How Important is the Host (Semiconductor Nanoparticles) Identity and

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How Important is the Host (Semiconductor Nanoparticles) Identity and Absolute Band Gap in Host Sensitized Dopant Photoluminescence? PRASENJIT MANNA, Arijita Chakraborty, Gouranga H. Debnath, and Prasun Mukherjee J. Phys. Chem. Lett., Just Accepted Manuscript • Publication Date (Web): 07 Jun 2017 Downloaded from http://pubs.acs.org on June 9, 2017

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The Journal of Physical Chemistry Letters

How Important is the Host (Semiconductor Nanoparticles) Identity and Absolute Band Gap in Host Sensitized Dopant Photoluminescence? Prasenjit Manna,1 Arijita Chakraborty,1 Gouranga H. Debnath1 and Prasun Mukherjee1,* 1

Centre for Research in Nanoscience and Nanotechnology, University of Calcutta, JD-2,

Sector-III, Salt Lake, Kolkata-700106, West Bengal, India E-mail: [email protected] * To whom correspondence should be addressed.

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Abstract This work reports the host (semiconductor nanoparticles) sensitized dopant (lanthanides, Ln) photoluminescence in near band gap matched Sn(Ln)O2 and Zn(Ln)S [Ln = Sm, Tb] nanoparticles, in order to address the importance of the nanoparticle identity and absolute band gap in the underlying process. While the sensitization was evident in the Sn(Sm)O2 and Zn(Tb)S nanoparticles, the same was not observed in the Sn(Tb)O2 and Zn(Sm)S nanoparticles. This observation stresses on the importance of nanoparticle identity as the determining factor in realizing the host sensitized dopant photoluminescence and provides important insight in developing novel doped inorganic nanoparticle based optical materials. TOC Graphic


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Incorporation of a foreign species (dopant) in an appropriate nanoparticle matrix (host) is an emerging way to develop novel optical materials. 1, 2 The choice of the dopant is oftentimes associated with their unique properties. Towards this goal, trivalent lanthanide cation (Ln3+) incorporated semiconductor nanoparticles have attracted significant attention due to the unconventional photoluminescence properties of these cations.

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The core like

feature of the 4f – 4f transitions produce sharp Ln3+ intra-configurational emission bands with minimum intra- and inter Ln3+ spectral band overlap covering the entire visible and near infrared (NIR) spectral region with luminescence lifetimes spanning in the range of microseconds to milliseconds. Moreover, the emission of Ln3+ is generally found to be resistant to photobleaching. Collectively these properties open up the avenue to generate multiplex assays, possibility of time-gated measurements and data acquisition over longer time frame; thus providing better sensitivity with improved signal to noise ratio. These features are generally difficult to realize using conventional luminophores based on organic molecules and d-block elements. Despite the unique photoluminescence properties, the realization of Ln3+ luminescence for practical purpose is challenging due to the very low molar extinction coefficient and the consequent quenching of Ln3+ luminescence by the vibrational overtones of common bonds (−OH, −NH, −CH) present in the nearby ligand and solvent molecules. 5, 7 A way to overcome these challenges associate with the incorporation of Ln3+ in an appropriate semiconductor nanoparticle matrix to generate C(Ln)A nanoparticles, with C and A being the cationic and anionic ingredients respectively; in which the nanoparticles act as the optical antenna and protector matrix simultaneously, thereby generating usable Ln3+ luminescence from the host (semiconductor nanoparticles) – guest (Ln3+) composite system.



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To this end, we have studied the photophysical properties of Zn(Ln)S [Ln = Sm, Eu, Tb, Dy],

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Zn(Tb)S, Zn(Tb)Se, Cd(Tb)S and Cd(Tb)Se,

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varying sized Zn(Tb)S

Ti(Ln)O2 [Ln = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb] nanoparticles.

