Electrodeposition Of AuNPs Research Articles

A label-free H1N1 influenza virus immunosensor based on an N-LIG/Au laser induced graphene microelectrode.

A label-free immunosensor based on an N-doped laser direct graphene (N-LIG)/Au electrode was proposed for H1N1 influenza virus detection. By utilizing the instantaneous high temperature of laser irradiation, N atoms are generated by the decomposition of melamine dripped onto the surface of an LIG electrode to obtain N-LIG with higher conductivity. The doping of N atoms provides a large number of active sites for LIG microelectrodes. Combined with the electrodeposition of Au NPs, and covalently crosslinking antibodies, a simple, highly sensitive and stable immunosensing interface is constructed. The proposed H1N1 influenza virus immunosensor has a detection range of 0.01 fg mL-1 to 10 ng mL-1 with a detection limit as low as 0.004 fg mL-1. The constructed sensor has ultra-high sensitivity and good selectivity and can be used for complex biological sample analysis, with potential application prospects in preventing the large-scale spread of influenza. Taking advantage of N-LIG electrode's properties will provide opportunities for developing portable electrochemical biosensors for health and environmental applications.

Optimization of Gold Nanoparticles Electrodeposition Duration on Screen Printed Electrode to Enhance Electrochemiluminescence of Nitrogen-doped Carbon Dots

In this work, the electrodeposition method was utilized to form gold nanoparticles on a carbon screen-printed electrode (SPE) using chronoamperometry at -0.4 V with various durations from 50 to 200 seconds. Scanning Electron Microscopy (SEM) images have proven that the electrodeposition method is capable of uniformly forming AuNPs on SPE (AuNPs- SPE). Apart from that, electrodeposition durations have increased the size of AuNPs by up to 66% based on average size measurements using ImageJ software. It can be observed that long electrodeposition durations permit the agglomeration of AuNPs on the electrode surface. The effect of electrodeposition duration on electrocatalytic performance in potassium ferricyanide and electrochemiluminescence (ECL) intensity of nitrogen-doped carbon dots (NCDs) was evaluated. Cyclic voltammetry (CV) of ferricyanide demonstrates that as the electrodeposition duration increases, AuNPs-SPE shows better electrochemical performance than bare SPE. ECL of NCDs displays that 100 s electrodeposition durations give the highest ECL intensity of 184% compared to bare SPE and have been chosen as the optimum parameter. The ECL mechanisms of bare SPE and AuNPs-SPE reveal that AuNPs- SPE has greater electrochemical and ECL performance than bare SPE, as evidenced by the CV of AuNPs-SPE having a faster reduction current, which rises to 87.2% ECL intensity and 510 mV faster ECL occurrence. These phenomena confirmed that the electrodeposition of AuNPs has improved the conductivity of SPE.

A label-free electrochemical aptasensor based on Ti3C2Tx-Ag/Au nanoparticles as a signal amplification strategy for CRP detection

C-reactive protein (CRP) is an essential biomarker that is associated to acute inflammation and infectious illnesses. This study developed a label-free electrochemical aptasensor utilizing Ti3C2Tx-silver/gold nanoparticles (Ti3C2Tx-Ag/Au NPs) for the first time for CRP detection. Based on the unique capacity of Ti3C2Tx of self-adsorbing and reducing silver ions (Ag+), Ag signal probes with strong redox activity and good electrical conductivity were synthesized. Electrodeposition of Au NPs on the electrode surface modified with Ti3C2Tx-Ag, not merely improved the adsorption capacity of the immobilized aptamer and prevented Ag loss; it also collaborated with Ti3C2Tx-Ag to create a dual-amplified signal strategy. Aptamer molecules bind to Au NPs through the Au-S bond for precise capture of CRP. The detection was performed by differential pulse voltammetry (DPV), the current was proportional to the logarithm of CRP antigen, and the linear range of CRP detection was 0.1–200 ng mL−1 with a limit of detection (LOD) 41 pg mL−1. Simultaneously, the label-free aptasensor presented superior detection selectivity, reproducibility, and stability. This study provided an ideal electrochemical biosensor for determining CRP in serum, with an excellent prospect for clinical diagnostic applications at the point of care testing (POCT).

