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International audience; We present in here a simple and low cost continuous segmented-flow process for the synthesis of Ag and Au spherical-shaped nanoparticles. Different residence times (RT) were used to perform the nanoparticle synthesis, observing that at low RT, the Ag nanoparticles production, which uses a fast reduction reaction with NaBH4, is improved due to an enhancement in the mixing of the reactants. However, the flow conditions have an opposite effect in the case of Au nanoparticles synthesis. Indeed, since the chemical reduction process (Turkevich method) exhibit a much slower kinetics, high RT (low flowrates) improve the synthesis yield and the quality of the nanoparticles. The Ag and Au nanoparticles were characterized by UV-Vis spectrophotometry (UV-Vis) and Transmission Electron Microscopy (TEM). The Ag spherical-shaped nanoparticles presented a LSPR at 400 nm (size ≈ 4 nm), while the synthesized Au nanoparticles exhibit LSPR and sizes in the range 520 - 550 nm and 14 - 17 nm, respectively.

Effective removal of organic dyes from aqueous solution is an important task for targeted wastewater treatment. In this work, a mixed-ligand Zr(IV) metal organic framework based on terephthalic acid and 1,10-phenanthroline was used for the solid-phase extraction of dyes. The maximum adsorption capacity of the sorbent for Congo red and methylene blue dyes reached 40 mg/g. The adsorption behavior was studied, including the effect of time, temperature, adsorbent dosage, pH and coexisting ions. The reliability of the sorbent for removing artificial dyes from food samples and in artificial seawater was tested. The possibility of using the sorbent as a filler for column chromatography for dye separation is shown.

Background: In this work, a detector based on optical fiber covered with Multi-Wall Carbon Nanotubes (MWCNTs) was used for sensing and removal of Alizarin from wastewaters. Alizarin is a strong anionic red dye that is part of the anthraquinone dye group. As a rule, this dye is used in the textile industry as a coloring agent. Experiments showed a good efficiency of wastewater treatment. This development could resolve the problem of water contamination with Alizarin red dye. Methods: We used a single-mode fiber SMF-28e with a core diameter of 8.2 μm and a cladding diameter of 125 μm as a base for the tapered optical fiber detector. An MWCNTs array was synthesized on the tapered optical fiber detector surface by spray pyrolysis Chemical Vapor Deposition (CVD) method at 800oC for 20 min inside a tubular furnace, using ferrocene solution in toluene as a catalyst precursor. The formed structure was applied for Alizarin detection in water. Results: According to the patent studies, the nanotubes completely covered the optical fiber surface and the array had a high density with minimal distance between nearby nanotubes. Carbon nanotubes were oriented along the radius of the optical fiber. The average diameter of carbon nanotubes was 24 nm. The optical absorbance levels increased as the Alizarin concentration increased from 50 mg/L to 1000 mg/L. MWCNTs on the optical fiber tapered section adsorbed the dye molecules from aqueous solution. Three intensive absorption bands with the wavelength of the 700, 714 and 730 nm appeared and their intensity increased as the Alizarin concentration increased. The accumulated Alizarin can be recovered by multiple immersing clean water. This property may make tapered optical fiber detector reusable and increase the economic expediency of the sensor application. Conclusions: The study showed higher Alizarin adsorption efficiency of the tapered optical fiber detector compared with relative detectors. This structure can be reusable for dye detection. Removal efficiency for Alizarin reached 98.6%, which makes the tapered optical fiber detector promising for wastewater treatment and dye elimination.

Triboelectric nanogenerators (TENGs) are an advanced mechanical energy harvesting system that has a wide range of advantages and has great prospects for use in various fields of science and technology. Among the factors that have a significant impact on the performance of TENGs, a special role belongs to the nature of triboelectric polymer materials. Over the past few years, there has been an exponential growth in research on polymers with shape memory assisted self-healing (SMASH) properties for TENGs. This mini review presents the state of the art in SMASH polymers for TENGs and attempts to assess the impact of modern polymer chemistry on the development of advanced materials for TENGs. Particular attention is paid to the relationship between these polymeric materials and the performance of TENGs. Finally, the problems and promising research directions for polymers with SMASH properties for TENGs are outlined.