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and

These

exercises identify the Zn(Tb)S, Ti(Nd)O2 and Ti(Sm)O2 nanoparticles as potential candidates for significant host sensitized Ln3+ photoluminescence, with the other Ln3+ incorporated II-VI sulfide, selenide and TiO2 host nanoparticles comprising the cases having moderate or no sensitized emission. The underlying photophysical processes have been rationalized with the Ln3+ acting as the potential charge (electron and/or hole) traps in the semiconductor nanoparticles. The exciton recombination at these trap sites are responsible to populate the Ln3+ luminescent energy levels, thereby generating the Ln3+ luminescence from the composite host – guest system. The nanoparticles with appreciable sensitized Ln3+ emission have both the Ln3+ ground and luminescent energy levels lying within the band gap of the host lattice, allowing the exciton recombination in the Ln3+ related trap site with negligible contribution from auto-ionization of the excited electrons from the luminescent energy level. While this photophysical rationalization relies on the relative energy level positions of the Ln3+ ground and excited energy levels with respect to the valence and conduction bands of the host matrix,

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an alternate way to rationalize the experimental observations rely on a

relative energy level schematic where the Ln3+ luminescent energy level is populated either from the higher lying Ln3+ energy levels and/or the nanoparticle centered surface trap states. 13, 14

These two plausible sensitization processes have been shown in Scheme 1.


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Scheme 1. The energy level schematics are shown in which the dopants act as the charge traps with the exciton recombination at these trap sites populating the Ln3+ luminescent energy level (left panel) and the case where such a population results with the involvement of higher lying Ln3+ energy levels and/or the nanoparticle centered surface trap states (right panel). The downward vertical solid and squiggly lines represent the radiative and nonradiative transitions respectively.

The previous comparative accounts to understand the host sensitized dopant photoluminescence in nanoparticles with different elemental composition do not directly shed light on the relative importance of nanoparticle identity and the absolute band gap. In most of the cases, the change in the identity of the nanoparticles associates a change in the band gap value. For example, the Zn(Ln)S and Ti(Ln)O2 nanoparticles studied were having band gap values of 4.34 and 3.54 eV respectively,

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which is a consequence of their respective

bulk band gaps. The evaluation of relative importance of nanoparticle identity and absolute band gap in the host sensitized dopant photoluminescence is the primary objective of this study. The photoluminescence properties of Sm3+ and Tb3+ in band gap matched Sn(Ln)O2 and Zn(Ln)S [Ln = Sm, Tb] nanoparticles have been compared for this purpose. While the choice of the host materials is guided by the same (3.6 eV) bulk band gaps of the SnO2 and ZnS, the selection of Sm3+ and Tb3+ in the current study is guided by our observation of host sensitized dopant emission in the Ti(Sm)O2 and Zn(Tb)S nanoparticles respectively. 8, 11 The panel a in Figure 1 shows the transmission electron microscopy (TEM) image of the Sn(Tb)O2 nanoparticles studied, with the corresponding size distribution in the panel b. 5 ACS Paragon Plus Environment


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The size distribution histogram reveals the particles having a diameter of 2.7 ± 0.3 nm, reported as the average and standard deviation values. An estimation of band gap following the Brus model 15 reveals a value of 4.45 eV, using the effective electron mass, effective hole mass and dielectric constant of SnO2 from the report by Miglio and co-workers.

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The

synthetic protocol for the Zn(Ln)S nanoparticles has been adopted from our previous work which resulted in particles with a diameter of 3.0 ± 0.5 nm, corresponding to a band gap of 4.34 eV.

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The high resolution transmission electron microscopy (HRTEM) image in the

panel c of Figure 1 shows crystalline phase that has been correlated to the (110) plane of the SnO2 nanoparticles (JCPDS Card Number 88-0287). The energy dispersive X-ray spectra (EDS) of all the nanoparticles studied in the present work are shown in the panel d, indicating the presence of the constituent elements in the nanoparticles investigated. The difficulty in observing prominent Sm and Tb bands in the Sn(Ln)O2 [Ln = Sm, Tb] nanoparticles respectively most likely associate with the low doping extent (vide infra). It is to note that merely increasing the nominal doping extent beyond a certain limit does not increase the incorporation of Ln3+ in the Sn(Ln)O2 nanoparticles.

