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.
Highlights
Nanosized inorganic particles, in simple or composite formulation, have unique physical and chemical properties and represent an increasingly important material in the development of novel nanodevices that can be used in numerous fields such as catalysis, energy, optoelectronics, biomedicine, and sensors [1,2,3,4,5,6,7,8,9,10,11]
In this work AgNPs functionalized with hydrophilic capping agents, i.e., citric acid (Cit) and L-Cysteine (L-cys) were synthesized and characterized by means of UV-Vis, Fourier Transform Infrared (FTIR), Synchrotron radiation-X-ray photoelectron (SR-XPS), Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopies
AgNPs have been characterized by means of UV-Vis, FTIR and XPS spectroscopies, by Dynamic Light Scattering (DLS) and Transmission Electron Microscope (TEM) studies
Summary
In simple or composite formulation, have unique physical and chemical properties and represent an increasingly important material in the development of novel nanodevices that can be used in numerous fields such as catalysis, energy, optoelectronics, biomedicine, and sensors [1,2,3,4,5,6,7,8,9,10,11]. Many studies involved AgNPs as optical sensor, using the localized surface plasmon resonance (LSPR) that is specific feature of the colloidal silver nanoparticle solutions: the energy of the absorption maximum and the shape of the peak are strongly related with the size, shape and interparticle distance, and with the surrounding environment, which can influence the degradation or aggregation of the particles [23,24,25] These optical properties of NPs have allowed researchers to mature new diagnostic methods that are useful for optical and colorimetric measurements [26,27,28]
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