Enhanced photovoltaic performance of silver@titania plasmonic photoanode in dye-sensitized solar cells

In the present investigation, silver@titania (Ag@TiO2) plasmonic nanocomposite materials with different Ag content were prepared using a simple one-step chemical reduction method and used as a photoanode in high-performance dye-sensitized solar cells. Transmission electron microscopic images revealed the uniform distribution of ultra-small Ag nanoparticles with a particle size range of 2–4 nm on the TiO2 surface. The incorporation of Ag on the TiO2 surface significantly influenced the optical properties in the region of 400–500 nm because of the surface plasmon resonance effect. The dye-sensitized solar cells (DSSCs) assembled with the Ag@TiO2-modified photoanode demonstrated an enhanced solar-to-electrical energy conversion efficiency (4.86%) compared to that of bare TiO2 (2.57%), due to the plasmonic effect of Ag. In addition, the Ag nanoparticles acted as an electron sink, which retarded the charge recombination. The influence of the Ag content on the overall efficiency was also investigated, and the optimum Ag content with TiO2 was found to be 2.5 wt%. The enhanced solar energy conversion efficiency of the Ag@TiO2 nanocomposite makes it a promising alternative to conventional photoanode-based DSSCs

Palm-based nonionic surfactants as emulsifiers for high internal phase emulsions

In the present study, a series of as-synthesized palm-based nonionic surfactants with various hydrophile–lipophile balance values were successfully synthesized. The critical micelle concentration and the Gibbs energy of the surfactants were determined and discussed. For the first time, the surfactants were used to stabilize three-component olein oil-in-water high internal phase emulsions, with an oil volume fraction of 0.85, and which were easily prepared by one-pot homogenization. Proof of high stability was confirmed by the satisfactory rheological profiles and further enhanced by a three-month storage exercise at an elevated temperature which showed no significant physical and rheological changes. These results suggest that low concentration of the surfactants efficiently stabilized the emulsions with high content of oil. Based on the optical micrograph observation, an average droplet size of less than 10 μm increased with increasing ethylene oxide chain length and temperature. The varying degree of viscosity resulted from the various ethylene oxide chain lengths of the surfactants. The hydration efficacy of the emulsions was examined in vivo using a corneometer. The impressive hydration efficacy of olein oil suggests that it could well be a potential moisturizing lipid which might interest dermatologists

Microstructure of brushite crystals prepared via high internal phase emulsion

For the first time, various microstructures of calcium phosphates were successfully synthesized using a high internal phase emulsion process. The crystals were possessed in the brushite crystalline phase. The morphology of the crystals was influenced by the variables related to the emulsion process route, which consisted of flakes, dendrites and particulates structures

Aerosol assisted chemical vapour deposited (AACVD) of TiO2 thin film as compact layer for dye-sensitised solar cell

Compact TiO2 has been introduced onto the surface of an indium tin oxide glass slide (ITO), using an aerosol-assisted chemical vapour deposition method. This serves as a blocking layer for a dye-sensitised solar cell (DSSC). The thickness of the compact TiO2 could be controlled by deposition time. X-ray diffraction and Raman spectroscopy analyses reveal that the compact TiO2 is made up of mixed anatase and rutile phases. The field emission scanning electron microscopy image displays a pyramidal morphology of the compact TiO2. A layer of P25 paste was then smeared onto the compact TiO2-modified ITO, using the doctor's blade method. A post-treatment procedure was applied to remove the contaminants from the prepared hybrid film, by immersing in a hydrochloric acid solution. The photoelectrochemical measurements and J–V characterisation of the hybrid film show an approximately fourfold increase in photocurrent density generation (114.22 µA/cm2), and approximately 25% enhancement of DSSC conversion efficiency (4.63%), compared to the acid-treated P25 paste alone (3.68%)

Silver/titania nanocomposite-modified photoelectrodes for photoelectrocatalytic methanol oxidation

Silver deposited titania (Ag/TiO2) nanocomposite thin films were fabricated by the simple sonochemical deposition of Ag on preformed aerosol-assisted chemical vapor deposited TiO2 thin films. The photelectrocatalytic performance of a newly fabricated Ag/TiO2-modified photoelectrode was studied for methanol oxidation under simulated solar AM 1.5G irradiation (100 mW/cm2). The Ag/TiO2-modified photoelectrode showed a photocurrent density of 1 mA/cm2, which is four times that of an unmodified TiO2 photoelectrode. The modification of Ag on the TiO2 surface significantly enhanced the photoelectrocatalytic performance by improving the interfacial charge transfer processes, which minimized the charge recombination. Density functional theory (DFT) calculation studies revealed that methanol could be easily adsorbed onto the Ag surfaces of Ag/TiO2 via a partial electron transfer from Ag to methanol. The newly fabricated Ag/TiO2-modified photoelectrode could be a promising candidate for photoelectrochemical applications

