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Visible light assisted photocatalytic reduction of CO2 to ethane using CQDs/Cu2O nanocomposite photocatalyst
摘要： CO2 reduction through photocatalysis is considered a promising way to mitigate the abundance of this greenhouse gas in the earth’s atmosphere. In this work, blue-fluorescent carbon quantum dots (CQDs) were synthesized via a facile top-down hydrothermal method using biochar as the carbon source. The as-synthesized CQDs were incorporated together with commercial copper (I) oxide (Cu2O) nanoparticles to form CQDs/Cu2O nanocomposite. The CQDs, Cu2O and CQDs/Cu2O nanocomposite were then applied for gas phase photocatalytic reduction of CO2. The experiments were performed under visible light irradiation in a self-designated photoreactor which was connected to an online Gas Chromatography (GC). High resolution transmission electron microscopy (HRTEM) confirmed the uniform deposition of CQDs with size ranging from 2.5 to 6.0 nm on the surface of Cu2O nanoparticles. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy further revealed the presence of CQDs on the surface of Cu2O. The CQDs/Cu2O nanocomposite photocatalyst showed a considerable improvement in the CO2 photoreduction with an enhancement of 54% compared to the pure Cu2O. In addition, the band alignment of CQDs/Cu2O, charge carriers transfer and separation as well as possible reaction pathways for CO2 photoreduction was proposed. Finally, the photostability test revealed the CQDs/Cu2O nanocomposite was able to retain its photostability of up to ~90% under five cycles of photoreaction.
关键词： copper (I) oxide,carbon quantum dots,CO2 photoreduction,photocatalyst
更新于2025-09-23 15:21:01
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Design, synthesis, crystal structure and cytotoxicity studies of colorimetric fluorescent “OFF-ON” probes for rapid detection of hydrogen sulfide based on Cu(II) complex
摘要： Four colorimetric fluorescent probes based on copper(II) complexes were synthesized and the molecular structures were characterized by X-ray diffraction, ESI-HRMS and elemental analysis. When exposed to HS–, the synthesized probes showed significant color changes from yellow to red and remarkable increase of fluorescence intensity (over 80-fold). What’s more, the interaction of host-guest could be completed in 2 minutes. However, no clear color and fluorescence intensity changes were observed in the presence of other anions (AcO–, H2PO4–, F–, Cl–, Br–, I–, SO42-, SO32-, CO32-, Cys and GSH). The synthesized colorimetric fluorescent probes could detect HS– rapidly and conveniently. Cytotoxicity studies indicated that the synthesized fluorescent probes were low cytotoxicity in Hela cells and may be used to detect H2S level in vivo.
关键词： hydrogen sulfide,copper complex crystal,fluorescent probe,colorimetric detection,cytotoxicity
更新于2025-09-23 15:21:01
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Green Higha??Power Disk Lasers and Industrial Applications
摘要： In the publicly-funded ProLasKu project, the laser manufacturer Trumpf has developed a high-power laser with a wavelength of 515 nm. Substantial progress in the industrial applications of green lasers has been achieved in a cooperation between the Technical University of Munich and the companies Siemens and Continental. In addition, a camera-based system for process monitoring and quality assurance in real-time based on image processing methods has been developed.
关键词： green high-power disk lasers,industrial applications,copper,laser beam welding,process efficiency
更新于2025-09-23 15:21:01
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An experimental study on joining of AISI 304 SS to Cu by Nd-YAG laser welding process
摘要： In this current study, a challenging dissimilar metal combination AISI 304 stainless steel and copper is welded by pulsed wave Nd-YAG laser welding process without use of any filler material, followed by its mechanical as well as metallurgical investigation. Macroscopic as well as microscopic examination of the weld surface and weld bead has been carried out to observe the weld penetration depth and metallurgical behavior inside the weld zone. Weld pool geometry confirms about attainment of full penetration depth in pulsed wave Nd-YAG laser and also describes that the penetration depth is directly proportional pulse energy as (penetration depth7 J = 69%) < (penetration depth14 J = 82%) < (penetration depth21 J = 100%). The formed copper micro-channels suggest that the copper solidifies last and flows inside the weld zone matrix during the solidification. The average width of the heat affected zone (HAZ) and partially melting zone (PMZ) have been found to be 23.0 mm and 6.0 mm on the stainless steel (SS) side respectively. The microhardness (MH) study shows that (MHCopper = 75 HV0.1) < (MHWeld zone = 90–200 HV0.1) < (MHSS = 210 HV0.1).