Amongst the major challenges of our century are climate change and energy shortage. These issues stem from anthropogenic activities and their greenhouse emissions such as CO2. Artificial photosynthesis and semiconductors, together with suitable optoelectronic and surface properties, are an interesting and cutting-edge technology to tackle the aforementioned. Recently, MOF-derived nanomaterials have developed as a new type of versatile porous semiconductor in the field of CO2 photoreduction. This work provides a comprehensive overview of the recent advances of CO2 photoreduction by MOF-derived carbon nanomaterials to solar fuels. Lastly, the outlook and possible enhancements for these photocatalysts are discussed.

The manufacture of carbon–metal nanohybrids finds numerous applications in the catalysis, environmental remediation, supercapacitors, and batteries, among others. The use of organometallic frameworks (MOF) as precursors of these hybrids is of a great interest for numerous researchers. In the last two decades, it has been proven to be one of the most viable strategies, because these hybrids derived from MOFs have morphological properties, structural and chemical adjustable depending on the chosen precursor MOF. Currently, more than 20,000 MOFs have been reported, formed by different organic linkers and one or more metal centers. This allows researchers to create hybrids for specific applications and conditions without great difficulty. In this Review, we summarize different synthesis methods for these hybrids derived from MOFs and compare how their synthesis parameters influence on the yields of obtained products, their properties and respective applications.

Background: In this work, various carbon nanotubes (MWCNTs) were synthetized by the spray pyrolysis method. Resulting nanoforest-like and bamboo-like carbon nanotubes, as well as Yjunctions of carbon nanotubes, possess different shapes and morphology, depending on the kind of carbon source used and on the number of iron particles on the furnace tube surface, which derives from various concentrations of ferrocene catalyst. Methods: We used the spray pyrolysis method, using different carbon sources (n-pentane, n-hexane, nheptane, and acrylonitrile) as precursors and two different concentrations of ferrocene as a catalyst. Reactions of hydrocarbon decomposition were carried out at 800oC. The solution (hydrocarbon and catalyst) was introduced with a syringe, with a flow of 1 mL/min and the synthesis time of 20 min. Argon was used as carrier gas (1000 L/min). Preheater and oven temperatures were selected 180°C and 800°C, respectively, for each carbon source. The solution passed into a quartz tube placed in an oven. Results: According to the studies of carbon nanostructures, obtained from different precursors, it can be proposed that the structures synthesized from n-pentane, n-hexane and n-heptane are formed by the root growth method. The growth mechanism of MWCNTs was studied, confirming that the root growth formation of products takes place, whose parameters also depend on furnace temperature and gas flow rate. Dependence of interlayer distance (0.34-0.50 nm) in the formed MWCNTs on precursors and reaction conditions is also elucidated. The formation of carbon nanotubes does not merely depend on carbon precursors but also has strong correlations with such growth conditions as different catalyst concentrations, furnace temperature and gas flow rate. Such parameters as the amount of catalyst and synthesis time are also needed to be considered, since they are important to find minor values of these parameters in the synthesis of forest-like carbon nanotubes and other structures such as bamboo-like carbon nanotubes and Y-junctions in carbon nanotubes. Conclusions: As a result of the evaluation of interlayer distance in CNTs formed from different carbon sources, a standard value of interlayer distance normally for CNTs is 0.34 nm and for pentane A (0.5 wt.%), hexane B (1 wt.%), toluene A (0.5 wt.%) the range is from 0.33 to 0.35 nm. In case of pentane and acrylonitrile, under an increase of the catalyst concentration, an increase of the value of interlayer distance takes place from 0.35 and 0.4 to 0.4 and 0.5 nm, respectively, but for hexane, heptane and cyclohexane, an increase of the catalyst concentration maintains the same interlayer distance. This involves the use of lower quantities of raw materials and, therefore less cost for obtaining these materials.

