Platinum nanoparticle-decorated carbon nanotube clusters on screen-printed gold nanofilm electrode for enhanced electrocatalytic reduction of hydrogen peroxide

Continuous production of bimetallic nanoparticles on carbon nanotubes based on 3D-printed microfluidics

Nanoparticle-functionalized carbon nanotubes are promising in many research fields, especially in sensing, due to their intriguing performance in catalysis. However, these nanomaterials are mainly produced through batch processes under harsh conditions, thus encountering inherent limitations of low throughput and uncontrollable morphology of functional nanoparticles (NPs). In this work, we propose a method for high-yield and continuous production of bimetallic (Pt-Pd) NPs on multi-walled carbon nanotubes (MWCNTs) at room temperature through a custom 3D-printed microfluidic platform. A homogenous particle nucleation and growth environment could be created on the microfluidic platform that was equipped with two 3D-printed micromixers. Pt-Pd NPs loaded on MWCNTs were prepared in the microfluidic platform with high throughput and controlled size, dispersity and composition. The synthetic parameters for these nanocomposites were investigated to optimize their electrocatalytic performance. The optimized nanocomposites exhibited excellent electrocatalytic activity with exceptional sensitivity and wide detection range, superior to their counterparts prepared via conventional approaches. This method proposed here could be further adapted for manufacturing other catalyst support materials, opening more avenues for future large-scale production and catalytic investigation of functional nanomaterials.

Screen-Printed Electrodes Modified with Metal Nanoparticles for Small Molecule Sensing

Recent progress in the field of electroanalysis with metal nanoparticle (NP)-based screen-printed electrodes (SPEs) is discussed, focusing on the methods employed to perform the electrode surface functionalization, and the final application achieved with different types of metallic NPs. The ink mixing approach, electrochemical deposition, and drop casting are the usual methodologies used for SPEs' modification purposes to obtain nanoparticulated sensing phases with suitable tailor-made functionalities. Among these, applications on inorganic and organic molecule sensing with several NPs of transition metals, bimetallic alloys, and metal oxides should be highlighted.

Precise Micropatterning of a Porous Poly(ionic liquid) via Maskless Photolithography for High-Performance Nonenzymatic H2O2 Sensing

Porous poly(ionic liquid)s (PILs) recently have been serving as a multifunctional, interdisciplinary materials platform in quite a few research areas, including separation, catalysis, actuator, sensor, and energy storage, just to name a few. In this context, the capability of photopatterning PIL microstructures in a porous state on a substrate is still missing but is a crucial step for their real industrial usage. Here, we developed a method for in situ rapid patterning of porous PIL microstructures via a maskless photolithography approach coupled with a simple electrostatic complexation treatment. This breakthrough enables design of miniaturized sensors. As exemplified in this work, upon loading Pt nanoparticles into porous PIL microstructures, the hybrid sensor showed outstanding performance, bearing both a high sensitivity and a wide detection range.

Simple sonochemical synthesis of novel grass-like vanadium disulfide: A viable non-enzymatic electrochemical sensor for the detection of hydrogen peroxide

Design and fabrication of novel inorganic nanomaterials for the low-level detection of food preservative chemicals significant is of interest to the researchers. In the present work, we have developed a novel grass-like vanadium disulfide (GL-VS₂) through a simple sonochemical method without surfactants or templates. As-prepared VS₂ was used as an electrocatalyst for reduction of hydrogen peroxide (H₂O₂). The crystalline nature, surface morphology, elemental compositions and binding energy of the as-prepared VS₂ were analyzed by X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The electrochemical studies show that the GL-VS₂ modified glassy carbon electrode (GL-VS₂/GCE) has a superior electrocatalytic activity and lower-reduction potential than the response observed for unmodified GCE. Furthermore, the GL-VS₂/GCE displayed a wide linear response range (0.1-260 μM), high sensitivity (0.23 μA μM^-1 cm^-2), lower detection limit (26 nM) and excellent selectivity for detection of H₂O₂. The fabricated GL-VS₂/GCE showed excellent practical ability for detection of H₂O₂ in milk and urine samples, revealing the real-time practical applicability of the sensor in food contaminants.

