Search

Herein, TiO2 single-tube (TiO2 ST-NT) powders with and without magnetite Fe3O4 nanoparticles (TiO2 ST-NT@Fe3O4NPs) are presented for the first time as excellent photocatalysts for the degradation of one of the most popular non-steroidal anti-inflammatory drugs (NSAIDs), naproxen (NPX). The TiO2 ST-NT powders were synthesized by anodization followed by etching of the double wall, bending, sonication, ultra-centrifugation, and finally annealing at 600°C. A part of the obtained TiO2 ST-NT powders was decorated with Fe3O4 nanoparticles using a simple one-step decoration process. The best photocatalytic performance of TiO2 ST-NT and TiO2 ST-NT@Fe3O4NPs powders was obtained under the white light (6.2 x 10-4 s-1) and the blue light (2.7 x 10-4 s-1), respectively. During NPX photodegradation using TiO2 ST-NT powders, three main NPX transformation products (P1, P2, and P3) were detected. Upon excitation with the blue light illumination, TiO2 ST-NT@ Fe3O4NPs powders exhibited higher performance (~80%) than TiO2 ST-NT powders (~23%) within 1 h, resulting in an approximately three times increased photocatalytic rate constant. Moreover, under simulated sunlight conditions, TiO2 ST-NT powders demonstrated remarkable activity, achieving a 94% NPX degradation within 1 h. TiO2 ST-NT and TiO2 ST-NT@Fe3O4NPs powders represent excellent photocatalysts for NPX degradation. [ABSTRACT FROM AUTHOR]

This paper presents an effective hydrothermal route to decorate various types of anodic 1D TiO2 nanotubes (TiO2 NTs) with magnetite nanoparticles (Fe3O4 NPs), yielding a magnetically guidable and active photocatalyst. A unique portfolio of TiO2 NTs including single-tube, single-walled, and double-walled ones was used. Optimal conditions for uniform decoration of these nanotubes by Fe3O4 NPs (two different loadings) using a wet chemical synthesis based on an oleate hydrothermal approach were found. The resulting TiO2NTs@Fe3O4NPs were shown to be superparamagnetic at room temperature, to have a stable connection of NPs to NTs, and to have good magnetic response under an external applied magnetic field. The as-prepared materials were used as magnetically guidable photocatalyst for the decomposition of a model dye (methylene blue). Fe3O4 NPs enhanced the photocatalytic activity of TiO2 NTs under visible light. In principle, TiO2NTs@Fe3O4NPs could be used as magnetically guidable drug delivery system with photoinduced drug release. [ABSTRACT FROM AUTHOR]

Herein, the synthesis of BiOCl nanoplatelets of various dimensions is demonstrated. These materials were prepared by anodic oxidation of Bi ingots in diluted HCl under dielectric breakdown conditions, triggered by a sufficiently high anodic field. Additionally, it is shown that the use of several other common diluted acids (HNO3, H2SO4, lactic acid) resulted in the formation of various different nanostructures. The addition of NH4F to the acidic electrolytes accelerated the growth rate resulting in bismuth‐based nanostructures with comparably smaller dimensions and an enormous volume expansion observed during the growth. On the other hand, the addition of lactic acid to the acidic electrolytes decelerated the oxide growth rate. The resulting nanostructures were characterized using SEM, XRD and TEM. BiOCl nanoplatelets received by anodization in 1 M HCl were successfully employed for the photocatalytic decomposition of methylene blue dye and showed a superior performance compared to commercially available BiOCl powder with a similar crystalline structure, confirming its potential as a visible light photocatalyst. BiOCl nanoplatelets are produced by facile breakdown anodization of bismuth in diluted HCl electrolyte. The addition of lactic acid to the electrolyte decelerates the growth rate of the nanoplatelets while the addition of NH4F or accelerates the growth rate. The nanoplatelets are single crystalline and show a superior photocatalytic behaviour compared to commercial BiOCl powder. Similarly, Bi2O3 needles and Bi2O3 cubes are produced in H2SO4 and HNO3, respectively. [ABSTRACT FROM AUTHOR]

Abstract In this work, for the first time, an anodic TiO 2 nanotube layer of large area (~50 cm2) was used for photocatalysis in the gaseous phase. Hexane was chosen as model pollutant. The nanotube layer showed superior efficiency compared to a reference TiO 2 layer of the same thickness composed of immobilized P25 nanoparticles. An additional TiO 2 coating of the nanotube layer produced by atomic layer deposition did not enhance the photocatalytic degradation of hexane due to a decrease in the active surface area, in contrast to liquid state photocatalysis under applied external potential. Highlights • Large area anodic TiO 2 nanotube layers (~50 cm2) were obtained by anodization of Ti. • Proper electrolyte temperature control is required to synthesize layers of this area. • Gaseous photocatalysis of hexane as pollutant was investigated for these layers. • Performance was better than for a P25 nanoparticulate layer of the same thickness. [ABSTRACT FROM AUTHOR]

Abstract: Ultrathin molybdenum oxyselenide (MoSexOy) coatings are made first ever by atomic layer deposition (ALD) within anodic 1D TiO2 nanotube layers for photoelectrochemical and photocatalytic applications. The coating thickness is controlled through varying ALD cycles from 5 to 50 cycles (corresponding to ≈1–10 nm). In the ultraviolet region, the coatings have enhanced up to four times the incident photon‐to‐current conversion efficiency (IPCE), and the highest IPCE is recorded at 32% at (at λ = 365 nm). The coatings notably extend the photoresponse to the visible spectral region and remarkable improvement of photocurrent densities up to ≈40 times is registered at λ = 470 nm. As a result, the MoSexOy‐coated‐TiO2 nanotube layers have shown to be an effective photocatalyst for methylene blue degradation, and the optimal performance is credited to a coating thickness between 2 and 5 nm (feasible only by ALD). The enhancement in photoactivities of the presented heterojunction is mainly associated with the passivation effect of MoSexOy on the TiO2 nanotube walls and the suitability of bandgap position between MoSexOy and TiO2 interface for an efficient charge transfer. In addition, MoSexOy possesses a narrow bandgap, which favors the photoactivity in the visible spectral region. [ABSTRACT FROM AUTHOR]

