Kongchang Chen

A colorimetric and fluorescent chemodosimeter: fluoride ion sensing by an axial-substituted subphthalocyanine

An axially substituted subphthalocyanine (SubPc) was used as a selective chemodosimeter by the coordination of fluoride ion to the boron center. The UV-vis and fluorescence spectroscopic properties of the dosimetric system were studied. The results indicate that the SubPc is a sensitive and selective colorimetric and fluorescent dosimeter to fluoride ions.

Luminescent properties and photo-induced electron transfer of naphthalimides with piperazine substituent

Abstract Novel piperazine substituted naphthalimide model compounds 2-methyl-6-(4-methyl-piperazin-1-yl)-benzo[ de ] isoquinoline-1,3-dione ( NA1 ), 2-methyl-6-(4,4-dimethyl-piperazin-1-yl)-benzo[ de ] isoquinoline-1,3-dione iodide (NA2) and 2-methyl-6-(4-methyl-piperazin-1-yl)-benzo[ de ] isoquinoline-1,3-dione hydrochloride ( NA3 ) were synthesized. Fluorescence spectra data of NA1 showed the fluorescence quantum yields plot of NA1 versus pH value is typically characteristic of pH probe. The approximate free energy of charge separation (Δ G cs ) for the excited singlet state and the fluorescent lifetime data of NA1 showed that the fluorescence of 4-amino-1,8-naphthalimide fluorophore can be quenched by the PET process from the alkylated amine donor to the naphthalimide moiety. The PET path can be obviously switched off either by the protonation (as for NA3 ) or quarternization (as for NA2 ) of the alkylated amine donor.

Luminescent properties of copolymeric dyad compounds containing 1,8-naphthalimide and 1,3,4-oxadiazole

Abstract Several new 1,8-naphthalimide dyad compounds connected with 1,3,4-oxadiazole at different substitution positions were synthesized, in which there are two compounds to be copolymerized with N -vinyl carbazole to form a single-layer electroluminescence (EL) device film, which consists of electron-transporting unit (oxadiazole), hole-transporting unit (PVK) and emitting unit. The photoemission and electroemission of these dyad compounds are near 540 nm, with a maximum luminance of 350 cd/m 2 and luminous efficiency of 3.02 1m/W at 14 V.

Cyanine dye acting both as donor and acceptor in heterojunction photovoltaic devices

The use of cyanine dyes in thin-film heterojunction photovoltaic devices is investigated. It is demonstrated that a carbocyanine dye acts as donor in conjunction with buckminsterfullerene (C60). Due to its high electron affinity, the cyanine can also act as acceptor when using copoly(dicyano-phenylvinylene-triphenylamine) as donor. H and J aggregates of the cyanine dye play a determining role both in the photocurrent spectrum and in the open circuit voltage. Open-circuit voltages ranging from 0.25 to 1.28 V are obtained for devices using the cyanine as donor and acceptor, respectively. When the cyanine layer is sandwiched between the polymer donor and the C60 acceptor, incident photon to current conversion efficiencies greater than 10% are observed. The possibility of using cyanine dyes at the same time as donors and acceptors is a promising strategy to improve conversion efficiency.

Synthesis of novel dyes derived from 1-ethyl-3-cyano-6-hydroxy-4-methyl-5-amino-2-pyridone

The properties and the diazotisation process of 1-ethyl-5-cyano-6-hydroxy-4-methyl-5-amino-2-pyridone were described. The conditions of the coupling reaction were also discussed and a series of new azo dyes using 1-ethyl-5-cyano-6-hydroxy-4-methyl-3-amino-2-pyridone as diazo components were synthesized. The absorption properties of these new azo dyes were investigated in various solvents and the mixture solvent of chloroform/DMSO with different volume ratios.

Novel linear and tri-branched copolymers based on triphenylamine for non-doping emitting materials

Abstract Novel linear and tri-branched copolymers with triphenylamine and cyano groups in the main chain were synthesized by a concise route and an environment-friendly procedure without metal catalyst. They show strong fluorescence in solid state and can be used as non-doping emitter to fabricate emitting diodes. The single-layer electroluminescence devices with PVK or PEDOT buffer layer have been made with these copolymers as non-doping red–orange emitter, electron-transporting as well as hole-transporting material. The single-layer devices show preliminary results with maximum efficiency of 0.052% and EL wavelengths around 614 nm.

Photodegradation of cyanine and merocyanine dyes

The photodegradation kinetics for some cyanine and merocyanine dyes was studied by UV-visible spectroscopy and the results show that the fading process follows quasi-first-order or zero-order kinetics in acetonitrile. In other experiments, the principal photodegradation products of the dyes were identified with the aid of GC/MS, and it was found that those cyanine dyes holding a positive charge had higher photostability than the corresponding merocyanines. The relationship between photostability and chemical structure was established using PM3 and AMI MO calculations. Experimental results in this regard suggest that the species associated with the photodegradation of cyanine dyes may be the semioxidized dye free radical cation, Dye(dagger). The transient absorption spectra of Dye(dagger) were determined by nanosecond pump and probe spectroscopy

Synthesis of novel cyanine–fullerene dyads for photovoltaic devices

Two novel cyanine–fullerene dyads have been synthesized by means of the Prato reaction from the corresponding cyanine-aldehyde, N-methylglycine and C60. As well as a thorough characterization using MS-TOF, 1H-NMR, 13C-NMR and elemental analysis, the optical and electrochemical properties of these two dyads were investigated. The fluorescence of the cyanine–fullerene dyads was quenched efficiently as compared to the pristine cyanine, which we have attributed to photo-induced electron transfer from the cyanine to C60. The redox potentials obtained by cyclic voltammetry provide evidence that this electron transfer is energetically favorable. Single and double layer photovoltaic devices were fabricated to evaluate the photovoltaic properties of the dyad. The energetic conversion efficiency of the double layer device exceeds 0.1% under 3.1 mW cm−2 white light irradiation. The results show that cyanine–fullerene dyads are promising materials for photovoltaic devices.

Photostability of novel copolymers functionalized with laser dyes based on modified rhodamine 6G and 1,8-naphthalimide

Abstract Modified rhodamine 6G molecules (Rh-Al or Rh-Aln) with polymerizable double bonds had been copolymerized with 1,8-naphthalimide derivatives. In copolymers PRNAM, naphthalimide moieties are connected to rhodamine moieties at nitrogen atom of rhodamine moiety, and in copolymers PRNM naphthalimide moieties are connected to rhodamine moieties at ester group of rhodamine moiety. We report on their photostability in liquid solution and in solid film. The photodegradation kinetics of novel copolymers functionalized with laser dyes based on modified rhodamine 6G and 1,8-naphthalimide has been studied by UV–VIS absorption spectroscopy. The results show that the rates of the photofading reactions of these novel copolymers follow quasi-first-order. The photostability of the copolymers functionalized with laser dyes in solid films is better than that in solutions. The different type of the copolymer shows the different photostability.

Photocatalytic degradation of acid azo dyes in aqueous TiO2 suspensionII. The effect of pH values

The photocatalytic degradation of H/K acid derived 30 dyes in aqueous TiO2 suspension follows apparent first-order kinetics. The site near the azo bond (C–N=N– bond) is the attacked area in the photocatalytic degradation process, whilst the TiO2 photocatalytic destruction of the C–N(=) bond and –N=N– bonds leads to fading of the dyes. The pH effect on the TiO2 photocatalytic degradation of the H/K acid derived azo dyes varies with the different structure of the dyes. Hydroxyl radicals play an essential role in the fission of the C–N=N– conjugated system in azo dyes in TiO2 photocatalytic degradation.