Bio-based protic salts as precursors for sustainable free-standing film electrodes.

Transforming amines with low boiling points and high volatilities into protic salts is a versatile strategy to utilize low molecular weight compounds as precursors for N-doped carbon structures in a straightforward carbonization procedure. Herein, conventional mineral acids commonly used for the synthesis of protic salts were replaced by bio-derived phytic acid, which, combined with various amines and amino acids, yielded partially or fully bio-derived protic salts. The biomass-based salts showed higher char-forming ability than their mineral acid-based analogs (up to 55.9% at 800°), simultaneously providing carbon materials with significant porosity (up to 1177 m2g-1) and a considerable level of N,P,O-doping. Here, we present the first comprehensive study on the correlation between the structure of the bio-derived protic precursors and the properties of derived carbon materials to guide future designs of biomass-derived precursors for the one-step synthesis of sustainable carbon materials. Additionally, we demonstrate how to improve the textural properties of the protic-salt-derived carbons (which suffer from high brittleness) by simply upgrading them into highly flexible nanocomposites using high-quality single-walled carbon nanotubes. Consequently, self-standing electrodes for the oxygen reduction reaction were created.

Size Matters in Conjugated Polymer Chirality-Selective SWCNT Extraction.

Carbon-based nanomaterials have catalyzed breakthroughs across various scientific and engineering disciplines. The key to unlocking a new generation of tailor-made nanomaterials based on single-walled carbon nanotubes (SWCNTs) lies in the precise sorting of raw material into individual chiralities, each possessing unique properties. This can be achieved using conjugated polymer extraction (CPE), but to a very limited extent since the process generates only a few chirality-enriched suspensions. Therefore, it is imperative to comprehend the mechanism of the wrapping of SWCNTs by polymers to unleash CPE's full potential. However, the lack of a diverse palette of chirality-selective polymers with varying macromolecular parameters has hindered a comprehensive understanding of how the nature of the polymer affects the performance and selectivity of SWCNT isolation. To address this gap, multiple batches of such polymers are synthesized to elucidate the impact of molecular weight and dispersity on the purity and concentrations of the generated SWCNT suspensions. The obtained results explain the inconsistent outcomes reported in the literature, greatly improving the application potential of this promising SWCNT sorting approach. Concomitantly, the discovered significant influence of the macromolecular characteristics of conjugated polymers on the SWCNT isolation efficacy sheds considerable insight into the unresolved mechanism of this sorting technique.

Tuning the Structure of Pd@Ni-Co Nanowires and Their Electrochemical Properties.

One-dimensional transition metal materials are promising supports for precious metals used in energy production processes. Due to their electrochemical properties, 3d-group metals (such as Ni, Co, and Fe) can actively interact with catalysts by a strong metal-support interaction. This study shows that changing the Ni:Co ratio makes it possible to modulate the structure of the catalyst supports, which, in turn, provides a tool for designing their electrical and electrochemical properties. For example, Ni1-Co9 shows the highest electrical conductivity (5.8-10-4 S/cm) among all of the materials examined. On the contrary, the Pd@Ni7-Co3 system presents the highest mass activity (>2000 mA mg-1) at 0.7 V, exceeding by several times that of commercial Pt/C (>300 mA mg-1) at the same potential. Our study opens the gateway for applications of bimetallic transition metal nanowires in catalytic conversion and energy production processes.

Carbon-Based Functional Nanomaterials as Tools for Controlling the Kinetics of Tribochemical Reactions.

