Fluoride source-induced tuning of morphology and optical properties

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Article

Fluoride source-induced tuning of morphology and optical properties of YF: Eu , Bi and its application for luminescent ink 3

3+

3+

Lihua He, Tao Wang, Jirong Mou, Fengying Lei, Na Jiang, Xiao Zou, Kwok ho Lam, Yongfu Liu, and Dunmin Lin Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.7b00751 • Publication Date (Web): 07 Aug 2017 Downloaded from http://pubs.acs.org on August 7, 2017

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Crystal Growth & Design

Fluoride source-induced tuning of morphology and optical properties of YF3: Eu3+, Bi3+ and its application for luminescent inks Lihua He a, Tao Wang a, Jirong Moua, Fengying Lei a, Na Jiang a, Xiao Zou a, Kwok Ho Lam b, Yongfu Liu c,* and Dunmin Lin a,* a

College of Chemistry and Materials science, Sichuan Normal University, Chengdu 610066, China. b

Department of Electrical Engineering, the Hong Kong Polytechnic University Hunghom, Kowloon, Hong Kong

c

Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China.

*

Corresponding authors

E-mail: [email protected] (Y. Liu) E-mail: [email protected] (D. Lin) 1

ACS Paragon Plus Environment


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Abstract A variety of nano/microstructured YF3:0.125Eu3+, 0.5%Bi3+ samples with specific morphologies were successfully synthesized by a hydrothermal method using various fluoride sources as microstructure-directing agents, and the grain morphology and fluorescence were effectively tailored. The YF3:0.125Eu3+, 0.5%Bi3+ samples using NH4F, NH4HF2, LiF, NaF, KF, MgF2, CaF2, and BaF2 as fluoride source are abbreviated as S1-S8, respectively. Except for the sample S8, all the diffraction peaks of other materials (S1-S7) can be indexed to pure YF3 with orthorhombic symmetry. Granule-like nanoparticles, truncated octahedron, octahedron, and bipyramid morphologies were observed in S1-S2, S3-S4, S5-S7, and S8 samples, respectively. The grain size of the materials is positively correlated with the cationic radius in fluoride sources, which gives the values of 64 nm - 4.2 µm. The schematic diagram showing grain formation process has been proposed on the basis of fluoride source-induced

morphological

evolution.

The

morphology

dependence

of

fluorescence reveals that the NaF-controlled sample exhibits the strongest orange-yellow emission, while the emission intensity using NH4F as the fluoride source is the lowest. This wok offers us a method to effectively control the shape and size of inorganic photoluminescent materials so as to improve the fluorescence by tuning their morphology using different fluoride sources. Furthermore, it has been demonstrated that these luminescent nanoparticles can be used in luminescent ink.

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1. Introduction Nowadays, lanthanide inorganic nano/microcrystals with special size and morphology are burgeoning and have stimulated intensive interests owing to their outstanding optical properties and wide range of applications in optoelectronic devices, solid state lasers, catalysis, biological labeling and light-emitting displays1-9. Among those inorganic materials, fluoride-containing materials exhibit peculiar physical and chemical features, such as low phonon energy, high iconicity, and high up-conversion efficiency pumped with infrared excitation, and thus have been of great interest in recent decades10, 11. As one of the most important hosts, YF3, in which the formation of a variety of morphologies is easily obtained while trivalent rare earth ions can easily substitute for Y3+ owing to the similar ionic radius, has attracted the most extensive attention12-16. For example, the octahedral YF3 microcrystals reported by Qian et al.17,

18

have proven that the addition of inorganic salts can control the

morphology and phase structure of materials. These results imply that YF3 has been frequently used as host materials. To improve the fluorescence properties, many strategies have been put into practice including synthesis techniques19, composition24,

20

, doping metal ions21-23, the ratio of the

25

, and overall structural parameters such as the size and shape26.

Especially, the precise control of nanocrystals’ size and shape is always vital to determining fluorescence properties27. Up to now, the investigation on controllability of emission peaks through adjusting the morphology has been a hot issue. The distinct variation of emission intensity has been observed in Yb3+/Er3+ activated β-NaYF4 microtubes, microspheres, microrods, micro-bipyramids, microplates, and microprism by tuning the molar ratio of RE3+ (rare earth ions) to NaF28. For YF3:Eu3+ micro-single crystals, tuning the amount of dilute HNO3 and the molar ratio of 3



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KF/Y(NO3)3 leads to the morphology variation from diamond-like particles to octahedron and finally truncated octahedron, and thus induces the dramatic increment in the emission intensity29. Li’s group has proposed that the difference of morphology caused by altering the ratio of water to ethanol strongly affects the fluorescence30. Meanwhile, the pH value, reaction time and temperature, additive and the doping of lanthanide ions were used to alter size and morphology of ScPO4·2H2O, and thus affect their luminescence properties. Nonetheless, those work failed to give us a deep sight into the relationship between morphology and fluorescence. Moreover, it is important to synthesize special materials with various particle sizes, meeting the requirement to acquire high-quality fluorescent materials. Generally, the size and shape of nano/microcrystals rely on various kinds of conditions such as the type and concentration of surfactants and solvents, alteration of inorganic salts, reaction temperature and time, variation and levels of activators31, 32. Yu et al. have pointed out that different fluoride sources (NaF, NaBF4, and NH4F) can control the morphology of the final product effectively, but there was lack of detailed comparison of fluorescence in various fluoride sources33. As known, the energy can be transferred from Bi3+ to Eu3+ for the improvement of the fluorescent properties34. It is worth mentioning that our group has fabricated the Bi3+-sensitized YF3:Eu3+ with excellent fluorescence, and the optimal concentrations for fluorescence were Eu3+ = 0.125 and Bi3+ = 0.5%35. Additionally, no study about the regulated morphology of the YF3:0.125Eu3+, 0.5%Bi3+ by varying the fluoride source was reported. Meanwhile, YF3 in the form of nanomaterials is suitable for security ink applications due to its optical properties. A tremendous advantage of nanoparticles is that the amount of material can be adjusted effectively for the use in the security ink preparation, thus reducing the reproduction cost36. On the basis of this driving force, highly luminescent nanoparticles-based inks 4