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Further evidence arguing the

presence of Ln3+ in the Sn(Ln)O2 nanoparticles investigated appears from photoluminescence measurements (vide infra, see Supporting Information). Figure S1 summarizes the Fourier transform infrared (FTIR) spectra, suggesting the signature of Sn−O−Sn bond vibrations in the Sn(Ln)O2 nanoparticles. Moreover, the comparison of the spectral profile of the Ln(III) precursor salts with the corresponding spectra obtained in the nanoparticles indicates that the contribution from the free salts in the nanoparticles is not significant and that the Ln3+ has interacted with the nanoparticles (vide infra).


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Figure 1. The transmission electron microscopy (TEM) image with the corresponding size distribution of the Sn(Tb)O2 nanoparticles are shown in the panels a and b respectively. The high resolution transmission electron microscopy (HRTEM) image of the Sn(Tb)O2 nanoparticles is shown in the panel c. The energy dispersive X-ray spectra (EDS) of the Sn(Ln)O2 and Zn(Ln)S [Ln = Sm, Tb] nanoparticles are shown in the panel d. Figure 2 summarizes the Ln3+ photoluminescence excitation and emission spectra of the Sn(Ln)O2 and Zn(Ln)S [Ln = Sm, Tb] nanoparticles respectively (panel a), with the inclusion of the corresponding spectra of the free salts dissolved in water (panel b). The steady-state emission spectrum of the Sn(Sm)O2 nanoparticles is shown in Figure S2. Examination of the emission spectrum clearly reveals Sm3+ bands at 568, 624, 677 and 727



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nm respectively in the Sn(Sm)O2 nanoparticles, originating from the 4G5/2 → 6Hn [n = 5/2 – 11/2] transitions. The photoluminescence excitation spectrum upon monitoring the 568 nm emission in the Sn(Sm)O2 nanoparticles generates a broad profile that is distinctly different compared to that when Sm(III) acetate is dissolved in water. The observation of Sm3+ emission with a nominal Sm3+ concentration of ≤50 micromolar in the Sn(Sm)O2 nanoparticles dispersed in water and the broad excitation spectrum responsible for the Sm3+ emission collectively indicates the operation of an optical antenna effect. The acquisition of Sm(III) Ac spectra however requires Sm3+ concentration in the millimolar range.

The

observation of host sensitized Sm3+ emission in the Sn(Sm)O2 nanoparticles is explainable with either the charge trapping or a spectral overlap mediated mechanism (Figure 2). Given the rich population of higher lying excited energy levels in the Sn(Tb)O2 nanoparticles that are nearly iso-energetic with the band gap of the host lattice, a case with the spectral overlap mediated mechanism being operative would result in a sensitized Tb3+ emission from the Sn(Tb)O2 nanoparticles as well. On the contrary, remarkably no Tb3+ emission has been observed in the Sn(Tb)O2 nanoparticles under the same experimental conditions. A look at the relative energetic reveals that both the ground and luminescent energy levels lie closer and above the conduction band of the nanoparticles respectively. This suggests an inefficient hole trapping at the Tb3+ site in the Sn(Tb)O2 nanoparticles, with a concomitant competitive auto-ionization of any excited electrons that may originate by some other pathway (either direct excitation and/or other feeding energy level). Successful incorporation of Tb3+ in the Sn(Tb)O2 nanoparticles is evidenced from the time-gated photoluminescence emission spectrum acquired with an excitation and emission spectral resolution each of 14 nm (Figure S3). The extremely weak Tb3+ emission in the Sn(Tb)O2 nanoparticles even with such a larger spectral resolution relates to an absence of host sensitization.


