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Facile electrochemical graphite oxidation and functionalization with a selected array of amine moieties are carried out. The electrochemical oxidation offers the ability to preserve graphite morphological characteristics as intact adjacent surfaces yield collective van der Waals interactions. The different amine moieties are used to tether adjacent layers within graphite oxide (GO) to produce rigid framework materials. This interconnectedness is of utmost necessity for the structures to withstand cyclability in adsorptive and electronic applications. Utilizing well-ordered electrochemically-derived graphite oxide could be advantageous for the development of large-flake-size intact graphite oxide frameworks compared to inherently defective chemically-derived graphite oxide. The produced materials are extensively characterized to understand the extent, nature, and chemistry of the amine functionalization within GO domains. A balanced aromaticity in the intercalating amine species is found favorable in order to achieve a homogeneous distribution throughout graphite flakes while enhancing the interlayer spacing. Herein, notably by applying HR-TEM methods, turbostratic domains are successfully resolved in frameworks with relatively high nitrogen abundance and obtained results corroborate with 13C MAS NMR findings plausibly. The tethering mechanism induces layers rotation/twisting, giving rise to pronounced Moire patterns. The enhanced interlayer spacing in the frameworks makes them promising candidates for storage and electronic applications.

In this work the flower-like hierarchical structures (HS) based on 3D pristine ZnO, ZnO:Eu3+ and ZnO:Eu3+@Au were successfully obtained by a template-free solvothermal and deposition-precipitation method. The decolorization/photodegradation of these structures towards model organic dye (rhodamine 6G) was studied. The synthesized ZnO-based HS were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis and photoluminescence (PL) spectroscopies. The proposed synthesis approaches allow to obtain highly crystalline 3D ZnO, ZnO:Eu3+ and ZnO:Eu3+@Au composites. Results of scanning microscopy show that ZnO flower-like HS are assemblies from smaller components, forming larger ones, the whole ZnO structure was approximately 3 μm. Au nanoparticles (size ∼ 10 nm) are successfully deposited on ZnO HS surface. Luminescent studies show that ZnO is an ideal matrix for incorporation of Eu3+ ions in broad concentration range (Eu3+ = 1.0 at%–5.0 at%) with an efficient red luminescence. The strong UV emission in ZnO, as well as ZnO:Eu3+ HS is observed under 325 nm excitation. Doping of ZnO HS matrix by Eu3+ ions leads to the red shift of deep level emission peak (DLE). The PL intensity reaches the maximum up to 5 at% Eu3+. The photocatalytic properties of ZnO and ZnO:Eu3+@Au HS were investigated under UV–Vis light irradiation towards rhodamine 6G. The obtained results demonstrate the synergetic effect of the deposited gold nanoparticles and Eu3+ doping on photocatalytic activity of ZnO:Eu3+@Au HS in comparison to pristine ZnO and ZnO:Eu3+ HS.

ZnO (nano)structures remain of great interest in biomedical applications due to their unique properties and possible morphologies. Biocompatibility of typically fabricated ZnO structures remains questionable and they still lack desired biological functions, whence their functionalization is of high interest. In this work, we fabricated micro-sized ZnO hierarchical flower-like structures using facile template-free hydrothermal method to act as carriers for the delivery of gold nanoparticles (Au) and/or Biotin (Vitamin B) to cells. Au nanoparticles (~24 nm), as well as Biotin molecules were successfully deposited on the ZnO surface due to non-covalent physical interactions. We have then cultured two cells lines: SH-SY5Y (human malignant neural) and HEK-293 (human non-malignant) and observed that ZnO hierarchical particles exhibited cell line-dependent cytotoxicity. It appeared that further functionalization of ZnO with Au nanoparticles and subsequently with Biotin led to lower discrepancy between the two cell lines response indicating that cytotoxic pathways of pure ZnO were masked by the available surface adsorbed particles (Au/Biotin). Two-photon immunocytochemistry microscopy further confirmed that Biotin decorated particles affected neuroblastoma cells cytoskeleton. These findings contribute to the understanding of cytotoxic pathways of surface-decorated nano-micro-structures made from ZnO with two molecules typically used in anticancer and regenerative medicine therapies.

