New Application of Multiresonance Organic Delayed Fluorescence Dyes: High-Performance Photoinitiating Systems for Acrylate and Epoxy Photopolymerization and Photoluminescent Pattern Preparation.

The primary focus of photopolymerization research is to advance highly efficient visible photoinitiating systems (PISs) as alternatives to conventional ultraviolet (UV) photoinitiators. We developed four multiresonance emitters (BIC-pCz, BNO1, BO-DICz, and TPABO-DICz) to sensitize iodonium salt (Iod) and initiate free-radical and cationic photopolymerization under visible light for the first time. The TPABO-DICz/Iod system achieved a double-bond conversion of over 70% within just 4 s of exposure to green light (520 nm), while the BNO1/Iod system achieved a double-bond conversion exceeding 50% with 10 s of exposure to red light (630 nm). The photochemical properties were studied through thermodynamic research, steady-state photolysis, and electron spin resonance. Photolithography techniques were employed to fabricate photoluminescent films and micrometer-scale patterns utilizing the blue-emitting BIC-pCz dye, showcasing the potential of photolithography in the production of photoluminescent pixels. Additionally, the BIC-pCz/Iod and TPABO-DICz/Iod systems have been employed to rapidly fabricate photoluminescent polymer patterns using a digital-light-processing 3D printer with a low-intensity light (3.2 mW cm-2). These multiresonance emitters show exceptional photosensitizing effects and can act as fluorescent dyes in photoluminescent patterns, highlighting the potential of utilizing photopolymerization for OLED applications.

Coumarin Ketoxime Ester with Electron-Donating Substituents as Photoinitiators and Photosensitizers for Photopolymerization upon UV-Vis LED Irradiation.

High-performance photoinitiators (PIs) are essential for ultraviolet-visible (UV-Vis) light emitting diode (LED) photopolymerization. In this study, a series of coumarin ketoxime esters (COXEs) with electron-donating substituents (tert-butyl, methoxy, dimethylamino and methylthio) were synthesized to study the structure/reactivity/efficiency relationships for substituents for the photoinitiation performance of PIs. The introduction of heteroatom electron-donating substituents leads to a redshift in the COXE absorption of more than 60 nm, which matches the UV-Vis LED emission spectra. The PIs also show acceptable thermal stability via differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The results from real-time Fourier transform infrared (RT-FTIR) measurements indicate that COXEs show an excellent photoinitiation efficiency for free radical polymerization under UV-Vis LED irradiation (365-450 nm); in particular, the conversion efficiency for tri-(propylene glycol) diacrylate (TPGDA) polymerization initiated by COXE-O and COXE-S (4.8 × 10-5 mol·g-1) in 3 s can reach more than 85% under UV-LED irradiation (365, 385 nm). Moreover, the photosensitization of COXEs in the iodonium hexafluorophosphate (Iod-PF6) and hexaarylbiimidazole/N-phenylglycine (BCIM/NPG) systems was investigated via RT-FTIR. As a coinitiator, COXEs show excellent performance in dry film photoresist (DFR) photolithography. This excellent performance of COXEs demonstrates great potential for UV-curing and photoresist applications, providing a new idea for the design of PIs.

Reduced Graphene Oxide Quantum Dot Light Emitting Diodes Fabricated Using an Ultraviolet Light Emitting Diode Photolithography Technique.

Graphene quantum dots usually suffer from serious fluorescence quenching in aggregates and the solid state due to easy agglomeration and aggregation-induced quenching, which seriously restrict their practical applications. An ingenious strategy to kill three birds with one stone, the ultraviolet (UV) photolithography technique, was studied, and blue-emitting reduced graphene oxide quantum dot (rGOQD)-based light emitting diodes (LEDs) with efficient solid state emission were first fabricated using UV photolithography. First, rGOQDs were prepared by the in situ photoreduction of GOQDs by using the photoinitiator phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide with 395 nm UV LED exposure. Furthermore, rGOQD/photoresist patterns were prepared under the same conditions. Meanwhile, the in situ photoreduction of GO in the aforementioned photoresist to rGO was realized by UV photolithography to improve the conductivity of the rGOQD/photoresist films. Additionally, the in situ photoreduction of GOQDs in different surroundings was studied, with the results showing that GOQDs are more easily photoreduced in ionic liquids and that the photoluminescence spectrum obtained for rGOQDs exhibits a 70 nm blueshift with a narrow full-width at half-maximum compared to GOQDs.

