Used gold nano-particles as an on/off switch for response of a potentiometric sensor to Al(III) or Cu(II) metal ions

Chemically modified flubendazole carbon electrochemical sensor for aluminum determination in food stuff, Multivitamin syrup and real water samples supported by DFT calculations, IR and morphological tools

Aluminum is a key component in nearly nourishment stuffs and medications. It is also found in treated drinking water in the form of reactive species, and aluminum salts are commonly utilized as flocculants in water treatment. Meanwhile, it was not thought to be a dangerous metal for people, but research showed a possible link with Alzheimer's disease, breast cancer, autism, and aluminum. Controlling the amount of aluminum in food processing, agriculture, and drinking water is crucial, thus newly synthesized Al(III) ion selective electrode based on innocuous reagent, flubendazole drug, has been developed. The electrode displayed Nernstian slopes of 20.11 0.47 mV decade^-1 at 25 ± 1 °C, covering a wide concentration range of Al(III) from 1 × 10^-7 to 1 × 10^-1 mol L^-1. The response mechanism is studied using IR, computational calculations, morphological tools. The developed sensor has been utilized to accurately measure Al(III) ions in genuine water samples, multivitamin syrup, and food stuff.

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.

Platinum-Based Interdigitated Micro-Electrode Arrays for Reagent-Free Detection of Copper

Water is a precious resource that is under threat from a number of pressures, including, for example, release of toxic compounds, that can have damaging effect on ecology and human health. The current methods of water quality monitoring are based on sample collection and analysis at dedicated laboratories. Recently, electrochemical-based methods have attracted a lot of attention for environmental sensing owing to their versatility, sensitivity and their ease of integration with cost effective, smart and portable readout systems. In the present work, we report on the fabrication and characterization of platinum-based interdigitated microband electrodes arrays, and their application for trace detection of copper. Using square wave voltammetry after acidification with mineral acids, a limit of detection of 0.8 μg/L was achieved. Copper detection was also undertaken on river water samples and compared with standard analytical techniques. The possibility of controlling the pH at the surface of the sensors—thereby avoiding the necessity to add mineral acids—was investigated. By applying potentials to drive the water splitting reaction at one comb of the sensor’s electrode (the protonator), it was possible to lower the pH in the vicinity of the sensing electrode. Detection of standard copper solutions down to 5 μg/L (ppb) using this technique is reported. This reagent free method of detection opens the way for autonomous, in situ monitoring of pollutants in water bodies.

Layer-by-Layer Assembly of Electroactive Dye/LDHs Nanoplatelet Matrix Film for Advanced Dual Electro-optical Sensing Applications

It proved that the most destructive effects of the toxic Al3+ ion on the human nervous system and disease that are involved with this system, such as Alzheimer's. The development of solid-state electrodes is still in its infancy during the sensor-based detection methods for Al3+. Hence, in this study, a novel flexible ITO/PET-based electrochemical solid-state sensor was designed and constructed. Modification of the surface of electrode bedding was done by layer-by-layer (LbL) assembly of Mg-Al LDH. nanoplatelets along with alizarin red S (ARS) in an interconnected matrix film. In the molecular design of sensing base of the electrode, the electroactive organic units (ARS molecules) present in the ITO/PET-layered (ARS/LDHs)n matrix are involved in electrochemical reactions when exposed to the target molecule (Al3+ ion), so the electrochemical changes of the new formed Al-chelated system are detectable. This type of sensor is used for sensitive and selective detection of Al3+. The minimum sheet resistance, morphology and high electrocatalytic activity of the modified matrix film are obtained in the fifth cycle of LbL assembly technique. In this electrochemical sensor, both electrochemical and optical methods were detected with high sensitivity and selectivity of Al3+, so that in a cyclic voltammetry electrochemical method, the lower detection limit of 10.1 nM with a linear range of [0.2-120 μM] was obtained compared to the fluorescence-based optical method.

Highly selective and sensitive simultaneous nanomolar detection of Cs(i) and Al(iii) ions using tripodal organic nanoparticles in aqueous media: the effect of the urea backbone on chemosensing

Chemosensing plays a very important role in the detection of essential/pollutant ions in aqueous media. In this manuscript, two tripodal ligands, i.e., 1-(2-hydroxybenzyl)-3-(4-nitrophenyl)-1-phenylurea (ligand 1) and 1-(2-hydroxybenzyl)-3-(4-nitrophenyl)-1-phenylthiourea (ligand 2) have been synthesised, which differ in the linker molecule, i.e., urea and thiourea in ligand 1 and ligand 2, respectively. The ligands were characterised by NMR, IR and mass spectroscopic techniques. Ligands 1 and 2 (2 mM) were further employed for the generation of their organic nanoparticles (ONPs) (0.01 mM) of size 20-25 nm and 30-35 nm, respectively, by the reprecipitation method. The chemosensing properties of 1-ONP and 2-ONP solutions were investigated. 1-ONP showed simultaneous recognition behaviour towards Cs(i) and Al(iii) with the limits of detection of ∼220 and ∼377 nM, respectively, in an aqueous medium, while 2-ONP did not show any recognition behaviour towards any ion.

