Directed Self-assembly Approach Research Articles

Facile Synthesis of Multifunctional Mesoporous Starch-Based Microparticle for Effective Hemostasis and Wound Healing.

Uncontrolled hemorrhage and infection are the principal causes of mortality associated with trauma in both military and civilian medical settings. Modified starch granules have emerged as a safe hemostatic agent for irregular and noncompressible wounds, but their performance is constrained by limited hemostasis efficiency and modest antibacterial activity. This study reported a directed self-assembly approach for a multifunctional mesoporous starch-based microparticle loaded with chitosan and calcium ions (Ca@MSMP) used for rapid hemostasis and wound healing. Directed self-assembly of uniform Ca@MSMP with a hierarchical hollow structure in the presence of chitosan was confirmed by scanning electron microscopy (SEM) analysis and pore structure analysis. The resulting Ca@MSMP exhibited a well-defined spherical shape and uniform size of 1 μm and demonstrated excellent antibacterial activity (>95%) without hemolytic activity. Importantly, Ca@MSMP enhanced blood coagulation and platelet aggregation via the synergistic effect of rapid calcium release and chitosan-mediated electrostatic interactions, leading to a significant decrease in blood loss and reduction in hemostasis time in rat tail amputation and liver injury models. In comparative analyses, Ca@MSMP significantly outperformed the commercial hemostatic agent Quickclean, notably enhancing the healing of full-thickness skin wounds in vivo by effectively preventing infection. These results underscore the potential of this innovative hemostatic material in diverse clinical scenarios, offering effective solutions for the management of bleeding in wounds that are irregularly shaped and noncompressible.

Anisotropic nanocrystal superlattices overcoming intrinsic light outcoupling efficiency limit in perovskite quantum dot light-emitting diodes

Quantum dot (QD) light-emitting diodes (LEDs) are emerging as one of the most promising candidates for next-generation displays. However, their intrinsic light outcoupling efficiency remains considerably lower than the organic counterpart, because it is not yet possible to control the transition-dipole-moment (TDM) orientation in QD solids at device level. Here, using the colloidal lead halide perovskite anisotropic nanocrystals (ANCs) as a model system, we report a directed self-assembly approach to form the anisotropic nanocrystal superlattices (ANSLs). Emission polarization in individual ANCs rescales the radiation from horizontal and vertical transition dipoles, effectively resulting in preferentially horizontal TDM orientation. Based on the emissive thin films comprised of ANSLs, we demonstrate an enhanced ratio of horizontal dipole up to 0.75, enhancing the theoretical light outcoupling efficiency of greater than 30%. Our optimized single-junction QD LEDs showed peak external quantum efficiency of up to 24.96%, comparable to state-of-the-art organic LEDs.

Deterministic thermal micro-reflow of lithographic structures for Sub-10-nm metallic gaps fabrication

Metallic nanogaps are a kind of fundamental building blocks for nanoelectronics and nanoplasmonics. However, its reliable fabrication remains challenging and thus developing additional approaches to fabricate ultrasmall metallic nanogaps is still required. In this work, we report a directed self-assembly approach to fabricate metallic nanogaps based on glass-transition-induced micro-reflow of polymer/metal hybrid structures. The process involves three main steps: electron-beam lithography process to obtain initial polymer structures, metal deposition onto the pre-patterned polymer nanostructures, and the solvent-assisted reflow process. It is interesting that the flowing orientation of polymer/metal hybrid nanostructures undergoing glass transition can be determined via several asymmetrical geometrical parameters including shapes and initial nanogaps. Mechanical simulations based on thermo-mechanical coupled finite element method are used to qualitatively understand the mechanism of the deterministic thermal reflow phenomenon. We demonstrate that this method is effective to fabricate sub-10-nm metallic nanogaps in gold nanostructures, which may have potential applications in plasmon-enhanced light-matter interactions, ultrafast nanotransistors, nanoelectronics and molecular electronics.

Metallic Nanodot Patterns with Unique Symmetries Templated from ABC Triblock Terpolymer Networks.