The application of ionic liquids (ILs) has grown enormously, from their use as simple solvents, catalysts, media in separation science, or electrolytes to that as task-specific, tunable molecular machines with appropriate properties. A thorough understanding of these properties and structure–property relationships is needed to fully exploit their potential, open new directions in IL-based research and, finally, properly implement the appropriate applications. In this work, we investigated the structure–properties relationships of a series of alkyltriethylammonium bis(trifluoromethanesulfonyl)imide [TEA-R][TFSI] ionic liquids in relation to their thermal behavior, structure organization, and self-diffusion coefficients in the bulk state using DSC, FT-IR, SAXS, and NMR diffusometry techniques. The phase transition temperatures were determined, indicating alkyl chain dependency. Fourier-transformed infrared spectroscopy studies revealed the structuration of the ionic liquids along with alkyl chain elongation. SAXS experiments clearly demonstrated the existence of polar/non-polar domains. The alkyl chain length influenced the expansion of the non-polar domains, leading to the expansion between cation heads in polar regions of the structured IL. 1H NMR self-diffusion coefficients indicated that alkyl chain elongation generally caused the lowering of the self-diffusion coefficients. Moreover, we show that the diffusion of anions and cations of ILs is similar, even though they vary in their size.

Improvement in the performance of perovskite solar cells (PSC) and dye-sensitized solar cells (DSSC) upon modifications of mesoporous titania layers has been studied. For PSC with triple cation perovskite (FA0.76 MA0.19 Cs0.05 Pb (I0.81 Br0.19)3) about 40% higher photocurrent (up to ∼24 mA cm−2) was found for more homogenous, made of larger particles (30 nm) and thinner (150–200 nm) titania layer. For DSSC (both with liquid cobalt-based electrolyte as well as with solid state hole transporter – spiro-OMeTAD), a greater dye loading, rise in photovoltage, and the enhancement in relative photocurrent were observed for the cells prepared from the diluted titania paste (2 : 1 w/w ratio) with respect to those prepared from undiluted one. The impact of these improvements in titania layers on charge transfer dynamics in the complete solar cells as well as in pristine TiO2 layers was investigated by femtosecond transient absorption. Shorter photocarriers lifetime in perovskite material observed in better PSC, indicated that faster electron transfer at the titania interface was responsible for the higher photocurrent. Moreover, the photoinduced changes close to TiO2 interface were revealed in better PSC, which may indicate that in the efficient devices halide segregation takes place in perovskite material. In liquid DSSC, the fast component of unwanted recombination was slower in the samples with the diluted titania paste than in those made with undiluted ones. In solid state DSSC, hole injection from MK2 dye to spiro-OMeTAD takes place on the very fast ps time scale (comparable to that of electron injection) and the evidence of better penetration of spiro-OMeTAD into thinner and more porous titania layers was provided.

Perovskite solar cells with popular 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) as the hole transporting material are compared to those prepared with 2,2′,7,7′-tetrakis(N,N-di(4-methoxyphenyl)amino)-spiro-(fluorene-9,9′-xanthene) (X60), its recently proposed new and potentially cheaper alternative, and with a mixture of both materials. The cells with both small-molecule transporters have similar photocurrent and photovoltage, but the cells with X60 exhibit about 13% smaller fill factor than those with spiro-OMeTAD. The dynamics of the interfacial charge transfer occurring on the time scales from femtoseconds to seconds is explored. The overall hole injection is slower from methylammonium lead iodide to X60 than that to spiro-OMeTAD by about 0.04 ns−1. Similarly, slower hole recombination is found for the cells with X60, taking place on the millisecond time scale in the dark. The recombination under illumination is accelerated more for ×60 material, which might explain the differences in fill factor values. The cells with the 1:1 mixture of spiro-OMeTAD and X60 show intermediate behavior in all aspects, revealing that a simple combination of small molecule transporters can be used to tune the properties of HTM.

