Supramolecular architectures that work out-of-equilibrium or that can change in specific ways when absorbing external energy are ubiquitous in nature. Gaining the ability to create via self-assembly ...artificial materials possessing such fascinating behaviors would have a major impact in many fields. However, the rational design of similar dynamic structures requires to understand and, even more challenging, to learn how to master the molecular mechanisms governing how the assembled systems evolve far from the equilibrium. Typically, this represents a daunting challenge due to the limited molecular insight that can be obtained by the experiments or by classical modeling approaches. Here we combine coarse-grained molecular models and advanced simulation approaches to study at submolecular (<5 Å) resolution a supramolecular tubule, which breaks and disassembles upon absorption of light energy triggering isomerization of its azobenzene-containing monomers. Our approach allows us to investigate the molecular mechanism of monomer transition in the assembly and to elucidate the kinetic process for the accumulation of the transitions in the system. Despite the stochastic nature of the excitation process, we demonstrate how these tubules preferentially dissipate the absorbed energy locally via the amplification of defects in their supramolecular structure. We find that this constitutes the best kinetic pathway for accumulating monomer transitions in the system, which determines the dynamic evolution out-of-equilibrium and the brittle behavior of the assembly under perturbed conditions. Thanks to the flexibility of our models, we finally come out with a general principle, where defects explain and control the brittle/soft behavior of such light-responsive assemblies.
Supramolecular block copolymerzation with optically or electronically complementary monomers provides an attractive bottom-up approach for the non-covalent synthesis of nascent axial organic ...heterostructures, which promises to deliver useful applications in energy conversion, optoelectronics, and catalysis. However, the synthesis of supramolecular block copolymers (BCPs) constitutes a significant challenge due to the exchange dynamics of non-covalently bound monomers and hence requires fine microstructure control. Furthermore, temporal stability of the segmented microstructure is a prerequisite to explore the applications of functional supramolecular BCPs. Herein, we report the cooperative supramolecular block copolymerization of fluorescent monomers in solution under thermodynamic control for the synthesis of axial organic heterostructures with light-harvesting properties. The fluorescent nature of the core-substituted naphthalene diimide (cNDI) monomers enables a detailed spectroscopic probing during the supramolecular block copolymerization process to unravel a nucleation–growth mechanism, similar to that of chain copolymerization for covalent block copolymers. Structured illumination microscopy (SIM) imaging of BCP chains characterizes the segmented microstructure and also allows size distribution analysis to reveal the narrow polydispersity (polydispersity index (PDI) ≈ 1.1) for the individual block segments. Spectrally resolved fluorescence microscopy on single block copolymerized organic heterostructures shows energy migration and light-harvesting across the interfaces of linearly connected segments. Molecular dynamics and metadynamics simulations provide useful mechanistic insights into the free energy of interaction between the monomers as well as into monomer exchange mechanisms and dynamics, which have a crucial impact on determining the copolymer microstructure. Our comprehensive spectroscopic, microscopic, and computational analyses provide an unambiguous structural, dynamic, and functional characterization of the supramolecular BCPs. The strategy presented here is expected to pave the way for the synthesis of multi-component organic heterostructures for various functions.
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•ZnO NPs synthesized using extract of Artocarpus gomezianus fruits.•PXRD, SEM and UV–Visible studies confirm the formation of Nps.•PL spectra display blue, green and red emissions ...upon excitation at 325nm.•Nps exhibit excellent photocatalytic activity.•NPs show good antioxidant activity against DPPH radicals.
We report green synthesis of multifunctional ZnO nanoparticles (NPs) using Artocarpus gomezianus (AG) extract as fuel by solution combustion synthesis. The formation of NPs was confirmed by powder XRD, SEM, TEM and UV–Visible studies. The NPs were subjected for photoluminescence, photodegradative and antioxidant studies. XRD data reveals that the ZnO NPs possess wurtzite structure. UV–Visible spectrum shows absorbance maximum at 370nm which corresponds to the energy band gap of 3.3eV. Morphology studies indicate the highly porous nature of the NPs. PL spectra of NPs found to display very interesting blue, green and red emissions upon excitation at 325nm. The NPs exhibit potential photocatalytic activity towards the degradation of methylene blue (MB) dye upon exposure to sun light and UV light. ZnO NPs found to have considerable antioxidant activity against DPPH (2,2-diphenyl-1-picrylhydrazyl) free radicals. The study successfully demonstrates a simple and eco-friendly method for the synthesis of efficient multifunctional ZnO nanoparticles using green synthetic approach.
In this letter, we analyze the performance of the intelligent reflecting surface (IRS) assisted downlink non-orthogonal multiple access (NOMA) systems in the presence of imperfect phase compensation. ...We derive an upper bound on the imperfect phase compensation to achieve minimum required data rate for each user. Using this bound, we propose an adaptive user pairing algorithm to maximize the network throughput. We then derive bounds on the power allocation factors and propose power allocation algorithms for the paired users to achieve the maximum sum rate or ensure fairness. Through extensive simulations, we show that the proposed algorithms significantly outperform the state-of-the-art algorithms in the presence of phase imperfections.
Sentiment lexicon is a reliable resource in computing sentiment classification. However, a general purpose lexicon alone is not sufficient, since text sentiment classification is perceived as a ...context-dependent task in the literature. On the contrary, we observe that many people tend to imitate others while writing reviews. As such, the subject of all the public opinion towards an entity ends up as an imbalanced corpus. In this paper, we intend to induce a context-based lexicon as a resource to explore imbalanced text sentiment classification. This method addresses the above mentioned two critical problems in text sentiment classification. First, it identifies subjective words relative to the context and computes the weight scores for subjective terms and full review. Also, in recent years, the application of RNNs to a variety of problems has been incredible, especially in natural language processing tasks. Thus, we take the advantages of the context-based lexicon as well as a bidirectional LSTM to handle text sentiment classification. Second, it deals imbalanced data by deploying a text based oversampling method for creating new synthetic text samples. The reason behind using a text based oversampling method is to make use of semantics of the information while creating new text samples. Experimental results prove that leveraging sentiment lexicon relative to the context and application of Bidiricetional LSTM with text based oversampling is useful in imbalanced text sentiment classification and in achieving state-of-the-art results over deep neural learning model baselines.
