Gold Nanoparticle-modified Electrode Research Articles

Application of Graphdiyne Confined Gold Nanoparticles Modified Electrode as A Robust Sensing Platform for The Detection of 7-Hydroxy-6-Methoxy-Hydrocoumarin

A graphdiyne (gdy) and gold nanoparticles (aunps) nanocomposite was formed with aunps growing on the surface and between the layers of gdy, which was used as the sensing interface on carbon ionic liquid electrode (cile) to detect 7-hydroxy-6-methoxy-hydrocoumarin (7–6-hdc) that isolated from the noni juice. The GDY-Au nanocomposite was characterized by different spectroscopic techniques, which exhibited corrugated and folded morphology with large specific surface area. The GDY-Au nanocomposite modified electrode displayed excellent performance which is attributed to the highly conductive nanocomposite, where gdy structure with defects could immobilize more aunps to decrease the electron transfer resistance. In addition, the reaction mechanism of 7–6-hdc at GDY-Au surface was deduced based on the electrochemical kinetics investigations. Combined with density functional theory calculation, it was verified that the active site of 7–6-hdc and the presence of aunps enhanced the electrocatalytic capacity of GDY-Au nanocomposite. Under optimal conditions, the modified electrode displayed a wider linear range from 10.0 nm to 1.0 mm for 7–6-hdc analysis with a detection limit of 3.22 nm (3s0/s). This work provides a promising material to realize accurate analysis for 7–6-hdc, and the discovered sensing mechanism provides method guidance for the exploration of other novel electrochemical sensors.

Sensitive and point-of-care detection of lead ion in river water mediated by terminal deoxynucleotidyl transferase

Excessive lead ions (Pb2+) would make the human body suffer from anemia and neurological disorders. Therefore, it was of great significance to study an efficient method for the point-of-care (POC) detection of Pb2+. In this paper, an innovative method for sensitive detection of Pb2+ in river water was proposed, which combined blood glucose meter signal transduction with terminal deoxynucleotidyl transferase (TdT) mediated DNA extension amplification strategy. The gold nanoparticle-modified electrode was used as the sensing interface, which was fabricated through the choline monolayer electrodeposition method. The target Pb2+ initiated DNAzyme cyclic cleavage reaction on the magnetic bead, causing the substrate probe to generate 3′-OH terminus, which would induce the formation of polyadenine (polyA) sequences with the assistance of TdT. Ultimately, the numerous invertase tags on magnetic beads would be loaded on the sensing interface through the interaction between polyA and gold nanoparticles, which would catalyze the hydrolysis of sucrose to glucose with highly efficient enzymatic turnover, enabling the blood glucose meter for detection of Pb2+. The method exhibited a detection limit down to 0.6 pM, and can be used to detect Pb2+ in river water and tap water with high selectivity, offering the method great potential to be applied in environmental monitoring and point-of-care diagnostic applications.

Novel dual-recognition electrochemical biosensor for the sensitive detection of AFM1 in milk

Aflatoxin M1 (AFM1) is a highly carcinogenic and toxic compound that is commonly found in dairy foods such as milk. We developed an electrochemical MIP (molecularly imprinted polymer) and aptamer (Apt) based aptasensor (Apt-Au@PEIM/AFM1/MIP–Apt/AuNPs)/GCE) with dual-recognition signal amplification to detect AFM1 in milk. The MIP–Apt/AuNP/GCE sensor was prepared by synthesizing an MIP film through the electropolymerization of resorcinol on gold nanoparticles-modified electrodes. The dropwise addition of our cApt-Au@PEIM signal amplification probe could enhance the current signal response and improve the sensitivity of the sensor to detect AFM1. The AFM1 present in milk could prevent the probe from binding to the sensor, thereby drastically reducing the current signal. Under optimal experimental conditions, the sensor exhibits a linear range of 0.01–200 nM and a limit of detection of 0.07 nM (S/N = 3). The developed dual-recognition aptasensor would provide a novel and rapid method for specific detection of AFM1 in milk.

