Shape-Controlled Iron-Paraffin Composites as γ- and X-ray Shielding Materials Formable by Warmth-of-Hands-Derived Plasticity.

The design of shielding materials against ionizing radiation while simultaneously displaying enhanced multifunctional characteristics remains challenging. Here, for the first time, we present moldable paraffin-based iron nano- and microcomposites attenuating γ- and X-radiation. The moldability was gained by the warmth-of-hands-driven plasticity, which allowed for obtaining a specific shape of the composites at room temperature. The manufactured composites contained iron particles of various sizes, ranging from 22 nm to 63 µm. The target materials were widely characterized using XRD, NMR, Raman, TGA, SEM, and EDX. In the case of microcomposites, the shielding properties were developed at two concentrations: 10 and 50 wt %. The statistically significant results indicate that the iron particle size has a negligible effect on the shielding properties of the nano- and microcomposites. On the other hand, the higher iron particle contents significantly affected the attenuating ability, which emerged even as superior to the elemental aluminum in the X-ray range: at a 70 kV anode voltage, the half value layer was 6.689, 1.882, and 0.462 cm for aluminum, paraffin + 10 wt % Fe 3.5-6.5 µm, and paraffin + 50 wt % Fe 3.5-6.5 µm microcomposites, respectively. Importantly, the elaborated methodology-in situ cross-verified in the hospital studies recording real-life sampling-opens the pathway to high-performance, eco-friendly, lightweight, and recyclable shields manufactured via fully reproducible and scalable protocols.

Paintable Carbon Nanotube Coating-Based Textronics for Sustained Holter-Type Electrocardiography.

A growing population suffering from or at high risk of developing cardiovascular diseases can benefit from rapid, precise, and readily available diagnostics. Textronics is an interdisciplinary approach for designing and manufacturing high-performance flexible electronics integrated with textiles for various applications, with electrocardiography (ECG) being the most convenient and most frequently used diagnostic technique for textronic solutions. The key challenges that still exist for textronics include expedient manufacturing, adaptation to human subjects, sustained operational stability for Holter-type data acquisition, reproducibility, and compatibility with existing solutions. The present study demonstrates conveniently paintable ECG electroconductive coatings on T-shirts woven from polyester or 70% polyamide and 30% polyester. The up to 600-µm-thick coatings encompass working electrodes of low resistivity 60 Ω sq-1 sheathed in the insulated pathways-conjugable with a wireless, multichannel ECG recorder. Long (800 µm) multiwalled carbon nanotubes, with scalable reproducibility and purity (18 g per round of synthesis), constituted the electroactive components and were embedded into a commercially available screen-printing acrylic base. The resulting paint had a viscosity of 0.75 Pa·s at 56 s-1 and 25 °C and was conveniently applied using a paintbrush, making this technique accessible to manufacturers. The amplified and nondigitally processed ECG signals were recorded under dry-skin conditions using a certified ECG recorder. The system enabled the collection of ECG signals from two channels, allowing the acquisition of cardiac electrical activity on six ECG leads with quality at par with medical diagnostics. Importantly, the Holter-type ECG allowed ambulatory recording for >24 h under various activities (sitting, sleeping, walking, and running) in three male participants. The ECG signal was stable for >5 cycles of washing, a level of stability not reported yet previously. The developed ECG-textronic application possesses acceptable and reproducible characteristics, making this technology a suitable candidate for further testing in clinical trials.

High-Performance Ionanofluids from Subzipped Carbon Nanotube Networks.

