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1.
Nanotechnology ; 27(42): 425401, 2016 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-27632684

RESUMO

In this work, we demonstrate homogeneously distributed In0.3Ga0.7N/GaN quantum disks (QDs), with an average diameter below 10 nm and a high density of 2.1 × 10(11) cm(-2), embedded in 20 nm tall nanopillars. The scalable top-down fabrication process involves the use of self-assembled ferritin bio-templates as the etch mask, spin coated on top of a strained In0.3Ga0.7N/GaN single quantum well (SQW) structure, followed by a neutral beam etch (NBE) method. The small dimensions of the iron cores inside ferritin and nearly damage-free process enabled by the NBE jointly contribute to the observation of photoluminescence (PL) from strain-relaxed In0.3Ga0.7N/GaN QDs at 6 K. The large blueshift of the peak wavelength by over 70 nm manifests a strong reduction of the quantum-confined Stark effect (QCSE) within the QD structure, which also agrees well with the theoretical prediction using a 3D Schrödinger equation solver. The current results hence pave the way towards the realization of large-scale III-N quantum structures using the combination of bio-templates and NBE, which is vital for the development of next-generation lighting and communication devices.

2.
Sci Rep ; 5: 9371, 2015 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-25792119

RESUMO

Quantum dots photonic devices based on the III-V compound semiconductor technology offer low power consumption, temperature stability, and high-speed modulation. We fabricated GaAs nanodisks (NDs) of sub-20-nm diameters by a top-down process using a biotemplate and neutral beam etching (NBE). The GaAs NDs were embedded in an AlGaAs barrier regrown by metalorganic vapor phase epitaxy (MOVPE). The temperature dependence of photoluminescence emission energies and the transient behavior were strongly affected by the quantum confinement effects of the embedded NDs. Therefore, the quantum levels of the NDs may be tuned by controlling their dimensions. We combined NBE and MOVPE in a high-throughput process compatible with industrial production systems to produce GaAs NDs with tunable optical characteristics. ND light emitting diode exhibited a narrow spectral width of 38 nm of high-intensity emission as a result of small deviation of ND sizes and superior crystallographic quality of the etched GaAs/AlGaAs layer.

3.
J Nanosci Nanotechnol ; 14(4): 2891-4, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24734706

RESUMO

In this study, we produced europium-doped yttoria (Y2O3:Eu) nanoparticles and investigated their photoluminescent properties and biocompatibility. The Y2O3:Eu nanoparticles showed excellent photoluminescent properties and cytocompatibility. We also analyzed the photophysical properties of the nanoparticles in PMMA films. When the Y2O3:Eu nanoparticles were incorporated in the polymer film, they showed a strong red emission spectrum, similar to that seen with the particles alone. Energy dispersive X-ray spectroscopy (EDS) measurements indicated that the particles were distributed homogeneously in the PMMA film. Such materials could be applied not only to optoelectronic devices but also to biomedical applications such as bioimaging tools or luminescent medical/dental adhesive materials.

4.
Nanotechnology ; 24(28): 285301, 2013 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-23787817

RESUMO

We successfully fabricated defect-free, distributed and sub-20-nm GaAs quantum dots (named GaAs nanodisks (NDs)) by using a novel top-down technique that combines a new bio-template (PEGylated ferritin) and defect-free neutral beam etching (NBE). Greater flexibility was achieved when engineering the quantum levels of ND structures resulted in greater flexibility than that for a conventional quantum dot structure because structures enabled independent control of thickness and diameter parameters. The ND height was controlled by adjusting the deposition thickness, while the ND diameter was controlled by adjusting the hydrogen-radical treatment conditions prior to NBE. Photoluminescence emission due to carrier recombination between the ground states of GaAs NDs was observed, which showed that the emission energy shift depended on the ND diameters. Quantum level engineering due to both diameter and thickness was verified from the good agreement between the PL emission energy and the calculated quantum confinement energy.


Assuntos
Arsenicais/química , Gálio/química , Nanoestruturas/química , Nanotecnologia/métodos , Pontos Quânticos , Biotecnologia/métodos , Ferritinas/química , Microscopia Eletrônica de Varredura , Nanoestruturas/ultraestrutura , Tamanho da Partícula , Polietilenoglicóis/química
5.
Nanoscale Res Lett ; 8(1): 223, 2013 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-23663680

RESUMO

We study the temperature dependence of time-resolved photoluminescence (PL) in closely packed alignment of Si nanodisks (NDs) with SiC barriers, fabricated by neutral beam etching using bio-nano-templates. The PL time profile indicates three decaying components with different decay times. The PL intensities in the two slower decaying components depend strongly on temperature. These temperature dependences of the PL intensity can be quantitatively explained by a three-level model with thermal activation energies of 410 and 490 meV, depending on the PL components. The activation energies explain PL quenching due to thermal escape of electrons from individual NDs. This thermal escape affects the PL decay times above 250 K. Dark states of photo-excited carriers originating from the separate localization of electron and hole into different NDs are elucidated with the localization energies of 70 and 90 meV. In contrast, the dynamics of the fastest PL decaying component is dominated by electron tunneling among NDs, where the PL intensity and decay time are constant for temperature.

