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Silver–bismuth iodide (Ag–Bi–I) rudorffites are chemically stable and non-toxic materials that can act as a possible lead-free replacement for methylammonium lead halides in optoelectronic applications. We report on a simple route for fabricating Ag–Bi–I colloidal nanoplatelets approximately 160 nm in lateral dimensions and 1–8 nm in thickness via exfoliation of Ag–Bi–I rudorffite powders in acetonitrile. The valence band electronic structure of isolated Ag–Bi–I nanoplatelets was investigated using synchrotron radiation to perform X-ray aerosol photoelectron spectroscopy (XAPS). The ionization energy of the material was found to be 6.1 ± 0.2 eV with respect to the vacuum level. UV–vis absorption and photoluminescence spectroscopies of the Ag–Bi–I colloids showed that the optical properties of the nanoplatelets originate from I 5p to Bi 6p and I 5p to I 5p transitions, which is further confirmed by density functional theory (DFT) calculations. Finally, calculations based on the DFT and k · p theoretical methods showed that the quantum confinement effect is very weak in the system studied.

We report on the aerosol generation of ligand-free silver iodobismuthate (Ag-Bi-I) nanoparticles (NPs) and on in situ investigation of their electronic structure using synchrotron radiation soft X-ray aerosol photoelectron spectroscopy (XAPS). The structural and morphological characterizations revealed the aerosol to be composed of spherical rudorffite Ag3BiI6 particles, approximately 100 nm in size. The XAPS showed well-resolved signals from all expected elements (Ag, Bi, and I) and allowed estimation of the NP work function to be about 4.5 eV. The ionization energy of Ag3BiI6 NPs was determined to be 6.1 eV that is in good agreement with our calculations based on a hybrid functional approach. The presented method of production of Ag3BiI6 aerosol can prove beneficial for the future development of Ag-Bi-I-based photovoltaic materials, since it allows the deposition of Ag-Bi-I particles on large surface areas of arbitrary shape and roughness.

Nitrogen-functionalized graphene quantum dots (N-GQDs) were synthesized by hydrothermal transformation of glycine precursors in glycerol. Functionalization of GQDs with nitrogen was confirmed with FTIR spectroscopy. Atomic force microscopy (AFM) analysis revealed that the thickness of the quantum dots is around ~10 Å while the lateral dimensions are the in range from 20 to 80 nm. N-GQDs exhibit strong fluorescence in blue (420 nm) region and they are suitable for bioimaging applications.

Fluorescent nanocomposite films were prepared by solution mixing of polyvinyl alcohol (PVA) and tryptophan functionalized silver (AgTrp) nanoparticles. Synchrotron excitation deep-ultraviolet (DUV) fluorescence imaging was used to follow the distribution of AgTrp nanoparticles within the polymer matrix. Pronounced growth of dendrite-like structures in the presence of AgTrp nanoparticles was confirmed by bright field and fluorescence imaging as well as with atomic force microscopies. Both tryptophan and AgTrp nanoparticles influence thermal properties of the matrix. Differential scanning calorimetry measurements showed that they reduce crystallinity and significantly increase the glass transition temperature of PVA (in the case of PVA-AgTrp film the Tg increases by ~20 °C). Dielectric properties of the films were studied under two different conditions (dark and illumination). The illumination with 250 nm light induces a significant increase in conductance of the PVA-AgTrp nanocomposite. The relative changes, with respect to the conductance measured in the dark, were almost ~200%.

Na0.25K0.25Bi0.5TiO3 (NKBT) perovskite particles are synthesized by solid-state method and used as a filler for polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) co-polymer. X-ray diffraction analysis of NKBT powders shows that the particles have a rhombohedral perovskite crystal structure (R3c symmetry). Raman spectroscopy reveals that the co-polymer crystallizes predominantly into the mixture of polar β- and γ-crystals, while there is also a contribution of the non-polar α-crystal phase. The introduction of the NKBT into the PVDF-HFP results with an increase in effective dielectric permittivity and this effect depends on the inorganic content in the composite. The most interesting result of the present study is that the introduction of NKBT particles induces the appearance of an additional transition peak in the dielectric spectra of the co-polymer matrix. At the fixed frequency of ~2 kHz, the observed process appears at ~10 °C (about 45° above the glass transition temperature) and its magnitude strongly depends on the amount of the NKBT in the composite. Dielectric spectroscopy measurements of the composites are carried out in the wide range of frequencies (from 0.1 Hz to 1 MHz) and temperatures (from −100 to 100 °C). They reveal that the novel process can be clearly distinguished in the frequency range between 160 Hz and ~50 kHz. © 2021 The Authors