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for security have been developed. Herein, a series of fluoride sources (S1-S8: NH4F, NH4HF2, LiF, NaF, KF, MgF2, CaF2 and BaF2) have been used as the ‘morphology modifier’ to control synthesis of YF3:0.125Eu3+, 0.5%Bi3+ (YF3:Eu3+/Bi3+) by a hydrothermal method. The morphology dependence of fluorescence properties of the materials has been investigated. Our study revealed that the fluoride source has remarkable effects on the size and shape of the products. Besides, significant improvement in fluorescence can be achieved by tuning the YF3:Eu3+/Bi3+ morphologies through using different fluoride sources. The precise control of shape and size can broaden the applications of rare-earth nanomaterials. The promising use of this nanoparticles-based security ink on Al foil using a screen printing technique was also demonstrated.

2. Experimental 2.1 Synthesis of YF3:Eu3+/Bi3+ A typical hydrothermal method was used to prepare the YF3:Eu3+/Bi3+ samples. All chemicals were directly used without further purification. In a representative preparation procedure, 5 mmol Eu2O3 (99.99%), 5 mmol Y2O3 (99.99%), and 5 mmol Bi2O3 (99.999%) were mixed together in 11 mL 65% HNO3 and magnetically stirred at 60 °C for 40 min to form an aqueous solution. Next, 0.06 mol KF·2H2O (99%) was dissolved in distilled water, and then added dropwise into the above solution with vigorous stirring at room temperature. Finally, the resulting suspension was transferred into a 100 mL Teflon flask held in a stainless steel autoclave, and the autoclave was sealed and heated at 200 °C for 18 h in an oven. After the autoclave was naturally cooled to room temperature, white precipitates were collected and separated by centrifugation, washed several times with distilled water and ethanol, 5



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and finally dried at 80 °C in air for 20 h. A similar synthesis process was employed using varying fluoride source, while the other reaction conditions keep constant. The products were denoted as S1-S8, respectively. (S1:NH4F, 96%; S2:NH4HF2, 97%; S3:LiF, 98%; S4:NaF, 99%; S5:KF·2H2O, 99%; S6:MgF2, 98%; S7:CaF2, 98.5%; S8:BaF2, 99%). Summary of the raw materials of S1-S8 is including in Table 1. Table 1 Summary of raw materials of S1-S8 Sample

Purity

Cationic Radii37

Amount

Y2O3

99.99%

-

0.05 mol

Eu2O3

99.99%

-

0.05 mol

Bi2O3

99.999%

-

0.05 mol

NH4F (S1)

96%

-

0.06 mol

NH4HF2(S2)

97%

-

0.03 mol

LiF(S3)

98%

60 pm

0.06 mol

NaF(S4)

99%

95 pm

0.06 mol

KF•2H2O(S5)

99%

135 pm

0.06 mol

MgF2(S6)

98%

65 pm

0.03 mol

CaF2(S7)

98.5%

100 pm

0.03 mol

BaF2(S8)

99%

135 pm

0.03 mol

2.2 Characterizations The crystal structures of the powders were examined using X-ray diffraction (XRD) with Cu Kα radiation (SmartLab, Rigaku, Japan), and the powder diffraction data was calculated by the Rietveld refinement using the General Structure Analysis System (GSAS). The microstructures (SEM) were observed by field-emission scanning electron microscopy (Gemini500, Zeiss, Germany). The mapping and composition measurements were performed by a field-emission scanning electron microscope 6


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(SEM) (JSM-7500; Hitachi; Japan) with energy-dispersive spectroscopy (EDS). Transmission electron microscopy (TEM) and high resolution TEM (HRTEM) were performed using JEM2100F( JEOL, Japan). The fluorescence spectral information as well as the decay curves was recorded using a fluorescence spectrophotometer (F-7000) with a xenon lamp. In order to ensure that the peaks intensity in XRD patterns and PL spectra can be compared 0.3430g YF3:0.125Eu3+, 0.5%Bi3+ powders were used to measure XRD and PL spectra and the amount of powders keep constant for every measurement. CIE chromatic coordinates for the prepared phosphors were calculated by CIE 1931 chromaticity coordinate calculation based on the emission data. 2.3 Formation of luminescent inks The disperse medium is important for the quality of luminescent inks. Firstly, earth metals can be well dispersed into the medium through choosing the excellent disperse medium without formation of clusters or agglomerates. Secondly, the viscosity of the disperse medium can also provide the sticky nature of the printing paper. The polyvinylidene fluoride (PVDF) and N-methyl-2-pyrrolidone (NMP) solvent were used to be the binder solution and the disperse solution, respectively. The inks were prepared by 60 wt% as-prepared powders and 40 wt% PVDF in NMP solvent to form a homogenous slurry by continuously stirring for 3 h. A screen printing technique was used for object printing.

