Controlled synthesis and luminescent properties of different morphologies GdBO3:Eu3+ phosphors self-assembled of nanoparticles

Accepted Manuscript Title: Controlled synthesis and luminescent properties of different morphologies GdBO3 :Eu3+ phosphors self-assembled of nanoparticles Author: Zhihua Leng Yali Liu Nannan zhang Linlin Li Shucai Gan PII: DOI: Reference:

S0927-7757(15)00176-4 http://dx.doi.org/doi:10.1016/j.colsurfa.2015.02.046 COLSUA 19788

To appear in:

Colloids and Surfaces A: Physicochem. Eng. Aspects

Received date: Accepted date:

4-12-2014 27-2-2015

Please cite this article as: Z. Leng, Y. Liu, N. zhang, L. Li, S. Gan, Controlled synthesis and luminescent properties of different morphologies GdBO3 :Eu3+ phosphors selfassembled of nanoparticles, Colloids and Surfaces A: Physicochemical and Engineering Aspects (2015), http://dx.doi.org/10.1016/j.colsurfa.2015.02.046 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

*Graphical Abstract (for review)

Graphical Abstract Small amount of ethanol has an favorable effect on controlling the products' morphology. The formation of cake-like and olive-like GdBO3 microcrystals

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self-assembled of nanoparticles can be assigned to the Ostwald ripening process.

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Highlights 1. Cake-like and olive-like GdBO3 self-assembled of nanoparticles were synthesized. 2. This method used Gd(OH)CO3 and NaBO2·4H2O as the precursors for the first

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time.

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3. When small amount of ethanol was added, different morphologies can be obtained.

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Controlled synthesis and luminescent properties of different morphologies GdBO3:Eu3+ phosphors self-assembled of nanoparticles

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College of Chemistry, Jilin University, Changchun 130026, PR China Corresponding author. Tel.: +86 431 88502259.

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Zhihua Lenga, Yali Liua, Nannan zhanga, Linlin Lia, Shucai Gana,1

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E-mail address: [email protected] (S.C. Gan)

Abstract

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Uniform cake-like and olive-like GdBO3 samples have been successfully synthesized for the first time via a simple solution-based hydrothermal method using

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Gd(OH)CO3 colloid spheres and NaBO2·4H2O as the precursors. It was found that small amount ethanol in the hydrothermal process was responsible for determining the

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shape of products. The FT-IR analysis indicates that vaterite-type GdBO3 can be synthesized by this method. The obtained cake-like and olive-like GdBO3 with rough

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surfaces have similar mircostructures which are composed of numerous nanoparticles. Time-dependent experiments were employed to study the possible formation mechanism. The formation of cake-like and olive-like GdBO3 mircostructures self-assembled of nanoparticles can be ascribed to the Ostwald ripening process. A detailed investigation on the photoluminescence (PL) properties of GdBO3:Eu3+ samples with different morphologies indicates that the PL properties of as-obtained GdBO3:Eu3+ phosphors are dependent on their morphologies. The effect of Eu3+ doping concentration on PL intensity was also investigated and the quenching concentration of GdBO3:Eu3+ is 20%.

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Keywords: Microcrystal, Recrystallization, Ostwald ripening, Photoluminescence 1. Introduction In recent years, controlled synthesis of inorganic functional nano-/micro-materials

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with well-defined morphology has been an important goal of modern materials

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chemistry not only because of their aesthetic appearances but also their

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shape-dependent properties [1-3]. Among various morphologies and structures, self-assembly of inorganic nanobuilding blocks into one-dimensional (1D), (2D),

and

three-dimensional

(3D)

ordered

hierarchical

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two-dimensional

nanostructures is fascinating because the variation of the arrangements of the building

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blocks provides a means to tune the properties of the materials. Up to now, great interests and tremendous efforts have been progressively devoted to the exploration of

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various convenient and efficient approaches to fabricate different kinds of lanthanide compounds with the controlled shape, size distribution , and dimensionality [4-6].

