Sol-gel hydrothermal synthesis and enhanced biosensing properties of nanoplated lanthanum-substituted bismuth titanate microspheres

Nanoplated lanthanum-substituted bismuth titanate (Bi(3.25)La(0.75)Ti(3)O(12), BLTO) microspheres constructed with tens of BLTO nanoplates were synthesized by a sol-gel hydrothermal method. Using nanoplated BLTO microspheres, a novel third-generation H(2)O(2) biosensor was fabricated with loading of myoglobin (Mb) and chitosan (Chi). Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) measurements reveal that partial Bi ions of bismuth titanate (BTO, Bi(4)Ti(3)O(12)) are successfully substituted with La ions by the sol-gel hydrothermal method. UV-visible (UV-vis) and Fourier-transform infrared (FTIR) spectra show that Mb encapsulated in the Mb-Chi-BLTO film can retain its bioactivity well. Comparative experiments witness that the Mb-Chi-BLTO biosensor, compared with the Mb-Chi-BTO biosensor, not only has enhanced direct electron-transfer capacity (e. g., stronger redox peak currents (approximately 3-fold) and a larger heterogeneous electron-transfer rate constant of 12.8 +/- 3.3 s(-1)), but also exhibits a wider linear response to H2O2 in the concentration range of 2-490 mu M, higher sensitivity (88 mA cm(-2) M(-1)), a lower Michaelis-Menten constant (0.55 mM) and detection limit (0.14 mu M), a shorter response time (2.8 s), and better reproducibility and stability. These results imply that La doping greatly improves electrochemical and electrocatalytic properties of the Mb-Chi-BLTO biosensor, which will open up a new idea for the design of third-generation electrochemical biosensors, and the BLTO-based biosensors are also expected to find potential applications in many areas such as clinical diagnosis and food and environmental detection.