The book explores the fundamentals of nanochemistry and its role in modern science. It discusses how nanoscale materials exhibit unique properties due to quantum confinement, surface effects, and structural control. Various synthesis methods such as sol-gel, hydrothermal, and green synthesis are highlighted along with characterization techniques like XRD, SEM, TEM, FTIR, and UV-Vis. The focus is on doped and composite photocatalysts that enhance visible-light absorption, charge separation, and catalytic performance. Applications include environmental remediation, hydrogen production, CO2...