Elaboration of conjugated polymer nanowires and nanotubes for tunable photoluminescence properties

International audiencePrototypal photoluminescent nanofibres of poly-(p-phenylene-vinylene) (PPV) were prepared by the wetting template method in polycarbonate nanoporous membranes with an easy all-in solution polymer precursor route. Both nanowires and nanotubes were obtained by varying the dilution of the polymer precursor in methanol prior to thermal conversion. PPV nanotubes exhibit unique features, such as blue-shifted emission at 2.80 eV, higher quantum yield, and longer fluorescence lifetime with respect to PPV films. These effects are attributed to the cancellation of interchain interactions that are consistent with nanoscale tubular structures formed from weakly interacting and short polymer chain segments. The synthesis of these objects opens up perspectives for tunable photoluminescence properties in the blue spectral range and for biochemical applications

Ultrafast photoluminescence spectroscopy of exciton-exciton annihilation in oligoaniline films with nanoscale ordering

The exciton dynamics and optical characteristics of blue-emitting N,N'-diphenyl-1,4-phenylene-diamine oligoaniline films have been determined. Transient photoluminescence experiments are consistent with internal quantum yields of 5.3% and 10.1% measured for oriented and nonoriented films, respectively. The data indicate a drastic dependence on nanoscale ordering which promotes photoluminescence quenching, a large annihilation rate, and fast exciton diffusion. Therefore, the emission properties can be controlled by the textural morphologies of the layers

Steady state and transient photoluminescence in poly-p-phenylene vinylene films and nanofibers

International audienceWe report in this paper experimental data on steady state and transient photoluminescence of poly-p-phenylene vinylene in the form of nanofibers prepared with a template method and converted at 110 degrees C. Results are compared to those obtained from films of different thicknesses converted at the same temperature. Data are analyzed by a model of bimodal distribution of conjugation lengths and the photoluminescence band shapes, evaluated in the framework of this model, are also presented

Ultrafast photoluminescence spectroscopy of exciton-exciton annihilation in oligoaniline films with nanoscale ordering

The exciton dynamics and optical characteristics of blue-emitting N,N'-diphenyl-1,4-phenylene-diamine oligoaniline films have been determined. Transient photoluminescence experiments are consistent with internal quantum yields of 5.3% and 10.1% measured for oriented and nonoriented films, respectively. The data indicate a drastic dependence on nanoscale ordering which promotes photoluminescence quenching, a large annihilation rate, and fast exciton diffusion. Therefore, the emission properties can be controlled by the textural morphologies of the layers

Microwave-assisted synthesis of multi-walled carbon nanotubes for enhanced removal of Zn(II) from wastewater

Removal of toxic metals is one of the biggest challenges in ensuring safe water for all as well as protecting the environment. Novel multi-walled carbon nanotubes (MCNTs) have been successfully synthesised by microwave techniques and improved to be an outstanding adsorbent for the removal of Zn(II) from wastewater. The adsorption of Zn(II) was studied and optimized as a function of pH, initial Zn(II) concentration, MCNT dosage, agitation speed, and adsorption time. In order to investigate the dynamic behavior of MCNTs as an adsorbent, the kinetic data were modeled using pseudo-first-order and second-order kinetic models. Different thermodynamic parameters, viz., ∆H°, ∆S° and ∆G° have also been evaluated and it has been found that the adsorption was feasible, spontaneous and endothermic in nature. Statistical analysis reveals that the optimum conditions for the highest removal (99.9 %) of Zn(II) are at pH 10, a MCNT dosage 0.05 g, an agitation speed and time of 160 rpm and 60 min, respectively, with an initial concentration of 10 mg/L. On the basis of the Langmuir model, qm was calculated to be 90.9 mg/g for microwave-synthesized MCNTs. Our results proved that MCNTs can be used as an effective Zn(II) adsorbent due to their high adsorption capacity as well as the short adsorption time needed to achieve equilibrium. Hence, MCNTs serve an important role in the removal of heavy metals from wastewater