Fluorescent quantum dots (QDs) modified with polyethylene glycol (PEG) and albumin bovine serum (BSA) have profound application in the detection and treatment of hepatocellular carcinoma (HCC) cells. In the present study, the effects and mechanism of PEG and BSA modification on the cytotoxicity of QDs have been explored. It was found that the diameter of the as-prepared QDs, PEG@QDs, BSA@QDs is 3–5 nm, 4–5 nm, and 4–6 nm, respectively. With increase of the treatment time from 0 to 24 h, the HCC cell viability treated with QDs, PEG@QDs, and BSA@QDs obviously decreases, showing a certain time-dependent manner. When the concentration of several nanomaterials is increased from 10 to 90 nM, the cell viability decreases accordingly, exhibiting a certain concentration-dependent manner. Under the same concentration change conditions, the reactive oxygen species contents of cells treated by QDs, PEG@QDs, and BSA@QDs also rise from 7.9 × 103, 6.7 × 103, and 4.7 × 103 to 13.2 × 103, 14.3 × 103, and 12.3 × 103, respectively. In these processes, superoxide dismutase does not play a major role. This study provides strong foundation and useful guidance for QD applications in the diagnosis and treatment of HCC.

Historically, alloy development with better radiation performance has been focused on traditional alloys with one or two principal element(s) and minor alloying elements, where enhanced radiation resistance depends on microstructural or nanoscale features to mitigate displacement damage. In sharp contrast to traditional alloys, recent advances of single-phase concentrated solid solution alloys (SP-CSAs) have opened up new frontiers in materials research. In these alloys, a random arrangement of multiple elemental species on a crystalline lattice results in disordered local chemical environments and unique site-to-site lattice distortions. Based on closely integrated computational and experimental studies using a novel set of SP-CSAs in a face-centered cubic structure, we have explicitly demonstrated that increasing chemical disorder can lead to a substantial reduction in electron mean free paths, as well as electrical and thermal conductivity, which results in slower heat dissipation in SP-CSAs. The chemical disorder also has a significant impact on defect evolution under ion irradiation. Considerable improvement in radiation resistance is observed with increasing chemical disorder at electronic and atomic levels. The insights into defect dynamics may provide a basis for understanding elemental effects on evolution of radiation damage in irradiated materials and may inspire new design principles of radiation-tolerant structural alloys for advanced energy systems.

Dense networks of amorphous GaSb nanofibers were fabricated by ion irradiation of bulk GaSb, and following formation, they were thermally annealed at a low temperature. Contrary to expectations, annealing of the GaSb fibers at just 50% of their melting temperature resulted in complete chemical decomposition of the nanofibers into core-shell structures consisting of crystalline Sb cores surrounded by amorphous shells. In this study, we investigate the transition of the single-phase nanofibers to their core-shell configuration, and we analyze the unique, temperature-dependent phase decomposition process. Thermodynamic considerations are discussed, and a model is presented to explain the thermally induced decomposition of the GaSb semiconductor fibers into core-shell structures, based upon the singular interaction of several size-dependent material properties.

The TRISO fuel has been used in some of the Generation IV nuclear reactor designs [1,2]. It consists of a fuel kernel of UOx coated with several layers of materials with different functions. Pyrolytic carbon (PyC) is one of the materials in the layers. In this study we investigate the possibility of using Glassy Polymeric Carbon (GPC) as an alternative to PyC. In this work, we are comparing the changes in physical and microstructure properties of GPC after exposure to irradiation fluence of 5 MeV Au equivalent to a 1 displacement per atom (dpa) at samples prepared at 1000, 1500 and 2000°C. The GPC material is manufactured and tested at the Center for Irradiation Materials (CIM) at Alabama A&M University. Transmission electron microscopy (TEM), Rutherford backscattering spectroscopy (RBS), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used for the analysis.

Ge nanocrystals embedded in an amorphous SiO2 film on Si matrix were prepared by ion implantation and subsequent annealing. Neutron transmutation doping (NTD) technique was used for doping Ge nanocrystals with As impurities. The microstructure, phase and photoluminescence of NTDed Ge nanocrystals were analyzed and compared with undoped Ge nanocrystals. A new photoluminescence peak related to As impurities was found. It is discovered that impurities are expelled from larger clusters resulted from Ge nanocrystal aggregation on the sample surface. To prevent nanocrystal aggregation and assure uniform doping of As, it is necessary to adopt appropriate implantation and annealing conditions.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Carbon nanofibers were well aligned in polymer composite magnetically at moderate fields up to 3 T. Due to the NiO-coating, carbon nanofibers exhibited strong magnetic moments that lead to alignment. Both TEM and SEM results showed the well-aligned nano-fibers in a polymer matrix. Mechanical testing showed a pronounced anisotropy in tensile strength in directions normal (12.1MPa) and parallel (22MPa) to the applied field, resulting from the well-aligned nanofibers in the polymer matrix. The mechanism of magnetic alignment due to coating of NiO on the nano fiber surface is discussed.

