New Titanium Dioxide-Based Heterojunction Nanohybrid for Highly Selective Photoelectrochemical–Electrochemical Dual-Mode Sensors

A new titanium dioxide (TiO₂)-based heterojunction nanohybrid (HJNH) composed of TiO₂, graphene (G), poly[3-aminophenylboronic acid] (PAPBA), and gold nanoparticles (Au NPs) was synthesized and designated as TiO₂(G) NW@PAPBA-Au HJNH. The TiO₂(G) NW@PAPBA-Au HJNH possesses dual-mode signal photoelectrochemical (PEC) and electrochemical transduction capabilities to sense glucose and glycated hemoglobin (HbA1c) independently. The synthesis of the HJNH material involved two sequential stages: (i) simple electrospinning synthesis of G-embedded TiO₂ nanowires [TiO₂(G) NWs] and (ii) one-step synthesis of Au NP-dispersed PAPBA nanocomposite (NC) in the presence of TiO₂(G) NWs. The as-synthesized TiO₂(G) NW@PAPBA-Au HJNH was characterized by field emission scanning electron microscopy, field emission transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared, thermogravimetric analysis, and UV-visible diffuse reflectance spectroscopy. A PEC platform was developed with TiO₂(G) NW@PAPBA-Au HJNH for the selective detection of glucose without any enzyme auxiliary. The PEC glucose sensor presents an acceptable linear range (from 0.5 to 28 mM), good sensitivity (549.58 μA mM⁻¹ cm⁻²), and low detection limit (0.11 mM), which are suited for diabetes glucose monitoring. Besides, the boronic acid groups in PAPBA were utilized as a host to capture HbA1c. We fabricated the electrochemical HbA1c sensor based on monitoring the electrocatalytic reduction current of hydrogen peroxide produced by HbA1c tethered to the sensor probe. The amperometric electrochemical sensor for HbA1c exhibited linear responses to HbA1c levels from 2.0 to 10% (with a detection limit of 0.17%). Notably, the performances of the fabricated glucose and HbA1c sensors are superior in the dual-signal transduction modes as compared to the literature, suggesting the significance of the newly designed bifunctional TiO₂(G) NW@PAPBA-Au HJNH.