Cu-doped TiO2 Research Articles

Synthesis and charcterization of Cu-doped TiO2 (Cu/TiO2) nanoparticle as antifungal phytophthora palmivora

Preparation of Cu-doped TiO2 nanoparticles (Cu/TiO2) as antifungal Phytophthorapalmivorahas been carried out. In this study, we did a synthesis of Cu/TiO2 nanoparticles by the sol-gel method and determine the performance of the modification of Cu/TiO2 nanoparticles as antifungal agents P. palmivora. The stages of this research include synthesis of Cu/TiO2 nanoparticles using the sol-gel method, characterization of Cu/TiO2 nanoparticles using UV-Vis DRS and characterization of Cu/TiO2 nanoparticles using SEM-EDX, and P. palmivora antifungal activity test. TiO2 is known to be used as an antifungal agent and to increase photocatalyticactivity, TiO2 is doped with Cu metal ions to be active in visible light. The results showed that Cu/TiO2 has a band gap energy of 3.12 eV. Based on the results of SEM-EDX analysis of TiO2-Cu nanoparticles confirmed the presence of elements Cu (2.16%), Ti (28.74%) and O (69.10%) with morphological shapes such as irregular spheres. Cu/TiO2 nanoparticles have a strong ability at concentrations of 0.05% and 2.5% in inhibiting the growth of the fungus P. palmivora. Percent inhibition respectively 60.41% and 75% and at concentrations>3% have activities that can kill P. palmivora fungus.

Cu-doped TiO2 hollow nanostructures for the enhanced photocatalysis under visible light conditions

We report a synthetic strategy for fabricating Cu-doped TiO2 hollow nanostructure for visible light responsive photocatalysis. Hollow Cu-doped TiO2 photocatalysts were prepared by sol–gel coating of TiO2 on the surface of SiO2, removal of sacrificial core, Cu2+ ion exchange, and calcination followed by acid leaching. The ion exchanged Cu species allows TiO2 shell to be preferentially crystallized rutile phase, even at low calcination temperature. The acid leaching allows the excess bulk CuO to be dissolved out and Cu-doped TiO2 to expose more reactive TiO2 surface. No measurable CuO composites were observed while uniformly distributed Cu species is detected in acid treated CT–X–HCl samples indicating the Cu2+ ions were homogeneously doped into crystalline TiO2 frameworks. In particular, the CT–650–HCl catalyst that was prepared by calcination at 650°C, followed by HCl leaching, showed beneficial physio-chemical properties, such as narrow bandgap, mixed anatase-rutile crystalline phase, and more reactive TiO2 surface with high surface area, resulting in the best photocatalytic performance towards phenol degradation under visible light conditions.

Sol-gel TiO2 nanostructures single doped with copper and nickel as nanocatalysts for enhanced performance for the Liebeskind–Srogl reaction

Design of nanostructured catalytic materials plays a strategic role in the synthesis of organic compounds with outstanding physicochemical properties. In this regard, titanium dioxide nanostructures doped with a single metal, namely, nickel and copper, were successfully prepared by a sol-gel method, and their phase structures, elemental compositions and morphologies were extensively characterised. In particular, X-ray diffraction (XRD) diffractograms and Raman spectra mainly revealed a rutile-phase structure for Cu-doped TiO2 and a biphasic anatase–rutile structure for Ni-doped TiO2. In addition, catalytic activities of Cu- and Ni-doped titanium dioxide nanostructures were evaluated for the synthesis of pyridopyrimidine derivatives from sulphur intermediates by the Liebeskind–Srogl reaction under UV illumination. Under the optimized reaction conditions, the target compounds were obtained in a yield of up to 87% by using the Cu-doped TiO2 catalyst and with a slightly lower yield of up to 79% for Ni-doped TiO2 in 12 h. Overall, the catalytic activity of Cu-doped TiO2 was greater than that of Ni-doped TiO2.