This work aimed to study for the first time to our knowledge the influence of the structure of the dental flosses (DF) coated by hydroxyapatite nanoparticles (HAP NPs) on the biological performance of saliva probiotic bacteria (S. salivarius), and human dermal and osteoblast-like cells. We used three types of HAP@DF composites (based on two unwaxed dental flosses - “fluffy” and “smooth”, and one waxed “smooth”) with different morphologies. Obtained composites were characterized from the point of view of their structure, morphological characteristics, elemental and chemical composition. We observed that HAP NPs coated “smooth” dental flosses led to an increase of viability and proliferation of oral cavity probiotic bacteria (Streptococcus salivarius) and human cells (dermal fibroblasts and osteoblast-like). In contrast, the highest viability loss of probiotic bacteria (S. salivarius), fibroblasts, and osteoblast-like cells were observed for “fluffy” unwaxed dental flosses due to high cytotoxicity. Our studies showed that HAP NPs significantly improved the biological properties of “fluffy” dental floss. Pristine “smooth” DFs (waxed and unwaxed), as well as all HAP-coated DFs, induced acceptable biocompatibility toward selected human cells.

The main aim of this research was the synthesis of the multimodal hybrid ZnO@Gd 2 O 3 nanostructures as prospective contrast agent for Magnetic Resonance Imaging (MRI) for bio-medical applications. The nanoparticles surface was functionalized by organosilicon compounds (OSC) then, by folic acid (FA) as targeting agent and doxorubicin (Dox) as chemotherapeutic agent. Doxorubicin and folic acid were attached to the nanoparticles surface by amino groups as well as due to attractive physical interactions. The morphology and crystallography of the nanostructures were studied by HRTEM and SAXS techniques. After ZnO nanoparticles surface modification by Gd 3+ and annealing at 900 °C, ZnO@Gd 2 O 3 nanostructures are polydispersed with size 30–100 nm. NMR (Nuclear Magnetic Resonance) studies of ZnO@Gd 2 O 3 were performed on fractionated particles with size up to 50 nm. Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy, zeta-potential measurements and energy dispersive X-ray analysis (EDX) showed that functional groups have been effectively bonded onto the nanoparticles surface. The high adsorption capacity of folic acid (up to 20%) and doxorubicin (up to 40%) on nanoparticles was reached upon 15 min of adsorption process in a temperature-dependent manner. The nuclear magnetic resonance (NMR) relaxation measurements confirmed that the obtained ZnO@Gd 2 O 3 nanostructures could be good contrast agents, useful for magnetic resonance imaging.

In this research a graphite oxide (GO) was synthesized by electrochemical oxidation of natural graphite in aqueous solution of perchloric acid. The process of anodic oxidation of graphite was performed by linear sweep voltammetry (LSV) from the rest potential of electrode to 1.4 V. In consequence of the electrochemical treatment graphite was fully transformed yielding GO. Formation of GO was proved by X-ray diffraction (XRD) and Raman spectroscopy analysis. The synthesis product was also characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).

In the present work we demonstrate a simple and effective way to produce bulk quantities of graphene material. For the first time, graphite oxide (GO), synthesized by electrochemical treatment of natural graphite in HClO4 aqueous solution, was used to obtain thermally exfoliated-reduced graphite oxide (TRGO). Herein, GO was thermally exfoliated and reduced at 500 °C in air, giving the final product of TRGO. Due to shock treatment, the volume of the synthesized TRGO drastically increased compared to the starting GO. Furthermore, the exfoliation process resulted in a significant decrease in the concentration of oxygen functionalities. The choice of GO exfoliation temperature was preceded by thermogravimetric analysis (TGA). TRGO was characterized using X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis.

ZnO:Tb3+ hierarchical structures (HS) were synthesized via efficient and facile template-free wet chemistry methods - precipitation and solvothermal ones. Obtained Tb3+-doped HS were functionalized by organosilicon compounds (OSC) for use it as a drug carrier to loading of the doxorubicin (Dox). X-Ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectrum (EDS), UV, photoluminescence (PL) and Fourier transform infrared (FT-IR) spectroscopies, nitrogen adsorption/desorption (BET), and cytotoxicity tests were employed to characterize the obtained ZnO and ZnO:Tb3+ HS. Results showed that proposed approach allows to obtain highly crystalline microspheres composed of nanosheets. XRD analysis of the obtained samples showed presence of two-phased system: ZnO and Tb(OH)3. SEM results demonstrated that obtained ZnO:Tb3+ HS have flower-like spherical shape with mean size approximately 4 μm. The Tb3+-doping do not change the original morphology of ZnO HS. The Brunauer-Emmett-Teller (BET) measurements showed that unique morphology allowed to obtain surface area of ZnO/ZnO:Tb3+ HS in range of 5 ÷ 13 m2g-1. ZnO and ZnO:Tb3+ HS showed high drug loading and low cytotoxicity.