An electrochemical biosensor for the highly sensitive detection of Staphylococcus aureus based on SRCA-CRISPR/Cas12a

As one of the major foodborne pathogens, Staphylococcus aureus (S. aureus) can cause infectious diseases. In the current study, a novel electrochemical biosensor based on saltatory rolling circle amplification (SRCA) combined with CRISPR/Cas12a system was developed for the accurate detection of S. aureus. The thio-modified reporter probes (SH-ssDNA-MB) was immobilized on the surface of gold nanoparticle-modified electrode through the Au–S bond. In the presence of S. aureus, the target DNA double strands obtained by SRCA can be specifically recognized with Cas12a/crRNA complex. The trans-cleavage activity of Cas12a induces SH-ssDNA-MB to be cleaved from the electrode surface, resulting in a decrease in the current signal. Subsequently, the ratio of the current can be calculated as the detection result. Under optimal conditions, the detection limits were 2.51 fg/μL for genomic DNA and 3 CFU/mL for S. aureus in pure cultures, respectively. Moreover, the method demonstrated satisfactory specificity, acceptable stability and reproducibility. In comparison with ISO methods, the sensitivity, specificity and accuracy of the developed method were 100%, 97.8% and 98%, respectively. In conclusion, the developed novel electrochemical biosensor provides a potential powerful platform for the accurate detection of S. aureus.

Arsenic (III) detection with underpotential deposition on gold

We report a new, sensitive stripping voltammetric method for the detection of As(III) in aqueous solution using either a gold macroelectrode or a gold nanoparticle-modified glassy carbon electrode (GCE) based on the underpotential deposition (UPD) of As ad-atoms. The pre-concentration step deposits and accumulates As ad-atoms onto gold and is followed by a potential sweep to strip the ad-atoms with no interference from Cu(II) or Cl- at either electrode. Linear responses were found for the range 0.01 μM to 0.1 μM or 0.005 μM to 0.1 μM at gold macroelectrodes and gold nanoparticle-modified electrodes, respectively. The visually clearly discernable signals recorded at 0.005 μM (0.4 ppb) on gold nanoparticle-modified electrodes suggests that this method has practical value given the WHO limit of 0.13 μM (10 ppb) for drinking water.

Ultrasensitive detection of mercury(II) ions on a hybrid film of a graphene and gold nanoparticle-modified electrode.

Aggravated by human and industrial activities, heavy metal pollution has become a severe problem, causing widespread concern in society, and cannot be ignored. Herein, a graphene/gold nanoparticle-hybrid (AuNPs/ERGO) was proposed and synthesized by electrochemical methods. Based on the AuNPs/ERGO hybrid, a novel electrochemical sensing platform was established and successfully applied for the selective, quantitative detection of Hg2+, taking advantage of the well-established anodic stripping voltammetry (ASV). This hybrid material not only increases the surface area and charge transfer rate but also provides more active sites for Hg deposition due to the formation of homogeneous, high density and monodispersed AuNPs on the ERGO film. The prepared AuNPs/ERGO hybrid was modified on a glassy carbon electrode (GCE) to detect Hg2+ with a linear range from 0.5 to 20 μg L-1 and a low limit of detection (LOD) of 0.06 μg L-1. The selectivity and stability of the as-prepared electrode were investigated and showed promising results. In addition, a screen-printed carbon electrode (SPCE) was also employed to verify the practical application ability of our assay with an excellent performance, which presents a bright application prospect for in situ Hg2+ detection.

Novel fluoride selective voltammetric sensing method by amino phenylboronic acid-zirconium oxide nanoparticles modified gold electrode

A novel fluoride selective voltammetric method has been developed by using the 3-amino phenylboronic acid (APBA)-zirconium oxide (ZrO2) nanoparticles modified gold (APBA-ZrO2-NPs/Au) electrode for sensitive detection of F− at trace levels in water and toothpaste. A co-precipitation approach was applied to synthesize ZrO2 nanoparticles (ZrO2-NPs) using Salvadora oleoides leaves extract and characterized by UV–Visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and X-Ray Diffraction (XRD) for morphological and structural analysis. The APBA-ZrO2-NPs/Au electrode was fabricated by coated of ZrO2-NPs on the surface of Au electrode by drop costing method followed by electrochemical polymerization of APBA. The reduction response of peak current of potassium ferricyanide was achieved by the interaction of the phenylboronic acid with F−to produce the boronate anions. Thus, the method was optimized in detailed for successive electrochemical detection of F−. Two linear relations were observed in reduction peak current and logarithm of F− concentration in the range of 1.0 × 10–9 – 3.0 × 10–4 M and 3.0 × 10–4 – 1.0 × 10–2M, respectively. The limits of detection (LOD) and limit of quantification (LOQ) were calculated as 3.0 × 10–10 and 1.0 × 10–9 M, respectively. Interference of other competing anions, including chloride, bromide, iodide, acetate, sulphate, carbonate, and nitrate, was also investigated. Furthermore, the developed APBA-ZrO2-NPs/Au was employed to the fast detection, wide range of response, and high selectivity of F− in water and toothpaste samples.

