Room Temperature Research Articles

Modulation of fluorescence and phosphorescence of organoboron compounds from ortho-substituted phenolic Schiff bases by structural modification.

Light emission from organoboron compounds of Schiff bases is found to depend strongly on their chemical structure. Two of these compounds (OB1 and OB2), which contain a benzene ring between the Schiff base moieties, exhibit weak fluorescence in methanol, with marked viscosity dependence. Fluorescence lifetimes of these compounds are in picosecond timescale, as determined by femtosecond optical gating (FOG). A significant enhancement in fluorescence intensity and lifetime is observed at 77 K, indicating the operation of an activated nonradiative process. Using fluorescence lifetime imaging microscopy (FLIM), OB1 and OB2 are shown to be potential membrane probes. The third (OB3), which is devoid of this benzene ring, exhibits relatively stronger fluorescence with nanosecond lifetimes at room temperature. No viscosity dependence is observed in this case. The emission spectrum at 77 K is markedly more intense and exhibits an additional red shifted structured feature, which persists for a few seconds. Hence, OB3 seems to have greater promise not only as fluorescent probe but also for light harvesting. The marked improvement of the light emission properties of OB3 compared with OB1 and OB2 is likely to serve as a pointer for the design of Schiff base-derived organoboron luminophores with diverse potential applications.

A Radical Solution to Nucleophilic Substitution: Photocatalyzed Phosphinylation of Alkyl Halides at Room Temperature

A Radical Solution to Nucleophilic Substitution: Photocatalyzed Phosphinylation of Alkyl Halides at Room Temperature

Chemical modification of Aspergillus flavus extracted chitosan for uranium remediation from aqueous solution

ABSTRACT Fungal chitosan derived from Aspergillus flavus AFC was employed in the synthesis of a cross-linked polystyrene biopolymer, P-AFC, which was investigated as a biosorbent material for the effective removal of uranium ions U(VI) from aqueous solutions. The characterisation of both fungal biopolymers was achieved using Brunauer-Emmett-Teller (BET) analysis, scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR) spectroscopy. The efficacy of the P-AFC biosorbent in removing uranium from an aqueous solution reached equilibrium in 240 minutes at an initial uranium concentration of 50 ppm, a biosorbent amount of 0.4 g/L, and a pH of 4.0. The maximum biosorption capacity for U(VI) was determined to be 128.21 mg g−1 at room temperature, calculated using the Langmuir model. Furthermore, kinetic and thermodynamic analyses indicated that the biosorption process was characterised by chemisorption, was exothermic, and occurred spontaneously (ΔHo = –59.98 kJ mol−1 and ΔSo = –113.32 J K−1 mol−1). Recycling experiments demonstrated that the material could be reused up to five times without a noticeable decrease in removal efficiency.

Convergent Paired Electrolysis for [3+2] Cycloaddition of Azidotrimethylsilane with N-Heterocycles.

A widely used method to obtain tetrazoles is through the azide and nitrile [3+2] cycloaddition. However, this process often involves using non-recyclable transition metals or Lewis acid catalysts and stoichiometric amounts of oxidants and additives, which reduces atom efficiency. We have discovered a convergent paired electrochemical reaction to perform this cycloaddition reaction, without the need for metal catalysts or oxidants. This tetrazolation strategy uses azidotrimethylsilane (TMSN3) and N-heterocycles in an undivided cell at a constant current. We use a mixture of CH3CN and equivalent amounts of H2O as co-solvent at room temperature. It is crucial to produce a stoichiometric amount of active hydroxyl ions through the cathodic reduction of water. Cyclic voltammetry (CV) studies and control experiments confirm that the cycloaddition reaction is specific to the electrode electron transfer process, eliminating the need for a mediator to shuttle electrons. This metal- and oxidant-free strategy is highly compatible with different functional groups and produces products with moderate to good yields. We have successfully tetrazolated bioactive compounds at a late stage, scaled up batches efficiently, and synthesized free amino-containing N-heterocycles via denitrogenation of tetrazoles.

