Fast Amperometric Response Time Research Articles

Highly efficient Ag doped δ-MnO2 decorated graphene: Comparison and application in electrochemical detection of H2O2

Cytotoxic H2O2 is an inevitable part of our life, even during this contemporary pandemic COVID-19. Personal protective equipment of the front line fighter against coronavirus could be sterilized easily by H2O2 for reuse. In this study, Ag doped δ-MnO2 nanorods supported graphene nanocomposite (denoted as Ag@δ-MnO2/G) was synthesized as a nonenzymatic electrochemical sensor for the sensitive detection of H2O2. The ternary nanocomposite has overcome the poor electrical conductivity of δ-MnO2 and also the severe aggregation of Ag NPs. Furthermore, δ-MnO2/G provided a rougher surface and large numbers of functional groups for doping more numbers of Ag atoms, which effectively modulate the electronic properties of the nanocomposite. As a result, electroactive surface area and electrical conductivity of Ag@δ-MnO2/G increased remarkably as well as excellent catalytic activity observed towards H2O2 reduction. The modified glassy carbon electrode exhibited fast amperometric response time (<2 s) in H2O2 determination. The limit of detection was calculated as 68 nM in the broad linear range (0.005–90.64 mM) with high sensitivity of 104.43 µA mM−1 cm−2. No significant interference, long-term stability, excellent reproducibility, satisfactory repeatability, practical applicability towards food samples and wastewater proved the efficiency of the proposed sensor.

Synthesis of porous CuO microspheres assembled from (001) facet-exposed nanocrystals with excellent glucose-sensing performance

Hierarchical porous CuO microspheres are successfully synthesized through a facile hydrothermal method using Na2HPO4-NaOH buffer solution as solvent. The SEM and TEM results reveal that the CuO microspheres are assembled by (001) facet-exposed nanocrystals. The BET result indicates that the CuO microspheres have a surface area of 61.9 m2 g−1 and an average pore size of ∼3.7 nm. Moreover, it is found that the buffer solution not only serves as reactant and medium, but also affects the final shape of the CuO microspheres. The buffer solution can supply a suitable amount of OH− ions, which leads to no extra OH− ions absorb on the original crystals, thus favoring to form into 3D spherical microstructure. In addition, the CuO microspheres are used as the electrodic material for non-enzymatic glucose sensor, which present low detection limit (0.50 μM), fast amperometric response time (3 s), and wide linear range (0.001–4.0 mM). The improved electrocatalytic performance is ascribed to the synergistic effect of exposure of (001) facet, large special surface area, and porous structure.

Silver nanoparticles selectively deposited on graphene-colloidal carbon sphere composites and their application for hydrogen peroxide sensing

In this study, we report the fabrication of a novel graphene-colloidal carbon sphere composite decorated with silver nanoparticles (Gr-CCS-AgNPs). Graphene-colloidal carbon sphere (Gr-CCS) and silver nanoparticles (AgNPs) were prepared under hydrothermal conditions step by step. The obtained Gr-CCS-AgNPs composite was characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffracmeter (XRD), X-ray photoelectron spectroscopy (XPS) and the energy dispersive X-ray spectroscopy (EDX), and a forming mechanism was suggested. A glassy carbon electrode was modified with the Gr-CCS-AgNPs to construct an electrochemical sensor, and our results demonstrated that the modified electrode had electrocatalytic activity for the reduction of hydrogen peroxide (H2O2) in 0.1M phosphate buffer solution (PBS, pH=7.0). The proposed H2O2 sensor displayed many good characteristics, such as a simple preparation procedure, fast amperometric response time (approximately 1s), excellent selectivity and sensitivity. The first linear section was in the range of 2×10−5M to 5.02×10−3M with a correlation coefficient of 0.9998 and a limit of detection of 2.49μM (S/N ratio is 3). The second linear response occurred from 5.02×10−3M to 3.41×10−2M with a correlation coefficient of 0.9995 and a limit of detection of 9.51μM (S/N ratio is 3).

