Hydrothermal synthesis of Mn3O4 nanorods modified indium tin oxide electrode as an efficient nanocatalyst towards direct urea electrooxidation

Control fabrication of metal-oxide nanocatalysts for electrochemical reactions has received considerable research attention. Here, manganese oxide (Mn₃O₄) nanorods modified indium tin oxide (ITO) electrodes were prepared based on the in-situ one-step hydrothermal methods. The nanorods were well characterized using field emission scanning electron microscopy, Fourier transform infrared, and X-ray diffraction spectroscopy. The results showed the formation of pure crystalline Mn₃O₄ nanorods with a length of approximately 1.4 μm and a thickness of approximately 100 ± 30 nm. The Mn₃O₄ nanorod-modified ITO electrodes were used for accelerating urea electrochemical oxidation at room temperature using cyclic and square wave voltammetry techniques. The results indicated that the modified electrode demonstrated excellent electrocatalytic performance toward urea electrooxidation in an alkaline medium over concentrations ranging from 0.2 to 4 mol/L. The modified electrode showed high durability, attaining more than 88% of its baseline performance after 150 cycles; furthermore, the chronoamperometry technique demonstrated high stability. Thus, the Mn₃O₄ nanorod-modified ITO electrode is a promising anode for direct urea fuel cell applications.

Synthesis of gold nanoparticles@reduced porous graphene-modified ITO electrode for spectroelectrochemical detection of SARS-CoV-2 spike protein

Here, we reported the synthesis of reduced porous graphene oxide (rPGO) decorated with gold nanoparticles (Au NPs) to modify the ITO electrode. Then we used this highly uniform Au NPs@rPGO modified ITO electrode as a surface-enhanced Raman spectroscopy-active surface and a working electrode. The uses of the Au nanoparticles and porous graphene enhance the Raman signals and the electrochemical conductivity. COVID-19 protein-based biosensor was developed based on immobilization of anti-COVID-19 antibodies onto the modified electrode and its uses as a probe for capturing the COVID-19 protein. The developed biosensor showed the capability of monitoring the COVID-19 protein within a concentration range from 100 nmol/L to 1 pmol/L with a limit of detection (LOD) of 75 fmol/L. Furthermore, COVID-19 protein was detected based on electrochemical techniques within a concentration range from 100 nmol/L to 500 fmol/L that showed a LOD of 39.5 fmol/L. Finally, three concentrations of COVID-19 protein spiked in human serum were investigated. Thus, the present sensor showed high efficiency towards the detection of COVID-19.

A simple HPLC method containing greener modifier and slighter temperature elevated for simultaneous determination of three statin drugs in tablets

Statins drugs are thought to be among the most prescribed drugs worldwide for the treatment of hypercholesterolaemia. A simple and reliable RP-HPLC method has been successfully employed for simultaneously separating and qualifying three statin drugs including atorvastatin, rosuvastatin and simvastatin in pharmaceutical tablets. The optimal conditions were mobile phase 50:50 (v/v) (formic acid pH 2.50: ETOH), column temperature 40.00 °C, detection wavelength 238.00 nm, and flow rate 1.00 mL/min. The proposed method has been validated based on the ICH guidelines in terms of linearity, precision, accuracy, and limit of detection and limit of quantification. The linear range investigated 2.0–80.0, 4.0–100.00, and 12.00–120.00 µg/mL for rosuvastatin, atorvastatin and simvastatin respectively with coefficients of determination (R2) within the range of 0.9993–0.9995. The LOD and LOQ for rosuvastatin, atorvastatin and simvastatin were (1.57, 4.76 µg/mL), (1.87, 5.66 µg/mL), (3.46, 10.49 µg/mL) respectively. In addition, in order to evaluate the feasibility of the method developed, it was employed towards the quantification of the pharmaceutical tablets for the analytes investigated and excellent recovery was obtained.

