Silver molybdate
{{Overly detailed|section=|details=|date=August 2020}}{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 464391198
| Name = Silver molybdate
| ImageFile =
| OtherNames =
| Section1 = {{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 10801079
| PubChem = 16217378
| InChI = 1/2Ag.Mo.4O/q2*+1;;;;2*-1/r2Ag.MoO4/c;;2-1(3,4)5/q2*+1;-2
| InChIKey = ^@€×,&#+=+÷×¥× ndnzjsnssi-QWQXGURBAC
| SMILES = [Ag+].[Ag+].[O-][Mo]([O-])(=O)=O
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/2Ag.Mo.4O/q2*+1;;;;2*-1
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = MHLYOTJKDAAHGI-UHFFFAOYSA-N
| CASNo_Ref = {{cascite|changed|??}}
| CASNo = 13765-74-7
}}
| Section2 = {{Chembox Properties
| Formula = Ag2MoO4
| MolarMass = 375.67 g/mol
| Appearance = yellow crystals
| Density = 6.18 g/cm3, solid
| Solubility = slightly soluble
| MeltingPtC = 483
| BoilingPt =
}}
| Section3 = {{Chembox Structure
| CrystalStruct = cubic
}}
}}
Silver molybdate (Ag2MoO4), a chemical compound, is a yellow, cubic crystalline substance often used in glass. Its crystals present two types of electronic structure, depending on the pressure conditions to which the crystal is subjected.{{Cite journal|title = Behavior of silver molybdate at high-pressure|journal = Journal of Solid State Chemistry|date = 2012-12-01|pages = 391–397|volume = 196|doi = 10.1016/j.jssc.2012.07.003|first1 = A. K.|last1 = Arora|first2 = R.|last2 = Nithya|first3 = Sunasira|last3 = Misra|first4 = Takehiko|last4 = Yagi|bibcode = 2012JSSCh.196..391A}} At room temperature, Ag2MoO4 exhibits a spinel-type cubic structure, known as β-Ag2MoO4, which is more stable in nature. However, when exposed to high hydrostatic pressure, the tetragonal α-Ag2MoO4 forms as a metastable phase.{{Cite journal|title = First-Principles Study of Pressure-Induced Phase Transitions and Electronic Properties of Ag2MoO4|journal = The Journal of Physical Chemistry C|date = 2014-02-20|issn = 1932-7447|pages = 3724–3732|volume = 118|issue = 7|doi = 10.1021/jp4118024|first1 = Armando|last1 = Beltrán|first2 = Lourdes|last2 = Gracia|first3 = Elson|last3 = Longo|first4 = Juan|last4 = Andrés}}
Synthesis and properties
Research published in 2015{{Cite journal|title = Uncovering Metastable α-Ag2MoO4 Phase Under Ambient Conditions. Overcoming High Pressures by 2,3-Bis(2-pyridyl)pyrazine Doping|journal = Crystal Growth & Design|date = 2015-06-03|issn = 1528-7483|pages = 3032–3037|volume = 15|issue = 6|doi = 10.1021/acs.cgd.5b00455|first1 = Choon Hwee Bernard|last1 = Ng|first2 = Wai Yip|last2 = Fan}} reported the formation of α-Ag2MoO4 by solution-phase precipitation under ambient conditions, using 3-bis(2-pyridyl)pyrazine (dpp) as a doping agent. The influence of the pH of the starting solution on the growth and formation processes of distinct heterostructures (brooms, flowers and rods) was investigated by Singh et al.{{Cite journal|title = Broom-like and flower-like heterostructures of silver molybdate through pH controlled self assembly|journal = Journal of Nanoparticle Research|date = 2012-03-09|issn = 1388-0764|pages = 781|volume = 14|issue = 4|doi = 10.1007/s11051-012-0781-0|first1 = D. P.|last1 = Singh|first2 = B.|last2 = Sirota|first3 = S.|last3 = Talpatra|first4 = P.|last4 = Kohli|first5 = C.|last5 = Rebholz|first6 = S. M.