Non-enzymatic electrochemical hydrogen peroxide biosensor based on reduction graphene oxide-persimmon tannin‑platinum nanocomposite

Hydrogen peroxide (H₂O₂) is one of the most universal and essential ingredients in distinct biological tissues. Herein, a novel non-enzymatic sensor based on reduction graphene oxide-persimmon tannin‑platinum nanocomposite (RGO-PT-Pt) was exploited for H₂O₂ detection. RGO-PT-Pt nanocomposite was prepared by reduction procedure with ascorbic acid as reducing agent and characterized by Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), ultraviolet visible spectroscopy (UV-vis) and Fourier infrared spectroscopy (FT-IR). Taking advantage of high electro-catalytic efficiency of Pt nanoparticles, high electronic conductivity and large surface area of RGO, and significant adsorption ability of PT on metal ions and its prevention of agglomeration to promote RGO dispersion, RGO-PT-Pt nanocomposite revealed better catalytic ability towards H₂O₂ via a synergistic effect. Under the optimal conditions, the RGO-PT-Pt non-enzymatic biosensor exhibited outstanding electrocatalytic activity towards H₂O₂ reduction. The amperometric response demonstrated a linear relationship with H₂O₂ concentration from 1.0 to100 μM with the correlation coefficient of 0.9931. The limit of detection was 0.26 μM (S/N = 3) and the response time was 3 s. Furthermore, the fabricated sensor exhibited a practical applicability in the quantification of H₂O₂ in human serum samples with an excellent recovery rate. Due to excellent performance such as fast response time, low detection limit, high stability and selectivity, the RGO-PT-Pt non-enzymatic biosensor has potential application in clinical diagnostics.

Electrochemical Hydrogen Peroxide Sensor Based on Macroporous Silicon

Macroporous silicon was prepared through an anodization process; the prepared samples showed an average pore size ranging from 4 to 6 microns, and the depth of the pores in the silicon wafer was approximately 80 microns. The prepared samples were tested for hydrogen peroxide (H₂O₂) concentrations, which can be used for industrial and environmental sensing applications. The selected H₂O₂ concentration covered a wide range from 10 to 5000 μM. The tested samples showed a linear response through the tested H₂O₂ concentrations with a sensitivity of 0.55 μA μM^-1∙cm^-2 and lower detection limits of 4.35 μM at an operating voltage of 5 V. Furthermore, the electrode exhibited a rapid response with a response time of ca. two seconds. Furthermore, the prepared sensor showed a reasonable stability over a one-month time period.

Pt-grown carbon nanofibers for detection of hydrogen peroxide

Removal of left-over catalyst particles from carbon nanomaterials is a significant scientific and technological problem. Here, we present the physical and electrochemical study of application-specific carbon nanofibers grown from Pt-catalyst layers. The use of Pt catalyst removes the requirement for any cleaning procedure as the remaining catalyst particles have a specific role in the end-application. Despite the relatively small amount of Pt in the samples (7.0 ± 0.2%), they show electrochemical features closely resembling those of polycrystalline Pt. In O₂-containing environment, the material shows two separate linear ranges for hydrogen peroxide reduction: 1–100 μM and 100–1000 μM with sensitivities of 0.432 μA μM⁻¹ cm⁻² and 0.257 μA μM⁻¹ cm⁻², respectively, with a 0.21 μM limit of detection. In deaerated solution, there is only one linear range with sensitivity 0.244 μA μM⁻¹ cm⁻² and 0.22 μM limit of detection. We suggest that the high sensitivity between 1 μM and 100 μM in solutions where O₂ is present is due to oxygen reduction reaction occurring on the CNFs producing a small additional cathodic contribution to the measured current. This has important implications when Pt-containing sensors are utilized to detect hydrogen peroxide reduction in biological, O₂-containing environment.

Application specific Pt-grown carbon nanofibers for H₂O₂ detection were characterized and the roles of dissolved oxygen and chloride ions on the electrochemical performance were assessed in detail.

