C. Aviles-Martin, L. Alamo-Nole
Pontifical Catholic University of Puerto Rico,
Keywords: quantum dots, CdSTe, photodegradation
Summary:The inappropriate disposal of organic dyes used in a variety of industrial applications has become the contamination source of many water sources. This environmental problem has created the need for more effective and simple methods of purifying contaminated water sources. Sorption methodologies have been used to remove the most common contaminants at high concentrations. The disadvantages to use sorbents are their high cost and the generation of waste after saturation of the material. The application of photodegradation techniques has the advantages to degrade totally the contaminants and they can also be reused multiple times without the waste production. Photocatalytic agents should require low amounts energy and eliminate the contaminants in short periods of time. Therefore, researching the synthesis of novel catalytic materials for these processes is of great importance. In this project, the potential use of CdSTe quantum dots (QDs) as a photocatalytic agent was evaluated. Water stable CdSTe QDs were synthesized at 180° C under microwave irradiation, a solvent free methodology (ecofriendly). The purified QDs were characterized by UV-Vis, photoluminescence, X-ray diffraction (XRD) and High Resolution Transmission Electron Microscopy (HR-TEM). The QDs crystal size was about 7 nm. The photodegradation of Victoria blue (VB) was monitored using High Performance Liquid Chromatography at 600 nm. For the photodegradation experiments, a 10 µM solution of Victoria blue and 100 mg/L of CdSTe was mixed and irradiated using a ultraviolet lamp at 365nm under constant agitation. The initial pH values of the solutions were adjusted at 5.0, 6.6 and 8.0 to evaluate their effect in the photodegradation. After 270 minutes of irradiation, 91% of VB degradation was observed at 6.2 pH value. Two photodegradation steps were observed during all photodegradation experiments of VB. When methylene blue (MB) was evaluated, the MB concentration was constant indicating that this dye cannot be degraded by CdSTe QDs. Photoluminescence analysis confirmed a quenching of the QDs florescence when the CdSTe and VB were mixed. Nevertheless, a slight decrease of the CdSTe florescence was observed when the QDs was mixed with VB.