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The proposed heat treatment of tool steels by quenching with intermediate tempering improves the durability of a high-precision die by a factor of 1.5–2 relative to standard heat treatment. [ABSTRACT FROM AUTHOR]

In this study, 3,4-diaminobenzoic acid (DABA) was introduced into the porphyrin metal–organic framework (PCN-224) for the first time to prepare a ratiometric fluorescent probe (PCN-224-DABA) to quantitatively detect ferric iron (Fe(III)) and selenium (IV) (Se(IV)). The fluorescence attributed to the DABA of PCN-224-DABA at 345 nm can be selectively quenched by Fe(III) and Se(IV), but the fluorescence emission peak attributed to tetrakis (4-carboxyphenyl) porphyrin (TCPP) at 475 nm will not be disturbed. Therefore, the ratio of I345nm/I475nm with an excitation wavelength of 270 nm can be designed to determine Fe(III) and Se(IV). After the experimental parameters were systematically optimized, the developed method shows good selectivity and interference resistance for Fe(III) and Se(IV) detection, and has good linearity in the ranges of 0.01–4 μM and 0.01–15 μM for Fe(III) and Se(IV) with a limit of detection of 0.045 μM and 0.804 μM, respectively. Furthermore, the quenching pattern was investigated through the Stern–Volmer equation, and the results suggest that both Se(IV) and Fe(III) quenched on PCN-224-DABA can be attributed to the dynamic quenching. Finally, the constructed ratiometric fluorescent probe was applied in the spiked detection of lake water samples, which shows good applicability in real sample analysis. Moreover, the Fe(III) and Se(IV) contents in spinach and selenium-enriched rice were determined, respectively.

Background: Distortion arises during machining of metallic parts from two main mechanisms: 1) release of bulk residual stress (BRS) in the pre-form, and 2) permanent deformation induced by cut tools. Interaction between these mechanisms is unexplored. Objective: Assess this interaction using aluminum samples that have a flat surface with variations of BRS, where that surface is subsequently milled, and we observe milling-induced residual stress (MIRS) and distortion. Methods: Plate samples are cut from two kinds of large blocks, one kind stress-relieved by stretching and a second kind solution heat treated, quenched and aged. The BRS field in the plates is known from a recent series of measurements, being small in the stress relieved plates (within ±20 MPa) and large (±100 MPa) in the quenched plates, varying from tension to compression over the surface that is milled. MIRS is measured following milling using hole-drilling. Distortions of thin wafers cut at the milled surfaces are used to elucidate BRS/MIRS interactions. A finite element (FE) model and a strength of materials model are each used to assess consistency between wafer distortion and measured MIRS. Results: Milling in samples with high BRS magnitude changes the directions of MIRS and distortion relative to the milling direction, with the direction of maximum curvature rotating toward or away from the milling direction depending on the sign and direction of BRS. High magnitude BRS was also found to increase the wafer peak arc height, nearly doubling the amount found in low BRS samples. Conclusion: Measured residual stress and observed wafer distortion both show interactions between MIRS and BRS. Stress analysis models show that the differences in measured MIRS are consistent with the differences in observed distortion.

The objective of this paper is to validate a measurement-driven, model-based approach to estimate residual stress (RS) in samples machined from quenched aluminum stock. Model input is derived from measurement of RS in the parent stock. Validation is performed for prismatic T-sections removed from bars at different locations. We find RS predicted agrees with RS measured, by contour and neutron diffraction methods, with root-mean-square model-measurement difference of 22 MPa. Follow-on work (in Part 2) applies the RS estimation to samples representative of aircraft structures and examines the effects of RS on fatigue crack growth in the RS-bearing samples.

This paper assesses the accuracy of fatigue crack growth (FCG) predictions for high-strength aluminum samples containing residual stress (RS) and complex two-dimensional cracks subjected to constant amplitude load. FCG predictions use linear-elastic, multi-point fracture mechanics. A first prediction includes RS estimated by the model described in Part 1; a second prediction includes RS measured by the contour method. FCG test data show a significant influence of RS. Ignoring the RS results in a +60% error in predicted FCG life (non-conservative). Including RS improves predictions of crack growth significantly (errors better than +26% (estimated RS) and −14% (measured RS)).

The emission of highly polarized light by organic light‐emitting diodes (OLEDs) is crucial for various applications; however, achieving such emission requires the use of polarizers, which reduce the device efficiency and durability. In this study, ultrahigh‐polarized light with a polarization ratio (PR) of 407:1 is achieved via the rapid thermal quenching (RTQ) of OLEDs. Poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) films, molybdenum disulfide (MoS2) nanosheets, and tungsten disulfide (WS2) nanosheets are applied as hole transport layers and surface‐alignment layers through surface treatment, including rubbing and/or ion‐beam exposure to align the molecules of the emissive materials, namely, {poly(9,9‐dioctylfluorene‐alt‐benzothiadiazole) (F8BT). Quenching is performed at 240 °C, at which F8BT has a nematic liquid crystal (NLC) phase with high molecular ordering. Upon quenching, the high molecular ordering of the NLC‐phased emissive layer instantaneously froze via RTQ, leading to the emission of highly polarized light. Consequently, the PEDOT:PSS‐, MoS2‐, and WS2‐based OLEDs exhibit ultrahigh PRs of 407:1, 349:1, and 328:1, respectively, for photoluminescence at a 540 nm peak wavelength. In contrast, for electroluminescence, the PEDOT:PSS‐based OLED exhibits a high PR of 395:1. This result is the best reported to date and is comparable to the PRs generated by polarizers, indicating that quenching can be utilized for the development of ultrahigh‐polarized light‐emitting devices. [ABSTRACT FROM AUTHOR]

Borophene is a relatively unexplored two-dimensional (2D) layered material known for its high carrier mobility and robustness. Being the lightest 2D layered material, borophene quantum dots (BQDs) with small lateral dimensions have triggered a surge of interest in the material research community due to their distinct electronic and optical properties. In this work, we have carried out a contamination-free liquid-phase exfoliation of crystalline boron chunks to synthesize ultrasmall crystalline BQDs of sizes ∼4.1 and ∼9.2 nm. The BQDs are few-layered in nature, as confirmed by atomic force microscopy. The as-synthesized BQDs exhibit extraordinary visible photoluminescence (PL) with a high PL quantum yield (∼40%), and the emission wavelength is independent of the excitation wavelength, unlike many other 2D quantum dots. The PL spectrum could be deconvoluted with four peaks, which are marginally size-dependent. The selective coordination of different metal ions (Fe3+, Cu2+, Ag+, Zn2+, K+, Pb2+, Mg2+, Na+, Ni2+, Hg2+, Mn2+, Ce4+, and Fe2+) with the BQDs has been studied systematically through PL and density functional theory (DFT) analyses. Interestingly, the BQDs show a high PL quenching ratio (>90%) and ultralow limit of detection (∼5 nM) through PL in the presence of Fe3+ ions. The proposed sensor is successfully implemented, for the first time, for the sensitive detection of Fe3+ ions at the nanomolar level, and the sensing mechanism, including selectivity, is explored in detail using DFT calculation and phenomenological modeling of the experimental data to account for the sensing quantitatively over a wide dynamic range. Our results indicate that BQDs hold great potential for developing highly sensitive gas, molecular, bio-, and optoelectronic sensors in the future. [ABSTRACT FROM AUTHOR]

