Cheng-Hsuan Lai

Iridium-complex-functionalized Fe3O4/SiO2 core/shell nanoparticles: a facile three-in-one system in magnetic resonance imaging, luminescence imaging, and photodynamic therapy.

Highly uniform Fe3O4/SiO2 core/shell nanoparticles functionalized by phosphorescent iridium complexes (Ir) have been strategically designed and synthesized. The Fe3O4/SiO2(Ir) nanocomposite demonstrates its versatility in various applications: the magnetic core provides the capability for magnetic resonance imaging and the great enhancement of the spin-orbit coupling in the iridium complex makes it well suited for phosphorescent labeling and simultaneous singlet oxygen generation to induce apoptosis.

Excited-state intramolecular proton transfer molecules bearing o-hydroxy analogues of green fluorescent protein chromophore.

o-Hydroxy analogues, 1a-g, of the green fluorescent protein chromophore have been synthesized. Their structures and electronic properties were investigated by X-ray single-crystal analyses, electrochemistry, and luminescence properties. In solid and nonpolar solvents 1a-g exist mainly as Z conformers that possess a seven-membered-ring hydrogen bond and undergo excited-state intramolecular proton transfer (ESIPT) reactions, resulting in a proton-transfer tautomer emission. Fluorescence upconversion dynamics have revealed a coherent type of ESIPT, followed by a fast vibrational/solvent relaxation (<1 ps) to a twisted (regarding exo-C(5)-C(4)-C(3) bonds) conformation, from which a fast population decay of a few to several tens of picoseconds was resolved in cyclohexane. Accordingly, the proton-transfer tautomer emission intensity is moderate (0.08 in 1e) to weak (∼10(-4) in 1a) in cyclohexane. The stronger intramolecular hydrogen bonding in 1g suppresses the rotation of the aryl-alkene bond, resulting in a high yield of tautomer emission (Φ(f) ≈ 0.2). In the solid state, due to the inhibition of exo-C(5)-C(4)-C(3) rotation, intense tautomer emission with a quantum yield of 0.1-0.9 was obtained for 1a-g. Depending on the electronic donor or acceptor strength of the substituent in either the HOMO or LUMO site, a broad tuning range of the emission from 560 (1g) to 670 nm (1a) has been achieved.

Highly luminescent, homogeneous ZnO nanoparticles synthesized via semiconductive polyalkyloxylthiophene template

We report here the preparation of ZnO/polythiophene-based conjugated polymer nanocomposites that retain especially highly luminescent (Φf > 0.5) and semiconductive properties without the addition of capping agents. The as-prepared nanocomposites have been well characterized by UV-Vis, fluorescence, TEM/EDS, etc. This method provides several advantages in terms of homogeneous size distribution, good dispersion and intense, distinctive band-gap emission free from defect trapping. The results thus demonstrate the great potential of alkyloxyl modified polythiophene-based nanocomposites in the field of optoelectronics and microelectronics devices.

Cu(I) chelated poly-alkoxythiophene enhancing photovoltaic device composed of a P3HT/PCBM heterojunction system

We report the Cu+ chelated poly-alkoxythiophene (P3MEET) enhancement of a solar cell device consisting of a P3HT/PCBM heterojunction system. Compared to the reference P3HT/PCBM system, a consistent increase of conversion efficiency of 0.9% via an apparent increase of incident-photon-to-current conversion efficiency (IPCE) is achieved upon optimizing the ratio of P3MEET-Cu+ : P3HT : PCBM to 1 : 9 : 6 by weight, in which 7.5 mol% of CuBr is added upon synthesizing P3MEET-Cu+. The results, in combination with relevant data gathered from atomic force microscopy, cyclic voltammetry, and electrochemical impedance spectra, lead us to conclude that the match in redox potential and increase of ordering of the film upon doping P3MEET-Cu+ play two key roles in enhancing the performance.

All chemically deposited, annealing and mesoporous metal oxide free CdSe solar cells

A facile, all chemical bath deposition process to fabricate CdSe (quantum dots) solar cells is presented, which is free from mesoporous metal oxides, high-temperature annealing and ligand encapsulation, showing great perspective in cost-effectiveness, reproducibility and flexibility.

Design and Synthesis of Trithiophene-Bound Excited-State Intramolecular Proton Transfer Dye: Enhancement on the Performance of Bulk Heterojunction Solar Cells

In an aim to harvest UV-near-visible (360-440 nm) photons as well as to increase the morphology in the bulk heterojunction solar cells, we report herein the strategic design, synthesis, and characterization of a novel excited-state intramolecular proton-transfer dye, 3-hydroxy-2-(5-(5-(5-(3-hydroxy-4-oxo-4H-chromen-2-yl)thiophen-2-yl)thiophen-2-yl)thiophen-2-yl)-4H-chromen-4-one (FT), which bears two key functional groups, namely 3-hydroxychromone chromophore and trithiophene backbone and is then exploited into the blends of regioregular poly(3-hexylthiophene) (RR-P3HT) and phenyl-C(61)-butyric acid methyl ester (PCBM). FT acts as an excellent UV-near visible absorber, which then undergoes excited-state intramolecular proton transfer, giving rise to an orange-red proton-transfer emission that was reabsorbed by P3HT via a Forster type of energy transfer. Introduction of FT to P3HT/PCBM blend films also improves the morphology of phase separated structure, in particular, enhances the interaction of P3HT chains and the hole mobility. In this work, under the optimized condition of P3HT: PCBM:FT of 15:9:2 in weight ratio, the best performance of the device B-FT2 revealed consistent enhancements in the efficiency (eta) 4.28% and short-circuit current (J(sc)) 12.53 mAcm(-2), which are higher than that (3.68% and 10.28 mAcm(-2)) of the best performance of the control device B (P3HT:PCBM 15:9 in weight ratio) by 16 and 22%, respectively.