3. Results and discussion 3.1 Crystal structure

7



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Figure 1. XRD patterns of YF3:Eu3+/Bi3+ samples using different fluoride sources, S1-S8 Table 2. Diffraction intensity ratios of 020 (I020) to 111 (I111) for S1-S7 as well as standard diffraction pattern Sample

JCPDS#74-0911

S1

S2

S3

S4

S5

S6

S7

I020

57.3

27637

9074

10162

6619

3267

6841

9912

I111

100

28211

9761

11499

7669

4662

7285

12866

Ratios

0.573

0.98

0.93

0.88

0.86

0.70

0.94

0.77

Figure 1 depicts the XRD patterns of as-prepared products using different fluoride sources as structure-directing agent. Except for S8 with BaF2, all diffraction peaks of S1-S4 can be indexed to a pure YF3 (JCPDS #74-0911) phase with an orthorhombic symmetry of Pnma and lattice parameters of a = 6.353 Å, b = 6.850 Å, and c = 4.393 Å. No other phase or impurity can be detected, implying that Eu3+ and Bi3+ can be doped into the YF3 host without inducing significant changes of the crystal structure. 8


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However, for S5, the weak signal between (020) and (111) peaks is observed, which should be assigned to KY3F10 (JCPDS # 27-0465), implying that the reaction process is not complete and the impurity of intermediate products KY3F10 exists, while for S6 and S7, the shoulder to the left and the right in the (111) peak exists in the XRD patterns, belonging to MgF2 (JCPDS # 27-0465) and CaF2 (JCPDS # 77-2096), respectively. The diffraction intensity ratios of 020 (I020) to 111 (I111) for S1-S7 as well as standard diffraction pattern are shown in Table 2. It can be seen that the (020) peak intensities of S1-S8 are much stronger than that of the standard diffraction pattern, suggesting that the grains grow preferentially along (020) direction. For S5, the (020) peak intensity is weak relative to the (101) and (111), which means that S5 preferentially grows along the (101) and (111) directions. Consequently, the fluoride sources play an important role in the crystallization of the final product YF3. However, S8 using BaF2 as the fluoride source only contains a little of YF3, while Ba(NO3)2 (JCPDS#76-1376) is dominant in S8, which could be attributed to the size mismatch between Ba2+ and Y3+. In our experiment, the following reactions should exist in the turbulent and boiling hydrothermal environments29, 35: 10nF-+Mn++3nY3+=

M(Y3F10)n

(1)

4nF-+Mn++nY3+= M(YF4)n

(2)

H++F- = HF

(3)

M(Y3F10)n+nH+ =Mn++nHF+3nYF3

(4)

M(YF4)n+nH+ = Mn++nHF+nYF3

(5)

The reaction process was carried out including three steps. At the early stage, the excess F- ions are coupled with cations M to be rapidly crystallized into multiple fluorides (M(Y3F10)n and M(YF4)n) as shown in formulas (1) and (2); then, the H+ ions reduce the amount of F- through forming a weak acid HF as shown in formula (3); 9



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and finally, the previously formed multiple fluoride transforms into more stable ternary YF3 as shown in formulas (4) and (5). The key to formation of a pure YF3 phase should be ascribed to whether the cations in inorganic salts can transform into multiple fluorides. Alkali metal fluoride (LiF, NaF and KF) exhibits a better solubility than alkaline-earth metals fluoride, thus the anticipated YF3 can be easily obtained. However, for alkaline-earth metals fluoride, compared to Mg2+(65 pm) and Ca2+(100 pm), Ba2+(135 pm) 37 possesses larger radius, it is relatively difficult to be introduced into matrices to come into multiple fluorides. Consequently, the YF3:Eu3+/Bi3+ is hardly formed when the sample was synthesized using BaF2 as the fluoride source. Several elements in other fluoride sources can enter into matrices, and there is no significant influence on the overall crystal environment. As a result, the charge in the fluoride source has no direct influence on the phase structure of YF3:Eu3+/Bi3+ samples.

10


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Figure 2. Rietveld refinement patterns of XRD profiles for YF3:Eu3+/Bi3+ using different fluoride sources: (a) S1, (b) S2, (c) S3, (d) S4, (e) S5, (f) S6, (g) S7, and (h) schematic representation of orthorhombic YF3. Table 2. Refinement results and cell parameters of S1-S7 sample

space group

a(Å)

b(Å)

c(Å)

V(Å3)

Rwp

Rp

x2

S1

Pnma

6.3876

6.8922

4.4226

194.708

3.95

2.94

4.79

S2

Pnma

6.3908

6.8870

4.4113

194.160

4.77

3.68

1.96

S3

Pnma

6.3973

6.8817

4.3993

193.684

4.58

3.50

1.79

S4

Pnma

6.3949

6.8845

4.4059

193.976

4.83

3.84

1.46

S5

Pnma

6.3876

6.8746

4.3952

193.006

3.66

2.71

2.52

S6

Pnma

6.3937

6.8839

4.4055

193.903

7.94

5.01

3.66

S7

Pnma

6.4115

6.8861

4.3863

193.656

12.67

8.44

10.9

Based on the XRD patterns as shown in Figure 1, Rietveld refinements were carried out to perform the full-pattern matching and calculate lattice parameters, and the 11



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results are shown in Figure 2 and listed in Table 2. Crystal structure data of YF3 (ICDS 26595) was used as an original mode to do the full-pattern matching. Almost all the refinements of the XRD patterns of YF3:Eu3+/Bi3+ using different fluoride sources give low R-factors, suggesting that the observed and calculated patterns are well matched. From Figure 1, S7 exhibits the high crystallinity, thus its fitted value is relatively larger in Table 238. As shown in Figures 2(a)-(g), all the diffraction data could be indexed to the orthorhombic structure as shown in Figure 2(h). Meanwhile, the refinement results further confirm that Eu3+ and Bi3+ have been successfully introduced into the host lattice. 3.2 Morphology

