The most effective method for synthesizing metal nanoparticles with a size range of 10-50 nm using environmentally friendly and cost-effective approaches is the green synthesis method. This method utilizes plant extracts, microorganisms, or biopolymers as reducing and stabilizing agents for the synthesis of metal nanoparticles.Green synthesis has several advantages over traditional methods, such as chemical reduction and physical methods. It is eco-friendly, cost-effective, and does not require high temperatures, pressures, or toxic chemicals. Additionally, the use of biological materials provides better control over the size and shape of the nanoparticles, which is crucial for their applications in various fields.Some common green synthesis methods include:1. Plant-mediated synthesis: In this method, plant extracts containing various phytochemicals act as reducing and stabilizing agents for metal ions. The choice of plant species, extract concentration, and reaction conditions can be optimized to obtain the desired size and shape of nanoparticles.2. Microbial-mediated synthesis: Microorganisms, such as bacteria, fungi, and algae, can reduce metal ions to form nanoparticles. The size and shape of the nanoparticles can be controlled by varying the microbial species, culture conditions, and reaction parameters.3. Biopolymer-mediated synthesis: Biopolymers, such as chitosan, alginate, and gelatin, can serve as reducing and stabilizing agents for metal ions. The choice of biopolymer, its concentration, and reaction conditions can be optimized to obtain the desired size and shape of nanoparticles.Overall, the green synthesis method is an effective and environmentally friendly approach for synthesizing metal nanoparticles with a size range of 10-50 nm.