• Anodization of Ti spheres using bipolar electrochemistry is shown for the first time. • The entire surface area of the Ti spheres was anodized into TiO 2 nanotubes. • Several Ti spheres can be anodized simultaneously. • The anodized Ti spheres are shown to have good photocatalytic performance. In this work, the anodization of Ti spheres using bipolar electrochemistry is reported for the first time. TiO 2 nanotubes were found over the entire surface area of the Ti spheres when a square-wave potential was employed. The TiO 2 nanotubes were ~77 nm in inner diameter and had a thickness of ~2 µm on the extremities of the Ti spheres. Due to their increased surface area, the Ti spheres covered with TiO 2 nanotubes had a rate constant for the photocatalytic degradation of methylene blue which was approximately 2.15 times higher than that of non-anodized Ti spheres with a thin thermal oxide layer. [ABSTRACT FROM AUTHOR]

The influence of annealing temperature, the crystallinity, textural properties of magnetically guidable anodic TiO 2 nanotubes in form of single tube powders on the photocatalytic decomposition of model organic dye is investigated for the first time. The powders were prepared from self-organized anodic TiO 2 nanotube layers (grown on Ti) by etching in piranha solution, detaching them from the Ti substrate, and annealing in a wide range of temperatures (400–900 °C). The nanotubular shape was preserved up to 800 °C. Powders annealed up to 800 °C did not contain any detectable rutile phase, which is unique among other TiO 2 nanomaterials at this temperature. Part of the obtained TiO 2 ST-NT powders was decorated with Fe 3 O 4 nanoparticles using an oleic acid-based synthesis. The TiO 2 ST-NT and TiO 2 ST-NT@Fe 3 O 4 NPs powders were characterized in terms of morphology, crystallinity, and specific surface area. Finally, all materials were exploited for the photocatalytic decomposition of a model dye. The best photocatalytic performance of TiO 2 ST-NT and TiO 2 ST-NT@Fe 3 O 4 NPs powders were obtained at annealing temperatures of 600 and 700 °C, respectively. The synergy resulting from annealing, crystallite size, and specific surface area enhances the photocatalytic activity of TiO 2 ST-NT and TiO 2 ST-NT@Fe 3 O 4 NPs powders under UV light. This approach goes beyond the classical Kasuga alkaline hydrothermal approach, enabling the preparation of large quantity of TiO 2 nanotubes without any impurities (such as e.g. Na or Ca content resulting from the Kasuga approach). [ABSTRACT FROM AUTHOR]

[Display omitted] • Self-organized anodic double-wall TiO 2 nanotube layers reconstructed. • Inner wall was removed via chemical etching to obtain single-wall nanotubes. • TiO 2 coatings coated by Atomic Layer Deposition replaced the inner wall. • Significant enhancement in photoelectrochemical performance was obtained. • Superior photocatalytic activity under UV light was achieved. A reconstruction process of TiO 2 nanotube (TNT) layers towards their superior photoelectrochemical performance and photocatalytic activity is presented. At first, TNT layers (~5 μm thick, ~250 nm in diameter) were prepared via electrochemical anodization to obtain double-wall (DW) TNT layers. Second, a selective chemical treatment was conducted to etch the inner wall, yielding single-wall (SW) TNT layers. Third, TNT layers were coated by an additional approx. 5.5 nm, 11 nm, and 16 nm thick TiO 2 coatings, respectively, using Atomic Layer Deposition (ALD). A pronounced increase in the incident photon-to-electron conversion efficiency (reaching ~85% at λ = 350 nm) was achieved on SW TNT layers coated with 11 nm thick ALD coatings compared to SW without coating (~35% at λ = 350 nm). This is due to the optimal thickness of the ALD TiO 2 coating that passivates surface states and improves the separation of the photogenerated charge carriers. Photocatalytic performance of SW TNT layers with 11 nm thick ALD coatings (rate constant; k = 0.1156 min−1) was increased by approx. 10-times compared to that of the nowadays most reported blank DW TNT layers (rate constant; k = 0.0119 min−1). [ABSTRACT FROM AUTHOR]

In this work, a two-step treatment of TiO 2 nanotube (TNT) layers towards enhanced photocatalytic performance is presented. TNT layers with a thickness of ∼7 μm and an average inner diameter of ∼190 nm were prepared via electrochemical anodization of Ti foil in a fluoride containing ethylene glycol-based electrolyte. To improve the photocatalytic activity of the produced TNT layers a two-step post-treatment was conducted. First, the inner shell of the native double-wall TNT layers was removed via a mild pre-annealing followed by a selective etching treatment of the inner shell in piranha solution yielding single-wall TNT layers. Second, reduction via annealing in H 2 /Ar atmosphere was performed. The resulting Ti3+ doped single-wall TNT layers possess 100% enhancement of photocatalytic activity compared to their non-treated counterparts. • A two-step treatment for Ti3+rich single wall anodic TiO 2 nanotubes is presented. • Inner shell of TiO 2 nanotubes layers is removed by selective etching. • Hydrogenation in H 2 /Ar partly reduces Ti4+ to Ti3+ on the surface nanotubes walls. • Their photocatalytic activity is enhanced compared to regular double-wall nanotubes. [ABSTRACT FROM AUTHOR]