A new two-dimensional material, few-layer black phosphorus (FL-BP), has been successfully produced in large quantities through liquid phase exfoliation in solvents like N-cyclohexyl-2-pyrrolidone (CHP). This method allows for the creation of nanosheets with controllable size and observable photoluminescence, which are stable in CHP due to a protective solvation shell. Experiments and simulations show that degradation occurs primarily at the nanosheet edges, with the rate and extent of reaction depending on water and oxygen content. These nanosheets have potential applications in ultrafast saturable absorbers, gas sensors, and composite reinforcement. FL-BP, a 2D material derived from black phosphorus, has a direct bandgap that varies with nanosheet thickness, making it attractive for electronics and optoelectronics. It has been studied for applications such as transistors, photodetectors, and solar cells. Beyond electronics, FL-BP shows potential in gas sensing and thermoelectrics. Liquid-exfoliated FL-BP nanosheets are inherently processable and can be easily formed into composites, coatings, or films, facilitating their use in various applications. The stability of FL-BP in CHP is attributed to the solvation shell protecting the nanosheets from reacting with water or oxygen. However, degradation occurs when water or oxygen is added, primarily at the nanosheet edges. The reaction mechanism involves acid-base disproportionation at the edges, leading to the formation of defective structures and phosphorous compounds. This degradation is slower in CHP compared to other solvents, allowing for practical applications. FL-BP nanosheets have been demonstrated to be effective in gas sensing, showing resistance changes when exposed to ammonia. They also exhibit strong nonlinear optical properties, making them suitable for use as ultrafast saturable absorbers in mode-locking lasers. Additionally, FL-BP can act as a reinforcing filler in composites, improving mechanical properties such as tensile strength and toughness. The study highlights the potential of FL-BP for a wide range of applications, emphasizing the importance of using appropriate solvents to maintain stability. The results suggest that FL-BP can be produced in large quantities under ambient conditions, which is crucial for its development in various fields. The findings also indicate that the degradation of FL-BP primarily affects the size of the nanosheets rather than their fundamental properties, making them suitable for many applications.A new two-dimensional material, few-layer black phosphorus (FL-BP), has been successfully produced in large quantities through liquid phase exfoliation in solvents like N-cyclohexyl-2-pyrrolidone (CHP). This method allows for the creation of nanosheets with controllable size and observable photoluminescence, which are stable in CHP due to a protective solvation shell. Experiments and simulations show that degradation occurs primarily at the nanosheet edges, with the rate and extent of reaction depending on water and oxygen content. These nanosheets have potential applications in ultrafast saturable absorbers, gas sensors, and composite reinforcement. FL-BP, a 2D material derived from black phosphorus, has a direct bandgap that varies with nanosheet thickness, making it attractive for electronics and optoelectronics. It has been studied for applications such as transistors, photodetectors, and solar cells. Beyond electronics, FL-BP shows potential in gas sensing and thermoelectrics. Liquid-exfoliated FL-BP nanosheets are inherently processable and can be easily formed into composites, coatings, or films, facilitating their use in various applications. The stability of FL-BP in CHP is attributed to the solvation shell protecting the nanosheets from reacting with water or oxygen. However, degradation occurs when water or oxygen is added, primarily at the nanosheet edges. The reaction mechanism involves acid-base disproportionation at the edges, leading to the formation of defective structures and phosphorous compounds. This degradation is slower in CHP compared to other solvents, allowing for practical applications. FL-BP nanosheets have been demonstrated to be effective in gas sensing, showing resistance changes when exposed to ammonia. They also exhibit strong nonlinear optical properties, making them suitable for use as ultrafast saturable absorbers in mode-locking lasers. Additionally, FL-BP can act as a reinforcing filler in composites, improving mechanical properties such as tensile strength and toughness. The study highlights the potential of FL-BP for a wide range of applications, emphasizing the importance of using appropriate solvents to maintain stability. The results suggest that FL-BP can be produced in large quantities under ambient conditions, which is crucial for its development in various fields. The findings also indicate that the degradation of FL-BP primarily affects the size of the nanosheets rather than their fundamental properties, making them suitable for many applications.