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Comparative Analysis of Raman Signal Amplifying Effectiveness of Silver Nanostructures with Different Morphology
To increase the attractiveness of the practical application of molecular sensing methods, the experimental search for the optimal shape of silver nanostructures allowing to increase the Raman cross section by several orders of magnitude is of great interest. This paper presents a detailed study of spatially separated plasmon-active silver nanostructures grown in SiO2/Si template pores with crystallite, dendrite, and “sunflower-like” nanostructures shapes. Nile blue and 2-mercaptobenzothiazole were chosen as the model analytes for comparative evaluation of the Raman signal amplification efficiency using these structures. It was discussed the features of the structures for the enhancement of Raman intensity. Finally, we showed that silver crystals, dendrites, and “sunflower-like” nanostructures in SiO2/Si template could be used as the relevant materials for Raman signal amplification, but with different efficiency
Electrochemical behaviour of Ti/Al2O3/Ni nanocomposite material in artificial physiological solution: Prospects for biomedical application
Inorganic-based nanoelements such as nanoparticles (nanodots), nanopillars and nanowires, which have at least one dimension of 100 nm or less, have been extensively developed for biomedical applications. Furthermore, their properties can be varied by controlling such parameters as element shape, size, surface functionalization, and mutual interactions. In this study, Ni-alumina nanocomposite material was synthesized by the dc-Ni electrodeposition into a porous anodic alumina template (PAAT). The structural, morphological, and corrosion properties were studied using x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and electrochemical techniques (linear sweep voltammetry). Template technology was used to obtain Ni nanopillars (NiNPs) in the PAAT nanocomposite. Low corrosion current densities (order of 0.5 μA/cm2) were indicators of this nanocomposite adequate corrosion resistance in artificial physiological solution (0.9% NaCl). A porous anodic alumina template is barely exposed to corrosion and performs protective functions in the composite. The results may be useful for the development of new nanocomposite materials technologies for a variety of biomedical applications including catalysis and nanoelectrodes for sensing and fuel cells. They are also applicable for various therapeutic purposes including targeting, diagnosis, magnetic hyperthermia, and drug delivery. Therefore, it is an ambitious task to research the corrosion resistance of these magnetic nanostructures in simulated body fluid. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Government Council on Grants, Russian FederationBelarusian Republican Foundation for Fundamental Research, BRFFR: Ф18Д-00720163522Funding: The work was performed with support of State Scientific and Technical Program “Nanotech” (ГБЦ No 20163522), Belarusian Republican Foundation for Fundamental Research (Grant No. Ф18Д-007), Act 211 of Government of Russian Federation (contract No. 02.A03.21.0011). Additionally, the work was partially supported by the Grant of World Federation of Scientists (Geneva, Switzerland)
Peculiarities of the crystal structure evolution of Bifeo3-batio3 ceramics across structural phase transitions
Evolution of the crystal structure of ceramics BiFeO3-BaTiO3 across the morphotropic phase boundary was analyzed using the results of macroscopic measuring techniques such as X-ray diffraction, differential scanning calorimetry, and differential thermal analysis, as well as the data obtained by local scale methods of scanning probe microscopy. The obtained results allowed to specify the concentration and temperature regions of the single phase and phase coexistent regions as well as to clarify a modification of the structural parameters across the rhombohedral-cubic phase boundary. The structural data show unexpected strengthening of structural distortion specific for the rhombohedral phase, which occurs upon dopant concentration and temperature-driven phase transitions to the cubic phase. The obtained results point to the non-monotonous character of the phase evolution, which is specific for metastable phases. The compounds with metastable structural state are characterized by enhanced sensitivity to external stimuli, which significantly expands the perspectives of their particular use. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Instituto Nacional de Ciência e Tecnologia para Excitotoxicidade e Neuroproteção, INCT-EN: UID/04564/2020, UIDB/50011/2020, UIDP/50011/2020Russian Science Foundation, RSF: 18-19-00307Funding: This work was supported by the RSF (project #18-19-00307). Investigations performed at the Center for Physics of the University of Coimbra were supported by Fundação para a Ciência e a Tecnologia (project UID/04564/2020). M.V.S. acknowledges Russian academic excellence project “5-100” for Sechenov University. Part of work done at the University of Aveiro was developed within the scope of the project CICECO-Aveiro Institute of Materials, refs. UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the FCT/MEC
