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Abstract The as-grown structure of electrochemically synthesized titania nanotube arrays is investigated by scanning electron microscope (SEM) in combination with transmission electron microscope (TEM) as well as X-ray diffraction (XRD). The analysis reveals a preferred growth direction of the nanotubes relative to the substrate surface and the well control on the nanotube arrays morphology. The crystal structure of the anatase phase is detected and exists in the tube walls without any thermal treatment, which makes it possible to realize the application of as-formed TiO2 nanotubes avoiding the degradation of the nanotube structures when sintering. In addition, a new growth, layered model of the anodic TiO2 nanotubes is presented to obtain further understanding of the growth mechanism.

Summary: In this paper, to improve the usage of visible light in titanium dioxide nanorod arrays (TNR), MoS2/TiO2 heterostructure arrays modified with Ag nanoparticles are successfully synthesized by hydrothermal and photodeposition methods. The morphology, microstructure, photoelectrochemical and photocatalytic properties of samples are discussed. The experimental results show that Ag/MoS2/TNR can effectively extend the absorption edge of visible light, retard the charge recombination and reduce the interface resistance, which greatly enhances the performance of photoelectrochemistry and photocatalysis. When the hydrothermal reaction time is 12 h, the sample exhibits the best transient photocurrent (120 μA/cm2) and photodegradation efficiency (75%); the values are 12 and 5 times than those of bare TNR, respectively. Based on the above results, the synergistic effect of MoS2/TiO2 heterostructure, surface plasmon resonance of Ag nanoparticles and narrow bandgap of MoS2 is proposed to explain the enhancement of these properties. [ABSTRACT FROM AUTHOR]

Ag/TiO2 nanostructure arrays were constructed on fluorine-doped tin oxide (FTO) via a controllable hydrothermal route and a magnetron sputtering method with a variety of TiO2 arrays decorated by Ag nanoparticles. Effects of different TiO2 arrays on the microstructure, composition, and optical properties of the samples were revealed. As surface enhanced Raman scattering (SERS) active substrates, we discussed the sensitivity and reproducibility of Ag/TiO2 nanostructure arrays for Rhodamine 6G (R6G) molecule detection. It was found that TiO2 nanosheet (TiO2(S)) array as a supporting made Ag nanoparticles have a uniform and continuous distribution, which achieved much higher SERS signals. The obtained Ag/TiO2(S) substrate had an improved enhancement factor of 4.31 × 105 compared with the other Ag/TiO2 nanostructure arrays of nanorods, nanotubes, and nanotrees. Furthermore, Ag/TiO2(S) active substrate showed good reproducibility with low relative standard deviation values. Such a remarkable SERS activity could be due to the synergistic effect of electromagnetic enhancement and charge transfer enhancement. Moreover, the TiO2(S) array with high-exposed {101} facets provided a large adhesion area and generated a strong interaction with external atoms, which would produce high-density 'hot spots' of SERS. [ABSTRACT FROM AUTHOR]

In this study, TiO2 nanorod arrays (TNR), Ag quantum dots (QDs) sensitized with TNR TiO2/Ag, bismuth oxyhalide (BiOI) nanosheets, and Ag QDs co‐modified with TNR and TiO2/BiOI/Ag (TBA) were prepared by a stepwise process. The morphological, structural, compositional, optical, photocatalytic (PC), and photoelectrochemical (PEC) properties of the samples were investigated. The TBA‐2 sample exhibited the highest photocurrent density (281.8 μA/cm2) and photodegradation efficiency (93.3%), with values 9.7 times and 2.25 times higher than those for TNR, respectively. The improvement in sample performance can be attributed to the formation of a heterojunction between BiOI and TiO2, thereby enhancing the absorption of visible light and improving the charge separation efficiency; Ag QDs limit interfacial electron‐hole pair recombination. The experimental results show that TBA can effectively promote light‐induced carrier transport and visible light absorption, while inhibiting the recombination rate of the electron‐hole pairs, PEC, and PC. [ABSTRACT FROM AUTHOR]

Cu2O-decorated TiO2 nanotube arrays (NTAs) are obtained using a two-step approach on Ti sheets. The applied voltage of Cu2O is − 0.2 V and − 0.3 V, respectively. The morphology and structure of these samples have been studied by field-emission scanning electron microscope (FESEM) and an x-ray diffractometer (XRD). FESEM analyses show that nanometre-sized Cu2O particles are attached to the TiO2 NTAs and the quantity of the Cu2O has greatly increased when the applied voltage tends to be more cathodic. The diffraction peaks for the anatase TiO2 and Cu2O are detected from XRD analysis. The bandgaps of TiO2 NTAs shift from 3.27 eV to 3.11 eV based on UV–Vis absorption spectra measurements. The photocatalytic performance of the Cu2O-TiO2 NTAs depends on the Cu2O deposition voltage. [ABSTRACT FROM AUTHOR]