Cu-BTC metal organic framework (MOF) derived Cu-doped TiO2 nanoparticles and their use as visible light active photocatalyst for the decomposition of ofloxacin (OFX) antibiotic and antibacterial activity

Herein, we report the ultrasonic-assisted precipitation technique for the fabrication of Cu-doped TiO2 nanoparticles. The prepared sample showed high crystallinity, purity and nanoparticles like structure with the diameter in the range of 10–22 nm. The bandgap for Cu-doped TiO2 nanoparticles was estimated to be 2.91 eV using Tauc plot, which is considerable for improving the light-harvesting capacity. Further, the prepared Cu-doped TiO2 was used as photocatalyst for the eradication of ofloxacin (OFX), an antibiotic from an aqueous phase under visible illuminations. About 72% degradation of OFX (10 mg/L, pH 7) was achieved with Cu-doped TiO2 nanoparticles after 180 min of visible illumination. The probable photocatalytic mechanism for the decomposition of OFX has been proposed based on reactive species trapping study. Moreover, the antibiotic efficiency of OFX was investigated against Escherichia coli and it was observed that its antimicrobial activity was significantly diminished after the photocatalytic decomposition of the OFX solution with synthesized nanoparticles.

Cu-doped TiO2 nanoparticles/graphene composites for efficient dye-sensitized solar cells

Graphene (GR) demonstrates excellent photoelectrochemical properties, including its large specific surface area, unique structure, chemical stability, high conductance, and fast electron transfer. These parameters are crucial for the performance improvement and photoanode optimization of a dye-sensitized solar cell (DSSC). In this study, Cu-doped TiO2/graphene (CuTGR) composites have been prepared for the first time by the sol–gel-assisted hydrothermal method for the DSSC photoanode application. The prepared CuTGR composites have been coated on Fluorine-doped tin oxide (FTO) glass substrates using the doctor blade method. The surface morphological and elemental analysis reveals the presence of Cu and graphene into CuTGR nanocomposite with uniform distribution and desired morphology. The addition of graphene further improves the dye loading ability of the CuTGR photoanodes with improved current density and faster charge transport as observed in current–voltage (J-V) and intensity-modulated photocurrent spectroscopy (IMPS) measurements. Our findings demonstrate that an optimal loading of Cu and graphene can boost the power conversion efficiency (PCE) of the DSSC (9.81%) by 47% higher than undoped DSSC (6.66%).

Oxygen-vacancy-anchoring NixOy loading towards efficient hydrogen evolution via photo-thermal coupling reaction

Oxygen vacancy (VO) is a significant component in defect engineering. The present work reports the anchoring effects of initial VO for further loading modifications and the reducing capacity of photo-induced VO for pure water splitting. Herein, we propose Ni-loaded Cu-doped TiO2 (NCT) materials by successive doping and loading. The continuously added Ni ions should accumulate around the VOs and gradually grow into complete nickel oxide crystals, achieving a higher average valence state of the Ni species. NiO crystals can be detected on a 0.5% NCT sample, while the structure of Ni2O3 has been confirmed with a higher nickel mass ratio. Moreover, the introduction of nickel oxide effectively improves the photochemical and electrochemical performance by the interface charge separation, finally reaching an H2 yield of 30.6 μmol/g-cat on 0.5% NCT for VO-based photo-thermal coupling reaction, which consists of VO generation in photo and VO consumption in thermal environment. In situ infrared spectroscopy further indicated that the presence of high valence state nickel oxide hindered the H2 formation but effectively promoted the conventional oxidizing reaction, with an H2 yield of 20.6 mmol/g-cat in a methanol–water reaction on the 2.0% NCT material. In summary, VO controls the morphological structure of Ni loading and produces diverse effects for reactions with dissimilar mechanisms, which provides a novel way to design modifications for promoting various chemical reactions.

Preparation, Characterization, and Photocatalytic Properties of Self-Standing Pure and Cu-Doped TiO2 Nanobelt Membranes.

