研究目的
To develop a simple and inexpensive method for Cr3+ doping into nanoporous anodic alumina (NAA) using microwave-assisted solution technique and to investigate the phase-dependent photoluminescence properties of Cr3+ doped NAA for potential applications in nano-optics and composite luminescent nanomaterials.
研究成果
Microwave-assisted solution technique is an effective method for homogeneous Cr3+ doping into NAA, enabling phase transitions from amorphous to δ, θ, and α-alumina with annealing. The phase-dependent photoluminescence, characterized by intense R-line emission at 694 nm for α-alumina and variations in other phases, confirms the strong crystal field environment for Cr3+ ions. This work provides insights into phase-dependent emission behavior and offers a facile approach for developing luminescent nanomaterials for applications in nano-optics, bioimaging, and composite materials.
研究不足
The NAA membranes broke into pieces during annealing due to curling up and phase change, which is a known issue for heat-treated ceramics. The method may require optimization for large-scale production and integration into devices. The study focused on Cr3+ doping and phase transitions in NAA, but other dopants or nanostructures were not explored.
1：Experimental Design and Method Selection:
The study employed microwave-assisted solution technique (MAST) for homogeneous Cr3+ doping into NAA, followed by heat treatment at various temperatures (700°C to 1350°C) to induce phase transitions. The rationale was to achieve facile doping and study phase-dependent luminescence. Theoretical models included crystal field theory for analyzing photoluminescence properties.
2：Sample Selection and Data Sources:
NAA samples were prepared by two-step electrochemical anodization of high-purity aluminum foils in 10 wt% phosphoric acid at 175 V. Cr3+ doping was performed using Cr(acac)3 precursor dissolved in ethylene glycol and water, with microwave irradiation.
3：List of Experimental Equipment and Materials:
Equipment included Rigaku Ultima eIV powder X-ray Diffractometer (XRD), ZEISS EVO 18 analytical scanning electron microscope (SEM), Perkin Elmer Lambda 950 UV/VIS/NIR spectrophotometer with integrating sphere for diffuse reflectance spectroscopy (DRS), and Jasco FP8300 fluorescence spectrometer for photoluminescence (PL) measurements. Materials included high-purity aluminum foils, phosphoric acid, Cr(acac)3, ethylene glycol, and deionized Millipore water.
4：Experimental Procedures and Operational Workflow:
NAA preparation involved pre-treatment of aluminum foils (degreasing, ultrasonic cleaning, annealing, cleaning in NaOH and nitric acid), electrochemical polishing, anodization, and separation from substrate. Cr3+ doping was done by dipping NAA in precursor solution and microwave irradiation (220°C, 200 psi, 300 W) for 1 h. Annealing was performed at temperatures from 700°C to 1350°C. Characterization included XRD for phase analysis, SEM for morphology, DRS for absorption, and PL for emission properties.
5：Data Analysis Methods:
XRD patterns were compared with JCPDS standards for phase identification. DRS and PL spectra were analyzed for band positions and intensities. Crystal field parameters (Dq, B) were calculated from PL excitation spectra using equations based on crystal field theory. Lifetimes were obtained by fitting single exponential decay curves. CIE chromaticity coordinates were determined from PL data.
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