Now showing 1 - 10 of 15
  • Publication
    A Low-Temperature-Resistant Flexible Organic Crystal with Circularly Polarized Luminescence
    (2022) ;
    Pan, Xiuhong
    ;
    Zheng, Anyi
    ;
    Di, Qi
    ;
    Duan, Pengfei
    ;
    Ye, Kaiqi
    ;
    Naumov, Panče
    ;
    Zhang, Hongyu
    ;
    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 1  28  15
  • Publication
    Comparative Study of Polyethylene Films Embedded with Oxide Nanoparticles of Granulated and Free-Standing Nature
    (2022) ; ; ;
    Le Guyon, Valerie
    ;
    ; ;
    Angastiniotis, Nicos
    ;
    Koutsokeras, Loukas
    ;
    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.
      58  44
  • Publication
    Electrically conductive hybrid organic crystals as flexible optical waveguides
    (2022) ;
    Yang, Xuesong
    ;
    Lan, Linfeng
    ;
    Pan, Xiuhong
    ;
    Liu, Xiaokong
    ;
    Song, Yilong
    ;
    Yang, Xueying
    ;
    Dong, Qingfeng
    ;
    Naumov, Panče
    ;
    Zhang, Hongyu
    Hybrid materials capitalize on the properties of individual materials to attain a specific combination of performance assets that is not available with the individual components alone. We describe a straightforward approach to preparation of sandwich-type hybrid dynamic materials that combine metals as electrically conductive components and polymers as bending, momentum-inducing components with flexible organic crystals as mechanically compliant and optically transducive medium. The resulting hybrid materials are conductive to both electricity and light, while they also respond to changes in temperature by deformation. Depending on the metal, their conductivity ranges from 7.9 to 21.0 S µm. The elements respond rapidly to temperature by curling or uncurling in about 0.2 s, which in one typical case corresponds to exceedingly fast deformation and recovery rates of 2187.5° and 1458.3° , respectively. In cyclic operation mode, their conductivity decreases less than 1% after 10,000 thermal cycles. The mechanothermal robustness and dual functionality favors these materials as candidates for a variety of applications in organic-based optics and electronics, and expands the prospects of application of organic crystals beyond the natural limits of their dynamic performance.
      9
  • Publication
    Exceptionally high work density of a ferroelectric dynamic organic crystal around room temperature
    (2022) ;
    Karothu, Durga Prasad
    ;
    Ferreira, Rodrigo
    ;
    Dushaq, Ghada
    ;
    Ahmed, Ejaz
    ;
    Catalano, Luca
    ;
    Halabi, Jad Mahmoud
    ;
    Alhaddad, Zainab
    ;
    Tahir, Ibrahim
    ;
    Mohamed, Sharmarke
    ;
    Rasras, Mahmoud
    ;
    Naumov, Panče
    Dynamic organic crystals are rapidly gaining traction as a new class of smart materials for energy conversion, however, they are only capable of very small strokes (<12%) and most of them operate through energetically cost-prohibitive processes at high temperatures. We report on the exceptional performance of an organic actuating material with exceedingly large stroke that can reversibly convert energy into work around room temperature. When transitioning at 295–305 K on heating and at 265–275 K on cooling the ferroelectric crystals of guanidinium nitrate exert a linear stroke of 51%, the highest value observed with a reversible operation of an organic single crystal actuator. Their maximum force density is higher than electric cylinders, ceramic piezoactuators, and electrostatic actuators, and their work capacity is close to that of thermal actuators. This work demonstrates the hitherto untapped potential of ionic organic crystals for applications such as light-weight capacitors, dielectrics, ferroelectric tunnel junctions, and thermistors.
      14
  • Publication
    Fluorescence-based thermal sensing with elastic organic crystals
    (2022) ;
    Di, Qi
    ;
    Miao, Xiaodan
    ;
    Lan, Linfeng
    ;
    Yu, Xu
    ;
    Liu, Bin
    ;
    Yi, Yuanping
    ;
    Naumov, Panče
    ;
    Zhang, Hongyu
    Operation of temperature sensors over extended temperature ranges, and particularly in extreme conditions, poses challenges with both the mechanical integrity of the sensing material and the operational range of the sensor. With an emissive bendable organic crystalline material, here we propose that organic crystals can be used as mechanically robust and compliant fluorescence-based thermal sensors with wide range of temperature coverage and complete retention of mechanical elasticity. The exemplary material described remains elastically bendable and shows highly linear correlation with the emission wavelength and intensity between 77 K to 277 K, while it also transduces its own fluorescence in active waveguiding mode. This universal new approach expands the materials available for optical thermal sensing to a vast number of organic crystals as a new class of engineering materials and opens opportunities for the design of lightweight, organic fluorescence-based thermal sensors that can operate under extreme temperature conditions such as are the ones that will be encountered in future space exploration missions.
      16
  • Publication
    Hybrid Elastic Organic Crystals that Respond to Aerial Humidity
    (2022) ;
    Xu, Yu
    ;
    Lan, Linfeng
    ;
    Yang, Xuesong
    ;
    Tang, Baolei
    ;
    Liu, Xiaokong
    ;
    Naumov, Panče
    ;
    Zhang, Hongyu
    Reshaping of elongated organic crystals that can be used as semiconductors, waveguides or soft robotic grippers by application of force or light is now a commonplace, however mechanical response of organic crystals to changes in humidity has not been accomplished yet. Here, we report a universal approach to instigating a humidity response into elastically bendable organic crystals that elicits controllable deformation with linear response to aerial humidity while retaining their physical integrity entirely intact. Hygroresponsive bilayer elements are designed by mechanically coupling a humidity-responsive polymer with elastic molecular crystals that have been mechanically reinforced by a polymer coating. As an illustration of the application of these cladded crystalline actuators, they are tested as active optical transducers of visible light where the position of light output can be precisely controlled by variations in aerial humidity. Within a broader context, the approach described here provides access to a vast range of mechanically robust, lightweight hybrid hygroresponsive crystalline materials.
