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 J_KL (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 ⁿJ_KL 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 J_KL, 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 ⁿJ_KL we calculated the values of scalar J-constants ⁿJ=Sp(ⁿJ_KL)/3 for different ¹³C_i-¹³C_j 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 ⁿJ_KL for the adamantane and found that for this molecule the calculated value ¹J = Sp(¹J_KL)/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.

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.

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.

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 Fe@MWCNT-OH/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 α_CO2/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 Fe@MWCNTs. 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.

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.