12


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Figure 3. SEM images of YF3:Eu3+/Bi3+ samples using different fluoride sources: (a) S1, (b) S2, (c) S3, (d) S4, (e) S5, (f) S6, (g) S7, and (h) S8 The SEM images for YF3:Eu3+/Bi3+ samples using various fluoride sources are shown in Figure 3. As shown in Figure 3(a), S1 consists of granule-like nanoparticles with a length of 100 nm and a diameter of 58 nm while the inset in Figure 3(a) clearly shows the smooth surface of S1. The average size of granular-like nanoparticles (S2) is calculated to be about 113 nm in length and 65 nm in diameter. From the amplified image in Figure 3(b), the surface of S2 is also smooth. Thus, S1 13



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and S2 share the granular-like morphology, while S2 exhibits larger size. It can be observed that S3 displays the truncated octahedron with an average length of 127 nm and diameter of 83 nm. Meanwhile, the surface of the grains is relatively smooth, and some octahedrons are observed as shown in the enlarged image. S5 exhibits the octahedron with a length of 359 nm and a diameter of 543 nm. The size of YF3:Eu3+/Bi3+ continuously increases from 83 to 543 nm with increasing the cationic radius from 60 to 133 pm in the fluoride source, as depicted in Figures 3(c), (d), and (e). In addition, larger nanoparticle size for S6-7 is also observed in the case of a larger cationic radius in the fluoride source. From Figure 3(h), bipyramids with the smooth surface and small irregular crystals aggregated on the surface of the grains can be observed, and it is calculated to be 4.14 µm in length and 3.26 µm in diameter. The results evidence that the shape and size of YF3:Eu3+/Bi3+ crystals can be easily affected by the fluoride source. The observations of the morphology of YF3:Eu3+/Bi3+ samples prove that the morphologies should originate from the same octahedron model. Granule-, truncated octahedron-, octahedron-, and bipyramid-like morphologies can be attributed to the preferential growth along crystal planes resulted by different growth rates.

14


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Figure 4. TEM and HRTEM images of the synthesized YF3:Eu3+/Bi3+ samples using different fluoride sources: (a1-a2) S1, (b1-b2) S2, (c1-c2) S3, (d1-d2) S4, (e1-e2) S5, (f1-f2) S6, (g1-g2) S7, and (h1-h2) S8 TEM characterization was performed to confirm the changes of YF3:Eu3+/Bi3+ samples in the morphology induced by different fluoride sources. From Figures 4(a1) and (b1), it can be clearly seen that S1 and S2 exhibit the granule-like nanoparticles with uniform morphology. From HRTEM images (Figures 4(a2) and (b2)), the high crystallinity is confirmed by the clear lattice fringes. The determined interplanar distances of 0.29 nm and 0.34 nm are in good agreement with the d220 and d020 spacing of YF3, respectively. Figures 4(c1), (d1) and (e1) show that the morphology of S3-S5 transforms from the granule-like nanoparticles to octahedrons. The HRTEM images (Figures 4(c2), (d2) and (e2)) display the interplanar distances of 0.29 nm and 15



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0.34 nm, corresponding to the d220 and d020 spacing of orthorhombic phase YF3, respectively. The octahedron particles exhibit a uniform morphology as shown in Figures 4(f1) and (g1), their interplanar distances are 0.34 nm and 0.29 nm, respectively, which are consistent with the (020) and (220) planes of orthorhombic YF3. The interplanar distance of S8 does not only include 0.32 nm and 0.34 nm, which are assigned to the YF3, but also 0.40 nm that indexes to the (200) plane of Ba(NO3)2. These results indicate clearly that the fluoride sources play a significant role in tuning the morphology of the materials.

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Figure 5. EDS spectra of YF3:Eu3+/Bi3+ synthesized using different fluoride sources The EDS spectra and corresponding elemental analysis of YF3:Eu3+/Bi3+ samples using various fluoride sources are shown in Figure 5. Y, F, Eu, and Bi can be detected for all samples and their molar ratios are very close to the stoichiometric ratios of the YF3:0.125Eu3+, 0.5%Bi3+. As NH4F or NH4HF (S1, S2) is used as fluoride source, the molar fraction of N element is 0 from element analysis, suggesting that target material YF3:0.125Eu3+, 0.5%Bi3+ is obtained without the presence of NH4+. For S4-S5 (Li 17



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element in the sample (S3) using LiF as fluoride source can’t be detected by EDS), a very small amount of cations exists in the samples. However, for S6 and S7, Mg of 14.63% and Ca of 11.09% are detected, which is consistent with XRD patterns in Figure 1. In case of S8, N of 13.62%, O of 33.04%, and Ba of 5.33% are detected and these results further confirm the existence of Ba(NO3)2; meanwhile, F of 30.4% should be assigned to YF3 as shown in Figure 1. The existence of CaF2 and MgF2 in the samples (S6-S7) may result in the formation of defects, and thus may reduce the emission intensity of the materials. Mappings for the elements of YF3:Eu3+/Bi3+ samples using different fluoride sources are displayed in Figures S1-S8 in supporting information. It can be seen that all elements are uniformly distributed. 3.3 Formation mechanism

Figure 6. The proposed schematic diagram of the formation process of YF3:Eu3+/Bi3+ samples using different fluoride sources In our experiment, all microcrystals were synthesized under the same reaction condition except with different fluoride sources. Careful morphological observations of samples obtained using different fluoride sources suggest that fluoride sources have a significant influence on the microstructure of YF3:Eu3+/Bi3+ particles. The selective absorption of released cations from the fluoride source onto the different facets of 18