Rutile (TiO2) single crystals of (110) or (001) orientation were irradiated by high fluence protons with the energy of 0.5, 4.9 and 18 MeV and with the fluence of 1×1018 and 1.9×1022 m-2. UV-VIS-IR, LRS and HRTEM were used to analyze the optical absorption and microstructure of samples. The UV-VIS-IR results showed that proton irradiation induces two absorption peaks centered at 760 and 1700 nm respectively, even high fluence irradiation induces absorption plateau at 600∼2500 nm. LRS results showed that the related intensity of common vibration modes is different for different planes. Proton irradiation induces the vibration frequency and related intensity change for inherent LRS modes, and several new vibration modes also appear. High fluence proton irradiation induced large defect clusters, i.e. stacking faults, which is demonstrated by HRTEM observation. The optical absorption mechanism also has been discussed.

The investigation of nanocrystalline Ge (nc-Ge) directly prepared with high dose Ge ion implantation of 1×1016, 1×1017, 5×1017 and 1×1018cm-2 respectively without subsequent annealing is presented in this paper. The specimens were measured by means of GIXRD, LRS and PL. The results show the nc-Ge, which possesses strong compressive stress, can be fabricated when the implanting dose of Ge ions is over the threshold dose∼1×1017cm-2. The content and size of nc-Ge will enlarge with increasing dose. The nc-Ge formation mechanism may be the Ge atoms in the amorphous Ge (a-Ge) clusters, which are formed through the aggregation of implanted Ge ions, obtain energy from the instant local annealing zone induced by the incident Ge ion and reconstruct to nc-Ge existing in a-Ge clusters. The PL results indicate the strong PL peaks centered at about 295, 400 and 570 nm can be observed in implanted samples. The intensity of these PL peaks increases with increasing dose. The related PL mechanism in Ge-ion-implanted SiO2 film has also been discussed.

Ultrathin polymer films have been deposited on both multi-wall and aligned carbon nanotubes using a plasma polymerization treatment. TEM experimental results showed that a thin film of polystyrene layer (several nanometers) was uniformly deposited on the surfaces of the nanotubes including inner wall surfaces of the multi-wall nanotubes. The coated multi-wall nanotubes were mixed in polymer solutions for studying the effects of plasma coating on dispersion. It was found that the dispersion of multi-wall carbon nanotubes in polystyrene composite was significantly improved. The deposition mechanisms and the effects of plasma treatment parameters are discussed.

Acrylic acid polymer thin films were deposited on the surfaces of nanoparticles of ZnO using a plasma polymerization treatment. The average size of nanoparticles was on the order of 50 nm in irregular shapes. High-resolution transmission electron microscopy (HRTEM) experiments showed that an extremely thin film of the acrylic acid layer (15 nm) was uniformly deposited on the surfaces of the nanoparticles. The HRTEM results were confirmed by time-of-flight secondary ion mass spectroscopy. The effect of plasma power on the polyacrylic thin film was studied by Fourier transform infrared experiments. The deposition mechanisms and the effects of plasma treatment parameters are discussed.

Ultrathin polymer films have been deposited on both single- and multi-wall carbon nanotubes using a plasma polymerization treatment. HRTEM experiments showed that an extremely thin film of the pyrrole layer (2–7 nm) was uniformly deposited on the surfaces of the nanotubes including inner wall surfaces of the multi-wall nanotubes. Time-of-Flight Secondary ion mass spectroscopy (TOFSIMS) experiments confirmed the nanosurface deposition of polymer thin films on the nanotubes. The deposition mechanisms and the effects of plasma treatment parameters are discussed.

