Sonochemical synthesis is becoming a popular method of preparing various nanomaterials, including metals, carbons, oxides, and chalcogenides. This method is relatively cheap and responds to the challenges of green chemistry as it typically does not involve high temperatures, high pressures, inert atmospheres, or long reaction times in comparison to other conventional methods. The utilization of ultrasound in synthesis makes the elimination of toxic solvents possible, as well as the execution of the synthesis without the use of reducing and stabilizing agents, while receiving products with the same or even better properties. The application of ultrasound allows for the synthesis of various nanomaterials with different properties for use in fields such as catalysis, electrochemistry, medicine, and biosensors. The final product is influenced by multiple variables such as temperature, pH, reagents, capping agents, time of reaction, and the addition of dopants.

Nanomaterials are the subject of an increasingly growing number of investigations. Due to their unique characteristics, they have found wide applications in disciplines like electronics, catalysis, and medicine. In the field of catalysis, one can mention their application for the photocatalytic removal of various contaminants, both inorganic (e.g., toxic chromates) and organic (pesticides, dyes, pharmaceuticals, etc.). Such applications are important because the contamination of the natural environment is constantly growing. Distinct nanomaterials, such as quantum dots, have been widely utilized for photo-based wastewater treatment, but the current research activity is directed toward investigations of combined nanometric heterostructures which exhibit additional and useful properties in comparison with standalone components. However, the preparation of such heterostructures may be demanding and more complicated than that of standalone components, and the mechanism of improved photocatalytic performance may vary among different types of heterostructures. The aim of this review is to fill the existing gap in the literature and present mechanisms (type-II, Z-scheme, and S-scheme), methods of preparation (sol–gel, hydrothermal, solvothermal, sonochemical methods, and others), and applications of nanometric heterostructures in the photocatalytic degradation of organic pollutants.