Enhanced Electrochemical Performance by Strongly Anchoring Highly Crystalline Polyaniline on Multiwalled Carbon Nanotubes

Highly crystalline polyaniline (PANI) was strongly anchored on a multiwalled carbon nanotube (MWNT) surface, slowly grown from a controlled isothermal crystallization method utilizing π-π interactions. The crystalline PANI particles are approximately 10-38 nm thick, and the space between them varies from near 0 to 55 nm as reaction conditions vary. The highly crystalline nanohybrid (CNH) showed electrochemical performance enhancement compared with that of neat MWNTs, PANI, and the reference hybrid synthesized from chemical polymerization. The specific capacitance (SC) of CNHs was 726 F g^-1 coupled with an excellent rate capability. Moreover, the strong combination between PANI and MWNTs as well as the crystalline structure in PANI improved the bulk conductivity, the interfacial charge transportation, and the cycling stability of the CNHs. The SC value of the CNHs remained almost unchanged upon 1000 charge-discharge cycles, followed by just a slight decline of 2.6% after 10 000 cycle tests. X-ray diffraction data shows the SC decline mainly resulted from the structural variation of crystalline PANI. Furthermore, the resulting CNHs showed significant electrocatalytic behavior toward H₂O₂ and exhibited a low detection limit of 4.4 μM due to the enhanced electron transportation between MWNTs and PANI. The reported method opens a gateway to design high-performance MWNT/PANI hybrids for use in electrochemical sensors, fuel cells, and energy-storage related devices.

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.

An electrochemical sensor based on reduced graphene oxide and copper sulfide hollow nanospheres

A nonenzymatic sensor for the detection of hydrogen peroxide (H₂O₂) was fabricated with reduced graphene oxide (RGO) and copper sulfide hollow nanospheres (CuSHNs).

Synthesis and optical enhancement of amorphous carbon nanotubes/silver nanohybrids via chemical route at low temperature

We report the synthesis of amorphous carbon nanotubes/silver (αCNTs/Ag) nanohybrids via simple chemical route without additional reactant and surfactant at low temperature. Field emission scanning microscope (FESEM) and transmission electron microscope (TEM) confirmed formation of CNTs. X-ray diffraction (XRD) pattern confirmed the amorphous phase of carbon and the formation of Ag nanoparticles crystalline phase. Raman spectra revealed the amorphous nature of α CNTs. UV-visible spectroscopy showed enhancement of optical properties of α CNTs/Ag nanohybrids.

First report for voltammetric determination of methyldopa in the presence of folic acid and glycine

In this study, a carbon paste electrode modified with TiO2 nanoparticles and ferrocene monocarboxylic acid (FM) was used to prepare a novel electrochemical sensor. The objective of this novel electrode modification was to seek new electrochemical performances for the detection of methyldopa in the presence of folic acid and glycine. The peak potentials recorded in a phosphate buffer solution (PBS) of pH7.0 were 325, 750 and 880 mV vs. Ag/AgCl/KCl (3.0M) for methyldopa, folic acid and glycine, respectively. Under the optimum pH of 7.0, the oxidation of methyldopa occurred at a potential about 160 mV less positive than that of the unmodified carbon paste electrode (CPE). The response of catalytic current with methyldopa concentration showed a linear relation in the range from 2.0×10(-7) to 1.0×10(-4)M with a detection limit of 8.0 (± 0.2)×10(-8)M.

Nonenzymatic electrochemical glucose sensor based on novel Pt-Pd nanoflakes

The sluggish kinetic-controlled glucose oxidation reaction on Pt electrodes is well recognized as the most critical issue that blocks the development and commercialization of enzyme-free glucose sensors, and increasing attention is being focused on improving the analytical performances of these nonenzymatic sensors through exploring new Pt-based catalysts. In the present research, we synthesized novel Pt-Pd nanoflakes (Pt-Pd NFs) with three-dimensional architectures on a homemade screen-printed gold film electrode (SPGFE) substrate using a facile electrochemical deposition without any template, and further investigated the properties of the as-fabricated Pt-Pd NFs/SPGFE for enzymeless glucose detection. The results reveal that the proposed Pt-Pd nanostructure can provide preeminent electrocatalytic activity and excellent selectivity for enzyme-free glucose sensing under simulative physiological conditions, mainly attributing to its attractive structure, large active surface and appropriate applied potential. The resulting Pt-Pd NFs/SPGFE offers linear current responses for glucose with the concentration upper limit to 16 mM. The obtained sensitivity is calculated to be as high as 48.0 μA cm(-2) mM(-1) in the presence of 0.15 M chlorides ions, and practical applications for blood sample analysis are also demonstrated. The proposed Pt-Pd structure is considered as a great potential building block for the fabrication of nonenzymatic electrochemical glucose sensors.