Recent trends in the area of catalytic applications of metal–organic framework (MOF)-derived nanocarbons are covered. These highly porous nanostructures, convenient for the green chemistry processes, are generally formed by the direct carbonization of a variety of MOF, mainly MOF-5, ZIF-8, ZIF-67, UiO-66-NH2, MIL-101-NH2 at 700–1000 °C in argon or nitrogen flow. Differences between conventional porous carbons and MOF-derived carbons are in pore volumes, surface area, and presence of ad-atoms. The morphology of the MOF-derived nanocarbons can be adjustable with uniform dopant distribution. Resulting nanocarbons are widely applied in heterogeneous catalysis, photocatalysis and are very promising as electrocatalysts, having excellent performance in oxygen evolution reaction, oxygen reduction reaction, and hydrogen evolution reaction. Catalytic applications for environmental purposes are also discussed. Good catalytic performance is related with highly dispersed heteroatoms, density of catalytic active sites, controllable porosity, and high surface area. Opportunities for further research are indicated, in particular, the creation of low pH-stable electrocatalysts and novel strategies for the preparation of 1÷3D single-atom catalysts.

Metal–organic frameworks (MOFs) possess tuneable properties and a variety of important applications in the areas of catalysis, adsorption, gas storage, and separation, among others. Herein, recent computational studies by density functional theory (DFT) applied for simulations of MOF structure and complex architecture determination, prediction of properties, and computational characterization, including large-scale screening and geometrical properties of hypothetical MOFs, diffusion and adsorption processes in MOFs, are reviewed. DFT calculations have been applied in the MOF area to study chemical stability; mechanical, photophysical, optical, and magnetic properties; photoluminescence; porosity; and semiconductor or metallic character. The prediction of MOF analogs with open-metal sites, studies of chemical bonding and the prediction of energies by quantum mechanics allows reducing experimental efforts in the creation of MOF/polymer membranes, adsorbents for CO2 uptake, separation of C2H2/CH4, C2H2/CO2, and inert gases, radionuclides sequestration, and water adsorption, as well as other promising advances. For the MOF-derived carbons, a lack of profound DFT investigations is currently observed, being mainly restricted to the electrocatalysis area (nitrogen reduction reaction, oxygen evolution reaction, and hydrogen evolution reaction), resulting applications in batteries and other storage devices, CO2 sequestration, and absorbance of organic substances.

We report the preparation of carbon sponges with highly hydrophobic and superhydrophobic metal nanoparticles from melamine–formaldehyde sponges coated with metal–organic structures based on Co, Ni and Ni–Co with rod morphology using a simple one-step carbonization method at temperatures of 300, 500 and 700 °C.

The influence of synthesis method, cycles quantity and sonication time in the gold nanoparticles size and plasmon resonance were analyzed to establish the synthesis with smaller nanoparticle size and higher absorbance. Gold nanoparticles were analyzed by UV-Vis spectrophotometry, dynamic light scattering (DLS) and surface electron microscopy (SEM). The results indicate that the nanoparticles obtained by microwave have bigger size but higher absorption. These nanoparticles were analyzed one year after its synthesis and it was found that the plasmon resonance signal remains almost unchanged. Finally, two equation were derived from the analyzes for estimate molar extinction coefficient, molar concentration and nanoparticle average diameter.

Carbon hybrid aerogels (CAs), formed by different carbon allotropes and/or nanostructures, are reviewed. Hybrid aerogels are composed by CNT–graphene (graphene oxide and reduced graphene oxide), CN...

Background: Methods for obtaining the hybrids of multi-wall carbon nanotubes (MWCNTs) and rare earths are in progress. Such composites may possess luminescent properties, which could be of interest for various areas, in particular, medicine (imaging), engineering (fluorescent polymers, LED and relative materials), among other applications. Lanthanide oxides, additionally, can serve as catalysts for MWCNTs formation and catalysts of several organic reactions. Objective: The goal of this work is to obtain the composites of MWCNTs with strontium aluminate, doped with several lanthanides (Eu, Ce, La, Nd, and Sm), via the spray pyrolysis method and to study the properties of the formed hybrids. Methods: The spray pyrolysis method in the temperature range from 780 to 850oC, starting from toluene as a carbon source and ferrocene as a catalyst precursor. SrAl12O19 doped with rare-earths were added to carbon matter in the ultrasonic field. Methods: Among various structures, the forest-like nanostructures have been observed in some cases. The formed coated carbon nanotubes possess fluorescent properties due to the attachment of lanthanide- doped ceramic compound (SrAl12O19) to their surface, allowing the emission control for each dopant: yellow (Nd2O3), blue (Eu2O3 and Sm2O3), intense orange (La2O3), light orange (Ce2O3). Conclusion: MWCNTs decorated with strontium aluminate (SrAl12O19), doped with a series of lanthanide oxides (Nd2O3, Eu2O3, La2O3, Ce2O3, Sm2O3), were obtained by the spray pyrolysis technique on the surface of optical fibers. Lanthanum- and cerium-containing coatings were found to show a better deposition on the MWCNTs surface, exhibiting uniform coating. MWCNTs, coated with Nd-, Ce-, and Eu-doped SrAl12O19 were shown to reveal the best conductive properties.