Defect-free thin-walled samples were built using wire arc additive manufacturing (WAAM) combined with the "coldArc" deposition technique by feeding a Ti-6Al-4V welding wire and using two deposition strategies, namely with and without the welding torch weaving. The microstructures formed in these samples were examined in relation to mechanical characteristics. The arc torch weaving at 1 Hz allowed us to interfere with the epitaxial growth of the β-Ti columnar grains and, thus, obtain them a lower aspect ratio. Upon cooling, the α/α′+β structure was formed inside the former β-Ti grains, and this structure proved to be more uniform as compared to that of the samples built without the weaving. The subtransus quenching of the samples in water did not have any effect on the structure and properties of samples built with the arc torch weaving, whereas a more uniform grain structure was formed in the sample built without weaving. Quenching resulted also in a reduction in the relative elongation by 30% in both cases. [ABSTRACT FROM AUTHOR]

Bulk samples of Tris (8-hydroxyquinoline) aluminium (Alq3) were prepared using wet synthesis method followed by annealing at 50 °C, 100 °C, 150 °C and 200 °C for 2 h. X ray diffraction pattern showed the formation of Alq3 crystal which is constituted of Al atom, anions of 8-hydroxyquinoline (8-Hq) and porous Al2O3–Al(OH)3. structure. The spectra of FTIR (Fourier-transform infrared) reveals that annealing Alq3 at 50 °C reduces the C=C peak to negligible but reappears when annealed at 150 °C. FESEM on as-prepared Alq3 shows hexagonal rod shaped stacked structures which on annealing at 50 °C changes to tetragonal agglomerated grains along with appearance of oval and circular shaped pores on it. From fluorescence spectroscopy it is found that the peak intensity changes non-monotonically with annealing temperatures followed by red shift and blue shift of peak maximum at 150 °C and 200 °C respectively. The temperature dependent change in the properties are mainly attributed to the onset of hydrolysis in Alq3 and change in the electronic transition levels. [ABSTRACT FROM AUTHOR]

A new method for obtaining graded amorphous carbon using quenching of a graphite melt on a diamond substrate is proposed. Using molecular dynamics modeling of liquid carbon quenching on a cold diamond substrate, it is shown that the amorphous carbon obtained in the experiment is a material with a strongly gradient structure and properties along the depth of the sample. This is due to the quenching rate decrease with the distance from the substrate in the range of 1014–1012 K/s. In this case, the density of amorphous carbon varies from 1.50 to 1.93 g/cm3. The spatial change in the structural characteristics of the obtained amorphous carbon was studied: the distribution of carbon atoms according to the degree of chemical bond hybridization (sp1-, sp2-, sp3-), the radial distribution function, the angular distribution function, and a statistical analysis of carbon rings were carried out. It is shown that at a pressure in liquid of 1 GPa, the carbon structure within the quenched zone changes from a highly porous structure with a large number of sp1 chains of carbon atoms near the substrate to an amorphous graphene structure at the periphery. [ABSTRACT FROM AUTHOR]

Interaction of neutral and charged lipophilic beta-blocker drug, propranolol (PPL) with biomimicking nanocavities formed by micelles bearing same and opposite charges namely, cationic cetyltrimethylammonium bromide (CTAB), a surface-active ionic liquid 1-hexadecyl-3-methylimidazolium chloride (HDMIC) and anionic sodium dodecyl sulphate (SDS) have been investigated using fluorescence and absorption spectroscopic techniques. Binding of PPL to SDS at pH < pKa is characterised by biphasic interactions with decrease in fluorescence intensity at lower concentrations and subsequent increase post micellization. All the surfactants show significant interactions with the neutral drug molecule at pH > pKa, which is evident from the strongest binding constant ( K b ) values at pH 10.4. Results of quenching studies indicate that the location of drug molecule is determined by its charge, which is influenced by both pH and charge on micelle surface. For PPL-CTAB and PPL-HDMIC systems, quenching was strongest at pH 10.4, moderate at pH 7.4 and was absent at pH 3.5. However, the PPL-SDS system displayed similar K SV values at all pH conditions, suggesting that the probe is at the same position regardless of pH. Non-covalent interactions, which play crucial role in biological systems, are similarly the primary driving force governing the interaction between PPL and surfactant micelles. [ABSTRACT FROM AUTHOR]

5,10,15,20-tetramethoxyphenylporphyrinatotin (IV) (SnTMPP) was synthesised. SnTMPP exhibited Soret band at 432 nm and emission peaks at 629 and 682 nm. The fluorescence intensity of SnTMPP was quenched in the presence of guanine linearly in the range 4 × 10–9 M to 7.2 × 10–8 M and the quenching response was found to be stable even in the presence of other nucleosides such as adenine, cytosine, uracil, thymine, alanine, aspartic acid and ascorbic acid. The detection limit was found to be 0.17 nM and the mechanism behind the decrease in the fluorescence intensity of SnTMPP in the presence of guanine is due to dynamic quenching, which was confirmed by cyclic voltammetric studies and life time studies. The CV studies illustrates the possibilty for an electron transfer between the guanine and the electron deficient metal core of SnTMPP. [ABSTRACT FROM AUTHOR]

ASTM D6200 is a standard test method published by ASTM International for evaluating the cooling characteristics of quench oils. The results obtained through this standard can serve as a guide for quench oil selection and for comparing quench severities among different quench oils, whether they are new or used. The standard provides six parameters representing the cooling characteristics of the reference quench oil: three time-based scales (time to cool to 600, 400, and 200 °C), two cooling rates (maximum cooling rate and cooling rate at 300 °C), and one temperature scale (at the maximum cooling rate). ASTM D6200 is widely used in production plants to monitor the quality of the quench oil so that parts can be produced with consistent properties, such as hardness, and dimensions. However, it is important to note that the current ASTM D6200 standard only references one specific quench oil, and its usages are limited to characterizing quench severity in physical prototyping or production in the plants. The aim of this research is to explore the possibility of extending the application of the standard to more quenchants in addition to one specific quench oil and expanding the support of the standard beyond physical testing to include virtual engineering by simulations. This research comprises two main portions. The first one involves developing a systematic method for identifying the characteristic points of a time series of thermocouple data. The second one involves constructing an analytical cooling curve based on these characteristic points. This analytical cooling curve is a closed-form mathematical function that relates temperature to time, providing temperature value at any given time during the quenching process. Furthermore, this curve is second-order differentiable, allowing users to derive cooling rate information at any specific time. [ABSTRACT FROM AUTHOR]

