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In this investigation, we achieved successful deposition of nanostructured cupric oxide (CuO) thin films onto glass substrates through implementation of successive ionic layer adsorption and reaction (SILAR), all carried out at room temperature. This approach has proven to be highly efficient and yielded favorable results in terms of film quality and uniformity. A comprehensive investigation was conducted to analyze the effect of gold (Au) on the structural, morphological, optical, and electrical properties of nanocrystalline CuO thin films. The structural analysis confirmed that the films were polycrystalline, exhibiting a monoclinic crystal structure with preferential orientations along the ( 1 ¯ 11 ) and (111) planes. The estimated crystallite sizes ranged from 20.37 to 30.77 nm, indicating the nanoscale nature of the films. Scanning electron microscopy/energy-dispersive x-ray analysis (SEM/EDX) was executed to reveal the Au dopant on the surface of CuO thin films. Surface analysis revealed the presence of uniformly dispersed CuO nanostructures across the film surfaces. Through optical investigations, it was observed that the bandgap energy of the CuO thin films decreased from 1.52 to 1.45 eV with increasing Au concentration. Furthermore, the average transmittance of the films exhibited a decrease from 4.9% to 1.3% as the Au concentration increased. The electrical properties of the Al/Au:CuO/n-Si heterojunction were studied using current–voltage (I–V) measurements for various light power densities. The Al/Au:CuO/n-Si heterojunction exhibited good photodiode behavior, with 3.44 A/W responsivity and 1.58 × 1010 Jones specific detectivity for the 2% Au-doped CuO interfacial layer. [ABSTRACT FROM AUTHOR]

Intense electrolyte loss as a result of excessive sweating can disrupt the electrolyte balance in the body and cause damage to many organs, as well as potentially fatal disturbances in even brain functions. There are commercial sensors developed to monitor users' physical activity, however, few of them can provide information on users' health status through sweat analysis. Herein we report a chemiresistive sensor to monitor the sweat electrolyte concentration level. Metal oxide semiconducting CuO films were deposited on Au electrodes as sensing layers. Ca2+ ions were doped into the CuO lattice as sensitizer. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and UV–Vis spectroscopy were used to characterize the films. Sensors produced with pure and Ca-doped CuO films were tested against different concentrations of artificial sweat. The sensors responded well to sweat electrolyte concentration with a linear detection range of 20–80 mM. Detection limits between 6.64 and 9.86 mM were estimated using standard deviation methods. Average sensor response times were found to be 12 s. [ABSTRACT FROM AUTHOR]

CuO thin films were spray-deposited onto a glass substrate and the deposition temperature was varied from 450 to 550° C with 25° C steps. The 450° C deposition temperature was found to be the optimum condition for crystal growth. However, the FESEM images revealed that the grain size increases with raising the deposition temperature. To investigate the optical properties, the transmittance and reflectance data of the resulting films were recorded, and their optical constants, including absorption coefficient, band gap, Urbach energy, refractive index, extinction coefficient, and real and imaginary parts of the dielectric constant were calculated. All the prepared CuO thin films exhibited band gap values around 2.00 eV, which slightly declined with increasing the substrate temperature. The general trend of real and imaginary parts of the dielectric constant was increment and decrement, respectively, with increasing the substrate temperature. The spraydeposited CuO thin films were also excited at 486 nm, and the resulting photoluminescence (PL) spectra were recorded at room temperature. Three main and three shoulder peak emissions were detected in the recorded PL of all CuO thin films. The lowest peak intensity was related to the CuO thin film deposited at 500° C. [ABSTRACT FROM AUTHOR]

