Microwave-Assisted Synthesis as a Promising Tool for the Preparation of Materials Containing Defective Carbon Nanostructures: Implications on Properties and Applications.

In this review, we focus on a small section of the literature that deals with the materials containing pristine defective carbon nanostructures (CNs) and those incorporated into the larger systems containing carbon atoms, heteroatoms, and inorganic components.. Briefly, we discuss only those topics that focus on structural defects related to introducing perturbation into the surface topology of the ideal lattice structure. The disorder in the crystal structure may vary in character, size, and location, which significantly modifies the physical and chemical properties of CNs or their hybrid combination. We focus mainly on the method using microwave (MW) irradiation, which is a powerful tool for synthesizing and modifying carbon-based solid materials due to its simplicity, the possibility of conducting the reaction in solvents and solid phases, and the presence of components of different chemical natures. Herein, we will emphasize the advantages of synthesis using MW-assisted heating and indicate the influence of the structure of the obtained materials on their physical and chemical properties. It is the first review paper that comprehensively summarizes research in the context of using MW-assisted heating to modify the structure of CNs, paying attention to its remarkable universality and simplicity. In the final part, we emphasize the role of MW-assisted heating in creating defects in CNs and the implications in designing their properties and applications. The presented review is a valuable source summarizing the achievements of scientists in this area of research.

Three-dimensional organization of pyrrolo[3,2-b]pyrrole-based triazine framework using nanostructural spherical carbon: enhancing electrochemical performance of materials for supercapacitors.

Covalent triazine-based frameworks have attracted much interest recently due to their high surface area and excellent thermal and electrochemical stabilities. This study shows that covalently immobilizing triazine-based structures on spherical carbon nanostructures results in the organization of micro- and mesopores in a three-dimensional manner. We selected the nitrile-functionalized pyrrolo[3,2-b]pyrrole unit to form triazine rings to construct a covalent organic framework. Combining spherical carbon nanostructures with the triazine framework produced a material with unique physicochemical properties, exhibiting the highest specific capacitance value of 638 F g-1 in aqueous acidic solutions. This phenomenon is attributed to many factors. The material exhibits a large surface area, a high content of micropores, a high content of graphitic N, and N-sites with basicity and semi-crystalline character. Thanks to the high structural organization and reproducibility, and remarkably high specific capacitance, these systems are promising materials for use in electrochemistry. For the first time, hybrid systems containing triazine-based frameworks and carbon nano-onions were used as electrodes for supercapacitors.

Composites containing resins and carbon nano-onions as efficient porous carbon materials for supercapacitors.

Herein, we report the functionalization of carbon nano-onions (CNOs) with the hydroxyaryl group and subsequent modifications with resins: resorcinol-formaldehyde using porogenic Pluronic F-127, resorcinol-formaldehyde-melamine, benzoxazine made of bisphenol A and triethylenetetramine, and calix[4]resorcinarene-derived using F-127. Following the direct carbonization, extensive physicochemical analysis was carried out, including Fourier transform infrared, Raman and X-ray photoelectron spectroscopy, scanning and transmission electron microscopy, and adsorption-desorption of N2. The addition of CNO to the materials significantly increases the total pore volume (up to 0.932 cm3 g-1 for carbonized resorcinol-formaldehyde resin and CNO (RF-CNO-C) and 1.242 cm3 g-1 for carbonized resorcinol-formaldehyde-melamine resin and CNO (RFM-CNO-C)), with mesopores dominating. However, the synthesized materials have poorly ordered domains with some structural disturbance; the RFM-CNO-C composite shows a more ordered structure with amorphous and semi-crystalline regions. Subsequently, cyclic voltammetry and galvanostatic charge-discharge method studied the electrochemical properties of all materials. The influence of resins' compositions, CNO content, and amount of N atoms in carbonaceous skeleton on the electrochemical performance was studied. In all cases, adding CNO to the material improves its electrochemical properties. The carbon material derived from CNO, resorcinol and melamine (RFM-CNO-C) showed the highest specific capacitance of 160 F g-1 at a current density of 2 A g-1, which is stable after 3000 cycles. The RFM-CNO-C electrode retains approximately 97% of its initial capacitive efficiency. The electrochemical performance of the RFM-CNO-C electrode results from the hierarchical porosity's stability and the presence of nitrogen atoms in the skeleton. This material is an optimal solution for supercapacitor devices.

