Dong-Jin Qian

Metal-mediated coordination polymer nanotubes of 5,10,15,20-tetrapyridylporphine and tris(4-pyridyl)-1,3,5-triazine at the water–chloroform interface

Coordination polymer nanotubes have been prepared by using the Hg2+-mediated co-assembly of two ligands, tetrapyridylporphine (TPyP) and tris(4-pyridyl)-1,3,5-triazine (TPyTa), at the water-chloroform interface.

Reducing Properties of Polymers in the Synthesis of Noble Metal Nanoparticles

The use of different polymers as both reducing agent and stabilizers has gained wide attention for its simplicity and impressive efficiency when being applied to synthesis noble metal nanoparticles. This article concludes reports published recently on specific polymers used to reduce metal precursors and protect metal nanoparticles. The control of the size and morphology of nanoparticles tuned by changing the polymer structure and experiment conditions has been concluded and the possible redox mechanisms of different polymer-metal systems have been illustrated.

Spectroscopic studies of the multiporphyrin arrays at the air–water interface and in Langmuir–Blodgett films

Abstract We describe the spectroscopic studies of the monolayers and Langmuir–Blodgett (LB) films of tetrapyridylporphyrin (TPyP), its mixture with a phospholipid (DPPTE) and the (2DPPTE–)Cd 2+ –TPyP multiporphyrin arrays. Red-shift of the porphyrin Soret band was 23–27 nm in the monolayers and LB films of TPyP or the TPyP–2DPPTE mixture; while it was only 3–11 nm in the monolayers and LB films of the (2DPPTE–)Cd 2+ –TPyP multiporphyrin arrays. This difference has been attributed to the weakened TPyP–TPyP interaction in the multiporphyrin arrays. Immersion of an intercalation phospholipid layer in the matrix of the monolayers and LB films of TPyP or the Cd 2+ –TPyP multiporphyrin array further reduced this interaction and made it possible for the fabrication of three-dimensional layered multiporphyrin arrays. The fluorescence spectra of TPyP in the LB films of the (2DPPTE–)Cd 2+ –TPyP multiporphyrin array were also quite different from those in the solutions and TPyP(–2DPPTE) LB films. The average molecular orientation angle θ between the mean porphyrin plane and the substrate surface was approximately 26–31° for the LB films of the TPyP and the Cd 2+ –TPyP multiporphyrin array, and approximately 35–38° for the LB films of the TPyP–2DPPTE and 2DPPTE–Cd 2+ –TPyP multiporphyrin array.

Synthesis and assembly of gold nanoparticle-doped polymer solid foam films at the liquid/liquid interface and their catalytic properties.

Gold nanoparticle-doped poly(2-vinylpyridine) (P2VP) microcapsules and foam films were synthesized and assembled at the P2VP chloroform solution/HAuCl(4) aqueous solution interface at 25 °C. It was found that Au nanoparticles with the average diameter of 2.1 nm were homogeneously embedded in and adsorbed on the walls of the capsules and foams, the nanoparticles were composed of Au(0) and Au(III) with the molar ratio of about 75/25, and the mass percent of Au elements was measured to be 19.65%. The formation of the nanostructures was attributed to the self-assembly of P2VP at the liquid/liquid interface, the simultaneous reduction of AuCl(4)(-) ions by a small amount of ethanol in the chloroform and adsorption of AuCl(4)(-) ions. After irradiated by UV-light for 1h, the average diameter of the nanoparticles was found to be 2.2 nm, and the AuCl(4)(-) ions were transformed to Au(0) completely. The catalytic performance of these composite nanostructures were evaluated by using the reduction of 4-nitrophenol (4-NP) by potassium borohydride in aqueous solutions. The catalytic activity was very high in the first cycle, decreased rapidly and slightly in the second and third cycles, respectively, due to the aggregation of some nanoparticles, and stabilized after the third cycle.

A hydrogen biosensor made of clay, poly(butylviologen), and hydrogenase sandwiched on a glass carbon electrode

A hydrogen gas (H(2)) biosensor was developed in which hydrogenase (H(2)ase) was immobilized and sandwiched between two layers of a montmorillonite clay and poly(butylviologen) (PBV) mixture on a glass carbon electrode. The immobilized PBV efficiently enhanced the electron transfer among the electrode, H(2)ase, and methyl viologen in solution. Both PBV and methyl viologen acted as the electron carrier in the clay-PBV-H(2)ase modified electrode. The clay-PBV-H(2)ase electrode catalyzed the oxidation of H(2) to protons (H(+)) with the electrons being transferred by viologen groups to the electrode. The activation energy of this process was 38+/-2 kJ/mol at pH 7. The catalytic current of the clay-PBV-H(2)ase electrode increased linearly when exposed to increasing concentrations of H(2) gas. In contrast, this electrode showed no activity when exposed to three combustible compounds, namely, carbon monoxide, methane and methanol. The optimum pH range for the oxidation of H(2) by the clay-PBV-H(2)ase electrode was from 7 to 10. Electron transfer process in the clay-PBV-H(2)ase electrode is discussed.