An FTO thin film was first deposited onto a glass substrate via the spray pyrolysis technique. To investigate the influence of the used salt and, consequently, structural properties on electrochemical performance, two precursor solutions were prepared from copper chloride dihydrate and copper acetate monohydrate and spray-deposited onto the FTO thin films. Considerable differences were observed in the physical characteristics of the resulting CuO thin films derived from different precursor solutions. The XRD results were employed to estimate the crystallite size and strain for the prepared CuO thin films via the Williamson–Hall method, as well as lattice parameters. Accordingly, the CuO thin film deposited from chlorine salt showed a greater crystallite size, lower strain, and unit volume cell. The Hall effect measurement revealed that there is slightly less resistivity for the CuO prepared from chlorine salt; however, mobility and carrier concentration were significantly different for the CuO thin films. The Randles–Sevcik equation was used to calculate the diffusion coefficient, and it is found that the structural characteristics of CuO grown from acetate salt (6.43 × 10–6 cm2/s) are in favor of better ion diffusion in compare with chloride salt (4.72 × 10–6 cm2/s). Similarly, the estimated equivalent distribution resistance from the Nyquist plot for CuO thin films spray-deposited from chlorine (250.11 Ω) and acetate (130.01 Ω) confirmed the better ion diffusion for the acetate solution-derived CuO thin film. Capacitance was calculated from cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy, all of which confirmed better ion storage performance in CuO deposited from acetate salt due to the superior ion diffusion characteristics of the mentioned thin film. [ABSTRACT FROM AUTHOR]

CuO thin film has a promising opto-electrical properties which make it used as absorber layer in thin film solar cell. So, in this work, CuO thin film has been synthesized and prepared by precipitation method and spin coating technique. It was observed it has narrow band gap (1.38 eV), high absorption coefficient (5.5 × 104 cm–1), optimum optical conductivity and high refractive index accompanied by low transmittance. XRD pattern is showed CuO nanocrystal has high crystallinity and low disorder which resulted in good optical absorption in the visible region. From SEM, it was observed the morphology of the CuO nanoparticles was rod-like particles which led to improve the opto-electrical properties. I–V curve is showed the current of CuO thin film is (0.6mA) which revels its photo-responsivity under light due to its high absorption coefficient. From the above results, CuO is a good absorber in thin film solar cell. [ABSTRACT FROM AUTHOR]

In this work, CuO thin films about the synthesis of the thin films are prepared on glass substrate using spray pyrolysis technique at room temperature different annealing times in temperature 450 0C.In order to study the effect of annealing times onthe structural, optical and electrical properties.XRD analysis has shown that films with a polycrystalline structurehave a(Monoclinic) structure. In addition, the crystallite phase CuO increases with increasing of annealing temperature. Moreover, with a preferred orientation along (002) peak. The optical properties confirmed that the elaborated films have a transmittance of 70%. We have found that the band gap energy (Eg) is a decreasing function with respect to the annealing temperature time. In addition, the electrical resistivity varies from 18.97 to 4.58 KOhm.cm for the films grown at different annealing times. [ABSTRACT FROM AUTHOR]

Bu çalışmada, CuO ince filmler, ultrasonik sprey piroliz (USP) yöntemi ile farklı alttaş sıcaklıklarında (350, 400, 450 ve 500 ºC) cam altlıklar üzerine biriktirilmiştir ve ardından 525 ºC’de tavlanmıştır. X-ışını kırınımı (XRD) analizlerinde, 350 ºC alttaş sıcaklığında ve tavlanmayan durumda ince filmlerde pik şiddetine rastlanmamıştır. Diğer filmlerin XRD desenlerinde ~36º ve ~39º’de iki belirgin pik gözlemlenmiştir. Bu pikler CuO’in monoklinik kristal yapısına ait karakteristik piklerdir. Atomik kuvvet mikroskobu (AFM) ve taramalı elektron mikroskobu (SEM) görüntülerinden, CuO ince filmlerin yüzeylerinin pürüzsüz olmadığı ve tavlama ile tane yığınlarının meydana geldiği gözlenmiştir. CuO ince filmlerin optik özellikleri ultraviyole- görünür bölge (UV-Vis) ölçümleri ile analiz edilmiştir. Tauc grafiklerinden yasak band aralığı değerleri (Eg), tavlanmamış ve tavlanan numuneler için hesaplanmıştır. USP yöntemiyle üretilen CuO ince filmlerin yapısal, morfolojik ve optik özelliklerinin alttaş sıcaklığı ile kontrol edilebileceği görülmüştür.

