Self-assembly Of Frameworks Research Articles

Strategic framework for harnessing luminescent metal nanocluster assemblies in biosensing applications.

The distinctive physicochemical attributes of ultra-small metal nanoclusters (MNCs) resembling those of molecules make them versatile constituents for self-assembled frameworks. This critical review scrutinizes the influence of assembly on the photoluminescence (PL) properties of MNCs and investigates their utility in biosensing applications. The investigation isinitiated with an assessment of the shift from individual MNCs to assemblies and its repercussions on PL efficacy. Subsequently, two distinct biosensing modalities are explored: assembly-driven detection mechanisms and detection predicated on structural modifications in assembled MNCs. Through meticulous examination, we underscore the potential of self-assembly methodologies in tailoring the PL behavior of MNCs for the detection of diverse biological analytes and diseases.

Enhancing long-term stability and energy/power density of sodium ion battery through fluorination-induced electron density engineering in covalent organic nanosheets

The structure-related performance of covalent organic nanosheets (CONs) as anode materials in sodium-ion batteries is investigated by the introduction of an electron-withdrawing atom such as fluorine in the unit structure of CON. Then, strong permanent dipoles induced by fluorine are well preserved through the CON framework; these dipoles can provide a large number of accessible sites for Na+ on the self-assembled frameworks. The effect of the dipole on the Na+ storage capacity of fluorinated CON-37 is demonstrated by subsequently comparing that of non-fluorinated CON-35 with respect to various electrochemical behaviors. As a result, the interaction between Na+ and the π framework of CON-37 is reduced with respect to CON-35 as fluorine could withdraw the electron density of the framework. Therefore, the charging/discharging capacity of CON-37 can be improved as a result of better ion and charge carrier conductivity with high stability for up to 2500 subsequent cycles. Furthermore, its chemical structure is extremely well maintained for up to 2500 cycles. The CON-37 electrode exhibits stable cycling performance and a rate capability, maintaining a highly improved reversible discharge capacity of ∼ 350 mA h g−1 for up to 2500 cycles at a current density of 100 mA g−1.

Multi-functionalized Metallo-Supramolecular Spoked Wheels: Their Emission-Tunable Hierarchically Assembled System with Dye Molecules.

Supramolecular architectures with multiple emissive units are especially appealing due to their desired properties, such as artificial light harvesting and white-light emission. But fully achieving multi-wavelength photoluminescence in a single supramolecular architecture remains a challenge. In this paper, functionalized supramolecular architectures containing twelve metal centers and six pyrene moieties were nearly quantitatively synthesized by multi-component self-assembly and fully characterized by 1D and 2D nuclear magnetic resonance, dynamic light scattering, electrospray ionization mass spectrometry, traveling-wave ion mobility mass spectrometry, and transmission electron microscopy. Moreover, the hierarchical nano-assemblies were prepared by introducing anionic dyes to the positively charged self-assembled framework, which contained three luminescence centers, namely, pyrene, tpy-Cd coordination parts, and Sulforhodamine B anions. Such a hierarchically assembled system displayed tunable emission by taking full advantage of aggregation-induced emission enhancement, aggregation-caused quenching, and fluorescence resonance energy transfer effects and showed the diverse emission colors. This research provides a new insight for constructing multiple emissive metallo-supramolecular assemblies.

Biomimetic Platelet Nanomotors for Site-Specific Thrombolysis and Ischemic Injury Alleviation.

