Measurement of 222Rn and 220Rn decay product deposition velocities using SSNTD based passive detectors

In the present study, the deposition velocities of ²²²Rn/²²⁰Rn decay products were measured experimentally using SSNTD based passive detectors, direct radon progeny sensor (DRPS) and direct thoron progeny sensor (DTPS) and the results were compared with obtained values by Monte-Carlo simulations. In both cases, deposition velocities were found to be log-normally distributed and also the experimentally measured geometric mean (GM) and geometric standard deviation (GSD) of (0.12, 1.85) m h^?1 for radon decay products and (0.07, 1.75) m h^?1 for thoron decay products were found to be in good agreement with the simulated values.     

Prebiotically Plausible Autocatalytic Peptide Amyloids

The prebiotic emergence of molecules capable both of self-replication and of storing information was a defining event at the dawn of life. Still, no plausible prebiotic self-replication of biologically relevant molecules has been demonstrated. Building upon the known templating nature of amyloids, we present two systems in which the products of a peptide-bond-forming reaction act as self-replicators to enhance the yield and stereoselectivity of their formation. This first report of an amino acid condensation that can undergo autocatalysis further supports the potential role of amyloids in prebiotic molecular evolution as an environment-responsive and information-coding system capable of self-replication.     

Electrochemical biosensors based on Ti3C2Tx MXene: future perspectives for on-site analysis

MXenes are recently developed two-dimensional layered materials composed of early transition metal carbides and/or nitrides that provide unique characteristics for biosensor applications. This review presents the recent progress made on the usage and applications of MXenes in the field of electrochemical biosensors, including microfluidic biosensors and wearable microfluidic biosensors, and highlights the challenges with possible solutions and future needs. The multilayered configuration and high conductivity make these materials as an immobilization matrix for the biomolecule immobilization with activity retention and to be explored in the fabrication of electrochemical sensors, respectively. First, how the MXene nanocomposite as an electrode modifier affects the sensing performance of the electrochemical biosensors based on enzymes, aptamer/DNA, and immunoassays is well described. Second, recent developments in MXene nanocomposites as wearable biosensing platforms for the biomolecule detection are highlighted. This review pointed out the future concerns and directions for the use of MXene nanocomposites to fabricate advanced electrochemical biosensors with high sensitivity and selectivity. Specifically, possibilities for developing microfluidic electrochemical sensors and wearable electrochemical microfluidic sensors with integrated biomolecule detection are emphasized.     

Synthesis,structure and antibacterial activity of manganese(III) complexes of a Schiff base derived from furfurylamine

Two new mononuclear complexes of manganese(III) viz. [MnL₂(LH)₂]ClO₄ (1) and [MnL₂(N₃)]·0.5CH₃OH (2) have been synthesized by reacting manganese perchlorate with furfurylamine and salicylaldehyde (plus sodium azide in 2) where L = (2-hydroxybenzyl-2-furylmethyl)imine, an asymmetric bidentate Schiff base formed in situ to bind the Mn(III) ion. The complexes have been characterized by elemental analysis, IR spectroscopy, TGA and single crystal X-ray diffraction studies. Structural studies reveal that the complexes 1 and 2 adopt an octahedral and a square pyramidal geometry, respectively. The antibacterial activity of the complexes has been tested against Gram(+) and Gram(?) bacteria.     

Growth of carbon nanotubes from waste blast furnace gases at atmospheric pressure

Carbon emissions from industrial sources are of major global concern, especially contributions from the steel manufacturing process which accounts for the majority of emissions. Typical blast furnace gases consist of CO₂ (20‐25%), CO (20‐25%), H₂ (3‐5%) and N₂ (40‐50%) and trace amounts of other gases. It is demonstrated that gas mixtures with these compositions can be used at atmospheric pressure to grow carbon nanotubes (CNTs) by chemical vapor deposition (CVD) on to steel substrates, which act as catalysts for CNT growth. Computational modelling was used to investigate the CNT growth conditions inside the CVD chamber. The results show that industrial waste pollutant gases can be used to manufacture materials with significant commercial value, in this case CNTs.     

