Synthesis and characterization of heteronanostructured Ag nanoparticles/MoO3 nanobelts composites
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 (Eg) 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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