Broom-like and flower-like heterostructures of silver molybdate through pH controlled self assembly

  • D. P. Singh
  • B. Sirota
  • S. Talpatra
  • P. Kohli
  • C. Rebholz
  • S. M. Aouadi
Research Paper


Silver molybdate microrods are self-assembled into micron sized, broom-like and flower-like structures. Our investigations indicate that through a simple hydrothermal process, large scale production of such structure is possible. Using ammonium molybdate and silver nitrate solutions as precursors, we were able to show that the self assembled architectures were dependent on the pH of the starting precursor material. To understand the formation and destructions of the flower-like morphology, a systematic broad range (from acidic to basic) of pH-controlled experiments were performed and its influence on the structure/microstructure of synthesized materials was investigated. Scanning electron microscopy studies revealed that the morphology and microstructure of the products varied significantly by changing pH values from 3 to 8 during mixing of the reactants. pH = 3 and 4 resulted in the self assembly of monoclinic Ag2(Mo2O7) microrods into broom-like structures, whereas pH = 5 resulted into the flower-like morphology of mixed phase of monoclinic and triclinic Ag2Mo2O7. We also found that increasing the pH after a certain threshold value (for example pH > 6) resulted in total collapse of the flower-like morphology. Further increase of the pH to 7 and 8 resulted, the formation of microparticles of Ag2MoO4. A tentative scheme based on the pH-driven evolution of the self-assembly has been given to explain the formation of the observed heterostructures. Preliminary electrical characterization of thin films of the flower-like structures rendered non-linear current–voltage (I–V) responses. We also observed a strong hysteresis in the I–V responses of the flower-like structures developed under high bias conditions.


Silver molybdate Broom-like Flower-like Hydrothermal method Microrods Synthesis method 



This research is supported by the National Science Foundation (Award # CMMI-0653986), the U.S. Department of the ARMY (Award # W911NF-08-1-0460), an award from the Air Force Summer Fellowship Program and author D P Singh acknowledge the financial support from the CONICYT CHILE (FONDECYT REGULAR) Project award no 1120644. The authors also wish to thank Professor Naushad Ali and Dr. Igor Dubenko of the Southern Illinois University Laboratory for their assistance with X-ray measurements.


