Understanding of vibrational and thermal behavior of bio-based doped alginate@nickel cross-linked beads: A combined experimental and theoretical study

Herein, in-situ doping of Alginate-Nickel (Alg@Ni) beads by strontium (Sr) and indium (In) was realized via alginate gelation method based on metal cation cross-linking. Three gel beads named Alg@Ni, Alg@Ni/Sr and Alg@Ni/In were prepared by alginate cross-linking of Ni²⁺ cation, Ni²⁺/Sr²⁺ cations and Ni²⁺/In³⁺, then characterized by Fourier transformed spectroscopy (FTIR), thermal gravimetric (TGA) and differential scanning calorimeter analyses (DSC) to exhibit different properties of gel beads. As a result, FTIR confirmed that the presence of Sr or In dopant could affect Alg@Ni vibrations. Moreover, the thermal stabilities of Alg@Ni beads were improved after Sr and In doping. Besides, theoretical studies were employed to gain more insight into experimental results. In this context, Alg@M (M= Ni²⁺, Sr²⁺and In³⁺) complexes were studied individually by using density theory functional (DFT) calculations. The electronic and chemical properties of each complex were calculated and discussed. The correlation between the thermal stability and molecular structure of the Alg@Ni, Alg@Sr, and Alg@In was evaluated using ab initio molecular dynamic (MD) simulation.