM A, V117, P12719, DOI 10.1021-jp4095479; Vanag VK, 2001, SCIENCE, V294, P835, DOI 10.1126-science.1064167; van Baalen G, 2000, COMMUN MATH PHYS, V210, P145, DOI 10.1007-s002200050775; Volford A, 2007, LANGMUIR, V23, P961, DOI 10.1021-la0623432; von Kameke A, 2010, PHYS REV E, V81, DOI 10.1103-PhysRevE.81.066211; WOOD PM, 1985, J CHEM PHYS, V82, P1924, DOI 10.1063-1.448376; ZAIKIN AN, 1970, NATURE, V225, P535, DOI 10.1038-225535b0; ZRINYI M, 1991, J PHYS CHEM-US, V95, P1618, DOI 10.1021-j100157a0221
Generalized hydrodynamics and microflows
No full textA mathematical model was developed within the framework of generalized hydrodynamics for the description of flows in microsystems where the Knudsen number is largest and the aspect ratio is not so small. The model was based on a set of empirical generalized hydrodynamic equations, fashioned from the steady-state generalized hydrodynamic equations derived from the boltzmann equation in a manner consistent with the laws of thermodynamics. Unlike the Newtonian law of viscosity and the Fourier law of heat conduction, the equations used for the model were highly nonlinear but thermodynamically consistent. To obtain an analytic formula for the flow rate, which exhibits a knudsen minimum, the differential equation for pressure distribution was also solved.Al-Ghoul M, 2001, PHYS REV LETT, V86, P4294, DOI 10.1103-PhysRevLett.86.4294; Al-Ghoul M, 2001, PHYS REV E, V64, DOI 10.1103-PhysRevE.64.046303; AlGhoul M, 1997, PHYS REV E, V56, P2981, DOI 10.1103-PhysRevE.56.2981; Arkilic EB, 1997, J MICROELECTROMECH S, V6, P167, DOI 10.1109-84.585795; Batchelor GK, 1967, FLUID DYNAMICS; Beskok A, 1999, MICROSCALE THERM ENG, V3, P43; BHATTACHARYA DK, 1987, PHYS REV A, V35, P821, DOI 10.1103-PhysRevA.35.821; Bird G. A., 1994, MOL GAS DYNAMICS DIR; Cai CP, 2000, J THERMOPHYS HEAT TR, V14, P368, DOI 10.2514-2.6534; Chapman S., 1970, MATH THEORY NONUNIFO; Cieplak M, 2000, PHYSICA A, V287, P153, DOI 10.1016-S0378-4371(00)00353-8; Clausing P, 1930, Z PHYS, V66, P471, DOI 10.1007-BF01402029; Deissler R.G., 1964, International Journal of Heat and Mass Transfer, V7, DOI 10.1016-0017-9310(64)90161-9; Eu B. C., 1992, KINETIC THEORY IRREV; Eu B. C., 1998, NONEQUILIBRIUM STAT; EU BC, 1987, CAN J PHYS, V65, P1090; EU BC, 1989, PHYS REV A, V40, P6395, DOI 10.1103-PhysRevA.40.6395; Eu BC, 2001, PHYS FLUIDS, V13, P744, DOI 10.1063-1.1343908; EU BC, 1985, J CHEM PHYS, V82, P4683, DOI 10.1063-1.448677; EU BC, 1988, PHYS REV A, V37, P4504, DOI 10.1103-PhysRevA.37.4504; Eu B.C., 2002, GEN THERMODYNAMICS T; EU BC, 1980, J CHEM PHYS, V73, P2958, DOI 10.1063-1.440469; EU BC, 1984, P INT S RAR GAS DYN, P27; EU BC, 1987, PHYS REV A, V36, P400, DOI 10.1103-PhysRevA.36.400; Gad-el-Hak M, 1999, J FLUID ENG-T ASME, V121, P5, DOI 10.1115-1.2822013; Goodman F. O., 1976, DYNAMICS GAS SURFACE; Gumhalter B, 2001, PHYS REP, V351, P1, DOI 10.1016-S0370-1573(00)00143-5; HARLEY JC, 1995, J FLUID MECH, V284, P257, DOI 10.1017-S0022112095000358; Ho CM, 1998, ANNU REV FLUID MECH, V30, P579, DOI 10.1146-annurev.fluid.30.1.579; HOOGEVEEN RWM, 1989, PHYS REV A, V39, P5539, DOI 10.1103-PhysRevA.39.5539; HURLBUT FC, 1994, PROGR ASTRONAUT AERO, V158, P494; Karniadakis G. E., 2002, MICRO FLOWS; Ketsdever AD, 2001, J THERMOPHYS HEAT TR, V15, P302, DOI 10.2514-2.6626; KHAYAT RE, 1989, PROG ASTRONAUT AERON, V118, P396; KHAYAT RE, 1988, PHYS REV A, V38, P2492, DOI 10.1103-PhysRevA.38.2492; KHAYAT RE, 1989, PHYS REV A, V40, P946, DOI 10.1103-PhysRevA.40.946; Knudsen M., 1909, ANN PHYS, V333, P75, DOI DOI 