Recent Submissions

  • Self-Assembly and Regrowth of Metal Halide Perovskite Nanocrystals for Optoelectronic Applications

    Liu, Jiakai; Zheng, Xiaopeng; Mohammed, Omar F.; Bakr, Osman (Accounts of Chemical Research, American Chemical Society (ACS), 2022-01-16) [Article]
    Conspectus Over the past decade, the impressive development of metal halide perovskites (MHPs) has made them leading candidates for applications in photovoltaics (PVs), X-ray scintillators, and light-emitting diodes (LEDs). Constructing MHP nanocrystals (NCs) with promising optoelectronic properties using a low-cost approach is critical to realizing their commercial potential. Self-assembly and regrowth techniques provide a simple and powerful “bottom-up” platform for controlling the structure, shape, and dimensionality of MHP NCs. The soft ionic nature of MHP NCs, in conjunction with their low formation energy, rapid anion exchange, and ease of ion migration, enables the rearrangement of their overall appearance via self-assembly or regrowth. Because of their low formation energy and highly dynamic surface ligands, MHP NCs have a higher propensity to regrow than conventional hard-lattice NCs. Moreover, their self-assembly and regrowth can be achieved simultaneously. The self-assembly of NCs into close-packed, long-range-ordered mesostructures provides a platform for modulating their electronic properties (e.g., conductivity and carrier mobility). Moreover, assembled MHP NCs exhibit collective properties (e.g., superfluorescence, renormalized emission, longer phase coherence times, and long exciton diffusion lengths) that can translate into dramatic improvements in device performance. Further regrowth into fused MHP nanostructures with the removal of ligand barriers between NCs could facilitate charge carrier transport, eliminate surface point defects, and enhance stability against moisture, light, and electron-beam irradiation. However, the synthesis strategies, diversity and complexity of structures, and optoelectronic applications that emanate from the self-assembly and regrowth of MHPs have not yet received much attention. Consequently, a comprehensive understanding of the design principles of self-assembled and fused MHP nanostructures will fuel further advances in their optoelectronic applications. In this Account, we review the latest developments in the self-assembly and regrowth of MHP NCs. We begin with a survey of the mechanisms, driving forces, and techniques for controlling MHP NC self-assembly. We then explore the phase transition of fused MHP nanostructures at the atomic level, delving into the mechanisms of facet-directed connections and the kinetics of their shape-modulation behavior, which have been elucidated with the aid of high-resolution transmission electron microscopy (HRTEM) and first-principles density functional theory calculations of surface energies. We further outline the applications of assembled and fused nanostructures. Finally, we conclude with a perspective on current challenges and future directions in the field of MHP.
  • Using Triethylborane to Manipulate Reactivity Ratios in Epoxide-Anhydride Copolymerization: Application to the Synthesis of Polyethers with Degradable Ester Functions

    Chidara, Vamshi Krishna; Gnanou, Yves; Feng, Xiaoshuang (Molecules, MDPI AG, 2022-01-11) [Article]
    The anionic ring-opening copolymerization (ROCOP) of epoxides, namely of ethylene oxide (EO), with anhydrides (AH) generally produces strictly alternating copolymers. With triethylborane (TEB)-assisted ROCOP of EO with AH, statistical copolymers of high molar mass including ether and ester units could be obtained. In the presence of TEB, the reactivity ratio of EO (rEO), which is normally equal to 0 in its absence, could be progressively raised to values lower than 1 or higher than 1. Conditions were even found to obtain rEO equal or close to 1. Samples of P(EO-co-ester) with minimal compositional drift could be synthesized; upon basic degradation of their ester linkages, these samples afforded poly(ethylene oxide) (PEO) diol samples of narrow molar mass distribution. In other cases where rEO were lower or higher than 1, the PEO diol samples eventually isolated after degradation exhibited a broader distribution of molar masses because of the compositional drift of initial P(EO-co-ester) samples.
  • Bimetallic Cu(I)/Rh(II) Relay Catalysis for Multicomponent Polymerization through Carbene Intermediates