The reuse of gutter oil has always been a sensitive social issue. In the heat treatment industry, engineers have also been troubled by the need to move away from dependence on petroleum derivatives for cleaner production. While vegetable oils appear to be a viable alternative, the higher cost and poor thermal and oxidative stability limit their use in the heat treatment industry. The use of gutter oil as a quenchant raw material not only makes the quenchant cost effective but also environmentally friendly. In this study, the cooling performance of fatty acid methyl ester prepared from gutter oil was evaluated and compared with soybean oil and mineral oil. Firstly, fatty acid methyl ester was obtained by esterification and transesterification of gutter oil to reduce the free fatty acid content and make it suitable for quenching and heat treatment. The experiments were carried out using an Inconel 600 standard probe according to ISO 9950. The cooling behavior of the quenching media was tested at oil bath temperatures of 40 °C, 60 °C, and 80 °C. Quenching was carried out using AISI 4340 to obtain Vickers microhardness distributions on cross-sections of heat-treated specimens and residual stresses were determined by x-ray diffraction for all test materials. The fatty acid methyl ester used for analysis produced a hardening depth equivalent to that of commercial mineral oil when quenching the AISI 4340 alloy steel. And the test results achieved cooling properties and quenching intensity comparable to mineral oil. This indicates that fatty acid methyl ester prepared from gutter oil has the potential to replace mineral oil. [ABSTRACT FROM AUTHOR]

Fluorescence imaging is an invaluable tool to investigate biomolecular dynamics, mechanics, and interactions in aqueous environments. Two‐dimensional materials offer large‐area, atomically smooth surfaces for wide‐field biomolecule imaging. Despite the success of graphene for on‐chip biosensing and biomolecule manipulation, its strong fluorescence‐quenching properties pose a challenge for biomolecular investigations that are based on direct optical readouts. Here, we employ few‐layer hexagonal boron nitride (hBN) as a precisely tailorable fluorescence spacer between labelled lipid membranes and graphene substrates. By stacking high‐quality hBN crystals in the 10–20 nm thickness range on monolayer graphene, we observe distance‐dependent fluorescence intensity variations. Remarkably, with hBN spacers as thin as 20 nm, the fluorescence intensity is comparable to bare SiO2/Si substrates, while the intensity was reduced to 60 % and 80 % with ~10 nm and ~16 nm hBN thicknesses respectively. We confirm that pre‐determined hBN thicknesses can be employed to control the non‐radiative energy transfer properties of graphene, with fluorescence quenching following a d−4 distance‐dependent behaviour. This seamless integration of electronically active and dielectric van der Waals materials into vertical heterostructures enables multifunctional platforms addressing the manipulation, localization, and visualization of biomolecules for fundamental biophysics and biosensing applications. [ABSTRACT FROM AUTHOR]

Oats are one of the most useful and widespread cereal crops in the world. In permafrost conditions (Central Yakutia), based on metabolic changes in late summer-sown oat plants (Avena sativa L.), the key processes involved in the cold acclimation of a valuable cereal species were identified. During the onset of low ambient temperatures, metabolites from leaf samples were profiled using gas chromatography with mass spectrometry (GC-MS) and were analyzed using principal component analysis (PCA). A total of 41 metabolites were identified in oat leaves. It was found that acclimation to suboptimal temperatures during the fall period leads to biochemical (accumulation of mono- and disaccharides and decrease in fatty acids and polyols) as well as physiological and biophysical changes (decrease in leaf PRI reflectance indices and chlorophyll a fluorescence). Therefore, the study contributes to a more holistic understanding of oat metabolism under low-temperature cryolithozone stress. It is believed that the analysis of changes in leaf reflection properties and JIP-test parameters of chlorophyll a fluorescence using leaf metabolomic profiling can be used in the selection of valuable varieties of cereal crops to obtain plant fodders with high nutrient contents under conditions of a sharply continental climate. [ABSTRACT FROM AUTHOR]

Heat treatment is a common manufacturing process in the automotive industry used to produce high-performance metal components such as aluminum cylinder heads and steel gear sets. While a heat treatment schedule incorporating a quenching cycle, either through high-velocity air flow or immersion in liquids, can yield parts with durable mechanical properties, an unintended consequence of the intense quenching process is the introduction of thermal residual stress. This stress often is identified as a leading cause for quality issues related to high-cycle fatigue in aluminum engine components or geometric distortion in steel gear sets. Since thermal residual stress is caused by uneven cooling of the materials within the parts, an effective strategy for controlling thermal residual stress would involve directly managing the quenching processes. By reducing the temperature gradient inside the parts during quenching, the quality issues can be improved. Prior to the advent of computer simulation technology, the choice of quench media and the design of quenching recipes were often based on intuitive engineering judgment at best and trial-and-error iterative methods at worst. With the advancements in computational fluid dynamics (CFD) methodology, the quenching process can now be modeled through computer simulations for accurate calculation of temperature profiles and cooling histories of quenched parts. While CFD methods have the potential to manage quenching processes and mitigate thermal residual stress, it is important to note that CFD methods are not a one-size-fits-all solution for all quenching problems. Different quenching processes require different simulation strategies. Furthermore, CFD methods still require calibration and validation before they can be effectively utilized as virtual engineering tools, replacing traditional physical tryouts and experimental methods. The objective of this paper is to develop quenching simulation methodologies that can accommodate various heat treatment requirements and be used to optimize quenching processes, thereby managing quality concerns associated with thermal residual stress. While this research focuses only on two common quenching methods in engine component manufacturing, namely air quenching and water quenching for aluminum components, the principles and methodologies can be extended to other quenching methods based on convective motion of quenching media. Additionally, this research includes the parameterization and calibration of conjugate heat transfer models at the fluid-metal interface, which form the core of CFD simulation technologies. [ABSTRACT FROM AUTHOR]

