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Eu-Doped BaF2 Nanoparticles for Bioimaging Applications
摘要： Pure Eu3+ ion doped BaF2 nanoparticles with tunable properties or property combinations are accessible via an ionic liquid-assisted solvothermal method. Structural parameters such as cell parameters, lattice strain and especially morphology are judiciously tuned with calcination temperatures. For example, tensile strain is observed in samples calcined up to 400oC, however compressive strain appears in samples calcined at 600oC and beyond. Larger surface area up to the sample calcined at 400oC and observation of layer structure at higher calcinations temperature (650oC and beyond) have been rationalized based on secondary nucleation. 3-dimensional island-like morphology with step-like layer structure caused by secondary nucleation and self-assembly are visualized and explained by Scanning Electron Microscope analysis. Moreover, emission intensity, decay time, quantum yield and Judd-Ofelt parameter of the Eu3+ ions increase systematically with calcinations temperature to a maximum at 400oC, above which they decrease and finally vanish at 800oC. Our results suggest that, smaller sized nanoparticles with 3-dimensional island-like structures, generated due to secondary nucleation at higher calcinations temperature may cause the increase of surface defects and subsequent luminescence quenching. To the best of our knowledge, the interplay between calcinations and secondary nucleation followed by drastic changes in the luminescence properties is new and previously unreported for the nanopowders. In addition, to improve the dispersibility, as-prepared nanoparticles are coated with silica and solubility of nanoparticles is measured in different solvents so that it can be useful for bio-imaging applications also.
关键词： calcination,photoluminescence,rare-earth ion,secondary nucleation,nanoparticles
更新于2025-09-23 15:23:52
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Studies on structural and optical properties of pure and transition metals (Ni, Fe and co-doped Ni–Fe) doped tin oxide (SnO2) nanoparticles for anti-microbial activity
摘要： In this present work, pure and transition metal ions (Ni, Fe and co-doped Ni–Fe) doped SnO2 nanoparticles (NPs) were synthesized using a simple chemical co-precipitation method. Transition metal ions (Ni, Fe and co-doped Ni–Fe) were doped in order to study the influence of structural and optical properties. The synthesized samples were analyzed by using powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, UV–Visible spectroscopy, FT-IR, and photoluminescence spectroscopic techniques. SnO2 crystallites were found to exhibit tetragonal rutile structure with space group P42/mnm (136) with average particle size in the range of 20–30 nm. Also confirmed that all the doped metal ions were incorporated to SnO2. The UV–Vis-NIR spectroscopy revealed a significant red shift in the absorbing band edge due to increase in the amount of Ni, Fe and co-doped Ni–Fe contents. The SEM image shows the morphology of pure and doped (Fe, Ni and Fe–Ni co-doped) SnO2 NPs with large spherical shapes. In FT-IR spectra, the strong peaks are attributed to the antisymmetric stretching mode of O-Sn-O. The PL spectrum exhibits a strong blue emission peak. The antimicrobial studies were investigated against standard bacterial strains and enhanced anti-bacterial activity in doped and co-doped samples was observed, which can be attributed to the ROS and the particles were in the nanoscale regime.
关键词： Antibacterial activity,Photoluminescence,Co-precipitation,Nanoparticle,Co-dopant
更新于2025-09-23 15:23:52
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Reducing aggregation caused quenching effect through co-assembly of PAH chromophores and molecular barriers
摘要： The features of well-conjugated and planar aromatic structures make π-conjugated luminescent materials suffer from aggregation caused quenching (ACQ) effect when used in solid or aggregated states, which greatly impedes their applications in optoelectronic devices and biological applications. Herein, we reduce the ACQ effect by demonstrating a facile and low cost method to co-assemble polycyclic aromatic hydrocarbon (PAH) chromophores and octafluoronaphthalene together. Significantly, the solid photoluminescence quantum yield (PLQYs) for the as-resulted four micro/nanococrystals are enhanced by 254%, 235%, 474 and 582%, respectively. Protection from hydrophilic polymer chains (P123 (PEO20-PPO70-PEO20)) endows the cocrystals with superb dispersibility in water. More importantly, profiting from the above-mentioned highly improved properties, nano-cocrystals present good biocompatibility and considerable cell imaging performance. This research provides a simple method to enhance the emission, biocompatibility and cellular permeability of common chromophores, which may open more avenues for the applications of originally non- or poor fluorescent PAHs.
