Showing papers by "Wai Yeung Wong published in 2023"

Non-covalent interactions (NCIs) in π-conjugated functional materials: advances and perspectives.

Abstract: The design and development of functional materials with real-life applications are highly demanding. Understanding and controlling inter- and intra-molecular interactions provide opportunities to design new materials. A judicious manipulation of the molecular structure significantly alters such interactions and can boost selected properties and functions of the material. There is burgeoning evidence of the beneficial effects of non-covalent interactions (NCIs), showing that manipulating NCIs may generate functional materials with a wide variety of physical properties leading to applications in catalysis, drug delivery, crystal engineering, etc. This prompted us to review the implications of NCIs on the molecular packing, optical properties, and applications of functional π-conjugated materials. To this end, this tutorial review will cover different types of interactions (electrostatic, π-interactions, metallophilic, etc.) and their impact on π-conjugated materials. Attempts have also been made to delineate the effects of weak interactions on opto-electronic (O-E) applications.

A Cobalt‐Based Metal‐Organic Framework Nanosheet as the Electrode for High‐Performance Asymmetric Supercapacitor

Abstract: Inspired by the significant advantages of the bottom‐up synthesis whose structures and functionalities can be customized by the selection of molecular components, a 2D metal‐organic framework (MOF) nanosheet Co‐BTB‐LB has been synthesized by a liquid–liquid interface‐assisted method. The as‐prepared Co‐BTB‐LB is identified by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDX) and X‐ray photoelectron spectroscopy (XPS), and the sheet‐like structure is verified by scanning electron microscopy (SEM), high‐resolution transmission electron microscopy (HRTEM), and atomic force microscopy (AFM). Co‐BTB‐LB electrode exhibits an excellent capacity of 4969.3 F g−1 at 1 A g−1 and good cycling stability with 75% capacity retention after 1000 cycles. The asymmetric supercapacitor device with Co‐BTB‐LB as the positive electrode shows a maximum energy density of 150.2 Wh kg−1 at a power density of 1619.2 W kg−1 and good cycling stability with a capacitance retention of 97.1% after 10000 cycles. This represents a state‐of‐the‐art performance reported for asymmetric supercapacitor device using electroactive bottom‐up metal‐complex nanosheet, which will clearly lead to a significant expansion of the applicability of this type of 2D nanomaterials.

Visible-to-near-infrared light-harvesting A-π-D-π-A porphyrins for boosted photocatalytic hydrogen evolution

Abstract: Developing visible-to-near-infrared light-harvesting porphyrin photosensitizers is very important for efficient photocatalytic hydrogen evolution (PHE) since most of the tetra-meso-substituted porphyrins absorb up to the visible region only. Herein, two new...

Construction of an Artificial Interfacial Layer with Porous Structure toward Stable Zinc‐Metal Anodes

Abstract: Aqueous zinc‐ion batteries possess great potential in stationary energy storage devices. Nevertheless, the occurrence of zinc dendrite growth and hydrogen evolution reaction severely hinders the utilization efficiency and service life of zinc‐metal anodes. Herein, an in situ etching strategy is proposed to construct an interfacial layer with porous structure on the surface of zinc foil under the assistance of tartaric acid (denoted as TA@Zn). The optimized anode surface is beneficial to not only achieve uniform Zn deposition behavior due to the low nucleation overpotential, but also enhance the interfacial reaction kinetics due to the reduced activation energy barrier. As expected, the TA@Zn‐based symmetric cell delivers small voltage hysteresis and superior stability for 5000 h at the current density of 1 mA cm−2. Moreover, the TA@Zn|NH4V4O10 cell also exhibits high specific capacity and long‐term cycling stability.

