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Simulation of Indirect 13C–13C J-Coupling Tensors in Diamond Clusters Hosting the NV Center

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In the past decade there was rapid progress in development of quantum magnetic sensing technology based on nitrogen-vacancy (NV) color centers in diamond (see, e.g. [1,2] for recent reviews). Magnetometer based on single NV center can have nanometer-scale spatial resolution and exceptional sensitivity (up to ~Hz) allowing to detect target single 13C nuclear spins or coupled 13C-13C pairs located within the diamond which can be used as long-lived quantum memory [3]. Moreover, NV-based magnetometer allows to distinguish (by their chemical shifts) inequivalent nulear spins of molecules located at diamond surface [4], thus enabling new exciting research area of single-spin nuclear magnetic resonance (NMR) for investigating important issues ranging from determination of molecular structures of inorganic/biological compounds up to medical imaging for therapeutic matters.

In these respects, predicting of high-resolution NMR characteristics for studied spin systems is essential. Among them, those of indirect nuclear spin–spin coupling (the J-coupling), that arise due to second-order hyperfine interactions, are important. Here we are presenting for a first time the results of simulation of full tensors JKL (K,L=X,Y,Z) describing the J-couplings of nucler spins 13C in H-terminated NV-hosting diamond clusters. We have optimized the cluster geometry using the ORCA 5.0.1 software package with the B3LYP/def2/J/RIJCOSX level of theory and then simulated the n-bond J-coupling tensors nJKL for all possible 13C-13C pairs in the clusters using B3LYP/TZVPP/AUTOAUX/decontract level of theory. We found that, in addition to usually considered isotropic Fermi-contact contribution to JKL, the anisotropic contributions resulted from dia- and paramagnetic, spin-dipolar and spin-dipolar/Fermi-contact cross terms are essential and can manifest in NMR spectra of 13C dimers recorded using the NV centers. Using simlated tensors nJKL we calculated the values of scalar J-constants nJ=Sp(nJKL)/3 for different 13Ci-13Cj pairs in the examplary C33[NV]-H36 cluster. The highest ones are those for neighboring 13C: one-bond constant 1J were 30-37 Hz depending on the position of the 13C dimer in the cluster with respect to the NV center. Moreover, using the same theory level we also simulated full tensors nJKL for the adamantane and found that for this molecule the calculated value 1J = Sp(1JKL)/3=29.9 Hz correlates well with the isotropic constant 1J=31.4 Hz obtained experimentally in [5].

References

[1] Schwartz I. et al. Blueprint for nanoscale NMR. Scientific Reports. 9 (2019) 6938.

[2] Barry J.F. et al. Sensitivity optimization for NV-diamond magnetometry. Rev. Mod. Phys. 92 (2020) 015004.

[3] Chen Q. et al. Steady-state preparation of long-lived nuclear spin singlet pairs at room temperature. Phys. Rev. B. 95 (2017) 224105.

[4] Glenn D.R. et al. High-resolution magnetic resonance spectroscopy using a solid-state spin sensor.

Nature.555 (2018) 351.

[5] Gay I.D. et al, INADEQUATE in the Solid State. HomonuclearCouplings in [(CH3)2SnE]3. J .Magn. Res. 91 (1991) 185.

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  • 31 Reads

Novel Electrodes Based on the Electropolymerized Nanocoatings for the Selective Voltammetric Quantification of Flavanones

Chemically modified electrodes are one of the most intensively developed areas in modern electroanalysis due to the appearance of a wide range of nanomaterials used as sensitive layers. One of the approaches for electrode surface modification is the coverage with the electropolymerized films based on phenolic compounds. Among a wide range of analytes, flavanones – flavonoids of Citrus fruits are less investigated in comparison to other natural phenolics and almost out of consideration in electroanalysis. The major natural flavanones are naringin and hesperidin which control in the real samples is required due to the possible prooxidant effect. Novel electrodes based on a layer-by-layer combination of carbon nanotubes and electropolymerized ellagic acid or aluminon were developed for the direct quantification of naringin and hesperidin. Conditions of monomers' potentiodynamic electropolymerization were optimized. SEM and electrochemical methods were used for the electrode surface characterization . The parameters of flavanones electrooxidation on the modified electrodes were found. A glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes and electropolymerized ellagic acid was developed for selective naringin determination. Simultaneous voltammetric quantification of naringin and hesperidin was shown for the first time using GCE modified with polyaminobenzene sulfonic acid functionalized single-walled carbon nanotubes and polyaluminon. The analytical characteristics obtained were significantly improved in comparison to other methods including electrochemical approaches. High selectivity of the electrodes’ response to flavanones in the presence of typical interferences and structurally related compounds was confirmed. The approaches developed were successfully applied for the analysis of citrus juices and a good agreement with the independent methods was shown. Thus, the novel highly sensitive and selective voltammetric methods for the direct flavanone quantification characterized by the simplicity of electrode fabrication, reliability, cost-efficiency can be applied for routine analysis as an alternative to chromatographic methods.

