Thermal Exfoliated Graphite/Chitosan Modified Glassy Carbon Electrode for Cu(II) Ion Sensing

Aim:

Here, we report a simple strategy for the preparation of thermally exfoliated graphite (EG) and its application to modify glassy carbon electrode (GCE) surfaces for electrochemical Cu2+ ion sensing.

Method:

The electrochemical Cu2+ sensor was constructed by a layer modification of a glassy carbon electrode (GCE) with exfoliated graphite (EG) and chitosan (CS) as a binder, and CS also supports a large number of -NH2 functional groups for Cu2+ capture.

Result:

Due to the creation of a three-dimensional (3D) structure, the EG/CS-coated GCE (EG/CS/GCE) electrode exhibited a higher sensitivity towards Cu2+ detection than that of modification by graphite/chitosan (GP/CS), chitosan (CS) or graphite intercalated compounds (GIC)/chitosan.

Conclusion:

The proposed method could detect Cu2+ in the range of 10 µM to 3 mM with a detection limit of 0.5 µM and sensitivity of 43.62 μA mM-1.

Catalytic coupling of biomass-derived aldehydes into intermediates for biofuels and materials

Catalytic upgrading of biomass-based aldehydes into chain-extended intermediates for downstream applications in biofuels, fine chemicals, and renewable materials, is reviewed.

Tetrabutylammonium-modified clay film electrodes: characterization and application to the detection of metal ions

This work describes the preparation and characterization of smectite clay partially exchanged with tetrabutylammonium ions (TBA(+)) and its subsequent deposition onto glassy carbon electrode (GCE) for application to the preconcentration electroanalysis of metal ions (Cd, Pb, and Cu). Such partial exchange of TBA(+) induces the expansion of the interlayer region between the clay sheets (as ascertained by XRD) while maintaining its ion exchange capacity, which resulted in enhanced mass transport rates (as pointed out by electrochemical monitoring of permeability properties of these thin (organo)clay films on GCE). This principle was applied here to the anodic stripping square wave voltammetric analysis of metal ions after accumulation at open circuit. Among others, detection limits as low as 3.6×10(-8)M for copper and 7.2×10(-8)M for cadmium have been achieved.

Carbon paste electrodes in the new millennium

In this review (with 500 refs), both electrochemistry and electroanalysis with carbon paste-based electrodes, sensors, and detectors are of interest, when attention is focused on the research activities in the years of new millennium. Concerned are all important aspects of the field, from fundamental investigations with carbon paste as the electrode material, via laboratory examination of the first electrode prototypes, basic and advanced studies of various electrode processes and other phenomena, up to practical applications to the determination of inorganic ions, complexes, and molecules. The latter is presented in a series of extensive tables, offering a nearly complete survey of methods published within the period of 2001–2008. Finally, the latest trends and outstanding achievements are also outlined and future prospects given.

Organically nanoporous silica gel based on carbon paste electrode for potentiometric detection of trace Cr(III)

A new ion-selective electrode (ISE) for the detection of trace chromium(III) was designed by using 2-acetylpyridine and nanoporous silica gel (APNSG)-functionalized carbon paste electrode (CPE). The presence of APNSG acted as not only a paste binder, but also a reactive material. With 7.5 wt% APNSG proportions, the developed electrode exhibited wide dynamic range of 1.0 x 10(-8) to 1.0 x 10(-3) M toward Cr(III) with a detection limit of 8.0 x 10(-9) M and a Nernstian slope of 19.8 +/- 0.2 mV decade(-1). The as-prepared electrode displayed rapid response (approximately 55 s), long-time stability, and high sensitivity. Moreover, the potentiometric responses could be carried out with wide pH range of 1.5-5.0. In addition, the content of Cr(III) in food samples, e.g. coffee and tea leaves, has been assayed by the developed electrode, atomic absorption spectrophotometer (AAS) and atomic emission spectrometer (ICP-AES), respectively, and consistent results were obtained. Importantly, the response mechanism of the proposed electrode was investigated by using AC impedance and UV-vis spectroscopy.

Use of organofunctionalized nanoporous silica gel to improve the lifetime of carbon paste electrode for determination of copper(II) ions

A new functionalized nanoporous silica gel with dipyridyl group (DPNSG) was synthesized. Then, the potentiometric response of the copper(II) ion was investigated at a carbon paste electrode chemically modified with this newly designed functionalized nanoporous silica gel. The electrodes with DPNSG proportions of 15.0% (w/w) demonstrated very stable potentials. Calibration plots with Nernstian slopes for Cu2+ were observed, 28.4 (+/-1.0) mV decade(-1), over a wide linear concentration range (1.0x10(-7) to 1.0x10(-2) M). The electrode exhibited a detection limit of 8.0x10(-8) M. Moreover, the selectivity coefficients measured by the match potential method in acetate buffer, pH 5.5, were investigated. The electrode presented a response time of approximately 50s, high performance, high sensitivity in a wide range of cation activities and good long-term stability (more than 9 months). The method was satisfactory and was used to determine the copper ion concentration in waste waters, contaminated by this metal.

Selective response of dopamine in the presence of ascorbic acid on carbon paste electrode modified with titanium phosphated silica gel

Titanium phosphate grafted on the surface of silica gel (devoted briefly as Si-TiPH) was synthesized and used as bulk modifier to fabricate a renewable three-dimensional chemically modified electrode. The Si-TiPH bulk modified carbon paste electrode was used for the selective determination of dopamine (DA) in the presence of ascorbic acid (AA). The modified electrode offers an excellent and stable response for the determination of DA in the presence of AA. The differential pulse voltammetry peak current was found to be linear with the DA concentration in the range 2 x 10(-7) to 1 x 10(-6) and 2 x 10(-6) to 6 x 10(-5) mol L(-1). The detection limit of the proposed method in the presence of 2.0 x 10(-5) M of AA was found to be 4.3 x 10(-8) mol L(-1) for DA determination. The proposed method was successfully applied for the determination of DA in injections.

Surfactant templated sulfonic acid functionalized silica microspheres as new efficient ion exchangers and electrode modifiers

Porous sulfonic acid functionalized silica spheres have been prepared by oxidation ofthiol-functionalized mesoporous silica samples obtained by co-condensation of (mercaptopropyl)trimethoxysilane and tetraethoxysilane in the presence ofcetyltrimethylammonium as a template. The physicochemical characteristics of the resulting ion exchangers have been analyzed by various techniques and discussed with respect to the amount of functional groups in the materials. Their ion exchange behavior was then studied from batch experiments (determination of cation exchange capacities) and by electrochemistry at carbon paste electrodes modified with these solids. In particular, ion exchange voltammetry applied to two model electroactive cations, Cu2+ and Ru(NH3)6(3+), has pointed out the key role played by the content of organofunctional groups in the materials (which strongly affects their structure and porosity) on their performance as electrode modifiers for preconcentration of target analytes prior to electrochemical detection.