Sensitive voltammetric determination of rifaximin by electrode modified by nanocomposite of MWCNT/MnO2/Au NPs

Antibiotics are a group of antimicrobial compounds that are used in human medicine, aquaculture, and the livestock industry to treat and prevent disease and improve growth. However, improper use of antibiotics may lead to antibiotics entrance in the environment through water and land, which may cause various toxic effects. Therefore, it is necessary to use easy, fast and sensitive methods like electrochemical methods to detect them. Herein, Au-decorated Multi-walled carbon nanotubes (MWCNTs) /MnO2 nanocomposites which seems as a Gypsophila paniculata flower were utilized to detection of Rifaximin (RFX). In this method MWCNT/MnO2 nanocomposites were first drop-casted onto the GCEs then the electro-deposition of Au NPs onto the modified GCEs was done. The formation and electroanalytical performance of the fabricated sensor were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) Spectroscopy, X-ray diffraction (XRD), cyclic and linear sweep voltammetry (LSV). The LSV response of the electrode to RFX was linear in the range 0.75–200μΜ with a detection limit of 0.25 μM, a sensitivity of 0.38μA μM−1 cm−2 and the relative standard deviation (RSD) of 7.0 % under the optimum conditions. Besides, the RFX is successfully measured in human blood serum and RFX tablet samples, in conditions close to the physiological environment (pH = 6) without any sample pre-treatment. The stability, reproducibility, and repetitive usability exhibited by the fabricated modified electrode are very good to make it a suitable electrochemical sensor for the determination of RFX in pharmaceutical preparations and its quality control and moreover in real samples.

Electrochemical sensor for simultaneous determination of paracetamol, propyphenazone, and caffeine – Electrodes based on poly(L-cystine)/gold nanoparticles plating on pencil graphite

An electrode based on pencil leads (PGE) coated with gold nanoparticles (AuNPs) and poly(L-cystine) (P(L-cyst)) was devised and used for the simultaneous analysis of ternary drug combinations, namely, paracetamol (PA), propyphenazone (PRO) and caffeine (CA). The sensor is designed step-by-step by electro-polymerization: P(L-cyst) plating on the surface of PGE and then electrodeposition of AuNPs. The electrode performance was investigated using cyclic voltammetry (CV). Changes on the electrode surface were elucidated by electrochemical impedance spectroscopy (EIS), field emission scanning electron microscopy (FE-SEM), and Energy Dispersive X-ray analysis (EDX). Compared to bare PGE, the modified sensor proved to be better in electrochemical current density for the analytes. The improvement was attributed to the synergistic effects of AuNPs and the organic matrix. The linear ranges were 0.023–90.0 µM (for PA), 0.009 – 30.0 µM (for PRO), and 0.454–600.0 µM (for CA). Trial studies were also done on real samples to reveal the accuracy and reproducibility of the method.

Synergetic Effect of Three-in-One Nanocomposite Based on AuNPs and rGO-MWCNTs for Ultrasensitive Electrochemical Bio-Diagnostic Applications

A simple, two-step AuNPs/rGO-MWCNTs nanocomposite fabrication methodology, via drop-casting of rGO-MWCNTs on bare screen printed electrode (SPE) followed by electrodeposition of AuNPs through voltammetric scanning, without using any toxic reducing agents is reported. Each step of the synthesized nanocomposite is characterized using state-of-art spectroscopic and electrochemical methods. Our results demonstrate that the nanostructured AuNPs/rGO-MWCNTs/SPE showed synergistic effects of high electrocatalytic and electron transfer activity, high surface area to volume ratio, that confirms our synthesized material is the best material to fabricate a portable device for rapid, inexpensive, and sensitive electrochemical biosensors. For validation, the fabricated material subjected to electrochemical sensing of BSA protein. Our AuNPs/rGO-MWCNTs nanocomposite exhibited significant and good linear response over 2.5–12.5 μg ml−1 BSA concentration range, with sensitivity of 1.723 μAμg ml−1 and limit of detection (LOD) 0.23 μg/ml. This portable sensing system with enhanced performance demonstrates great potential for our synthesized AuNPs/rGO-MWCNs/SPE nanocomposite in application of point of care applications, and offers a universal and reliable platform for in biomarker detection.

