Generation of spatiotemporal vortices in nonlinear photonic crystals.

Spatiotemporal vortices (STOVs) are a new, to the best of our knowledge, type of structured light in which the optical phase circulates in space-time. In this work, we propose to generate STOVs via second harmonic generation in lithium niobate nonlinear photonic crystals (NPCs) with a linearly chirped Gaussian pulse as the fundamental wave. The structural function of the NPC is derived by the inverse design method. Numerical simulations of the intensity and phase profiles of the generated second harmonic waves are performed with both the amplitude-phase-modulated and the simplified binary-phase-modulated NPCs. We anticipate our study will be valuable for the experimental generation and manipulation of STOVs in NPCs.

Oriented Mn-doped CuO nanowire arrays.

Using anodic aluminum oxide membranes as the nanoreactors and controller, oriented nanowire arrays of the diluted magnetic semiconductor Mn-doped CuO have been successfully fabricated using Mn(NO3)2 · 4H2O and Cu(NO3)2 · 3H2O as the starting materials. X-ray diffraction measurements showed that the as-prepared oriented nanowire arrays are of high purity. Scanning electron microscope and transmission electron microscope studies showed the nanowires are oriented, continuous and uniform with a diameter and length of about 170 nm and several tens of micrometers, respectively, and thus of a high aspect ratio. Low-temperature magnetic measurements showed the ferromagnetic property of the oriented Mn-doped CuO nanowire arrays with the critical temperature at around 80 K, which will endow them with great potential applications in spintronics in the future.

Aberrant expression and significance of OCT-4A transcription factor in leukemia cells.

OBJECTIVE: To determine the contribution of the OCT-4 to the pathogenesis of leukemia. METHODS: Bone marrow (BM) samples obtained from 72 patients with leukemia, and 18 normal healthy subjects were assayed for their OCT-4 expression using both flow cytometry and RT-PCR. RESULTS: OCT-4 expression in BM nucleated cells of acute leukemia patients (n=33) was significantly higher than that of complete remission and chronic phase leukemia patients (n=39, p<0.001) and healthy donors (n=18, p<0.001). OCT-4 expression had a significant positive relation with CD34 expression (n=43, r=0.721, p<0.001) and the proportion of naive cells (n=60, r=0.687, p<0.001). In addition, the results of QRT-PCR detection showed that the OCT-4A had increased expression in BM nucleated cells in the patients with acute leukemia (n=33, median 16.585, range 0.38-169.62) compared to that in leukemia patients with chronic phase and in complete remission (n=39, median 3.34, range 0.04-44.49, p<0.001) and that of normal controls (n=18, median 2.89, range 0.18-16.23, p<0.001). CONCLUSION: OCT-4A expression was significantly increased in the BM nucleated cells of patients with acute leukemia, indicating that OCT-4A may play an important role in the pathogenesis of leukemia and may serve as a molecular target for the development of novel diagnostic and treatment strategies in leukemia.

Expression and role of Toll-like receptors on human umbilical cord mesenchymal stromal cells.

BACKGROUND AIMS: Toll-like receptors (TLRs) play an important role in innate and adaptive immunity by recognizing pathogen-associated molecular patterns (PAMPs). METHODS: In the present study, we investigated the expression and role of TLRs on human umbilical cord mesenchymal stromal cells (UC-MSCs). The proliferation, differentiation and immunoregulatory activity of UC-MSCs primed with or without TLR ligands were determined. RESULTS: At the RNA level, the expression of TLR2, 4, 6 and 9 was relatively higher than that of other TLRs. However, TLR3 and TLR4 expression were relatively higher at the protein level. UC-MSCs expressed functional TLRs by nuclear factor-κB activation and cytokine expression assay. Poly-inosinic acid:cytidylic acid [Poly(I:C)] stimulation inhibited the proliferation of UC-MSCs, but the ligand of other TLRs had no significant effect. Poly(I:C) stimulation enhanced the adipogenic differentiation capability of UC-MSCs, but lipopolysaccharide inhibited the adipogenic differentiation. Poly(I:C) and CpG-oligonucleotide promoted the immunosuppressive potentiality of UC-MSCs, accompanied with the phosphorylation of interferon regulatory factor 3 (IRF3) and increased expression of indoleamine 2,3-dioxygenase and interferon ß, whereas activation of other TLR ligands (synthetic analog fibroblast-stimulating lipopeptide-1 and lipopolysaccharide) failed to affect the immunoregulatory activity of UC-MSCs. CONCLUSIONS: Taken together, our data demonstrated that TLR activation influenced the function of UC-MSCs, which might have important implications in future efforts to explore the clinical potentials of UC-MSCs.

