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Structural, optical and magnetic properties of YIG and TbErIG nanofilms prepared using a sol-gel method
摘要： A series of yttrium iron garnet (YIG) and terbium erbium iron garnet (TbErIG) nanocrystalline films were successfully grown using a sol-gel method. A crystalline analysis carried out using an X-ray diffractometer confirmed that all films had a single-phase garnet structure. The TbErIG films annealed in O2 and Ar gas had a larger number of crystallisation peaks, with a lattice constant that was close to the standard value for ErIG. The transparency increased from 94% for YIG (O2) to 98% for TbErIG (O2) films in the near-infrared region. All films were soft ferrite materials, as indicated by their magnetic hysteresis loops. The value of saturated magnetisation was increased for samples annealed in air, and was markedly decreased for samples subjected to O2 and Ar atmospheres. An increase in the coercivity value (91 Oe) was also observed for the TbErIG (Ar) film. YIG and TbErIG showed a phase transition from ferrimagnetic to paramagnetic at the Curie temperature, Tc = 556 K and 557.3 K, respectively. The low saturation magnetisation, low optical absorption and highly crystalline structure of TbErIG (O2 and Ar) films mean that these films may potentially be used in a magneto-optical compact isolator in the visible and NIR regions.
关键词： nanostructures,Sol-gel,magnetic properties,X-ray diffraction,optical properties
更新于2025-09-10 09:29:36
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Fluorescence Properties of Tb-Doped ZnO Porous Network Thin Film Grown on Monocrystalline Silicon Substrate
摘要： This research presents a new perspective on optical biosensors based on zinc oxide nanoparticles. The widely known and successfully applied nanostructured material is modified by the dopant - the green phosphor Terbium, which embedded in the structure of zinc oxide and makes a significant contribution to the fluorescent response of the material in both the UV and visible spectral regions. The effect of various dopant concentrations on the fluorescence of nanostructures was studied; the nanostructures were examined by SEM.
关键词： fluorescence,biosensors,nanostructures,zinc oxide,terbium
更新于2025-09-10 09:29:36
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Physical properties of Cd-doped ZnS thin films
摘要： In this research, un- and Cd-doped ZnS nanostructures were synthesized using an electrodeposition method. The electrolyte contained 20 mM ZnCl2, 20 mM Na2S2O3 and the various amounts of CdCl2 solution. The X-ray diffraction (XRD) patterns of the as-deposited samples exhibited that Cd doping lead to decrease the crystallite size (D) of ZnS meanwhile the lattice strain, lattice stress, dislocation density (γ), and stacking fault energy (SF) were increased. Field emission scanning electron microscopy (FESEM) images depicted very fine equiaxed grains (20 to 50 nm), in addition to big grains (200 to 400 nm) with the preferential orientation. The reflectance spectra of ZnS thin films indicated a decrease in the reflectance peaks and refractive index (n), after Cd doping. Based on the transmission spectra, the un- and Cd-doped ZnS samples showed an absorption edge between 328 – 357 nm. The band gap energy for undoped ZnS sample was estimated as 3.95 eV, which it was reduced to 3.63 eV for the Cd-doped ZnS samples owing to the presence of imperfections and crystalline disorder in the Cd-doped samples. Furthermore, the obtained dielectric constant of the Cd-doped ZnS thin films was smaller than undoped ZnS sample, which means that the Cd-doped ZnS samples were more appropriate than the undoped ZnS sample for application in the fast photodetectors. The photoluminescence (PL) spectra of the undoped ZnS thin film was presented six emission peaks at 340, 413, 536, 574, 748, and 878 nm as an outcome of near band emission (NBE) and crystalline defects such as zinc interstitials (IZn), zinc vacancies (VZn), sulfur interstitials (IS), ZnS self-defect, and the defect states between the valence band (VB) and the conduction band (CB) of ZnS. Moreover, the PL emission of the Cd-doped ZnS samples demonstrated a red-shift relative to the undoped sample, which verified the UV-vis spectroscopy results.