Investments in the transfer and storage of thermal energy along with renewable energy sources strengthen health and economic infrastructure. These factors intensify energy diversification and the more rapid post-COVID recovery of economies. Ionanofluids (INFs) composed of long multiwalled carbon nanotubes (MWCNTs) rich in sp2-hybridized atoms and ionic liquids (ILs) display excellent thermal conductivity enhancement with respect to the pure IL, high thermal stability, and attractive rheology. However, the influence of the morphology, physicochemistry of nanoparticles and the IL-nanostructure interactions on the mechanism of heat transfer and rheological properties of INFs remain unidentified. Here, we show that intertube nanolayer coalescence, supported by 1D geometry assembly, leads to the subzipping of MWCNT bundles and formation of thermal bridges toward 3D networks in the whole INF volume. We identified stable networks of straight and bent MWCNTs separated by a layer of ions at the junctions. We found that the interactions between the ultrasonication-induced breaking nanotubes and the cations were covalent in nature. Furthermore, we found that the ionic layer imposed by close MWCNT surfaces favored enrichment of the cis conformer of the bis(trifluoromethylsulfonyl)imide anion. Our results demonstrate how the molecular perfection of the MWCNT structure with its supramolecular arrangement affects the extraordinary thermal conductivity enhancement of INFs. Thus, we gave the realistic description of the interactions at the IL-CNT interface with its (super)structure and chemistry as well as the molecular structure of the continuous phase. We anticipate our results to be a starting point for more complex studies on the supramolecular zipping mechanism. For example, ionically functionalized MWCNTs toward polyionic systems─of projected and controlled nanolayers─could enable the design of even more efficient heat-transfer fluids and miniaturization of flexible electronics.

Electrical Properties of the Carbon Nanotube-Reinforced Geopolymer Studied by Impedance Spectroscopy.

Geopolymers, recognized as an ecological alternative to cement concrete, are gaining more and more interest from researchers and the construction industry. Due to the registrable electrical conductivity, this material also attracts the interest of other fields of science and industry as a potential functional material. The article discusses the used geopolymer material, created on the basis of metakaolin and waste Cathode Ray Tubes (CRT) glass, reinforced with ultra-long in-house carbon nanotubes (CNT), in the context of its use as a smart material for Structural Health Monitoring. Long in-house made carbon nanotubes were added to enhance the electrical conductivity of the geopolymer. The impedance spectroscopy method was applied to investigate the conductive properties of this material. The paper shows the microscopic and mechanical characteristics of the materials and presents the results of promising impedance spectroscopy tests.

Biomimetically Inspired Highly Homogeneous Hydrophilization of Graphene with Poly(l-DOPA): Toward Electroconductive Coatings from Water-Processable Paints.

Water-based processing of graphene-typically considered as physicochemically incompatible with water in the macroscale-emerges as the key challenge among the central postulates of green nanotechnology. These problematic concerns are derived from the complex nature of graphene in the family of sp2-carbon nanoallotropes. Indeed, nanomaterials hidden under the common "graphene" signboard are very rich in morphological and physicochemical variants. In this work, inspired by the adhesion chemistry of mussel biomaterials, we have synthesized novel, water-processable graphene-polylevodopa (PDOPA) hybrids. Graphene and PDOPA were covalently amalgamated via the "growth-from" polymerization of l-DOPA (l-3,4-dihydroxyphenylalanine) monomer in air, yielding homogeneously PDOPA-coated (23 wt %) (of thickness 10-20 nm) hydrophilic flakes. The hybrids formed >1 year stable and water-processable aqueous dispersions and further conveniently processable paints of viscosity 0.4 Pa·s at 20 s-1 and a low yield stress τ0 up to 0.12 Pa, hence exhibiting long shelf-life stability and lacking sagging after application. Demonstrating their applicability, we have found them as surfactant-like nanoparticles stabilizing the larger, pristine graphene agglomerates in water in the optimized graphene/graphene-PDOPA weight ratio of 9:1. These characteristics enabled the manufacture of conveniently paintable coatings of low surface resistivity of 1.9 kΩ sq-1 (0.21 Ω·m) which, in turn, emerge as potentially applicable in textronics, radar-absorbing materials, or electromagnetic interference shielding.

Effect of ultrasonication time on microstructure, thermal conductivity, and viscosity of ionanofluids with originally ultra-long multi-walled carbon nanotubes.

