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Facile synthesis approach for core-shell TiO2–CdS nanoparticles for enhanced photocatalytic H2 generation from water
摘要： With the ambition to design a cost-effective and highly stable photocatalyst with improved photocatalytic activity towards H2 generation by water splitting, herein we report a two-step facile synthesis approach for core-shell structure of TiO2-CdS nanocomposites. The synthesized photocatalysts are comprehensively characterized by SEM, XRD, BET, UV-vis DRS, Photoluminescence and XPS to investigate the morphological, crystalline, structural, optical properties and surface analysis. The photocatalytic activity is evaluated by measuring the ability of TiO2-CdS to generate H2 gas by water splitting in the presence of hole scavengers under simulated solar light at AM 1.5G conditions. Our optimized sample TiO2-CdS (3:2) exhibited an enhanced photocatalytic activity by generating 954 μmol g-1 h-1 of hydrogen which is ~1.4 and ~1.7 times higher than pure CdS nanoparticles and pure TiO2, respectively. The optimized sample achieved an apparent quantum efficiency of 3.53% along with good stability by generating a similar amount of H2 for 40 consecutive hours. The enhanced photocatalytic activity and stability of the core-shell TiO2-CdS nanocomposite is attributed to the broader solar spectrum absorption, efficient photo-induced charge separation on the interface of TiO2-CdS due to the formation of heterojunction and high surface area with a large fraction of mesopores.
关键词： Photocatalytic H2 generation,Core-Shell TiO2-CdS nanocomposite,hydrothermal approach,CdS nanoparticles,Heterojunction
更新于2025-09-23 15:21:21
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Core-shell Structured TiO2@In2O3 for Highly Active Visible-light Photocatalysis
摘要： Core-shell structured TiO2@In2O3 with high visible-light photocatalytic activity have been successfully fabricated by solvothermal method. The as-obtained products were characterized by field transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-visible diffuse reflectance spectra (UV-vis DRS). Structural characterizations demonstrated that the In2O3 layers were comprised of nanocrystallites ca. 14 nm in size and displayed rough surfaces. The UV-vis DRS data showed that In2O3 greatly expanded the visible light absorption band edge of TiO2. The results revealed that the obtained TiO2@In2O3 with core-shell structure showed enhancement of the visible-light photocatalytic activity to degrade methyl orange (MO) comparing with the pure TiO2 and In2O3 products.
关键词： TiO2@In2O3,Nanocomposites,Semiconductors,Core-shell structure
更新于2025-09-23 15:21:21
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Comparative study of structural, magnetic and dielectric properties of CoFe2O4 @ BiFeO3 and BiFeO3@ CoFe2O4 core-shell nanocomposites
摘要： Nano-sized CoFe2O4 (CFO), BiFeO3 (BFO) and their core-shell composites BFO@CFO and CFO@BFO were synthesized by chemical co-precipitation method. X-ray di?raction pattern con?rmed the crystallinity and phase formation of bare CFO, BFO and their core-shell composites. Morphology and core-shell nature of these nano-particles is justi?ed by ?eld emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). Magnetization curve showed the weak ferromagnetic behaviour of BFO. Typical ferrimagnetic behaviour is shown by bare CFO and core-shell nanocomposites. The value of maximum magnetization, remanence magnetization and coercivity of CFO@ BFO were found to be greater than the BFO@ CFO. Also, CFO@ BFO showed the highest value of dielectric constant in the frequency range of 104–106 Hz. Dielectric constant versus temperature curve of BFO and core-shell composites exhibit incongruity close to the anti-ferromagnetic transition temperature (370 °C) of BFO indicating presence of magnetoelectric (ME) coupling.
关键词： Multiferroic,Nanocomposite,Core-shell,Co-precipitation
更新于2025-09-23 15:21:21
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<i>(Invited)</i> Large-Scale DFT Study of Ge/Si 3D Nanoislands and Core-Shell Nanowires
摘要： Density functional theory (DFT) calculations have been playing important roles to clarify the structures of semiconductor surfaces at atomic scale. However, DFT studies of complex nanostructures are usually impossible because conventional DFT methods cannot treat large systems containing many thousands of atoms. In this paper, we survey our large scale DFT study on (i) the growth of Ge 3D nanostructure on Si(001) substrate and (ii) the atomic and electronic structures of Si/Ge or Ge/Si core-shell nanowires, using our linear-scaling DFT code CONQUEST. The code uses large-scale DFT techniques and has high efficiency on massively parallel computers. We demonstrate that CONQUEST can calculate the atomic positions of the realistic models of nanostructures observed in experiments and can clarify the unique electronic properties of these nano-structured materials.
