Practical applications of ZnO are widely known, and it is one of the more prevalent wide band gap semiconductors being explored in research. It is most known for its potential as an n-type window material in solar cells. 1,2 ZnO has been thoroughly explored in many forms: as a thin film, nanowires, nanoparticles, etc. 3À5 It has also been demonstrated that Mn-doped ZnO has ferromagnetic properties at room temperature and is therefore of interest in spintronics applications. 6À8 In addition, the introduction of such impurities has been shown to red-shift the band gap of ZnO and cause other changes in its optical characteristics, such as its photoluminescence. 9 This allows the material to be potentially beneficial for solar cells, as the dopants can cause reduction of near band-edge electron-hole pair recombination as well as internal down-conversion of higher energy photons, which could be absorbed by a narrow band gap material. The ZnO/Mn 3 O 4 core-shell structures produced in this study also show promise for lithium-ion battery applications. The substrate-grown nanowires provide a large functional surface area and the manganese oxide crystallites would be a highly favorable cathode material once enriched with lithium. Based on the length and density of the structures grown in this study, an estimated 20À30-fold increase in surface area would be observed in comparison to a thin film. This would result in a corresponding increase in battery capacity. To explore the potential of this material, optimize synthesis procedures, and develop further insights about the doping mechanism, a study of growth processes and properties was implemented. Reagent concentrations were varied to establish doping and crystallite formation regimes. Upon establishment of optimal ratios, reactions were carried out for various times, and the results are presented herein.' EXPERIMENTAL METHODS Synthesis. Synthesis of nanowires was carried out by a seeded chemical bath method. The seed solution was prepared as 0.750 M Zn(CH 3 COO) 2 and 0.750 M methenamine in deionized (DI) H 2 O. To assist in dissolution of the zinc acetate, the solution was heated to 60°C for 30 min under agitation. SnO 2 :F-coated SiO 2 substrates were cleaned for use by a two-part washing process: a 10 min isopropyl alcohol bath followed by a 10 min DI-H 2 O bath, both involving sonication. The substrates were allowed to air-dry. The seed was transferred to the substrates via pipet and distributed via spin coating at 1500 rpm for 90 s. To ensure a uniform seed layer, the substrates were then annealed for 1 h at 400°C. To reduce thermal strain on substrates, the samples were inserted after the furnace was preheated to 100°C; the furnace was subsequently ramped to the target temperature at an average rate of 20°C/min. The samples were permitted to cool in the furnace after it was turned off until they had reached room temperature. Growth of ZnO nanowires was carried out by use of a growth solution of 27.8 mM Zn(NO 3 ) 2 and 27.8 mM methenamine in DI-H 2 O. The samples w...

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

One of the most effective methods for detection and destruction of tumor cells is therapeutic cancer vaccination. The induction of tumor-specific T-cell immunity relies on efficient cross presentation of tumor associated antigens. We previously showed that α-Al 2 O 3 nanoparticles (NPs), as antigen carriers, are phagocytosed favorably by dendritic cells (DCs) and efficiently enhance cross-presentation of ovalbumin (OVA) to Thy1.1 + OT-I CD8 + T cells.[1] The morphological differences between the nanowires and nanoparticles may affect the antigen delivery and the efficacy for antigen cross-presentation.To test this hypothesis, we synthesized α-Al 2 O 3 NWs via chemical vapor deposition of Al sheet (98.5% purity) and TiO 2 nanoparticles (97.5% purity) in an alumina boat. Similar to the method reported by Peng et al., [2, 3] the chemical vapor deposition reactor was heated to 1050 -1150 o C with a ramp rate of 25 o C/min under flow of 100 sccm of argon. After reactions for 60 min and cooling with argon flow, the resulting fine white-grey powder was collected and characterized by a scanning electron microscope (SEM) and a transmission electron microscope (TEM). FIG 1a shows that high yield branched NWs were grown. Energy dispersive X-ray spectroscopy (EDX) analyses reveals that these NWs are Al 2 O 3 (FIG 1b). The branched Al 2 O 3 NW consisted of a thick trunk and many thin needle-like NWs, well-aligned, on the surface of the trunk (FIG 1c). HRTEM imaging of a partial Al 2 O 3 NW indicates that these NW are single crystalline and the lattice spacing in two directions of 2.379Å, 3.500 Å match (110) and (012) planes of α-Al 2 O 3 . As-synthesized α-Al 2 O 3 NWs were ultrasonicated and purified using centrifuge forming the suspension of well-dispersed α-Al 2 O 3 NWs. Using the same protocol as conjugating OVA to α-Al 2 O 3 NPs, we conjugated OVA to α-Al 2 O 3 NWs. To compare the efficiency of cross-presenting α-Al 2 O 3 NP-OVA or α-Al 2 O 3 NW-OVA, we used these conjugates to pulse 0.2 million DCs. Six hours later, the pulsed DCs were washed and employed to prime 1 million CFSE-labeled Thy1.1 + OT-I CD8 + T cells. After a 66 hour incubation, cells were collected and treated with marked antibodies of CD8-PE and Thy1.1-APC. The percentage of proliferated Thy1.1 + OT-I CD8 + T cells was measured using BD FACS Calibur flow cytometry. α-Al 2 O 3 NW-OVA successfully cross-primed antigen-specific T cells, however the efficiency was 15 % lower in comparison to the α-Al 2 O 3 NP-OVA. To clarify the shape-induced efficiency difference of crosspresentation, tracking the antigen carriers of α-Al 2 O 3 NW and α-Al 2 O 3 NP in sub-cellular compartments will be conducted.[1] H. Li et al., has been submitted