An overview on AIEgen‐decorated porphyrins: Current status and applications

Abstract: One of the major obstacles of porphyrins is the aggregation‐caused quenching (ACQ) of photoluminescence due to the strong intermolecular π–π interaction of the planar porphyrin core in the solid state. However, ACQ leads to the nonradiative deactivation of the photoexcited states which results in short‐lived charge‐separated states and thus low photoluminescence and singlet quantum yields. This phenomenon would limit the utilization of porphyrins in near‐infrared fluorescent bioimaging, photodynamic therapy, photocatalytic hydrogen evolution, electrochemiluminescence, and chiroptical applications. Hence, to address the ACQ property of porphyrins and enhance the performance of the above applications, a limited number of AIEgen‐decorated porphyrins have been designed, synthesized, and tested for their applications. It has been found that the introduction of AIEgens, such as tetraphenylethylene, diphenylacrylonitrile, (3,6‐bis‐(1‐methyl‐4‐vinylpyridinium)‐carbazole diiodide, and iridium motif into the porphyrin core, transformed the porphyrins from ACQ to aggregation‐induced emission (AIE) in their solid state due to the reduced strong intermolecular π–π stacking of porphyrins. Consequently, such porphyrins containing AIE features are employed as potential candidates in the above‐mentioned applications. In this review, we summarize the AIEgen‐decorated porphyrins which have been published to date, and also discuss the benefits of converting porphyrins from ACQ to AIE for enhanced performance within each application. As far as we know, there is no review that summarizes the structures and applications of AIEgen‐decorated porphyrins to date. Therefore, we presume that this review would be helpful to design more efficient AIEgen‐decorated porphyrins for a wide range of applications in the future.

Recent Advances in Triplet–Triplet Annihilation-Based Materials and Their Applications in Electroluminescence

Abstract: Efficient and stable blue organic light-emitting devices (OLEDs) represent one of the most important components in future solid-state lighting and full color displays. Although red and green OLEDs have been successfully commercialized, it remains challenging to realize blue OLEDs showing high efficiency and high stability simultaneously, restricting their commercialization. Triplet–triplet annihilation (TTA)-based materials have been emerging as a new category of electroluminescent or host materials with promising potential for highly efficient and stable blue devices due to their appealing photophysical properties (e.g., ability to generate emissive singlet excited states through TTA process, high photoluminescence quantum yield, ease of molecular design, etc.). Recently, research on TTA-based materials toward high-performance blue OLEDs has received an increasing attention. In this review, recent research advances on the molecular design strategies, photophysical properties of TTA-based materials (both blue emitters and host materials), mechanism of TTA-based electroluminescence, as well as their OLED applications are presented comprehensively. Moreover, potential perspectives with future research opportunities in this field are also described. We believe that the emerging TTA-based materials will bring more opportunities for developing a large family of novel photofunctional materials showing appealing and tunable photophysical properties, thus providing new opportunities for high-efficiency and stable blue electroluminescence in the future.

One-Pot Synthesis of Acetylacetonate-Based Isomeric Phosphorescent Cyclometalated Iridium(III) Complexes via Random Cyclometalation: A Strategy for Excited-State Manipulation.

Abstract: The excited-state manipulation of the phosphorescent iridium(III) complexes plays a vital role in their photofunctional applications. The development of the molecular design strategy promotes the creative findings of novel iridium(III) complexes. The current molecular design strategies for iridium(III) complexes mainly depend on the selective cyclometalation of the ligands with the iridium(III) ion, which is governed by the steric hindrance of the ligand during the cyclometalation. Herein, a new molecular design strategy (i.e., random cyclometalation strategy) is proposed for the effective excited-state manipulation of phosphorescent cyclometalated iridium(III) complexes. Two series of new and separable methoxyl-functionalized isomeric iridium(III) complexes are accessed by a one-pot synthesis via random cyclometalation, resulting in a dramatic tuning of the phosphorescence peak wavelength (∼57 nm) and electrochemical properties attributed to the high sensitivity of their excited states to the position of the methoxyl group. These iridium(III) complexes show intense phosphorescence ranging from the yellow (567 nm) to the deep-red (634 nm) color with high photoluminescence quantum yields of up to 0.99. Two deep-red emissive iridium(III) complexes with short decay lifetimes are further utilized as triplet emitters to afford efficient solution-processed electroluminescence with reduced efficiency roll-offs.

Strongly coupled interface facilitating charge separation to the improved visible light driven hydrogen production on CdS@polydopamine/NiS photocatalyst

Abstract: The high-quality interfacial coupling and chemical bond are effectively instrumental for boosting photo-generated charge separation/transfer ability. Herein, the features of organic compound surface modification and Schottky-junction are simultaneously gathered in...

