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Ternary nanocomposites including cellulose nanocrystals/silver nanohybrids (CNC-Ag) and biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were prepared by using solution casting. The effect of different AgNPs contents in the nanohybrids on crystallization ability and properties of PHBV was comprehensively investigated. Compared to binary PHBV/CNC nanocomposite, the ternary nanocomposites with high AgNPs contents showed larger improvements in the thermal stability, mechanical, barrier, overall migration and antibacterial properties. The property transitions at various AgNPs contents were due to transition of the nanohybrids induced PHBV crystallization ability (from single CNC nucleation to synergistic nucleation of CNC and AgNPs), and increased crystallinity without compromising the amounts of hydrogen bonds. Especially, the PHBV/CNC-Ag-1.7 showed the good barrier property and lower migration levels in food simulants, high antibacterial ratio of 99.9% and biocompatibility to human MG-63 cells, suggesting its potential application in food packaging related materials. [ABSTRACT FROM AUTHOR]

• Synthesis of bimetallic silver-gold NPs was realized in a cellulose dope. • The dissolved cellulose played as reductant and support matrix for the NPs. • Structure of the NPs was facially tuned by adjusting the feeding operations. • Correlation of bioactivity with nanostructure of the NPs was investigated. • Flexible cellulose decorated with the NPs endowed its efficient SERS activity. Introducing functional metal nanoparticles (NPs) into flexible substrate is being increasingly attempted to expand their application. Here, we extend the synthesis of cellulose to its unmodified dope achieving freestanding nanocomposite decorated with bimetallic Ag-Au NPs through the one pot reaction. In the procedure, cellulose chain not only acts as a reducing agent but also a biocompatible support for NPs with a mean size of 7.9–9.7 nm. Meanwhile, changing the addition order of Ag+ and AuCl 4 − generated different atom arrangement in the bimetallic NPs. Moreover, the correlation of bioactivity to NP atom arrangement was studied. The result revealed that the nanocomposite containing NPs with an ultrathin Ag-rich outermost shell around an Au-rich core showed better bactericidal ability while lower cytotoxicity. In addition, the nanocomposite exhibited a sensitive SERS property for determination of R6G with a high enhancement factor of 108. [ABSTRACT FROM AUTHOR]