A traditional hydrothermal method was modified to synthesize ultra-long sodium titanate nanobelts by simultaneously stirring the solution. The ultra-long sodium titanate nanobelts were converted to hydrogen titanate nanobelts through an ion exchanging way. A method was then used to prepare self-standing flexible large-area membranes; they were then subject to post-annealing at different temperatures to obtain a self-standing TiO2 nanobelt membrane with a slight decrease in flexibility. Cu-doped TiO2 membranes were prepared by ion exchanging and post-annealing in the same manner. X-ray diffractions, scanning electron microscopy, field-emission scanning electron microscopy, field-emission transmission electron microscopy, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, and UV–vis spectroscopy were used to characterize the samples. Photodegradation of methylene blue (MB) water solutions was used to evaluate the photocatalytic activity. It was seen that the pure sample presented obvious visible-light responding photocatalytic activity, possibly due to the self-sensitization of the MB molecule. The UV-induced photocatalytic activity is higher because of the photoinduced holes and electrons. It was suggested that the Cu dopant induced intra-gap states from electron traps and recombination centers, resulting in the decrease in both of the visible and UV induced photocatalysis.

Selective CO2 Photoreduction with Cu-Doped TiO2 Photocatalyst: Delineating the Crucial Role of Cu-Oxidation State and Oxygen Vacancies

Cu-doped TiO2 photocatalysts [Cu-(1 to 10) atom %] synthesized by the sol–gel method and thoroughly characterized using several techniques were evaluated for photocatalytic reduction of CO2 under ambient conditions. These photocatalysts converted the reactant mixture of CO2 and moisture selectively into methane and oxygen under visible irradiation without the use of any sacrificial agent. The Cu dopant considerably lowered the bandgap of TiO2, thereby making it feasible for doped TiO2 to absorb light in the visible region. Beyond 1% Cu doping the Cu-doped TiO2 materials were far superior as compared to anatase TiO2 for the reduction of CO2 to CH4, and the lowest doping (Cu-1%) concentration in TiO2 lattice shows the maximum production of CH4 (1081 μL/h/g), whereas the highest doping (Cu-10%) shows the least activity (200 μL/h/g). The photoreduction activity was found to decrease with increasing Cu concentration; under similar conditions without use of any cocatalysts. X-ray photoelectron spectroscopy (XPS) results along with cyclic voltammetry data (CV) indicate that the doped Cu exists in the two stable oxidation states of Cu1+ and Cu2+. The electron paramagnetic resonance (EPR) results show that there are two distinct types of Cu2+ species in the doped system and clustering of the Cu2+ states at higher doping concentrations may be detrimental for the photoactivity. The electronegative surface Cu1+ species along with O-vacancies seem to play the most important role in the photocatalytic reduction of CO2 to CH4.

Thermal behavior of Cu-doped TiO2 gels synthesized by the sol-gel method

The thermal behavior of Cu-doped TiO2 gels obtained by the sol-gel method was investigated by thermogravimetric and differential thermal analysis (TG/DTG/DTA) and differential scanning calorimetry (DSC) measurements. The comparative investigation of the structure and morphology of the as-prepared gels and of the nanopowders obtained by annealing them was realized by transmission electron microscopy (TEM), Fourier transmission infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Significant differences were noticed depending on the amount of dopant (0.5 or 2.0 mol % CuO). A higher dopant concentration resulted in a more complex decomposition of the sample. This behavior was associated with the formation of various molecular species in the sol-gel solutions before gelation, determined by the different amount of the dopant used.

