Sol-Gel-derived Mesoporous Calcium Aluminum Phosphate Bioactive Glasses with High Surface Area

doi:10.15541/jim20160143

Abstract

Abstract:

High surface area mesoporous bioactive glasses (MBGs) with composition CaO-Al₂O₃-P₂O₅ were fabricated using a simple aqueous Sol-Gel method without any template. Structural characterization of the phosphate-based MBGs was performed by BET, DTA, XRD and FTIR, and MBGs’ in vitro bioactivity was evaluated by soaking them in simulate body fluid for up to 15 d at 36.5℃. The highest specific surface area is found to be 461.1 m²/g for the MBG with 5mol% CaO, and it decreased with increasing CaO content. And the glass structure for all the samples was confirmed by XRD and FTIR. However, the MBG with 20mol% CaO exhibits the best in vitro bioactivity using simulated body fluid among all samples. The unique combination of a higher specific surface area and relatively high CaO content enables mesoporous calcium aluminum phosphate bioactive glasses to be promising candidates for biomedical applications.

Key words: mesoporous, phosphate glass, bioactive, Sol-Gel

CLC Number:

TQ174

MA Peng-Fei, LI Ri-Hong, ZHANG Long. Sol-Gel-derived Mesoporous Calcium Aluminum Phosphate Bioactive Glasses with High Surface Area[J]. Journal of Inorganic Materials, 2017, 32(1): 107-112.

Figures/Tables 11

Table 1 The phosphate coding, corresponding molar composition, annealing temperature and Tc temperature

Glass code	CaO/mol%	AlO_3/2/mol%	PO_5/2/mol%	Annealing, T/℃	T_c(℃) (glass), T/℃
5%CaO-MBG	5	45	50	600	806.75
10%CaO-MBG	10	40	50	600	738.00
15%CaO-MBG	15	35	50	600	728.08
20%CaO-MBG	20	30	50	600	717.66
25%CaO-MBG	25	25	50	600	709.58
30%CaO-MBG	30	20	50	600	701.10

Fig. 1 N2 adsorption/desorption isotherms with different content samples

Fig. 2 The pore size distribution of different samples

Table 2 Specific surface area, pore volume and pore size of the series sample of different samples

Glass code	Specific surface area/ (m²·g^-1)	Pore volume/ (mL·g^-1)	Pore size/nm
5%CaO-MBG	461.1	0.697	4.3
10%CaO-MBG	332.6	0.412	3.0
15%CaO-MBG	251.3	0.421	2.9
20%CaO-MBG	246.2	0.380	2.7
25%CaO-MBG	125.7	0.195	2.3
30%CaO-MBG	25.6	0.066	1.9

Fig. 3 shows the DTA traces collected for the different compositions with the increasing calcium oxide. And the Tc temperatures are presented in Table 1. Due to the Sol-Gel methods and the thermal treatment at 600℃, the Tg temperature can’t be reflected clearly from the tracts of DTA. As seen from the Fig. 3, a decrease in Tc temperature is obtained with increasing content of calcium oxide.

Fig. 3 The DTA curves of different samplesa) 5%CaO-MBG; b) 10%CaO-MBG; c) 15%CaO-MBG; d) 20%CaO-MBG; e) 25%CaO-MBG; f 30%CaO-MBG

Fig. 4 XRD natterns of samplesa) 5%CaO-MBG; b) 10%CaO-MBG; c) 15%CaO-MBG; d) 20%CaO-MBG; e) 25%CaO-MBG; f) 30%CaO-MBG

Fig. 5 shows the FTIR spectra of the phosphate glass samples. Almost no change is seen in the samples with the increasing content of calcium oxide. Each FTIR spectra shows the characteristic 490 cm-1 which correspond to the flexural vibration of the O-P-O bond correspond to P=O at 1250 cm-1, which appears on the occasion of crystallization in phosphate glass, proving the amorphous form of phosphate glass. The result of FTIR spectra is in line with the conclusion of X-Ray diffraction patterns.

Fig. 5 FTIR spectra of different samplesa) 5%CaO-MBG; b) 10%CaO-MBG; c) 15%CaO-MBG; d) 20%CaO-MBG; e) 25%CaO-MBG; f) 30%CaO-MBG

Fig. 6 shows the XRD patterns of the samples with the increasing content of calcium oxide before and after soaking in SBF solution. The presence of a broad band between 20° and 30° (2θ value) with no diffraction is observed, which confirms the amorphous structure of the phosphate matrix of glasses without dipping in SBF. After soaking, the major hydroxyapatite diffraction peaks [JCPDS 09-0432] (International Center for Diffraction Data, Swarthmore, PA, 2002) on the patterns at the different time periods, illustrating the change bioactive of the varying content glasses.

Fig. 6 XRD patterns of the samples before and after soaking in SBF solutiona) 5%CaO-MBG; b) 10%CaO-MBG; c) 15%CaO-MBG; d) 20%CaO-MBG; e) 25%CaO-MBG; f) 30%CaO-MBG

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