关键词： nanostructures,electrodeposition,wide band gap,dielectric constant,Cd-doped ZnS
更新于2025-09-10 09:29:36
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Photocatalytic Reduction of Bicarbonate to Formic Acid using Hierarchical ZnO Nanostructures
摘要： Zinc oxide (ZnO) is an earth abundant, non-toxic, and low-cost material that has been used widely for photocatalytic water splitting, gas sensing, and dye degradation. In this study, several ZnO structures were tested for the photochemical reduction of bicarbonate to formic acid, an intermediate to methanol, a high-octane-number fuel with higher energy density than compressed hydrogen. The different ZnO morphologies studied included micron- and nano-particulate ZnO, rods, wires, belts, and flowers. ZnO was also synthesized from the direct calcination of zinc acetate, which provided a cheap and large-scale synthesis method to produce ZnO. The photocatalytic efficiency of the synthesized ZnO was compared to commercial micron- and nano-particulate ZnO, and was proven to be just as efficient. ZnO flowers, possessing the largest surface area of 12.9 m2/g, were found to be the most efficient reaching an apparent quantum efficiency (AQE) of 10.04±0.09%, with a superior performance over commercial TiO2 (P25), a benchmark photocatalyst. This is the first study to compare different shapes and sizes of ZnO for bicarbonate reduction in an aqueous system with excellent photocatalytic performance.
关键词： solar fuels,ZnO nanostructures,zincite,bicarbonate photoreduction
更新于2025-09-10 09:29:36
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The effect of morphology and functionalization on UV detection properties of ZnO networked tetrapods and single nanowires
摘要： Rapid detection and fast response of nanoelectronic devices based on semiconducting oxides is nowadays a modern and stringent subject of research. Device performances depend mainly on the morphologies of the metal oxide nanostructures. In the scope of this work, the influence of the structural morphology of three-dimensional (3-D) ZnO nano- and microstructured networks on the room temperature UV detection properties is studied in detail. We show that the formation of multiple potential barriers between the nanostructures, as well as the diameter of the nanostructures, which is in the same order of magnitude as the Debye length, strongly influence the UV sensing properties. Consequently, 3-D ZnO networks consisting of interconnected ultra-long wire-like tips (up to 10 μm) and with small wire diameters of 50–150 nm, demonstrated the highest UV sensing performances (UV response ratio of ～3100 at 5 V applied bias voltage). Furthermore, we demonstrate the possibility of substantially increasing the UV sensing performances of individual ZnO nanowire (NW) (diameter of ～50 nm) by surface functionalization with carbon nanotubes (CNTs), showing high response ratio (～60–50 mW/cm2), as well as fast response (～1 s) and recovery (～1 s) times. The obtained results thus provide a platform with respect to the next generation of portable UV radiation detectors based on semiconducting oxide networks.
关键词： CNT,UV photodetector,ZnO,Device,Individual nanostructures,Nanosensor
更新于2025-09-10 09:29:36
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Light absorption by surface nanoholes and nanobumps
摘要： This paper deals with a numerical investigation of the energy deposition induced by ultrafast laser interaction with nanostructures. We calculate and analyze the intensity near-field reactive and radiative patterns resulted from the interference of the incident light with light scattered by individual subwavelength holes and bumps on the surface of metallic and dielectric materials. The role of light polarization, optical material properties, collective effects and nature of the imperfections in localized energy absorption is elucidated. The results open new perspectives in precise light manipulation by surface inhomogeneities and well-controlled surface nanostructuring by ultrashort laser.
