Changqing Ye

Oil-in-water microemulsion: an effective medium for triplet–triplet annihilated upconversion with efficient triplet acceptors

The oil-in-water (o/w) microemulsion containing bimolecular system of acceptor (9,10-dinaphthylanthracene) and sensitizer (Pd(II)tetratolylporphyrin), i.e., upconverted o/w microemulsion, was firstly reported for the triplet–triplet annihilated upconversion (TTA-UC) by temperature effects. The correlation between structure/up-conversion performance of three 9,10-dinaphthylanthracenes doped with Pd(II)tetratolylporphyrin were investigated. Under excitation at an ultralow power density at 60 mW cm−2, the up-converted o/w microemulsion emits green-to-blue upconversion and an efficiency (ΦUC) increase is accompanied by an increase in temperature. The maximum ΦUC value for the upconverted o/w microemulsion obtained was as high as 33.12%, which is comparable to its counterpart in a pure organic solvent. Very importantly, there is no need for the upconverted o/w microemulsion to deaerate, which is of critical importance for applications such as upconversion-powered photoelectrochemistry. To the best of our knowledge, the current study represents a simple approach to obtain high TTA-UC without degassing.

A new medium for triplet–triplet annihilated upconversion and photocatalytic application

Since the triplet-triplet annihilated upconversion (TTA-UC) materials work efficiently only in degassing organic solvents, it is of significance to find a new medium without toxicity and volatility and that promotes TTA-UC. Here, we firstly reported the effect of an OH-containing medium on low power upconversion and found that in alcohol solvent containing β-cyclodextrin (β-CD), the phosphorescence lifetime (τp) of the sensitizer (PdTPP) and the fluorescence quantum yield (Φf) of the acceptor (DPA) were enhanced with the increase in the number of OH-groups of the medium. A large triplet-triplet quenching constant (kq, 1.91 × 10(9) M(-1) s(-1)) and high upconversion efficiency (ΦUC, ∼ 36%) of PdTPP/DPA were obtained under the excitation of a diode laser (532 nm, 60 mW cm(-2)). Under our green-to-blue upconversion irradiation, in a demonstration experiment the photocurrent was recorded at 0.09 μA cm(-2), resulting from photocatalytic water splitting by a Cd0.7Zn0.3S photoanode and a Pt counter-electrode in a photoelectrochemical cell. The importance of this study suggests that upconversion-powered photoelectrochemistry possesses potential application for hydrogen generation from water under excitation of sun energy.

The solvatochromism and aggregation-induced enhanced emission based on triphenylamine-propenone

Three new donor–π bridge–acceptor (D–π–A) compounds based on triphenylamine-propenone, namely 4-(1-phenylprop-2-en-1-one-3-yl)triphenylamine (PhO-TPA), 4-(1-(pyridin-2-yl)prop-2-en-1-one-3-yl)triphenylamine (PyO-TPA) and 4,4′,4′′-(tri(1-(pyridin-2-yl)prop-2-en-1-one-3-yl))triphenylamine (TPyO-TPA), were synthesized through an aldol addition reaction. Their intramolecular charge transfer (ICT) and aggregation emission properties as well as packing structures were investigated. All of them show solvent polarity dependent emission. The density function theory calculations reveal that the ICT characteristic of the HOMO–LUMO transition is responsible for the large solvent effect. In aggregates, PhO-TPA and PyO-TPA exhibit aggregation-induced enhanced emission (AIEE). However, TPyO-TPA displays a different fluorescence behavior. Single-crystal analyses of PhO-TPA and PyO-TPA show that the weak intermolecular interactions and the suppression of the ICT state result in the efficient AIEE. The understanding on the AIEE fluorophores together with ICT characteristic will help to develop materials with color tenability, especially the ones with efficient emission in solid states.

New Anthracene Derivatives as Triplet Acceptors for Efficient Green‐to‐Blue Low‐Power Upconversion

Three new anthracene derivatives [2-chloro-9,10-dip-tolylanthracene (DTACl), 9,10-dip-tolylanthracene-2-carbonitrile (DTACN), and 9,10-di(naphthalen-1-yl)anthracene-2-carbonitrile (DNACN)] were synthesized as triplet acceptors for low-power upconversion. Their linear absorption, single-photon-excited fluorescence, and upconversion fluorescence properties were studied. The acceptors exhibit high fluorescence yields in DMF. Selective excitation of the sensitizer Pd(II)octaethylporphyrin (PdOEP) in solution containing DTACl, DTACN, or DNA-CN at 532 nm with an ultralow excitation power density of 0.5 W cm(-2) results in anti-Stokes blue emission. The maximum upconversion quantum yield (Φ(UC) =17.4%) was obtained for the couple PdOEP/DTACl. In addition, the efficiency of the triplet-triplet energy transfer process was quantitatively studied by quenching experiments. Experimental results revealed that a highly effective acceptor for upconversion should combine high fluorescence quantum yields with efficient quenching of the sensitizer triplet.