Absorbance Spectra Of Dyes Research Articles

Luminescence and sensitivity enhancement of oxygen sensors through tuning the spectral overlap between luminescent dyes and SiO2@Ag nanoparticles

AbstractWe utilized a seeded growth method to synthesize SiO2@Ag NPs with tunable plasmonic resonance peak to investigate the effect of spectral overlap between the SiO2@Ag plasmonic resonance spectrum and the PtTFPP‐based oxygen sensors’ absorbance spectra on luminescence enhancement and performance optimization. An organic silicate was used as the matrix. Oxygen‐sensors were produced by directly casting the mixture of NPs and dyes with silicate gels onto glass slides. Oxygen‐induced spectral response of the PtTFPP was obtained as the analytical signal. Our results show that when the plasmonic resonance spectrum of SiO2@Ag has a maximum wavelength overlap with the absorbance spectra of dyes, the Stern‐Volmer slopes were enhanced by almost an order of magnitude. At 21% O2, the Stern‐Volmer plot achieved a maximum seven‐fold increase over the oxygen sensor without the metal‐enhanced luminescence. Our results also show that 10% wt NPs is the optimal amount for the PtTFPP‐SiO2@Ag based oxygen sensors that can eliminate self‐quenching and the NRET process. These data confirm that the spectral overlap between the dyes and noble metal NPs and how to eliminate self‐quenching and the NRET process are vital to high‐sensitive oxygen sensors. We have also shown that our fabrication process of these oxygen sensors is repeatable.

Effect of organic dyes on the performance of ZnO based dye-sensitized solar cells

The present paper reports the synthesis and performance study of ZnO based Dye-sensitized solar cells (DSSC). ZnO nanorods were fabricated by sol-gel technique using. Three types of DSSCs were fabricated by two different classes of organic dyes using, namely xanthenes, anthocyanins and a mixed-dye with equal proportion mixture of xanthenes and anthocyanins. The absorbance spectra of dyes were compared with performances of the cells. The parasitic resistances of the cells were determined from the I–V characteristics of the cells and various parameters of DSSCs like Ideality factor, Fill factor and Energy conversion efficiency were determined. Among the three kinds of dyes tested, the efficiency of cell with mixed dye was intermediate but its value was found to be higher than the average efficiency of cells with two individual dyes. This is due to the improvement in ideality factor of the cell.

SYNTHESIS AND PHOTOSENSITIVE PERFORMANCE OF NANOSTRUCTURED ZnO/DYE HYBRID FILM FOR ENERGY CONVERSION

The ZnO film prepared by doctor blade method are highly porous in presence of structure directing agent PEG and then can be easily sensitized by various molecules. In the present work, the nanostructured ZnO /dye hybrid film prepared by doctor blade method has been investigated in conductivity and photoconductivity measurements in view of applications in dye-sensitized solar cells (DSSC) and in optoelectronics, since electron transport in these devices plays a decisive role for the electron collection efficiency and therefore for the overall efficiency. The absorption of ZnO film sensitized by Rose Bengal dye (RB) has been studied by UV spectroscopy which indicates that after the dye is adsorbed on the ZnO electrode, its absorption spectra showed red-shift in the peak position compared to the absorbance spectra of dye in ethanol. Highly porous ZnO films are found to have high dark conductivity, probably because of a higher n-doping, which is due to higher concentration of Zn atoms in the film. On the other hand, ZnO /RB hybrid film is found to show a much higher sensitivity to illumination with visible light in photoconductivity measurements due to a higher absolute photoconductivity and lower conductivity in the dark.

Photocatalytic Decolorization of Dyes for Nano-Structures of Titanium Dioxide (TiO<sub>2</sub>) Films

Application of nano-structures of titanium dioxide (TiO2) films on photocatalytic activities of organic dyes was investigated. Methylene blue (MB) and cation yellow X-Gl 200% were used as organic dyes to observe decolorization. The TiO2 films were prepared on glass substrate by reactive DC magnetron sputtering. The films had thickness, grain size and root mean square surface roughness of 300 nm,  40 nm and  4 nm, respectively. Coated-TiO2 on glass and uncoated TiO2 (glass) were immerged in MB and cation yellow dyes solution. A weak ultraviolet (UV) A at peak wavelength  365 nm and intensity of 0.19 mW/cm2 was irradiated. Absorbance spectra of dyes at different UV irradiation time were observed. The efficiency of decolorization increased as UV irradiation time increased. At UV irradiation time 120 hours, coated-TiO2 showed higher percentage decolorization of MB than uncoated-TiO2 about 64%. While, at UV irradiation time 48 hours, coated-TiO2 showed higher percentage decolorization of cation yellow than uncoated-TiO2 about 84%. Under photocatalysis process of TiO2 films, at the end, MB (about 120 hours) and cation yellow dyes (about 48 hours) change to be colorless.