Gemma Aragay

Recent Trends in Macro-, Micro-, and Nanomaterial-Based Tools and Strategies for Heavy-Metal Detection

Recent Trends in Macro-, Micro-, and Nanomaterial-Based Tools and Strategies for Heavy-Metal Detection Gemma Aragay, Josefina Pons, and Arben Merkoc-i* Nanobioelectronics & Biosensors Group, Institut Catal a de Nanotecnologia (CIN2, ICN-CSIC), 08193, Bellaterra, Barcelona, Spain Departament of Chemistry, Universitat Aut onoma de Barcelona, 08193, Bellaterra, Barcelona, Spain ICREA, Barcelona, Spain

Sensitive and stable monitoring of lead and cadmium in seawater using screen-printed electrode and electrochemical stripping analysis.

Sensitive and stable monitoring of heavy metals in seawater using screen-printed electrodes (SPE) is presented. The analytical performance of SPE coupled with square wave anodic stripping voltammetry (SWASV) for the simultaneous determination of Pb and Cd in seawater samples, in the low microgL(-1) range, is evaluated. The stripping response for the heavy metals following 2min deposition was linear over the concentration range examined (10-2000microgL(-1)) with detection limits of 1.8 and 2.9microgL(-1) for Pb and Cd, respectively. The accuracy of the method was validated by analyzing metal contents in different spiked seawater samples and comparing these results to those obtained with the well-established anodic stripping voltammetry using the hanging mercury drop electrode. Moreover, a certified reference material was also used and the results obtained were satisfactory.

Enhanced electrochemical detection of heavy metals at heated graphite nanoparticle-based screen-printed electrodes

The effect of temperature upon the electrochemical stripping performance of a heavy metal sensor based on carbon nanoparticles is studied. The morphological changes of the sensing surface during the multidetection of Cd2+, Pb2+, Cu2+ and Hg2+ ions are studied by TEM and SEM. The effect of the temperature on the heavy metal deposition using carbon nanoparticle-based SPEs is also compared to a sensor that does not contain carbon nanoparticles. The effect of temperature seems to be more pronounced for the nanoparticle-based sensor. This phenomenon is clarified by the electrochemical response as well as the TEM and SEM images of the sensing materials used. In addition, the response performance of the nanoparticle-based sensors for increasing concentrations of heavy metals from 5–100 μg L−1 for Cd2+, Pb2+ and Cu2+ and from 1 to 10 μg L−1 for Hg2+, in both single and multiple detections with potential for real applications, is presented. The nanoparticle-based sensor seems to be stable for up to one month while being used in continuous monitoring of heavy metals in seawater.

Ion-directed assembly of gold nanorods: a strategy for mercury detection.

Water-soluble gold nanorods (Au NRs) have been functionalized with an N-alkylaminopyrazole ligand, 1-[2-(octylamino)ethyl]-3,5-diphenylpyrazole (PyL), that has been demonstrated able to coordinate heavy metal ions. The N-alkylaminopyrazole functionalized Au NRs have been characterized by electron microscopy and spectroscopic investigation and tested in optical detection experiments of different ions, namely, Zn(2+), Cd(2+), Hg(2+), Cu(2+), Pb(2+), and As(3+). In particular, the exposure of the functionalized NRs to increasing amounts of Hg(2+) ions has resulted in a gradual red-shift and broadening of the longitudinal plasmon band, up to 900 nm. Interestingly, a significantly different response has been recorded for the other tested ions. In fact, no significant shift in the longitudinal plasmon band has been observed for any of them, while a nearly linear reduction in the plasmon band intensity versus ion concentration in solution has been detected. The very high sensitivity for Hg(2+) with respect to other investigated ions, with a limit of detection of 3 ppt, demonstrates that the functionalization of Au NRs with PyL is a very effective method to be implemented in a reliable colorimetric sensing device, able to push further down the detection limit achieved by applying similar strategies to spherical Au NPs.

Rapid and highly sensitive detection of mercury ions using a fluorescence-based paper test strip with an N-alkylaminopyrazole ligand as a receptor

Easy-to-synthesize N-alkylaminopyrazole ligands are used in a proof-of-concept fluorescent sensor that can operate as a simple ‘paper test’ for rapid and highly sensitive mercury detection in water. A significant enhancement of fluorescence emission in aqueous media for the Hg2+ detection at concentrations lower than 0.1 ppb is achieved. A linear range from 10 to 100 ppb [Hg2+] was obtained in the paper-based system. The respective Turn-ON and Turn-OFF fluorescence mechanisms in the paper test and water solution (pH 1) systems are also shown.