  1. Appell D (2002) Nanotechnology: wired for success. Nature 419:553–555CrossRefGoogle Scholar
  2. Bazarov BG, Grossman VG, Klevtsova RF, Anshits G, Vereshchagina TA, Glinskaya LA, Tushinova YL, Fedorov KN, Bazarova ZG (2009) Crystal structure of binary molybdate Pr2Hf3(MoO4)9. J Struct Chem 50:566–569CrossRefGoogle Scholar
  3. Bertoni MI, Kidner NJ, Mason TO, Albrecht TA, Sorensen EM, Poeppelmeier KR (2007) Electrical and optical characterization of Ag2V4O11 and Ag4V2O6F2. J Electroceram 18:189–195CrossRefGoogle Scholar
  4. Bhattacharya S, Ghosh A (2005) Transport properties of AgI doped silver molybdate superionic glass-nanocomposites. J Phys Condens Matter 17:5655–5662CrossRefGoogle Scholar
  5. Cheng L, Shao Q, Shao M, Wei X, Wu Z (2009) Photoswitches of one-dimensional Ag2MO4 (M = Cr, Mo, and W). J Phys Chem C 113:1764–1768CrossRefGoogle Scholar
  6. Cui X, Yu SH, Li L, Biao L, Li H, Mo M, Liu XM (2004) Selective synthesis and characterization of single-crystal silver molybdate/tungstate nanowires by a hydrothermal process. Chem Eur J 10:218–223CrossRefGoogle Scholar
  7. Dong F, Huang Y, Zou S, Liu J, Lee SC (2011) Ultrasonic spray pyrolysis fabrication of solid and hollow PbWO4 spheres with structure-directed photocatalytic activity. J Phys Chem C 115:241–247CrossRefGoogle Scholar
  8. Driscoll S, Ozkan US (1994) Isotopic labeling studies on oxidative coupling of methane over alkali promoted molybdate catalysts. Stud Surf Sci Catal 82:367–375CrossRefGoogle Scholar
  9. Ehrenberg E, Weitzely H, Heidy C, Fuessy H, Wltschekz G, Kroenerx T, van Tol J, Bonnet M (1997a) Magnetic phase diagrams of MnWO4. J Phys Condens Matter 9:3189–3203CrossRefGoogle Scholar
  10. Ehrenberg H, Weitzel H, Paulus H, Wiesmann M, Wltschek G, Geselle M, Fuess H (1997b) Crystal structure and magnetic properties of CuMoO4 at low temperature (γ-phase). J Phys Chem Solids 58:153–160CrossRefGoogle Scholar
  11. Feilchenfeld H, Siiman O (1986) Adsorption and aggregation kinetics and its fractal description for chromate, molybdate, and tungstate ions on colloidal silver from surface Raman spectra. J Phys Chem 90:4590–4599CrossRefGoogle Scholar
  12. Goldberger J, He R, Zhang Y, Lee S, Yan H, Choi HJ, Yang P (2003) Single-crystal gallium nitride nanotubes. Nature 422:599–602CrossRefGoogle Scholar
  13. Gulbinski W, Suszko T (2006) Thin films of MoO3–Ag2O binary oxides the high temperature lubricants. Wear 261:867–873CrossRefGoogle Scholar
  14. Gulbinski W, Suszko T, Sienicki W, Warcholinski B (2003) Tribological properties of silver- and copper-doped transition metal oxide coatings. Wear 254:129–135CrossRefGoogle Scholar
  15. Guo J, Zavalij P, Stanley WM (1995) Metastable hexagonal molybdates: hydrothermal preparation, structure, and reactivity. J Solid State Chem 117:323–332CrossRefGoogle Scholar
  16. Holtz RD, Filho AGS, Brocchi M, Martins D, Durán N, Alves OL (2010) Development of nanostructured silver vanadates decorated with silver nanoparticles as a novel antibacterial agent. Nanotechnology 21:185102–185110CrossRefGoogle Scholar
  17. Hu B, Mai L, Chen W, Yang F (2009) From MoO3 nanobelts to MoO2 nanorods: structure transformation and electrical transport. ACS Nano 3:478–482CrossRefGoogle Scholar
  18. Ito T, Takagi H, Asano T (2009) Drastic and sharp change in color, shape, and magnetism in transition of CuMoO4 single crystals. Chem Mater 21:3376–3379CrossRefGoogle Scholar
  19. Kozma P, Bajgar R, Kozma JP (2002) Radiation damage of PbWO4 crystals due to radiation by 60Co gamma-rays. Radiat Phys Chem 65:127–130CrossRefGoogle Scholar
  20. Krol R, Liang Y, Schoonman J (2008) Solar hydrogen production with nanostructured metal oxides. J Mater Chem 18:2311–2320CrossRefGoogle Scholar
  21. Li X, Zang J (2009) Facile hydrothermal synthesis of sodium tantalate (NaTaO3) nanocubes and high photocatalytic properties. J Phys Chem C 113:19411–19418CrossRefGoogle Scholar
  22. Li Y, Qian F, Xiang J, Lieber CM (2006) Nanowire electronic and optoelectronic devices. Mater Today 9:18–27CrossRefGoogle Scholar
  23. Liao HW, Wang YF, Liu XM, Li YD, Qian YT (2000) Hydrothermal preparation and characterization of luminescent CdWO4 nanorods. Chem Mater 12:2819–2821CrossRefGoogle Scholar
  24. Lu J, Li Y, Shen E, Yuan M, Wang E, Hu C, Xu L (2004) Hydrothermal synthesis and crystal structure of a novel two-dimensional organic–inorganic hybrid copper molybdate with mixed organodiamine and dicarboxyl ligands. J Solid State Chem 177:1771–1775CrossRefGoogle Scholar
  25. Machida N, Eckert H (1998) FT-IR, FT-Raman and 95MoMAS–NMR studies on the structure of ionically conducting glasses in the system AgI–Ag2O–MoO3. Solid State Ion 107:255–268CrossRefGoogle Scholar