Carbon nano-onion induced organization of polyacrylonitrile-derived block star polymers to obtain mesoporous carbon materials.

Herein, we report the synthesis of mesoporous carbon materials from diblock star copolymers derived from polyacrylonitrile. The size of the pores was controlled by manipulating the length of the polymer blocks. Furthermore, the organization of polymers on the carbon nano-onion's surface resulted in materials of higher surface area and superficial electrochemical performance.

Polymeric Network Hierarchically Organized on Carbon Nano-onions: Block Polymerization as a Tool for the Controlled Formation of Specific Pore Diameters.

The organization of specific pores in carbonaceous three-dimensional networks is crucial for efficient electrocatalytic processes and electrochemical performance. Therefore, the synthesis of porous materials with ordered and well-defined pores is required in this field. The incorporation of carbon nanostructures into polymers can create material structures that are more ordered in comparison to those of the pristine polymers. In this study we applied polymer-templated methods of carbon material preparation, in which outer blocks of the star copolymers form the carbon skeleton, while the core part is pore-forming. Well-defined 6-star-(poly(methyl acrylate)-b-poly(4-acetoxystyrene)) dendrimers were synthesized by reversible addition-fragmentation chain-transfer polymerization. They were then transformed into poly(4-vinylphenol) derivatives (namely 6-star-(poly(methyl acrylate)-b-poly(4-vinylphenol)), subjected to polycondensation with formaldehyde, and pyrolyzed at 800 °C. Cross-linking of phenolic groups provides a polymer network that does not depolymerize by pyrolysis, unlike poly(methyl acrylate) chains. The selected star polymers were attached to carbon nano-onions (CNOs) to improve the organization of the polymer chains. Herein, the physicochemical properties of CNO-polymer hybrids, including the textural and the electrochemical properties, were compared with those of the pristine pyrolyzed polymers obtained under analogous experimental conditions. For these purposes, we used several experimental and theoretical methods, such as infrared, Raman, and X-ray photoelectron spectroscopy, nitrogen adsorption/desorption measurements, scanning and transmission electron microscopy, and electrochemical studies, including cyclic voltammetry. All of the porous materials were evaluated for use as supercapacitors.

Synthesis and Structural Characterization of Pyridine-2,6-dicarboxamide and Furan-2,5-dicarboxamide Derivatives.

Derivatives based on pyridine-2-6- and furan-2,5-dicarboxamide scaffolds reveal numerous chemical properties and biological activities. This fact makes them an exciting research topic in supramolecular and coordination chemistry and in discovering new pharmacologically-active compounds. This work aimed to obtain a series of symmetrical pyridine-2-6- and furan-2,5-dicarboxamides through a condensation reaction of the appropriate acyl chlorides and aromatic amides. Successful syntheses were confirmed with NMR spectroscopy. We solved their crystal structures for seven compounds; two pyridine and five furan derivatives. Based on our crystallographic studies, we were able to indicate supramolecular features of the crystals under investigation. Additionally, Hirshfeld surface analysis allowed us to calculate a distribution of intermolecular contacts in the dicarboxamide crystals.

Microwave-Assisted Synthesis of Modified Glycidyl Methacrylate-Ethyl Methacrylate Oligomers, Their Physico-Chemical and Biological Characteristics.

In this study, well-known oligomers containing ethyl methacrylate (EMA) and glycidyl methacrylate (GMA) components for the synthesis of the oligomeric network [P(EMA)-co-(GMA)] were used. In order to change the hydrophobic character of the [P(EMA)-co-(GMA)] to a more hydrophilic one, the oligomeric chain was functionalized with ethanolamine, xylitol (Xyl), and L-ornithine. The oligomeric materials were characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy, scanning electron microscopy, and differential thermogravimetric analysis. In the final stage, thanks to the large amount of -OH groups, it was possible to obtain a three-dimensional hydrogel (HG) network. The HGs were used as a matrix for the immobilization of methylene blue, which was chosen as a model compound of active substances, the release of which from the matrix was examined using spectrophotometric detection. The cytotoxic test was performed using fluid extracts of the HGs and human skin fibroblasts. The cell culture experiment showed that only [P(EMA)-co-(GMA)] and [P(EMA)-co-(GMA)]-Xyl have the potential to be used in biomedical applications. The studies revealed that the obtained HGs were porous and non-cytotoxic, which gives them the opportunity to possess great potential for use as an oligomeric network for drug reservoirs in in vitro application.