关键词： light absorption,surface nanoholes,ultrafast laser,nanostructures,nanobumps
更新于2025-09-10 09:29:36
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Non-monotonous wetting of graphene-mica and MoS2-mica interfaces with a molecular layer of water
摘要： Hydration of interfaces with a layer of water is a ubiquitous phenomenon, which has important implications for numerous natural and technologically important processes. Nevertheless, at the nanoscale the understanding of the wetting process is still limited, since it is experimentally difficult to follow. Here, graphene and monolayers of MoS2 deposited on dry mica are used to investigate wetting of the 2D material-mica interfaces with a molecularly thin layer of water employing scanning force microscopy in different modes. Wetting occurs non-monotonously in time and space for both types of interfaces. It starts at relative humidities (RH) of 10-17 % for graphenes and 8-9 % for MoS2, and it concludes with a homogeneous layer at 25-30 % and 15-20 %, respectively. Investigation of the process at the graphene-mica interface indicates that up to about 25 % RH, initially a highly compliant and unstable layer of water spreads, which subsequently stabilizes by developing labyrinthine nanostructures. Moreover, these nanostructures exhibit distinct mechanical deformability and dissipation, which is ascribed to different densities of the confined water layer. The laterally structured morphology is explained by the interplay of counteracting long-range dipole-dipole repulsion and short-range line tension, with the latter caused at least in part by the mechanical deformation of the 2D material. The proposed origins of the interactions are common for thin layers of polar molecules at interfaces, implying that the lateral structuring of thin wetting layers at sub-monolayer concentrations may also be a quite general phenomenon.
关键词： confinement,energy dissipation,hydration,slit pore,nanostructures,mechanical compliance,2D material
更新于2025-09-10 09:29:36
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Over 1000-fold enhancement of upconversion luminescence using water-dispersible metal-insulator-metal nanostructures
摘要： Rare-earth activated upconversion nanoparticles (UCNPs) are receiving renewed attention for use in bioimaging due to their exceptional photostability and low cytotoxicity. Often, these nanoparticles are attached to plasmonic nanostructures to enhance their photoluminescence (PL) emission. However, current wet-chemistry techniques suffer from large inhomogeneity and thus low enhancement is achieved. In this paper, we report lithographically fabricated metal-insulator-metal (MIM) nanostructures that show over 1000-fold enhancement of their PL. We demonstrate the potential for bioimaging applications by dispersing the MIMs into water and imaging bladder cancer cells with them. To our knowledge, our results represent one and two orders of magnitude improvement, respectively, over the best lithographically fabricated structures and colloidal systems in the literature. The large enhancement will allow for bioimaging and therapeutics using lower particle densities or lower excitation power densities, thus increasing the sensitivity and efficacy of such procedures while decreasing potential side effects.
关键词： upconversion nanoparticles,plasmonic enhancement,bioimaging,photoluminescence,metal-insulator-metal nanostructures
更新于2025-09-10 09:29:36
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Shape-modulated multiple exciton generation and optoelectronic properties in PbSe nanostructures
摘要： Multiple exciton generation (MEG) in semiconductor nanostructures is of great interest for the enhancement of related performances in optoelectronic devices and for the shape dependence of conversion ef?ciency with which absorbed photons are converted into electron-hole pairs. However, theoretical insight into the coupling effects from the size and shape gradient on the MEG and related optoelectronic properties at the atomic level remains unclear. Here, we investigate the MEG and optoelectronic properties in PbSe nanostructures with different morphologies (nanocrystals, nanowires, and nanocones) based on the bond relaxation correlation mechanism, detailed balance principle, and Fermi statistical theory. It is found that size reduction of nanostructures can increase the bandgap, suppress the threshold energy, and enhance the MEG ef?ciency. Moreover, optimal conversion ef?ciency of PbSe nanostructures can be achieved by modulating the geometrical parameters.
关键词： bond relaxation correlation mechanism,PbSe nanostructures,Fermi statistical theory,Multiple exciton generation,optoelectronic properties
更新于2025-09-10 09:29:36
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Morphology Effect on SERS Activity of Embedded Silver Nanostructures
摘要： Embedded silver nanostructures with different shapes and sizes are grown in Si substrates by chemical vapor deposition (CVD) method. Systematic study of their surface-enhanced Raman properties is performed. Influence of shape, size, and coverage of the nanoparticles on the average enhancement factors is calculated with the help of standard analyte molecules viz. crystal violet and Rhodamine 6G to optimize the substrates for future sensing applications.
关键词： embedded nanostructures,chemical vapor deposition,silver nanostructures,surface-enhanced Raman scattering
更新于2025-09-09 09:28:46