In situ synthesis of silver nanocomposites on paper substrate for the pre-concentration and determination of iron(III) ions.

[Display omitted] • The silver nanocomposite is in situ synthesized on paper substrate. • Detection of Fe3+ is based on the aggregation of silver nanocomposite. • The sensitivity for Fe3+ detection can be tuned by the pre-concentration steps. • On site detection of Fe3+ can be realized with the aid of a smartphone. In this study, a green and novel method for in situ synthesis of silver nanocomposites on paper substrate was developed and used for the pre-concentration and determination of Fe3+. Silver nanocomposites were in situ synthesized using tannic acid as reducing and capping agent under a mildly alkaline condition. The mechanism for the Fe3+ detection is based on its coordination with the tannic acid present on the surface of the silver nanocomposites and the formation of aggregates. The colorimetric response between Fe3+ and tannic acid modified silver nanocomposites deposited on the surface of the paper substrate was collected by a smartphone followed by processing with Adobe Photoshop CS 5.1 software. Under the optimal conditions, the color response showed a good linear relationship with Fe3+ concentration in the range of 25.0–500.0 μM. The limit of detection for Fe3+ was calculated to be 10.0 μM. Finally, the developed smartphone assisted paper-based chemical sensor was used to detect Fe3+ in two lake water samples, and the recoveries are in the range of 83.5 %−106.7 %. The sensitivity for Fe3+ detection can be tuned through the pre-concentration steps based on the porous nature of the filter paper. The platform highlights the advantage of simplicity, ease of synthesis, fast response time, and low reagent/analyte volume requirement, which is suitable for point-of-use application in iron ions contamination, especially in the remote or resource-limited regions. [ABSTRACT FROM AUTHOR]