The aim of this article is to experimentally determine the role of the environment, consisting of a base oil (PAO), carbon nanomaterials, and optional other additives, as well as the kind of metal in contact with the lubrication film, in the stimulation of zinc dialkyldithiophosphate (ZDDP) additives' effectiveness during protective film formation. This paper focuses on the role of carbon nanostructures in energy transportation and conversion during tribological processes. An antistatic additive (ASA) (not used in lubricating oils) for jet fuels was added to disturb the process of energy conduction (electric charges) through the lubricant film and thus determine how this disturbance affects the kinetics of the ZDDP triboreaction and, consequently, the linear wear. To achieve this research goal, two types of tribological testing devices were used: an Anton Paar tribometer (TRB) and a triboelectric tribometer (TET). The novelty of the present research is in the use of the method for disturbing the flow of charge/energy through the lubricant film with an antistatic additive for jet fuels, ASA, to influence the impact of this energy on the antiwear properties of ZDDP. The following conclusions were drawn: (1) carbon-based nanostructures, i.e., CNTs, AuCNTs, graphene, and fullerenes, are able to change the rate of chemical reactions of ZDDP during tribological processes; (2) CNTs have the ability to catalyze tribochemical reactions of ZDDP, while graphene and fullerenes are not able to perform this effectively; (3) AuCNT takes the role of an inhibitor during ZDDP's triboreaction; and (4) by discharging electric charge/energy, ASA, in cooperation with CNT and AuCNT significantly reduces the rate of the ZDDP reaction.

PdNPs/NiNWs as a welding tool for the synthesis of polyfluorene derivatives by Suzuki polycondensation under microwave radiation.

Conjugated polymers are promising tools to differentiate various types of semiconducting single-walled carbon nanotubes (s-SWCNTs). However, their synthesis is challenging. Insufficient control over molecular weights, and unpredictive/unrepeatable batches hinder possible applications and scale-up. Furthermore, commercial homogeneous catalysts often require inert conditions and are almost impossible to recycle. To overcome these problems, we present a nanocatalyst consisting of magnetic nickel nanowires decorated with highly active palladium nanoparticles. A two-step wet chemical reduction protocol with the assistance of sonochemistry was employed to obtain a heterogeneous catalyst capable of conducting step-growth Suzuki polycondensation of a fluorene-based monomer. Additionally, we enhanced the performance of our catalytic system via controlled microwave irradiation, which significantly shortened the reaction time from 3 d to only 1 h. We studied the influence of the main process parameters on the yield and polymer chain length to gain insight into phenomena occurring in the presence of metallic species under microwave irradiation. Finally, the produced polymers were used to extract specific s-SWCNTs by conjugated polymer extraction to validate their utility.

Mixed-Solvent Engineering as a Way around the Trade-Off between Yield and Purity of (7,3) Single-Walled Carbon Nanotubes Obtained Using Conjugated Polymer Extraction.

The inability to purify nanomaterials such as single-walled carbon nanotubes (SWCNTs) to the desired extent hampers the progress in nanoscience. Various SWCNT types can be purified by extraction, but it is challenging to establish conditions giving rise to the isolation of high-purity fractions. The problem stems from the fact that common organic solvents or water cannot provide an optimal environment for purification. Consequently, one must often decide between the separation yield and purity of the product. This article reports how through the self-synthesis of poly(9,9-dioctylfluorene-alt-benzothiadiazole) with tailored characteristics, in-depth elucidation of the extraction process, and mixed-solvent engineering, a high-yield isolation of monochiral (7,3) SWCNTs is developed. The combination of toluene and tetralin affords a separation medium of unique properties, wherein both high yield and exceptional purity can be attained simultaneously. The reported results pave the way for further research on this rare chirality, which, as illustrated herein, is much more reactive than any of the previously separated SWCNTs.

Solvatochromism in SWCNTs suspended by conjugated polymers in organic solvents.

Despite the extensive utilization of carbon nanostructures as sensors, the factors that most affect their performance remain insufficiently understood. Many nanocarbon-based sensors are either processed in liquid environments or applied as liquid suspensions, which leads to solvatochromism, substantially influencing the underlying optical transitions. Most of the principles established so far apply only to nanocarbon species dispersed in polar environments by common surfactants, so the reported findings are not universal. For instance, they cannot describe the behavior of single-walled carbon nanotubes (SWCNTs) suspended in organic solvents by conjugated polymers (CPs), which have recently received considerable attention from the scientific community. Our research responds to this lack of knowledge and provides a thorough understanding of this topic by investigating SWCNT nanocomposites based on polyfluorenes and their co-polymers. A careful selection of an autonomous reference and precise spectral analysis allowed us to measure absolute solvatochromic shifts, by using which we identified and derived the underlying relationships affecting the optical properties of the material. Elucidation of the complex interactions between the polymer structure, SWCNT chirality, and solvent characteristics gave rise to the formulation of a revised mechanism of solvatochromism in SWCNTs. The in-depth experimental and theoretical examination revealed that in the case of CP-solubilized SWCNTs, the solvatochromic shifts strictly depend on the assignment of individual chiral types to mods and families, which experience the strain exerted by the polymer chains in different ways.

