Platinum Octaethylporphyrin Research Articles

Measurement methods for triplet-triplet annihilation photon upconversion

Triplet-triplet annihilation photon upconversion (TTA-UC) has made significant progress in recent decades and has shown high potential in solar energy harvesting and photocatalysis. There is a high demand for detailed and standardized descriptions of measurement protocols for TTA-UC, particularly regarding instrumentation, controlling software, and standard measurement procedures. Here, we present the hardware, software, and comprehensive guidelines for conducting TTA-UC testing. Our system successfully measured two typical TTA-UC samples containing palladium (II) octaethylporphine (PdOEP) and platinum (II) octaethylporphyrin (PtOEP) as the sensitizers and 9,10-diphenylanthracene (DPA) as the annihilator. The obtained key parameters of TTA-UC demonstrate the reliability and accuracy of our design and methods.

Integrative approach to fluorescence-based oxygen sensing in polymer optical fibers with surface plasmon resonance

This study demonstrates a technique to enhance oxygen (O2) concentration measurement by combining surface plasmon resonance (SPR) and fluorescence-based sensor on polymer optical fiber (POF). The SPR was generated using silver (Ag) and the fluorescence was generated by organic dye. Three fluorescence dyes were used, Tris (4, 7-diphenyl-1, 10-phenanthroline) ruthenium (II) dichloride ([Ru(dpp)3]2+), platinum octaethylporphyrin (PtOEP) and 5,10,15,20-tetrakis (pentafluorophenyl) 21 H,23H-porphine palladium (II) (PdTFPP). The sensor was tested in a gas chamber with different concentration level of O2. Sensitivity values for the fluorescence dyes for [Ru(dpp)₃]²⁺, PtOEP, and PdTFPP were 0.0099 a.u/%, 0.0343 a.u/% and 0.05 a.u/% respectively. When SPR was implemented, the sensitivity values for Ag/[Ru(dpp)₃]²⁺, Ag/PtOEP, and Ag/PdTFPP were 0.0589 nm/%, 0.0345 nm/%, and 0.118 nm/% respectively. PdTFPP and Ag/PdTFPP exhibit highest sensitivity in each experiment. Therefore, the further analysis for the sensing performance of PdTFPP and Ag/PdTFPP were held. As a result, Ag/PdTFPP exhibits lower limit of detection (LOD), and limit of quantification (LOQ) with 3.054 % and 9.254 %, respectively, with higher R2 of 0.9971 and lower mean standard deviation of 0.174, compared to PdTFPP 16.496 % and 49.988 % respectively, with R2 of 0.9211 and higher mean standard deviation of 2.003. This improvement can benefit researchers and professionals in medical diagnostics, environmental monitoring, and industrial process control by providing a more sensitive and accurate method for measuring O2 levels.

Triplet-Triplet Annihilation-Based Photon Upconversion with a Macrocyclic Parallel Dimer.

The integration of multiple chromophore units into a single molecule is expected to improve the performance of photon upconversion based on triplet-triplet annihilation (TTA-UC) that can convert low energy photons to higher energy photons at low excitation intensity. In this study, a macrocyclic parallel dimer of 9,10-diphenylanthracene (DPA) with a precisely parallel orientation, named MPD-2, is synthesized, and its TTA-UC properties are investigated. MPD-2 shows a green-to-blue TTA-UC emission in the presence of a triplet sensitizer, platinum octaethylporphyrin (PtOEP). Compared to monomeric DPA, MPD-2 results in an enhancement of the spin statistical factor of TTA and a decrease in the excitation light intensity due to the intramolecular TTA process. The obtained structure-property relationship provides important information for the further improvement of TTA-UC properties.

Homomolecular Triplet-Triplet Annihilation in Metalloporphyrin Photosensitizers.