关键词： PMZ,Copper micro-channels,HAZ,Dissimilar metal,Nd-YAG laser
更新于2025-09-23 15:21:01
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Plasmonic solar cells using mohite Cu2SnS3 nanoparticles
摘要： In this paper, we introduce a new technique for the synthesis of mohite copper tin sulphide (Cu2SnS3) nanoparticles. The method employed is cost effective, non-vacuum, room temperature colloidal synthesis. Here two sulphur sources are used in the synthesis process, sodium sulphide and thioacetamide where the latter is assumed responsible for the mohite crystal structure. The as-prepared sample was characterized using XRD, Laser Raman Spectrometer, SEM/EDS, UV–VIS-NIR spectrophotometer and FTIR spectrophotometer. The sample synthesized appears greenish-black with a metallic lustre. Due to the presence of free electrons on the nanoparticle surface, surface plasmon resonance occurs at 807 nm. Using the uncertainty principle, the plasmon lifetime has been calculated to be 42.5 ns, which is a reasonably longer lifetime, enabling higher photon absorption. Thus mohite copper tin sulphide nanoparticles have a potential application in the absorber layer of low cost plasmonic solar cells.
关键词： Absorber layer,Surface plasmon resonance,Copper tin sulphide,Plasmonic solar cells,Mohite CTS
更新于2025-09-23 15:21:01
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Tunable Localized Surface Plasmon Resonance and Broadband Visible Photo-response of Cu Nanoparticles/ZnO Surfaces
摘要： Plasmonic Cu nanoparticles (NP) were successfully deposited on ZnO substrates by atomic layer deposition (ALD) owing to the Volmer–Weber island growth mode. An evolution from Cu NP to continuous Cu films was observed with increasing the number of ALD cycles. Real and imaginary parts of the NP dielectric functions, determined by spectroscopic ellipsometry using an effective medium approach, evidence a localized surface plasmon resonance that can be tuned between the visible and near infrared ranges by controlling the interparticle spacing and size of the NP. The resulting Cu NP/ ZnO device shows an enhanced photo-response under white light illumination with good responsivity values, fast response times and stability under dark/light cycles. The significant photocurrent detected for this device is related with the hot electron generation at the NP surface and injection into the conduction band of the ZnO. The possibility of tuning the plasmon resonance together with the photo-responsivity of the device is promising in many applications related with photo-detection, photonics and photovoltaics.
关键词： atomic layer deposition,hot electrons,copper nanoparticles,photodetectors,localized surface plasmon resonance
更新于2025-09-23 15:21:01
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Limit characteristics of switches based on planar open discharge
摘要： The limit characteristics of switches based on open discharge (OD) with counter-propagating electron beams were studied. Such switches (kivotrons) are able to generate high-voltage pulses with a sub-nanosecond leading edge. Separately obtained limit values of the switch parameters are as follows: current density up to 1000 A cm?2, operating voltage up to 100 kV, switching time τs down to 100 ps, the degree of pulse compression up to 100, a pulse repetition frequency up to 100 kHz (in burst mode), and an efficiency of more than 0.9. It was shown that the fast current development arises when the discharge self-sustaining mode is caused by the photoemission from the cathodes due to the resonant radiation emitted by fast helium atoms that have a large Doppler shift with respect to the line center. As a result, the emitted radiation reaches the cathodes without absorption by the helium gas. The presence of a fast atom group with an energy determined by the applied voltage was experimentally demonstrated. The dynamics of the plasma decay was studied. It is shown that the radiative, collisional-radiative, and three-body collision recombination mechanisms significantly contribute to the afterglow decay only when the plasma density remains higher than 1012 cm?3. The main mechanism of the further plasma decay is the diffusion of plasma particles onto the wall. Therefore, the effect of recombination in the plasma bulk is observed only during the first 10–20 μs of the afterglow. The results of the lasing characteristics of a copper vapor laser excited by pulses generated by an OD-based switch are presented.
