Now showing 1 - 10 of 41
  • Publication
    A catalytic enantioselective stereodivergent aldol reaction
    (2023)
    Rahman, Md. Ataur
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    Cellnik, Torsten
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    Ahuja, Brij Bhushan
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    ;
    Healy, Alan R.
    The aldol reaction is among the most powerful and strategically important carbon–carbon bond–forming transformations in organic chemistry. The importance of the aldol reaction in constructing chiral building blocks for complex small-molecule synthesis has spurred continuous efforts toward the development of direct catalytic variants. The realization of a general catalytic aldol reaction with control over both the relative and absolute configurations of the newly formed stereogenic centers has been a longstanding goal in the field. Here, we report a decarboxylative aldol reaction that provides access to all four possible stereoisomers of the aldol product in one step from identical reactants. The mild reaction can be carried out on a large scale in an open flask, and generates CO2 as the only by-product. The method tolerates a broad substrate scope and generates chiral β-hydroxy thioester products with substantial downstream utility.
      31  291Scopus© Citations 6
  • Publication
    A Low-Temperature-Resistant Flexible Organic Crystal with Circularly Polarized Luminescence
    (2022) ;
    Pan, Xiuhong
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    Zheng, Anyi
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    Di, Qi
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    Duan, Pengfei
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    Ye, Kaiqi
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    Naumov, Panče
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    Zhang, Hongyu
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    Yu, Xu
    Flexible organic crystals with unique mechanical properties and excellent optical properties are of paramount significance for their wide applications in various research fields such as adaptive optics and soft robotics. However, low-temperature-resistant flexible organic crystal with circularly polarized luminescence (CPL) ability has never been reported. Herein, chiral organic crystals with CPL activity and low-temperature flexibility (77 K) are fabricated by the solvent diffusion method from chiral Schiff bases, S(R)-4- b romo-2-(((1- p henyl e thyl)imino) m ethyl) p henol (S(R)-BPEMP). The corresponding chiroptical properties for the two enantiomeric crystals were thoroughly investigated, including the measurements of circular dichroism (CD) and CPL. To the best of our knowledge, this is the first report on low-molecular-weight flexible organic crystals with CPL activity, and we believe that the results will give a new impetus to the research of organic crystals.
    Scopus© Citations 34  43  272
  • Publication
    A Thermosalient and Mechanically Compliant Organic Crystalline Optical Waveguide Switcher
    (2024)
    Di, Qi
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    Al‐Handawi, Marieh B.
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    ;
    Naumov, Panče
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    Zhang, Hongyu
    The dense and ordered molecular arrangements endow dynamic molecular crystals with fast response, rapid energy conversion, low energy dissipation, and strong coupling between heat/light and mechanical energy. Most of the known dynamic crystals can only respond to a single stimulus, and materials that can respond to multiple stimuli are rare. Here, we report an organic crystalline material that can be bent plastically and is also thermosalient, as its crystals can move when they undergo a reversible phase transition. The crystals transmit light regardless of their shape or crystalline phase. The combination of light transduction and reversible thermomechanical deformation provides an opportunity to switch the waveguiding capability of the material in a narrow temperature range, which holds a tremendous potential for applications in heat‐averse electronic components, such as central processing units. Unlike existing electronics, the material we report here is completely organic and therefore much lighter, potentially reducing the overall weight of electronic circuits.
      11
  • Publication
    Autonomous and directional flow of water and transport of particles across a subliming dynamic crystal surface
    (2023)
    Commins, Patrick
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    Al-Handawi, Marieh B.
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    Rezgui, Rachid
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    ;
    McNamara, Mark
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    Naumov, Panče
    Chemical and morphological traits of natural substrates that can propel and transport fluids over their surfaces have long provided inspiration for the engineering of artificial materials that can harvest and collect water from aerial humidity. Here we report that the gradual widening of parallel microchannels on a surface of a slowly subliming hexachlorobenzene crystal can promote the autonomous and bidirectional transduction of condensed aerial water. Driven by topology changes on the surface of the crystal and water exchange with the gas phase, droplets of condensed water migrate over the crystal. These droplets are also able to transport silver particles and other particulate matter, such as dust. The velocity of the particles was shown to be dependent on both the sublimation rate of the crystal and the relative humidity of its environment. This example of a sublimation-powered water flow demonstrates that topological surface changes accompanying crystal phase transitions can be harnessed to transport liquid and solid matter over surfaces.
