High performance optical sensing nanocomposites for low and ultra-low oxygen concentrations using phase-shift measurements

Abstract

The accurate and real-time measurement of low and ultra-low concentrations of oxygen using non-invasive methods is a necessity for a multitude of applications, from brewing beer to developing encapsulating barriers for optoelectronic devices. Current optical methods and sensing materials often lack the necessary sensitivity, signal intensity, or stability for practical applications. In this report we present a new optical sensing nanocomposite resulting in an outstanding overall performance when combined with the phase-shift measurement method (determination of luminescence lifetime in the frequency domain). For the first time we have incorporated the standard PtTFPP dye (PtTFPP = platinum(II) 5,10,15,20-meso-tetrakis-(2,3,4,5,6-pentafluorophenyl)-porphyrin) into AP200/19, a nanostructured aluminium oxide-hydroxide solid support. This sensing film shows an excellent sensitivity between 0 and 1% O₂ (KSV = 3102 ± 132 bar⁻¹) and between 0 and 10% O₂ (KSV = 2568 ± 614 bar⁻¹) as well as Δτ0.05% (62.53 ± 3.66%), which makes it 62 times more sensitive than PtTFPP immobilized in polystyrene and also 8 times more sensitive than PtTFPP immobilized on silica beads. Furthermore the phase-shift measurement method results in a significant improvement (about 23 times) in stability compared to the use of intensity recording methods. The film also displays full reversibility, long shelf stability (no change observed after 12 months), and it is not affected by humidity. To establish this sensing methodology and develop sensors over the full range of the visible light, we also studied three other dye-AP200/19 nanocomposites based on phosphorescent cyclometalated iridium(III) complexes.

Copper(i) complexes as alternatives to iridium(iii) complexes for highly efficient oxygen sensing

“…Only PtTFPP shows higher sensitivity in the same condition (Ksv = 25.68 kPa -1 ). 5 Intensity measurements are not sensitive enough to characterize the sensing films in the range 0-1 kPa pO 2 . Therefore we used a multifrequency phase-modulation method for luminescence spectroscopy using a rectangular-wave modulated excitation source with a short duty cycle 19 for measuring lifetime for this range of oxygen concentrations.…”

“…In practice, the emission intensity of the dye diminishes as the concentration of oxygen increases. The best reported dyes to date (Table 1) are Pt/ PdTFPP (platinum(II)/palladium(II) meso-tetrakis(pentafluorophenyl) porphyrin) 5,6 and N969, 5 a cationic cyclometallated iridium complex. Although Pt/PdTFPP are much better performing than iridium complexes, an important advantage of the latter is the possibility to vary the emission colour over the entire visible spectrum.…”

A Polynomial-Exponent Model for Calibrating the Frequency Response of Photoluminescence-Based Sensors

“…The LIA instrument provided the phase-shift between the excitation and emission signals. Details about the N1008-AP200/19 sensing film, the involved instruments, and the procedure for estimating the phase-shift can be found in our previous works [ 33 , 34 ].…”

Luminescent Oxygen Gas Sensors Based on Nanometer-Thick Hybrid Films of Iridium Complexes and Clay Minerals

“…The applicability of Ir(III) complexes for this purpose is based on the premise that energy transfer takes place efficiently from the triplet excited state of an Ir(III) complex to an oxygen molecule in a triplet ground state [30]. In order to enhance robustness and reliability of sensing devices, Ir(III) complexes are often immobilized into organic or inorganic host materials such as polymers, silica and clay minerals [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51]. The inclusion of an Ir(III) complex, for example, [Ir(2-phenylpyridine) 2 (4,4′-bis(2-(4-N,N-methylhexylaminophenyl)ethyl)-2-2′-bipyridine)]Cl in polymer matrices has been reported for probing oxygen molecules [43].…”