10.1002-ANDP.19093330106; Knudsen M., 1934, KINETIC THEORY GASES; Kogan M., 1969, RAREFIED GAS DYNAMIC; Langmuir I, 1916, PHYS REV, V8, P149, DOI 10.1103-PhysRev.8.149; Langmuir I, 1916, J AM CHEM SOC, V38, P2221, DOI 10.1021-ja02268a002; MAO KF, 1993, PHYS REV A, V48, P2471, DOI 10.1103-PhysRevA.48.2471; MAXWELL JC, 1927, COLLECTED WORKS JC M, V2, P682; Meinhart CD, 1999, EXP FLUIDS, V27, P414, DOI 10.1007-s003480050366; Myong R. S., 2001, 20013076 AIAA; OHWADA T, 1989, PHYS FLUIDS A-FLUID, V1, P2942; Oran ES, 1998, ANNU REV FLUID MECH, V30, P403, DOI 10.1146-annurev.fluid.30.1.403; Pong K., 1994, ASME FED, V197, P51; Rettner C. T., 1991, DYNAMICS GAS SURFACE; Santiago JG, 1998, EXP FLUIDS, V25, P316, DOI 10.1007-s003480050235; Schaaf S.A., 1963, HDB PHYSIK 2, VVIII, P591; STECKELMACHER W, 1983, J PHYS D APPL PHYS, V16, P1453, DOI 10.1088-0022-3727-16-8-012; STECKELMACHER W, 1986, REP PROG PHYS, V49, P1083, DOI 10.1088-0034-4885-49-10-001; Sun QH, 2002, J COMPUT PHYS, V179, P400, DOI 10.1006-jcph.2002.706179
Theoretical modeling of front propagation of CdS nanoparticles in a gel
No full textWe report a theoretical model to describe the spatiotemporal dynamics of a new system consisting of sulfide ions diffusing into an organic gel containing mercaptoethanol-capped cadmium ions. The product, cadmium sulfide, exhibits a faint yellow transparent propagating front starting at the gel-outer electrolyte interface. When subjected to UV light, this system reveals fluorescing CdS nuclei localized spatially in a narrow region (constant width), called pulse, that leads the front and propagates down the tube. The reported model is based on reaction-diffusion equations coupled to dynamical competitive particle growth. The resulting evolution equations were solved numerically and the results are shown. © (2010) Trans Tech Publications, Switzerland.Al-Ghoul M, 2009, J PHYS CHEM B, V113, P11594, DOI 10.1021-jp9022647; Bao YH, 2007, J AM CERAM SOC, V90, P1063, DOI 10.1111-j.1551-2916.2007.01504.x; Barkema GT, 1996, PHYS REV E, V53, pR2017; Baroud CN, 2003, PHYS REV E, V67, DOI 10.1103-PhysRevE.67.060104; Cabarcos EL, 1996, PHYS REV LETT, V77, P2834; Chong TH, 2001, CHEM ENG SCI, V56, P5391, DOI 10.1016-S0009-2509(01)00237-8; GALFI L, 1988, PHYS REV A, V38, P3151, DOI 10.1103-PhysRevA.38.3151; HAMPTON JHD, 1993, CHEM ENG SCI, V48, P1601, DOI 10.1016-0009-2509(93)80120-F; KOO YEL, 1991, J STAT PHYS, V65, P893, DOI 10.1007-BF01049588; Kravchenko VV, 1999, DOKL AKAD NAUK+, V364, P114; Kravchenko VV, 1999, DOKL AKAD NAUK+, V364, P687; LARRALDE H, 1992, PHYS REV A, V46, P855, DOI 10.1103-PhysRevA.46.855; Magnico P, 2000, CHEM ENG SCI, V55, P4323, DOI 10.1016-S0009-2509(00)00047-6; Ortoleva PJ, 1994, GEOCHEMICAL SELF ORG; Park SH, 2007, PHYS REV E, V75, DOI 10.1103-PhysRevE.75.026107; Park SH, 2001, PHYS REV E, V64, DOI 10.1103-PhysRevE.64.055102; Sinder M, 2000, PHYS REV E, V62, P3340, DOI 10.1103-PhysRevE.62.3340; TAITELBAUM H, 1992, PHYS REV A, V46, P2151, DOI 10.1103-PhysRevA.46.2151; Taitelbaum H, 1996, PHYS REV LETT, V77, P1640, DOI 10.1103-PhysRevLett.77.1640; TAITELBAUM H, 1991, J STAT PHYS, V65, P873, DOI 10.1007-BF01049587; Yen A, 1996, PHYS REV E, V54, P2447, DOI 10.1103-PhysRevE.54.2447; 2002, PHYS CHEM CHEM PHYS, V4, P125312
Vertex-based finite volume simulation of Liesegang patterns on structureless meshes