Ultrasensitive zero-background photoelectrochemical biosensor for analysis of organophosphorus pesticide based on in situ formation of DNA-templated Ag2S photoactive materials.

Herein, a novel signal-on photoelectrochemical (PEC) biosensor with nearly zero background noise (ZBN) was first fabricated to determine the presence of organophosphorus pesticide based on in situ formation of DNA-templated Ag2S photoactive materials, accompanied by hybridization chain reaction (HCR) signal amplification. The capture probe (S1) on the gold nanoparticle-modified electrode can hybridize with the aptamer molecule to generate a simple PEC biosensor. In the presence of a target molecule, the aptamer molecule is released on the double-stranded DNA (dsDNA)-modified PEC biosensor. Meanwhile, the capture probe remains on the electrode and can open the DNA hairpins (H1, H2) which are rich in cytosine, to trigger the HCR reaction. The rich "C" strands are uncovered after formation of a long dsDNA polymer strand, which can assemble multiple silver ions (Ag+) by means of by C-Ag+-C chelation. Then, a large number of Ag2S can be generated by challenging with S2- solution, producing a satisfactory photocurrent signal. The photoactive material is formed in situ, which eliminates the laborious operation. Moreover, the signal can be highly amplified with nearly zero background noise and HCR signal amplification. Under optimal conditions, the ZBN aptasensor exhibited high sensitivity and selectivity, with a low detection limit of 2pgmL-1 for malathion. Importantly, the sensing platform can also be applied to determine the presence of malathion in real samples. In this assay, a novel signal-on photoelectrochemical biosensor with nearly zero background noise was first fabricated to determine the presence of organophosphorus pesticide based on in situ formation of DNA-templated Ag2S photoactive materials, accompanied by hybridization chain reaction signal amplification.

On Site Determination of Heavy Metal Ions with Portable Electrochemical Instrument Based on Smartphone

Introduction Most heavy metal ions are harmful to human body and may cause a variety of diseases, among which chromium(VI), cadmium, arsenic and their compounds are classified as Group 1 (human carcinogen) by IARC [1]. Heavy metal ions can enter the human body through direct drinking and the enrichment of food chain. Therefore, the allowed concentration of heavy metal ions are recommend by WHO, which are 50 μg/L for chromium(VI), 3 μg/L for cadmium, 10 μg/L for arsenic, respectively [2].Compared with other methods, electrochemical method is gaining wide recognition and has the advantages of fast speed, simple operation and possibility of use in portable detection on site [3]. Therefore, a portable electrochemical instrument based on smartphone was designed, in order to detect the concentration of heavy metal ions in the field. Method A block diagram of the portable electrochemical instrument is shown in Fig. (a). The instruction of controlling electrochemical process is sent out by MCU and executed by potentiostat. The electrochemical signal obtained is simply processed and returned to MCU. The communication between MCU and smartphone software based on Android system is realized through Bluetooth. The completed printed circuit board (PCB) of the instrument is shown in Fig. (b).The determination of chromium(VI) is realized by gold nanoparticles modified gold electrode, in order to obtain a larger electrochemical response. The gold nanoparticle modification was achieved by applying a potential of -0.3 V for 120 seconds with stirring in 0.2 mmol/L chloroauric acid with 0.5 mol/L sulphuric acid, which is simple, stable and repeatable for on site determination. As shown in Fig. (c), the increase of electrode surface area can be observed by Atomic Force Microscope (AFM).After parameters optimization, the detection of Chromium(VI) was carried out in 0.3 mol/L nitric acid by linear sweep voltammetry (LSV) with a potential range of 0.8 V to 0.2 V. There is no accumulation process during detection, so it takes less than 10 seconds. Results and Conclusions The linear sweep voltammograms in chromium(VI) concentration range of 10 μg/L to 100 μg/L with a step of 10 μg/L are shown in Fig. (d). The standard curve of Cr(VI) is shown in Fig. (e), where it shows a linear relationship with the correlation coefficient of 0.98. A detection limit of 6.4 μg/L can be calculated, suggesting the sensitivity of the method for Cr(VI) detection. These results indicate that the portable electrochemical instrument based on smartphone can be a promising alternative for heavy metal ions detection on site. References International Agency for Research on Cancer. (2020). Agents classified by the IARC Monographs, volumes 1-128. http://monographs. iarc. fr/ENG/Classification/index. php.Edition, F. (2011). Guidelines for drinking-water quality. WHO chronicle, 38(4), 104-8.Holmes, J. , Pathirathna, P. , & Hashemi, P. . (2019). Novel frontiers in voltammetric trace metal analysis: towards real time, on-site, in situ measurements. TrAC Trends in Analytical Chemistry, 111, 206-219. Figure 1

