Structural Characterizations for Glass Ionomer Cement Doped with Transition Metal Phthalocyanines

Glass and Glass iomomer cement (GICs) based on a specific composition of cerium phosphate glass (40 CeO2-60P2O5) have been prepared. Effect of the doping type at a fixed doping concentration from metal-phthalocyanines (M-PCs) on material structure and morphologies has been carefully studied. The corresponding changes in the material structure were widely followed up by 31P MAS NMR, X-Ray diffraction and FTIR spectroscopy. The network structure of both base glass and GIC which all free from metal phthalocyanines has been confirmed to be amorphous. GIC doped with M-PCs has shown a more ordered structure. There were clear changes in the position and intensities of 31P NMR spectral peaks of glasses upon changing the dopant type. In all cases, a little concentration from M-Phthalocyanine (0.8 mol%) leads to changing the network structure from amorphous to a more ordered structure. Phosphate structural phases are evidenced to be formed upon addition of a fixed amount of M-PCs (Ga, Co, Fe). The morphologies of some selected samples were characterized by SEM. The micrographs have revealed that formulating of cerium phosphate powder of the amorphous glass with a polymeric acid successfully led to the formation of CePO4-H2O bundles phases. But formulation with GIC containing Co or Fe or Ga Phthalocyanine can simply form co-aligned linear slaps and elongated nanofibers which are consisted of hydrated and carbonated CePO4 a GaPO4, FePO4 or CoPO4 crystals. The structure of all doped materials has a lower crack length than that of base glass. This was discussed on bases of formation of more aligned and elongated tough-fibers in matrix of all doped materials. Such tough fibers have ability to withstand breaking stress via suppressing crack propagation.


Introduction
Some of Phthalocyanine (PCs) derivatives have been considered among the most important functional materials in many fields of applications [1]- [7]. PCs are characterized with their molecular structure which offers specific properties required for various technical and academic applications. PCs can be used as pigments in paints, data storage, IR security devices, printing inks, and computer disk writing [3] [4] [5] [6] [7]. In addition, PCs are known to have some specific medical application [8] [9]. They can be applied in photodynamic therapy of cancer [8] [9] [10]. They have several useful characteristics which have been related to their efficient ability for the electron transfer process [6] [7] [8] [9]. The central cavity of phthalocyanines is simply capable for accommodation of different elemental ions, including hydrogen and metal cations. A phthalocyanine containing one or two metal ions is called a metal phthalocyanine (M-PC). The high electron transfer abilities of M-PC have recommended them to be utilized in many fields such as molecular electronics, optoelectronics, photonics, etc.
[2]- [7]. The behaviors of M-PCs are almost based on electron transfer reactions which originate from the 18 π electron conjugated ring system found in their molecular structure.
The strongest absorption of M-PC in the visible region can be attributed to the electron transition from the allowed highest occupied molecular orbital to the lowest unoccupied molecular orbital which is called (π − π*) transition. For many applications the maximum absorption of M-PC has to move toward near the infrared region. In such a case, M-PC will be formulated with some types of organic solvent to yield a high strain structure. There are further additional particular derivatives which are known to have specific potential applications as second-generation photosensitisers for photodynamic therapy (PDT) of cancer [8] [9] [10]. These materials have shown a strong absorption of the far-red light between the wavelengths of 600 and 850 nm, which has greater tissue penetration properties. Phosphate glasses which were modified by metal oxides, fluoride and Phthalocyanine (CeO 2 , Ag 2 O, CrF 2 , C 32 H 16 ClGaN 8 ) [11] [12] [13] [14] have increasing scientific interests. This may be due to their appropriate state which is closely connected with application in biology, materials science and engineering [1]- [9].
The structure of vitreous P 2 O 5 consists of tetrahedral groups represented by Q n notations (Q is phosphors cation, n is the number of bridging oxygen atoms).
A gradual increasing of a modifier oxide in P 2 O 5 network could result in transforming (Q 3 ) to another phosphate units of more non bridging oxygen (NBO) ions (Q 2 , Q 1 and Q 0 ) [11] [12] [13]. As a result, the well-formed chains of P 2 O 5 become shorter and transformed into isolated rings like structure through increasing NBO atoms. In the glasses enriched with NBO atoms, separated rings containing only two identical molecules called dimers species can be formed.
The latter species are the most formed structural configuration in phosphate glass which is considered as an essential counterpart in obtaining the desired In terms of bioengineering applications, GICs is considered as an important type which can be prepared by mixing the fine powder of the glass sample with soluble type of weak acids. As a result of base-acid interaction between the glass powder and the poly acid, GIC can be simply formed [14] [15] [16] [17]. Specifically, GICs based on phosphate glasses are the most useful type. This may because P 2 O 5 based glasses are characterized with their higher basic reaction than that of germinate, telluride, silicate and borate glasses. For this reason, the characteristic of glass ionomer cements might be dominantly based on reaction between polymeric acid and the powder of phosphate glass.
Some important types of additional row materials such as metals or rare earth oxides or fluorides have to be added to the base GIC, since they can play the role of enhancing both bioactivity and compatibility of the used materials. Some of specific dopants can be added to stimulate the growth rates of the nucleation and crystallization processes of the mineral phase of bio hydroxyl phosphate structure [14] [15]. GICs involving crystalline phases can simply possess more enhanced properties than that non biocompatible amorphous GIC.
Majority of previous studies on GICs were concerned with effect of specific types of transition oxides on biocompatibility [11] [12] [13]. Whereas, modifications of GIC with a metallic Phthalocyanine species as an organic agent for nucleation, crystallization and as antimicrobial agents, are limited [14]. Therefore this study is devoted to explore the role played by different TM Phthalocyanines in modification of cerium phosphate based GIC to become appropriate in the field of tissue engendering applications. The main objective is to characterize both the structure and properties of the well-prepared glass ionomer cements. In addition, the structural role of M-PCs in achieving such properties can be determined.