Engineering Catalytically Active Sites by Sculpting Artificial Edges on MoS2 Basal Plane for Dinitrogen Reduction at a Low Overpotential.

Engineering catalytically active sites have been a challenge so far and often relies on optimization of synthesis routes, which can at most provide quantitative enhancement of active facets, however, cannot provide control over choosing orientation, geometry and spatial distribution of the active sites. Artificially sculpting catalytically active sites via laser-etching technique can provide a new prospect in this field and offer a new species of nanocatalyst for achieving superior selectivity and attaining maximum yield via absolute control over defining their location and geometry of every active site at a nanoscale precision. In this work, a controlled protocol of artificial surface engineering is shown by focused laser irradiation on pristine MoS2 flakes, which are confirmed as catalytic sites by electrodeposition of AuNPs. The preferential Au deposited catalytic sites are found to be electrochemically active for nitrogen adsorption and its subsequent reduction due to the S-vacancies rather than Mo-vacancy, as advocated by DFT analysis. The catalytic performance of Au-NR/MoS2 shows a high yield rate of ammonia (11.43×10-8 mol s-1 cm-2 ) at a potential as low as -0.1V versus RHE and a notable Faradaic efficiency of 13.79% during the electrochemical nitrogen reduction in 0.1m HCl.

Novel electrochemical biosensing platform based on conductive multilayer for sensitive and selective detection of CYFRA 21-1

In the present work, an electrochemical biosensor modified with a conductive multilayer composed of gold nanoparticles and amino-substituted-pyrrole polymer (AuNPs/P(PyAmn)) was constructed for label-free detection of cytokeratin 19 fragment 21-1 (CYFRA 21-1), one of the most important lung cancer biomarkers. The electrochemical biosensor was fabricated by electropolymerization of PyAmn on an indium tin oxide (ITO) platform with electrodeposition of AuNPs and binding of an anti-CYFRA 21-1 recognition element on the P(PyAmn)-coated electrode via glutaraldehyde crosslinking. In the present immunosensor, AuNPs deposition provided excellent conductivity and good electron transfer. The electropolymerization of the P(PyAmn) polymer layer ensured a large surface area that increased the amount of anti-CYFRA 21-1 antibodies that could be attached. A specific immunoreaction occurred between anti-CYFRA 21-1 antibody and CYFRA 21-1 antigen when the immunosensor was successively reacted with the target CYFRA 21-1 protein. According to specific immunoreactions, the resulting biosensor produced an impedimetric signal proportional to the amount of CYFRA 21-1 in the linear detection range of 0.015–90 pg/mL. With optimal fabrication parameters, the detection limit, quantification limit and sensitivity for CYFRA 21-1 were 4.59 pg/mL, 15.31 pg/mL and 0.21 kΩ pg−1 mL cm−2, respectively. Meanwhile, this biosensor had good stability and high specificity for CYFRA 21-1 detection, and it was successfully applied to real serum samples. It also had a satisfactory rate of R2 = 0.9984. The use of a disposable ITO substrate as a basis for this immunosensor allowed the use of simple instrumentation. This study illustrates a new approach to fabricate an ultrasensitive and label-free electrochemical biosensor based on a disposable platform for CYFRA 21-1 analysis in clinical biosensing.

Conductive metal-organic framework based label-free electrochemical detection of circulating tumor DNA.

