Spiral Nanofibers Research Articles

A chiral supramolecular hydrogel for selective loading of chiral drugs and pH-responsive drug delivery

A chiral supramolecular hydrogel (CSH) is designed for selective loading of chiral drugs and pH-responsive drug delivery. A derivative of phenylalanine is first synthesized as the gelator, which can be self-assembled to the CSH via intermolecular hydrogen bonding. The resultant CSH is composed of spiral nanofibers and exhibits reversible phase transition behavior (sol–gel) depending on heating/cooling process and pH values. More importantly, the CSH can be used for the selective loading of chiral drug naproxen (NPX) due to the stronger attractive interactions between CSH and S-NPX resulted from their same optical activity. Interestingly, the delivery of S-NPX from the CSH is pH-sensitive and the cumulative release of S-NPX is significantly enhanced in alkaline solutions (pH = 10.0), which might be ascribed to the broken hydrogen bonding and the consequently ruined nanostructure of the CSH under alkaline conditions.

In Ukrainian

The goal of the research work was the pyrolytic synthesis of straight and spiral carbon nanotubes of approximately the same diameter, as well as their comprehensive analysis. To solve the given problem, a new installation for the pyrolytic synthesis of carbon nanostructures (CNS) with a fusion reactor, which for each fusion process can have its own angle relative to the classical horizontal position of the reactor axis. This reactor made it possible to develop a method for obtaining conglomerates of spiral-shaped multi-walled carbon nanotubes with a diameter of 15–60 nm and to synthesize straight multi-walled carbon nanotubes with a diameter of 5 to 60 nm. The research of pyrolytic synthesis of carbon nanostructures in a vertical reactor allows to work out the technology of purposeful synthesis of nanotubes that have a spiral shape with a certain diameter and pitch of the turn. As part of the work, a new mechanism for the formation of spiral multi-walled carbon nanotubes is also considered and proposed, which is important for their further industrial synthesis and their use in related composites. A scheme is proposed of conditions for the synthesis of carbon nanostructures by the pyrolytic method. Thermal analysis was carried out in the work, which recorded the presence of two different structures with low thermal stability (probably amorphous carbon and higher hydrocarbons). When using scanning and transmission electron microscopy, the formation of spiral nanofibers with a diameter of 15–60 nm in the vertical position of the reactor was recorded, and in the horizontal position of the reactor, the formation of straight and slightly curved MWCTs with a diameter of nanofibers from 5 to 60 nm was found. Raman spectroscopy confirms the presence of multi-layered carbon tubular formation, i.e. MWCT, in both synthesis products.

High Melting Point of Linear, Spiral Polyethylene Nanofibers and Polyethylene Microspheres Obtained Through Confined Polymerization by a PPM‐Supported Ziegler‐Natta Catalyst

In this work, different types of polyethylene (linear, spiral nanofibers and microspheres) were obtained via confined polymerization by a PPM‐supported Ziegler‐Natta catalyst. Firstly, the Ziegler‐Natta catalyst was chemical bonded inside the porous polymer microspheres (PPMs) supports with different pore diameter and supports size through chemical reaction. Then slightly and highly confined polymerization occurred in the PPM‐supported Ziegler‐Natta catalysts. SEM results illustrated that the slightly confined polymerization was easy to obtain linear and spiral nanofibers, and the nanofibers were observed in polyethylene catalyzed by PPMs‐1#/cat and PPMs‐2#/cat with low pore diameter (about 23 nm). Furthermore, the highly confined polymerization produced polyethylene microspheres, which obtained through other PPM‐supported Ziegler‐Natta catalysts with high pore diameter. In addition, high second melting point (T m2: up to 143.3 °C) is a unique property of the polyethylene obtained by the PPM‐supported Ziegler‐Natta catalyst after removing the residue through physical treatment. The high T m2 was ascribed to low surface free energy (σ e), which was owing to the entanglement of polyethylene polymerized in the PPMs supports with interconnected multi‐modal pore structure.

A facile N doping strategy to prepare mass-produced pyrrolic N-enriched carbon fibers with enhanced lithium storage properties

Carbon-based nanomaterials with suitable morphology, structure and composition are promising candidates for lithium-ion battery (LIB) anode materials. In this work, the chemical vapor deposition technique followed by a facile gas-solid phase doping strategy is exploited to prepare mass-produced pyrrolic N-enriched carbon fibers (PN-CFs). The effect of N doping on the morphology, structure, composition and LIB performance of PN-CFs is investigated. The results show that intrinsic structure defects existing in raw carbon fibers act as active sites for effective N doping. The obtained PN-CFs possess unique spiral nanofiber morphology, high defect degree and dominated pyrrolic N (∼96% for the total doped N), which result in super-long cycling lifespan (370.9 mAh g−1 at 5 A g−1 after 1000 cycles) and superior high-rate capability (171.1 mAh g−1 at 20 A g−1) when used as LIB anode material.

Preparation and characterization of twisted periodic mesoporous ethenylene-silica nanorods

Twisted periodic mesoporous ethenylene-silica nanorods were prepared using cetyltrimethylammonium bromide in concentrated aqueous ammonia solutions at the stirring rate of 600 rpm. The pore channels run along the long axis of the nanorod. The helical pitches are about 1.2 micrometers. Small-angle X-ray diffraction pattern was indexed to the p6 mm hexagonal symmetry. The morphologies of the ethenylene-silicas are sensitive to stirring conditions. For example, twisted nanorods and spiral nanofibers combined with nanospheres were obtained under static condition. With increasing stirring speed, both the length and helical pitch of the nanorod increased slightly. With decreasing the concentration of ammonia, the particle lengths decreased, while the particle diameters increased. Chiral mesostructures were obtained when the ammonia concentration was ≥ 20 wt%. The formation of the twisted mesoporous ethenylene-silica nanorods was studied by taking TEM images after different reaction time.

Regulation of Supramolecular Chirality and Morphology of the LB Film of Achiral Barbituric Acid by Amphiphilic Matrix Molecules

Previously, we have found that an achiral barbituric acid (BA) derivative, 5-(4-(N-methyl-N-hexadecylaminobenzylidene))-2,4,6-(1H,3H)-pyrimidinetrione (BAC16), could form molecular assemblies showing supramolecular chirality through the organization at the air/water interface. To acquire more knowledge of the formation mechanism of such supramolecular assemblies, some achiral molecules, such as stearic acid (SA), octadecylamine (ODA), and an analogue of BA without an alkyl chain, were mixed into the BAC16 system. The effects of these matrix molecules on the supramolecular chirality and surface morphologies of Lanmuir-Blodgett (LB) films were investigated. It was observed that, at a low molar ratio of the matrix molecules (below 10%), the chirality of the BAC16 assemblies could be maintained with only a reduction in the intensity. When the matrix fraction was increased, the supramolecular chirality of the mixed films disappeared. The addition of the matrix molecules can greatly change the surface morphologies of the mixed films. When SA was mixed with BAC16, the spiral nanofibers of BAC16 were changed to long nanofibers. When ODA was mixed, the hydrolytic cleavage reaction of BAC16 took place at the air/water interface and disordered spirals were obtained. When the analogous BA derivate without an alkyl chain was mixed, the phase-separating morphology was observed. These changes in the chirality and surface morphologies indicated firmly that the supramolecular chirality of BAC16 films were formed due to the cooperative arrangement of the molecules. A certain amount of matrix molecules will destroy the cooperative arrangement and thus the chirality.