Highly sensitive detection of hydrogen peroxide at a carbon nanotube fiber microelectrode coated with palladium nanoparticles

Nanomaterial-Based Label-Free Electrochemical Aptasensors for the Detection of Thrombin

Thrombin plays a central role in hemostasis and its imbalances in coagulation can lead to various pathologies. It is of clinical significance to develop a fast and accurate method for the quantitative detection of thrombin. Electrochemical aptasensors have the capability of combining the specific selectivity from aptamers with the extraordinary sensitivity from electrochemical techniques and thus have attracted considerable attention for the trace-level detection of thrombin. Nanomaterials and nanostructures can further enhance the performance of thrombin aptasensors to achieve high sensitivity, selectivity, and antifouling functions. In highlighting these material merits and their impacts on sensor performance, this paper reviews the most recent advances in label-free electrochemical aptasensors for thrombin detection, with an emphasis on nanomaterials and nanostructures utilized in sensor design and fabrication. The performance, advantages, and limitations of those aptasensors are summarized and compared according to their material structures and compositions.

Rigid anchoring of highly crystallized and uniformly dispersed Pd nanocrystals on carbon fibers for ambient electrocatalytic reduction of nitrogen to ammonia

Developing efficient and stable electrocatalysts for ammonia synthesis via the nitrogen reduction reaction (NRR) is essential for the Earth's nitrogen cycle. Herein, a palladium nanocrystals anchored carbon fibers (PdNCs@CNFs) composite was prepared via electrospinning and carbonization processes. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization studies show that the as-prepared Pd grains are homogeneously anchored on the outer/inner section of the carbon nanofibers. Benefiting from the sufficient exposure and stress effect of active sites, the resultant PdNCs@CNFs achieves a high Faraday efficiency of ∼14.8% with a current density of 0.028 mA cm-2 at -0.2 V vs. reversible hydrogen electrode (RHE) in 0.1 M Na2SO4 solution, surpassing those of many catalysts previously reported. Density functional theory (DFT) calculations reveal that the rationality of the distal associative mechanism on PdNCs@CNFs and Pd nanocrystals on the surface of PdNCs@CNFs is more favorable for nitrogen (N2) molecule adsorption and polarization.

In vivo detection of salicylic acid in sunflower seedlings under salt stress

A Pt nanoflowers/ERGO modified Pt microelectrode was proposed to detect salicylic acid in plants under salt stress in vivo.

General Metal-Ion Mediated Method for Functionalization of Graphene Fiber

Graphene fibers (GFs) are attractive materials for wearable electronics because of their lightness, superior flexibility, and electrical conductivity. However, the hydrophobic nature and highly stacked structure endow GFs similar characteristics in nature to solid carbon fibers. Therefore, the interior functionalization of GFs so as to achieve synergistic interaction between graphene nanosheets and active materials thus enhance the performance of hybrid fibers remains a challenge. Herein, a general metal-ion mediated strategy is developed to functionalize GFs and nanoparticles of Cu, Fe₂O₃, NiO, and CoO are successfully incorporated into GFs, respectively. As proof-of-concept applications, the obtained functionalized GFs are used as electrodes for electrochemical sensors and supercapacitors. The performances of thus-devised fiber sensor and supercapacitor are greatly improved.

Rapid production of Pd nanoparticle by a marine electrochemically active bacterium Shewanella sp. CNZ-1 and its catalytic performance on 4-nitrophenol reduction

Microbial recovery of Pd through Pd(ii) reduction is emerging as a clean alternative to traditional physical and chemical reclaiming treatments.

