Non-covalent Modification Research Articles

Effect of dual-modified CNTs on strength and chloride resistance of cementitious systems

This study is undertaken to explore, first, the dispersibility of dual-modified carbon nanotubes (CNTs) by way of non-covalent modification. Various non-ionic and ionic surfactants were employed and mutually combined with varying relative proportions. Then, the best few combinations from the dispersion test were used further for producing mortar mixtures reinforced with CNTs. These samples were later assessed for their mechanical strength and chloride resistance. A suite of morphological, thermal and microstructural characterisations was carried out to understand the underlying mechanisms. The results show that, compared with the single modification, the dispersibility of CNT could be improved more significantly by way of the dual modification. In particular, 70–90% of non-ionic surfactant, in proportion to the total surfactant addition, imparted the best dispersibility to CNTs in an aqueous solution. In addition, X-ray diffraction, thermogravimetric analysis, mercury intrusion porosimetry and scanning electron microscopy outputs reveal that the enhanced dispersion of CNTs by dual modification promoted the hydration process and the ensuing microstructure evolution of mortar specimens. Together, these offset the strength reduction imparted by entrained pores when introducing chemical surfactants and, more importantly, empowered the chloride resistance of CNT-reinforced mortars.

Load transfer mechanism at the calcium silicate hydrate/carbon nanotubes interface changed by carbon nanotubes surface modification investigated from atomic simulation

The surface modification of carbon nanotubes (CNT) can further improve the ductility of the cement/CNT composites. Atomic simulations were employed to decode the alteration of the interfacial load transfer mechanism by PVA addition, non-covalent bond modification of CNTs. The results of the pull-out simulations show that PVA significantly enhances the load transfer at the organic–inorganic interface. Interfacial load transfer depends on effective interfacial interactions, which in turn depend on interfacial chemical bonding. The interfacial region is more complexly reorganized by PVA, accompanied by the renewal of interfacial bonding. The addition of PVA could add new ion pairs (OCNT-Ca-OPVA-Ca-OCSH and HCNT-OPVA-Ca-OCSH) and lots of hydrogen bonds without detriment to the original linkage (OCNT-Ca-OCSH), in turn forming a strong network of chemical bonds intertwined with direct and indirect connections. Due to the intertwined network, the load transfer at the interface is partitioned and transferred in multiple paths, contributing to an increased interfacial strength. During the pull-out process, the load distribution between CNT, PVA and CSH evolves constantly, which is beneficial to damage retardation of the cement/CNT composites.

A permselective and multifunctional 3D N-doped carbon nanotubes interlayer for high-performance lithium-sulfur batteries

Here in-situ Raman indicates that the shuttle effect induced by polysulfides occurs during the whole discharge and charge process in lithium-sulfur batteries (LSBs), leading to irreversible loss of sulfur and generation of lithium dendrites. To solve the above problems, we construct a N-doped carbon nanotubes/carbonized cellulose paper (IF-N-CNTs-CCP) with three-dimensional conductive network structure through noncovalent modification assisted high-temperature carbonization. IF-N-CNTs-CCP interlayer can effectively block the shuttle effect by strong chemisorption and physical barrier, improving the utilization of sulfur. However, it doesn't prevent the free migration of lithium ions, resulting in a remarkable acceleration of electrochemical reaction kinetics. Moreover, the three-dimensional IF-N-CNTs-CCP interlayer can provide a large number of lithiophilic sites and significantly reduce the regional current density, thus inhibiting the growth of lithium dendrites, enhancing the safety of LSBs. As a result, the LSBs with IF-N-CNTs-CCP interlayer deliver a negligible capacity fading rate of 0.037% per cycle after 500 cycles at 2.0 C, and a high-capacity retention of 95% at 0.2 C with a sulfur loading of 3 mg/cm2 with a correspondingly lean electrolyte condition (E/S ratio = 6 µL/mg). This work provides an effective strategy for the application of functional interlayer in LSBs, which can suppress the shuttle effect and lithium dendrite.

Modification of Cellulose Micro- and Nanomaterials to Improve Properties of Aliphatic Polyesters/Cellulose Composites: A Review.