Ag-supported nanozeolite L-modified electrode: a new high performance nonenzymatic hydrogen peroxide sensor

In this study, nanozeolite L is synthesized using an organic template-free system via hydrothermal approach. Its characterization shows that spherical nanoparticles with diameter in the range of 40–70 nm and high surface area are formed. After loading nanozeolite L with silver ions, it was mixed with carbon paste to prepare the modified electrode. The modified electrode was activated at an appropriate potential to convert Ag ions into Ag particles (Ag/LCPE) and its electrochemical properties were studied by cyclic voltammetry and amperometry methods. The results show that the constructed sensor has high catalytic activity and responds to H2O2 in a wide linear range with high sensitivity. The sensor had a low detection limit of 2 µM (S/N = 3) with a fast amperometric response time of 2 s. The high catalytic activity of proposed sensor results from the porous structure of nanozeolite L which provides high surface area for the formation of Ag active centers. Other features of the proposed sensor are high selectivity, stability, reproducibility, and repeatability. Also, the practical feasibility of the proposed sensor has been evaluated for the determination of H2O2 in human urine samples with good recoveries.

One-Step Synthesis of Different Silver-Polyaniline Composite Morphologies for Enzymless Hydrogen Peroxide Detection

Silver nanoparticle-decorated polyaniline nanorods (AgNPs-PANINRs) and silver nanoparticle-decorated polyaniline nanotubes (AgNPs-PANINTs) composites were prepared through a one-step modified methods by immobilizing a mixture of AgNO3, aniline and ammonium per sulfate (APS) as an oxidant without adding any extra acids, templates or surface modifiers. The composites were characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The reactivity of the prepared composites towards hydrogen peroxide (H2O2) was analyzed using cyclic voltammetry and chronoamperometry. The AgNPs-PANINRs composite exhibits better electrochemical performance than the AgNPs-PANINTs composite due to higher content of silver nanoparticle (AgNPs). The sensor has a fast amperometric response time which less than 3 s. The detection limit and limit of quantification (S/N = 3) of two linear range (low and high concentration of H2O2) are estimated as 0.13 μM and 0.45 μM and 0.33 μM and 1.12 μM, respectively.

Ordered-standing nickel hydroxide microchannel arrays: Synthesis and application for highly sensitive non-enzymatic glucose sensors

A non-enzymatic glucose sensor is constructed by using nickel hydroxide (Ni(OH)2) modified silicon microchannel plates (MCP) as the sensing materials. The 3D ordered Si MCP is fabricated by electrochemical etching and the Ni(OH)2 coating are prepared by electroless plating. The nanocomposite electrode exhibits good catalytic activity toward oxidation of glucose in 0.1M KOH. This non-enzymatic glucose sensor boasts a fast amperometric response time of less than 5s, sensitivity of 0.25mAmM−1cm−2, and detection limit of 3.5μM at a signal-to-noise ratio of 3. The sensor shows superior stability, anti-interference capability, and selectivity. The good analytical capability, low cost, and compatibility with silicon technology make the Ni(OH)2/Si MCP electrode promising in amperometric non-enzymatic glucose detection.

One-step hydrothermal green synthesis of silver nanoparticle-carbon nanotube reduced-graphene oxide composite and its application as hydrogen peroxide sensor

A novel sensing composite of silver nanoparticles (AgNPs)-reduced graphene oxide (rGO)-carbon nanotube (MWCNT) was successfully synthesized by a simple one-step hydrothermal method without reducing agent. Mild reduction of GO was carried out under hydrothermal condition. While most conventional approaches make use of multistep chemical methods wherein strong reducing agents, such as hydrazine, hydroquinone, and sodium borohydride are employed, our method provides the notable advantage of a single-step reaction without employing any toxic solvent or reducing agent by providing a novel green synthetic route to produce the nanocomposites of rGO, carbon nanotube and silver. The results of X-ray diffraction (XRD) and Fourier-transform infrared transmission spectroscopy (FT-IR) confirmed the simultaneous formation of silver nanoparticles in the GO and MWCNT matrix. Field emission scanning electron microscope (FESEM) images and transmission electron microscopy (TEM) showed uniform distribution of nanometer-sized silver nanoparticles and narrow-sized MWCNT on GO sheets, which was achieved using silver ammonia complex as the precursor, instead of the commonly used silver nitrate. The composite exhibited excellent electrocatalytic activity for the reduction of H2O2 with a fast amperometric response time less than 3s. The electrocatalytic activity for the reduction was strongly affected by the concentration of silver ammonia solution in the nanocomposites, with the best electrocatalytic activity observed for the composite of 6:1 volume ratios of MWCNT–GO (3:1, v/v) to Ag(NH3)2OH (0.04M). The corresponding calibration curve for the current response showed a linear detection range of 0.1–100mM (R2=0. 9985), while the limit of detection was estimated to be 0.9μM.