[Culture of pancreatic progenitor cells in hanging drop and on floating filter].

OBJECTIVE: To construct a method to culture pancreatic progenitor cells in hanging drop and on floating filter,and to examine if pancreatic progenitor cells can differentiate into mature endocrine cells with this method. METHODS: Murine embryos at day 12.5 were isolated and digested into single cells,which were then cultured in hanging drop for 24h and formed spheres.Spheres were cultured on the filter for 6 days,which floated in the dish containing medium.During culture,the expressions of pancreas duodenum homeobox-1(PDX-1)and neurogenin3(Ngn3)were determined.The expressions of endocrine and exocrine markers,insulin,glucagon,and carboxypeptidase(CPA)were determined on day 7 by immunohistochemistry.Insulin secretion of spheres stimulated by glucose was detected by ELISA.The changes of pancreatic marker expressions during culture were monitored by real-time polymerase chain reaction(PCR). RESULTS: One day after the culture,there were still a large amount of PDX-1 positive cells in pancreatic spheres,and these cells proliferated.On day 3,high expression of Ngn3 was detected,and the Ngn3-positive cells did not proliferate.On day 7,The expressions of endocrine and exocrine markers in the differentiated pancreatic progenitor cells were detected,which were consistent with that in vivo.Insulin was secreted by spheres upon the stimulation of glucose. CONCLUSION: In hanging drop and on floating filter,pancreatic progenitor cells can differentiate into mature endocrine cells.

Effect of Annealing Temperature on Mechanical Properties and Work Hardening of Nickel-Saving Stainless Steel.

Compared to Cr-Ni stainless steel, nickel-saving stainless steel is a low-cost austenitic stainless steel. We studied the deformation mechanism of stainless steel at various annealing temperatures (850 °C, 950 °C, and 1050 °C). The grain size of the specimen increases with increasing annealing temperature while the yield strength decreases, which follows the Hall-Petch equation. When plastic deformation occurs, dislocation increases. However, the deformation mechanisms can vary between different specimens. Stainless steel with smaller grains is more likely to transform into martensite when deformed. While twinning occurs when the grains are more prominent, the deformation results in twinning. The phase transformation during plastic deformation relies on the shear, so the orientation of the grains is relevant before and after plastic deformation.

Establishment of a new method to induce the differentiation of embryonic pancreatic cells into mature endocrine cells.

OBJECTIVE: To establish a new culture method to induce the differentiation of embryonic pancreatic cells into mature endocrine cells. METHODS: Mouse embryos at day 12.5 were used and embryonic pancreata were isolated. The isolated embryonic pancreata were cultured on the filter for 7 days, which floated in the dish containing medium. During culture, the expression of pancreas duodenum homeobox-1 (PDX-1), a pancreatic stem cell marker, was examined at day 1. The expression of neurogenin 3 (Ngn3), a pancreatic progenitor cell marker, was examined at day 3. The expressions of endocrine and exocrine markers, insulin, glucagon, and carboxypeptidase (CPA) were examined at day 7 by immunohistochemistry. The kinetics of pancreatic marker expression during culture was assayed by real-time PCR. RESULTS: Many pancreatic stem cells still existed in embryonic pancreata cultured for 1 day; meanwhile, these pancreatic stem cells proliferated in high rate. A large amount of pancreatic progenitor cells were found in embryonic pancreata cultured for 3 days.Pancreatic stem/progenitor cells differentiated into mature endocrine and exocrine cells in embryonic pancreata after having been cultured for 7 days. Furthermore, the expression pattern of pancreatic marker is consistent with that in vivo. CONCLUSION: We successfully established a new culture method, with which embryonic pancreatic cells can efficiently differentiate into mature endocrine cell.