Aliphatic polyesters/cellulose composites have attracted a lot attention due to the perspectives of their application in biomedicine and the production of disposable materials, food packaging, etc. Both aliphatic polyesters and cellulose are biocompatible and biodegradable polymers, which makes them highly promising for the production of “green” composite materials. However, the main challenge in obtaining composites with favorable properties is the poor compatibility of these polymers. Unlike cellulose, which is very hydrophilic, aliphatic polyesters exhibit strong hydrophobic properties. In recent times, the modification of cellulose micro- and nanomaterials is widely considered as a tool to enhance interfacial biocompatibility with aliphatic polyesters and, consequently, improve the properties of composites. This review summarizes the main types and properties of cellulose micro- and nanomaterials as well as aliphatic polyesters used to produce composites with cellulose. In addition, the methods for noncovalent and covalent modification of cellulose materials with small molecules, polymers and nanoparticles have been comprehensively overviewed and discussed. Composite fabrication techniques, as well as the effect of cellulose modification on the mechanical and thermal properties, rate of degradation, and biological compatibility have been also analyzed.

Boron Nitride Nanosheets Reinforced Thermoplastics Nanocomposites for Thermal Management Applications: A Mini Review

AbstractIn this review, the synthesis methods and their characterization of boron nitride nanosheets (BNNs) are discussed along with their advantages and limitations. The BNNs functionalization using covalently and noncovalently routes are discussed. Further, the incorporation of BNNs in thermoplastics matrix nanocomposites on thermal properties in specific is discussed in detail. The influence of functionalization of BNNs using covalent and noncovalent modification routes on dispersion and thermal properties of thermoplastic matrix nanocomposites is discussed in detail. A brief roadmap for future research in the area of BNNs filled polymer nanocomposites is also discussed.

Functionalization of Graphene by π–π Stacking with C60/C70/Sc3N@C80 Fullerene Derivatives for Supercapacitor Electrode Materials

Non-covalent modification of graphene is one of the strategies used for enhancing its energy storage properties. Herein, we report the design and synthesis of a series of fullerene derivatives that are capable of assembly on graphene sheets by π–π stacking interactions. Newly synthesized graphene-fullerene hybrid nanomaterials were characterized using spectroscopic and microscopic techniques. In order to determine the specific capacitance of obtained electrode materials galvanostatic charge-discharge measurements were performed. The obtained results allowed the determination of which fullerene core and type of substituent introduced on its surface can increase the capacitance of resulting electrode. Benefiting from introduced fullerene derivative molecules, graphene with naphthalene functionalized C70 fullerene showed specific capacitance enhanced by as much as 15% compared to the starting material.

Noncovalent Modification Strategy with Achiral Phosphoric Acid Diesters for Designing a Chiral Brønsted Base Organocatalyst

Abstract A strategy for designing chiral Brønsted base organocatalysts through noncovalent modification of a chiral dibasic molecule with an achiral phosphoric acid diester is introduced for the first time. Such a molecular modification concept utilizing acid-base interactions may facilitate the on-demand design of asymmetric organocatalysts, as preliminarily demonstrated in this work.

Non-covalent interaction of soy protein isolate and catechin: Mechanism and effects on protein conformation

Understanding the molecular mechanism behind protein–polyphenol interactions is critical for the application of protein–polyphenol compounds in foods. The purpose of this research was to investigate the non-covalent interaction mechanism between soy protein isolate (SPI) and catechin and its effect on protein conformation. We observed that particle size, ζ-potential, and polyphenol bound equivalents of SPI increased significantly after non-covalent modification with catechin. These changes caused SPI to aggregate and form a network-like structure. Fourier transform infrared spectroscopy (FTIR) indicated that increased catechin concentrations caused SPI to become looser and more disordered as its α-helix and β-sheet transformed into β-turn and random coil. Furthermore, internal structure of SPI was opened and its hydrophobic groups were exposed to a polar environment, which was demonstrated by decreased surface hydrophobicity. Thermodynamic analysis and molecular docking results showed that the main forces present between SPI and catechin were hydrophobic interactions and hydrogen bonds.

Impact of phosphonium-based ionic liquids-modified carbon nanotube on the microwave absorbing properties and crystallization behavior of poly(vinylidene fluoride) composites

Poly(vinylidene fluoride) (PVDF)/multi-walled carbon nanotube (CNT) conducting composites were prepared using two procedures: melt mixing and dry-mixing in a ball-mill. Alkyl-phosphonium – based ionic liquids were also employed as noncovalent modifier for CNT. The composites prepared by dry-blending displayed higher conductivity. The β/γ crystal formation in the PVDF matrix was induced by CNT modified with ionic liquids using melt blending approach, as indicated by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analysis. The composite prepared by melt mixing, loaded with 0.5 wt% of CNT modified with trihexyl-(tetradecyl) phosphonium bistriflimide and 3 mm thick displayed outstanding microwave absorbing properties with minimum reflection loss (RL) of −13.6 dB at 11 GHz. Moreover, broad bandwidth (>3.1 GHz with microwave attenuation higher that 90%) and minimum RL of −39 dB were achieved using triple layered structure with PVDF/CNT composites with 1 mm thickness stacked together in appropriate arrangement.

