Interaction of Mitomycin C with DNA Immobilized onto Single‐walled Carbon Nanotube/Polymer Modified Pencil Graphite Electrode

The electrochemical investigation of the interaction between the anticancer drug mitomycin C (MC) and DNA was described using a single‐walled carbon nanotube (SWCNT)/poly(vinylferrocenium) (PVF⁺) modified pencil graphite electrode (PGE). The electrochemical oxidation signals of guanine were monitored before and after the interaction between MC and DNA by using differential pulse voltammetry. The effects of DNA and MC concentration and MC interaction time were examined based on the electrode response. Cyclic voltammetry and electrochemical impedance spectroscopy were used for the characterization of SWCNT/PVF⁺ modified and PVF⁺ modified PGEs. The detection limit corresponded to 625 ng/mL for MC using calf thymus double‐stranded DNA immobilized SWCNT/PVF⁺ modified PGE.     

G‐Quadruplex‐Based DNAzymes Aptasensor for the Amplified Electrochemical Detection of Thrombin

A novel G‐quadruplex‐based DNAzymes aptasensor for the amplified electrochemical detection of thrombin has been described. The aptasensor utilized a combination of hemin and guanine‐rich thrombin‐binding aptamer (TBA) to form horseradish peroxidase (HRP)‐mimicking DNAzymes with peroxidase catalytic activity. In the presence of thrombin, the enzyme activity could be extensively promoted, thereby providing the amplified electrochemical readout signals for detecting thrombin. This aptasensor exhibited high sensitivity and selectivity for thrombin determination, which enabled the analysis of thrombin with a detection limit of 6×10^–11 M. On the basis of results, this method could have broad applications in the detection of proteins and other biomolecules.     

Poly(γ‐benzyl‐L‐glutamate)‐functionalized single‐walled carbon nanotubes from surface‐initiated ring‐opening polymerizations of N‐carboxylanhydride

Single‐walled carbon nanotubes (SWCNTs) have been functionalized with poly(γ‐benzyl‐L ‐glutamate) (PBLG) by ring‐opening polymerizations of γ‐benzyl‐L ‐glutamic acid‐based N‐carboxylanhydrides (NCA‐BLG) using amino‐functionalized SWCNTs (SWCNT‐NH₂) as initiators. The SWCNT functionalization has been verified by FTIR spectroscopy and transmission electron microscopy. The FTIR study reveals that surface‐attached PBLGs adopt random‐coil conformations in contrast to the physically absorbed or bulk PBLGs, which exhibit α‐helical conformations. Raman spectroscopic analysis reveals a significant alteration of the electronic structure of SWCNTs as a result of PBLG functionalization. The PBLG‐functionalized SWCNTs (SWCNT‐PBLG) exhibit enhanced solubility in DMF. Stable DMF solutions of SWCNT‐PBLG/PBLG with a maximum SWCNTs concentration of 259 mg L^?1 can be readily obtained. SWCNT‐PBLG/PBLG solid composites have been characterized by differential scanning calorimetry, thermogravimetric analysis, wide/small‐angle X‐ray scattering (W/SAXS), scanning electron microscopy, and polarized optical microscopy for their thermal or morphological properties. Microfibers containing SWCNT‐PBLG and PBLG can also be prepared via electrospinning. WAXS characterization reveals that SWCNTs are evenly distributed among PBLG rods in solution and in the solid state where PBLGs form a short‐range nematic phase interspersed with amorphous domains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2340–2350, 2010     

Electrochemical Analysis of Acrylamide Using Screen‐Printed Carboxylated Single‐Walled Carbon Nanotube Electrodes

Acrylamide (AA) was electrochemically detected and quantified by means of its voltammetric response on carboxylic modified Single‐Walled Carbon Nanotube Screen Printed Electrodes (COOH‐SWCNT‐SPEs). The electroreduction signal of AA was proportional to AA concentration at low values (below 300 µM) and the observed sensitivity was explained in terms of AA adsorption on the COOH‐SWCNT‐SPEs that was demonstrated using the electrochemical response of [Fe(CN)₆]^3? and [Fe(CN)₆]^4? and Raman spectroscopy experiments. In order to test the suggested analytic approach (LOD of 0.03 µM, LOQ of 0.04 µM), detection and quantification of AA in fried potatoes was carried out using the proposed electrochemical method and HPLC. Both techniques showed similar contents of AA.     