N-Alkyl Linkers for DNA-Encoded Chemical Libraries.

A series of novel N-alkyl linkers that connect small-molecule library members with their encoding DNA oligonucleotides has been developed. In comparison with the standard amide linker (usually constructed with oligo-AOP-NH2 ), the N-alkyl linker is not only more chemically stable, but also provides better structural diversity at the linkage point. Chemical variety in the vicinity of the polyglycol terminus, in particular, could affect binding interactions with the target protein. It could have been neglected in previous DNA-encoded chemical library (DEL) synthesis and screening studies due to the limited linkage alternatives. With these linkers, one can produce versatile key intermediates as Cycle 1 products directly amenable to Cycle 2 chemistry without the use of protecting groups. As a result, a DEL synthesis process that uses the fewest chemical conversions, such as 3-step, 3-cycle DELs, can achieve higher synthetic efficiency while creating less DNA tag degradation, resulting in higher quality DELs.

p38 MAPK contributes to the growth inhibition of leukemic tumor cells mediated by human umbilical cord mesenchymal stem cells.

BACKGROUND/AIMS: Mesenchymal stem cells (MSCs) have been implicated in antitumor therapy for hematopoietic and non-hematopoietic tumors. Cell-contact and soluble factors are demonstrated to play a role in the growth inhibition of tumor cells mediated by MSCs in vitro, while there is little clue about signaling pathways involved in the process. P38 MAPK has been implicated as a suppressor of cell proliferation and tumorigenesis. We here investigate whether p38 MAPK is involved in MSC-induced growth inhibition of leukemic tumor cells. METHODS: We characterized the effect of human umbilical cord mesenchymal stem cells (UC-MSCs) on proliferation, cell cycle and phosphorylation pattern of p38 MAPK in HL60 and K562 cells. SB203580, a specific inhibitor of p38 MAPK, or p38 MAPK-small interfering RNA (siRNA), were used to identify the role of p38 in growth suppression by UC-MSCs. We also investigated the expression of cell cycle regulators. RESULTS: Treatment with UC-MSCs led to potent proliferation-inhibition of HL60 and K562 cells without inducing apoptosis. Growth inhibition by UC-MSCs was due to G0/G1 arrest. UC-MSCs increased phosphorylation of p38 MAPK in HL60 and K562 cells. Pharmacological inhibition or genetic silencing (through siRNA) of p38 MAPK partially abrogated the proliferation-suppression and cell cycle arrest caused by UC-MSCs. UC-MSCs also modulated the expression of cell cycle regulatory proteins in HL60 and K562 cells while SB203580 reversed the effect. CONCLUSION: Taken together, our findings indicate that p38 MAPK is critical for the growth inhibitory effect of UC-MSCs on leukemic tumor cells.

No contribution of umbilical cord mesenchymal stromal cells to capillarization and venularization of hepatic sinusoids accompanied by hepatic differentiation in carbon tetrachloride-induced mouse liver fibrosis.

