Sacrificed Carbon-Assisted Synthesis of Î²-Tricalcium Phosphate

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Sacrificed Carbon-Assisted Synthesis of #Tricalcium Phosphate Nanostructures Wenjie Huang, Yushi Yang, Zhou Mao, Jialiang Li, and Qingzhi Wu Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.6b00717 • Publication Date (Web): 08 Aug 2016 Downloaded from http://pubs.acs.org on August 13, 2016

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Crystal Growth & Design

Sacrificed Carbon-Assisted Synthesis of βTricalcium Phosphate Nanostructures ‡

Wenjie Huang,† Yushi Yang,† Zhou Mao,† Jialiang Li,‡ and Qingzhi Wu*,† †

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, and

Biomedical Material and Engineering Center, Wuhan University of Technology, Wuhan 430070, China ‡

School of Chemical Engineering, Shangdong University of Technology, Zibo 255049, China

KEYWORDS: β-tricalcium phosphate, graphene oxide, activated carbon

ABSTRACT: β-tricalcium phosphate (β-TCP) has attracted particular attention in bone tissue engineering because of its excellent biocompatibility, absorbability, and osteoinductivity. In the present, β-TCP nanoparticles (NPs) and triangular cones were synthesized by co-precipitation method combined with calcination under high temperature. Different carbon materials, including graphene oxide (GO) and activated carbon (AC), were employed as the sacrificed support in order to prevent the sintering and agglomeration during high temperature calcination. Monodispersed β-TCP NPs were obtained using GO as the sacrificed support, while β-TCP triangular cones were obtained using AC as the sacrificed support. GO not only provided anchoring sites for the nucleation and growth of the precursor through numerous oxygencontaining functional groups on the surface of nanosheets, but also promoted the nucleation and

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growth of β-TCP NPs by decreasing phase transformation temperature and time due to excellent thermal conductivity. These results provide a novel strategy using GO as the sacrificed support for the high-temperature synthesis of β-TCP NPs and other nanomaterials.

1. INTRODUCTION Calcium phosphates are of great significance for their promising applications in biomedical fields, such as orthopedics, dentistry, and drug delivery, due to the remarkable biocompatibility and bioactivity.1 Among various calcium phosphate compounds, hydroxyapatite (HA) and βtricalcium phosphate (β-TCP) have attracted particular attention in bone tissue engineering because both of them exhibit excellent osteoinductivity.2,3 HA presents as the main inorganic component of bone is thermodynamically the most stable phase in physiological conditions and exhibits strong affinity to direct chemical bonding to the bone.4,5 By comparison, β-TCP is absorbable in vivo and exhibits much higher solubility and degradation rate than those of HA, which could accelerate the formation of new bone and replace the implanted β-TCP with new bone growth.6,7 Numerous studies have demonstrated that the physic-chemical properties of βTCP, such as the size, and phase purity displayed significant influences on the bioactivity in vivo.8-11 For example, it was reported that β-TCP nanoparticles (NPs) with the size ranging from 100 to 150 nm were particularly active in vivo, while the phase purity of β-TCP NPs played important roles to the formation of new bone.10,11 β-TCP belongs to the large calcium phosphate family, which includes HA, α- and β-TCP, tetracalcium phosphate, octacalcium phosphate, amorphous calcium phosphate, and so on.12,13 Therefore, it is crucial for the synthesis of pure β-TCP NPs to precisely control the reaction parameters, such as pH value of reaction system, stoichiometry of the raw materials, ripening


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time, and reaction temperature. So far, a series of solid state methods14-17 and wet-chemical methods18-25 have been developed for the tunable synthesis of β-TCP NPs. In a typical synthesis of β-TCP NPs using either solid state methods or wet-chemical methods, the precursors were usually calcined under high temperature above 800°C for several hours, resulting in serious sintering and agglomerations.14-19 The study by Bow et al. showed that the synthesis of β-TCP NPs at room temperature resulted in the imperfection crystal where the long-range order failed to be completely constructed.20,21 Therefore, it is still of great interest to explore the synthesis of βTCP NPs with uniform size and morphology. In this study, β-TCP NPs were synthesized by calcining the precursor prepared with calcium chloride and diammonium hydrogen phosphate as the raw materials. The different carbon materials (graphene oxide denoted as GO and activated carbon denoted as AC) were introduced as the sacrificed support in order to decrease sintering and agglomeration of β-TCP NPs during calcination. The as-synthesized samples were characterized through X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and thermogravimetric-differential scanning calorimetry (TG-DSC).