Quenching procedures are effective in enhancing the low depolarization temperature of sodium bismuth titanate (NBT) relaxor ferroelectrics. In the present work, the influence of thermal processing parameters on the structure and electrical properties of NBT ceramics modified with 5 mol% sodium niobate (NBT-5NN) are evaluated. It is shown that quenching leads to higher electrical conductivity due to reduction at high temperatures, resulting in a higher oxygen vacancy concentration. The quenched materials also exhibit enhanced rhombohedral distortion and ferroelectric properties. The reduction process is largely reversible by reoxidation during annealing at intermediate temperatures in the region of 550 °C, which helps to recover the bulk resistivity to values close to those of the as-sintered materials. On the other hand, the rhombohedral distortion and ferroelectric properties were not affected significantly by the annealing procedure, indicating that the mechanisms responsible for the modification of electrical conductivity and structural distortion/ferroelectric properties have a different origin. [ABSTRACT FROM AUTHOR]

Accurate and rapid detection of nucleic acid sequences is of utmost importance in various fields, including disease monitoring, clinical treatment, gene analysis and drug discovery. In this study, we developed a "turn-on" fluorescence biosensor that enables simple and highly efficient detection of nucleic acid biomarkers. Our approach involves the utilization of 6-carboxyfluorescein modified single-stranded DNA (FAM-ssDNA) as molecular recognition element, along with polydopamine-functionalized dendritic fibrous nanosilica (DFNS). FAM-ssDNA serves as both specific molecular recognition element for the target analyte and reporter capable of transducing a detectable signal through Watson–Crick base pairing. The polydopamine-functionalized DFNS (DFNS@DA) exhibits strong binding to FAM-ssDNA via polyvalent metal mediated coordination leading to effective quenching by fluorescence resonance energy transfer. In the presence of a complementary target sequence, FAM-ssDNA forms hybridized structure and detaches from DFNS@DA, which causes an increased fluorescence emission. The analytical system based on FAM-ssDNA and DFNS@DA demonstrates exceptional sensitivity, selectivity, and rapid response for the detection of nucleic acid sequences, leveraging the high adsorption and quenching properties of DFNS@DA. For the first proof of concept, we demonstrated the successful detection of microRNA (miR-21) in cancer cells using the FAM-ssDNA/DFNS@DA system. Our results highlight the promising capabilities of DFNS@DA and nucleic acid-based biosensors, offering a generic and cost-effective solution for the detection of nucleic acid-related biomarkers. [ABSTRACT FROM AUTHOR]

Residual strength tests are commonly used to characterize the high‐temperature mechanical properties of concrete materials. In these tests, the specimens are heated to a target temperature in a furnace and then cooled down to room temperature, followed by mechanical testing at room temperature. This research investigates the influence of the cooling method on the residual strength of Strain Hardening Cementitious Composites (SHCC) after exposure to 400°C and 600°C. Two types of cooling methods — furnace‐cooling (within a closed furnace) and water‐cooling (immersed in a water tank) — were adopted. Four different SHCC previously investigated by the authors for high‐temperature residual mechanical and bond behavior with steel were studied. Two different specimen sizes were tested under uniaxial compression and flexure to characterize the residual compressive strength and modulus of rupture. The effect of the cooling method was prominent for the normalized residual modulus of rupture at 400°C, but not at 600°C. The cooling method had no effect on the normalized residual compressive strength of any material at either of the two temperatures, except one of the SHCC (PVA‐SC) at 400°C. Specimen size also had no effect on the normalized residual compressive strength and modulus of rupture irrespective of the cooling method. [ABSTRACT FROM AUTHOR]

Transparent photovoltaic (TPV) devices offer the potential to generate power without being visible to the human eye, making them ideal for use in building integrated photovoltaic applications. TPV devices based on inorganic materials offer eco‐friendly frameworks with stable performances. However, their low power conversion efficiency and incapacity to produce onsite power for real‐time practical applications limit their widespread deployment. Mitigation of exciton quenching by reducing the interface and bulk recombination can significantly improve the performance of TPVs. To address this, the present study investigates the effect of passivation layers (PLs) in all‐metal‐oxide TiO2/Cu2O TPV. The TiO2/Cu2O TPV interface is passivated by depositing thin Al2O3 and Ga2O3 films. The study comprehensively analyzes how passivation controls the interfacial and bulk defects. Electrochemical impedance spectroscopy and X‐ray photoelectron spectroscopy are used to elucidate exciton quenching mechanisms. The results show that the insertion of a thin PL on top of TiO2 effectively mitigates exciton quenching by suppressing hydroxyl ions, Ti2+, and Ti3+ bulk states. Ga2O3 PL, in particular, leads to a substantial enhancement in short‐circuit current density (12.4 mA cm−2) and open‐circuit voltage (669 mV). The study also demonstrates the real‐time onsite energy production and its utilization through the operation of an electric fan. [ABSTRACT FROM AUTHOR]

Erythrosine B (EB) is a food colorant antiviral xanthene dye that has many applications as a color additive in pharmaceuticals and cosmetics. Its use as a sensor for spectrofluorimetric and spectrophotometric analysis of amine‐based pharmaceuticals renders many advantages because of its availability, low cost, rapid labeling, and high sensitivity. Herein, two fast and sensitive spectrofluorimetric and spectrophotometric methods were established for the estimation of the anti‐Parkinson drug, biperiden (BIP) hydrochloride (HCl), in its raw material and tablet forms. The proposed methods depended on the interaction between the phenolic group of EB and the tertiary amino group of the studied analyte to form an ion‐pair complex at pH 4 using the Britton Robinson buffer. The spectrofluorimetric method is based on the measurement of the quenching power of BIP HCl on the fluorescence intensity of EB at λex/em = 527.0/550.9 nm. This method was rectilinear over the concentration range of 0.1–1.0 μg/mL with a limit of detection (LOD) = 0.017 μg/mL and a limit of quantification (LOQ) = 0.05 μg/mL. Meanwhile, the colorimetric method involved monitoring the absorbance of the formed ion‐pair complex at 555 nm, showing a linearity range of 0.4–5.0 μg/mL with LOD = 0.106 μg/mL and LOQ = 0.322 μg/mL. The proposed methods were assessed for the greenness, indicating the greenness of the developed methods. [ABSTRACT FROM AUTHOR]

The thermal behavior of a poly(methylmethacrylate) (PMMA) pigmented with titanium dioxide (TiO2) is studied in both Steady state and transient regimes in the present work. The numerical results of thermal conductivity, based on the finite element method, are compared to theoretical models and experimental measurements, which varies depending on the quenching temperature and pigment content. Time evolution of temperatures during the quenching of the composite is taken into account for different quenching temperatures and different pigment contents. It is noted that the heat exchange becomes slower for a pigment fraction of 0.5%, and the steady state is reached more rapidly for higher pigment content. The AFM image of the PMMA/TiO2 composite with content equal to 3% of titanium dioxide. This demonstrates a good distribution of the particles throughout the matrix, with the individual particles being uniformly dispersed and securely embedded in the polymer matrix, thereby avoiding any clustering. An improvement in heat exchange is observed in the composite with a high content of titanium dioxide. This improvement is attributed to the increase in the thermal conductivity of the PMMA/TiO2 composite. [ABSTRACT FROM AUTHOR]