Quantitative Determination of Triiodothyronine by Electrochemical Impedance Spectroscopic Biosensor Using Gold Nanoparticle-Modified Electrode.

A label-free electrochemical impedimetric immunosensor for the detection of Triiodothyronine-a thyroid hormone that functions as the biomarker for monitoring for thyroid dysfunction was developed. The gold nanoparticle-modified electrode was employed to achieve the sensitive determination of Triiodothyronine at a low concentration level. The gold nanoparticle layer on the gold electrode was generated by chronoamperometry method and its resulting characteristics were investigated by scanning electron microscopy. Redox probe [Fe(CN)6]3-/4- and electrochemical impedance spec-troscopy was used for both evaluation of the immobilization of anti-Triiodothyronine antibody on the electrode surface and quantitative determination of target Triiodothyronine in different concentrations. The electrode with absorbed antibodies showed significant changes in charge transfer resistance upon binding the antigen, which resulted in an increase in normalized impedance change as the addition of antigen concentrations over a dynamic linear range of 0.01-100 ng/ml. These results indicated that the proposed immunosensor could be a potential alternative method for determination of Triiodothyronine in clinics with the advantage of low cost and less time-consuming.

Electrochemical sensing by a covalently bonded biotin–avidin couple on a silver nanoparticle modified gold electrode

A gold electrode was modified with cysteamine by a self-assembly monolayer technique and covalently coupled with 3-mercaptopropionic acid functionalized silver nanoparticles. The free carboxylic acid groups of the 3-mercaptopropionic acid functionalized silver nanoparticles assembled on gold electrode were bonded with the amine groups of biotin or avidin trough amide linkages. The changes in the interfacial properties of gold electrode modified stepwise were examined by cyclic voltammetry and electrochemical impedance spectroscopy using the ferric/ferrous redox system. The electrochemical sensing properties of covalently bonded biotin or avidin on a gold electrode modified with silver nanoparticle were studied by cyclic voltammetry and electrochemical impedance spectroscopy by the varying concentrations of the bio-affinity molecules in the same redox system. The charge transfer resistance was directly proportional to the concentration of analyte while the response was weakly dependent upon the change in the respective peak anodic currents. The sensing mechanism was established to explain the role of the silver nanoparticles.

An Excellent Electrochemical Sensor Based on Highly Porous Gold Film Modified Gold Electrode for Detecting Quercetin in Food and Medicine

Quercetin is one of the most important nutrients in human daily diet, the accurate and efficient analytical approaches for quercetin is highly required as it’s closely related to many biological activities. In this paper, the three-dimensional highly porous gold film (hp-Au) modified gold electrode (Au) was prepared by a facile two steps self-templating method, it was found that hp-Au possess high surface-to-volume ratio and excellent conductivity. Combining with the multiple merits of hp-Au, the hp-Au/Au showed an excellent detection performance towards quercetin compared with bare electrode and Au nanoparticles modified gold electrode (AuNPs/Au), the detection limit was 3.9 nM in a wide concentration range from 20 nM to 100 μM. Meantime hp-Au/Au also showed decent stability, satisfied selectivity and desirable reproducibility. Moreover, the practical application of this sensor was verified by detecting QR in drink or food and medicine samples and the satisfactory recoveries of 97.43% to 101.59% and low RSD value (n = 3) no more than 3% were obtained.