    Wang, Ying; Zhu, Linlin; Chen, Wenhao; Zhou, Zhi; Zhang, Zhen; Hadjichristidis, Nikos (Macromolecules, American Chemical Society (ACS), 2022-01-05) [Article]
    A highly efficient and multicomponent step-growth polymerization via carbene intermediates is established by bimetallic relay catalytic systems. This strategy, which provides a facile synthetic pathway to novel luminescent polysulfonamides, could overcome the limitation on the choice of carbene monomers and their difficulty in achieving high-molecular-weight polymers. The polymerizations occur through a tandem Cu(I)-catalyzed click reaction and an Rh(II)-catalyzed carbene 1,3-insertion reaction. The high reactivity of Rh(II)-bonded imino carbene intermediates allows a wide range of reactivity with various carboxylic acids, alcohols, and phenols. These results point to an untapped pathway for the use of metal carbene intermediates to construct new macromolecules.
  • Organic Acid Etching Strategy for Dendrite Suppression in Aqueous Zinc-Ion Batteries

    Wang, Wenxi; Huang, Gang; Wang, Yizhou; Cao, Zhen; Cavallo, Luigi; Hedhili, Mohamed N.; Alshareef, Husam N. (Advanced Energy Materials, Wiley, 2022-01-05) [Article]
    Aqueous zinc ion batteries (AZIBs) represent a promising technology for grid-scale energy storage due to their innate safety, low cost, and environmental friendliness. However, planar Zn foil intrinsically suffers from limited ion and electron transport pathways, poor wettability, and surface passivation, preventing the homogenous deposition of metallic Zn and poor durability of AZIBs. Herein, a 3D Zn foil with hierarchical porous architecture is developed through a facile non-aqueous organic acid etching strategy. The 3D Zn anode is pore-rich and cavity-rich, leading to significantly enhanced accessibility to aqueous electrolytes. Accordingly, this 3D Zn anode enables preferential plating of Zn in the porous texture with suppressed dendrite growth, as confirmed by ex situ scanning electron microscopy and finite element analysis. The cycle life of the 3D Zn anode is sustained over 930 and 1500 h at 4.0 mA cm−2-2.0 mAh cm−2 and 1.0 mA cm−2-1.0 mAh cm−2, respectively. Furthermore, the assembled 3D Zn and α-MnO2 full batteries demonstrate a prolonged cycle life of 3000 cycles with improved rate performance. The etching strategy using non-aqueous organic acid paves a new way to fabricate 3D metal anodes for Zn and other metal anode batteries.
  • Selective benzylic Csp3–H bond activations mediated by a phosphorus–nitrogen PN3P-nickel complex

    Huang, Kuo-Wei; Yao, Changguang; Zhang, Tonghuan; Goncalves, Theo (Chemical Communications, Royal Society of Chemistry (RSC), 2022) [Article]
    In contrast to the typical Csp2−H activation, a PN3P-Nickel complex chemoselectively cleaved the benzylic Csp3–H bond of toluene in the presence of KHMDS, presumably via an in situ generated potassium benzyl intermediate. Under similar conditions, CO underwent deoxygenation to afford the corresponding nickel cyano complex, and ethylbenzene was dehydrogenated to give styrene and a nickel hydride compound. 2,6-xylyl isocyanide was transformed into an unprecedented indolyl complex, likely by trapping the activated benzyl species with a isocyanide moiety.
  • Efficient generation of remarkably long-lived charges in organic semiconductor heterojunction nanoparticles enables high photocatalytic efficiency

    Kosco, Jan; Gonzalez-Carrero, Soranyel; Howells, Calvyn T.; Fei, Teng; Dong, Yifan; Sougrat, Rachid; Harrison, George T.; Firdaus, Yuliar; Sheelamanthula, Rajendar; Purushothaman, Balaji; Moruzzi, Floriana; Xu, Weidong; Zhao, Lingyun; Basu, Aniruddha; De Wolf, Stefaan; Anthopoulos, Thomas D.; Durrant, James R.; McCulloch, Iain (Accepted by Nature Energy, Springer Nature, 2022) [Article]
    There is a growing interest in developing organic semiconductor photocatalysts for the synthesis of solar fuels. Most organic photocatalysts rely on exciton dissociation by sacrificial reagents to drive charge separation. We demonstrate that organic semiconductor nanoparticle (NP) photocatalysts comprising the conjugated polymer PM6 matched with PCBM or Y6 electron acceptors can intrinsically generate remarkably long-lived reactive charges, which enable them to efficiently drive the H2 evolution reaction (HER). The optimized PM6:Y6 NPs achieved external quantum efficiencies (EQEs) of 1.0% to 5.0% at 400 to 900 nm and the optimized PM6:PCBM NPs achieved EQEs of 8.7% to 2.6% at 400 to 700 nm. Selective Pt photodeposition was observed on the PCBM domain in the PM6:PCBM NPs and its location was rationalized based on the location of photogenerated electrons in the heterojunction. Employing transient and operando photoinduced optical absorption spectroscopies on ps-s timescales, we find that the heterojunction structure in these NPs greatly enhances the generation of long-lived charges (ms-s timescale) even in the absence of electron/hole scavengers or Pt. The generation of such long-lived reactive charges is striking and opens potential applications for driving kinetically slow and technologically desirable oxidations, or in water splitting Z-schemes.
  • Preferred Orientation of TiN Coatings Enables Stable Zinc Anodes