Solid oxide electrolysis cell (SOEC) industrialization has been developing for many years. Commercial materials such as 8 mol% Y2O3-stabilized zirconia (YSZ), Gd0.1Ce0.9O1.95 (GDC), La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF), La0.6Sr0.4CoO3−δ (LSC), etc., have been used for many years, but the problem of mismatched thermal expansion coefficients of various materials between cells has not been fundamentally solved, which affects the lifetime of SOECs and restricts their industry development. Currently, various solutions have been reported, such as element doping, manufacturing defects, and introducing negative thermal expansion coefficient materials. To promote the development of the SOEC industry, a direct treatment method for commercial materials—quenching and doping—is reported to achieve the controllable preparation of the thermal expansion coefficient of commercial materials. The quenching process only involves the micro-treatment of raw materials and does not have any negative impact on preparation processes such as powder slurry and sintering. It is a simple, low-cost, and universal research strategy to achieve the controllable preparation of the thermal expansion coefficient of the commercial material La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) through a quenching process by doping elements and increasing oxygen vacancies in the material. Commercial LSCF materials are heated to 800 °C in a muffle furnace, quickly removed, and cooled and quenched in 3.4 mol/L of prepared Y(NO3)3. The thermal expansion coefficient of the treated material can be reduced to 13.6 × 10−6 K−1, and the blank sample is 14.1 × 10−6 K−1. In the future, it may be possible to use the quenching process to select appropriate doping elements in order to achieve similar thermal expansion coefficients in SOECs. [ABSTRACT FROM AUTHOR]

Herein, we have prepared a 5,10,15,20-Tetrakis(4-hydroxyphenyl) porphyrin (P) which acts as a probe for selective and sensitive detection of Bi3+ ions. Probe P was obtained by reacting pyrrole with 4-hydroxyl benzaldehyde and characterized by NMR, IR, and ESI-MS. All photo-physical studies of P were tested in DMSO:H2O (8:2, v/v) media by spectrophotometry and spectrofluorometry respectively. The selectivity of P was tested with different metal ions in solution as well as in the solid phase, only Bi3+ showed red fluorescence quenching while with other metal ions, no such effect was observed. The Job's plot unveiled the 1:1 stoichiometric binding ratio of the probe with Bi3+ and anticipated association constant of 3.4 ×105 M-1, whereas the Stern-Volmer quenching constant was noticed to be 5.6 ×105 M-1. Probe P could detect Bi3+ down to 27 nM by spectrofluorometric. The binding mechanism of P with Bi3+ was well supported with NMR, mass, and DFT studies. Further, the P was applied for the quantitative determination of Bi3+ in various water samples and the biocompatibility of P was examined using neuro 2A (N2a) cells. Overall, probe P proves promising for the detection of Bi3+ in the semi-aqueous phase and it is the first report as a colorimetric and fluorogenic probe. [ABSTRACT FROM AUTHOR]

A low-alloy steel with specific properties is developed for the manufacture of automobile starter shafts by a low-waste automated technology: rotary compression. When using this steel, the production time is shortened, and metal consumption is decreased. [ABSTRACT FROM AUTHOR]

The influence of the degree of plastic deformation at room temperature, followed by aging, on the amplitude dependence of internal friction and microstructure of the pre-hardened alloy ZA27 was investigated. The main structural mechanism affecting the amplitude dependence of internal friction under these treatments was analyzed. [ABSTRACT FROM AUTHOR]

Diiminic Schiff bases (DSBs) were proven to be an intriguing candidate for coinage metal-enhanced fluorescence (MEF). DSBs were synthesized via the condensation reaction of salicylaldehyde (SL) and diamines. Silver and copper nanoparticles (synthesized in situ with the reaction of SL) showed significant enhancement of fluorescence selectively depending on the experimental conditions. SL was oxidized to its quinone form, while Ag+ or Cu2+ was reduced to its zero-valent state at the alkaline condition. DSBs acted as reducing as well as stabilizing agents. By changing diamines, the distance between two iminic bonds was manipulated and different extents of MEF were obtained. Detection of highly toxic metal ions is a challenge in an aqueous system in the context of water pollution. Ionic mercury, copper, and silver (released from natural as well as anthropogenic activities) were sensed selectively using turn-on/off fluorescence with a significant limit of detections involving DSBs-induced MEF. Biological compounds are found in remarkable quantities in natural water, creating a long-lasting effect on the food chain and ecology. Cysteine and dopamine were also sensed via the quenching of DSBs-stimulated MEF. Here, we summarized the toxicity of water pollutants and intriguing role of DSBs in coinage MEF for the decontamination of water with plausible mechanism. Such MEF sensed a series of inorganic and biological emerging pollutants in the water system selectively and sensitively. Imine-induced selectivity and manipulation of experimental conditions help to design intriguing sensing platform for the detection of water pollutants. [ABSTRACT FROM AUTHOR]

Abstract—The methods of scanning electron microscopy, X-ray diffraction analysis, and microindentation are used to study the effect of alloying with zirconium (within 3 to 6 at %) and complex Zr + Sn and Zr + Sn + Ta additions on the evolution of the structure, phase composition, and properties (effective modulus of elasticity, hardness, and wear-resistance parameters) of quenched biocompatible β-titanium (at %) Ti–26% Nb–3% Zr, Ti–26% Nb–5% Zr, Ti–26% Nb–6% Zr, Ti–26% Nb–3% Zr–1% Sn, and Ti–26% Nb–3% Zr–1% Sn–0.7Ta alloys during aging (at 400°C for 4, 16, and 64 h) after multipass cold rolling with a total degree of strain of 85%. As compared to the quenching, the cold rolling of the studied Ti–Nb–Zr alloys is shown to suppress the occurrence of the β → ω transformation in the course of aging and to favor the acceleration of the decomposition of β solid solution with the formation of nonequilibrium αl phase in the course of aging. The increase in the zirconium content from 3 to 6 at % in the cold-rolled ternary Ti–26% Nb – х% Zr alloys and introduction of complex Zr + Sn and Zr + Sn + Ta additions to the Ti–26% Nb alloy instead of only zirconium addition hinder the decomposition processes of the β phase during aging; this impacts the intensity of variations of the effective modulus of elasticity and microhardness. The aging of the cold-rolled alloys under study was found to allows us to obtain the higher values of the parameters H/Er and (Н is the hardness and Er is the resolved modulus of elasticity) associated with the wear resistance as compared to those for the widely used medical Ti–6Al–4V alloy. The compositions of the alloys and conditions of their treatment are determined, which allow us to obtain the combination of the highest-level properties. [ABSTRACT FROM AUTHOR]