Green Synthesis of Ag Nanoparticles by Callicarpa Maingayi: Characterization and Its Application with Graphene Oxide for Enzymeless Hydrogen Peroxide Detection

AbstractA facile green synthesis of silver nanoparticles (AgNPs) was achieved using aqueous leaf extract of Callicarpa Maingayi as a reducing and stabilizing agent during the synthesis from its salt solutions. The synthesized silver nanoparticles were analyzed with transmission electron microscopy (TEM), X‐ray diffraction (XRD) and energy dispersive spectrometer (EDS). XRD study shows that the particles are crystalline in nature with face centered cubic geometry. The crystallite size obtained from XRD is about 15 nm which is in agreement well with the TEM results. A new nanostructure sensor was constructed by immobilizing silver nanoparticles and graphene oxide (AgNPs‐GO) composite film on a glassy carbon electrode (AgNPs‐GO/GCE). It was found that the AgNPs‐GO composite exhibits good catalytic activity toward the reduction of hydrogen peroxide (H2O2), leading to an enzymeless sensor with a fast amperometric response time of less than 5 s, high selectivity, good reproducibility and stability. The linear range was 5.0 μM to 700 μM with a detection limit of 0.6 μM (S/N = 3).

A new non-enzymatic glucose sensor based on copper/porous silicon nanocomposite

Cu/PSi (copper/porous silicon) nanocomposite powder was prepared by chemical etching of silicon (Si) powder in a HF/HNO3 solution, followed by electrodless plating of copper nanoparticles on the etched PSi powder in a solution containing CuSO4 as a metal precursor. The resulting nanocomposite was characterized by X–ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV) and FT–IR spectroscopy. The copper nanoparticles in PSi support show the good chemical and electrochemical stability as well as electrocatalytic effect on Glc oxidation, hence the Cu/PSi nanocomposite was used to modify carbon paste electrode (CPE) to fabricate non-enzymatic Glc sensor. The electrocatalytic activity of Cu/PSi nanocomposite was investigated for Glc oxidation in alkaline and neutral solutions using cyclic voltammetry and chronoamperometry. The novel developed sensor displayed a fast amperometric response time of less than 4 s, long time stability, good signal reproducibility and two linear ranges from 1.0 to 190.0μmol dm−3 and 190μmol dm−3 to 2.3mmol dm−3 of Glc with a detection limit of 0.2μmol dm−3. The sensor exhibited no interference from common interferences such as ascorbic acid, dopamine, uric acid, fructose and citric acid. The good analytical performance, low cost and easy preparation method made this novel electrode material promising for the development of effective Glc sensor.

Synthesis of Polypyrrole Coated Silver Nanostrip Bundles and Their Application for Detection of Hydrogen Peroxide

We reported a facile synthesis of a stable polypyrrole coated silver nanostrip bundles (Ag NSBs-PPy) by direct reduction of Ag cations in the presence of pyrrole monomers in an aqueous solution of AgNO3 and NaOH. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) observations reveal that the Ag cations were completely reduced to Ag and the Ag NSBs-PPy morphology respectively. The observations show that the modified glassy carbon electrode with the Ag NSBs-PPy exhibits a remarkable catalytic performance for hydrogen peroxide (H2O2) detection. This is due to the large surface area of Ag NSBs-PPy which increases the ability of the modified electrode to react with H2O2. The sensor has a fast amperometric response time of less than 5 s. The detection limit and limit of quantification (S/N = 3) of two linear segments (low and high concentration of H2O2) are estimated as 0.68 μmol L−1, 2.27 μmol L−1 and 13.10 μmol L−1, 43.60 μmol L−1, respectively. In addition, the sensitivity for these two linear segments is 9.701 μA μM−1 and 0.506 μA μM−1 respectively.

A sensitive hydrogen peroxide and glucose biosensor based on gold/silver core–shell nanorods

Au core/Ag shell nanorods (Au@Ag NRs) were synthesized through the seed-mediated growth procedure using Au nanorods (Au NRs) as templates and characterized by UV–vis and TEM methods. The as-prepared Au@Ag NRs were used as a new electrode material for construction of sensor by surface casting of Au@Ag NRs aqueous solution on a glassy carbon electrode (GCE). The fabricated sensor exhibits excellent catalytic performance toward H2O2 reduction with a fast amperometric response time of less than 2s, a wide linear response ranging from 0.02 to 7.02mM (R=0.99), and a lower detection limit of 0.67μM estimated on a signal-to-noise ratio of 3. A glucose biosensor was further fabricated by immobilization of glucose oxidase (GOD) onto the core/shell Au@Ag NRs-modified GCE. The resultant biosensor exhibits high sensitivity, selectivity and stability for glucose detection in phosphate buffer solution. Even in human blood serum, the biosensor also exhibits good performance for glucose detection with an enhanced sensitivity of 33.67μAmM−1cm−2.