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The corresponding experiments with the near band gap matched Zn(Ln)S nanoparticles [Ln = Sm, Tb] provide an interesting comparative account. While the similar band gap of the host nanoparticles yields comparable spectral overlap, the relative energetic position would however be drastically different. It is important to note that the relative energetic positions of the Ln3+ ground and excited energy levels with respect to the valence and conduction band of the host lattice depends on the charge transfer energy from the anion valence band to the Ln3+ species. The anionic ingredients of the Sn(Ln)O2 and Zn(Ln)S [Ln = Sm, Tb] being the oxide and sulfide moieties, this charge transfer energy is going to be different in the two cases. Jørgensen’s model,

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For example, based on Pauling electronegativity scale and

the charge transfer energy from the oxide and sulfide anions to Eu3+

has been estimated to be 5.36 and 2.16 eV respectively.

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Correspondingly, the charge

trapping model envisages a different behavior of host sensitized Ln3+ photoluminescence in the Zn(Ln)S nanoparticles, compared to that observed in the Sn(Ln)O2 nanoparticles. Experimentally this has been observed indeed. In the Zn(Ln)S [Ln = Sm, Tb] nanoparticles, host sensitized Tb3+ emission has been observed in the Zn(Tb)S nanoparticles, while the corresponding Zn(Sm)S case did not produce any characteristic Sm3+ emission. Although valence band to Sm2+ transition could be a viable pathway to populate the Sm3+ luminescent energy level in the Zn(Sm)S nanoparticles, the efficiency of such a process would not be significant due to the close proximity of Sm2+ ground state energy level to the conduction band of the host lattice. Moreover, the energy gap between the luminescent energy level 4

G5/2 and the highest spin orbit level of the ground state multiplet 6F11/2 is 7400 cm−1,

suggesting an efficient environment induced Sm3+ luminescence quenching by the vibrational overtones of ligand and solvent molecules. This explains the difficulty in observing the Sm3+ emission in the Zn(Sm)S nanoparticles.



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Figure 2. Photoluminescence excitation and emission spectra of the Ln3+ in the Sn(Sm)O2 and Zn(Tb)S nanoparticles dispersed in water are shown in panel a. The corresponding spectra in the freely floating Ln(III) acetate salts dissolved in water are included in panel b. The Sn(Tb)O2 and Zn(Sm)S nanoparticles did not show characteristic Ln3+ emission bands. The panel c and d summarize the relative position of the Ln3+ ground and luminescent energy levels with respect to the valence and conduction bands of the host lattice, within the framework of charge trapping mediated sensitization. For each lanthanide moiety, the lower and upper dots represent the position of the ground state energy level of Ln3+ and Ln2+ respectively. The panel e shows the relative energy levels for a spectral overlap mediated energy transfer for the corresponding sensitization process.


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The luminescence lifetime decay profiles of the relevant systems studied are shown in Figure 3. The corresponding lifetime decay parameters have been summarized in Table S1. The luminescence lifetime decay analysis for Sm3+ emission in the Sn(Sm)O2 nanoparticles reveals a bi-exponential behavior with time constants of 0.52 and 4.4 ms respectively. The corresponding values for Tb3+ emission in the Zn(Tb)S nanoparticles were found to be 0.94 and 3.8 ms respectively. The two lifetime components have been correlated with lesser protected surface and more protected core sites respectively. Furthermore a comparison with the corresponding decay traces for the freely floating Ln(III) acetate salts dissolved in water indicates a lengthening of lifetime in the nanoparticles.

This indicates a protected

environment of Ln3+ in the nanoparticles, additionally arguing the absence of free Ln(III) in the nanoparticles investigated.