Structural and Binding Effects of Chemical Modifications on Thrombin Binding Aptamer (TBA)

The thrombin binding aptamer (TBA) is a promising nucleic acid-based anticoagulant. We studied the effects of chemical modifications, such as dendrimer Trebler and NHS carboxy group, on TBA with respect to its structures and thrombin binding affinity. The two dendrimer modifications were incorporated into the TBA at the 5′ end and the NHS carboxy group was added into the thymine residues in the thrombin binding site of the TBA G-quadruplex (at T4, T13 and both T4/T13) using solid phase oligonucleotide synthesis. Circular dichroism (CD) spectroscopy confirmed that all of these modified TBA variants fold into a stable G-quadruplex. The binding affinity of TBA variants with thrombin was measured by surface plasmon resonance (SPR). The binding patterns and equilibrium dissociation constants (K_D) of the modified TBAs are very similar to that of the native TBA. Molecular dynamics simulations studies indicate that the additional interactions or stability enhancement introduced by the modifications are minimized either by the disruption of TBA–thrombin interactions or destabilization elsewhere in the aptamer, providing a rational explanation for our experimental data. Overall, this study identifies potential positions on the TBA that can be modified without adversely affecting its structure and thrombin binding preference, which could be useful in the design and development of more functional TBA analogues.     

Electrocatalytic Oxidation of Hydrogen Peroxide on Poly(m‐toluidine)‐Nickel Modified Carbon Paste Electrode in Alkaline Medium

The poly(m‐toluidine) film was prepared by using the repeated potential cycling technique in an acidic solution at the surface of carbon paste electrode. Then transition metal ions of Ni(II) were incorporated to the polymer by immersion of the modified electrode in a 0.2 M NiSO₄, also the electrochemical characterization of this modified electrode exhibits stable redox behavior of the Ni(III)/Ni(II) couple. The electrocatalytic ability of Ni(II)/poly(m‐toluidine)/modified carbon paste electrode (Ni/PMT/MCPE) was demonstrated by electrocatalytic oxidation of hydrogen peroxide with cyclic voltammetry and chronoamperometry methods in the alkaline solution. The effects of scan rate and hydrogen peroxide concentration on the anodic peak height of hydrogen peroxide oxidation were also investigated. The catalytic oxidation peak current showed two linear ranges with different slopes dependent on the hydrogen peroxide concentration and the lower detection limit was 6.5 μM (S/N=3). The catalytic reaction rate constant, (k_h), was calculated 5.5×10² M^?1 s^?1 by the data of chronoamperometry. This modified electrode has many advantages such as simple preparation procedure, good reproducibility and high catalytic activity toward the hydrogen peroxide oxidation. This method was also applied as a simple method for routine control and can be employed directly without any pretreatment or separation for analysis cosmetics products.     

Selective Detection of Dopamine in Presence of Ascorbic Acid by Use of Glassy‐Carbon Electrode Modified with Amino‐β‐Cyclodextrin and Carbon Nanotubes

A glassy carbon electrode modified with per‐6‐amino‐β‐cyclodextrin (β‐CDNH₂) and functionalized single‐walled carbon nanotubes (SWCNT‐COOH) was elaborated. This structure was investigated for the detection of dopamine acid (DA) in presence of ascorbic acid (AA). The sensor behavior was studied by cyclic voltammetry, square wave voltammetry and electrochemical impedance spectroscopy. The analysis results show that the electrode modification with CD derivative improves the sensitivity and selectivity of the DA recognition; the electrochemical response was further improved by introduction of SWCNT‐COOH. The sensor shows good and reversible linear response toward DA within the concentration range of 7×10^?7–10^?4 M with a detection limit of 5×10^?7 M.     

Residual Metal Impurity Aids Facile In Situ Electrochemical Surface Derivatization of Single‐Walled Carbon Nanotubes

Residual metal impurities were exploited as reactants in the functionalization of the surface of single‐walled carbon nanotubes (SWCNT) with nickel hexacyanoferrate (NiHCF) by simple electrochemical cycling in ferricyanide solutions. This facile in situ electrochemical modification process provides intimate contact between NiHCF and SWCNTs that improves the stability of the redox property and reactivity of NiHCF. The characteristic redox behavior of NiHCF on SWCNT surfaces can be used as an electrochemical probe to access qualitative and quantitative information on unknown electroactive metal impurities in SWCNTs. Significantly, the NiHCF‐modified SWCNTs exhibit pseudocapacitive behavior, and the calculated specific capacitances are 710 and 36 F g^?1 for NiHCF‐SWCNTs and SWCNTs respectively. Furthermore, NiHCF‐SWCNTs were transformed into Ni(OH)₂/SWCNTs and used for enzymeless glucose oxidation.     