In this study, the effect of annealing temperature on the extended gate field effect transistor (EGFET) for pH sensors of CuO thin film was investigated. The CuO thin films were deposited on an indium tin oxide (ITO) substrate using the sol-gel spin-coating method. The thin films were then annealed in air ambient at 200 to 500 °C for 30 minutes. The sensitivity and linearity of the sensing electrodes were determined in a pH range from pH 2, 4, 7, 10 and 12. The sensing electrode annealed at 400 °C showed the highest pH sensitivity of 47.3 mV/pH. It showed that the post-annealing process improved the sensing performance of the device. The morphology characteristic was characterized by field emission scanning electron microscopy (FESEM) and showed a porous structure as the annealing temperature increased, indicating that the porous film could be the sensing electrode of an EGFET pH sensor. The hysteresis of the sensing electrode was measured in buffer solutions prepared at pH 7, pH 4, pH 7, pH 10, and pH 7 to find its pH response delay. These findings indicated that sol-gel spin-coated CuO thin film can be considered a promising candidate for applications as an EGFET-pH sensor. [ABSTRACT FROM AUTHOR]

CuO thin films with broccoli-like structure were prepared using a facile hydrothermal method to construct photocathodes for water-splitting application. The morphological, structural, and optical properties of thin films were characterized and measured using several techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and ultraviolet-visible spectroscopy (UV-Vis). The thickness, structure, and morphology of CuO thin films can be controlled by varying the precursor concentration (Cp) and reaction temperature (Tr), which are also discussed. Moreover, the electrical properties of CuO thin films were also measured in the three-electrode system. The photocurrent density of photocathodes, when synthesized by a 0.5 M solution at 150 °C for 12 h, was 0.5 mA/cm2 at −0.6 V vs. Ag/AgCl, which is 1.8 times higher than that of photocathodes synthesized in a 0.1 M solution at 100 °C with the same reaction time. In addition, increasing the reaction temperature and precursor concentration aided in the enhancement of the IPCE and APCE values, which peaked at a wavelength range of 330–400 nm. [ABSTRACT FROM AUTHOR]

In this study, the CuO thin films were deposited on glass substrates at different substrate temperatures (350, 400, 450, and 500 C) by the ultrasonic spray pyrolysis (USP) method and then annealed at 525 C. In X-ray diffraction (XRD) analysis, the peak intensity was not found in thin films at 350 C substrate temperature and as-grown conditions. Two distinct peaks were observed at 36 and 39 in the XRD patterns of other films. These peaks are characteristic peaks of the monoclinic crystal structure of CuO. Atomic force microscopy (AFM) and scanning electron microscope (SEM) images of the produced thin films were examined. The surfaces of thin films are not smooth. After annealing, grain agglomerations were formed. The optical properties of the CuO thin films were analyzed by ultraviolet-visible region (UV-Vis) measurements. Forbidden band gap values (Eg) were calculated from Tauc graphs for as-grown and annealed samples. It has been observed that the structural, morphological, and optical properties of CuO thin films produced by the USP method can be controlled by the substrate temperature. [ABSTRACT FROM AUTHOR]

This study reports the influences of gamma irradiation (GI) in the range of 20–100 kGy on CuO thin films via thermal spray pyrolysis technique on the glass substrates. The results demonstrate significant influences of GI on the crystallographic, microstructural and optical characteristics of CuO thin films. The obtained XRD results showed that the crystallinity of the films deteriorates by gradually decreasing crystallite size (from 59.13 to 46 nm) as applied gamma doses increases. However, the basic monoclinic crystal structure remains same. The dislocation density and lattice strain increased with the rise of GI absorbed dose due to the creation of defects. The values of number of crystallites per unit surface area increased as dose increased indicating the abundance of crystallization of nano CuO thin films. A UV–Vis–NIR spectrophotometer was utilized to determine the optical properties and obtained results indicated that the optical energy band gap (OBG) energies reduced from 2.00 to 1.72 eV as the doses increased from 0 to 100 kGy. No distinctions of the monoclinic phase of virgin CuO thin film have been perceived under applied absorbed doses, notwithstanding the slight deterioration of the crystallinity and narrowing the OBG. [ABSTRACT FROM AUTHOR]