Natural and synthetic nanovectors for cancer therapy.

Nanomaterials have been extensively studied in cancer therapy as vectors that may improve drug delivery. Such vectors not only bring numerous advantages such as stability, biocompatibility, and cellular uptake but have also been shown to overcome some cancer-related resistances. Nanocarrier can deliver the drug more precisely to the specific organ while improving its pharmacokinetics, thereby avoiding secondary adverse effects on the not target tissue. Between these nanovectors, diverse material types can be discerned, such as liposomes, dendrimers, carbon nanostructures, nanoparticles, nanowires, etc., each of which offers different opportunities for cancer therapy. In this review, a broad spectrum of nanovectors is analyzed for application in multimodal cancer therapy and diagnostics in terms of mode of action and pharmacokinetics. Advantages and inconveniences of promising nanovectors, including gold nanostructures, SPIONs, semiconducting quantum dots, various nanostructures, phospholipid-based liposomes, dendrimers, polymeric micelles, extracellular and exome vesicles are summarized. The article is concluded with a future outlook on this promising field.

Highly-Selective Harvesting of (6,4) SWCNTs Using the Aqueous Two-Phase Extraction Method and Nonionic Surfactants.

Monochiral single-walled carbon nanotubes (SWCNTs) are indispensable for advancing the technology readiness level of nanocarbon-based concepts. In recent times, many separation techniques have been developed to obtain specific SWCNTs from raw unsorted materials to catalyze the development in this area. This work presents how the aqueous two-phase extraction (ATPE) method can be enhanced for the straightforward isolation of (6,4) SWCNTs in one step. Introducing nonionic surfactant into the typically employed mixture of anionic surfactants, which drive the partitioning, is essential to increasing the ATPE system's resolution. A thorough analysis of the parameter space by experiments and modeling reveals the underlying interactions between SWCNTs, surfactants, and phase-forming agents, which drive the partitioning. Based on new insight gained on this front, a separation mechanism is proposed. Notably, the developed method is highly robust, which is proven by isolating (6,4) SWCNTs from several raw SWCNT materials, including SWCNT waste generated over the years in the laboratory.

Green synthesis of silver nanoparticles based on the Raphanus sativus leaf aqueous extract and their toxicological/microbiological activities.

Silver nanoparticles (AgNPs) have several uses. Many scientists are working on producing AgNPs from plant extracts for use as biomedicines against drug-resistant bacteria and malignant cell lines. In the current study, plant-based AgNPs were synthesized using Raphanus sativus L. (RS) leaf aqua extract. Different concentrations of AgNO3 were used to optimize the synthesis process of RS-AgNPs from the aqueous leaf extract. Energy-dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscope (AFM), and UV-vis spectroscopy were used to analyze the generated materials. Furthermore, to evaluate the biological properties of the obtained materials, Bacillus subtilis (B. subtilis), Pseudomonas aeruginosa (P. aeruginosa), Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Candida albicans (C. albicans) pathogen strains were used for the minimum inhibitory concentration (MIC) assays. Subsequently, healthy cell lines (human dermal fibroblast (HDF)) and cancerous cell lines (glioma/U118, Ovarian/Skov-3, and colorectal adenocarcinoma/CaCo-2) were engaged to determine the cytotoxic effects of the synthesized NPs. The cytotoxic and anti-pathogenic potential of AgNPs synthesized by the proposed green approach was investigated. The results were encouraging compared to the standards and other controls. Plant-based AgNPs were found to be potential therapeutic agents against the human colon cancer cell (CaCo-2) and showed strong inhibitory activity on Candida albicans and Staphylococcus aureus growth. The RS-AgNPs generated have highly effective antimicrobial properties against pathogenic bacteria. Our findings also show that green RS-AgNPs are more cytotoxic against cancerous cell lines than normal cell lines. Synthesized nanoparticles with desirable morphology and ease of preparation are thought to be promising materials for antimicrobial, cytotoxic, and catalytic applications.