Detection of pH and Enzyme-Free H2O2 Sensing Mechanism by Using GdO x Membrane in Electrolyte-Insulator-Semiconductor Structure

A 15-nm-thick GdO x membrane in an electrolyte-insulator-semiconductor (EIS) structure shows a higher pH sensitivity of 54.2 mV/pH and enzyme-free hydrogen peroxide (H2O2) detection than those of the bare SiO2 and 3-nm-thick GdO x membranes for the first time. Polycrystalline grain and higher Gd content of the thicker GdO x films are confirmed by transmission electron microscopy (TEM) and X-ray photo-electron spectroscopy (XPS), respectively. In a thicker GdO x membrane, polycrystalline grain has lower energy gap and Gd(2+) oxidation states lead to change Gd(3+) states in the presence of H2O2, which are confirmed by electron energy loss spectroscopy (EELS). The oxidation/reduction (redox) properties of thicker GdO x membrane with higher Gd content are responsible for detecting H2O2 whereas both bare SiO2 and thinner GdO x membranes do not show sensing. A low detection limit of 1 μM is obtained due to strong catalytic activity of Gd. The reference voltage shift increases with increase of the H2O2 concentration from 1 to 200 μM owing to more generation of Gd(3+) ions, and the H2O2 sensing mechanism has been explained as well.

A Simple Green Synthesis of Palladium Nanoparticles with Sargassum Alga and Their Electrocatalytic Activities Towards Hydrogen Peroxide

This study presents the synthesis of palladium nanoparticles (PdNPs) using the extract derived from the marine alga, Sargassum bovinum, collected from Persian Gulf area. Water-soluble compounds that exist in the marine alga extract were the main cause of the reduction of palladium ions to Pd nanoparticles. The basic properties of PdNPs produced in this method were confirmed by UV-visible spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX) analysis, and Fourier transform infrared spectroscopy (FTIR). TEM confirmed the monodispersed and octahedral shape of PdNPs within the size ranges from 5 to 10 nm. Catalytic performance of the biosynthetic PdNPs was investigated by electrochemical reduction of hydrogen peroxide (H2O2). PdNP-modified carbon ionic liquid electrode (PdNPs/CILE) was developed as a nonenzymatic sensor for the determination of hydrogen peroxide. Amperometric measurements showed that PdNPs/CILE is a reliable sensor for the detection of hydrogen peroxide in the range of 5.0 μM-15.0 mM with a sensitivity of 284.35 mAmM(-1) cm(-2) and a detection limit of 1.0 μM. Moreover, PdNPs/CILE exhibits a wide linear range, high sensitivity and selectivity, and excellent stability for the detection of H2O2 in aqueous solutions.

Cost-effective flow injection amperometric system with metal nanoparticle loaded carbon nanotube modified screen printed carbon electrode for sensitive determination of hydrogen peroxide

Various metal nanoparticles (NPs) decorated on carbon nanotube (CNT) was modified on the home-made screen printed carbon electrode (SPCE) in order to enhances sensitivity of hydrogen peroxide (H2O2) determination. The simple casting method was used for the electrode modification. The monometallic and bimetallic NPs modified electrodes were investigated for their electrochemical properties for H2O2 reduction. The Pd-CNT/SPCE is appropriated to measure the H2O2 reduction at a potential of -0.3 V, then this modified electrode was incorporated with a home-made flow through cell and applied in a simple flow injection amperometry (FI-Amp). Some parameters influencing the resulted modified electrode and the FI-Amp system were studied. The proposed detection system was able to detect H2O2 in the range of 0.1-1.0 mM, with detection limit of 20 µM. Relative standard deviation for 100 replicated injections of 0.6 mM H2O2 was 2.3%. The reproducibility of 6 electrodes preparing in 3 different lots was 8.2%. It was demonstrated for determination of H2O2 in disinfectant, hair colorant and milk samples. Recoveries in the range of 90-109% were observed. The developed system provided high stability, good repeatability, high sample throughput and low reagent consumption.

Fabrication of ultralong hybrid microfibers from nanosheets of reduced graphene oxide and transition-metal dichalcogenides and their application as supercapacitors

Two-dimensional materials have attracted increasing research interest owing to their unique electronic, physical, optical, and mechanical properties. We thus developed a general strategy for the fabrication of ultralong hybrid microfibers from a mixture of reduced graphene oxide and transition-metal dichalcogenides (TMDs), including MoS2 , TiS2 , TaS2 , and NbSe2 . Furthermore, we prepared fiber-based solid-state supercapacitors as a proof-of-concept application. The performance of thus-prepared supercapacitors was greatly improved by the introduction of the TMDs.