Duc Nghia Nguyen

Unusually High‐Performing Organic Field‐Effect Transistors Based on π‐Extended Semiconducting Porphyrins

Highly conjugated porphyrin derivatives, H(2) TP and ZnTP, are synthesized. J-aggregations of the H-aggregated dimeric porphyrin pairs are clearly observed by their single crystal structures that facilitate slip-stacked charge transport phenomenon. In particular, their SC-FETs show the highest field-effect mobilities of 0.85-2.90 cm(2) V(-1) s(-1) . Furthermore, the ZnTP-based OPT displays a dramatic photoinduced current enhancement with a high photoresponsivity of 22 000 A W(-1) under a very low light intensity (5.6 m W cm(-2) ).

Surface modification and functionalization of carbon nanotube with some organic compounds

In this work the surface modification and functionalization of carbon nanotubes (CNTs) were investigated. CNTs were firstly treated by acid mixture H2SO4/HNO3 to introduce the carboxylic group onto the surface of CNTs. This carboxylic group was used as reaction precursor in the functionalization. Two functional groups, dodecylamine (DDA) and 3-aminopropyl triethoxysilane (3-APTES), were successfully covalently attached to CNTs. The functionalized CNTs were characterized by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, differential scanning calorimetry and thermal gravimetric analysis (DSC/TGA) and transmission electron microscopy (TEM) methods. The CNTs attached to the organofunctional moieties have greater versatility for further utilization in different application fields such as biology, nanocomposites, solar energy, etc.

Glass transition of PCBM, P3HT and their blends in quenched state

In this work the thermal behavior with the glass transition of phenyl-C61-butyric acid methyl ester (PCBM), poly(3-hexylthiophene) (P3HT) and their blends was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Both TGA and DSC measurements show that PCBM contains around 1% residual solvent in the crystalline structure. The glass transition of PCBM, P3HT and their blends was determined by quenching techniques. The quenched state of the materials has a strong effect on the glass transition of the materials, especially in the case of PCBM. In all blend compositions only one glass transition temperature was found. These results indicate that PCBM and P3HT are thermodynamically miscible in all blend compositions.

CdTe and CdSe quantum dots: synthesis, characterizations and applications in agriculture

This paper highlights the results of the whole work including the synthesis of highly luminescent quantum dots (QDs), characterizations and testing applications of them in different kinds of sensors. Concretely, it presents: (i) the successful synthesis of colloidal CdTe and CdSe QDs, their core/shell structures with single- and/or double-shell made by CdS, ZnS or ZnSe/ZnS; (ii) morphology, structural and optical characterizations of the synthesized QDs; and (iii) testing examples of QDs as the fluorescence labels for agricultural-bio-medical objects (for tracing residual pesticide in agricultural products, residual clenbuterol in meat/milk and for detection of H5N1 avian influenza virus in breeding farms). Overall, the results show that the synthesized QDs have very good crystallinity, spherical shape and strongly emit at the desired wavelengths between ~500 and 700 nm with the luminescence quantum yield (LQY) of 30–85%. These synthesized QDs were used in fabrication of the three testing fluorescence QD-based sensors for the detection of residual pesticides, clenbuterol and H5N1 avian influenza virus. The specific detection of parathion methyl (PM) pesticide at a content as low as 0.05 ppm has been realized with the biosensors made from CdTe/CdS and CdSe/ZnSe/ZnS QDs and the acetylcholinesterase (AChE) enzymes. Fluorescence resonance energy transfer (FRET)-based nanosensors using CdTe/CdS QDs conjugated with 2-amino-8-naphthol-6-sulfonic acid were fabricated that enable detection of diazotized clenbuterol at a content as low as 10 pg ml−1. For detection of H5N1 avian influenza virus, fluorescence biosensors using CdTe/CdS QDs bound on the surface of chromatophores extracted and purified from bacteria Rhodospirillum rubrum were prepared and characterized. The specific detection of H5N1 avian influenza virus in the range of 3–50 ng μl−1 with a detection limit of 3 ng μL−1 has been performed based on the antibody-antigen recognition.