2. EXPERIMENTAL SECTION Materials. Diammonium hydrogen phosphate ((NH4)2HPO4, DAP, 99%), calcium chloride (CaCl2, 96%), and ammonia (NH3·H2O, 25%) were of analytical grade (Sinopharm. Chemical Reagent Co., Ltd.). All reagents were used as received without further purification. Deionized water (16 MΩ·cm) was obtained from a Nanopure Water Systems UV (Thomas Scientific, Swedesboro, NJ).


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Synthesis of β-TCP Nanostructures. Graphene oxide (GO) was prepared according to the modified Hummers’ method. In a typical synthesis,26 20 mg of GO was dispersed in 100 mL of deionized water under ultrasonication, CaCl2 (2.0810 g, 0.01875 mol) was added and dissolved in the GO solution (Solution A). (NH4)2HPO4 (1.6507 g，0.0125 mol) was dissolved in another 100 mL of deionized water, and NH3·H2O was added dropwise in (NH4)2HPO4 solution in order to adjust pH value of the solution (pH = 10) (Solution B). Solution A was added dropwise to solution B at a constant rate (1 mL/min) under vigorous stirring at room temperature. The total Ca/P molar ratio of the reaction system was 1.5. After 3 h of stirring, the mixture was collected and washed alternately with ethanol and deionized water by centrifugation (9000 rpm, 5 min), and then dried at 80°C for 12 h. The black precursor was then calcined at 750°C in air for different times (1 h and 2 h) at a heating rate of 10°C/min. The white sample was obtained after the carbon support was burn out. In a series of syntheses, the reaction parameters, including the concentration of the reactants and the carbon support, and the calcination temperature were adjusted in order to explore the influence of the precursors and carbon support on the formation of β-TCP nanostructures. The different concentrations of the reactants and carbon support used in the synthesis were listed in Table 1. Table 1. The concentration of the reactants and carbon support used for the synthesis of β-TCP nanostructures.

No.

CaCl2 (NH4)2HPO4 (mmol/mL) (mmol/mL)

GO AC (mg/mL) (mg/mL)

S1

0.09375

0.0625

0.1

S2

0.09375

0.0625

0.2

S3

0.09375

0.0625

0.4

S4a

0.01172

0.0078

0.2


4

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a

S5a

0.02344

0.0156

0.2

S6a

0.04688

0.0313

0.2

S7a

0.07031

0.0469

0.2

P1

0.09375

0.0625

0.1

P2

0.09375

0.0625

0.2

P3

0.09375

0.0625

0.4

The concentrations of the raw materials used for preparing the precursor in S4, S5, S6, and S7

corresponds to 12.5 %, 25 %, 50 %, and 75 % of those in S2, respectively. Characterizations of the samples. The phase structure of the samples was identified by powder X-ray diffraction (XRD) on a D8 Advance diffractometer using Cu Kα radiation (λ = 1.5418 Å) at a scan speed of 0.5 Sec/step (increment=0.05). The average size of the samples was calculated from the XRD patterns according to the Scherrer equation.27-29 The morphology and structure of the samples were observed using field-emission scanning electron microscopy (FESEM, S-4800, Hitachi Corp, Japan) and high-resolution transmission electron microscopy (HRTEM, JEM-2100F STEM/EDS, JEOL Corp, Japan). The average size of the samples was also analyzed by counting at least 100 particles from SEM images using a software (Image J). Thermogravimetric analysis-differential scanning calorimetry (TG-DSC) was carried out on a simultaneous thermal analyzer (STA449F3, Netisch, Germany). Samples were heated from room temperature to 900°C with 10°C/min in the air.

