The development of three dimensional dendritic growth patterns of conductive polythiophene and its copper composite by electrochemical method from systems containing (A) thiophene, perchloric acid, acetonitrile and (B) thiophene, perchloric acid, cupric chloride and acetonitrile have been studied. Height of three dimensional hyper branched polymer aggregates is measured at different time of polymerization. Morphology and growth kinetic studies have been made and aggregates have been characterized by electrical conductivity, FT-IR, X-ray diffraction and TGA/DTG analysis. ESR and SEM-EDS studies confirm the presence of metal ion in the polymer composite. SEM studies show the formation of globular aggregates while TEM studies reveal the formation of nanosized polythiophene particles in the range 20-50 nm which increase on addition of copper salt. Solid-state potassium ion sensor with conductive polythiophene copper composite as novel matrix for assembling ion sensing membrane has been demonstrated. Cyclic voltammetric and amperometric studies show excellent electrocatalytic ability for H2O2 sensing at lower operating potential.