Understanding the partitioning behavior of single-walled carbon nanotubes using an aqueous two-phase extraction system composed of non-ionic surfactants and polymers.

In this work, a Pluronic/Dextran system was developed to discover the mechanism of the aqueous two-phase extraction (ATPE) technique, which is widely employed for the sorting of single-walled carbon nanotubes (SWCNTs) and other types of nanomaterials. The role of the phase-forming components and partitioning modulators was comprehensively investigated to gain greater insights into the differentiation process. The obtained results revealed that sodium dodecyl sulfate and sodium dodecylbenzene sulfonate operated as excellent partitioning modulators, enabling the diameter-based sorting of SWCNTs. Additionally, the data strongly suggested that different densities of various SWCNT species drove the movement of SWCNTs in the ATPE system. Consequently, the largest diameter SWCNTs were first influenced by surfactants and, thus, the nanotubes migrated towards a lower density top phase in the following order (7,5) > (8,3) > (6,5) > (6,4). Based on the in-depth analysis of the partitioning system, a mechanism was proposed that described the method in which the popular ATPE separation technique operates.

Nanofiber scaffolds based on extracellular matrix for articular cartilage engineering: A perspective.

Articular cartilage has a low self-repair capacity due to the lack of vessels and nerves. In recent times, nanofiber scaffolds have been widely used for this purpose. The optimum nanofiber scaffold should stimulate new tissue's growth and mimic the articular cartilage nature. Furthermore, the characteristics of the scaffold should match those of the cellular matrix components of the native tissue to best merge with the target tissue. Therefore, selective modification of prefabricated scaffolds based on the structure of the repaired tissues is commonly conducted to promote restoring the tissue. A thorough analysis is required to find out the architectural features of scaffolds that are essential to make the treatment successful. The current review aims to target this challenge. The article highlights different optimization approaches of nanofibrous scaffolds for improved cartilage tissue engineering. In this context, the influence of the architecture of nanoscaffolds on performance is discussed in detail. Finally, based on the gathered information, a future outlook is provided to catalyze development in this promising field.

Surprising Solid-State ESIPT Emission from Apparently Ordinary Salicyliden Glycinates Schiff Bases.

Excited-State Intramolecular Photon Transfer (ESIPT) is known for the geometry-related phenolic and imine groups. The Schiff bases formed upon condensation of salicyl aldehyde and glycine led to the formation of ESIPT models. A series of alkali metal salicyliden glycinates were analyzed by X-ray diffraction of their monocrystals and spectroscopy measurements. The X-ray analysis revealed varied hydration levels between the salts. They adapted trans geometry on the imine groups and mostly anticlinal conformation with the neighboring atoms, which is different from the other structurally-related compounds in literature. Fluorescence of these compounds was found for the crystalline forms only. Protonation of the imine nitrogen atom and further proton distribution was consistent with the ESIPT theory, which also explained the observed fluorescence with the highest Stokes shift of 10,181 cm-1 and 10.1% of fluorescence quantum yield for the sodium salt.

Azide modification forming luminescent sp2 defects on single-walled carbon nanotubes for near-infrared defect photoluminescence.

Azide functionalization produced luminescent sp2-type defects on single-walled carbon nanotubes, by which defect photoluminescence appeared in near infrared regions (1116 nm). Changes in exciton properties were induced by localization effects at the defect sites, creating exciton-engineered nanomaterials based on the defect structure design.

Doping Engineering of Single-Walled Carbon Nanotubes by Nitrogen Compounds Using Basicity and Alignment.

Charge transport properties in single-walled carbon nanotubes (SWCNTs) can be significantly modified through doping, tuning their electrical and thermoelectric properties. In our study, we used more than 40 nitrogen-bearing compounds as dopants and determined their impact on the material's electrical conductivity. The application of nitrogen compounds of diverse structures and electronic configurations enabled us to determine how the dopant nature affects the SWCNTs. The results reveal that the impact of these dopants can often be anticipated by considering their Hammett's constants and pKa values. Furthermore, the empirical observations supported by first-principles calculations indicate that the doping level can be tuned not only by changing the type and the concentration of dopants but also by varying the orientation of nitrogen compounds around SWCNTs.

