Energetic Salts Based on an Oxygen‐Containing Cation: 2,4‐Diamino‐1,3,5‐triazine‐6‐one

A family of energetic salts with high thermal stability and low impact sensitivity based on an oxygen‐containing cation, 2,4‐diamino‐1,3,5‐triazine‐6‐one, were synthesized and fully characterized by IR and multinuclear (¹H, ¹³C) NMR spectroscopy, elemental analysis, and differential scanning calorimetry. Insights into their sensitivities towards impact, friction, and electrostatics were gained by submitting the materials to standard tests. The structures of 2,4‐diamino‐1,3,5‐triazine‐6‐one nitrate, 2,4‐diamino‐1,3,5‐triazine‐6‐one sulfate, 2,4‐diamino‐1,3,5‐triazine‐6‐one perchlorate, 2,4‐diamino‐1,3,5‐triazine‐6‐one 5‐nitrotetrazolate were determined by single‐crystal X‐ray diffraction; their densities are 1.691, 1.776, 1.854, and 1.636 g cm^?3, respectively. Most of the salts decompose at temperatures over 180 °C; in particular, the salts 2,4‐diamino‐1,3,5‐triazine‐6‐one nitrate and 2,4‐diamino‐1,3,5‐triazine‐6‐one perchlorate, which decompose at 303.3 and 336.4 °C, respectively, are fairly stable. Furthermore, most of the salts exhibit excellent impact sensitivities (>40 J), friction sensitivities (>360 N), and are insensitive to electrostatics. The measured densities of these energetic salts range from 1.64 to 2.01 g cm^?3. The detonation pressure values calculated for these salts range from 14.6 to 29.2 GPa, and the detonation velocities range from 6536 to 8275 m s^?1; these values make the salts potential candidates for thermally stable and insensitive energetic materials.     

Asymmetric Michael Addition/Intramolecular Cyclization Catalyzed by Bifunctional Tertiary Amine–Squaramides: Construction of Chiral 2‐Amino‐4H‐chromene‐3‐Carbonitrile Derivatives

The efficient asymmetric Michael addition/intramolecular cyclization of malononitrile with dienones catalyzed by a chiral bifunctional tertiary amine–squaramide catalyst for the synthesis of chiral 2‐amino‐4H‐chromene‐3‐carbonitrile derivatives was developed. The corresponding products were obtained in good to excellent yields (up to 99 %) with excellent enantioselectivities (up to 98 % ee) for most of the bisarylidenecyclopentanones.     

Comparison of Loading Efficiency between Hyperbranched Polymers and Cross‐Linked Nanogels at Various Branching Densities

The effect of branching point structures and densities is studied between azido‐containing hyperbranched polymers and cross‐linked nanogels on their loading efficiency of alkynyl‐containing dendron molecules. Hyperbranched polymers that contained “T”‐shaped branching linkage from which three chains radiated out and cross‐linked nanogels that contained “X”‐shaped branching linkage with four radiating chains are synthesized in microemulsion using either atom transfer radical polymerization (ATRP) or conventional radical polymerization (RP) technique. Both polymers have similar density of azido groups in the structure and exhibit similar hydrodynamic diameter in latexes before purification. Subsequent copper‐catalyzed azide–alkyne cycloaddition reactions between these polymers and alkynyl‐containing dendrons in various sizes (G1–G3) demonstrate an order of dendron loading efficiencies (i.e., final conversion of alkynyl‐containing dendron) as hyperbranched polymers > nanogels synthesized by ATRP > nanogels synthesized by RP. Decreasing the branching density or using smaller dendron molecules increases the click efficiency of both polymers. When G2 dendrons with a molecular weight of 627 Da are used to click with the hyperbranched polymers composed of 100% inimer, a maximum loading efficiency of G2 in the loaded hyperbranched polymer is 58% of G2 by weight. These results represent the first comparison between hyperbranched polymers and cross‐linked nanogels to explore the effect of branching structures on their loading efficiencies.

     

Well‐Defined High Molecular Weight Polystyrene with High Rates and High Livingness Synthesized via Two‐Stage RAFT Emulsion Polymerization

A highly living polymer with over 100 kg mol⁻¹ molecular weight is very difficult to achieve by controlled radical polymerization since the unavoidable side reactions of irreversible radical termination and radical chain transfer to monomer reaction become significant. It is reported that over 500 kg mol⁻¹ polystyrene with high livingness and low dispersity could be synthesized by a facile two‐stage reversible addition–fragmentation transfer emulsion polymerization. The monomer conversion reaches 90% within 10 h. High livingness of the product is ascribed to the extremely low initiator concentration and the chain transfer constant for monomer unexpectedly much lower than the well‐accepted values in the conventional radical polymerization. The two‐stage monomer feeding policy much decreases the dispersity of the product.