Nanotemplates derived from the self-assembly of AB-type block copolymers provide an elegant route to achieve well-defined metallic dot arrays, even if the variety of pattern symmetries is restricted due to the limited number of structures offered by microphase separated diblock copolymers. A strategy that relies on the use of complex network structures accessible through the self-assembly of linear ABC-type terpolymers is presented for the formation of metallic nanodots arrays with "outside-the-box" symmetries. Patterned templates formed by the cubic Q214 and orthorhombic O70 network structures are used as excellent platforms to build well-ordered gold nanodot arrays with unique p3m1 and p2 symmetries, respectively. A simple yet efficient blending strategy is used to tune the critical dimensions of the p3m1 pattern while laterally ordered gold nanodot arrays are also demonstrated through a directed self-assembly approach. Such highly ordered gold nanodots with tunable particle dimensions and array periods, enabling the control of their plasmonic responses, are attractive probes for biological imaging.

Synthesis, characterization and ROS-mediated antitumor effects of palladium(II) complexes of curcuminoids

Based on the synthesis of curcumin and its derivatives from aromatic aldehydes, a novel series of palladium(II) complexes with curcumin (or its derivatives) and 2,2′-bipyridine have been synthesized through a directed self-assembly approach that involves spontaneous deprotonation of the curcuminoid ligands in H2O/acetone solution. These complexes have been characterized by 1H (13C) NMR, HRMS and elemental analysis. Crystal structure of 3h has been determined by X-ray diffraction analysis. Their cytotoxicity was tested by MTT. The preliminary results showed that complexes 3d, 3f, 3h have significant inhibition on proliferation of three carcinoma cells such as MCF-7, HeLa and A549 cells, which were more active than cisplatin. Further mechanistic studies indicated that the tested complex 3h arrested the cell cycle in the S phase and can disrupted mitochondrial membrane potential and induced tumor cell apoptosis through reactive oxygen species (ROS)-dependent pathway.

Linear and nonlinear optical characterization of self-assembled, large-area gold nanosphere metasurfaces with sub-nanometer gaps.

We created centimeter-scale area metasurfaces consisting of a quasi-hexagonally close packed monolayer of gold nanospheres capped with alkanethiol ligands on glass substrates using a directed self-assembly approach. We experimentally characterized the morphology and the linear and nonlinear optical properties of metasurfaces. We show these metasurfaces, with interparticle gaps of 0.6 nm, are modeled well using a classical (without charge transfer) description. We find a large dispersion of linear refractive index, ranging from values less than vacuum, 0.87 at 600 nm, to Germanium-like values of 4.1 at 880 nm, determined using spectroscopic ellipsometry. Nonlinear optical characterization was carried out using femtosecond Z-scan and we observe saturation behavior of the nonlinear absorption (NLA) and nonlinear refraction (NLR). We find a negative NLR from these metasurfaces two orders of magnitude larger (n2,sat = -7.94x10-9 cm2/W at Isat,n2 = 0.43 GW/cm2) than previous reports on gold nanostructures at similar femtosecond time scales. We also find the magnitude of the NLA comparable to the largest values reported (β2,sat = -0.90x105 cm/GW at Isat,β2 = 0.34 GW/cm2). Precise knowledge of the index of refraction is of crucial importance for emerging dispersion engineering technologies. Furthermore, utilizing this directed self-assembly approach enables the nanometer scale resolution required to develop the unique optical response and simultaneously provides high-throughput for potential device realization.

Rare earth silicates as gain media for silicon photonics [Invited

ErxY2−xSiO5 and ErxYbyY2−x−ySiO5 crystalline thin films were investigated to apply to the high-gain media for silicon photonics. In addition to the sol–gel method, the directed self-assembly approach, using layer-by-layer deposition techniques, was also introduced to improve the crystallinity. The relaxation processes in Er ions were discussed to clarify the contribution of the energy transfer and cooperative upconversion. After optimization of the Er content, a Si photonic crystal slot ErxY2−xSiO5 waveguide amplifier was fabricated, and a 30 dB/cm modal gain was demonstrated. This achievement demonstrates the potential for compact and high optical gain devices on Si chips.