Direct competitive immunosensor for Imidacloprid pesticide detection on gold nanoparticle-modified electrodes

A direct competitive immunosensor for the electrochemical determination of Imidacloprid (IMD) pesticide on gold nanoparticle-modified screen-printed carbon electrodes (AuNP-SPCE) is here reported for the first time. Self-obtained specific monoclonal antibodies are immobilized on the AuNP-SPCE taking advantage of the AuNPs biofunctionalization abilities. In our biosensor design, free IMD in the sample competes with IMD conjugated with horseradish peroxidase (IMD-HRP) for the recognition by the antibodies. After that, 3,3′,5,5′-Tetramethylbenzidine (TMB) is enzymatically oxidized by HRP, followed by the oxidized TMB reduction back at the surface of the SPCE. This process gives an associated catalytic current (analytical signal) that is inversely proportional to the IMD amount. The main parameters affecting the analytical signal have been optimized, reaching a good precision (repeatability with a RSD of 6%), accuracy (relative error of 6%), stability (up to one month), selectivity and an excellent limit of detection (LOD of 22 pmol L−1), below the maximum levels allowed by the legislation, with a wide response range (50–10000 pmol L−1). The detection through antibodies also allows to have an excellent selectivity against other pesticides potentially present in real samples. Low matrix effects were found when analysing IMD in tap water and watermelon samples. The electrochemical immunosensor was also validated with HPLC-MS/MS, the reference method used in official laboratories for IMD analysis, through statistical tests. Our findings make the electrochemical immunosensor as an outstanding method for the rapid and sensitive determination of IMD at the point-of-use.

Relay-race RNA/barcode gold nanoflower hybrid for wide and sensitive detection of microRNA in total patient serum

Development of a very sensitive biosensor is accompanied with an inevitable shrinkage in the linear detection range. Here, we developed an electrochemical biosensor with a novel methodology to detect microRNA-21 (miR21) at an ultralow level and broad linear detection range. A three-way junction RNA structure was designed harboring (i) a methylene blue (MB)-modified hairpin structure at its one leg to function as the sensing moiety and (ii) the other two legs to be further hybridized with barcode gold nanoparticles (MB/barG) as the signal amplifiers. Addition of target miR21 resulted in opening the hairpin moiety and subsequent hybridization with DNA-modified gold nanoflower/platinum electrode (GNF@Pt) to form the MB-3 sensor. Inspired by the relay-race run, to extend the dynamic detection range and increase the sensitivity of the biosensor, MB/barG was added to form the second detection modality (MBG-3). The combined sensor required very low sample volume (4 μL) and could identify 135 aM or 324 molecules of miR21 with the ability to operate within a wide linear range from 1 μM down to 500 aM. The fabricated GNF@Pt showed a remarkable conductivity compared with the gold nanoparticle-modified electrode. Addition of MB/barG boosted the electrochemical signal of the MB by almost 230 times. Moreover, a new protocol was introduced by the authors to increase the efficiency of microRNA extraction from the total serum. Possessing a sound selectivity and specificity towards single base-pair mutations, the developed biosensor could profile cancer development stages of two patient serums.

Electrocatalytic oxidation of water at a polyoxometalate nanoparticle modified gold electrode.

Spherical polyoxometalate nanoparticles, [HPMo]NPs, were synthesized from a very well known Keggin-type polyoxometalate [H3PMo12O40] in the presence of sodium dodecyl sulphate (SDS) and polyvinyl pyrrolidine (PVP) in aqueous medium and characterized by UV-Vis spectroscopy and Transmission Electron Microscopy (TEM). The [HPMo]NPs were used to modify a gold working electrode and they were characterized by SEM, EDX, elemental mapping, cyclic voltammetry and electrochemical impedance spectroscopy and applied for the electrocatalytic oxidation of water in a phosphate buffer solution at neutral pH. The modified electrode showed excellent electrocatalytic activity towards oxidation of water at an impressively low overpotential ∼350 mV with a high current density of around 1.7 mA cm−2, good stability under exhaustive electrolysis conditions and also showed long term stability.