    Zheng, Jiaxian; Cao, Zhen; Ming, Fangwang; Liang, Hanfeng; Qi, Zhengbing; Liu, Wanqiang; Xia, Chuan; Chen, Cuixue; Cavallo, Luigi; Wang, Zhoucheng; Alshareef, Husam N. (ACS Energy Letters, American Chemical Society (ACS), 2021-12-13) [Article]
    Metallic Zn is considered as an ideal anode while its widespread use in rechargeable aqueous batteries still faces many challenges, mostly associated with the dendritic growth and corrosion of Zn and the side reactions. In this work, we demonstrate that a TiN protective coating layer with the preferential (200) orientation can effectively suppress both the Zn dendritic growth and side reactions; more interestingly, it can regulate the growth pattern of the byproduct (zinc hydroxide sulfate or ZHS) by inducing a lateral growth. As a result, reversible Zn plating/stripping over 2300 h at a practical current density of 1 mA cm–2 is achieved along with a nearly 100% Coulombic efficiency. This work not only establishes TiN (200) coatings as an effective Zn anode protective layer but also provides insights into the role of ZHS byproduct as well as strategies to inhibit side reaction and to regulate the growth pattern of ZHS.
  • A Random Forest Classifier for Protein-Protein Docking Models

    Barradas Bautista, Didier; Cao, Zhen; Vangone, Anna; Oliva, Romina; Cavallo, Luigi (Bioinformatics Advances, Oxford University Press (OUP), 2021-12-10) [Article]
    Herein, we present the results of a machine learning approach we developed to single out correct 3D docking models of protein-protein complexes obtained by popular docking software. To this aim, we generated 3 × 104 docking models for each of the 230 complexes in the protein-protein benchmark, version 5 (BM5), using three different docking programs (HADDOCK, FTDock and ZDOCK), for a cumulative set of ≈ 7 × 106 docking models. Three different machine-learning approaches (Random Forest, Supported Vector Machine and Perceptron) were used to train classifiers with 158 different scoring functions (features). The Random Forest algorithm outperformed the other two algorithms and was selected for further optimization. Using a features selection algorithm, and optimizing the random forest hyperparameters, allowed us to train and validate a random forest classifier, named CoDES (COnservation Driven Expert System). Testing of CoDES on independent datasets, as well as results of its comparative performance with machine-learning methods recently developed in the field for the scoring of docking decoys, confirm its state-of-the-art ability to discriminate correct from incorrect decoys both in terms of global parameters and in terms of decoys ranked at the top positions.
  • Organic neuromorphic electronics for sensorimotor integration and learning in robotics

    Krauhausen, Imke; Koutsouras, Dimitrios A.; Melianas, Armantas; Keene, S. T.; Lieberth, Katharina; Ledanseur, Hadrien; Sheelamanthula, Rajendar; Giovannitti, Alexander; Torricelli, Fabrizio; McCulloch, Iain; Blom, Paul W. M.; Salleo, Alberto; van de Burgt, Yoeri; Gkoupidenis, Paschalis (Science Advances, American Association for the Advancement of Science (AAAS), 2021-12-10) [Article]
    In living organisms, sensory and motor processes are distributed, locally merged, and capable of forming dynamic sensorimotor associations. We introduce a simple and efficient organic neuromorphic circuit for local sensorimo-tor merging and processing on a robot that is placed in a maze. While the robot is exposed to external environ-mental stimuli, visuomotor associations are formed on the adaptable neuromorphic circuit. With this on-chip sensorimotor integration, the robot learns to follow a path to the exit of a maze, while being guided by visually indicated paths. The ease of processability of organic neuromorphic electronics and their unconventional form factors, in combination with education-purpose robotics, showcase a promising approach of an affordable, versatile, and readily accessible platform for exploring, designing, and evaluating behavioral intelligence through decen-tralized sensorimotor integration.
  • Propane Dehydrogenation Catalyzed by Isolated Pt Atoms in ≡SiOZn–OH Nests in Dealuminated Zeolite Beta

