No abstract

In order to accommodate an increasing demand for glassy carbon products with tailored characteristics, one has to understand the origin of their structure-related properties. In this work, through the use of high-resolution transmission electron microscopy, Raman spectroscopy, and electron energy loss spectroscopy it has been demonstrated that the structure of glassy carbon at different stages of the carbonization process resembles the curvature observed in fragments of nanotubes, fullerenes, or nanoonions. The measured nanoindentation hardness and reduced Young's modulus change as a function of the pyrolysis temperature from the range of 600-2500°C and reach maximum values for carbon pyrolyzed at around 1000°C. Essentially, the highest values of the mechanical parameters for glassy carbon manufactured at that temperature can be related to the greatest amount of non-planar sp 2 -hybridized carbon atoms involved in the formation of curved graphene-like layers. Such complex labyrinth-like structure with sp 2 -type bonding would be rigid and hard to break that explains the glassy carbon high strength and hardness.

Transmission electron microscopy and neutron or X-ray diffraction are powerful techniques available today for characterization of the structure of various carbon materials at nano and atomic levels. They provide complementary information but each one has advantages and limitations. Powder X-ray or neutron diffraction measurements provide structural information representative for the whole volume of a material under probe but features of singular nano-objects cannot be identified. Transmission electron microscopy, in turn, is able to probe single nanoscale objects. In this review, it is demonstrated how transmission electron microscopy and powder X-ray and neutron diffraction methods complement each other by providing consistent structural models for different types of carbons such as carbon blacks, glass-like carbons, graphene, nanotubes, nanodiamonds, and nanoonions.

The intentional design of chemical architecture of lanthanide doped luminescent nanoparticles through the proper selection of dopants in core−shell and core−shell−shell structures enables optimization of their optical properties. Such an approach allows one to achieve energy transfer upconversion (ETU) and energy migration mediated upconversion (EMU) and green emission from Tb 3+ ions with the Yb 3+ and Nd 3+ sensitizers at 980 and 808 nm photoexcitation, respectively. The [Nd 3+ → Yb 3+ ]→ [Yb 3+ → Tb 3+ ] EMU phenomenon was significantly enhanced by spatial displacement of the sensitizing Nd 3+ ions from the activator Tb 3+ ions by intentionally introducing an intermediate Yb 3+ sensitizer layer forming a [Nd 3+ → Yb 3+ ] → [Yb 3+ ] → [Yb 3+ → Tb 3+ ] system. Otherwise Tb 3+ emission was considerably quenched by Nd 3+ ions even though they were spitted between the core and shell, respectively. Moreover, (Tb 3+ ,Yb 3+ ) → (Tb 4+ ,Yb 2+ ) valence change has been discovered to limit the Tb 3+ upconversion emission. The studies explain how the chemical architecture of the smartly designed

No abstract

Inorganic nanomaterials able to generate reactive oxygen species (ROS) are promising components for modern medical applications. Activated by near-infrared light, up-converting b-NaYF 4 doped with Er 3+ -Yb 3+ and Tm 3+ -Yb 3+ pair ions nanoparticles (UCNPs), have a wide range of applications in biological imaging as compared to traditional reagents excited by ultra-violet or visible light. We analysed the green-red and the blue-red luminescence to explain the mechanism of the upconversion depended on the surface condition. The influence of SiO 2 coating on the cytotoxicity of the as-produced UCNPs towards HeLa cancer cells was reported. We demonstrated a possibility of a direct UCNPs application to photodynamic therapy, without need to attach additional molecules to their surface. The presence of Tm 3+ -Yb 3+ pair ions, thus ROS generation capability, renders the SiO 2 shell coated nanoparticles to become potentially useful theranostic agent.

No abstract

Interest in graphene oxide nature and potential applications (especially nanocarriers) has resulted in numerous studies, but the results do not lead to clear conclusions. In this paper, graphene oxide is obtained by multiple synthesis methods and generally characterized. The mechanism of GO interaction with the organism is hard to summarize due to its high chemical activity and variability during the synthesis process and in biological buffers’ environments. When assessing the biocompatibility of GO, it is necessary to take into account many factors derived from nanoparticles (structure, morphology, chemical composition) and the organism (species, defense mechanisms, adaptation). This research aims to determine and compare the in vivo toxicity potential of GO samples from various manufacturers. Each GO sample is analyzed in two concentrations and applied with food. The physiological reactions of an easy model Acheta domesticus (cell viability, apoptosis, oxidative defense, DNA damage) during ten-day lasting exposure were observed. This study emphasizes the variability of the GO nature and complements the biocompatibility aspect, especially in the context of various GO-based experimental models. Changes in the cell biomarkers are discussed in light of detailed physicochemical analysis.