Metalloporphyrins are ubiquitous in their applications as triplet photosensitizers, particularly for promoting sensitized photochemical upconversion processes. In this study, bimolecular excited state triplet-triplet quenching kinetics, termed homomolecular triplet-triplet annihilation (HTTA), exhibited by the traditional triplet photosensitizers-zinc(II) tetraphenylporphyrin (ZnTPP), palladium(II) octaethylporphyrin (PdOEP), platinum(II) octaethylporphyrin (PtOEP), and platinum(II) tetraphenyltetrabenzoporphyrin (PtTPBP)─were revealed using conventional transient absorption spectroscopy. Nickel(II) tetraphenylporphyrin was used as a control sample as it is known to be rapidly quenched intramolecularly through ligand-field state deactivation and, therefore, cannot result in triplet-triplet annihilation (TTA). The single wavelength transients associated with the metalloporphyrin triplet excited state decay─measured as a function of incident laser pulse energy in toluene─were well modeled using parallel first- and second-order kinetics, consistent with HTTA being operable. The combined transient kinetic data enabled the determination of the first-order rate constants (kT) for excited triplet decay in ZnTPP (4.0 × 103 s-1), PdOEP (3.6 × 103 s-1), PtOEP (1.2 × 104 s-1), and PtTPBP (2.1 × 104 s-1) as well as the second-order rate constant (kTT) for HTTA in ZnTPP (5.5 × 109 M-1 s-1), PdOEP (1.1 × 1010 M-1 s-1), PtOEP (7.1 × 109 M-1 s-1), and PtTPBP (1.6 × 1010 M-1 s-1). In most instances, triplet excited state extinction coefficients are either reported for the first time or have been revised using ultrafast transient absorption spectroscopy and singlet depletion: ZnTPP (78,000 M-1 cm-1) at 470 nm, PdOEP (67,000 M-1 cm-1) at 430 nm, PtOEP (51,000 M-1 cm-1) at 418 nm, and PtTPBP (100,000 M-1 cm-1) at 460 nm. The combined experimental results establish competitive time scales for homo- and heteromolecular TTA rate constants, implying the significance of considering HTTA processes in future research endeavors harnessing TTA photochemistry using common metalloporphyrin photosensitizers.

Detecting Nanotopography Induced Changes in Cell Migration Directions Using Oxygen Sensors.

This study investigates the oxygen (O2) consumption of single cells during changes in their migration direction. This is the first integration of nanotopographies with an O2 biosensor in a platform, allowing the real-time monitoring of O2 consumption in cells and the ability to distinguish cells migrating in the same direction from those migrating in the opposite direction. Advanced nanofabrication technologies were used to pattern nanoholes or nanopillars on grating ridges, and their effects were evaluated using fluorescence microscopy, cell migration assays, and O2 consumption analysis. The results revealed that cells on the nanopillars over grating ridges exhibited an enhanced migration motility and more frequent directional changes. Additionally, these cells showed an increased number of protrusions and filopodia with denser F-actin areas and an increased number of dotted F-actin structures around the nanopillars. Dynamic metabolic responses were also evident, as indicated by the fluorescence intensity peaks of platinum octaethylporphyrin ketone dye, reflecting an increased O2 consumption and higher mitochondria activities, due to the higher energy required in response to directional changes. The study emphasizes the complex interplay between O2 consumption and cell migration directional changes, providing insights into biomaterial science and regenerative medicine. It suggests innovative designs for biomaterials that guide cell migration and metabolism, advocating nanoengineered platforms to harness the intricate relationships between cells and their microenvironments for therapeutic applications.

(Invited) Exciton Dynamics in Triplet Fusion of Diphenylanthracene in Fluid Solution and Crystalline Solid

Triplet fusion (TF) has recently attracted attention because of its great potential of various applications. Since high reaction efficiency of TF is demanded in any applications, it is necessary to clarify the mechanism of triplet exciton dynamics that is an important elementary process to enhance the TF efficiency. Therefore, in this paper, we study the triplet exciton dynamics of 9,10-diphenylanthracene (DPA), which shows the TF-based fluorescence, in a solvent of tetraethylene glycol dimethyl ether and in polycrystal of DPA, in combination with the triplet sensitization using platinum octaethylporphyrin. The observed emission kinetics and their magnetoluminescence effect indicate that the rotational and the multitrapping diffusions of the triplet exciton play an inherent role respectively in the fluid solution and in the polycrystalline solid.