Monocarbonyl Analogs of Curcumin Based on the Pseudopelletierine Scaffold: Synthesis and Anti-Inflammatory Activity.

Curcumin (CUR) is a natural compound that exhibits anti-inflammatory, anti-bacterial, and other biological properties. However, its application as an effective drug is problematic due to its poor oral bioavailability, solubility in water, and poor absorption from the gastrointestinal tract. The aim of this work is to synthesize monocarbonyl analogs of CUR based on the 9-methyl-9-azabicyclo[3.2.1]nonan-3-one (pseudopelletierine, granatanone) scaffold to improve its bioavailability. Granatane is a homologue of tropane, whose structure is present in numerous naturally occurring alkaloids, e.g., l-cocaine and l-scopolamine. In this study, ten new pseudopelletierine-derived monocarbonyl analogs of CUR were successfully synthesized and characterized by spectral methods and X-ray crystallography. Additionally, in vitro test of the cytotoxicity and anti-inflammatory properties of the synthesized compounds were performed.

Linking the Defective Structure of Boron-Doped Carbon Nano-Onions with Their Catalytic Properties: Experimental and Theoretical Studies.

Defects are widely present in nanomaterials, and they are recognized as the active sites that tune surface properties in the local region for catalysis. Recently, the theory linking defect structures and catalytic properties of nanocatalysts has been most commonly described. In this study, we prepared boron-doped carbon nano-onions (B-CNOs) by applying an annealing treatment of ultradispersed nanodiamond particles and amorphous boron. These experimental conditions guarantee doping of CNOs with boron atoms in the entire carbon nanostructure, thereby ensuring structural homogeneity. In our research, we discuss the correlations between defective structures of B-CNOs with their catalytic properties toward SO2 and tert-butanol dehydration. We show that there is a close relationship between the catalytic properties of the B-CNOs and the experimental conditions for their formation. It is not only the mass of the substrates used for the formation of B-CNOs that is crucial, that is, the mass ratio of NDs to amorphous B, but also the process, including temperature and gas atmosphere. As it was expected, all B-CNOs demonstrated significant catalytic activity in HSO3- oxidation. However, the subsequent annealing in an air atmosphere diminished their catalytic activity. Unfortunately, no direct relationship between the catalytic activity and the presence of heteroatoms on the B-CNO surface was observed. There was a linear dependence between catalytic activity and Raman reactivity factors for each of the B-CNO materials. In contrast to SO2 oxidation, the B-CNO-a samples showed higher catalytic activity in tert-butanol dehydration due to the presence of Brønsted and Lewis acid sites. The occurence of three types of boron-Lewis sites differing in electron donor properties was confirmed using quantitative infrared spectroscopic measurements of pyridine adsorption.

Hydrogel Properties and Their Impact on Regenerative Medicine and Tissue Engineering.

Hydrogels (HGs), as three-dimensional structures, are widely used in modern medicine, including regenerative medicine. The use of HGs in wound treatment and tissue engineering is a rapidly developing sector of medicine. The unique properties of HGs allow researchers to easily modify them to maximize their potential. Herein, we describe the physicochemical properties of HGs, which determine their subsequent applications in regenerative medicine and tissue engineering. Examples of chemical modifications of HGs and their applications are described based on the latest scientific reports.

Evaluation of the Covalent Functionalization of Carbon Nano-Onions with Pyrene Moieties for Supercapacitor Applications.