The Vibrational Spectroscopy of the Valence Bonds of Cu-Doped TiO2 Using Electronegativity Principle Quantitative Calculations

The purpose of this study is to investigate the influence of Cu on TiO2 phase transformation and regioselectivity. TiO2 samples doped with different amounts of Cu2+ ions were synthesized by the sol-gel method. The phase and vibrational mode were characterized by X-ray diffraction (XRD), Fourier infrared spectroscopy (FTIR), and transmission electron microscope (TEM). The XRD phase analysis shows that the lattice parameters have not changed after Cu incorporation. In addition, the content of rutile increased obviously after Cu doping. This indicated that the addition of Cu obviously promoted the transformation from anatase phase to rutile phase. The vibration frequencies were calculated based on the principle of electronegativity. All types of bonds were qualitatively and quantitatively analyzed. The content of TiA-O, TiR-O, and H-O in the undoped TiO2 samples is 23.87%, 16.30%, and 7.41%, respectively. In the same way, the content of TiA-O, TiR-O, H-O, Cu A i -O, and Cu R i -O in the 2.5 mol%Cu-doped TiO2 samples is 21.23%, 18.56%, 7.34%, and 0.98%, respectively. For the 5 mol%Cu-doped TiO2 samples, the content of TiA-O, TiR-O, H-O, Cu A i -O, Cu R i -O, Cu A s -O, and Cu R s -O is 18.75%, 20.11%, 7.47%, 2.56%, 3.9%, 1.55%, and 2.35%, respectively. Cu was not present at substitutional sites in the 2.5 mol% doped sample, but Cu was present in the 2.5 mol% doped sample. It is indicated that Cu was more likely to exist in the form of interstitial position in the TiO2 lattice, with the number of Cu atoms in the interstitial position reaching saturation, and this forced Cu to replace Ti. The TEM shows that the stripes of different periods and orientations overlapped each other to form the Moiré patterns. In addition, the diffraction patterns of the Moiré image were slightly different from that of the matrix. The Cu replaced Ti position and the Cu atoms mixed into interstitial sites in the TiO2 lattice. The theoretical calculation was consistent with the experimental results.

A coordinated regulation strategy to improve electronic conductivity and Li-ion transport for TiO2 lithium battery anode materials

Titanium dioxide (TiO2) is considered as one of the most promising anode materials for lithium-ion batteries. However, improving the poor electronic conductivity and slow Li-ion diffusion of TiO2 anode materials are urgently required. In this study, we design a Cu-doped TiO2 hollow nanosphere structure based on the coordinated regulation strategy of size, nanostructure and doping. The results revealed the cause of the oxygen vacancy generation and its mechanism of action in the battery electrode reaction process. Moreover, the electrochemical results showed that Cu-doped hollow nanosphere structure significantly improves the low conductivity and the slow Li-ion diffusion rate of TiO2. These findings show that our work provides a new modification idea to improve the electrochemical performance of TiO2 anode materials for LIBs.

Cu-doped TiO2 brookite photocatalyst with enhanced visible light photocatalytic activity

Abstract Cu-doped TiO2 having a brookite phase and showing enhanced visible light photocatalytic activity was synthesized using a mild solvothermal method. The as-prepared samples were characterized by various techniques, such as X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectroscopy. Photocatalytic activity of Cu-doped brookite TiO2 nanoparticles was evaluated by photodegradation of methylene blue under visible light irradiation. The X-ray diffraction analysis showed that the crystallite size of Cu-doped brookite TiO2 samples decreased with the increase of Cu concentration in the samples. The UV-Vis diffuse reflectance spectroscopy analysis of the Cu-doped TiO2 samples showed a shift to lower energy levels in the band gap compared with that of bare phase brookite TiO2. Cu doped brookite TiO2 can obviously improve its visible light photocatalytic activity because of Cu ions acting as electron acceptors and inhibiting electron-hole recombination. The brookite TiO2 sample with 7.0 wt.% Cu showed the highest photocatalytic activity and the corresponding degradation rate of MB (10 mg/L) reached to 87 % after visible light illumination for 120 min, much higher than that of bare brookite TiO2 prepared under the same conditions (78 %).