Copyright of Iron Steel Vanadium Titanium is the property of Iron Steel Vanadium Titanium Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Even with significant developments in nanoscience, relatively little is known about the interactions of nanocrystal semiconducting materials with bio-macromolecules. To investigate the interfacial phenomena of cadmium selenide quantum dot (CdSe QD) nanocrystals with proteins extracted from Moringa oleifera seeds, different concentrations of cadmium selenide quantum dots–Moringa oleifera seed protein (CdSe–MSP) complexes were prepared. Respective CdSe QDs with hexagonal phase and crystalline size in the range of 4–7 nm were synthesized and labelled with the purified mesoporous MSP having a surface area of 8.4 m2/g. The interaction mechanism between CdSe QDs and MSP was studied using UV–Vis absorption, fluorescence emission and Fourier Transform Infrared spectroscopies. The UV–Vis absorption spectra showed absorption bands of CdSe–MSP complexes at 546.5 nm. The fluorescence intensity of CdSe QDs was found to decrease with increasing concentration of MSP. The thermodynamic potentials ∆ H θ (−321.3 ×   10 3 Jmol−1);   ∆ S θ (156.0 JK−1mol−1) and ∆ G θ (−46.6 ×   10 3 Jmol−1) were also calculated. The stability of the complex found is strongly influenced by electrostatics interaction and surface-bound complexation equilibrium attraction. This information can help to elucidate the surface characteristics of MSP and its potential interactions with other molecules or nanoparticles. [ABSTRACT FROM AUTHOR]

In this paper, we study a stochastic parabolic problem involving a nonlocal diffusion operator associated with nonlocal Robin-type boundary conditions. The stochastic dynamics under consideration is driven by a mixture of a classical Brownian and a fractional Brownian motion with Hurst index $ H\in(\frac{1}{2}, 1). $ We first establish local in time existence results and then explore conditions under which the resulting SPDE exhibits finite-time quenching. Using results on the probability distribution of perpetual integral functionals of Brownian motion as well as tail estimates for the fractional Brownian motion we provide analytic estimates for certain quantities of interest, such as upper bounds for quenching times and the corresponding quenching probabilities. The existence of global in time solutions is also investigated and as a consequence a lower estimate of the quenching time is also derived. Our analytical results demonstrate the non-trivial impact of the noise on the dynamics of the system. The analytic results are complemented with a detailed numerical study of the model under Dirichlet boundary conditions. A possible application concerning MEMS technology is considered and the implications of the results in this context are commented upon. [ABSTRACT FROM AUTHOR]

The structural, surface morphological, optical absorption and emission features of Y2O3:Ce (0%–5%) were studied. The samples had a body‐centred cubic crystal structure. The undoped sample had a crystallite size of 29.03 nm, and it varied after doping with Ce. The grain size of the samples varied from 23.00 to 50.78 nm. All the samples exhibited a strong absorption band at 206 nm due to F‐centre absorption and absorption involving the delocalised bands. In addition, the doped samples exhibited a secondary band at ~250 nm due to 4f → 5d transitions of Ce3+ ions. The optical bandgap of the undoped sample was found to be ~5.37 eV, and it decreased to 5.20 eV with an increase in Ce concentration to 5%. The undoped sample under 350‐nm excitation exhibited a broad photoluminescence (PL) emission band with the maxima at 406 nm and a secondary band at 463 nm. In contrast, multiple PL peaks were centred at ~397, 436, 466, 488 and 563 nm in all the doped samples. The average lifetime of the emission band at 406 nm was 1.05 ns and that of the emission band at ~466 nm was 1.63 ns. The material has potential for solid‐state lighting applications. [ABSTRACT FROM AUTHOR]

Measurement of photosensitized luminescence of singlet oxygen has been applied to studies of singlet oxygen generation and quenching by C40 carotenoids (neurosporene, lycopene, rhodopin, and spirilloxanthin) with long chain of conjugated double bonds (CDB) using hexafluorobenzene as a solvent. It has been found that neurosporene, lycopene, and rhodopin are capable of the low efficient singlet oxygen generation in aerated solutions upon photoexcitation in the spectral region of their main absorption maxima. The quantum yield of this process was estimated to be (1.5–3.0) × 10−2. This value is near the singlet oxygen yields in solutions of ζ-carotene (7 CDB) and phytoene (3 CDB) and many-fold smaller than in solutions of phytofluene (5 CDB) (Ashikhmin et al. Biochemistry (Mosc) 85:773–780, https://doi.org/10.1134/S0006297920070056, 2020, Biochemistry (Mosc) 87:1169–1178, 2022, https://doi.org/10.1134/S00062979221001082022). Photogeneration of singlet oxygen was not observed in spirilloxanthin solutions. A correlation was found between the singlet oxygen yields and the quantum yields and lifetimes of the fluorescence of the carotenoid molecules. All carotenoids were shown to be strong physical quenchers of singlet oxygen. The rate constants of 1O2 quenching by the carotenoids with long chain of CDB (9–13) were close to the rate constant of the diffusion-limited reactions ≈1010 M−1 s−1, being many-fold greater than the rate constants of 1O2 quenching by the carotenoids with the short chain of CDB (3–7) phytoene, phytofluene, and ζ-carotene studied in prior papers of our group (Ashikhmin et al. 2020, 2022). To our knowledge, the quenching rate constants of rhodopin and spirilloxanthin have been obtained in this paper for the first time. The mechanisms of 1O2 photogeneration by carotenoids in solution and in the LH2 complexes of photosynthetic cells, as well as the efficiencies of their protective action are discussed. [ABSTRACT FROM AUTHOR]