Coexistence of molecular Pd6 triangle and Pd8 square self-assembled from naphthyl-dipyrazole with di-palladium motifs

Two novel nanosized bipyrazolate-bridged metallo-macrocycles with dipalladium(II,II) corners, {[(bpy)Pd]8L4}(NO3)8 and {[(bpy)Pd]6L3}(NO3)6 [L = 1, 4-di(3′,5′-dimethyl-1H-pyrazolyl-4yl)naphthalene] have been synthesized through a directed self-assembly approach that involves spontaneous deprotonation of the 1H-bipyrazolyl ligand in aqueous solution. These crown-shaped complexes with deep cavities potentially served as the host to solvent molecules and anions. Such metallo-macrocyclic structures have been characterized by single-crystal X-ray diffraction analysis, elemental analysis, 1H and 13CNMR, high resolution electrospray ionization mass spectrometry, UV–visible spectroscopy, and luminescence spectroscopy.

Self-assembly of bowl-like trinuclear metallo-macrocycles

By employing different diimine complexes and a naphthanoimidazolate (L(1)) or benzoimidazolate (L(2)) anion ligand as linker, a series of trimetallo-macrocycles have been synthesized through a directed self-assembly approach that involves spontaneous deprotonation of the ligands in aqueous solution. Some compounds, namely, [M(3)L(3)](NO(3))(3) (M = (18-crown-6-phen)Pt, 1 or 7; (15-crown-5-phen)Pt, 2; (benzo-24-crown-8-phen)Pt, 8; (benzo-24-crown-8-phen)Pd, 9; (15-crown-5-phen)Pd, 4 or 11; (18-crown-6-phen)Pd, 3 or 10; (dmbpy)Pd, 6 or 14; (bpy)Pd, 5 or 13; (bpy)Pt, 12; (N4-Phen)Pd, 15) were synthesized. In all of these compounds, the L(1)or L(2) anion ligands are in a syn, syn, syn orientation which result in a bowl-like cavity that can serve as a host to bind the methyl of a solvent CH(3)CN within the naphthanoimidazolate or benzoimidazolate-built cavity through C-H...pi hydrogen bonds in the crystal state. The structures are characterized by elemental analysis, (1)H NMR, ESI-MS, and in the cases of 4a, 11, 13, and 14a by single-crystal X-ray diffraction analysis.

Functional-template directed self-assembly (FTDSA) of mesostructured organic-inorganic hybrid materials

Since the discovery of a surfactant directed self-assembly approach for the fabrication of mesoporous silica in 1992, increasing attention has been focused on the design and synthesis of mesostructured functional materials. Organic functionalization is becoming a major topic in this research field, since highly ordered mesostructured organic-inorganic hybrids offer novel functionalities and enhanced performance over their individual components. We begin with a brief overview of the three fundamental methods (post-synthetic grafting technique, co-condensation method, and preparation of periodic mesoporous organosilicas) for the preparation of organically functionalized mesostructured silica, and focus on one of the most promising approaches, which herein was named as functional-template directed self-assembly (FTDSA) approach, and in the eyes of the authors it has a special position in the preparation of this class of hybrid materials. A comprehensive overview of the state of research in the area of FTDSA and its potential applications will be given.

A Unidirectional Energy Transfer Cascade Process in a Ruthenium Junction Self-Assembled by α- and β-Cyclodextrins

A Ru(II) complex, Ru(alpha2beta), with a trisbipyridyl core and two different receptor sites, alpha- and beta-cyclodextrins, acts as a junction to recognize photoactive guests based on anthracene, Anth, and Os(II), Os-ada, in aqueous solution. Upon light excitation of the self-assembled system Anth.Ru(alpha2beta).Os-ada, an energy cascade process takes place from the Anth guest to the Ru(alpha2beta) core, and subsequently, the energy is funneled to the Os-ada guest. The rates of the two photoinduced processes are determined by time-resolved emission and transient absorption spectroscopic techniques. The system introduces a directed self-assembly approach to unidirectional wires that can lead to nanosized arrays by judicious selection of the individual components.