Impedimetric Aptasensors Based on Carbon Nanotubes – Poly(methylene blue) Composite

The effect of aptamer structure and immobilization platform on the efficiency of thrombin binding and its detection using electrochemical impedance spectroscopy (EIS) characteristics was investigated with aptasensors based on glassy carbon electrodes covered with multiwalled carbon nanotubes (MWNTs). Aptamers with one or two binding sequences GGTTGGTGTGGTTGG specific for thrombin and poly(dA) and poly(dT) tags able to form dimeric products (aptabodies) were used to establish significance of steric and electrostatic factors in aptasensor performance. We have shown that electropolymerization of methylene blue onto MWNTs significantly improved electrochemical characteristics and sensitivity of thrombin detection against bare MWNTs. Charge transfer resistance and capacitance of the surface layer were measured in the presence of redox probe [Fe(CN)₆]^3?/4?. Aptasensors make it possible to detect thrombin in the concentration range 1 nM–1 µM with the limit of detection of 0.7 nM (monitoring resistance changes) and 0.5 nM (capacitance changes), respectively.     

Two‐Photon Chemistry in Ruthenium 2,2′‐Bipyridyl‐Functionalized Single‐Wall Carbon Nanotubes

Ruthenium polypyridyl complexes are widely used as light harvesters in dye‐sensitized solar cells. Since one of the potential applications of single‐wall carbon nanotubes (SWCNTs) and their derived materials is their use as active components in organic and hybrid solar cells, the study of the photochemistry of SWCNTs with tethered ruthenium polypyridyl complexes is important. A water‐soluble ruthenium tris(bipyridyl) complex linked through peptidic bonds to SWCNTs (Ru‐SWCNTs) was prepared by radical addition of thiol‐terminated SWCNT to a terminal C?C double bond of a bipyridyl ligand of the ruthenium tris(bipyridyl) complex. The resulting macromolecular Ru‐SWCNT (≈500 nm, 15.6 % ruthenium complex content) was water‐soluble and was characterized by using TEM, thermogravimetric analysis, chemical analysis, and optical spectroscopy. The emission of Ru‐SWCNT is 1.6 times weaker than that of a mixture of [Ru(bpy)₃]²⁺ and SWCNT of similar concentration. Time‐resolved absorption optical spectroscopy allows the detection of the [Ru(bpy)₃]²⁺‐excited triplet and [Ru(bpy)₃]⁺. The laser flash studies reveal that Ru‐SWCNT exhibits an unprecedented two‐photon process that is enabled by the semiconducting properties of the SWCNT. Thus, the effect of the excitation wavelength and laser power on the transient spectra indicate that upon excitation of two [Ru(bpy)₃]²⁺ complexes of Ru‐SWCNT, a disproportionation process occurs leading to delayed formation of [Ru(bpy)₃]⁺ and the performance of the SWCNT as a semiconductor. This two‐photon delayed [Ru(bpy)₃]⁺ generation is not observed in the photolysis of [Ru(bpy)₃]³⁺; SWCNT acts as an electron wire or electron relay in the disproportionation of two [Ru(bpy)₃]²⁺ triplets in a process that illustrates that the SWCNT plays a key role in the process. We propose a mechanism for this two‐photon disproportionation compatible with i) the need for high laser flux, ii) the long lifetime of the [Ru(bpy)₃]²⁺ triplets, iii) the semiconducting properties of the SWNT, and iv) the energy of the HOMO/LUMO levels involved.     

