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Graphene Nucleation Preference at CuO Defects Rather Than Cu2O on Cu(111): A Combination of DFT Calculation and Experiment
摘要： It is well-known that reducing the nucleation density is an effective way to enhance the growth quality of graphene. In this work, we explore the mechanism of graphene nucleation and growth around CuO defects on a Cu(111) substrate by using density functional theory (DFT) combined with the nudged elastic band (NEB) method. The defect formation mechanism at the initial nucleation stage is also studied. Our calculation results of the C adsorption energy and the reaction barrier of C–C dimer formation illustrate that the initial nucleation of graphene could be promoted by artificially introducing CuO defects on a Cu(111) surface and the nucleation on the clean Cu(111) substrate could thus be suppressed. These conclusions have been verified by graphene growth experiments using a chemical vapor deposition (CVD) method. Further studies showed that graphene grown around CuO “seed crystals” could maintain its structural integrity without significantly producing defective carbon rings. This work provides fundamental understanding and theoretical guidance for controllable preparing large dimension and high quality graphene by artificially introducing CuO seeds.
关键词： CuO,Cu2O,Graphene,DFT,Nucleation
更新于2025-09-23 15:21:21
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Controlled Synthesis of Coral-Like CuO Dendrites with Enhanced Photocatalytic Performance
摘要： In this work, coral-like CuO dendrites were successfully synthesized by a solvothermal method in the mixed solvent of distilled water and ethanol with assistance of dodecyl trimethyl ammonium bromide (DTAB). The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analysis techniques, to investigate their structure and morphology. The coral-like CuO dendrites were about 1 μm in length, with many dendrites pointing to a common center. The influence of experimental conditions on morphology, such as volume ratio of water to ethanol, surfactant DTAB and molar ratio of Na2CO3 and Cu(CH3COO)2, was also discussed. Time-dependent experiment was carried out to explore the formation mechanism while a “particle-sheet-dendrite (PSD)” mechanism was proposed to explain the growth process. The as-prepared CuO dendrites were used to degrade methylene blue (MB) under visible light irradiation in the presence of H2O2, where over 98% of methylene blue (MB) was degraded in 1 h. Results from the study demonstrated that the as-prepared coral-like CuO dendrites exhibited enhanced photocatalytic performance and excellent stability and reusability.
关键词： Photocatalytic Performance,Solvothermal Method,Coral-Like CuO Dendrites
更新于2025-09-23 15:21:01
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Enhancement in the performance of nanostructured CuOa??ZnO solar cells by band alignment
摘要： In this study, we investigated the effect of cobalt doping on band alignment and the performance of nanostructured ZnO/CuO heterojunction solar cells. ZnO nanorods and CuO nanostructures were fabricated by a low-temperature and cost-effective chemical bath deposition technique. The band offsets between Zn1?xCoxO (x = 0, 0.05, 0.10, 0.15, and 0.20) and CuO nanostructures were estimated using X-ray photoelectron spectroscopy and it was observed that the reduction of the conduction band offset with CuO. This also results in an enhancement in the open-circuit voltage. It was demonstrated that an optimal amount of cobalt doping could effectively passivate the ZnO related defects, resulting in a suitable conduction band offset, suppressing interface recombination, and enhancing conductivity and mobility. The capacitance–voltage analysis demonstrated the effectiveness of cobalt doping on enhancing the depletion width and built-in potential. Through impedance spectroscopy analysis, it was shown that recombination resistance increased up to 10% cobalt doping, thus decreased charge recombination at the interface. Further, it was demonstrated that the insertion of a thin layer of molybdenum oxide (MoO3) between the active layer (CuO) and the gold electrode hinders the formation of a Schottky junction and improved charge extraction at the interface. The ZnO/CuO solar cells with 10% cobalt doped ZnO and 20 nm thick MoO3 buffer layer achieved the best power conversion efficiency of 2.11%. Our results demonstrate the crucial role of the band alignment on the performance of the ZnO/CuO heterojunction solar cells and could pave the way for further progress on improving conversion efficiency in oxide-based heterojunction solar cells.
关键词： nanostructured,solar cells,X-ray photoelectron spectroscopy,power conversion efficiency,molybdenum oxide,chemical bath deposition,band alignment,CuO–ZnO,cobalt doping
更新于2025-09-23 15:21:01
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Controlled synthesis of CuO decorated defect enriched ZnO nanoflakes for improved sunlight-induced photocatalytic degradation of organic pollutants
摘要： We report synthesis and application of a unique heterojunction nanocomposite formed between copper nanoparticles (CNPs) and defect rich ZnO nanoflakes for application towards water remediation. Systemic variation in CNPs functionalization was seen to modulate the optical, structural and photocatalytic properties of the heterojunction, which were found to be well in accordance with the results from TEM, UV-DRS and EPR. The remediation ability of the heterojunction measured in terms of its photocatalytic ability was studied by degrading three different organic dye pollutants Rhodamine 6G (R6G), Methylene Blue (MB) and Methyl Orange (MO) using solar light (850 W/cm2) as the renewable excitation source. CNPs loading density was seen to follow a direct linear relationship to optical absorbance and band gap narrowing. The initial increase in photolytic efficiency is associated with improved visible light response and reduced band gap due to attachment of CNPs while reduction in activity was found to be associated with generation of self-recombination centres in CuO functionalization. Optimized CNP modified ZnO nanoflakes was able to decompose 10 μM of R6G, MB and MO dye solutions in 80, 40 and 60 min respectively.
