Using localized surface plasmon resonance (LSPR) from novel metal nanoparticles for spectrometry-based sensing have been widely investigated. However, sensitivity of conventional plasmonic spectrometry is not high enough for rapid and quantitative detection of molecules. Using LSPR in amperometric sensing is, therefore, considered to be a promising alternative, which may open new possibilities for rapid quantitative detection and fulfill portable sensing requirements by offering low fluid level detection and real-time feedback. However, progress in plasmonic amperometric sensing was slow because it is still challenging to fabricate ideal plasmonic platforms without suffering from powdered nanomaterials aggregation and performance degradation. In this work, a facile solution to these issues is developed using periodically patterned Au-TiO₂ heterostructures (Au nanorods on TiO₂ nanocavities, Au NRs@TiO₂) for photoelectrochemical sensor. Generation of plasmonic "hot electron" at Au/TiO₂ interfaces was investigated for an enhanced photoelectrochemical detection of glucose and lactose. These rationally designed Au NRs@TiO₂ patterned nanostructures possess enhanced sensitivities with a low detection limit of 1 μM (10 μM) and a high sensitivity of 812 μA mM^-1 cm^-2 (270 μA mM^-1 cm^-2) for glucose (lactose) detection, which are superior to other Au nanoparticle-based plasmonic sensing systems.