|last6 = Aouadi|bibcode = 2012JNR....14..781S|hdl = 10533/128243|s2cid = 96310636|hdl-access = free}} and Fodjo et al.,{{Cite journal|title = Low temperature synthesis and SERS application of silver molybdenum oxides|journal = Journal of Materials Chemistry A|volume = 1|issue = 7|pages = 2558–2566|doi = 10.1039/c2ta01018f|first1 = Essy Kouadio|last1 = Fodjo|first2 = Da-Wei|last2 = Li|first3 = Niamien Paulin|last3 = Marius|first4 = Trokourey|last4 = Albert|first5 = Yi-Tao|last5 = Long|date = 2013-01-23}} in which sodium borohydride was employed to induce the reduction of silver nanoparticles on the surface of Ag2MoO4 crystals in order to enhance Raman scattering. In other studies, Ag-Ag2MoO4 composites prepared by microwave-assisted hydrothermal synthesis presented interesting photocatalytic activity for the degradation of rhodamine B under visible light.{{Cite journal|title = Microwave-assisted hydrothermal synthesis of cube-like Ag-Ag2MoO4 with visible-light photocatalytic activity|journal = Science China Chemistry|date = 2013-02-22|issn = 1674-7291|pages = 443–450|volume = 56|issue = 4|doi = 10.1007/s11426-013-4845-5|first1 = ZhaoQian|last1 = Li|first2 = XueTai|last2 = Chen|first3 = Zi-Ling|last3 = Xue|s2cid = 100948033}} In addition, Ag2MoO4 mixed with graphite acts as a good lubricant for Ni-based composites, improving the tribological properties of this system.{{Cite journal|title = Friction and Wear Behaviors of Ni-based Composites Containing Graphite/Ag2MoO4 Lubricants|journal = Tribology Letters|date = 2013-03-24|issn = 1023-8883|pages = 313–322|volume = 50|issue = 3|doi = 10.1007/s11249-013-0131-0|first1 = Eryong|last1 = Liu|first2 = Yimin|last2 = Gao|first3 = Junhong|last3 = Jia|first4 = Yaping|last4 = Bai|s2cid = 137297325}} Different synthetic methods have been employed to obtain pure β-Ag2MoO4 crystals, including solid-state reaction or oxide mixture at high temperature,{{Cite journal|title = Molecular structural analysis of 55mol% CuI-45mol% Ag2MoO4 solid electrolyte using XPS and laser raman techniques|journal = Ionics|date = 2004-05-01|issn = 0947-7047|pages = 254–257|volume = 10|issue = 3–4|doi = 10.1007/BF02382825|first1 = S. Austin|last1 = Suthanthiraraj|first2 = Y. Daniel|last2 = Premchand|s2cid = 95974644}} melt-quenching,{{Cite journal|title = XANES and EXAFS at Mo K-edge in (AgI)1−x(Ag2MoO4)x glasses and crystals|journal = Solid State Ionics|date = 1999-06-01|pages = 189–192|volume = 121|issue = 1–4|doi = 10.1016/S0167-2738(98)00546-3|first1 = F|last1 = Rocca|first2 = A|last2 = Kuzmin|first3 = P|last3 = Mustarelli|first4 = C|last4 = Tomasi|first5 = A|last5 = Magistris}} and Czochralski growth.{{Cite journal|title = The growth of single crystals of lead molybdate by the Czochralski technique|journal = Materials Science and Engineering: A|date = 1993-12-20|pages = 23–27|volume = 173|issue = 1–2|doi = 10.1016/0921-5093(93)90179-I|first1 = Stephen|last1 = Brown|first2 = Alison|last2 = Marshall|first3 = Philip|last3 = Hirst}} Particularly, high temperatures, long processing times, and/or sophisticated equipment are necessary in these synthetic routes. Moreover, the final products may be composed of irregular particle shapes with nonhomogeneous size distribution as well as contain the presence of secondary phases. In recent years, pure β-Ag2MoO4 crystals have been synthesized by co-precipitation,{{Citation needed|date=December 2019|reason=removed citation to predatory publisher content}} microwave-assisted hydrothermal synthesis,{{Cite journal|title = Experimental and Theoretical Investigations of Electronic Structure and Photoluminescence Properties of β-Ag2MoO4 Microcrystals|journal = Inorganic Chemistry|date = 2014-06-02|issn = 0020-1669|pages = 5589–5599|volume = 53|issue = 11|doi = 10.1021/ic500335x|pmid = 24840935|first1 = A. F.|last1 = Gouveia|first2 = J. C.|last2 = Sczancoski|first3 = M. M.|last3 = Ferrer|first4 = A. S.|last4 = Lima|first5 = M. R. M. C.|last5 = Santos|first6 = M. Siu|last6 = Li|first7 = R. S.|last7 = Santos|first8 = E.|last8 = Longo|first9 = L. S.