High-efficiency triplet-triplet annihilation upconversion microemulsion with facile preparation and decent air tolerance.

Current research of triplet-triplet annihilation upconversion (TTA-UC) faces difficulty such as overuse of organic solvents and quenching of excited triplet sensitizers by molecular oxygen. Herein, we propose an efficient and facile preparation strategy of TTA-UC microemulsion to overcome these issues. With simple device and short preparation process, air-stable TTA-UC with a high upconversion efficiency of 16.52% was achieved in microemulsion coassembled from TritonX114, tetrahydrofuran and upconverting chromophores (platinum octaethyl-porphyrin and 9,10-diphenylanthracene). This is comparable to the highest UC efficiency ever reported for TTA-UC microemulsion systems. The excellent UC performance of TX114-THF could be attributed to two perspectives. Firstly, small-size micelle accommodated chromophores up to high concentrations in organic phase, which promoted efficient molecular collision. Additionally, high absorbance at 532nm ensured full use of excitation light, getting more long wavelength photons involved in the TTA-UC process. Moreover, air-stable TTA-UC also performed well in microemulsion with various surfactants, including nonionic surfactants (Tween 20, Tween 80, Triton X-110, Triton X-114), ionic surfactants (sodium dodecyl sulfate, cetyltrimethyl ammonium bromide) and block copolymers (pluronic F127, pluronic P123), through three conjectural assembly models according to the structural characteristics of surfactant molecules (concentrated, uncompacted and scattered). These discoveries could provide estimable reference for selection of surfactants in relevant fields of TTA-UC.

Simultaneous enhancement in phosphorescence and its lifetime of PtOEP-peptide assembly triggered by protein interaction

We fabricated hybrid nanoparticles consisting of organic semiconducting material with peptide sequence to reflect the target protein interaction. A phosphorescent OLED material, platinum octaethylporphyrin (PtOEP) was self-assembled by reprecipitation with the A17 peptide (YCAYYSPRHKTTF) selected as a probe ligand in order to recognize heat shock protein 70 (HSP70). The phosphorescence intensity of the PtOEP-A17 assembly was enhanced by 125 % after treatment with HSP70. The specificity of the protein interaction was confirmed in both solution and solid states of the PtOEP-A17 assembly against to BSA and nucleolin. We figured out that the phosphorescence lifetime of PtOEP-A17 assembly after exposed to HSP70 increased significantly to 153 ns from initial 115 ns. These simultaneous enhancements in phosphorescence and lifetime triggered by the specific protein interaction would open new applications of PtOEP, a representative material of light-emitting device fields.

Diphenylanthracene-based amorphous molecular fluorophores for triplet–triplet annihilation upconversion system

Abstract Novel diphenylanthracene-based amorphous molecular fluorophores have been designed and synthesized. They were found to exhibit fluorescence emission with fairly high quantum efficiencies both in solution, crystalline state, and amorphous state. Triplet–triplet annihilation upconversion emissions have been achieved not only in toluene solutions but also as amorphous solids using present novel fluorophores as acceptors combined with platinum(II) octaethylporphyrin as a donor.