Optical and dielectric properties of isothermally crystallized nano-KNbO3 in Er3+-doped K2O–Nb2O5–SiO2 glasses

Precursor glass of composition 25K₂O–25Nb₂O₅–50SiO₂ (mol%) doped with Er₂O₃ (0.5 wt% in excess) was isothermally crystallized at 800 °C for 0–100 h to obtain transparent KNbO₃ nanostructured glass–ceramics. XRD, FESEM, TEM, FTIRRS, dielectric constant, refractive index, absorption and fluorescence measurements were carried out to analyze the morphology, dielectric, structure and optical properties of the glass–ceramics. The crystallite size of KNbO₃ estimated from XRD and TEM is found to vary in the range 7–23 nm. A steep rise in the dielectric constant of glass–ceramics with heat-treatment time reveals the formation of ferroelectric nanocrystalline KNbO₃ phase. The measured visible photoluminescence spectra have exhibited green emission transitions of ²H_11/2, ⁴S_3/2 → ⁴I_15/2 upon excitation at 377 nm (⁴I_15/2 → ⁴G_11/2) absorption band of Er³⁺ ions. The near infrared (NIR) emission transition ⁴I_13/2 → ⁴I_15/2 is detected around 1550 nm on excitation at 980 nm (⁴I_15/2 → ⁴I_11/2) of absorption bands of Er³⁺ ions. It is observed that photoluminescent intensity at 526 nm (²H_11/2 → ⁴I_15/2), 550 nm (⁴S_3/2 → ⁴I_15/2) and 1550 nm (⁴I_13/2 → ⁴I_15/2) initially decrease and then gradually increase with increase in heat-treatment time. The measured lifetime (τ_f) of the ⁴I_13/2 → ⁴I_15/2 transition also possesses a similar trend. The measured absorption and fluorescence spectra reveal that the Er³⁺ ions gradually enter into the KNbO₃ nanocrystals.     

Rietveld refinement, microstructure, conductivity and impedance properties of Ba[Zr0.25Ti0.75]O3 ceramic

In this work, we report the Rietveld refinement, microstructure, conductivity and impedance properties of Ba[Zr_0.25Ti_0.75]O₃ ceramic synthesized by solid state reaction. This ceramic was characterized by X-ray diffraction, Rietveld refinement, scanning electron microscopy and energy dispersive X-ray spectrometry. Impedance spectroscopy analyses reveals a non-Debye relaxation phenomenon being its relaxation frequency moving toward to positive side with increase of temperature. A significant shift in impedance loss peaks toward higher frequency side indicates conduction in material and favoring the long range motion of mobile charge carriers. The frequency dependent ac conductivity at different temperatures indicates that the conduction process is thermally activated. The variation of dc conductivity exhibited a negative temperature coefficient of resistance behavior. The ac conductivity data are used to evaluate the density of states at Fermi level and activation energy of this ceramic. The dc electrical and thermal conductivities of grain and grain boundary have been discussed.     

Cu(II) catalyzed imine C-H functionalization leading to synthesis of 2,5-substituted 1,3,4-oxadiazoles

A direct access to symmetrical and unsymmetrical 2,5-disubstituted [1,3,4]-oxadiazoles has been accomplished through an imine C-H functionalization of N-arylidenearoylhydrazide using a catalytic quantity of Cu(OTf)(2). This is the first example of amidic oxygen functioning as a nucleophile in a Cu-catalyzed oxidative coupling of an imine C-H bond. These reactions can be performed in air atmosphere and moisture making it exceptionally practical for application in organic synthesis.     

Optical Analysis of Er3+:Boro-Fluoro-Phosphate Glasses

This paper deals with the preparation and optical analysis of Er³⁺ (0.2 mol%) boro-fluoro-phosphate glasses in the following glass compositions:

• Series A: 69.8 B₂O₃–10 P₂O₅–10(ZnO/CdO/TeO₂)–10 AlF₃

• Series B: 69.8 B₂O₃–10 P₂O₅–10(ZnO/CdO/TeO₂)–10 LiF

Measured Vis-NIR absorption spectra of Er³⁺:boro-fluoro-phosphate glasses have revealed nine absorption bands at 377 nm, 405 nm, 450 nm, 486 nm, 519 nm, 543 nm, 649 nm, 973 nm and 1529 nm, which correspond with the transitions of ⁴I_15/2 → ⁴G_11/2, (²G_9/2,⁴H_9/2), ⁴F_5/2, ⁴F_7/2, ²H_11/2, ⁴S_3/2, ⁴F_9/2, ⁴I_11/2, and ⁴I_13/2, respectively. With an excitation at λ _exci = 375 nm, a bright green emission (⁴S_3/2 → ⁴I_15/2) at 547 nm has been observed from these erbium glasses. Judd–Ofelt characteristic intensity Ω_λ (λ = 2, 4, 6) parameters are obtained from the absorption spectra, and these results were used to compute the radiative properties of Er³⁺:boro-fluoro-phosphate glasses. The NIR emission (⁴I_13/2 → ⁴I_15/2) at 1547 nm from these glasses was measured with an Ar⁺ laser (514.5 nm) as an excitation source.