Synthesis and Characterization of New Palladium(II) Complexes Containing N-Alkylamino-3,5-diphenylpyrazole Ligands. Crystal Structure of [PdCl(L2)](BF4) {L2 = Bis[2-(3,5-diphenyl-1-pyrazolyl)ethyl]ethylamine}

In this paper, the synthesis of two new N,N′,N-ligands, bis[2-(3,5-diphenyl-1-pyrazolyl)ethyl]amine (L1) and bis[2-(3,5-diphenyl-1-pyrazolyl)ethyl]ethylamine (L2) is reported. These ligands form complexes with the formula [PdCl(N,N′,N)]Cl when reacting with [PdCl2(CH3CN)2] in a 1:1 metal-to-ligand molar ratio. Treatment of these ligands with [PdCl2(CH3CN)2] in a 1:1 metal-to-ligand molar ratio in the presence of AgBF4 or NaBF4 gave [PdCl(N,N′,N)](BF4) complexes. These PdII complexes were characterized by elemental analyses, conductivity measurements, mass spectrometry, and IR, 1H, and 13C{1H} NMR spectroscopies. The X-ray structure of the complex [PdCl(L2)](BF4) has been determined. The metal atom is coordinated by two azine nitrogen atoms and one amine nitrogen atom of the aminopyrazole ligand. The distorted square planar coordination is completed by one chlorine atom. In this complex, intermolecular π–π stacking interactions are present.

Synthesis and Characterization of New N-Alkylamino-3,5-diphenylpyrazole Ligands and Reactivity Toward PdII and PtII. Study of the cis–trans Isomerization

In this paper, the synthesis and characterization of two new N-alkylaminopyrazole ligands, 1-[2-(ethylamino)ethyl]-3,5-diphenylpyrazole (dpea) and 1-[2-(octylamino)ethyl]-3,5-diphenylpyrazole (dpoa) are reported. The reaction of these ligands with [MCl2(CH3CN)2] (M = PdII, PtII) affords the following square planar complexes: cis-[MCl2(NN′)] (M = PdII: NN′ = dpea, 1; dpoa, 2; M = PtII: NN′ = dpea, 3; dpoa, 4). Reaction of [PdCl2(CH3CN)2] and dpea or dpoa in 1:2 M:NN′ molar ratio, in the presence of NaBF4, yields complexes [Pd(NN′)2](BF4)2 (NN′ = dpea, [5](BF4)2); dpoa, [6](BF4)2). The solid-state structures of complexes 1, 3, and [5](BF4)2 have been determined by single-crystal X-ray diffraction methods. In complexes 1 and 3, the dpea ligand is coordinated through the Npz and Namino atoms to the metallic centre, which completes its coordination with two chlorine atoms in a cis disposition. For complex [5](BF4)2, the crystal structure consists of cations involving a [Pd(Npz)2(Namino)2]2+ core with a cis disposition of the two dpea ligands in a square-planar geometry and BF4 – anions. Theoretical calculations were carried out to optimize the geometries of the cis and trans isomers of the [Pd(dpea)2]2+ cation and of the [Pd(dpea)2](BF4)2 complex. The results show that the trans isomer is the most stable for [Pd(dpea)2]2+, in contrast with the cis stereochemistry observed in the crystal structure of [Pd(dpea)2](BF4)2. The calculations also predict that in acetonitrile solution, the dissociation of this complex into the corresponding ions is thermodynamically favourable. The cis–trans isomerization process of [Pd(dpea)2]2+ in acetonitrile solution has been studied by NMR spectroscopy at different temperatures. These experimental results confirm that the trans isomer is the thermodynamically most stable form of the complexes [5](BF4)2 and [6](BF4)2.

Screen-printed electrodes incorporated in a flow system for the decentralized monitoring of lead, cadmium and copper in natural and wastewater samples

Mercury-based screen-printed electrodes (SPE) combined with square-wave anodic stripping voltammetry (SWASV) techniques for the analysis of copper, cadmium, lead, and zinc in different water samples have been applied. The detection system has been implemented in a flow cell and different experimental conditions have been tested in view of its application for in-situ monitoring. In particular, an acetate buffer together with a low chloride concentration (0.025 M NaCl) provided best performance and reproducible results. Additionally, the flow system was validated for the first time in terms of limits of detection, linearity, repeatability and recovery. Limits of detection of 2.8 µg L−1, 4.1 µg L−1, and 7.5 µg L−1 for cadmium, lead and copper respectively and repeatabilities lower than 10% (as RSD) were found. Good recoveries have been obtained for the three cations and in particular for copper, even in the presence of zinc. Finally, the method has shown its efficiency for the rapid screening of lead, cadmium and copper contained in both natural waters and wastewater samples.