Ascorbic Acid Sensor Research Articles

Electrochemical ascorbic acid/hydroquinone detection on graphene electrode and the electro-active site study

In this article, graphite oxide (GO) and graphene have been prepared by chemical method and applied to modify electrodes in electrochemical detection of hydroquinone and ascorbic acid (AA). It is confirmed that the as-prepared GO- and graphene-modified electrodes own good electro-sensitivity for detecting hydroquinone and AA by cyclic voltammogram measurements. The detection limit of hydroquinone on graphene electrode was 3.8 × 10−7 mol L−1 (S/N = 3). Graphene has lowered the over-potential of hydroquinone and improved its electrochemical reversibility. The redox process of hydroquinone is more prone to be diffusion-controlled, as shown by the relationship between anodic peak currents and scan rate results. Different from hydroquinone detecting, both GO- and graphene-modified electrodes have favourable oxidation peaks in detecting AA, as the oxygen content sites on GO and graphene have been tested to be the electro-active sites for AA detecting. The redox process of AA on GO- and graphene-modified electrodes is more prone to be absorption-controlled. The results presented in this article demonstrate that GO and graphene have a good prospect in the making of an AA sensor device.

Electrostatic Attachment of Ferrocene Monolayer to a Gold Electrode for Use as Ascorbic Acid Sensor

A new ascorbic acid electrochemical sensor was made by electrostatic assembly of ferrocene polymer monolayer on the surface of gold electrode which modified with negatively charged alkanethiol. Cyclic voltammetry and current-time curve were employed to investigate the electrochemical characteristics of the sensor. The ferrocene monolayer modified electrode exhibit excellent electrocatalytic response to the oxidation of ascorbic acid. The anodic overpotential was reduced by about 180 mV compared with that obtained at a bare gold electrode in cyclic voltammetry. Under the optimal conditions, the linear range of the sensor response to ascorbic acid was from 0.05 to 1 mM and the detection limit was 2.710-5 M. The sensor possesses simple preparation, fast response and good electrochemical stability.

Determination of Ascorbic Acid Based on a Platinum Nanoparticles Modified Au Electrode

A Platinum nanoparticles modified Au electrode has been successfully fabricated by using an in situ growth method. In this method, the Platinum nanoparticles could be grown on the Au electrode surface via the one-step immersion into the mixture of H2PtCl6 (analytical grade, 1g/L), NaBH4 (analytical grade) and polyvinylpyrrolidone K30 (PVP, analytical grade). A certain amount of PVP was added into the reaction system to prevent the coagulation of the Platinum nanoparticles, which obtained by the chemical redox reaction of H2PtCl6 and NaBH4. The structures and morphologies of the Platinum nanoparticles were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) . The direct electrochemical behavior of ascorbic acid in 0.3 mol/L NaCl medium at the Platinum nanoparticles modified electrode has been investigated in detail. Compared to a bare Au electrode, a substantial decrease in the overvoltage of the ascorbic acid was observed at the Platinum nanoparticles modified electrode with oxidation starting at ca. 0.20 V vs. SCE (saturated KCl). At an applied potential of 0.18V, this modified electrode produced high and reproducible sensitivity to ascorbic acid and linear responses were obtained over a concentration range from 0.600 to 3.267 μmol/L with a detection limit of 1.9 nmol/L(S/N=3). The fabrication method of this sensor, which has highly sensitive, low working potential, and fast amperometric sensing to ascorbic acid, is simple and without using complex equipment. In addition, the sensor has been successfully used to detect ascorbic acid in real sample, thus is promising for the future development of ascorbic acid sensors.

A highly sensitive non-enzymatic ascorbate sensor based on copper nanoparticles bound to multi walled carbon nanotubes and polyaniline composite

A novel, stable and highly sensitive non-enzymatic ascorbic acid sensor was developed using copper nanoparticles (CuNPs), carboxylated multi-walled carbon nanotubes (MWCNTs) and polyaniline (PANI) composite electrodeposited on gold electrode. The modified Au electrode was characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry and impedance spectroscopy. The linear sweep voltammetry peak current showed a linear dependence on the ascorbic acid concentration and a linear calibration curve was obtained in the range, 5–600 μM of ascorbic acid with a correlation coefficient ( r) of 0.998. The sensors response time was less than 2 s and detection limit was 1.0 μM (at signal/noise = 3). When tested with serum, fruits and vegetables, the sensor exhibited high electrocatalytic activity, fast response and good selectivity against common interfering species, suggesting its potential to be developed as a non-enzymatic ascorbic acid sensor.

