Structural and optical property studies on Fe doped CuO nanoparticles

The Cupric oxide (CuO) nanostructures and Fe doped CuO nanomaterials are synthesized by microwave irradiation method. The effect of Fe doping on the crystal structure, band gap and optical properties of synthesized samples were characterized by using x-ray diffraction, ultraviolet-visible spectrometer, photoluminescence spectrometer and Fourier transform infrared spectrometer. X-ray diffraction study confirms the size of the particle in nanometer. The optical band gap calculated from UV–Vis absorption spectrum, reveals the change in band gap energy due to the presence of dopants. The photoluminescence spectrum suggests that Fe doped CuO nanoparticles may be used in optoelectronic devices. The functional group analysis carried out by Fourier transform infrared spectroscopy confirmed the substitution of Fe in the samples.

Three-Layer PdO/CuWO4/CuO System for Hydrogen Gas Sensing with Reduced Humidity Interference

The growing hydrogen industry is stimulating an ongoing search for new materials not only for hydrogen production or storage but also for hydrogen sensing. These materials have to be sensitive to hydrogen, but additionally, their synthesis should be compatible with the microcircuit industry to enable seamless integration into various devices. In addition, the interference of air humidity remains an issue for hydrogen sensing materials. We approach these challenges using conventional reactive sputter deposition. Using three consequential processes, we synthesized multilayer structures. A basic two-layer system composed of a base layer of cupric oxide (CuO) overlayered with a nanostructured copper tungstate (CuWO4) exhibits higher sensitivity than individual materials. This is explained by the formation of microscopic heterojunctions. The addition of a third layer of palladium oxide (PdO) in forms of thin film and particles resulted in a reduction in humidity interference. As a result, a sensing three-layer system working at 150 °C with an equalized response in dry/humid air was developed.

Effects of Differently Incubated Cupric Oxide Nanoparticles on the Granulosa Cells of Caprine Ovary in Vitro

Present study was aimed to investigate the effect of temperature on the shape and size of nanoparticles and related cytotoxicity of these particles on ovarian granulosa cells. Cupric oxide nanoparticles (CuONPs) were synthesized using a simple, efficient, and reproducible precipitation method involving reduction of Cu metal salt with sodium hydroxide and then incubation of the precipitates at 70oC for 5 hrs. Subsequently, this prepared sample was divided into 3 subsamples and incubated at 3 different temperatures i.e. 70oC, 150oC, and 350oC for a time duration of 5 hrs. to study the effect of temperature on the particles. The products were characterized by XRD, FTIR, HRTEM, and FESEM. Characterization of the particles revealed that all particles were monoclinic crystalline in nature and had a size range from 9 nm - 60 nm. Particles were of different shapes; spherical, needle, and capsule. Toxicity of each particle was determined on granulosa cells by exposing them for 24 hrs. at 2 different doses. Toxicological results showed the size and shape-related toxicity of nanoparticles; particles which were spherical shape were significantly more toxic than capsule-shaped particles.

Kinetic Behavior of Fabricated CuO/ZrO2 Oxygen Carriers for Chemical Looping Oxygen Uncoupling

Chemical looping with oxygen uncoupling (CLOU) is an innovative alternative to conventional combustion. CuO/ZrO2 oxygen carriers were tested in this system for their effectiveness and resilience. Cupric oxide (CuO) was demonstrated to be a reliable oxygen carrier for oxygen-uncoupling with consistent recyclability even after 50 redox cycles in a thermogravimetric analyzer (TGA). The reduction of CuO to generate Cu2O and oxygen was observed to be improved markedly for experiments operated at higher temperatures; however, the oxidation of Cu2O by air to generate CuO was hindered for experiments carried out at elevated temperatures. The reduction rate of fabricated CuO/ZrO2 particles containing 40% CuO was enhanced with increasing temperature and decreased with increasing particle size for experiments operated in a fixed bed reactor. The geometrical contraction and Avrami-Erofe’ev models were demonstrated to be appropriate for describing the reduction and oxidation of CuO/ZrO2, respectively. The activation energies for the reduction and oxidation were determined to be 250.6 kJ/mol and 57.6 kJ/mol, respectively, based on experimental results in the temperature range between 850 and 1000 °C.

Synthesis of Antibacterial Oxide of Copper for Potential Application as Antifouling Agent

Background: Copper oxide nanoparticles have become very important due to their numerous applications and ease of synthesis. Out of the two oxides of copper, cuprous oxide exhibits better antibacterial, antimicrobial, and antifouling properties. Objective: The study aimed to find a way of synthesizing stable and eco-friendly oxide of copper and test it for antibacterial properties. Methods: The precipitation method was employed for the synthesis of nanoparticles. NaOH and Moringa Oleifera leaves extract were used as the reducing agents to obtain two different sets of samples. Results: Good phases of copper oxides were formed for all the samples (cuprous as well as cupric oxides). SEM studies showed that the structure of cupric oxide (CuO), formed at higher calcination temperatures, is well defined when synthesized using a hybrid method. Conclusion: Our studies indicate that the hybrid method of synthesis used by us is a more effective and quicker way of synthesizing cuprous oxide (Cu2O), which exhibits higher antibacterial properties as compared to cupric oxide (CuO).