Encapsulation of Cu-doped TiO2 nanocomposites with the understanding of weak photocatalytic properties for sunscreen applications

We report the fabrication and characterization of varying concentration (x) of copper (Cu)-doped TiO2 nanocomposites [Cu( x )TiO2(1- x )] exploring the photocatalytic properties for sunscreen applications. The Cu-doped TiO2 nanocomposite [Cu( x )TiO2(1- x )] has been synthesized by the low-temperature lab-scale sol-gel hydrothermal method. The concentration of Cu in TiO2 has been chosen as 1%, 2%, 3%, and 4% by weight. With varying concentrations of [Cu( x )TiO2(1- x )], the structural and morphological properties are obtained using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of optical properties for varying concentrations of Cu2+ ions in TiO2 has been studied using Fourier transform infrared spectroscopy (FTIR), UV-Vis absorption spectroscopy. Further, by exploring the photocatalytic properties of fabricated [Cu( x )TiO2(1- x )] has been utilized for sunscreen applications. The concept of sunscreen application of Cu-doped TiO2 can be viewed from the fact that the bare TiO2 generates free radicals that can raise the risk of harmful effects on the skin. Our aim is to synthesize the nontoxic material which can either stop or slow the process of generation of free radicals under sun exposure. In the sun exposure, the risk of free radicals produces by pristine TiO2 can be reduced by doping of copper with titania. We have been observed that [Cu( x )TiO2(1- x )] with x equaling 4% (rutile phase) displays the most effective UV-blocking property with weak photocatalytic activity and is found to be better for sunscreen application. Therefore, Cu-doped TiO2 nanocomposite maintains all the properties of TiO2 at nanoscale as well as improves the concerning property of the cosmetic industry.

Dye wastewater degradation by the synergetic effect of an atmospheric pressure plasma treatment and the photocatalytic activity of plasma-functionalized Cu‒TiO2 nanoparticles

In this paper, the photocatalytic activity of plasma-functionalized Cu-doped TiO2 nanoparticles (NPs) and the oxidization process of atmospheric pressure plasma jet were combined for the degradation of reactive red-198 (RR-198) in aqueous solution. The first part of the study was thus devoted to subject Cu-‒TiO2 NPs synthetized by the sol-gel method to various plasma treatments operating in air, argon, oxygen and nitrogen to improve their degradation efficiency. The physicochemical properties of the NPs were then assessed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) measurements. XRD results indicated the predominant presence of the anatase phase which is the most photoactive form of TiO2. The XPS analysis revealed that the different plasma treatments triggered the formation of oxygen vacancies, Ti3+ oxidation state and Cu2+ oxidation state on the surface of Cu-‒TiO2 NPs. These changes, known to prevent the recombination of electron–hole pair, have led to a reduction in the bandgap that was more pronounced for the N2 plasma-treated NPs. The second part of the paper explored the actual degradation of RR-198 in aqueous solution by an Ar plasma treatment alone or combined with the plasma pre-treated Cu-‒TiO2 NPs. Optical emission spectroscopy (OES) and spectrophotometric analyses showed that the synergetic effect of Ar plasma and N2 plasma-treated NPs produced the highest concentration of OH• radicals and H2O2 species which led to the highest RR-198 degradation efficiency. This was further confirmed by pH, electrical conductivity and total organic carbon (TOC) removal measurements. The degradation of RR-198 was determined using UV-Vis spectroscopy and high-performance liquid chromatography (HPLC). Overall, it can be concluded that plasma-assisted processes illustrated by a combination of a direct plasma treatment with plasma-functionalized Cu-‒TiO2 NPs can be used in various textile and pharmaceutical industries as a highly effective treatment of their effluents before discharging.

Enhancement of Titania Photoanode Performance by Sandwiching Copper between Two Titania Layers.

