One-dimensional CuO nanowire: synthesis, electrical, and optoelectronic devices application

Electrical and Thermal Conductivities of Single CuxO Nanowires

Copper oxide nanowires (NWs) are promising elements for the realization of a wide range of devices for low-power electronics, gas sensors, and energy storage applications, due to their high aspect ratio, low environmental impact, and cost-effective manufacturing. Here, we report on the electrical and thermal properties of copper oxide NWs synthetized through thermal growth directly on copper foil. Structural characterization revealed that the growth process resulted in the formation of vertically aligned NWs on the Cu growth substrate, while the investigation of chemical composition revealed that the NWs were composed of CuO rather than Cu2O. The electrical characterization of single-NW-based devices, in which single NWs were contacted by Cu electrodes, revealed that the NWs were characterized by a conductivity of 7.6 × 10-2 S∙cm-1. The effect of the metal-insulator interface at the NW-electrode contact was analyzed by comparing characterizations in two-terminal and four-terminal configurations. The effective thermal conductivity of single CuO NWs placed on a substrate was measured using Scanning Thermal Microscopy (SThM), providing a value of 2.6 W∙m-1∙K-1, and using a simple Finite Difference model, an estimate for the thermal conductivity of the nanowire itself was obtained as 3.1 W∙m-1∙K-1. By shedding new light on the electrical and thermal properties of single CuO NWs, these results can be exploited for the rational design of a wide range of optoelectronic devices based on NWs.

High performance 1D-2D CuO/MoS2 photodetectors enhanced by femtosecond laser-induced contact engineering

The integration of 2D materials with other dimensional materials opens up rich possibilities for both fundamental physics and exotic nanodevices. However, current mixed-dimensional heterostructures often suffer from interfacial contact issues and environment-induced degradation, which severely limits their performance in electronics/optoelectronics. Herein, we demonstrate a novel BN-encapsulated CuO/MoS₂ 2D-1D van der Waals heterostructure photodetector with an ultrahigh photoresponsivity which is 10-fold higher than its previous 2D-1D counterparts. The interfacial contact state and photodetection capabilities of 2D-1D heterojunctions are significantly improved via femtosecond laser irradiation induced MoS₂ wrapping and contamination removal. These h-BN protected devices show highly sensitive, gate-tunable and robust photoelectronic properties. By controlling the gate and bias voltages, the device can achieve a photoresponsivity as high as 2500 A W^-1 in the forward bias mode, or achieve a high detectivity of 6.5 × 10¹¹ Jones and a typical rise time of 2.5 ms at reverse bias. Moreover, h-BN encapsulation effectively protects the mixed-dimensional photodetector from electrical depletion by gas molecules such as O₂ and H₂O during fs laser treatment or the operation process, thus greatly improving the stability and service life in harsh environments. This work provides a new way for the further development of high performance, low cost, and robust mixed-dimensional heterostructure photodetectors by femtosecond laser contact engineering.

Tuning the basicity of the Ni@MCM-41 catalyst via alkaline earth metal oxide promoters for CO2 reforming of CH4

Dry reforming of methane (DRM) is an effective method to change two main greenhouse gases (CH4 and CO2) into valuable chemicals such as hydrogen.

Laser modification of Au-CuO-Au structures for improved electrical and electro-optical properties

CuO nanomaterials are one of the metal-oxides that received extensive investigations in recent years due to their versatility for applications in high-performance nano-devices. Tailoring the device performance through the engineering of properties in the CuO nanomaterials thus attracted lots of effort. In this paper, we show that nanosecond (ns) laser irradiation is effective in improving the electrical and optoelectrical properties in the copper oxide nanowires (CuO NWs). We find that ns laser irradiation can achieve joining between CuO NWs and interdigital gold electrodes. Meanwhile, the concentration and type of point defects in CuO can be controlled by ns laser irradiation as well. An increase in the concentration of defect centers, together with a reduction in the potential energy barrier at the Au/CuO interfaces due to laser irradiation increases electrical conductivity and enhances photo-conductivity. We demonstrate that the enhanced electrical and photo-conductivity achieved through ns laser irradiation can be beneficial for applications such as resistive switching and photo-detection.

