Nanostructured CuO Thin Films Research Articles

Effects of cadmium doping on the physical and sensing properties of nanostructured CuO thin films

This investigation used sol-gel deposition to create undoped CuO and CuO: Cd thin films. All films of undoped CuO and CuO: Cd phase exhibit four dominating peaks at 35.52°, 38.84°, 53.37°, and 68.23°, which are correspondingly assigned to the (022), (200), (020), and (220) planes, according to X-ray diffraction analysis. The dislocation density reduced from 60.55 to 49.94, the strain decreased from 26.98 to 24.60, and the grain size of the produced films measured by XRD was 12.85–14.15 nm. Atomic force microscopy (AFM) was used to study the morphology. SEM analysis showed increased aggregation with higher Cd content, resulting in a more uniform porous structure. The optical band gap decreases for all samples as the cadmium content increases, ranging from 2.28 to 2.14 eV. Similarly, the refractive index and extinction coefficient values decrease as the cadmium content increases for all samples. The gas sensor detects H2 (375 ppm) using CuO film cadmium doping, which enhances sensitivity, CuO: 4% exhibits highest resistance. Sensitivity decreases with higher doping, indicating reduced sensor responsiveness.

Thickness effects on the physical characterization of nanostructured CuO thin films for hydrogen gas sensor

In these studies, radio frequency (RF) magnetron sputtering was used to produce nanostructured CuO thin films on glass bases with different thicknesses of (250, 300, and 350 nm). X-ray diffraction (XRD) analysis of these films revealed a polycrystalline structure with a preferred peak along the (111) plane. The Scherrer formula was used to compute the grain size. It was found that the average grain sizes are 10.78 nm, 11.36 nm, and 11.84 nm for film thicknesses of 250, 3000, and 300 nm, respectively, while the dislocation density and strain values decline. The surface roughness decreased from 9.30 nm to 4.71 nm as the thickness increased, according to atomic force microscopy (AFM) data. As the thickness of the film grew, the root mean square (RMS) roughness likewise decreased from 9.18 nm to 4.29 nm. The homogenous, semi-spherical structure comprises uniformly distributed particles, as demonstrated by SEM images. The optical properties of the grown films showed that the absorption coefficient considerably increased with film thickness. Transmittance, band gap, refractive index, and extinction coefficient all decrease with increasing film thickness. The hydrogen gas measurements, indicated a reduction in sensitivity as the thickness and gas concentration increased at 30°C.

Superior photoelectrodes of nanostructured Mo-doped CuO thin film for green hydrogen generation from photoelectrochemical water-splitting

Green hydrogen has an audible echo in the clean energy field. In this piece of work, pure and Mo-doped CuO thin films were deposited at different substrate temperatures on the Indium Tin Oxide (ITO) by the DC/RF sputtering technique. The prepared samples were utilized to generate hydrogen gas within the photoelectrochemical water-splitting mechanism. Crystallographic planes (−111), and (200) were the preferred orientations for pure and Mo-doped CuO thin films. Moreover, the average crystallite size was doubled by Mo doping reaching 25.8 nm. FE-SEM microscopic image exhibits that the pure and Mo–CuO thin films have a regular distribution with a small size. The optical band gap has rosed by doping from 1.8 eV to 2.05 eV. Then, it increased to 2.3 eV and 2.4 eV at temperatures of 100 °C and 200 °C respectively. Pure and Mo–CuO thin films were applied as photocathodes for hydrogen generation with water water-splitting technique. The photoelectrochemical application revealed a photocurrent density of ∼2.25 mA/cm2 for Mo-doped CuO photoelectrode at room temperature. This optimum photoelectrode was studied for stability and electrochemical impedance. In addition, the incident photon to current efficiency (IPCE%) was 4.47 % at 500 nm. The applied bias photon to current conversion efficiency (ABPE%) was 4.25 % at −0.38V. As a result of the above, pure and Mo-doped CuO photoelectrodes are low-cost thin films and have a high-efficiency performance for green hydrogen generation industrially.

