101 research outputs found
Resonant exciton transfer in mixed-dimensional heterostructures for overcoming dimensional restrictions in optical processes
Nanomaterials exhibit unique optical phenomena, in particular excitonic
quantum processes occurring at room temperature. The low dimensionality,
however, imposes strict requirements for conventional optical excitation, and
an approach for bypassing such restrictions is desirable. Here we report on
exciton transfer in carbon-nanotube/tungsten-diselenide heterostructures, where
band alignment can be systematically varied. The mixed-dimensional
heterostructures display a pronounced exciton reservoir effect where the
longer-lifetime excitons within the two-dimensional semiconductor are funneled
into carbon nanotubes through diffusion. This new excitation pathway presents
several advantages, including larger absorption areas, broadband spectral
response, and polarization-independent efficiency. When band alignment is
resonant, we observe substantially more efficient excitation via tungsten
diselenide compared to direct excitation of the nanotube. We further
demonstrate simultaneous bright emission from an array of carbon nanotubes with
varied chiralities and orientations. Our findings show the potential of
mixed-dimensional heterostructures and band alignment engineering for energy
harvesting and quantum applications through exciton manipulation.Comment: 9 pages, 4 figure
Room-temperature quantum emission from interface excitons in mixed-dimensional heterostructures
The development of van der Waals heterostructures has introduced
unconventional phenomena that emerge at atomically precise interfaces. For
example, interlayer excitons in two-dimensional transition metal
dichalcogenides show intriguing optical properties at low temperatures. Here we
report on room-temperature observation of interface excitons in
mixed-dimensional heterostructures consisting of two-dimensional tungsten
diselenide and one-dimensional carbon nanotubes. Bright emission peaks
originating from the interface are identified, spanning a broad energy range
within the telecommunication wavelengths. The effect of band alignment is
investigated by systematically varying the nanotube bandgap, and we assign the
new peaks to interface excitons as they only appear in type-II
heterostructures. Room-temperature localization of low-energy interface
excitons is indicated by extended lifetimes as well as small excitation
saturation powers, and photon correlation measurements confirm single-photon
emission. With mixed-dimensional van der Waals heterostructures where band
alignment can be engineered, new opportunities for quantum photonics are
envisioned.Comment: 8 pages, 4 figure
Switching Mechanism in Single-Layer Molybdenum Disulfide Transistors: an Insight into Current Flow across Schottky Barriers
In this article, we study the properties of metal contacts to single-layer
molybdenum disulfide (MoS2) crystals, revealing the nature of switching
mechanism in MoS2 transistors. On investigating transistor behavior as contact
length changes, we find that the contact resistivity for metal/MoS2 junctions
is defined by contact area instead of contact width. The minimum gate dependent
transfer length is ~0.63 {\mu}m in the on-state for metal (Ti) contacted
single-layer MoS2. These results reveal that MoS2 transistors are Schottky
barrier transistors, where the on/off states are switched by the tuning the
Schottky barriers at contacts. The effective barrier heights for source and
drain barriers are primarily controlled by gate and drain biases, respectively.
We discuss the drain induced barrier narrowing effect for short channel
devices, which may reduce the influence of large contact resistance for MoS2
Schottky barrier transistors at the channel length scaling limit.Comment: ACS Nano, ASAP (2013
CAXII Is a Sero-Diagnostic Marker for Lung Cancer
To develop sero-diagnostic markers for lung cancer, we generated monoclonal antibodies using pulmonary adenocarcinoma (AD)-derived A549 cells as antigens by employing the random immunization method. Hybridoma supernatants were immunohistochemically screened for antibodies with AMeX-fixed and paraffin-embedded A549 cell preparations. Positive clones were monocloned twice through limiting dilutions. From the obtained monoclonal antibodies, we selected an antibody designated as KU-Lu-5 which showed intense membrane staining of A549 cells. Based on immunoprecipitation and MADLI TOF/TOF-MS analysis, this antibody was recognized as carbonic anhydrase XII (CAXII). To evaluate the utility of this antibody as a sero-diagnostic marker for lung cancer, we performed dot blot analysis with a training set consisting of sera from 70 lung cancer patients and 30 healthy controls. The CAXII expression levels were significantly higher in lung cancer patients than in healthy controls in the training set (P<0.0001), and the area under the curve of ROC was 0.794, with 70.0% specificity and 82.9% sensitivity. In lung cancers, expression levels of CAXII were significantly higher in patients with squamous cell carcinoma (SCC) than with AD (P = 0.035). Furthermore, CAXII was significantly higher in well- and moderately differentiated SCCs than in poorly differentiated ones (P = 0.027). To further confirm the utility of serum CAXII levels as a sero-diagnostic marker, an additional set consisting of sera from 26 lung cancer patients and 30 healthy controls was also investigated by dot blot analysis as a validation study. Serum CAXII levels were also significantly higher in lung cancer patients than in healthy controls in the validation set (P = 0.030). Thus, the serum CAXII levels should be applicable markers discriminating lung cancer patients from healthy controls. To our knowledge, this is the first report providing evidence that CAXII may be a novel sero-diagnostic marker for lung cancer
Lack of significant association of an insertion/deletion polymorphism in the angiotensin converting enzyme (ACE) gene with tropical calcific pancreatitis
BACKGROUND: The genetic basis of tropical calcific pancreatitis (TCP) is different and is explained by mutations in the pancreatic secretory trypsin inhibitor (SPINK1) gene. However, mutated SPINK1 does not account for the disease in all the patients, neither does it explain the phenotypic heterogeneity between TCP and fibro-calculous pancreatic diabetes (FCPD). Recent studies suggest a crucial role for pancreatic renin-angiotensin system during chronic hypoxia in acute pancreatitis and for angiotensin converting enzyme (ACE) inhibitors in reducing pancreatic fibrosis in experimental models. We investigated the association of ACE gene insertion/deletion (I/D) polymorphism in TCP patients using a case-control approach. Since SPINK1 mutations are proposed a modifier role, we also investigated its interaction with the ACE gene variant. METHODS: We analyzed the I/D polymorphism in the ACE gene (g.11417_11704del287) in 171 subjects comprising 91 TCP and 80 FCPD patients and compared the allelic and genotypic frequency in them with 99 healthy ethnically matched control subjects. RESULTS: We found 46% and 21% of TCP patients, 56% and 19.6% of FCPD patients and 54.5% and 19.2% of the healthy controls carrying the I/D and D/D genotypes respectively (P>0.05). No significant difference in the clinical picture was observed between patients with and without the del allele at the ACE in/del polymorphism in both categories. No association was observed with the presence or absence of N34S SPINK1 mutation in these patients. CONCLUSION: We conclude that the ACE insertion/deletion variant does not show any significant association with the pathogenesis, fibrosis and progression of tropical calcific pancreatitis and the fibro-calculous pancreatic diabetes
High-risk oral leukoplakia is associated with aberrant promoter methylation of multiple genes
Upconversion 32Nb2O5–10La2O3–16ZrO2 glass activated with Er3+/Yb3+ and dye sensitized solar cell application
The important role of the receptor for activated C kinase 1 (RACK1) in nasopharyngeal carcinoma progression
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