  • Open access
  • 37 Reads
Resonance Fluorescence of a Quantum Dot near a Metallic Nanoparticle: Quantum Interference Effects

In recent years, significant attention has been given to the quantum or nonlinear optical properties of semiconductor quantum dots coupled to plasmonic (metal or metal-dielectric) nanostructures. This happens as the optical properties of quantum dots can be modified, enhanced and efficiently controlled, when placed in the vicinity of plasmonic nanostructures. Among the various quantum optical effects that have been studied in coupled quantum dot – plasmonic nanostructures, particular attention has been given to the modification of the resonance fluorescence spectrum of the quantum dot by the presence of the plasmonic nanostructure, which mainly occurs due to the modification of the spontaneous decay rate of the quantum dot near the plasmonic nanostructure. The most common plasmonic nanostructure that has been studied is the metallic (mainly gold or silver) nanosphere and in most studies the quantum dot is modeled as a two-level quantum system. In this work, we model the quantum dot structure with a three-level V-type quantum system, which can naturally arise in quantum dots, and study the resonance fluorescence spectrum near a metallic nanosphere. We show that the present system leads to quantum interference effects due to the presence of the metallic nanoparticle and specifically due to the anisotropic Purcell effect that occurs in the photon emission of the quantum dot near the metallic nanosphere. We then study the resonance fluorescence spectrum for different distances between the quantum dot and the metallic nanosphere and show that the resonance fluorescence spectrum changes significantly from a single peak spectrum to a multipeak spectrum, an effect that can be explained using a dressed state analysis. The effects of quantum interference in the resonance fluorescence spectrum are also explored.

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Hybrid Inorganic-Organic Membranes Based on Iron-Encapsulated Carbon Nanotubes and Their Application in CO2 Separation

Published: 22 April 2022 by MDPI in 3rd International Online-Conference on Nanomaterials session Poster

Nowadays, considering the problems with climate change and global warming caused by the increase in greenhouse gas emissions, mainly CO2, (mainly from energy production and transport), there was a need to reduce it. Conventional methods are very energy intensive. Therefore, alternative methods, such as membrane technologies and appropriate materials, are being searched for. In this work, we present the new data concerning the novel type of hybrid organic-inorganic membranes [email protected]/FeSPEEK with a new kind of CNTs with increased iron-encapsulated content, characterization of their magnetic, mechanical, thermal, gas transport parameters, and their potential application in CO2 separation. It was found that incorporation of nanofillers with increased iron content (5.80 wt%) into the modified polymer matrix had significantly improved magnetic, thermal, mechanical, and gas transport (D, P, S, and αCO2/N2) parameters of analyzed membranes, especially after application of magnetic casting and chemical modification of inorganic and organic phase. Magnetic casting has improved the alignment and dispersion of [email protected] At the same time, CNT's and polymer chemical modification increased interphase compatibility, CO2 affinity and membrane’s separation efficiency. The obtained novel composites were characterized by improved thermooxidative stability, mechanical (extremely especially important in high-pressure processes), and magnetic parameters, which rise with the increase of CNT loading. It was also stated that Cherazi’s model turned out to be suitable for describing the CO2 transport through analyzed hybrid membranes. The enhanced parameters of obtained membranes could translate directly to their future potential use in gas separation. This type of solution in the form of selective membranes for CO2 separation, e.g., from flue gases from coal combustion, may find future applications in the power industry.

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  • 15 Reads

Self-Assembly of Polydisperse Y-Shaped Polymer Brushes under Good Solvent Conditions

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Polymers attached to the surface, e.g. polymer brushes, represent a unique way how to functionalize the surface. Its morphology is controlled by brush parameters such as grafting density, composition, chemical nature etc. and determine the response of the surface to external environment. Mixed binary brushes contain two different homopolymer branches attached to single point on the surface and exhibit a wide range of morphologies ranging from aggregates to ripple structure. Compositional fluctuations during the grafting process that hampers formation of morphology can be controlled by using Y-shaped initiators where each deposition point accepts different type of polymer. Phase behavior of Y-shaped brushes is described in theory and by simulation studies mainly for monodisperse cases. Nevertheless, real polymers are always polydisperse and using highly polydisperse polymer brings new options to control the formation of surface morphology.