Anultrasensitive electrochemical biosensor was designedfor the rapid label-free detection of circulating tumor DNA (ctDNA, EGFR 19 Dels for non-small cell lung cancer, NSCLC). We linked the highly conjugated tricatecholate, 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) with Ni(II) ions into the two-dimensional porous conductive metal-organic frameworks (MOFs), which istermed Ni-catecholates (Ni-CAT). Then, the AuNPs/Ni-catecholates/carbon black/polarized pencil graphite electrode (AuNPs/Ni-CAT/CB/PPGE) was obtained by electrodeposition of AuNPs on the surface of PPGE modified with Ni-CAT/CB composite materials. The AuNPs/Ni-CAT/CB/PPGE were used for label-less detection of ctDNA, with a total detection time of only 30min. Under optimal detection conditions, the AuNPs/Ni-CAT/CB/PPGE sensor exhibited excellent detection performance with good linear response to ctDNA over a wide concentration range and the detection limit down to the femtomolar level. The sensor was applied to the determination of ctDNA in serum samples withhigh sensitivity. This simple, efficient, and expeditious method has practical value in liquid biopsy of ctDNA and has potential for development in early detection, treatment, and prognosis of tumors. Herein, an ultrasensitive electrochemical biosensor was designed for the rapid label-free detection of ctDNA (EGFR 19 Dels for non-small cell lung cancer, NSCLC). We linked the highly conjugated tricatecholate, 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) with Ni(II) ions into the two-dimensional porous conductive metal-organic frameworks (MOFs), which is termed as Ni-catecholates (Ni-CAT). Then, the AuNPs/Ni-catecholates/carbon black/polarized pencil graphite electrode (AuNPs/Ni-CAT/CB/PPGE) was obtained by electrodeposition of AuNPs on the surface of PPGE modified with Ni-CAT/CB composite materials. The AuNPs/Ni-CAT/CB/PPGEs were used for label-less detection of ctDNA, with a total detection time of only 30min. Under optimal detection conditions, the AuNPs/Ni-CAT/CB/PPGE sensor exhibited excellent detection performance with good linear response to ctDNA in the concentration range of 1 × 10-15M to 1 × 10-6M and with a detection limit as low as 0.32 fM. The sensor was applied for determination of ctDNA in serum samples and gave high sensitivity. This simple, efficient and expeditious method has practical value in liquid biopsy of ctDNA and has potential for development in early detection, treatment and prognosis of tumors.

Mechanism and kinetics of Gold Nanoparticles Electrodeposited from Au (III) Ions Dissolved in a Deep Eutectic Solvent and Its Analytical Performance Towards Dopamine Quantification

The mechanism and kinetics of the electrochemical nucleation and growth of gold nanoparticles, AuNPs, onto a glassy carbon electrode, GCE, from Au(III) dissolved in the reline deep eutectic solvent, DES, at 70 °C, were assessed, for the first time. From the potentiodynamic technique it was found that gold electrodeposition onto the GCE substrate (Au(III)DES + 3e− (GCE) = Au(s)/GCE) is a diffusion-controlled process that requires of an overpotential nucleation to occur. The potentiostatic current density transients, recorded at different applied overpotentials, during the electrodeposition of AuNPs were described by a mechanism where multiple nucleation of 3D gold centers with mass-transfer controlled growth, occurs simultaneously with Au(III) adsorption (at the early stages) and the DES residual water reduction on the growing surfaces of the Au nuclei. From this analysis the diffusion coefficient of Au(III) ions was estimated as (2.56 ± 0.12) × 10−9 cm s−1 and it was found that the number density of Au nuclei, N s, depends exponentially on the applied overpotential while the nucleation frequency, A, was practically constant and the water reduction contribution increases linearly. From SEM images and EDX spectrum of the GCE surface, electrodeposited with gold (GCE/AuNPs), it was found that the Au deposit was formed by aggregates, (183 ± 37) nm average size, of AuNPs (of ca 50 nm diameter) and a density of (1.8 ± 0.3) × 109 aggregates cm−2. The GCE/AuNPs was used for the Dopamine, DA, electrochemical quantification in the presence of uric acid, UA, with the following analytical performance: sensitivity of (32.49 ± 0.37) μA mM−1 and (28.6 ± 0.2) μM detection limit.