One-step electrodeposition synthesis of silver-nanoparticle-decorated graphene on indium-tin-oxide for enzymeless hydrogen peroxide detection

Silver-nanoparticles-decorated reduced graphene oxide (rGO) was electrodeposited on indium tin oxide (ITO) by a cyclic voltammetry method. The results of X-ray diffraction, Fourier-transform infrared transmission spectroscopy and Raman spectroscopy confirmed the simultaneous formation of cubic phase silver nanoparticles and reduction of GO through the electrodeposition process. Field emission scanning electron microscope images showed a uniform distribution of nanometer-sized silver nanoparticles with a narrow size distribution on the RGO sheets, which could only be achieved using silver ammonia complex instead of silver nitrate as precursor. The composite deposited on ITO exhibited notable electrocatalytic activity for the reduction of H2O2, leading to an enzymeless electrochemical sensor with a fast amperometric response time less than 2s. The corresponding calibration curve of the current response showed a linear detection range of 0.1–100mM (R2=0.9992) while the limit of detection was estimated to be 5μM.

A novel non-enzymatic glucose sensor based on NiO hollow spheres

A novel non-enzymatic glucose sensor has been constructed by using NiO hollow spheres (NiO-HSs) as sensing materials, which were prepared by a glycerin-assisted hydrothermal synthesis method. The analytical techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) indicate the successful formation of NiO-HSs, assembled by NiO nanoflakes with the length of about 500nm and the width of about 50nm. It was found that the resulting NiO-HSs exhibit good catalytic activity toward the oxidation of glucose in 0.1M NaOH, leading to a non-enzymatic glucose sensor with a fast amperometric response time of less than 3s, and the detection limit is estimated to be 0.3 μM at a signal-to-noise ratio of 3. Furthermore, this sensor shows good response to glucose in comparison to other normally co-existing electroactive species (such as dopamine, ascorbic acid and uric acid).

Synthesis of PtAu bimetallic nanoparticles on graphene–carbon nanotube hybrid nanomaterials for nonenzymatic hydrogen peroxide sensor

PtAu bimetallic nanoparticles (NPs) were successfully synthesized on graphene sheets-multi walled carbon nanotubes (G-CNTs) hybrid nanomaterials via a simple one-step chemical co-reduction method in ethylene glycol (EG)–water system. The nanocomposites (PtAu/G-CNTs) were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Then a sensitive nonenzymatic hydrogen peroxide (H2O2) sensor was fabricated based on PtAu/G-CNTs nanocomposites modified glassy carbon electrode (GCE). The results of electrochemical experiments demonstrated that the sensor exhibited excellent electrocatalytic activity to the reduction of H2O2. The sensor displayed a fast amperometric response time of less than 4s with linear detection range from 2.0 to 8561μM and a relatively low detection limit of 0.6μM (S/N=3). In addition, the sensor also showed good selectivity for H2O2 detection, long-term stability and reproducibility.

Carbon nanoparticles-induced formation of polyaniline nanofibers and their subsequent decoration with Ag nanoparticles for nonenzymatic H2O2 detection

The present communication reports on the preparation of polyaniline nanofibers (PANINFs) by chemical oxidative polymerization of aniline under rapid stirring using ammonium persulfate as the oxidant in acidic aqueous media in the presence of carbon nanoparticles. The subsequent treatment of such nanofiber with a AgNO3 aqueous solution leads to in situ chemical reduction of Ag+ on them to form Ag nanoparticle-decorated PANINFs. The resultant composites show good catalytic activity toward the reduction of H2O2. An effective enzymeless H2O2 sensor based on such composites is also constructed. It exhibits a fast amperometric response time 2 s, and it has a linear detection range from 0.1 to 60 mM and detection limit of 0.9 μM at a signal-to-noise ratio of 3, respectively.