Room-temperature fabrication of a heterostructure Cu2O@CuO nanosheet electrocatalyst for non-enzymatic detection of glucose and H2O2

• Binder-free Cu 2 O@CuO nanosheets were deposited on FTO using vacuum kinetic spray at room temperature. • Cu 2 O@CuO nanosheets exhibited high sensitivity toward detection of glucose at 818.5 μA·mM −1 ·cm −2 . • Cu 2 O@CuO nanosheets exhibited wide linear detection range of glucose from 0.02 to 5 mM. Heterostructure Cu 2 O@CuO nanosheets are spontaneously formed during the kinetic-spraying of nanostructured CuO thin film on the fluorine-doped tin oxide (FTO) substrate at room temperature under low vacuum conditions by the NPDS technique. The Cu 2 O@CuO nanosheets fabricated as a heterogeneous electrocatalyst are utilized for free enzyme detection of glucose and H 2 O 2 in 0.1 M NaOH, whereby the synergy between the multivalent copper species (I and II) results in an overall improvement of electrocatalytic performance. The in-situ formation of interfacial Cu 2 O@CuO heterostructure is verified using a high-resolution transmission microscope and X-ray photon electron spectroscopy. The fabricated electrocatalysts exhibit high sensitivity toward glucose oxidation of 818.5 μA·mM −1 ·cm −2 with a wide linear detection range extending from 0.02 to 5 mM and a limit of detection (LOD) of 5.8 μM. Also, the heterostructure Cu 2 O@CuO nanosheets show a very wide linear detection range of H 2 O 2 oxidation from 0.02 to 11 mM with a good detection sensitivity of 168 μA·mM −1 ·cm −2 and a LOD of 8.75 μM. The long-term stability for around 30 min and high oxidation selectivity with other interfering species are verified. Furthermore, Cu 2 O@CuO nanosheets exhibit higher catalytic rate constant and diffusion coefficient toward glucose species compared with H 2 O 2 .

Fabrication of nanostructured CuO thin films with controllable optical band gaps using a mist spin spray technique at 90 °C

A solution-based process, termed the mist spin spray method, was developed to fabricate nanostructured CuO thin films on seed-free glass substrates. In this method, a copper amine complex solution and a NaOH solution are separately atomized by ultrasonication to generate mists. These mists are subsequently sprayed onto a substrate heated to 90 °C and fixed on a rotating platform to grow crystalline CuO thin films at atmospheric pressure. This one-step method enables the generation of phase-pure, dense and crack-free CuO thin films below 100 °C. CuO thin films approximately 30 nm in thickness exhibited good adhesion to glass substrates, and the concentrations of NH3 and NaOH in the initial solutions were found to affect both the film morphology and optical band gap. Specimens prepared using higher NH3 and NaOH concentrations had larger grain sizes, while those fabricated using a low NaOH concentration showed a porous structure. A higher optical band gap was found to correlate with smaller grain sizes in the films.

Flexible nanostructured CuO thin film: A promising candidate for wearable real-time sweat rate monitoring devices

Hydration level monitoring ensures clinically convenient instructions for preventive medicine and disease diagnostics. This paper aims to develop a wearable metal-oxide based sensor for monitoring hydration levels using flexible nanostructured copper oxide (CuO) thin film. Nanostructured CuO thin films were designed and fabricated on flexible cellulose acetate (CA) substrates via the successive ionic layer adsorption and reaction (SILAR) method. The obtained CuO films vigorously adhered to the CA substrate, and the resulting coated substrates were efficiently flexible to be used as wearable hydration level monitoring systems to realize big data collection of human health. The sensing response of the CuO-based flexible sensors is heavily improved by optimizing the growth process.

Enhanced ethanol sensing response of nanostructured Ce-doped CuO thin films

CuO based thin films doped with Ce concentrations varying from 0 to 8 mol% were prepared by chemical spray pyrolysis. X-ray diffraction analysis revealed bandgap modulation which is dependant on Ce doping and also showed perservation of the single phased monoclinic CuO structure for all the films after doping indicating successful substitution of Ce4+ ions in host matrix. SEM and AFM microscopy showed changes in morphology as Ce doping was increased. And this appeared to have a significant role on the ethanol sensing capabilities of the thin films which were measured at different working temperatures. Good gas sensing stability and maximum response was observed for the 4% Ce thin film. The sensing device was found to be more responsive towards ethanol than other common volatile organic compounds such as methanol, acentronile, ammonia and acetone. The response and recovery times for the sensing suggest a chemosorbption mechanism.