Sandwich photoelectrochemical biosensing of concanavalin A based on CdS/AuNPs/NiO Z-scheme heterojunction and lectin-sugar binding

A CdS/AuNPs/NiO Z-scheme heterojunction was prepared on a fluorine-doped tin oxide (FTO) electrode by hydrothermal synthesis of NiO on FTO, electrodeposition of AuNPs on NiO/FTO electrode and then cast-coating of CdS quantum dots. The CdS/AuNPs/NiO/FTO electrode gave a notably increased photocurrent versus NiO/FTO, CdS/FTO, AuNPs/NiO/FTO, CdS/AuNPs/FTO and CdS/NiO/FTO electrodes. The CdS/AuNPs/NiO/FTO electrode was further cast-coated with chitosan to immobilize d-mannose by Schiff base reaction, and concanavalin A (ConA) and then horseradish peroxidase (HRP) were captured on the electrode surface by lectin-sugar binding. 4-Chloro-1-naphthol (4-CN) was oxidized to form an insoluble precipitate catalyzed by HRP in the presence of H2O2, and the presence of precipitate on the photoelectrode inhibited the photocurrent in the presence of holes scavenger ascorbic acid. The relevant electrodes were characterized by electrochemistry, quartz crystal microbalance (QCM), UV–vis spectrophotometry, scanning electron microscopy/energy dispersive spectroscopy, and transmission electron microscopy. The QCM revealed that the collection efficiency (η) of the 4-CN-electrooxidation precipitate on the electrode can be as high as 91.8%. Under the optimal conditions, the decline of photocurrent responded linearly to the common logarithm of ConA concentration from 50 pM to 500 nM, with a limit of detection of 17 pM (S/N = 3). Satisfactory results were obtained in the detection of real soybean samples.

CoNi bimetallic metal–organic framework and gold nanoparticles-based aptamer electrochemical sensor for enrofloxacin detection

In this study, an electrochemical aptasensor was established for the ultrasensitive detection of enrofloxacin (ENR) based on a CoNi-based metal–organic framework (MOF) and gold nanoparticles (AuNPs). Co-MOF, Ni-MOF, and CoNi-MOF were optimized by characterization techniques like scanning electron microscope (SEM), Fourier-transform infrared spectrophotometer (FT-IR), and X-ray diffraction (XRD). The optimal CoNi-MOF has waxberry-like structure, mixed metal valences, and π-conjugated structure, which show biocompatibility, high hydrophilicity, and good electrochemical stability. In order to enhance the electrochemical performance of the sensor, electrodeposition of AuNPs was used to improve conductivity and increase the load of sulfhydryl group-modified aptamer (Apt) by Au-S bond. The electrochemical behavior was studied by cyclic voltammetry (CV) and electrochemical impedance spectrum (EIS). The Apt/AuNPs/CoNi-MOF/GCE exhibits an extensive detection range of 1 × 10−3 pg·mL−1 to 1 × 105 pg·mL−1 (S/N = 3) and a detection limit of 3.3 × 10−4 pg·mL−1 for ENR under optimal conditions. The arranged sensor demonstrates a high sensitivity, satisfactory reproducibility, and long-time stability. Furthermore, the obtained sensor reveals a high practical prospect for the sensitive detection of ENR in meat samples.

A novel “signal on-off-super on” sandwich-type aptamer sensor of CRISPR-Cas12a coupled voltage enrichment assay for VEGF detection

Vascular endothelial growth factor (VEGF) plays an important role in atherosclerosis, and the detection of VEGF is critical for the prevention, monitoring, and diagnosis of cardiovascular diseases. Here, a novel “signal on-off-super on” sandwich-type aptamer sensor with a triple signal amplification strategy was developed for the first time. Based on the capture aptamer was labeled with methylene blue (MB) on the internal bases, clustered regularly interspaced short palindromic repeats (CRISPR)-Cas12a-coupled voltage enrichment was used to amplify the electrochemical signal. To improve the analytical performance of the aptamer sensor, gold nanoparticles@Ti3C2Tx-Mxene (AuNPs@Ti3C2Tx-Mxene) were synthesized through the electrodeposition of AuNPs on the Ti3C2Tx-Mxene surface, providing active sites for the immobilization of the aptamer and amplifying the electrochemical signals. The excellent trans-cleavage activity of the CRISPR-Cas12a system was harnessed to cleave signal probes. The cleaved signal probes were enriched using an electrochemical signal instead of complicated target amplification steps before detection. Hence, we report a simplified detection process for amplifying electrochemical signals. Under optimal conditions, the aptamer sensor exhibited high sensitivity, acceptable stability, and reproducibility with a wide linear range from 1 pM to 10 μM (R2 = 0.9917) and an ultralow detection limit of 0.33 pM (S/N = 3). Therefore, we propose a novel strategy of CRISPR-Cas12a-based protein detection that opens a new window for the diagnostic applications of various biomarkers.