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Lanthanide orthoborates belong to a group of traditional phosphors, which were

widely used in the plasma display panels, the Hg-free fluorescence lamps and bioimaging materials [7]. Among a variety of borate phosphors, GdBO3:Eu3+ is one of

the excellent and efficient phosphors available for the red primary of the color picture in plasma display panels due to its special optical properties, high stability, low synthesis temperature, and high ultraviolet and optical damage threshold [8]. Compared with bulk materials, lanthanide compounds nanocrystals have better shape tailoring ability to improve nanodevice fabrication [9]. Furthermore, most of the previous works about rare earth orthoborates were mainly concentrated on using

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H3BO3 as boron source to obtain different structures via hydrothermal process [10-13], and few studies used NaBO2·4H2O as boron source [14, 15]. Recently, Ln(OH)CO3 colloid spheres as precursors have been widely used to

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fabricate different kinds of lanthanide compounds [16-19]. In our previous work,

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Y(OH)CO3 colloid spheres have been used as precursors treated with Na2B4O7·10H2O

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to fabricate ellipsoid-like YBO3 [20]. In this paper, for the first time, large-sized cake-like and olive-like GdBO3 self-assembled of nanoparticles was synthesized via a

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simple solution-based hydrothermal method using Gd(OH)CO3 colloid spheres and NaBO2·4H2O as the precursors.

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2. Experimental section 2.1. Materials

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Ln(NO3)3 (Ln = Gd, and Eu) aqueous solutions was obtained by dissolving the corresponding metal oxide in dilute HNO3 solution under heating, respectively. All

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the other reagents are of analytical grade and used directly without further purification. Distilled water was used throughout. 2.2. Preparation of monodisperse Gd(OH)CO3 colloid spheres The monodisperse colloid spheres of Gd(OH)CO3 were prepared via a urea-based

homogeneous precipitation process [21]. 10 ml Gd(NO3)3 (0.1 M) and 2 g urea were

dissolved in distilled water, and the total volume of the solution was about 67 ml to keep the Gd3+ constant at 0.015 M and the urea constant at 0.5 M. The above solution was first homogenized under magnetic stirring at room temperature. After that, the resultant solution was heated at 90 oC for 2 h in the water bath. The obtained

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suspension was separated by centrifugation and collected after washing with distilled water several times. 2.3. Preparation of cake-like and olive-like GdBO3

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In a typical procedure for the preparation of cake-like GdBO3, the as-obtained 1

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mmol of Gd(OH)CO3 was firstly redispersed into distilled water by ultrasonic

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treatment. 10 ml NaBO2·4H2O (0.4M) aqueous solution was dripped into the dispersion followed by further stirring. After that, the resultant mixture was

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subsequently diluted to 40 ml with distilled water and transferred into a 50 ml Teflon-lined autoclave. The hydrothermal reaction was conducted at 180 oC for 24 h.

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After the autoclave was cooled to room temperature, the obtained white products were washed with distilled water and ethanol several times and then dried in vacuum at 60 o

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C. Olive-like GdBO3 was prepared in similar manner to that for cake-like GdBO3,

except that 5ml anhydrous ethanol instead of equal volume of distilled water was

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added in the hydrothermal process.

A similar process was employed to prepare GdBO3:Eu3+ using a stoichiometric

amount of Eu(NO3)3 aqueous solution instead of Gd(NO3)3 solution for the precursors at the initial stage as described above. 2.4. Characterization

All the samples were investigated by X-ray diffraction (XRD) measurements performed on a Rigaku D/max-II B X-ray diffractometer with monochromatic Cu Kα radiation. The morphology and composition of the samples were characterized by field-emission scanning electron microscopy (FE-SEM, S-4800, Hitachi), employing

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the accelerating voltage of 10 kV. The infrared spectra of the samples was taken in KBr pressed pellets on a NEXUS 670 infrared fourier transform spectrometer (Nicolet Thermo, Waltham, MA). The photoluminescence excitation and emission spectra

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were recorded with a Hitachi F-7000 spectrophotometer equipped with a 150W Xe

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lamp as the excitation source. All the measurements were performed at room

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temperature. 3. Results and discussion

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3.1. Phase identification and morphology

Fig. 1 shows the XRD patterns of the products obtained when the amorphous

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Gd(OH)CO3 colloid spheres were treated with NaBO2·4H2O at 180 oC for 24 h in the hydrothermal process. All of the diffraction peaks can be indexed to pure phase

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GdBO3 (PDF # 74-1932). No peaks of impurities can be observed, indicating the high-purity of the well-crystallized products.