A highly sensitive ascorbic acid sensor using a Ni–Pt electrode

An amperometric sensor that measured ascorbic acid by the oxidation of the ascorbic acid on a Ni–Pt electrode was fabricated. The Ni component of the Ni–Pt alloy played a crucial role as a modifier that developed an erinaceous surface, which enlarged the sensing area and increased the sensitivity of the electrode. The Pt82Ni18 electrode exhibited the best sensitivity of 333μAcm−2mM−1 for ascorbic acid sensing. This electrode was further tested for reproducibility of the sensitivity, endurance, and interference; it exhibited excellent performance compared with electrodes reported in the literature.

Electrochemical impedance spectroscopy sensor for ascorbic acid based on copper(I) catalyzed click chemistry

Copper(I) species can be acquired from the reduction of copper(II) by ascorbic acid (AA) in situ, and which in turn quantitative catalyze the azides and alkynes cycloaddition reaction. In this study, propargyl-functionalized ferrocene (propargyl-functionalized Fc) has been modified on the electrode through reacting with azide terminal modified Au electrode via copper(I) catalyzed azides and alkynes cycloaddition (CuAAC) reaction. The electrochemical impedance spectroscopy (EIS) measurement has been applied to test the electron transfer resistance of the Au electrode before and after click reaction. The changes of the fractional surface coverage ( θ) with different AA concentrations are characterized. It is found that the θ value has a linear response to the logarithm of AA concentration in the range of 5.0 pmol/L to 1.0 nmol/L with the detection limits of 2.6 pmol/L. The sensor shows a good stability and selectivity. And it has been successfully applied to the AA detection in the real samples (urine) with satisfactory results.

Layer-by-layer assembly of electroactive dye/inorganic matrix film and its application as sensor for ascorbic acid

A novel inorganic–organic composite ultrathin film was fabricated by layer-by-layer assembly of naphthol green B (NGB) and layered double hydroxides (LDHs) nanoplatelets, which shows remarkable electrocatalytic behavior for oxidation of ascorbic acid. LDHs nanoplatelets were prepared using a method involving separate nucleation and aging steps (particle size: 25±5nm; aspect ratio: 2–4) and used as building blocks for alternate deposition with NGB on indium tin oxide (ITO) substrates. UV–vis absorption spectroscopy and XRD display regular and uniform growth of the NGB/LDHs ultrathin film with extremely c-orientation of LDHs nanoplatelets (ab plane of microcrystals parallel to substrates). A continuous and uniform surface morphology was observed by SEM and AFM image. The film modified electrode displays a couple of well-defined reversible redox peaks attributed to Fe2+/Fe3+ in NGB (ΔEp=68mV and Ia/Ic=1.1). Moreover, the modified electrode shows a high electrocatalytic activity towards ascorbic acid in the range 1.2–55.2μM with a detection limit of 0.51μM (S/N=3). The Michaelis–Menten constant was calculated to be KMapp=67.5 μM.

Electrochemical behavior of graphene doped carbon paste electrode and its application for sensitive determination of ascorbic acid

In present paper, the graphene doped carbon paste electrode (CPE) was firstly prepared with the addition of graphene into the carbon paste mixture. Compared with conventional CPE, an improved electrochemical response of graphene doped CPE toward the redox couple of Fe(CN) 6 3−/4− was demonstrated owing to the excellent electrical conductivity of graphene. The graphene doped CPE was further used for the successful determination of ascorbic acid (AA), and it showed an excellent electrocatalytic oxidation activity toward AA with a lower overvoltage, pronounced current response, and good sensitivity. Under the optimized experimental conditions, the proposed electrochemical AA sensor exhibited a rapid response to AA within 5 s and a linear calibration plot ranged from 1.0 × 10 −7 to 1.06 × 10 −4 M was obtained with a detection limit of 7.0 × 10 −8 M.