Preparation
Glasses of a chemical composition 400CeO 2 •60P 2 O 5 have been prepared using ordinary slowly cooling technique. Reagent grades (Aldrich company) CeO 2 and NH 4 H 2 PO 4 (purity 98.93, 99.89) are the raw materials used in glass preparation.
The glasses were prepared by melting the mixtures in an aluminum crucible in an electric furnace at about 1250˚C. After solidification of the glass, it reheated in an electric furnace at tempering temperature of 300˚C for 3 hours to release internal stresses.

Measurements and Techniques
XRD diffraction measurements were carried out on a Brucker Axs-D8 spectrometer. Emitting source of type (λCuKα) has been utilized. The numerical data were frequently accumulated with a small scanning step, 2θ rang of 5˚ -70˚ and a dwell time of 0.4 seconds have been applied. The obtained X-ray diffraction spectra were revised to reference samples related to standards which were ga-New Journal of Glass and Ceramics thered by the technique of powder diffraction and standards (JCDPS). The surface structure of the investigated samples was characterized using JEOL JSM-6510 LV electron microscope operated at accelerating voltage 30 KV, with a magnification 10× up to 400.000×. For the SEM study, the samples were coated with gold to prevent scattering of the electron beam. The FTIR absorption spectra were recorded using the KBr pellet technique. A Mattson 5000 FTIR spectrometer, with a 2 cm −1 resolution, was used to obtain the spectra in the range 400 -4000 cm −1 at room temperature. In average 20 scans are accumulated to form the spectrum of each sample. 31 P NMR spectra of powdered samples were recorded with a spectrometer operating at 11.74T (Joel -500, Mansoura University). Pulses with 10 s delay time were used and about 500 scans are obtained.

31 P NMR Spectroscopy
As can be observed in Figure 2, it is interesting to compare the peak position  are larger compared to the cement based on the metal. In addition, the peak intensity is increased and shifted toward more negative direction (spectra d). The change of the chemical shift is considered not only due to changing of the valence state of the metallic cation but also due to change of coordination number of phosphors atoms in the corresponding matrix of GIC.

XRD Analysis
X-ray diffraction spectra of the as prepared glass sample are presented by Figure   3(a). As can be seen from this figure, a broad band in the range of 25˚ -40˚ of diffraction angles has been simply appeared. The broadening of this band can confirm the disordered structure of the base glassy material. Figure 3 [20]. This intense peak didn't appear in the spectra of the oxide glass, Figure 4(a). These changes may be considered due to the base-acid reaction which leads to degradation processes in material network [14] [20].

FTIR Spectroscopy
Increasing crystallization (as presented by XRD, Figure 3) is also evidenced from IR spectra of GIC containing distinguished types from metal-Phthalocyanine

Morphological Studies (SEM)
The GIC could simply be prepared by the method of acid-base reaction [14] [16] [17] [18] [19] [20]. Presence of metal-Phthalocyanine (PCs) as an essential counterpart of the present investigated GIC is necessary to control the synthesis and achieve their application [14] since they can play a role of chelating or com- The investigated morphology of the base glass is shown in Figure 6. It can observe that an extremely homogenous glass network is the dominant. On the other hand, formulating the glass powder with the acid successfully results in forming some types of structural species called pitted glass particles [14]. The latter has been embedded in a polysalt main glass matrix (Figure 7). But formulation  of GIC with Co-Phthalocyanine has formed a morphology containing bundles like species (Figure 8). The latter type is changed to more thinner, elongated and aligned rod-like species (Figure 9). The well-formed fibers are characterized with very lower thickness and much higher length, as shown in Figure 9. The well-formed nano fibers with more enhanced shapes may be recommended as important materials which have specific applications in tissue engineering Figure 8. GIC containing 0.8 mol% Co-Phthalocyanine, the morphology appears as bundles structure. Figure 9. GIC containing. 8 mol% Fe Phthalocyanine, the morphology appears as elongated fibers or wafers like structure. New Journal of Glass and Ceramics or bio scaffolds. This may because the good affinity of carboxylate or peptide moieties for cerium phosphates pecies enhances the structure to simultaneously incorporate the precursor phosphate moieties which is called (grafting, Figure   9) throughout the self-assembled nano fibrous. The latter can be used as templates hybrid biomaterials [25] [26] [27] [28].
Finally, we recommend that the acid-base reaction applied to get GIC has to be performed under relatively specific circumstances (pH around 4 -4.5) which may help in minimizing the strict characteristics of phosphates of reduced pH values (<1.5). Such cases are considered to have importance to offer an elongated CePO 4 fiber which can be reflected from SEM micrograp (Figure 9).