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Fig. 2a and b show the SEM images of the as-obtained Gd(OH)CO3 colloid

spheres. It can be seen that the obtained Gd(OH)CO3 exhibits uniform colloid spheres with smooth surfaces and has an average diameter of about 300 nm. As shown in Fig. 2c, it can be seen that the sample obtained without anhydrous ethanol is composed of uniform cake-like particles with a diameter of approximately 2.5 μm. When the

anhydrous ethanol is used, the morphology is changed and uniform olive-like particles with an average diameter of about 800 nm and average length of about 1.5 μm can be observed (Fig. 2e). As shown in the magnified SEM images (Fig. 2d and f), the

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cake-like and olive-like GdBO3 structures with rough surfaces have the similar microstructures which are composed of numerous nanoparticles. 3.2. FT-IR analysis

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Fig. 3 shows the FT-IR spectra of the as-obtained GdBO3 samples. Generally,

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calcite, aragonite, or vaterite are three isostructural forms of orthoborates. Depending

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on the size of lanthanide cations, their orthoborates usually exhibit the aragonite-type (La-Nd), vaterite-type (Sm-Yb), or calcite-type (Lu) structure [22]. The vibrational

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spectra of vaterite-type orthoborates are found to be markedly different from those of calcite-type and aragonite-type orthoborates due to the presence of B3O99- groups. The

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intense absorption bands in the region 800-1200 cm-1 (centered at around 850, 905, and 1036 cm-1) which can be ascribed to the characteristic vibration modes of B3O99-

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groups in the vaterite-type orthoborates [23, 24]. Two strong peaks at 850 and 905

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cm-1 are ascribed to ring stretching vibration modes, whereas the peak at 1036 cm-1 is

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ascribed to a terminal B-O stretching vibration mode. The above results are consistent with those of the corresponding XRD, providing additional evidence that vaterite-type GdBO3 can be synthesized by the solution-based hydrothermal method. Fig. 4 schematically shows the crystal structure of vaterite-type GdBO3 with space

group R32 [25]. The structure is composed of alternative stacking of cation planes and polyborate layers. The boron atoms are four-coordinated in the tetrahedral BO4 groups,

which create three-membered rings of polyborate B3O99- units. The gadolinium atoms are located on a position with a bicapped trigonal prism constructed by eight coordinative oxygen atoms.

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3.3. Influences of solvent and reaction time In order to investigate the influences of the volume ratio of water/ethanol on the structural properties of the products, samples were prepared with different amounts of

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ethanol at 180 oC for 36 h. Fig. 5 shows the SEM images of the products prepared

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with different amounts of ethanol. When 5 ml ethanol was added into the reaction

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system, the morphologies were changed into uniform olive-like microparticles. As shown in Fig. 5b–d, the mount of irregular shaped particles increases gradually with

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increasing mount of ethanol. The above results indicate that excess ethanol has an adverse effect on controlling the products' morphology and only small amount of

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ethanol contributes to control the morphology of the product.