We report an investigation of lead halide perovskite CH3NH3PbBr3 nanocrystals and associated ligand molecules by combining several different state-of-the-art experimental techniques, including synchrotron radiation-based XPS and VUV PES of free-standing nanocrystals isolated in vacuum. By using this novel approach for perovskite materials, we could directly obtain complete band alignment to vacuum of both CH3NH3PbBr3 nanocrystals and the ligands widely used in their preparation. We discuss the possible influence of the ligand molecules to apparent perovskite properties, and we compare the electronic properties of nanocrystals to those of bulk material. The experimental results were supported by DFT calculations. Supporting information: [https://figshare.com/articles/Electronic_Properties_of_Free-Standing_Surfactant-Capped_Lead_Halide_Perovskite_Nanocrystals_Isolated_in_Vacuo/6584018]

The investigation of the interaction of silver nanoparticles and live bacteria cells is of particular importance for understanding and controlling their bactericidal properties. In this study, the process of internalization of silver nanoparticles in Escherichia coli cells was followed by means of synchrotron excitation deep ultraviolet (DUV) fluorescence imaging. Antimicrobial nanostructures that can absorb and emit light in the UV region were prepared by functionalization of silver nanoparticles with tryptophan amino acid and used as environmentally sensitive fluorescent probes. The nanostructures were characterized by morphological (TEM) and spectroscopic methods (UV-vis, FTIR, XPS, and photoluminescence). The TEM images and the analyses of the UV-vis spectra suggested that the addition of tryptophan led to the formation of hybrid nanostructures with pronounced eccentricity and larger sizes with respect to that of the initial silver nanoparticles. The DUV imaging showed that it was possible to distinguish the fluorescent signal pertaining to silver-tryptophan nanostructures from the autofluorescence of the bacteria. The spatial resolution of the fluorescence images was 154 nm which was sufficient to perform analyses of the accumulation of the nanostructures within a single bacterium. The DUV imaging results imply that the tryptophan-functionalized silver nanoparticles interact with cell membranes via insertion of the amino acid into the phospholipid bilayer and enter the cells.

The interaction of partially reduced graphene oxide (prGO) and Huh7.5.1 liver cancer cells was investigated by means of DUV fluorescence bioimaging. The prGO sample was obtained by the reduction (to a certain extent) of the initially prepared graphene oxide (GO) nanosheets with hydrazine. The fluorescence of the GO nanosheets increases with time of the reduction due to a change in ratio of the sp2 and sp3 carbon sites and the prGO sample was extracted from the dispersion after 6 min, when the intensity of the fluorescence reached its maximum. The reduction process was left to proceed further to saturation until highly reduced graphene oxide (denoted here as rGO) was obtained. GO, prGO and rGO samples were investigated by structural (scanning electron microscopy (SEM), scanning transmission electron microscopy coupled with energy dispersive spectrometry (STEM-EDS)) and spectroscopic (UV-vis, photoluminescence (PL), Raman) methods. After that, Huh7.5.1 cells were incubated with GO, prGO and rGO nanosheets and used in bioimaging studies, which were performed on DISCO beamline of synchrotron SOLEIL. It was found that the prGO significantly enhanced the fluorescence of the cells and increased the intensity of the signal by ~2.5 times. Time-lapse fluorescence microscopy experiments showed that fluorescence dynamics strongly depends on the type of nanosheets used. The obtained prGO nanostructure can be easily conjugated with aromatic ring containing drugs, which opens a possibility for its applications in fluorescence microscopy monitored drug delivery. © 2018 IOP Publishing Ltd. This is the peer-reviewed version of the article: Dojčilović, R., Pajović, J.D., Božanić, D.K., Jović, N., Pavlović, V.P., Pavlović, V.B., Acković, L.L., Zeković, I., Dramićanin, M., Kaščaková, S., Réfrégiers, M., Rašić, G., Vlahović, B., Djoković, V., 2018. DUV fluorescence bioimaging study of the interaction of partially reduced graphene oxide and liver cancer cells. 2D Materials 5. [https://doi.org/10.1088/2053-1583/aad72b]