Semiconducting polymer dots based l-lactate sensor by enzymatic cascade reaction system

Backgroundl-lactate detection is important for not only assessing exercise intensity, optimizing training regimens, and identifying the lactate threshold in athletes, but also for diagnosing conditions like L-lactateosis, monitoring tissue hypoxia, and guiding critical care decisions. Moreover, l-lactate has been utilized as a biomarker to represent the state of human health. However, the sensitivity of the present l-lactate detection technique is inadequate. ResultsHere, we reported a sensitive ratiometric fluorescent probe for l-lactate detection based on platinum octaethylporphyrin (PtOEP) doped semiconducting polymer dots (Pdots-Pt) with enzymatic cascade reaction. With the help of an enzyme cascade reaction, the l-lactate was continuously oxidized to pyruvic and then reduced back to l-lactate for the next cycle. During this process, oxygen and NADH were continuously consumed, which increased the red fluorescence of Pdots-Pt that responded to the changes of oxygen concentration and decreased the blue fluorescence of NADH at the same time. By comparing the fluorescence intensities at these two different wavelengths, the concentration of l-lactate was accurately measured. With the optimal conditions, the probes showed two linear detection ranges from 0.5 nM to 5.0 μM and 5.0 μM–50.0 μM for l-lactate detection. The limit of detection was calculated to be 0.18 nM by 3σ/slope method. Finally, the method shows good detection performance of l-lactate in both bovine serum and artificial serum samples, indicating its potential usage for the selective analysis of l-lactate for health monitoring and disease diagnosis. SignificanceThe successful application of the sensing system in the complex biological sample (bovine serum and artificial serum samples) demonstrated that this method could be used for sensitive l-lactate detection in practical clinical applications. This detection system provided an extremely low detection limit, which was several orders of magnitude lower than methods proposed in other literatures.

Multiple Force-Triggered Downconverted and Upconverted Emission in Polymers Containing Diels-Alder Adducts.

Fluorescent mechanophores can indicate the deformation or damage in polymers. The development of mechanophores with multi-triggered response is of great interest. Herein, Diels-Alder (DA) adducts are incorporated into linear poly(methyl acrylate) PMA-BA and network poly(hexyl methacrylate) (PHMA) as mechanophores to detect the stress caused by ultrasound, freezing, and compression. The DA mechanophores undergo retro-DA reaction to release 9-styrylanthracene chromophore upon applying force, resulting in cyan fluorescence. The dissociation ratio of the DA mechanophore after pulsed ultrasonication of PMA-BA solution for 240 minutes is estimated to be 52 % by absorption spectra and 1H NMR. Additionally, the rate constant of mechanical cleavage is calculated to be 1.2×10-4 min-1⋅kDa-1 with the decrease in molecular weight from 69 to 22 kDa measured by gel permeation chromatography. Freezing of PHMA gels as well as compression of PHMA bulk samples turn-on the DA mechanophores, revealing the microscale fracture. Photon upconversion responses toward various force stimuli are also achieved in both polymer solutions and bulk samples by doping platinum octaethylporphyrin (PtOEP) or palladium meso-tetraphenyltetrabenzoporphyrin (PdTPTBP) sensitizers with multiple excitation wavelengths.

Improvement in the upconversion efficiency of an alternating multilayer structure based on 9,10-bis(4-methylphenyl) anthracene and platinum octaethylporphyrin vacuum deposited on an in-plane oriented polythiophene film

Alternating layers of 9,10-bis(4-methylphenyl) anthracene (diMe-DPA) and platinum octaethylporphyrin were fabricated via vacuum deposition on an in-plane-oriented polythiophene (PT) film. The multilayer film showed higher upconversion (UC) quantum efficiency than bilayer films with similar composition and total thickness. The UC quantum efficiency of the multilayer structure deposited on the oriented PT film was three times higher than those deposited on glass substrates, suggesting that the molecular alignment of diMe-DPA increases the UC quantum efficiency.

Enhancing Triplet-Triplet Annihilation Upconversion of Pyrene Derivatives for Photoredox Catalysis via Molecular Engineering.