In this paper, TiO2/In2S3/CdS ternary porous heterostructure arrays are successfully synthesized on FTO (fluorine-doped tin oxide) substrates through a hydrothermal reaction and an in situ cation exchange method. The microstructure, morphology, and composition, as well as the optical, photoelectrochemical and photocatalytic properties, of the obtained samples are studied. The results demonstrate that the TiO2/In2S3/CdS ternary heterostructure arrays can significantly enhance the separation rate of electron–hole (e−–h+) pairs, improve the absorption of visible light, and augment the photoelectrochemical and photocatalytic properties. The resulting photocurrent density (0.18 mA cm−2) and photodegradation efficiency (58.8%) of TiO2/In2S3/CdS (30 min) are approximately 18 and 6 times higher than those of TiO2 nanorod (TNR) arrays, respectively. The excellent performance can be ascribed to the synergistic effect of the components in the TiO2/In2S3/CdS ternary porous heterostructure arrays, such as (i) the presence of a double type-II band alignment at the interfaces, (ii) increasing the absorption of visible light through the large specific surface area of porous In2S3, and (iii) the ideal band gaps of In2S3 and CdS. [ABSTRACT FROM AUTHOR]

A multifunctional Ag/TiO2/reduced graphene oxide (rGO) ternary nanocomposite was prepared by a one‐step photochemical reaction with TiO2 and Ag nanoparticles successively deposited on reduced graphene oxide. The structure, morphology, composition, optical, and photoelectrochemical properties of Ag/TiO2/rGO were investigated in detail. Meanwhile, the ternary nanocomposite possessed much higher adsorption capacity to organic dyes compared with bare TiO2 and binary Ag/TiO2, which would help to its use for surface‐enhanced Raman scattering detection and photocatalytic degradation. Due to the charge transfer between rGO and organic dyes and enhanced electromagnetic mechanism of Ag, Ag/TiO2/rGO nanocomposites as surface‐enhanced Raman scattering substrates demonstrated dramatically improved sensitivity and good uniformity. The detection limit of rhodamine 6G (R6G) was as low as 10−9 mol/L, and the relative standard deviation values of the intensities remained below 5%. Most importantly, the synergistic coupling effect of three components extended the photoresponse range and accelerated separation of the electron‐hole pairs, leading to greatly improved photocatalytic activity under simulated sunlight. The maximum rate constant (k, 0.06243 min−1) of Ag/TiO2/rGO was 50 and four times higher than that of TiO2 and Ag/TiO2, respectively. [ABSTRACT FROM AUTHOR]

A series of TiO2 nanostructures with rutile phase were synthesized on arbitrary substrates of conductive transparent fluorine-doped tin oxide (FTO), tin-doped indium oxide (ITO), and glass at the low temperature of 150 °C by the hydrothermal method. The samples were characterized by XRD, SEM, TEM, XPS, UV–Vis absorption, and micro-Raman spectroscopy. The effects of growth substrates on the morphologies and optical properties of nanostructures were investigated. TiO2 nanorods were grown on the FTO substrate, while TiO2 nanoflowers were grown on the ITO and glass substrates, and the growth mechanism for these different nanostructures is discussed in detail. The results show that the TiO2 nanorods can improve photocatalytic properties and photoelctrochemical (PEC) performance for its unique structure and optical properties. The TiO2 nanorods exhibited a maximal photocatalytic rate of 4.42 min−1 and photocurrent density of 0.049 mA/cm2, which is about 1.52 and 3.03 times higher than those of TiO2 nanoflowers grown on the ITO substrates, respectively. These findings are quite promising and encouraging for the use of TiO2 nanoarrays in photocatalysis and energy applications. [ABSTRACT FROM AUTHOR]

Abstract: TiO2 thin films were fabricated through hydrothermal method. Silver nanoparticles were loaded on TiO2 thin films via photoreduction technique. Subsequently, the graphene quantum dots (GQDs) were spin‐coated on the Ag/TiO2 nanocomposites thin films. The crystal structure, surface morphology and UV‐vis absorbance were tested by XRD, SEM and ultraviolet‐visible spectrophotometer. These results indicated that Ag nanoparticles and GQDs are anchored on the TiO2 nanorods. Absorbance of Ag/TiO2 and GQDs/Ag/TiO2 nanocomposite thin films have been extended into the visible region. Visible‐light response of the samples were investigated by electrochemical workstation. The photoresponse of the sample can be enhanced by sensitization of the Ag nanoparticles and GQDs. The enhanced visible‐light response may be due to the surface plasmon resonance of silver nanoparticles and visible absorbance of GQDs. The highest photocatalytic activity has been observed in the 9‐GQDs/Ag/TiO2 composite thin film. The efficient charge separation and transportation can be achieved by introducing the Ag nanoparticles and GQDs in the TiO2 thin film. [ABSTRACT FROM AUTHOR]