Get PDFA computational method is suggested for the simulation of Liesegang patterns in two dimensions on structureless meshes. The method is based on a model that incorporates dynamical equations for the nucleation and growth of solid particles of different sizes into reaction-diffusion equations. We find the model cannot be numerically solved with Galerkin-based finite element methods and cell-centered finite volume methods. Instead, the vertex-based finite volume method is used to correctly reproduce the Liesegang pattern on structureless meshes. The numerical solution is then compared with specially designed experiments on Liesegang patterns in various geometries, and it is shown to be in good agreement. © 2014 American Physical Society.Al-Ghoul M, 2001, J PHYS CHEM A, V105, P8053, DOI 10.1021-jp011158o; Al-Ghoul M, 2003, J PHYS CHEM A, V107, P1095, DOI 10.1021-jp022433p; Al-Ghoul M, 2010, J CRYST GROWTH, V312, P856, DOI 10.1016-j.jcrysgro.2009.11.053; Baliga B. R., 1980, Numerical Heat Transfer, V3, DOI 10.1080-10407798008547056; Baliga B. R., 1983, Numerical Heat Transfer, V6, DOI 10.1080-10407798308546969; Batlouni H., 2008, J PHYS CHEM A, V112, P7755; Byrne G. D., 1975, ACM Transactions on Mathematical Software, V1, DOI 10.1145-355626.355636; CHERNAVSKII DS, 1991, PHYSICA D, V54, P160, DOI 10.1016-0167-2789(91)90115-P; Davis TA, 2006, FUND ALGORITHMS, V2, P1, DOI 10.1137-1.9780898718881; Gear CW, 1971, NUMERICAL INITIAL VA; Geiser J, 2008, J COMPUT APPL MATH, V217, P227, DOI 10.1016-j.cam.2007.06.028; Geiser J., 2009, NUMERICAL ANAL SCI C; Gladwell I., 2003, SOLVING ODES MATLAB; Grzybowski BA, 2004, CHEM ENG SCI, V59, P1667, DOI 10.1016-j.ces.2004.01.023; Henisch H., 1988, CRYSTALS GELS LIESEG; Izsak F., 2010, PRECIPITATION PATTER, P207; Jablczynski M. C. K., 1955, J COLLOID SCI, V10, P46; JACKSON KR, 1980, ACM T MATH SOFTWARE, V6, P295, DOI 10.1145-355900.355903; KAI S, 1982, J CHEM PHYS, V76, P1392, DOI 10.1063-1.443131; Kelly C. T., 1995, ITERATIVE METHODS LI; Lebon Gerard S. B., 2012, J ALGORITHM COMPUT T, V6, P129; L'Heureux I, 2008, PHYS LETT A, V372, P3001, DOI 10.1016-j.physleta.2007.12.066; Liesegang R. L., 1896, PHOT ARCH, V37, P305; LIFSHITZ IM, 1961, J PHYS CHEM SOLIDS, V19, P35, DOI 10.1016-0022-3697(61)90054-3; Lloyd FE, 1928, PLANT PHYSIOL, V3, P101, DOI 10.1104-pp.3.2.101; Matalon R., 1923, B SOC CHIM FR, V4, P1592; Morse HW, 1903, PHYS REV, V17, P129, DOI 10.1103-PhysRevSeriesI.17.129; MULLER SC, 1982, J PHYS CHEM-US, V86, P4078; Nash PL, 2008, J COMPUT PHYS, V227, P2073, DOI 10.1016-j.jcp.2007.10.012; Nocedal J., 2000, NUMERICAL OPTIMIZATI; Polezhaev AA, 1994, CHAOS, V4, P631, DOI 10.1063-1.166040; Saad Y., 2003, ITERATIVE METHODS SP; Shewchuk JR, 2002, COMP GEOM-THEOR APPL, V22, P21, DOI 10.1016-S0925-7721(01)00047-5; Strang G., 1968, SIAM J NUMER ANAL, V5, P1; TURING AM, 1952, PHILOS T ROY SOC B, V237, P37, DOI 10.1098-rstb.1952.0012; Voller V.R., 2009, BASIC CONTROL VOLUME2
Pulse-front propagation and interaction during the growth of CdS nanoparticles in a gel
No full textWe studied the spatiotemporal dynamics of a new system consisting of sulfide ions (outer electrolyte) diffusing into an organic gel (gelatin) containing mercaptoethanol-capped cadmium ions (inner electrolyte). The product, cadmium sulfide, exhibits a faint yellow transparent propagating front starting at the gel-outer electrolyte interface. When subjected to UV light, this system reveals fluorescing CdS nuclei localized spatially in a narrow region, called pulse, that leads the front and propagates down the tube. We show that the pulse consists of CdS nanoclusters of an average size of about 4 nm, whereas the trailing front consists of 6-8 nm cubicphase CdS crystallites. The width of the pulse remains constant in