Bifunctionalized Silver Nanoparticles as Hg2+ Plasmonic Sensor in Water: Synthesis, Characterizations, and Ecosafety

Abstract

In this work, hydrophilic silver nanoparticles (AgNPs), bifunctionalized with citrate (Cit) and L-cysteine (L-cys), were synthesized. The typical local surface plasmon resonance (LSPR) at λ max = 400 nm together with Dynamic Light Scattering (DLS) measurements (<2RH> = 8 ± 1 nm) and TEM studies (Ø = 5 ± 2 nm) confirmed the system nanodimension and the stability in water. Molecular and electronic structures of AgNPs were investigated by FTIR, SR-XPS, and NEXAFS techniques. We tested the system as plasmonic sensor in water with 16 different metal ions, finding sensitivity to Hg2+ in the range 1–10 ppm. After this first screening, the molecular and electronic structure of the AgNPs-Hg2+ conjugated system was deeply investigated by SR-XPS. Moreover, in view of AgNPs application as sensors in real water systems, environmental safety assessment (ecosafety) was performed by using standardized ecotoxicity bioassay as algal growth inhibition tests (OECD 201, ISO 10253:2006), coupled with determination of Ag+ release from the nanoparticles in fresh and marine aqueous exposure media, by means of ICP-MS. These latest studies confirmed low toxicity and low Ag+ release. Therefore, these ecosafe AgNPs demonstrate a great potential in selective detection of environmental Hg2+, which may attract a great interest for several biological research fields.

Silver Nanoparticles as Colorimetric Sensors for Water Pollutants

“…The nanospheres, highly symmetrical particles, are the most studied because of their monodispersity and synthetic reproducibility, that assure the repeatability of experiments and results. Spherical AgNPs and their composites have a widely application range, mostly in biotechnology and sensors [79][80][81]85,95,96]. The AgNPs show a typical localized surface plasmon resonance (LSPR) whereby the electrons on the AgNPs surface interact with electromagnetic radiation, generating LSPR and producing extinction and scattering spectra, with absorption bands in the 370-470 nm range.…”

“…On the other hand, the void area has been used to tune the refractive index, increase the active region for catalysis, and advance the ability to tolerate cyclic volume modifications. The morphology plays a key role, especially for the possibility of having materials with different symmetries (spheres, AgNPs, cubes AgNCs) [79][80][81][82][83][84][85][86][87] or without defined and reproducible symmetry (stars, AgNSs, flower, AgNFs, wires, AgNWs) [69,[88][89][90][91][92][93][94]. TEM images of silver nanoparticles of different geometries and shape are presented in Figure 4.…”

Gum acacia-based silver nanoparticles as a highly selective and sensitive dual nanosensor for Hg(ii) and fluorescence turn-off sensor for S2− and malachite green detection

“…14 AgNPs are known to be photostable and are less likely to undergo photobleaching, thereby allowing these nanoparticles to be utilized as optical sensors for ultrasensitive mercury detection. [15][16][17] Hazardous sulde ions (S 2À ) have a widespread distribution in both natural and wastewater and are frequently found in industrial areas, such as food processing units, petroleum reneries, and paper and pulp production plants. 18 Sulde in its protonated state becomes even more toxic and poisonous as it turns into bisulde and gaseous hydrogen sulde.…”

Silver Nanoparticles with Different Thiol Functionalization: An Opposite Optical Behaviour in Presence of Hg(II)

“…AgNPs-3MPS 4.1 ± 0.4 nm [39] AgNPs-L-Cys/Cit 5 ± 2 nm [43] When both systems were contaminated with 5ppm of Hg(II) ions showed an opposite behaviour, the LSPR band of AgNPs-3MPS system shifted from about 400 to 350 nm (blue solid line), whereas for the AgNPs-L-Cys/Cit from 400 to around 430 nm (red dashed curve). Measuring the effect of different Hg(II) concentrations with step of 1 ppm, we obtained a linear behaviour from 0 to 5 ppm and a limit of detection (LOD, 3σ) of 240 ppb for the AgNPs-3MPS system.…”

“…The AgNPs stabilized with citrate and L-Cysteine were prepared and characterized in analogy to literature reports [41][42][43]. Sodium citrate, L-Cys and AgNO3 were dissolved separately in distilled water and then the three solutions were mixed under magnetic stirring.…”