Background: Synthesis and applications of Ag-coated carbon nanotubes are currently under intensive research, resulting in a series of recent patents. Silver nanoparticles are normally obtained from silver nitrate. However, there are also other silver-containing compounds that can facilitate the production of silver nanoparticles, such as silver(I) acetate and silver(II) oxide. Being combined with carbon nanotubes, silver nanoparticles can transfer to them some of their useful properties, such as conductivity and antibacterial properties, and contribute to improving their dispersion in solvents. Objective: To apply three different silver-containing precursors of Ag nanoparticles for the decoration of carbon nanotubes and study the morphology of formed composites by several methods. Method: Three different silver compounds were used as Ag source to carry out the functionalization and decoration of carbon nanotubes under ultrasonic treatment of the reaction system, containing, commercial carbon nanotubes, organic peroxides as oxidants or hydrazine as a reductant, and a surfactant. Resulting samples were analyzed by XRD and XPS spectroscopy, as well as TEM and SEM microscopy to study the morphology of formed nanocomposites. Results: Silver nanoparticles can be produced without the presence of a reducing agent. Applying hydrazine, as a reducing agent, it is possible to obtain functionalized carbon nanotubes doped with silver nanoparticles, in which their sizes are smaller (1-5 nm) compared to those obtained without using hydrazine. Conclusion: Silver nanoparticles having a size range between 2-60 nm can be produced without the presence of a reducing agent. The use of a reducing agent, such as hydrazine, affects the size of silver nanoparticles.

In this paper, we present a greener synthesis of silver and gold nanoparticles using an aqueous extract of Ficus benjamina leaves. The metal nanoparticles were synthesized via conventional heating and microwave-assisted methods using the aqueous extract as reducing and capping agent. It was observed that the use of a Ficus benjamina leaf aqueous extract via microwave-assisted heating represent a faster, greener and easier method than a conventional heating procedure for the synthesis of silver and gold nanospheres , also leading to narrower nanoparticle size. The sensing characteristics of the microwave-assisted silver nanoparticles were evaluated for the specific determination and semiquantification of Zn(II) ions. The colorimetric semiquantification of Zn(II) ions was achieved by UV–vis spectroscopy, using an empirical model in a concentration range between 0.2 and 2.0 mM, reaching total precipitation at concentrations higher than 2.0 mM.

Carbon–carbon allotropic hybrids and their composites are reviewed. Carbon–carbon hybrids are mainly composed of graphene, graphite, graphene oxide, reduced graphene oxide, carbon nanotubes, carbyn...

Carbon hybrids and composites are materials that have promoted technological advances in different applications such as energy storage, catalysis, solar cells, environmental remediation, manufacture of biosensors, etc. For this reason, in this chapter we make an analysis of composites, the synergies of their components and the advantages of incorporating these materials in modern technologies, focusing mainly on those that have graphite, graphene and graphene oxide as the base component in their structure. Since these carbon structures alone have attractive properties for a wide variety of applications, they can also function as host material that promotes synergy between the components of the hybrid material through their covalent or van der Waals interactions between the carbon atoms, granting significant improvements to its original properties or, in some cases, allowing the appearance of unusual properties compared to their individual counterparts.

It is well known that hybrid and composite materials exhibit improved properties in comparison with their individual components. Carbon–carbon materials have excellent thermal, mechanical and electrical properties. In this chapter, hybrids and compounds based on classic carbon nanostructures like CNTs and/or less common structures like nanospheres, nanoballs, or nanorings are reviewed. The main applications of these carbon–carbon materials include catalysis, energy storage, sensors, among others.