Electrodeposition of Gold Nanoparticles on Halloysite Nanotubes Modified Glassy Carbon Electrode for Detection of Dopamine and Serotonin

We report a novel nanocomposite composed of halloysite nanotubes (HNT) and gold nanoparticles (AuNPs) as an excellent sensing platform. Electrodeposition of AuNPs was carried out by cyclic voltammetry for 120 seconds on HNT/GCE in acidic medium to form Au/HNT/GCE. The nanocomposite was characterized by UV-visible spectroscopy and Scanning Electron Microscopy. Higher surface area was created by drop casting HNT which helped in adhering high number of AuNPs that gave rise to enhanced catalytic sites. The modified electrode was used to simultaneously detect dopamine (DA) and serotonin (SE) at nanomolar concentrations. Oxidation peaks of DA and SE was found at 0.3 V and 0.6 V adapting the differential pulse voltammetry. The limit of detection was calculated to be 9.7 × 10-6 M and 92 × 10-9 M for DA and SE respectively with S/N=3. The modified electrode exhibited high sensitivity and stability towards detection of DA and SE.

An aptasensor for arsenic on a carbon‑gold bi-nanoparticle platform

We report an electrochemical aptasensor for the detection of As (III) in water based on carbon nanoparticle (CNPs) and gold nanoparticles (AuNPs) immobilisation platform. The carbon and gold nano-platform was prepared by drop coating CNPs on a glassy carbon electrode (GCE) followed by electrodeposition of AuNPs on the CNPs modified electrode by cyclic voltammetry from −300 mV to 1200 mV at 50 mVs−1 scan rate. The aptamer biosensor was prepared by the immobilisation of a 100-base thiolated Ars-3 aptamer on the nano-platform (CNPs/AuNPs) modified GCE by chemisorption. A detection limit of 0.092 ppb was obtained and the biosensor was not susceptible to interferences from Cd, Cu and Hg. This work thus presents an alternative approach to mitigating interferences in the electrochemical sensing of arsenic.

Altering polythiophene derivative substrates to control the electrodeposition morphology of Au particles toward ultrafine nanoparticles

A novel strategy for controlling the morphology of AuNPs by altering polythiophene derivative substrates was developed, and the nucleation mechanism of AuNPs on PTs was further explored theoretically. It is found that PTs with longer side chains can induce the electrodeposition of AuNPs with different morphologies and smaller particle sizes.

Electrodeposition⁻Assisted Assembled Multilayer Films of Gold Nanoparticles and Glucose Oxidase onto Polypyrrole-Reduced Graphene Oxide Matrix and Their Electrocatalytic Activity toward Glucose.

The study reports a facile and eco-friendly approach for nanomaterial synthesis and enzyme immobilization. A corresponding glucose biosensor was fabricated by immobilizing the gold nanoparticles (AuNPs) and glucose oxidase (GOD) multilayer films onto the polypyrrole (PPy)/reduced graphene oxide (RGO) modified glassy carbon electrode (GCE) via the electrodeposition and self-assembly. PPy and graphene oxide were first coated on the surface of a bare GCE by the electrodeposition. Then, AuNPs and GOD were alternately immobilized onto PPy-RGO/GCE electrode using the electrodeposition of AuNPs and self-assembly of GOD to obtain AuNPs-GOD multilayer films. The resulting PPy-RGO-(AuNPs-GOD)n/GCE biosensors were used to characterize and assess their electrocatalytic activity toward glucose using cyclic voltammetry and amperometry. The response current increased with the increased number of AuNPs-GOD layers, and the biosensor based on four layers of AuNPs-GOD showed the best performance. The PPy-RGO-(AuNPs-GOD)4/GCE electrode can detect glucose in a linear range from 0.2 mM to 8 mM with a good sensitivity of 0.89 μA/mM, and a detection limit of 5.6 μM (S/N = 3). This study presents a promising eco-friendly biosensor platform with advantages of electrodeposition and self-assembly, and would be helpful for the future design of more complex electrochemical detection systems.

