Mercaptosuccinic-Acid-Functionalized Gold Nanoparticles for Highly Sensitive Colorimetric Sensing of Fe(III) Ions

The development of reliable and highly sensitive methods for heavy metal detection is a critical task for protecting the environment and human health. In this study, a qualitative colorimetric sensor that used mercaptosuccinic-acid-functionalized gold nanoparticles (MSA-AuNPs) to detect trace amounts of Fe(III) ions was developed. MSA-AuNPs were prepared using a one-step reaction, where mercaptosuccinic acid (MSA) was used for both stabilization, which was provided by the presence of two carboxyl groups, and functionalization of the gold nanoparticle (AuNP) surface. The chelating properties of MSA in the presence of Fe(III) ions and the concentration-dependent aggregation of AuNPs showed the effectiveness of MSA-AuNPs as a sensing probe with the use of an absorbance ratio of A530/A650 as an analytical signal in the developed qualitative assay. Furthermore, the obvious Fe(III)-dependent change in the color of the MSA-AuNP solution from red to gray-blue made it possible to visually assess the metal content in a concentration above the detection limit with an assay time of less than 1 min. The detection limit that was achieved (23 ng/mL) using the proposed colorimetric sensor is more than 10 times lower than the maximum allowable concentration for drinking water defined by the World Health Organization (WHO). The MSA-AuNPs were successfully applied for Fe(III) determination in tap, spring, and drinking water, with a recovery range from 89.6 to 126%. Thus, the practicality of the MSA-AuNP-based sensor and its potential for detecting Fe(III) in real water samples were confirmed by the rapidity of testing and its high sensitivity and selectivity in the presence of competing metal ions.

Transition Metal (II) Complexes of (E)-N-(4-methylbenzylidene)-2-((Z)-(4-methylbenzylidene)amino)benzamides: Synthesis, Characterization and their Biological Evaluation

In this paper, cerium sulfate tetrahydrate (Ce(IV)) dissolved in acid-aqueous medium and mercaptosuccinic acid (MSA) redox couple was used to synthesize the crosslinked copolymer of acrylamide (AAm), lithium methacrylate (LiMA), and N,N’-methylene bisacrylamide (MBAAm) in the presence of ethylenediaminetetraacetic acid tetrasodium salt (EDTANa4). The effects of various mole amounts of AAm and LiMA at constant crosslinker concentration and mole amounts of total monomer/MBAAm at constant amounts of AAm and LiMA on the swelling behaviors and swelling kinetics of synthesized hydrogels were investigated in distilled water. The use of hydrogel, including lithium methacrylate ionic groups, for the removal of copper ions from aqueous solutions was examined by using the batch adsorption method. In the adsorption process of copper ions on hydrogels containing LiMA groups, the effects of parameters such as the amount of hydrogel, initial Cu(II) concentration, adsorption time, and pH of solution were investigated.

Synthesis and Swelling Behaviors of Hydrogels Containing LiMA Groups and its Use in Cu(II) Adsorption from Aqueous Solution

In this paper, cerium sulfate tetrahydrate (Ce(IV)) dissolved in acid-aqueous medium and mercaptosuccinic acid (MSA) redox couple was used to synthesize the crosslinked copolymer of acrylamide (AAm), lithium methacrylate (LiMA), and N,N’-methylene bisacrylamide (MBAAm) in the presence of ethylenediaminetetraacetic acid tetrasodium salt (EDTANa4). The effects of various mole amounts of AAm and LiMA at constant crosslinker concentration and mole amounts of total monomer/MBAAm at constant amounts of AAm and LiMA on the swelling behaviors and swelling kinetics of synthesized hydrogels were investigated in distilled water. The use of hydrogel, including lithium methacrylate ionic groups, for the removal of copper ions from aqueous solutions was examined by using the batch adsorption method. In the adsorption process of copper ions on hydrogels containing LiMA groups, the effects of parameters such as the amount of hydrogel, initial Cu(II) concentration, adsorption time, and pH of solution were investigated.

