Present crisp and brief review is specifically focused on mechanism and role of optical properties of nano material in enhancement of absorptance or extinction coefficients from solar spectrum. By proper selection of size and shape along with optimum concentration, optimum absorptance can be achieved. This systematic study provides valuable information about various key nanomaterials and base fluids which are more specific in band splitting of spectrum, tunable to size, shape and particle volume concentration on optical properties. Based on simulation model and experimental observations performed by researchers, it is inferred that optical properties of nanofluids are function of type of material, size and shape. Base fluids also have influence on optical absorptance but it is a constant variable. By appropriate selection, morphological design of particle, efficient and suitable environment (design aspect of system) desired spectral absorptance and selective filtering can be achieved.