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The interaction of carbon-based nanomaterials and ionic liquids (ILs) has been thoroughly exploited for diverse electroanalytical solutions since the first report in 2003. This combination, either through covalent or non-covalent functionalization, takes advantage of the unique characteristics inherent to each material, resulting in synergistic effects that are conferred to the electrochemical (bio)sensing system. From one side, carbon nanomaterials offer miniaturization capacity with enhanced electron transfer rates at a reduced cost, whereas from the other side, ILs contribute as ecological dispersing media for the nanostructures, improving conductivity and biocompatibility. The present review focuses on the use of this interesting type of nanocomposites for the development of (bio)sensors specifically for pharmaceutical detection, with emphasis on the analytical (bio)sensing features. The literature search displayed the conjugation of more than 20 different ILs and several carbon nanomaterials (MWCNT, SWCNT, graphene, carbon nanofibers, fullerene, and carbon quantum dots, among others) that were applied for a large set (about 60) of pharmaceutical compounds. This great variability causes a straightforward comparison between sensors to be a challenging task. Undoubtedly, electrochemical sensors based on the conjugation of carbon nanomaterials with ILs can potentially be established as sustainable analytical tools and viable alternatives to more traditional methods, especially concerning in situ environmental analysis. [ABSTRACT FROM AUTHOR]

The enrichment of groundwater with different nutrients (Na + , Ca 2+ , Mg 2+ , Cl − , CO 3 2− , among others) triggers the salinization of the aquifer and makes it inappropriate for many purposes. In this work, we developed a highly sensitive and selective electrochemical sensor, based on Ni -inorganic films electrosynthetized in situ onto multi-walled carbon nanotubes composite paste electrode (MWCNE), which allows the early detection of salinization. The working sensor ( β - NiO x /MWCNE) was derivatized from nickel hexacyanoferrate modified electrode in strong alkaline medium (pH = 12), producing a hybrid film composed by β - Ni ( OH ) 2 and β - NiO ( OH ). The electrochemical properties, morphology and chemical composition of the formed β - NiO x thin films were evaluated by voltammetry, scanning electron microscopy and X-ray spectroscopy. The developed β - NiO x /MWCNE sensor was highly sensitive to the presence of Na + cation by ion-exchange, and the increase of Na + concentration in the range 4.46 × 10 −7 to 4.93 × 10 −6 mol L −1 inhibited linearly the reversible electrochemical signal of the device, allowing to determine trace concentrations of this ion (LOD = 9.86 × 10 −8 mol L −1 ) with high correlation coefficient of the data ( r = 0.999) and suitable precision/reproducibility of the measurements (RSD < 9%). Using Na + as salinization marker and β - NiO x /MWCNE as electroanalytical device, we found evidences of groundwater salinization in Grossos, a Brazil coast city, whose inhabitants have hypertension above the national average. The attained results were comparable to those obtained by the standard methods for Na + analysis (percentage error ranging from 0.5 to 1.6%), confirming the accuracy of the proposed electroanalytical platform. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Interaction between sensor models and paracetamol (ACOP) were investigated. • There is an optimal concentration of ionic liquid (IL) for ACOP detection. • Moderate amounts of IL modulate ACOP/ACOP+ adsorptionin a cooperative effect. • IL facilitate charge transfer from ACOP to the nanotube. Abstract The interactions between multi-walled carbon nanotubes and different amounts of an ionic liquid (IL), as well as the interactions between this system (used as electrochemical sensor) and acetaminophen (ACOP), were investigated through both experimental and theoretical methodologies. Experiments indicated that there is an optimal concentration of ionic liquid for ACOP detection. A host of techniques and model systems were employed to investigate the adsorption and oxidation processes. To investigate the source of the increased electrochemical current in the presence of an IL, we computed the adsorption energy values of ACOP in the nanotube – IL system via Monte Carlo simulations and Density Functional Theory (DFT). DFT allowed us to explore the changes in adsorption energy due to oxidation. Our theoretical results support the experimental findings that moderate amounts of IL modulates ACOP/ACOP+ adsorption, pointing to a cooperative effect that tends to wane with increasing amounts of IL pairs. We observed that the IL favors desorption of the oxidized species and facilitates charge transfer from the ACOP to the nanotube. Therefore, our studies point towards multifactorial effects with clear physical basis that modulates binding leading to an optimal ratio to promote ACOP detection. [ABSTRACT FROM AUTHOR]

• BPEI functionalized Fe 3 O 4 NPs enhanced the electron flow in glassy carbon electrodes. • GCE/Fe 3 O 4 @BPEI sensor exhibited great performance in cabendazim sensing. • The developed sensor exhibited a low detection limit of 10 nM for carbendazim. • Carbendazim was successfully detected and quantified in natural waters. • An alternative mechanism for carbendazim electrooxidation was proposed. Functionalized magnetic nanoparticles (MNPs) can boost the performance of electrochemical sensors, increase their sensitivity, and modulate electrode-analyte interactions. In this work we used MNPs functionalized with poly(sodium acrylate) (Fe 3 O 4 @PAANa), trisodium citrate (Fe 3 O 4 @CIT) and branched polyethylenimine (Fe 3 O 4 @BPEI) to modify glassy carbon electrodes (GCE) towards the development of electrochemical sensors. Fe 3 O 4 @BPEI was selected to design an electrochemical sensor for carbendazim (CBZ) once this sample exhibited better performance in the enhancement of the electroactive area of GCE and decrease of the charge transfer resistance. Furthermore, we propose a pathway for the electrooxidation reaction of CBZ based on electrochemical measurements and the oxidation products detected by performing mass spectrometry. Our findings indicated that oxidation of CBZ occurs through the insertion of hydroxyl radicals and that the redox reaction involves the same number of protons and electrons. This electroanalytical methodology using Fe 3 O 4 @BPEI exhibited limit-of-detection and limit-of-quantitation values of 10 and 33 nmol L–1, respectively. Moreover, the proposed sensor exhibited high stability (%RSD = 1.31, n = 7), reproducibility (%RSD = 2.84, n = 5), and anti-interference ability. In addition, an electroanalytical methodology was successfully developed for the detection of CBZ in natural waters. This study presents the potential multidisciplinary application of functionalized MNPs as sensors for quantifying CBZ in natural waters and a likely reaction pathway for the electrochemical oxidation of CBZ. [Display omitted] [ABSTRACT FROM AUTHOR]

