Fig 1.
Schematic diagram of molecular imprinted sensor preparation.
(a) Image of a mobile phone-based detection system including screen-printed electrodes, a miniature electrochemical workstation and a smartphone connected via bluetooth. (b) Schematic diagram of a molecularly-imprinted sensor preparation. (c) Internal structural changes of the elution step.
Fig 2.
GO parameter optimization diagram.
The original potassium ferricyanide curve without GO (black; a), the potassium ferricyanide curve after the original GO parameters (parameters of -1.6 - +0.6V) (red; b) and the potassium ferricyanide curve after the optimized GO parameters (parameters of -1.7 - +0.2V)(blue; c).
Fig 3.
Cyclic Voltammetry (CV) curves for different electrodes.
Bare electrode (bare SPCE)(black; a), GO modified post electrode (GO/SPCE)(red; b), GO and Au nanoparticle modified post electrode (Au/rGO/SPCE)(blue; c), chitosan polymerized glutaraldehyde cross-linked post electrode (CS/glutaraldehyde/SPCE)(green; d), molecularly imprinted sensor (Thiamethoxam-MIP/Au/rGO/SPCE)(purple; e), and non-molecularly imprinted sensor (N-Thiamethoxam-MIP/Au/rGO /SPCE) (CK)(yellow; f).
Fig 4.
Exchanges impedance analysis (EIS) curves for different electrodes.
Bare electrode (bare SPCE)(black; a), GO modified post electrode (GO/SPCE)(red; b), GO and Au nanoparticle modified post electrode (Au/SPCE)(green; c), Electrode after chitosan deposition (CS/SPCE)(blue; d), Glutaraldehyde crosslinked electrode (glutaraldehyde/SPCE)(wathet; e), molecularly imprinted sensor (Thiamethoxam-MIP/Au/rGO/SPCE)(purple; f).
Fig 5.
Electron microscopic analysis of each electrode.
(A) The bare electrode surface of screen printed carbon electrode. (B) The electrode surface after graphene oxide (Go) modification (C) The electrode surface after chloroauric acid modification. (D)The electrode surface after chitosan deposition.(E) The electrode surface after glutaraldehyde crosslinking. (F) The electrode surface of molecularly imprinted sensor after elution.
Fig 6.
Comparison of commercial electrochemical workstations and portable sensors for smartphone platforms.
(A) DPV curves of molecular imprinting sensor on electrochemical workstation for different concentrations of thiamethoxam. (B) DPV curves of portable molecular imprinting sensor based on cell phone for different concentrations of thiamethoxam. (C) Inhibition rate curves of molecular imprinting sensor on electrochemical workstation for different concentrations of thiamethoxam. (D) Inhibition rate curves of portable molecular imprinting sensor based on cell phone for different concentrations of thiamethoxam. Note: 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 are different concentrations of thiamethoxam, where the concentration units are μmol/L.
Fig 7.
Results of the repeatability analysis of the sensor.
Fig 8.
Anti-interference DPV analysis.
(A) DPV curve of imidacloprid as interfering substance. (B) DPV curve of acetamiprid as interfering substance. (C) DPV curve of dinotefuran as interfering substance. (D) DPV curve of clothianidin as interfering substance. For the curves in the above four figures: Original DPV curve (black;a), DPV curve after immersion in 1μmol/L thiamethoxam solution (stock solution)(red; b), DPV curve after immersion in 1μmol/L thiamethoxam mixed with 5μmol/L Interfering substance (blue; c), DPV curve after immersion in 1μmol/L thiamethoxam mixed with 10μmol/L Interfering substance (green; d), and DPV curve after immersion in 1μmol/L thiamethoxam mixed with 20μ mol/L Interfering substance (purple; e).
Table 1.
Results of interference immunity analysis of sensors.
Table 2.
Analytical results of thiamethoxam residues in actual samples.