Electrochemical Microbiosensor for Detecting COVID-19 in a Patient Sample Based on Gold Microcuboids Pattern

As continues increasing the COVID-19 infections, there is an urgent need for developing fast, simple, selective, and accurate COVID-19 biosensors. A highly uniform gold (Au) microcuboid pattern was used as a microelectrode that allowed monitoring a small analyte. The electrochemical biosensor was used to monitor the COVID-19 S protein within a concentration range from 100 to 5 pmol L⁻¹; it showed a lower detection limit of 276 fmol L⁻¹. Finally, the developed COVID-19 sensor was used to detect a positive sample from a human patient obtained through a nasal swab; the results were confirmed using the PCR technique. The results showed that the SWV technique showed high sensitivity towards detecting COVID-19 and good efficiency for detecting COVID-19 in a positive human sample.

A 2D Graphitic-Polytriaminopyrimidine (g-PTAP)/Poly(ether-block-amide) Mixed Matrix Membrane for CO2 Separation

Poly(ether-block-amide)/g-PTAP mixed matrix membranes (MMMs) were developed by incorporating different wt.% (1-10%) of a novel 2D g-PTAP nanofiller and its effects on membrane structure and gas permeability were studied. The novel 2D material g-PTAP was synthesized and characterized by various analytical techniques including field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Raman spectroscopy. The fabricated MMMs were investigated to study the interaction and compatibility between Pebax and g-PTAP. The MMMs showed an effective integration of g-PTAP nanofiller into the Pebax matrix without affecting its thermal stability. Gas permeation experiments with MMMs showed improved CO₂ permeability and selectivity (CO₂ /N₂ ) upon incorporation of g-PTAP in the Pebax polymer matrix. The maximum CO₂ permeability enhancement from 82.3 to 154.6 Barrer with highest CO₂ /N₂ selectivity from 49.5 to 83.5 were found with 2.5 wt.% of nanofiller compared to neat Pebax membranes.

Layer-by-Layer Motif Heteroarchitecturing of N,S-Codoped Reduced Graphene Oxide-Wrapped Ni/NiS Nanoparticles for the Electrochemical Oxidation of Water

A new heterostructured material is synthesized with lamellar arrangements in nanoscale precision through an innovative synthetic approach. The self-assembled Ni-based cyano-bridged coordination polymer flakes (Ni-CP) and graphene oxide (GO) nanosheets with a layered morphology (Ni-CP/GO) are used as precursors for the synthesis of multicomponent hybrid materials. Annealing of Ni-CP/GO in nitrogen at 450 °C allows the formation of Ni₃ C/rGO nanocomposites. Grinding Ni-CP/GO and thiourea and annealing under the same conditions produces N,S-codoped reduced GO-wrapped NiS₂ flakes (NiS₂ /NS-rGO). Interestingly, further heating up to 550 °C allows the phase transformation of NiS₂ into NiS accompanied by the formation of a face-centered cubic (FCC-Ni) metal phase between NS-rGO layers (FCC-Ni-NiS/NS-rGO). Among all the materials, the resulting FCC-Ni-NiS/NS-rGO exhibits good electrocatalytic activity and stability toward the oxygen evolution reaction (OER) owing to the synergistic effect of multiphases, the well-designed alternating layered structures on the nanoscale with abundant active sites.

Cyclodextrin-Modified Micellar UPLC for Direct, Sensitive and Selective Determination of Water Soluble Vitamins in Milk