The development of powerful methods for living covalent polymerization has been a key driver of progress in organic materials science. While there have been remarkable reports on living ...supramolecular polymerization recently, the scope of monomers is still narrow and a simple solution to the problem is elusive. Here we report a minimalistic molecular platform for living supramolecular polymerization that is based on the unique structure of all-cis 1,2,3,4,5,6-hexafluorocyclohexane, the most polar aliphatic compound reported to date. We use this large dipole moment (6.2 Debye) not only to thermodynamically drive the self-assembly of supramolecular polymers, but also to generate kinetically trapped monomeric states. Upon addition of well-defined seeds, we observed that the dormant monomers engage in a kinetically controlled supramolecular polymerization. The obtained nanofibers have an unusual double helical structure and their length can be controlled by the ratio between seeds and monomers. The successful preparation of supramolecular block copolymers demonstrates the versatility of the approach.
Supramolecular polymers are composed of monomers that self-assemble non-covalently, generating distributions of monodimensional fibres in continuous communication with each other and with the ...surrounding solution. Fibres, exchanging molecular species, and external environment constitute a sole complex system, which intrinsic dynamics is hard to elucidate. Here we report coarse-grained molecular simulations that allow studying supramolecular polymers at the thermodynamic equilibrium, explicitly showing the complex nature of these systems, which are composed of exquisitely dynamic molecular entities. Detailed studies of molecular exchange provide insights into key factors controlling how assemblies communicate with each other, defining the equilibrium dynamics of the system. Using minimalistic and finer chemically relevant molecular models, we observe that a rich concerted complexity is intrinsic in such self-assembling systems. This offers a new dynamic and probabilistic (rather than structural) picture of supramolecular polymer systems, where the travelling molecular species continuously shape the assemblies that statistically emerge at the equilibrium.
Dendrimers are well-defined macromolecules whose highly branched structure is reminiscent of many natural structures, such as trees, dendritic cells, neurons or the networks of kidneys and lungs. ...Nature has privileged such branched structures for increasing the efficiency of exchanges with the external medium; thus, the whole structure is of pivotal importance for these natural networks. On the contrary, it is generally believed that the properties of dendrimers are essentially related to their terminal groups, and that the internal structure plays the minor role of an 'innocent' scaffold. Here we show that such an assertion is misleading, using convergent information from biological data (human monocytes activation) and all-atom molecular dynamics simulations on seven families of dendrimers (13 compounds) that we have synthesized, possessing identical terminal groups, but different internal structures. This work demonstrates that the scaffold of nanodrugs strongly influences their properties, somewhat reminiscent of the backbone of proteins.
The rational design of supramolecular polymers that can adapt or respond in time to specific stimuli in a controlled way is interesting for many applications, but this requires understanding the ...molecular factors that make the material faster or slower in responding to the stimulus. To this end, it is necessary to study the dynamic adaptive properties at submolecular resolution, which is difficult at an experimental level. Here we show coarse-grained molecular dynamics simulations (<5 Å resolution) demonstrating how the dynamic adaptivity and stimuli responsiveness of a supramolecular polymer is controlled by the intrinsic dynamics of the assembly, which is in turn determined by the structure of the monomers. As a representative case, we focus on a water-soluble 1,3,5-benzenetricarboxamide (BTA) supramolecular polymer incorporating (charged) receptor monomers, experimentally seen to undergo dynamic clustering following the superselective binding to a multivalent recruiter. Our simulations show that the dynamic reorganization of the supramolecular structure proceeds via monomer diffusion on the dynamic fiber surface (exchange within the fiber). Rationally changing the structure of the monomers to make the fiber surface more or less dynamic allows tuning the rate of response to the stimulus and of supramolecular reconfiguration. Simple in silico experiments draw a structure–dynamics–property relationship revealing the key factors underpinning the dynamic adaptivity and stimuli-responsiveness of these supramolecular polymers. We come out with clear evidence that to master the bioinspired properties of these fibers, it is necessary to control their intrinsic dynamics, while the high-resolution of our molecular models permits us to show how.
Identification and isolation of low-frequency cells of interest from a heterogeneous cell mixture is an important aspect of many diagnostic applications (including enumeration of circulating tumor ...cells) and is integral to various assays in (cancer) biology. Current techniques typically require expensive instrumentation and are not amenable to high throughput. Here, we demonstrate a simple and effective platform for cell detection and isolation using gold nanoparticles (Au NPs) conjugated with hyaluronic acid (HA) i.e. Au-PEG-HA NPs. The proposed platform exploits ligand-receptor chemistry to detect/isolate cells with high specificity and efficiency. When the Au-PEG-HA NPs come in contact with cells that express CD44 (the receptor for HA), a clear colorimetric change occurs (along with an accompanying SPR peak shift from 521 nm to 559 nm) in the solution due to NPs-cell interaction. This clearly discernible, colorimetric change can be leveraged by point-of-care devices employed in diagnostic applications. Finally, we show that we can successfully isolate viable cells from a heterogeneous cell population (including from human blood samples) with high specificity, which can be used in further downstream applications. The developed NPs-based platform can be a convenient and cost-efficient alternative for diagnostic applications and for cell isolation or sorting in research laboratories.
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