A novel label-free electrochemical aptasensor for thrombin based on the {nano-Au/thionine}n multilayer films as redox probes

Herein, a novel label-free electrochemical aptasensor based on direct immobilization of the redox probes on an electrode surface was reported. Gold electrode coated Nafion was firstly modified with redox probe-thionine (Thi) through ion exchange adsorption. Then, with the help of chemisorption and electrostatic adsorption, negatively charged nano-Au and positively charged Thi were layer-by-layer (LBL) self-assembled onto the modified electrode surface, which formed {nano-Au/Thi⁺}_n multilayer films for improving the amount of redox probes and immobilizing thiolated thrombin aptamers (TBA). In the presence of target thrombin (TB), the TBA on the multilayer film could catch the TB onto the electrode surface, which resulted in a barrier for electro-transfer, leading to decrease of the current. The proposed method avoided the cubsome redox probe labeling process, increased the amount of redox probe and reduced the distance between the redox probe and electrode surface. Thus, the approach showed a high sensitivity and a wider linearity to TB in the range from 0.12 nM to 46 nM with a detection limit of 40 pM.     

Cu(II) and Ni(II)‐1,10‐phenanthroline‐ 5,6‐dione‐amino acid ternary complexes exhibiting pH‐sensitive redox properties

Syntheses, and electrochemical properties of two novel complexes, [Cu(phendio)(L ‐Phe)(H₂O)](ClO₄) ·H₂O (1) and [Ni(phendio)(Gly)(H₂O)](ClO₄)·H₂O (2) (where phendio = 1,10‐phenanthroline‐5,6‐dione, L ‐Phe = L ‐phenylalanine, Gly = glycine), are reported. Single‐crystal X‐ray diffraction results of (1) suggest that this complex structure belongs to the orthorhombic crystal system. The electrochemical properties of free phendio and these complexes in phosphate buffer solutions in a pH range between 2 and 9 have been investigated using cyclic voltammetry. The redox potential of these compounds is strongly dependent on the proton concentration in the range of ? 0.3–0.4 V vs SCE (saturated calomel reference electrode). Phendiol reacts by the reduction of the quinone species to the semiquinone anion followed by reduction to the fully reduced dianion. At pH lower than 4 and higher than 4, reduction of phendio proceeds via 2e^?/3H⁺ and 2e^?/2H⁺ processes. For complexes (1) and (2), being modulated by the coordinated amino acid, the reduction of the phendio ligand proceeds via 2e^?/2H⁺ and 2e^?/H⁺ processes, respectively. Copyright © 2006 John Wiley & Sons, Ltd.     

Voltammetric Determination of Phenoxybenzyl‐Type Insecticides at Chemically Modified Conducting Polymer‐Carbon Nanotubes Coated Electrodes

The electrochemical reduction of three common insecticides such as cypermethrin (CYP), deltamethrin (DEL) and fenvalerate (FEN) was investigated at glassy carbon electrode (GCE), multiwalled carbon nanotubes modified GCE (MWCNT‐GCE), polyaniline (herein called as modifier M₁) and polypyrrole (herein called as modifier M₂) deposited MWCNT/GCE using cyclic voltammetry. Influences of pH, scan rate, and concentration were studied. The surface morphology of the modified film was characterized by scanning electron microscopy (SEM) and X‐ray diffraction analysis (XRD). A systematic study of the experimental parameters that affect differential pulse stripping voltammetry (DPSV) was carried out and the optimized experimental conditions were arrived at. The calibration plots were linear over the insecticide's concentration range 0.1–100 mg L^?1 and 0.05–100 mg L^?1 for all the three insecticides at MWCNT‐GCE and MWCNT(M₁)‐GCE respectively. The MWCNT(M₂)‐GCE performed well among the three electrode systems and the determination range obtained was 0.01–100 mg L^?1 for CYP, DEL and FEN. The limit of detection (LOD) was 0.35 μg L^?1, 0.9 μg L^?1 and 0.1 μg L^?1 for CYP, DEL and FEN respectively on MWCNT(M₂)‐GCE modified system. Suitability of this method for the trace determination of insecticide in spiked soil sample was also determined.     