Due to the mortality associated with thrombosis and its high recurrence rate, there is a need to investigate antithrombotic approaches. Noninvasive site-specific thrombolysis is a current approach being used; however, its usage is characterized by the following limitations: low targeting efficiency, poor ability to penetrate clots, rapid half-life, lack of vascular restoration mechanisms, and risk of thrombus recurrence that is comparable to that of traditional pharmacological thrombolysis agents. Therefore, it is vital to develop an alternative technique that can overcome the aforementioned limitations. To this end, a cotton-ball-shaped platelet (PLT)-mimetic self-assembly framework engineered with a phototherapeutic poly(3,4-ethylenedioxythiophene) (PEDOT) platform has been developed. This platform is capable of delivering a synthetic peptide derived from hirudin P6 (P6) to thrombus lesions, forming P6@PEDOT@PLT nanomotors for noninvasive site-specific thrombolysis, effective anticoagulation, and vascular restoration. Regulated by P-selectin mediation, the P6@PEDOT@PLT nanomotors target the thrombus site and subsequently rupture under near-infrared (NIR) irradiation, achieving desirable sequential drug delivery. Furthermore, the movement ability of the P6@PEDOT@PLT nanomotors under NIR irradiation enables effective penetration deep into thrombus lesions, enhancing bioavailability. Biodistribution analyses have shown that the administered P6@PEDOT@PLT nanomotors exhibit extended circulation time and metabolic capabilities. In addition, the photothermal therapy/photoelectric therapy combination can significantly augment the effectiveness (ca. 72%) of thrombolysis. Consequently, the precisely delivered drug and the resultant phototherapeutic-driven heat-shock protein, immunomodulatory, anti-inflammatory, and inhibitory plasminogen activator inhibitor-1 (PAI-1) activities can restore vessels and effectively prevent rethrombosis. The described biomimetic P6@PEDOT@PLT nanomotors represent a promising option for improving the efficacy of antithrombotic therapy in thrombus-related illnesses.

Novel Phytic Acid-Based Supramolecular Material for Uranium Removal from Highly Acidic Media: Synthesis, Performance, and Mechanistic Insights

The efficient adsorption and removal of U(VI) from nuclear wastewater is fetching growing interest due to its importance for the ecological environment and human health. In this study, we report a facile ionic self-assembly method to synthesize a phytic acid-based material denoted PE-x using phytic acid and ethylenediamine. PE-x was applied to remove U(VI) from a highly acidic aqueous solution with pH = 1.0. In batch adsorption experiments, PE-x showed fast removal kinetics for U(VI) with an equilibrium time around 10 min, excellent selectivity for An-Ln and U(VI) with a maximum selectivity of 97.8% and 76.2%, and a remarkable maximum adsorption capacity of 689.7 mg/g toward U(VI). Additionally, PE-x exhibited a considerable adsorption capacity of 282.6 mg/g in the fixed bed column test. The adsorption mechanism was investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The results indicate a unique mechanism based on the reconstruction of the self-assembly framework involving U(VI) building blocks driven by positively charged species exchange. This study provides new insights and strategies for the design of enhanced uranium adsorbents under highly acidic conditions and extends the potential practical application of phytic acid for uranium capture from radioactive wastewater.

Supramolecular framework membrane for precise sieving of small molecules, nanoparticles and proteins

Synthetic framework materials have been cherished as appealing candidates for separation membranes in daily life and industry, while the challenges still remain in precise control of aperture distribution and separation threshold, mild processing methods, and extensive application aspects. Here, we show a two-dimensional (2D) processible supramolecular framework (SF) by integrating directional organic host-guest motifs and inorganic functional polyanionic clusters. The thickness and flexibility of the obtained 2D SFs are tuned by the solvent modulation to the interlayer interactions, and the optimized SFs with limited layers but micron-sized areas are used to fabricate the sustainable membranes. The uniform nanopores allow the membrane composed of layered SF to exhibit strict size retention for substrates with the rejection value of 3.8 nm, and the separation accuracy within 5 kDa for proteins. Furthermore, the membrane performs high charge selectivity for charged organics, nanoparticles, and proteins, due to the insertion of polyanionic clusters in the framework skeletons. This work displays the extensional separation potentials of self-assembled framework membranes comprising of small-molecules and provides a platform for the preparation of multifunctional framework materials due to the conveniently ionic exchange of the counterions of the polyanionic clusters.

