Unzipping Of Multi-walled Carbon Nanotubes Research Articles

Viscoelastic and thermal properties of unzipped multiwalled carbon nanotubes reinforced polyamide-6 composites

The excellent reinforcing capability of carbon nanofillers along with increasing demand for advanced polymer composites in automobiles, aircraft, and defense sectors motivate the research community to explore detailed mechanical, thermal, and electrical properties of carbon-based polymer nanocomposites for various applications. In this work, 0.1 to 7 parts per hundred ratios (phr) of multiwalled carbon nanotubes (MWCNTs) and unzipped MWCNTs (referred to as graphene oxide nanoribbons (GONRs)) were individually reinforced into polyamide-6 (PA6) matrix by twin-screw extrusion and standard sized specimens were prepared by the injection molding process. The interaction among PA6 and nanofillers were analyzed using Raman and FTIR spectroscopy. The oscillatory rheometry measurement at 0.1 rad/s angular frequency showed a 110.7 % rise in storage modulus and a 12.6 % rise in loss modulus for 0.1 phr GONRs reinforcements. Both the values raised by 100 % and 12.5 %, respectively for similar amounts of MWCNTs reinforcements. The thermo-gravimetric analysis (TGA) indicated the optimum thermal stability at 1 phr of GONRs content compared to the increasing stability with increasing MWCNTs content within PA6. The differential scanning calorimetry (DSC) curves indicated the optimum reinforcing capacity of GONRs at 0.5–3 phr reinforcements, as compared to those increasing for increasing MWCNTs content. An optimum reinforcing capacity at lower amounts of GONRs as compared to MWCNTs was confirmed from shifting trends of intensity peaks in Raman and FTIR spectra curves of the composites. It was attributed to high surface area and functional groups along the edges of GONRs. Altogether, the GONRs/PA6 composites possess excellent potential for applications in automotive and aerospace components, ballistics equipments, electronics, biomedicals, sensors, etc., requiring high mechanical and thermal stability.

Compositing LaSrMnO3 perovskite and graphene oxide nanoribbons for highly stable asymmetric electrochemical supercapacitors

The anticipated large contribution of renewable energy resources to the sector of energy production strongly motivated the development of energy storage technologies, of which supercapacitors have drawn a lot of attention. In this work, Lanthanum-Strontium-Manganese-oxide (LSMO) perovskite nanoparticles, graphene oxide nanoribbons (GONRs), and LSMO-GONRs composite were synthesized and tested as electrode materials for supercapacitor applications. The LSMO was synthesized using the co-precipitation/calcination method, while the GONRs were synthesized using the oxidative unzipping of multi-walled carbon nanotubes. The physical/chemical structures were studied using XRD, FT-IR, SEM, TEM, SAED, and XPS. In 1 M KOH, the LSMO-GONRs electrode exhibited a specific capacitance of 490F/g compared to 342F/g and 294F/g for GONRs and LSMO electrodes, respectively, at 1 A/g, showcasing a performance that is not just superior but truly impressive, to the different types of perovskite/carbon-based material composites. The fabricated asymmetric SC device of LSMO-GONRs//GONRs exhibited a potential window of 1.7 V, a specific capacitance of 92.3F/g, an energy density of 38 Wh/kg, and a power density of 860 W/kg at 1 A/g. Moreover, the LSMO-GONRs//GONRs device showed excellent capacity retention and Coulombic efficiency after 10,000 cycles at 10 A/g, revealing the promising employment of LSMO-GONRs composite as a highly stable material for supercapacitor applications.

Continuous flow laser-induced unzipping of multiwalled carbon nanotubes

Unzipped multiwalled carbon nanotubes (MWCNTs) provide a route to graphene carbon ribbons (GNRs), which have application in electronic devices. Pulsed irradiation using an Nd:YAG laser operating at 1064 nm mediates such unzipping of MWCNTs dispersed in ethanol under shear stress within the vortex fluidic device (VFD). The method is scalable with the thin film device operating under continuous flow, while also avoiding the use of harsh chemicals and auxiliary substances. Unzipped MWCNTs are formed in 90% yield and have been characterized using scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis, X-ray powder diffraction and X-ray photoelectron spectroscopy. The systematically derived optimal laser power for unzipping was 250 mJ and increasing the laser power results in the fragmentation of the MWCNTs.

