Mesoporous TiO2 from Metal-Organic Frameworks for Photoluminescence-Based Optical Sensing of Oxygen

Abstract

Metal−organic frameworks (MOFs) are a class of porous coordination networks extraordinarily varied in physicochemical characteristics such as porosity, morphologies, and compositions. These peculiarities make MOFs widely exploited in a large array of applications, such as catalysis, chemicals and gas sensing, drug delivery, energy storage, and energy conversion. MOFs can also serve as nanostructured precursors of metal oxides with peculiar characteristics and controlled shapes. In this work, starting from MIL125-(Ti), a 1,4-benzenedicarboxylate (BDC)-based MOF with Ti as metallic center, mesoporous TiO2 powders containing both anatase and rutile crystalline phases were produced. A challenging utilization of these porous MOF-derived Ti-based oxides is the optically-based quantitative detection of molecular oxygen (O2) in gaseous and/or aqueous media. In this study, the photoluminescence (PL) intensity changes during O2 exposure of two MOF-derived mixed-phase TiO2 powders were probed by exploiting the opposite response of rutile and anatase in VIS-PL and NIR-PL wavelength intervals. This result highlights promising future possibilities for the realization of MOF-derived doubly-parametric TiO2-based optical sensors.

Phase Transformation Strategies for the Construction of Heterojunction TiO2 Photocatalysts

“…[129] At present, most of the studies on MOF-induced TiO 2 phase transformation are achieved via heat treatment at high temperature. [130][131][132][133][134][135][136][137][138] In the study of Derakhshani et al various phases of TiO 2 were synthesized by utilizing MOF-5 as template, and the mixed phases of anatase and rutile emerged at 800 °C. [139] Kampouri et al prepared TiO 2 derived from MIL-125-NH 2 and controlled the phase ratio by calcining it at different temperatures.…”

“…At present, most of the studies on MOF‐induced TiO 2 phase transformation are achieved via heat treatment at high temperature [130–138] . In the study of Derakhshani et al.…”

Novel Au Nanoparticle-Modified ZnO Nanorod Arrays for Enhanced Photoluminescence-Based Optical Sensing of Oxygen

“…Compared with the traditional electrical gas-sensing method, the photoluminescence (PL)-based optical gas-sensing method offers several distinct advantages, including good precision and accuracy, high sensitivity, good reversibility, non invasive measurement, no electrical contacts, ease of miniaturization, simple device fabrication, use in the presence of strong electromagnetic radiation, and remote operation [ 15 , 16 , 17 , 18 ]. Typical semiconductor oxide nanomaterials such as WO 3 [ 19 ], TiO 2 [ 20 , 21 ], ZnO [ 22 , 23 ], and SnO 2 [ 24 ] have been successfully applied as PL-based gas-sensing materials due to their unique structure-related characteristics. In general, their sensing mechanism depends on the adsorption of gas releasing or capturing electrons from oxides, resulting in enhancement or quenching of the PL emission [ 19 , 25 , 26 ].…”

Electronic Bulk and Surface Properties of Titanium Dioxide Studied by DFT-1/2

“…Surface and interface properties of ionic wide-band-gap semiconductors or transparent conductive oxides (TCOs) like titanium dioxide, TiO 2 , provide important functions to solid-state devices for light harvesting, − energy conversion, water splitting, solid-state lighting, or gas sensing . The two prominent crystalline phases of TiO 2 , rutile and anatase, are nontoxic, stable, abundant, and cheap .…”