Electrochromic properties and coloration mechanisms of sol-gel NiO-TiO2 layers and devices built with them

Electrochromic films of NiO-TiO2 with Ni concentration of 100, 90, 87, 83, 75, 66, 50 and 33 mol % have been obtained via the sol-gel route by dip coating technique using ethanolic sols of nickel acetate tetrahydrate (Ni(CH3COO)2•4H2O) and titanium n—propoxide Ti(C3H7O)4 precursors and sintered in air between 250 and 500 °C. Xerogels obtained by drying the sols have been studied up to 900 °C by thermal analysis (DTA/TG) coupled to mass and IR spectroscopy. The crystalline structure and morphology of the layers in the as deposited, bleached and colored states was determined by X-ray diffractometry, scanning electron microscopy and transmission electron microscopy. Their electrochromic properties have been studied in 1 M KOH aqueous electrolyte as a function of the layer composition, thickness and sintering temperature. Deep brown color with reversible transmittance changes have been obtained using cycling voltammetry and chronoamperometry processes. The best composition to get stable sols, a high reversible transmittance change and fast switching times (10 s) was obtained with double NiO-TiO2 layers 160 nm thick having 75 % Ni molar concentration, and sintered between 300 and 350 °C. The electrochromism of the layer was also studied in LiClO4-PC electrolyte. The mechanism of coloration and morphology transformation of the layer during cycling in 1 M KOH electrolyte are discussed in terms of an activation and degradation period. The nature of the ions involved in the coloration process has been studied using an Electrochemical Quartz Crystal Microbalance (EQCM). It was found that the activation period was associated with an increase of the mass of the layer after each cycle due to a gradual incorporation of OH- groups and the transformation of Ni(OH)2 into hydrated NiOOH giving the brown coloration as well as the formation of lattice water (OH- + H+→ H2O). The gradual change of the layer composition led to a much more open and fragile morphology that eventually allowed the incorporation of K+ ions and more water molecules associated with unusual large increase of the mass of the layer after each cycle and responsible for the degradation period. Finally, devices have been mounted and tested using either NiO-TiO2 layers or NiO-TiO2 layers covered with a thin anticorrosion dielectric layers as a working electrode together with CeO2-TiO2 layer or with a WO3 or a Nb2O5 cathodic layer acting as an active counter electrode. Also a new type of electrolyte based on KOH mixed with starch has been also developed and tested with complete windows.Elektrochrome Schichten bestehend aus NiO und TiO2 mit Ni-Gehalten von 33 bis 100 mol % wurden mit Hilfe des Sol-Gel-Prozesses durch Tauchbeschichtung aus alkoholischen Lösungen von Nickelacetat-Tetrahydrat (Ni(CH3COO)2•4H2O) und Titan-n-propoxid (Ti(O-CH(CH3)2)4) hergestellt und bei Temperaturen zwischen 250 und 500°C an Luft gesintert. Xerogele, die durch die Trocknung der Sole erhalten wurden, wurden bis zu einer Temperatur von 900 °C mittels thermischer Analysen (DTA/TG) in Verbindung mit Massen- und IR-Spektroskopie untersucht. Die kristalline Struktur und Morphologie der Schichten im abgeschiedenen, entfärbten und gefärbten Zustand wurde durch Röntgendiffraktrometrie, Elektronenmikroskopie und Transmissionselektronenmikroskopie untersucht. Die Analyse ihrer elektrochromen Eigenschaften erfolgte unter Verwendung eines wässrigen Elektrolyten (1 mol/l KOH) in Bezug auf die Schichtzusammensetzung, Dicke und Sintertemperatur. Eine dunkelbraune Farbe mit einer reversiblen Transmissionsänderung wurde durch Cyclovoltammetrie- und Chronoamperometrie-Prozesse erzielt. Die beste Zusammensetzung zur Erzielung stabiler Sole, einer hohen, reversiblen Transmissionsänderung und schneller Schaltzeiten (10 s) wurde mit NiO-TiO2 Doppelschichten (Dicke ca. 160 nm) mit einem Nickelgehalt von 75 mol % und für Sintertemperaturen zwischen 300 und 350°C erreicht. Die Elektrochromie der Schichten wurde darüber hinaus in einem LiClO4-Polycarbonat-Elektrolyten untersucht. Ein Mechanismus für Farb- und Morphologieänderung der Schicht während des Schaltzyklus in KOH-Elektrolyt wird im Sinne eines Aktivierungs- und Degradierungsprozesses diskutiert. Die Art der Ionen, die am Färbungsprozess beteiligt sind, wurde mit Hilfe der elektrochemischen Quarzmikrowaage (EQCM) untersucht. Es wurde beobachtet, dass der Aktivierungsprozess mit einer Zunahme der Schichtmasse nach jedem Zyklus aufgrund einer sukzessiven Aufnahme von OH-Gruppen und der Umwandlung von Ni(OH)2 in hydratisiertes NiOOH einhergeht, was schließlich eine braune Färbung und den Einbau von Wasser (OH- + H+  H2O) in das Kristallgitter zur Folge hat. Die allmähliche Veränderung der Schichtzusammensetzung führte zu einer porösen und zerbrechlichen Morphologie, die letztendlich eine Aufnahme von K+-Ionen und weiterer Wassermoleküle ermöglichte und für den einsetzenden Degradierungsprozess in Verbindung mit einem ungewöhnlich starken Anstieg der Schichtmasse nach jedem Zyklus verantwortlich ist. Schließlich konnten elektrochrome Fenster konstruiert werden, welche zum einen reine NiO-TiO2-Schichten, zum anderen NiO-TiO2-Schichten, die mit einer dünnen dielektrischen Antikorrosionsschicht versehen sind, als Arbeitselektrode enthielten. Als kathodische Gegenelektrode fungierten Schichten von CeO2-TiO2 bzw. WO3 oder Nb2O5. Des Weiteren erfolgte die Entwicklung eines neuen Elektrolyt-Typs basierend auf KOH in Verbindung mit Stärke, der an kompletten Fenstern getestet wurde