BACKGROUND AIMS: The acceleration of capillarization and venularization of hepatic sinusoids after cell therapy would not be beneficial to restoration after liver disease. The goal was to observe the effects of umbilical cord (UC)-derived mesenchymal stromal cells (MSC) on liver microcirculation and their therapeutic potential in liver fibrosis. METHODS: Human UC MSC labeled with or without CM-DIL were transplanted into NOD/SCID mice with carbon tetrachloride (CCl4)-induced chronic liver fibrosis models. Because of the high autofluorescence on the injured liver sections, we used immunohistochemistry, Western blot and reverse transcriptase-polymerase chain reaction (RT-PCR), but not immunofluorescence, in order to avoid false images under a confocal fluorescence microscope. RESULTS: Human-specific alpha-fetoprotein and albumin mRNA and proteins were detected in CCl4-treated mouse livers receiving human UC MSC transplants. We only observed the gene expression of human-specific endothelial-like cells markers CD31 and KDR by RT-PCR, but not protein expression by immunohistochemistry, in UC MSC-transplanted mouse livers. Vascular endothelial growth factor (VEGF) expression in injured livers 4 weeks after UC MSC transplantation was higher than in normal livers. However, UC MSC injection did not increase significantly the vascular density labeled by CD31 and (vWF) in the injured livers of UC MSC-transplanted mice compared with non-transplanted mice after CCl4 treatment. In addition, liver function was partly improved after UC MSC transplantation. CONCLUSIONS: Human UC MSC can differentiate into hepatocyte-like cells but do not accelerate the capillarization and venularization of hepatic sinusoids, finally leading to the partial improvement of liver function in mice with CCl4-mediated chronic liver fibrosis.

[Differentiation of human umbilical cord derived mesenchymal stem cells into low immunogenic and functional hepatocyte-like cells in vitro].

OBJECTIVE: To investigate the biological function of hepatocyte-like cells derived from mesenchymal stem cells that isolated from human umbilical cord UC-MSCs in vitro, and to detect the changes in the immunogenicity of the differentiated hepatocyte-like cells (DHC). METHODS: Transdifferentiation of UC-MSCs into hepatic lineage in vitro was induced in modified two-step induction medium. The expressions of hepatic specific markers were detected by RT-PCR analysis and immunofluorescence staining at different time points after induction. The levels of albumin and urea in the supernatants of cultures were measured by enzyme-linked immunosorbent assay. Furthermore, the immunosuppressive property of DHC was detected by one-way mixed lymphocyte culture. RESULTS: The mRNA and proteins of alpha fetoprotein (AFP), albumin (ALB),and cytokeratin-19 (CK-19) were expressed in naive UC-MSCs at low levels. DHC highly expressed hepatic markers AFP, ALB, CK-19, and tryptophan 2, 3-dioxygenase 14 and 28 days after hepatic differentiation and were accompanied by an increased production of ALB and urea in supernatant in a time-dependent manner. DHC did not express human leukocyte antigen DR antigen and significantly decreased the lymphocyte proliferation. CONCLUSION: UC-MSCs are able to differentiate into functional hepatocyte-like cells in vitro, while the immunogenicity of DHC remains low.

Therapeutic benefit of human umbilical cord derived mesenchymal stromal cells in intracerebral hemorrhage rat: implications of anti-inflammation and angiogenesis.

Cell-based therapy represents a promising strategy in the treatment of neurological disorders. Human umbilical cord tissue has recently been recognized as an ideal source of mesenchymal stromal cells due to accessibility, vast abundance and safety. Here, an intracerebral hemorrhage (ICH) rat model was established by injection of bacterial collagenase VII and CM-DiI labeled human umbilical cord tissue derived mesenchymal stromal cells (UC-MSC) were intracerebrally transplanted into rat brain 24 h after ICH. The results demonstrated that UC-MSC treatment significantly improved neurological function deficits and decreased injury volume of ICH rats. Leukocytes infiltration, microglial activation, ROS level and matrix metalloproteinases (MMPs) production were substantially reduced in peri-ICH area in cell-treated group as compared with PBS control at day 3 post-transplantation. In addition, UC-MSC treatment significantly increased vascular density in peri-ICH area and transplanted UC-MSC were found to be able to incorporate into cerebral vasculature in ipsilateral hemisphere at 14 days after transplantation. In summary, intracerebral administration of UC-MSC could accelerate neurological function recovery of ICH rat, the underlying mechanism may ascribe to their ability to inhibit inflammation and promote angiogenesis. Thus UC-MSC may provide a potential cell candidate for cell-based therapy in neurological disorders.