3. RESULTS Figure 1 shows the FESEM image and the size distribution of the samples (P1, P2, and P3) synthesized at different AC concentrations calcined at 750°C for 2 h. The sample (P1) in the shape of triangular cone was obtained when the AC concentration was 0.1 mg/mL,


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Figure 1. FESEM images and size distribution of the samples synthesized at different AC concentrations calcined at 750 °C for 2 h. (a), (b) P1, the AC concentration of 0.1 mg/L; (d), (e) P2, the AC concentration of 0.2 mg/L; (g), (h) P3, the AC concentration of 0.4 mg/L. The histograms in (c), (f), and (i) show the size distribution of the samples by counting at least 100 particles from SEM images. as shown in Figure 1a and b. The average size of the triangular cones was approximately 252±15 nm. Increasing the AC concentration to 0.2 mg/mL, triangular cones (P2) were obtained with an average size of approximately 232±14 nm (Figure 1d and e). However, further increasing the AC concentration to 0.4 mg/mL, irregular particles (P3) were obtained and serious agglomerations were observed (Figure 3g and h). The average size of P3 was approximately 252±15 nm. The phase structure of the samples synthesized with the AC support was identified by powder X-ray diffraction (XRD). Figure 2 shows the XRD patterns of the samples (P1, P2, and P3). All the peaks in XRD patterns could be identified and indexed to β-TCP (JCPDS No.70-2065). The


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(2 0 20)

(0 2 10)

(2 2 0)

(1 0 10) (2 1 4)

(0 2 4)

(1 1 0)

(c)

Intensity

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(0 1 2) (1 0 4)

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(b)

(a) JCPDS No. 70-2065 10

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40

50

60

70

80

2θ (degree) Figure 2. XRD patterns of the samples synthesized at different AC concentrations calcined at 750°C for 2 h. (a) P1, the AC concentration of 0.1 mg/L; (b) P2, the AC concentration of 0.2 mg/L; (c) P3, the AC concentration of 0.4 mg/L. sharp diffraction peaks indicated high crystallization of the as-synthesized samples. No peaks derived from other calcium phosphates were observed in the XRD patterns. The size of the samples calculated according to Scherrer equation was approximately 90±4 nm for P1, 74±3 nm for P2, and 95±5 nm for P3. Figure 3 shows the FESEM images and size distribution of the samples (S1, S2, and S3) synthesized at different GO concentrations calcined at 750°C for 1 h. As shown in Figure 3a and b, β-TCP NPs (S1) were obtained at an average size of approximately 144±10 nm when the GO concentration was 0.1 mg/mL. When the GO concentration was increased to 0.2 mg/mL, monodispersed β-TCP NPs (S2) with an average size of approximately 117±6 nm was obtained (Figure 3d and e). However, further enhancing the GO concentration to 0.4 mg/mL resulted in slight increase of the average size to approximately 129±9 nm (S3, Figure 3g and h), and some


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Figure 3. FESEM images and size distribution of the samples synthesized at different GO concentrations calcined at 750 °C for 1h. (a), (b) S1, the GO concentration of 0.1 mg/L; (d), (e) S2, the GO concentration of 0.2 mg/L; (g), (h) S3, the GO concentration of 0.4 mg/L. The histograms in (c), (f), and (i) show the size distribution of the samples by counting at least 100

(2 0 20)

(0 2 10)

(2 2 0)

(1 0 10) (2 1 4)

(0 2 4)

(1 1 0)

(0 1 2) (1 0 4)

particles from SEM images.

(c)

Intensity

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

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(b)

(a)

JCPDS No. 70-2065 10

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30

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2θ (degree) Figure 4. XRD patterns of the samples synthesized at different GO concentrations calcined at 750 °C for 1 h. (a) S1, the GO concentration of 0.1 mg/L; (b) S2, the GO concentration of 0.2 mg/L; (c) S3, the GO concentration of 0.4 mg/L.