Vacancies in semiconductors can play a versatile role in boosting their photocatalytic activity. In this work, a novel TiO2/Cu/TiO2 sandwich structure is designed and constructed. Abundant vacancies were introduced in TiO2 lattice by Cu reduction under heat treatment. Meanwhile, Cu atom could diffuse into TiO2 to form Cu-doped TiO2. The synergistic effect between oxygen vacancies and Cu atoms achieved about 2.4 times improved photocurrent of TiO2/Cu/TiO2 sandwich structure compared to bare TiO2 thin film. The enhanced photoactivity may be attributed to regulated electron structure of TiO2 by oxygen vacancies and Cu dopant from experimental results and density functional theory calculations. Oxygen vacancies and Cu dopant in TiO2 formed through copper metal reduction can introduce impurity levels and narrow the band gap of TiO2, thus improve the visible light response. More importantly, the Cu2+ and oxygen vacancies in TiO2 lattice can dramatically increase the charge density around conduction band and promote separation of photo-induced charge carriers. Furthermore, the oxygen vacancies on the surface may serve as active site for sufficient chemical reaction. This work presents a novel method to prepare doped metal oxides catalysts with abundant vacancies for improving photocatalytic activity.

High-performance and long-term stability of mesoporous Cu-doped TiO2 microsphere for catalytic CO oxidation

Although the low-temperature reaction mechanism of catalytic CO oxidation reaction remains unclear, the active sites of copper play a crucial role in this mechanism. One-step aerosol-assisted self-assembly (AASA) process has been developed for the synthesis of mesoporous Cu-doped TiO2 microspheres (CuTMS) to incorporate copper into the TiO2 lattice. This strategy highly enhanced the dispersion of copper from 41.10 to 83.65%. Long-term stability of the as-synthesized CuTMS materials for catalytic CO oxidation reaction was monitored using real-time mass spectrum. Isolated CuO and Cu-O-Ti were formed as determined by X-ray photoelectron spectroscopy (XPS). The formation of the Cu-O-Ti bonds in the crystal lattice changes the electron densities of Ti(IV) and O, causing a subsequent change in Ti(III)/Ti(IV) and Onon/OTotal ratio. 20CuTMS contained the highest lattice distortion (0.44) in which the Onon/OTotal ratio is lowest (0.18). This finding may be attributed to the absolute formation of the Cu-O-Ti bonds in the crystal lattice. However, the decrease of Ti(III)/Ti(IV) ratio to about 0.35 of 25CuTMS was caused by the CuO cluster formation on the surface. N2O titration-assisted H2 temperature-programmed reduction and in-situ Fourier transform infrared spectroscopy revealed the properties of copper and effects of active sites.

Photocatalytic inactivation of viral particles of human norovirus by Cu-doped TiO2 non-woven fabric under UVA-LED wavelengths

Metal-doped TiO2 photocatalysis are recognized as effective materials for eliminating human norovirus (HuNoVs). In recent years, the airborne transmission of viral particles of HuNoVs has been a cause for concern. In this study, we evaluated the virucidal effects of a Cu/TiO2 non-woven fabric (NWF) on viral particles of HuNoV genogroup II genotype 4 (HuNoV GII.4) under an ultraviolet A light-emitting diode (UVA-LED) source. For the optimized parameters, a multivariate statistical analysis using the Box-Behnken design (BBD) technique combined with the response surface methodology (RSM) was applied. The experimental results showed that the Cu/TiO2-based NWF degraded HuNoV viral particles in the air samples. The BBD-based RSM indicated that the optimum treatment conditions for inactivating the HuNoV GII.4 droplets with the Cu/TiO2 NWF were a 1:7.7 ratio of Cu:TiO2 and the use of a 373-nm UVA-LED source for 48.08 min. The optimal conditions for the photocatalytic efficacy in HuNoV GII.4 of Cu/TiO2 NWF were verified experimentally, giving a value of 2.89 ± 0.11 log10 genomic copies, which was the same as the predicted value (2.91611) within experimental uncertainty. This result adequately validated the predicted model and confirmed that viral particles of HuNoVs could efficiently be disinfected using Cu/TiO2 NWF stimulated by UVA-LED light.

