In this work, a highly sensitive electrochemical sensor based on Zn-doped copper gallium oxide@ordered mesoporous carbon (Zn-CuGaO₂@CMK-3) for signal amplification was successfully developed for the simultaneous detection of sunset yellow (SY) and tartrazine (TZ) in foods. Compared with CuGaO₂@CMK-3, Zn-CuGaO₂@CMK-3 offered enhanced conductivity and catalytic properties owing to the improved carrier density, which was beneficial to the electrooxidation of SY and TZ. Under the optimal testing conditions, the constructed Zn-CuGaO₂@CMK-3/GCE sensor offered a wide linear concentration range (0.25 to 100.00 μmol/L) for the detection of both SY and TZ. The limits of detection for SY and TZ were 0.044 μmol/L and 0.059 μmol/L, respectively. Recovery experiments were performed in milk, white vinegar and biscuit samples, yielding satisfactory recoveries (82.70%-114.80%). Furthermore, the sensor was successfully applied to the determination of the SY and TZ residues in two kinds of carbonated drinks, and the results were nearly consistent with those detected by the high performance liquid chromatography (HPLC) method (P＞0.05).

In this work, a novel electrochemical sensor based on covalent organic framework@carbon black@molecularly imprinted polydopamine (COF@CB@MPDA) was developed for selective recognition and determination of ciprofloxacin (CF). COF@CB@MPDA possessed good water dispersibility and was synthesized by the self-polymerization of dopamine under alkaline conditions in the presence of the COF, CB and CF. The high surface area COF enhanced the adsorption of CF, whilst CB gave the composites high electrical conductivity to improve the sensitivity of the proposed COF@CB@MPDA/GCE sensor. The specific recognition of CF by COF@CB@MPDA involved hydrogen bonding and van der Waals interactions. Under optimized conditions, the sensor showed a good linear relationship with CF concentration over the range 5.0 × 10^-7 M and 1.0 × 10^-4 M, with a limit of detection (LOD) of 9.53 × 10^-8 M. Further, the developed sensor exhibited high selectivity, repeatability and stability for CF detection in milk and milk powders. The method used to fabricate the COF@CB@MPDA/GCE sensor could be easily adapted for the selective recognition and detection of other antibacterial agents and organic pollutants in the environment.

Herein, a novel interference-free surface-enhanced Raman spectroscopy (SERS) strategy based on magnetic nanoparticles (MNPs) and aptamer-driven assemblies was proposed for the ultrasensitive detection of histamine. A core-satellite SERS aptasensor was constructed by combining aptamer-decorated Fe₃O₄@Au MNPs (as the recognize probe for histamine) and complementary DNA-modified silver nanoparticles carrying 4-mercaptobenzonitrile (4-MBN) (Ag@4-MBN@Ag-c-DNA) as the SERS signal probe for the indirect detection of histamine. Under an applied magnetic field in the absence of histamine, the assembly gave an intense Raman signal at “Raman biological-silent” region due to 4-MBN. In the presence of histamine, the Ag@4-MBN@Ag-c-DNA SERS-tag was released from the Fe₃O₄@Au MNPs, thus decreasing the SERS signal. Under optimal conditions, an ultra-low limit of detection of 0.65 × 10^-3 ng/mL and a linear range 10^-2–10⁵ ng/mL on the SERS aptasensor were obtained. The histamine content in four food samples were analyzed using the SERS aptasensor, with the results consistent with those determined by high performance liquid chromatography. The present work highlights the merits of indirect strategies for the ultrasensitive and highly selective SERS detection of small biological molecules in complex matrices.