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agglomerations were obviously observed due to sintering. Figure 4 shows the XRD patterns of the samples (S1, S2, and S3) synthesized at different GO concentrations. All of the peaks in the XRD pattern of S1, S2, and S3 could be indexed to β-TCP （JCPDS No.70-2065). No peaks derived from other calcium phosphates were observed in the XRD patterns. The sharp diffraction peaks imply the high crystallization of β-TCP NPs. The size of the as-synthesized β-TCP NPs calculated according to Scherrer equation was approximately 120±9 nm for S1, 69±3 nm for S2, and 79±4 nm for S3. In order to investigate the influence of the precursor concentration on the formation of β-TCP NPs, a series of syntheses were carried out by decreasing the precursor concentration to 12.5 %, 25 %, 50 %, and 75 % compared with that of S2, corresponding to the sample of S4, S5, S6, and S7, respectively. Figure 5 shows the SEM images and size distribution of these samples. The larger size distribution and obvious agglomerations were observed in the samples of S4, S6, and S7 compared with that of S5. The average size by counting at least 100 particles from SEM images was approximately 132±7 nm for S4, 105±5 nm for S5, 122±10 nm for S6, and 150±8 nm for S7, respectively. These results suggest that decreasing the concentration of the precursor may be in favorable of the formation of monodispersed β-TCP NPs with a smaller size. Figure 6 shows the XRD patterns of the samples (S4, S5, S6, and S7). All of the peaks in the XRD patterns could be indexed to β-TCP（JCPDS no.70-2065). No peaks derived from other calcium phosphates were observed in the XRD patterns. The sharp diffraction peaks imply the high crystallization of these samples. The size of the as-synthesized β-TCP NPs calculated according to Scherrer equation was approximately 83±4 nm for S4, 88±5 nm for S5, 92±5 nm for S6, and 74±3 nm for S7.


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Figure 5. FESEM images and size distribution of the samples (S4, S5, S6, and S7) synthesized by decreasing the precursor concentration compared with that for the synthesis of S2. (a), (b) S4, 12.5 % of S2; (d), (e) S5, 25 % of S2; (g), (h) S6, 50 % of S2; (j), (k) S7, 75 % of S2. The histograms in (c), (f), (i), and (l) show the size distribution of the samples by counting at least

(2 0 20)

(0 2 10)

(2 2 0)

(1 0 10) (2 1 4)

(1 1 0)

(0 2 4)

(0 1 2) (1 0 4)

100 particles.

(d)

(c)

Intensity

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

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(b) (a)

JCPDS No. 70-2065 10

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30

40

50

60

70

80

2θ (degree) Figure 6. XRD patterns of the samples (S4, S5, S6, and S7) synthesized by decreasing the precursor concentration compared with that for the synthesis of S2. (a) S4, 12.5 % of S2; (b) S5, 25 % of S2; (c) S6, 50 % of S2; (d) S7,75 % of S2.


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Figure 7. TEM and HRTEM images of β-TCP NPs (S5) and triangular cones (P2). (a), (b) S5; (d), (e) P2.(c), (f) SAED images of S5 and P2, respectively. Figure 7 shows TEM, HRTEM, and selected area electron diffraction (SAED) images of βTCP NPs (S5) and triangular cones (P2). The perfectly aligned lattice planes confirmed the single-crystal nature of S5 (Figure 7b), consistent with the result from the XRD pattern. The interplanar distance obtained from the HRTEM image (Figure 7b) was approximately 0.522 nm, which could be ascribed to the adjacent (110) planes of β-TCP crystal. The regular spot array appeared in the SAED image (Figure 7c) further confirms the phase transformation of the precursor into β-TCP. Figure 7d shows the TEM image of P2 with irregular shape. The triangular cone-like structures were indistinct in two-dimensional electron images. The well aligned lattice planes also confirmed the single-crystal nature of P2 (Figure 7e). Two different interplanar distances obtained from the HRTEM image were approximately 0.522 nm and 0.648 nm, respectively, which could be ascribed to the adjacent (110) and (104) planes of β-TCP crystal. A series of regular spots appeared in the SEAD pattern (Figure 7f) also confirm the phase transformation of the precursor into β-TCP.