As described above, the microstructure of olive-like particles is similar to that of

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cake-like ones, so the growth mechanism of cake-like GdBO3 is typically discussed. In order to reveal the morphological evolution of the cake-like GdBO3 particles, a

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series of time-dependent control experiments were carefully and systematically carried out to gain deeper insight into the formation process. Fig. 6 and Fig. 7a show the corresponding SEM images and the XRD patterns of

the products obtained at different reaction stages. When the reaction time reached 3 h, irregular particles with rough surfaces appeared among the monodisperse Gd(OH)CO3 colloid spheres (Fig. 6a). After reacting for 6 h, the primary particles developed into microcakes due to anisotropic growth (Fig. 6b). Only some weak peaks are clearly visible in the XRD pattern and they can be attributed to GdBO3 (Fig. 7a). As the reaction proceeded to 9 h, the cake-like morphology with rough surfaces

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formed. As can be seen from the magnified SEM image (Fig. 6d), the cake-like microparticles consist of numerous fine nanoparticles. Correspondingly, the GdBO3 phase formed in the XRD pattern of 9 h, in which the relative intensity of the

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diffraction peak (002) is particularly strong (Fig. 7a). The preference of GdBO3

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crystals growing into cake-like structures can be attributed to the surface energy

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difference between the different lattice planes: growth along the 002 direction should be faster than others. With further increase the hydrothermal time, the morphology of

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the obtained GdBO3 products remained unchanged except the diameter of the formed GdBO3 nanoparticles gradually increasing (Fig. 6d–f and Fig. 2d). Interestingly, the

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intensity of diffraction peak (002) obviously decreased with the hydrothermal time (Fig. 7a and b), suggesting that a dissolution and recrystallization process occurred in

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this stage [14, 20]. According to the above morphological evolution evidence, the formation of cake-like GdBO3 via a self-assembly of primary nanoparticles can be

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ascribed to Ostwald ripening.

On the basis of all the above experimental results, the possible detailed conversion

processes from the precursors to the final products can be described as follows: Gd(OH)CO3 → Gd3+ + OH- + CO32-

(1)

Gd3+ + BO2- + H2O→ GdBO3 + 2H+

(2)

When the NaBO2·4H2O aqueous solution was dropped into Gd(OH)CO3 precursor, the initial pH value of the mixture remained at about 11 due to the hydrolysis of NaBO2·4H2O. In alkaline environment, the reaction Eq. (1) is inhibited and the concentration of Gd3+ could be remained at a lower level. Under the hydrothermal

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condition, as shown in Eq. (2), the reaction between Gd3+ and BO2- was sluggishly in the initial stage. And the reaction (Eq. (2)) in the liquid phase leads to form prime GdBO3 nanoparticles which random aggregate in irregular shape in the beginning of

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stage. As the reaction proceeds, these irregular units continue to grow and form the

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larger cake-like GdBO3 particles. As the reaction further proceeds, more and more

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GdBO3 nanoparticles formed and aggregated at the surfaces of cake-like structures driven by the minimization of the interfacial and surface energy. According to the

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Gibbs-Thomson effect, small particles have a higher solubility than large ones. Meanwhile, induced by the excess NaBO2·4H2O, small particles in contact with

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saturated solution have a tendency to dissolve because the Ostwald ripening: large particles grow at the cost of smaller ones [26].

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3.4. Photoluminescence Properties

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It is well-known that the PL properties of nano-/micro-crystals doped with

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lanthanide ions depend not only on their compositions, but also on their morphologies. In this work, Eu3+ was selected as the doping ion to investigate the PL

properties of the products with different morphologies. Fig. 8a displays the excitation spectrum of cake-like GdBO3:0.05Eu3+. The strong

broad band with a maximum at 234 nm is due to the charge transfer (CT) transition between O2- and Eu3+. The peak (centered at 273 nm) overlapped with the above CT transition is due to the transition of 8S7/2→6IJ of Gd3+ and the two peaks centered at 306 and 311 nm are the transitions of 8S7/2→6PJ of Gd3+. These results indicate that the energy transfer from Gd3+ to Eu3+ had efficiently taken place. In the longer wavelength region, the weak peaks from 318 to 464 nm are the characteristic f→f

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transitions of Eu3+. Under identical measurement conditions, two samples show identical spectral patterns without any emission band shift, but the cake-like crystals possess the higher emission intensity than the olive-like ones (Fig. 8b). That possibly

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because the intrinsic geometry of approximately spherical cake-like particles

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minimizes scattering of light from the sample's surfaces [27]. In the emission spectra,

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three major emissions are at 592 nm (5D0→7F1), 610 nm and 625 nm (5D0→7F2), respectively. Fig. 9a shows the emission spectra of a series of cake-like products with

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different Eu3+ concentrations. The emission intensity increases with Eu3+ substitution up to 0.20 and then decreases for additional concentrations of Eu3+ (Fig. 9a and b).