Unzipped multiwalled carbon nanotube oxide / PEG based phase change composite for latent heat energy storage

Polyethylene glycol (PEG) as a phase change material (PCM) is being explored for latent heat energy storage systems due to its high thermal storage capacity. In the current study, PCM composites were synthesized with different mass fractions of unzipped multiwalled carbon nanotube oxides (UMCNOs) in PEG by melt mixing method. The influence of UMCNOs loading on the thermal conductivity (TC), phase change properties such as temperatures and latent heats of melting and solidifying, thermal energy storage and release rates were investigated. At a loading of 6 mass% of UMCNOs, the TC of the prepared PCM composite increased by 2.1 times as compared to that of pure PEG (0.21 W/m-K). Differential scanning calorimetry analysis showed that as the concentration of UMCNOs increased, there was a slight decrease in the melting temperature. Additionally, the latent heats of melting were found to be reduced by 1.11–9.46 % with the addition of 0.5–6 mass% UMCNOs. Further, the thermal energy storage and release rates were improved with the addition of UMCNOs in PCM composites. In addition, there was negligible change in phase change properties after 100 melting and solidifying cycles of PCM composite, indicating the great prospects for the latent heat energy storage application.

Synergistic effect of Mn2+ with unzipped carbon nanotubes on enhancement of mechanical properties of polyamide 66

Multi-walled carbon nanotubes (MWCNTs) are widely recognized for their exceptional mechanical properties and potential to reinforce composite materials. However, the requirement for high MWCNT concentration remains a challenge in achieving effective reinforcement. In this study, using unzipped multi-walled carbon nanotubes (uMWCNTs) and transition metal filler as a means to significantly enhance the mechanical properties of polyamide 66 (PA66) and incorporating 0.2% w/w of uMWCNTs-Mn as filler allowed us to increase PA66's tensile strength by over 74% and its Young's modulus by over 100%. The structural and functional integrity of uMWCNTs-Mn and PA66 matrix were investigated in detail. This work reveals that the enhancement of mechanical properties is mainly due to the interfacial interaction between uMWCNTs-Mn sheets and the PA66 matrix, the coupling effect of manganese ions, and increases the crystallinity and reduces the size of microcrystals. This work's findings provide a novel approach to the preparation of high-performance composites with low concentrations of carbon nanostructures, which holds significant implications for the development of advanced materials.

Assembly of partially unzipped multiwalled carbon nanotubes into ultralight, highly efficient and multifunctional electromagnetic wave absorbing aerogel

Efficient electromagnetic wave absorbing materials with lightweight and multifunctional integrated applications have broad development application prospects. Carbonaceous materials are one of the promising candidates due to their low density, high conductivity, diverse structure and tunable composition. Here, we prepared nitrogen-doped graphene nanoribbon/carbon nanotube (N-GNR/CNT) hybrid aerogel by assembling and annealing partially unzipped carbon nanotubes. The remaining CNTs serve as skeletons to maintain GNR unfolding, while the unfolded GNRs serve as “wings” to interconnect and form a 3D network. The 3D network provides channels for fast electron transmission, and meanwhile GNRs offer rich edges for N doping. Benefitting from the synergistic effect of CNTs and GNRs, this aerogel shows the characteristics of ultralight, ultrathin, strong electromagnetic wave absorption and efficient joule heating. This study presents a new strategy for preparing multifunctional electromagnetic wave absorbing materials, and broadens the application of graphene nanoribbons.

Chemically engineered unzipped multiwalled carbon nanotube and rGO nanohybrid for ultrasensitive picloram detection in rice water and soil samples

Picloram (4-Amino-3,5,6-trichloro pyridine-2-carboxylic acid) is a chlorinated herbicide that has been discovered to be tenacious and relatively durable in both soil and water. It is known to have adverse and unpleasant effects on humans causing several health complications. Therefore, the determination of picloram is profoundly effective because of its bio-accumulative and persistent nature. Because of this, a sensitive, rapid, and robust detection system is essential to detect traces of this molecule. In this study, we have constructed a novel nanohybrid system comprising of an UZMWCNT and rGO decorated on AuNPs modified glassy carbon electrode (UZMWCNT + rGO/AuNPs/GCE). The synthesized nanomaterials and the developed system were characterized using techniques such as SEM, XRD, SWV, LSV, EIS, and chronoamperometry. The engineered sensor surface showed a broad linear range of 5 × 10–2 nM to 6 × 105 nM , a low limit of detection (LOD) of 2.31 ± 0.02 (RSD < 4.1%) pM and a limit of quantification (LOQ) of 7.63 ± 0.03 pM. The response time was recorded to be 0.2 s, and the efficacy of the proposed sensor system was studied using rice water and soil samples collected from the agricultural field post filtration. The calculated recovery % for picloram in rice water was found to be 88.58%—96.70% (RSD < 3.5%, n = 3) and for soil it was found to be 89.57%—93.24% (RSD < 3.5%, n = 3). In addition, the SWV responses of both the real samples have been performed and a linear plot have been obtained with a correlation coefficient of 0.97 and 0.96 for rice and soil samples, respectively. The interference studies due to the coexisting molecules that may be present in the samples have been found to be negligible. Also, the designed sensor has been evaluated for stability and found to be highly reproducible and stable towards picloram detection.

