Nanostructured Semiconductors for High-Sensitivity Solid-State Sensors: A Physics-Oriented Review

­­­­­­­­­Abstract Nanostructured semiconductor materials have emerged as key building blocks for next-generation solid-state sensor technologies due to their size-dependent electrical, optical, and surface-dominated properties. Nanoscale dimensional reduction introduces quantum confinement effects, high surface defect density, and enhanced surface-to-volume ratio, leading to significant modulation of charge carrier transport and surface interaction mechanisms. These effects result in improved sensitivity, selectivity, response–recovery characteristics, and lower detection limits compared to conventional bulk semiconductor sensors. This review presents a physics-oriented analysis of major nanostructured materials including ZnO, SnO₂, TiO₂, and graphene-based composites for high-sensitivity sensing applications. Solid-state electronic principles such as band structure modification, surface states, depletion layer modulation, and interfacial charge transfer are emphasized to explain sensing mechanisms. Key challenges related to selectivity, stability, and large-scale integration are discussed, along with emerging strategies such as hybrid material systems and heterostructure engineering. The review provides a coherent framework for developing intelligent, miniaturized, and sustainable solid-state sensor technologies.