A host of classic and some less-common synthesis methods have been applied for the synthesis of carbon–carbon composites, in particular, high-temperature techniques such as CVD/pyrolysis/carbonization, their combination with next-step nitrogen-plasma treatment, by middle-temperature methods under pressure, solution-based techniques, air-spraying and flash light irradiation methods. Some processes need subsequent oxidation and reduction steps. The resulting 3D hybrids possess novel properties, which are frequently not a sum of those of their counterparts, in particular an improved electrical conductivity, better “solubility”, improved gas adsorption capacity and metal insertion ability. These properties can be varied upon addition or elimination of oxygen-containing and other groups. To elucidate in detail these and other effects, DFT calculations are frequently applied. As a result of carbon–carbon hybrid formation, the counterparts can remain practically unchanged or distorted in distinct grades. Different parts of a hybrid system could possess distinct reactivity. The carbon–carbon hybrids are applied for catalysis, photocatalytic energy generation, degradation of pollutants, Li-ion insertion and storage, as supercapacitors, sensors, lateral heat spreaders for commercial portable electronics, thermal absorbers, and for orthopedic and dental applications, among others.

Nanobiotechnology utility has been emphasized with the interaction of nanosystem of microbial strain bioprocess for the development of useful bioproducts that are utilized for different sectors of biological-based industries or sector. Several successful applications for nanoengineer devices have been developed that can applied in addressing many unsolved problems in the biological or medical fields. In the medical fields, the best example is reported for Averrhoa carambola L. species assisted and phytonanofabricated zinc oxide nanoparticles (NPs) that are found to be more effective agents in bioreduction processes. Bionanoparticles have been developed with demonstration of respective nanosystem via analysis through UV-visible, X-Ray Diffraction (XRD), and scanning electron microscope techniques for its fabrication, characterization, and measurement of effective interaction, respectively. These NPs are reported with properties of antibacterial activity in the range of 0.25–0.0025 μg/mL and antifungal activity in the range of 100–700 μg/mL for pathogenic microbial strain infections. Biosynthesis of NPs from microbial-assisted agents is found to be a safer, greener, and eco-friendly technology and has shown broad applications in agriculture, medicine, others sectors, etc. Microbial-assisted agents are reported with intracellular and extracellular processes for the synthesis and design of NPs. Biogenic synthesis will be discussed with the optimum selection of biological source, incubation period, pH, temperature, or other parameters that could be cost-effective, safe, and easy work possessing. The development of nanosized vectors is found to be a powerful tool approach utilized in the current medical field to solve the various challenges such as efficient and targeted treatments for several diseases. This proposed chapter will focus on various types of nanosystem development for the effective NPs for industrial useful bioproducts or devices to solve the various challenges in an effective, safe, and eco-friendly manner.

Nanohybrids and nanocomposites have gained interest in different fields due to the synergy of the properties from each of the components integrated into a single material. A hybrid material is composed of organic and inorganic components in an intimate mixture. On the other hand, a composite can be described as a material constituted of two or more components with different physical and chemical properties combined in one identity. A material can be labeled as nanocomposite or nanohybrid according to the size of the components. To develop greener procedures for the synthesis of nanocomposites and nanohybrids there have been proposed several strategies such as new methods that are cheaper, faster, or less hazardous than the classical techniques as well as some improvements in their conditions. The aim of this chapter is to explore these methodologies, greener materials, applications, as well as some future prospective.

Natural sorbent materials have practical advantages for the oil spill cleanup, whose advantages are their low-cost, feasibility for real-life applications and environmental adaptability. In this work, absorption capacity was determined for lyophilized aloe, nopal and agar and their composites with silica, Fe3O4/polysterene and multi-wall carbon nanotubes (MWCNTs). Freeze-drying was performed in order to preserve the structure and increase the internal volume of sorbents. The structures of lyophilized sorbents and composites were analyzed by scanning electron microscopy (SEM). SEM images for lyophilized sorbents show a tridimensional arrangement formed by plant-derived materials, which allows the oil absorption. The composites keep their tridimensional structure after freeze-drying and composite formation and exhibit coupling between both materials. Absorption capacity of aloe, nopal and agar are 9 g/g, 3 g/g, and 26 g/g, respectively without any pretreatment. Composites with Fe3O4/polysterene own capacities of 5.8 g/g, 2.8 g/g, and 14 g/g, respectively. Finally, for MWCNT composites, capacities are 7.8 g/g, 2.9 g/g and 23 g/g. A significant difference of adsorption capacity between lyophilized sorbents and composites is attributed to lyophilized materials absorbing oil, water and other compounds. Meanwhile, for composites the absorption is a more selective process, since the hydrophobization does not allow the absorption of water.

