Differential Pulse Voltammetric Research Articles

Challenge Approach of an Inexpensive Electrochemical Sensor for Rapid Selective Determination of two Non‐classical β‐Lactams in Presence of Different Degradants and Interference Substances

AbstractAn inexpensive stability−indicating anodic voltammetric method for rapid determination of two non‐classical β‐lactam antibiotics; Meropenem (MP) and Ertapenem (EP) has been developed and validated. The method was based on the enhancement of voltammetric response at a disposable graphite pencil electrode (GPE). Differential pulse voltammetric (DPV) method was developed for quantification of both drugs in B−R buffer solution (pH 2.0) at GPE. The GPE displayed very good voltammetric behavior with significant enhancement of the peak current compared to glassy carbon electrode (GCE). Stress stability studies were performed using 0.5 M of either HCl or NaOH and H2O2. Mass and infrared spectroscopy were used for identification of degradants and their pathways were illustrated. Under optimal conditions, the peak currents showed a linear dependence with drug concentrations. The achieved limits of detection (LOD) were 1.23, 2.07 and 1.50 μM for MP and two waves of EP, respectively. The developed voltammetric method was successfully applied for direct determination of MP and EP in drug substances, pharmaceutical vials and in presence of either their corresponding hydrolytic, oxidative‐degradants or interfering substances with no potential interferences. The differential pulse voltammograms were highly advantageous and applicable in QC laboratories for rapid, selective micro‐determination of MP and EP.

Modification of carbon paste electrode by electrochemical polymerization of neutral red and its catalytic capability towards the simultaneous determination of catechol and hydroquinone: A voltammetric study

In this study, a new electrochemical sensor was developed and fabricated based upon the electrochemical polymerization of neutral red (NR) on the surface of carbon paste electrode (CPE). The newly developed sensor shows electrocatalytic capability towards the simultaneous determination of catechol (CC) and hydroquinone (HQ) in presence of 0.2M phosphate buffer solution (PBS) at pH7.4 with the scan rate of 50mVs−1. Electrochemical measurements were performed using both cyclic voltammetry (CV) and differential pulse voltammetric (DPV) methods at poly (neutral red) modified carbon paste electrode (PNR/MCPE). The effects of scan rate, concentration and pH variation for CC and HQ was investigated at PNR/MCPE. The proposed sensor exhibits adsorption-controlled type of electrode process, moreover it show good detection limit (LOD) (CC=6.46μM and HQ=4.97μM) and limit of quantification (LOQ) (CC=21.5μM and HQ=16.5μM). Hence, the proposed sensor was successfully applied in the simultaneous determination of CC and HQ with satisfied results.

Enantioselective analysis of Moxifloxacin hydrochloride enantiomers with graphene-β-Cyclodextrin-nanocomposite modified carbon paste electrode using adsorptive stripping differential pulse Voltammetry

Enantioselective analysis of Moxifloxacin hydrochloride (MOX) enantiomers was investigated on carbon paste electrode (CPE) modified with chiral selector β-Cyclodextrin and graphene nanosheets (GNS) employing adsorptive stripping differential pulse voltammetric (AdSDPV) technique. Electrochemical chiral discrimination was obtained due to β-Cyclodextrin, which has 35 chiral centres as a binding site resulting in very tight fit inclusion complex based on host-guest interactions. Enantioselectivity of present electrode system of graphene nanosheets and β-cyclodextrin modified carbon paste electrode (GNS-β-CD-CPE) gives difference in anodic oxidation peak potential of enantiomers S,S-MOX and R,R-MOX at 1.039V and 0.917V in B.R buffer solution in pH 7 confirming successful enantiomer detection respectively. Various techniques such as X-Ray diffraction (XRD), Scanning electron microscopy (SEM), Thermogravimetric analysis (TGA) and Fourier transform infra red spectroscopy (FT-IR) were employed for characterization of electrode surface. The electrocatalytic response of MOX at GNS-β-CD-CPE was measured using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Electrical conductivity of modified electrode was investigated by electrochemical impedance spectroscopy (EIS) which indicates its good conductivity over plain CPE. The proposed enantioselective electrochemical sensor was highly efficient and capable of sensing optically active isomers of MOX which is the S,S-enantiomer from its potential chiral antipode R,R-MOX enantiomer with large difference of 122mV shift in peak potential which suggests great stereoselectivity is achieved due to chiral environment provided by chiral selector β-Cyclodextrin. Determination of percentage enantiomeric composition of S,S-MOX in racemic mixture extend future applications of chiral electroanalytical system of β-CD. In the present work, it is for the first time enantiomeric electrochemical recognition of multi-chiral drug with two chiral centres has been done voltammetrically.