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Given that luminescence quenching is caused by the energy transfer within the same rare earth ions, the critical distance between the doped ions can be calculated by the

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concentration quenching method using the following equation [28]: 1

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 3V  RC  2    4NxC 

Where N represents the number of sites that Eu3+ ion can occupy in the host, xC is

the critical concentration, and V stands for the unit cell volume. Under present condition, xC =0.20, N =Z=18, V =1018.39 Å3. Thus, the RC for Eu3+ is 8.14 Å in

the GdBO3 host. EDS spectrum shown in Fig. 9c reveals the chemical composition of the GdBO3:0.20Eu3+ sample. 4. Conclusion In summary, uniform cake-like and olive-like vaterite-type GdBO3:Eu3+ microcrystals were successfully synthesized via a solution-based hydrothermal method using Gd(OH)CO3 colloid spheres as precursor and NaBO2·4H2O as boron

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source. Small amount of ethanol plays an important role in controlling the products' morphology. The formation of cake-like and olive-like GdBO3 microcrystals went through similar Ostwald ripening process. The cake-like GdBO3:Eu3+ phosphors

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exhibit the stronger red emission and the quenching concentration of GdBO3:Eu3+ is

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20%.

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Acknowledgments

This present work has been supported by Mineral and Ore resources

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Comprehensive Utilization of Advanced Technology Popularization and Practical Research (MORCUATPPR) and funded by China Geological Survey (Grant No.

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References

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Oil Shale Resources, No: OSR-5.

M

12120113088300); and the Key Technology and Equipment of Efficient Utilization of

[1] N. Liu, D. Zhao, L.X. Yu, K.Z. Zheng, W.P. Qin, Controlled synthesis and

Ac ce p

photoluminescence of europium doped barium borate nanorods, nanowires, and flower-like assemblies, Colloid Surf. A 363 (2010) 124-129. [2] H. Bar, D.K. Bhui, G.P. Sahoo, P. Sarkar, S.P. De, A. Misra, Green synthesis of silver nanoparticles using latex of Jatropha curcas, Colloid Surf. A 339 (2009) 134-139.

[3] R. Srivastava, M.U.A. Prathap, R. Kore, Morphologically controlled synthesis of copper oxides and their catalytic applications in the synthesis of propargylamine and oxidative degradation of methylene blue, Colloid Surf. A 392 (2011) 271-282.

13

Page 13 of 25

[4] L. Yang, L.Q. Zhou, Y. Huang, Z.W. Tang, Controlled synthesis of different morphologies of GdBO3:Eu3+ crystals and shape-dependent luminescence properties, Mater. Chem. Phys. 131 (2011) 477-484.

ip t

[5] X.W. Zhang, A. Marathe, S. Sohal, M. Holtz, M. Davis, L.J. Hope-Weeks, J.

cr

Chaudhuri, Synthesis and photoluminescence properties of hierarchical architectures

us

of YBO3:Eu3+, J. Mater. Chem. 22 (2012) 6485-6490.

[6] Z.H. Xu, C.X Li, Z.Y. Cheng, C.M. Zhang, G.G. Li, C. Peng, J. Lin,

an

Self-assembled 3D architectures of lanthanide orthoborate: hydrothermal synthesis and luminescence properties, CrystEngComm 12 (2010) 549-557.