Herein, we report the surface functionalization of carbon nano-onions (CNOs) through an amidation reaction that occurs between the oxidized CNOs and 4-(pyren-4-yl)butanehydrazide. Raman and Fourier transform infrared spectroscopy methods were used to confirm the covalent functionalization. The percentage or number of groups in the outer shell was estimated with thermal gravimetric analysis. Finally, the potential applications of the functionalized CNOs as electrode materials in supercapacitors were evaluated by cyclic voltammetry and electrochemical impedance spectroscopy. Functionalization increased the specific capacitance by approximately 138% in comparison to that of the pristine CNOs, while acid-mediated oxidation reduced the specific capacitance of the nanomaterial by 24%.

A glassy carbon electrode modified with carbon nanoonions for electrochemical determination of fentanyl.

Fentanyl is a pain reliever stronger and deadlier than heroin. This lethal drug has killed many people in different countries recently. Due to the importance of the diagnosis of this drug, a fentanyl electrochemical sensor is developed based on a glassy carbon electrode (GCE) modified with the carbon nanoonions (CNOs) in this study. Accordingly, the electrochemical studies indicated the sensor is capable of the voltammetric determination of traces of fentanyl at a working potential of 0.85 (vs. Ag/AgCl). To obtain the great efficiency of the sensor some experimental factors such as time, the potential of accumulation and pH value of the electrolyte were optimized. The results illustrated a reduction and two oxidation peaks for fentanyl in phosphate buffer (PB) with pH = 7.0 under a probable mechanism of electrochemical-chemical-electrochemical (ECE). The differential pulse voltammetry (DPV) currents related to the fentanyl detection were linear with an increase of fentanyl concentrations in a linear range between 1 µM to 60 µM with a detection limit (LOD) of 300 nM. Furthermore, the values of the diffusion coefficient (D), transfer coefficient (α) and catalytic constant rate (kcat) were calculated to be 2.76 × 10-6 cm2 s-1, 0.54 and 1.76 × 104 M-1 s-1, respectively. These satisfactory results may be attributed to utilizing the CNOs in the electrode modification process due to some of its admirable characterizations of this nanostructure including high surface area, excellent electrical conductivity and good electrocatalytic activity. Consequently, these finding points the achieving a simple sensing system to measure of the fentanyl as an important drug from the judicial perspective might be a dream coming true soon.

Hydrogels as Potential Nano-, Micro- and Macro-Scale Systems for Controlled Drug Delivery.

This review is an extensive evaluation and essential analysis of the design and formation of hydrogels (HGs) for drug delivery. We review the fundamental principles of HGs (their chemical structures, physicochemical properties, synthesis routes, different types, etc.) that influence their biological properties and medical and pharmaceutical applications. Strategies for fabricating HGs with different diameters (macro, micro, and nano) are also presented. The size of biocompatible HG materials determines their potential uses in medicine as drug carriers. Additionally, novel drug delivery methods for enhancing treatment are discussed. A critical review is performed based on the latest literature reports.

Nanostructural catalyst: metallophthalocyanine and carbon nano-onion with enhanced visible-light photocatalytic activity towards organic pollutants.

Metallophthalocyanine (MPc) and carbon nano-onion (CNO) derivatives were synthesized and characterized by using ultraviolet-visible spectroscopy, infrared and Raman spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy and X-ray powder diffraction. The unmodified CNOs and MPc-CNO derivatives were used as photocatalysts for rhodamine B (RhB) degradation under visible-light irradiation. The photocatalytic studies revealed that the MPc-CNO nanostructural materials simultaneously exhibited a high absorption capacity and an excellent visible-light-driven photocatalytic activity towards RhB. These nanostructures possess great potential for use as active photocatalysts for organic pollutant degradation.

Opening the internal structure for transport of ions: improvement of the structural and chemical properties of single-walled carbon nanohorns for supercapacitor electrodes.

We investigated the electrochemical performance of single-walled carbon nanohorns (SWCNHs) for use as supercapacitor electrodes. For the first time, we used acid-treatment for oxidation of SWCNHs and hole creation in their structure. A detailed study was performed on the correlation between the oxidation of SWCNHs via acid treatment and variable acid treatment times, the structural properties of the oxidized carbon nanostructures, and the specific capacitance of the SWCNH electrodes. We showed that simple functionalization of carbon nanostructures under controlled conditions leads to an almost 3-fold increase in their specific capacitance (from 65 to 180 F g-1 in 0.1 M H2SO4). This phenomenon indicates higher accessibility of the surface area of the electrodes by electrolyte ions as a result of gradual opening of the SWCNH internal channels.