关键词： nanoislands,CONQUEST,Ge/Si,DFT,core-shell nanowires
更新于2025-09-23 15:21:21
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Silver-Gold Bimetallic Alloy versus Core-Shell Nanoparticles: Implications for Plasmonic Enhancement and Photothermal Applications
摘要： Bimetallic plasmonic nanoparticles enable tuning of the optical response and chemical stability by variation of the composition. The present numerical simulation study compares Ag-Au alloy, Ag@Au core-shell, and Au@Ag core-shell bimetallic plasmonic nanoparticles of both spherical and anisotropic (nanotriangle and nanorods) shapes. By studying both spherical and anisotropic (with LSPR in the near-infrared region) shapes, cases with and without interband transitions of Au can be decoupled. Explicit comparisons are facilitated by numerical models supported by careful validation and examination of optical constants of Au-Ag alloys reported in literature. Although both Au-Ag core-shell and alloy nanoparticles exhibit an intermediary optical response between that of pure Ag and Au nanoparticles, there are noticeable differences in the spectral characteristics. Also, the effect of the bimetallic constitution in anisotropic nanoparticles is starkly different from that in spherical nanoparticles due to the absence of Au interband transitions in the former case. In general, the improved chemical stability of Ag nanoparticles by incorporation of Au comes with a cost of reduction in plasmonic enhancement, also applicable to anisotropic nanoparticles with a weaker effect. A photothermal heat transfer study confirms that increased absorption by the incorporation of Au in spherical Ag nanoparticles also results in an increased steady state temperature. On the other hand, anisotropic nanoparticles are inherently better absorbers, hence better photothermal sources and their photothermal properties are apparently not strongly affected by the incorporation of one metal in the other. This study of the optical/spectral and photothermal characteristics of bimetallic Au-Ag alloy versus core-shell nanoparticles provides a detailed physical insight for the development of new taylor-made plasmonic nanostructures.
关键词： Localized Surface Plasmon Resonance (LSPR),Au@Ag core-shell,Ag-Au alloy,Ag@Au core-shell,Bimetallic plasmonic nanoparticles,Photothermal applications
更新于2025-09-23 15:21:01
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Oxide-Core Pt-Shell Electrocatalysts for PEFCs: Photochemical Preparation Using SnO <sub/>2</sub> Nanoparticles
摘要： Core-shell electrocatalyst, in which a Pt atomic layer covers a nano-size core of a different metal, is attractive in reducing Pt usage for PEFC cathode electrocatalyst. Whilst such core-shell electrocatalysts exhibit very high mass activity for oxygen reduction reaction (ORR), their cost and durability still remain as a challenge. If inexpensive and thermochemically-stable conductive oxide could be applied to the core instead of a noble metal, cost reduction and durability improvement of such core-shell electrocatalysts may be expected. In this study, we try to develop oxide-core Pt-shell electrocatalysts by directly depositing Pt on SnO2 at an atomic level via a photochemical preparation procedure. SnO2 cores with a diameter down to ca. 3 nm could be prepared by comparing various preparation procedures of SnO2 and types of fillers. Electrochemical activities of such oxide-core Pt-shell electrocatalysts are characterized and discussed.
关键词： PEFC,SnO2,photochemical preparation,Pt-shell,Core-shell electrocatalyst
更新于2025-09-23 15:21:01
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Synthesis of SiO <sub/>2</sub> @Ag core-shell photonic crystals for SERS application
摘要： Core-shell SiO2@Ag composite spheres with dense, complete and nanoscaled silver shell were prepared by using facile chemical reduction method. Self-assembly of the composite microspheres into 3D photonic crystals (PhCs) was carried out using the vertical deposition method. The core-shell PhCs composites were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), UV-Vis spectroscopy and energy dispersive X-ray spectroscopy (EDX). The results of amplification of Raman scattering by these composite substrates are presented.
