*2.1. Green Synthesis of Nd2Se<sup>3</sup> NPs*

The reaction mixture (3 mL), containing NdCl<sup>2</sup> (1 mM), SeCl<sup>4</sup> (1 mM), NaNO<sup>3</sup> (5 mM), 100 <sup>µ</sup>g (2.66 <sup>×</sup> <sup>10</sup>−<sup>2</sup> mM) of synthetic peptide having the amino acid sequence (Glu-Cys)n-Gly, 1.0 mM α-NADPH (a reduced form of nicotinamide adenine di-nucleotide phosphate sodium salt), and 1.66 U of nitrate reductase, was incubated under anaerobic conditions at 25 ◦C. After 12 h, the reaction mixture was exposed to UV-Vis spectrophotometric measurements. On completion of the reaction, Nd2Se<sup>3</sup> NPs were subjected to treatment with 50% *v*/*v* of ethanol to eliminate unbound proteins and were then used for further characterization. Eventually, NPs were precipitated at 30,000 g for half an hour.