The deformed biomedical Ti-(18-20)Nb-(3-4)Zr-(1-1.2)Si (% wt.) alloys are studied. Their rolling is carried out at 950°С by means of the air- and water-cooling; the quenching in water and oil with heating up to 1050°С is also used. As established with the x-ray phase analysis, the hot deformation of Ti-(18-20)Nb-(3-4)Zr-(1-1.2)Si alloys contributes to the β-solid-solution heterogeneity into β1 phase based on Ti-Nb and β2 phase based on Zr-Ti, as a result of which a final dispersed nonequilibrium (α′′ + α′) structure is formed after cooling, that reflects the (β1 + β2) microstructure formed due to the previous decomposition. After deformation with air cooling, the experimental alloys contain the largest amount of α′ phase and have high strength and low plasticity. As shown, a rising of the cooling rate and temperature during quenching leads to the predominance of the orthorhombic α′′ phase, while the strength of the alloys decreases with a significant increase in plasticity. In the process of deformation and heat treatment, densely and uniformly distributed disperse silicides are also released in the structure, which contribute to the strengthening. For Ti-(18-20)Nb-(3-4)Zr-(1-1.2)Si alloys, the temperature range Т = 1040 ± 20°С is established, the quenching from which allows to obtain high mechanical properties: σв = 1100-1150 МPа, σ0.02 = 800-850 МPа, δ = 11-11.5%. By deformation and quenching of the experimental alloys, a composite material with alloyed soft matrix strengthened by the uniformly distributed dispersed hard particles of silicides is fabricated. [ABSTRACT FROM AUTHOR]

This article demonstrates how different cooling rates and precipitation hardening affected the mechanical properties of AA2024. Three impact test samples were chosen. Solution heat treatment was conducted at 500 °C for 2 hrs., followed by quenching in three different quenching media (Sunflower Oil, Sesame Oil, and Corn Oil). As a result, the Sunflower Oil showed the lowest shock absorption rate; hence, it was chosen as the quenching medium for this study. Consequently, all samples of tensile, hardness, and impact tests were solution heat treated at 500 °C for 2 hours, then quenched in Sunflower Oil to room temperature and artificially aged at temperatures of 180°C for 1,2,4 hour, 195°C for 1, 2, 4 hour, and 210°C for 1,2,4 hour. Considerable improvements in strength and hardness were observed while decreasing the ductility Due to the production of finely dispersed grains. Precipitation hardening at 180°C for 1 hour was the overall optimum achievement, which enhanced the UTS by 28.7% to 579 MPa, compared to the as-received sample with UTS 450 MPa. While annealing has reduced the UTS by 32.7% to 303 MPa.

A novel, highly sensitive, and cost-effective biosensor for prostate-specific antigen (PSA) detection has been developed using bioengineered nanotechnology. This biosensor integrates a Fe(III)-Gallic acid metal organic framework (Fe-GA MOF) embedded in a carboxymethyl cellulose polymer thin film, coupled with a PSA monoclonal antibody for capture. The resulting sensor demonstrates exceptional performance in detecting PSA levels within a wide concentration range (0.1–170 ng/mL), with a remarkable limit of detection of 0.06 ng/mL. This advanced technology surpasses conventional methods by providing enhanced sensitivity, stability, and reduced interference. The biosensor holds immense potential for early prostate cancer diagnosis, monitoring treatment response, and detecting recurrence. Moreover, its applicability may extend to other cancers characterized by elevated PSA levels, ultimately improving patient outcomes through timely intervention and optimized care.

Even with significant developments in nanoscience, relatively little is known about the interactions of nanocrystal semiconducting materials with bio-macromolecules. To investigate the interfacial phenomena of cadmium selenide quantum dot (CdSe QD) nanocrystals with proteins extracted from Moringa oleifera seeds, different concentrations of cadmium selenide quantum dots–Moringa oleifera seed protein (CdSe–MSP) complexes were prepared. Respective CdSe QDs with hexagonal phase and crystalline size in the range of 4–7 nm were synthesized and labelled with the purified mesoporous MSP having a surface area of 8.4 m2/g. The interaction mechanism between CdSe QDs and MSP was studied using UV–Vis absorption, fluorescence emission and Fourier Transform Infrared spectroscopies. The UV–Vis absorption spectra showed absorption bands of CdSe–MSP complexes at 546.5 nm. The fluorescence intensity of CdSe QDs was found to decrease with increasing concentration of MSP. The thermodynamic potentials ∆Hθ (−321.3 × 103 Jmol−1); ∆Sθ (156.0 JK−1mol−1) and ∆Gθ (−46.6 × 103 Jmol−1) were also calculated. The stability of the complex found is strongly influenced by electrostatics interaction and surface-bound complexation equilibrium attraction. This information can help to elucidate the surface characteristics of MSP and its potential interactions with other molecules or nanoparticles.

This work presents a novel InGaAs/InP avalanche photodiode, fabricated in the separate absorption, grading, charge, and multiplication configuration operated at non-cryogenic conditions under low-frequency ramp gating. An optimized three stage InP multiplication layer of $1\mu m$ thickness offers an extended linear mode operation by reducing the punch-through voltage, and indefinitely increasing the avalanche threshold voltage. A large background dark current is observed following steady, and linear multiplication in approximately direct relationship with the ramp gating. For 1310 nm short-wave infrared, normal incidence pulsed illumination at instant-to-peak voltage ratios of $(0.11,0.2,0.6, 0.89, 0.98, 0.9)$ , a sort of negative differential resistance is incorporated into the device in a qualitative sense, owing to the illumination induced switching/variations in the intrinsic values of electron, and hole avalanche coefficients in the multiplication region. Under fixed illumination, an interesting deduction from the transient photo response is the slow quenching phenomenon prolonging $\sim 120 \mu s$ for all the electrical field establishments in the device. The related measurement scheme paves the way for futuristic ramp-driven InGaAs/InP APDs for detecting SWIR wavelengths under required low power consumption environments.

Cu–Ni–Sn spinodal alloys (Spinodal bronze) are potential materials with robust applications in components associated with defence applications like bearings, propellers, bushes, and shafts of heavily loaded aircraft, off-road vehicles, and warships. This paper presents a comparative study using water, Brine solution, and SAE 40 oil as the quenching media in regular bronze (Cu–6Sn) and spinodal bronze (Cu–9Ni–6Sn) alloys. Morphological analysis was conducted by optical microscopy, transmission electron microscopy (TEM), and X-ray diffraction technique (XRD) on bronze and spinodal bronze samples immersed in the three different quenching media to understand the grain size and hardness values better. Tribological analysis was performed to analyze the effect of quenching media on the wear aspects of bronze and spinodal bronze samples. The hardness value of the brine-aged spinodal bronze samples was as high as 320 Hv, and the grain size was very low in the range of 60 μm. A quantitative comparison between brine-aged regular bronze and brine-aged spinodal bronze showed that the hardness (Hv) was almost 80% higher for brine-aged spinodal bronze. Further, the grain size was approximately 30% finer for spinodal bronze when compared with regular bronze. When the load was increased in spinodal bronze samples, there was an initial dip in wear rate followed by a marginal increase. There was a steady increase in friction coefficient with a rise in load for brine-aged regular bronze and spinodal bronze samples. These results indicate that brine solution is the most effective quenching medium for cast Cu–Ni–Sn spinodal alloys.