     

Ultrabroadband superoscillatory lens composed by plasmonic metasurfaces for subdiffraction light focusing

Conventional optics is diffraction limited due to the cutoff of spatial frequency components, and evanescent waves allow subdiffraction optics at the cost of complex near‐field manipulation. Recently, optical superoscillatory phenomena were employed to realize superresolution lenses in the far field, but suffering from very narrow working wavelength band due to the fragility of the superoscillatory light field. Here, an ultrabroadband superoscillatory lens (UBSOL) is proposed and realized by utilizing the metasurface‐assisted law of refraction and reflection in arrayed nanorectangular apertures with variant orientations. The ultrabroadband feature mainly arises from the nearly dispersionless phase profile of transmitted light through the UBSOL for opposite circulation polarization with respect to the incident light. It is demonstrated in experiments that subdiffraction light focusing behavior holds well with nearly unchanged focal patterns for wavelengths spanning across visible and near‐infrared light. This method is believed to find promising applications in superresolution microscopes or telescopes, high‐density optical data storage, etc.

     

Broadband spin‐controlled focusing via logarithmic‐spiral nanoslits of varying width

This work presents analytical, numerical and experimental demonstrations of light diffracted through a logarithmic spiral (LS) nanoslit, which forms a type of switchable and focus‐tunable structure. Owing to a strong dependence on the incident photon spin, the proposed LS‐nanoslit converges incoming light of opposite handedness (to that of the LS‐nanoslit) into a confined subwavelength spot, while it shapes light with similar chirality into a donut‐like intensity profile. Benefitting from the varying width of the LS‐nanoslit, different incident wavelengths interfere constructively at different positions, i.e., the focal length shifts from 7.5 μm (at λ = 632.8 nm) to 10 μm (at λ = 488 nm), which opens up new opportunities for tuning and spatially separating broadband light at the micrometer scale.

     

Unveiling the correlation between non‐diffracting tractor beam and its singularity in Poynting vector

This paper investigates the singular optics of nonparaxial light beams in the near field when the light behaves as a tractor beam. New insights into the optical pulling force, which is usually represented by integrating the stress tensor at a black box enclosing the object, are interpreted by the optical singularity of the Poynting vector. The negative nonconservative pulling force originates from the transfer of the azimuthal Poynting vector to the longitudinal component partly owing to the presence of a scatterer. The separatrice pattern and singularity shifts of the Poynting vector unanimously exhibit a differentiable near‐field distribution in the presence of optical pulling force. A new method is established to calculate the near‐field optical force using the differential Poynting vector in the far field. The results obtained provide a clear physical interpretation of the light–matter interaction and manifest the significance of singular optics in manipulating objects.

     

Solidification of LiCl–Li2O oxide reduction salt into sodalite by a spark plasma sintering

Journal of Radioanalytical and Nuclear Chemistry - The waste LiCl–Li2O oxide reduction salt was solidified and transformed into sodalite by the spark plasma sintering method. Compared with...     

Energy Band Alignment and Redox-Active Sites in Metalloporphyrin-Spaced Metal-Catechol Frameworks for Enhanced CO2 Photoreduction

Two new chemically stable metalloporphyrin-bridged metal-catechol frameworks, InTCP-Co and FeTCP-Co, were constructed to achieve artificial photosynthesis without additional sacrificial agents and photosensitizers. The CO₂ photoreduction rate over FeTCP-Co considerably exceeds that obtained over InTCP-Co, and the incorporation of uncoordinated hydroxyl groups, associated with catechol, into the network further promotes the photocatalytic activity. The iron-oxo coordination chain assists energy band alignment and provides a redox-active site, and the uncoordinated hydroxyl group contributes to the visible-light absorptance, charge-carrier transfer, and CO₂-scaffold affinity. With a formic acid selectivity of 97.8 %, FeTCP-OH-Co affords CO₂ photoconversion with a reaction rate 4.3 and 15.7 times higher than those of FeTCP- Co and InTCP-Co, respectively. These findings are also consistent with the spectroscopic study and DFT calculation.     

Vitamin D Inhibits the Early Aggregation of α-Synuclein and Modulates Exocytosis Revealed by Electrochemical Measurements

Alpha-synuclein (α-Syn) localizes at presynaptic terminal and modulates synaptic functions. Increasing evidence demonstrate that α-Syn oligomers, forming at the early of aggregation, are cytotoxic and is thus related to brain neurodegenerative diseases. Herein, we find that vitamin D (VD) can reduce neurocytotoxicity. The reduced neurocytotoxicity might be attributed to the less amount of large-sized α-Syn oligomers inhibited by VD, measured by electrochemical collision at single particle level, which are not observable with traditionally ensembled method. Single-cell amperometry (SCA) results show that VD can recover the amount of neurotransmitter release during exocytosis induced by α-Syn oligomers, further verifying the neuroprotection of VD. Our study reveals the neuroprotective role of VD through inhibiting α-Syn aggregation, which is envisioned to be of great importance in treatment and prevention of the neurodegenerative diseases.