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Open access

M. Khalid Hossain, M. F. Pervez, M. Jalal Uddin, S. Tayyaba, M. N. H. Mia, M. S. Bashar, M. K. H. Jewel, M. A. S. Haque, M. A. Hakim and Mubarak A. Khan

Abstract

Porous photoanodes of dye-sensitized solar cells (DSSCs) can adsorb specific type of natural or organic dyes. Adsorption of the dye results in a change of the structural, morphological and optical characteristics of the photoanode. In this work, we present a comparative study on the adsorption effect of natural dye (Curcuma Longa sp.) on the structural, morphological and optical properties of mesoporous titanium dioxide (TiO2) photoanode on indium tin oxide (ITO) coated glass. A number of investigations including XRD, UV-Vis spectroscopy, EDS, and SEM were carried out to observe the variations due to adsorbed dye on TiO2 surface. XRD characterization revealed the effect of dye adsorption on specific surface area (SSA), crystallite size, and morphological index (MI). In this case, increasing SSA with decreasing particle size was found for both dye adsorbed and dye free DSSC photoanode samples. Also, the MI and SSA were found to be directly and inversely proportional to the crystallite size respectively. UV-Vis-NIR spectroscopy showed that dye adsorption changes the light absorption, transmittance, and optical bandgap of the photoanode. Average atomic mass percentage of titanium (Ti) and oxygen (O) obtained from EDS analysis proved the presence of TiO2 in the mesoporous photoanode. In SEM images, significant morphological changes of mesoporous TiO2 surface appeared because of dye adsorption.

Open access

Damian Wojcieszak, Michal Mazur, Danuta Kaczmarek and Jaroslaw Domaradzki

Abstract

In this paper, structural and photocatalytic properties of TiO2 nanopowders doped with 1 at.% of cerium, cobalt, cooper and iron have been compared. Nanoparticles were synthesized by sol-gel technique and characterized by SEM, EDS and XRD methods. Moreover, their photocatalytic activity was determined based on decomposition of methyl orange. Results were compared with undoped powder. The structural investigations have revealed that all prepared nanopowders were nanocrystalline and had TiO2-anatase structure. The average size of crystallites was ca. 4 nm to 5 nm. The distribution of the dopant was homogenous in case of all manufactured powders. Moreover, for TiO2 doped with Co, Ce and Cu, aggregation effect was not as large as for TiO2:Fe. The results of photocatalytic decomposition showed that self-cleaning activity of all prepared nanopowders was higher as compared to undoped one. Due to the efficiency of these reactions (after 5 hours) nanopowders can be ordered as: TiO2:Co > TiO2:Ce > TiO2:Cu > TiO2:Fe > TiO2.

Open access

Maria Arshad, Abbas Khan, Zahoor H. Farooqi, Muhammad Usman, M. Abdul Waseem, Sayyar Ali Shah and Momin Khan

Abstract

Due to their potential application in various fields of science and technology, the eco-friendly bio-synthesis of silver (Ag) nanoparticles (NPs) is a growing area for researchers. In this study, we report the green synthesis of Ag nanoparticles and their characterization by using various techniques. For the preparation of Ag particles, aqueous plant extract of ailanthus altissima was used as a reducing medium for Ag+ ions of silver nitrate to Ag0. UV-Vis spectrophotometry was used to trace the formation of Ag particles by noting their surface plasmon resonance peaks (400 nm to 440 nm). Fourier transform infrared spectroscopy (FT-IR) was employed to reveal the chemical composition of Ag nanoparticles which were capped by plant extract. Scanning electron microscopy (SEM) was used to get the lattice image, morphology and average size of Ag particles. The average size distribution of Ag NPs dispersed in aqueous media was also measured using dynamic light scattering (DLS). It was found that DLS results are in good agreement with those obtained from SEM. The synthesized particles were then subjected to the antibacterial and antifungal activities by studying them against various species, such as bacillus cereus, staphylococcus aureus, pseudomonas aeruginosa, E. coli and A. parasiticus, A. niger and A. flavus fungi. It was noted from the growth curves of both bacteria and fungi that in the presence of silver nanoparticles they show more in-zone growth as compared to the plant extract.