A first-principle study of nanostructured CuO thin film-based caffeine sensing scheme

In this study, we demonstrated the feasibility of nanostructured CuO thin film usage for caffeine sensing. Our morphological studies revealed that ellipse- or spiral-shaped nanostructured were formed with good crystal qualities. It was shown that the film thickness was decreased from 803 nm to 717 nm with annealing. Better crystalline quality of annealed films resulted in higher sensing response. Moreover, caffeine sensing response time was decreased to 19 s from 28 s for annealed films compared to as-grown CuO films. Both films exhibited excellent linearity with higher than 0.93 R2 values for the caffeine values from 0.5 mM to 10 mM, which is the range for most caffeinated hot and cold beverages. Caffeine is considered the only legal stimulant and its excessive use is not healthy. Knowing the caffeine content of beverages using portable, cheap sensor devices will be beneficial for the health-conscious society. We believe our sensing scheme in using nanostructured semiconductor thin films will pave the way to ultimately create advanced materials-based portable sensor devices.

Role of Zn dopants on the surface morphology, chemical structure and DC electrical transport properties of nanostructured p-type CuO thin films

This paper is based on the studies of surface morphology, chemical structure and DC electrical transport properties of zinc (Zn) doped copper oxide (CuO:Zn) thin films synthesized by spray pyrolysis technique. CuO and CuO:Zn thin films were deposited onto ultrasonically cleaned microscope glass substrates at the substrate temperature 623 K. Zn concentration (conc.) in CuO:Zn thin films was varied from 1 to 6 at%. In field emission scanning electron microscopic images of CuO:Zn thin films nanostructures are observed around the nucleation center. The maximum average particle size is found about 18 nm for 5 at% Zn doped CuO:Zn thin film. X-ray photoelectron spectroscopy confirms the chemical structure and composition of the films. Activation energy of CuO:Zn thin films in the temperature range 350–423 K increases from 0.17 to- 0.39 eV with the rise of Zn conc. In the range of 2–6 at%. DC electrical resistivity of CuO:Zn thin films is found in the order of 104 Ω-cm. Hall effect measurements confirms the p-type conductivity of CuO:Zn thin films with the carrier conc. In the order of 1018 cm-3. Carrier mobility of 5 at% CuO:Zn thin film is as high as 84.83 cm2 V-1 s-1.

Nanostructured CuO Thin Films Prepared by Aqueous Based Novel Reflux Method

AbstractCopper oxide (CuO) thin films have been deposited on glass and steel substrates but here work is done on steel substrate by novel aqueous based Reflux method whereas deposition of CuO thin film uses copper sulfate as copper ion source from an aqueous alkaline medium. The effects of copper ion concentration, temperature, and deposition time are studied for deposition of thin films. The CuO thin films are characterized by XRD, UV, SEM, and contact angle. The X‐Ray diffraction results reveal that CuO is monoclinic in nature. Optical band gap is observed from UV–visible spectrophotometer which is 1.9 eV. The surface morphological studies obtained from SEM micrograph show rice shape of exterior. While wettability test shows hydrophobic nature of CuO. This material characterization of CuO thin film clearly indicates that these films can be widely used in various applications such as gas sensor, transducers such as thermocouple to measure thermo e.m.f, solar cells, and super capacitor.