Brown coloring electrochromic devices based on NiO-TiO2 layers

Brown coloring electrochromic

Electrochromism of NiO-TiO2 sol gel layers

Films of NiO-TiO2 with Ni concentration of 100, 90, 87, 83, 75, 66, 50 and 33 mol% have been obtained via the sol-gel route by dip coating technique and sintered in air between 250 and 500°C using ethanolic sols of nickel acetate tetrahydrate (Ni(CH3COO)2·4H2O) and titanium n-propoxide (Ti(O-CH(CH3)2)4) precursors. Xerogels obtained by drying the sols have been studied up to 900°C by thermal analysis (DTA/TG) coupled to mass and IR spectroscopy. The crystalline structure and morphology of the layers in the as deposited, bleached and colored states were determined by X-ray diffractometry, scanning electron microscopy and transmission electron microscopy Their electrochromic properties have been studied in 1 M KOH aqueous electrolyte as a function of the layer composition, thickness and sintering temperature. Deep brown colour with reversible transmittance changes have been obtained using cycling voltammetry and chronoamperometry processes. The best composition to get stable sols, a high reversible transmittance change and fast switching times (<10 s) was obtained with double NiO-TiO2 layers 160 nm thick having 75% Ni molar concentration, and sintered between 300 and 350°C. The mechanism of coloration and morphology transformation of the layer during cycling are discussed in terms of an activation and degradation period. The results are in agreement with the accepted Bode model

Aqueous Extract Of Origanum Syriacum Inhibits Proliferation, Migration, Adhesion As Well As Erk1/2 Phosphorylation In Aggressive Breast Cancer

Background: Breast Cancer is one of the leading causes of cancer related mortality in women, both in Qatar and the world. Despite the available treatments the incidence of breast cancer is increasing. This highlights the need for new approaches for cancer. One of the fields that is gaining attention nowadays is herbal medicine. Herbs are known to have bioactive compounds that affect many diseases one of which is cancer. Origanum syriacum is an herb that is frequently used in Mediterranean region. Recently, it has been established that O. syriacum possess anti-proliferative activity in non-invasive breast cancer. Although it has some medicinal values, it remains poorly investigated. Here we tested the anti-tumor activity of O. syriacum extract (OSE) on the aggressive human breast cancer cell line, MDA-MB-231. Methods: The extract was prepared by dissolving the leaves of Origanum syriacum in water and drying it using rotarvapor. MDA-MB-231 cell viability was tested by MTT assay as well as trypan blue exclusion in the presence or absence of increasing concentrations of OSE. Scratch assay as well as Boyden-chamber were used to determine effect of OSE on migratory capacity. Furthermore, the ability of MDA-MB-231 to adhere to fibronectin was investigated using adhesion assay. Phosphorylated ERK1/2 was measured using Western blotting. Results: OSE reduced proliferation of MDA-MB-231 cells in a concentration and time dependent manner. The optimum concentration was determined according to the significance of decrease in viability. Also, in the presence of OSE, there was a decrease in migration of cells. Furthermore, a dose-dependent inhibition of adhesion was seen in MDA when treated with OSE. Moreover, preliminary results indicate that OSE decreased ERK1/2 phosphorylation in MDA-MB-231 cells. Conclusion: O. syriacum may be considered a supplementary drug for patients with malignant breast cancer. Further studies should be conducted to elucidate the molecular mechanism of the anti-cancer property exerted by OSE.qscienc