time, f, at about 2 mm and independent of the outer concentration So. It was found that the speed of the pulse fluctuates as the concentration of the capping agent is varried, with fastest pulses attained at a concentration of 40 mM for two different outer concentrations of sulfide ions. The origin of the yellow fluorescence of the pulse originates from emission from surface states. This dynamical system was then theoretically studied using a competitive particle growth model. The resulting evolution equations were solved numerically, and the results were compared to the experimental findings. It was shown that the model agrees in many aspects with the experiment. The densities of small particles p and large particles p were shown to evolve like a pulse and a front, repectively. The front was shown to extend diffusively as t1-2, as found experimentally. The distance traveled by the pulse Xpeak was shown to increase with outer concentraion S0 and obeys a concentration power law Xpeak ∼ S1-4 0. The width w of the pulse also obeys a time power law w ∼t a with a crossover between early times (a = 1-3) and intermediate times (a = 0). 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Polymorphic and Morphological Transformation during the Transition from a Propagating Band to Static Bands in the Nickel Hydroxide/Ammonia Liesegang System
No full textWe present an experimental study of the Ni+2/Ni(OH)2/NH3 reaction-diffusion system in a gel (agar). The system, which consists of a gel containing an inner electrolyte Ni+2 and a diffusing outer electrolyte (NH3/OH-), exhibits pulse propagation due to the concomitant precipitation reaction between Ni+2 and hydroxide ions and re-dissolution due to ammonia. During the propagation of the pulse, a transition to Liesegang banding is shown to take place. The bands are characterized by IR and XRD and are shown to consist of the polymorph -Ni(OH)2 whereas the pulse contains the other polymorph -Ni(OH)2. SEM measurements also reveal a morphological change accompanying the polymorphic transition between the pulse and the bands and uncovering an Ostwald ripening mechanism.</jats:p
Reaction-diffusion framework: The mechanism of the polymorphic transition of α- To β-cobalt hydroxide
No full textA new and simple method is proposed to explore the mechanism of the intercalation-deintercalation of a variety of anions throughout the formation of α-Co(OH)2 crystals and their polymorphic conversion to β-Co(OH)2. This method is based on the reaction-diffusion of hydroxide ions in a gel matrix containing the cobalt salt. The spatiotemporal evolution of each polymorph and their interaction is revealed by tracking the location of the two sharp interfaces between the two polymorphs (conversion zone) and between the gel and α-Co(OH)2 (formation zone) and by measuring the weight composition of each zone. We thereby find that the dynamics of the transformation reaction are correctly described by the two-dimensional Avrami-Erofe'ev equation at different temperatures. The data suggest that the structural redistribution of the atoms inside the α-Co(OH)2 particles plays the fundamental role in establishing the overall rate of the reaction. On the other hand, we notice that other factors such as the nature of the intercalated anions and the concentration of the polymer matrix alter considerably the final rate of the transition reaction through increasing the stability of the α phase. © 2013 American Chemical Society.Al-Ghoul M, 2010, J CRYST GROWTH, V312, P856, DOI 10.1016-j.jcrysgro.2009.11.053; AUGIS