Sodium Hypochlorite Pentahydrate as a Chlorinating Reagent: Application to the Tandem Conversion of β,γ-Unsaturated Carboxylic Acids to α,β-Unsaturated Lactones

Sodium hypochlorite pentahydrate (NaClO·5H2O, 1) has recently been employed in organic synthesis as an oxidant for alcohols, sulfides, glycols, etc. In most of these reactions, however, reagent 1 functions just as a simple oxidant, and the variations of the reactions have not been well explored. In this study, we report another useful and fascinating reaction, in which reagent 1 functions as a green chlorinating reagent toward β,γ-unsaturated carboxylic acid (2). When substrate 2 was stirred at room temperature with 1 (2 eq) in acetonitrile for 1 h, α,β-unsaturated lactone (3) was obtained in moderate yields (up to 62%). The same reaction proceeded in various organic and aqueous solvents as well. When excess reagent 1 was employed, lactone 3 was further oxidized to the corresponding epoxide (4) for some cases. The conversion is initiated by electrophilic attack of HOCl to the C=C bond of 2 to generate a chloronium ion intermediate, which is cyclized to β-chlorolactone (5) and then 3 through the elimination of HCl. The usefulness of 1 as a chlorinating reagent was further demonstrated in the electrophilic substitution of activated aromatic compounds.

High-entropy oxide (FeCoNiCrMn)3O4 for room-temperature NO2 sensors

High-entropy oxides (HEOs) with a multi-cation structure have attracted significant attention in the fields of electrochemistry owing to their high entropy stability and cocktail effect. However, there has been very limited research on the use of HEO in the field of sensing. In this work, we utilized FeCoNiCrMn high-entropy alloys as the precursor to synthesize (FeCoNiCrMn)3O4 HEO and investigated their crystal structure, microscopic morphology, elemental valence state information, and gas sensing performance. The sensor exhibited decent response to NO2 at room temperature (RT) without any modification or sensitization methods. To verify the gas sensing mechanism, we simulated the interaction between five metal elements in HEO and the NO2 molecules by density functional theory, which reveals a crucial synergistic effect from the multiple cations to enhance the adsorption and charge transfer of NO2 molecules. This work explores the application potential of (FeCoNiCrMn)3O4 in low-power gas sensors and enriches the material selection for RT sensors.

Ultrasound-assisted Cu(II) Strecker-functionalized organocatalyst for green azide-alkyne cycloaddition and Ullmann reactions.

A new aminonitrile-functionalized Fe3O4 has been synthesized via the Strecker reaction, the designed aminonitrile ligand on the surface of the magnetic core coordinated to copper(II) to obtain the final new catalyst. The fabricated nanocatalyst was characterized by Fourier transform Infrared (FT-IR), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray spectroscopy (EDX), Transmission Electron Microscopy (TEM), Vibrating-Sample Magnetometer (VSM), Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), and Thermogravimetric Analysis (TGA). The high tendency of nitrogens in the aminonitrile functional group to make a complex with Cu(II) has caused the practical activity of this nucleus in this catalyst. This nanocatalyst performance was investigated in azide-alkyne Huisgen cycloaddition (3 + 2) reaction for achieving to 1,4-disubstituted 1,2,3-triazoles in water as a green media at room temperature. In another try, Classic Ullmann Reaction was investigated for the synthesis of biaryls at 85°C promoted by ultrasonic condition (37 kHz). The reaction scope was explored using different reactants and the results of using this developed catalytic system demonstrated its capacity to reduce the reaction time and enhance the reaction efficiency to provide good to excellent product yield. Conversely, the simple recycling and reusability of this catalyst for at least six times without any noticeable leaching of copper makes it a potential future catalyst for synthesizing such compounds.

Epitaxially regrown quantum dot photonic crystal surface emitting lasers

Quantum dot-based epitaxially regrown photonic crystal surface emitting lasers are demonstrated at room temperature. The GaAs-based devices, which are monolithically integrated on the same wafer, exhibit ground state lasing at ∼1230 nm and excited state lasing at ∼1140 nm with threshold current densities of 0.69 and 1.05 kA/cm2, respectively.

Dehydration‐Induced Cluster Consolidation in a Metal‐Organic Framework for Sieving Hexane Isomers

AbstractMetal‐organic frameworks (MOFs) that exhibit dynamic phase‐transition behavior under external stimuli could have great potential in adsorptive separations. Here we report on a zinc‐based microporous MOF (JNU‐80) and its reversible transformation between two crystalline phases: large pore (JNU‐80‐LP) and narrow pore (JNU‐80‐NP). Specifically, JNU‐80‐LP can undergo a dehydration‐induced cluster consolidation under heat treatment, resulting in JNU‐80‐NP with a reduced channel that allows exclusion of di‐branched hexane isomers while high adsorption of linear and mono‐branched hexane isomers. We further demonstrate the fabrication of MOF‐polymer composite (JNU‐80‐NP‐block) and its application in the purification of di‐branched isomers from liquid‐phase hexane mixtures (98 % di‐branched) at room temperature, affording the di‐branched hexane isomers with 99.5 % purity and close to 90 % recovery rate over ten cycles. This work illustrates an interesting dehydration‐induced cluster consolidation in MOF structure and the ensuing channel shrinkage for sieving di‐branched hexane isomers, which may have important implications for the development of MOFs with dynamic behavior and their potential applications in non‐thermal driven separation technologies.