Electrochemical detection of plant virus using gold nanoparticle-modified electrodes

Tristeza is one of the destructive diseases of citrus causing by citrus tristeza virus (CTV). Historically, CTV has been associated with serious outbreaks of quick decline of citrus, therefore CTV monitoring is important aspect for avoiding such re-emerging epidemics, which would threat citrus production through the world. In this context, we have designed for the first time a label-free impedimetric biosensor for the detection of nucleic acid of CTV. The sensing platform based on a screen-printed carbon electrode (SPCE) was modified by electrodeposited gold nanoparticles (AuNPs), which allowed to efficiently immobilizing thiolated ssDNA probes as well to enhance the electrode conductivity. The growth of AuNPs was optimized and characterized using scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). We investigated the behavior of thiolated ssDNA probe layer and its hybridization with target DNA onto AuNP surfaces by EIS measurements in Fe(CN6)4-/Fe(CN6)3- red-ox system. The main sensor design aspects such as AuNPs size, probe DNA concentration and immobilization time together with DNA hybridization time were optimized so as to achieve the best performance. Impedance values of DNA hybridization increased with Citrus tristeza-related synthetic DNA concentration, showing a logarithmic relation in the range of 0.1–10 μM. The results also indicate that the biosensor was able to selectively detect CTV nucleic acids in the presence of other non-specific DNAs. Moreover, we have demonstrated the good performance of the system in a real plant sample matrix. In addition, the sensor reproducibility enhanced after the hybridization onto MCH/poly (AT) thiolated DNA probes which was confirmed by intra- and inter-day variability assays.

Synthesis, characterization and electrochemical applications of Ir@SiO2 composite microspheres

Ir nanoparticles have been synthesized by using a sample hydrothermal method while well dispersed Ir@SiO2 composite microspheres could be obtained hydrothermally after adding SiO2 microspheres into the synthesis system. Particles of Ir formed on the surface of SiO2 microspheres were well crystalline similar to the pure Ir nanoparticles. Both the glassy carbon electrodes modified by Ir nanoparticles and Ir@SiO2 composite microspheres showed weak electrochemical activities toward oxidation of dopamine and ascorbic acid. However, the Ir nanoparticles modified gold electrode displayed an obvious catalytic activity toward electrooxidation of either dopamine or ascorbic acid. For the gold electrode modified with Ir@SiO2 composite microspheres, the electrochemical behavior could be affected obviously by the quantity of the electrocatalyst on the surface of bare gold electrode. The relationship between structure and property of both samples have been studied and analyzed based on the experimental data.

A Novel Photo‐Induced Electrochemical Biosensing Method Based on Fluorescent Labeled Molecular Beacon

AbstractA novel photo‐induced electrochemical biosensing method has been developed based on fluorescence quenching effect and electrochemical method. In this sensing strategy, the molecular beacon probes labeled with methylene blue were immobilized on the gold nanoparticles modified gold electrode surface firstly; then dopamine was assembled on the electrode surface through electrostatic interaction with gold nanoparticles. Under the continuous illumination, the fluorescence of the methylene blue was quenched by the gold nanoparticles before hybridization; after hybridization with the complementary DNA, methylene blue was far away from the gold nanoparticles and the fluorescence recovered, and then singlet oxygen was generated in the photosensitive reaction of methylene blue in the presence of dissolved oxygen. Singlet oxygen reacted with dopamine, which resulted in the reduction of concentration of the dopamine on the electrode surface. The current of the dopamine on the electrode was used for the sensing of the conformational change of molecular beacon and hence for the detection of target DNA.

Electro-oxidation and determination of 2-thiouracil at TiO2 nanoparticles-modified gold electrode

Electrochemical behavior studies were carried out for 2-thiouracil, using TiO2 nanoparticles modified gold electrode. As compared with the bare electrode, there was appreciable enhancement in the peak current and sensitivity for the modified electrode. The effect of pH was investigated in the range of 3.0–11.2pH. Scan rate variation were performed to calculate the number of electrons transferred, heterogeneous rate constant and diffusion coefficient. A probable electrode reaction mechanism was proposed for 2-thiouracil in the present work. A differential voltammetric technique was used for the analytical application in the range of 1.0 × 10−7M–5.0 × 10−8M. Limit of detection and quantification were calculated and found to be 1.68nM and 5.60nM. The proposed method was applied for the determination of 2-thiouracil in pharmaceutical and human urine samples.

A gold nanoparticle chemically modified gold electrode for the determination of surfactants

A gold nanoparticles modified gold electrode was developed for the determination of surfactants in solution, using a redox probe and exploiting the tendency of surfactants to adsorb onto the nanoparticles' surface.