Templateless Infrared Heating Process for Fabricating Carbon Nitride Nanorods with Efficient Photocatalytic H2 Evolution

The bottom-up fabrication of carbon nitride nanorods is realized through the direct infrared heating of dicyandiamide. The approach requires no templates or extra organics. The controlled infrared heating has a major influence on the morphology of the obtained carbon nitrides. The precursors assemble into carbon nitride nanorods at low power levels, and they grow into nanoplates at high power levels. The formation mechanism of the carbon nitride nanorods is proposed to be a kinetically driven process, and the photocatalytic activity of the carbon nitride nanorods prepared at 50% power for hydrogen evolution is about 2.9 times that of carbon nitride nanoplates at 100% power. Structural, optical, and electronic analysis demonstrates that the enhancement is primarily attributed to the elimination of structural defects and the improved charge-carrier separation in highly condensed and oriented carbon nitride nanorods.

Monolayers of a series of viologen derivatives and the electrochemical properties in Langmuir-Blodgett films

Abstract The effects of a hydrocarbon layer on the electrochemical property of viologens were studied by immobilizing a series of symmetrically bis-alkylated viologens (C n V, n =12–18) on an indium–tin oxide electrode surface by using the Langmuir–Blodgett (LB) method. The electrochemical properties of viologen LB films were studied for different parameters; length of alkyl chains, the nature of counterions in the subphase, and deposition model (X- and Z-type LB films). Cyclic voltammetric measurements indicated that π-complex dimers were easily formed for viologens that had a ‘thin’ hydrocarbon barrier (CH 2 =11 and 13) in Z-type LB films, but formed with difficulty for viologens that had a ‘thick’ barrier (CH 2 ≥15) and for all viologens in X-type LB films. A weak peak current and a small surface coverage of ‘electroactive’ viologens were observed for X-type LB films. For every viologen-modified In and Sn oxide (ITO) electrode, the reduced potential was negatively shifted; the thicker the barrier, the larger the shift.

Biomolecular device for photoinduced hydrogen production

In order to construct a molecular device for photoinduced hydrogen production, a model has been designed and first results in the framework of this multicomponent system are presented. This device should involve Photosystem 1, Photosystem 2 and hydrogenase in a modular configuration which allows to combine appropriate proteins from various-mainly thermophilic-organisms. Parts of this modular system can be easily exchanged and separately characterized and optimized. Here the optimization of one component of this device, the hydrogenase from Thiocapsa roseopersicina, is shown. The isolated hydrogenase was deposited as Langmuir-Blodgett (LB) film on quartz glass and ITO electrodes, respectively, and its activity was measured in dependence of counter ions, presence of oxygen and number of immobilized layers. While poly-L-lysine or poly-butyl-viologen as counter ion in the subphase stabilized the protein complex on quartz glass (up to about 30 mN/m surface pressure), Ca 2+ resulted in a dramatic activity loss at a much lower surface pressure (15 mN/m). Also, the presence of even smallest amounts of oxygen or an excess amount of protein on an ITO electrode resulted in a significant decrease of the hydrogen production as did the increase in the number of layers-as shown by electrochemical measurements.

Photoinduced hydrogen evolution by use of porphyrin, EDTA, viologens and hydrogenase in solutions and Langmuir?Blodgett films

Abstract Photoinduced hydrogen evolution was investigated by use of a zinc porphyrin, EDTA, viologens and hydrogenase (H2ase) in the solutions and Langmuir–Blodgett (LB) films. An almost linear increase of hydrogen evolution rate was observed with the increase of H2ase concentrations from 1 to 5 μg / ml . For the zinc porphyrin, EDTA and methyl viologen, when their concentrations increased to a given value, hydrogen evolution did not show obvious increase. Phospholipid-porphyrin mixed LB films were prepared and used as photosensitizer for the photoinduced hydrogen evolution. Spectroscopic studies of the deoxygenated solutions indicated a “new” absorption band (in the solutions) or sharp peaks (in the LB films) when the sample solutions were irradiated, which was ascribed to the formation of an excited complex of porphyrin–EDTA (or -EDTA breakdown products). This excited complex was unstable to air.

Langmuir-Blodgett films of pyridyldithio-modified multiwalled carbon nanotubes as a support to immobilize hydrogenase.

Pyridylthio-modified multiwalled carbon nanotubes (pythio-MWNTs) have been prepared by a reaction of the oxidized MWNTs with S-(2-aminoethylthio)-2-thiopyridine hydrochloride. The obtained pythio-MWNTs nanocomposites formed stable floating monolayers at the air-water interface, which were transferred onto substrate surfaces by the Langmuir-Blodgett (LB) method. Compositions and morphologies of the LB films were characterized by absorption, Raman, X-ray photoelectron spectra as well as by scan electron microscopy and atomic force microscopy. These pythio-MWNTs LB films were then used as a support to immobilize hydrogenase (H(2)ase) to form bionanocomposite of pythio-MWNTs-H(2)ase. Cyclic voltammograms for indium tin oxide electrode covered with the pythio-MWNTs-H(2)ase films were investigated in both Ar and H(2) saturated 0.05 M KCl electrolyte solutions at pH from 4.0 to 9.0. A reversible redox couple of [4Fe-4S](2+/1+) clusters of H(2)ase was recorded when the pH value was 6.0 and 9.0, with reduction and oxidation potentials appearing at about -0.70 and -0.35 V vs Ag/AgCl, respectively. It was revealed that the H(2)ase was of high catalytic activity and strong stability in the LB films of pythio-MWNTs-H(2)ase. Hence, we suggested that the present bionanocomposites could be used as heterogeneous biocatalyst to catalyze reversible reaction between protons and H(2), resulting in potential applications in biohydrogen evolution and H(2) biofuel cells.