Expanding DNA Origami Design Freedom with De Novo Synthesized Scaffolds.

The construction of DNA origami nanostructures is heavily dependent on the folding of the scaffold strand, which is typically a single-stranded DNA genome extracted from a bacteriophage (M13). Custom scaffolds can be prepared in a number of methods, but they are not widely accessible to a broad user base in the DNA nanotechnology community. Here, we explored new design and construction possibilities with custom scaffolds prepared in our cost- and time-efficient production pipeline. According to the pipeline, we de novo produced a variety of scaffolds of specified local and global sequence characteristics and consequent origami constructs of modular arrangement in morphologies and functionalities. Taking advantage of this strategy of template-free scaffold production, we also designed and produced three-letter-coded scaffolds that can fold into designated morphologies rapidly at room temperature. The expanded design and construction freedom immediately brings in many new research opportunities and invites many more on the horizon.

Synthesis of Tetracyclic Benzazole–Condensed Quinazolinones through Triphenylbismuth Dichloride Assisted Cyclodesulfurization

AbstractBenzazole-condensed quinazolinones, such as benzo[4,5]imidazo[2,1-b]- and benzo[4,5]oxazolo[2,3-b]quinazolinones are of a great interest because of their potential applications as biologically active­ substances. Herein, we report that the treatment of various o-phenylenediamines with methyl 2-isothiocyanatobenzoate afforded thioxoquinazolinones, which were reacted in situ with triphenylbismuth dichloride in the presence of K2CO3 to give the desired benzimidazoquinazolinones in good to excellent yields under mild conditions. Triphenylbismuth dichloride promoted the conversion of thioxoquinazolinone to tetracyclic products as an efficient cyclodesulfurization reagent. All the steps in this tandem reaction were performed at room temperature. The present reaction system can also be applied to benzoxazoloquinazolinone synthesis by using 2-aminophenols as the starting material.

Preparation, Characterization, and High-Temperature Anti-Seizing Application of CrAlN-Based Gradient Multilayer Coatings

High-temperature fasteners are metal parts of gas turbines and steam turbines, which work at high temperatures and under stress for a long time. However, the frequent seizures of fasteners bring great trouble to the normal maintenance of power plants. In this paper, three kinds of dense and controllable CrAlN-based gradient multilayer coatings were prepared on the samples and screws by arc ion plating (AIP) technology. The morphology, composition, structure, nano hardness, adhesion, residual stress, and room temperature tribological performance of the coating were investigated. To evaluate the high-temperature, anti-seizing performance, coated screws were heated to 700 °C for 140 h with a torque of 20 N·m. The results indicate that the CrN/CrAlN multilayer coating shows better comprehensive properties. The characterization of coated screws proved that the coating structures obtained on the screws were similar to the flat samples. However, the as-prepared coating on the screws showed different thickness variation rules, which was related to the clamping method, deposition distance, and screw shape. After a simulation service, the thread of the screw remained intact with similar structure and thinner thickness. The above results indicate that the high-temperature seize prevention of fasteners can be successfully achieved by preparing a CrAlN-based multilayer coating, which is suitable for fasteners with service temperatures below 700 °C.

3D Printing of Composite Radiation Shielding for Broad Spectrum Protection of Electronic Systems.

The miniaturization of satellite systems has compounded the need to protect microelectronic components from damaging radiation. Current approaches to mitigate this damage, such as indiscriminate mass shielding, built-in redundancies, and radiation hardened electronics, introduce high size, weight, power, and cost penalties that impact the overall performance of the satellite or launch opportunities. Additive manufacturing provides an appealing strategy to deposit radiation shielding only on susceptible components within an electronic assembly. Here, we describe a versatile material platform and process to conformally print customized composite inks at room temperatures directly and selectively onto commercial-off-the-shelf electronics. The suite of inks uses a flexible styrene-isoprene-styrene block copolymer binder that can be filled with particles of varying atomic densities for varying radiation shielding capabilities. Additionally, the system readily allows blended composites that contain multiple particle species with varying atomic composition within the same structure. The method can produce graded shielding that offers improved radiation attenuation via exquisite control over both shield geometry and composition. We anticipate this alternative to traditional shielding methods will enable the rapid proliferation of the next generation of compact satellite designs. This article is protected by copyright. All rights reserved.