Synthesized partially unzipped carbon nanotubes and potential DNA/CNTs interactions

Carbon nanotubes (CNTs) are structurally considered to be graphene nano-ribbons (GNRs) that rolled up into seamless tubes. While CNTs nanotechnology is advancing, synthesis of GNRs from CNTs is sought after for precise and integrative graphene applications. Acid treatment of CNTs can generate longitudinal unzipping in an effective, large scale and economic approach. However, further understanding of CNTs-to-GNRs degradation, which mimics biodegradation molecular processes by oxidants, can also aid to assess toxicological impact of biodegraded CNTs. In this study, unzipping of multi-wall carbon nanotubes (MWCNTs) was established using a strong oxidizing agent. The influence of oxidation on the morphological, crystalline quality and dielectric properties was investigated. In particular, partial unzipping of CNTs was confirmed by transmission electron microscopy (TEM), and scanning electron microscopy (SEM) images. Broad band dielectric spectroscopy (BDS) was utilized to depict the influence of the applied frequency on the dielectric properties. GNRs exhibited a lag in the drop of capacitance and impedance to higher values of frequency with respect to the starting MWCNTs. Furthermore, DNA interactions with partially unzipped carbon nanotubes, were computationally assessed by employing molecular docking. The obtained potential DNA-CNT molecular conformations were illustrated and their biomolecular implications were discussed.

Graphene Nanoribbons/Manganese Oxide Nanocomposite Modified Electrode for Detection of Antimicrobial Drug Nitrofurantoin

The design and development of a new kind of cost-effective electrode material with excellent selectivity and stability are still a great challenge in the field of electrochemical sensors. Recently, researchers have paid more attention to the electrochemical reduction of nitro compounds due to their hazardous nature. Nitro compounds play a vital role in various industrial applications. However, the direct discharge of nitro compounds to the environment as industrial wastewater is harmful. In this study, a nanocomposite made of 1D graphene nanoribbons decorated with manganese dioxide (GNR-MnO2) was prepared to fabricate an electrochemical transducer for the determination of nitrofurantoin (NFT) in biofluids. First, 1D GNR was prepared by unzipping of multiwalled carbon nanotubes. Second, the GNR was decorated with MnO2 by the hydrothermal reduction method. As-prepared GNR-MnO2 nanocomposite was comprehensively characterized by field emission scanning electron microscopy with EDX, XRD, UV–visible, electrochemical impedance spectroscopy, and cyclic voltammetry. Moreover, GNR-MnO2-coated glassy carbon electrode (GCE) exhibited good electrocatalytic activity toward NFT. The electroreduction of NFT was found at −0.40 V which was 50 mV lower than bare GCE. GNR-MnO2 nanocomposite modified GCE showed a well-defined linear reduction peak current for NFT from 10 nM to 1,000 µM. The selectivity of the sensor was also analyzed in the presence of other nitro compounds which confirmed that NFT can be selectively detected at −0.4 V. The GNR-MnO2 modified electrode was also able to separate reduction peaks of other nitro compounds. In addition, the detection of NFT was carried out in human urine samples with a good recovery of 99.60%–98.60%.

