This implies that the enhancement factor brought about by the AuNPs will be highest at this wavelength. As a result, after the conjugation of the AuNPs, the photocurrent is increased by more than eight times. As shown in Figures ) and (d), the theoretical near-field enhancement is more than 6-fold close to the particle surface, which is 50% higher compared to excitation by the red laser. Due to this significantly higher near-field enhancement at LSPR with green laser as compared to red-laser, a proportionately higher photocurrent increase (by a factor of eight) was also measured as shown in Figure (b). In addition, the PEC activity of AuNPs alone was also tested in the presence of HQ (Figure ) but no photocurrent response was observed, giving further evidence that AuNPs did not produce enough 1 O2 to oxidize the HQ molecule. activity by 27% for ZnPc and 30% for ZnPc-AuNPs at 1mM NaN3. Upon further increasing the concentration of NaN3 to 10 mM the PEC activity is suppressed by 70% and 46% for ZnPc and ZnPc-AuNPs, respectively. These experimental results are in accordance with our previous work, and ascertain that 1 O2 is the predominant reactive oxygen species that are produced by both ZnPc and ZnPc-AuNPs upon illumination. with ZnPc was found to be 2.61 µM L -1 with a sensitivity of 0.00991 A M -1 cm -2 . The LOD for HQ with ZnPc-AuNPs was observed as the lowest LOD of 0.018 µM which is ∼142 times lower than with ZnPc alone with a high sensitivity of 1.4883 A M -1 cm -2 . enhancement. At the resonance (~532 nm), the plasmonic enhancement is significantly higher than the enhancement away from the resonance (~659 nm). On the other hand, even with a relatively lower plasmonic enhancement, the photocurrent at 659 nm is still much larger due to the illumination very close to the Q band of the Pc. This work shows the potential of AuNPs-Pc conjugated systems realized by click chemistry to be used in 1 O2-based applications such as PDT, antimicrobial activity and the detection of phenolic compounds.