Ruthenium Nanoparticles Mediated Electrocatalytic Reduction of UO22+ Ions for Its Rapid and Sensitive Detection in Natural Waters.

Reduction of UO22+ ions to U4+ ions is difficult due to involvement of two axially bonded oxygen atoms, and often requires a catalyst to lower the activation barrier. The noble metal nanoparticles (NPs) exhibit high electrocatalytic activity, and could be employed for the sensitive and rapid quantifications of U022+ ions in the aqueous matrix. Therefore, the Pd, Ru, and Rh NPs decorated glassy carbon electrode were examined for their efficacy toward electrocatalytic reduction of UO22+ ions and observed that Ru NPs mediate efficiently the electro-reduction of UO22+ ions. The mechanism of the electroreduction of UO22+ by the RuNPs/GC was studied using density functional theory calculations which pointed different approach of 5f metal ions electroreduction unlike 4p metal ions such as As(III). RuNP decorated on the glassy carbon would be hydrated, which in turn assist to adsorb the uranyl sulfates through hydrogen bonding thus facilitated electro-reduction. Differential pulse voltammetric (DPV) technique, was used for rapid and sensitive quantification of UO22+ ions. The RuNPs/GC based DPV technique could be used to determine the concentration of uranyl in a few minutes with a detection limit of 1.95 ppb. The RuNPs/GC based DPV was evaluated for its analytical performance using seawater as well lake water and groundwater spiked with known amounts of UO22+.

Novel approach for the voltammetric evaluation of antioxidant activity using DPPH[rad]-modified electrode

The electrochemical behavior of 2,2-diphenyl-1-picrylhydrazyl (DPPH) immobilized on the electrode surface has been studied. Bare glassy carbon electrode (GCE) and modified with dispersions of CeO2 nanoparticles in water (CeO2-H2O/GCE) and cationic surfactant cetylpyridinium bromide medium (CeO2-CPB/GCE) has been investigated as a platform for the DPPH immobilization. The best voltammetric characteristics (peak potential separation of 70mV, system reversibility with currents ratio of 0.98 and the highest peaks currents) have been observed on CeO2-CPB/GCE. The effect of CeO2 nanoparticles concentration has been evaluated. Scanning electron microscopy and electrochemical impedance spectroscopy have been applied for the electrode characterization. DPPH/CeO2-CPB/GCE has been used for the estimation of the antioxidants activity of natural phenolic antioxidants (quercetin, tannin, catechin and ferulic acid) expressed as the EC50 parameter according to differential pulse voltammetric (DPV) data. The EC50 decreased in the following order: quercetin (29±1μM), tannin (29±4μM), catechin (117±4μM) and ferulic acid (731±17μM). These data are in a good agreement with the results of standard spectrophotometric determination. The developed approach has been successfully applied for the antioxidant activity evaluation of medicinal herbs tinctures, infusions and decoctions.

Square wave and differential pulse voltammetric methods for the analysis of olivetol at gold electrode

<p class="PaperAbstract"><span lang="EN-US">Few electrochemical techniques have been employed for the determination of the powerful antitumor agent olivetol (OLV) in real samples at gold electrode. An intense and well pronounced oxidation peak was obtained at 1.04 V in the phosphate buffer pH 5.0 as the supporting electrolyte. The effects of pH and scan rate on the oxidation peak were studied. The electrochemical behavior of OLV was investigated using cyclic voltammetric (CV), square wave voltammetric (SWV) and differential pulse voltammetric (DPV) techniques. In DPV and SWV, the gold electrode showed a good sensitivity for OLV in a linear range of 0.1-1.5 µM and 0.1-1.3 µM and detection limits of 1.936×10<sup>-9</sup> M and 4.754</span><span lang="EN-US">×</span><span lang="EN-US">10<sup>-9</sup> M, respectively. A plausible mechanism involving an adsorption controlled oxidation reaction was deduced. The effect of various excipients was also studied and the method was successfully applied for the determination of OLV in human biological samples. </span></p>