Aligned CuO nanowire array for a high performance visible light photodetector

Recently, copper oxide (CuO) has drawn much attention as a promising material in visible light photodetection with its advantages in ease of nanofabrication. CuO allows a variety of nanostructures to be explored to enhance the optoelectrical performance such as photogenerated carriers scattering and bandgap engineering. However, previous researches neglect in-depth analysis of CuO’s light interaction effects, restrictively using random orientation such as randomly arranged nanowires, single nanowires, and dispersed nanoparticles. Here, we demonstrate an ultra-high performance CuO visible light photodetector utilizing perfectly-aligned nanowire array structures. CuO nanowires with 300 nm-width critical dimension suppressed carrier transport in the dark state and enhanced the conversion of photons to carriers; additionally, the aligned arrangement of the nanowires with designed geometry improved the light absorption by means of the constructive interference effect. The proposed nanostructures provide advantages in terms of dark current, photocurrent, and response time, showing unprecedentedly high (state-of-the-art) optoelectronic performance, including high values of sensitivity (S = 172.21%), photo-responsivity (R = 16.03 A/W, λ = 535 nm), photo-detectivity (D^* = 7.78 × 10¹¹ Jones), rise/decay time (τ_r/τ_d = 0.31 s/1.21 s).

Growth of 1D TiO2nanostructures on Ti substrates incorporated with residual stress through humid oxidation and their characterizations

Different Ti substrates, such as particles (as-received and ball milled), plate and TEM grid were oxidized for the growth of one dimensional (1D) TiO₂nanostructures. The Ti substrates were oxidized for 4 h at temperatures of 700 °C-750 °C in humid and dry Ar containing 5 ppm of O₂. The effects of residual stress on the growth of 1D TiO₂nanostructures were investigated. The residual stress inside the Ti particles was measured by XRD-sin²ψtechnique. The oxidized Ti substrates were characterized using field emission scanning electron microscope equipped with energy dispersive x-ray spectroscope, transmission electron microscope, x-ray diffractometer and x-ray photoelectron spectroscope. Results revealed that humid environment enhances the growth of 1D TiO₂nanostructures. Four different types of 1D morphologies obtained during humid oxidation, e.g. stacked, ribbon, plateau and lamp-post shaped nanostructures. The presence of residual stress significantly enhances the density and coverage of 1D nanostructures. The as-grown TiO₂nanostructures possess tetragonal rutile structure having length up to 10μm along the 〈1 0 1〉 directions. During initial stage of oxidation, a TiO₂layer is formed on Ti substrate. Lower valence oxides (Ti₃O₅, Ti₂O₃and TiO) then form underneath the TiO₂layer and induce stress at the interface of oxide layers. The induced stress plays significant role on the growth of 1D TiO₂nanostructures. The induced stress is relaxed by creating new surfaces in the form of 1D TiO₂nanostructures. A diffusion based model is proposed to explain the mechanism of 1D TiO₂growth during humid oxidation of Ti. The 1D TiO₂nanostructures and TiO₂layer is formed by the interstitial diffusion of Ti⁴⁺ions to the surface and reacts with the surface adsorbed hydroxide ions (OH^-). Lower valence oxides are formed at the metal-oxide interface by the reaction between diffused oxygen ions and Ti ions.

Dual-functioning porous catalysts: robust electro-oxidation of small organic molecules and water electrolysis using bimetallic Ni/Cu foams

The simultaneous co-deposition of Cu within the matrix of Ni foams (utilizing DHBT) increases their intrinsic catalytic activity towards water electrolysis, urea oxidation reaction (UOR), and glycerol oxidation reaction (GOR) in alkaline media.

Cu/CuO Composite Track-Etched Membranes for Catalytic Decomposition of Nitrophenols and Removal of As(III)

One of the promising applications of nanomaterials is to use them as catalysts and sorbents to remove toxic pollutants such as nitroaromatic compounds and heavy metal ions for environmental protection. This work reports the synthesis of Cu/CuO-deposited composite track-etched membranes through low-temperature annealing and their application in catalysis and sorption. The synthesized Cu/CuO/poly(ethylene terephthalate) (PET) composites presented efficient catalytic activity with high conversion yield in the reduction of nitro aryl compounds to their corresponding amino derivatives. It has been found that increasing the time of annealing raises the ratio of the copper(II) oxide (CuO) tenorite phase in the structure, which leads to a significant increase in the catalytic activity of the composites. The samples presented maximum catalytic activity after 5 h of annealing, where the ratio of CuO phase and the degree of crystallinity were 64.3% and 62.7%, respectively. The catalytic activity of pristine and annealed composites was tested in the reduction of 4-nitroaniline and was shown to remain practically unchanged for five consecutive test cycles. Composites annealed at 140 °C were also tested for their capacity to absorb arsenic(III) ions in cross-flow mode. It was observed that the sorption capacity of composite membranes increased by 48.7% compared to the pristine sample and reached its maximum after 10 h of annealing, then gradually decreased by 24% with further annealing.