Inorganic Nanostructures Decorated Graphene

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Effect of calcination temperature on performance of ZnO nanoparticles for dye-sensitized solar cells

The photovoltaic performances of ZnO-based dye-sensitized solar cells (DSSCs) were studied using ZnO nanoparticles prepared via the sol–gel method in gelatin medium at different calcination temperatures. The effects of the calcination temperature on the size, surface area, photoluminescence properties, and dye adsorption ability of ZnO nanoparticles were investigated. The results showed that the size of the nanoparticles increased and the surface area decreased with an increase in the calcination temperature. In addition, the oxygen vacancies of the nanoparticles increased with an increase in the calcination temperature. Moreover, although the surface area of the nanoparticles prepared at 600 °C was lower than that of those prepared at 500 °C, their dye adsorption abilities were the same, and both were higher than that of those prepared at 700 °C. Electrochemical impedance spectroscopy and open-circuit voltage decay measurements were carried out to investigate the cell functions. The DSSC based on ZnO nanoparticles calcined at 600 °C exhibited the highest conversion efficiency because of its higher dye adsorption ability and lower recombination rate compared to the others.This work was supported by a High Impact Research Grant from the Ministry of Higher Education of Malaysia. A. Moradi Golsheikh would like to thank Iran Nanotechnology Initiative Council

In-situ formation of electron acceptor to inhibit charge separation of photo-electrochemical sensor of dopamine-based CdS/Au/GQDs

A versatile photo-electrochemical (PEC) sensor protocol was established to quantitatively monitor dopamine (DA) levels by utilizing a triple interconnected structure of cadmium sulfide (CdS) modified with gold and graphene quantum dots (Au/GQDs). The introduction of Au and GQDs on the photocatalytic active center of CdS act as a charge separation mediator and photosensitizer, respectively, which are favorable for charge separation and transportation and PEC conversion. When the CdS/Au/GQDs photoelectrode was utilized for DA sensing in a weak alkaline solution, DA was oxidized and converted to poly(dopamine) (PDA), which possesses abundant benzoquinone (BQ) groups that act as electron acceptors. Consequently, the electron acceptors formed in-situ on the surface of the photoelectrode, reducing the anodic photocurrent signal. Under the optimal conditions, the photocurrent decreased when the DA concentration increased in a dynamic working range from 0.1 to 350 µM and with a limit of detection (LoD) of 0.0078 μM. Herein, the proposed strategy involving photoelectron transfer between the electron acceptor and semiconductor provides a new and versatile protocol for PEC sensor development

Enhanced electrocatalytic performance of cobalt oxide nanocubes incorporating reduced graphene oxide as a modified platinum electrode for methanol oxidation

Herein, we report a facile hydrothermal method for the preparation of cobalt oxide nanocubes incorporating reduced graphene oxide (rGO–Co3O4 nanocubes) for electrocatalytic oxidation of methanol. The synthesized rGO–Co3O4 nanocubes were characterized using transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and Raman techniques. The electrochemical behavior of an rGO–Co3O4 nanocube modified electrode was studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. The electrocatalytic performances of rGO–Co3O4 nanocube-modified electrodes with different wt% of GO were investigated in relation to methanol oxidation in an alkaline medium. The rGO–Co3O4 nanocube modified electrode showed enhanced current density due to oxidation of methanol when compared to the bare Pt, rGO, and Co3O4 nanocube modified electrodes. The optimal GO content for an rGO–Co3O4 nanocube-modified electrode to achieve a high electrocatalytic oxidation of methanol was 2 wt%, and it showed an anodic peak current density of 362 μA cm−2

Facile synthesis of graphene via direct water-sodium dodecylbenzenesulfonate exfoliation

In this study, a mild, one-step electrochemical exfoliation was demonstrated for the synthesis of graphene with the assistance of water and a surfactant, particularly sodium dodecylbenzenesulfonate and sodium dodecyl sulphate. Different types of water-surfactant solutions in different concentrations could influence the exfoliation of graphite rods. From one to several layers of graphene flakes (with a thickness of approximately 1 nm) could be produced directly after sonication. AFM images showed that the flake diameters from this source were typically small. Raman and IR spectroscopic analyses of the dispersed phase suggested that the exfoliation of graphene sheets was accomplished. The flakes were also characterized using field emission scanning electron microscopy, X-ray diffraction, and cyclic voltammetry techniques. Further improvements in this methodology may pave the way to develop green, cost-effective, and large-scale production methods for graphene sheets