Available methods for solubilization and dispersion of several carbon allotropes (with the exception of dispersions in polymers) in organic solvents and water are reviewed. Main attention is paid to graphite, graphene, fullerenes, nanoonions, nanodiamonds, carbon nanotubes, and carbon nanodots. The techniques to increase the “solubility” of carbon allotropes include chemical functionalization of the carbon surface (covalent and non-covalent functionalization, oxidation via ozonation, insertion of electron-withdrawing atoms (fluorination), polymer grafting, swelling and biomolecule treatments, use of molecular “wedges” for intercalation, thermal reduction, etc.). The combination of functionalization with the use of surfactants, ultrasound, laser ablation, milling, microwave expansion, hydrothermal methods, and other treatments leads to better results. The possibility of dispersion and the size of the formed particles depend on a series of factors, in particular the nature of the solvent, its viscosity and ...

Multi-wall carbon nanotubes and graphite are relatively stable carbon allotropes, which could be solubilized and/or unfolded by a series of physical and chemical methods. Here, we present a low-temperature formation of several nanocarbons starting from these precursors, such as nano-onions, graphene sheets, and carbon nanoribbons. The experiments were carried out under ultrasonic treatment of aqueous systems “carbon allotrope − theraphthal − ascorbic acid” at various ratios and concentrations. Resulting nanocarbons were studied by scanning electron microscopy, transmission electron microscopy, XPS, FTIR, and Raman spectroscopy. Based on the experimental results, the mechanisms for carbon nanotube unfolding and separation of graphite layers were proposed. These reactions are based on the formation of reactive oxygen species by theraphthal in ultrasonic conditions and their further interaction with carbon precursors. These transformations can be considered as greener methods for obtaining nanocarbons.

Sm1−xCaxFe0.7Co0.3O3 thin film gas sensors with different calcium concentrations (x = 0.0–0.3) were prepared using a modified sol–gel spin-coating method and then annealed at 650 °C for 2 h in air. The thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and electrical resistance measurements at concentrations from 1 to 200 ppm for carbon monoxide (CO) and from 1 to 500 ppm for propane (C3H8) in the temperature range of 25–300 °C for both gases. The resulting XRD data reveal that a pure phase with perovskite structure was obtained for each substitution in x and corresponds to the orthorhombic system with a Pbnm space group. Topography and roughness of the coating were obtained by AFM; roughness results of the sample do not significantly affect the response of the sensor, but the Ca2+ content does. Morphology of the nanoparticles and the thickness of each doping in calcium were observed by SEM, and the thickness was around 300 nm. The gas-sensing characteristics of the Sm–Ca–Fe–Co–O system were investigated in CO and C3H8 gases. It was found that the electrical resistance and gas-sensing characteristics were influenced by the substitution of Sm2+ by Ca2+ ions. When x was greater than or equal to 0.2 and CO concentration was 200 ppm and operating temperature was 300 °C, there was a higher response of the sensor, reaching up to 100%. For operating temperatures below 100 °C, the response of the Sm1−xCaxFe0.7Co0.3O3-based sensors to CO or C3H8 was

A Cu–Ni-containing bimetallic carbon-based material was prepared by the pyrolysis of a metal-organic framework (MOF) synthesized from copper and nickel salts and trimesic acid precursors at room temperature. This material was tested as a counter electrode for the reduction of I3− by means of cyclic voltammetry.

Although an astounding variety of Metal-Organic Frameworks (MOFs) has been synthesized so far, the search for fast and efficient methods that yield greener and superior crystalline structures is yet an ongoing challenge. For the first time, the Hong Kong University of Science and Technology (HKUST-1) MOF has been synthesized by an efficient non-conventional solvothermal method through a Monowave 50 (Anton Paar) reactor. The synthesis has been carried out at 5, 10, 15, and 30 min instead of staggering times of 10 to 24 h. Its crystalline structure, crystallite size, morphology, particle size, specific surface, and optical properties have been characterized. The presumed presence of monocrystalline structures along with a roughly band gap energy at 3.5 eV makes them compelling nanostructures for a variety of applications.

