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Several natural dyes have been extracted from tropical fruit shells such as Musa aromatica and Citrus medica var Lemon fruit shells. The resulting dyes have been used as sensitizer at dye sensitized solar cell (DSSC). The main pigments, which are carotenoids, was obtained by extraction and purification at dark room. Ethanol and water are used as solvents. The dyes have been characterized through UV–Vis spectrophotometer. The thin film of TiO2 anatase has been sintered at 450°C to enhance film compactness. According to the experimental results, the DSSC conversion efficiency which has been prepared by carotenoid dye from Musa aromatica fruit shell extract is 0.21%, 0.614 V of open-circuit voltage (VOC), 0,280 of short-circuit current density (JSC) mA/cm2, 56 μW of maximum power (Pmax) and 0.43 of fill factor (FF). Then, the DSSC conversion efficiency which has been prepared by carotenoid dye from Citrus medica var Lemon fruit shell extract is 0.05%, 0.460 V of VOC, 0.093 mA/cm2 of JSC, 14 μW of Pmax and 0.44 of FF. The measurement of I-V curve demonstrated that carotenoid was potential component as sensitizer for DSSC.

The aim of this study is to analyze dye electronic properties of anthocyanin aglycones to be used as photosensitizers for TiO2solar cells. The dye properties will be examined by the density functional theory (DFT) method at IEF-PCM(UFF)/B3LYP/6-31+G(d,p) levels under ethanol and water environments. The results show that the position of LUMOs of all dyes lying over TiO2ECBwill facilitate good electron transfer while their HOMOs, which are lower than the electrolyte redox potential energy, can facilitate good oxidized-dye regeneration. Flavilium cation dye is the best anthocyanidin aglycone due to the best electron injection spontaneity of -0.807 eV as well as the highest open circuit voltage of 1.669 V. On the other hand, quinonoidal base dye gives the best light harvesting efficiency of 69.24% due to the best oscillating strength character. Moreover, the solvent effect is the important aspect regarding the dye oxidation potential stabilization as well as the electron injection driving force.

Nano composite MWCNT-ZnO thin films have been synthesized to investigate their methanol sensing properties. MWCNTs have a large surface area, many adsorption site, are sensitive to their chemical environmental, and can be operated at room temperature. While zinc oxide was popular as gas sensor because its easy to fabricate, fast response, easy to control their morphology, and has unique properties depend on their size and shape. In this study, combination of MWCNT and ZnO were made to get their advantages. These nano composites were prepared with weight percent ratio 63:37. MWCNT-ZnO were synthesized by reflux method at 197°C in ethylene glycol. Heat treatment at 300°C were done to obtain powder of nano composite. X-ray diffraction (XRD) and scanning electron microscope were used to investigate the crystal phase and morphology of nano composite. Sensing behavior was investigated at 100°C to 300°C. The best response of 200 ppm methanol occurred at 300°C.

The morphology of porous anodic alumina (PAA) formed by anodizing in inorganic electrolytes is reported. An impure aluminum was anodized in sulfuric acid, phosphoric acid and chromic acidat room temperature with a constant applied potential 2 – 30 V. The formation of porous anodic alumina was carried out by one and two steps anodization. It is clearly noted that anodizing impure aluminum at room temperature provide higher kinetic of oxide dissolution compared to oxide growth. Two steps anodizing aluminum in sulfate electrolyte always resulted in random porous alumina, while phosphate electrolyte provided strong anodization producing irregular porous alumina with average diameter of 61.6 nm. Two steps anodizing aluminum in chromate electrolyte produce better pore ordering with relatively large size pore distributions. The average pore diameter of alumina increases linearly with applied voltage, with proportionality factor lp 0.83 nmV-1. Annealing the sample increased the interpore distance, removed stresses providing lower activation energy for pore formation.

Metal oxide semiconductors materials such as zinc oxide (ZnO) are often used in the fabrication of chemoresistive gas sensors, but ZnO materials require high operating temperatures to operate. In another side, carbon nanotubes (CNT) have many distinct properties and recently have been exploited as the next generation of sensors, including chemoresisitive type gas sensors. This study was aimed to investigate the performance of MWNT-ZnO composites as SO2 gas sensitive layer. By fabricate composites of MWNT and ZnO, have been obtained a sensitive layer that can be utilized for application as gas sensitive layer with relatively lower operating temperature. A sensitive layer of MWNT-ZnO based composites have been successfully fabricated on a alumina substrate and several characterization techniques has been performed, i.e. XRD, SEM and EDS to study the formed crystalline phase, the morphology of the nanostructures, and the elemental composition of synthesized composites. MWNT-ZnO sensitive layer was tested by exposure to SO2 gas at various operating temperatures and gas concentration. From the performance testing results, it could be found that the composite materials have a prospective as a gas sensor at lower operating temperature with short response time and good sensitivity.