International Journal of Materials Science ISSN 0973-4589 Volume 12, Number 1 (2017) © Research India Publications http://www.ripublication.com One step and facile hydrothermal synthesis of hexagonal molybdenum trioxide nanorods and its photo response Himanshu Mishra Department of Physics, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India. Anchal Srivastava * Department of Physics, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India. * Corresponding author Email: anchalbhu@gmail.com Abstract Present study reports the one pot facile synthesis of metastable hexagonal phase of molybdenum trioxide (h-MoO 3 ) using ammonium heptamolybdate (AHM) as starting material and HNO 3 as reducing agent. The synthesized nanostructures are nanorods in shape having length ~ 50 μm and diameter ~ 200 nm. The samples have been characterized by using X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The photoresponse of micrometer thick h-MoO 3 film on glass substrate also have been studied. It was found that the amount of photocurrent increases with increase in the frequency of the incident radiation. Keywords: MoO 3 , nanorods, photocurrent. Introduction Since last few decades, nanostructures have gained much attention in the field of energy, electronics, optical and sensing applications [1, 2]. Various transition metal oxides have been extensively studied in this regards [3, 4]. Among various transition metal oxides molybdenum oxide (MoO 3 ) is one of the most studied materials. As we know, MoO 3 exists in three different phases, orthorhombic (α-MoO 3 ), hexagonal (h-MoO 3 ) and monoclinic (β-MoO 3 ). Among these three, α- MoO 3 is the most studied as it is thermodynamically stable phase and exhibits a unique layered structure which permits it to be cleaved easily along their basal planes [5-7]. h-MoO 3 is a metastable phase whose basic building unit is a distorted MoO 6 octahedron to form layered structure through corner- sharing mode. Two adjacent layers of h-MoO 3 are joined together with weak Vander Waals forces [6]. Sometimes metastable phases provide much novel and enhanced results in comparison to their thermodynamically stable structures but their synthesis is usually difficult. Till date, several methods for the synthesis of h-MoO 3 have been reported [8-10]. But there are very few reports about its photoresponsivity. So, a facile and fast synthesis route and its photoresponsivity need further investigation. Present study focuses the one pot, facile and fast synthesis of h-MoO 3 using hydrothermal method. A micrometer thick film of h-MoO 3 have been prepared onto a glass substrate using nebulizer coating method and photoresponse of the h-MoO 3 film have been studied. Methods Ammonium heptamolybdate ( (NH 4 ) 6 Mo 7 O 24 , AHM) and nitric acid (HNO 3 ) have procured from Hi-Media, India. All the chemicals were of analytical grade and used without any further purifications. Throughout the experiment de-ionized (DI) water has been used for the solution preparation. Ethanol has been used for the dispersion of h-MoO 3 for thin film deposition. In a typical hydrothermal synthesis route of h-MoO 3 , 4.8 g of AHM is dissolved in 68.8 ml of DI and stirred for 10 min. at 40ᴼC to make a transparent solution. After that 11.2 ml of HNO 3 has been added to this transparent solution and again stirred for 10 min. at 40ᴼC. After that the solution is transferred into a stainless steel lined Teflon autoclave having capacity 100 ml and put for the hydrothermal reaction for 8 hrs. at 180ᴼC (figure 1). After the completion of th e reaction the light white precipitate has been filtered and washed thrice with DI and ethanol. The filtered and washed precipitate has been dried for 8 hrs. at 60ᴼC. Finally the dried sample has been crushed into tiny powder form. 67