Copyright of Metal Working (1674-165X) is the property of Metal Working Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Differential scanning calorimetry (DSC) was used to study the transformation process of 1Cr13 steel under quenching condition. The DSC curves were measured from 1 050 °C to room temperature at the cooling rate of 10, 20, 30, 50 °C/min, respectively. The Flynn-Wall-Ozawa method was used to obtain the activation energy of the transformation process of 1Cr13 steel under quenching condition. The kinetic mechanism functions of the transformation process of 1Cr13 steel under quenching condition were also investigated by Criado-Ortega methods. The results show that the activation energy is related to the phase transition fraction. It means the transformation process of 1Cr13 steel under quenching condition is not a simple one-step reaction but a complex multi-step reaction. [ABSTRACT FROM AUTHOR]

This study used an experimental research method, which is a research method that aims to understand the causal process by treatment and conducting controlled testing on a sample of research subjects. This research uses quantitative methods by taking research data in the form of numbers. The material used in this study is the gear sprocket. A gear sprocket is a motor component that transmits power from the engine to the rear wheels so that the motor can run optimally. The sprocket gear was heat treated at 850 ℃ with a holding time of 20 minutes. The variations of quenching media are mineral water, dromus coolant, and SAE 40 oil. Hardness and microstructure tests were carried out for each specimen to determine the effect of different cooling media on the quenching process. The results of this study indicate the highest specimen hardness value was obtained at 301 HV by immersion in mineral water media. The lowest hardness was obtained at 207 HV with SAE 40 oil media immersion. Meanwhile, the non-treatment material hardness is 150 HV. In this case, there was an increase in the highest hardness of about two times compared to non-treated specimens. Observation of the microstructure shows that the grain size of the mineral water quenching specimens looks smaller than that of the non-treatment models. This phenomenon supports the idea that quenching can increase the surface hardness of the gear sprocket.

2-dimensional mathematical model of axisymmetric transient industrial quenched low carbon steel bar, to examine the influence of process history on metallurgical and material characteristics, a water-cooled model based on the finite element technique was adopted. A 2-dimensional axisymmetric mathematical model was utilized to predict temperature history and, as a result, the hardness of the quenched steel bar at any node (point). The LHP (lowest hardness point) is evaluated. In this paper, specimen points hardness was evaluated by the transformation of determined characteristic cooling time for phase conversion t8/5 to hardness. The model can be used as a guideline to design cooling approach to attain the desired microstructure and mechanical properties, for example, hardness. The mathematical model was verified and validated by comparing its hardness results to the results of commercial finite element software. The comparison demonstrates that the proposed model is reliable.

Differential scanning calorimetry (DSC) was used to study the transformation process of 1Cr13 steel under quenching condition. The DSC curves were measured from 1 050 °C to room temperature at the cooling rate of 10, 20, 30, 50 °C /min, respectively. The Flynn-Wall-Ozawa method was used to obtain the activation energy of the transformation process of 1Cr13 steel under quenching condition. The kinetic mechanism functions of the transformation process of 1Cr13 steel under quenching condition were also investigated by Criado-Ortega methods. The results show that the activation energy is related to the phase transition fraction. It means the transformation process of 1Cr13 steel under quenching condition is not a simple one-step reaction but a complex multi-step reaction.

Fluorescent sensors have emerged as powerful tools in analytical chemistry, enabling the detection and quantification of specific analytes or target molecules. This review provides an indepth analysis of different approaches in designing of fluorescent sensors. It explores the selection and modification of fluorophores, the incorporation of molecular recognition elements, and the utilization of various sensing mechanisms. Research and advancements in this field continue to enhance the capabilities of fluorescent sensors, making them indispensable in various scientific disciplines and driving future developments in analytical chemistry. [ABSTRACT FROM AUTHOR]

A rapid, novel and cost‐effective spectrofluorimetric method developed to determine moxifloxacin (MFX) in pharmaceutical preparations because MFX in a pH 10 medium could reduce the fluorescence intensity of l‐tryptophan. The maximum fluorescence excitation and emission wavelengths were found to be 280 and 363 nm respectively. A range of factors affecting fluorescence quenching and the effect of co‐existing substances were investigated. Fluorescence quenching values (ΔF = FL‐tryptophan − FMoxi‐L‐tryptophan) displayed a strong linear relationship with the MFX concentration ranging from 0.2 to 8.0 μg/ml under optimum conditions. The limit of detection was found to be 6.1 × 10−4 μg/ml. The proposed method was shown to be suitable for MFX determination in pharmaceutical tablets and biological fluids by the linearity, recovery and limit of detection. The spectrofluorimetric approach that has been developed is extremely eco‐friendly, as evidenced by the fact that all the experimental components and solvents were safe for the environment. [ABSTRACT FROM AUTHOR]

To achieve sustainable production of hydrogen fuel through electrochemical water splitting, efficient and low-cost electrocatalysts for the kinetically sluggish oxygen evolution reaction (OER) are urgently desirable. Herein, a calcination-quenching strategy to synthesize core-shell NiO@NiSe x nanorods (NiSe x is the core and NiO is the shell) with tailored surface compositions and structures is reported. In the calcination step, a NiO@NiSe x nanostructure supported on nickel foam (NF) (denoted as NiO@NiSe x /NF) was formed via oxidative calcination of highly conductive NiSe in situ grown on NF (denoted as NiSe/NF). Subsequently, the as-obtained NiO@NiSe x /NF electrode at the high temperature state was rapidly placed in a cold iron salt solution to achieve the quenching process. The results conclusively demonstrated that the quenching process resulted in iron doping and vacancies generation on the surface of NiO, effectively reconfiguring the desired surface of the catalyst, thus giving rise to notably enhanced electrocatalytic performance for OER in alkaline media. As a result, the quenched-engineered NiO@NiSe x /NF electrode requires ultralow overpotentials of 231 and 265 mV to yield current densities of 10 and 100 mA cm−2, respectively, and presents a very low Tafel slope of 28.9 mV dec−1 as well as excellent durability, with the performance superior to most of metal oxide catalysts reported to date. This work extends the use of quenching chemistry in fabrication of high-performance metal oxide catalysts for energy related applications. Self-supported NiO@NiSe x hybrid grown on NF with tailored surface compositions and structures was successfully prepared through a calcination-quenching strategy and demonstrated to be a highly efficient electrocatalyst for oxygen evolution reaction. [Display omitted] [ABSTRACT FROM AUTHOR]