Here, we employ Dissipative Particle Dynamics (DPD) to study the influence of polydispersity on self-assembly of Y-shaped polymer brushes. We vary brush grafting density, composition of the branches and their incompatibility to describe complex behavior of brushes at good solvent conditions. Moreover, we introduce the polydispersity by varying chain length of one branch and keeping other branch of the brush monodisperse. We consider low and high polydispersity and restrict our investigations to polydispersity indexes (PDI) that are used in experiments. We model the polydispersity by Schultz-Zimm distribution.

We show that our results for monodisperse systems agree with previous experimental and theoretical works and that ripple structure and aggregates are observed. Furthermore, the scaling of the brush height in our model agrees with theoretical predictions and with previous modeling results. In polydisperse systems, only disordered structures or aggregates are assembled by brushes with PDI < 1.5 sparsely grafted onto the surface with grafting density lower that 0.1 chains/nm2. Moreover, increasing the grafting density above 0.5 chains/nm2 triggers formation of perforated layer (PL) that is not observed in monodisperse systems. PL phase window widens with increasing the PDI up to 2 and the grafting density up to 1.0 chains/nm2. At high grafting densities and PDIs the PL phase is stable over wide range of phase diagram.

Finally, we show that increasing PDI lead to asymmetry of phase diagrams. High content of polydisperse chains prefer formation of aggregates over the ripple structure and increase the order-disorder transition while high content of monodisperse chains favours ripple structure and lowers the order-disorder transition.

  • Open access
  • 45 Reads

Spectroscopic Studies of Interaction of Iron Oxide Nanoparticles with Ovalbumin Molecules

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Introduction. Recent studies show the possibility of using iron oxide nanoparticles as a food additive with certain functional and technological properties. However, when developing technologies for food products, the interaction of these particles with the main components of the food matrix, in particular, proteins, takes on special significance. The aim of the present research was to study the interaction of iron oxide nanoparticles with ovalbumin molecules.

Methods. Fourier-transform infrared and fluorescence spectroscopy were used to study interaction between iron oxide nanoparticles and ovalbumin molecules.

Results: It was found that the interaction of Iron oxide nanoparticles with ovalbumin molecules was going by the mechanism of static quenching with the formation of an intermolecular non-fluorescent complex that changes the native structure of the protein. The binding constant varied from 3.3•105 to 4.8•105 l mol-1 depending on the pH value of the medium and temperature. The calculated thermodynamic parameters of binding indicate the spontaneity of the process with the predominance of the enthalpy factor. The interaction between iron nanoparticles and ovalbumin occurred mainly due to hydrogen bonds and van der Waals forces.

Conclusion: The obtained data on the mechanism of interaction of iron oxide nanoparticles with proteins should be taken into account when developing food technologies to control functional properties of products.

  • Open access
  • 37 Reads
Fullerenes: Oral Toxicity and Biological Effects
Published: 22 April 2022 by MDPI in 3rd International Online-Conference on Nanomaterials session Poster

Among the various products of the nano industry, fullerenes occupy a special place. Fullerenes have many applications, including pharmacology, biosensors, packaging composites, plant protection products, etc. Fullerenes and their polyhydroxylated derivatives have pronounced antioxidant, hepatoprotective, radioprotective, and other types of protective action on the human body. However, the introduction into the circulation of products containing fullerenes is hindered by the ambiguity of the properties exhibited, consisting of the presence of signs of nanotoxicity for biological systems in vitro and in vivo. This study aimed to evaluate the oral toxicity of the fullerene C60 and its water-soluble derivative C60(OH)24 at their daily doses from 0.1 to 10 mg/kg body weight (bw) in the long-term experiments on Wistar rats. According to research results, C60 exhibited a general toxic effect in animals, expressed in a dose-dependent decrease in relative liver weight, impairment of barrier function of the small intestine, and an increase in the number of CD106+ granular cells in the liver parenchyma. The NOAEL for C60 on oral subacute administration was at least 1 mg/kg bw/day. Negative effects of C60(OH)24 in animals were manifested starting from a dose of 1 mg/kg bw and consisted in an increase of adrenal mass, changes in the leukocyte blood count, including an increase of monocytes, and immature granulocytes. Based on the results, it can be assumed that the NOAEL of C60(OH)24 for rats in a one-month experiment is at least 0.1 mg/kg bw. Among other biological effects, it is possible to note the dose-dependent increase in the selenium content in the blood, liver, and brain of rats, which consumed C60 for 92 days. Given the role of selenium compounds as indirect-acting antioxidants, there is no reason to interpret the detected effect as unfavorable. Nevertheless, the results of the toxicological assessment of fullerenes indicate the risks associated with their adverse effects on the human body when ingested and point out the necessity for the regulation of these compounds in consumer products and environmental objects.