关键词： cocrystals,aggregation caused quenching,bioimaging,polycyclic aromatic hydrocarbon,photoluminescence quantum yield
更新于2025-09-23 15:23:52
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Crystal structure and photoluminescence properties of novel garnet Y2-LaCaGa3ZrO12:xLn3+ (Ln = Eu and Tb) phosphors
摘要： A series of novel garnet Y2-xLaCaGa3ZrO12:xLn3+ (0 ≤ x ≤ 0.12; Ln = Eu and Tb) phosphors was prepared by a solid-state reaction. Their structural and photoluminescence properties were characterized by X-ray diffraction, Rietveld refinement, and photoluminescence spectroscopy. The studied Y2-xLaCaGa3ZrO12:xLn3+ phosphors crystallized in a cubic garnet crystal structure and Ia3ˉ d space group. The Eu3+- and Tb3+-doped Y2-xLaCaGa3ZrO12 phosphors exhibited strong red and green light emissions, respectively, and high emission color purity. With increasing Tb3+ content, the emitting color of the Y2-xLaCaGa3ZrO12:xTb3+ phosphors shifted to the green spectral region because of cross-relaxation among Tb3+ ions. The Y2-xLaCaGa3ZrO12:xLn phosphors are suitable for applications in white light-emitting diode and other optoelectronic devices.
关键词： Emission,Photoluminescence,Phosphor,Y2LaCaGa3ZrO12
更新于2025-09-23 15:23:52
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Structural, photoluminescence and magnetic properties of Cu-doped SnO2 nanoparticles co-doped with Co
摘要： Co doped Sn0.98Cu0.02O2 nanoparticles have been synthesized by co-precipitation method. The prepared nanoparticles were characterized by X-ray diffraction, scanning electron microscope (SEM), transmission electron microscopy, Fourier transform infrared spectroscopy, photoluminescence and magnetic measurements. The observed tetragonal rutile structure confirmed by XRD patterns was not altered by Co-doping and the value of average crystallite size lies within 8–14 nm. The formation of high density defect states and the new phases of Co and Sn were responsible for the reduction of energy gap (Eg) with Co-doping; Eg varied between 3.12 and 3.58 eV. The tuning of band gap and luminescence properties by Co-doping suggested that Co = 4% doped sample is a promising material for selective coatings for solar cells; use as antireflective coating materials, and for fabrication of optoelectronic devices. FTIR spectrum has been used to authenticate the formation of Sn–O bond and the existence of Co in Sn–Cu–O. The promotion of higher local disorders and the oxygen-related defects during growth process of SnO2 nanoparticles at Co = 4% is responsible for the higher UV/violet/blue band photoluminescence emission intensity. The overlapping between bound magnetic polarons (BMP) by Co-doping induced the room temperature ferromagnetism. The existence of high density charge carriers and oxygen vacancies at Co = 4% sample might be responsible for highest magnitude of ferromagnetism. The noticed suppression of RTFM at Co = 6% may be due to the enhanced antiferromagnetic interaction between neighbouring Co–Co ion.
关键词： Photoluminescence,SnO2 nanoparticles,XRD,Energy gap,Magnetic properties
更新于2025-09-23 15:23:52
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Flexible photoluminescent humidity sensing material based on electrospun PVA nanofibers comprising surface-carboxylated QDs
摘要： Flexible humidity-sensitive materials have drawn increasing attention due to their vital function in monitoring ambient humidity for tactile sensors, allowing them to approach the functionality of human skin. In this work, an electrospun polyvinyl alcohol (PVA)-based nanofiber film comprising surface-carboxylated CdSe/CdxZn1-xS quantum dots (QDs) is fabricated as a high-performance flexible humidity sensing material, based on the relationship between its photoluminescence (PL) and the humidity. The as-prepared film shows excellent PL-humidity linearity, a wide sensing range from 10% to 90% relative humidity, a relatively fast response time, good recoverability, and flexibility. The humidity sensing mechanism can be attributed to the breaking and reforming of hydrogen bonds and proton transfer occurring at the PVA-QD interfaces. This flexible humidity-sensitive material is believed to be a good candidate for humidity-sensitive components in electronic skin.
关键词： Humidity sensing,Polymer,Photoluminescence,Quantum dots
更新于2025-09-23 15:23:52
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Hydrothermal growth and their optoelectronic device application of CuI nanostructure
摘要： Cuprous iodide (CuI) was grown on the Si (100) and Cu films/Si(100) substrate by hydrothermal reaction and hydrothermal evaporation methods. It has been found that all the hydrothermal methods. Different nanostructured CuI have been obtained using photoluminescence (PL) character of nanostructured CuI, the origin of different PL emissions and the different growth mechanisms have been discussed. Then, the nanostructured CuI films have a γ phase with polycrystalline structure. Having analyzed the short-wavelength optoelectronic devices [1-3]. Moreover, CuI possesses some superior properties, such as high hole mobility, excellent p-type conductivity and high transmissivity. These properties make CuI a promising material for applications in the photodetectors [2], transparent conducting films [4], solid-state dye solar cells [5-8] and light-emitting diode [9]. Though different fabrication methods have been used to synthesize CuI [10-14], it is still a challenge to grow epitaxial thin films of CuI with high quality due to the lack of lattice-matched substrates. Commonly for the mismatch substrate, interface strain can be much easier accommodated in the nanostructure than the films. Furthermore, owing to their large surface-to-volume ratio, nanostructured CuI can exhibit special advantage in devices applications, especially for the solid state electrolyte in solar cell and hole transport layer in photodetector applications [1-3]. Here, nanostructured CuI have been synthetized on the Si (100) substrate by hydrothermal methods. The structure and optical properties have been investigated. Photodetector based on n-ZnO/p-CuI heterojunction have been fabricated and the photoelectric properties are also discussed.
