Synthesis and characterization of heteronanostructured Ag nanoparticles/MoO3 nanobelts composites

doi:10.1016/j.matchemphys.2011.11.037

Materials Chemistry and Physics

Volume 132, Issues 2–3, 15 February 2012, Pages 358-363

https://doi.org/10.1016/j.matchemphys.2011.11.037 Get rights and content

Abstract

MoO₃ nanobelts have been successfully synthesized by a conventional hydrothermal method at 180 °C for 24 h, and followed by sonication of Ag⁺ and MoO₃ nanobelts in 1,2-propanediol to produce Ag/MoO₃ nanocomposites. The as-synthesized heteronanostructured Ag/MoO₃ composites were investigated by XRD, Raman, SEM, TEM and UV–visible absorption analyses. XRD, SEM and TEM results show that the as-synthesized Ag/MoO₃ composites were composed of orthorhombic α-MoO₃ nanobelts with good dispersion of cubic Ag nanoparticles on the surfaces. The optical property presented UV–visible absorption peaks at 231 and 312 nm for the Ag/MoO₃ nanocomposites. Furthermore the decolorization of rhodamine-B (RhB) for the synthesized Ag nanoparticles deposited on MoO₃ nanobelts as a photocatalyst was investigated.

Highlights

► α-MoO₃ nanobelts have been successfully synthesized by conventional hydrothermal method at 180 °C for 24 h. ► Reduction of Ag⁺ ions to Ag nanoparticles using 1,2-propanediol as a reducing agent supports on α-MoO₃ nanobelts. ► Decolorization of rhodamine-B of heteronanostructured Ag/MoO₃ composites as a photocatalyst was investigated.

Introduction

In recent years, heteronanostructures such as nanorods-on-nanoplates, and nanoparticles-on-nanofibers have been widely studied, due to their unusual properties [1]. In the photocatalysis, the enhanced photocatalytic activity originated by the increase in the transfer rate of photogenerated electrons to the photocatalytic surfaces. To improve the activity of semiconducting photocatalysts, the noble transition metals such as the deposited Ag, Au, Pt and Ir have been intensively investigated. The noble metal/semiconducting oxide composite materials exhibited the reduction in the rate of electron–hole recombination, due to the better charged separation between electrons and holes, which the electrons accumulated on the metal and the holes remained on the photocatalytic surfaces [2], [3], [4].

MoO₃ is an n-type semiconductor with a wide band gap (E_g) of 3.15 eV. It is an important electrochromic and photochromic sensitive material for optical device applications. MoO₃ has been known very well as one of the most widely used as a photocatalyst. Its catalytic efficiency has long been known, such as in alcohol and methane [3], [5]. Silver nanoparticles exhibited unexpectedly high catalytic activities toward different types of reactions in contrast to its bulk. These silver nanoparticles were generally deposited on materials to obtain high catalytic activity [6]. There are different methods used to deposit silver nanoparticles on substrates: polyol organic agent as reducing agent in assisting the nucleation and growth of nanoparticles, and for preventing the nanoparticles from undesired irreversible aggregations, by depositing nanoparticles on a variety of substrates including carbon nanotubes, polymer nanofibers, and TiO₂ nanofibers [1], [7], [8]. In the present research, the synthetic metallic silver by facile deposition on the surface of MoO₃ to form heteronanostructured Ag/MoO₃ composites was developed and used as new candidate for photocatalysis.

Section snippets

Experimental

To synthesize MoO₃ nanobelts, 0.005 mole ammonium molybdate tetrahydrate ((NH₄)₆Mo₇O₂₄·4H₂O) was dissolved in 20 ml deionized water with 30 min continuous stirring at room temperature. The 15 ml 2 M HNO₃ solution was added to this colorless solution, and followed by 30 min stirring. Then the mixture was transferred into a lab-made Teflon-lined stainless steel autoclave to 50 ml capacity. The autoclave was tightly closed and heated in an electric oven at 180 °C for 24 h. Finally, light-blue precipitates

Results and discussion

Fig. 1 shows the XRD patterns of heteronanostructured Ag/MoO₃ composites. All the identified peaks for the as-synthesized composites were specified as orthorhombic α-MoO₃ in agreement with the JCPDS database no. 05-0508 [9], [10]. It should be noted that all diffraction peaks were high diffraction intensities, indicating of good crystalline degree. In the present research, the intensities of the {0 k 0} including the (0 2 0), (0 4 0), and (0 6 0) planes at 2θ = 12.77°, 25.71° and 39.01°, respectively,

Conclusions

In summary, we have developed a simple synthetic process of Ag nanoparticles deposited on MoO₃ nanobelts. The MoO₃ nanobelts with 20 nm thick, 150 nm wide and 10 μm long were synthesized by a simple hydrothermal method, and followed by the reduction of AgNO₃ to be Ag nanoparticles deposited on MoO₃ nanobelts. The in situ formation of Ag nanoparticles on MoO₃ nanobelts was a candidate for the photocatalytic applications.

Acknowledgements

We wish to thank the National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency, for providing financial support through the project code: P-10-11345, and Thailand's Office of the Higher Education Commission through the National Research University (NRU) Project, including Graduate School of Chiang Mai University through the general support.

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Synthesis and characterization of heteronanostructured Ag nanoparticles/MoO3 nanobelts composites

Abstract

Highlights

Introduction

Section snippets

Experimental

Results and discussion

Conclusions

Acknowledgements

Mater. Sci. Eng. B

Appl. Surf. Sci.

Ultrason. Sonochem.

Mater. Lett.

Mater. Chem. Phys.

J. Alloys Compd.

Spectrochim. Acta A

J. Colloid Interface Sci.

J. Colloid Interface Sci.

J. Mol. Liq.

J. Phys. Chem. B

Synthesis and characterization of heteronanostructured Ag nanoparticles/MoO₃ nanobelts composites