Raman and Conduction Studies on Carbon Nanotube Networks and Cupric Oxide Nanostructures

<p>This thesis presents detailed temperature-dependent Raman and conduction studies on two materials: cupric oxide (CuO) nanostructures and single-walled carbon nanotube (SWNT) networks. SWNT networks are a promising alternative to indium tin oxide as the transparent conducting material in electronic displays. A key factor that complicates fundamental studies on SWNT networks is surfactant residue. Our study utilises SWNTs (HiPCO) dispersed in volatile solvents, which can be removed by annealing to only 100°C. Using this unique solvent system, we have systematically studied charge transport mechanisms in surfactant-free networks using a percolation approach; where sample resistance can be controlled by the amount of deposited material. The chemical environment of these networks was found to be unchanged using Raman spectroscopy; i.e. film fabrication did not cause any significant doping of the network. Around 15 surfactant-free networks, with resistances between 300 kΩ and 8 kΩ, were found to follow a 'universal' charge transport model. Most of the networks could be described by two dimensional variable range hopping (VRH) and thermal activation. The barrier energy or, To parameter, for the VRH mechanism was independent of resistance with a value of 20x 10ᵌ ± 9.4x 10ᵌ K. The activation energy also had a resistance-independent value of 160 ± 20 meV. Four terminal measurements confirm that the activation mechanism is due to processes within the network not, Schottky barriers at the nanotube/metal interface. The effects of extrinsic adsorbants on the network resistance provides evidence for dominant non-metallic conduction pathways within the studied range of resistances. These results strongly suggest a characteristic barrier size in our SWNT networks where non-metallic tubes dominate the resistance. The surfactant-free networks were also used to study the temperature-dependent behaviour of the radial breathing modes (RBM) in bundled nanotubes. Deconvolution of complex RBM spectra was made possible using an interactive routine: based on the higher resolution of second derivatives for fitting spectra with washed-out features. Using this routine, the temperature-dependent characteristics of the RBM lineshape could be identified. We find that RBM modes in our bundled networks soften at the same rate as individual tubes; the linewidth follows a three phonon decay process with a temperature-independent component and the intensity can be modelled from the change in Eii with temperature. The second part of this thesis addresses the unique asymmetric lineshape of the A1g mode in CuO nanowire forests. A symmetric lineshape is recovered at low powers indicating that the underlying mechanism is thermal. To study this effect, the high temperature behaviour of the A1g mode is first analysed in a `bulk' form of CuO. The analytical temperature dependence of the A1g mode frequency, linewidth and intensity were used as the basis of a physical model that connects lineshape asymmetry to laser-induced, spatial temperature gradients in the sample.The peak temperature (under the laser hotspot) was found to be proportional to laser power until it reaches a critical value. We believe that regions with temperature above the critical value cool by radiation rather than convection.</p>

Raman and Conduction Studies on Carbon Nanotube Networks and Cupric Oxide Nanostructures

<p>This thesis presents detailed temperature-dependent Raman and conduction studies on two materials: cupric oxide (CuO) nanostructures and single-walled carbon nanotube (SWNT) networks. SWNT networks are a promising alternative to indium tin oxide as the transparent conducting material in electronic displays. A key factor that complicates fundamental studies on SWNT networks is surfactant residue. Our study utilises SWNTs (HiPCO) dispersed in volatile solvents, which can be removed by annealing to only 100°C. Using this unique solvent system, we have systematically studied charge transport mechanisms in surfactant-free networks using a percolation approach; where sample resistance can be controlled by the amount of deposited material. The chemical environment of these networks was found to be unchanged using Raman spectroscopy; i.e. film fabrication did not cause any significant doping of the network. Around 15 surfactant-free networks, with resistances between 300 kΩ and 8 kΩ, were found to follow a 'universal' charge transport model. Most of the networks could be described by two dimensional variable range hopping (VRH) and thermal activation. The barrier energy or, To parameter, for the VRH mechanism was independent of resistance with a value of 20x 10ᵌ ± 9.4x 10ᵌ K. The activation energy also had a resistance-independent value of 160 ± 20 meV. Four terminal measurements confirm that the activation mechanism is due to processes within the network not, Schottky barriers at the nanotube/metal interface. The effects of extrinsic adsorbants on the network resistance provides evidence for dominant non-metallic conduction pathways within the studied range of resistances. These results strongly suggest a characteristic barrier size in our SWNT networks where non-metallic tubes dominate the resistance. The surfactant-free networks were also used to study the temperature-dependent behaviour of the radial breathing modes (RBM) in bundled nanotubes. Deconvolution of complex RBM spectra was made possible using an interactive routine: based on the higher resolution of second derivatives for fitting spectra with washed-out features. Using this routine, the temperature-dependent characteristics of the RBM lineshape could be identified. We find that RBM modes in our bundled networks soften at the same rate as individual tubes; the linewidth follows a three phonon decay process with a temperature-independent component and the intensity can be modelled from the change in Eii with temperature. The second part of this thesis addresses the unique asymmetric lineshape of the A1g mode in CuO nanowire forests. A symmetric lineshape is recovered at low powers indicating that the underlying mechanism is thermal. To study this effect, the high temperature behaviour of the A1g mode is first analysed in a `bulk' form of CuO. The analytical temperature dependence of the A1g mode frequency, linewidth and intensity were used as the basis of a physical model that connects lineshape asymmetry to laser-induced, spatial temperature gradients in the sample.The peak temperature (under the laser hotspot) was found to be proportional to laser power until it reaches a critical value. We believe that regions with temperature above the critical value cool by radiation rather than convection.</p>