Role of various defects in the photoluminescence characteristics of nanocrystalline Nd2Zr2O7: an investigation through spectroscopic and DFT calculations

Gupta, Santosh K.; Sudarshan, K.; Ghosh, P. S.; Srivastava, Ankit; Bevara, Samatha; Pujari, P. K.; Kadam, R.M.

doi:10.1039/c6tc01032f

Cited by 112 publications

(79 citation statements)

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“…Figure 3B Oxygen vacancies induced emission in blue and green regions have been observed previously from rare earth zirconate Gd 2 Zr 2 O 7 and Nd 2 Zr 2 O 7 . 28,29 To confirm the origin of the emission bands from the LZO and LHO NPs, they were further annealed in oxidizing and reducing atmospheres.…”

Section: Probing Observed Pl Differences Of Lzo and Lho Nps By Dft mentioning

confidence: 99%

“…However, the literature pertaining to photoluminescence study in undoped La 2 B 2 O 7 (B = Zr and Hf) and their comparison is completely missing, though there have been reports for Nd 2 Zr 2 O 7 , Gd 2 Zr 2 O 7 , Y 2 Zr 2 O 7 , and Eu 2 Zr 2 O 7 . Eagleman et al observed blue emission in bulk La 2 Hf 2 O 7 powder induced by oxygen vacancies but could not assign the exact types of oxygen vacancies involved .…”

Section: Introductionmentioning

confidence: 99%

“…27 However, the literature pertaining to photoluminescence study in undoped La 2 B 2 O 7 (B = Zr and Hf) and their comparison is completely missing, though there have been reports for Nd 2 Zr 2 O 7 , Gd 2 Zr 2 O 7 , Y 2 Zr 2 O 7 , and Eu 2 Zr 2 O 7 . [28][29][30] Eagleman et al observed blue emission in bulk La 2 Hf 2 O 7 powder induced by oxygen vacancies but could not assign the exact types of oxygen vacancies involved. 31 Zhang et al did not observe any appreciable emission from their La 2 Zr 2 O 7 nanocrystals, but after sensitizing with a Pb 2+ ions, they observed weak emission which was attributed to the transition between valence band and oxygen vacancies (mid-gap level).…”

Section: Introductionmentioning

confidence: 99%

“…In that context, density functional theory (DFT) studies stand out in deciphering the suitable model and mechanism involved in defect induced emission as reported for perovskite, pyrochlore, and spinel, etc. 28,29,32,33 Most optical and structural investigations of A 2 B 2 O 7 pyrochlores have been focused on the effect of substitutions in the A 3+ ions, especially in cases where the substitution is not charge compensated. Much less attention has been paid to the impact by B 4+ site substitution, which could have significant effects on the structure of pyrochlore hosts that consequently affect the spectral properties.…”

Section: Introductionmentioning

confidence: 99%

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On comparison of luminescence properties of La₂Zr₂O₇ and La₂Hf₂O₇ nanoparticles

et al. 2019

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Unveiling the underlying mechanisms of properties of functional materials, including the luminescence differences among similar pyrochlores A2B2O7, opens new gateways to select proper hosts for various optoelectronic applications by scientists and engineers. For example, although La2Zr2O7 (LZO) and La2Hf2O7 (LHO) pyrochlores have similar chemical compositional and crystallographic structural features, they demonstrate different luminescence properties both before and after doped with Eu3+ ions. Based on our earlier work, LHO‐based nanophosphors display higher photo‐ and radioluminescence intensity, higher quantum efficiency, and longer excited state lifetime compared to LZO‐based nanophosphors. Moreover, under electronic O2−→Zr4+/Hf4+ transition excitation at 306 nm, undoped LHO nanoparticles (NPs) have only violet blue emission, whereas LZO NPs show violet blue and red emissions. In this study, we have combined experimental and density functional theory (DFT) based theoretical calculation to explain the observed results. First, we calculated the density of state (DOS) based on DFT and studied the energetics of ionized oxygen vacancies in the band gaps of LZO and LHO theoretically, which explain their underlying luminescence difference. For Eu3+‐doped NPs, we performed emission intensity and lifetime calculations and found that the LHOE NPs have higher host to dopant energy transfer efficiency than the LZOE NPs (59.3% vs 24.6%), which accounts for the optical performance superiority of the former over the latter. Moreover, by corroborating our experimental data with the DFT calculations, we suggest that the Eu3+ doping states in LHO present at exact energy position (both in majority and minority spin components) where oxygen defect states are located unlike those in LZO. Lastly, both the NPs show negligible photobleaching highlighting their potential for bioimaging applications. This current report provides a deeper understanding of the advantages of LHO over LZO as an advanced host for phosphors, scintillators, and fluoroimmunoassays.

