Influence of Surfactants on The Optical Properties of WO 3 Nanoparticles Synthesis by Precipitation Method

/ Ceteareth-25 and WO 3 /HY nanoparticles showed ultraviolet emissions (369, 373 and 354nm) and red emissions (624nm). Abbreviations: XRD: X-ray Diffraction Technique; CPYB: Cetylpyridinium Bromide; HTAC: Hexadecyl Trimethyl Ammonium Bromide; TTAB: Tetradecyl Trimethyl Ammonium Bromide; SEM: Scanning Electron Microscopy; FWHM: Full Width at Half


Introduction
In many fields of chemistry, physics and material science, metal oxides play a very important role [1][2][3][4][5][6]. The metal elements are capable to make a huge sort of oxide compounds [7]. These can receive countless basic geometry with an electronic structure, which will show metallic, semiconductor or insulator character. Oxides are used in the manufacture of microelectronic circuits, sensors, piezoelectrical devices, fuel cells, surface passivation coating against corrosion and in technological applications ascatalysts.
Within the emerging field of nanotechnology, the objective is to create nanostructures or nanoarrays with unique properties that are appreciated by large or single particle species [8][9][10][11][12]. Because of dimension their small and high density of corner or edge surface sites, oxide nanoparticles can show specific physical and chemical properties. Tungsten oxide (WO 3 ) may be well known n-type wide band gap semiconductor, inexpensive, environmentally friendly and chemically stable [13][14][15] among the prevailing metal-oxide semiconductors. Tungsten oxide has been investigated for photo catalysts thanks to their fantastic electrochromic, gaschromic and optochromic properties [16]. Its other unique properties have additionally been explored in flat panel displays [17], optoelectronics [18], energy devices [19] and gas sensors [20].
In recent years, due to photochromic effect, WO 3 based materials have been utilized in clinical and natural examination as antibacterial coatings, biosensors, the ranostic materials, and materials for proliferation control [21]. Various methods are made to organize WO 3 nano-particles like template assisted growth [22], anodization [23], conventional thermal evaporation [24], hot wall chemical vapor deposition [25], arc discharge [26], pulsed laser deposition [27], hydrothermal method [28] and solvothermal method [29]. Previous studies are conducted to synthesize WO3 nanoparticles. Priya [34]. Another researcher developed WO 3 square nanoplates using natural acids specifically L (+)-tartaric acid and acid as assistant agents [35]. Hexagonal WO 3 phase used to be determined in the presence of hydroxy acid with particle size ~200nm and thickness ~100nm, whereas orthorhombic phase was once came about in the presence of acid with average particle length ~500nm and thickness ~100nm, respectively. The SAED pattern suggests that the pure WO 3 square nanoplates are single crystalline.
The precipitation technique among these methods is reasonable, easy and yields small particle size, excessive homogeneity, and stoichiometry that could not be performed at high temperatures. These serve as double need: initially, functionalization of the nanoparticles beside controling the stoichiometry, subsequently preventing the agglomeration in the nanoparticles [36]. The use of different types of surfactants offers the potential to accumulate control over the WO 3 nanoparticle measurement, morphology and size distribution, which is essential for customizing optical, electrical, chemical, and magnetic properties of nanoparticles for special applications [37][38]. To our knowledge, however, tungsten oxide nanoparticles are synthesized using a chemical method of co-precipitation within the presence of nonionic Ceteareth-25 (polyoxyethylene ether of higher saturated fatty alcohols) and cationic HY surfactants and their optical properties were presented for the first time during this study.

Spectra
UV-vis absorption spectra were obtained using a UV -3101PC spectrophotometer (Shimadzu, UV-VIS-NIR scaning spectrophotometer) between 200 and 700nm in the wavelength range. A spectrofluorometer (JASCO, FP6500) was used to record PL spectra; the wavelength of extinction was 300 nm.

SEM and X-ray Diffraction (XRD)
The X-ray diffraction pattern (XRD) of the dried as prepared and labeled samples was obtained using a PANalytical X0 pert

Result and Discussion
where D is the particle size, k a fixed number of 0.9, λ the X-ray wavelength, θ the Bragg's angle in radians, and B the full width at samples. (Figure 2a & 2b) shows some SEM micrographs of WO 3 and WO 3 / Ceteareth-25, and WO 3 /HY nanoparticles. Figure 2 shows the surface morphologies of all samples, which have agglomerated irregular particle structure. Obviously, the WO3 nanoparticles have grainy shapes and tend to form aggregations. The optical measurement of the prepared sample was performed at room temperature by using UV-visible absorbance spectrophotometer.
The recorded absorbance spectra of WO 3 , WO 3 / Ceteareth-25, WO 3 / HY nanoparticles are shown in (Figure 3). The absorption peak corresponding to WO 3 , WO 3 / Ceteareth-25, WO 3 /HY nanoparticles samples are obtained at 303, 306 and 300 nm, respectively ( Figure   3). Absorption is generallydependent on several parameters, such as band gap differences and Impurity centers [39]. The optical band gap samples can be calculated using the Tauc equation that shows a relationship between the photon energy incident of semiconductors and the absorption coefficient [40]: (2)

Funding
On behalf of all authors, the corresponding author states that there is no funding for this paper

Compliance with Ethical Standards
Conflict of interest on behalf of all authors, the corresponding author states that there is no conflict of interest.