关键词： copper vapor laser,subnanosecond switch,open discharge
更新于2025-09-23 15:21:01
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Ultrasonic spray pyrolyzed copper oxide and copper-aluminum oxide thin films: optical, structural and electronic properties
摘要： A study of the structural, electrical and optical properties of copper oxide and copper-aluminum oxide thin films deposited by ultrasonic spray pyrolysis is presented in this work. On one hand copper oxide films were deposited at working temperatures in the range from 300 °C to 500 °C. These films present a mixture of Cu2O and CuO phases, CuO phase being more abundant at higher temperatures; all samples present p-type conductivity. On the other hand, copper-aluminum oxide samples were deposited at 350 °C but with different copper-aluminum ratios in the start solution (0, 12.5, 25, 50, 100, and 200 at.%). The films present a mixture of Cu2O and Al2O3 phases, being the Cu2O the most abundant and becoming amorphous as aluminum concentration rises. Electrical characterization indicates that electronic conductivity depends on the amount of Cu2O, while ionic conductivity increases with aluminum concentration. Aluminum concentration also provokes a shift in the valence band towards lower binding energies, as well as an increase in the optical band gap (from 2.6 to 3.7 eV). Upon a thermal annealing at 800 °C the samples turned to CuAl2O4 spinel structure.
关键词： Optical characterization,Electrical characterization,Semiconducting copper-aluminum compounds,Spray pyrolysis
更新于2025-09-23 15:21:01
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Origin of Photoinduced Geometrical Change of Copper (I) Complexes from the Quantum Chemical Topology View.
摘要： Copper (I) complexes (CIC) have been of great interest due to their applications as redox mediators and molecular switches. CIC present drastic geometrical change at excited states that interfere with their luminescence properties. The photophysical process has been extensively studied by several time-resolved methods to understand the dynamics and the mechanism of the torsion, which has been explained in terms of a Jahn-Teller effect. Here, we propose an alternative explanation for the photoinduced structural change of CIC, based on the electron density redistribution. After photoexcitation of a CIC (S0?S1), a metal-to-ligand charge transfer produces a stabilization of the ligand and destabilization of the metal. A subsequent electron transfer, through an intersystem crossing process, followed by an internal conversion (S1?T2?T1), intensify the metal-ligand energetic differences within the complex. The energy profile of each state is the results of the balance between the metal and the ligand energy changes. The electrons losses originate an increase of the attractive potential energy within the copper basin, which is not compensated by the associated reduction of the repulsive atomic potential. To counterbalance the atomic destabilization, the copper center polarizes its valence shell (defined by ?2ρ(r) and ?2Vne(r)) during the deactivation path. This polarization increases the magnitude of the intra-atomic nuclear-electron interactions within the copper atom and provokes the flattening of the structure to obtain the geometry with the maximum interaction between the charge depletions of the metal with the charge concentrations of the ligand.
关键词： Copper (I) complexes,metal-to-ligand charge transfer,Quantum Chemical Topology,Jahn-Teller effect,photoinduced structural change
更新于2025-09-23 15:21:01
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Novel and Easy Accessible Method for the Estimation of Copper Spectrophotometrically in Water and Soil Samples
摘要： A simple and sensitive spectrophotometric method has been established for the determination of copper in water and soil sample. The method simply involves the chelation of Dimethylglyoxime ligand with Copper under optimal conditions. The method is based on the formation of 1:2 complexes between Copper and Dimethylglyoximine. The optimal condition for the determination of copper was established. The Beer’s law was applicable in the range 0.05 to 0.995 μg/ml. The molar extinction coefficient of the said complex was found to be 1.2 × 105 mol-1 cm-1. The method was successfully applied for the determination of Copper in the water and soil samples.
关键词： Copper,Dimethylglyoximine,Mole ratio method,Chelate complex,Spectrophotometry
更新于2025-09-23 15:21:01