Sunlight driven photocatalysis and non-enzymatic glucose sensing performance of cubic structured CuO thin films

Cubic structured CuO thin films were fabricated through a combined effort of electrochemical and thermal annealing processes, and their solar light-induced photodegradation and non-enzymatic sensing behavior were well studied. Nanocubes like structures were achieved by varying the time during the electrochemical deposition. Raman spectroscopy and X-ray diffraction studies reveal the monoclinic phase of CuO thin films while scanning electron microscopy highlights the modulation in the size and density of cube-like morphology of CuO thin films. Atomic force microscopy also assures the existence of cube-like nanostructures. Modulation in the optical behavior of CuO thin films was explored by the UV–visible spectroscopy, which indicates the bandgap narrowing in CuO thin films with the deposition time. Sunlight driven photodegradation performance of CuO thin films was explored by decomposition of Methylene Blue molecules. CuO thin films with different nanocubes density exhibit outstanding sunlight-induced photodegradation activity by degrading 5 µM MB dye solution in 90 min. Cubic nanostructured CuO thin film also reveals the outstanding non-enzymatic glucose sensing behavior with a high sensitivity of 1311.83 μA mM−1 cm−2, the wide linear range of 0.001–1.8 mM, fast response times (less than 5) and low detection limit (LOD) of 0.068 µM under a signal/noise ratio of 3.

Influence MgO Dopant on Structural and Optical Properties of Nanostructured CuO Thin Films

Influence MgO Dopant on Structural and Optical Properties of Nanostructured CuO Thin Films

Copper Oxide Thin Films Synthesized by SILAR: Role of Varying Annealing Temperature

To coat CuO thin films on the glass surface, an easily controlled successive ionic layer absorption and reaction method was used. CuO thin films were grown at room temperature. The CuO thin films obtained were annealed for 30 min at 200, 300 and 400 °C. The changes caused by annealing temperature on nanostructured CuO thin films were studied. Structural, morphological, optical and molecular properties of annealed CuO thin films were investigated. For this analysis, X-ray diffraction, Scanning electron microscopy, Atomic force microscopy, RAMAN and Optical absorption spectroscopy (UV–Vis) and Fourier transform infrared spectroscopy devices were used.

Engineering of morphological, optical, structural, photocatalytic and catalytic properties of nanostructured CuO thin films fabricated by reactive DC magnetron sputtering

Nanostructured thin films of CuO were deposited on silica glass substrates using reactive DC magnetron sputtering technique. Microstructural, morphological, optical, catalytic and photocatalytic properties of the prepared CuO thin films were examined using FESEM, AFM, Rutherford backscattering spectrometry, XRD, XPS, UV–Vis absorption and PL spectroscopy. FESEM showed nanostructures in the thin films, which were confirmed to be of monoclinic CuO by XRD analysis. Substrate temperature variation (40 °C, 100 °C and 300 °C) was found to significantly alter the optical, morphological, photocatalytic and structural properties of the CuO nanostructured thin film coatings. FESEM and AFM analyses showed decrease in size of nanostructures and surface roughness increase with increase in substrate temperature. Increase in UV–Vis absorbance and PL intensity of CuO thin films with decrease in crystallite size were noticed as the substrate temperature was increased. The prepared nanostructured CuO thin films exhibited highly enhanced photocatalytic activities and degraded dyes (MB and MO) in water in just 40 min under solar exposure and catalytic transformation of 4-nitrophenol (4-NP) took place in just 15 min. The developed CuO nanostructured thin film coatings are very promising for large scale, practical and advanced catalytic reduction of toxic 4-NP and photocatalytic applications in solar driven water purification.

Fabrication of Au-CuO hybrid plasmonic nanostructured thin films with enhanced photocatalytic activity

Thin films of Au-CuO plasmonic nanohybrids were fabricated by simple thermal evaporation. SEM and XRD investigations unveiled the impact of annealing on the structural properties and morphology of the synthesized Au-CuO hybrid thin film. Au nanoparticle decoration onto CuO thin film significantly altered the photocatalytic activity, structural and optical properties of CuO thin film. The as-prepared Au-CuO nanostructured hybrid plasmonic thin film showed improved photocatalytic efficiency for decomposition of MG and MB than pristine CuO and annealed Au-CuO thin film samples. The improved photocatalytic efficiency of Au-CuO hybrid nanostructured thin film is attributed to reduction in the recombination of charge carriers in CuO nanostructures and improvement in light utilization capability due to attachment of Au nanoparticles on nanostructured CuO thin film. Cracks in Au-CuO nanohybrid thin film facilitated enhanced adsorption of dye molecules and played an essential role in improving the photocatalytic efficiency.

