Polymers effects on synthesis of AuNPs, and Au/Ag nanoalloys: Indirectly generated AuNPs and versatile sensing applications including anti-leukemic agent

• Synthesis of polymers coated monodisperse AuNPs and Au/Ag nanoalloys.
• Polymers as size controlling agents/conferring stability to these nanocomposites.
• FRET analysis of anti-leukemic drug Doxorubicin through PEI–AuNPs.
• Sensing of PEI–Au/Ag nanoalloys on addition of halides (Cl−, Br-, I−).
• Fluorescence enhancement effects on PDDA protected AuNPs facilitate the detection of ascorbic acid.

Polymers either serve as shielding or capping agents to restrict the nanoparticle size. This study demonstrates the polymer depositions and their effects in synthesis and sharp stabilization of gold nanoparticles (AuNPs) and to develop gold/silver nanoalloys (Au/Ag nanoalloys). Effects of different polymers are tested to justify their role in synthesis and stability of phloroglucinol (PG) coated AuNPs and Au/Ag nanoalloys. Cationic and anionic i.e. [Polydiallyldimethylammonium]+ (PDDA), [Polyethyleneimine]+ (PEI), [Polystyrene sulfonate]2− (PSS) and neutral polymer Polychlorotriflouroethylene (PCTFE) produce praiseworthy stable AuNPs and Au/Ag nanoalloy. To prove polymer effects characterization protocols including UV–vis, Fluorescence (PL), IR and AFM imaging are performed to fully investigate the mechanism and size characteristics of these nanoparticles/nanoalloys. In this study sharp size controlling/sheilding effects were observed particularly with cationic polymers simply through the favorable electrostatic interactions with the terminal ends of PG Potent/significant detection of doxorubicin (DOX, an antileukemic agent) via fluorescence resonance energy transfer (FRET) between PEI shielded AuNPs (AuNPEI) and DOX was achieved upto 10 pM level, while PDDA protected AuNPs facilitated the detection of ascorbic acid based on fluorescence enhancement effects in wide range (10–200 nM) and with detection limit of 200 pM. Similarly sensing performance of PEI stabilized Au/Ag nanoalloys on addition of halides (Cl−, Br-, I−) is evaluated through red shifted SPR along with continuous increase in absorbance and also through AFM. Moreover the addition of halide ions also helped the regeneration of AuNPs by taking away silver from the Au/Ag nanoalloys enabling their detections upto subnanomolar levels.