CuO thin films with broccoli-like structure were prepared using a facile hydrothermal method to construct photocathodes for water-splitting application. The morphological, structural, and optical properties of thin films were characterized and measured using several techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and ultraviolet-visible spectroscopy (UV-Vis). The thickness, structure, and morphology of CuO thin films can be controlled by varying the precursor concentration (Cp) and reaction temperature (Tr), which are also discussed. Moreover, the electrical properties of CuO thin films were also measured in the three-electrode system. The photocurrent density of photocathodes, when synthesized by a 0.5 M solution at 150 °C for 12 h, was 0.5 mA/cm2 at −0.6 V vs. Ag/AgCl, which is 1.8 times higher than that of photocathodes synthesized in a 0.1 M solution at 100 °C with the same reaction time. In addition, increasing the reaction temperature and precursor concentration aided in the enhancement of the IPCE and APCE values, which peaked at a wavelength range of 330–400 nm.

• CuO TFs having different thicknesses prepared by sol–gel dip coating method. • XRD with Raman FT-IR profiles revealed the monoclinic symmetry of CuO TFs. • High absorption in visible region made it a suitable material as photocatalyst. • Surface-dependent electrical properties are evaluated by surface resistance mapping. • CuO TFs shows excellent photocatalytic efficiency for MO dye in water. In the present study, Cupric oxide thin films with varying thicknesses were successfully fabricated on a glass substrate at room temperature via dip coating technique. Highly crystalline CuO films with monoclinic symmetry were examined from XRD which was further confirmed with the help of Raman spectra. FESEM results showed a uniform coating surface with nano-sized grains without any agglomerations. The elemental composition of Cu and O atoms is in a 1:1 stoichiometric ratio for samples having higher thickness values. Strong absorption in the visible and nearby IR region makes the sample a viable choice in the field of photovoltaics. The estimated band gap values from the Tauc plot ranges from 1.10 eV to 1.26 eV. All the samples exhibited a p-type nature and their uniformity of resistance over the film surface was examined by resistance mapping. Hall measurements indicated the direct proportionality of sample resistivity with thickness. [ABSTRACT FROM AUTHOR]

CuO thin films were successfully deposited using a simple, cost-effective and nearly room-temperature successive ionic layer adsorption and reaction routes. The material has been characterized using x-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. Increase of grain size and decrease of microstrain were observed for a particular level of dipping (30 cycles) and further increase in dipping cycles shows a reverse tendency. The effect of the dipping cycle of the synthesized films on their supercapacitive, photocatalytic and ethanol-sensing performance were investigated. A 30-cycle dipped CuO thin film-based electrode provides a maximum specific capacitance of 585 Fg−1 at the voltage scan rate of 2 mVs−1 from cyclic voltammetry measurement and 554 Fg−1 at a current density of 1 Ag−1 from the charging to discharging curve. This electrode exhibited long-term cycle stability with 92.3% capacitance retention after 4000 cycles. CuO films synthesized for 30 dipping cycles showed the highest photocatalytic activities with 91.1% degradation of methylene blue under exposure to visible light of 200-W energy in a time duration of 4 h. Maximum sensitivity of 67% in the presence of 1500 ppm ethanol at the operating temperature 160°C was obtained for 30 dipping cycles film. Such attractive properties of low cost and facile synthesized CuO thin films makes them a suitable candidate for different commercial applications. [ABSTRACT FROM AUTHOR]