Coloration mechanisms of sol-gel NiO-TiO2 layers studied by EQCM

An electrochemical quartz crystal microbalance was used as a sensitive detector to analyse the mass changes occurring during the coloration/bleaching processes of sol—gel NiO—TiO2 electrochromic layers. Double layers were deposited on gold-coated quartz crystal electrode and sintered at 300 °C in air. The electrochemical process was studied in KOH electrolyte in the potential range -0.4 to +0.57 V vs. SCE during 650 CV cycles. The current density, charge and mass were found to increase with cycling. The shape of the mass spectrum is rather complex and changes continuously by cycling. The mass of the layer increases after each cycle slowly up to about the 150th cycle then it increases strongly after about the 250th cycle. It passes through a maximum around the 570th cycle with high amplitude variation within each cycle and then decreases fast without drastic change of the cathodic charge. Finally, a complete breakdown occurs around the 650th CV cycle impeding to record any further mass variation. The study is divided in two typical regions where the mechanism of coloration is found to change by cycling. During the first 150 CV cycles, the reversible change of the mass with the charge (increase in the anodic range for V>0.35 V vs. SCE and decrease in the cathodic range for V<-0.2 V) was related to exchange of OH- groups that involves a change of the oxidation state of Ni from 2+ to 3+ and vice versa leading to coloration and bleaching processes, respectively. For further cycling a model is proposed taking into account the incorporation of K(H2O)n+ ions in the hydrated structure of the layer. The irreversible increase of both the mass and charge exchanged during each cycle is interpreted as due to an increase of the amount of Ni(OH)2

Natural Dyes as Photosensitizers for Dye-sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) were assembled using Zinc oxide (ZnO) nanoparticles as a photoelectrode and natural dyes extracted from eight natural plants as photosensitizers. The structural properties of the synthesized ZnO nanoparticles were studied using XRD, SEM and TEM characterizations. Photovoltaic parameters such as short circuit current density Jsc, open circuit voltage Voc, fill factor FF, and overall conversion efficiency η for the fabricated cells were determined under 100 mW/cm2 illumination. It was found that the DSSC fabricated with the extracted safflower dye as a sensitizer showed the best performance. Also, its performance increased with increasing the sintering temperature of the semiconductor electrode with highest performance at 400 °C. Moreover, it was found that a semiconductor electrode of 7.5 μm thickness yielded the highest response

Synthesis and characterization of ZnO nanoparticles using sol gel technique for dye sensitized solar cells applications

