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Comparative study on blue-turquoise silicate apatite phosphors prepared via different synthesis routes
摘要： Different types of gel precursors were obtained via microwave-assisted precipitation, gel-combustion, sol–gel, and Pechini methods in order to prepare Ca2Y7.76Ce0.12Tb0.12(SiO4)6O2 phosphors with apatite structure. The processes involved during the thermal treatment of precursors were revealed by TGA– FT-IR coupling. ICP-OES reveals that the incorporation degree of dopants (Ce3+, Tb3+) in silicate lattice are close to theoretical values while Ca2+ and Y3+ values shows differences depending on the synthesis route. The phosphors composition, morphology, structure, and optical characteristics are revealed by SEM, XRD, FTIR, and luminescent investigations. Pure hexagonal apatite with crystallite size of 76.5 nm was identi?ed in sample prepared by gel-combustion, while cubic-Y2O3 and monoclinic-Y2SiO5, as secondary phases, were found in precipitated samples. The purity phase was enhanced by increasing the TEOS amount during precipitation. As a result of the Ce3+ incorporation into different symmetry sites, the excitation spectra are dominated either by 321 or 360 nm band. Turquoise emission of apatites is shifted toward blue region by increasing the excitation wavelength from 231 to 360 nm.
关键词： Silicate apatite,Luminescence,Wet chemical synthesis,Phosphors
更新于2025-09-23 15:22:29
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Low-cost uncooled MWIR PbSe quantum dots photodiodes
摘要： A mid-wave infrared (MWIR) uncooled PbSe-QDs/CdS p–n heterojunction photodiode has been fabricated using a wet-chemical synthesis route. This offers a low-cost alternative to traditional monocrystalline photodiodes relying on molecular beam epitaxy (MBE) technology. It was demonstrated that the post-annealing is critical to tailor the photoresponse wavelength and to improve the performance of photodiodes. After annealing at 673 K in air for 0.5 h, the ligand-free PbSe-QDs/CdS photodiode exhibits a MWIR spectral photoresponse with a cutoff wavelength of 4.2 mm at room temperature. Under zero-bias photovoltaic mode, the peak responsivity and specific detectivity at room temperature are 0.36 (cid:1) 0.04 A W(cid:3)1 and (8.5 (cid:1) 1) (cid:4)108 cm Hz1/2 W(cid:3)1, respectively. Temperature-dependent spectral response shows an abnormal intensity variation at temperatures lower than 200 K. This phenomenon is attributed to the band alignment transition from type II to type I, resulting from the positive temperature coefficient of PbSe. In addition, it was proved that In doped CdSe (CdSe:In) films could be used as a promising new candidate of infrared transparent conductive electrodes, paving the way for monolithic integration of uncooled low-cost MWIR photodiodes on Si readout circuitry.
关键词： infrared transparent conductive electrodes,MWIR,photodiode,CdSe:In,wet-chemical synthesis,PbSe-QDs,annealing
更新于2025-09-16 10:30:52
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Towards understanding the enhancement of antibacterial activity in manganese doped ZnO nanoparticles
摘要： In this work we focus on enhancing the antibacterial activity of ZnO nanoparticles by Mn doping, synthesized using a wet-chemical method. The as-obtained precursor powders were deeply investigated by thermal analyses correlated with the evolved gas analysis (TG-DTA-FT-IR) and by in situ high-temperature XRD to elucidate the thermally induced processes and to understand the manganese doped ZnO nanoparticles formation. The hexagonal wurtzite-type structure and the morphological characteristics of the thermally treated samples have been investigated by X-ray diffraction, and HRTEM. An average particle size ranging between 10 to 29 nm and a polyhedral and spherical morphology with a tendency to form aggregates were evidenced by TEM images. Optical absorption measurements reveal that the band gap of ZnO decreased from 3.19 to 2.99 eV, which confirmed the existence of Zn-O-Mn interaction. The incorporation of the Mn ions into the ZnO lattice has been studied by EPR spectroscopy and also, the generation of reactive oxygen species (ROS) has been evidenced by using the EPR coupled with the spin trapping probe technique. Here, we report that in addition to altering the crystallite size, morphology and optical absorption characteristics of ZnO, the introduction of Mn dopant also improves the antibacterial efficiency against pathogenic microorganisms, namely Escherichia coli and Bacillus cereus.
关键词： Mn doping,antibacterial activity,ZnO nanoparticles,reactive oxygen species,wet-chemical synthesis
更新于2025-09-04 15:30:14