Temperature induced structural and polarization features in BaFe12O19
We report the observation of a peculiar polarization behavior of BaFe12O19 in electric field where the linear polarization is detected at temperatures below 150 K whereas at higher temperatures a hysteresis-like polarization response is observed. At the same time, the performed neutron diffraction analysis shows no variations in crystal or magnetic structures with temperature. Based on the results of ab initio calculations we suggest the mechanism able to explain the experimentally observed behavior. We show that specific Fe atoms do not occupy the positions formally assigned to them by the conventional centrosymmetric P63/mmc (#194) space group (z = 0.25; 0.75) as these positions correspond to local energy maxima. Instead, these Fe atoms are shifted along the z-axis to positions z = 0.259 (0.241) and z = 0.759 (0.741), which correspond to local energy minima. To an inversion center move between these minima Fe atoms need to overcome an energy barrier. This barrier is rather insignificant for smaller volumes but it becomes larger for expanded volumes due to coupling between the displacements of these Fe atoms. Additionally, our analysis suggests that the non-centrosymmetric and polar P63mc (#186) space group could be appropriate for the description of the BaFe12O19 structure
Fe 3 O 4 nanoparticles for complex targeted delivery and boron neutron capture therapy
Magnetic Fe 3 O 4 nanoparticles (NPs) and their surface modification with therapeutic substances are of great interest, especially drug delivery for cancer therapy, including boron-neutron capture therapy (BNCT). In this paper, we present the results of boron-rich compound (carborane borate) attachment to previously aminated by (3-aminopropyl)-trimethoxysilane (APTMS) iron oxide NPs. Fourier transform infrared spectroscopy with Attenuated total reflectance accessory (ATR-FTIR) and energy-dispersive X-ray analysis confirmed the change of the element content of NPs after modification and formation of new bonds between Fe3O4 NPs and the attached molecules. Transmission (TEM) and scanning electron microscopy (SEM) showed Fe3O4 NPs’ average size of 18.9 nm. Phase parameters were studied by powder X-ray diffraction (XRD), and the magnetic behavior of Fe 3 O 4 NPs was elucidated by Mössbauer spectroscopy. The colloidal and chemical stability of NPs was studied using simulated body fluid (phosphate buffer-PBS). Modified NPs have shown excellent stability in PBS (pH = 7.4), characterized by XRD, Mössbauer spectroscopy, and dynamic light scattering (DLS). Biocompatibility was evaluated in-vitro using cultured mouse embryonic fibroblasts (MEFs). The results show us an increasing of IC50 from 0.110 mg/mL for Fe 3 O 4 NPs to 0.405 mg/mL for Fe 3 O 4 -Carborane NPs. The obtained data confirm the biocompatibility and stability of synthesized NPs and the potential to use them in BNCT. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This study was funded by the Ministry of Education and Science of the Republic of Kazakhstan (grant No AP05130947 “Setting the stage for boron neutron capture therapy of cancer in the Republic of Kazakhstan”) and Nazarbayev University “Social Policy Grant” (project title: “Research and development of the new Nano-Optical Sensor based on Polymer Optical Fiber for Near-Field Scanning Optical Microscopy”, PI: Kanat Dukenbayev). The authors also gratefully acknowledge the financial support of the Ministry of Education and Science of the Russian Federation in the framework of Increase Competitiveness Program of NUST «MISiS» (NoK4-2018-036, P02-2017-2-4), implemented by a governmental degree dated 16th of March 2013, No 211. The work was partially supported by Act 211 Government of the Russian Federation, contract No 02.A03.21.0011. This work was partially supported by the Ministry of Education and Science of the Russian Federation (Government task in SUSU 5.5523.2017/8.9)
Electrochemical behaviour of Ti/Al2O3/Ni nanocomposite material in artificial physiological solution: Prospects for biomedical application