Figure 3. The Ln3+ emission lifetime decay profiles for the Sn(Sm)O2 and Zn(Tb)S nanoparticles dispersed in water are shown, with the corresponding decay profiles for the freely floating salts dissolved in water. Overall, the comparison of the photoluminescence properties of the Ln3+ in the near band gap matched Sn(Ln)O2 and Zn(Ln)S [Ln = Sm, Tb] nanoparticles reveals that the identity of the host semiconductor nanoparticles and guest Ln3+ is more important in determining the host sensitized dopant photoluminescence instead of considering the absolute band gap value of the host nanoparticles. Moreover, the results discussed in this work along 11 ACS Paragon Plus Environment


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with our previous work on the Ti(Ln)O2 nanoparticles

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suggest that while the oxide based

nanoparticles are better candidates to realize host sensitized Sm3+ emission, the corresponding effect with Tb3+ is more evident from the sulfide based nanoparticles. This finding provides important insight for the development of novel doped semiconductor nanoparticles based luminophores. Materials and Methods Lanthanide (Ln) [Ln = Sm, Tb] incorporated tin oxide [Sn(Ln)O2] nanoparticles were synthesized by a solvothermal method followed by annealing at 950°C; using Sn(IV) chloride hydrate, Ln(III) acetate hydrate and ethylene glycol as the precursors.

The Zn(Ln)S

nanoparticles were synthesized using Zn(II) acetate hydrate, Ln(III) acetate hydrate and thiourea as the cationic and anionic precursors respectively, in presence of 1-thioglycerol as the capping ligand. The electron microscopy, energy dispersive X-ray, electronic absorption, infrared absorption and photoluminescence spectroscopy measurements were performed using the JEOL (Model: JEM-2100), Zeiss (Model: EVO 18), Perkin Elmer (Model: Lambda 1050), Jasco FTIR (Model: 6300) and Horiba (Model: Fluorolog 3-22) respectively. Acknowledgment Financial assistance from the Science and Engineering Research Board (SERB), Department of Science and Technology (DST) (SB/S1/PC-040/2013) is gratefully acknowledged.

Mr. Prasenjit Manna acknowledges University Grants Commission for

supporting a fellowship. The authors thank Ms. Urmila Goswami and Mr. Pratyush Sengupta for the electron microscopy measurements. Supporting Information Synthesis and characterization of the nanoparticles, FTIR, photoluminescence spectra and lifetime decay parameters 12 ACS Paragon Plus Environment

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References (1) (2) (3) (4) (5) (6) (7)

(8)

(9)

(10)

(11)

(12)

(13)

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(15)