|last9 = Cavalcante|url = http://www.producao.usp.br/handle/BDPI/50833}} a dynamic template route using polymerization of acrylamide assisted templates,{{Cite journal|last1=Jiang|first1=Hao|last2=Liu|first2=Jin-Ku|last3=Wang|first3=Jian-Dong|last4=Lu|first4=Yi|last5=Yang|first5=Xiao-Hong|date=2015-07-14|title=Thermal perturbation nucleation and growth of silver molybdate nanoclusters by a dynamic template route|journal=CrystEngComm|volume=17|issue=29|pages=5511–5521|doi=10.1039/c5ce00039d}} and an impregnation/calcination method.{{Cite journal|title = Co-benefit of Ag and Mo for the catalytic oxidation of elemental mercury|journal = Fuel|date = 2015-10-15|pages = 891–897|volume = 158|doi = 10.1016/j.fuel.2015.05.034|first1 = Songjian|last1 = Zhao|first2 = Zhen|last2 = Li|first3 = Zan|last3 = Qu|first4 = Naiqiang|last4 = Yan|first5 = Wenjun|last5 = Huang|first6 = Wanmiao|last6 = Chen|first7 = Haomiao|last7 = Xu}}
In 2015, the literature reported the formation of β-Ag2MoO4 crystals using different chemical solvents in the reaction medium. These β-Ag2MoO4 microcrystals were synthesized by the precipitation method, employing several polar solvents: deionized water (H2O), methanol (CH4O), ethanol (C2H6O), 1-propanol (C3H8O) and 1-butanol (C4H10O) at 60 °C for 8 h. X-ray diffraction (XRD), Rietveld refinements and field emission scanning electron microscopy (FESEM) were employed in structural and morphological characterizations.{{Cite journal|title = Structural, morphological and optical investigation of β-Ag 2 MoO 4 microcrystals obtained with different polar solvents|journal = CrystEngComm|volume = 17|issue = 43|pages = 8207–8211|doi = 10.1039/c5ce01662b |first1 = F. S.|last1 = Cunha|first2 = J. C.|last2 = Sczancoski|first3 = I. C.|last3 = Nogueira|first4 = V. G. de|last4 = Oliveira|first5 = S. M. C.|last5 = Lustosa|first6 = E.|last6 = Longo|first7 = L. S.|last7 = Cavalcante|date = 2015-10-28}} Moreover, some researchers have investigated new ways to improve the photocatalytic properties of β–Ag2MoO4 crystals through hydrothermal processing at different temperatures (100, 120, 140 and 160 °C) for 2 h and replacement of Ag atoms by Zn to formation of silver zinc molybdate [β–(Ag2−2xZnx)MoO4] microcrystals by a sonochemical method at 30 °C for 3 h. These new crystals were able to degrade the organic cationic dye rhodamine B{{cite journal |last1=Sousa|first1=Giancarlo da Silva |last2=Nobre|first2=Francisco Xavier |last3=Júnior|first3=Edgar lves Araújo |last4=Sambrano|first4=Julio Ricardo |last5=Albuquerque|first5=Anderson dos Reis |last6=Bindá|first6=Rosane dos Santos |last7=Couceiro|first7=Paulo Rogério da Costa |last8=Brito|first8=Walter Ricardo |last9=Cavalcante|first9=Laecio Santos |date=20 July 2018 |title=Hydrothermal synthesis, structural characterization and photocatalytic properties of β--Ag2MoO4 microcrystals: Correlation between experimental and theoretical data |journal=Arabian Journal of Chemistry |doi=10.1016/j.arabjc.2018.07.011 |last10=Santos|first10=Maria Rita Morais|last11=Matos|first11=Jose Milton Elias|volume=13 |pages=2806–2825 |doi-access=free}} and the anionic dye Remazol Brilliant Violet 5R{{cite journal |last1=Coimbra |first1=D.W. |last2=Cunha |first2=F.S. |last3=Sczancoski |first3=J.C. |last4=de Carvalho |first4=J.F.S. |last5=de Macêdo |first5=F.R.C. |last6=Cavalcante |first6=L.S. |title=Structural refinement, morphology and photocatalytic properties of β-(Ag2−2xZnx)MoO4 microcrystals synthesized by the sonochemical method |journal=Journal of Materials Science: Materials in Electronics |volume=30 |issue=2 |pages=1322–1344 |date=2019 |doi=10.1007/s10854-018-0401-6|s2cid=139865569 }}