NIR-Sensitized Cationic and Hybrid Radical/Cationic Polymerization and Crosslinking.

NIR-sensitized cationic polymerization proceeded with good efficiency, as was demonstrated with epoxides, vinyl ether, and oxetane. A heptacyanine functioned as sensitizer while iodonium salt served as coinitiator. The anion adopts a special function in a series selected from fluorinated phosphates (a: [PF6 ]- , b: [PF3 (C2 F5 )3 ]- , c: [PF3 (n-C4 F9 )3 ]- ), aluminates (d: [Al(O-t-C4 F9 )4 ]- , e: [Al(O(C3 F6 )CH3 )4 ]- ), and methide [C(O-SO2 CF3 )3 ]- (f). Vinyl ether showed the best cationic polymerization efficiency followed by oxetanes and oxiranes. DFT calculations provided a rough pattern regarding the electrostatic potential of each anion where d showed a better reactivity than e and b. Formation of interpenetrating polymer networks (IPNs) using trimethylpropane triacrylate and epoxides proceeded in the case of NIR-sensitized polymerization where anion d served as counter ion in the initiator system. No IPN was formed by UV-LED initiation using the same monomers but thioxanthone/iodonium salt as photoinitiator. Exposure was carried out with new NIR-LED devices emitting at either 805 or 870 nm.

NIR-Sensitized Activated Photoreaction between Cyanines and Oxime Esters: Free-Radical Photopolymerization.

Cyanines comprising either a benzo[e]- or benzo[c,d]indolium core facilitate initiation of radical photopolymerization combined with high power NIR-LED prototypes emitting at 805 nm, 860 nm, or 870 nm, while different oxime esters function as radical coinitiators. Radical photopolymerization followed an initiation mechanism based on the participation of excited states, requiring additional thermal energy to overcome an existing intrinsic activation barrier. Heat released by nonradiative deactivation of the sensitizer favored the system, even under conditions where a thermally activated photoinduced electron transfer controls the reaction protocol. The heat generated internally by the NIR sensitizer promotes generation of the initiating reactive radicals. Sensitizers with a barbiturate group at the meso-position preferred to bleach directly, while sensitizers carrying a cyclopentene moiety unexpectedly initiated the photosensitized mechanism.

Refactoring and Optimization of Bridge Dynamic Displacement Based on Ensemble Empirical Mode Decomposition.

Considering the lack of precision in transforming measured micro-electro-mechanical system (MEMS) accelerometer output signals into elevation signals, this paper proposes a bridge dynamic displacement reconstruction method based on the combination of ensemble empirical mode decomposition (EEMD) and time domain integration, according to the vibration signal traits of a bridge. Through simulating bridge analog signals and verifying a vibration test bench, four bridge dynamic displacement monitoring methods were analyzed and compared. The proposed method can effectively eliminate the influence of low-frequency integral drift and high-frequency ambient noise on the integration process. Furthermore, this algorithm has better adaptability and robustness. The effectiveness of the method was verified by field experiments on highway elevated bridges.

High photocatalytic activity of ZnO-graphene composite.

In this work, ZnO nanoparticles-reduced graphene oxide (rGO) composites were fabricated via a novel one-step photochemical method. The developed nanocomposite offered high photodegradation efficiency of methylene blue (MB) under UV and visible light. In the proposed route, the reduction of graphene oxide (GO) and formation of ZnO nanoparticles occurred simultaneously, which results in high synthesis efficiency of ZnO/rGO nanocomposites. The electron microscopy confirmed that the ZnO nanoparticles were uniformly anchored on rGO sheets. The structure and quality of prepared nanocomposite were assessed by X-ray diffraction, Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Furthermore, the synthesis of the nanocomposite and degradation of MB, along with a mechanistic insight, is discussed in detail.

catena-Poly[europium(III)-tri-micro-2,3-dimethoxybenzoato].

The title compound, [Eu(C(9)H(9)O(4))(3)](n) or [Eu(2,3-DMOBA)(3)](n), where 2,3-DMOBA is 2,3-dimethoxybenzoate, is an infinite one-dimensional non-centrosymmetric coordination polymer. The unique Eu(III) atom is bridged by six carboxylate ligands; it is ennea-coordinated and has a distorted tricapped trigonal prism geometry. The Eu-O distances are in the range 2.315 (3)-2.959 (5) A.