Microelectrode glucose biosensor based on nanoporous platinum/graphene oxide nanostructure for rapid glucose detection of tomato and cucumber fruits

Microelectrode glucose biosensor based on three-dimensional hybrid nanoporous platinum/graphene oxide nanostructure was developed for rapid glucose detection of tomato and cucumber fruits. The nanostructure was fabricated by a two-step modification method on microelectrode for loading a larger amount of glucose oxidase. The nanoporous structure was prepared on the surface of the platinum microelectrode by electrochemical etching, and then graphene oxide was deposited on the prepared nanoporous electrode by electrochemical deposition. The nanoprorous platinum/graphene oxide nanostructure had the advantage of improving the effective surface area of the electrode and the loading quantity of glucose oxidase. As a result, the biosensor achieved a wide range of 0.1-20.0 mM in glucose detection, which had the ability to accurately detect the glucose content. It was found that the three-dimensional hybrid nanostructure on the electrode surface realized the rapid direct electrochemistry of glucose oxidase. Therefore, the biosensor achieved high glucose detection sensitivity (11.64 μA mM -1cm -2), low detection limit (13 μM) and rapid response time (reaching 95% steady-state response within 3 seconds), when calibrating in glucose standard solution. In agricultural application, the as-prepared biosensor was employed to detect the glucose concentration of tomato and cucumber samples. The results showed that the relative deviation of this method was less than 5% when compared with that of HPLC, implying high accuracy of the presented biosensor in glucose detection in plants.

Influence of the Structural-Phase State of a Copper Substrate upon Modification with Titanium Ions on the Thermal Cyclic Resistance of a Coating Based on Zr-Y-O

The results of investigation of the surface of a copper substrate modified with titanium ions are presented. The phase composition, the structure, and the morphology of the surface of the copper alloy modified by titanium ions have been investigated by X-ray, SEM, and TEM. It has been established that there are the intermetallic phases of the Cu-Ti equilibrium diagram in the surface layer during the treatment of copper by the titanium ions. A multilevel micro- and nanoporous structure is formed in the modified layer. It has been established that the structure-phase state and morphology of the surface layers of copper directly effects on the thermocycler resistance and adhesion of the Zr-Y-O coating. The thermocyclic resistance of the Zr-Y-O coating increases by an order of magnitude, the adhesion to the substrate is 2 times if the substrate surface is treated with titanium ions for 6 min.

Study of the influence of various solvents on the properties of hydrophobic silica xerogels

Silica aerogels are low-density inorganic aerogels with a three-dimensional nanoporous structure. Due to the inherent properties of nanoporous materials, the possibility of using silica airgel is of great interest in various fields. To simplify the process and reduce costs, the use of atmospheric pressure drying (APD) is promising, the resulting materials are called xerogels. Silica xerogels based on methyltrimethoxysilane were synthesized using various alcohol solvents. The optimal combination of properties is possessed by a sample obtained using methanol as a solvent. The wetting angle of all xerogels was 158°, which characterizes the resulting material as superhydrophobic.

Rapid and tunable growth of well-ordered hexagonal nanoporous anodic aluminum oxide (AAO) structure by two step high temperature anodization

In this study, we have developed a swift and well-ordered growth of the Anodic Aluminum Oxide (AAO) nanoporous structure by two-step high temperature anodization of pure Aluminum substrate. The pre-anodization surface treatment of the aluminum substrate assists in the formation of well-organized nanoporous structures. The two-step anodization process was performed in 0.3 M of oxalic acid at 20 °C for 40 V and 45 V to obtain tunable pore diameters. The high temperature of the electrolyte solution helps in the rapid growth of the AAO nanoporous structure. The top surface image of AAO shows a well-ordered nanoporous structure with an average pore diameter of 70 nm at 40 V and 100 nm at 45 V. The SEM cross sectional view also illustrates the well-ordered nano channel and the elemental mapping elaborates the presence of aluminum and oxygen. The thickness of the AAO nanoporous structure was determined by using SEM for three anodization time spans (20, 24 and 28 hours), in which an increasing trend was observed. The fabricated AAO has a higher thickness and a well-ordered nanoporous structure that shows it can be used as a template for fabricating nanostructured materials.

ITO/Poly-3-Methylaniline/Au Electrode for Electrochemical Water Splitting and Dye Removal

Application of aniline derivative semiconductor nanopolymer and its Au composite for H2 generation and dye removal were investigated. Electrochemical polymerization of poly-3-methylaniline (P3MA) on ITO glass was carried out for acid medium. Au nanoparticles with crystal sizes of 15 and 30 nm were sputter coated on the surface. Chemical structure of the polymer and its composite was characterized using FTIR, XRD, 1HNMR, SEM, and UV-Vis. All function groups were confirmed using FTIR analyses. XRD confirmed the formation of nanopolymer with a crystal size of ~15 nm. SEM confirmed the formation of smooth lamellar surface feature with a <20 nm nanoporous structure. Porosity and particle sizes increases with Au coating, confirmed using the modeling Image J program. Optical analysis also demonstrated that the strength of P3MA absorption peaks increases with rising Au coating time, in which the bandgap values changed from 1.64 to 1.63 eV for 15 and 30 nm Au, respectively. The photoelectrode ITO/PMT/30 nm Au was applied for H2 generation and dye removal. The current density (Jph) values were -0.3 and -1.6 mA.cm-2 in the absence and presence of the Congo red dye, respectively. The incident photon-to-current conversion efficiency (IPCE%) for the electrode was 2.3 at 390 nm. The activation energy (Ea) was 31.49 KJ mol-1. The enthalpy (∆H*) and entropy (∆S*) values were 114.49 and 160.46 JK-1 mol-1, respectively. A simple mechanism for the H2 generation and dye removal is mentioned

