Silver Nanoplates: From Biological to Biomimetic Synthesis

TLDR

The study reports the room‑temperature synthesis of single‑crystalline silver nanoplates using an extract from the green alga *Chlorella vulgaris*. Algal extract proteins act as both Ag⁺ reducers and shape‑directing agents, with custom peptides probing reduction kinetics and carboxyl groups influencing nanoplate formation. Hydroxyl groups on Tyr residues and carboxyl groups on Asp/Glu residues were identified as key for reduction and anisotropic growth, and a bifunctional tripeptide DDY‑OMe was designed to yield small, low‑polydispersity Ag nanoplates (>55 % yield).

Abstract

This paper describes the synthesis of single-crystalline Ag nanoplates using the extract of unicellular green alga Chlorella vulgaris at room temperature. Proteins in the extract were involved in the biological synthesis, providing the dual function of Ag ion reduction and shape-controlled synthesis of nanosilver. Hydroxyl groups in Tyr residues and carboxyl groups in Asp and/or Glu residues were further identified as the most active functional groups for Ag ion reduction and for directing the anisotropic growth of Ag nanoplates, respectively. The kinetics of Ag ion reduction in biological systems was discussed and probed by using custom-designed peptides. The results showed the Tyr content (the reduction source) and the content of Ag complexers (the reaction inhibitors, e.g., His and Cys) in the protein molecules as important factors affecting the reduction kinetics. The comprehensive system identification effort has led to the design of a simple bifunctional tripeptide (DDY-OMe) with one Tyr residue as the reduction source and two carboxyl groups in the Asp residues as shape-directors, which could produce small Ag nanoplates with low polydispersivity in good yield (>55%). The roles of the carboxyl groups in the formation of Ag nanoplates were also discussed.