An ultra-sensitive electrochemical sensor for ascorbic acid based on click chemistry

A highly selective and sensitive electrochemical sensor for ascorbic acid (AA) assay has been prepared through Cu(I) catalyzed azide-alkyne cycloaddition reaction (CuAAC). The catalyst, Cu(I) species, is acquired from the reduction of Cu(II) by AA in situ. In the presence of Cu(I) catalyst, the azide modified Au electrode surface is shown to react quantitatively with terminal propargyl-functionalized ferrocene forming 1,2,3-triazoles. The electrochemical response of propargyl-functionalized ferrocene modified Au electrode surface can be monitored using differential pulse voltammetry (DPV) technique. Under optimal conditions, it is found that the current intensity has a linear relationship with the logarithm of AA concentration in the range of 5.0 × 10(-12) to 1.0 × 10(-9) M. Furthermore, the proposed electrochemical sensor shows a good stability (RSD 4.2%), high selectivity and low detection limit for AA detection. In addition, it also demonstrates that the proposed sensor can be applied to detect AA in real urine samples with satisfactory results.

A novel bio-electrochemical ascorbic acid sensor modified with Cu4(OH)6SO4nanorods

Cu(4)(OH)(6)SO(4) (brochantite) is an undesirable oxidation product of copper-bearing sulfides, and it is seldom considered to be biologically and electrochemically active. In this paper, we report that Cu(4)(OH)(6)SO(4) nanoparticles in fact possess an intrinsic electrocatalytic activity, which is explored as a biosensing material to oxidize L-ascorbic acid (AA). The Cu(4)(OH)(6)SO(4) nanorod modified biosensor exhibits excellent performance for the determination of l-ascorbic acid with a response time of less than 8 s, a linear range between 0.017 and 6 mM, and a sensitivity of 17.53 μA mM(-1). A high selectivity towards the oxidation of AA in the presence of dopamine (DA) and acetyl aminophenol (AP) is also observed at their maximum physiological concentrations. The good analytical performance and long-term stability, low cost and straightforward fabrication method made the Cu(4)(OH)(6)SO(4) nanomaterials promising for the development of effective electrochemical sensors for a wide range of potential applications in medicine, biotechnology and environmental chemistry.

Selective determination of ascorbic acid with a novel hybrid material based 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid and the Dawson type ion [P2Mo18O62]6− immobilized on glassy carbon

In this study, we synthesized a new hybrid material using well-Dawson K6[P2Mo18O62]·nH2O and a room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]). CHN elemental analysis showed that one mole of [P2Mo18O62]6− reacts with 6 moles of [BMIM]+ to form [BMIM]6P2Mo18O62. FT-IR spectra showed the presence of both 1-butyl-3-methylimidazolium cation and the Dawson anion. TG analysis displayed a relative thermal stability of the hybrid material compared to the parent Dawson POM. The new hybrid material [BMIM]6P2Mo18O62 was immobilized on glassy carbon (GC) electrode and the modified electrode was investigated by cyclic voltammetry and amperometry. Compared to the electrochemical behavior of dissolved [P2Mo18O62]6−, a slight shift in the redox peaks towards negative potentials is observed for the immobilized [BMIM]6P2Mo18O62. The relationship between the peak currents of the deposited [BMIM]6P2Mo18O62 film and scan rate is shown to be linear, which demonstrates a surface-confined electron transfer processes. [BMIM]6P2Mo18O62 modified electrode showed high sensitivities towards pH and shown to be active even at neutral pH. [BMIM]6P2Mo18O62 modified GC electrode was subjected to cyclic voltammetry and amperometry in the presence of ascorbic acid (AA) and found to exhibit a remarkable catalytic activity towards the oxidation of AA. The catalytic oxidation peak of AA at [BMIM]6P2Mo18O62 modified GC electrode occurs at low potential of ∼0V vs Ag/AgCl at neutral pH and shifts to more positive potentials when pH decreases. Comparison between [BMIM]6P2Mo18O62 and [P2Mo18O62]6− modified GC films towards the oxidation of AA suggests that the significant decrease in the overpotentials recorded with [BMIM]6P2Mo18O62 film is related to the presence of ionic liquid cation in the hybrid material, which probably plays the role of the redox mediator. The resulting AA sensor [BMIM]6P2Mo18O62/GC has a significant sensitivity of ∼63nA/μM AA, fast response time (<9s), low detection limit (<0.1μM), high selectivity towards endogenous interferences such as uric acid, acetaminophen and dopamine, a linear range from 0.1μM to at least 22mM AA and was stable for at least 2weeks. In addition, such AA sensors can operate in a pH range from 0 to at least 7.

