Alexey Pavlovich Dovzhenko

This work presents an energy-efficient and simple method for producing luminescent, antibacterial sulfur quantum dots (SQDs). For the first time, polyethyleneimine (PEI)-coated SQDs were synthesized via a mechanochemical technique, utilizing either elemental sulfur or sodium thiosulfate as the sulfur source. The roles of hydrogen peroxide (H₂O₂) as an etching agent and of sodium hydroxide (NaOH) in the PEI-mediated SQD formation were investigated. The as-synthesized SQDs were characterized by UV-visible, Raman, infrared (IR), and photoluminescence (PL) spectroscopy, as well as by transmission electron microscopy (TEM) and atomic force microscopy (AFM). Both TEM and AFM analyses revealed similarly small SQD sizes (average diameter ~3 nm), independent of the sulfur source used. The influence of synthesis conditions on the optical properties, including the photoluminescence quantum yield (QY), was evaluated. SQDs derived from elemental sulfur, PEI, and NaOH exhibited the best water solubility and the strongest photoemission in the 400–550 nm range. Antibacterial activity was assessed against representative Gram-positive and Gram-negative strains, and minimum inhibitory concentration (MIC) values were determined. The PEI-coated SQDs demonstrated antibacterial activity against the Gram-positive bacteria Bacillus subtilis, Staphylococcus aureus, and Staphylococcus epidermidis, which is attributed primarily to the sulfur component.

This work presents novel diphenylphosphoryl-substituted 1,3-diketone derivatives and demonstrates their potential as ligands for the design of Eu³⁺-containing nanoparticles with reproducible thermally dependent photoluminescence. Structural analysis of the synthesized lanthanide complexes in acetonitrile medium using NMR, IR spectroscopy, and computational modeling revealed weak coordination of the phosphoryl group to the central Ln³⁺ ion. Nevertheless, the presence of this group in the ligand molecule enhances the sensitization efficiency of Eu³⁺ luminescence due to a shielding effect. This effect was confirmed by comparing the quantum yields of Eu³⁺ complexes with diphenylphosphoryl-substituted 1,3-diketone ligands to their structural analogs lacking the phosphoryl group. The shielding of the lanthanide coordination sphere by the diphenylphosphoryl substituent promotes more efficient incorporation of the complexes into polystyrene sulfonate nanoparticles. The resulting polyelectrolyte colloids exhibit chemically stable luminescent properties in the presence of biologically relevant amino acids and phosphates. Additionally, they demonstrate reproducible thermally dependent luminescence in the biologically relevant temperature range of 25–50°C, with a sensitivity of 1.73–1.76%/°C.

Lanthanide complexes with organic ligands exhibit unique photophysical properties, including long-lived emission lifetimes, large Stokes shifts, and sharp emission bands, making them highly attractive for bioanalytical and biomedical applications. Incorporating these complexes into nanoparticles can further enhance signal intensity and assay sensitivity in both in vitro and in vivo settings. Here, we report the first successful use of the desolvation method to synthesize bovine serum albumin (BSA) nanoparticles loaded with europium complexes. This simple approach involved the dropwise addition of an ethanolic solution of europium complex precursors into an aqueous BSA solution, followed by thermal cross-linking to generate disulfide bonds. We systematically optimized synthesis parameters—including pH, precursor concentration, and addition rate—to produce nanoparticles with high brightness and low polydispersity. Under optimized conditions, the resulting nanoparticles exhibited a uniform size of 150–160 nm (PDI<0.15) as determined by dynamic light scattering and electron microscopy. Each nanoparticle encapsulated approximately 350 europium complexes, achieving quantum yields of 0.77–1.18% with excitation/emission maxima at 360/615 nm. The synthesis yield was ~80%, and the nanoparticles demonstrated excellent size stability across physiological pH conditions and after three months of storage. However, luminescence intensity decreased over time and under certain buffer conditions. Cytotoxicity studies using Vero cells showed cell viability above 80% at nanoparticle concentrations up to 1 mg/mL. The key challenges to be addressed are the improvement of synthesis reproducibility and the stability of luminescent properties.

Linear N‐substituted polyacrylamides bearing tricarboxylic moieties pendant to the backbone are synthesized, and coordinative binding approach is developed to convert them into Gd³⁺/Eu³⁺‐metallopolymers. Inner‐sphere coordination of the lanthanide ions with the pendant chelating moieties, together with their outer‐sphere stabilization by the randomly coiled backbone, are the reasons for peculiar water proton relaxation and luminescence properties of the metallopolymers obtained. Indeed, for Gd³⁺‐metallopolymer, the values of longitudinal and transverse relaxivity (r₁ and r₂) are 50 and 60 mm⁻¹·s⁻¹, respectively, while for the Eu³⁺‐counterpart, Eu³⁺‐centered luminescence is significantly raised compared to Eu³⁺ aquaions. Coil‐like conformation of the metallopolymer molecules undergoes a swelling at pH values above 5.0 as evidenced by transmission electron microscopy TEM and dynamic light scattering (DLS) data, which is followed by the changes in the Eu³⁺‐centered luminescence and r₁₍₂₎‐values of Gd³⁺/Eu³⁺‐metallopolymers. The phosphates additives (adenosine monophosphoric acid (AMP), adenosine diphosphoric acid (ADP), HPO₄²⁻ and adenosine triphosphoric acid (ATP) induce well detectable changes in both water proton relaxation and luminescence of Gd³⁺/Eu³⁺‐metallopolymers. The luminescent changes distinguish AMP from the other phosphates, while the changes in water proton relaxation are greater for HPO₄²⁻ and ATP compared to AMP and ADP. This study explains this by interplay of the effects associated with the formation of ternary phosphate‐lanthanide‐polymer complexes and stripping of lanthanide ions from the polymer molecules.

