Non-enzymatic sensing of hydrogen peroxide using a glassy carbon electrode modified with a composite consisting of chitosan‐encapsulated graphite and platinum nanoparticles

We report on a non-enzymatic hydrogen peroxide (H₂O₂) sensor which makes use of a nanocomposite consisting of platinum nanoparticles (PtNPs) and chitosan-encapsulated graphite (graphite-CS). The composite was prepared by sonication of pristine graphite in chitosan (CS) in 5 % acetic acid. The PtNP decorated graphite-CS (graphite-CS/PtNPs) composite was prepared by electrodeposition of PtNPs on the graphite-CS modified glassy carbon electrode. The graphite-CS/PtNP composite was characterized by scanning electron microscopy, elemental analysis and FTIR spectroscopy. The modified electrode displays an enhanced reduction peak current for H₂O₂ when compared with electrodes modified with graphite/PtNPs and PtNPs. The modified electrode exhibits excellent electrocatalytic activity towards the reduction of H₂O₂, and the amperometric response is linear over the concentration range from 0.25 to 2890 μM. The sensitivity and the detection limit are 0.465 μA?μM￣¹ ? cm￣² and 66 nM, respectively. The sensor shows fast response (3 s) in detecting H₂O₂. It is also highly selective in the presence of potentially interfering compounds, and may therefore be used as a feasible platform for sensing H₂O₂ in real samples.

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Graphical abstract Preparation of graphite-CS/PtNP composite, and its application to electrochemical reduction of H₂O₂.

     

A Facile Synthesis of New 4,6‐Dichloropyridine Derivatives,Their Biological Evaluation for Antimicrobial and Antioxidant Activity,and Docking Studies

A facile synthesis of new 4,6‐dichloropyridine derivatives 5 ( a–f ), 6 ( a–c ), and 7 ( a–c ) were synthesized using both conventional heating and solvent‐free microwave irradiation techniques. The results revealed that the latter method is superior to the conventional heating method. The easy work‐up of the products, rapid reaction, and mild conditions are noticeable features of this protocol. Structural elucidation of the synthesized compounds was made on the basis of various spectroscopic methods. The synthesized compounds were evaluated for their in vitro antimicrobial activity (minimum inhibitory concentration; MIC) against various microbial strains using the agar well‐diffusion method. Among the compounds, 5c showed best antimicrobial activity against most of the employed strains, especially against Staphylococcus aureus, Escherichia coli, Rhizopus arrhizus, and Candida albicans. Compounds 5a , 6a , 6c , 7a , and 7c showed significant antioxidant activity when compared to the other compounds. In addition to this, theoretical docking studies were performed for the highly potent compounds 5a , 6a , 6c , 7a , and 7c against three different drug targets belonging to the oxidoreductase family, and the results were found to be highly satisfactory.     

TiO2 as a Photocatalyst for Water Splitting—An Experimental and Theoretical Review

Hydrogen produced from water using photocatalysts driven by sunlight is a sustainable way to overcome the intermittency issues of solar power and provide a green alternative to fossil fuels. TiO₂ has been used as a photocatalyst since the 1970s due to its low cost, earth abundance, and stability. There has been a wide range of research activities in order to enhance the use of TiO₂ as a photocatalyst using dopants, modifying the surface, or depositing noble metals. However, the issues such as wide bandgap, high electron-hole recombination time, and a large overpotential for the hydrogen evolution reaction (HER) persist as a challenge. Here, we review state-of-the-art experimental and theoretical research on TiO₂ based photocatalysts and identify challenges that have to be focused on to drive the field further. We conclude with a discussion of four challenges for TiO₂ photocatalysts—non-standardized presentation of results, bandgap in the ultraviolet (UV) region, lack of collaboration between experimental and theoretical work, and lack of large/small scale production facilities. We also highlight the importance of combining computational modeling with experimental work to make further advances in this exciting field.     

Catalyst-free Chemisorption-based Spectrophotometric Technique for Analysis of Toxic Acidic Vapors of Solid Propellant Exhaust

Journal of Analytical Chemistry - A simple, cost effective and room temperature compatible spectrophotometric technique is developed for the detection and quantification of hydrochloric acid gas...     

