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Pandey P, Kaushik SD, Rajput P, Singh MN, Sharma RK, Giri S. Nature of local disorder in β-NaYF 4-based, near-infrared upconverting core nanocrystals due to deliberate incorporation of a symmetry perturbing agent. NANOSCALE 2025; 17:2269-2280. [PMID: 39665566 DOI: 10.1039/d4nr03951c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2024]
Abstract
As nanocrystalline materials exhibit complex disorders, assessment of the local disorder at the nanoscale induced by implanted lattice defects plays a crucial role in understanding the structure-function relationship in these materials. In this report, a comprehensive structural analysis was performed on upconverting nanocrystals (UCNCs) of NaYF4/Nd/Yb/Tm, containing varying concentrations of Li+ to induce deliberate lattice defects. Subsequently, a comprehensive structural analysis of the UCNCs was performed using synchrotron radiation-based high-resolution X-ray diffraction (HRXRD), high-energy total angle scattering coupled with pair distribution function (PDF) analysis, neutron diffraction (ND) and EXAFS probing. The incorporation of Li+ was studied up to a theoretical maximum of 60% with predominantly single-phase β-NaYF4 (P6̄) NCs synthesized. These UCNCs exhibited varying particle morphologies with the average longest dimension ranging from 13 to 94 nm. Rietveld refinement of the ND data confirmed the incorporation of Li+ in the octahedral voids with some Li+ ions occupying lattice positions. The HRXRD results revealed no significant variation in the lattice parameters. However, the local disorder within the NCs, as determined from the PDF analysis, exhibited a distinct trend that correlated with changes in the upconversion luminescence (UCL) intensity. Since the Laporte parity selection rule governs UCL intensity through perturbations of local symmetry, this study established a definite relationship between lattice defects and crystal symmetry modifications induced by atomic-level disorder. The existence of such disorders was further corroborated by EXAFS, HRXRD and ND studies, which provided insights into the local lattice environment and disorder. In essence, this study elucidated a predictive model for understanding how local disorder propagates within a single-phase nanocrystal, particularly in relation to implanted lattice imperfections.
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Affiliation(s)
- Panchanan Pandey
- Department of Chemistry, National Institute of Technology, Rourkela, 769008, India.
| | - S D Kaushik
- UGC - DAE Consortium for Scientific Research Mumbai Centre, Bhabha Atomic Research Centre, 246 C Common Facility Building, Mumbai-400085, India
| | - Parasmani Rajput
- Beamline Development and Application Section, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai, 400094, India
| | - Manvendra Narayan Singh
- Hard X-ray Applications Lab., Accelerator Physics and Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore - 452013, India
| | - Rajendra Kumar Sharma
- Technical Physics Division, Bhabha Atomic Research Centre, Trombay Mumbai-400085, India
| | - Supratim Giri
- Department of Chemistry, National Institute of Technology, Rourkela, 769008, India.
- Centre for Nanomaterials, National Institute of Technology, Rourkela, 769008, India
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Pandey P, Tripathi S, Singh MN, Sharma RK, Giri S. Behavior of Microstrain in Nd 3+-Sensitized Near-Infrared Upconverting Core-Shell Nanocrystals for Defect-Induced Tailoring of Luminescence Intensity. NANO LETTERS 2024; 24:6320-6329. [PMID: 38701381 DOI: 10.1021/acs.nanolett.4c01077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2024]
Abstract
In an attempt to optimize the upconversion luminescence (UCL) output of a Nd3+-sensitized near-infrared (808 nm) upconverting core-shell (CS) nanocrystal through deliberate incorporation of lattice defects, a comprehensive analysis of microstrain both at the CS interface and within the core layer was performed using integral breadth calculation of high-energy synchrotron X-ray (λ = 0.568551 Å) diffraction. An atomic level interpretation of such microstrain was performed using pair distribution function analysis of the high-energy total scattering. The core NC developed compressive microstrain, which gradually transformed into tensile microstrain with the growth of the epitaxial shell. Such a reversal was rationalized in terms of a consistent negative lattice mismatch. Upon introduction of lattice defects into the CS systems upon incorporation of Li+, the corresponding UCL intensity was maximized at some specific Li+ incorporation, where the tensile microstrain of CS, compressive microstrain of the core, and atomic level disorders exhibited their respective extreme values irrespective of the activator ions.
