Spherical citrate stabilized AuNPs were synthesized using the well-known Turkevich method. The AuNPs were further functionalized with azidothiol linker. For the coupling of AuNPs with Pc, the click reaction was chosen due to the high yield of the product. The schematic illustration of the coupling of AuNPs with ZnPc via click chemistry is shown in scheme 1. The ZnPc-AuNPs conjugate was characterized thoroughly using ultraviolet-visible (UV-Vis), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and x-ray diffraction (XRD). The 1 O2-based PEC activity of the ZnPc-AuNPs conjugate was tested in an organic solvent (methanol) and the plasmonic enhancement of the 1 O2 generation by Pcs was demonstrated by a complementary experimental and theoretical investigation. The 1 O2 quantum yield of ZnPc alone and ZnPc clicked with AuNPs was measured using an indirect method, and a significant increase in the photocatalytic 1 O2 production was observed for ZnPc-AuNPs due to a synergistic effect between the plasmon resonance of AuNPs and ZnPc which subsequently enhances the PEC activity towards the sensing of hydroquinone (HQ). Scheme 1. Schematic representation of coupling of ZnPc to AuNPs via click chemistry approach in the presence of Cu(I) catalyst. Characterization. For the UV-Vis spectroscopy of AuNPs and Pcs, a Shimadzu UV 2550 spectrophotometer was used. Attenuated transmittance reflection-Fourier transform infrared (ATR-FTIR) spectra were collected in the range of 4000 and 400 cm -1 using a Bruker Alpha II machine with a DTGS detector. For each sample, 128 scans were accumulated with a resolution of 4 cm -1 .