      15Scopus© Citations 7
  • Publication
    Bending, Twisting, and Propulsion of Photoreactive Crystals by Controlled Gas Release
    (2024)
    Yu, Chunjiao
    ;
    Jiang, Xiaofan
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    Al‐Handawi, Marieh B.
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    Naumov, Panče
    ;
    ;
    Yu, Qi
    ;
    Wang, Guoming
    The rapid release of gas by a chemical reaction to generate momentum is one of the most fundamental ways to elicit motion that could be used to sustain and control the motility of objects. We report that hollow crystals of a three‐dimensional supramolecular metal complex that releases gas by photolysis can propel themselves or other objects and advance in space when suspended in mother solution. In needle‐like regular crystals, the reaction occurs mainly on the surface and results in the formation of cracks that evolve due to internal pressure; the expansion on the cracked surface of the crystal results in bending, twisting, or coiling of the crystal. In hollow crystals, gas accumulates inside their cavities and emanates preferentially from the recess at the crystal terminus, propelling the crystals to undergo directional photomechanical motion through the mother solution. The motility of the object which can be controlled externally to perform work delineates the concept of “crystal microbots”, realized by photoreactive organic crystals capable of prolonged directional motion for actuation or delivery. Within the prospects, we envisage the development of a plethora of light‐weight, efficient, autonomously operating robots based on organic crystals with high work capacity where motion over large distances can be attained due to the large volume of latent gas generated from a small volume of the crystalline solid.
    Scopus© Citations 2  8
  • Publication
    Bioinspired soft robots based on organic polymer-crystal hybrid materials with response to temperature and humidity
    (2023)
    Yang, Xuesong
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    Lan, Linfeng
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    Pan, Xiuhong
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    Di, Qi
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    Liu, Xiaokong
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    Naumov, Panče
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    Zhang, Hongyu
    The capability of stimulated response by mechanical deformation to induce motion or actuation is the foundation of lightweight organic, dynamic materials for designing light and soft robots. Various biomimetic soft robots are constructed to demonstrate the vast versatility of responses and flexibility in shape-shifting. We now report that the integration of organic molecular crystals and polymers brings about synergistic improvement in the performance of both materials as a hybrid materials class, with the polymers adding hygroresponsive and thermally responsive functionalities to the crystals. The resulting hybrid dynamic elements respond within milliseconds, which represents several orders of magnitude of improvement in the time response relative to some other type of common actuators. Combining molecular crystals with polymers brings crystals as largely overlooked materials much closer to specific applications in soft (micro)robotics and related fields.
      50  1Scopus© Citations 58
  • Publication
    Comparative Study of Polyethylene Films Embedded with Oxide Nanoparticles of Granulated and Free-Standing Nature
    (2022) ; ; ;
    Le Guyon, Valerie
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    ; ;
    Angastiniotis, Nicos
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    Koutsokeras, Loukas
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    Duponchel, Benoît
    Nanocomposite polymer films are a very diverse research field due to their many applications. The search for low-cost, versatile methods, producing regulated properties of the final products, has thus become extremely relevant. We have previously reported a bulk-scale process, dispersing granulated metal oxide nanoparticles, of both unary and multi-component nature, in a low-density polyethylene (LDPE) polymer matrix, establishing a reference in the produced films’ optical properties, due to the high degree of homogeneity and preservation of the primary particle size allowed by this method. In this work, unmodified, free-standing particles, namely zinc oxide (ZnO), titanium dioxide (TiO2), aluminum oxide (Al2O3), and silicon dioxide (SiO2) are blended directly with LDPE, and the optical properties of the fabricated films are compared to those of films made using the granulation process. The direct blending process evidently allows for control of the secondary particle size and ensures a homogeneous dispersion of the particles, albeit to a lesser extent than the granulation process. Despite the secondary particle size being comparatively larger than its granulated counterpart, the process still provides a regulated degree of deagglomeration of the free-standing oxide particles, so it can be used as a low-cost alternative. The regulation of the secondary particle size tunes the transmission and reflection spectra, in both unary and mixed oxide compositions. Finally, the direct blending process exhibits a clear ability to tune the energy band gap in mixed oxides.