    Qi, Liang; Babucci, Melike; Zhang, Yanfei; Lund, Alicia; Liu, Lingmei; Li, Jingwei; Chen, Yizhen; Hoffman, Adam S.; Bare, Simon R.; Han, Yu; Gates, Bruce C.; Bell, Alexis T. (Journal of the American Chemical Society, American Chemical Society (ACS), 2021-12-09) [Article]
    Atomically dispersed noble metal catalysts have drawn wide attention as candidates to replace supported metal clusters and metal nanoparticles. Atomic dispersion can offer unique chemical properties as well as maximum utilization of the expensive metals. Addition of a second metal has been found to help reduce the size of Pt ensembles in bimetallic clusters; however, the stabilization of isolated Pt atoms in small nests of nonprecious metal atoms remains challenging. We now report a novel strategy for the design, synthesis, and characterization of a zeolite-supported propane dehydrogenation catalyst that incorporates predominantly isolated Pt atoms stably bonded within nests of Zn atoms located within the nanoscale pores of dealuminated zeolite Beta. The catalyst is stable in long-term operation and exhibits high activity and high selectivity to propene. Atomic resolution images, bolstered by X-ray absorption spectra, demonstrate predominantly atomic dispersion of the Pt in the nests and, with complementary infrared and nuclear magnetic resonance spectra, determine a structural model of the nested Pt.
  • Straightforward synthesis of [Cu(NHC)(alkynyl)] and [Cu(NHC)(thiolato)] complexes (NHC = N-heterocyclic carbene).

    Ibni Hashim, Ishfaq; Scattolin, Thomas; Tzouras, Nikolaos V; Bourda, Laurens; Van Hecke, Kristof; Ritacco, Ida; Caporaso, Lucia; Cavallo, Luigi; Nolan, Steven P.; Cazin, Catherine S. J. (Dalton transactions, Royal Society of Chemistry (RSC), 2021-12-09) [Article]
    Synthetic access to monomeric copper-alkynyl and copper-thiolato complexes of the type [(NHC)Cu(R)] (R = alkynyl or thiolato) using a weak base approach is reported. All reported reactions proceed under mild conditions in air and in environmentally acceptable solvents. The novel complexes are fully characterized and single crystal X-ray analyses unambiguously establish the atom connectivity in these mononuclear complexes. The importance of the supporting NHC ligand's steric properties in stabilizing mononuclear complexes is discussed.
  • Optimizing Host–Guest Selectivity for Ethylbenzene Capture Toward Superior Styrene Purification

    Ding, Yanjun; Dey, Avishek; Alimi, Lukman Olawale; Bhatt, Prashant; Du, Jing; Maaliki, Carine; Eddaoudi, Mohamed; Jacquemin, Johan; Khashab, Niveen M. (Chemistry of Materials, American Chemical Society (ACS), 2021-12-08) [Article]
    The separation of ethylbenzene (EB) and styrene (ST) mixtures to obtain pure ST has been an enduring challenge for the petrochemical industry. So far, adsorptive separation using porous materials has mainly focused on capturing ST rather than EB, where high temperatures are needed to reactivate the sieving materials and collect the product. Here, we tuned the host–guest interactions in thienothiophene-based trianglimine (ThT-TI) macrocycles to selectively adsorb the unreacted EB over ST, after a dehydrogenation reaction, to readily provide pure ST without the need for further thermal treatments. This is the first report on the selective adsorptive separation of EB over ST using macrocycles as molecular hosts. Both crystalline and amorphous ThT-TI can be used to separate EB with 96% uptake capacity. Single-crystal and powder X-ray diffraction patterns suggest that this selective adsorption arises from a guest-induced structural reordering and involvement of the sulfur atoms in host/guest C–H···π interactions. We believe that this work paves the way for a new generation of molecular sieves that are designed to afford high-purity products by in situ capturing of the unreacted starting materials.
  • Diblock dialternating terpolymers by one-step/one-pot highly selective organocatalytic multimonomer polymerization