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(b)

-6.25% 220°C -0.36%

492°C

752°C

85

0

80 -5 75 70

10

-1.44% -2.29% 534°C

95 5

DSC (mW/mg) Weight loss (%)

95 90

100

(a)

- 2.79%

-0.33%

5 90 765°C

85

0

80 -5

DSC (mW/mg)

10

100

Weight loss (%)

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

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75

0

200

400

600

800

-10

70

0

200

Temperature (°C)

400

600

800

-10

Temperature (°C)

Figure 8. TG-DSC curves of β-TCP NPs (S5) and triangular cones (P2). (a) S2; (b) P2. Figure 8 shows the TG-DSC curves of the precursors for the synthesis of S2 and P2. In the case of S2, a weight loss of approximately 2.79% was observed in the initial stage of heating up to 220°C, which could be ascribed to desorption of the adsorbed water in the precursor. Further heating up to approximately 750°C, the weight loss of the precursor was approximately 6.25%, accompanied with an exothermic peak on the DSC curve at 492°C, implying that the precursor was transformed into certain calcium phosphate intermediate. Almost no significant weight loss was observed in the temperature range of 750-900°C, implying that the phase transformation had completed near 750°C, as confirmed by XRD characterization (Figure 4b). In the case of P2, a weight loss of approximately 1.44% was observed, implying that the adsorbed water in the precursor was less than that in S2. This could be ascribed to the higher capacity of the GO nanosheets retaining water than that of the AC powder. Further heating up to approximately 750°C, the weight loss of the precursor was approximately 2.29%, accompanied with an exothermic peak on the DSC curve at 534°C, implying that the temperature for the transformation from the precursor into calcium phosphate intermediate was higher than that in the case of S2. Similarly, no significant weight loss was observed in the temperature range of


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750-900°C, implying that the phase transformation had completed, as confirmed by XRD characterization (Figure 2b).

4. DISCUSSION In the past decades, β-TCP NPs have been successfully synthesized by various solid state or wetchemical methods, such as sol-gel, hydrothermal, microemulsion, and co-precipitation.18-25 Among these methods, sol-gel method has attracted more attention because of easily controlling the stoichiometry of both the raw materials and the final product, and the other reaction parameters. However, a calcination process at high temperature ranging from 800-1000°C is necessary for the transformation from the precursor into β-TCP crystal.14-19 Accordingly, serious sintering and agglomeration occurred during the high temperature calcination. In this work, carbon materials (AC and GO) were employed as the sacrificed support for the synthesis of β-TCP nanostructures in order to decrease sintering and agglomeration during calcination. The precursors were formed on the surface of the carbon support, which were subsequently calcined and transformed into β-TCP crystal. β-TCP triangular cones were obtained with obvious sintering and agglomeration using AC as the sacrificed support, while monodispersed β-TCP NPs were obtained using GO as the sacrificed support. It is also noticeable that the formation of β-TCP NPs underwent a shorter calcination time of 1 h compared with that of 2 h for β-TCP triangular cones. Graphene is two-dimensional honeycomb-like nanosheet and consisted of sp2 hybrid carbon atoms. A great deal of attention has been attracted on the synthesis, modification, and applications of graphene and its derivate in the past several years because of their exceptional properties, such as high Young’s modulus (1.0 TPa), large theoretical specific surface area (2630


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m2/g), excellent thermal conductivity (5000 W/m/K), and high mobility of charge carriers (2×105 cm2/V/s).30,31 GO is usually prepared by oxidizing graphite using the strong oxidants (the modified Hummer method), resulting in the formation of numerous oxygen-containing functional groups (such as carboxyl, carbonyl, hydroxyl, and epoxy group) on the plane and edge of nanosheets. Studies by our and other groups have demonstrated that these oxygen-containing functional groups are ready to act as anchoring sites for the nucleation and growth of nanocrystals. 32,33 Therefore, GO has been widely utilized as the supporting matrix for loading various catalysts. In the present synthesis of β-TCP nanostructures, the precursors were firstly formed on the surface of the carbon support. Oxygen-containing functional groups in the surface of GO nanosheets acted as anchoring sites capturing Ca2+ and HPO42-, resulted in the homogeneous nucleation and growth of the precursor. On the other hand, the nucleation and growth of the precursor were random and uncontrolled around the AC support due to the absence of anchoring sites on the AC surface. Therefore, GO played an important role as the dispersing agent during the nucleation and growth of the precursor. The precursors were subsequently transformed into β-TCP nanostructures upon calcination. Although both of the carbon supports are thermal conductive materials, GO displayed more excellent thermal conductivity than that of AC. As shown by TG-DSC curves in Figure 8, two different exothermic peaks were observed at approximately 492°C for the GO support and 534°C for the AC support, which could be attributed to the transition from amorphous Ca2P2O7 to crystalline Ca2P2O7.18,34-36 The other two exothermic peaks at approximately 752°C and 765°C was inductive of the transformation from crystalline Ca2P2O7 into β-TCP crystal. The more gently exothermic curve and lower phase transformation temperature in the case of S2 than those


