Abstract Physical chemistry is one of the fundamental branches of chemistry that focuses on studying the physical properties of matter and its behavior at the molecular and atomic levels. Its development has played a crucial role in the emergence and advancement of nanotechnology. This article aims to highlight the role of physical chemistry in understanding and designing nanomaterials and to present the most important applications of nanotechnology in industrial, medical, environmental, and energy fields. Introduction In recent decades, nanotechnology has witnessed remarkable scientific progress. This field is concerned with the study and fabrication of materials with dimensions ranging from 1 to 100 nanometers. Physical chemistry has provided the theoretical and experimental foundations necessary to understand the phenomena occurring at the nanoscale, where materials exhibit physical and chemical properties that differ significantly from those of bulk materials. Role of Physical Chemistry in Nanotechnology Nanotechnology relies heavily on several core concepts of physical chemistry, including: Thermodynamics, which explains the stability and formation of nanomaterials. Chemical kinetics, which helps in understanding reaction rates and mechanisms during nanoparticle growth. Surface chemistry, as nanomaterials possess a high surface-to-volume ratio that strongly affects their chemical reactivity. Quantum mechanics, which is essential for interpreting the electronic and optical behavior of materials at the nanoscale. Physical Properties of Nanomaterials Nanomaterials exhibit unique physical properties such as: Enhanced catalytic activity. Improved electrical and optical characteristics. Altered melting points and thermal conductivity. These properties arise from quantum size effects and the increased surface area, both of which are extensively studied within physical chemistry. Preparation and Characterization Techniques Various methods are used to synthesize nanomaterials, including: Chemical reduction methods. Chemical vapor deposition. Sol–gel techniques. Characterization of nanomaterials depends on advanced physical techniques such as: Spectroscopic methods (UV–Vis, IR). Electron microscopy (SEM and TEM). X-ray diffraction (XRD). Applications of Nanotechnology Medical applications: targeted drug delivery, disease diagnosis, and advanced therapeutic techniques. Industrial applications: development of lightweight and high-strength materials. Environmental applications: water purification and removal of environmental pollutants. Energy applications: improving the efficiency of solar cells, batteries, and fuel cells. Conclusion It is evident that physical chemistry represents the scientific foundation upon which nanotechnology is built. Through its principles and analytical tools, physical chemistry has enabled scientists to understand nanoscale phenomena and develop innovative materials with advanced properties. With continued research and technological progress, physical chemistry is expected to play an even greater role in expanding nanotechnology applications and supporting sustainable development. Al-Mustaqbal University Ranked First among Iraqi Private Universities