Estimation of the surface area of a screen-printed carbon electrode modified with gold nanoparticles and cysteine using electrochemical impedance spectroscopy

This work concerns with the estimation of the surface area of a screen-printed carbon electrode (SPCE) modified with gold nanoparticles (AuNPs) and cysteine, using electrochemical impedance spectroscopy (EIS). Interpretation of EIS results was based on charge-transfer reactions at high frequencies, followed by diffusion through the monolayers at lower frequencies. Estimates of the electrode fractional surface coverage (?), active site radius (ra), and the distance between two adjacent sites (2rb) were obtained by assuming that charge transfer occurred at the active sites and that there were planar diffusions of redox species to these sites. Using EIS, fractional surface coverage was estimated to be around 0.467 for EC modified SPCE, 0.497 for ETSC modified SPCE, and 0.25 for ETSTSC modified SPCE. For the EC modified SPCE, the ra and 2rb were estimated to be 14.8 µm and 68 µm. For the ETSC modified SPCE, the estimated ra and 2rb were 14.3 µm and 63.6 µm. The estimated ra and 2rb for ETSTSC were 13.42 µm and 85 µm. respectively. The inactive site areas for EC, ETSC and ETSTSC modified SPCEs were 0.0587 m2, 0.0624 m2, and 0.0314 m2. The results obtained during this research work suggest that modifying SPCEs using gold and cysteine through electrodeposition of AuNPs, linking with thiourea, self-assembly of AuNPs and self-assembly of cysteine (ETSC) resulted in an electrode with sufficiently high surface area that has the potential to be used as a biosensor for skin sensitiser detection.

An impedimetric biosensor for DNA damage detection and study of the protective effect of deferoxamine against DNA damage

The detection and inhibition of DNA damage are of great importance in the prevention and treatment of diseases. Developing a simple and sensitive tool for this purpose would be a chance to monitor the DNA damage and could be helpful in introducing some drugs which can prevent this phenomenon. Here, we report a novel and sensitive electrochemical biosensor based on DNA/Au nanoparticles (AuNPs) modified screen printed gold electrode (DNA/AuNPs/SPGE) to investigate the DNA damage process and also to study the protective behavior of deferoxamine (DFO). The proposed biosensor was fabricated by electrodeposition of AuNPs onto SPGE, followed by chemical immobilisation of thiol-terminated DNA. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) have been used to characterise this biosensor. Hydroxyl radical (OH), which is generated during the Fenton reaction, is responsible for the induced damage to DNA. EIS technique was applied to monitor the DNA damage, and the increase in charge transfer resistance (Rct) following the DNA damage, was considered as an indicator. Furthermore, the ability of the electrochemical screening system was proved by the investigation of the antioxidant effect of DFO in prohibiting the DNA damage.

Efficient hydrogen and oxygen evolution on the AuNPs@CaFe-LDH composite in alkaline media

In this work, AuNPs@CaFe-LDH composite was fabricated by the electrodeposition of AuNPs on CaFe-LDH film coated on a glassy carbon electrode. Field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDX) were used to investigate the surface morphology and chemical composition of the AuNPs@CaFe-LDH. The catalytic activity of the catalyst was studied for OER and HER in alkaline media and was compared with CaFe-LDH@AuNPs, AuNPs and CaFe-LDH catalysts using electrochemical methods such as linear sweep voltammetry, electrochemical impedance spectroscopy and chrono-analysis. The AuNPs@CaFe-LDH featured a low onset potential of 1.68V for OER and −0.30V for HER. The current density, reaction kinetics and stability for both OER and HER at the AuNPs@CaFe-LDH were much higher than those of the AuNPs, LDH and CaFe-LDH@AuNPs. The results indicated that in addition to the synergistic effects between the AuNPs and CaFe-LDH, high electrochemically active surface area of AuNPs plays a key role in the enhancement of catalytic activity of the AuNPs@CaFe-LDH. Therefore, this catalyst could be applied as an efficient bifunctional electrocatalyst to use in alkaline water electrolyzers.