Homophily-Based Social Group Formation in a Spin Glass Self-Assembly Framework.

Homophily, the tendency of humans to attract each other when sharing similar features, traits, or opinions, has been identified as one of the main driving forces behind the formation of structured societies. Here we ask to what extent homophily can explain the formation of social groups, particularly their size distribution. We propose a spin-glass-inspired framework of self-assembly, where opinions are represented as multidimensional spins that dynamically self-assemble into groups; individuals within a group tend to share similar opinions (intragroup homophily), and opinions between individuals belonging to different groups tend to be different (intergroup heterophily). We compute the associated nontrivial phase diagram by solving a self-consistency equation for "magnetization" (combined average opinion). Below a critical temperature, there exist two stable phases: one ordered with nonzero magnetization and large clusters, the other disordered with zero magnetization and no clusters. The system exhibits a first-order transition to the disordered phase. We analytically derive the group-size distribution that successfully matches empirical group-size distributions from online communities.

Self-Assembly of Precisely Fluorinated Albumin for Dual Imaging-Guided Synergistic Chemo-Photothermal-Photodynamic Cancer Therapy.

Although albumin has been extensively used in nanomedicine, it is still challenging to fluorinate albumin into fluorine-19 magnetic resonance imaging (19F MRI)-traceable theranostics because existing strategies lead to severe 19F signal splitting, line broadening, and low 19F MRI sensitivity. To this end, 34-cysteine-selectively fluorinated bovine serum albumins (BSAs) with a sharp singlet 19F peak have been developed as 19F MRI-sensitive and self-assembled frameworks for cancer theranostics. It was found that fluorinated albumin with a non-binding fluorocarbon and a long linker is crucial for avoiding 19F signal splitting and line broadening. With the fluorinated BSAs, paclitaxel (PTX) and IR-780 were self-assembled into stable, monodisperse, and multifunctional nanoparticles in a framework-promoted self-emulsion way. The high tumor accumulation, efficient cancer cell uptake, and laser-triggered PTX sharp release of the BSA nanoparticles enabled 19F MRI-near infrared fluorescence imaging (NIR FLI)-guided synergistic chemotherapy (Chemo), photothermal and photodynamic therapy of xenograft MCF-7 cancer with a high therapeutical index in mice. This study developed a rational synthesis of 19F MRI-sensitive albumin and a framework-promoted self-emulsion of multifunctional BSA nanoparticles, which would promote the development of protein-based high-performance biomaterials for imaging, diagnosis, therapy, and beyond.

Supramolecular Self-assembly of Symmetric Tetramethyl Cucurbit[6]uril and Catechol

A supramolecular self-assembly framework has been formed via the interaction of symmetrical tetramethyl cucurbit[6]uril (TMeQ[6]) with catechol (G). Its structure was characterized using 1H NMR, X-ray single crystal diffraction, Fourier infrared spectroscopy and UV–vis spectroscopy. The spectral properties show that the compound is a triclinic system that crystallises in the P-1 space group. G does not enter the cavity of the host and the positive electrostatic potential outer surface of TMeQ[6] interacts with the benzene ring of G to form a 1:1 supramolecular self-assembly.

A renewable electrochemical sensor based on a self-assembled framework of chiral molecules for efficient identification of tryptophan isomers

Molecular self-assembly provides a reasonably effective strategy for the design and construction of chiral sensors. Here, Cu2+ was connected to β-cyclodextrin (β-CD) through coordination to synthesize Cu2-β-CD, subsequently assembled with ammoniated chitosan-MWCNTs (NH2-CS-MWCNTs) by the effect of coordination driver to form a chiral sensing interface Cu2-β-CD/NH2-CS-MWCNTs. Using the electrochemical method, the valid recognition of tryptophan (Trp) isomers was achieved on the self-assembly interface. Under the optimal experimental conditions, the developed sensor exhibited good linearity and satisfactorily renewable ability. Cu2-β-CD/NH2-CS-MWCNTs/GCE showed the capacity to predict the ratio of D-Trp and L-Trp in racemic mixtures and the possibility of qualitative and quantitative determination for Trp isomers. Finally, the electrochemical sensor was used to detect the Trp enantiomers in rat serum, further verifying the feasibility of the sensor in the determination of actual samples. Therefore, the electrochemical chiral sensor not only is used for the recognition of Trp enantiomers but shows great potential in practical applications.

