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single crystals
摘要： 3at.%Tm3+:Ca1?xGdxF2+x (x = 0, 0.005, 0.01, 0.02) single crystals were grown by the vertical Bridgman method, where Gd3+ ions play the role of manipulating ions for local structure to form a disordered lattice site. Spectral properties of these crystals were investigated. Compared to 3at.%Tm3+:CaF2, the spectral parameters of 3at.%Tm3+:Ca1?xGdxF2+x were drastically enhanced in a large scale. LD pumped lasers have been demonstrated in the crystals for the first time. For CW operation, the slope efficiency up to 49.7% was achieved with output power of 1.927 W at 1970 nm. With a birefringent quartz plate, wavelength-tunable laser operation with a tuning range of more than 176 nm was realized.
关键词： Spectral properties,Single crystals,Gd3+ ions,LD pumped lasers
更新于2025-09-23 15:23:52
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Reusable surface plasmon resonance sensor for rapid detection of Cu2+ based on modified-chitosan thin film as an active layer
摘要： In this article, a reusable surface plasmon resonance (SPR) sensor for rapid detection of copper ions (Cu2+), based on optimized silver/gold (Ag/Au) composite film modified by modified-chitosan (MCS) thin film as an active layer, was achieved. We employed a four-layer Kretchmann semi-cylindrical prism configuration and induced a reference beam into the experimental system to improve the sensitivity and stability, and investigated the cross-linking technique of CS solution, the spin coating process of MCS film, the stability of active layer, the rebirth power of SPR sensor, and the detection for trace Cu2+. The rate of swelling or dissolution of MCS film after flushing sensor chip for four times is less than 9×10?4/min, and the decline of signal value is less than 1.5% after MCS film adsorbing Cu2+ and multiple flushing. The elution and capacity rates are above 96% after five times of elution for the sensor by EDTA solution with 0.5mmol/L. Within 1-5ppm, the SPR sensor was found to possess sensitivity of 0.7271ppm?1. The LOD is 18ppb for the trace Cu2+. The present SPR sensor not only could be used in trace monitoring of Cu2+ but also could be extended to other potential applications.
关键词： Copper ions,Reutilization,Composite film,Modified-chitosan,Surface plasmon resonance
更新于2025-09-23 15:23:52
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Optical and Magnetic Properties of Cobalt Ions Doped Calcium Phosphate by Ultrasonication
摘要： Background: Hydroxyapatite (HAp) is a remarkable member of the calcium phosphate family. It resembles natural bone in both structure and chemical composition. Owing to its bioactive and chemical properties, it has been used as a biocompatible osteogenesis and energy materials as discussed in patents. Objective: To study the structural, optical properties and magnetic properties of hydroxyapatite and cobalt ions doped hydroxyapatite for biomedical application. Method: Hydroxyapatite and cobalt ions doped hydroxyapatite were synthesized by ultrasonication assisted wet chemical synthesis. Results: X-ray diffraction analysis confirmed the phase and crystallite size of hydroxyapatite. There was a 12% decrease in crystallite size compared to pristine. The functional groups and vibrational assignments of the samples were observed in infra-red and Raman spectra. Optical properties of the samples were analyzed by Diffuse Reflectance Spectroscopy, ultraviolet-visible and photoluminescence emission spectroscopy. Doped samples showed paramagnetic in nature. Conclusion: Therefore, the cobalt doped samples could be employed in biomedical applications.
关键词： optical,luminescence,hyperthermia,bioceramics,Cobalt ions,magnetic,hydroxyapatite
更新于2025-09-23 15:23:52
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Optical Pressure Sensor Based on the Emission and Excitation Band Width (FWHM) and Luminescence Shift of Ce3+ Doped Fluorapatite – High-Pressure Sensing
摘要： A novel, contactless optical sensor of pressure based on the luminescence red-shift and band width (full width at half maximum - FWHM) of the Ce3+-doped fluorapatite - Y6Ba4(SiO4)6F2 powder, has been successfully synthesized via a facile solid-state method. The obtained material exhibits a bright blue emission under UV light excitation. It was characterized using powder X-ray diffraction, scanning electron microscopy and luminescence spectroscopy, including high-pressure measurements of excitation and emission spectra, up to above ≈30 GPa. Compression of the material resulted in a significant red-shift of the allowed 4f→5d and 5d→4f transitions of Ce3+ in the excitation and emission spectra, respectively. The pressure-induced monotonic shift of the emission band, as well as changes in the excitation/emission band widths, have been correlated with pressure for sensing purposes. The material exhibits a high pressure sensitivity (dλ/dP ≈0.63 nm/GPa), and outstanding signal intensity at high-pressure conditions (≈90% of the initial intensity at around 20 GPa) with minimal pressure-induced quenching of luminescence.