M

[7] X.W. Zhang, Z. Zhao, X. Zhang, A. Marathe, D.B. Cordes, B. Weeks, J. Chaudhuri, Tunable photoluminescence and energy transfer of YBO3:Tb3+, Eu3+ for

te

d

white light emitting diodes, J. Mater. Chem. C 1 (2013) 7202-7207. [8] A. Szczeszak, T. Grzyb, S. Lis, R.J. Wiglusz, Revision of structural properties of

Ac ce p

GdBO3 nanopowders doped with Eu3+ ions through spectroscopic studies, Dalton Trans. 41 (2012) 5824-5831.

[9] Z.G. Yan, C.H. Yan, Controlled synthesis of rare earth nanostructures, J. Mater. Chem. 18 (2008) 5046-5059.

[10] Z.Q. Li, Y.B. Zeng, H.S. Qian, R. Long, Y.J. Xiong, Facile synthesis of GdBO3 spindle assemblies and microdisks as versatile host matrices for lanthanide doping, CrystEngComm 14 (2012) 3959-3964.

14

Page 14 of 25

[11] G. Jia, H.P. You, M. Yang, L.H. Zhang, H.J. Zhang, Uniform lanthanide orthoborates LnBO3 (Ln = Gd, Nd, Sm, Eu, Tb, and Dy) microplates: general synthesis and luminescence properties, J. Phys. Chem. C 113 (2009) 16638-16644.

ip t

[12] Y.B. Zeng, Z.Q. Li, Y.F. Liang, X.Q. Gan, M.M. Zheng, A general approach to

us

Eu3+/Tb3+ doping, Inorg. Chem. 52 (2013) 9590− 9596.

cr

spindle-assembled lanthanide borate nanocrystals and their photoluminescence upon

[13] J. Yang, C.X. Li, X.M. Zhang, Z.W. Quan, C.M. Zhang, H.Y. Li, J. Lin,

an

Self-assembled 3D architectures of LuBO3:Eu3+: phase-selective synthesis, growth mechanism, and tunable luminescent properties, Chem. Eur. J. 14 (2008) 4336-4345.

M

[14] S.S. Liu, D.K. Ma, Y.Q. Zhang, P. Cai, X.A. Chen, S.M. Huang, Controlled synthesis of orange-like LnBO3:Eu3+ (Ln = Y, Tb) mesocrystals via a facile organic

te

d

additive-free hydrothermal route, CrystEngComm 14 (2012) 2899-2905. [15] X.H. Yin, Q. Zhao, B.Q. Shao, W. Lv, Y.H. Li, H.P. You, Synthesis and

Ac ce p

luminescent properties of uniform monodisperse YBO3:Eu3+/Tb3+ microspheres,

CrystEngComm 16 (2014) 5543-5550. [16] L.H. Zhang, G. Jia, H.P. You, K. Liu, M. Yang, Y.H. Song, Y.H. Zheng, Y.J. Huang, N. Guo, H.J. Zhang, Sacrificial template method for fabrication of submicrometer-sized YPO4:Eu3+ hierarchical hollow spheres, Inorg. Chem. 49 (2010) 3305-3309. [17] L.H. Zhang, M.L. Yin, H.P. You, M. Yang, Y.H. Song, Y.J. Huang, Mutifuntional GdPO4:Eu3+ hollow spheres: synthesis and magnetic and luminescent properties, Inorg. Chem. 50 (2011) 10608-10613.

15

Page 15 of 25

[18] X.Y. Yang, Y. Zhang, L. Xu, Z. Zhai, M.Z. Li, M. Li, X.L. Liu, W.H. Hou, Surfactant-free sacrificial template synthesis of submicrometer-sized YVO4:Eu3+ hierarchical hollow spheres with tunable textual parameters and luminescent

ip t

properties, Dalton Trans. 42(2013) 3986-3993.

cr

[19] Z.H. Xu, P.A. Ma, C.X. Li, Z.Y. Hou, X.F. Zhai, S.S. Huang, J. Lin,

us

Monodisperse coreeshell structured up-conversion Yb(OH)CO3@YbPO4:Er3+ hollow spheres as drug carriers, Biomaterials 32 (2011) 4161-4173.

an

[20] Z.H. Leng, L. Liu, L.L. Li, S.C. Gan, Synthesis and luminescent properties of ellipsoid-like YBO3:Ln3+ (Ln = Eu, Tb), Colloid Surf. A 463 (2014) 1-7.