Abstract In the present work, nanostructured cupric oxide (CuO) thin films have been successfully deposited on glass substrates by successive ionic layer adsorption and reaction (SILAR) technique at room temperature. The influence of complexing agent as triethanolamine (TEA) on the structural, morphological, optical and electrical characteristics of nanocrystalline CuO thin films have been examined in detail. Structural studies confirm that all the films were polycrystalline nature having a monoclinic crystalline form and displayed ( 1 ¯ 11) and (111) preferential orientations. The estimated crystallite values ranged from 17.47 to 19.95 nm. The surface morphology of CuO thin films was examined through scanning electron microscopy and materials microscope studies. Surface studies revealed that homogeneously distributed CuO nanostructures on the film surfaces. The optical studies showed that band gap energy values of the CuO thin films were increased from 1.33 to 2.00 eV as a function of increasing TEA concentration. Meanwhile, the average transmittance of all the films had increased from 2.5 to 42.5% with the increasing TEA concentration. FTIR studies identified the formation of single phase CuO and chemical bonding of the complexing agent. The resistivity value of CuO thin film synthesized without TEA was 3.74 × 105 Ω cm and the resistivity consequently increased to 509 × 105 Ω cm with TEA concentration of 1.0 M%. A high figure of merit (786 × 10−12 Ω−1) was obtained for complexing agent concentration of 0.25 M%. Highlights • Nanocrystalline CuO thin films with and without TEA synthesized by SILAR method. • The physical characteristics of CuO thin films were significantly affected by increased TEA concentration. • The optical band gap increased after the addition of TEA from 1.33 to 2.00 eV. [ABSTRACT FROM AUTHOR]

In previous decades, investigation of superconductors was aimed either at finding materials with higher critical temperatures or at discovering nontypical superconducting behavior. Here, we present the cupric (CuO) thin films, which were synthesized by atomic layer deposition by using a metal-organic precursor, copper (II)-bis-(-dimethylamino-2-propoxide), and ozone as an oxidizer. The deposition process was optimized by employing a quartz crystal monitoring, and the contact between the deposited films and planar and three-dimensional SiO2/Si substrates was examined by scanning electron microscopy with a focused ion beam module. Phase and elemental composition were analyzed by X-ray diffraction and X-ray fluorescence. Two-probe electrical resistivity measurements revealed a resistivity drop below the critical temperature of 4 K, which may indicate low-temperature superconductivity of the CuO thin films.

In this study, CuO thin films were deposited on glass substrates at a wide range of temperatures from 450ºC to 550ºC with steps of 25ºC by chemical spray pyrolysis technique. Aiming to investigate the effect of annealing process, one of the resulting films was annealed at 450ºC for 3 hours under ambient air. Based on X-ray diffraction, all the resulting films are monoclinic with two prominent peaks at ~36º and ~39º. The crystallite size of the CuO film deposited at 450ºC was found to be the largest in comparison with the others. As the substrate temperature increased, a gradual change was observed for the CuO thin film surface morphology and in the case of annealed film, the grains and their boundaries became indistinguishable. The resistivity of the films was reduced by virtue of increasing the substrate temperature and also, both the mobility and carrier concentration of the annealed film were improved drastically after annealing. As expected, the CuO thin films absorption was considerable in the visible region and gradually declined after 800nm. The estimated band gap value of the CuO film deposited at 450ºC were fairly close to the optimum band gap for solar applications.

Binders are usually used in lithium ion batteries for electrode fabrication, but they may make the production process complex, increase the inner resistance and reduce electrochemical performance. A facile and effective gas-etch method was employed in this work to prepare binder-free Cu(OH) 2 /CuO electrodes which directly grew on Cu foils at ambient temperature. The evolution process of 3D hierarchical structural Cu(OH) 2 /CuO thin film during the gas-etching and heat treatment was discussed by XRD, SEM and TEM analyses. The hierarchical snowflake structure with high specific surface of the prepared thin films could not only accelerate the electronic/ionic migration but also enhance the electrochemical performance. As Li-ion storage electrodes, the binder- and conductor-free CuO thin films exhibit a cycling capacity of 568 mAh g −1 at 0.1 C current density. The gas-etch method operated at ambient temperature is promisingly suitable for applications in the scaled production of thin-film electrodes. [ABSTRACT FROM AUTHOR]