Inorganic-based nanoelements such as nanoparticles (nanodots), nanopillars and nanowires, which have at least one dimension of 100 nm or less, have been extensively developed for biomedical applications. Furthermore, their properties can be varied by controlling such parameters as element shape, size, surface functionalization, and mutual interactions. In this study, Ni-alumina nanocomposite material was synthesized by the dc-Ni electrodeposition into a porous anodic alumina template (PAAT). The structural, morphological, and corrosion properties were studied using x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and electrochemical techniques (linear sweep voltammetry). Template technology was used to obtain Ni nanopillars (NiNPs) in the PAAT nanocomposite. Low corrosion current densities (order of 0.5 μA/cm2) were indicators of this nanocomposite adequate corrosion resistance in artificial physiological solution (0.9% NaCl). A porous anodic alumina template is barely exposed to corrosion and performs protective functions in the composite. The results may be useful for the development of new nanocomposite materials technologies for a variety of biomedical applications including catalysis and nanoelectrodes for sensing and fuel cells. They are also applicable for various therapeutic purposes including targeting, diagnosis, magnetic hyperthermia, and drug delivery. Therefore, it is an ambitious task to research the corrosion resistance of these magnetic nanostructures in simulated body fluid. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Government Council on Grants, Russian FederationBelarusian Republican Foundation for Fundamental Research, BRFFR: Ф18Д-00720163522Funding: The work was performed with support of State Scientific and Technical Program “Nanotech” (ГБЦ No 20163522), Belarusian Republican Foundation for Fundamental Research (Grant No. Ф18Д-007), Act 211 of Government of Russian Federation (contract No. 02.A03.21.0011). Additionally, the work was partially supported by the Grant of World Federation of Scientists (Geneva, Switzerland)
Morphology and microstructure evolution of gold nanostructures in the limited volume porous matrices
The modern development of nanotechnology requires the discovery of simple approaches that ensure the controlled formation of functional nanostructures with a predetermined morphology. One of the simplest approaches is the self-assembly of nanostructures. The widespread implementation of self-assembly is limited by the complexity of controlled processes in a large volume where, due to the temperature, ion concentration, and other thermodynamics factors, local changes in diffusion-limited processes may occur, leading to unexpected nanostructure growth. The easiest ways to control the diffusion-limited processes are spatial limitation and localized growth of nanostructures in a porous matrix. In this paper, we propose to apply the method of controlled self-assembly of gold nanostructures in a limited pore volume of a silicon oxide matrix with submicron pore sizes. A detailed study of achieved gold nanostructures’ morphology, microstructure, and surface composition at different formation stages is carried out to understand the peculiarities of realized nanostructures. Based on the obtained results, a mechanism for the growth of gold nanostructures in a limited volume, which can be used for the controlled formation of nanostructures with a predetermined geometry and composition, has been proposed. The results observed in the present study can be useful for the design of plasmonic-active surfaces for surface-enhanced Raman spectroscopy-based detection of ultra-low concentration of different chemical or biological analytes, where the size of the localized gold nanostructures is comparable with the spot area of the focused laser beam. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.3.1.5.1Ministry of Education and Science of the Russian Federation, Minobrnauka: К-2018-036, N 211Russian Foundation for Fundamental Investigations, RFFI: 19-32-50058European Commission, ECMinistry of Science and Technology, MOSTFunding: This research was funded by H2020-MSCA-RISE2017-778308-SPINMULTIFILM Project, the scientific– technical program, ‘Technology-SG’ [project number 3.1.5.1], Ministry of Education and Science of the Russian Federation in the framework of Increase Competitiveness Program of NUST «MISiS» [№ К-2018-036], implemented by a governmental decree dated 16th of March 2013, N 211 and Russian Foundation for Fundamental Investigations [project number 19-32-50058].Acknowledgments: D.V.Y. greatly acknowledges the World Federation of Scientists National Scholarship Program. E.Yu.K., D.V.Y., V.D.B., and V.S. greatly acknowledge the European Union program Mobility Scheme for Targeted People-to-People-Contacts (MOST) for supporting research visits
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