Herein, a highly sensitive and selective simultaneous electrochemical method to monitor the emerging organic contaminants tartrazine (TRT), dexamethasone (DMZ) and diclofenac (DCL) in sewage treatment plants was developed. The sensing was based on electroreduction of TRT (−0.22 V), DMZ (−0.93 V) and DCL (−1.12 V) on hanging mercury drop electrode (HMDE), using citrate buffer pH 2.5 as electrolyte. The fast electrodic kinetics of these chemicals provided improvements on selectivity at high scan rates. The unique electrochemical properties of HMDE were associated to analytical performance of the square-wave voltammetry to quantify trace concentrations of TRT, DMZ and DCL, with detection limits ranging from 2.78 × 10 −8 to 1.48 × 10 −7 mol L −1 . After wastewater treatment by using solid-phase extraction, the proposed procedure was successfully applied for the direct quantification of the studied compounds with high precision, accuracy and stability of the measurements, even in the presence of other electroactive contaminants. [ABSTRACT FROM AUTHOR]

Abstract: Modification of gold electrode by self-assembled trans-[Fe(cyclam)(NCS)2]+ complex ion to produce an electrochemical sensor for nitric oxide detection was investigated. Dopamine, serotonin and nitrite were examined as interferents. The synthesized complex was characterized by X-ray diffraction and by infrared spectroscopy. The modified electrode was characterized by cyclic voltammetry and by surface enhanced Raman spectroscopy, analytical curves were obtained by square wave voltammetry and Monte Carlo calculations were made to model the interaction of NO molecules with the unmodified and modified surfaces. The complex has distorted octahedron geometry with the thiocyanate groups bonded to the iron ion by the nitrogen atom and in the trans orientation. SERS spectrum and Monte Carlo calculations supported that the complex ion is adsorbed on Au surface from the Au-S bond. The electrochemical current for NO oxidation on the modified electrode was higher than that presented by the bare Au electrode and a good correlation was presented by the experimental analytical curve and the calculated Monte Carlo interaction energy versus amount NO molecules plot. The Monte Carlo calculations indicated that the higher current response for NO oxidation on the Au/trans-[Fe(cyclam)(NCS)2]+ surface was due to the stronger interaction of the NO molecules with complex adsorbed on the Au surface than the interaction of NO with the bare Au surface. The theoretical analyses also revealed that NO molecules cluster on Au surface. Dopamine, serotonin and nitrite were interferents for the detection of NO with dopamine and serotonin was less significant interferents than the nitrite. The proposed modified electrode presented good electrochemical stability, detection limit and quantification limit of 5.15×10−8 molL−1 and 1.72×10−7, respectively, which were about one order of magnitude lesser than the corresponding values obtained for the bare Au electrode. The results indicated that the proposed electrode has potential to be applied as a sensor for NO detection. [Copyright &y& Elsevier]

Abstract: The modification of a gold electrode surface by electropolymerization of trans-[Ru(NH3)4(Ist)SO4]+ to produce an electrochemical sensor for nitric oxide was investigated. The influence of dopamine, serotonin and nitrite as interferents for NO detection was also examined using square-wave voltammetry (SWV). The characterization of the modified electrode was carried out by cyclic voltammetry, electrochemical quartz crystal microbalance (EQCM) and SERS techniques. The gold electrode was successfully modified by the trans-[Ru(NH3)4(Ist)SO4]+ complex ion using cyclic voltammetry. The experiments show that a monolayer of the film is achieved after ten voltammetric cycles, that NO in solution can coordinate to the metal present in the layer, that dopamine, serotonin and nitrite are interferents for the detection of NO, and that the response for the nitrite is much less significant than the responses for dopamine and serotonin. The proposed modified electrode has the potential to be applied as a sensor for NO. [Copyright &y& Elsevier]

Carbamate pesticides (CBMs) are esters and thioesters derived from carbamic acid, which are widely used to increase agricultural productivity and to protect human and animal health from insect-vector-mediated diseases. However, they can be highly toxic when not appropriately applied. Electrochemical carbon-based sensors and biosensors gather a plethora of advantages for reliable, low cost, rapid and even in loco quality control and surveillance of CBMs levels in all systems related to environmental and human health. Thus, this review presents a broad overview of the state-of-art of design and applications of these (bio)sensors for CBMs electroanalysis in environmental, food and biological matrices with emphasis in the role of the carbon (nano)materials. The latest advances and trends but also the main (bio)sensors limitations and research gaps are highlighted. Highly selective, robust and novel carbon-based (bio)sensors with multiplexing CBMs capability are envisaged to emerge shortly for in-field applicability. • (Bio)sensors have been developed for detection of the main carbamate pesticides. • Detection limits in the nano and sub-nanomolar range have been reported. • Platforms for selective multiplexed analysis need to be increasingly developed. • Further advances in (bio)sensors robustness and stability are necessary. • More in-field applications of carbon-based (bio)sensors are required. [ABSTRACT FROM AUTHOR]