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Section: Probing Observed Pl Differences Of Lzo and Lho Nps By Dft mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On comparison of luminescence properties of La₂Zr₂O₇ and La₂Hf₂O₇ nanoparticles

et al. 2019

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“…Relative low synthesis temperature: The processing temperature of the MSS method is relatively low compared to that required in a conventional solid-state reaction 26 or a sol-gel combustion reaction 27 . This lower temperature saves energy while producing high-quality NPs.…”

Section: Introductionmentioning

confidence: 99%

Molten-Salt Synthesis of Complex Metal Oxide Nanoparticles

Zuniga¹,

Abdou²,

Gupta³

et al. 2018

JoVE

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The development of feasible synthesis methods is critical for the successful exploration of novel properties and potential applications of nanomaterials. Here, we introduce the molten-salt synthesis (MSS) method for making metal oxide nanomaterials. Advantages over other methods include its simplicity, greenness, reliability, scalability, and generalizability. Using pyrochlore lanthanum hafnium oxide (La 2 Hf 2 O 7 ) as a representative, we describe the MSS protocol for the successful synthesis of complex metal oxide nanoparticles (NPs). Furthermore, this method has the unique ability to produce NPs with different material features by changing various synthesis parameters such as pH, temperature, duration, and post-annealing. By fine-tuning these parameters, we are able to synthesize highly uniform, non-agglomerated, and highly crystalline NPs. As a specific example, we vary the particle size of the La 2 Hf 2 O 7 NPs by changing the concentration of the ammonium hydroxide solution used in the MSS process, which allows us to further explore the effect of particle size on various properties. It is expected that the MSS method will become a more popular synthesis method for nanomaterials and more widely employed in the nanoscience and nanotechnology community in the upcoming years.

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Surface Acidic Species‐Driven Reductive Amination of Furfural with Ru/T‐ZrO₂

Saini,

Arulananda Babu,

Saravanamurugan

2024

ChemSusChem

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Catalyst development for upgrading bio‐based chemicals towards primary amines has increasingly attracted owing to their applications in the pharmaceutical and polymer industries. The surface acidic sites in metal oxide‐based catalysts play a key role in the reductive amination of aldehydes/ketones involving H2 and NH3; however, the crucial role of the type of surface acidic species and their strength remains unclear. Herein, this study exhibits the catalytic reductive amination of furfural (FUR) to furfurylamine (FUA) with Ru supported on tetragonal (Ru/T‐ZrO2) and monoclinic (Ru/M‐ZrO2) ZrO2. Ru/T‐ZrO2 exhibited an 11.8‐fold higher rate of reductive amination than Ru/M‐ZrO2, giving a quantitative yield of FUA (99%) at 80 °C in 2.5 h and is recyclable up to four runs. Catalyst surface investigation using spectroscopic techniques, like X‐ray photoelectron, electron paramagnetic resonance, and Raman, confirm higher oxygen vacancy sites (1.6 times) on the surface of Ru/T‐ZrO2 compared to Ru/M‐ZrO2. Moreover, in‐situ NH3‐diffuse reflectance infrared Fourier transform spectroscopy studies display that Ru/T‐ZrO2 has more moderate Bronsted acidic sites (surface H‐bonded hydroxyl groups) than Ru/M‐ZrO2. Further, the controlled experiments and poisoning studies with KSCN and 2,6‐lutidine suggest the crucial role of Ov sites (Lewis acidic sites) and surface hydroxyl groups (Bronsted acidic sites) for selective FUA formation.

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Role of various defects in the photoluminescence characteristics of nanocrystalline Nd₂Zr₂O₇: an investigation through spectroscopic and DFT calculations

Abstract: Photoluminescence in the blue and green regions is observed for the first time in nanocrystals of Nd2Zr2O7 synthesized by gel combustion method. This emission is attributed to the presence of oxygen vacancies.

Cited by 112 publications

References 75 publications

On comparison of luminescence properties of La₂Zr₂O₇ and La₂Hf₂O₇ nanoparticles

On comparison of luminescence properties of La₂Zr₂O₇ and La₂Hf₂O₇ nanoparticles

Molten-Salt Synthesis of Complex Metal Oxide Nanoparticles

Surface Acidic Species‐Driven Reductive Amination of Furfural with Ru/T‐ZrO₂

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Role of various defects in the photoluminescence characteristics of nanocrystalline Nd2Zr2O7: an investigation through spectroscopic and DFT calculations

Abstract: Photoluminescence in the blue and green regions is observed for the first time in nanocrystals of Nd2Zr2O7 synthesized by gel combustion method. This emission is attributed to the presence of oxygen vacancies.

Cited by 112 publications

References 75 publications

On comparison of luminescence properties of La2Zr2O7 and La2Hf2O7 nanoparticles

On comparison of luminescence properties of La2Zr2O7 and La2Hf2O7 nanoparticles

Molten-Salt Synthesis of Complex Metal Oxide Nanoparticles

Surface Acidic Species‐Driven Reductive Amination of Furfural with Ru/T‐ZrO2

Contact Info

Product

Resources

About

Role of various defects in the photoluminescence characteristics of nanocrystalline Nd₂Zr₂O₇: an investigation through spectroscopic and DFT calculations

On comparison of luminescence properties of La₂Zr₂O₇ and La₂Hf₂O₇ nanoparticles

On comparison of luminescence properties of La₂Zr₂O₇ and La₂Hf₂O₇ nanoparticles

Surface Acidic Species‐Driven Reductive Amination of Furfural with Ru/T‐ZrO₂