Isolation and characterization of human umbilical cord mesenchymal stem cells with hematopoiesis-supportive function and other potentials.

BACKGROUND AND OBJECTIVES: Adult bone marrow (BM) is the major source of mesenchymal stem cells (MSC) for cell therapy. However, aspiration of BM involves invasive procedures. We isolated MSC from human full term umbilical cord tissues (UC). The biological characteristics of MSC derived from UC (UC-MSC) were further determined and compared with normal adult bone marrow-derived MSC (BM-MSC). DESIGN AND METHODS: MSC were isolated from UC by enzyme digestion and cultured in appropriate growth medium. The isolation efficiency, cell yield, colony-forming unit-fibroblast (CFU-F) frequency, growth kinetics, phenotypic characteristics, multi-lineage differentiation capacity, cytokine spectrum as well as hematopoiesis-supportive function of UC-MSC were determined and compared with those of BM-MSC. RESULTS: MSC were successfully isolated from all 36 UC and six BM samples we collected for this study. The mean number of nucleated cells isolated from UC was 1yen106/cm and the yield of adherent cells was 8.6yen105/cm. UC-MSC shared most of the characteristic of BM-MSC, including fibroblastic-like morphology, immunophenotype, cell cycle status, adipogenic and osteogenic differentiation potentials, and hematopoiesis-supportive function. The CFU-F frequency was higher in UC nucleated cells (1:1609 +/- 0.18) than in BM nucleated cells (1:35700 +/- 0.01) (p < 0.05). Furthermore, in comparison with BM-MSC, the UC-MSC had a higher proliferation capacity and lower levels of expression of CD106 and HLA-ABC (p < 0.05). Immunofluoresent and western blot assays revealed that UC-MSC had a higher percentage of neuron specific enolase-positive cells than had BM-MSC after neuronal induction. Finally, reverse transcriptase polymerase chain reaction analysis showed that UC-MSC had a cytokine spectrum very similar to that of BM-MSC, including expression of the mRNA of stem cell factor, leukemia inhibitor factor, macrophage-colony stimulating factor, Flt3-ligand, interleukin-6, vascular endothelial growth factor and stromal-derived factor-1, but UC-MCS additionally expressed mRNA of granulocyte macrophage and granulocyte colony-stimulating factors. After co-culture with CD34+ cord blood cells for 5 weeks, no significant difference in colony-forming cells was observed between the CD34+ cells/UC-MSC and CD34+ cells/BM-MSC co-cultures (p > 0.05). INTERPRETATION AND CONCLUSIONS: We have established a protocol to isolate abundant MSC from human umbilical cords with a 100% success rate. The comparative study indicates that UC is an excellent alternative to BM as a source of MSC for cell therapies.

VCAM-1+ placenta chorionic villi-derived mesenchymal stem cells display potent pro-angiogenic activity.

