A novel 1540 nm light emission from erbium doped hydroxyapatite

Materials Letters 167 (2016) 145–147 Contents lists available at ScienceDirect Materials Letters journal homepage: www.elsevier.com/locate/matlet A novel 1540 nm light emission from erbium doped hydroxyapatite/ β-tricalcium phosphate through co-precipitation method Vuong-Hung Pham a,n, Hoang Nhu Van a, Phuong Dinh Tam a, Hanh Nguyen Thi Ha b a b Advanced Institute for Science and Technology (AIST), Hanoi University of Science and Technology (HUST), No 01, Dai Co Viet Road, Hanoi, Viet Nam Lab of Petrochemical and Catalysis Materials, Hanoi University of Science and Technology (HUST), No 01, Dai Co Viet Road, Hanoi, Viet Nam art ic l e i nf o a b s t r a c t Article history: Received November 2015 Received in revised form 30 December 2015 Accepted January 2016 Available online January 2016 This paper reports a novel way for the synthesis of erbium (Er) doped hydroxyapatite (HA) nanostructure to achieve strong and stable near-infrared light emission at ∼1540 nm of hydroxyapatite, particularly, by applying an optimum annealing temperature The Er doped HA was observed to have a nanowire structure As annealed 600 °C specimens, the XRD diffraction peaks were to be hydroxyapatite; however a mixture of hydroxyapatite and β-tricalcium phosphate phase (β-TCP) when annealed temperatures of 800–1200 °C were used The formation of HA/β-TCP of the Er doped HA specimens resulted in a significantly enhanced light emission at ∼1540 nm, which was potential application in waveguide telecommunication and biomedicine & 2016 Elsevier B.V All rights reserved Keywords: Hydroxyapatite Luminescence β-tricalcium phosphate phase (β-TCP) Erbium Nanowires Introduction Development of strong, and stable near-infrared light emission materials is particular important for designed optical properties in the field of optical telecommunication applications such as waveguides and biomedicine [1,2] Fundamentally, the optical properties of materials are strongly affected by their host matrices, dopants, defects and crystallinity of materials [3,4] This encouraged scientists and engineers to explore new ways of designing materials with controlling the chemical and physical characteristics of materials, for example, by doping with strong and stable light emission materials and designing the suitable host materials for stimulating energy transfer from the host matrix to the activators [5,6] As one of useful rare earth elements, erbium (Er) is a suitable activator for doping into host matrixes in optical telecommunication due to their exhibiting importance light emission at ∼1540 nm which is exact by the region used in the telecommunication band for transmission of information [7,8] Similarly, Er is also a suitable material for doping into materials for designing up conversion luminescence and biocompatible materials because of its light emission and excellent biocompatibility [9,10] Compared to other host matrices, hydroxyapatite (HA) has received considerable attention as a host material in achieving high n Corresponding author E-mail address: vuong.phamhung@hust.edu.vn (V.-H Pham) http://dx.doi.org/10.1016/j.matlet.2016.01.002 0167-577X/& 2016 Elsevier B.V All rights reserved efficiency the luminescence materials because HA can incorporate a wide variety of substitutions for Ca2 þ and PO34 − and or OH À ion based on flexibility of the apatitic structure [11,12] These materials have been introduced to optical engineering for synthesis red and blue luminescent materials, which demonstrated positive effects on the high efficiency of luminescent hydroxyapatite [13,14] Although the physico-chemical properties of HA are well documented, but thus far, only one paper have been reported on the blue luminescence of Er doped hydroxyapatite [15] and, to the best of our knowledge, no attempts have been made to report the nearinfrared emission at ∼1540 nm from Er doped HA by coprecipitation method with a well-crystalline structure, which would open new avenues for designing strong and stable near-infrared emission for waveguide telecommunication and biomedicine Therefore, in this letter, we demonstrate a novel way of controlling the strong near-infrared emission of Er doped HA, which can be achieved by co-precipitation synthesis method followed by a thermal annealing process Er concentrations as high as 5.5 wt% was achieved Room temperature photoluminescence (PL) was observed with strong and extremely narrow band spectra at ∼1540 nm Experimental procedure Erbium doped hydroxyapatite was synthesized though a coprecipitation method, as follows: an aqueous solution with 146 V.-H Pham et al / Materials Letters 167 (2016) 145–147 stoichiometric amount of (NH4)2 HPO4 (0.2 M, 99% purity, Aldrich) solution was added over an aqueous solution containing Ca (NO3)2 Á 4H2O (0.2 M, 99% purity, Aldrich), and 0.006 mol % ErCl3 Á 6H2O (99.9% purity, Aldrich) with vigorous stirring The reaction mixture was stirred for 0.5 h followed by precipitation method at 80 °C and the pH was adjusted to 11 by using aqueous ammonia The resulting precipitates were washed three times, and then dried at 100 °C for h A fraction of each as-prepared sample was treated at 600 °C, 800 °C, 1000 °C, 1100 °C and 1200 °C for h in air The crystalline structures of the Er doped HA were characterized by X-ray diffraction (XRD, D8 Advance, Bruker, Germany) The Er doped HA powders were placed on a silicon (Si) wafer, and the microstructure as well as chemical composition of the Er doped HA were determined by field emission scanning electron microscopy (JEOL, JSM-6700F, JEOL Techniques, Tokyo, Japan) Photoluminescence (PL) tests were performed to