Chemical oxidation of graphite by strong oxidant in strong acid medium produces graphite oxide (GO) with a plausible oxidation degree, however the precursor is susceptible to exfoliation and structural deformations. In this work, we present a two-step preparation method of highly oxidized GO flakes with well-ordered layered structure. Firstly, graphite was electrooxidized in HClO4 electrolyte yielding electrochemically gathered graphite oxide (EGO). Next, EGO was chemically overoxidized by modified Hummers method to prepare overoxidized electrochemically gathered graphite oxide (OEGO). Due to the increased interlayer distances of EGO, MnO3+ ions are able to penetrate the interlayer spaces and oxidize the unreacted graphitic domains. Hence, the synthesized OEGO is characterized by minor structure deformation and high oxidation degree. In case of our investigations most of well-ordered layered domains have been preserved, in contrast to the GO obtained directly from graphite. It is also noted that the overoxidation of EGO mainly results in formation of hydroxyl and epoxy groups. Additionally, rinsing OEGO with acetone helps prevent the tearing of oxidized graphene layers by O2 evolution arising from the reaction of H2O2 with MnO2 precipitated on the surface of water-washed samples.

Fluorescent core-shell particles are used as versatile fluorophores in confocal microscopy based image analysis and as a colloidal model system to study short and long-range interactions. Bright and stable microspherical probes are proposed as promising materials, especially in bioimaging applications. The release of dyes from fluorescent polymer microspheres is undesirable. Covalent linking of dyes within polymeric spheres during the polymerization process can solve the problem of dye leaching. This requires, e.g. the introduction of reactive groups into the dyes. Its more lipophilic ester-ether derivatives considerably reduced fluorescence. The fluorescent quantum yield of prepared nanoparticles was determined to be below 10%. As-prepared nanoparticles exhibited a low refractive index (1.293–1.349), hence their use is recommended. Scanning electron microscope (SEM) images and the fluorescence correlation spectroscopy (FCS) measurements confirmed high polydispersity of synthesized particles (40–230 nm), and are in agreement with the dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA) results (hydrodynamic diameters 203 ± 9, 548 ± 50, 146 ± 2 nm). The zeta potential of fluorescent 1H,1H-heptafluoro-n-butyl methacrylate (HFBMA) shell nanoparticles (NPs) with propargyl ether-esters, 2-methyl allyl ether-esters and allyl ether-esters of fluorescein was -44.5,-14, -44.7 mV, respectively. The values are different despite the slight difference in the structure of ester-ether derivatives.

We report a research study on reduced graphene oxide conducted with electron paramagnetic resonance and impedance spectroscopy techniques. Coupling of the two experimental methods allowed us to obtain detailed information on the charge carrier transport in the graphene material and make an attempt at explaining the peculiar behaviour of para- and ferromagnetic properties of the studied system. Two scattering processes characterized by different dynamics were found. An ambipolar-like character of the charge transport was observed with transition between holes and electrons driven by the bias voltage, temperature, and adsorption. Electron paramagnetic resonance spectra showed a typical signal from localized centers as well as weak ferromagnetism. The latter correlates with the change of carriers' polarity. This indicates that ferromagnetic coupling between the localized states in graphene is related to the type of charge carriers. Such behavior points to the similarity of reduced graphene oxide to the dilute (ferro)magnetic semiconductors.

We report the observations of electronic properties of graphene oxide and reduced graphene oxide, performed with electron paramagnetic resonance technique in a broad temperature range. Both materials were examined in pure form and saturated with air, helium, and heavy water molecules. We show that spin localization strongly depends on the type and amount of molecules adsorbed at the graphene layer edges (and possible in-plane defects). Physical and chemical states of edges play crucial role in electrical transport within graphene-based materials, with hopping as the leading mechanism of charge carrier transport. Presented results are a good basis to understand the electronic properties of other carbon structures made of graphene-like building blocks. Most active carbons show some degree of functionalization and are known of having good adsorptive properties; thus, controlling both phenomena is important for many applications. Sample treatment with temperature, vacuum, and various adsorbents allowed for th...