A self-assembled framework that interpenetrates in crystal but does not interpenetrate in solution

A self-assembled framework that interpenetrates in crystal but does not interpenetrate in solution

Structural elucidation, DFT calculations and catalytic activity of dioxomolybdenum(VI) complexes with N[sbnd]N donor ligand: Role of halogen atom coordinated to the molybdenum centre

Two new isostructural mononuclear dioxomolybdenum(VI) complexes of the formula MoO2X2L [where, X = Cl (1), Br (2)] have been synthesized with a NN donor 2-(3-methyl-5-phenyl pyrazol-1-yl) benzthiazole ligand (L). The reaction is carried out in open air and the MoVO3+ centre in the precursor molecule, MoOX3L undergoes spontaneous aerial oxidation, leading to the formation of molybdenum(VI) complexes 1 and 2. The complexes are characterized by a wide range of spectroscopic techniques (IR, UV–Vis and 1H NMR) and elemental analyses. Crystal structures of the ligand and complexes 1 and 2 have been determined by single crystal X-ray diffraction which reveal a distorted octahedral geometry around the molybdenum(VI) centre in both the complexes. The ligand and the complexes build up fascinating supramolecular assembly via several non-covalent interactions including hydrogen bonding, CH···π and π···π interactions. Further, a detailed study of Hirshfeld surface analysis and fingerprint plots of complexes 1 and 2 are presented for understanding the intermolecular interactions involved in building self-assembled frameworks. Supportive DFT and TD-DFT calculations have also been carried out. Electrochemical properties of the complexes have been examined by cyclic voltammetry. Catalytic performance of the synthesized complexes has been evaluated for the oxidation of different olefins in the presence of hydrogen peroxide.

Water-Mediated Attractive Interaction between Negatively Charged GO Nanosheets at the Air–Water Interface

Understanding the interaction of ionized two-dimensional (2D) graphene oxide (GO) nanosheets at the air–water interface can improve the self-assembly framework of GO sheets. Herein, the potential o...

Electrochemical chiral sensing of tryptophan enantiomers by using 3D nitrogen-doped reduced graphene oxide and self-assembled polysaccharides.

A chiral sensor is described for the enantioselective recognition of L- and D-tryptophan (Trp). The sensor is based on the use of (a) Cu(II) ions coordinated with β-cyclodextrin (Cu-β-CD) that was self-assembled with carboxymethyl cellulose (CD-Cu-CMC) as a chiral selector, (b) of N-doped reduced graphene oxide (N-rGO) as substrate materials, and (c) of differential pulse voltammetry that was used for enantiorecognition. The 3D N-rGO was prepared by using reduced graphene oxide and pyrrole as the starting materials. Electrostatic interaction occurs between the carboxy groups of CMC and Cu(II) ions in Cu-β-CD. The FT-IR, SEM, XRD and XPS techniques showed that 3D N-rGO and the CD-Cu-CMC composite were successfully synthesized. The 3D N-rGO enabled the immobilization of the chiral selector (CD-Cu-CMC) and improves the active areas. A glassy carbon electrode was modified with N-rGO/CD-Cu-CMC and then showed a stronger electrochemical signal for L-Trp than for D-Trp, typically at a working potential of around 0.78V (vs. SCE). UV-vis spectroscopy proved that CD-Cu-CMC has a higher affinity for D-Trp. The enantioselectivity for D-Trp over L-Trp is 4.72. The modified electrode had a limit of detection of 0.063μM and 0.0035μM for L-Trp and D-Trp, respectively, with a linear response range of 0.01mM to 5mM. The sensor was used to detect Trp (D- or L-Trp) in spiked real human urine and human serum protein samples. Graphical abstract Schematic representation of an electrochemical chirality sensor based on the merits of N-rGO and CD-Cu-CMC. It involves the preparation of a chiral selector and a substrate material. N-Doped graphene oxide (N-rGO) was prepared by using graphene oxide (GO) and pyrrole as precursor. The combination of carboxymethyl cellulose (CMC) with Cu-β-CD leads to a novel self-assembly framework.

