Hebeish, A. A., et al. Carbohydrate polymers 82.3 (2010): 933-941.
Challenge: Common methods for making concentrated stable silver nanoparticles (AgNPs) involve toxic chemicals which cause environmental and safety issues and have been found difficult to scale, which is a concern for many applications (e.g., antimicrobial textiles) that require high concentrations of AgNPs.
Solution: Carboxymethyl Cellulose (CMC) was used as a green reducing agent (convert Ag+ ions to Ag0 metal) as well as a stabilizing agent for the formed AgNPs. Synthesis of AgNPs was achieved using CMC with a specific Degree of Substitution (DS, 1.22-2.2) and Degree of Polymerization (DP), and with specific other key parameters including a pH of 12.5, temperature of 70°C, a reaction time of 60 min, and ratio of 0.017g AgNO3:0.3g CMC in 100ml total solution. It was found that a higher DS provided a greater electrostatic stabilization effect.
Preparation Details: In the optimized synthesis method, a particular CMC with specific DP (~350) and DS (1.22) was dissolved in water, pH adjusted to 12.5, then heated to 70°C and stirred, followed by addition of AgNO3 solution dropwise; real time formation of the AgNPs was indicated by the color change of the solution to yellow and also confirmed by UV-Vis spectroscopy.
Key Findings: By using CMC, a very high AgNP concentration of 1000 ppm was achieved, with a 86% reduction efficiency. The particles are small (10-25 nm), with narrow size distribution and spherical shape, and have greater colloidal stability, particularly with higher DS CMC.
Habib, Ahasan, et al. Materials 11.3 (2018): 454.