Gold Nanoparticles Functionalized with Mercaptosuccinic Acid as a Means for Detecting Fe(III) Ions

The application of mercaptosuccinic acid-capped gold nanoparticles as a sensing probe for the colorimetric detection of Fe(III) is reported. The well-dispersed gold nanoparticles (AuNPs) with a diameter of around 20 nm were obtained by a one-step reaction of tetrachloroauratic acid with mercaptosuccinic acid (MSA) as a reducing and capping agent, respectively. Fe(III) reportedly causes the aggregation of prepared MSA-capped AuNPs followed by a change in color and a shift to long wavelengths in the absorbance spectra. The resulting method allows for a visual and spectrophotometric Fe(III) determination with detection limits of 30 ng/mL and 23 ng/mL, respectively. MSA-capped AuNPs have been used as sensing probes for the detection of Fe(III) in drinking water samples with a detection limit that is much lower than the maximum permissible level of Fe(III) specified by official regulations (300 ng/mL).

Bioconjugation Between CdTe Quantum Dots and a Cationic Protein: An Analytical Method to Determine Protamine in Drug and Urine Samples

CdTe quantum dots (QD-CdTe) functionalized with mercaptosuccinic acid (MSA) were synthesized in an aqueous medium, varying synthesis time from 0.5 to 4 h. The nanoprobe were characterized by a direct relationship between synthesis time and QD size (2.61-3.04 nm). The QD-CdTe-MSA interacted with protamine (PT), a cationic protein, forming a bioconjugate, thus quenching the photoluminescence intensity and generating an on-off system. The nanoprobe produced at a synthesis time of 1 h (QD-CdTe1) presented PT’s best sensitivity in a succinate buffer (pH = 5). Under the optimized conditions, the proposed method presented a linear range of 0.05-0.5 mg L-1 (10-100 nM), limit of detection (LOD) 0.01 mg L-1 (2 nM), and relative standard deviation (RSD) ≤ 2.01% (n = 10). The interaction of the nanoprobe and PT led to aggregation due to a bioconjugate formation. The systems’ hydrodynamic radius varied from 4.31 nm (QD‑CdTe1) to 30.50 nm for the bioconjugate (QD-CdTe1-PT). The method was sensitive to variation in ionic strength and based on thermodynamic parameters; it was demonstrated that the interaction mechanism occurred preferentially through electrostatic forces. Finally, the method proved to be fast, sensitive, and viable for quantifying PT in drugs and synthetic urine samples with recoveries above 95%.

Highly selective piezoresistive sensor for mercury (Hg2+) ions detection using mercaptosuccinic acid-functionalized microcantilevers with cross-linked pyridinedicarboxylic acid

Purpose This paper aims to report an insightful portable microfluidic system for rapid and selective sensing of Hg2+ in the picomolar (pM) concentration using microcantilever-based piezoresistive sensor. The detection time for various laboratory-based techniques is generally 12–24 h. The majority of modules used in the proposed platform are battery oriented; therefore, they are portable and handy to carry-out on-field investigations. Design/methodology/approach In this study, the authors have incorporated the benefit of three technologies, i.e. thin-film, nanoparticles (NPs) and micro-electro-mechanical systems, to selectively capture the Hg2+ at the pM concentration. The morphology and topography of the proposed sensor are characterized using field emission scanning electron microscopy and verification of the experimental results using energy dispersive X-ray. Findings The proposed portable microfluidic system is able to perform the detection in 5 min with a limit of detection (LOD) of 0.163 ng (0.81 pM/mL) for Hg2+, which perfectly describes its excellent performance over other reported techniques. Research limitations/implications A microcantilever-based technology is perfect for on-site detection, and a LOD of 0.163 ng (0.81 pM/mL) is outstanding compared to other techniques, but the fabrication of microcantilever sensor is complex. Originality/value Many researchers used NPs for heavy metal ions sensing, but the excess usage and industrialization of NPs are rapidly expanding harmful consequences on the human life and nature. Also, the LOD of the NPs-based method is limited to nanomolar concentration. The suggested microfluidic system used the benefit of thin-film and microcantilever devices to provide advancement over the NPs-based approach and it has a selective sensing in pM concentration.