Bi-functional photocatalytic heterostructures combining titania thin films with carbon quantum dots (C-QDs/TiO2) for effective elimination of water pollutants

Abstract

In this study, carbon quantum dots (C-QDs), prepared via hydrothermal-microwave procedures, were successfully combined with nanostructured titania (TiO2). The photocatalytic oxidation/reduction activity of the C-QDs/TiO2 composite films was evaluated in the decomposition of organic-inorganic contaminants from aqueous solutions under UV illumination. Physicochemical characterizations were applied to investigate the crystal structure of the carbon quantum dots and the composites. It was found that the prepared C-QDs/TiO2 composites had great contribution to the photocatalytic reduction of hexavalent chromium (Cr+6) species and 4-Nitrophenol (PNP) as well as to the photocatalytic oxidation of methylene blue (MB) and Rhodamine B (RhB) dyes. The mechanism of the photocatalytic reaction was studied with trapping experiments, revealing that the electron (e−) radical species were powerfully supported for the photocatalytic reduction of Cr+6 and PNP and the holes (h+) are the main active species for the photocatalytic oxidation reactions.

Microwave-assisted synthesis of amphoteric fluorescence carbon quantum dots and their chromium adsorption from aqueous solution

“…For example, R % was 48, 45, and 37% for carbon dots modified mesoporous organosilica as an adsorbent for the removal of Hg(II), Cu(II), and Pb(II), respectively 22 . In addition, the maximum R % of Cr(VI) by TiO 2 /CQDs was 43.39% 23 .…”

Carbon Dots: Synthesis, Characterizations, and Recent Advancements in Biomedical, Optoelectronics, Sensing, and Catalysis Applications

“…Through the use of trapping experiments, the mechanism of the photocatalytic reaction was examined. It was shown that the holes (h + ) are the primary active species in the photocatalytic oxidation processes and that the electron (e – ) radical species were strongly supported in the reduction of Cr 6+ and PNP …”

“…It was shown that the holes (h + ) are the primary active species in the photocatalytic oxidation processes and that the electron (e − ) radical species were strongly supported in the reduction of Cr 6+ and PNP. 246…”

Novel Bi-Functional MoS2/α-Fe2O3 Nanocomposites for High Photocatalytic Performance

“…Next, the acquired Nyquist plots from impedance spectroscopy (Figure 7) provide insights into the charge transfer resistance of the photoexcited electron-hole pairs. The shorter semicircle diameters of the composite materials demonstrate that the incorporation of α-Fe2O3 with MoS2 improves the charge carriers' separation and limits the recombination effects [29]. Even if there is no specific tendency between the oxide quantity in the composites and reduced resistance, an obvious improvement is observed; therefore, the enhanced generation of reactive radicals is also predicted during photocatalysis compared to the reference molybdenum disulfide sample.…”

“…Following this, a doctor blade technique was utilized to fabricate a uniform 1 cm 2 active area on a clean FTO electrode. The sample was then annealed at 450 • C. The solution used for the electrochemical measurements contained a sodium sulfate (Na 2 SO 4 ) electrolyte with a concentration of 0.2 M [29].…”