Niobium oxide dispersed on a carbon–ceramic matrix, SiO 2/C/Nb 2O 5, used as an electrochemical ascorbic acid sensor

A film of niobium oxide was immobilized on a SiO 2/C carbon–ceramic matrix (specific surface area 270 m 2 g −1) and characterized by N 2 adsorption–desorption isotherms, scanning electron microscopy, X-ray photoelectron spectroscopy and atomic force microscopy. This new carbon–ceramic material, SiO 2/C/Nb 2O 5, was used for construction of electrodes, and it shows ability to improve the electron-transfer between the electrode surface and ascorbic acid. The electrocatalytic oxidation of ascorbic acid was made by differential pulse and cyclic voltammetry techniques, making it potentially useful for developing a new ascorbic acid sensor.

Assembly of ferrocenylhexanethiol functionalized gold nanoparticles for ascorbic acid determination

Gold nanoparticles functionalized with self-assembled films of ferrocenylhexanethiol and mercaptoundecanoic acid (MUA) were used for the determination of ascorbic acid (AA). The modified nanoparticles (mNPs) were prepared by a combination of the modified Schifrin’s and the place-exchange methods. Well-organized films were obtained due to electrostatic attraction between the carboxy groups of MUA and cationic surface of poly(diallyldimethylammonium chloride). The mNP films are highly stable and can be exploited to fabricate an enzyme-less sensor for AA whose function is based on the highly electrocatalytic activity of ferrocene in the mNPs towards AA. The sensor was characterized by cyclic voltammetry and chronoamperometry. Under optimal conditions, the response current towards AA is proportional to its concentration in the range from 8.0 μM to 6.0 mM, with a detection limit of 0.14 μM (at a signal-to-noise ratio of 3). This work represents a simple controlled test-bed for fundamental studies on the use of self-assembled mNPs for sensor applications.

A Dialysis Membrane-Covered Graphite Paste Electrode as a Sensor for Ascorbic Acid

A Dialysis Membrane-Covered Graphite Paste Electrode as a Sensor for Ascorbic Acid

A highly selective amperometric sensor for ascorbic acid based on mesopore-rich active carbon-modified pyrolytic graphite electrode

A kind of new mesopore-rich active carbon (MRAC) was firstly prepared by carbonizing bamboo micro-particles, which was utilized for constructing MRAC-modified pyrolytic graphite electrode (MRAC/PGE). The electrochemical behavior of ascorbic acid (AA) was in detail investigated at the MRAC/PGE. The proposed MRAC/PGE showed an excellent electrocatalytic response towards AA oxidation in neutral buffer solution. The oxidation potential of AA significantly decreased at MRAC/PGE. The oxidation current of AA obtained at the MRAC/PGE is 4.6-fold higher than that of the bare PGE. Using amperometric method, the anodic current is linear with AA concentration in the range of 0.5–2000 μM, with a detection limit about 0.3 μM. Furthermore, the proposed electrode can also avoid major interferences such as dopamine, uric acid, urea, and so on. This new method has been successfully applied for AA assay in urine and pharmaceutical preparations.

Electrochemical ascorbic acid sensor based on DMF-exfoliated graphene

This paper describes the electron transfer properties of graphene nano-sheets (GNSs) immobilised on pyrolysed photoresist film (PPF) electrodes. The former are produced by the dispersion and exfoliation of graphite in dimethylformamide, and they are characterised using transmission electron microscopy, scanning electron microscopy and Raman spectroscopy. Cyclic voltammetry and electrochemical impedance spectroscopy are used to quantify the effect of the GNSs on electrochemical surface area and on electron transfer kinetics. Compelling evidence is reported in relation to the importance of edge-plane sites and defects in the promotion of electron transfer at carbon nanostructures. A novel ascorbic acid (vitamin C) sensor is presented based on the PPF/GNS system, which is effective in the range 0.4 to 6.0 mM, with a 0.12 mM detection limit. The selectivity of the sensor is demonstrated using a commercially available vitamin C supplement. This is the first report of the electrochemical properties of graphene nano-sheets produced using liquid-phase exfoliation, and it will serve as an important benchmark in the development of inexpensive graphene-based electrodes with high surface area and electro-catalytic activity.