This work presents the effects of five inorganic nanoparticles as additives, i.e., CNp (carbon nanotori particles), TiO2, MoS2, MoO3, and HcNT (halloysite clay nanotubes), in three different lubricants (oil-based, grease, and water-based). Nanolubricants were prepared by adding 1 wt% particles into each type of lubricant. Tribological properties of nanolubricants were determined and compared under anti-wear (AW) and extreme pressure (EP) conditions. CNp showed a decrease in coefficient of friction (COF) by 22% when added to water-based lubricant. Additionally, CNp demonstrated an improvement in limiting pressure of seizure (poz) of 74%, 52%, and 1621% for oil-based lubricant, grease, and water-based lubricant, respectively. Comparing 1 wt% CNp added to water-based lubricant with oil-based lubricant and grease, the improvements become outstanding under EP conditions. An increase in poz by 2479% compared to oil-based lubricant, and 789% compared to grease, was observed. In addition, a decrease of 66–69% in average wear scar diameter (AWSD) was obtained in comparison to oil-based lubricant and grease. Tribological mechanisms of carbon nanotori provide a rolling/sliding effect under AW conditions, and a load-bearing effect under EP conditions.

One of the modern areas of research in analytical chemistry is the development and use of new materials with higher selectivity and improved analytical performance in both sample preparation and separation science. Among them, metal‐organic frameworks (MOFs) are a potential alternative to current commercially available materials. Given the outstanding properties of MOFs and their ability to interact with various compounds, there has been an increasing number of studies in recent years showing their usefulness as sorbents in solid extraction (SPE) schemes. This review article aims to summarize the most recent (over the past 5 years) applications of MOFs in SPE of organic dyes. Particular attention has been paid to provide an overview of the MOF performance enhancement strategies currently being developed in this area. These include increasing the water stability of MOFs, functionalization of MOFs, defect engineering, design of charged MOFs, and modulation of non-covalent interactions. The issues of using MOF in the separation of specific dyes and in the analysis of real objects are considered. The ways of further research in the field of using MOF in SPE of organic dyes are outlined.

In this work, a combined electrophoretic/electrochemical deposition is reported for the formation of CaCO3 hierarchical structures. In a first step, CaCO3 microparticles with bar shape were synthesized under a microwave-assisted methodology. According to the characterization techniques, aragonite is the main polymorph in the sample, with a small amount of calcite. The as-obtained particles were dispersed in isopropyl alcohol (IPA) with calcium nitrate as charging agent for colloidal stabilization. Then, a voltage of 30 V was applied for 30 min between two aluminum plates at 5 mm of distance. Under these conditions, IPA is electrochemically decomposed in CO2 which then reacts with calcium ions forming new CaCO3 particles over the microparticles previously synthesized. The result is a hierarchical structure which could be promising for bone-tissue engineering and catalysis.

Single-walled carbon nanotubes (SWCNTs) were functionalized by means of a series of aromatic and heterocyclic amines (4-anisidine, 5-aminobenzene-1,3-dicarboxylic acid (5-aminoisophthalic acid), 1,3-dimethyl-5-aminobenzene-1,3-dicarboxylate, dimethyl 5-aminoisophthalate, 4-aminopyridine, 2-aminothiazole, 4-sulfanilamide) by two methods: acidic treatment and molten urea-assisted synthesis. The reactions products were characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis. The dispersion ability of several solvents (acetone, water, dimethylformamide, ethanol, toluene, and ethylene glycol) to “dissolve” the functionalized SWCNTs was determined for each product. The dispersion ability of the used solvents with respect to the functionalized SWCNTs was found to be considerably dependent on the nature of the solvent (in particular, its polarity), the organic compound used as the functionalizing agent, and, in a lesser account, on the functionalization method followed.

Advances in technologies for a variety of materials adsorbing asphaltenes have a great importance in the hydrocarbon industry because of several problems, in particular the decrease of yields in oil extraction. For asphaltene remediation, a series of minerals and materials (feldspar, clays, quartz, montmorillonites, kaolinite, illite), several metals (Fe, Al, Ni), oxides (Fe2O3, Fe3O4, TiO2, SiO2), inorganic salts (CaCO3, BaSO4, FeS), and nanomaterials (on the basis of metals and their oxides) are applied. This article generalizes available materials for asphaltene removal, comparing conditions of their adsorption capacities, providing a view of the variables and emphasizing main trends of their use.