Circularly polarized luminescence: a themed collection

Abstract: Guest editors Jeanne Crassous, Lorenzo Di Bari, Wai-Yeung Wong and You-Xuan Zheng introduce this themed collection on circularly polarized luminescence.

Orthogonal Anthracene and Pyrene Derivatives for Efficient Pure Deep-Blue Organic Light-Emitting Diodes

Abstract: Two new deep-blue emitters based on anthracene and pyrene moieties (9,10-di(pyren-1-yl)anthracene (PyAnPy) and 1,1'-(2,6-di-tert-butylanthracene-9,10-diyl)dipyrene (PyTAnPy)) were designed and synthesized for application in highly efficient triplet-triplet annihilation (TTA)-based organic light-emitting diodes...

Insights on advanced substrates for controllable fabrication of photoanodes toward efficient and stable photoelectrochemical water splitting

Abstract: Conversion of solar energy into H2 by photoelectrochemical (PEC) water splitting is recognized as an ideal way to address the growing energy crisis and environmental issues. In a typical PEC cell, the construction of photoanodes is crucial to guarantee the high efficiency and stability of PEC reactions, which fundamentally rely on rationally designed semiconductors (as the active materials) and substrates (as the current collectors). In this review work, we start with a brief introduction of the roles of substrates in the PEC process. Then, we provide a systematic overview of representative strategies for the controlled fabrication of photoanodes on rationally designed substrates, including conductive glass, metal, sapphire, silicon, silicon carbide, and flexible substrates. Finally, some prospects concerning the challenges and research directions in this area are proposed.

Polymetallaynes and molecular metallaynes containing platinum, mercury and gold for optoelectronic and magnetic applications

Abstract: Polymetallaynes are a promising branch of metallopolymers, in which the introduction of metal building blocks to organic conjugated backbones leads to their unique skeletons and versatile properties. Notably, the chemical structures, geometric configurations and functional properties in these organometallic systems can be adjusted flexibly by the appropriate selection of metal centers, auxiliary ligands, or bridging spacers. In recent years, both one-dimensional and two-dimensional polymetallaynes have attracted considerable attention owing to their excellent electronic, optical and magnetic properties. Furthermore, the studies on molecular metallaynes provide substantial insights for the exploration of the structure-property-activity relationships in these organometallic acetylide-containing systems. The recent research progress of polymeric and molecular metallaynes containing platinum, mercury and gold is discussed in this article. A series of functional properties have been realized in these acetylide-containing compounds by the rational structural design and refined synthetic strategies, leading to their emerging applications including energy conversion, nonlinear optics, data storage and memory, as well as chemo/biosensing. What is the most favorite and original chemistry developed in your research group? Chemistry plays a key role in providing solutions to many of the challenges facing the world today. In particular, an understanding of chemistry is essential as the basis for medicine and public health, in addressing challenges such as global climate change, in providing sustainable sources of clean energy, and in maintaining the environment for the well-being of people. We aim at the cutting-edge research areas of photofunctional metal-organic molecules and polymers for optoelectronic and energy-related applications. Photofunctional molecular materials are considered as versatile materials for energy interconversions and optoelectronic/photonic applications, including electrical energy generation in organic solar cells (OSCs) and light generation in organic light-emitting diodes (OLEDs), as they offer a low cost, light weight and simple option for device fabrication. We have developed new synthetic methods to produce technologically useful materials (e.g., metallopolymers and metallophosphors) with specific functional roles. Such research clearly presents a promising way out of the worldwide energy problem. What is the most important personality for scientific research? Although there is no guarantee of success and practical gains in doing research, it is my belief that our efforts will get harvest if we work hard and do not give up. Patience, diligence, perseverence and confidence are the prerequisites for the successful research study. Besides, there are many good research opportunities in the Greater Bay Area and the Mainland by collaborating with the top researchers there in various joint projects, which would create more impact cases for the betterment of our society. How do you get into this specific field? Could you please share some experiences with our readers? Global energy consumption is depleting non-renewable fossil fuels at a staggering rate. Mankind's life quality depends on the development of renewable energy sources. As such, our research is dedicated to advancing technologies in energy conversion and translating light into electricity and electricity into light, hence contributing to the sustainability of human life on earth. So, we moved to work in this field by developing molecular materials for fabricating OSCs and OLEDs. These developments are complementary in that solar devices produce energy, and light-emitting devices save energy. How do you supervise your students? I was deeply inspired by the passion of my former supervisors for research when I did my PhD and postdoctoral studies. Their ability to captivate me with the inherently intriguing essence of science and to share with me their passion for the discipline was particularly rewarding for me. Certain qualities I developed, such as an analytic mind and creative thinking, are the key factors that help me handle my job well nowadays. I hope that young talents will make full use of the word “Chem-is-try” to try more in chemical research and explore new interesting science topics. Besides, students can realize the magic of scientific research which probes them to achieve more.