Ultra‐Narrow Linewidth Polariton Lasing in Optically Trapped Bose‐Einstein Condensates at Room Temperature

AbstractPolariton lasing via Bose‐Einstein condensation (BEC) provides a peculiar method to achieve low threshold coherent light sources. Until now, the cryogenic operating temperature required for polariton lasers has hampered the development of polaritonics. Here, a novel approach is first reported to realize the ultra‐narrow linewidth polariton lasing under quasi‐3D quantum confinement at room‐temperature (RT). The potential trap landscape is constructed by ring‐shaped optical excitation, wherein the continuum polariton dispersion is modulated into discrete simple harmonic oscillator (SHO) states. The coherent condensation lasing of trapped polaritons occurs beyond the threshold power. Benefiting from the horizontal quantum confinement, the trapped polariton lasing exhibits an ultra‐narrow linewidth (0.7 meV) and excellent quality factor (Q = 3510). Moreover, the second‐order quantum coherence properties of trapped polariton condensation are determined to reveal the quantum phase transition of Bosonic system. The results offer a feasible route for realizing a low‐threshold ultra‐narrow linewidth polariton laser at RT, which significantly facilitates the fabrication of polariton laser and switches on opportunities for future applications.

Nitrogen‐containing microporous carbon with specific morphology for non‐metallic catalytic NO oxidation at room temperature: The effect of morphology and nitrogen doping

Nitrogen‐containing microporous carbon with specific morphology for non‐metallic catalytic <scp>NO</scp> oxidation at room temperature: The effect of morphology and nitrogen doping

Influence of bonded joint configuration on the cryogenic strength of double-lap composite-metal adhesively bonded joints

The influence of bonded joint configuration on the strength of double-lap carbon fiber reinforced plastic (CFRP)-aluminum alloy bonded joints at cryogenic temperatures was investigated. The bonded joint configurations were double-lap bonded joints composed of CFRP inner and aluminum alloy outer adherends and aluminum alloy inner and CFRP outer adherends. Finite element method (FEM) analysis considering the temperature effect was conducted to evaluate the stress distribution in the adhesive layers of the bonded joints. The calculated peel and shear stresses near the edges of the adhesive layers with the metal inner adherends were lower than those with the composite inner adherends at cryogenic temperatures. The strength of the two types of bonded joints was obtained by tensile tests at room temperature, −50°C, and −150°C. The strength of the bonded joints with the metal inner adherends was higher than that with CFRP inner adherends at cryogenic temperatures because the thermal shrinkage of the metal inner adherends suppressed the stress at the adhesive layer edges.

Selective Oxidation of sp-Bonded Carbon in Graphdiyne/Carbon Nanotubes Heterostructures to Form Dominant Epoxy Groups for Two-Electron Oxygen Reduction.

Two-electron oxygen reduction reaction (2e- ORR) is of great significance to H2O2 production and reversible nonalkaline Zn-air batteries (ZABs). Multiple oxygen-containing sp2-bonded nanocarbons have been developed as electrocatalysts for 2e- ORR, but they still suffer from poor activity and stability due to the limited and mixed active sites at the edges as well as hydrophilic character. Herein, graphdiyne (GDY) with rich sp-C bonds is studied for enhanced 2e- ORR. First, computational studies show that GDY has a favorable formation energy for producing five-membered epoxy ring-dominated groups, which is selective toward the 2e- ORR pathway. Then based on the difference in chemical activity of sp-C bonds in GDY and sp2-C bonds in CNTs, we experimentally achieved conductive and hydrophobic carbon nanotubes (CNTs) covering O-modified GDY (CNTs/GDY-O) through a mild oxidation treatment combined with an in situ CNTs growth approach. Consequently, the CNTs/GDY-O exhibits an average Faraday efficiency of 91.8% toward H2O2 production and record stability over 330 h in neutral media. As a cathode electrocatalyst, it greatly extends the lifetime of 2e- nonalkaline ZABs at both room and subzero temperatures.

A binary ionogel electrolyte for the realization of an all solid-state electrical double-layer capacitor performing at low temperature.