Structures of the archaerhodopsin-3 transporter reveal that disordering of internal water networks underpins receptor sensitization

Like other photoreceptor proteins, the archaerhodopsin-3 (AR3) protein has a desensitized, inactive state which is formed in the prolonged absence of light. This dark-adapted (DA) state must be converted to the light-adapted (LA) or resting state, before the protein can generate a proton motive force. In general, receptor desensitization is commonly achieved through reversible covalent or non-covalent modifications, which typically modulate intramolecular bonding networks to stabilize a conformation that is distinct from the active resting or ground state.

Surface modification of carbon fiber with imidazolium ionic liquids

ABSTRACT Carbon fiber composites are high-performance materials commonly used in advanced applications and their performance is highly dependent on the fiber-matrix interfacial interaction. The non-polar carbon fiber surface may be modified via different techniques to improve adhesion with the polymer matrix. In this work, non-covalent surface modification of carbon fiber has been carried out using two different imidazolium ionic liquids, 1-n-butyl-3-methyl imidazolium bis(trifluoromethylsulfonyl) imide (hydrophobic) and 1-n-butyl-3-methylimidazolium chloride (hydrophilic). The treatment was performed by immersing the fiber into 10 wt. % methanolic ionic liquid solution for 10 min. Treated fibers were characterized using Fourier-transform infrared spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy confirmed the presence of ionic liquid on the carbon fiber surface. Surface morphology of treated fibers analyzed by scanning electron microscopy showed ionic liquid moieties. Wettability of the treated carbon fiber with epoxy resin significantly increased, with a decrease in contact angle greater than 15°. Interfacial shear strength between the modified carbon fiber and epoxy increased up to 56.5% with respect to the unsized carbon fiber, being comparable with epoxy-sized fibers. Thus, the proposed surface modification has the potential to improve the interfacial performance of carbon fiber polymer composites.

Bioengineering of virus-like particles as dynamic nanocarriers for in vivo delivery and targeting to solid tumours.

Virus-like particles (VLPs) are known as self-assembled, non-replicative and non-infectious protein particles, which imitate the formation and structure of original wild type viruses, however, lack the viral genome and/or their fragments. The capacity of VLPs to encompass small molecules like nucleic acids and others has made them as novel vessels of nanocarriers for drug delivery applications. In addition, VLPs surface have the capacity to achieve variation of the surface display via several modification strategies including genetic modification, chemical modification, and non-covalent modification. Among the VLPs nanocarriers, Hepatitis B virus core (HBc) particles have been the most encouraging candidate. HBc particles are hollow nanoparticles in the range of 30-34nm in diameter and 7nm thick envelopes, consisting of 180 or 240 copies of identical polypeptide monomer. They also employ a distinctive position among the VLPs carriers due to the high-level synthesis, which serves as a strong protective capsid shell and efficient self-assembly properties. This review highlights on the bioengineering of HBc particles as dynamic nanocarriers for in vivo delivery and specific targeting to solid tumours.

Green modification of graphene dispersion with high nanosheet content, good dispersibility, and long storage stability.

In this work, an easy, green, noncovalent surface modification of pristine graphene (GR) was carried out using a single-step method between sodium carboxymethyl cellulose (CMC) and pristine GR, resulting in the formation of a modified CMC–GR (CGR) dispersion with 15% nanosheet content, the first reported in water. Results obtained from thermogravimetry analysis (TGA), Raman spectroscopy, and atomic force microscopy (AFM) confirm that the CMC modifier is successfully decorated on the pristine GR surface. Analyses of transmittance spectrum, zeta potential and transmittance electron microscopy (TEM) images reveal that the modified CGR has a high degree of dispersion. More importantly, the pristine GR is insoluble, while the modified CGR-3, mixed with 1.1 wt% CMC modifier, is easily well dispersed in water and has good flowability, and no sedimentation is observed after more than 3 months.

A novel anti-tumor/anti-tumor-associated fibroblast/anti-mPEG tri-specific antibody to maximize the efficacy of mPEGylated nanomedicines against fibroblast-rich solid tumor.