    Xu, Jiaxi; Wang, Xin; Hadjichristidis, Nikos (Nature Communications, Springer Science and Business Media LLC, 2021-12-08) [Article]
    The synthesis of well-defined block copolymers from a mixture of monomers without additional actions (“one-pot/one-step”) is an ideal and industrially valuable method. In addition, the presence of controlled alternating sequences in one or both blocks increases the structural diversity of polymeric materials, but, at the same time, the synthetic difficulty. Here we show that the “one-pot/one-step” ring-opening terpolymerization of a mixture of three monomers ($\textit{N}$-sulfonyl aziridines; cyclic anhydrides and epoxides), with $\textit{tert}$-butylimino-tris(dimethylamino)phosphorene ($\textit{t}$-BuP$_1$) as a catalyst, results in perfect diblock dialternating terpolymers having a sharp junction between the two blocks, with highly-controllable molecular weights and narrow molecular weight distributions ($\textit{Ð}$ < 1.08). The organocatalyst switches between two distinct polymerization cycles without any external stimulus, showing high monomer selectivity and kinetic control. The proposed mechanism is based on NMR, in-situ FTIR, SEC, MALDI-ToF, reactivity ratios, and kinetics studies.
  • Advances in allylic and benzylic C–H bond functionalization enabled by metallaphotoredox catalysis

    Yue, Huifeng; Zhu, Chen; Huang, Long; Dewanji, Abhishek; Rueping, Magnus (Chemical Communications, Royal Society of Chemistry (RSC), 2021-12-06) [Article]
    Metallaphoto-catalysis has been established as a robust platform for efficient construction of a range of chemical bonds. Moreover, transformation of native functionalities such as C(sp3)–H bonds to produce functional molecules represents one of the most attractive strategies in organic synthesis. Merging two powerful methodologies, metallaphoto-catalyzed benzylic and allylic C(sp3)–H bond functionalizations provide a series of general and mild approaches for diversification of alkylbenzenes and alkenes.
  • Molecular engineering of intrinsically microporous polybenzimidazole for energy-efficient gas separation

    Abdulhamid, Mahmoud A.; Hardian, Rifan; Bhatt, Prashant; Datta, Shuvo Jit; Ramirez, Adrian; Gascon, Jorge; Eddaoudi, Mohamed; Szekely, Gyorgy (Applied Materials Today, Elsevier BV, 2021-12-04) [Article]
    Polybenzimidazole (PBI) is a high-performance polymer that exhibits high thermal and chemical stability. However, it suffers from low porosity and low fractional free volume, which hinder its application as separation material. Herein, we demonstrate the molecular engineering of gas separation materials by manipulating a PBI backbone possessing kinked moieties. PBI was selected as it contains NH groups which increase the affinity towards CO$_2$, increase sorption capacity, and favors CO$_2$ over other gasses. We have designed and synthesized an intrinsically microporous polybenzimidazole (iPBI) featuring a spirobisindane structure. Introducing a kinked moiety in conjunction with crosslinking enhanced the polymer properties, markedly increasing the gas separation performance. In particular, the BET surface area of PBI increased 30-fold by replacing a flat benzene ring with a kinked structure. iPBI displayed a good CO$_2$ uptake of 1.4 mmol g$^{−1}$ at 1 bar and 3.6 mmol g$^{−1}$ at 10 bar. Gas sorption uptake and breakthrough experiments were conducted using mixtures of CO$_2$/CH$_4$ (50%/50%) and CO$_2$/N$_2$ (50%/50%), which revealed the high selectivity of CO$_2$ over both CH$_4$ and N$_2$. The obtained CO$_2$/N$_2$ selectivity is attractive for power plant flue gas application requiring CO$_2$ capturing materials. Energy and process simulations of biogas CO$_2$ removal demonstrated that up to 70% of the capture energy could be saved when iPBI was used rather than the current amine technology (methyl diethanolamine [MDEA]). Similarly, the combination of iPBI and MDEA in a hybrid system exhibited the highest CO$_2$ capture yield (99%), resulting in nearly 50% energy saving. The concept of enhancing the porosity of PBI using kinked moieties provides new scope for designing highly porous polybenzimidazoles for various separation processes.
  • Tailored Pore Size and Microporosity of Covalent Organic Framework (COF) Membranes for Improved Molecular Separation

