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TiO2 nanoparticles for photocatalysis prepared by pulsed lased ablation of titanium in water

Introduction: TiO2 nanostructures have promising physical and chemical properties, such as a high specific surface area, the low costs of synthesis, a high photo-activity and environmental stability. Because of these properties the titania nanostructures can be used for photo-catalysis, in solar cells (DSSC) and sensors. In this study the colloid suspension of the TiO2 nanoparticles (NPs) was prepared by method of pulsed laser ablation (PLA) in water with the aim to obtain high efficient photocatalyst. PLA is simple, fast, inexpensive, ecologically acceptable method and do not introduce any impurities in prepared TiO2NP suspension. Methods: The colloid suspensions of the TiO2NPs in water was prepared by PLA using Nd-YAG laser operated at 1064 nm with 100 or 300 mJ energy. With the aim to obtain crystallinity of the NPs, the suspensions were heated at 90 or 80 °C. The crystallinity and crystalline phases of the NPs were studied by X-ray powder diffraction (XRD), Raman spectroscopy (RS) and selected area electron diffraction (SAED), while the NPs sizes distribution are determined from TEM measurements. For TEM and SAED measurements JEOL JEM2100 operated at 200 kV was used. Results: XRD, RS and SAED measurements of as prepared samples showed the amorphous nature of TiO2NP. The particle sizes vary between 3 and 40 nm (Fig. 1a) with similar distribution for both samples and maximum at around 7 nm. After heating at 80 or 90 °C, the crystallization of the NP was obtained. RS data show the broad bands at positions characteristic for both anatase and rutile. XRD patterns (Fig. 1b) indicated crystallization of the triclinic Magnéli phase (Tin O(2n-1), 4<=n<=9) that have possible valence state Ti3+. The photocatalytic performance of colloid suspensions of the TiO2NPs in water were tested at organic dye methylene-blue and it was shown that crystalline samples had considerably better photocatalytic properties than as prepared amorphous samples. Discussion and conclusions: The photocatalytic properties of TiO2NP will be discussed in frame of the structural characterization, comparing XRD, Raman spectroscopy and TEM results. Since it is known that Magnéli phases of TiO2 show improved photocatalytic properties, the existence of these phases will be considered with the future plan of X-ray photoelectron spectroscopy measurements.

TiO2 ; nanoparticles ; pulsed laser deposition ; HRTEM ; SAED

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