Bifunctional Photoelectrochemical Sensors Based on Co3O4/rGO/TiO2/NF Nanostructures for Depression Screening and Diagnosis

Fast-paced life brings great mental stress to many people and thus induces depression, and the level of L-tryptophan (L-Trp) in the human body is potentially related to the level of depression, and the detection of L-Trp content may become an auxiliary diagnostic modality. Therefore, in this article, Co3O4/reduced graphene oxide (rGO)/TiO2/NF composite electrodes were prepared on nickel foam (NF, surface area of 1 cm
$^{{2}}$
) by hydrothermal and calcination methods. We characterized the microscopic morphology of the composites and tested the electrochemical properties and concluded that the activity was high in L-Trp sensing at low concentrations, with detection limits calculated in the linear ranges of 0.01–30 and 30–
$80~\mu $
M of 0.004 versus
$0.006~\mu $
M, respectively, and sensitivities of 1469.861 and
$929.47~\mu \text {A}\cdot \mu $
M
$^{\text {-1}}\cdot \text {cm}^{\text {-2}}$
, respectively. The symmetric supercapacitor assembled with Co3O4/rGO/TiO2/NF has a specific capacitance of 1572.8 F/g at a current density of 2A/g, and an energy density of 17.6 Wh/kg at a high-power density of 2504.3 W/k. The stability of the symmetric supercapacitor after 5000 charging and discharging operations reaches 92%. Co3O4/rGO/TiO2/NF composites are not only beneficial to the development of medical and health care but also enrich the reserve of energy storage materials.