## 3 Biosynthesis of Core Shell Nanoparticles
### Greener Synthesis of Core-Shell Nanoparticles Using Plants
The friendlier members of synthetic polymers are polyethylene glycol (PEG, increased solubility in water), polyvinyl alcohol (PVA, preventing the accumulation of particles), poly lactic acid (PLA, low cytotoxicity for humans) and alginate (stability improvement). For instance, the use of Stevia (sweetener) leaf extract, due to its high Steviol glycosidic content, culminates in glycoside surface coating of the synthesized surface of the nanoparticles. Consequently, for greener synthesis of nanoparticles, one can select an extract that maintains the desired functional groups on their surface, which in addition to reducing the metal precursors, can provide the avenue to attach the selected desired material on to the surface of ensuing biosynthesized NPs. The careful selection of the reaction conditions, bioresource and its inherent coating material can lead to desired custom applications of engineered NPs. Biomolecules, such as collagen protein [56], amino acids, antibodies, polypeptides, nucleic acids, avidin, and biotin, etc., can also cover the surfaces of NPs, thus making them targeted NPs. Nanoparticles coated with biomolecules invariably lead to their enhanced biocompatibility property. The strong conviction for the deployment of biological resources is due to their better biocompatibility, chemical stability, and solubility of synthesized NPs in water in contrast to conventional chemical methods. Greener synthetic methods can also reduce the burden of environmental pollution to some extent, thus enhancing the economic growth story via green chemistry [57]. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**No. ** & \begin{tabular}{c} **Bioresource** \\ **Derivatives** \\ \end{tabular}  & **Type** & **Ions Source** & **Size (nm)** & **Biosynthesis Detail** & **Ref. ** \\ \hline
1 & \multirow{4}{*}{Starch} & \multirow{4}{*}{Cu-Ag} & \( \begin{array}{c}\text{Cu(NO_{3})_{2}\cdot 3H_{2}O}\\ \text{and (AgNO_{3}) and ascorbic acid and}\\ \text{starch}\end{array} \) & \multirow{4}{*}{\(20\pm 5\)} & \multirow{4}{*}{\(20\pm 5\)} & To the starch solution, equal volume of metal salt solution and ascorbic acid (10\%, \(v/v\), of starch) were added and reaction was carried out under microwave at full power for 90 s. \\ \hline
2 & \multirow{4}{*}{Tryptophan} & \multirow{4}{*}{Au@Pd} & \( \begin{array}{c}\text{HAuCl}_{4}\text{and}\\ \text{PdCl}_{2}\end{array} \) & \multirow{4}{*}{\(\simeq\)60} & \multirow{4}{*}{\(20\pm 5\)} & Palladium precursor solution (5 mL) was introduced to the gold NP seed solution (5 mL) along with 1 mL of tryptophan solution. The resulting mixture was stirred for 2 h followed by intermittent sonication for 10 s at every 30 min. \\ \hline
3 & \multirow{4}{*}{Gelatin} & \multirow{4}{*}{Au-Ag} & \( \begin{array}{c}\text{HAuCl}_{4}\text{and}\\ \text{AgNO}_{3}\end{array} \) & \multirow{4}{*}{\(30\)} & \multirow{4}{*}{\(5.0\) mL of \(1.0\times 10^{-2}\) mol/L HAuCl\({}_{4}\) solution to 50 mL of (1.0 wt %) gelatin solution, followed by 5.0 mL of \(1.0\times 10^{-2}\) mol/L AgNO\({}_{3}\) with vigorous stirring at 50 \({}^{\circ}\)C for 6 h} \\ \hline
4 & \begin{tabular}{c} Plant tannin \\ (bay berry) \\ \end{tabular}  & \multirow{4}{*}{Au@Pd} & \( \begin{array}{c}\text{HAuCl}_{4}\text{and}\\ \text{PdCl}_{2}\end{array} \) & \multirow{4}{*}{\(12\pm 6\)} & \multirow{4}{*}{\(10.0\) mL of HAuCl\({}_{4}\)/PdCl\({}_{2}\) mixture with different molar ratios was mixed with 40.0 mL of BT solution (0.02 g). The resultant mixture was shaken at 30 \({}^{\circ}\)C} \\ \hline
5 & \multirow{4}{*}{Gallic acid} & \multirow