CdS "Q-state" semiconductor particles from 2 to 10 nm diameter were nucleated and grown in 10,12-nonacosadiynoic acid (NCDA) polymer Langmuir-Blodgett (LB) films deposited on ITO plates. The polymerization process through exposure to UV-Visible light resulted in formation of the "blue form" followed by the final "red form" after 60 min. X-ray photoelectron spectroscopy (XPS) measurements confirmed the deposition of the NCDA cadmium salt and the formation of the CdS particles after exposure to H2S(g) in the LB matrix. A study of the photoelectrochemical behaviour of these systems was conducted through polarisation current-voltage (I-V) curves in the range of 0 to -1000 mV (Standard Calomel Electrode-SCE). An average open-circuit voltage ( VOC) from -600 to -700 mV values was observed for photoelectrochemical (PEC) cells constructed for the undoped NCDA polymer LB film with 10 nm diameter CdS particles. The I-2-doped NCDA polymer film presented an increase in the conductivity compared with the undoped film but with a deterioration of stability of the PEC system.