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growing YF3:Eu3+/Bi3+ particles, originated from the strong interaction between these cations and the fluoride anions on the particle surface, leads to the formation of unique particles. The proposed growth process for the formation of different morphologies of S1-S7 is illustrated in Figure 6. Reagents involved in the reaction medium of NH4F, HNO3, RE2O3 begin to be dissolved and exist as NH4+, F-, H+, NO3-, RE3+, in which the rare earth (RE) species are Eu, Y, and Bi. H+, Y3+, and F- are surrounded by the oppositely charged NO3-, NO3- and NH4+ as a result of coulombic attraction. It is reported that the chloride anions and bromide ions in the added salts are selectively adsorbed on the (001) and (111) faces to control the crystal growth39. The cations of fluoride source in our case play similar roles in the morphology of the YF3:Eu3+/Bi3+ products. It is easily referred that the cations are absorbed on the surface of the previously formed small YF3 particles at the early stage, which is attributed to the interaction between cations and fluoride anions on the surface of particles. As known, in the simple reaction, the main driving force is the reduction of surface energy such that further morphology evolution is derived from the reduction of high-energy faces40. On the basis of this viewpoint, the relative growth rates of various crystal planes mainly determine the shape of morphology41. As shown in Figure 6, the morphology shape of YF3 particles relies on the preferential orientations along the (111) or (020) crystal face. In other words, when the surface energy of the (111) lattice plane is lower than that of the (020) crystal face, the growth rate along the (111) direction should be slower than that along the (020) direction. Then, the fast-growing (020) face 19



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disappears quickly, and the (111) lattice plane dominates the shape such that the crystal is finally the octahedron. The results are consistent with the relative intensity between (111) and (020) lattice planes. As depicted in the XRD patterns, the relative intensity of S5 using KF as the fluoride source along the (020) plane is the lowest, which may facilitate the formation of (111) instead of (020) crystal face, and thus the octahedron can be observed. However, as for S1 using NH4F as the fluoride source, the diffraction intensities of (020) and (111) lattice planes are similar, thus forming the granule-like nanoparticles. In addition, the cationic radius and charge of fluoride source play determined roles in the morphology and the size of YF3:Eu3+/Bi3+ particles. As the cationic radius increases from 60 pm (Li+) to 135 pm (Ba2+) in the fluoride source, the size of YF3 samples increases obviously from 64 nm to 4.2 µm. In general, the size of resultant crystals, depending on the formation of crystal nucleation process, can be determined by the equation L = (cv/8N)1/3, where L represents crystal size, c is concentration, v is molecular volume, and N is the number of crystals, respectively40. According to the above equation, it is apparent that the migrating rate speeds up with decreasing molecular volume (eg. K+), and thus leads to the decrease of grain size. Meanwhile, the charge of fluoride source increases the nucleation rate by enlarging the attraction between cations and fluoride anions on the surface of grains, which induces the smaller crystal size. Therefore, the higher charge and smaller cationic radius give rise to the smaller grain size.

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3.4 Luminescence properties

Figure 7. (a) PLE, (b) PL for YF3:Eu3+/Bi3+ samples using different fluoride sources and (c) dependence of emission intensity on morphology with corresponding fluoride source The photoluminescence of excitation (PLE) and photoluminescence (PL) spectra for YF3:Eu3+/Bi3+ samples at room temperature are displayed in Figures 7(a) and (b), respectively. It is obvious that the samples using different fluoride sources exhibit similar spectra without wavelength shift. The excitation spectra, as shown in Figure 7(a), are obtained by monitoring the emission of Eu3+ 5D0-7F1 transition at 592 nm. It 21



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can be seen that the excitation peaks consist of the characteristic absorption 7F0-5H6, 7

F0-5D4, 7F0-5G2, and 7F0-5L6. The most intense peaks appear at 393 nm, which are

assigned to the transition between 7F0 and 5L6. Although the position of major peak in the excitation spectra stays constant, their intensities are different. Under the excitation at 393 nm, the emission peaks exhibit several sharp lines of Eu3+ ions from 500 to 725 nm, which can be attributed to 5D2−7F3, 5D1−7F0, 5D1−7F2, and 5D0−7FJ (J = 0 − 4) of Eu3+, respectively18, 42, 43. The position of the emission center does not shift since the 4f level of Eu3+ is hardly affected due to the shielding effect of 5s25p6 electrons44. The emission spectra (575 nm) of the samples are originated from the 3P1 → 1S0 electron transition of Bi3+45. The most intense peaks in Figure 7(b) are centered at 592 nm, corresponding to the electronic dipole transition 5D0−7F1 emission. Furthermore, the lines in the region from 612 to 626 nm (5D0−7F2) can be detected when the lattice environment is distorted46, 47. It can be clearly observed that the 5

D0−7F2 emission at 613 nm is weaker than the 5D0−7F1 emission at 592 nm. Generally,

emission intensity ratio of 5D0-7F1 to 5D0-7F1 indicates the sites of Eu3+ ions, and thus the Eu3+ ions have been frequently used as detectors to explore the crystal environment of rare earth ions20. It is well known that the 5D0-7F1 magnetic dipole transition will be strongest if Eu3+ ions occupy the sites with the inversion symmetry, while the 5D0-7F2 electric dipole transition is dominant if Eu3+ ions occupy the sites without the inversion symmetry48. In YF3 crystal structure, the Y ions possess Cs site symmetry, not inversion symmetry49, and thus it is expected that the 5D0-7F2 electric dipole transition exhibits a stronger emission intensity. However, from Figure 7(c), the emission of 5D0-7F1 is the strongest among all peaks. This unusual phenomenon should be ascribed to the high ionicity of the Eu-F bonds that only allows a little admixture of opposite parity states to the Eu3+ f-state. As a result, the 5D0-7F2 electric 22