Electrochemical sensor based on multiwalled carbon nanotube and gold nanoparticle modified electrode for the sensitive detection of bisphenol A

A novel electrochemical sensor for bisphenol A comprising a multiwalled carbon nanotube (MWCNT) and gold nanoparticle (AuNP) composite modified glassy carbon electrode has been developed. Differential pulse voltammetric and electrochemical impedance characterisation were carried out. Modified electrode architectures with different MWCNT loadings and different numbers of deposited AuNP layers were tested, as well as the influence of pH. Under the best experimental conditions, the sensor exhibited a linear response to BPA from 0.01μM to 0.7μM, with a limit of detection of 4nM, one of the lowest achieved up until now. The reproducibility, repeatability and stability of the sensor were examined and are superior to those reported in the literature using similar architectures for BPA sensors. Perspectives for an impedimetric sensor at micromolar concentrations were also assessed. Finally, the selectivity with respect to common interferents was demonstrated and practical application of the developed modified electrode for the determination of BPA in waters was successfully carried out.

Nano Fe<sub>3</sub>O<sub>4</sub>–graphite paste modified electrochemical sensor for phosphatic pesticide -chlorpyrifos

A sensitive, cost effective and selective electrochemical sensor has been developed by exploiting iron oxide nano-particles as modifier in the paste of graphite powder. Cyclic voltammetric (CV) and differential pulse voltammetric (DPV) working parameters have been standardized and used practically for the determination of chlorpyrifos (O, O-diethyl O-3, 5, 6-trichloropyridin-2-yl phosphorothioate) pesticide from its aqueous solutions. Both techniques were deployed to investigate the electro-chemical interactions between chlorpyrifos and modified carbon paste sensor along with the redox characteristics at analyte/ sensor interface. The significant enhancement in peak current signals and the improved magnitude of the redox peak potential indicated the awe-inspiring facilitation of the electron transfer process by the modifier at the sensor/ analyte interface. The difference in the redox -potential (ΔEp) and peak current ratio (Ipc/Ipa) have revealed a notable surface enhancement characteristic of the modifier that responds the higher concentration gradient of pesticide at the interface. In lower analyte’s concentration range i.e. from 1.0 to 100μM, the peak current varies directly to the pesticide concentration with detection limit of 2.8 x10-6 mol/L. The relative stability of the modified sensor is fine and the reproducibility of the results is up to 98%, even after a gap of two months. The proposed analytical method is quite successful when applied for the quantification of chlorpyrifos from its aqueous samples. The electrochemical sensing/ detection of the pesticide chlorpyrifos is confirmed by its two electrons redox behavior and the same have been explained by suitable reaction scheme as:Keywords: Nano-iron oxide, Chlorpyrifos, Modified graphite paste, Voltammetry, Electrochemical method

Voltammetric determination of catechol and hydroquinone at poly(niacinamide) modified glassy carbon electrode

Niacinamide was electropolymerised on the surface of glassy carbon electrode (GCE) by cyclic voltammetric technique (CV). The fabricated poly(niacinamide) modified glassy carbon electrode (MGCE) was used for the voltammetric determination of catechol (CC) and hydroquinone (HQ) in 0.2M phosphate buffer solution (PBS) at pH7.4 CV and differential pulse voltammetric (DPV) techniques. The study of concentration variation for both CC and HQ was conducted; the lower limit of detection was calculated to be 0.31μM and 0.24μM for CC and HQ by CV technique. The simultaneous separation of the analytes in a binary mixture was showed by the fabricated poly(niacinamide) MGCE by both CV and DPV techniques. The variation of applied scan rate on the binary mixture of CC and HQ was conducted and the results suggest the electrode process was diffusion controlled. The fouling effect by the adsorption of an oxidised product was eliminated by the modified electrode.

An Enzyme-Induced Novel Biosensor for the Sensitive Electrochemical Determination of Isoniazid.