  26. Mai L, Xu L, Gao Q, Han C, Hu B, Pi Y (2010) Single-AgVO3 nanowire H2S sensor. Nano Lett 10:2604–2612CrossRefGoogle Scholar
  27. Mougin O, Dubois JL, Mathieu F, Rousset A (2000) Metastable hexagonal vanadium molybdate study. J Solid State Chem 152:353–360CrossRefGoogle Scholar
  28. Nagaraju G, Tharamani CN, Chandrappa GT, Livage J (2007) Hydrothermal synthesis of amorphous MoS2 nanofiber bundles via acidification of ammonium heptamolybdate tetrahydrate. Nanoscale Res Lett 2:461–468CrossRefGoogle Scholar
  29. Newton MC, Leake SJ, Harder R, Robinson IK (2009) Three-dimensional imaging of strain in a single ZnO nanorod. Nat Mater 9:120–124CrossRefGoogle Scholar
  30. Nyman M, Rodriguez MA, Rohwer LES, Martin JE, Waller M, Osterloh FE (2009) Unique LaTaO4 polymorph for multiple energy applications. Chem Mater 21:4731–4737CrossRefGoogle Scholar
  31. Pan H, Feng YP (2008) Semiconductor nanowires and nanotubes: effects of size and surface-to-volume ratio. ACS Nano 2:2410–2414CrossRefGoogle Scholar
  32. Pan GT, Lai MH, Juang RC, Chung TW, Yang TCK (2011) Preparation of visible-light-driven silver vanadates by a microwave- assisted hydrothermal method for the photodegradation of volatile organic vapors. Ind Eng Chem Res 50:2807–2814CrossRefGoogle Scholar
  33. Panchal V, Garg N, Sharma SM (2006) Raman and X-ray diffraction investigations on BaMoO4 under high pressures. J Phys Condens Matter 18:3917–3929CrossRefGoogle Scholar
  34. Qu W, Wlodarski W, Meyer JU (2000) Comparative study on micromorphology and humidity sensitive properties of thin-film and thick-film humidity sensors based on semiconducting MnWO4. Sens Actuators B64:76–82Google Scholar
  35. Readman JE, Lister SE, Peters L, Wright J, Evans JSO (2009) Direct synthesis of cubic ZrMo2O8 followed by ultrafast in situ powder diffraction. J Am Chem Soc 131:17560–17562CrossRefGoogle Scholar
  36. Singh DP (2010) Synthesis and growth of ZnO nanowires. Sci Adv Mater 2:245–272CrossRefGoogle Scholar
  37. Singh DP, Ali N (2010) Synthesis of TiO2 and CuO nanotubes and nanowires. Sci Adv Mater 2:295–335CrossRefGoogle Scholar
  38. Singh DP, Polychronopoulou K, Rebholz C, Aouadi SM (2010) Room temperature synthesis and high temperature frictional study of silver vanadate nanorods. Nanotechnol 21:325601–325608CrossRefGoogle Scholar
  39. Song RQ, Xu AW, Deng B, Fang YP (2005) Novel multilamellar mesostructured molybdenum oxide nanofibers and nanobelts: synthesis and characterization. J Phys Chem B 109:22758–22766CrossRefGoogle Scholar
  40. Tian ZR, Voigt JA, Liu J, Mckenzie B, Mcdermott MJ, Rodriguez MA, Konishi H, Xu H (2003) Complex and oriented ZnO nanostructures. Nat Mater 2:821–826CrossRefGoogle Scholar
  41. Tian H, Wachs IE, Briand LE (2005) Comparison of UV and visible Raman spectroscopy of bulk metal molybdate and metal vanadate catalysts. J Phys Chem B 109:23491–23499CrossRefGoogle Scholar
  42. Van Uitert LG, Preziosi S (1962) Zinc tungstates for microwave maser applications. J Appl Phys 33:2908–2910CrossRefGoogle Scholar
  43. Vijayaraghavan A, Kanzaki K, Suzuki S, Kobayashi Y, Inokawa H, Ono Y, Kar S, Ajayan PM (2005) Metal-semiconductor transition in single-walled carbon nanotubes induced by low-energy electron irradiation. Nano Lett 5:1575–1579CrossRefGoogle Scholar
  44. Wang H, Medina FD, Zhou YD, Zhang QN (1992) Temperature dependence of the polarized Raman spectra of ZnWO4 single crystals. Phys Rev B 45:10356–10362CrossRefGoogle Scholar
  45. Wang H, Medina FD, Liu D, Zhou YD (1994) The line shape and zero-phonon line of the luminescence spectrum from zinc tungstate single crystals. J Phys Condens Matter 6:5373–5386CrossRefGoogle Scholar
  46. White CT, Todorov TN (2001) Quantum electronics: nanotubes go ballistic. Nature 411:649–651CrossRefGoogle Scholar
  47. Wu J, Duan F, Zheng Y, Xie Y (2007) Synthesis of Bi2WO6 nanoplate-built hierarchical nest-like structures with visible-light-induced photocatalytic activity. J Phys Chem C 111:12866–12871CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  • D. P. Singh
    • 1
  • B. Sirota
    • 2
  • S. Talpatra
    • 2
  • P. Kohli
    • 3
  • C. Rebholz
    • 4
  • S. M. Aouadi
    • 2
  1. 1.Departamento de FísicaUniversidad de SantiagoSantiagoChile
  2. 2.Department of PhysicsSouthern Illinois UniversityCarbondaleUSA
  3. 3.Department of Chemistry and BiochemistrySouthern Illinois UniversityCarbondaleUSA
  4. 4.Department of Mechanical and Manufacturing Engineering1687, University of CyprusNicosiaCyprus

Personalised recommendations