The therapeutic efficacy of methoxypolyethylene glycol (mPEG)-coated nanomedicines in solid tumor treatment is hindered by tumor-associated fibroblasts (TAFs), which promote tumor progression and form physical barriers. We developed an anti-HER2/anti-FAP/anti-mPEG tri-specific antibody (TsAb) for one-step conversion of mPEG-coated liposomal doxorubicin (Lipo-Dox) to immunoliposomes, which simultaneously target HER2+ breast cancer cells and FAP+ TAFs. The non-covalent modification did not adversely alter the physical characteristics and stability of Lipo-Dox. The TsAb-Lipo-Dox exhibited specific targeting and enhanced cytotoxicity against mono- and co-cultured HER2+ breast cancer cells and FAP+ TAFs, compared to bi-specific antibody (BsAb) modified or unmodified Lipo-Dox. An in vivo model of human breast tumor containing TAFs also revealed the improved tumor accumulation and therapeutic efficacy of TsAb-modified mPEGylated liposomes without signs of toxicity. Our data indicate that arming clinical mPEGylated nanomedicines with the TsAb is a feasible and applicable approach for overcoming the difficulties caused by TAFs in solid tumor treatment.

THE INFLUENCE OF POLYETHYLENE GLYCOL MODIFIERS ON THE DISTRIBUTION OF CARBON NANOTUBES IN THE POLYMER MATRIX

In polymer nanocomposites filled with carbon nanotubes (CNTs), it is very difficult to ensure the uniformity of the distribution of nanotubes in the polymer matrix, as well as the stability of this dispersion over time. Therefore, in such systems, over time, due to the strong van der Waals forces of attraction between individual nanotubes, the aggregation of filler particles takes place, which leads to the transition from the nano to the micro level of their structural organization. Such a transition negatively affects the set of functional properties of polymer nanocomposites filled with CNTs. Therefore, the development of new approaches to the stabilization of nanoparticles in order to prevent their aggregation for the creation of nanocomposite materials with improved functional characteristics is an urgent task. The paper studied the effect of non-covalent modification of carbon nanotubes using polyethylene glycol (PEG) of different molecular weight on the degree of their distribution in the polymer matrix. The peculiarities of the distribution of CNTs of various types: unmodified and non-covalently modified, using different molecules of PEG, nanotubes were studied. From the analysis of microscopic images, it was found that modified CNTs are more evenly distributed in the polymer matrix than unmodified nanotubes, which can be explained by the different nature of the interaction between the polymer matrix and CNTs. It was determined that for systems containing modified CNTs, a higher value of the fractal dimension is observed, which indicates the formation of looser CNT aggregates, while unmodified CNTs show a tendency to form denser aggregates. It was found that the value of the fractal dimension for functionalized CNTs is close to 3, which indicates a uniform distribution of CNTs. It was established that the modifier based on PEG-10000 exerts the highest stabilizing effect. At the same time, CNTs are most evenly distributed throughout the volume of the material.

ВПЛИВ МОДИФІКАЦІЇ ВУГЛЕЦЕВИХ НАНОТРУБОК НА МІКРОСТРУКТУРУ ТА ФУНКЦІОНАЛЬНІ ВЛАСТИВОСТІ ПОЛІМЕРНИХ НАНОКОМПОЗИТІВ НА ОСНОВІ ПОЛІЕТИЛЕНУ

To expand the operational characteristics of polymer materials, nanofillers are introduced into their composition, one of the most promising is carbon nanotubes. However, the creation of such nanocomposite materials is associated with a number of difficulties, in particular with the need to evenly distribute the filler in the polymer matrix.One of the promising directions for solving the distribution problem is the functionalization of carbon nanotubes using various methods. Each method has its advantages and disadvantages. Most of them lead to the growth of only certain propertiesof materials, but their application is an expensive and time-consuming process.The analysis of research and publications in the field of improving the functional characteristics of polymer nanocomposite materials showed that the issue of non-covalent modification of carbon nanotubes and their use as a filler for the creation of structural materials is currently receiving little attention in the scientific literature.The purpose of this work is to improve the functional characteristics of polymer nanocomposite materials based on high-density polyethylene by means of non-covalent modification of carbon nanotubes introduced into their composition.The scientific article presents the results of studies of the microstructure and functional characteristics of polymer nanocomposite materials based on polyethylene by introducing modified carbon nanotubes into their composition. In order to improve the properties of the materials, nanotubes were modified using polyethylene glycol. Using the methods of optical microscopy, impedance spectroscopy and mechanical tests the microstructure, electrical and mechanical characteristics of polymer nanocomposite materials were investigated. It is shown that the non-covalent functionalization of CNTs by means of treatment with polyethylene glycol leads to a better distribution of nanotubes in the polymer matrix and an improvement of the electrical and mechanical properties of polyethylene-based nanocomposite materials.