In this present work, a glassy carbon electrode (GCE) was modified primarily with multiwalled carbon nanotubes (MWCNTs) and a composite of MWCNTs and titanium oxide nanoparticles (TiO2NPs). The enzyme horseradish peroxidase (HRP) was immobilized to enhance the sensing ability of GCE. The proposed biosensor was used for the sensitive determination of isoniazid (INZ) in various pharmaceutical samples. The electrochemical behaviour of the developed MWCNT-TiO2NPs-HRP-GCE biosensor was studied by using cyclic voltammetry (CV) and differential pulse voltammetric (DPV) techniques. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetry (TGA) and transmission electron microscopy (TEM) techniques were used to characterize the developed sensor. Phosphate buffer solution (PBS) with pH 7 was used as supporting electrolyte in the present investigation. The cyclic voltammetric results revealed that the increment of anodic peak currents for the enzyme-induced sensor was almost 8-fold greater than that of a bare GCE. The DPV technique exhibited good limit of detection and limit of quantification values, viz., 0.0335 μM and 0.1118 μM, respectively. Moreover, the developed sensor showed long-lasting stability and repeatability without any interferents. This strongly indicates that the fabricated sensor shows outstanding electrochemical performance towards INZ, with excellent selectivity and sensitivity. The developed sensor was successfully applied to pharmaceutical samples and gave good percentages of recoveries.

Manganese dioxide nanosheet-decorated ionic liquid-functionalized graphene for electrochemical theophylline biosensing

In this study, a novel theophylline (TP) sensor based on MnO2 nanosheets/ionic liquid-functionalized graphene (MnO2 nanosheets/IL-graphene) was fabricated. Cyclic voltammetry (CV) was used to evaluate the electrochemical behavior of the modified electrode. The surface concentration of the electroactive species, Γ, was calculated to be approximately 2.316×10−10molcm−2 for MnO2 nanosheets on the modified electrode. The resulting system was suitable for electrochemical sensing because of the combined advantages of MnO2 nanosheets and IL-graphene. The differential pulse voltammetric (DPV) results indicated a high ability of the MnO2 nanosheets/IL-graphene/GCE to catalyze the oxidation of TP and, hence, to detect it. DPV determination of TP gave linear responses over the concentration range from 1 to 220μM, and the detection resolution limit was 0.1μM. Furthermore, the applicability of the MnO2 nanosheets/IL-graphene/GCE for analysis in real samples was successfully demonstrated.

Sensitive and Selective Determination of Uric Acid by Modified Glassy Carbon Electrodes with Multi-Walled Carbon Nanotubes Dispersed in Nafion®. Electroanalytical Applications for the Development as Sensors

This work reports the advantages of using glassy carbon electrodes modified with multiwall carbon nanotubes (MWCNT) dispersed in Nafion® (Naf). The selected conditions for the electrochemical sensing were 30.0 s. accumulation at -0.300 V under stirring conditions and quantification in 0.050 M phosphate buffer solution at pH 7.40 by Differential Pulse Voltammetric Adsortive Stripping after medium change. The platform allowed the successful application for the quantification of UA in urine.

CuS–MWCNT based electrochemical sensor for sensitive detection of bisphenol A

The rapid and simple detection of bisphenol A is very important for the safety and reproduction of organisms. Here, a sensitive and reliable electrochemical sensor was established for bisphenol A detection based on the high amplification effect of copper sulfide-multi-walled carbon nanotube (CuS–MWCNT) nanocomposites. The flower-like CuS–MWCNT were successfully synthesized by a simple hydrothermal method accompanied by polyvinylpyrrolidone (PVP). Compared with bare glassy carbon electrode (GCE), CuS–MWCNT modified GCE could amplify the electrochemical signals in about ten times, which was attributed to the synergistic effect of CuS and MWCNT. The MWCNT could increase the specific surface area of electrodes and improve the electrode activity. The integration of CuS could further enhance the electrode conductivity as well as accelerate the electron transfer rate. Raman spectra and transmission electron microscope (TEM) were used to characterize the successful fabrication of CuS–MWCNT nanocomposites and its uniform and monodispersed morphology. Under optimizing conditions, the oxidation currents of bisphenol A via the differential pulse voltammetric (DPV) showed a good linear relationship with its concentration in a wide range of 0.5–100 μM, with a detection limit of 50 nM. This electrochemical sensor of bisphenol A provided a convenient and economical platform with high sensitivity and reproducibility, which had great potential in environmental monitoring.