The influence of the mechanical activation of ZnO nanoparticle fillers on the structural and electrical properties of the matrix of poly(vinylidenefluoride)-ZnO (PVDF-ZnO) films was investigated. Transmission electron microscopy and scanning electron microscopy analyses showed that mechanical activation in a high energy planetary ball mill reduces the size of ZnO particles. X-ray diffraction and Raman spectroscopy revealed that PVDF crystallized predominantly as the γ-phase. Non-activated ZnO filler reduces the degree of the crystallinity of the matrix and promotes crystallization of α-phase of PVDF in the film, while the fillers activated for 5 and 10 min induce crystallization of β-phase, indicating that mechanical activation of the filler can be used as a general method for fabrication of PVDF composites with increased content of piezoelectric β-phase crystals. Dielectric spectroscopy measurements show that polymer composite with the high content of β-phase (with ZnO filler activated for 5 min) exhibits the highest value of dielectric permittivity in 150-400 K range of temperatures. Kinetic analysis shows combined effects of increased surface area and increased concentration of surface defects on the interactions between polymer chains and activated nanoparticles. © 2018 IOP Publishing Ltd. This is the peer-reviewed version of the article: Peleš, A., Aleksić, O., Pavlović, V.P., Djoković, V., Dojčilović, R., Nikolić, Z., Marinković, F., Mitrić, M., Blagojević, V., Vlahović, B., Pavlović, V.B., 2018. Structural and electrical properties of ferroelectric poly(vinylidene fluoride) and mechanically activated ZnO nanoparticle composite films. Physica Scripta 93. [https://doi.org/10.1088/1402-4896/aad749]

The interaction of the tryptophan functionalized Ag nanoparticles and live Candida albicans cells was studied by synchrotron excitation deep-ultraviolet (DUV) fluorescence imaging at the DISCO beamline of Synchrotron SOLEIL. DUV imaging showed that incubation of the fungus with functionalized nanoparticles results in significant increase in the fluorescence signal. The analysis of the images revealed that the interaction of the nanoparticles with (pseudo)hyphae polymorphs of the diploid fungus was less pronounced than in the case of yeast cells or budding spores. The changes in the intensity of the fluorescence signals of the cells after incubation were followed in [327-353 nm] and [370-410 nm] spectral ranges that correspond to the fluorescence of tryptophan in non-polar and polar environment, respectively. As a consequence of the environmental sensitivity of the silver-tryptophan fluorescent nanoprobe, we were able to determine the possible accumulation sites of the nanoparticles. The analysis of the intensity decay kinetics showed that the photobleaching effects were more pronounced in the case of the functionalized nanoparticle treated cells. The results of time-integrated emission in the mentioned spectral ranges suggested that the nanoparticles penetrate the cells, but that the majority of the nanoparticles attach to the cells surfaces. (C) 2017 Elsevier B.V. All rights reserved.

Fluorescent nanostructures were prepared by functionalization of gold nanoparticles with riboflavin molecules and used as probes for synchrotron radiation deep ultraviolet (SR-DUV) fluorescence imaging of gluteraldehyde-fixed Candida albicans cells. The nanoparticles were characterized by transmission electron microscopy (TEM) and optical spectroscopy techniques. The TEM analysis showed that the nanostructures were 6 nm in diameter, while the results of the fluorescence spectroscopies confirmed the photoluminescence of the nanoparticles. The SR-DUV imaging showed that it was possible to distinguish the fluorescence of the nanoparticles from the autofluorescence of the cells, as well as that the local maxima of the signal pertaining to the fluorescence of gold-riboflavin nanostructures were mostly positioned on the surfaces of the C. albicans cells of spherical morphology.