关键词： Semiconductor,CuO,Photocatalysis,ZnO,Dye degradation
更新于2025-09-23 15:21:01
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1D/2D WO3 nanostructure coupled with nanoparticulate CuO cocatalyst for enhancing solar-driven CO2 photoreduction: The impact of the crystal facet
摘要： Photocatalytic reduction of CO2 into solar fuels is regarded as one of the most promising approaches to address the issues of global warming and the energy crisis. The promotion of spatial charge separation and transfer through crystal facet engineering could be conducive to improved photocatalytic activity. In this study, one-dimensional (1D) WO3 nanowires with a {110} dominant facet (WO3-110) and two-dimensional (2D) WO3 nanosheets with a {001} dominant facet (WO3-001) coupled with CuO nanoparticles are fabricated by a facile method and used for CO2 photoreduction. Its composition and structural characterizations suggest that the WO3-CuO hybrid features good contact between the WO3 and CuO nanostructures. Under light irradiation, the WO3 and WO3-CuO nanostructures are able to photoreduce CO2 into CH4. Notably, the prepared WO3-CuO nanohybrids with different exposed facets show improved CO2 reduction capability compared to pure WO3 and CuO. The heterojunction interface between the WO3 photocatalyst and the CuO cocatalyst through p-n contact can facilitate electron-hole pair separation and accordingly results in enhanced photocatalytic performance. With the assistance of the CuO cocatalyst, the {110} facet WO3-CuO hybrid displays superior photoreduction capability compared to the {001} facet WO3-CuO, which is attributed to the difference in the crystal facets in the heterostructure. The {110} facet WO3 nanowires have a more negative conduction band edge, contributing to the higher reduction capacity of this sample. On the other hand, it is shown that faster charge carrier transfer efficiency would enable more photoinduced electrons to participate in CO2 photoreduction, especially with the involvement of the nanoparticulate CuO cocatalyst. This work provides guidance for designing a hetero-photocatalyst-cocatalyst system through crystal facet engineering.
关键词： WO3-CuO composite,CO2 Photoreduction,1D/2D WO3 nanostructures,heterojunction,crystal facet impact
更新于2025-09-23 15:21:01
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Bandgap engineering in CuO nanostructures: Dual-band, broadband, and UV-C photodetectors
摘要： In this work, the bandgap of CuO (p-type semiconductor) has been engineered from an indirect bandgap of (cid:2)1 eV to a direct bandgap of 4 eV just by tuning the nanostructure morphology and midgap defect states. The absorption in near-infrared (NIR) and visible regions is ordinarily suppressed by controlling the growth parameters. Considering the increasing scope and demand of varying spectral range (UV-C to NIR) photodetectors, the systematic variation of the available density of states (DOS) at a particular energy level in CuO nanostructures has been utilized to fabricate dual-band (250 nm and 900 nm), broadband (250 nm–900 nm), and UV-C (250 nm) photodetectors. The sensitivity and detectivity of the photodetector for broadband detectors were (cid:2)103 and 2.24 (cid:3) 1011 Jones for the wavelengths of 900 nm and 122 and 2.74 (cid:3) 1010 Jones for 250 nm wavelength light, respectively. The UV-C detector showed a sensitivity of 1.8 and a detectivity of 4 (cid:3) 109 Jones for 250 nm wavelength light. A plausible mechanism for the photoconduction has been proposed for explaining the device operation and the effect of variation in available DOS. The obtained photodetectors are the potential candidates for future optoelectronic applications.