关键词： SiO2@Ag,photonic crystals,SERS,core-shell,Raman scattering
更新于2025-09-23 15:21:01
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Multipoint Nanolaser Array in an Individual Core-Shell CdS Branched Nanostructure
摘要： Nanoscale laser arrays are attractive for their potential applications in highly integrated nanodevices, which are always obtained by nanowire arrays with complicated fabrication techniques. Here, a quite different nanolaser array is successfully realized based on a highly ordered core–shell CdS branched nanostructure with implanted Sn nanoparticles in junctions that split the individual multichannel nanostructures to various microcavities with effective light confinement and oscillation, thus to achieve a multipoint nanolaser array. Under the excitation of an ultraviolet laser, the strong band-edge emission can be well reflected between Sn nanoparticles at junctions and effectively scattered into branch segments due to Sn nanoparticles existence in junctions, furthermore oscillating in various microcavities along trunks or branches to form multipoint lasing from Fabry-Pérot (F-P) mode with a quality factor up to 990 and the low threshold at around 3.78 MW cm?2. The corresponding fluorescent microscope images further demonstrate the formation of multipoint F-P lasing at various segments. The theoretical simulation indicates that implanted Sn nanoparticles work as hot point to enhance the confinement of light around the Sn centers. The existence of surface plasmon from the Sn metal particles is further confirmed by the polarization dependent photoluminescence measurement. The results provide a new way to realize nanolaser arrays.
关键词： core–shell structures,CdS branched nanostructure,nanolaser arrays,electric field distribution
更新于2025-09-23 15:21:01
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Surface Engineered Hybrid Corea??Shell Sia??Nanowires for Efficient and Stable Broadband Photodetectors
摘要： Silicon nanostructures have gained intensive interest to develop broadband photodetectors at a large-scale due to their excellent electronic properties. Herein, Si-nanowires (SiNWs) decorated with reduced graphene oxide:carbon quantum dots (rGO:CQDs) nanocomposite (NC), as core–shell heterojunction building blocks for broadband (ultraviolet (UV)–near infrared (NIR)) photodetectors (PDs), are demonstrated. The SiNWs and CQDs are synthesized by wet-chemical etching and facile pyrolysis methods, respectively. Photogenerated carriers are transported through rGO because of its high electron mobility and favorable band alignment with CQDs and Si. Further, to minimize the recombination of photogenerated carriers, and enhance the response in the visible region, plasmon-enhanced AuCQDs are incorporated in the shell matrix. The optimized heterostructure (rGO:AuCQDs/undoped CQDs/SiNWs) is sensitive to a broad wavelength range covering the UV to NIR (360 to 940 nm) region, manifests the excellent responsivity of 16 A W?1 at 360 nm, detectivity (D*) of 2.2 × 1013 Jones, and noise equivalent power as low as 2.8 fW Hz?1/2. The optimized PDs heterostructure demonstrates excellent air-stability after 8 days of illumination without any encapsulation or protective coating. The proposed simple, cost-effective, and Si-process-line compatible fabrication of Si-based PD device structure imposes a great promise for highly efficient and stable advanced futuristic optoelectronic devices.
关键词： core–shell heterostructure,detectivity,responsivity,broadband photodetectors,reduced graphene oxide,carbon quantum dots,Si nanowires
更新于2025-09-23 15:21:01
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Self-assembled CdS@BN core-shell photocatalysts for efficient visible-light-driven photocatalytic hydrogen evolution
摘要： CdS@BN NRs core-shell photocatalysts for hydrogen evolution were synthesized by a solvothermal and chemical adsorption method. CdS NRs coated by 5 wt% boron nitride (BN) shell exhibited remarkably visible-light photocatalytic hydrogen evolution activity of up to 30.68 mmol g?1 h?1, nearly 6.79 times higher than that of pure CdS NRs, and the apparent quantum efficiency at 420 nm was 7.5%. Transmission electron microscopy showed the CdS NRs were coated with a thin (~5 nm) BN layer, which together with the hydrogen evolution results proved the photocatalytic ability of CdS NRs was significantly improved. The hydrogen evolution rate of CdS NRs coated by 5 wt% BN remained at 91.4% after four cycles, indicating the photocorrosion of CdS NRs was effectively alleviated. Moreover, the large and close coaxial interfacial contact between the CdS core and the BN shell was beneficial to the separation and transfer of photogenerated electron-hole pairs.
关键词： Core-shell structure,Photocatalytic hydrogen evolution,CdS Nanorods,Boron nitride
更新于2025-09-23 15:21:01