Solid-state electrolytes made of an ionic liquid (IL) confined in a solid matrix, also known as ionogels, have been proposed to prevent electrolyte leakage from electrical double-layer capacitors (EDLCs), and thereof improve their safety. However, making ionogel-based EDLCs performing with a reasonable power at low temperature is still a major challenge due to the high melting point of the confined IL. To overcome such limitations, this contribution discloses ionogel films prepared by encapsulating a binary mixture of 1‑ethyl‑3-methylimidazolium bis(fluorosulfonyl)imide and 1‑ethyl‑3-methylimidazolium tetrafluoroborate - [EMIm][BF4]0.5[FSI]0.5 - into a PVdF-HFP network. Contrary to ionogels prepared from either [EMIm][FSI] or [EMIm][BF4], which display freezing/melting, the crystallization of confined [EMIm][BF4]0.5[FSI]0.5 is quenched in the binary ionogel, which shows only a glass transition at -101 °C. This quenching enables an increased ionicity and ionic diffusion at the interface with the PVdF host network, leading the binary ionogel membrane to display higher ionic conductivity below -20 °C than the parent binary [EMIm][BF4]0.5[FSI]0.5 liquid. Laminate EDLCs built with a binary ionogel separator and hierarchical carbon electrodes operated ideally from -40 °C to room temperature, displaying ca. 4 times larger output energy than a cell implementing the same carbon electrodes together with the binary [EMIm][BF4]0.5[FSI]0.5 ionic liquid.

Elucidating the deformation characteristics of Ti–Ni–Fe based pseudo-binary B2 intermetallics

The room temperature uniaxial compression behavior of homogenized Ti50Ni50-xFex (5≤x ≤ 45) pseudo-binary B2 intermetallics has been investigated. The compressive stress-strain curves of these intermetallics exhibited three different characteristics (a) intermetallics with low Fe content (i.e., Ti50Ni45Fe5 and Ti50Ni40Fe10): exhibited stress induced martensite (SIM) transformation (B2 → B19 ') (marked by a plateau with non-linear elastic regime) followed by significant plastic deformation up to ∼ 40 % strain marked with significant strain hardening, (b) intermetallics with moderate Fe content (Ti50Ni35Fe15) showed no SIM transformation, but a typical smooth elastic-plastic transition with maximum strain to failure of ⁓ 11–12 % was observed, and (c) intermetallics with high Fe content (≥ 25 at. %) displayed a very small strain to failure (≤ 5 %) without visible plastic deformation. The TEM and XRD analysis of the deformed (15 % and 40 % strain) Ti50Ni45Fe5 and Ti50Ni40Fe10 intermetallics indicated the presence of internally twinned martensite variants (MVs) along with severely dislocated banded B2 matrix. The observed contrast in the deformation characteristics has been attributed to the variation in the values of elastic constants (C' and C44) and Zener anisotropy (A) with Fe content. The SIM transformation in Ti50Ni45Fe5 and Ti50Ni40Fe10 occurred at lower values of C' and C44 (due to elastic softening) and relatively low Zener anisotropy A. The significant plastic strain in these two intermetallics was accommodated by the presence and deformation of super intrinsic stacking faults (SISFs) formed by dissociation of 12⟨111⟩ screw super-partials. In contrast, the deformation in the intermetallics with high Fe content (≥ 25 at. %) was governed by the activation of ⟨100⟩ screw dislocations.

Above-room-temperature chiral skyrmion lattice and Dzyaloshinskii–Moriya interaction in a van der Waals ferromagnet Fe3−xGaTe2

Skyrmions in existing 2D van der Waals (vdW) materials have primarily been limited to cryogenic temperatures, and the underlying physical mechanism of the Dzyaloshinskii–Moriya interaction (DMI), a crucial ingredient for stabilizing chiral skyrmions, remains inadequately explored. Here, we report the observation of Néel-type skyrmions in a vdW ferromagnet Fe3−xGaTe2 above room temperature. Contrary to previous assumptions of centrosymmetry in Fe3−xGaTe2, the atomic-resolution scanning transmission electron microscopy reveals that the off-centered FeΙΙ atoms break the spatial inversion symmetry, rendering it a polar metal. First-principles calculations further elucidate that the DMI primarily stems from the Te sublayers through the Fert–Lévy mechanism. Remarkably, the chiral skyrmion lattice in Fe3−xGaTe2 can persist up to 330 K at zero magnetic field, demonstrating superior thermal stability compared to other known skyrmion vdW magnets. This work provides valuable insights into skyrmionics and presents promising prospects for 2D material-based skyrmion devices operating beyond room temperature.