Forced flow atomic layer deposition of TiO2 on vertically aligned Si wafer and polysulfone fiber: Design and efficacy of conduit plates and soak function.

The effectiveness of three different designs of conduit plates was verified for even distribution of precursors in a voluminous forced-flow atomic layer deposition (ALD) chamber designed to hold macroscopic elongated substrates vertically. Furthermore, a new "soak function" was introduced in the controlling software of the ALD instrument. This function enabled increase in residence time of the precursor in the chamber without escalating the dosage. The flow of precursors guided by the conduit plates with and without application of the soak function was simulated using computational fluid dynamics. A conformal coating of TiO2 with good uniformity on Si and porous polysulfone fibers was achieved to evidence the design and efficacy of conduit plates and soak function.

Fabrication of TiO2 on porous g-C3N4 by ALD for improved solar-driven hydrogen evolution.

Porous graphitic carbon nitride (P-g-C3N4) thin sheets were fabricated by a one-step calcination of a mixture of urea, melamine, and ammonia chloride at 550 °C. P-g-C3N4 showed 48% higher photocatalytic H2 production from methanol aqueous solution than conventional urea-derived graphitic carbon nitride (g-C3N4) because the existence of numerous pores reduces the recombination rate of charge carriers. In order to further enhance the photocatalytic activity, TiO2 was uniformly deposited on P-g-C3N4 by 60-300 cycles of atomic layer deposition (ALD) to form the TiO2@P-g-C3N4 composite. They exhibited much higher photocatalytic hydrogen production rates than both TiO2 and P-g-C3N4. Among all composites, the sample deposited with 180 ALD cycles of TiO2 showed the highest H2 production because of optimal diffusion length for electrons and holes. It also performed better than the sample of g-C3N4 deposited with 180 cycles of TiO2.

Green synthesis of carbon quantum dots embedded onto titanium dioxide nanowires for enhancing photocurrent.

The green synthesis of nanowired photocatalyst composed of carbon quantum dots-titanium hybrid-semiconductors, CQDs/TiO2, are reported. Where graphite-based CQDs with a size less than 5 nm are directly synthesized in pure water electrolyte by a one-step electrochemistry approach and subsequently electrodeposited onto as-prepared TiO2 nanowires through a voltage-driven reduction process. Electron paramagnetic resonance studies show that the CQDs can generate singlet oxygen and/or oxygen radicals to decompose the kinetic H2O2 intermediate species upon UV light illumination. With the effect of peroxidase-like CQDs, photocurrent density of CQDs/TiO2 is remarkably enhanced by a 6.4 factor when compared with that of as-prepared TiO2.

Plasmon-Enhanced Photocurrent using Gold Nanoparticles on a Three-Dimensional TiO2 Nanowire-Web Electrode.

In this study, an anatase/rutile mixed-phase titanium dioxide (TiO2) hierarchical network deposited with Au nanoparticles (Au/TiO2 ARHN) was synthesized using a facile hydrothermal method followed by a simple calcination step. Such a unique structure was designed for improving the light harvest, charge transportation/separation, and the performance of photo-electro-chemical (PEC) cells. The properties of the as-synthesized Au/TiO2 ARHN in PEC cells were investigated by electrochemical measurements using a three-electrode system in a 1 M NaOH electrolyte. Remarkably, a 4.5-folds enhancement of the photocurrent for Au/TiO2 ARHN was observed as compared to that for TiO2 nanowire (NW), under AM1.5G solar illumination, suggesting its potential application in PEC cells. A mechanism has been proposed to explain the high photocurrent of Au/TiO2 ARHN in PEC water splitting.

Plasmon-induced efficiency enhancement on dye-sensitized solar cell by a 3D TNW-AuNP layer.

A new 3D TNW-AuNP plasmonic electrode consists of antireflective (AR) TiO2 nanowires (TNWs) (∼600 nm thickness) serving as light-harvesting antennae coupling with Au nanoparticles (NPs). A huge red-shift of 55 nm is observed in surface plasmon spectra for the Au (11 nm) plasmonic electrode that has 11 nm size Au NPs, whereby (111) lattice planes have a specific bonding with the TiO2 (101) planes. Remarkable red-shift is mainly attributed to the localized electric field improvement resulting from the plasmonic coupling effect between the Au NPs and the Au-TiO2 hybrids. After TiCl4 treatment, this favorable Au (11 nm) nanostructure takes advantage of harvesting photons to increase the conversion efficiency of dye-sensitized solar cells (DSSCs) from 6.25% to 9.73%.

Chain-network anatase/TiO2 (B) thin film with improved photocatalytic efficiency.

A 3-dimensional chain-network anatase/TiO2 (B) was obtained via the basic hydrothermal treatment of a sandwich Ti/TiO2/Ti film on a glass substrate that was prepared from 16 nm anatase TiO2 nanoparticles. The Ti film was converted to the TiO2 (B) phase in a Teflon vessel containing a 10 M NaOH aqueous solution that was encapsulated in a stainless-steel autoclave and heated at 130 °C for 2 h. The TiO2 (B) then served as a binder layer that enabled the formation of pearl-necklace chains made of anatase TiO2 nanoparticles, and these chain-like structures thoroughly interpenetrated into the textured layer. Decomposition tests using methylene blue indicated that the chain-network anatase/TiO2 (B) mixed-phase film had a photocatalytic half-life that was 0.84 and 0.69 times shorter than those of as-prepared anatase TiO2 and P25, respectively. In addition, the intensity of the room temperature photoluminescence spectra of anatase TiO2 was 2.55-fold higher than that of the chain-network anatase/TiO2 (B). We thus conclude that the remarkable photocatalytic activity of the chain-network anatase/TiO2 (B) is attributed to the chain-network structural characteristics and a synergistic effect of the matching band gap potentials, which increases the transfer of photogenerated electrons and reduces electron-hole recombination.

Hydrothermally processed TiO2 nanowire electrodes with antireflective and electrochromic properties.

Dual functionalities of antireflective and electrochromic properties-based anatase TiO(2) nanowire devices with a high-porosity cross-linked geometry directly grown onto transparent conductive glass was achieved for the first time through a simple one-step hydrothermal process under mild alkali conditions. Devices fashioned from these TiO(2) nanowires were found to display enhanced optical transparency in the visible range, better color contrast, and faster color-switching time in comparison to devices made from nanoparticles. These improvements can be attributed to the low refractive index and high porosity of the TiO(2) nanowires and their larger accessible surface area for Li(+) intercalation and deintercalation, leading to enhanced capabilities for transparent electrochromic smart windows.