JA, 1978, J THERM ANAL, V13, P283, DOI 10.1007-BF01912301; Avrami M., 1940, Journal of Chemical Physics, V8, DOI 10.1063-1.1750631; Avrami M, 1941, J CHEM PHYS, V9, P177, DOI 10.1063-1.1750872; Avrami M, 1939, J CHEM PHYS, V7, P1103, DOI 10.1063-1.1750380; BOLDYREV VV, 1979, ANNU REV MATER SCI, V9, P455, DOI 10.1146-annurev.ms.09.080179.002323; Burnham AK, 2004, J PHYS CHEM B, V108, P19432, DOI 10.1021-jp0483167; CARTER RE, 1961, J CHEM PHYS, V34, P2010, DOI 10.1063-1.1731812; Du Y, 2008, J MATER CHEM, V18, P4450, DOI 10.1039-b809085h; El-Batlouni H, 2008, J PHYS CHEM A, V112, P7755, DOI 10.1021-jp804569b; Farvid SS, 2012, J AM CHEM SOC, V134, P7015, DOI 10.1021-ja211627r; Garner WE, 1955, CHEM SOLID STATE; Hu ZA, 2009, J PHYS CHEM C, V113, P12502, DOI 10.1021-jp8106809; Khan AI, 2002, J MATER CHEM, V12, P3191, DOI 10.1039-b204076j; Khawam A, 2006, J PHYS CHEM B, V110, P17315, DOI 10.1021-jp062746a; Liu ZP, 2005, J AM CHEM SOC, V127, P13869, DOI 10.1021-ja0523338; Ma RZ, 2006, INORG CHEM, V45, P3964, DOI 10.1021-ic052108r; Maaloum M, 1998, ELECTROPHORESIS, V19, P1606, DOI 10.1002-elps.1150191015; Metzler R, 2000, PHYS REP, V339, P1, DOI 10.1016-S0370-1573(00)00070-3; Neilson JR, 2009, INORG CHEM, V48, P11017, DOI 10.1021-ic901167u; RABU P, 1993, INORG CHEM, V32, P2463, DOI 10.1021-ic00063a043; Rahbani J, 2012, J MATER CHEM, V22, P16361, DOI 10.1039-c2jm31694c; Rajamathi M, 2000, MATER RES BULL, V35, P271, DOI 10.1016-S0025-5408(00)00199-9; Rees A.L.G., 1954, CHEM DEFECT SOLID ST; Schwenzer B, 2009, THIN SOLID FILMS, V517, P5722, DOI 10.1016-j.tsf.2009.02.131; Sestak J., 1971, THERMOCHIM ACTA, V3, P1, DOI 10.1016-0040-6031(71)85051-7; Van Vlierberghe S, 2007, BIOMACROMOLECULES, V8, P331, DOI 10.1021-bm060684o11
Kinetics and mechanism of ionic intercalation-de-intercalation during the formation of α-cobalt hydroxide and its polymorphic transition to β-cobalt hydroxide: Reaction-diffusion framework
No full textWe study the kinetics and mechanism of intercalation and de-intercalation of small anions during the formation of crystalline α-Co(OH) 2 and its transformation to β-Co(OH) 2 within a reaction-diffusion framework. We therein use fluorescence spectroscopy with Rhodamine 6G (Rh6G) as a probe as well as other spectroscopic and imaging techniques. The method is based on the reaction and diffusion of hydroxide ions into a gel matrix containing the Co(ii) ions, the conjugate anions to be intercalated and Rh6G. The advantage of this simple method is that it allows us to separate throughout space the various stages during the formation of α-Co(OH) 2 and its transformation to β-Co(OH) 2, thus enabling fluorescence measurements of the those stages by simply focusing on different areas of the tube. It also permits us to extract with ease the solids for characterization and image analysis. The macroscopic evolution of the system, which consists of a leading blue front designating the formation of α-Co(OH) 2 followed by a sharp blue-pink interface designating the transformation to the pink β-Co(OH) 2, exhibits different dynamics depending on the anion present in the gel. At a certain stage, the blue-pink interface stops its propagation and only the blue front continues. This represents clear evidence of the dependence of the kinetics of intercalation and de-intercalation on the nature of the anion. The coexisting polymorphs were collected and characterized using XRD, FTIR, Raman and UV-Vis. The fluorescence images of the α-Co(OH) 2 reveal clearly the presence of Rh6G between its layers, whereas