  • Open access
  • 18 Reads
Optically Controlled Energy Transfer between Two Molecules Near a MoS2 Nanodisk

In the last decade particular emphasis has been placed on the problem of optically controlled energy transfer in quantum systems near plasmonic nanostructures. It has also been shown that strong quantum coherence can lead to highly enhanced energy transfer between two molecules in a nanophotonic environment. Recent studies have also shown that using transition metal dichalcogenide nanostructures can achieve strong coupling in quantum systems, like molecules, at the nanoscale. In this work, we present a theoretical investigation of the role of coherence in the efficiency of energy transfer in a composite system of two molecules, a donor and an acceptor, located at the opposite side of a MoS2 nanodisk. We consider the molecules as two-level quantum systems, and, based on the Lindblad master equation combined with classical electromagnetic Green's tensor methodology, study the energy transfer efficiency and dynamics. Taking into consideration the dissipation in the donor and the charge separation rate, we focus on the transfer dynamics of the two molecules, with and without quantum coherence, for different distances and dipole orientations with respect to the surface of the MoS2 nanodisk. The presence of the MoS2 nanodisk enhances the relaxation rate, the coherent and the incoherent terms of coupling coefficients of the molecules, thus affecting their dynamic response. Our results show high efficiency energy transfer between the two molecules in the presence of strong coherence for small distances from the MoS2 nanodisk. Also, for specific dipole polarization, small dissipation in the donor and strong charge separation rate, we observe ultrafast, in the scale of picosecond, and largely improved energy transfer process compared with the case without coherence. The results are expected to have a positive impact on the coherent techniques of energy transfer for the design of new, improved and useful harvesting light devices in nanotechnology.

  • Open access
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Impurity Ferromagnetism of Pd-Fe and Pd-Co Alloys: Ab Initio vs. Experiment

We have performed full-stack research of Pd1-xFex and Pd1-xCox (x = 0.01-0.1) alloys. At the first stage, the occurrence of impurity ferromagnetism in considered alloys was studied employing the Density Functional Theory (DFT). Calculations revealed that considered impurities can initialize significant magnetization of the Pd atoms, in particular, the maximum magnetization for the Pd1-xFex system was found to be ~8μB at x = 0.07, whereas Co produces a much higher magnetization for the Pd1-xCox alloy which is equal to ~15 μB at x = 0.02, where μB is a Bohr magneton. We also found that the induced magnetization depends on the position of the impurities in the host matrix. The calculations showed that the maximum magnetization is observed with a uniform distribution of the dissolved impurity.

At the second stage, magnetic impurities of Fe and Co atoms were implanted into epitaxial Pd thin films to verify DFT results. The concentration of impurities in the Pd matrix was adjusted by the dose of implantation. Magnetic properties of implanted Pd films were investigated by Vibrating Sample Magnetometer (VSM) in the temperature range from 5K to 300K. The VSM data were recalculated to get the value of the magnetic moment in terms of Bohr magnetons per implanted magnetic ion of impurity.

It has been established that VSM results are in good agreement with ab initio calculations. It was shown that the value of the magnetic moments of the Pd films implanted with Fe+ (or Co+) ions are close to the calculated values for corresponding concentrations.

This work was supported by the RFBR Grant No. 20-02-00981.

  • Open access
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Comparison of Some Physical Properties of Doped and Pristine Nanotubes Based on Carbon and Tungsten Disulfide
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In this work, we present the experimental results on various spectroscopy measurements (including Raman, IR, optical, and terahertz spectroscopies) as well as the data on transmission and scanning electron microscopy of pristine and doped (with HAuCl4) nanotubes (NT) based on carbon (C) and tungsten disulfide (WS2). We observed the peaks of excitonic transitions (semiconducting ES11, ES22, and metallic EM11 transitions with wavelengths 2300, 1240, and 870 nm for CNT and A, B, C, D transitions with wavelengths 670, 550, 500, and 410 nm for WS2NT), Raman active modes (G-band 1585 cm-1 for CNT and E12g 417 cm-1, A1g 351 cm-1 for WS2NT). The behavior of conductivity of the pristine NT in the terahertz range was investigated. With the help of these measurements, the comparison of different pristine NT and their doped analogs was implemented and the shift of the Raman peaks and the changed conductivity behavior for doped nanotubes were found.

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