Elongated Thrombin Binding Aptamer: A G‐Quadruplex Cation‐Sensitive Conformational Switch

Aptamer‐based biosensors offer promising perspectives for high performance, specific detection of proteins. The thrombin binding aptamer (TBA) is a G‐quadruplex‐forming DNA sequence, which is frequently elongated at one end to increase its analytical performances in a biosensor configuration. Herein, we investigate how the elongation of TBA at its 5′ end affects its structure and stability. Circular dichroism spectroscopy shows that TBA folds in an antiparallel G‐quadruplex conformation with all studied cations (Ba²⁺, Ca²⁺, K⁺, Mg²⁺, Na⁺, NH₄⁺, Sr²⁺ and the [Ru(NH₃)₆]^2+/3+ redox marker) whereas other structures are adopted by the elongated aptamers in the presence of some of these cations. The stability of each structure is evaluated on the basis of UV spectroscopy melting curves. Thermal difference spectra confirm the quadruplex character of all conformations. The elongated sequences can adopt a parallel or an antiparallel structure, depending on the nature of the cation; this can potentially confer an ion‐sensitive switch behavior. This switch property is demonstrated with the frequently employed redox complex [Ru(NH₃)₆]³⁺, which induces the parallel conformation at very low concentrations (10 equiv per strand). The addition of large amounts of K⁺ reverts the conformation to the antiparallel form, and opens interesting perspectives for electrochemical biosensing or redox‐active responsive devices.     

A Polypyrrole‐Imprinted Electrochemical Sensor Based on Nano‐SnO2/Multiwalled Carbon Nanotubes Film Modified Carbon Electrode for the Determination of Oleanolic Acid

A sensitive molecularly imprinted electrochemical sensor with specific recognition ability for oleanolic acid was synthesized by modification of multiwalled carbon nanotubes (MWNTs) decorated with tin oxide nanoparticles (nano‐SnO₂/MWNTs) and polypyrrole‐imprinted polymer on a carbon electrode. The morphology and electrochemical performance of the imprinted sensor were investigated by using scanning electron microscope (SEM), X‐ray diffraction (XRD), cyclic voltammetry (CV), linear sweep voltammetry (LSV) and amperometric i–t curve. The results showed that the imprinted sensor displayed excellent selectivity toward oleanolic acid. A linear relationship between the response currents and oleanolic acid concentrations ranging from 5.0×10^?8 g/L to 2.0×10^?5 g/L was obtained for the imprinted sensor. The limit of detection (LOD) of the imprinted sensor toward oleanolic acid was calculated as 8.6×10^?9 g/L at a signal to noise ratio (S/N) of 3. This imprinted sensor was successfully applied to the determination of oleanolic acid in Acitinidia deliciosa root samples.     

A Sandwich‐type Electrochemiluminescence Aptasensor for Thrombin Based on Functional Co‐polymer Electrode Using Ru(bpy)32+ Doped Nanocomposites as Signal‐amplifying Tags

Herein, a signal‐on sandwich‐type electrochemiluminescence (ECL) aptasensor for the detection of thrombin (TB) was proposed. The graphene (GR) doped thionine (TH) was electropolymerized synchronously on the bare glassy carbon electrode (GCE) to form co‐polymer (PTG) electrode. The gold nanoparticles (AuNPs) were decorated on the surface of the PTG by in‐situ electrodeposition, and the functional co‐polymer (PTG‐AuNPs) electrode was utilized as sensing interface. Then, TB binding aptamer I (TBA I) as capture probes were modified on the PTG‐AuNPs electrode to capture TB, and Ru(bpy)₃²⁺/silver nanoparticles doped silica core‐shell nanocomposites‐labeled TB binding aptamer II (RuAg/SiO₂NPs@TBA II) were used as signal probes to further bind TB, resulting in a sandwich structure. With the assistant of silica shell and AgNPs, the enrichment and luminous efficiency of Ru(bpy)₃²⁺ were significantly improved. Under the synergy of PTG‐AuNPs and RuAg/SiO₂NPs, the ECL signal was dramatically increased. The proposed ECL aptasensor displayed a wide linear range from 2 fM to 2 pM with the detection limit of 1 fM, which is comparable or better than that in reported ECL aptasensors for TB using Ru(bpy)₃²⁺ and its derivatives as the luminescent substance. The excellent sensitivity makes the proposed aptasensor a promising potential in pharmaceutical and clinical analysis.     