Non-covalent modification of single wall carbon nanotubes (SWCNTs) by thienothiophene derivatives.

Non-covalent functionalization of single wall carbon nanotubes (SWCNTs) has been conducted using several binding agents with surface π-interaction forces in recent studies. Herein, we present the first example of non-covalent functionalization of sidewalls of SWCNTs using thienothiophene (TT) derivatives without requiring any binding agents. Synthesized TT derivatives, TT-CN-TPA, TT-CN-TPA2 and TT-COOH-TPA, were attached directly to SWCNTs through non-covalent interactions to obtain new TT-based SWCNT hybrids, HYBRID 1-3. Taking advantage of the presence of sulfur atoms in the structure of TT, HYBRID 1, as a representative, was treated with Au nanoparticles for the adsorption of Au by sulfur atoms, which generated clear TEM images of the particles. The images indicated the attachment of TTs to the surface of SWCNTs. Thus, the presence of sulfur atoms in TT units made the binding of TTs to SWCNTs observable via TEM analysis through adsorption of Au nanoparticles by the sulfur atoms. Surface interactions between TTs and SWCNTs of the new hybrids were also clarified by classical molecular dynamic simulations, a quantum mechanical study, and SEM, TEM, AFM and contact angle (CA) analyses. The minimum distance between a TT and a SWCNT reached up to 3.5 Å, identified with strong peaks on a radial distribution function (RDF), while maximum interaction energies were raised to -316.89 kcal mol-1, which were determined using density functional theory (DFT).

Chitosan Functionalization: Covalent and Non-Covalent Interactions and Their Characterization.

Chitosan (CS) is a natural biopolymer that has gained great interest in many research fields due to its promising biocompatibility, biodegradability, and favorable mechanical properties. The versatility of this low-cost polymer allows for a variety of chemical modifications via covalent conjugation and non-covalent interactions, which are designed to further improve the properties of interest. This review aims at presenting the broad range of functionalization strategies reported over the last five years to reflect the state-of-the art of CS derivatization. We start by describing covalent modifications performed on the CS backbone, followed by non-covalent CS modifications involving small molecules, proteins, and metal adjuvants. An overview of CS-based systems involving both covalent and electrostatic modification patterns is then presented. Finally, a special focus will be given on the characterization techniques commonly used to qualify the composition and physical properties of CS derivatives.

VirPorters: Insights into the action of cationic and histidine-rich cell-penetrating peptides

The utilization of nanoparticles for the intracellular delivery of theranostic agents faces one substantial limitation. Sequestration in intracellular vesicles prevents them from reaching the desired location in the cytoplasm or nucleus to deliver their cargo. We investigated whether three different cell-penetrating peptides (CPPs), namely, octa-arginine R8, polyhistidine KH27K and histidine-rich LAH4, could promote cytosolic and/or nuclear transfer of unique model nanoparticles—pseudovirions derived from murine polyomavirus. Two types of CPP-modified pseudovirions that carry the luciferase reporter gene were created: VirPorters-IN with CPPs genetically attached to the capsid interior and VirPorters-EX with CPPs noncovalently associated with the capsid exterior. We tested their transduction ability by luciferase assay and monitored their presence in subcellular fractions. Our results confirmed the overall effect of CPPs on the intracellular destination of the particles and suggested that KH27K has the potential to improve the cytosolic release of pseudovirions. None of the VirPorters caused endomembrane damage detectable by the Galectin-3 assay. Remarkably, a noncovalent modification was required to promote high transduction of the reporter gene and cytosolic delivery of pseudovirions mediated by LAH4. Together, CPPs in different arrangements have demonstrated their potential to improve pseudovirion invasion into cells, and these findings could be useful for the development of other nanoparticle-based delivery systems.

Applications of Pristine and Functionalized Carbon Nanotubes, Graphene, and Graphene Nanoribbons in Biomedicine.

This review is dedicated to a comprehensive description of the latest achievements in the chemical functionalization routes and applications of carbon nanomaterials (CNMs), such as carbon nanotubes, graphene, and graphene nanoribbons. The review starts from the description of noncovalent and covalent exohedral modification approaches, as well as an endohedral functionalization method. After that, the methods to improve the functionalities of CNMs are highlighted. These methods include the functionalization for improving the hydrophilicity, biocompatibility, blood circulation time and tumor accumulation, and the cellular uptake and selectivity. The main part of this review includes the description of the applications of functionalized CNMs in bioimaging, drug delivery, and biosensors. Then, the toxicity studies of CNMs are highlighted. Finally, the further directions of the development of the field are presented.