Synthesis of 5′-GMP-mediated porous hydrogel containing β-FeOOH nanostructures: optimization of its morphology, optical and magnetic properties

The present manuscript reports 5'-GMP-mediated b-FeOOH nanostructures with varied morphologies ranging from nanorods to porous structures via the formation of spherical nanoparticles (NPs). For the optimized 50-GMP-mediated b-FeOOH nanostructures (containing 2.5 x 10(-3) mol dm-3 of 5'-GMP), the freshly prepared colloidal solution contained nanochains consisting of spherical NPs with an average diameter of 8 nm as measured by TEM, which upon aging produced porous hydrogels. Similar morphological changes were also evidenced by AFM. The change in morphology is controlled by the concentration of 50-GMP, pH and the period of aging, which is clearly demonstrated by the z-potential measurements. Changing interactions in the hydrogel are clearly indicated by IR spectroscopy, where the functionalities of 50-GMP (C] O, -NH2, -C] N-, imidazole, pyrimidine, -C-O-of the sugar, PO32-, sugar ring and P-O-50-sugar) interact with b-FeOOH. Specific interactions of b-FeOOH through the N and P of 5'-GMP are also supported by XPS studies. These nanostructures exhibit superparamagnetism at room temperature, exhibiting a magnetization of 3.2 emu g(-1), which upon the formation of the hydrogel is increased to 4.8 emu g(-1). The superparamagnetic behavior is retained by these nanostructures in the hydrogel up to < 50 K. The observed morphology and stability of the 5'-GMP-bFeOOH nanohybrid at about pH 7.0, the low toxicity of beta-FeOOH and the biocompatiblity of 5'-GMP suggests the potential of these nanostructures for biomedical applications.