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dipole transition becomes less favorable49,50. It should be noted that all samples exhibit an identical spectrum shape except for emission intensity. Figure 7(c) exhibits the dependence of emission intensity on morphology with corresponding fluoride source. All samples with various fluoride sources can be classified into three classes including granule-like, truncated octahedral and octahedral morphology based on micromorphology. It is apparent that all samples possess the indentical spectra pattern with distinct difference in intensity. Among all samples, the samples with the truncated octahedral morphology show the strongest emission, while the octahedral morphology takes the second place, and the granule-like samples are relatively weak. The dramtic difference can be ascribed to the co-effects of grain size and amount of defects. For S1-S2, small particles with a large surface area generally lead to more defects that provide non-radiative recombination pathways as fluorescence quenching centers, and thus cause a decrease in the fluorescence intensity51. S3-S5 with truncated octahedron morphology exhibit strong emission intensity owing to the apparent sharp edges and corners of crystalline grains being truncated that would decrease the non-radiative energy transition. The octahedral samples (S6-S7) possess longer and thinner edges with more apexes compared with the truncated octahedral samples. There exist more defects at these unique sites near the edges and apxes, which will increase the non-radiative energy and thus result in the degradation in the fluorescence. Eventually, the samples with the truncated octahedral exhibit much stronger emission compared to the granule-like and octahedral morphologies.

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3.5 Fluorescence decays

Figure 8. Lifetime decay curves of the YF3:Eu3+/Bi3+ (λex = 393 nm, λem = 592 nm) samples using different fluoride sources The decay curves for 5D0−7F2 (592 nm) of YF3:Eu3+/Bi3+ samples using various fluoride sources were measured under the excitation of 393 nm at room temperature as shown in Figure 8. All the decay curves can be almost fitted by the single exponential function. The average fluorescence decay lifetime of the sample can be calculated by following equation52-55:

τ =

∫ I (t )dt ∞

(6)

0

where It is the luminescence intensity at time t with the normalized initial intensity. The average lifetime values of the samples using different fluoride sources are calculated to be 8.99, 8.88, 9.55, 9.30, 7.33, 8.09, 6.82, and 6.80 ms. It clearly shows that the decays speed up as the fluoride source extends from Li to K or Mg to Ba. Generally, a decrease in the lifetime values in the YF3:Eu3+/Bi3+ nano/microcrystals 24


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prepared using different fluoride sources is partly owing to the crystallite size of nano/microcrystals as well as the difference in the local environment around the earth ions31. However, the larger size of these materials leads to the longer fluorescence decay, which is not consistent with our experiment. It is reasonable that the probability of the transition increases as the symmetry is reduced. Meanwhile, the crystalline defect increases the possibilities of the formation of a quenching center that can accelerate the non-radioactive relaxation of photons. Therefore, the main factors that dominate the present decay lifetimes are the symmetry around earth ions and the surface defects of sample particles. In addition, the decay lifetime is contrary to the sum of the non-radioactive and radioactive probabilities, and is proportional to the emission intensity. However, the present samples do not follow the rule. The sample using BaF2 as the fluoride source exhibits a lifetime shorter than others, suggesting that the sample consists of the excess surface defects and the earth ions exist in the nonsymmetry environment.

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3.6 CIE chromaticity coordinates

Figure 9. Representation of the CIE chromaticity coordinate diagram of the YF3:Eu3+/Bi3+ (λex = 393 nm, λem = 592 nm) samples using different fluoride sources The CIE chromaticity coordinates of the as-prepared samples based on the PL spectra of the YF3:Eu3+/Bi3+ (λex = 393 nm, λem = 592 nm) samples using various fluoride sources are shown in Figure 9. The color of all samples is mainly orange-yellow, as depicted in Figure 9, suggesting that Eu3+ ions are located at low symmetry lattices.

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3.7 The applications in luminescent inks

Figure 10. (a) Schematic diagram of the screen printing process, printed pattern images of YF3:Eu3+/Bi3+ in printed pattern images of (b) S4 and (c) S1 under the excitation of 365 nm The detailed systematic process of screen printing on an Al foil in the present investigation is shown in Figure 10(a). The printed mesh (sicnu, YF3) was fitted in frame with the Al foil, and then the luminescent ink was poured onto the mesh and a squeegee was moved across the surface. Finally, the designed luminescent pattern was displayed on the Al foil. Figures 10(b) and (c) exhibit the printed pattern images of YF3:Eu3+/Bi3+ in the printed pattern images of S4 and S1 excited at 365 nm, respectively. When the printed patterns were excited under 365 nm UV-light, they show orange-yellow emissions. The results reveal that YF3:Eu3+/Bi3+ nanoparticles 27



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can be applied in luminescent inks.

