Hydrogen peroxide (H₂O₂) detection in both liquid and gas phases has garnered significant attention due to its importance in various biological and industrial processes. Monitoring H₂O₂ levels is essential for understanding its effects on biology, industry, and the environment. Significant advancements in the physical dimensions and performance of biosensors for H₂O₂ detection have been made, mainly through the integration of fluorescence techniques and nanotechnology. These advancements have resulted in more sensitive, selective, and versatile detection systems, enhancing our ability to monitor H₂O₂ in both liquid and gas phases effectively. However, limited comprehensive reviews exist on the detection of vaporized H₂O₂, which is used in disinfection and the production of explosive agents, making its detection vital. This review provides an overview of recent progress in nanostructured fluorescence sensors for H₂O₂ detection, covering both liquid and gas phases. It examines various fluorescence-based detection methods and focuses on emerging nanomaterials for sensor development. Additionally, it discusses the dual applications of H₂O₂ detection in biomedical and non-biomedical fields, offering insights into the current state of the field and future directions. Finally, the challenges and perspectives for developing novel nanostructured fluorescence sensors are presented to guide future research in this rapidly evolving area.

Black phosphorus nanosheets (BPNS) are emerging two-dimensional (2D) materials with exceptional optical and electronic properties, making them promising candidates for a wide range of nanotechnology applications. Their distinctive structural, electronic, and optical characteristics, particularly their thickness-dependent direct band gap, which varies from approximately 0.3 eV in bulk black phosphorus to 2.0 eV in the monolayer, have been extensively investigated using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations. This review focuses on the anisotropic optical responses of BPNS, including their polarization-dependent linear absorption and reflection, as well as nonlinear optical phenomena such as saturable absorption and the Kerr effect. In addition, the potential applications of BPNS in solar cells, sensors, and biomedical devices are discussed, with particular emphasis on their tunable band gap and enhanced sensitivity. Their reported biodegradability and generally favorable biocompatibility in preclinical studies further support their potential in nanomedicine, although these properties depend on formulation, dose, and surface modification. Despite these promising properties, challenges related to large-scale synthesis and environmental stability remain. Addressing these limitations through scalable synthesis approaches and improved stability will be essential for translating the unique capabilities of BPNS into practical applications.