A novel Z-scheme heterojunction g-C3N4/WS2@rGONR(x) nanocomposite for efficient photoelectrochemical water splitting

In the present work, 2D monolayers of WS2 and g-C3N4 were synthesized for the preparation of WS2/g-C3N4 nanostructure through a two-step process. 1D graphene oxide nanoribbons (GONRs) were synthesized via unzipping of multi-walled carbon nanotubes (MWCNTs) and applied for the preparation of three-component g-C3N4/WS2@rGONR(x) (x = 1, 2, and 5 wt%) nanocomposites. The synthesized nanocomposites were evaluated via Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), high-resolution transmission electron microscopy (HRTEM), and diffuse reflectance spectroscopy (DRS). The photocatalytic performance of the nanostructures was investigated in the hydrogen evolution reaction (HER) using the Fluorine-doped tin oxide (FTO) as the electrode. Subsequently, a possible photocatalytic mechanism was estimated. According to the results, the g-C3N4/WS2@rGONR(x) modified FTO has the lowest Tafel slope (60 mV dec−1), and overpotential (150 mV), the highest current density (47 mA cm−2) and also the maximum stability (19 mA for 3000s). Therefore, g-C3N4/WS2@rGONR(2) photocatalyst can be a novel and efficient candidate for hydrogen production as a clean fuel.

Functionalization of unzipped multi-walled carbon nanotube oxides with l-tyrosine for the adsorption of methylene blue

The present study was carried out to understand the ability of functionalized unzipped multi-walled carbon nanotube oxides for methylene blue dye adsorption. Parameters that influence the dye adsorption efficiency such as amount of adsorbent, adsorption time, stirring speed and pH of solution were optimized. Dye removal efficiency of 99.8% and maximum adsorption capacity of 420.14 mg/g were obtained with the optimum conditions such as 20 mg of adsorbent, pH 7–9 of the solution and stirring speed of 400 rpm for 15 min. The results from the kinetic study revealed that the adsorption of methylene blue dye on the prepared nano-adsorbent followed pseudo-second-order kinetic model. Langmuir isotherm was found to be best fit for the adsorption of methylene blue dye with functionalized nano-particles. Also, the reusability study showed a dye removal efficiency of 94% even after six cycles of adsorption–desorption. The nano-particles produced in the present study are found to be an effective adsorbent for the removal of methylene blue dye from waste water.

Nitrogen and sulfur co-doped graphene nanoribbons with well-ordered stepped edges for high-performance potassium-ion battery anodes

Graphitic carbon materials, particularly few-layered graphene, exhibit great potentials as potassium-ion battery (PIBs) anodes. However, bulk graphene-based materials have the disordered structure owing to randomly stacked graphene layers, which causes the high migration barrier during K+ intercalation/deintercalation reactions and thus the surface-dominated capacitive response. Here, we present a novel nanoarchitecture of nitrogen and sulfur co-doped graphene nanoribbons with well-ordered stepped edges (NS–sGNR) via the electrochemical unzipping of multiwalled carbon nanotubes (MWCNTs) and the subsequent N/S co-doping process for high-performance PIB anodes. As an anode material for PIBs, the prepared sample exhibits high initial capacity (329.1 mAh g−1 at 50 mA g−1), superior rate capability (211.7 mAh g−1 at high current density, 2000 mA g−1), outstanding reversibility of K-staging, and stable long-term cyclability. Theoretical calculations were conducted to demonstrate that sGNRs with NS co-doping (NS–sGNR) exhibit much improved K+ intercalation properties, such as the K+ adsorption energy, charge transfer, and migration barriers, compared with the parallel-edged GNRs. Particularly, the migration barrier (the rate-determining step) can be substantially reduced at the stepped edges during K+ intercalation.

Three-Dimensional Interconnected Porous Partially Unzipped MWCNT/Graphene Composite Aerogels as Electrodes for High-Performance Supercapacitors.

The self-restacking of graphene nanosheets inevitably compromises the electrochemical performance of conventional graphene-based materials. Herein, to solve this problem, we prepared a new type of three-dimensional porous aerogel with partially unzipped multiwalled carbon nanotubes inserted into graphene nanosheets via a reduction-reaction-induced self-assembly process. In the resulting aerogels, the inner carbon nanotubes (CNTs) tightly attach to the unzipped outer graphene nanoribbons (GNRs), which bridge with the graphene nanosheets. These interconnections bring them excellent electrical contact; the CNTs act as spacers to prevent the restacking of adjacent graphene nanosheets, and the abundant interconnected pores in the aerogels provide large channels for charge transfer. Accordingly, the aerogels exhibit a specific capacitance of 348.4 Fg−1 at a scan rate of 5 mVs−1, with capacitance retention remaining at 89.7% at a current density of 2 Ag−1 after 5000 cycles. The results show that the aerogels are promising electrode materials for supercapacitor applications.

Hydrothermal Unzipping of Multiwalled Carbon Nanotubes and Cutting of Graphene by Potassium Superoxide.