4. Conclusions In summary, uniform YF3:Eu3+/Bi3+ samples with distinct morphologies have been synthesized using different fluoride sources by the hydrothermal route. Almost all peaks of the XRD patterns of S1-S7 can be exactly assigned to the pure YF3 with the orthorhombic symmetry, while the materials using barium fluoride as the fluoride source mainly consist of Ba(NO3)2 due to the cation-size-mismatch. S1-S2, S3-S4, S6-S7, and S8 show the granule-like nanoparticles, truncated octahedron, octahedron, and bipyramid morphologies, respectively. Meanwhile, the particle size increases from 64 nm to 4.14 µm with the increasing cationic radius of fluoride source. The results evidence that the competition along (111) or (020) plane and the cationic radius in various fluoride sources should be responsible for the shape and size of YF3:Eu3+/Bi3+ samples. The corresponding formation process has also been proposed. The morphology-dependent luminescence properties investigations show that the NaF-controlled sample with the appropriate size and shape exhibits the strongest orange-yellow emission, while the emission intensity of NH4F-controlled sample with the smaller size is the lowest, which may be ascribed to the grain size and the amount of defects. The present study proposes a facile method to control the size of materials within the desired range, enriching their application prospects. The integration of luminescent nanoparticles with PVDF and NMP disperse medium provides a new opportunity for luminescent ink, which is very useful for protection against counterfeiting of important documents. Notes The authors declare no competing financial interest. 28


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Acknowledgements This work is financially supported by the National Natural Science Foundation of China (NSFC 11404351), the Ningbo Municipal Natural Science Foundation (2017A610001), the large precision instrument projects of Sichuan Normal University (DJGX 2017022) and the outstanding graduation thesis foundation of Sichuan Normal University (2017-17-32).

Reference: (1) Xu, Z.; Li, C.; Yang, P.; Zhang, C.; Huang, S. Cryst. Growth Des., 2009, 9, 4752-4758. (2) Archibald, D. D.; Mann, S. Nature, 1993, 364, 430-433. (3) Li, C.; Zhang, C.; Hou, Z.; Wang, L.; Quan, Z.; Lian, H.; Lin, J. J. Phys. Chem. C, 2009, 113, 2332-2339. (4) Zhao, Y. S.; Fu, H.; Hu, F.; Peng, A. D.; Yao, J. Adv. Mater., 2007, 19, 3554-3558. (5) Sivakumar, S.; van Veggel, F. C. M.; Raudsepp, M. J. Am. Chem. Soc., 2005, 127, 12464-12465. (6) Nyk, M.; Kumar, R.; Ohulchanskyy, T. Y.; Bergey, E. J.; Prasad, P. N. Nano Lett., 2008, 8, 3834-3838. (7) Feng, W.; Sun, L.-D.; Zhang, Y.-W.; Yan, C.-H. Coord. Chem. Rev., 2010, 254, 1038-1053. (8) Wang, G.; Peng, Q.; Li, Y. Acc. Chem. Res., 2011, 44, 322-332. (9) Li, C.; Lin, J. J. Mater. Chem., 2010, 20, 6831-6847. (10) Liu, Y.; Zhang, J.; Zhang, C.; Xu, J.; Liu, G.; Jiang, J.; Jiang, H. Adv Opt Mater, 2015, 3,1096-1101. 29



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

(11) Wang, X.; Zhuang, J.; Peng, Q.; Li, Y. Inorg. Chem, 2006, 45, 6661-6665. (12) Zhong, S.; Wang, S.; Xu, H.; Li, C.; Huang, Y.; Wang, S.; Xu, R. Mater. Lett., 2009, 63, 530-532. (13) Cao, C.; Qin, W.; Zhang, J.; Wang, Y.; Zhu, P.; Wang, G.; Wei, G.; Wang, L.; Jin, L. J. Fluorine Chem., 2008, 129, 204-209. (14) Nuñez, N. O.; Quintanilla, M.; Cantelar, E.; Cussó, F.; Ocaña, M. J. Nanopart. Res., 2010, 12, 2553-2565. (15) Peng, C.; Li, C.; Li, G.; Li, S.; Lin, J. Dalton Trans., 2012, 41, 8660-8668. (16) Li, C.; Ma, P. a.; Yang, P.; Xu, Z.; Li, G.; Yang, D.; Peng, C.; Lin, J. CrystEngComm, 2011, 13, 1003-1013. (17) Zhang, M.; Fan, H.; Xi, B.; Wang, X.; Dong, C.; Qian, Y. J. Phys. Chem. C, 2007, 111, 6652-6657. (18) Tao, F.; Wang, Z.; Yao, L.; Cai, W.; Li, X. J. Phys. Chem. C, 2007, 111, 3241-3245. (19) Liu, G.; Li, X.; Dong, X.; Wang, J. J. Nanopart. Res., 2011, 13, 4025-4034. (20) Li, D.; Yu, W.; Dong, X.; Wang, J.; Liu, G. J. Fluorine Chem., 2013, 145, 70-76. (21) Wang, J.; Miao, W.; Li, Y.; Yao, H.; Li, Z. Mater. Lett., 2009, 63, 1794-1796. (22) Arakcheeva, A.; Logvinovich, D.; Chapuis, G.; Morozov, V.; Eliseeva, S. V.; Bünzli, J.-C. G.; Pattison, P. Chem. Sci., 2012, 3, 384-390. (23) Ehlert, O.; Thomann, R.; Darbandi, M.; Nann, T. Acs Nano, 2008, 2, 120-124. (24) Blin, J. L.; Lorriaux-Rubbens, A.; Wallart, F.; Wignacourt, J. P. J. Mater. Chem., 1996, 6, 385-389. (25) Dong, G.; Hou, C.; Yang, Z.; Liu, P.; Wang, C.; Lu, F.; Li, X. Ceram. Int., 2014, 40, 14787-14792. (26) Sun, Y.; Chen, Y.; Tian, L.; Yu, Y.; Kong, X.; Zhao, J.; Zhang, H. 30