Electrochemically controlled growth of silver nanocrystals on graphene thin film and applications for efficient nonenzymatic H2O2 biosensor

We report a double pulse electrochemical method to controllably prepare silver nanocrystals (AgNCs) on graphene thin film electrode for fabricating a high performance H2O2 biosensor. The approach relies on two potential pulses that can independently control the nucleation and subsequent growth processes of AgNCs on graphene substrate. This method also allows the observation of AgNCs growing from a particle shape to a nanoplate form by increasing the growth time with the maximum lateral scale up to micrometer scale range. A proposed mechanism for these silver nanoplates (AgNPLs) formation was the oriented growth of small AgNCs and two-dimensional graphene template inducing effect. Such obtained graphene–AgNPLs hybrid thin films exhibit remarkable electrocatalytical activity toward H2O2 electrochemical reduction. Further fabricated nonenzymatic H2O2 biosensor displays a fast amperometric response time of less than 2s and a good linear range from 2×10−5M to 1×10−2M with an estimated detection limit of 3×10−6M. This biosensor also exhibits good stability (RSD, 1.3%), and high sensitivity of 183.5μAcm−2mM−1 as well as high selectivity. The results show that this powerful double pulse potential electrochemical method could enable new opportunities in controllable preparation of multifarious nanomaterials on graphene substrate for their future applications.

7,7,8,8-tetracyanoquinodimethane microsheets for hydrogen peroxide reduction

In this Letter, we demonstrate for the first time that 7,7,8,8-tetracyanoquinodimethane microsheets (TCNQMSs) can effectively catalyze the reduction of H2O2 because TCNQ is a strong electron acceptor, TCNQMSs modified glass carbon electrode (GCE) is prepared by a simple casting method. This H2O2 sensor shows a fast amperometric response time of less than 3 s, and the corresponding linear range is estimated to be from 3 to 238 mM (r = 0.992) and a detection limit of 4.76 μM at a signal-to-noise ratio of 3. Our present study is important because it provides us a new structure for H2O2 detection application.

One-pot synthesis of Ag nanoparticles/reduced graphene oxide nanocomposites and their application for nonenzymatic H2O2 detection

In this paper, we report on one-pot synthesis of Ag nanoparticles/reduced graphene oxide (AgNPs/rGO) nanocomposites by heating mixed solution of graphene oxide (GO) and AgNO3 with the use of diethylenetriamine as a reducing agent at 80°C for 30min. Several analytical techniques including UV–vis spectroscopy, Raman spectroscopy and transmission electron microscopy (TEM) have been employed to characterize the resulting nanocomposites. It was found that such nanocomposites exhibit good catalytic activity toward the reduction of H2O2. This nonenzymatic H2O2 sensor shows a fast amperometric response time of less than 2s. The linear detection range is estimated to be from 0.1 to 100mM (r=0.999), and the detection limit is estimated to be 3.6μM at a signal-to-noise ratio of 3.

Heat Treatment-Based One-Step Preparation of Highly Concentrated, Well-Stable Silver Colloids that Can Form Stable Films on Bare Electrodes for H2O2 Detection

A simple thermal process for the one-step preparation of highly concentrated (up to 0.21 M) but well-stable silver colloids with a bimodal size distribution is developed for the first time, carried out by directly heating an aqueous solution of concentrated AgNO3 and poly[(2-ethyldimethylammonioethyl methacrylate ethyl sulfate)-co- (1-vinylpyrrolidone)] (PQ11), a kind of cationic polyelectrolyte, at 100 °C without the extra introduction of other reducing agents and protective agents. Time-dependent UV-vis spectra were collected to gain further insight into the Ag nanoparticles (AgNPs) formation process. Most importantly, it is found that the colloidal solution can form stable films on bare electrode surfaces and the AgNPs contained therein exhibit notable catalytic activity toward the reduction of H2O2, leading to a H2O2 sensor with a fast amperometric response time of less than 2 s. The linear detection range is estimated to be from 100 μM to 150 mM (r = 0.9995), and the detection limit is estimated to be 1.8 μM at a signal-to-noise ratio of 3.

Supramolecular Microfibrils of O-Phenylenediamine Dimers: Oxidation-induced Formation of Au Nanoparticle-decorated Nanoplates for H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; Detection

The direct mix of aqueous FeCl3 and o-phenylenediamine (OPD) solutions at room temperature leads to supramolecular microfibrils of OPD dimers generated by the oxidation of OPD monomers by FeCl3. In this paper, we demonstrate that the subsequent treatment of such microfibrils with a HAuCl4 aqueous solution leads to Au nanoparticle (AuNP)-decorated nanoplates. The possible formation mechanism involved is also discussed. It is found that such nanocomposites can effectively catalyze both oxidization and reduction of H2O2. The sensor constructed with these nanocomposites exhibits a fast amperometric response time of less than 4 s. The linear detection range is estimated to be from 100 μM to 170 mM (r=0.997), and the detection limit is estimated to be 8 μM at a signal-to-noise ratio of 3. Keywords: Supramolecular microfibril, Au nanoparticle, nanoplate, H2O2 detection