Triplet-triplet annihilation upconversion (TTA-UC) has the potential to enhance photoredox catalysis yield. It includes a sensitizer and an annihilator. Efficient and stable annihilators are essential for photoredox catalysis, yet only a few examples are reported. Herein, we designed four novel pyrene annihilators (1, 2, 3 and 4) via introducing aryl-alkynyl groups onto pyrene to systematically modulate their singlet and triplet energies. Coupled with platinum octaethylporphyrin (PtOEP), the TTA-UC efficiency is enhanced gradually as the number of aryl-alkynyl group increases. When combining 4 with palladium tetraphenyl-tetrabenzoporphyrin (PdTPTBP), we achieved the highest red-to-green upconversion efficiency (22.4±0.3 %) (out of a 50 % maximum) so far. Then, this pair was used to activate photooxidation of aryl boronic acid under red light (630 nm), which achieved a great improved reaction yield compared to that activated by green light directly. The results not only provide a design strategy for efficient annihilators, but also show the advantage of applying TTA-UC into improving the photoredox catalysis yield.

Study on temperature-dependent thermal population and non-radiative relaxation process of the triplet states in Platinum(Ⅱ) octaethylporphyrin

The present study focused on examining the thermal population and non-radiative relaxation process by leveraging the unique characteristics of the triplet states of Platinum (Ⅱ) octaethylporphyrin (PtOEP). The investigation of the thermal population process involved the utilization of the luminescence exhibited by the PtOEP triplet state in an oxygen-free environment. Time-resolved spectroscopy was employed to investigate the non-radiative relaxation process occurring on the higher energy levels of the triplet states in the presence of oxygen. The findings indicate that both thermal population and non-radiative relaxation process follow the Boltzmann distribution law. Furthermore, the energy differences obtained from the fitting procedure closely aligned with the energy differences calculated based on the emission spectrum. This observation implies that the underlying reason for the congruence between these two processes is their inherent reversibility.

High-Level Reverse Intersystem Crossing and Molecular Rigidity Improve Spin Statistics for Triplet-Triplet Annihilation Upconversion.

The structural factors affecting triplet-triplet annihilation (TTA) at the molecular level are not well-understood. Here, our steady-state photoluminescence and transient absorption results demonstrate that the spin statistical factor, η, decreases from 0.60 to 0.46 and 0.14 going from 9,10-diphenylanthracene (DPA) to the 1,5-DPA and 2,6-DPA isomers, respectively, during photon upconversion with a platinum octaethylporphyrin sensitizer. Density functional theory (DFT) shows that η depends on the energetics of hot triplet states and molecular rigidity. The significantly high conical intersection energy between the S0 and T1 states for 9,10-DPA gives its longer triplet lifetime. Time-dependent DFT calculations show that 9,10-DPA and 1,5-DPA can undergo high-level reverse intersystem crossing from their T2 and T3 states, respectively, to the bright S1 state, increasing the limit of the spin statistical factor. Both factors ultimately serve to enhance the TTA efficiency. This work provides insight into designing molecules for efficient light-emitting and photon upconversion applications.

Diarylethene Isomerization by Using Triplet-Triplet Annihilation Photon Upconversion.

Green-to-blue triplet-triplet annihilation photon upconversion with the well-studied upconversion pair 9,10-diphenylanthracene (DPA)/platinum octaethylporphyrin (PtOEP) was used to reversibly drive the photoisomerization of diarylethene (DAE) photoswitches by using visible light. By carefully selecting the kinetic and spectral properties of the molecular system as well as the experimental geometry, a single green light source can be used to selectively trigger both the ring-opening and the ring-closing reactions, whilst also inducing fluorescence from the colored closed isomer that can be used as a readout to monitor the isomerization process in situ. The upconversion solution and the DAE solution are kept physically separated, allowing them to be characterized both concomitantly and individually without further separation processes. The ring-closing reaction using upconverted photons was quantified and compared to the efficiency of direct isomerization with ultraviolet light.