A new electrochemical platform for ultrasensitive detection of atrazine based on modified self-ordered Nb2O5 nanotube arrays

In this work, one dimensional self-ordered Nb2O5 nanotube arrays were grown from Nb substrate by anodization method and were modified with optimum amounts of chitosan (CS) and carboxyl-Fe3O4 nanoparticles. These nanocomposites were characterized by SEM, XRD, and XPS and used as electrode materials for the direct detection of atrazine traces in aqueous solution. The test signals were obtained from the interaction between anti-atrazine monoclonal antibody and atrazine and recorded using via differential pulse voltammetric (DPV) method in electrochemical system. These modified one-dimensional Nb2O5 nanotube arrays showed the linear detection ranges of 0.04ng/mL–0.6ng/mL and a detection limit of 0.018ng/mL for atrazine under the optimized conditions. These above results indicate that these Nb2O5 nanotube arrays are promising candidates for electrochemical sensors.

Covalently Anchored p‐Aminobenzene Sulfonate Multilayer on a Graphite Pencil Lead Electrode: A Highly Selective Electrochemical Sensor for Dopamine

AbstractAn electrochemical sensor for dopamine (DA) has been developed based on the electrografting of 4‐aminobenzene sulfonic acid (4‐ABSA) onto the graphite pencil lead electrode (GPLE). The process of covalent anchoring and presence of 4‐ABSA on the GPLE was studied using cyclic voltammetry and electrochemical impedance spectroscopy. Electrochemical behaviour of the sensor towards DA, ascorbic acid (AA), and uric acid (UA) was studied in detail in phosphate buffer of pH 7. After optimizing the various parameters that influence the differential pulse voltammetric (DPV) signal for DA, the sensor exhibited a linear response over the 0.5 – 10 μmol⋅L‐1concentration range with a limit of detection, 0.095 μmol⋅L‐1 (at an S/N of 3). The sensor can selectively quantify DA even in the presence of 1 mmol⋅L‐1 AA. Distinct DPV signals were obtained for DA (at 0.191 mV vs. Ag/AgCl) and for UA (at 0.343 mV vs. Ag/AgCl). The sensor is highly selective, sensitive and stable. It was applied to the quantification of DA in injections and urine. Recovery studies were done by spiking both the real samples with a known quantity of DA.

Electrochemical Characteristics and Electrosensing of an Antiviral Drug, Entecavir via Synergic Effect of Graphene Oxide Nanoribbons and Ceria Nanorods

AbstractA sensitive electrochemical sensor was fabricated based on ceria‐graphene oxide nanoribbons composite (CeO2‐GONRs) for an antiviral drug, entecavir (ETV). It was characterized by SEM, EDAX, AFM, IR and Raman spectroscopic techniques. The electrochemical behaviour of ETV was investigated by cyclic voltammetric, differential pulse voltammetric (DPV), linear sweep voltammetric (LSV) and square wave voltammetric (SWV) methods at CeO2‐GONRs modified glassy carbon electrode. Good linearity was observed between the peak current and concentration of ETV in the range of 0.51 ‐ 100 μM with a detection limit of 0.042 μM in DPV method, 2.1 – 61.1 μM with a detection limit of 0.7 μM in LSV method and 0.1 ‐ 80 μM with a detection limit of 68.1 nM in SWV method. The proposed sensitive DPV method was successfully applied for the determination ETV in tablets and biological samples.

Titanium dioxide anchored graphene oxide nanosheets for highly selective voltammetric sensing of dopamine

The authors report on an efficient method for the voltammetric sensing of dopamine (DA) by using an electrode modified with alternating monolayers of graphene oxide (GO) and Titanium dioxide (TiO2) nanoparticles anchored GO nanosheets (NSs)). The as-prepared nanostructures were characterized by photoluminescence spectroscopy, powder X-ray diffraction, Raman spectroscopy, FT-IR spectroscopy, transmission electron microscopy, scanning electron microscopy, atomic force microscopy and Energy Dispersive X-ray Analysis (EDAX) techniques. The GO/TiO2 nanocomposite (NC) was deposited on a glassy carbon electrode (GCE), where it displayed an excellent electrocatalytic activity toward the oxidation of DA, owing to its excellent conductivity, high specific surface area, enhanced interfacial contact and more negative zeta potential. Figures of merit include (a) a fast response (5 s), (b) a wide linear range (between 0.2 and 10 μM of DA) (c) a particularly low detection limit (27 nM), (d) a working potential as low as 0.25 V (vs. Ag/AgCl) and (e) a sensitivity of 1.549 μA·μM−1·cm−2. The GO/TiO2/GCE exhibited excellent selectivity over the other interferences as revealed by the differential pulse voltammetric and amperometric studies. The analysis of spiked urine samples resulted in recoveries in the range of 96 to 106%, with RSDs between 3.8 and 5.2%.

