Photocatalytic activity of quantum dot–magnetite nanocomposites to degrade organic dyes in the aqueous phase

Abstract

Quantum dots of Cd(Se,S) and fluorescent magnetic nanocomposites (Cd(Se,S)-magnetite) were used as photocatalytic agents in the photodegradation of methylene blue (MB) under UV irradiation at pH 6.5.Quantum dots and magnetic nanocomposites were characterized by X-ray diffraction (XRD), UV-Vis, photoluminescence and Fourier Transform Infrared (FT-IR) spectroscopy. The photo-induced degradation of MB was monitored using High Performance Liquid Chromatography (HPLC) at 660 nm and titanium dioxide (anatase and aeroxide P25 forms) was used as the photocatalyst standard. A degradation of 99.1% and 90.0% of MB was achieved in the presence of 160 mg L À1 -quantum dots and the magnetic nanocomposite, respectively, after 4.5 hours of UV-irradiation. Instead, 45.9% and 100% of MB degradation was achieved using 160 mg L À1 of TiO 2 anatase and aeroxide P25, respectively. The degradation products were studied by mass spectrometry (MS) and the results evidenced the formation of azure B, A, C and phenothiazine. The reuse of the magnetic nanocomposites (i.e., after one photodegradation cycle) allowed a maximum photo-degradation capacity of 65%. The results suggested that the nanocomposite has 10% less photodegradation capacity than the widely used catalytic agents such as TiO 2 aeroxide P25.

Catalytic Conversion of Fructose and 5-Hydroxymethylfurfural into 2,5-Furandicarboxylic Acid over a Recyclable Fe3O4–CoOx Magnetite Nanocatalyst

“…1,2 Although using a catalyst in nanometer dimensions may achieve a substantial enhancement in its catalytic activity, recycling of nano-catalysts is difficult, especially for large-scale processes. In particular, magnetically recoverable catalysts have been well designed and extensively used in many chemical reactions including oxidation 5 , hydrogenation 6 , coupling reactions, 7 cycloaddition, 8 acylation, 9 photocatalysis, 10 and so forth. In this context, magnetite nanoparticles have been attracted much attention for various organic reactions.…”

In-situ synthesis of high stable CdS quantum dots and their application for photocatalytic degradation of dyes

“…Recently, the use of QDs for photocatalytic degradation of organic pollutants has been proposed [25]. There are two major problems with using nanoparticles for photocatalytic degradation applications: First, nanoparticles are strongly tended to agglomerate and lose their efficiency.…”

Quantum Dots of ZnSe(S) Doped with Copper as Nanophotocatalyst in the Degradation of Organic Dyes

“…[14][15][16][17] Recently, quantum dots of CdS and CdSe have been used in processes of photo-catalysis to degrade cationic and anionic organic dyes; however their potential toxicity prevents the widespread use of these nanomaterials in water treatment schemes. [18][19][20][21][22][23] Indeed, Cd-free quantum dots like non-doped ZnSe(S) alloyed QDs and doped with copper show promising properties to be used as nanophoto-catalyst for organic dyes degradation. Although, the doping with copper does not change the absorption spectrum (or band gap energy) of the nondoped ZnSe(S) alloyed QDs, previous studies suggest that the presence of copper enhance the half-lifetime of the charge carriers (electrons/holes) which are responsible of the photocatalysis efficiency.…”