Cyclodextrin-modified micellar ultra pressure liquid chromatography (CD-MUPLC) was firstly developed and directly applied to the simultaneous determination of water-soluble vitamins thiamine hydrochloride (VB1), pyridoxine hydrochloride (VB6) and ascorbic acid (VC) in milk samples. A hybrid isocratic mobile phase consisting of β-cyclodextrin (β-CD, 5.0 mmol L-1) and cetyltrimethylammonium bromide (CTAB, 0.1 mol L-1) in the presence of acetic acid (0.1 mol L-1) at pH 2.9 on a RP-C18 column at 25.0°C was successfully used. The separation of vitamins was achieved in less than 10 min at a 0.2 mL min-1 flow rate showing adequate linearity at 245 nm in the ranges of 5.0-500.0 μg L-1 for VB1, 5.0-1000.0 μg L-1 for VB6 and 5.0-10000.0 μg L-1 for VC with coefficients of variation (r2) of 0.9999, 0.9987 and 0.9971, respectively. In addition, limits of detection obtained were 0.885, 1.352 and 1.358 μg L-1 and limits of quantification were 2.681, 4.096 and 4.115 μg L-1 for VB1, VB6 and VC, respectively. The high sensitivity of the proposed CD-MUPLC-UV method permitted its applications to the determination of water-soluble vitamins VB1 (32-488 μg L-1), VB6 (82-95 μg L-1) and VC (790-45000 μg L-1) in breast and bovine milk samples. The relative standard deviations and recoveries ranged between 0.07 and 2.14% and between 85.27 and 114.8%, respectively, indicating the accurate and precise measurements without any negative impact of matrix. The current analytical method illustrated several advantages including direct, sensitive, selective and non-consuming organic solvents over the hitherto published methods. These features could be attributed to the four-point competitive interactions among analytes, pseudostationary phases and modified C18 stationary phases.

Controlled fabrication of gold nanobipyramids/polypyrrole for shell-isolated nanoparticle-enhanced Raman spectroscopy to detect γ-aminobutyric acid

Shell-isolated nanoparticle-enhanced Raman Spectroscopy (SHINERS) has been a non-destructive, highly sensitive, specific and powerful sensing method. Detection of γ-aminobutyric acid (GABA) and glutamate, main neurotransmitters in the human brain, is important to diagnosis the neurological disorder. The purpose of this study is preparing a simple, rapid and inexpensive fabrication of Au nanobipyramids/polymer core/shell as a SHINERS-based biosensor to detect different neurotransmitters such as GABA and glutamate with high sensitivity and specificity. Au nanobipyramids/polymer core/shell was fabricated by using two steps process. In the first Au nanobipyramids with longitude and latitude axial of about 100 nm and 10 nm, respectively, was prepared based on the chemical reduction of Au ions by using sodium borohydride as a reducing agent. Then a thin layer of polypyrrole was used for decorating the Au nanobipyramids by using direct polymerization in the presence of Au nanobipyramids. The sensor composed Au nanobipyramids with a thin layer of polypyrrole that could measure GABA within a wide range of concentrations in the presence of human serum. And this sensor was used for direct monitoring of GABA and glutamate. The proposed biosensor can be applied to monitor the level of neurotransmitters accurately for the diagnosis of various neurological disorders with optical signal enhancement.

Response surface methodological optimization of batch Cu(II) sorption onto succinic acid functionalized SiO2 nanoparticles

Functionalizing nanosilica (n-SiO2) particles with suitable active organic moiety leads to the formation of surfaces with precisely controlled physical and chemical characteristics. In this work, a novel nanosorbent (31 ± 2.4 nm), namely succinic acid functionalized nanosilica (n-SiO2@SA), was synthesized via a simple protocol using microwave irradiation to remove Cu(II) ions from aqueous media. The successful functionalization of n-SiO2 was confirmed by FTIR, and the thermal stability of n-SiO2@SA was investigated by TGA study. Other techniques, including HRTEM, DLS and zeta-potential, were utilized to investigate the chemical, surface, and morphological properties of the fabricated n-SiO2@SA. The response surface methodology (RSM) combined with three-level, three-factorial Box–Behnken design (BBD) was applied to optimize the multivariable sorption system using data obtained from 17 batch runs to reach 98.9% of Cu(II) ion removal. The predicted optimal conditions were as follows: contact time = 30 min, pH = 7.1, initial Cu(II) concentration = 317.5 mg L−1, and sorbent dose = 15 mg at which the maximum sorption capacities for n-SiO2 and n-SiO2@SA were 209.3 and 386.4 mg g−1, respectively, at 25 °C, thus supporting the validity of functionalization process. Non-linear regression and linear least-squares methods confirm the suitability of Langmuir model to describe the experimental endothermic, feasible, and chemisorption data, whereas the normalized standard deviation Δq% recommends the pseudo second-order kinetic model to represent the kinetic data. Real Cu-contaminated wastewaters were used to examine n-SiO2@SA nanosorbent for removing Cu(II) ions.