Conducting polymers represent an important class of functional organic materials for next-generation electronic and optical devices. Advances in nanotechnology allow for the fabrication of various conducting polymer nanomaterials composites synthesis with the different methods. Conducting polymer nanomaterials composites featuring high surface area, small dimensions, and exhibit unique physical and chemical properties therefore they have been widely used for various purposes such as, they can be used as photocatalyst The present research work is divided in to two parts. First part of thesis deals with the synthesis of three different series of Polyaniline (PANI) composites in which two are Zr-Co-substituted nickel ferrite with formula (NiFe1.2 Zr0.4 Co0.4 O4) and (NiFe Zr0.5 Co0.5 O4), one with MnAl-substituted multiferroics with formula (BiAl0.3Mn0.3Fe0.4O3). The synthesis of composites of Polyaniline (PANI) is carried out with the variation of nanoparticles amount (12.5, 25, 37.5, and 50% w/w). These composites are characterized by different techniques such as Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), UV/Visible, X-ray photoelectron spectrometry (XPS), and scanning electron microscopy (SEM). The structure of PANI/nanomatrials composites was confirmed by XRD analysis while surface morphology was investigated by SEM analysis. The FTIR spectroscopy is used to identify their functional groups present in PANI/NPs composites and the shifting of the peaks has been found towards higher wave number side which exhibits the interaction between the polymer and the nanoparticles in synthesized photocatalyst. In UV/ Vis study blue shift has been found which give the information about the interaction between ferric ions of nanomaterial with nitrogen atom of PANI, shortening in the conjugation length, and coordinating complex formation. The XPS analysis has been carried out to determine oxidation states of the elements present in the synthesized composites materials. In the second part these synthesized PANI/NPs are used as photocatatlyst against toxic dyes such as Methylene Blue (MB) and Methyl Orange (MO). These synthetic dyes are most widely used in textile and leather tanning industries. These dyes are highly colored, toxic, and carcinogenic in nature. These effluents released from the textile and leather tanning industries containing 1mg/L of dye are enough to impart color to the water thus making it unpotable for daily use. The technology used to treat dyes is based on physical, chemical, and biological methods. Precipitation, coagulation, filtration, floatation, electrochemical degradation, and advanced oxidation techniques are considered as chemical methods. Adsorption, reverse osmosis, and ultrafiltration are treated as physical methods. Photochemical irradiation of toxic dyes in presence of a photocatalyst is one of the alternative methods developed recently. Theses composites are then used for the photoelectric degradation of methylene blue and methylene orange from aqueous media under UV light. Effect of reaction time, NPs concentration and the kinetics is studied. It has been found that the degradation of methylene blue and methylene orange increase with the increase in nanoparticles concentration in the composite material. This degradation rate has been found to be low for methylene blue which is cationic dye as compare to the methylene orange. The photoelectric degradation for both dyes is also examined under the similar conditions of UV light by pure PANI and nanoparticles. The degradation rate has been found very low because recombination of electron-holes occurs in pure PANI and pure nanomaterial very comfortably as compare to composites in which it is strictly prohibited. The NPs amount present in the composite shows remarkable influence on the degradation efficiency. Through several groups of univariate experiments, the optimum PANI/ NPs composite dosage of the photolysis process is found to be 0.2g at 40ml of 10-5M solution of both dyes. The photolysis process is relatively fast at the initial stage up to 30 minutes and later it become slow, moreover the degradation of both dyes is in accordance with the first-order kinetic equation.