One promising host for actinide wastes is garnet-type phases of general formula AVIII3BVI 2[XO4]3. To determine the isomorphic capacity of garnet for uranium, the CaO – Fe2O3 – Al2O3 – SiO2 – ZrO2 – Gd2O3 – UO2 system was studied. Experiments were performed in air medium at 1400 – 1500 °C and 1 atm. The garnets have high capacity for Gd and Zr, while incorporation of U was found to be greatly dependent on the phase composition. Uranium content decreased from 18 wt.% in Ca-Zr-Fe garnet to 0.6 wt.% in Si-doped phases. Heavy ion irradiation (1.0 MeV Kr++) experiments were carried out for a garnet with maximal U content, (Ca2.7U0.3)VIII(Zr1.7Fe0.3)VI(Al1.1Fe1.9)IVO12. Amorphization dose of the phase was equal to 1.63×1014 ions/cm2 that is close to the other actinide hosts, such as pyrochlore Gd2Ti2O7.

200 keV iodine and 400 keV strontium ions have been implanted into YSZ in order to study the effects of fission product incorporation in YSZ as an inert fuel matrix. The ion implantation was conducted at room temperature. The ion fluences reached 1×1021 ions/m2 which gives peak displacement damage levels of ~ 290 dpa for I ion implantation and ~ 200 dpa for Sr ion implantation. The peak concentration reaches ~26 at. % for implanted I ions and ~11.6 at.% for Sr ions. Cross-sectional transmission electron microscopy (TEM) was completed to investigate the microstructure changes caused by the implantation. No evidence of amorphization was detected in both samples although a high density of defect clusters was observed by TEM. Cross-sectional TEM revealed formation of iodine containing voids in I- implanted samples and crystalline precipitates of a few tens of nanometers in Sr-implanted samples after annealing of the implanted sample at 1000°C for 0.5 to 2 hours. The void size increased with increasing annealing time. The nano-crystalline precipitates in Sr-implanted YSZ are isometric SrZrO3 (a≅0.41 nm). The orientation relation between the matrix and precipitates, as determined by selected area diffraction pattern, was: [011]YSZ// [111]SrZrO3 and [200]YSZ// [110]SrZrO3.

Radiation effects on zeolite-NaY have been investigated by irradiation with a 500 keV H+ beam. The crystalline-to-amorphous transition occurs at a total dose equivalent to an ionizing energy deposition of 3×1010Gy and a displacement damage level of 0.05 dpa. The ion exchange capacity of the irradiated zeolite-NaY with 10 mN SrCl2 or 10 mN AgNO3 solutions varies with the extent of the damage to the crystalline structure. After 25 hours of exchange, the Sr concentration in the amorphous region is nearly zero. This result shows that radiation-induced amorphization can cause a significant loss in ion exchange capacity. The data also suggest that the radiation damage by proton radiation in zeolite-NaY is through both ionizing and displacement processes. The result from Ag-exchange reaction with the irradiated zeolite suggests that higher radiation dose is required to block the penetration of Ag into the supercages. The Ag concentration (∼3 at.%) in the fully damaged region suggests that the cations in the small cages are still exchangeable even when amorphization has been achieved.

Brannerite, UTi2O6, occurs in polyphase Ti-based, crystalline ceramics that are under development for plutonium immobilization. In order to investigate radiation effects caused by α- decay events of Pu, several brannerite compositions were synthesized: UTi2O6, ThTi2O6, CeTi2O6 and a more complex material, which is composed of Ca-containing brannerite and pyrochlore. An 1 MeV Kr+ irradiation was performed over a temperature range of 25 K to 1020 K with in-situ TEM. The ion irradiation-induced crystalline-to-amorphous transformation was observed in all brannerite samples. At room temperature, the critical amorphization dose, Dc, resulting from Kr+ ion irradiation increases in the order: Dc (CeTi2O6) < Dc (ThTi2O6) < Dc (Ca- containing brannerite) < Dc (UTi2O6) < Dc (Ca-containing pyrochlore). The critical amorphization dose for stoichoimetric brannerite increases at elevated temperature due to the effect of thermal annealing. The critical amorphization temperatures of the different brannerite compositions are: 970 K, UTi2O6; 990 K, ThTi2O6; 1020 K, CeTi2O6. The effects of structure and chemical composition on radiation resistance of brannerite-type and pyrochlore-type ceramics are discussed.

Zeolite-NaY is susceptible to both irradiation- and thermally-induced amorphization. Amorphized zeolite-NaY loses approximately 95 percent of its ion exchange capacity for cesium due to the loss of exchangeable cation species and /or the blockage of access to exchangeable cation sites. A secondary phase was formed during the ion exchange reaction with cesium. The Cs-exchanged zeolite-NaY phase has a slightly higher thermal stability than the unexchanged zeolite-NaY. A desorption study indicated that the amorphization of cesium-loaded zeolite-NaY enhances the retention capacity of Cs due to the closure of structural channels.