Multifunctional polymers were commonly ascribed as intelligent materials due to the presence of different functional groups on the polymeric skeleton which causes the high sensitivity to the interchanging of physicochemical conditions. Herein, under different temperatures, monitoring the pH response of lignin as intelligent nano-engineer (reducer and stabilizer) for synthesis of size and shape regulated silver nanoparticles (AgNPs), gold nanoparticles (AuNPs) & palladium nanoparticles (PdNPs) is systematically studied. The regulation of the particle size and stability of NPs were remarkably affected by acidity and basicity of the reaction medium at which they were prepared. TEM and zetasizer data showed that, highly size and shape regulated AgNPs & AuNPs is successively produced under acidic conditions with particle size of 13.8 and 5.7 nm, respectively. While basic conditions is more advisable in case of PdNPs to be produced with particle size of 4.5 nm. Catalytic performance of biphasic NPs in reductive discoloration of azo dye (reactive yellow dye 145) was followed the order of PdNPs > AuNPs > AgNPs. The half time for discoloration of dye with basic prepared NPs was dramatically decreased from 21.87 min for AgNPs and 18.34 for AuNPs to 1.45 min for PdNPs. (C) 2019 Elsevier Inc. All rights reserved.