We have investigated the chemical synthesis of gelatin functionalized silver nanoparticles (AgNPs) and their physico-chemical characteristics for sensing of mercury (II) ions (Hg2+). Gelatin functionalized AgNPs were prepared by chemical reduction method. The colorimetric sensing of Hg2+ was carried out in three different phases including solution, hydrogel network and paper substrate. AgNPs tend to aggregate upon addition of Hg2+ and exhibit a color change from yellow to colorless due to aggregation of AgNPs and leads to the formation of Ag/Hg amalgam. This nanosensor probe exhibited good sensitivity for the detection of He with detection limit of (LOD) 25 nM. In addition, we have studied the sensing of Hg2+ using disposable paper strips and 3D hydrogel matrix. In both cases, the sensor exhibits similar characteristics with respect to sensitivity and selectivity for Hg2+ detection under optimized conditions. This gelatin functionalized AgNPs probe is highly versatile and promising for various applications including sensor, antimicrobial coatings, catalysis and food monitoring. (C) 2016 Elsevier Ltd. All rights reserved.