The dual use of potassium superoxide (KO2) to unzip multiwalled carbon nanotubes (MWCNTs) and cut graphene under hydrothermal conditions is described in this work. The KO2-assisted hydrothermal treatment was proven to be a high-yield method for forming graphene nanoribbons and dots or sub-micro-sized graphene nanosheets. Starting with functionalized MWCNTs, the method produces water-dispersible graphene nanoribbons with characteristic photoluminescence depending on their width. Using pristine graphene, the hydrothermal treatment with KO2 produces nanosized graphene sheets and graphene quantum dots with diameters of less than 10 nm. The latter showed a bright white photoluminescence. The effective hydrothermal unzipping of MWNTs and the cutting of large graphene nanosheets is a valuable top-down approach for the preparation of graphene nanoribbons and small nanographenes. Both products with limited dimensions have interesting applications in nanoelectronics and bionanotechnology.

Electrochemical Detection of H2O2 on Graphene Nanoribbons/Cobalt Oxide Nanorods‐Modified Electrode

The most important biological changes which have to be monitored is the mechanism of ageing in the human body where the mitochondria play a major role. Hydrogen peroxide (H2O2) is one of the important markers for the reactive oxygen species (ROS), which denatures the protein and DNA, that was the main contributory factor of ageing. So, it is very important to monitor H2O2 levels in the biological samples. Herein, we reported the preparation of 1D graphene nanoribbon/cobalt oxide nanorod (GNR/Co3O4) based nanocomposite‐modified electrochemical sensor for H2O2. Firstly, GNR was synthesized by oxidative unzipping of multiwalled carbon nanotubes (MWCNTs). Secondly, cobalt oxide nanorods (Co3O4) were grown onto GNR by a chemical reduction process. As‐prepared nanocomposite was characterized by UV‐Visible spectroscopy (UV‐Vis) and HR‐TEM. Electrochemical properties of GNR/Co3O4‐coated electrode were studied by cyclic voltammetry (CV) which showed two redox peaks at 0.93 and 0.88 V in phosphate buffer solution. Next, the electrocatalytic activity of GNR/Co3O4‐coated electrode was studied against H2O2 oxidation. The electrochemical studies revealed that GNR/Co3O4‐coated electrode exhibited high electrocatalytic activity for H2O2 oxidation at 0.925 V. This sensor showed a linear response for H2O2 oxidation from 10 to 200 μM. The limit of detection (LOD) was calculated to be 1.27 μM. The selectivity of the sensor was also studied with other biomolecules associated in the human body, and the results showed that interference effect is negligible. Thus, the proposed GNR/Co3O4‐modified electrode can be used for H2O2 detection with excellent stability and selectivity.

Self-Photoluminescence of Unzipped Multi-Walled Carbon Nanotubes

Unzipping of carbon nanotubes (CNTs) has been widely explored to obtain new nanocarbon structures with promising properties. In this work, we report that unzipping of CNTs according to the well-established modified Hummers method produces unzipped CNTs (uCNTs) that exhibit self-photoluminescence that depends on the diameter of pristine CNTs. The uCNTs were characterized using FTIR spectroscopy, XRD, XPS, and Raman spectroscopy indicating that unzipping is accompanied by the introduction of defects and oxygen-containing functional groups. The morphology of CNTs and uCNTs was determined by TEM showing longitude unzipping of CNTs. Our study shows that increasing the diameter of pristine CNTs results in decreasing the edge etching effect and decreasing the functionality of uCNTs. Based on the UV-Vis spectra, the band gap of uCNTs was calculated using the Kubelka–Munk function. The band gap of uCNTs increased with decreasing diameter of pristine CNTs. The uCNTs exhibited photoluminescence with a good emission in the visible light region. The uCNTs with the largest band gap and the highest oxygen content had the strongest fluorescence intensity. Moreover, different metal ions produced different degrees of fluorescence quenching for uCNT-15, which verified the self-photoluminescence of uCNTs.

Enhanced osteogenic potential of unzipped carbon nanotubes for tissue engineering.