Page 30 of 34

Page 31 of 34

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


Nanotechnology, 2007, 18, 275609. (27) Ding, M.; Yin, S.; Chen, D.; Zhong, J.; Ni, Y.; Lu, C.; Xu, Z.; Ji, Z. Appl. Surf. Sci., 2015, 333, 23-33. (28) Ding, M.; Lu, C.; Cao, L.; Ni, Y.; Xu, Z. CrystEngComm, 2013, 15, 8366-8373. (29) Shao, B.; Zhao, Q.; Guo, N.; Jia, Y.; Lv, W.; Jiao, M.; Lu, W.; You, H. Cryst. Growth Des., 2013, 13, 3582-3587. (30) Huo, Z.; Chen, C.; Chu, D.; Li, H.; Li, Y. Chem. Eur. J., 2007, 13, 7708-7714. (31) Murali, G.; Lee, B. H.; Mishra, R.; Lee, J. M.; Nam, S.-H.; Suh, Y. D.; Lim, D.-K.; Lee, J. H.; Lee, S. H. J. Mater. Chem. C, 2015, 3, 10107-10113. (32) Sarkar, S.; Mahalingam, V. CrystEngComm, 2013, 15, 5750-5755. (33) Zhong, S. L.; Lu, Y.; Gao, M. R.; Liu, S. J.; Peng, J.; Zhang, L. C.; Yu, S. H. Chem. Eur. J., 2012, 18, 5222-5231. (34) Wang, L.; Qiao, J.; Liu, Y.; Huang, P.; Shi, Q.; Tian, Y.; Luo, Z. Opt. Mater., 2017, 67, 78-83. (35) Lei, F.; Zou, X.; Jiang, N.; Zheng, Q.; Lam, K. H.; Luo, L.; Ning, Z.; Lin, D. CrystEngComm, 2015, 17, 6207-6218. (36) Singh, A. P.; Gupta, B. K.; Mishra, M.; Chandra, A.; Mathur, R.; Dhawan, S. Carbon, 2013, 56, 86-96. (37) Shannon, R. D. Acta Crystallogr., Sect. A: Cryst. Phys., Diffr., Theor. Gen. Crystallogr. 1976, 32, 751−767. (38) Wang, C.; Zhao, Z.; Wu, Q.; Xin, S.; Wang, Y. CrystEngComm, 2014, 16, 9651-9656. (39) Filankembo, A.; Giorgio, S.; Lisiecki, I.; Pileni, M. J. Phys. Chem. B, 2003, 107, 7492-7500. (40) Fu, Z.; Cui, X.; Cui, S.; Qi, X.; Zhou, S.; Zhang, S.; Jeong, J. H. 31



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

CrystEngComm, 2012, 14, 3915-3922. (41) Yuvaraj, D.; Rao, K. N.; Barai, K. Solid State Commun., 2009, 149, 349-351. (42) Blasse, G.; Bril, A. Characteristic luminescence. Philips technical review,1970, 31, 303. (43) Jia, G.; Huang, C.; Wang, C.; Jiang, J.; Li, S.; Ding, S. CrystEngComm, 2012, 14, 4425-4430. (44) Gong, C.; Li, Q.; Liu, R.; Hou, Y.; Wang, J.; Dong, X.; Liu, B.; Yang, X.; Yao, Z.; Tan, X. Phys. Chem. Chem. Phys., 2013, 15, 19925-19931. (45) Chen, L.; Chen, K.-J.; Hu, S.-F.; Liu, R.-S. J. Mater. Chem., 2011, 21, 3677-3685. (46) Judd, B. Physical Review, 1962, 127, 750. (47) Ofelt, G. J. Chem. Phys., 1962, 37, 511-520. (48) Zheng, Y.; You, H.; Jia, G.; Liu, K.; Song, Y.; Yang, M.; Zhang, H. Cryst. Growth Des, 2009, 9, 5101-5107. (49) Shao, B.; Zhao, Q.; Guo, N.; Jia, Y.; Lv, W.; Jiao, M.; Lu, W.; You, H. Cryst. Growth Des., 2013, 13, 3582-3587. (50) Lezhnina, M.M.; Jüstel, T.; Kätker, H.; Wiechert, D.U.; Kynast, U.H. Adv. Funct. Mater., 2006,16, 935-942. (51) Yi-Chin Chen.; Yun-Chen Wu.; De-Yin Wang.; Teng-Ming Chen. J. Mater. Chem., 2012, 22, 7961. (52) Liu, Y.; Zhang, X.; Hao, Z.; Luo, Y.; Wang, X.; Zhang, J. J. Mater. Chem., 2011, 21, 16379-16384. (53) Liu, Y.; Zhang, X.; Hao, Z.; Wang, X.; Zhang, J. Chem. Commun., 2011, 47, 10677-10679. (54) Liu, Y.; Zhang, X.; Hao, Z.; Luo, Y.; Wang, X.; Ma, L.; Zhang, J. J. Lumin., 32


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2013, 133, 21-24. (55) Liu, Y.; Zhang, J.; Zhang, C.; Jiang, J.; Jiang, H. J. Phys. Chem. C, 2016, 120, 2362-2370.

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For Table of Contents Use Only Fluoride source-controlled morphology and optical properties of YF3: Eu3+, Bi3+ and its application for luminescent inks Lihua He a, Tao Wang a, Jirong Moua, Fengying Lei a, Na Jiang a, Xiao Zou a, Kwok Ho Lam b, Yongfu Liu c,* and Dunmin Lin a,*

TOC graphic

Synopsis The grain morphology, fluorescence and applications in luminescent ink of YF3: Eu3+, Bi3+ using different fluoride source were studied.

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Fluoride source-induced tuning of morphology and optical properties

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