ZnO nanoparticles were synthesized using sol gel technique at differentcalcination temperature. The effect of calcination temperature on the structure and opticalproperties of ZnO NPs were studied in detail by using different techniques, X-raydiffraction, high-resolution transmission electron microscope, UV-VIS spectroscopy andphotoluminescence spectroscopy.X-ray diffractionanalysis revealed that the ZnO NPs werecrystalized in a wurtzite structure and the estimated average particle size increased from24.7 to40.4 nm with increasingcalcinationtemperature. In addition, the d spacingincreased from 0.28196 nm to 0.28213 nm.High-resolution transmission electronmicroscopy analysisimage showed spherical ZnONPs were formed. UV-VIS absorptionmeasurement was employed to evaluate the absorption edge and the optical band gapusingTauc plot. Energy gaprevealed a red shift from 3.15 to 2.96 eV when thecalcinationtemperaturewas increased. Dye sensitized solar cells were fabricated using synthesizedZnO NPs as a semiconducting layer that were dyed withdifferentXanthene(CH2[C6H4]2O)dyesseparately;(Eosin B, Eosin Y and Rhodamine B) which arelow costdyes. Thin layer of ZnO were deposited on transparentfluorine doped tin oxideconductiveglass using doctor blade method. Eosin Y exhibited the bestphotosensitizing. Theconversion efficiency showed a significant improvement from 0.1% to 1.08%.This research activity carried out between Gaza-Palestine and Cairo-Egypt, which was financially supported by Qatar Charity IBHATH Project grant funded by the Gulf Cooperation Council for the Reconstruction of Gaza through the Islamic Development Bank.ZnO nanoparticles were synthesized using sol gel technique at differentcalcination temperature. The effect of calcination temperature on the structure and opticalproperties of ZnO NPs were studied in detail by using different techniques, X-raydiffraction, high-resolution transmission electron microscope, UV-VIS spectroscopy andphotoluminescence spectroscopy.X-ray diffractionanalysis revealed that the ZnO NPs werecrystalized in a wurtzite structure and the estimated average particle size increased from24.7 to40.4 nm with increasingcalcinationtemperature. In addition, the d spacingincreased from 0.28196 nm to 0.28213 nm.High-resolution transmission electronmicroscopy analysisimage showed spherical ZnONPs were formed. UV-VIS absorptionmeasurement was employed to evaluate the absorption edge and the optical band gapusingTauc plot. Energy gaprevealed a red shift from 3.15 to 2.96 eV when thecalcinationtemperaturewas increased. Dye sensitized solar cells were fabricated using synthesizedZnO NPs as a semiconducting layer that were dyed withdifferentXanthene(CH2[C6H4]2O)dyesseparately;(Eosin B, Eosin Y and Rhodamine B) which arelow costdyes. Thin layer of ZnO were deposited on transparentfluorine doped tin oxideconductiveglass using doctor blade method. Eosin Y exhibited the bestphotosensitizing. Theconversion efficiency showed a significant improvement from 0.1% to 1.08%

Elektrochrome Eigenschaften und Farb-Mechanismen von Sol-Gel-NiO-TiO2-Schichten und mit ihnen hergestellten Fenstern