关键词： photodetector,CuI,photoluminescence,hydrothermal
更新于2025-09-23 15:23:52
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Enhancement of multi-photon Raman scattering and photoluminescence emission from Li-doped ZnO nanowires
摘要： Uniform Li-doped ZnO nanowires have been fabricated by thermal evaporation method. The ZnO formation and the Li incorporation have been discussed and the formation path of preparation products has also been explained in terms of the stability of Zn and Li vapor in an aerobic atmosphere. The strongest vibration mode at 437.2 cm?1 in the multi-photon Raman scattering of the as-prepared products at room temperature indicates that the Li-doped ZnO nanowires still keep the hexagonal (wurtzite) structure. Raman spectra of Li-doped ZnO with different doping concentrations confirm that the variation of Raman peaks in the range of 550 cm?1～650 cm?1 is caused by the doping of lithium. The photoluminescence property at room temperature shows a blue-shift compared with undoped ZnO in the ultraviolet region. The Gauss fitting analyzed results indicate that the broad-band is composed of one green luminescence (GL) band, one yellow luminescence (YL) band, and one red luminescence (RL) band, respectively. The GL (2.447 eV) could be attributed to the singly ionized oxygen vacancies. The origin of the YL (2.245 eV) could be assigned to the transition of an electron from the conduction band (or a shallow donor) to the Li acceptor level. The RL (1.977 eV) could be assigned to the transitions between a shallow donor (at low temperature) or the conduction band (at higher temperature). Furthermore, the luminescence spectra at low temperature confirm the increase of defect levels like oxygen vacancies.
关键词： li-doped ZnO nanowires,formation process,photoluminescence,multi-photon raman scattering
更新于2025-09-23 15:23:52
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Photoluminescence properties of Er3+/Yb3+ doped ZrO2 coatings formed by plasma electrolytic oxidation
摘要： In the present work, down- and up-conversion photoluminescence properties of Er3+/Yb3+ doped ZrO2 coatings formed by plasma electrolytic oxidation of zirconium in electrolyte containing Er2O3 and Yb2O3 particles were investigated. Down-conversion PL analysis shows that emission spectra of ZrO2:Er3+/Yb3+ coatings excited with 280 nm radiation are composed of broad PL band related to ZrO2 host and bands assigned to f-f transitions of Er3+. The main PL emission bands of Er3+ at around 548 nm and 560 nm are related to 4S3/2→4I15/2 transition. PL excitation spectra monitored at 548 nm feature broad band in the region from 250 nm to 350 nm which is associated with the electron transfer transition from 2p orbital of O2? to 4f orbital of Er3+ and transitions of ZrO2. On the other hand, bands in PL excitation spectra ranging from 350 nm to 535 nm are related to 4f transitions of the Er3+ from the ground state 4I15/2 to higher energy levels. Down-conversion PL intensity decreases with increasing concentration of Yb3+ in coating due to energy transfer from Er3+ to Yb3+. ZrO2:Er3+/Yb3+ coatings show intense green (4S3/2→4I15/2) and red (4F9/2→4I15/2) up-conversion PL emission under the excitation with a 980 nm diode laser. With increasing Yb3+ concentration red up-conversion PL intensity increases more rapidly with respect to green emission, because red up-conversion PL intensity strongly depends on Yb3+ concentration, i.e. 4F9/2 state of Er3+ is directly excited by energy transfer from excited Yb3+.
关键词： up-conversion,Photoluminescence,Er3+/Yb3+,Down-conversion,Plasma electrolytic oxidation
更新于2025-09-23 15:23:52
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Investigation of gamma irradiation effects on the properties of CdS/p-Si heterostructure
摘要： Cadmium sulfide (CdS) thin films were deposited on p-type Si substrate by thermal evaporation to fabricate the CdS/p-Si heterojunction. Gamma irradiation has been used to modify the microstructural, optical and electrical characteristics of CdS/p-Si heterojunction of various doses in the range (0–80 kGy). X-ray diffraction measurements of the gamma irradiated show the reduction in crystallinity of the CdS thin films. While scanning electron microscope images depicted the average CdS particle size was found to be increased with increasing the gamma irradiation dose. Photoluminescence results revealed that at the specific dose of gamma irradiation was found to create the yellow emission in interstitial sites to the valence band. The I–V characteristics showed the current transport properties effected by the different gamma doses. The values of barrier height, saturation current and ideality factor for the CdS/p-Si heterostructure varied due to the causes like inhomogeneities in the interfacial, defect density, charge distribution on interfacial and interfacial layer thickness after gamma irradiation. The gamma irradiation induced effects and the possible mechanism in CdS/p-Si heterojunction is discussed.
关键词： Heterostructure,Diffuse reflectance,Photoluminescence,Gamma irradiation,Thermal evaporation
更新于2025-09-23 15:23:52