A simple and inexpensive technique to synthesize and deposit Cu(II) oxide (CuO) nanostructured layers is reported herein together with electrical and optical properties characterization. The 2-step deposition procedure consists of spin-coating a Cu(II) formate solution on fluorine-doped tin oxide (FTO) conducting glass substrate followed by a heat treatment. Fluorescence spectroscopy and Fourier transform infrared spectroscopy confirmed that the organic ligand precursor is absent in the obtained film. X-ray diffraction (XRD) experiments show that only CuO films are deposited on the FTO substrate ruling out the presence of other Cu x O oxides. Scanning-electron microscopy reveals their nanostructured morphology; which agrees with crystallite size domain (L = 21 nm) estimated from XRD width peak analysis. Absorption coefficient spectra, as well as direct-gap values (E g  = 1.52–1.55 eV), were obtained using optical transmittance and reflection spectroscopy. Finally, the as prepared CuO films are used as photoelectrodes in a photoelectrochemical cell with an aqueous electrolyte and short-circuit photocurrent under illumination and dark conditions is measured. [ABSTRACT FROM AUTHOR]

Thin film of p-type cupric oxide ( p -CuO) is grown on silicon (n-Si) substrate by using chemical bath deposition (CBD) technique and a precise control of thickness from 60 nm to 178 nm has been achieved. The structural properties and stoichiometric composition of the grown films are observed to depend significantly on the growth time. The chemical composition, optical properties, and structural quality are investigated in detail by employing XRD, ellipsometric measurements and SEM images. Also, the elemental composition and the oxidation states of Cu and O in the grown samples have been studied in detail by XPS measurements. Thin film of 110 nm thicknesses exhibited the best performance in terms of crystal quality, refractive index, dielectric constant, band-gap, and optical properties. The study suggests synthesis route for developing high quality CuO thin film using CBD method for electronic and optical applications. [ABSTRACT FROM AUTHOR]

The influence of the presence of HCl and methanol in the precursor on CuO absorber layers deposited by spray pyrolysis has been investigated. The films were deposited on glass substrate at fixed substrate temperature of 450°C using 0.05 molar CuCl·2HO in deionized water containing a specific amount of HCl and methanol. The structural, morphological, electrical, and optical properties of the resulting thin films were studied to evaluate their suitability for solar applications. Presence of HCl increased the concentration of Cu ions in the precursor, leading to a rise in the Cu concentration in the resulting film, which improved the crystallinity with increased mean grain size, surface roughness, and carrier mobility at the cost of decreased carrier concentration. However, film deposited with excess HCl suffered from corrosion and huge cracks, making it unfavorable for solar applications. On the other hand, although presence of methanol improved the crystallinity of the resulting film, the surface was smooth due to lower deposition rate. Kubelka-Munk theory was used to estimate the optical bandgap of the deposited thin films, revealing values fairly close to optimum for solar cell applications. [ABSTRACT FROM AUTHOR]

In this study, we fabricated CuO thin films using the sol-gel spin coating method. The fabricated thin films were utilized for electrocatalytic reduction of CO 2 (CO 2 ER). Fabrication of thin film is vital to provide a large surface area and a more exposed (111) crystal plane for ethanol selectivity. This is verified by comparing it with bulk powder material which does not give such activity. CO 2 ER over thin film electrode specifically forms CO(g) and Ethanol(l), 2 and 12 electron reduction products, and eliminates the possibility of unwanted HER as a side reaction in the CO 2 saturated NaHCO 3 electrolyte. We achieved significant product selectivity and faradaic efficiency, utilizing the very low potential for both CO and ethanol. Specific formation of only CO and ethanol makes the process efficient as the separation of gas and liquid is easy. Results based on density functional theory calculations suggest that CuO (111) and CuO (-111) surfaces promote CO 2 adsorption and subsequent formation of CO. However, a direct CO-dimerization is observed only on the CuO (111) surface that facilitates the formation of ethanol as the C2 product. This comparative study of bulk and thin-film opens new insight and highlights the importance of catalyst fabrication for the specific product formation utilizing significantly less energy. [ABSTRACT FROM AUTHOR]

In this work, the CuO nano-powder has been synthesized by employing chemical bath deposition technique for its subsequent use to grow ultrathin film (20 nm) of p-CuO on n-Si substrate for the fabrication of p-CuO/n-Si hetero-junction diodes. The thin CuO film has been grown by employing vapour-liquid-solid method. The crystalline structure and chemical phase of the film are characterized by employing field-emission scanning electron microscopy and X-ray diffraction studies. Chemical stoichiometry of the film has been confirmed by using energy dispersive X-ray spectroscopy. The potential for photovoltaic applications of such films is investigated by measuring the junction current-voltage characteristics and by extracting the relevant parameters such as open circuit photo-generated voltage, short circuit current density, fill-factor and energy conversion efficiency. [ABSTRACT FROM AUTHOR]