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in the case of P2 demonstrate the higher thermal conductive efficiency of GO than that of AC. As a comparison, the sample was also synthesized in the absence of carbon support (GO or AC). A mixture of β-TCP and uncertained calcium phosphates was obtained when the precursor was calcined at 750°C for 2 h, while pure β-TCP was obtained when the precursor was calcined at 800°C for 2 h (see Supporting Information Figure S1). These results indicate that the addition of carbon (GO or AC) is favorable to the phase transformation of β-TCP nanostructures at the lower temperature (750°C) and shorter calcination time (1 h). Meanwhile, the irregular particles were obtained with serious aggregation (see Supporting Information Figure S2). In addition, the mass loss of the precursor was lower in the absence of carbon support than that in the presence of carbon support (see Supporting Information Figure S3), providing an indirect evidence for the disappearance of GO or AC containing in the precursor during thermal analysis. Therefore, the nucleation and growth of β-TCP NPs on the GO surface were faster and more homogeneous than that around the AC surface, resulting in lower phase transformation temperature, shorter phase transformation time, smaller crystal size, and less agglomerations. More investigations are necessary to interpret the precise mechanisms by which the phase transformation and crystal growth kinetic of β-TCP NPs were influenced when the different carbon were used as the sacrificed support. Scheme 1 shows the speculated mechanisms for the formation of β-TCP nanostructures using the different carbon (GO and AC) as the sacrificed support.


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Scheme 1. Speculated mechanisms for the formation of β-TCP nanostructures using the different carbon (GO and AC) as the sacrificed support.

5. CONCLUSIONS In summary, β-TCP NPs and triangular cones were synthesized by calcining the precursors under 750°C for different times. The different carbon materials (GO and AC) were employed as the sacrificed support in order to decrease sintering and agglomeration of β-TCP nanostructures during calcination. The results show that the carbon supports played crucial roles to the phase transformation, nucleation, and growth of β-TCP nanostructures. Monodispersed β-TCP NPs were obtained using GO as the sacrificed support, while β-TCP triangular cones were obtained using AC as the sacrificed support. GO not only provided anchoring sites for the nucleation and growth of the precursor through numerous oxygen-containing functional groups on the surface of nanosheets, but also promoted the nucleation and growth of β-TCP NPs by decreasing phase transformation temperature and time due to excellent thermal conductivity. These results provide a novel strategy using GO as the sacrificed support for the high-temperature synthesis of β-TCP NPs and other nanomaterials. SUPPORTING INFORMATION.


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XRD patterns, SEM images, and TG-DSC curves of the precursors and the sample synthesized in the absence of the sacrificed carbon support. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]. Tel: +86 138 7131 4227. Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT This work was financially supported by the Natural Science Foundation of China (No. 30800256), and the basic research project of Wuhan Science and Technology Bureau (No. 2014060101010041).

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Table of Contents Graphic and Synopsis

Sacrificed Carbon-Assisted Synthesis of β-Tricalcium Phosphate Nanostructures ‡

Wenjie Huang,† Yushi Yang,† Zhou Mao,† Jialiang Li,‡ and Qingzhi Wu*,†

β-TCP NPs and triangular cones were synthesized by calcining the precursors at 750°C for different times. The different carbon materials (graphene oxide denoted as GO and activated carbon denoted as AC) were employed as the sacrificed support in order to decrease the sintering and agglomerations of β-TCP nanostructures during calcination. The results show that the sacrificed GO support not only provided anchoring sites for the nucleation and growth of the precursor through numerous oxygen-containing functional groups on the surface of nanosheets, but also promoted the nucleation and growth of β-TCP NPs by decreasing phase transformation temperature and time due to excellent thermal conductivity.


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Sacrificed Carbon-Assisted Synthesis of Î²-Tricalcium Phosphate

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