Background: The addition of nanoparticles to cellulose paper can improve its mechanical strength, chemical stability, biocompatibility and hydrophobic properties. Silica nanoparticles are known to be inert, hydrophobic, biocompatible, biodegradable and have a good distribution in being deposited on surfaces. The main characteristics of 20 nm SiO2 nanoparticles are good chemical and thermal stability with a melting point of 1610-1728°3C, a boiling point of 2230°C with a purity of 99.5%. Objective: To carry out the hydrophobization of paper based on Kraft cellulose and on cellulose obtained from soybean husk with 20-nm size SiO2 nanoparticles and to study hydrophobicity, morphology and topography of the prepared composites. Methods: The ground and roasted soybean husk was treated with a NaOH, washed and dried. Hydrophobization of paper was carried in aqueous medium by SiO2 addition in weight ratios “paper-SiO2” of 0.01-0.05 wt.%, stirring, filtration and drying. The obtained cellulose sheet composites were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), FTIRspectroscopy, Mullen proofs of hydrophobicity, and contact angle measurements. Results: The mechanical properties of paper nanocomposites (tensile strength and compression) increased considerably by varying the concentrations. The tensile strength increased by 41-46% and the compressive strength increased by 55-56%. The existence of fiber nanofoils, good adhesion of 20-nm SiO2 nanoparticles to the paper surface, and their homogeneous distribution were observed. Conclusion: Cellulose was successfully obtained from soybean husk, applying the alkaline-based extraction method. A good reinforcement of cellulose fibers is observed due to the outstanding characteristics of the silicon dioxide nanoparticles.

Carbon, the 6th element in the periodic table denoted by the letter “C” and true element of life, provides the chemical basis for life on Earth due to its ability to form stable bonds with other carbon atoms, oxygen, nitrogen, sulfur, and many other elements in Mendeleev’s Periodic Table. Carbon is found almost everywhere, and it is one of the most abundant materials on earth. It is the 4th most common element in the universe and 15th most common on earth’s crust. All life on Earth contains various forms of carbonic structures, from proteins to the tallest trees [1]. Existence of a host of carbon inorganic forms is the also responsibility of stable single and multiple carbon-carbon covalent bonds. This process is called catenation, in which an element can bond with itself to form long chains. During much time, only two conventional carbon allotropes, graphite (black, soft, and conductive) and diamond (shiny, transparent, and extremely hard), have been known. Only in the last few decades have new synthetic carbon allotropes such as carbon nanotubes, fullerenes (buckminsterfullerene C60, smaller and higher fullerenes), and graphene been discovered. Their outstanding properties, current and potential applications, testify their unique scientific and technological importance [2]. In addition, a host of other carbon structures, both obtained and still predicted, have been reported up to date.

Currently, the area of carbon allotropes, in particular nanocarbons, is one of the most developing fields in chemistry and nanotechnology, where carbon nanotubes and graphene are leaders in the number of publications. Taking into account their existing and potential technical, biological, medical applications (in particular for drug delivery purposes), and many others, we note that the main difficulty to integrate such materials into devices and biological systems derives from their lack of solubility in organic and physiological solutions. Functionalization of carbon allotropes with the assistance of biological molecules remarkably improves their solubility in aqueous or organic environment and, thus, facilitates the development of novel biotechnology, biomedicine, and bioengineering. For example, the nanodiamonds (NDs) have got a series of distinct applications in various areas, in particular medicine, electrochemistry and creation of novel materials. Biomedical applications of NDs are well-developed and related with the recently established fact that carbon NDs are much more biocompatible than most other carbon nanomaterials, including carbon blacks, fullerenes, and carbon nanotubes [1]. Their tiny size, large surface area, and ease functionalization with biomolecules make NDs attractive for various biomedical applications both in vitro and in vivo, for instance, for single particle imaging in cells, drug delivery, protein separation, and biosensing [2, 3]. Similarly, water-soluble carbon nanoonions (CNOs) are used for biological imaging [4] and as promising theranostic agents [5].