The stability along with thermal and rheological characteristics of ionanofluids (INFs) profoundly depend on the protocol of preparation. Therefore, in this work, the effect of ultrasonication time on microstructure, thermal conductivity, and viscosity of INFs containing 0.2 wt% of originally ultra-long multi-walled carbon nanotubes (MWCNTs) and four different ILs, namely 1-propyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium thiocyanate, or 1-ethyl-3-methylimidazolium tricyanomethanide, was studied. The INFs were obtained by a two-step method using an ultrasonic probe. The ultrasonication process was performed for 1, 3, 10, or 30 min at a constant nominal power value of 200 W. The obtained results showed that for the shortest sonication time, the highest thermal conductivity enhancement of 12% was obtained. The extended sonication time from 1 to 30 min caused the cutting of MWCNTs and breaking the nanoparticle clusters, leading to a decrease in the average length of the nanotube bundles by approx. 70%. This resulted in a decline in thermal conductivity even by 7.2% and small deviations from the Newtonian behavior of INFs.

Carbon nanotube materials for electrocardiography.

Carbon nanotubes (CNTs) as 1D nanomaterials of excellent physicochemical characteristics bring hope to compete and eventually conquer traditional solutions in electrocardiography - one of the most powerful and non-invasive diagnostic tools in cardiac disorders. Our review tracks (from 2008) the development of CNTs as critical components in the systems where CNTs serve mainly as electroconductive fillers hence enable recording electrocardiographs (ECG). The characteristics of the CNT-based ECG systems - mainly to-skin electrodes and in a few cases wiring - covers their electrical and mechanical performance (adhesivity, flexibility, elasticity) and qualitative biocompatibility. By comprehensive analysis of the state-of-art in this field, we intend to indicate the most important challenges for the CNT (and other) materials to be applied in scale-up solution for electrocardiography in the near future.

Ullmann Reactions of Carbon Nanotubes-Advantageous and Unexplored Functionalization toward Tunable Surface Chemistry.

We demonstrate Ullmann-type reactions as novel and advantageous functionalization of carbon nanotubes (CNTs) toward tunable surface chemistry. The functionalization routes comprise O-, N-, and C-arylation of chlorinated CNTs. We confirm the versatility and efficiency of the reaction allowing functionalization degrees up to 3.5 mmol g-1 by applying both various nanotube substrates, i.e., single-wall (SWCNTs) and multi-wall CNTs (MWCNTs) of various chirality, geometry, and morphology as well as diverse Ullmann-type reagents: phenol, aniline, and iodobenzene. The reactivity of nanotubes was correlatable with the nanotube diameter and morphology revealing SWCNTs as the most reactive representatives. We have determined the optimized conditions of this two-step synthetic protocol as: (1) chlorination using iodine trichloride (ICl3), and (2) Ullmann-type reaction in the presence of: copper(I) iodide (CuI), 1,10-phenanthroline as chelating agent and caesium carbonate (Cs2CO3) as base. We have analyzed functionalized CNTs using a variety of techniques, i.e., scanning and transmission electron microscopy, energy dispersive spectroscopy, thermogravimetry, comprehensive Raman spectroscopy, and X-ray photoelectron spectroscopy. The analyses confirmed the purely covalent nature of those modifications at all stages. Eventually, we have proved the elaborated protocol as exceptionally tunable since it enabled us: (a) to synthesize superhydrophilic films from-the intrinsically hydrophobic-vertically aligned MWCNT arrays and (b) to produce printable highly electroconductive pastes of enhanced characteristics-as compared for non-modified and otherwise modified MWCNTs-for textronics.

In Vitro Targeting and Selective Killing of T47D Breast Cancer Cells by Purpurin and 5-Fluorouracil Anchored to Magnetic CNTs: Nitrene-Based Functionalization versus Uptake, Cytotoxicity, and Intracellular Fate.