Sensitive Electrochemical Aptasensor for Thrombin Detection with Platinum Nanoparticles,Blocking Reagent‐Horseradish Peroxidase and Graphene Oxide as Enhancers

A highly sensitive thrombin electrochemical aptasensor with Pt nanoparticles, blocking reagent‐horseradish peroxidase (HRP) and inert graphene oxide (GO) as enhancers was successfully fabricated. Firstly, Pt nanoparticles with high surface to volume ratio could increase the amount of the immobilized redox probe hexacyanoferrate nanoparticles (NiHCFNPs) and effectively enhance the electron transfer. Secondly, HRP and Pt nanoparticles with high catalytic activity extremely amplify the electrochemical signal of NiHCFNPs toward H₂O₂. Lastly, inert graphene oxide (GO) labeled TBA could be used for enlarging the steric hindrance of thrombin. As a result, the aptasensor showed a high sensitivity with a detection limit of 500 fM.     

A label-free and high sensitive aptamer biosensor based on hyperbranched polyester microspheres for thrombin detection

In this paper, we have synthesized hyperbranched polyester microspheres with carboxylic acid functional groups (HBPE-CA) and developed a label-free electrochemical aptamer biosensor using thrombin-binding aptamer (TBA) as receptor for the measurement of thrombin in whole blood. The indium tin oxide (ITO) electrode surface modified with HBPE-CA microspheres was grafted with TBA, which has excellent binding affinity and selectivity for thrombin. Binding of the thrombin at the modified ITO electrode surface greatly restrained access of electrons for a redox probe of [Fe(CN)₆]^3−/4−. Moreover, the aptamer biosensor could be used for detection of thrombin in whole blood, a wide detection range (10 fM–100 nM) and a detection limit on the order of 0.90 fM were demonstrated. Control experiments were also carried out by using bull serum albumin (BSA) and lysozyme in the absence of thrombin. The good stability and repeatability of this aptamer biosensor were also proved. We expect that this demonstration will lead to the development of highly sensitive label-free sensors based on aptamer with lower cost than current technology. The integration of the technologies, which include anticoagulant, sensor and nanoscience, will bring significant input to high-performance biosensors relevant to diagnostics and therapy of interest for human health.     

Cyclic Voltammograms of Ferrocene on Multi‐Walled Carbon Nanotubes (MWCNTs)‐Modified Edge Plane Pyrolytic Graphite (EPPG) Electrode in Room Temperature Ionic Liquids (RTILs) of 1‐Ethyl‐3‐Methylimidazolium Tetrafluoroborate (EMIBF4)

In this work, the electrochemical behavior of ferrocene (Fc) was investigated by cyclic voltammetry (CV) in room temperature ionic liquids (RTILs) of 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMIBF₄) on glass carbon (GC), edge plane pyrolytic graphite (EPPG) and multi‐walled carbon nanotube (MWCNTs)‐modified EPPG electrodes, respectively. The results demonstrated that on GC electrode, pairs of well‐defined reversible peaks were observed, while for the electrode of EPPG, the peak potential separation (ΔE_p) is obviously larger than the theoretical value of 59 mV, hinting that the electrode of EPPG is distinguished from the commonly used electrode, consistent with the previous proposition that EPPG has many “defects”. To obtain an improved electrochemical response, multi‐walled carbon nanotubes (MWCNTs) were modified on the electrode of EPPG; the increased peak current and promoted peak potential separation not only proved the existence of “defects” in MWCNTs, but also supported that “creating active points” on an electrode is the main contribution of MWCNTs. Initiating the electrochemical research of Fc on the MWCNTs‐modified EPPG electrode in RTILs and verifying the presence of “defects” on both EPPG and MWCNTs using cyclic voltammograms (CVs) of Fc obtained in RTILs of EMIBF₄, is the main contribution of this preliminary work.     

Electrochemiluminescence Based on Solid State Tri(4,7‐diphenyl‐1,10‐phenanthroline) Ruthenium(II) Ditetrakis(4‐chlorophenyl) Borate Immobilized on Carbon Fibers

A simple method for immobilization of tri(4,7‐diphenyl‐1,10‐phenanthroline) ruthenium(II) ditetrakis(4‐chlorophenyl) borate ([Ru(dpp)₃][(4‐Clph)₄B]₂) on carbon fiber electrodes was developed. Excellent electrochemical activity and electrochemiluminescence (ECL) signal of the coated carbon fiber electrodes were observed using oxalate as the co‐reactant. In addition, the effects of pH, scan rate, nitrogen and oxygen on ECL intensity were also studied. To demonstrate the reliability, the coated carbon fiber electrodes were used as ECL detectors and very low concentration of phenol was detectable (5.0×10^?8 M).