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Affiliation(s)
- Panchanan Pandey
- Department of Chemistry, National Institute of Technology, Rourkela 769008, India
| | - Shilpa Tripathi
- Beamline Development and Application Section, Bhabha Atomic Research Centre, Mumbai 400085, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - Manvendra Narayan Singh
- Hard X-ray Applications Lab, Synchrotrons Utilization Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, India
| | - Rajendra Kumar Sharma
- Technical Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Supratim Giri
- Department of Chemistry, National Institute of Technology, Rourkela 769008, India
- Centre for Nanomaterials, National Institute of Technology, Rourkela 769008, India
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Ling S, Wang Y, Qin X, Chen C, Lu C, Chen J, Liao S, Huang Y, Hou L. Design of Eu 3+-Doped Fluoride Phosphor with Zero Thermal Quenching Property Based on Density Functional Theory. Inorg Chem 2024; 63:6660-6673. [PMID: 38572776 DOI: 10.1021/acs.inorgchem.3c04524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2024]
Abstract
Although being applied in various fields, white light emitting diodes (WLEDs) still have drawbacks that urgently need to be conquered: the luminescent intensity of commercial phosphors sharply decreases at working temperature. In this study, we calculated the forming energy of defects and confirmed that the VNa defect state can stably exist in β-NaGdF4, by density functional theory (DFT) calculation. Furthermore, we predicted that the VNa vacancies would provide a zero thermal quenching (ZTQ) property for the β-NaGdF4-based red-light phosphor. Then, a series of β-NaGdF4:xEu3+ and β-NaGdF4:0.25Eu3+,yYb3+ red-light phosphors were synthesized by the hydrothermal method. We found that β-NaGdF4:0.25Eu3+ and β-NaGdF4:0.25Eu3+,0.005Yb3+ phosphors possess ZTQ properties at a temperature range between 303-483 K and 303-523 K, respectively. The thermoluminescence (TL) spectra were employed to calculate the depth and density of the VNa vacancies in β-NaGdF4:0.25Eu3+ and β-NaGdF4:0.25Eu3+,0.005Yb3+. Combining the DFT calculation with characterization results of TL spectra, it is concluded that electrons stored in VNa vacancies are excited to the exited state of Eu3+ to compensate for the loss of Eu3+ luminescent intensity. This will lead to an increase of luminescent intensity at high temperatures and facilitate the samples to improve ZTQ properties. WLEDs were obtained with CRI = 83.0, 81.6 and CCT = 5393, 5149 K, respectively, when phosphors of β-NaGdF4:0.25Eu3+ and β-NaGdF4:0.25Eu3+,0.005Yb3+ were utilized as the red-light source. These results indicate that these two phosphors may become reliable red-light sources with high antithermal quenching properties for WLEDs.
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Affiliation(s)
- Shaokun Ling
- School of Resources, Environment and Materials, Guangxi University, Nanning, Guangxi 530004, China
| | - Yaxiong Wang
- School of Resources, Environment and Materials, Guangxi University, Nanning, Guangxi 530004, China
| | - Xiaoyan Qin
- School of Intelligent Equipment Engineering, Guangxi Agricultural Vocational and Technical University, Nanning 530009, China
| | - Chang Chen
- School of Resources, Environment and Materials, Guangxi University, Nanning, Guangxi 530004, China
| | - Chunchun Lu
- School of Resources, Environment and Materials, Guangxi University, Nanning, Guangxi 530004, China
| | - Jidong Chen
- School of Resources, Environment and Materials, Guangxi University, Nanning, Guangxi 530004, China
| | - Sen Liao
- School of Resources, Environment and Materials, Guangxi University, Nanning, Guangxi 530004, China
- School of Chemistry and Chemical Engineering, Guangxi University, Nanning, Guangxi 530004, China
| | - Yingheng Huang
- School of Resources, Environment and Materials, Guangxi University, Nanning, Guangxi 530004, China
| | - Lei Hou
- Publicity Department and United Front Work Department, Guangxi University of Information Engineering, Nanning 530200, China
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