INTRODUCTION: Mesenchymal stem cells (MSCs) represent a heterogeneous cell population that is promising for regenerative medicine. The present study was designed to assess whether VCAM-1 can be used as a marker of MSC subpopulation with superior angiogenic potential. METHODS: MSCs were isolated from placenta chorionic villi (CV). The VCAM-1(+/-) CV-MSCs population were separated by Flow Cytometry and subjected to a comparative analysis for their angiogenic properties including angiogenic genes expression, vasculo-angiogenic abilities on Matrigel in vitro and in vivo, angiogenic paracrine activities, cytokine array, and therapeutic angiogenesis in vascular ischemic diseases. RESULTS: Angiogenic genes, including HGF, ANG, IL8, IL6, VEGF-A, TGFß, MMP2 and bFGF, were up-regulated in VCAM-1(+)CV-MSCs. Consistently, angiogenic cytokines especially HGF, IL8, angiogenin, angiopoitin-2, µPAR, CXCL1, IL-1ß, IL-1α, CSF2, CSF3, MCP-3, CTACK, and OPG were found to be significantly increased in VCAM-1(+) CV-MSCs. Moreover, VCAM-1(+)CV-MSCs showed remarkable vasculo-angiogenic abilities by angiogenesis analysis with Matrigel in vitro and in vivo and the conditioned medium of VCAM-1(+) CV-MSCs exerted markedly pro-proliferative and pro-migratory effects on endothelial cells compared to VCAM-1(-)CV-MSCs. Finally, transplantation of VCAM-1(+)CV-MSCs into the ischemic hind limb of BALB/c nude mice resulted in a significantly functional improvement in comparison with VCAM-1(-)CV-MSCs transplantation. CONCLUSIONS: VCAM-1(+)CV-MSCs possessed a favorable angiogenic paracrine activity and displayed therapeutic efficacy on hindlimb ischemia. Our results suggested that VCAM-1(+)CV-MSCs may represent an important subpopulation of MSC for efficient therapeutic angiogenesis.

Controllable assembly of aligned ZnO nanowires/belts arrays.

We describe a simple method to assemble ZnO nanowires/belts into highly ordered arrays. ZnCu(2) alloy was used as the Zn source, which reacted with water vapor to generate ZnO nanocrystals. The reaction was performed in a mild way, which facilitated the easy control of the reaction conditions. By simply controlling the water bath temperature and carrier gas flux in our experiments, we obtained ZnO nanowires/belts aligned to form ordered arrays. The highly ordered nature of the ZnO arrays is suggested to be related both with the polarities of the H(2)O molecule and the ZnO (0001) surface. Photoluminescence (PL) microscopy revealed that the comblike structures had waveguide properties, where green light enhancement was observed at the tips of the branches. The light enhancement property reveals their promising applications as light source arrays.

Rapid synthesis and visible photoluminescence of ZnS nanobelts.

Belt-like ZnS with visible photoluminescence was synthesized rapidly with Zn and S in the vapor phase.

Systemic infusion of FLK1(+) mesenchymal stem cells ameliorate carbon tetrachloride-induced liver fibrosis in mice.

BACKGROUND: Fibrosis is the common end stage of most liver diseases, for which, unfortunately, there is no effective treatment available currently. It has been shown that mesenchymal stem cells (MSCs) from bone marrow (BM) could engraft in the lung after bleomycin exposure and ameliorate its fibrotic effects. This study was designed to evaluate the effect of Flk1 MSCs from murine BM (termed here Flk1 mMSCs) on fibrosis formation induced by carbon tetrachloride (CCl4). METHODS: A CCl(4)-induced hepatic fibrosis model was used. Flk1 mMSCs were systemically infused immediately or 1 week after mice were challenged with CCl(4). Control mice received only saline infusion. Fibrosis index and donor-cell engraftment were assessed 2 or 5 weeks after CCl(4) challenge. RESULTS: We found that Flk1 mMSCs transplantation immediately, but not 1 week after exposure to CCl(4), significantly reduced CCl(4)-induced liver damage and collagen deposition. In addition, levels of hepatic hydroxyproline and serum fibrosis markers in mice receiving immediate Flk1 mMSCs transplantation after CCl(4) challenge were significantly lower compared with those of control mice. More importantly, histologic examination suggested that hepatic damage recovery was much better in these immediately Flk1 mMSCs-treated mice. Immunofluorescence, polymerase chain reaction, and fluorescence in situ hybridization analysis revealed that donor cells engrafted into host liver, had epithelium-like morphology, and expressed albumin, although at low frequency. CONCLUSION: These results suggest that Flk1 mMSCs might initiate endogenous hepatic tissue regeneration, engraft into host liver in response to CCl(4) injury, and ameliorate its fibrogenic effects.

