Abstract:

BACKGROUND: Studieds about the synthesis and formation mechanism of bionanocomposites can provide theoretical basis for the design and wide application of inorganic/organic composites in biomedical area.
OBJECTIVE: To synthesize water-soluble PbS/gelatin micro-nano biocomposites at pH value of 7.40, and to study the intergration mechanism of PbS particles in the macromolecules of gelatin.
METHODS: The water-soluble PbS/gelatin micro-nano biocomposites were synthesized via one-pot chemical route involving the reaction of Pb²⁺ with S²⁻ in gelatin aqueous solution at pH value of 7.40. The particle shape, size and spectral quality of samples were characterized by scanning electron microscopy, dynamic light scattering, UV-vis spectroscopy and Fourier transform infrared spectroscopy.
RESULTS AND CONCLUSION: Scanning electron microscopy images showed that the morphologies of PbS particles were mainly irregular polyhedrons and olive-shape in the lower and higher concentration of Pb²⁺, respectively. Dynamic light scattering results indicated that the average particle sizes of PbS/gelatin micro-nano biocomposites were 75, 91 and 109 nm in the presence of 2.0×10^-5, 8.0×10^-5 and 2.0×10^-4 mol/L of Pb²⁺, respectively. And they showed an obvious quantum confinement effect. Based on the experimental results, the possible formation mechanism is proposed as follows: there is a main interaction between the Pb²⁺ ions and the ketonic oxygen on the peptide chain of gelatin macromolecules, which causes the gelatin macromolecules conformation changed from α-helix to β-sheet for the oriented nucleation of PbS; and then the S²⁻ is combined with Pb²⁺ to form PbS nanoparticles. The PbS/gelatin micro-nano biocomposites showed a better stability in aqueous solution, owing to gealtin polypeptide chain coating on the surface of PbS nanoparticles.