M

[21] E. Matijević, W.P. Hsu, Preparation and properties of monodispersed colloidal particles of lanthanide compounds, J. Colloid Interf. Sci. 118 (1987) 506-523.

te

d

[22] J. Ma, Q.S. Wu, Y. Chen, Y.J. Chen, A synthesis strategy for various pseudo-vaterite LnBO3 nanosheets via oxides-hydrothermal route, Solid State Sci. 12

Ac ce p

(2010) 503-508.

[23] M. Tukia, J. Holsa, M. Lastusaari, J. Niittykoski, Eu3+ doped rare earth

orthoborates, RBO3 (R = Y, La and Gd), obtained by combustion synthesis, Opt. Mater. 27 (2005) 1516-1522.

[24] A. Szczeszak, T. Grzyb, S. Lis, R.J. Wiglusz, Revision of structural properties of GdBO3 nanopowders doped with Eu3+ ions through spectroscopic studies, Dalton

Trans. 41 (2012) 5824-5831. [25] M. Ren, J.H. Lin, Y. Dong, L.Q. Yang, M.Z. Su, Structure and phase transition of GdBO3, Chem. Mater. 11 (1999) 1576-1580.

16

Page 16 of 25

[26] W.L. Noorduin, H. Meekes, A.A.C. Bode, W.J.P.V. Enckevort, B. Kaptein, R.M. Kellogg, E. Vlieg, Explanation for the emergence of a single chiral solid state during attrition-enhanced Ostwald ripening: survival of the fittest, Cryst. Growth Des. 8

ip t

(2008) 1675-1681.

cr

[27] J. Yang, Z.W. Quan, D.Y. Kong, X.M. Liu, J. Lin, Y2O3 :Eu3+ microspheres:

us

solvothermal synthesis and luminescence properties, Cryst. Growth Des. 7 (2007) 730-735.

an

[28] L. Wu, Y. Zhang, M.Y. Gui, P.Z. Lu, L.X. Zhao, S. Tian, Y.F. Kong, J.J. Xu, Luminescence and energy transfer of a color tunable phosphor: Dy3+-, Tm3+-, and

M

Eu3+-coactivated KSr4(BO3)3 for warm white UV LEDs, J. Mater. Chem. 22 (2012)

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te

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6463-6470.

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Figures captions Fig. 1 XRD patterns of the as-obtained GdBO3 samples. Fig.2 Panoramic and magnified SEM images of the Gd(OH)CO3 colloid spheres (a

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and b), the cake-like GdBO3 (c and d), and the olive-like GdBO3 (e and f).

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Fig. 3 FT-IR spectra of the as-obtained GdBO3 samples.

of B3O99- groups in vaterite-type GdBO3 (right).

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Fig. 4 crystal structure of vaterite-type GdBO3 (left) and the orientation arrangement

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Fig. 5 SEM images of samples prepared with different amounts of ethanol: (a) 5 ml, (b) 10 ml, (c) 15 ml, and (d) 20ml.

(c) and (d) 9 h, (e) 12 h, and (f) 18 h.

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Fig. 6 SEM images of products prepared for different reaction times: (a) 3 h, (b) 6 h,

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Fig. 7 The corresponding XRD patterns of the products prepared for different reaction times (a) and the intensity of diffraction peak (002) of as-obtained products vary as a

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function of hydrothermal time.

Fig. 8 Excitation spectrum of cake-like GdBO3:0.05Eu3+ (a), and emission spectra of

GdBO3:0.05Eu3+ with different morphologies. Fig. 9 Emission spectra of products with different Eu3+ concentrations (a). The

emission intensity at 592 nm of Gd1-xBO3:xEu vary as a function of Eu3+ concentration (b). EDS spectrum of GdBO3:0.20Eu3+ sample (c).

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Fig. 8

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Fig. 7

Fig. 9

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