Highly sensitive fluorescence resonance energy transfer (FRET)-based nanosensor for rapid detection of clenbuterol

In this study we investigate the fabrication of a fluorescence resonance energy transfer (FRET)-based nanosensor for the detection of clenbuterol. The nanosensor consists of CdTe quantum dots coated by clenbuterol recognizable agent naphthol and diazotized clenbuterol. Changes in maximal photoluminescent intensities of the nanosensor were utilized to measure clenbuterol concentrations. The maximal photoluminescent intensities of the nanosensor were found to decrease with increasing clenbuterol concentrations, following a linear correlation. We have successfully fabricated a nanosensor for detection of clenbuterol with sensitivity up to 10pgml 1 .

Effect of molecular packing of zinc(II) porphyrins on the performance of field-effect transistors

The charge-transport phenomena of organic conjugated materials have been intensively investigated because of the potential applications of these materials in electronics and optoelectronics. Among these applications, organic field-effect transistors (OFETs) fabricated from either thin films or well-defined single crystals as charge-transporting layers are the most promising electronic devices. In this work, the effect of molecular packing on the performance of OFETs is investigated through the fabrication and characterization of devices based on zinc(II) porphyrins TPZ and TBPZ. The field-effect mobility of the transistors is found to increase with decreasing intermolecular distance, attributable to greater overlap of ? orbitals among close-packed molecules and thereby enhance the charge transport.

Molecular engineering of carbazole functionalized ruthenium dyes for efficient dye-sensitized solar cells

A new ruthenium complex, coded HMP-12, incorporating an antenna ligand composed of the sequential connection of a conjugated segment and carbazole hole-transport moiety was synthesized. This dye exhibits a lower energy metal-to-ligand charge transfer (MLCT) band centered at 536 nm with a high molar absorption coefficient of 21.43×103 M−1 cm−1. Nanocrystalline ZnO dye-sensitized solar cells employing HMP-12 show good conversion efficiency (4.46%). It was found that the difference in light-harvesting properties between Rut-B1, HMP-11 and HMP-12 is associated mainly with dye structure. The power conversion efficiency of solar cells based on HMP-11 is 4.11% while the Rut-B1 delivered a lower efficiency of 3.57% under the same device fabrication and measuring conditions.

Rapid and sensitive detection of clenbuterol using a fluorescence nanosensor based on diazo coupling mechanism

In this paper, the fluorescence resonance energy transfer (FRET) effect has been used for fabrication of nanosensor for the detection of clenbuterol. In the nanosensor, the CdTe quantum dots (QDs) are the donors while the acceptor is the super-macromolecule formed by the diazoation coupling mechanism between diazo clenbuterol and naphthylethylene diamine. Changes in fluorescence intensities of nanosensor were used to determine the clenbuterol concentration. We have successfully fabricated a nanosensor for detection of clenbuterol sensible to clenbuterol concentration of 10−12 g ml−1.

Photocrosslinkable π-conjugated cruciform molecules for electronic/optoelectronic applications

The development of organic field-effect transistors (OFETs) and organic photovoltaic cells (OPV) has seen much progress using solution-processable organic semiconductors, which can combine high charge transport mobility, stability and patternability. In this work, we report on the design and synthesis of a new type of photopatternable π-conjugated cruciform molecule. These molecules are capable of photopatterning by virtue of photopolymerization of the reactive end-groups (pentadien or acrylate). Their solubility is very good for solution processing. Transistor devices using these molecules provided a maximum field-effect mobility of 3.7×10−3 cm2 V−1 s−1 as well as a high current on/off ratio. Remarkably, it was found that their charge carrier mobilities were well-maintained, even after the photocrosslinking process.