Complex wireframe DNA nanostructures from simple building blocks

DNA nanostructures with increasing complexity have showcased the power of programmable self-assembly from DNA strands. At the nascent stage of the field, a variety of small branched objects consisting of a few DNA strands were created. Since then, a quantum leap of complexity has been achieved by a scaffolded ‘origami’ approach and a scaffold-free approach using single-stranded tiles/bricks—creating fully addressable two-dimensional and three-dimensional DNA nanostructures designed on densely packed lattices. Recently, wireframe architectures have been applied to the DNA origami method to construct complex structures. Here, revisiting the original wireframe framework entirely made of short synthetic strands, we demonstrate a design paradigm that circumvents the sophisticated routing and size limitations intrinsic to the scaffold strand in DNA origami. Under this highly versatile self-assembly framework, we produce a myriad of wireframe structures, including 2D arrays, tubes, polyhedra, and multi-layer 3D arrays.

Investigation of BINOL-3,3′-dicarboxylate as a ligand for the formation of extended coordination-based structures

We provide a structural study of the ability of BINOL-3,3′-dicarboxylate, an inexpensive and readily accessible 1,1′-binaphthol-based ligand, to form extended self-assembled coordination polymers and frameworks in combination with divalent zinc and copper ions. While the structural diversity of herein described materials illustrates the untapped potential of the BINOL-3,3′-dicarboxylate in forming coordination polymer structures, we also provide the first example of an open two-dimensional framework established using this ligand as the only anionic, metal-bridging constituent.

Water mediated proton conductance in a hydrogen-bonded Ni(ii)-bipyridine-glycoluril chloride self-assembled framework

Proton conducting properties have been investigated in a new Ni(ii)-based hydrogen-bonded porous framework synthesized using bipyridine-glycoluril (BPG) tecton.

Self-Assembled Framework Formed During Lithiation of SnS2 Nanoplates Revealed by in Situ Electron Microscopy.

