Heatless synthesis of well dispersible Au nanoparticles using pectin biopolymer

• Alkali catalyzed pectin biopolymer was used to reduce Au ions to AuNPs.
• Small size spherical AuNPs were produced with size distribution of 2–16 depend on alkali type.
• Obtained AuNPs was well dispersed with PdI value of 0.24 and Zeta potential of −23.7 mV.
• The produced AuNPs achieved good stability with storage up to 5 months.

Due to its potency to utilize in enormous applications, preparation of nanogold is of interest. Moreover, getting of highly dispersed nanogold with small size is extremely needful in specific fields. Herein, Au nanocolloid was prepared using alkali catalyzed pectin biopolymer. Pectin was concurrently used as reductant for Au ions and stabilizer for the produced Au nanoparticles (AuNPs). Reducing sugars were evaluated in the colloidal solution reflecting the role alkali in catalytic degradation of pectin to produce much powerful reducing moieties. The obtained Au nanocolloid was monitored via changing in color, UV–visible spectral and transmission electron microscopy. Using of NaOH as strong alkali achieving rapid rate of degradation reaction, resulted in 0.45 g/L reducing sugars from 0.2 g/L pectin which produced AuNPs with mean size of 6.5 nm. In case of Na2CO3 which attained slow degradation rate led to, slightly low reducing sugar content (0.41 g/L), fabricated comparatively size of AuNPs (7.5 nm). In both cases, well distributed AuNPs was obtained with suitable stabilization up to 5 months and Na2CO3 exhibited higher stability. The current successful method used to produce small sized AuNPs with high dispersion is an innovative, one-step, easily, costless, energy saving and eco-friendly method.

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