    Shinde, Digambar; Cao, Li; Liu, Xiaowei; Wonanke, Dinga A.D.; Zhou, Zongyao; Hedhili, Mohamed N.; Addicoat, Matthew; Huang, Kuo-Wei; Lai, Zhiping (Journal of Membrane Science Letters, Elsevier BV, 2021-12) [Article]
    Three highly crystalline truxene-based β-ketoenamine COF membranes (TFP-HETTA, TFP-HBTTA and TFP-HHTTA) are fabricated via a de novo monomer design approach to understand the fundamental correlations between pore structure and molecular separation performance. By introducing bulky alkyl groups into the truxene framework, the pore size of TFP-HETTA, TFP-HBTTA, and TFP-HHTTA are systematically tuned from 1.08 to 0.72 nm. Accordingly, the TFP-HETTA showed good water permeance of 47 L m−2 h−1 bar−1 along with a prominent rejection rate of Reactive Blue (RB, 800 Da) but less than 10% rejection rate of inorganic salts. In contrast, the TFP-HHTTA membrane with pore size of 0.72 nm can reject small dye molecules (SO, 350 Da) and trivalent salts but with a moderate water permeance of 19 L m−2 h−1 bar−1. The pore-flow model rooted from the viscous flow could well fit the observed organic solvent nanofiltration results of all three COF membranes.
  • Stable near-to-ideal performance of a solution-grown single-crystal perovskite X-ray detector

    Kovalenko, Maksym V.; Sakhatskyi, Kostiantyn; Turedi, Bekir; Matt, Gebhard; Lintangpradipto, Muhammad; Naphade, Rounak; Mohammed, Omar F.; Yakunin, Sergii; Bakr, Osman (Research Square Platform LLC, 2021-12-01) [Preprint]
    Abstract The ideal photodetector is the one able to detect every single incoming photon. In particular, in X-ray medical imaging, the radiation dose for patients can then approach its fundamentally lowest limit set by the Poisson photon statistics. Such near-to-ideal X-ray detection characteristics have been demonstrated with only a few semiconductor materials such as Si1 and CdTe2; however, their industrial deployment in medical diagnostics is still impeded by elaborate and costly fabrication processes. Hybrid metal halide perovskites – newcomer semiconductors -– make for a viable alternative3,4,5 owing to their scalable, inexpensive, robust, and versatile solution growth and recent demonstrations of single gamma-photon counting under high applied bias voltages6,7. The major hurdle with perovskites as mixed electronic-ionic conductors, however, arises from the rapid material's degradation under high electric field8,9,10,11, thus far used in perovskite X-ray detectors12,13. Here we show that both near-to-ideal and long-term stable performance of perovskite X-ray detectors can be attained in the photovoltaic mode of operation at zero-voltage bias, employing thick and uniform methylammonium lead iodide (MAPbI3) single crystal (SC) films (up to 300 µm), solution-grown directly on hole-transporting electrodes. The operational device stability is equivalent to the intrinsic chemical shelf lifetime of MAPbI3, being at least one year in the studied case. Detection efficiency of 88% and noise equivalent dose of 90 pGyair (lower than the dose of a single incident photon) are obtained with 18 keV X-rays, allowing for single-photon counting, as well as low-dose and energy-resolved X-ray imaging. These findings benchmark hybrid perovskites as practically suited materials for developing low-cost commercial detector arrays for X-ray imaging technologies.
  • High Current-density Organic Electrochemical Diodes Enabled by Asymmetric Active Layer Design