Electrochromic films of NiO-TiO2 with Ni concentration of 100, 90, 87, 83, 75, 66, 50 and 33 mol % have been obtained via the sol-gel route by dip coating technique using ethanolic sols of nickel acetate tetrahydrate (Ni(CH3COO)2•4H2O) and titanium n—propoxide Ti(C3H7O)4 precursors and sintered in air between 250 and 500 °C. Xerogels obtained by drying the sols have been studied up to 900 °C by thermal analysis (DTA/TG) coupled to mass and IR spectroscopy. The crystalline structure and morphology of the layers in the as deposited, bleached and colored states was determined by X-ray diffractometry, scanning electron microscopy and transmission electron microscopy. Their electrochromic properties have been studied in 1 M KOH aqueous electrolyte as a function of the layer composition, thickness and sintering temperature. Deep brown color with reversible transmittance changes have been obtained using cycling voltammetry and chronoamperometry processes. The best composition to get stable sols, a high reversible transmittance change and fast switching times (10 s) was obtained with double NiO-TiO2 layers 160 nm thick having 75 % Ni molar concentration, and sintered between 300 and 350 °C. The electrochromism of the layer was also studied in LiClO4-PC electrolyte. The mechanism of coloration and morphology transformation of the layer during cycling in 1 M KOH electrolyte are discussed in terms of an activation and degradation period. The nature of the ions involved in the coloration process has been studied using an Electrochemical Quartz Crystal Microbalance (EQCM). It was found that the activation period was associated with an increase of the mass of the layer after each cycle due to a gradual incorporation of OH- groups and the transformation of Ni(OH)2 into hydrated NiOOH giving the brown coloration as well as the formation of lattice water (OH- + H+&#8594; H2O). The gradual change of the layer composition led to a much more open and fragile morphology that eventually allowed the incorporation of K+ ions and more water molecules associated with unusual large increase of the mass of the layer after each cycle and responsible for the degradation period. Finally, devices have been mounted and tested using either NiO-TiO2 layers or NiO-TiO2 layers covered with a thin anticorrosion dielectric layers as a working electrode together with CeO2-TiO2 layer or with a WO3 or a Nb2O5 cathodic layer acting as an active counter electrode. Also a new type of electrolyte based on KOH mixed with starch has been also developed and tested with complete windows.Elektrochrome Schichten bestehend aus NiO und TiO2 mit Ni-Gehalten von 33 bis 100 mol % wurden mit Hilfe des Sol-Gel-Prozesses durch Tauchbeschichtung aus alkoholischen Lösungen von Nickelacetat-Tetrahydrat (Ni(CH3COO)2•4H2O) und Titan-n-propoxid (Ti(O-CH(CH3)2)4) hergestellt und bei Temperaturen zwischen 250 und 500°C an Luft gesintert. Xerogele, die durch die Trocknung der Sole erhalten wurden, wurden bis zu einer Temperatur von 900 °C mittels thermischer Analysen (DTA/TG) in Verbindung mit Massen- und IR-Spektroskopie untersucht. Die kristalline Struktur und Morphologie der Schichten im abgeschiedenen, entfärbten und gefärbten Zustand wurde durch Röntgendiffraktrometrie, Elektronenmikroskopie und Transmissionselektronenmikroskopie untersucht. Die Analyse ihrer elektrochromen Eigenschaften erfolgte unter Verwendung eines wässrigen Elektrolyten (1 mol/l KOH) in Bezug auf die Schichtzusammensetzung, Dicke und Sintertemperatur. Eine dunkelbraune Farbe mit einer reversiblen Transmissionsänderung wurde durch Cyclovoltammetrie- und Chronoamperometrie-Prozesse erzielt. Die beste Zusammensetzung zur Erzielung stabiler Sole, einer hohen, reversiblen Transmissionsänderung und schneller Schaltzeiten (10 s) wurde mit NiO-TiO2 Doppelschichten (Dicke ca. 160 nm) mit einem Nickelgehalt von 75 mol % und für Sintertemperaturen zwischen 300 und 350°C erreicht. Die Elektrochromie der Schichten wurde darüber hinaus in einem LiClO4-Polycarbonat-Elektrolyten untersucht. Ein Mechanismus für Farb- und Morphologieänderung der Schicht während des Schaltzyklus in KOH-Elektrolyt wird im Sinne eines Aktivierungs- und Degradierungsprozesses diskutiert. Die Art der Ionen, die am Färbungsprozess beteiligt sind, wurde mit Hilfe der elektrochemischen Quarzmikrowaage (EQCM) untersucht. Es wurde beobachtet, dass der Aktivierungsprozess mit einer Zunahme der Schichtmasse nach jedem Zyklus aufgrund einer sukzessiven Aufnahme von OH-Gruppen und der Umwandlung von Ni(OH)2 in hydratisiertes NiOOH einhergeht, was schließlich eine braune Färbung und den Einbau von Wasser (OH- + H+ &#61664; H2O) in das Kristallgitter zur Folge hat. Die allmähliche Veränderung der Schichtzusammensetzung führte zu einer porösen und zerbrechlichen Morphologie, die letztendlich eine Aufnahme von K+-Ionen und weiterer Wassermoleküle ermöglichte und für den einsetzenden Degradierungsprozess in Verbindung mit einem ungewöhnlich starken Anstieg der Schichtmasse nach jedem Zyklus verantwortlich ist. Schließlich konnten elektrochrome Fenster konstruiert werden, welche zum einen reine NiO-TiO2-Schichten, zum anderen NiO-TiO2-Schichten, die mit einer dünnen dielektrischen Antikorrosionsschicht versehen sind, als Arbeitselektrode enthielten. Als kathodische Gegenelektrode fungierten Schichten von CeO2-TiO2 bzw. WO3 oder Nb2O5. Des Weiteren erfolgte die Entwicklung eines neuen Elektrolyt-Typs basierend auf KOH in Verbindung mit Stärke, der an kompletten Fenstern getestet wurde

Thermal treatment optimization of ZnO nanoparticles-photoelectrodes for high photovoltaic performance of dye-sensitized solar cells

Annealing temperature has pronounced effect on DSSC performance. ZnO nanoparticles photoelectrodes were prepared on FTO glass and annealed at different temperatures in the range 200–500 °C. The thermal properties of the paste were studied using DTA/TG technique which revealed that no changes are expected at temperatures higher than 350 °C. Electrical properties of the DSSCs using ZnO nanoparticles photoelectrodes annealed at different temperatures were studied using I–V characteristic and electrochemical impedance spectroscopy (EIS). The surface area and dye loading increased as the annealing temperature increased up to 350 °C. The electrical properties are found to be dependent on the photoelectrode annealing temperature. Annealing temperatures higher than 400 °C resulted in a decrease in current density. The highest value of current density Isc (15.6 mA/cm2), open circuit potential Voc (0.55 V) and efficiency (3.01%) is achieved at annealing temperature of 400 °C