Carbon nanotubes (CNTs) have attracted significant interest for various applications owing to their superior physicochemical properties. The unzipping of multi-walled carbon nanotubes was accomplished by strong acid treatment. The solution of unzipped carbon nanotubes (u-CNTs) was homogeneous and stable. The u-CNTs were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. The dimensions and morphologies of the synthesized u-CNTs were examined by transmission electron microscopy and scanning electron microscopy. The u-CNTs exhibited increased zeta potential and diameter compared with pure CNTs. A decrease in the thermal stability was observed in the u-CNTs compared with pure CNTs. The u-CNTs exhibited better biocompatibility than pure CNTs in the presence of bone marrow-derived mesenchymal stem cells, showing improved biocompatibility. The u-CNT-treated media generated lower amounts of reactive oxygen species than pure CNTs. Enhanced mineralization was observed in the u-CNT-treated groups compared with the pure CNTs and the control, indicating its better osteogenic potential. The upregulation of osteogenic-associated gene markers in u-CNT groups compared with pure CNTs confirms their superior osteogenic potential. Thus, u-CNTs are potential candidates for tissue engineering applications, especially bone tissue.

Graphene Quantum Dots from Partially Unzipped Multi-Walled Carbon Nanotubes: Promising Materials for Oxygen Electrodes

Photoluminescent graphene quantum dots (GQDs) the one- or two-layer graphene nanoparticles 1.5–3 nm in size with a blue emission have been obtained from electrochemically synthesized partially unzipped multi-walled carbon nanotubes ultrasonically treated for one hour. Various physicochemical methods including photoluminescence spectroscopy, XRD, TEM, and Raman spectroscopy, have been used to characterize the electrochemically synthesized partially unzipped multi-walled carbon nanotubes and GQDs. Two-layer oxygen electrodes were fabricated, where GQDs served as an active layer. The investigations of electrocatalytic characteristics of the oxygen electrodes fabricated of the obtained materials were carried out in a fuel half-cell with an alkaline electrolyte. The fabricated oxygen electrodes were stable for six months at a discharge current density of 200 mA cm−2. The obtained GQDs are promising materials as a new type of catalyst carriers for oxygen electrodes of fuel cells.

In English

Unlike ion-exchange resins, inorganic sorbents possess high selectivity towards heavy metal ions and stability against ionizing radiation. However, sorption on these materials is rather slow. Moreover, sorption capacity strongly depends on the solution pH. In order to improve sorption properties of inorganic ion-exchangers, composites containing advanced carbon materials are obtained. Regularities of sorption of U(VI) compounds from low-concentrated aqueous solutions (up to 0.1 mmol dm–3 of uranium) on hydrated zirconium dioxide and zirconium hydrophosphate are considered. The sorbents were modified with partially unzipped multiwalled carbon nanotubes (PUMWCNTs). Sorption isotherms were obtained and analyzed. They obey Dubinin-Radushkevich model indicating sorption sites, a size of which is comparable with that of ions being sorbed. As found, the sorption mechanism is ion exchange. The effect of the solution pH on the sorption rate of U(VI) ions and capacity of inorganic ion-exchangers and their composites has been considered. Carbon additions increase sorption capacity of zirconium dioxide and zirconium hydrophosphate, when the initial pH of one-component solution is 3–4 and 5–7 respectively. Under these conditions, U(VI)-containing cations are removed from the solution practically completely. The rate of sorption obeys the model of chemical reaction of pseudo-second order, when uranium is removed from one-component solution. PUMWCNTs slow down sorption on zirconium dioxide and accelerate it on zirconium hydrophosphate. The dependence of the pseudo second order equation constants on the pH of U(VI) solutions was analyzed. The reaction of the first order occurs, when the solution contains also Ca2+ and Mg2+ ions. Regeneration was carried out using HNO3 and NaHCO3 solutions: the rate-determining stage of desorption is particle diffusion. It has been shown that one-component ZHP can be regenerated with a NaHCO3 solution practically completely. The most suitable solution for U(VI) desorption from ZHP-PUMWCNTs composite is a 1 M HNO3 solution.

Simple Method of Graphene Quantum Dots Preparation from Partially Unzipped Multi-Walled Carbon Nanotubes

A method for producing graphene quantum dots (GQDs) by ultrasonic grinding of e1lectrochemically obtained partially unzipped multi-walled carbon nanotubes is proposed. As a result, photoluminescent GQDs with a blue glow have been obtained from partially unzipped multi-walled carbon nanotubes processed two hours by ultrasonic grinding (UZ-CNTs). Various physicochemical methods including photoluminescence spectroscopy have been used to study the electrochemically synthesized UZ-CNTs GQD. After ultrasonic grinding of electrochemically synthesized UZ-CNTs the GQDs were obtained as a result of the exfoliation from the stress-bent MWCNTs walls one- or two-layer cup-shaped graphene nanoparticles 1.5-3 nm in size. The obtained GQDs are promising materials as a new type of catalyst carriers for oxygen electrodes of fuel cells.