Preparation and Characterization of Magnetic Fe3O4/CdWO4 and Fe3O4/CdWO4/PrVO4 Nanoparticles and Investigation of Their Photocatalytic and Anticancer Properties on PANC1 Cells.

Fe3O4/CdWO4 and Fe3O4/CdWO4/PrVO4 magnetic nanoparticles were prepared at different molar ratios of PrVO4 to previous layers (Fe3O4/CdWO4) via the co-precipitation method assisted by a sonochemical procedure, in order to investigate the photocatalytic performance of these systems and their cytotoxicity properties. The physico-chemical properties of these magnetic nanoparticles were determined via several experimental methods: X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier transformation infrared spectroscopy and ultraviolet-visible diffuse reflection spectroscopy, using a vibrating sample magnetometer and a scanning electron microscope. The average sizes of these nanoparticles were found to be in the range of 60-100 nm. The photocatalytic efficiency of the prepared nanostructures was measured by methylene blue degradation under visible light (assisted by H2O2). The magnetic nanosystem with a 1:2:1 ratio of three oxide components showed the best performance by the degradation of ca. 70% after 120 min of exposure to visible light irradiation. Afterwards, this sample was used for the photodegradation of methyl orange, methyl violet, fenitrothion, and rhodamine-B pollutants. Finally, the mechanism of the photocatalytic reaction was examined by releasing ˙OH under UV light in a system including terephthalic acid, as well as O2-, OH, and hole scavengers. Additionally, the cytotoxicity of each synthesized sample was assessed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay against the human cell line PANC1 (cancer), and its IC50 was approximately 125 mg/L.

Carbon nanoonion-ferrocene conjugates as acceptors in organic photovoltaic devices.

Many macromolecular systems, including carbon nanostructures (CNs), have been synthesized and investigated as acceptors in photovoltaic devices. Some CNs have shown interesting electrochemical, photophysical and electrocatalytic properties and have been used in energy and sustainability applications. This study focuses on the covalent functionalization of carbon nanoonion (CNO) surfaces with ferrocene moieties to obtain donor-acceptor systems involving CNOs as acceptors. The systems were synthesized and characterized by infrared, Raman, UV-vis and fluorescence spectroscopies, thermogravimetric analysis, scanning electron microscopy, nitrogen adsorption and electrochemical measurements. The HOMO-LUMO levels were calculated to evaluate the possibility of using these systems in photoactive devices. In this study, for the first time, the CNO-based derivatives were applied as acceptors in the active layer of photovoltaic devices. This study is the first to use large CNO-based derivatives as acceptors in organic photovoltaic devices, and a power conversion efficiency as high as 1.89% was achieved.

Onion-Like Carbon Nanostructures: An Overview of Bio-Applications.

This article presents a brief review of the knowledge concerning onion-like carbons (OLCs). These nanostructures are some of the most fascinating carbon forms due to their unusual structure and physico-chemical properties. Generally, OLCs consist of a hollowspherical fullerene core surrounded by concentric graphitic layers with increasing diameter. Nevertheless, they can have different size, shape and type of core, which determine their physicochemical properties. In this article, we review the most important literature reports in this area and briefly describe these nanostructures, their physical and chemical properties and their potential uses with a focus on biomedicine.

Nanoforest: Polyaniline Nanotubes Modified with Carbon Nano-Onions as a Nanocomposite Material for Easy-to-Miniaturize High-Performance Solid-State Supercapacitors.

This article describes a facile low-cost synthesis of polyaniline nanotube (PANINT)⁻carbon nano-onion (CNO) composites for solid-state supercapacitors. Scanning electron microscopic (SEM) analyses indicate a uniform and ordered composition for the conducting polymer nanotubes immobilized on a thin gold film. The obtained nanocomposites exhibit a brush-like architecture with a specific capacitance of 946 F g-1 at a scan rate of 1 mV s-1. In addition, the nanocomposites offer high conductivity and a porous and well-developed surface area. The PANINT⁻CNO nanocomposites were tested as electrodes with high potential and long-term stability for use in easy-to-miniaturize high-performance supercapacitor devices.