关键词： Ce3+ doping,Contactless pressure gauge,Y6Ba4(SiO4)6F2 apatite phosphors,Lanthanide ions (Ln3+),Compression in DAC,Luminescent functional materials
更新于2025-09-23 15:23:52
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IR photodissociation spectra of SixH4x-4+ (x?=?4–8): Evidence for Si H Si proton bridges
摘要： Although silane-type cations of the form SixHy+ are thought to play a significant role in plasma chemistry and astrochemistry, their structural and energetic properties are largely unexplored in the size range x ≥ 3. Herein, infrared photodissociation (IRPD) spectra of mass-selected SixHy+ with x = 4–8, specifically SixH4x-4+, are recorded in the Si–H stretch range and analyzed by dispersion-corrected density functional calculations at the B3LYP-D3/aug-cc-pVDZ level. The SixH4x-4+ ions are produced in a SiH4/H2/He plasma molecular beam expansion. The IRPD process leads to the loss of SiH4 ligands, which corresponds to the lowest-energy fragment channel. Spectral analysis of the IRPD spectra reveals that all SixH4x-4+ ions have at least one Si–H–Si bridge. The characteristic fingerprint of these three-center two-electron (3c-2e) bonds is the highly IR active antisymmetric stretch fundamental of the Si–H–Si bridge (νSiHSi) occurring in the 1600–2100 cm?1 range, whose frequency strongly depends on the structural and energetic details of the Si–H–Si bridge. Although the investigated SixH4x-4+ ions can formally be described by the formula Si2H4+(SiH4)x-2, the cluster growth is more complex. The appearance of the νSiHSi bands confirms that all considered SixH4x-4+ ions with x ≤ 5 are formed by polymerization reactions. Larger clusters (x ≥ 6) show evidence for the additional presence of weakly-bonded SiH4 ligands attached to smaller chemically-bonded core ions. Correlations of the properties of the Si–H–Si bridges (bond distances, bond angles, binding energies, Si–H stretch frequencies), which vary between strong symmetric 3c-2e chemical bonds and weak hydrogen bonds, are discussed.
关键词： Silane ions,IR spectroscopy,Structure elucidation,3c-2e bond,Si H Si bridge
更新于2025-09-23 15:23:52
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The role of incidence angle in the morphology evolution of Ge surfaces irradiated by medium-energy Au ions
摘要： Germanium (Ge) surfaces have been irradiated with 26 keV gold (Au) ions at a constant fluence and at incidence angles varying from 0° to 85°. The evolution of the emerging nanostructures is studied by atomic force microscopy (AFM), scanning electron microscopy, x-ray photoelectron spectroscopy (XPS), and cross-sectional transmission electron microscopy. The obtained results are compared with findings reported in the literature. Periodic rippled patterns with the wave vector parallel to the projection of the ion beam direction onto the Ge surface develop between 30° and 45°. From 75° the morphology changes from parallel-mode ripples to parallel-mode terraces, and by further increasing the incidence angle the terraces coarsen and show a progressive break-up of the front facing the ion beam. No perpendicular-mode ripples or terraces have been observed. The analysis of the AFM height profiles and slope distributions shows in the 45°–85° range an angular dependence of the temporal scale for the onset of nonlinear processes. For incidence angles below 45°, the surface develops a sponge-like structure, which persists at higher incidence angles on the top and partially on the face of the facets facing the ion beam. The XPS and the energy-dispersive x-ray spectroscopy evidence the presence of Au nano-aggregates of different sizes for the different incidence angles. This study points out the peculiar behavior of Ge surfaces irradiated with medium-energy Au ions and warns about the differences to be faced when trying to build a universal framework for the description of semiconductor pattern evolution under ion-beam irradiation.
关键词： ion beam irradiation,gold ions,terraces,germanium,binary system,sponge-like structures,ripples
更新于2025-09-23 15:23:52
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Characterization of ECR plasma by means of radial and axial X-ray diagnostics
摘要： This work presents the X-ray characterization of the plasma generated in a simple mirror axis symmetric trap as a function of the magnetic field profile. A Si-Pin detector has been used to characterize warm electron population in axial and radial directions at 6.83 GHz. Moreover, the hot electrons emitted in axial direction has been measured by means of a HyperPure Germanium (HpGe) detector. Results show that X-ray emission is not homogenous, and its homogeneity and temperature depend strongly on the magnetic field profile, and especially on the Bmin/BECR ratio.