In situ synthesis and photocatalytic hydrogen production of plate‐like Cu‐doped TiO 2 polycrystal with crystal‐axis orientation

The Cu-doped TiO2 plate-like particle was synthesised via using the layered H1.07Ti1.73O4·H2O (HTO) plate-like particle as a precursor. The Cu-doped TiO2 particle consists of nanocrystals and holes, and these nanocrystals are oriented at [ 1 ¯ 1 ¯ 1 ]-crystal-axis direction. Firstly, the HTO particle was treated in a copper acetate solution, forming Cu2+-exchanged HTO plate-like particles. And then Cu2+-exchanged HTO in situ transformed into Cu-doped TiO2 via heat-treating and further acid washing. The Cu-doped TiO2 particle has a stronger absorption in the visible light region of 400–800 nm and the visible photocatalytic H2 production activity.

Combining energy efficiency with self-cleaning properties in smart glass functionalized with multilayered semiconductors

We propose here a new approach based on a combined study of the self-cleaning and energy-efficiency properties of stratified WO3/Cu–TiO2 coatings for glazing applications. The multifunctional performance was investigated by varying the number of layers deposited on the glass substrate (i.e., 1, 2, 4 layers), while energy efficiency was assessed using building energy modeling. Results indicate that the self-cleaning ability can be boosted by a multilayer configuration due to the inhibited charge recombination and to a gradual rise in surface roughness and porosity with the increasing number of layers. In particular, the highest wettability and degradation of toluene under simulated solar light were achieved over the coating consisting of Cu-doped TiO2 stacked with WO3 in a 4-layer configuration. On the other hand, the analogous sample, but in the 2-layer configuration, was the most active sample in the oxidation of carbon monoxide. In terms of energy efficiency, the applied coatings led to important energy savings, exceeding 8% in total energy consumption and 18% in cooling loads. The best energy efficiency levels in the tested glazing configurations were achieved with single-layer WO3. However, its low visible transmittance reduced the amount of natural daylight entering the studied buildings, unintentionally increasing the electric lighting loads. The results highlight the importance of alternative configurations, such as Cu-doped TiO2 in a dual-layer arrangement with WO3, which provide a better balance between energy efficiency and access to daylight, an important driver of occupant comfort and wellbeing.

A SYSTEMATIC STUDY ON THE DIELECTRIC RELAXATION, ELECTRIC MODULUS AND ELECTRICAL CONDUCTIVITY OF Al/Cu:TiO2∕n-Si (MOS) STRUCTURES/CAPACITORS

The various levels (5%, 10% and 15%) of Cu-doped TiO2 thin films were grown on the [Formula: see text]-type silicon (Si) wafer by spin coating technique to obtain Al/(Cu:TiO[Formula: see text]/[Formula: see text]-Si (MOS) capacitors. Both the real and imaginary components of complex dielectric ([Formula: see text], complex electric modulus ([Formula: see text], loss tangent (tan [Formula: see text] and alternating electrical conductivity ([Formula: see text] of the obtained Al/(Cu:TiO[Formula: see text]-Si (MOS) capacitors were studied by taking into account the effects of Cu-doping levels into TiO2 viaimpedance spectroscopy method (ISM) in the wide range voltage ([Formula: see text][Formula: see text]V) and frequency (10[Formula: see text]kHz–1[Formula: see text]MHz). All the obtained dielectric parameters were obtained as strongly dependent on frequency, voltage and Cu doping level. The observed anomalous peak in the forward bias region both in the real and imaginary components of [Formula: see text], tan [Formula: see text], complex electric modulus ([Formula: see text] and [Formula: see text] were attributed to the Cu:TiO2 interlay er, series resistance ([Formula: see text], surface states ([Formula: see text], interfacial/surface and dipole polarizations. The higher values of [Formula: see text] at low and intermediate frequencies implied that [Formula: see text] have enough time to follow external ac signal, and also dipoles respond to the applied field to reorient themselves. Consequently, the fabricated Al/(Cu:TiO[Formula: see text]-Si can be successfully used as MOS capacitor or MOS-field-effect transistor (MOSFET) in the industrial applications in near future.