Size Distribution, Mechanical and Electrical Properties of CuO Nanowires Grown by Modified Thermal Oxidation Methods

Size distribution, Young's moduli and electrical resistivity are investigated for CuO nanowires synthesized by different thermal oxidation methods. Oxidation in dry and wet air were applied for synthesis both with and without an external electrical field. An increased yield of high aspect ratio nanowires with diameters below 100 nm is achieved by combining applied electric field and growth conditions with additional water vapour at the first stage of synthesis. Young's moduli determined from resonance and bending experiments show similar diameter dependencies and increase above 200 GPa for nanowires with diameters narrower than 50 nm. The nanowires synthesized by simple thermal oxidation possess electrical resistivities about one order of magnitude lower than the nanowires synthesized by electric field assisted approach in wet air. The high aspect ratio, mechanical strength and robust electrical properties suggest CuO nanowires as promising candidates for NEMS actuators.

High-Performance Copper Oxide Visible-Light Photodetector via Grain-Structure Model

Recently, copper oxide (CuO)-based visible-light photodetectors have attracted great interest due to their narrow bandgap (1.2 eV), low cost, and ease of fabrication. However, there has been insufficient theoretical analysis and study of CuO-based photodetectors, resulting in inferior performance in terms of responsivity, detectivity, and response speed. This work develops a method to enhance the performance of CuO photodetectors by engineering a grain structure based on a newly-developed theoretical model. In the developed theoretical grain-structure model, the grain size and the connections between grains are considered because they can strongly affect the optoelectronic characteristics of CuO photodetectors. Based upon the proposed model, the engineered CuO device achieves enhanced optoelectronic performance. The engineered device shows high responsivity of 15.3 A/W and detectivity of 1.08 × 10¹¹ Jones, which are 18 and 50 times better than those of the unoptimized device, and also shows fast rising and decaying response speeds of 0.682 s and 1.77 s, respectively. In addition, the proposed method is suitable for the mass-production of performance-enhanced, reliable photodetectors. By using a conventional semiconductor fabrication process, a photodetector-array is demonstrated on a 4-inch wafer. The fabricated devices show uniform, high, and stable optoelectronic performance for a month.

Photoelectric Detectors Based on Inorganic p-Type Semiconductor Materials

Photoelectric detectors are the central part of modern photodetection systems with numerous commercial and scientific applications. p-Type semiconductor materials play important roles in optoelectronic devices. Photodetectors based on p-type semiconductor materials have attracted a great deal of attention in recent years because of their unique properties. Here, a comprehensive summary of the recent progress mainly on photodetectors based on inorganic p-type semiconductor materials is presented. Various structures, including photoconductors, phototransistors, homojunctions, heterojunctions, p-i-n junctions, and metal-semiconductor junctions of photodetectors based on inorganic p-type semiconductor materials, are discussed and summarized. Perspectives and an outlook, highlighting the promising future directions of this research field, are also given.

Nanotransition Materials (NTMs): Photocatalysis, Validated High Effective Sorbent Models Study for Organic Dye Degradation and Precise Mathematical Data's at Standardized Level

The present work describes the synthesis of copper oxide nanoparticles (CuONPs) via a solution process with the aim of applying the nano-adsorbent for the reduction of methylene blue (MB) dye in alkaline media. These NPs were characterized via Field emission scanning electron microscopy (FE-SEM), X-ray diffraction, high-resolution Transmission electron microscopy (TEM), and ultra violet UV-visible spectroscopy to confirm their morphology and crystalline and optical properties in order to design an adsorption-degradation process. The photocatalytic CuONPs exhibited dynamic properties, great adsorption affinity during the chemisorption process, and operated at various modes with a strong interaction between the adsorbent and the adsorptive species, and equilibrium isotherm, kinetic isotherm, and thermodynamic activities in the presence of UV light. All basic quantities, such as concentration, pH, adsorbent dose, time, and temperature, were determined by an optimization process. The best-fitted adsorption Langmuir model (R² = 0.9988) and performance, including adsorption capacity (350.87 mg/g), photocatalytic efficiency (90.74%), and degradation rate constant (Ks = 2.23 ×10-2 min-1), illustrate good feasibility with respect to sorption-reduction reactions but followed a pseudo-second-order kinetic on the adsorbent surface, reaching an equilibrium point in 80 min. The thermodynamic analysis suggests that the adsorption reaction is spontaneous and endothermic in nature. The thermodynamic parameters such as enthalpy (∆H°), entropy (∆S°), and Gibbs free energy (∆G°) give effective results to support a chemical reduction reaction at 303 K temperature. The equilibrium isotherm and kinetic and thermodynamic models with error function analysis explore the potential, acceptability, accuracy, access to adsorbents, and novelty of an unrivaled-sorption system.

