Yun Chen

Bio: Yun Chen is an academic researcher from National Cheng Kung University. The author has contributed to research in topics: HOMO/LUMO & Triphenylamine. The author has an hindex of 29, co-authored 159 publications receiving 3126 citations. Previous affiliations of Yun Chen include Soochow University (Suzhou) & University of Tokyo.

Synthesis and Electrochemical and Optical Properties of Novel Poly(aryl ether)s with Isolated Carbazole and p-Quaterphenyl Chromophores

Abstract: Two novel poly(aryl ether)s consisting of alternate isolated chromophores, poly[oxy-[9-(2-ethylhexyl)carbazole-3,6-oxy]-3,3‘ ‘‘-dicyano-p-quaterphenyl-4,4‘ ‘‘-ylene] (PCNCA) and poly[oxy-[9-(2-ethylhexyl)carbazole-3,6-oxy]-3,3‘ ‘‘-bis(trifluoromethyl)p-quaterphenyl-4,4‘ ‘‘-ylene] (PCFCA), have been synthesized and characterized. The synthesized polymers are completely soluble in common organic solvents such as tetrahydrofuran (THF) and chloroform. The two poly(aryl ether)s exhibit good thermal stability with 5% weight loss temperature above 400 °C in nitrogen. The UV/vis and photoluminescent spectra of the two polymers show maximum peaks at around 318−319 and 407−413 nm in the film state, respectively. The HOMO and LUMO energy levels of these polymers, which have been measured by cyclic voltammetry, are −5.23, −3.25 eV for PCNCA and −5.41, −3.32 eV for PCFCA. The p-quaterphenyl segments are regarded as electron transporting units because the electron withdrawing substitutes (cyano and trifluoromethyl) enh...

Photoluminescent and electrochemical properties of novel poly(aryl ether)s with isolated hole-transporting carbazole and electron-transporting 1,3,4-oxadiazole fluorophores

Abstract: Four novel poly(aryl ether)s consisting of alternate isolated hole-transporting carbazole and electron-transporting 1,3,4-oxadiazole segments were synthesized from the nucleophilic displacement reaction of bis(fluoride) monomers with bis(phenol) monomers. These poly(aryl ether)s are soluble in common organic solvents and exhibit good thermal stability with 5% weight loss temperature above 400 °C under a nitrogen atmosphere. The photoluminescent (PL) spectra and quantum yields of these polymers are dependent on the composition of the two isolated fluorophores. The formation of exciplex in P3 was observed in the film and solution state and resulted in the lower quantum yield. The quantum yields of P4 in solutions can increase from 0.04 of P3 to 0.36, due to the dilute effect, by introducing the inert bisphenol A segments. However, the PL spectra of P4 only showed a little blue shift in the film state. This means the interchain exciplex still dominated the emission of polymeric films. The HOMO and LUMO energ...

Dynamic stability improvement of an integrated offshore wind and marine-current farm using a flywheel energy-storage system

Abstract: This study presents a control scheme using a flywheel energy-storage system (FESS) to simultaneously achieve power-fluctuation mitigation and dynamic-stability enhancement of an offshore wind farm (OWF) and marine-current farm (MCF) connected to a power grid. The performance of the studied OWF is simulated by an equivalent aggregated 80-MW doubly-fed induction generator (DFIG), while the characteristics of the studied MCF are simulated by an equivalent aggregated 40-MW squirrel-cage induction generator. A proportional–integral–derivative (PID) damping controller of the proposed FESS which is connected to the common AC bus of the OWF and MCF is designed by using modal control theory to contribute effective damping characteristics to the studied OWF and MCF under different operating conditions. A frequency-domain approach based on a linearised system model using eigenvalue analysis is performed. A time-domain scheme based on a non-linear system model subject to disturbance conditions is also carried out. It can be concluded from the simulation results that the proposed FESS combined with the designed PID damping controller can effectively stabilise the studied OWF and MCF under various disturbance conditions. The inherent power fluctuations injected to the power grid can also be effectively mitigated by the proposed control scheme.

Fluorescence Development of Latent Fingerprint with Conjugated Polymer Nanoparticles in Aqueous Colloidal Solution

Abstract: Poly(p-phenylenevinylene) (PPV) nanoparticles in aqueous colloidal solution have been prepared via a modified Wessling method, with the addition of surfactant. The fluorescent colloidal solution was used as the developing solution to develop the fingerprints on different substrates. The developing process was accomplished simply by immersing the substrates into developing solution and then taking out, followed by rinsing with deionized water. The initial study about the fingerprints on the adhesive tapes showed that the developing solution is very effective in fluorescence development on both fresh and aged visible fingerprints; and such an effect was negligibly affected by treating the fingerprints with water or other organic solvents, whether before developing or after. Further study on latent fingerprints (LFPs) demonstrated that PPV nanoparticles in colloidal solution have high sensitivity in developing fingerprints to give very clearly fluorescent patterns. At least 6 months of storage of the colloid...

Chemical sensors based on amplifying fluorescent conjugated polymers.

Abstract: The field of chemical sensing is becoming ever more dependent upon novel materials. Polymers, crystals, glasses, particles, and nanostructures have made a profound impact and have endowed modern sensory systems with superior performance. Electronic polymers have emerged as one of the most important classes of transduction materials; they readily transform a chemical signal into an easily measured electrical or optical event. Although our group reviewed this field in 2000,1 the high levels of activity and the impact of these methods now justify a subsequent review as part of this special issue. In this review we restrict our discussions to purely fluorescence-based methods using conjugated polymers (CPs). We further confine our detailed coverage to articles published since our previous review and will only detail earlier research in this Introduction to illustrate fundamental concepts and terminology that underpin the recent literature.

Synthesis of Light-Emitting Conjugated Polymers for Applications in Electroluminescent Devices

Abstract: A review was presented to demonstrate a historical description of the synthesis of light-emitting conjugated polymers for applications in electroluminescent devices. Electroluminescence (EL) was first reported in poly(para-phenylene vinylene) (PPV) in 1990 and researchers continued to make significant efforts to develop conjugated materials as the active units in light-emitting devices (LED) to be used in display applications. Conjugated oligomers were used as luminescent materials and as models for conjugated polymers in the review. Oligomers were used to demonstrate a structure and property relationship to determine a key polymer property or to demonstrate a technique that was to be applied to polymers. The review focused on demonstrating the way polymer structures were made and the way their properties were controlled by intelligent and rational and synthetic design.

Dendron-Mediated Self-Assembly, Disassembly, and Self-Organization of Complex Systems

Abstract: Dendron-mediated self-assembly, disassembly, and self-organization of complex systems have been investigated. The most ideal building blocks would need to display shape persistence in solution and in the solid state, since only this feature provides access to the use of complementary methods of structural analysis. Most supramolecular dendrimers are chiral even when they are constructed from nonchiral building blocks and are equipped with mechanisms that amplify chirality. This poses additional challenges associated with the understanding of the structural origin of chirality in different supramolecular structures through combinations of structural analysis methods. While many supramolecular structures assembled from dendrimers and dendrons resemble some of the related morphologies generated from block-copolymers, they are much more complex and are not determined by the volume ratio between the dissimilar parts of the molecule.