Novel 1-phenyl(1-thiophen-2-yl)-4-(diphenylphosphoryl)butane-1,3-diones were synthesized by the Claisen-type condensation of 1-(diphenylphosphoryl)propan-2-one with ethyl phenyl(thiophene-2-yl)carboxylates. The tautomeric equilibrium of diketone moiety of phosphine oxides was investigated by ¹H and ¹³C{¹H} NMR spectroscopy. Two species out of five possible tautomers (diketo and mono-enol) were observed in the solution of 1-phenyl(1-thiophen-2-yl)-4-(diphenylphosphoryl)butane-1,3-diones. The major tautomer was the mono-enol form with content 80–90%. Furthermore, the double bond position at C³ atom was determined by ¹³C{¹H} NMR spectroscopy.

Novel 4-(diphenylphosphoryl)-1-phenylbutane-1,3-dione was synthesized by the reaction of diketone enamine with diphenylchloro phosphine followed by oxidation and hydrolysis of the enamine phosphine formed. Tautomeric transformation of the diketone moiety of phosphine oxide was investigated by ¹H NMR. Three out of five possible tautomers were observed in the 4-(diphenylphosphoryl)-1-phenylbutane-1,3-dione solution. The major tautomer was the form with a diketone fragment.

In this study, Nickel oxide-based catalysts (Ni_xO_x) were synthesized and used for the in-situ upgrading process of heavy crude oil (viscosity 2157 mPa·s, and API gravity of 14.1° at 25 °C) in aquathermolysis conditions for viscosity reduction and heavy oil recovery. All characterizations of the obtained nanoparticles catalysts (Ni_xO_x) were performed through Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), X-Ray and Diffraction (XRD), and ASAP 2400 analyzer from Micromeritics (USA), methods. Experiments of catalytic and non-catalytic upgrading processes were carried out in a discontinuous reactor at a temperature of 300 °C and 72 bars for 24 h and 2% of catalyst ratio to the total weight of heavy crude oil. XRD analysis revealed that the use of nanoparticles of NiO significantly participated in the upgrading processes (by desulfurization) where different activated form catalysts were observed, such as α-NiS, β-NiS, Ni₃S₄, Ni₉S₈, and NiO. The results of viscosity analysis, elemental analysis, and ¹³C NMR analysis revealed that the viscosity of heavy crude oil decreased from 2157 to 800 mPa·s, heteroatoms removal from heavy oil ranged from S—4.28% to 3.32% and N—0.40% to 0.37%, and total content of fractions (ΣC₈–C₂₅) increased from 59.56% to a maximum of 72.21%, with catalyst-3 thank to isomerization of normal and cyclo-alkanes and dealkylation of lateral chains of aromatics structures, respectively. Moreover, the obtained nanoparticles showed good selectivity, promoting in-situ hydrogenation-dehydrogenation reactions, and hydrogen redistribution over carbons (H/C) is improved, ranging from 1.48 to a maximum of 1.77 in sample catalyst-3. On the other hand, the use of nanoparticle catalysts have also impacted the hydrogen production, where the H₂/CO provided from the water gas shift reaction has increased. Nickel oxide catalysts have the potential for in-situ hydrothermal upgrading of heavy crude oil because of their great potential to catalyze the aquathermolysis reactions in the presence of steam.

The present work demonstrates the optimization of the ligand structure in the series of bis(phosphine oxide) and β-ketophosphine oxide representatives for efficient coordination of Tb³⁺ and Eu³⁺ ions with the formation of the complexes exhibiting high Tb³⁺- and Eu³⁺-centered luminescence. The analysis of the stoichiometry and structure of the lanthanide complexes obtained using the XRD method reveals the great impact of the bridging group nature between two phosphine oxide moieties on the coordination mode of the ligands with Tb³⁺ and Eu³⁺ ions. The bridging imido-group facilitates the deprotonation of the imido- bis(phosphine oxide) ligand followed by the formation of tris-complexes. The spectral and PXRD analysis of the separated colloids indicates that the high stability of the tris-complexes provides their safe conversion into polystyrenesulfonate-stabilized colloids using the solvent exchange method. The red Eu³⁺-centered luminescence of the tris-complex exhibits the same specificity in the solutions and the colloids. The pronounced luminescent response on the antibiotic ceftriaxone allows for sensing the latter in aqueous solutions with an LOD value equal to 0.974 μM.

The present work demonstrates the optimization of the ligand structure in the series of bis-phosphine oxide and carbamoylphosphine oxide representatives for efficient coordination of Tb3+ and Eu3+ ions with the formation of the complexes exhibiting high Tb3+- and Eu3+-centered luminescence. The analysis of the stoichiometry and structure of the lanthanide complexes obtained by XRD method reveals the great impact of the bridging group nature between two phosphine oxide moieties on the coordination mode of the ligands with Tb3+ and Eu3+ ions. The bridging imido-group facilitates the deprotonation of imido-bisphosphine oxide ligand followed by the formation of tris-complexes. The spectral and PXRD analysis of the separated colloids indicates that the high stability of the tris-complexes provides their safe conversion into polystyrenesulfonate-stabilized colloids under the solvent exchange method. The red Eu3+-centered luminescence of the tris-complex exhibits the same specificity in the solutions and the colloids. The pronounced luminescent response on the antibiotics ceftriaxone allows to sense the latter in aqueous solutions with the LOD value equal to 0.974 M.