π-π nanoassembly of water-soluble metalloporphyrin of ZnTCPP on RGO/AuNPs/CS nanocomposites for photoelectrochemical sensing of hydroquinone
The RGO/AuNPs/CS/ZnTCPP nanocomposites were successfully prepared with reduced graphene oxide (RGO) loaded with Au nanoparticles (AuNPs) existed in chitosan (CS) and water-soluble zinc meso-tetra (4-carboxylphenyl) porphyrin (ZnTCPP) by π-π nanoassembly method and were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), 1 H NMR spectra and UV–vis absorption spectroscopy. The most important advantage of the RGO/AuNPs/CS/ZnTCPP nanocomposites was environmentally friendly. Indium tin oxide (ITO) electrode surface was modified with the RGO/AuNPs/CS/ZnTCPP nanocomposites exhibited a good photocurrent response at −0.2 V under whitelight of Xenon lamp illumination. The photocurrent response could be greatly increased by adding hydroquinone (HQ) to the solution. Electrons of ZnTCPP were excited from HOMO to LUMO by irradiating light. The photoexcited electrons injected into the RGO , and then transferred to AuNPs further to the ITO. Addition of HQ resulted in the enhanced photocurrent signal by acting as a sacrificial electron donor ; Thereby scavenged the photogenerated holes of the excited ZnTCPP and oxidized to benzoquinone (BQ). Based on the above interaction, detection of HQ was developed by a novel photoelectrochemical (PEC) sensor (S/N = 3) with a linear range from 5 to 300 nmol/L (r = 0.997) and detection limit of 0.5 nmol/L. Proposed biosensor is simple, rapid and this was successfully applied for the quantification HQ in the real sample matrices.
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