Development of an electrochemical ascorbic acid sensor based on the incorporation of a ferricyanide mediator with a polyelectrolyte–calcium carbonate microsphere

A novel electro-active material was successfully prepared with Fe(CN) 6 3− ions loaded by electrostatic interaction onto the layer of poly(allylamine) hydrochloride (PAH), which was first assembled on prepared poly(sodium 4-styrenesulfonate) (PSS)-doped porous calcium carbonate (CaCO 3) microspheres. Further, an electrochemical sensor for use in ascorbic acid (AA) detection was constructed with the use of the above electro-active materials embedded into a chitosan (CS) sol–gel matrix as an electron mediator. The electrocatalytic oxidation of AA by ferricyanide was observed at the potential of 0.27 V, which was negative-shifted compared with that by direct electrochemical oxidation of AA on a glassy carbon electrode. The experimental parameters, including the pH value of testing solution and the applied potential for detection of AA, were optimized. The current electrochemical sensor not only exhibited a good reproducibility and storage stability, but also showed a fast amperometric response to AA in a linear range (1.0 × 10 −6 to 2.143 × 10 −3 M), a low detection limit (7.0 × 10 −7 M), a fast response time (<6 s), and a high sensitivity (−4.5127 μA mM −1).

Layer-by-layer electrochemical assembly of poly(diphenylamine)/phosphotungstic acid as ascorbic acid sensor

A layer-by-layer (LbL) film assembly was constructed that comprises alternative layers of poly(diphenylamine) (PDPA) and phosphotungstic acid (PTA). First, a layer of oxidized PDPA (referred to as PDPA(+)) was deposited by electropolymerization. Then, a layer of negatively charged PTA was deposited on the PDPA(+) layer . This processes was repeated several times to obtain multilayer LbL film (PDPA/PTA)n, where n is the number of double layers. The LbLs were characterized by UV-Vis spectroscopy, FT-IR spectroscopy and X- ray diffraction spectroscopy. The process of formation of the LbL assembly was monitored by electrochemical methods. Electrochemical studies revealed that this LbL film possesses a remarkable electrocatalytic activity towards oxidation of ascorbic acid in neutral aqueous medium. The enhanced electrocatalytic activity of (PDPA/PTA)n LbL film is attributed to the existence of tungsten atoms in the interlayers of PDPA.

Optical ascorbic acid sensor based on the fluorescence quenching of silver nanoparticles

A sensitive and selective fluorimetric sensor for the assay of ascorbic acid (AA) using silver nanoparticles as emission reagent was investigated. In this study, silver nanoparticles were prepared based on aqueous-gaseous phase reaction of silver nitrate solution and ammonia gas. The nanoparticles were water-soluble, stable and had a narrow emission band. They were used as a fluorescence probe for the assay of ascorbic acid on its quenching effect on the emission of silver nanoparticles. The principal reason for quenching is likely to be a complexation between ascorbic acid and silver nanoparticles. The quenching mechanism was established by Stern-Volmer law. Under the optimum conditions, the quenched fluorescence intensity was linear with the concentration of ascorbic acid in the range of 4.1 x 10(-6) to 1.0 x 10(-4) m (r = 0.9985) with a detection limit of 1.0 x 10(-7) m. The RSD for repeatability of the sensor for the assay of ascorbic acid concentration of 3.0 x 10(-5) and 4.0 x 10(-6) m was found to be 1.5 and 1.3%, respectively. The proposed method was applied to the determination of ascorbic acid in vegetables and vitamin C tablets.

Ascorbic acid sensor based on molecularly imprinted polymer-modified hanging mercury drop electrode

Ascorbic acid sensor based on molecularly imprinted polymer (MIP) is reported for sensitive and selective analysis, without any cross-reactivity or matrix effect, in aqueous, blood serum and pharmaceutical samples. The sensor was developed by the direct coating of ascorbic acid-imprinted polymer, prepared from melamine and chloranil, on the surface of a hanging mercury drop electrode (HMDE) at + 0.4 V (vs. Ag/AgCl). The molecular recognition of ascorbic acid was highly specific using non-covalent (hydrophobically driven hydrogen-bonding and electrostatic) interactions. The analyte was preconcentrated and oxidised instantaneously in the imprinted polymer layer giving voltammetric signal on cathodic stripping at optimised operational conditions: accumulation potential + 0.4 V (vs. Ag/AgCl), polymer deposition time 120 s, template accumulation time 120 s, pH 7.0, scan rate 10 mV s − 1 , pulse amplitude 25 mV. The proposed MIP sensor is able to enhance sensitivity substantially so as to detect serum ascorbic acid level as low as 0.26 ng mL − 1 (R.S.D. 0.5%, S/N 3) for the diagnosis of hypovitaminosis C (Vitamin C deficiency).