Bhargava, R. N.; Gallagher, D.; Hong, X.; Nurmikko, A. Optical Properties of Manganese-Doped Nanocrystals of ZnS. Phys. Rev. Lett. 1994, 72, 416-419. Wu, P.; Yan, X.-P. Doped Quantum Dots for Chemo/Biosensing and Bioimaging. Chem. Soc. Rev. 2013, 42, 5489-5521. Bünzli, J.-C. G.; Piguet, C. Taking Advantage of Luminescent Lanthanide Ions. Chem. Soc. Rev. 2005, 34, 1048-1077. Eliseeva, S. V.; Bünzli, J.-C. G. Lanthanide Luminescence for Functional Materials and Bio-Sciences. Chem. Soc. Rev. 2010, 39, 189-227. Bünzli, J.-C. G. Lanthanide Luminescence for Biomedical Analyses and Imaging. Chem. Rev. 2010, 110, 2729-2755. Binnemans, K. Lanthanide-Based Luminescent Hybrid Materials. Chem. Rev. 2009, 109, 4283-4374. Beeby, A.; Clarkson, I. M.; Dickins, R. S.; Faulkner, S.; Parker, D.; Royle, L.; de Sousa, A. S.; Williams, J. A. G.; Woods, M. Non-radiative Deactivation of the Excited States of Europium, Terbium and Ytterbium Complexes by Proximate Energy-Matched OH, NH and CH Oscillators: An Improved Luminescence Method for Establishing Solution Hydration States. J. Chem. Soc., Perkin Trans. 2 1999, 493503. Mukherjee, P.; Shade, C. M.; Yingling, A. M.; Lamont, D. N.; Waldeck, D. H.; Petoud, S. Lanthanide Sensitization in II-VI Semiconductor Materials: A Case Study with Terbium (III) and Europium (III) in Zinc Sulfide Nanoparticles. J. Phys. Chem. A 2011, 115, 4031-4041. Chakraborty, A.; Debnath, G. H.; Ahir, M.; Bhattacharya, S.; Upadhyay, P.; Adhikary, A.; Mukherjee, P. Towards the Realization of Luminescence from Visible Emitting Trivalent Lanthanides (Sm, Eu, Tb, Dy) in Polar Zinc Sulfide Nanoparticles: Evaluation of in vitro Cytotoxicity. RSC Adv. 2016, 6, 43304-43315. Debnath, G. H.; Chakraborty, A.; Ghatak, A.; Mandal, M.; Mukherjee, P. Controlled Terbium(III) Luminescence in Zinc Sulfide Nanoparticles: An Assessment of Competitive Photophysical Processes. J. Phys. Chem. C 2015, 119, 24132-24141. Chakraborty, A.; Debnath, G. H.; Saha, N. R.; Chattopadhyay, D.; Waldeck, D. H.; Mukherjee, P. Identifying the Correct Host−Guest Combination To Sensitize Trivalent Lanthanide (Guest) Luminescence: Titanium Dioxide Nanoparticles as a Model Host System. J. Phys. Chem. C 2016, 120, 23870-23882. Klik, M. A. J.; Gregorkiewicz, T.; Bradley, I. V.; Wells, J.-P. R. Optically Induced Deexcitation of Rare-Earth Ions in a Semiconductor Matrix. Phys. Rev. Lett. 2002, 89, 227401-1-227401-4. Luo, W.; Li, R.; Chen, X. Host-Sensitized Luminescence of Nd3+ and Sm3+ Ions Incorporated in Anatase Titania Nanocrystals. J. Phys. Chem. C 2009, 113, 87728777. Planelles-Aragó, J.; Cordoncillo, E.; Ferreira, R. A. S.; Carlos, L. D.; Escribano, P. Synthesis, Characterization and Optical Studies on Lanthanide-Doped CdS Quantum Dots: New Insights on CdS / Lanthanide Energy Transfer Mechanisms. J. Mater. Chem. 2011, 21, 1162-1170. Brus, L. E. Electron-Electron and Electron-Hole Interactions in Small Semiconductor Crystallites: The Size Dependence of the Lowest Excited Electronic State. J. Chem. Phys. 1984, 80, 4403-4409.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(16)

(17)

(18) (19) (20)

Page 14 of 14

Miglio, A.; Saniz, R.; Waroquiers, D.; Stankovski, M.; Giantomassi, M.; Hautier, G.; Rignanese, G.-M.; Gonze, X. Computed Electronic and Optical Properties of SnO2 Under Compressive Stress. Optical Materials 2014, 38, 161-166. Kong, J.; Zhu, H.; Li, R.; Luo, W.; Chen, X. Carrier-mediated 1.55 mm Photoluminescence from Single Er3+ Center in SnO2 Nanocrystals. Optics Lettters 2009, 34, 1873-1875. Jørgensen, C. K. Modern Aspects of Ligand Field Theory. North-Holland, Amsterdam, 1971. Dorenbos, P.; van der Kolk, E. Location of Lanthanide Impurity Levels in the III-V Semiconductor GaN. Appl. Phys. Lett. 2006, 89, 061122-1-061122-3. Dorenbos, P. Lanthanide Charge Transfer Energies and Related Luminescence, Charge Carrier Trapping, and Redox Phenomena. J. Alloys Compd. 2009, 488, 568573.


How Important is the Host (Semiconductor Nanoparticles) Identity and

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