Flexible Photodetectors Based on Novel Functional Materials

Flexible photodetectors have attracted a great deal of research interest in recent years due to their great possibilities for application in a variety of emerging areas such as flexible, stretchable, implantable, portable, wearable and printed electronics and optoelectronics. Novel functional materials, including materials with zero-dimensional (0D) and one-dimensional (1D) inorganic nanostructures, two-dimensional (2D) layered materials, organic semiconductors and perovskite materials, exhibit appealing electrical and optoelectrical properties, as well as outstanding mechanical flexibility, and have been widely studied as building blocks in cost-effective flexible photodetection. Here, we comprehensively review the outstanding performance of flexible photodetectors made from these novel functional materials reported in recent years. The photoresponse characteristics and flexibility of the devices will be discussed systematically. Summaries and challenges are provided to guide future directions of this vital research field.

Photocatalytic TMO-NMs adsorbent: Temperature-Time dependent Safranine degradation, sorption study validated under optimized effective equilibrium models parameter with standardized statistical analysis

In this paper, chemically synthesized copper oxide nanoparticles (CuO-NPs), were employed for two processes: one is photocatalytic degradation and second one adsorption for the sorption of safranine (SA) dye in an aqueous medium at pH = 12.01. The optimized analytes amount (nano-adsorbent = 0.10 g, conc. range of SA dye 56.13 ppm to 154.37 ppm, pH = 12.01, temperature 303 K) reached to equilibrium point in 80 min, which acquired for chemical adsorption-degradation reactions. The degredated SA dye data’s recorded by UV-visible spectroscopy for the occurrence of TMO-NMs of CuO-NPs at anticipated period of interval. The feasible performance of CuO-NPs was admirable, shows good adsorption capacity qm = 53.676 mg g⁻¹ and most convenient to best fitted results establish by linear regression equation, corresponded for selected kinetic model (pseudo second order (R² = 0.9981), equilibrium isotherm models (Freundlich, Langmuir, Dubnin-Radushkevich (D-R), Temkin, H-J and Halsey), and thermodynamic parameters (∆H° = 75461.909 J mol⁻¹, ∆S° = 253.761 J mol⁻¹, ∆G° = −1427.93 J mol⁻¹, Ea = 185.142 J mol⁻¹) with error analysis. The statistical study revealed that CuO-NPs was an effective adsorbent certified photocatalytic efficiency (η = 84.88%) for degradation of SA dye, exhibited more feasibility and good affinity toward adsorbate, the sorption capacity increases with increased temperature at equilibrium point.

Hollow CuxO (x = 2, 1) micro/nanostructures: synthesis, fundamental properties and applications

In this review, we comprehensively summarize the important advances in hollow Cu_xO micro/nanostructures, including the universal synthesis strategies, the interfacial Cu–O atomic structures as well as the intrinsic properties, and potential applications. Remarks on emerging issues and promising research directions are also discussed.

The Sensing Properties of Single Y-Doped SnO2 Nanobelt Device to Acetone

Pure SnO₂ and Y-doped SnO₂ nanobelts were prepared by thermal evaporation at 1350 °C in the presence of Ar carrier gas (30 sccm). The samples were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersion spectrometer (EDS), X-ray photoelectron spectrometer (XPS), UV-Vis absorption spectroscopy, Raman spectroscopy, and Fourier transform infrared spectrum (FTIR). The sensing properties of the devices based on a single SnO₂ nanobelt and Y-doped SnO₂ nanobelt were explored to acetone, ethanol, and ethanediol. It reveals that the sensitivity of single Y-doped SnO₂ nanobelt device is 11.4 to 100 ppm of acetone at 210 °C, which is the highest response among the three tested VOC gases. Y³⁺ ions improve the sensitivity of SnO₂ sensor and have an influence on the optical properties of Y-doped SnO₂ nanobelts.

Surfactant-free Synthesis of CuO with Controllable Morphologies and Enhanced Photocatalytic Property

A green synthesis for nanoleave, nanosheet, spindle-like, rugby-like, dandelion-like and flower-like CuO nanostructures (from 2D to 3D) is successfully achieved through simply hydrothermal synthetic method without the assistance of surfactant. The morphology of CuO nanostructures can be easily tailored by adjusting the amount of ammonia and the source of copper. By designing a time varying experiment, it is verified that the flower- and dandelion-like CuO structures are synthesized by the self-assembly and Ostwald ripening mechanism. Structural and morphological evolutions are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-visible diffuse reflectance spectra. Additionally, the CuO nanostructures with different morphologies could serve as a potential photocatalyst on the photodecomposition of rhodamine B (RhB) aqueous solutions in the presence of H2O2 under visible light irradiation.