Open access

Marta Przychodnia, Ryszard Czajka and Wojciech Koczorowski

Abstract

The present paper aims at describing a source designed and constructed to generate an organic molecular beam under ultrahigh vacuum conditions. The presented construction solution of the evaporation source allows for independent deposition of three different kinds of molecules. The probability of molecules fragmentation is minimized by using a thermocouple being in contact with a molecular crucible, which enables precise temperature control. In addition, cleanness and molecular beam density are monitored using a quadrupole mass spectrometer and quartz microbalance, respectively. The operational parameters of the molecular source are optimized and deposition rates are measured for the coronene molecule in the sublimation temperature range between 430 K and 460 K. The analysis of scanning tunneling microscope images of the Si(1 1 1) 7 × 7 substrate covered with the sub-monolayer of coronene molecules and comparison with previously published data has been used for verification of the molecular source operation.

Open access

Yasemin Caglar, Saliha Ilican and Mujdat Caglar

Abstract

In this study, the effect of boron (B) incorporation into zinc oxide (ZnO) has been investigated. The undoped, 2 at.%. and 4 at.% B doped ZnO films were deposited on p-type silicon (Si) substrates by electrodeposition method using chronoamperometry technique. Electrochemical depositions were performed by applying a constant potentiostatic voltage of 1.1 V for 180 min at 90 °C bath temperature. To analyze the surface morphology, field emission scanning electron microscopy (FESEM) was used and the results revealed that while a small amount of boron resulted in smoother surface, a little more incorporation of boron changed the surface morphology to dandelion-like shaped rods on the whole surface. By using X-ray diffraction (XRD) analysis, the crystal structures of the films were detected and the preferred orientation of the ZnO, which exhibited polycrystalline and hexagonal wurtzite structure, changed with B doping. For the estimation of the optical band gap of obtained films, UV-Vis diffuse reflectance spectra (DRS) of the films were taken at room temperature and these data were applied to the Kubelka-Munk function. The optical band gap of ZnO narrowed due to incorporation of B, which was confirmed by red-shift.

Open access

Dnyaneshwar Shinde, Popat Tambade, Habib Pathan and Kisan Gadave

Abstract

A dye-sensitized solar cell (DSSC) was assembled using a dye 4-(3-chloro-1, 4-dioxo-1, 4-dihydronaphthalen-2-ylamino) benzoic acid with ZnO as a photoanode. It was synthesized using 2, 3-dichloro 1, 4-naphthoquinone and p-amino benzoic acid. The spectral features of the dye were analyzed in ethanol using experimental and computational methods. The theoretical investigations revealed that the synthesized dye may act as a sensitizer in DSSCs. The photoelectrochemical performance was tested under direct sunlight using a sandwich type DSSC. The photovoltaic data of the dye adsorbed on ZnO films indicated thepower conversion efficiency of 1.07 % under sunlight with a light intensity of 39 mW·cm-2.

Open access

G.S. Orudzhev, N.A. Ismayilova and V.N. Jafarova

Abstract

We have studied the band structure and the band gap closure of TlInSe2 under pressure in the range of 0 GPa to 21 GPa, by employing the first-principles method based on the density functional theory. We discuss the possible metallic transition in the tetragonal phase of TlInSe2 crystal. Our calculation results show that the value of the pressure at the crossover from the direct to the indirect gap is found to be 8 GPa. The “semiconductor-metal” transition is determined to occur at 14 GPa. The study of the pressure effect on the effective masses for semiconductor state shows that with increasing pressure, the effective masses of holes and electrons decrease and the anisotropy of effective masses of holes is weakening.