关键词： Broadband photodetectors,Bandgap engineering,CuO nanostructures,Dual-band photodetectors,UV-C photodetectors
更新于2025-09-23 15:21:01
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[IEEE 2019 International Energy and Sustainability Conference (IESC) - Farmingdale, NY, USA (2019.10.17-2019.10.18)] 2019 International Energy and Sustainability Conference (IESC) - Metal oxide-based heterojunction thin films for solar cell applications
摘要： The interest and development in a fully green future towards sustainable technology and environmental preservation has spurred exponentially for the past few years. The adoption in clean energy is underway with solar photovoltaic (PV) technology leading the race. To keep PV sector competitive with current conventionally generated electricity, an alternative economic PV module using cheap materials with low-cost deposition method is needed. Among the candidate, metal oxides (MO) semiconductors are great potential materials to achieve this goal due to its massive availability, non-toxicity, chemically stable, and can be deposited using low-cost techniques at ambient condition. In this report, the p-n junction solar cell was fabricated using layer by layer deposition of n-type and p-type metal oxide semiconductors. Co3O4 and CuO were used as absorbing layers and ZnO as a window layer in contact with each other using simple spin coating deposition method. Photocurrent density (JSC), photo voltage (VOC) and the crystallinity of materials were investigated to characterize their optoelectronic properties. It is observed that Co3O4 shows larger crystallite size compared to CuO at 26.66 nm and 24.86 nm, respectively. Samples consisting of Co3O4 and CuO p-n junction solar cell exhibits high absorbance in the visible spectral region of 350 nm to 750 nm. J-V measurement of FTO/ZnO/Co3O4/In heterojunction films exhibits short-circuit current density of 0.391 mA/cm-1 and open-circuit voltage of 0.476 V under the illumination of AM1.5 solar simulation (100mW/cm2). Meanwhile, FTO/ZnO/CuO/In shows short-circuit current density of 0.429 mA/cm-1 and open-circuit voltage of 0.048 V. Thus, it shows that green materials without any environmental issue has high potential in solar cells application.
关键词： CuO,Co3O4,Sol-Gel,Solar Cell,Spin Coating,Heterojunction
更新于2025-09-23 15:21:01
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Visible Light Photocatalytic Activity of NaYF4:(Yb,Er)-CuO/TiO2 Composite
摘要： TiO2 photocatalysts are limited to ultraviolet light photo-activation, however, by coupling with NaYF4:(Yb,Er) they can utilize visible light activation, but with low efficiencies. In order to enhance visible light photo-activity, CuO nanoparticles were coupled with NaYF4:(Yb,Er) by mechanical ball-milling and coated with TiO2-sol. The coupling of CuO nanoparticles with NaYF4:(Yb,Er)/TiO2 caused the formation of a NaYF4:(Yb,Er)-CuO/TiO2 composite capable of visible absorption with a remarkably reduced band gap of ~2.5 eV. The NaYF4:(Yb,Er)-CuO/TiO2 composite in H2O2 showed the most efficient methylene blue (MB) degradation efficiency of more than 99.5% after exposure to visible light.
关键词： visible light,NaYF4:(Yb,Er)-CuO/TiO2,composites,photocatalyst
更新于2025-09-23 15:21:01
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Sputtered cobalt doped CuO nano-structured thin films for photoconductive sensors
摘要： Pure and cobalt (Co) doped CuO thin films have been deposited by DC and AC reactive magnetron sputtering technique. The doping ratio has been controlled by the RF power of the AC sputtering unit. The sputtering power ranges from 0 to 50 W. The crystal structure of the films has been identified by X-ray diffraction. One of the peaks has been shifted toward the high diffraction angle. Energy dispersive analysis shows cationic deficiency of the pure and doped samples. Morphology of the films has been investigated by atomic force microscopy. Film roughness decrease with the increase of sputtering power. Spectrophotometry studies reveal that films darken with the increase of sputtering power. The current–voltage curves show Ohmic contacts and an enhancement in the conductivity with the increase of Co concentrations. Photoresponse measurements have shown that the film doped at 50 W is the best photodetector sensor.
关键词： photoconductive sensors,thin films,magnetron sputtering,Co doped CuO
更新于2025-09-23 15:21:01
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Ultraviolet photodetectors using hollow p-CuO nanospheres/n-ZnO nanorods with a pn junction structure
摘要： We report on ultraviolet (UV) photodetectors with a pn junction structure consisting of hollow p-CuO (h-CuO) nanospheres and n-ZnO nanorods (NRs). To form the pn junction structure, thermal annealing was conducted using a transferred monolayer of Cu-ion-incorporated polymer spheres onto the n-ZnO NRs/n-Si substrate. Device performance was evaluated by comparing the effects of h-CuO nanosphere coverage changed by sphere shrinkage during thermal annealing of Cu-ion-incorporated polymer spheres. Three samples were prepared by varying the transfer times of h-CuO on ZnO NRs: 0 times (Reference), 1 time (CZ-I), and 2 times (CZ-II). The CZ-II-based UV detector shows a fast rising time of 1.8 s and a falling time of 0.26 s, which are faster rising by 2.2 and 1.3 times and faster falling by 3.1 and 32.6 times than those of the CZ-I and Reference UV detectors, respectively, under illumination with UV light at 254 nm. Moreover, the On/Off current ratio of the CZ-II UV detector is 4.58, which is about 3.3 times and 3.5 times higher than that of the CZ-I and Reference devices, respectively. The higher h-CuO coverage on the ZnO NRs that form the pn junction structure can effectively separate the electron and hole and suppress recombination by mutual transfer of photo-generated electrons and holes in the heterojunction.
关键词： Hollow CuO,ZnO,UV detector,transfer of spheres monolayer
更新于2025-09-23 15:19:57