      85  174
  • Publication
    Construction of Microporous Zincophilic Interface for Stable Zn Anode
    (2023)
    Yang, Xin
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    Shu, Tie
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    Huang, Haoyu
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    Yi, Hongquan
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    Zhang, Yanchi
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    Wei, Xiao
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    Zhang, Yuxin
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    Ma, Minghao
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    Liu, Xingyuan
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    Yao, Kexin
    Aqueous zinc ion batteries (AZIBs) are promising electrochemical energy storage devices due to their high theoretical specific capacity, low cost, and environmental friendliness. However, uncontrolled dendrite growth poses a serious threat to the reversibility of Zn plating/stripping, which impacts the stability of batteries. Therefore, controlling the disordered dendrite growth remains a considerable challenge in the development of AZIBs. Herein, a ZIF-8-derived ZnO/C/N composite (ZOCC) interface layer was constructed on the surface of the Zn anode. The homogeneous distribution of zincophilic ZnO and the N element in the ZOCC facilitates directional Zn deposition on the (002) crystal plane. Moreover, the conductive skeleton with a microporous structure accelerates Zn2+ transport kinetics, resulting in a reduction in polarization. As a result, the stability and electrochemical properties of AZIBs are improved. Specifically, the ZOCC@Zn symmetric cell sustains over 1150 h at 0.5 mA cm−2 with 0.25 mA h cm−2, while the ZOCC@Zn half-cell achieves an outstanding Coulombic efficiency of 99.79% over 2000 cycles. This work provides a simple and effective strategy for improving the lifespan of AZIBs.
      18  1Scopus© Citations 2
  • Publication
    Effects of the addition of a high energy density fuel, adamantane to diesel on its cetane number, sooting propensity, and soot nanostructural properties
    (2022)
    Al Zaabi, Alanood
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    Raj, Abhijeet
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    Elkadi, Mirella
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    Anjum, Dalaver
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    George, Abraham
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    Al Shebli, Mariam Nasser
    Soot particles, released during diesel combustion, adversely affect human health and the environment. Some studies suggest blending diesel with oxygenated fuels to reduce soot emissions, though it also reduces fuel economy and may produce new pollutants such as aldehydes. Another method to reduce soot could be to increase its reactivity by altering its physicochemical properties (e.g., introducing curvatures in its nanostructures) so that it oxidizes inside the engine or flame. In this direction, a cyclic high-density hydrocarbon fuel, adamantane is studied as an additive for diesel to determine its effect on cetane number, threshold sooting index, soot reactivity, and soot nanostructural properties. The addition of up to 6.75 wt% of adamantane in diesel significantly increased the smoke point of diesel from 18 to 29 mm (and threshold sooting index decreased by 44%), indicating a drastic drop in fuel sooting tendency. Adamantane addition in a small amount to diesel minimally affected the cetane number. To understand the impact of adamantane addition to diesel on the characteristics of soot particles, different techniques including TGA, HRTEM, XRD, EDX, and EELS were used. It is observed that adamantane enhances curvatures in soot nanostructures and reduces the size of fringes in soot and its aromatic content, and all of these property variations improve soot reactivity to improve its oxidation in flames or engines and reduce soot emission.
      1  8
  • Publication
    Elastic Organic Crystals as Bioinspired Hair‐Like Sensors
    (2023)
    Yousuf, Soha
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    Halabi, Jad Mahmoud
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    Tahir, Ibrahim
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    Ahmed, Ejaz
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    Rezgui, Rachid
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    Laws, Praveen
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    Daqaq, Mohammed
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    Naumov, Panče
    One of the typical haptic elements are natural hairy structures that animals and plants rely on for feedback. Although these hair sensors are an admirable inspiration, the development of active flow sensing components having low elastic moduli and high aspect ratios remains a challenge. Here, we report a new sensing approach based on a flexible, thin and optically transmissive organic crystal of high aspect ratio, which is stamped with fluorescent dye for tracking. When subjected to gas flow and exposed to laser, the crystal bends due to exerted pressure and acts as an optical flow (hair) sensor with low detection limit (≈1.578 m s−1) and fast response time (≈2.70 s). The air-flow-induced crystal deformation and flow dynamics response are modelled by finite element analysis. Due to having a simple design and being lightweight and mechanically robust this prototypical crystal hair-like sensor opens prospects for a new class of sensing devices ranging from wearable electronics to aeronautics.
      15Scopus© Citations 18