Circularly polarized (CP) white organic light-emitting diode (WOLED) based on chiral organo-Sm3+ complex

Abstract: Using the designed chiral [Sm(tta)3(D-phen)] as emitter, the first example of chiral organo-Ln3+-based CP-WOLED with both attractive white-light efficiencies (EQEMax = 1.55% and CEMax = 1.61 cd/A) and high dissymmetry...

Efficient Red Organic Light Emitting Diodes of Nona Coordinate Europium Tris(β-diketonato) Complexes Bearing 4'-Phenyl-2,2':6',2''-terpyridine.

Abstract: Two novel nona coordinated Eu(III) complexes [Eu(btfa)3(Ph-TerPyr)] (Eu-1) and [Eu(NTA)3(Ph-TerPyr)] (Eu-2) have been synthesized and characterized. The structure of the complexes was elucidated by density functional theory (DFT) methods. The experimental photophysical properties of the complexes were investigated and complemented with theoretical calculations. Effective energy transfer (ET) pathways for the sensitized red luminescence is discussed. The complexes were tested as emitting layers (EML) in OLEDs. At the optimum doping concentration of 4 wt%, the double-EML OLEDs of Eu-1 exhibited red electroluminescence (EL) with an EQE of 4.0% and maximum brightness (B) = 1179 cd/m2, maximum current efficiency (ηc) = 5.64 cd/A, maximum power efficiency (ηp) = 4.78 lm/W with very low turn-on voltage (Vturn-on) = 3.6 V at the current density (J) of 10 mA/cm2. Interestingly, the double-EML OLEDs of Eu-2 at the optimum concentration of 3 wt%, displayed an outstanding EL performance with EQE of 7.32% and B = 838 cd/m2, ηc = 10.19 cd/A, ηp = 10.33 lm/W, and Vturn-on = 3.1 V at J =10 mA/cm2. The EL performance of this device is among the best reported for devices incorporating a europium complex as a red emitter.

Design of AIEgen‐based porphyrin for efficient heterogeneous photocatalytic hydrogen evolution

Abstract: Tetraphenylethylene (TPE)-conjugated porphyrin TPE-ZnPF is synthesized in high yield and characterized by single-crystal X-ray diffraction. The propeller-shaped TPE groups not only enable exceptional aggregation-induced emission (AIE) in the solid state but also abolish the strong π-π stacking of porphyrin moieties and thus prohibit aggregation-caused quenching (ACQ). TPE-ZnPF aggregates feature long-lived photoexcited states, which subsequently suppress non-radiative decay channels and enhance emission intensity. Moreover, its aggregates show more efficient light-harvesting ability due to the Förster resonance energy transfer from the TPE energy donor to the porphyrin core energy acceptor, well-defined nanosphere morphology, and more efficient photoinduced charge separation than the porphyrin Ph-ZnPF, which possesses ACQ and agglomerated morphology. As a result, an excellent photocatalytic hydrogen evolution rate (ηH2) of 56.20 mmol g‒1 h‒1 is recorded for TPE-ZnPF aggregates, which is 94-fold higher than that of the aggregates of Ph-ZnPF (0.60 mmol g‒1 h‒1) without the TPE groups.