• Synthesis of CuO/ZnO (C/Z) bilayer thin film via sol gel spin coating technique. • Improved CO 2 response of C/Z bilayer thin film with respect to CuO and ZnO thin films. • CO 2 adsorption modeling of C/Z bilayer thin film. • Estimation of activation energy, E A , and heat of adsorption, Q for CO 2 adsorption on C/Z bilayer thin film. • Description of CO 2 sensing mechanism in CuO, ZnO and C/Z bilayer thin films. A CuO/ZnO (C/Z) bilayer thin film was fabricated with a porous top CuO layer to facilitate a sensitive and selective response towards CO 2 gas. Such a sensor architecture allowed optimum oxygen and CO 2 gas adsorption in the interfacial region. The C/Z thin-film sensor exhibited a good response (47%) for 2500 ppm CO 2 at 375 °C as opposed to CuO (15%) at 300 °C and ZnO (16%) at 350 °C. The sensor was selective to CO 2 in respect of CO and CH 4 gases at 375 °C with selectivity factor κ CO2 ∼ 5 and ∼ 8 for CO and CH 4 respectively. By analyzing the conductance-time transients for the gas, the adsorption behavior of CO 2 on the heterogenous C/Z bilayer thin-film sensor was established. CO 2 obeyed an extended Freundlich model of adsorption. Theoretical analysis of the said adsorption model was performed through which the activation energy (E A) and heat of adsorption (Q) of CO 2 gas were estimated. A complementary relationship between E A and Q was established. It was shown that E A decreases with increasing concentration from 123.95 to 108.36 kJ/mol for 1000–2500 ppm CO 2 for energetically heterogeneous surfaces. Alternatively, Q values increase with increasing concentration from 59.73 to 71.65 kJ/mol for 500–2500 ppm CO 2. The CO 2 sensing mechanism was elucidated based on surface defects for CuO and ZnO. CO 2 sensing in the C/Z bilayer thin-film sensor was controlled by the adsorption of oxygen forming a space charge layer at the surface and interface of the p-n heterojunction and by band-bending as a result of the change of electron concentration across the junction. [ABSTRACT FROM AUTHOR]

A general gas diffusion equation was used to predict the variation of sensor response with operating temperature and thickness for p-type CuO thin films for ethanol and acetone vapours. Assuming Langmuir-Hinshelwood mechanism and non-linear variation of sensor conductance with gas concentration, the response transients were modelled for a wide concentration range under isothermal conditions and fitted with extended Freundlich and Langmuir isotherms for ethanol and acetone respectively. Maximum responses of 144% and 168% were obtained for 300 ppm ethanol and acetone respectively at 300 °C for 240 nm CuO thin films. For CuO thin films of thickness 120–240 nm, response (S) versus temperature (T) exhibited a bell-shaped dependence with peak maxima of ethanol and acetone varying only slightly. Irreversible type gas response was obtained for a concentration range of 300–50 ppm for both ethanol and acetone vapours wherein response time systematically decreases with an increase in target gas concentration. • Synthesis of CuO thin film via sol gel spin coating technique. • Ethanol and acetone sensing characteristics of CuO thin film. • Application of gas diffusion theory to p-type CuO thin film. • Variation of gas response with film thickness. • Irreversible sensing of ethanol and acetone. [ABSTRACT FROM AUTHOR]

In previous decades, investigation of superconductors was aimed either at finding materials with higher critical temperatures or at discovering nontypical superconducting behavior. Here, we present the cupric (CuO) thin films, which were synthesized by atomic layer deposition by using a metal-organic precursor, copper (II)-bis-(-dimethylamino-2-propoxide), and ozone as an oxidizer. The deposition process was optimized by employing a quartz crystal monitoring, and the contact between the deposited films and planar and three-dimensional SiO2/Si substrates was examined by scanning electron microscopy with a focused ion beam module. Phase and elemental composition were analyzed by X-ray diffraction and X-ray fluorescence. Two-probe electrical resistivity measurements revealed a resistivity drop below the critical temperature of 4 K, which may indicate low-temperature superconductivity of the CuO thin films. [ABSTRACT FROM AUTHOR]