    Kim, Youngseok; Kim, Gunwoo; Ding, Bowen; Jeong, Dahyun; Lee, Inho; Park, Sungjun; Kim, Bumjoon J.; McCulloch, Iain; Heeney, Martin; Yoon, Myung-Han (Advanced Materials, Wiley, 2021-12) [Article]
    Owing to outstanding electrical/electrochemical performance, operational stability, mechanical flexibility, and decent biocompatibility, organic mixed ionic-electronic conductors have shown great potential as implantable electrodes for neural recording/stimulation and as active channels for signal switching/amplifying transistors. Nonetheless, no studies exist on the general design rule for high-performance electrochemical diodes, which are essential for highly functional circuit architectures. Herein, we report on generalizable electrochemical diodes with very high current density over 30 kAcm-2 by introducing an asymmetric active layer based on organic mixed ionic-electronic conductors. The underlying mechanism on polarity-sensitive balanced ionic doping/dedoping is elucidated by numerical device analysis and in operando spectroelectrochemical potential mapping, while the general material requirements for electrochemical diode operation are deduced using various types of conjugated polymers. In parallel, analog signal rectification and digital logic processing circuits are successfully demonstrated to show the broad impact of organic electrochemical diode-incorporated circuits. We expect that organic electrochemical diodes will play vital roles in realizing multifunctional soft bioelectronic circuitry in combination with organic electrochemical transistors. This article is protected by copyright. All rights reserved.
  • Nearly 100% energy transfer at the interface of metal-organic frameworks for X-ray imaging scintillators

    Wang, Jian-Xin; Gutierrez Arzaluz, Luis; Wang, Xiaojia; Almalki, Maram M.; Yin, Jun; Czaban-Jozwiak, Justyna; Shekhah, Osama; Zhang, Yuhai; Bakr, Osman; Eddaoudi, Mohamed; Mohammed, Omar F. (Matter, Elsevier BV, 2021-12) [Article]
    In this work, we describe a highly efficient and reabsorption-free X-ray-harvesting system using luminescent metal-organic framework (MOF)-fluorescence chromophore composite films. The ultrafast time-resolved experiments and density functional theory calculations demonstrate that a nearly 100% energy transfer from a luminescent MOF with a high atomic number to an organic chromophore with thermally activated delayed fluorescence (TADF) character can be achieved. Such an unprecedented efficiency of interfacial energy transfer and the direct harnessing of singlet and triplet excitons of the TADF chromophore led to remarkable enhancement of radioluminescence upon X-ray radiation. A low detection limit of 256 nGy/s of the fabricated X-ray imaging scintillator was achieved, about 60 times lower than the MOF and 7 times lower than the organic chromophore counterparts. More importantly, this detection limit is about 22 times lower than the standard dosage for a medical examination, making it an excellent candidate for X-ray radiography.
  • AIE-Based Fluorescent Triblock Copolymer Micelles for Simultaneous Drug Delivery and Intracellular Imaging

    Kulkarni, Bhagyashree; Qutub, Somayah S.; Ladelta, Viko; Khashab, Niveen M.; Hadjichristidis, Nikos (Biomacromolecules, American Chemical Society (ACS), 2021-12-01) [Article]
    Fluorescent drug delivery systems have received increasing attention in cancer therapy because they combine drug delivery and bioimaging into a single platform. For example, polymers with aggregation-induced emission (AIE) fluorophores, such as tetraphenylethylene (TPE), have emerged as an elegant choice for drug delivery/bioimaging applications. In this work, we report one-pot sequential organocatalytic ring-opening polymerization of ε-caprolactone (CL) and ethylene oxide (EO) using TPE-(OH)2 as a difunctional initiator, in the presence of a t-BuP2/TEB Lewis pair (catalyst), in THF at room temperature. Two well-defined triblock copolymers with inverse block sequences, TPE-(PCL-b-PEO)2 and TPE-(PEO-b-PCL)2, were synthesized by altering the sequential addition of CL and EO. The physicochemical properties, including hydrodynamic diameter, morphology, and AIE properties of the synthesized amphiphilic triblock copolymers were investigated in aqueous media. The block copolymer micelles were loaded with anticancer drugs doxorubicin and curcumin to serve as drug delivery vehicles. In vitro studies revealed the accelerated drug release at lower pH (5.5), which mimics the tumor microenvironment, different from the physiological pH (7.4). In vitro cytotoxicity studies demonstrated that the neat block copolymer micelles are biocompatible, while drug-loaded micelles exhibited a significant cytotoxic effect in cancer cells. Cellular uptake, examined by confocal laser scanning microscopy, showed that the block copolymer micelles were rapidly internalized by the cells with simultaneous emission of TPE fluorophore. These results suggest that these triblock copolymers can be utilized for intracellular bioimaging.

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