images from the β polymorph indicate the opposite. Moreover, the fluorescence of Rh6G is monitored during the formation of α-Co(OH) 2 and its conversion to β-Co(OH) 2. During the formation, the fluorescence intensity and lifetime are significantly increased whereas the opposite happens during the transformation to the β phase. We are able to calculate the activation energies associated with the intercalation and de-intercalation of anions and show using SEM that the polymorphic transformation is accompanied by an Ostwald ripening mechanism whereby the smaller crystals of α-Co(OH) 2 dissolve to reappear as larger crystals of β-Co(OH) 2. We find that the activation energies of de-intercalation are systematically smaller than those of intercalation. 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Characterization of internal structure of hydrated agar and gelatin matrices by cryo-SEM
No full textThere has been a considerable interest in recent years in developing polymer gel matrices for many important applications such as 2DE for quantization and separation of a variety of proteins and drug delivery system to control the release of active agents. However, a well-defined knowledge of the ultrastructures of the gels has been elusive. In this study, we report the characterization of two different polymers used in 2DE: Gelatin, a naturally occurring polymer derived from collagen (protein) and agar, a polymer of polysaccharide (sugar) origin. Low-temperature SEM is used to examine the internal structure of these gels in their frozen natural hydrated states. Results of this study show that both polymers have an array of hollow cells that resembles honeycomb structures. While agar pores are almost circular, the corresponding Gaussian curve is very broad exhibiting a range of radii from nearly 370 to 700 nm. Gelatin pores are smaller and more homogeneous reflecting a narrower distribution from nearly 320 to 650 nm. Overall, these ultrastructural findings could be used to correlate with functions of the polymers. © 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim.ARAKI C, 1960, B CHEM SOC JPN, V33, P291, DOI 10.1246-bcsj.33.291; ARNOTT S, 1974, J MOL BIOL, V90, P269, DOI 10.1016-0022-2836(74)90372-6; Celis JE, 1998, FEBS LETT, V430, P64, DOI 10.1016-S0014-5793(98)00527-4; Choi NS, 2004, J BIOCHEM MOL BIOL, V37, P298; CHUI MM, 1995, J COLLOID INTERF SCI, V174, P336, DOI 10.1006-jcis.1995.1399; KUGA S, 1981, J CHROMATOGR, V206, P449, DOI 10.1016-S0021-9673(00)88914-1; Kuwana R, 2002, MICROBIOL-SGM, V148, P3971; Maaloum M, 1998, ELECTROPHORESIS, V19, P1606, DOI 10.1002-elps.1150191015; McKerrow JH, 2000, MOL MED, V6, P450; Michon C, 1997, INT J BIOL MACROMOL, V20, P259, DOI 10.1016-S0141-8130(97)00024-X; MICHON C, 1993, RHEOL ACTA, V32, P94, DOI 10.1007-BF00396681; Pernodet N, 1997, ELECTROPHORESIS, V18, P55, DOI 10.1002-elps.1150180111; ROSSMURPHY SB, 1992, POLYMER, V33, P2622, DOI 10.1016-0032-3861(92)91146-S; Schwartz SA, 2004, CLIN CANCER RES, V10, P981, DOI 10.1158-1078-0432.CCR-0927-3; Stoeckli M, 2001, NAT MED, V7, P493, DOI 10.1038-86573; Tannu NS, 2006, PROG BRAIN RES, V158, P41, DOI 10.1016-S0079-6123(06)58003-3; Van Vlierberghe S, 2007, BIOMACROMOLECULES, V8, P331, DOI 10.1021-bm060684o; Vilain S, 2004, PROTEOMICS, V4, P1996, DOI 10.1002-pmic.20030707; WAKI S, 1982, BIOPOLYMERS, V21, P1909, DOI 10.1002-bip.360210917; WHYTOCK S, 1991, BIOPOLYMERS, V31, P1025, DOI 10.1002-bip.360310902; WIEME R. J., 1965, AGAR GEL ELECTROPHOR24
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