Effect of Dealloying Time and Post-Annealing on the Surface Morphology and Electrocatalytic Behavior of Nanoporous Copper Films for CO2 Reduction Reaction

Electrocatalytic reduction reaction of CO2 (CO2RR) is one of the promising routes to mitigate global warming via transforming greenhouse gas into valuable chemical feedstocks. By adding proper electrocatalysts, such as nanoporous copper (NPC) with an average ligament size of 37 ± 6 nm, hydrocarbons could be produced at a relatively low overpotential. As the dealloying time increased to 156 hrs, the NPC was transformed into CuO nanosheet structure, which yielded larger electrochemical surface area (ECSA) and current density than the as-prepared NPC films. However, the Faraday efficiency (FE) of the major conversion product, formic acid (HCOOH), decreased from 29 to 8% when the nanosheet structure was used as electrocatalyst. On the other hand, the surface morphology of the NPC films remained similar while the average ligament size increased from 37 to 63 nm after a post-annealing treatment at 500 °C for 4 hrs. Both the current density and ECSA of this post-annealed NPC film were nearly 3 times higher than those of as-prepared NPC film, and the FE toward HCOOH increased from 29 to 45%. X-ray photoelectron spectroscopy and Raman spectroscopy revealed that Cu2O were present on the nanoporous structure, which enhanced the selectivity and FE toward HCOOH in CO2RR.

Effects of Siliceous Natural Nanomaterials Applied in Combination with Foliar Fertilizers on Physiology, Yield and Fruit Quality of the Apricot and Peach Trees

Siliceous natural nanomaterials (SNNMs), i.e., diatomaceous earth and natural zeolites, have a nanoporous structure with large active surfaces that adsorb cations or polarized molecules. Such nanoporous feature determines the effects related to SNNM utilization as low-risk plant protectants and soil improvers. This work used SNNMs from Romanian quarries as carriers for foliar fertilizers applied to stone-fruit trees, apricot and peach. We determined the effects of SNNMs on the physiology, yield and fruit quality of the treated stone-fruit trees. SNNM application determined impacts specific to the formation of particle films on leaves: reduced leaf temperature (up to 4.5 °C) and enhanced water use efficiency (up to 30%). Foliar fertilizers’ effects on yield are amplified by their application with SNNMs. Yield is increased up to 8.1% by the utilization of SNNMs with foliar fertilizers, compared to applying foliar fertilizer alone. Diatomaceous earth and natural zeolites promote the accumulation of polyphenols in apricot and peach fruits. The combined application of SNNMs and foliar fertilizer enhance the performance of peach and apricot trees.

A Novel N-Doped Nanoporous Bio-Graphene Synthesized from Pistacia lentiscus Gum and Its Nanocomposite with WO3 Nanoparticles: Visible-Light-Driven Photocatalytic Activity

This paper reports the synthesis of a new nitrogen-doped porous bio-graphene (NPBG) with a specific biomorphic structure, using Pistacia lentiscus as a natural carbon source containing nitrogen that also acts as a bio-template. The obtained NPBG demonstrated the unique feature of doped nitrogen with a 3D nanoporous structure. Next, a WO3/N-doped porous bio-graphene nanocomposite (WO3/NPBG-NC) was synthesized, and the products were characterized using XPS, SEM, TEM, FT-IR, EDX, XRD, and Raman analyses. The presence of nitrogen doped in the structure of the bio-graphene (BG) was confirmed to be pyridinic-N and pyrrolic-N with N1 peaks at 398.3 eV and 400.5 eV, respectively. The photocatalytic degradation of the anionic azo dyes and drugs was investigated, and the results indicated that the obtained NPBG with a high surface area (151.98 m2/g), unique electronic properties, and modified surface improved the adsorption and photocatalytic properties in combination with WO3 nanoparticles (WO3-NPs) as an effective visible-light-driven photocatalyst. The synthesized WO3/NPBG-NC with a surface area of 226.92 m2/g displayed lower bandgap and higher electron transfer compared with blank WO3-NPs, leading to an increase in the photocatalytic performance through the enhancement of the separation of charge and a reduction in the recombination rate. At the optimum conditions of 0.015 g of the nanocomposite, a contact time of 15 min, and 100 mg/L of dyes, the removal percentages were 100%, 99.8%, and 98% for methyl red (MR), Congo red (CR), and methyl orange (MO), respectively. In the case of the drugs, 99% and 87% of tetracycline and acetaminophen, respectively, at a concentration of 10 mg/L, were removed after 20 min.