Biocompatible fluorescent nanostructures were prepared by a functionalization of gold nanoparticles with the amino acid tryptophan. The gold-tryptophan bioconjugates were investigated by TEM and HRTEM and various spectroscopy methods (XPS, FTIR, UV-vis and photoluminescence). It was found that the gold nanoparticles, initially 8. nm in diameter, aggregate in the presence of the amino acid. From the XPS and FTIR spectroscopy results, it was concluded that the tryptophan gold interactions mainly take place via indole and carboxyl groups. Although the indole group is involved in the interaction with the gold surfaces, the tryptophan-gold hybrids showed strong fluorescence due to the presence of multilayers of tryptophan. Deep ultra violet (DUV) imaging performed at the SOLEIL synchrotron showed that it is possible to detect these hybrid nanostructures within Escherichia coli cells. Ministry of Education and Science of the Republic of Serbia (Project Nos. 172056, 45020, and 171020). Scopus

We consider the slow highly charged ions impinging upon a metal surface covered with a thin dielectric film, and formation of the surface nanostructures (craters) from the standpoint of the required energy. For the moderate ionic velocities, the size of the surface features depends on the deposited kinetic energy of the projectile and the ionic neutralization energy. The neutralization energy is calculated by employing the recently developed quasi-resonant two-state vector model for the intermediate Rydberg state population and the micro-staircase model for the cascade neutralization. The electron interactions with the ionic core, polarized dielectric and charge induced on the metal surface are modelled by the appropriate asymptotic expressions and the method for calculation of the effective ionic charges in the dielectric is proposed. The results are presented for the interaction of XeZ+ ions (velocity v = 0.25 a.u.; 25 LT Z LT 45) with the metal surface (Co) covered with a thin dielectric film, for model values of dielectric constant inside the interaction region. In the absence of dielectric film, the neutralization energy is lower than the potential (ionization) energy due to the incomplete neutralization. The presence of dielectric film additionally decreases the neutralization energy. We calculate the projectile neutralization energy in the perturbed dielectric (perturbation is caused by the ionic motion and the surface structure formation). We correlate the neutralization energy added to the deposited kinetic energy with the experimentally obtained energy necessary for the formation of the nano-crater of a given depth.

Nanocomposites of electroactive ceramics and ferroelectric polymers exploit favorable features of the matrix polymer and the nanostructured filler to produce new functional materials for pressure and IR sensors. In this study, the influence of mechanical activation of barium titanate (BaTiO3) particles on the structural properties of BaTiO3/polyvinylidene fluoride (PVDF) nanocomposites was investigated. Nanocomposite films were prepared by the solution casting method and characterized by scanning electron microscopy, x-ray diffraction and Raman spectroscopy. It was found that mechanically activated fillers promote the formation of a ferroelectric beta-phase during crystallization of PVDF. 3rd International Conference on the Physics of Optical Materials and Devices, Sep 02-06, 2012, Belgrade, Serbia

We consider the population dynamics of the intermediate Rydberg states of highly charged ions (core charge Z GT GT 1, principal quantum number n(A) GT GT 1) interacting with solid surfaces at arbitrary collision geometry. The recently developed resonant two-state vector model for the grazing incidence (2012 J. Phys. B: At. Mol. Opt. Phys. 45 215202) is extended to the quasi-resonant case and arbitrary angle of incidence. According to the model, the population probabilities depend both on the projectile parallel and perpendicular velocity components, in a complementary way. A cascade neutralization process for XeZ+ ions, for Z = 15-45, interacting with a conductive-surface is considered by taking into account the population dynamics. For an arbitrary collision geometry and given range of ionic velocities, a micro-staircase model for the simultaneous calculation of the kinetic energy gain and the charge state of the ion in front of the surface is proposed. The relevance of the obtained results for the explanation of the formation of nanostructures on solid surfaces by slow highly charged ions for normal incidence geometry is briefly discussed.