Fabrication and Application of Ferrierite–Modified Carbon Ceramic Electrode in Sensitive Determination of Estradiol

The preparation and characterization of entire volume modified carbon ceramic electrode (CCE) produced by the sol-gel method was reported. For the first time, this type of electrode was modified using ferrierite (FER) belonging to zeolites. The morphology and topography of FER–modified CCE were analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. The electrochemical behavior of FER-CCE in presence of estradiol was tested via cyclic voltammetry. Moreover, the differential pulse voltammetric (DPV) procedure for determination of estradiol was developed. For the comparison the bare ceramic electrode (GP-CCE) was also prepared and investigated in analogous way. The introduction of ferrierite into carbon-ceramic matrix influenced the surface properties and analytical performance of fabricated CCE. The electrode with FER possessed better analytical properties - lower limit of detection (LOD) and lower limit of quantification (LOQ) in comparison to bare electrode. Additionally, the estimated linear dynamic range (LDR) showed better usability of FER-CCE for determination of lower amount of estradiol, since LDR was 0.2–30 μmol L−1 and 4–40 μmol L−1 for FER-CCE and GP-CCE, respectively. Finally, the developed FER-CCE and DPV procedure were successfully used to determine estradiol in pharmaceutical sample–Estrofem tablets.

Electrochemical Sensor Based on Reduced Graphene Oxide Nanoribbons for the Determination of Baicalein in Urine Samples

Electrochemically reduced graphene oxide nanoribbons (ErGONRs) have been prepared, characterized and utilized for sensing of a flavone, baicalein (BAI) by adsorptive stripping differential pulse voltammetric (AdSDPV) and square wave voltammetric (SWV) methods. BAI showed redox peaks (Epa = 0.582 V and Epc = 0.557 V) and an irreversible oxidation peak at 1.402 V on ErGONRs/GCE in phosphate buffer of pH 3. A 50-fold enhanced electrochemical response was observed at ErGONRs/GCE for BAI when compared to that noticed at bare GCE. The parameters concerning the electrochemical behavior of BAI were carefully optimized. Under optimized conditions, SWV and AdSDPV methods showed linearity in the range of 10 nM–87.4 μM and 0.4 μM–50 μM, respectively. Applicability of the proposed electrode was demonstrated by determining BAI in urine samples

Homogeneous Electrochemical Method for Ochratoxin A Determination Based on Target Triggered Aptamer Hairpin Switch and Exonuclease III-Assisted Recycling Amplification

A simple, fast, sensitive, and homogeneous electrochemical method has been developed for ochratoxin A (OTA) determination, which combines the advantage of the high selectivity of aptamer to OTA and high efficiency of exonuclease (Exo) III-assisted recycling amplification mechanism. The metastable hairpin probe (HP) was designed into three parts: regions I is the aptamer of OTA as the target recognition; regions II is poly[dA] sequence as extended DNA (E-DNA); regions III as the target DNA (T-DNA) is complementary to a part of the aptamer to stabilize the hairpin-sharp form of the HP in the absence of OTA. The DNA probe with a methylene blue tag at its 3′ terminus (MB-DNA) was designed to be complementary with T-DNA. Introduction of OTA into the assay leads to the formation change of HP from hairpin shape to open form, thus facilitating the hybridization between T-DNA and MB-DNA. The electrochemical signal is amplified through continuous Exo III cleavage. Under the optimal conditions, the differential pulse voltammetric (DPV) response had a linear relationship with the logarithm of OTA concentration in the range of 0.001~0.5 ng mL−1. In addition, the developed method has been successfully applied to detect OTA in wheat standard quality control sample. This homogeneous electrochemical sensor may have a potential prospect in detecting other molecules or proteins, which possesses the corresponding aptamer, through easily designing the hairpin probe.