Photochromism and magneto-optic response of ZnO:Mn semiconductor quantum dots fabricated by microemulsion route

Misra, Nirmal; Roy, Mohendra; Mohanta, Dambarudhar; Baruah, Kishor Kumar; Choudhury, Arup

doi:10.2478/s11534-008-0025-1

Cited by 6 publications

(3 citation statements)

References 24 publications

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“…If this is caused by the absorption of light, as in the current case, this phenomenon is referred to as photochromism. It is known to occur in numerous organic and inorganic materials, of which many are Eu-activated phosphors. − From this list, CaAl 2 O 4 :Eu 2+ ,Nd 3+ is also known as a persistent phosphor, but in contrast to the case of SrAl 2 O 4 :Eu 2+ ,Dy 3+ it seems that the absorption bands of the color center do not show overlap with the absorption bands of the Eu 2+ activator, although it is yet unclear whether the color centers in CaAl 2 O 4 :Eu 2+ ,Nd 3+ are also responsible for the trapping related to the persistent luminescence as is the case for SrAl 2 O 4 :Eu 2+ ,Dy 3+ …”

Section: Results and Discussionmentioning

confidence: 99%

Importance of Evaluating the Intensity Dependency of the Quantum Efficiency: Impact on LEDs and Persistent Phosphors

2018

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The quantum efficiency is a key metric in lighting technology and for the quantification of luminescent processes, indicating how many photons are emitted with respect to the number of absorbed photons. Ideally, this value should approach unity to reduce losses, for instance in the common phosphor converted white LEDs. In this work we demonstrate that in luminescent materials where energy can be stored at defect centers, like in the extreme case of persistent phosphors, the quantum efficiency depends on the excitation intensity. For the green emitting SrAl 2 O 4 :Eu 2+ ,Dy 3+ , which has been proposed for use in AC-LEDs, the internal quantum efficiency drops for increasing excitation intensity from 71% to 54%. At elevated excitation intensities, as encountered in LEDs, the trapped charge carriers can be optically detrapped by the excitation light, leading to this strong reduction of the overall quantum efficiency. Considering that the absorption cross section for this process is 6−29× larger than the absorption cross section for the luminescent ion, the efficiency of LED phosphors can be increased by avoiding the presence of defects acting as trapping centers. Finally, designing persistent phosphors with defects that show a limited optical response for the excitation light could strongly increase their energy storage capacity.

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Section: Results and Discussionmentioning

confidence: 99%

Importance of Evaluating the Intensity Dependency of the Quantum Efficiency: Impact on LEDs and Persistent Phosphors

2018

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“…All the described mechanisms have their own merits and limitations. In a recent work, an appreciable photochromism was demonstrated in Mn incorporated ZnO nanosystems (Misra et al 2008). At present, it is difficult to predict a suitable model that fits well to our system, but we expect that the overall cause is due to the transitory variation of the oxidation state of W as a result of absorption of em radiation by the tungsten oxide system.…”

Section: Photochromic Propertiesmentioning

confidence: 87%

Formation of nanoscale tungsten oxide structures and colouration characteristics

Kumar

Mohanta

2011

Bull Mater Sci

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In this work, pH dependent evolution of tungsten oxide (WO 3 ) nanostructures is being reported along with physical characteristics. The synthesis was carried out via an inexpensive solvothermal cum chemical reduction route, with sodium tungstate (Na 2 WO 4 ) and cetyl trimethyl ammonium bromide (C 19 H 42 NBr) as main reactants. The X-ray diffraction, together with transmission electron microscopic studies have revealed formation of regular polyhedral nanocrystalline structures and fractals as one goes from higher pH (= 5·5) to lower pH (= 2) values. The average crystallite size, as calculated through Williamson-Hall plots, was varied within 2·8-6·8 nm for different pH samples. Fourier transform infrared spectroscopy reveals in-plane bending vibration δ (W-OH), observable at ∼1630 cm −1 and strong stretching ν (W-O-W) located at ∼814 cm −1 . Raman spectroscopy has divulged WO 3 Raman active optical phonon modes positioned at ∼717 and 805 cm −1 . The thermochromic and photochromic properties of the nanoscale WO 3 sample prepared at pH = 5·5, are also highlighted.

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“…Faraday active materials are used as optical isolators and magnetic field sensors, among other applications [49]. Santiago [52]. Savchuk et al [53] and Oliveira et al [54] reported FE for Mn doped ZnO with different wavelengths.…”

Section: Introductionmentioning

confidence: 99%

Effect of (Li, Mn) co-doping on structural, optical and magnetic properties of chunk-shaped nano ZnO

Rajamanickam

Mariammal

Rajashabala

et al. 2014

Journal of Alloys and Compounds

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Photochromism and magneto-optic response of ZnO:Mn semiconductor quantum dots fabricated by microemulsion route

Cited by 6 publications

References 24 publications

Importance of Evaluating the Intensity Dependency of the Quantum Efficiency: Impact on LEDs and Persistent Phosphors

Importance of Evaluating the Intensity Dependency of the Quantum Efficiency: Impact on LEDs and Persistent Phosphors

Formation of nanoscale tungsten oxide structures and colouration characteristics

Effect of (Li, Mn) co-doping on structural, optical and magnetic properties of chunk-shaped nano ZnO

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