    Scopus© Citations 4  42  3
  • Publication
    Ionic Liquid Engineering in Perovskite Photovoltaics
    (2022) ;
    Wang, Fei
    ;
    Duan, Dawei
    ;
    Singh, Mriganka
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    Sutter‐Fella, Carolin M
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    Lin, Haoran
    ;
    Naumov, Panče
    ;
    Hu, Hanlin
    Over the past decade, perovskite photovoltaics have approached other currently available technologies and proven to be the most prospective type of solar cells. Although the many-sided research in this very active field has generated consistent results with regards to their undisputed consistently increasing power conversion efficiency, it also produced several rather contradictory opinions. Among other important details, debate surrounding their proneness to surface degradation and poor mechanical robustness, as well as the environmental footprint of this materials class remains a moot point. The application of ionic liquids appears as one of the potential remedies to some of these challenges due to their high conductivity, the opportunities for chemical ‘tuning’ of the structure, and relatively lower environmental footprint. This article provides an overview, classification, and applications of ionic liquids in perovskite solar cells. We summarize the use and role of ionic liquids as versatile additives, solvents, and modifiers in perovskite precursor solution, charge transport layer, as well as for interfacial and stability engineering. Finally, challenges and the future prospects for the design and/or selection of ionic liquids with a specific profile that meets the requirements for next generation highly efficient and stable perovskite solar cells are proposed.
    Scopus© Citations 1  113  17
  • Publication
    Organic Crystalline Optical Waveguides That Remain Elastic from -196 to ≈ 200°C
    (2022) ;
    Tang, Shiyue
    ;
    Ye, Kaiqi
    ;
    Commins, Patrick
    ;
    Naumov, Panče
    ;
    Zhang, Hongyu
    Organic crystals that are capable to deform (reversibly or irreversibly) similar to polymer materials have been widely reported over the past ten years. However, most of the reported organic crystals can only be elastically bent within a narrow temperature range, and reports on their thermal behavior that would encourage applications of these energy-transducing elements in extreme conditions are not readily available. This work designs a linear and flat π-conjugated molecule with double intramolecular hydrogen bonds that prevent thermally induced conformational distortions. The molecule assembles as a rigid building block into centimeter-sized wide organic crystals that can be elastically bent over a temperature range spanning close to 400 °C, from −196 to ≈200 °C. The emission wavelength of the crystals is also temperature dependent, and can be continually tuned from 547 to 577 nm upon heating from 20 to ≈200 °C. This inspires the design of a lightweight, organic, elastic optical waveguide where the output energy is controlled by the operating temperature. The wide range of crystal flexibility expands the range of conditions for application of organic crystals as optical waveguides.
      15
  • Publication
    Organic Single‐Crystal Actuators and Waveguides that Operate at Low Temperatures
    (2022) ;
    Linfeng Lan
    ;
    Qi Di
    ;
    Xuesong Yang
    ;
    Xiaokong Liu
    ;
    Panče Naumov
    ;
    Hongyu Zhang
    Applications in extreme conditions, such as those encountered in space exploration, require lightweight materials that can retain their elasticity in extremely cold environments. However, cryogenic treatment of most soft polymeric and elastomeric materials results in complete loss of their ability for elastic flow, whereby such materials that are normally ductile become stiff, brittle, and prone to cracking. Here, a facile method for preparation of hybrid organic crystalline materials that are not only cryogenically robust but are also capable of large, recoverable, and reversible deformation at low temperatures is reported. To that end, flexible organic crystals are first mechanically reinforced by a polymer coating and combined with a thermally responsive polymer. The resulting hybrid materials respond linearly and reversibly to temperatures from −15 to −120 °C without fatigue in air as well as in cold vacuum. The approach proposed here not only circumvents one of the main drawbacks that are inherent to the amorphous nature and has thus far limited the applications of polymeric materials at low temperatures, but it also provides a cost-effective access to a myriad of lightweight sensing, electronic, optical or actuating devices that can operate in low-temperature environmental settings.
      34  6
  • Publication
    Packing-Dependent Mechanical Properties of Schiff Base Crystals
    (2022) ;
    Lan, Linfeng
    ;
    Di, Qi
    ;
    Liu, Bin
    ;
    Xu, Yu-xin
    ;
    Naumov, Panče
    ;
    Zhang, Hongyu
    Flexible luminescent crystals endowed with mechanical compliance are emerging as materials that could be the foundation of future lightweight single-crystal flexible optoelectronics. Multiple mechanical responses (for example, elastic and plastic deformation) are rarely observed with the same material among the reported examples of such materials. Here, we report a Schiff base, (Z)-3-(4-ethoxyphenyl)-2-(4-(((E)-2-hydroxy-5-methoxybenzylidene)amino)phenyl)acrylonitrile, which crystallizes as two polymorphs and one tetrahydrofuran solvate. All three forms are emissive, but they have different mechanical properties. Specifically, two of the forms that are unsolvated polymorphs (denoted A and B) were found to be brittle and plastic, respectively, while the third form, which is a solvate (denoted C), showed excellent elasticity. Notably, form C becomes plastic after the crystal is desolvated. Single-crystal X-ray diffraction (SCXRD) and mechanical testing were performed to obtain better insight into the root-cause for the observed difference in mechanical properties. Since crystals of forms B and C are mechanically compliant as well as optically transparent, they were tested as flexible single-crystal optical waveguides.
    Scopus© Citations 2  14