Facile Template-Free Fabrication of Aluminum-Organophosphorus Hybrid Nanorods: Formation Mechanism and Enhanced Luminescence Property

Recently, much effort has been directed toward fabrication of metal-organophosphorus hybrids with microporous, fibered, layered, and open structures to obtain desired mechanical, optical, electric, and catalytic properties. In this work, aluminum–phosphorus hybrid nanorods (<b>APHNRs</b>) with regular morphology were prepared by a template-free hydrothermal reaction of aluminum hydroxide with diphenylphosphinic acid (DPPA). Structure characterization of <b>APHNRs</b> by Fourier transform infrared spectroscopy, laser Raman spectroscopy, and X-ray diffraction demonstrate a structure with aluminophosphate main chains and phenyl pendant groups, which enable self-assembly into nanorods. The reaction conditions and the structures of phosphinic acids appear to have a significant impact on the morphology and size of nanorods. Moreover, the evolution of morphology and structure assembly during the forming process of <b>APHNRs</b>, as monitored by SEM and XRD, reveal a decomposition-assembly propagation process where the driving force of assembly is attributed to π–π stacking interactions between phenyl pendant groups. <b>APHNRs</b> show a significant increase in light emission relative to pure DPPA due to their compact structure resulting from the π–π stacking interaction. Detailed investigation revealed that photoluminescence was remarkably amplified by enhancing the compactness of <b>APHNRs</b>

Entropy-Driven Pattern Formation of Hybrid Vesicular Assemblies Made from Molecular and Nanoparticle Amphiphiles

Although an analogy has been drawn between them, organic molecular amphiphiles (MAMs) and inorganic nanoparticle (NP) amphiphiles (NPAMs) are significantly different in dimension, geometry, and composition as well as their assembly behavior. Their concurrent assembly can synergetically combine the inherent properties of both building blocks, thus leading to new hybrid materials with increasing complexity and functionality. Here we present a new strategy to fabricate hybrid vesicles with well-defined shape, morphology, and surface pattern by coassembling MAMs of block copolymers (BCPs) and NPAMs comprising inorganic NPs tethered with amphiphilic BCPs. The assembly of binary mixtures generated unique hybrid Janus-like vesicles with different shapes, patchy vesicles, and heterogeneous vesicles. Our experimental and computational studies indicate that the different nanostructures arise from the delicate interplay between the dimension mismatch of the two types of amphiphiles, the entanglement of polymer chains, and the mobility of NPAMs. In addition, the entropic attraction between NPAMs plays a dominant role in controlling the lateral phase separation of the two types of amphiphiles in the membranes. The ability to utilize multiple distinct amphiphiles to construct discrete assemblies represents a promising step in the self-assembly of structurally complex functional materials

Janus Particles Synthesis by Emulsion Interfacial Polymerization: Polystyrene as Seed or Beyond?

New strategies for synthesis of Janus particles are of essential importance in the advancement of material science and technology. However, it remains a great challenge to synthesize uniform Janus particles with controllable topological and chemical anisotropy. To overcome this challenge, we have recently developed a general emulsion interfacial polymerization approach. This approach can be applicable to a wide variety of vinyl monomers, including positively charged, neutrally charged, and negatively charged monomers. Different from the traditional seed swelling emulsion polymerization that usually involved using cross-linked polystyrene (PS) particles as seeds to produce Janus particles, we preloaded non-cross-linked PS particles in the emulsion system to construct an interfacial polymerization system. However, the role of these non-cross-linked PS particles in the emulsion interfacial polymerization is unclear. In this work, we revealed the role of non-cross-linked PS particles preloaded in emulsion interfacial polymerization for fabricating uniform Janus particles with controllable topology. We found that the introduction of non-cross-linked PS particles could significantly control the topology and uniformity of Janus particles. Theoretical simulation results by dissipative particle dynamics simulation coupled with stochastic reaction model revealed that the polymer chains of PS inside oil droplets play a decisive role in the topographic control of Janus particles. These hydrophobic PS chains could slow down the polymerization inside oil droplets due to shielding effect of the PS chains to the newly formed poly­(styrene–divinylbenzene) (PSDVB) nucleus. Meanwhile, we demonstrated that the diverse topology features of Janus particles could be tuned by regulating the concentration of PS polymer and monomers. These results may help us to comprehensively understand the mechanism of emulsion interfacial polymerization methodology and design new functional particle materials

Synergistic Tailoring of Electrostatic and Hydrophobic Interactions for Rapid and Specific Recognition of Lysophosphatidic Acid, an Early-Stage Ovarian Cancer Biomarker

Early detection of ovarian cancer, the most lethal type of gynecologic cancer, can dramatically improve the efficacy of available treatment strategies. However, few screening tools exist for rapidly and effectively diagnosing ovarian cancer in early stages. Here, we present a facile “lock–key” strategy, based on rapid, specific detection of plasma lysophosphatidic acid (LPA, an early stage biomarker) with polydiacetylenes (PDAs)-based probe, for the early diagnosis of ovarian cancer. This strategy relies on specifically inserting LPA “key” into the PDAs “lock” through the synergistic electrostatic and hydrophobic interactions between them, leading to conformation transition of the PDA backbone with a concomitant blue-to-red color change. The detailed mechanism underlying the high selectivity of PDAs toward LPA is revealed by comprehensive theoretical calculation and experiments. Moreover, the level of LPA can be quantified in plasma samples from both mouse xenograft tumor models and patients with ovarian cancer. Impressively, this approach can be introduced into a portable point-of-care device to successfully distinguish the blood samples of patients with ovarian cancer from those of healthy people, with 100% accuracy. This work provides a valuable portable tool for early diagnosis of ovarian cancer and thus holds a great promise to dramatically improve the overall survival