Effect of O-4-ethoxyl-butyl-berbamine in combination with pegylated liposomal doxorubicin on advanced hepatoma in mice.

AIM: To study the synergistic effects of calmodulin (CaM) antagonist O-4-ethoxyl-butyl-berbamine (EBB) and pegylated liposomal doxorubicin (PLD) on hepatoma-22 (H(22)) in vivo. METHODS: Hepatoma model was established in 50 Balb/c mice by inoculating H(22) cells (2.5 x 10(6)) subcutaneously into the right backs of the mice. These mice were divided into 5 groups, and treated with saline only, PLD only, doxorubicin (Dox) only, PLD plus EBB and Dox plus EBB, respectively. In the treatment groups, mice were given 5 intravenous of PLD or Dox on days 0, 3, 6, 9 and 12. The first dosage of PLD or Dox was 4.5 mg/kg, the other 4 injections was 1 mg/kg. EBB (5 mg/kg) was coadministered with PLD or Dox in the corresponding groups. The effect of drugs on the life spans of hepatoma-bearing mice and tumor response to the drugs were recorded. Dox levels in the hepatoma cells were measured by a fluorescence assay. Light microscopy was performed to determine the histopathological changes in the major organs of these tumor-bearing mice. The MTT method was used to analyze the effect of Dox or PLD alone, Dox in combination with EBB, or PLD in combination with EBB on the growth of H(22) cells in an in vitro experiment. RESULTS: EBB (5 mg/kg) significantly augmented the antitumor activity of Dox or PLD, remarkably prolonged the median survival time. The median survival time was 18.2 d for control group, but 89.2 d for PLD+EBB group and 70.1 d for Dox+EBB group, respectively. However, Dox alone did not show any remarkable antitumor activity, and the median survival time was just 29.7 d. Addition of EBB to Dox or PLD significantly increased the level of Dox in H(22) cells in vivo. Moreover, EBB diminished liver toxicity of Dox and PLD. In vitro, EBB reduced the IC50 value of Dox or PLD on H(22) cells from 0.050+/-0.006 mg/L and 0.054+/-0.004 mg/L to 0.012+/-0.002 mg/L and 0.013+/-0.002 mg/L, respectively (P<0.01). CONCLUSION: EBB and liposomization could improve the therapeutic efficacy of Dox in liver cancer, while decreasing its liver toxicity.

Origin of luminescence from ZnO/CdS core/shell nanowire arrays.

Chemical imaging, electronic structure and optical properties of ZnO/CdS nano-composites have been investigated using scanning transmission X-ray microscopy (STXM), X-ray absorption near-edge structure (XANES) and X-ray excited optical luminescence (XEOL) spectroscopy. STXM and XANES results confirm that the as-prepared product is ZnO/CdS core/shell nanowires (NWs), and further indicate that ZnS was formed on the surface of ZnO NWs as the interface between ZnO and CdS. The XEOL from ZnO/CdS NW arrays exhibits one weak ultraviolet (UV) emission at 375 nm, one strong green emission at 512 nm, and two broad infrared (IR) emissions at 750 and 900 nm. Combining XANES and XEOL, it is concluded that the UV luminescence is the near band gap emission (BGE) of ZnO; the green luminescence comes from both the BGE of CdS and defect emission (DE, zinc vacancies) of ZnO; the IR luminescence is attributed to the DE (bulk defect related to the S site) of CdS; ZnS contributes little to the luminescence of the ZnO/CdS NW arrays. Interestingly, the BGE and DE from oxygen vacancies of ZnO in the ZnO/CdS nano-composites are almost entirely quenched, while DE from zinc vacancies changes little.