Synthesis of 5'-GMP-mediated porous hydrogel containing β-FeOOH nanostructures: optimization of its morphology,...

The present manuscript reports 5'-GMP-mediated β-FeOOH nanostructures with varied morphologies ranging from nanorods to porous structures via the formation of spherical nanoparticles (NPs). For the optimized 5'-GMP-mediated β-FeOOH nanostructures (containing 2.5 × 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 5'-GMP, pH and the period of aging, which is clearly demonstrated by the ζ-potential measurements. Changing interactions in the hydrogel are clearly indicated by IR spectroscopy, where the functionalities of 5'-GMP (C[double bond, length as m-dash]O, -NH₂, -C[double bond, length as m-dash]N-, imidazole, pyrimidine, -C-O- of the sugar, PO₃ ^2-, sugar ring and P-O-5'-sugar) interact with β-FeOOH. Specific interactions of β-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-β-FeOOH nanohybrid at about pH 7.0, the low toxicity of β-FeOOH and the biocompatiblity of 5'-GMP suggests the potential of these nanostructures for biomedical applications.