The influence of non-radiative relaxation on the room-temperature phosphorescence of metalloporphyrin

The room-temperature phosphorescence (RTP) of metalloporphyrins, induced by the heavy atom effect (HAE), has been widely concerned in many fields, and the intense emission of RTP is highly desired. The phosphorescent transition rate ([Formula: see text] has been used to quantitatively characterize the HAE’s intrinsic nature. However, the phosphorescent intensity was not determined by [Formula: see text] alone, non-phosphorescent transition ([Formula: see text] induced by surrounding factors was also involved. In this study, the influence of [Formula: see text] on the RTP of palladium octaethylporphyrin (PdOEP), platinum octaethylporphyrin (PtOEP), and platinum tetraphenylporphyrin (PtTPP) was studied. The effect of [Formula: see text] can be quantitatively described by an introduced parameter [Formula: see text], which was defined as [Formula: see text] = [Formula: see text]/([Formula: see text]. The method is proposed for determining the [Formula: see text] of PdOEP, PtOEP, and PtTPP by the UV-visible absorption spectra, luminescence spectra, and phosphorescence dynamic curves. Our research provides a way to understand the effect of knP on the RTP, and may benefit the development and optimization of metalloporphyrins aiming at intense RTP.

Strongly Improving the Sensitivity of Phosphorescence-Based Optical Oxygen Sensors by Exploiting Nano-Porous Substrates.

Sensitivity is one of the crucial factors in determining the quality of a fluorescence/phosphorescence-based gas sensor, and is estimated from the measurement of responses (I0/I, where I0 and I refer to the measured optical intensity of a sensor in absence and presence of analyte molecules) at various concentrations of analytes. In this work, we demonstrate phosphorescence-based optical oxygen sensors fabricated on highly porous anodic aluminum oxide (AAO) membranes showing dramatically high response. These sensors exploit the enormous surface area of the AAO to facilitate the effective interaction between the sensing molecules and the analytes. We spin-coat an AAO membrane (200 nm pore diameter) with a platinum-based oxygen sensing porphyrin dye, platinum(II) meso-tetrakis (pentafluorophenyl) porphyrin (PtTFPP), to fabricate a sensor exhibiting I0/I ~400 at 100% oxygen atmosphere. To address the generality of the AAO membrane, we fabricate a separate sensor with another porphyrin dye, platinum octaethylporphyrin (PtOEP), which exhibits an even higher I0/I of ~500. Both of these sensors offer the highest responses as an optical oxygen sensor hitherto reported. SEM and EDS analysis are performed to realize the effect of the increased surface area of the AAO membrane on the enhanced sensitivity.

Platinum octaethylporphyrin-diphenylanthracene dyad with an ethynylene linker

A platinum octaethylporphyrin (PtOEP)-diphenylanthracene (DPA) dyad with an ethynylene linker was synthesized. PtOEP and DPA were used as a triplet sensitizer/energy donor and energy acceptor, respectively. UV–vis spectra suggested significant electronic coupling between PtOEP and the ethynylene linker in the ground state. Compared with the non-substituted PtOEP, emission from PtOEP in the dyad was almost completely quenched probably due to triplet excitation energy transfer from PtOEP to DPA.

Triplet–triplet annihilation-based photon-upconversion to broaden the wavelength spectrum for photobiocatalysis

Photobiocatalysis is a growing field of biocatalysis. Especially light-driven enzyme catalysis has contributed significantly to expanding the scope of synthetic organic chemistry. However, photoenzymes usually utilise a rather narrow wavelength range of visible (sun)light. Triplet–triplet annihilation-based upconversion (TTA-UC) of long wavelength light to shorter wavelength light may broaden the wavelength range. To demonstrate the feasibility of light upconversion we prepared TTA-UC poly(styrene) (PS) nanoparticles doped with platinum(II) octaethylporphyrin (PtOEP) photosensitizer and 9,10-diphenylanthracene (DPA) annihilator (PtOEP:DPA@PS) for application in aqueous solutions. Photoexcitation of PtOEP:DPA@PS nanoparticles with 550 nm light led to upconverted emission of DPA 418 nm. The TTA-UC emission could photoactivate flavin-dependent photodecarboxylases with a high energy transfer efficiency. This allowed the photodecarboxylase from Chlorella variabilis NC64A to catalyse the decarboxylation of fatty acids into long chain secondary alcohols under green light (λ = 550 nm).