evaluate the optical properties of the Er doped HA NANO LOG spectrofluorometer (Horiba, USA) equipped with 450 W Xe arc lamp and double excitation monochromators was used The PL spectra were recorded automatically during the measurements Fig XRD diffraction patterns of Er doped HA annealed at different temperature (A) 600 °C, (B) 800 °C, (C) 1000 °C, (C) 1100 °C, (C) 1200 °C (*HA and #β-TCP) Results and discussion Fig shows XRD diagram of the Er doped HA prepared by coprecipitation with different thermal annealing As annealed 600 °C specimen showed peaks which match the standard patterns of Ca10 (PO4)6(OH) 2, calcium hydroxyapatite (PDF 01-084-1998) (Fig 1(A)) On the other hand, when the higher thermal annealing was used, all of the three XRD patterns showed a mixture of HA and β-tricalcium phosphate (β-TCP) (PDF 09-0169) with good crystallinity (Fig 1(B–D)) This suggests that the phase characteristic of Er doped HA can be controlled by applying the thermal annealing It is also can be seen that XRD diagram obtained for all Er doped HA specimens not reveal the presence of any phases related to erbium species, suggesting the successful preparation of Er doped HA It is well documented that the chemical composition of the synthesized HA play important role in the phase formation at high temperature [16] In this research, the HA that may contain HPO24− ion will be condensed into P2O74 − ion when heated about 650 °C [17,18] The presence of P2O74 − ion will then react with OH À and turned into β-TCP during thermal annealing process [19,20] The mixture of HA and β-TCP found on the specimens after thermal annealing would be expected to enhance the luminescence of the Er doped HA The representative microstructure and chemical composition of the Er doped HA specimen annealed at 600 °C was characterized by SEM and EDS, as shown in Fig 2(A) and (B) The specimen showed a long nanowire microstructure (Fig 2(A)) with a smooth surface, as is often the case with hydroxyapatite synthesized without surfactance [4,13] Peaks corresponding to Er elements was observed (Fig 2(B)), indicating the presence of the Er into the hydroxyapatite In addition, a calculated weight concentration of the Er incorporated was as high as $ 5.5%, which would be permeably suggested to the successful doping of Er ion in to the host hydroxyapatite It can be seen that the presence of Si peak in the EDS spectrum was very high because the Er doped HA powders were attached on smooth and conductive Si wafer for SEM observation Photoluminescence measurements (PL) were used throughout this study to optically characterize Er doped HA The typical photoluminescence spectra of the Er doped HA are shown in Fig All the Er doped HA showed strong near-infrared emission peaks appeared at about ∼1540 nm and they can attributed to the transition from the first excited level 4I13/2 to the ground state 4I15/ within the incomplete 4f electronic level However, it should be noted that the PL spectra of specimens increased with the Fig Microanalysis of the Er doped HA annealed at 600 °C (A) SEM image and (B) EDS analysis of chemical composition of specimens V.-H Pham et al / Materials Letters 167 (2016) 145–147 147 ∼1540 nm, which was much stronger than those of the lower annealed Er doped HA This enhancement of the PL was mainly attributed to the containing β-TCP phase in the microstructure which is inhibitor of photo quenching in luminescent hydropxyapatite for potential application in waveguide telecommunication and biomedicine Acknowledgment This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant Number 103.99-2013.05 References Fig Photoluminescence spectra of Er doped HA with various annealing temperature increasing of the annealed temperature significantly This significant enhancing PL was mainly attributed to the achievement of β-TCP phase in the HA/β-TCP system, which can be explained by considering the photo quenching effect of the hydroxyl group (OH) in optical HA/β-TCP system [4] More specifically, under an excitation source, a fraction of excited Er3 þ ion can transfer the excitation to the neighboring non-excited Er3 þ ion in the few step and finally not be prevented by hydroxyl group in the transfer route, consequently, leading to increase photoluminescence [21,22] However, other factors, such as crystallinity of Er doped HA powders should also be taken into account since heating at higher annealing temperatures crystallinity increased as indicating by XRD results Conclusions We herein demonstrated that the near-infrared luminescence emission of hydroxyapatite could be obtained effectively by doping with rare earth erbium In particular, the X-ray diffraction patterns of the Er doped HA was controlled by thermal annealing The photoluminescence of the Er doped HA with thermal annealing temperature of 1100–1200 °C was showed strong band at [1] A Mech, A Monguzzi, F Meinardi, J Mezyk, G Macchi, R.J Tubino, Am Chem Soc 132 (2010) 4574–4576 [2] R Kumar, M Nyk, T.Y Ohulchanskyy, C.A Flask, P.N Prasad, Adv Funct Mater 19 (2009) 853–859 [3] J.C.G Bünzli, C Piguet, Chem Soc Rev 34 (2005) 1048–1077 [4] C.X Thang, V.H Pham, Mater Sci Eng B 197 (2015) 18–24 [5] X.T Zhang, Z Liu, C.C Wong, S.K Hark, N Ke, S.P.J Wong, Phys 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Pham, N.N Trung, Mater Lett 136 (2014) 359–361 [14] O Graeve, R Kanakala, A Madadi, B.C William, K.C Glass, Biomaterials 31 (2010) 4259–4267 [15] A. Z Alshemary, M Akram, Y.F Goh, M.R .A Kadir, A. .. luminescence emission of hydroxyapatite could be obtained effectively by doping with rare earth erbium In particular, the X-ray diffraction patterns of the Er doped HA was controlled by thermal annealing