Abstract
Gold nanoparticles (Au NPs) was synthesized with Chitosan different molecular weight (MW) using a microwave as a heating source. Since, Chitosan acts as a reducing and stabilizing agent. The as-synthesized Au NPs were characterized by transmission electron microscopy (TEM) images and selected area electron diffraction patterns (SAED). Furthermore, the Au NPs fabrication was ascertained by UV–Visible spectroscopy (UV–Vis) through the detection of the localized surface plasmon resonance (LSPR) characteristic peak, X-ray powder diffraction (XRD), and energy dispersive X-Ray Spectroscopy (EDS). The formation of the Au NPs was confirmed by the detection of a LSPR peak at 518–527 nm in the UV–Vis spectrum. In addition, the XRD studies depicted that the obtained Au NPs were highly crystalline with ‘face-centered’ cubic geometry. Moreover, TEM micrographs showed that the most Monodispersed AuNPs was synthesized with low molecular weight (LMW) Chitosan with particle size 4.48±0.09 nm. The synthesized Chitosan-Au nanocomposite exhibited an efficient catalytic property in the reduction of two organic environmental pollutants which are, 4-nitrophenol (4-NP) and methyl orange (MO) dye in the presence of sodium borohydride (NaBH4).
Highlights
Many aromatic compounds, such as dyes and phenols, are released from industrial processes
These NPs have vast optical properties which are so sensitive to shape, size, concentration, agglomeration state, and refractive index near the NPs surface according to the most popular form of Mie’s theory for spherical NPs within quasi-static limit is given as where Cext is the extinction cross section of the spheres, R is the radius of a homogeneous sphere εm is the dielectric constant of the surrounding medium, λ is the wavelength of the radiation, and ε1 and ε2 denote the real and imaginary part of the complex dielectric function of the particle material, respectively
To investigate the effect of the microwave irradiation time on the fabrication of Au NPs, a solution of 20 mL HMW Chitosan (1%, w/v) mixed 5 mL (1.5 mM) gold chloride solution was chosen. This is due to, the UV-Vis spectrum of the aforementioned reaction mixture characterized with a narrow full width at half maximum (FWHM) which was 112 nm which is attributed to the particle size [27, 34]
Summary
Many aromatic compounds, such as dyes and phenols, are released from industrial processes. In order to remove complex dye these organic compounds from the water waste, the microscale nanoparticles (NPs) such as silver [17, 18], gold [19, 20], zinc oxide [21], and titanium oxide [22] were used Natural polymers such as starch, cellulose, gelatin, chitin, can be widely used as an adequate matrix for the synthesized nanoparticles. The main objective of this work is to study the efficacy of the catalytic activity of the synthesized AuNPs towards a two organic toxic pollutants that are 4-NP and MO This was carried out using Chitosan different MW (i.e., HMW, MMW, LMW) via simple microwave heating irradiation method. To obtain a nearly monodispersed AuNPs, various experimental synthesis conditions were studied such as HAuCl4 salt molar concentration, irradiation time, and microwave radiation power
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