Gold Nanoparticles Capped With Schiff Base Enable Optical Silver Ion Detection

Gold nanoparticles capped with a specialized Schiff base provide dual-mode optical sensing for the detection of silver ions in analytical samples.

In the study, the Schiff base 2,2’-((1E,1’E)-((1,2-diphenylethane-1,2-diylidene)bis(hydrazine-2,1-diylidene))bis(methaneylylidene))bis(4-nitrophenol), designated DPHNP, was utilized as a capping reagent to synthesize the gold nanoparticle composite DPHNP@AuNPs (L).

The synthesized nanocomposite probe was systematically characterized using spectroscopic, microscopic, and computational methods to evaluate its structural and functional properties.

Upon exposure to silver ions (Ag+), the probe produced pronounced colorimetric and fluorescent responses driven by coordination-induced alterations in electronic transitions and plasmonic properties.

Analytical evaluations revealed a colorimetric detection limit of 1.56 × 10−6 M with a binding constant of 2.7 × 106 M−1, while the fluorometric assay achieved a detection limit of 2.60 × 10−6 M and a binding constant of 1.0 × 104 M−1.

The proposed sensor demonstrated high recovery rates for determining silver ions in diverse food and water samples, showing notable selectivity, reversibility, and tolerance to interfering ions alongside antioxidant and antibacterial properties.

The investigation focused on employing the Schiff base DPHNP as a capping reagent during the synthesis of gold nanoparticles to construct an integrated, dual-mode optical sensing system. The researchers thoroughly characterized the resulting DPHNP@AuNPs (L) probe through spectroscopic, microscopic, and computational methods to evaluate its properties. Upon exposure to silver ions (Ag+), the nanocomposite probe produced strong colorimetric and fluorescent responses driven by coordination-induced alterations in electronic transitions and plasmonic properties. This dual-mode operational approach enables two complementary optical readouts for detecting the target analyte within a single sensing platform.

Quantitative analytical evaluations established clear performance parameters for each optical detection mode under study. For the colorimetric assay, experimental testing demonstrated a limit of detection of 1.56 × 10−6 M paired with a binding constant of 2.7 × 106 M−1. In comparison, the fluorometric test yielded a limit of detection of 2.60 × 10−6 M and an associated binding constant of 1.0 × 104 M−1. These reported measurements reveal distinct differences between the two optical modalities, with the colorimetric test displaying a lower numerical detection limit and a substantially higher binding constant than the fluorometric test for the optical recognition of silver ions. The quantification confirmed that both channels offer sensitive optical responses with distinct binding affinities.

To evaluate practical analytical utility, the proposed sensing platform was applied to the determination of silver ions in diverse real-world sample matrices. The experimental results demonstrated high recovery values when analyzing silver ions across various food and water samples. Alongside these recovery measurements, analytical evaluations indicated that the sensor exhibited good selectivity for silver ions, maintained notable tolerance against interfering ions that might otherwise disrupt measurements, and showed reversibility, confirming the operational reliability of the probe in challenging analytical conditions.

Beyond its primary optical detection capabilities, the synthesized DPHNP@AuNPs nanocomposite demonstrated notable biological activity during experimental evaluation. Specifically, the material exhibited both antioxidant and antibacterial properties, establishing it as a multifunctional composite. Based on this dual combination of optical sensing performance and biological activity, the study highlights the nanocomposite as a versatile platform that holds potential for environmental monitoring alongside broader analytical applications. These combined characteristics emphasize the dual functionality of the system across analytical detection and biological evaluation.

Subject of Research: Optical silver ion sensing using Schiff base capped gold nanoparticles

Article Title: Multifunctional Schiff base capped gold nanoparticles for optical recognition of silver ions with analytical applications and biological evaluation

Article References: Dutta, S., Kumar, D., Pandey, A., Sahu, D., Radheshyam, Suryavanshi, A., & Patra, G. K. (2026). Multifunctional Schiff base capped gold nanoparticles for optical recognition of silver ions with analytical applications and biological evaluation. Discover Materials. https://doi.org/10.1007/s43939-026-01010-w

Image Credits: AI Generated

DOI: 10.1007/s43939-026-01010-w

Keywords: gold nanoparticles, Schiff base, silver ion detection, optical sensing, colorimetric sensor, fluorometric test, DPHNP, plasmonic properties, electronic transitions, coordination chemistry, detection limit, binding constant, food analysis, water samples, sensor selectivity, sensor reversibility, antioxidant activity