Fe-encapsulated multiwall carbon nanotubes (Fe@MWCNTs) are candidates for magnetically targeted Drug Delivery Systems (mt-DDSs) against breast cancer. However, their full potential as versatile and biosafe vectors has yet to be developed. Key challenges that remain are relating surface functionalization to cytotoxicity and inducing selective cytotoxicity to cancer cells. We have studied quantitative uptake of pristine and functionalized Fe@MWCNTs (f-Fe@MWCNTs) in correlation to their in vitro cytotoxicity. Human monocyte macrophages (HMMs) and T47D breast cancer cells were selected as models to test selective cytotoxicity. [2+1]-Cycloaddition of nitrenes to Fe@MWCNTs yielded both effective functionalization and drug "tethering". Hydrophilization of Fe@MWCNTs was critical for efficient active cell uptake. f-Fe@MWCNTs were considerably more toxic to T47D cells than HMMs, in spite of longer exposure times of the latter. Eventually, Fe@MWCNTs loaded with 5-fluorouracil in a ß-cyclodextrin cage or with covalently linked purpurin emerged as the most cytotoxic and steerable in a magnetic field toward promising mt-DDSs.

Amalgamation of complex iron(III) ions and iron nanoclusters with MWCNTs as a route to potential T2 MRI contrast agents.

Iron-filled multiwall carbon nanotubes (Fe@MWCNTs) were functionalized toward a variety of potential magnetic resonance imaging contrast agents. Oxidized Fe@MWNCTs were covered with PEG5000 via direct esterification or using acyl chloride derivatives. Alternatively, the latter were functionalized with an aminophenol ligand (Fe@O-MWCNT-L). Moreover, pristine Fe@MWCNTs were functionalized with N-phenylaziridine groups (Fe@f-MWCNT) via [2+1] cycloaddition of nitrene. All of these chemically modified nanotubes served as a vehicle for anchoring Fe(3+) ions. The new hybrids--Fe(III)/Fe@(f-/O-)MWCNTs--containing 6%-14% of the "tethered" Fe(3+) ions were studied in terms of the acceleration of relaxation of water protons in nuclear magnetic resonance. The highest transverse relaxivity r2=63.9±0.9 mL mg(-1) s(-1) was recorded for Fe(III)/Fe@O-MWCNT-L, while for Fe(III)/Fe@f-MWCNT, with r2=57.9±2.9 mL mg(-1) s(-1), the highest impact of the anchored Fe(III) ions was observed. The T1/T2 ratio of 30-100 found for all of the nanotube hybrids presented in this work is a very important factor for their potential application as T2 contrast agents. Increased stability of the hybrids was confirmed by ultraviolet-visible spectrophotometry.

1-Aryl-4-nitro-1H-imidazoles, a new promising series for the treatment of human African trypanosomiasis.

Nitroimidazoles are a well-known class of antibacterial and antiprotozoal drugs but in spite of the widespread clinical and veterinary use of these drugs, this family has been stigmatized in part due to associated genotoxicity problems. Here we report the synthesis, the anti-trypanosomal activity and a structure-activity relationship (SAR) study of a series of about fifty 1-aryl-4-nitro-1H-imidazoles, with an emphasis on selected in vivo active molecules. Compounds 4-nitro-1-{4-(trifluoromethoxy)phenyl}-1H-imidazole and 1-(3,4-dichlorophenyl)-4-nitro-1H-imidazole are curative in mouse models of both acute and chronic African trypanosomiasis when given orally at doses of 25-50 mg/kg for 4 days for the acute infection, and 50-100 mg/kg (bid) for 5 days in the chronic model. While both compounds are bacterial mutagens, activity is lost in strains lacking bacterial specific nitro-reductases. Mammalian nitro-reductases do not reduce nitroaromatic compounds with low redox potentials with same avidity as their bacterial counterparts and these compounds were shown to be devoid of genotoxicity in mammalian cells. Both compounds are promising leads for the treatment of human African trypanosomiasis (HAT or sleeping sickness), including the fatal stage 2 of the disease, for which new treatments are urgently needed.