Zece Zhu

Tetracoordinated heteroleptic Cu(I) complexes have gained prominence as prospective thermally activated delayed fluorescence (TADF) emitters, where both the structural framework and substituent effects of the diimine ligands critically influence their photophysical behavior. Herein, we report the design, synthesis, and characterization of two [Cu(N^N)(P^P)]PF ₆ complexes, T1 and P1 , featuring an imidazo[4,5‐f][1,10]phenanthroline (Imphen) diimine ligand functionalized with 3,6‐di‐ tert ‐butylcarbazole ( t Cz) donor units or H in combination with conventional chelating diphosphine ligands. The optimization of the diimine structure for T1 in which the 3,6‐di‐ tert ‐butylcarbazole ( t Cz) was introduced to the Imphen fragment to form a donor–acceptor (D–A) type diimine ligand facilitates pronounced spatial separation of the frontier molecular orbitals, leading to a remarkably small singlet–triplet energy gap (Δ E _ST ) of 516 cm ⁻¹ , as confirmed by photophysical and theoretical analyses. The complex T1 exhibit microsecond‐range delayed fluorescence ( τ = 12.05 μs) with a radiative decay rate ( k _r ) of 1.33 × 10 ⁴ s ⁻¹ . The theoretical calculations further attribute the moderate oscillator strength and spin–orbit coupling (SOC) to the separation of frontier orbitals. Notably, T1 displays a distinct “turn‐on” luminescent response upon deprotonation of the Imphen ligand in different basic media (e.g., NaOH, triethylamine, and DBU), underscoring its potential in pH‐responsive sensing. These results demonstrate that heteroleptic [Cu (Imphen)(P^P)] ⁺ complexes incorporating D–A type diimine ligands represent a versatile platform for the development of efficient TADF materials and stimuli‐responsive optical devices.

Solid-state lasers are usually used as excitation light sources for measuring the upconversion luminescence spectra. But the output power of this kind of laser usually jitters at unsaturated output circumstances, leading to unstable luminescence intensity and affecting the accuracy of excitation threshold measurement. Herein, pulse width modulation was used for adjusting the power of a 532 nm solid-state laser for measuring the upconversion threshold. The average output power of lasers can be adjusted by changing the pulse width at a constant pulse frequency. The stability is significantly higher than that of the output power using current modulation. The excitation threshold estimated by this method is similar to that of the continuous light excitation. Pulse width modulation is expected to be applied to other lasers in power modulation and will play an important role in fluorescence detection and imaging.

A novel hydro-isocyanurate, N ₂ H ₄ Zn(HC ₃ N ₃ O ₃ ), possessing an asymmetric topological diamond-like 3D network exhibits the strongest second harmonic generation among cyanurates (13 × KDP) and ultra-long room-temperature phosphorescence (448 ms).

Heavy-atom-free triplet-triplet annihilation (TTA) upconversion sensitized by a thermally activated delayed fluorescence (TADF) molecule is investigated in a dried gel made of a photo-cross-linked polymer as the solid-state matrix. The upconversion fluorescence quantum yields, Φ_UC, of the solid-gel TTA system at different penetration depths are measured accurately based on a developed internal-reference method. It is found that Φ_UC is greatest at the surface and then decreases exponentially with increasing depth, influenced by the substrate absorption. The same process is also performed in a TTA solution at different depths, but a completely different result is obtained; there is little difference for Φ_UC. To the best of our knowledge, this is the first time the quantum yields at different transmission depths have been mentioned and calculated experimentally. These results illustrate the importance of accurately measuring the quantum yield of solid-phase TTA upconversion and provide a novel way to improve the solid-phase TTA quantum yield by reducing the thickness of the substrate.

Fluorescence detection has always suffered from high background fluorescence from real samples such as milk. Therefore, cumbersome pretreatments of samples were necessary to remove the fluorescent substances but led to long processing times and low efficiency. Time-resolved luminescence detection is a powerful technique for eliminating short-lived background fluorescence without additional pretreatments. However, the related instruments are usually equipped with high-speed excitation sources and detectors, which are always bulky and expensive. Herein, we developed a low-cost and miniaturized imaging system for high-throughput time-gated luminescence detection. An UV LED array was used to excite multiple samples, the luminescence of which could be detected by a smartphone simultaneously. An analog circuit was designed to synchronize the LED to the mechanical chopper to eliminate the background signals resulting from scattering and short-lived autofluorescence. Compared to other synchronous circuits based on FPGAs and microcontrollers, this analog circuit required no programming and memory. For the first time, high-throughput time-resolved luminescence detection of tetracycline in milk without any separation or enrichment was achieved by utilizing a smartphone as a camera, and the scattered signals and the background fluorescence were eliminated efficiently. The limit of detection reached as low as 53 nM (∼0.024 ppm), lower than the residue limit set by the European Union. This high-throughput time-gated luminescence detection method can be used for quantitative analysis of many real samples with high background fluorescence.