关键词： Ion sources (positive ions, negative ions, electron cyclotron resonance (ECR), electron beam (EBIS)),Solid state detectors,X-ray detectors
更新于2025-09-23 15:22:29
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MPA-GSH functionalized AlGaN/ GaN High Electron Mobility Transistor based sensor for Cadmium ion detection
摘要： This work demonstrates a novel AlGaN/GaN high electron mobility transistor (HEMT) based cadmium ion (Cd2+) sensor with Mercaptopropionic Acid (MPA) and Glutathione (GSH) functionalization. The sensing response of the sensor was analysed by detecting Cd2+ ions at different concentrations. The AlGaN/GaN HEMT sensor exhibits excellent response with the sensitivity of 0.241 μA/ppb, a fast response time of ~ 3 seconds and a lower detection limit of 0.255 ppb. The observed lower detection limit is significantly lower than the World Health Organization (WHO) standard recommended limit for Cd2+ ions in drinking water. Furthermore, the sensor showed good selectivity of Cd2+ ions towards other heavy metal ions. The results indicate that the binding properties of GSH to Cd and the sensitivity of 2-D electron gas (2DEG) towards the variation of charges at the gate region makes the device highly sensitive with rapid detection of Cd2+ ions.
关键词： MPA,Cd2+ ions,AlGaN/GaN HEMT,sensing,GSH
更新于2025-09-23 15:22:29
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Development of UVB Radiation-Emitting Gd3+-Doped Na3YSi2O7 Host Material
摘要： In this work, we synthesized and characterized a narrow-band, ultraviolet-emitting Na3YSi2O7:Gd3+ material. A series of Na3Y1-xSi2O7:Gdx (x = 0.01 ≤ x ≤ 0.11) samples were synthesized using a sol–gel process. X-ray diffraction patterns of all the samples were found to be similar to the hexagonal Na3YSi2O7 phase. Morphology and functional group analysis were performed using scanning electron microscopy and Fourier transform infrared spectroscopy. The effects of gadolinium concentration on the luminescence intensity of the Na3YSi2O7:Gd3+ samples were investigated. The developed sample exhibited an ultraviolet emission peaking at 313 nm under 273-nm excitation. The dominant band at 313 nm was attributed to 6P7/2 → 8S7/2 transition of Gd3+ ions. The electron paramagnetic resonance (EPR) studies revealed the presence of Gd3+ ions in octahedral Y3+ sites in the host lattice.
关键词： EPR,Na3YSi2O7,photoluminescence,XRD,Gd3+ ions,Sol–gel
更新于2025-09-23 15:22:29
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Enhanced NIR-NIR luminescence from CaWO4: Nd3+/Yb3+ phosphors by Li+ codoping for thermometry and optical heating
摘要： Rare earth ions doped luminescent materials have demonstrated their potentiality as sensitive thermometers with good accuracy and high spatial resolution. Nevertheless, low luminescence efficiency, especially at high temperature, still limits the development of this thermometry technique. Here, Nd3+/Yb3+ codoped CaWO4 phosphors were synthesized using high temperature solid-state method, and Li+ ions were introduced aiming to improve the near-infrared (NIR) emissions from Nd3+ in the spectral range of 725-950 nm. The influence of Li+ codoping on the structure and NIR luminescence in CaWO4: Nd3+/Yb3+ when excited by a 980 nm laser diode was investigated. NIR-NIR emissions from Li+ codoped samples are successfully strengthened compared with that without Li+ ions, which is mainly attributed to the distortion of the crystal structure and the increase of crystalline size by Li+. The optical temperature sensing behavior of NIR luminescence from Nd3+ was studied based on fluorescence intensity ratio (FIR). Assisted by Li+ ions, the NIR-NIR emissions are observed to be effectively enhanced with the increment of temperature. And a new pair of thermally coupled levels in Nd3+ ions with excellent thermometry characteristics is explored, through which superior measurement sensitivity as well as accuracy could be achieved. In addition, light-induced temperature rise was realized in the phosphors, which makes CaWO4: Nd3+/Yb3+/Li+ excellent candidate for luminescence thermometry and optical heaters.
关键词： Li+ codoping,thermometry,Nd3+ ions,NIR luminescence
更新于2025-09-23 15:22:29