Application of carbon nanotubes in sensing/monitoring of pancreas and liver cancer.

Liver and pancreatic tumors are among the third leading causes of cancer-associated death worldwide. In addition to poor prognosis, both cancer types are diagnosed at advanced and metastatic stages without typical prior symptoms. Unfortunately, the existing theranostic approaches are inefficient in cancer diagnosis and treatment. Carbon nanotubes (CNTs) have attracted increasing attention in this context due to their distinct properties, including variable functionalization capability, biocompatibility, and excellent thermodynamic and optical features. As a consequence, they are now regarded as one of the most promising materials for this application. The current review aims to summarize and discuss the role of CNT in pancreatic and liver cancer theranostics. Accordingly, the breakthroughs achieved so far are classified based on the cancer type and analyzed in detail. The most feasible tactics utilizing CNT-based solutions for both cancer diagnosis and treatment are presented from the biomedical point of view. Finally, a future outlook is provided, which anticipates how the R&D community can build on the already developed methodologies and the subsequent biological responses of the pancreatic and liver cancer cells to the directed procedures.

Doping of carbon nanotubes by halogenated solvents.

Carbon nanotubes (CNTs) play a unique role in the area of flexible conductors as they have remarkably high electrical conductivity and bend easily without deformation. Consequently, CNTs are commonly deposited on substrates as conductive tracks/coatings. Halogenated solvents are often employed to facilitate the deposition process because they dry rapidly due to their high volatility. In this work, we report that halogenated solvents can dope CNTs considerably. The study showed that the use of dichloromethane, chloroform, or bromoform for the CNT deposition significantly impacts the chemical potential of the material, thereby modifying its charge transport characteristics. As a consequence, up to four-fold improvement in electrical conductivity is noted due to doping.

Special Issue of Materials Focused on "Electrical, Thermal and Optical Properties of Nanocarbon Materials".

Due to their extraordinary properties, nanocarbon materials such as carbon nanotubes (CNTs) or graphene have been at the forefront of research for the past few decades [...].

Carbon Nanotube-Based Thermoelectric Modules Enhanced by ZnO Nanowires.

Carbon nanotubes (CNTs) have a wide range of unique properties, which have kept them at the forefront of research in recent decades. Due to their electrical and thermal characteristics, they are often evaluated as key components of thermogenerators. One can create thermogenerators exclusively from CNTs, without any metal counterpart, by properly selecting dopants to obtain n- and p-doped CNTs. However, the performance of CNT thermogenerators remains insufficient to reach wide commercial implementation. This study shows that molecular doping and the inclusion of ZnO nanowires (NWs) can greatly increase their application potential. Moreover, prototype modules, based on single-walled CNTs (SWCNTs), ZnO NWs, polyethyleneimine, and triazole, reveal notable capabilities for generating electrical energy, while ensuring fully scalable performance. Upon doping and the addition of ZnO nanowires, the electrical conductivity of pure SWCNTs (211 S/cm) was increased by a factor of three. Moreover, the proposed strategy enhanced the Power Factor values from 18.99 (unmodified SWCNTs) to 34.9 and 42.91 µW/m∙K2 for CNTs triazole and polyethyleneimine + ZnO NWs inclusion, respectively.

Tuning wettability and electrical conductivity of single-walled carbon nanotubes by the modified Hummers method.

Partial oxidation of nanocarbon materials is one of the most straightforward methods to improve their compatibility with other materials, which widens its application potential. This work studied how the microstructure and properties of high crystallinity single-walled carbon nanotubes (SWCNTs) can be tailored by applying the modified Hummers method. The influence of temperature (0, 18, 40 °C), reaction time (0 min to 7 h), and the amount of KMnO4 oxidant was monitored. The results showed that depending on the oxidation conditions, the electronic characteristics of the material could be adjusted. After optimizing the parameters, the SWCNTs were much more conductive (1369 ± 84 S/cm with respect to 283 ± 32 S/cm for the untreated material). At the same time, the films made from them exhibited hydrophilic character of the surface (water contact angle changed from 71° to 27°).