Lithium-ion batteries (LIBs) commercially dominate portable energy storage and have been extended to hybrid/electric vehicles by utilizing electrode materials with enhanced energy density. However, the energy density and cycling life of LIBs must extend beyond the current reach of commercial electrodes to meet the performance requirements for transportation applications. Carbon-based anodes, serving as the main negative electrodes in LIBs, have an intrinsic capacity limitation due to the intercalation mechanism. Some nanostructured carbon materials offer very interesting reversible capacities and can be considered as future anode materials. However, their fabrication processes are often complicated and expensive. Theoretically, using a lithium metal anode is the best way of delivering high energy density due to its largest theoretical capacity of more than 3800 mAh g-1; however, lithium metal is highly reactive with liquid electrolytes. Alternative anodes are being explored, including other lithium-reactive metals, such as Si, Ge, Zn, V, and so forth. These metals react reversibly with a large amount of Li per formula unit to form lithium-metal alloys, rendering these materials promising candidates for next-generation LIBs with high energy density. Though, most of these pure metallic anodes experience large volume changes during lithiation and delithiation processes that often results in cracking of the anode material and a loss electrical contact between the particles. Nanosized metal sulfides were recently found to possess better cycling stability and larger reversible capacities over pure metals. Further improvements and developments of metal sulfide-based anodes rely on a fundamental understanding of their electrochemical cycling mechanisms. Not only must the specific electrochemical reactions be correctly identified, but also the microstructural evolution upon electrochemical cycling, which often dictates the cyclability and stability of nanomaterials in batteries, must be clearly understood. Probing these dynamic evolution processes, i.e. the lithiation reactions and morphology evolutions, are often challenging. It requires both high-resolution chemical analysis and microstructural identification. In situ transmission electron microscopy (TEM) coupled with electron energy loss spectroscopy (EELS) has recently been raised as one of the most powerful techniques for monitoring electrochemical processes in anode materials for LIBs. In this work, we focus on elucidating the origin of the structural stability of SnS2 during electrochemical cycling by revealing the microstructural evolution of SnS2 upon lithiation using in situ TEM. Crystalline SnS2 was observed to undergo a two-step reaction after the initial lithium intercalation: (1) irreversible formation of metallic tin and amorphous lithium sulfide and (2) reversible transformation of metallic tin to Li-Sn alloys, which is determined to be the rate-determining step. More interestingly, it was discovered that a self-assembled composite framework formed during the irreversible conversion reaction, which has not been previously reported. Crystalline Sn nanoparticles are well arranged within an amorphous Li2S "matrix" in this self-assembled framework. This nanoscale framework confines the locations of individual Sn nanoparticles and prevents particle agglomeration during the subsequent cycling processes, therefore providing desired structural tolerance and warranting a sufficientelectron pathway. Our results not only explain the outstanding cycling stability of SnS2 over metallic tin anodes, but also provide important mechanistic insights into the design of high-performance electrodes for next-generation LIBs through the integration of a unique nanoframework.

Supramolecular organic frameworks (SOFs): homogeneous regular 2D and 3D pores in water

Abstract Studies on periodic porosity and related properties and functions have been limited to insoluble solid-state materials. Self-assembly provides a straightforward and efficient strategy for the construction of soluble periodic porous supramolecular organic frameworks (SOFs) in water from rationally designed molecular building blocks. From rigid tri- and tetra-armed building blocks and cucurbitu[8]ril (CB[8]), a number of two-dimensional (2D) honeycomb, square and rhombic SOFs can be generated, which is driven by CB[8]-encapsulation-enhanced dimerization of two aromatic units on the periphery of the multi-armed molecules. By utilizing the same three-component host−guest motif as the driving force, three-dimensional (3D) diamondoid and cubic SOFs can be obtained from tetrahedral and [Ru(bipy)3]2+-derived octahedral monomers and CB[8]. All of the 2D and 3D periodic frameworks are soluble in water, and are able to maintain the periodicity as well as the pore sizes in the solid state. 3D SOFs are highly efficient homogeneous polycationic frameworks for reversible adsorption of anionic species including organic dyes, peptides, nucleic acids, drugs, dendrimers and Wells-Dawson-typed polyoxametallates (WD-POMs). WD-POM molecules adsorbed in the [Ru(bipy)3]2+-based SOF can catalyse the reduction of proton to H2 upon visible-light sensitization of [Ru(bipy)3]2+, which allows multiple electron transfer from [Ru(bipy)3]2+ to WD-POM. This review summarizes the design, formation and characterization of this new family of self-assembled frameworks, highlights their applications as homogeneous porous materials and finally outlines some future research directions.

Electrochemical Enantioselective Recognition in a Highly Ordered Self-Assembly Framework.

Construction of convenient systems for isomer discrimination is of great importance for medical and life sciences. Here, we report a simple and effective chiral sensing device based on a highly ordered self-assembly framework. Cu2+-modified β-cyclodextrin (Cu-β-CD) was self-assembled to the ammonia-ethanol cotreated chitosan (ae-CS), and the highly ordered framework was gradually formed during the "re-growth" process of the shrinked ae-CS films. Tryptophan (Trp) isomers were well discriminated with the highly ordered framework by electrochemical approach. This study is the first example showing how an ordered structure influences chiral recognition.