Hydrogen Bonding Stabilized Self-Assembly of Inorganic Nanoparticles: Mechanism and Collective Properties

Developing a simple and efficient method to organize nanoscale building blocks into ordered superstructures, understanding the mechanism for self-assembly and revealing the essential collective properties are crucial steps toward the practical use of nanostructures in nanotechnology-based applications. In this study, we showed that the high-yield formation of ZnO nanoparticle chains with micrometer length can be readily achieved by the variation of solvents from methanol to water. Spectroscopic studies confirmed the solvent effect on the surface properties of ZnO nanoparticles, which were found to be critical for the formation of anisotropic assemblies. Quantum mechanical calculations and all atom molecular dynamic simulations indicated the contribution of hydrogen bonding for stabilizing the structure in water. Dissipative particle dynamics further revealed the importance of solvent–nanoparticle interactions for promoting one-dimensional self-assembly. The branching of chains was found upon aging, resulting in the size increase of the ensembles and network formation. Steady-state and time-resolved luminescent spectroscopes, which probed the variation of defect-related emission, revealed stronger Forster resonance energy transfer (FRET) between nanoparticles when the chain networks were formed. The high efficiency of FRET quenching can be ascribed to the presence of multiple energy transfer channels, as well as the short internanoparticle distances and the dipole alignment

A Supramolecular Janus Hyperbranched Polymer and Its Photoresponsive Self-Assembly of Vesicles with Narrow Size Distribution

Herein, we report a novel Janus particle and supramolecular block copolymer consisting of two chemically distinct hyperbranched polymers, which is coined as Janus hyperbranched polymer. It is constructed by the noncovalent coupling between a hydrophobic hyperbranched poly­(3-ethyl-3-oxetanemethanol) with an apex of an azobenzene (AZO) group and a hydrophilic hyperbranched polyglycerol with an apex of a β-cyclodextrin (CD) group through the specific AZO/CD host–guest interactions. Such an amphiphilic supramolecular polymer resembles a tree together with its root very well in the architecture and can further self-assemble into unilamellar bilayer vesicles with narrow size distribution, which disassembles reversibly under the irradiation of UV light due to the <i>trans</i>-to-<i>cis</i> isomerization of the AZO groups. In addition, the obtained vesicles could further aggregate into colloidal crystal-like close-packed arrays under freeze-drying conditions. The dynamics and mechanism for the self-assembly of vesicles as well as the bilayer structure have been disclosed by a dissipative particle dynamics simulation

Photoinduced Conversion of Cu Nanoclusters Self-Assembly Architectures from Ribbons to Spheres

Two-dimensional (2D) nanomaterials have attracted much attention because of the unique layered structures and charming properties in many applications. However, with respect to stimulus-responsive 2D nanomaterials, the rigidity of most 2D nanostructures sheds doubt on achieving morphology response. In this paper, a photoresponsive 2D nanostructure is fabricated on the basis of the self-assembly of ultrasmall Cu nanoclusters (NCs) in colloidal solution. The Cu NCs are foremost decorated by the capping ligands with photoresponsive azobenzene (Azo) groups and by virtue of the flexibility of self-assembly techniques to produce nanoribbons. Because the ribbons are composed of individual NCs rather than a rigid whole, the ultraviolet (UV)-induced Cu NCs disassembly permits achieving morphology transformation. The disassembly of Cu ribbons is controlled by the Cu NCs rather than the surface ligands. However, the disassembled Cu NCs will reassemble into spheres if they are coated with Azo groups. The electrocatalytic performance of Cu self-assembly ribbons and spheres in oxygen reduction reaction is further compared. The ribbons show better catalytic activity than the spheres

Self-Assembly of Amphiphilic Plasmonic Micelle-Like Nanoparticles in Selective Solvents

Amphiphilic plasmonic micelle-like nanoparticles (APMNs) composed of gold nanoparticles (AuNPs) and amphiphilic block copolymers (BCPs) structurally resemble polymer micelles with well-defined architectures and chemistry. The APMNs can be potentially considered as a prototype for modeling a higher-level self-assembly of micelles. The understanding of such secondary self-assembly is of particular importance for the bottom-up design of new hierarchical nanostructures. This article describes the self-assembly, modeling, and applications of APMN assemblies in selective solvents. In a mixture of water/tetrahydrofuran, APMNs assembled into various superstructures, including unimolecular micelles, clusters with controlled number of APMNs, and vesicles, depending on the lengths of polymer tethers and the sizes of AuNP cores. The delicate interplay of entropy and enthalpy contributions to the overall free energy associated with the assembly process, which is strongly dependent on the spherical architecture of APMNs, yields an assembly diagram that is different from the assembly of linear BCPs. Our experimental and computational studies suggested that the morphologies of assemblies were largely determined by the deformability of the effective nanoparticles (that is, nanoparticles together with tethered chains as a whole). The assemblies of APMNs resulted in strong absorption in near-infrared range due to the remarkable plasmonic coupling of Au cores, thus facilitating their biomedical applications in bioimaging and photothermal therapy of cancer