Growth and characterization of pure and metal doped bis(thiourea) zinc chloride single crystals

Metal (Cd²⁺ and Cu²⁺) substituted single crystals of Bis(thiourea) zinc chloride (BTZC) are grown by slow solvent evaporation technique, with the vision to improve the physicochemical properties of the sample. Single crystal XRD studies of both pure and doped samples are carried out and the results are compared. Optical absorption and FTIR studies are performed to identify the UV cut‐off range and the presence of various functional groups in the grown crystals. The thermogravimetric (TG) analysis of metal doped BTZC indicates a marginal increase in the thermal stability of the crystals. The dielectric response of the samples have been studied in the frequency range 100 Hz to 5 MHz at room temperature and the results are discussed. Photoconductivity studies carried out on pure and metal doped BTZC crystals revealed the negative photoconducting nature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thermal and sensitivity analysis of nano aluminium powder for firework application

The performance of the fireworks is governed by the sound level it produces. As per Govt. of India notification, crackers sound level should not exceed 125 dB (AI) or 145 dB(C) pk. In this study, nAl powder was synthesised at different particle sizes of 113, 187 and 218 nm as a fuel. These powders are well mixed with the oxidizer (KNO₃) and the igniter (S), and the cake bomb was manufactured with various compositions and checked for their performance. The thermal analysis was performed by DSC and DTA, and the impact sensitivity was analysed for all compositions. The nano-sized chemicals showed high thermal energy content and high sensitivity for various compositions. Further it is observed that the nAl chemical for producing the optimum sound level in the cake bomb has been reduced to 62.5% when compared with μm powder.     

Lanthanide(III) Complexes of Bis‐semicarbazone and Bis‐imine‐Substituted Phenanthroline Ligands: Solid‐State Structures,Photophysical Properties,and Anion Sensing

Phenanthroline‐based hexadentate ligands L¹ and L² bearing two achiral semicarbazone or two chiral imine moieties as well as the respective mononuclear complexes incorporating various lanthanide ions, such as La^III, Eu^III, Tb^III, Lu^III, and Y^III metal ions, were synthesized, and the crystal structures of [ML¹Cl₃] (M=La^III, Eu^III, Tb^III, Lu^III, or Y^III) complexes were determined. Solvent or water molecules act as coligands for the rare‐earth metals in addition to halide anions. The big Ln^III ion exhibits a coordination number (CN) of 10, whereas the corresponding Eu^III, Tb^III, Lu^III, and Y^III centers with smaller ionic radii show CN=9. Complexes of L², namely [ML²Cl₃] (M=Eu^III, Tb^III, Lu^III, or Y^III) ions could also be prepared. Only the complex of Eu^III showed red luminescence, whereas all the others were nonluminescent. The emission properties of the Eu derivative can be applied as a photophysical signal for sensing various anions. The addition of phosphate anions leads to a unique change in the luminescence behavior. As a case study, the quenching behavior of adenosine‐5′‐triphosphate (ATP) was investigated at physiological pH value in an aqueous solvent. A specificity of the sensor for ATP relative to adenosine‐5′‐diphosphate (ADP) and adenosine‐5′‐monophosphate (AMP) was found. ³¹P NMR spectroscopic studies revealed the formation of a [EuL²(ATP)] coordination species.     

A facile hydrothermal route to synthesize novel PbI2 nanorods

We report the synthesis of PbI₂ nanorods by reacting lead acetate with elemental iodine at room temperature by virtue of a wet chemical method at mild reactions. The diameters of the obtained PbI₂ nanorods are about 54 nm. The present technique may open a new doorway to one-dimensional nanosized rods from the same kind of materials with irregular shape or large size. X-ray powder diffraction (XRD), Fourier transform infrared analysis (FTIR), ultraviolet–visible–near infrared analysis (UV–vis–NIR), photoluminescence measurements (PL) and scanning electron microscopy (SEM) were used to characterize PbI₂ nanorods. The as obtained products were analyzed by X-ray powder diffraction, which confirms the formation of solid PbI₂ nanorods. From the UV–vis–NIR studies the band gap of PbI₂ nanorod was estimated. The various functional groups present in the PbI₂ nanorods were identified by FTIR analysis. Intense photoluminescence was also observed with some spectral tuning possibly giving a range of emission photon energies approximately spanning from 2.1 to 3.5 eV.     

Dopamine sensor based on a glassy carbon electrode modified with a reduced graphene oxide and palladium nanoparticles composite

We report on a sensitive electrochemical sensor for dopamine (DA) based on a glassy carbon electrode that was modified with a nanocomposite containing electrochemically reduced graphene oxide (RGO) and palladium nanoparticles (Pd-NPs). The composite was characterized by scanning electron microscopy, energy dispersive spectroscopy, and electrochemical impendence spectroscopy. The electrode can oxidize DA at lower potential (234 mV vs Ag/AgCl) than electrodes modified with RGO or Pd-NPs only. The response of the sensor to DA is linear in the 1–150 μM concentration range, and the detection limit is 0.233 μM. The sensor was applied to the determination of DA in commercial DA injection solutions.