In this study, copper oxide (CuO) thin films were synthesized at different deposition temperatures on fluorine doped tin oxide coated glass (FTO) substrates by spray pyrolysis for supercapacitor applications. The physical and electrochemical properties of the as-synthesized CuO samples were characterized via different analytical techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy, scanning electron (SEM) microscopy, surface wettability tests, and electrochemical measurements. The results showed that the deposition temperature affected their structural, morphological, and supercapacitor properties. The higher specific capacitance and extensive charge/discharge capability of the nanoparticle-like CuO thin films demonstrated their suitability as outstanding candidates in electrochemical applications. The evaluated specific capacitance further confirmed the effect of the deposition temperature on the supercapacitor performance of the CuO electrodes; its values for the thin films synthesized at 300, 350, and 400 °C were 363, 691, and 487 F g−1, respectively, at a scan rate of 5 mV s−1 in a 2 M Na 2 SO 4 aqueous electrolyte. Hence, this study demonstrates that the surface morphology and electrochemical supercapacitive properties of materials are dependent on the deposition temperature of CuO thin films. Experimental setup and growth process of spray pyrolysis synthesized CuO thin films. Unlabelled Image • Novel route for the synthesis of CuO thin films • Different size of nanoparticles likes nanostructure of CuO thin films. • 350 °C shows the higher reactive area. • 350 °C electrodes demonstrated outstanding supercapacitive performance. [ABSTRACT FROM AUTHOR]

Inefficient visible light photocatalytic degradation of organic pollutants, such as acetaminophen (ACE) and triclosan (TS), is one of the main limiting factors for implementing cost‐effective metal oxide photocatalyst for large‐scale deployment. Here, a highly efficient CuO thin film photocatalyst is developed through rapid thermal annealing. The CuO thin film is decorated with Pd nanostructures for enhanced visible light degradation of ACE and TS. It is shown that compared to the as‐deposited thin CuO film photocatalyst, the rapid thermal assisted CuO photocatalyst can significantly enhance charge generation and separation efficiency through improvement of crystallinity and reduction of recombination centres. Furthermore, it is demonstrated that the incorporation of Pd nanostructures can considerably increase optical absorption, which further improve the photocatalytic performance through the enhancement of surface plasmon resonance. The CuO film with the 40 s of Pd sputtering (Pd40–CuO) shows the highest performance for photocatalytic degradation of both ACE and TS. The Pd40–CuO film shows good stability and does not show any considerable reduction in photocatalytic activity after five cycles. This indicates the high potential of Pd40–CuO for water and wastewater treatment on industrial scale. Application of Pd‐decorated CuO thin film for photocatalytic degradation of acetaminophen and triclosan in aqueous solution is presented. The effect of thermal treatment on the photocatalytic activity of the CuO thin film is investigated. The photocatalytic degradation mechanism is comprehensively discussed in this article. The stability and recycling of photocatalysts are investigated. [ABSTRACT FROM AUTHOR]

Abstract: This study investigates a solar-thermoelectric module for power generation from solar energy. The proposed method uses recycled external exhaust heat to generate electric power, further enhancing the thermoelectric conversion efficiency of the thermoelectric generator (TEG). Using electrophoresis deposition, self-prepared CuO nanofluid is deposited onto a Cu plate and then adheres to the surface of a thermoelectric generator (TEG). Experimental results show that the CuO thin film coating on the TEG surface can elevate the temperature by around 2 °C and the voltage by around 14.8%, thus enhancing the thermoelectric conversion efficiency of the thermoelectric generator by 10% and increasing the overall power output by 2.35%. It was found that this solar-thermoelectric module can generate about 4.95 mW/cm2 under solar radiation intensity of about 100 mW/cm2. [Copyright &y& Elsevier]