In-situ interaction of nano-PbS with gelatin

Abstract

Water-soluble gelatin-PbS bionanocomposites (BNCs) were synthesized via a facile one-pot chemical reaction method at pH 7.40. The samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis absorption spectra (UV-vis), Fourier transform infrared spectra (FT-IR) and circular dichroism (CD). FT-IR data were used to envisage the binding of PbS particles with oxygen atoms of carbonyl groups of gelatin molecule. The possible integration mechanism between gelatin and PbS was discussed in detail. The effect of Pb2+ and PbS on the conformations of gelatin has also been analyzed by means of UV-vis, CD and FT-IR spectra, resulting in less α-helix content and more open structures (β-sheet, β-turn, or expanded). A new formula to calculate the association constant was proposed according to the relationship between the absorbance of gelatin-PbS BNCs and the free concentration of PbS, and apparent association constants K (298/303/308 K: 3.11/2.00/1.60 × 106 mol/L) at three different temperatures were calculated based on this formula. Thermodynamic parameters such as ΔGθ, ΔHθ and ΔSθ were also determined. The results of the thermodynamic investigations indicated that the reaction was spontaneous (ΔGθ < 0), and enthalpy-driven (ΔHθ < 0).