Voltammetric determination of aluminum(III) as Al-Alizarin S complex in tea leaves and infusions

This work presents, for the first time, DPV methodology of indirect aluminum (III) determination in tea leaves and infusions using the renewable silver amalgam electrode. A self-referencing strategy was proposed which relies on alternate voltammetric curves registration with and without conditioning of the electrode surface. The developed procedure utilizing formation of aluminum-Alizarin S complex shows linearity in the range of 2-50 μg L^-1 of Al(III) concentration, with r > 0.997. In the case of the electrode conditioning LOD is 0.2 μgL^-1 and repeatability expressed by CV is 1-2%. Introducing an additional operation i.e. electrode activation results in decrease of sensitivity from 0.0162 to 0.0043 μA/μgL^-1. The method was verified using CRM (tea leaves). Due to the wide variety of tea origin, types and producers, four most popular sorts (black, green, red and white) were chosen, made by one manufacturer. It was demonstrated that the proposed methodology may be applied in Al(III) determination in tea leaves and infusions. Al(III) extraction effectiveness was also examined. It was verified, that lemon juice addition during brewing increases aluminum concentration in infusions. Using Principal Components Analysis it was demonstrated that automatic distinction of infusions brewed with and without lemon juice, based on unprocessed voltammetric signal, may be successfully realized.

Nanomaterials: Electrochemical Properties and Application in Sensors

The unique properties of nanoparticles make them an extremely valuable modifying material, being used in electrochemical sensors. The features of nanoparticles affect the kinetics and thermodynamics of electrode processes of both nanoparticles and redox reactions occurring on their surface. The paper describes theoretical background and experimental studies of these processes. During the transition from macro- to micro- and nanostructures, the analytical characteristics of sensors modify. These features of metal nanoparticles are related to their size and energy effects, which affects the analytical characteristics of developed sensors. Modification of the macroelectrode with nanoparticles and other nanomaterials reduces the detection limit and improves the degree of sensitivity and selectivity of measurements. The use of nanoparticles as transducers, catalytic constituents, parts of electrochemical sensors for antioxidant detection, adsorbents, analyte transporters, and labels in electrochemical immunosensors and signal-generating elements is described.

Synergistic effect of magnetite and gold nanoparticles onto the response of a label-free impedimetric hepatitis B virus DNA biosensor

A magnetite and gold nanoparticle modified carbon paste electrode (CPE) was prepared for the immobilization of a thiol modified Hepatitis B virus (HBV) probe DNA and determination trace amount of target HBV DNA. Indeed, the sensing platform integrated two nanoparticles that had previously been employed individually in the DNA biosensors. The proposed DNA biosensor could measure target HBV DNA virus concentration with a low detection limit of 3.1 (±0.1)×10-(13)M, which was greatly lower than the detection limit reported with gold or magnetite nanoparticles alone. The change of interfacial charge transfer resistance (RCT) was confirmed the hybrid formation between probe and target HBV DNA. The RCT difference (before and after hybridization with the target HBV DNA) was in a linear relationship with the logarithm of complementary oligonucleotide concentrations in the range of 8.3 (±0.1)×10(-13) to 6.4 (±0.2)×10(-7)M. In addition, the novel methodology for specific DNA sequence detection was highly selective, repeatable, and reproducible. Finally, this work was successfully utilized for the sensitive and label free impedimetric determination of HBV target DNA in the urine and blood plasma samples.

Gold nanoparticles deposited on fluorine-doped tin oxide surface as an effective platform for fabricating a highly sensitive and specific digoxin aptasensor

Fabrication steps of digoxin aptasensor. The DPVs are for accumulated MB at FTO/GNPs/Ap, before (a) and after (b) incubation with digoxin.

A novel optical DNA biosensor for detection of trace amounts of mercuric ions using gold nanoparticles introduced onto modified glass surface

In this work we report a DNA spectrophotometric biosensor for detection of Hg2+ ions in which a pair of oligonucleotides with four thymine-thymine (T-T) mismatched bases was immobilized onto modified glass surface. Firstly, glass surface modified with 3-(mercaptopropyl) trimethoxysilane (MSPT) and gold nano-particles respectively and then one oligonucleotide (P1) modified with hexanthiol at 5-terminal was immobilized on gold nano-particles via self-assembly and inserted in methylene blue. Methylene blue can intercalate on single strand DNA (ss-DNA) and its absorption peak can measure spectrophotometrically. Then the other oligonucleotide was able to hybridize with P1 by forming thymine-Hg2+-thymine (T-Hg2+-T) complexes in the presence of Hg2+, and absorption signal of methylene blue reduced upon Hg2+ increasing concentration because inaccessibility of guanine base in DNA duplex. However, when Hg2+ was absent, the two oligonucleotides could not hybridize due to the T-T mismatched bases, and P2 could not be fixed on the modified glass surface and any change in absorption peak of methylene blue takes place. The UV-Vis spectrum showed a linear correlation between the absorption peak of methylene blue and the concentration of Hg2+ over the range from 10 nM to 10 μM (R2=0.9985) with a detection limit of 6 nM. This spectrophotometric biosensor could be widely used for selective detection of Hg2+.