Optimizing the photochemical conversion of UV–vis light of silver-nanoparticles decorated TiO₂ nanotubes based photoanodes

Abstract

Homogeneous decoration of TiO nanotubes (NTs) by Ag metallic nanoparticles (NPs) was carried out by a relatively simple photoreduction process. This Ag-NPs decoration was found to improve the photoconversion efficiency of the TiO-NTs based photoanodes. The x-ray photoelectron spectroscopy and x-ray diffraction analyses confirmed that all the Ag-NPs are metallic and the underlying TiO-NTs crystallize in the anatase phase after their annealing at 400 °C, respectively. Transmission electron microscopy observations have confirmed the effective decoration of the TiO-NTs' surface by Ag-NPs, and allowed to measure the average Ag-NPs size, which was found to increase linearly from (4 ± 2) nm to (16 ± 4) nm when the photoreduction time is increased from 5 to 20 min. The diffuse reflectivity of the Ag-NPs decorated TiO-NTs was found to decrease significantly as compared to the undecorated TiO-NTs. Interestingly, the Ag-NPs decorated TiO-NTs exhibited a significantly enhanced photochemical response, under visible radiation, with regards to the undecorated NTs. This enhancement was found to reach its maximum for the TiO-NTs decorated with Ag-NPs having the optimal average diameter of ∼8.5 nm. The maximum photoconversion efficiency of Ag-NPs decorated TiO-NTs was about two times greater than for the undecorated ones. This improved photo-electro-chemical response is believed to be associated with the additional absorption of visible light of Ag-NPs through the localized surface plasmon resonance phenomenon. This interpretation is supported by the fact that the photoluminescence intensity of the Ag-NPs decorated TiO-NTs was found to decrease significantly as compared to undecorated NTs, due to charge carriers trapping in the Ag NPs. This demonstrates that Ag-NPs decoration promotes photogenerated charges separation in the TiO-NTs, increasing thereby their capacity for current photogeneration. The surface decoration of TiO NTs by noble metals NPs is expected to impact positively the use of TiO-NTs based photoanodes in some energetic applications such as hydrogen generation and photo-electrochemical solar cells.

Highly ordered TiO2 Nanotubes decorated with plasmonic silver nanoparticles (TiO2/Ag) for ultra-sensitive SERS detection of textile dye contaminant Rhodamine 6 G

“…An electrochemical anodization process [11,12] was carried out to obtain TiO2 NT arrays. Firstly, Titanium foils (TF-99% purity) were polished with abrasive paper and then cleaned in deionized water (DI), ethanol, and acetone under ultrasonication for 15-20 minutes each, respectively, and finally rinsed with DI water.…”

Fabrication of Surface Enhanced Raman Spectroscopy based sensor using Ag NPs on copper tape flexible substrate

“…In SERS, the intensity of scattered Raman signals can be enhanced when analyte molecules are deposited on metal nanoparticle surfaces. Local surface Plasmon Resonance (LSPR) of metal nanostructures is responsible for electromagnetic enhancement (EM), whereas the charge transfer between the metal nanoparticles to analyte molecules leads to chemical enhancement (CM) [5][6][7]. In the case of EM, the intensification in the Raman signal is observed by 10 6 to 10 8 folds of its magnitude when the analyte has adsorbed on SERS active 'hotspot'.…”

Synthesis and Characterization of TiO2 Nanotubes (TiO2-NTs) Decorated with Platine Nanoparticles (Pt-NPs): Photocatalytic Performance for Simultaneous Removal of Microorganisms and Volatile Organic Compounds

“…Indeed, TiO 2 is a wide band gap (3.2 eV for anatase) semiconductor that absorbs light only in the ultraviolet frequency range, representing only 4% of the solar spectrum [26], which significantly hampers its photocatalytic efficiency in the direct use of sunlight. Consequently, it is essential to develop an effective solution to improve the efficiency of charge separation and the photoactivity of TiO 2 nanotubes by doping with metals (Ag [27][28][29][30], Cu, Au, etc.) or sensitizing with metallic nanoparticles or semiconductors (PbS [31,32] and Cu 2 O [33,34]) or decorating the surface with nanostructured noble metals (Pt [35] and Pd [36]).…”