Green synthesis of La2O3–LaPO4 nanocomposites using Charybdis natator for DNA binding, cytotoxic, catalytic, and luminescence applications

Abstract

Abstract A one-step biosynthetic pathway for the fabrication of La2O3–LaPO4 nanocomposites (NCs) was developed, employing Charybdis natator. The structure and phase changes of the NCs were confirmed, and their diverse applications were explored. The peaks at 206, 332, and 442 nm in UV-DRS studies confirmed the formation of La2O3–LaPO4 NCs. Fourier transform infrared spectral analysis revealed La–O stretching at 716 cm−1 and the presence of PO 4 3 − {\text{PO}}_{4}^{3-} bands at 532, 560, 578, and 618 cm−1. X-ray diffraction patterns showed a hexagonal phase of La2O3 with peaks at 2θ 11.04 and 28.57 and monoclinic LaPO4 phases at 2θ = 18.79 and 41.88. X-ray photoelectron spectroscopy data showed binding energy peaks at 836.04 and 852.77 eV, corresponding to 3d5/2 and 3d3/2 of the lanthanum. The average particle size from HR-TEM analysis was 28.95 nm after annealing at 800°C and SAED patterns confirmed their crystalline nature. The high affinity of the NCs towards ctDNA was established by a binding constant value of 2.08 (mg·mL−1)−1. Under UV exposure, 96% degradation efficiency for methyl orange within 120 min at pH 4 was displayed, with a rate constant of 2.72 × 10−2 min−1 affirming their photocatalytic potential. Their biocompatibility was assessed through MTT assay and luminescence characteristics were evaluated.