Open access

Agnieszka Banaszak-Piechowska, Kazimierz Fabisiak, Elżbieta Staryga and Kazimierz Paprocki

Abstract

The influence of diamond crystallinity and preferred orientation on electronic conductivity of synthetic diamond films grown by hot filament chemical vapor deposition (HFCVD) was investigated. The CVD diamond films of different morphologies and crystallite sizes varying from 36 nm to 67 nm, measured in h2 2 0i direction were considered. The charge transport mechanism in the diamond samples was studied using temperature dependent DC conductivity measurements. The obtained results showed that in the temperature range of 90 K to 300 K charge transport is realized via Variable Range Hopping (VRH, m = 1/4) mechanism. Using VRH model, the Mott parameters were evaluated i.e. density of states at Fermi level N(EF) (0.22 × 1015 eV-1·cm-3 to 1.7 × 1015 eV-1·cm-3), hopping energy W (43.5 meV to 142.3 meV) and average hopping distance R (1.49 × 10-5cm to 2.56 × 10-5cm). It was shown that above mentioned parameters strongly depend on diamond film preferential orientation.

Open access

M. Khalid Hossain, M.F. Pervez, S. Tayyaba, M. Jalal Uddin, A.A. Mortuza, M.N.H. Mia, M.S. Manir, M.R. Karim and Mubarak A. Khan

Abstract

Efficiency of dye-sensitized solar cell (DSSC) depends on several interrelated factors such as type and concentration of dye, type and thickness of photoelectrode and counter electrode. Optimized combination of these factors leads to a more efficient cell. This paper presents the effect of these parameters on cell efficiency. TiO2 nanoporous thin films of different thicknesses (5 μm to 25 μm) were fabricated on indium doped tin oxide (ITO) coated glass by doctor blading method and characterized by inverted microscope, stylus surface profiler and scanning electron microscope (SEM). Natural organic dye of different concentrations, extracted from turmeric, was prepared with ethanol solvent. Different combinations of dye concentrations and film thicknesses along with different types of carbon catalyst have been investigated by I-V characterization. The result shows that the cell made of a counter electrode catalyst material prepared by candle flame carbon combined with about 15 μm thick photoelectrode and 100 mg/mL dye in ethanol solvent, achieves the highest efficiency of 0.45 %, with open circuit voltage of 566 mV and short circuit current density of 1.02 mA/cm2.

Open access

Witold Posadowski, Artur Wiatrowski and Grzegorz Kapka

Abstract

Magnetron sputtered nickel and nickel oxide films have been studied for various applications. We may find, among others, these films in electrochromic display devices, in resistive type gas sensors, as metal electrodes in electronic devices, in solar thermal absorbers. Pure nickel films deposited using PVD technique possess good corrosion and wear resistant properties. Magnetron sputtering has several advantages in film deposition (in comparison to other methods) such as relatively low heating temperature of the deposited substrate during sputtering process, high energy of sputtered atoms (about 10 eV) at the substrate, which influences positively the films adhesion. From application point of view, the most valuable feature of these films is the possibility of scaling target dimensions, which makes feasible the deposition on a several square meter surfaces. The improvement of magnetron sputtering devices design may influence positively the optimization of the deposition technology and its efficiency. The thin nickel and nickel oxide films were prepared by pulsed magnetron sputtering using original type WMK magnetron device. Ni (99.9 %) has been used as a sputtering target of 100 mm in diameter and different thicknesses (3 mm, 5 mm, and 6 mm). The distance between the substrate and target was the same in all experiments and equal to 120 mm. Argon and oxygen gases were introduced during the reactive process through needle gas valves at a total pressure of 0.4 Pa. The sputtering power, sputtering pressure and oxygen partial pressure have been used as technological knobs for deposition processes. The helpful tool for controlling the pulsed magnetron sputtering process was the original parameter of supply (so called circulating power). Results from our experiments showed that the deposition of Ni films is possible even from targets of 6 mm thickness. Deposition rate increased proportionally with the sputtering power. The aim of this work is to use the acquired expertise to develop an efficient technology of thin nickel oxide layers for electrochromic systems.