Improved sensing response of nanostructured CuO thin films towards sweat rate monitoring: Effect of Cr doping

In this research, we have studied the effect of chromium doping of CuO on the main physical properties and hydration level sensing ability of thin-film samples synthesized by SILAR method on soda-lime glass substrates. The structural, morphological and optical properties as well as hydration level sensing behavior of pristine and CrxCu1-xO (x = 0.01 and 0.02) films were investigated under different Cr concentrations. Optical and structural analysis verified the Cr-doping into CuO films without degrading the uniformity of the metal oxide semiconductor structure. It was shown that the resistivity increases with Cr-doping, which was attributed to the additional holes introduced to the semiconductor crystal. Sweat sensing response of the metal oxide films improved significantly with doping (sensing response from 0.45 to 8.50 for heavy doping). Transient analysis of the sweat response also showed that response time is less than 60 s. We conclude that Cr-doping improves the sensing performance of CuO thin films and offers to be implemented in sweat sensing devices as the sensing material.

Thermal evolution of morphological, structural, optical and photocatalytic properties of CuO thin films

Nanostructured CuO thin films were synthesized by thermal evaporation and annealing. Structural, optical and morphological changes in the CuO film upon annealing and their overall impact on its photocatalytic activity were investigated employing X-ray diffraction, UV–Vis absorption spectroscopy, atomic force microscopy and field emission scanning electron microscopy. Significant modifications in the morphological, optical, structural and photocatalytic behavior of nanostructured CuO thin film were observed upon thermal annealing. Thermal annealing led to the growth of CuO nanoparticles and the average size of CuO nanoparticles increased from 23 nm to 293 nm as the annealing temperature was increased to 600oC. CuO thin film sample annealed at 400 °C exhibited superior photocatalytic activities over other samples for the degradation of malachite green and methylene blue dyes in 120 and 160 min, respectively. The improved photocatalytic behavior of CuO thin film annealed at 400 °C is attributed to its narrower band gap, improved utilization of sunlight and enhanced adsorption of dye due to increased surface area arising from formation of CuO nanoparticles and their aggregates at the surface.

Preparation and characterization of nanostructured CuO thin films using spray pyrolysis technique

In this work, the suitability of CuO thin films on gas sensors and solar cells applications was investigated. CuO thin films were deposited using spray pyrolysis. The effect of substrates temperature on the films structural and optical properties was discussed. X-ray diffraction showed the appearance of tenorite phase of cupric oxide CuO without impurities indicating the formation of pure cupric oxide material. Raman spectroscopy confirmed the results obtained in XRD and showed CuO phase formation. A crystallinity improvement was measured increasing the temperature from 300 °C to 375 °C. Optical properties such as band gap energy, refractive index, extinction coefficient and optical conductivity were extracted using transmittance/absorbance data giving by UV-Visible spectrophotometer. Low transmittance, high absorbance and small band gap energy were observed at the highest substrate temperature, these characteristics make CuO an appropriate material to be used as absorber layer in photovoltaic applications. The performances of CuO thin film for acetone sensing were proved: 33% of response, 160 s and 360 s as response and recovery time, respectively.

Spray Deposited Nanostructured CuO Thin Films: Influence of Substrate Temperature and Annealing Process

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.

Improved photon trapping by combined use of dye-synthesized and one-dimensional fiber-like nanostructured CuO thin film

Photon trapping and absorption are affected strongly by surface morphology and chemical composition. Here, we have developed a novel synthetic recipe based on the electrochemical deposition of CuO in the form of cubic-like nanostructural (CLN) morphology on glass substrate coated ITO. Deposition conditions were carefully manipulated to build up a thin film of CLN on the pre-deposited seeds. NaOH solution of adjusted concentration was used as a modifying agent that converted three-dimensional CLN into one-dimensional fiber-like nanostructure (FLN) thin film, which showed a dramatic increase in photon trapping. For the first time, an optically stable dye N,N'-bis(4-pyridyl)-3,4:9,10-perylenebis (dicarboximide) (BPPD) was used to enhance photon absorption by the FLN thin film. The photon absorption of the dye-sensitized FLN showed enhanced and stable behavior compared to the bare FLN thin film.