6.
Nanoscale Res Lett ; 7(1): 629, 2012 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-23158215

RESUMO

The authors study plasmonic enhancements of photoluminescence (PL) in Si nanodisk (ND) arrays hybridized with nanostructures such as nanoplates of Au, where these hybrid nanostructures are fabricated by fully top-down lithography: neutral-beam etching using bio-nano-templates and high-resolution electron-beam lithography. The separation distance between the Si ND and Au nanostructure surfaces is precisely controlled by inserting a thin SiO2 layer with a thickness of 3 nm. We observe that PL intensities in the Si NDs are enhanced by factors up to 5 depending on the wavelength by integrating with the Au nanoplates. These enhancements also depend on the size and shape of the Au nanoplates.

7.
Nanoscale Res Lett ; 7(1): 587, 2012 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-23095286

RESUMO

The picosecond carrier dynamics in a closely packed Si-nanodisk (Si-ND) array with ultrathin potential barrier fabricated by neutral beam etching using bio-nano-templates was investigated by time-resolved photoluminescence (PL). The PL decay curves were analyzed as a function of photon energy by the global fitting method. We show three spectral components with different decay times, where the systematic energy differences of the spectral peaks are clarified: 2.03 eV for the fastest decaying component with a decay time τ = 40 ps, 2.02 eV for τ = 300 ps, and 2.00 eV for τ = 1.6 ns. These energy separations ranging from 10 to 30 meV among the emissive states can be attributed to the coupling of wavefunctions of carriers between neighboring NDs.

8.
J Nanosci Nanotechnol ; 12(3): 2919-23, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22755142

RESUMO

The ultrafast spin dynamics of the bright exciton in CdSe/ZnS nanocrystal quantum dots has been investigated using a circularly polarized pump-probe experiment. A remarkably fast spin flip (-500 fs) of the bright exciton was observed at 4 K, which is attributed to the anisotropic electron-hole exchange interaction and the random positioning of nanocrystal quantum dots. In the presence of an applied magnetic field (5 T), the exciton spin parallel to the external magnetic field was favored due to Zeeman splitting. We found that this imbalance can possibly be suppressed by the state-blocking and the mixing of the 1(L) and 1(U) states in asymmetric quantum dots.

9.
Nanotechnology ; 23(6): 065302, 2012 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-22248504

RESUMO

A sub-10 nm, high-density, periodic silicon-nanodisc (Si-ND) array has been fabricated using a new top-down process, which involves a 2D array bio-template etching mask made of Listeria-Dps with a 4.5 nm diameter iron oxide core and damage-free neutral-beam etching (Si-ND diameter: 6.4 nm). An Si-ND array with an SiO(2) matrix demonstrated more controllable optical bandgap energy due to the fine tunability of the Si-ND thickness and diameter. Unlike the case of shrinking Si-ND thickness, the case of shrinking Si-ND diameter simultaneously increased the optical absorption coefficient and the optical bandgap energy. The optical absorption coefficient became higher due to the decrease in the center-to-center distance of NDs to enhance wavefunction coupling. This means that our 6 nm diameter Si-ND structure can satisfy the strict requirements of optical bandgap energy control and high absorption coefficient for achieving realistic Si quantum dot solar cells.

10.
Nanotechnology ; 22(10): 105301, 2011 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-21289397

RESUMO

We created a two-dimensional array of sub-10 nm Si-nanodiscs (Si-NDs), i.e. a 2D array of Si-NDs, with a highly ordered arrangement and dense NDs by using a new top-down technique comprising advanced damage-free neutral-beam (NB) etching and a bio-template (iron oxide core) as a uniform sub-10 nm etching mask. The bandgap energy (E(g)) of the fabricated 2D array of Si-NDs can be simply controlled from 2.2 to 1.3 eV by changing the ND thickness from 2 to 12 nm. Due to weak quantum confinement existing in the diameter direction resulting from the sub-10 nm Si-ND diameter, even though the thickness of the Si-ND is much larger than the Bohr radius of Si, E(g) is still larger than the 1.1 eV E(g) of bulk Si. Si-ND not only has wide controllable E(g) but also a high absorption coefficient due to quantum confinement in three dimensions. This new technique is a promising candidate for developing new nanostructures and could be integrated into the fabrication of nanoelectronic devices.

11.
Gan To Kagaku Ryoho ; 37(5): 899-902, 2010 May.
Artigo em Japonês | MEDLINE | ID: mdl-20495324

RESUMO

In 2001, a 72-year-old woman, who had undergone left mastectomy for breast carcinoma 36 years ago, was admitted because of dysphagia. Chest CT showed pleural effusion in the right side and no tumor in the breast. Chest drainage was performed. Cytology of chest effusion revealed adenocarcinoma. A high serum CA15-3 level was noted. She was diagnosed with a pleural recurrence of breast cancer, so administration of CAF agents (4 courses) was started. Pleural effusion was improved and the serum CA15-3 level was reduced. She was then clinically followed on medication with oral anastrozole (AI). After 4 years, progression of disease was noted. The serum CA15-3 level was elevated. A tumor measuring 3 cm was confirmed on the right chest wall. The tumor was removed under local anesthesia and pathological findings showed invasive ductal carcinoma expressing estrogen receptor. Chemotherapy with taxane had to be withdrawn because of its side effect. Administration of S-1 was then started. The serum CA15-3 level was gradually elevated. Thereafter, the regimen was switched to combined S-1 and toremifene citrate. The serum CA15-3 level was reduced and sustained for several months. However, she died of multiple organ metastasis in 2008.


Assuntos
Antineoplásicos/uso terapêutico , Carcinoma Ductal de Mama/tratamento farmacológico , Idoso , Carcinoma Ductal de Mama/diagnóstico por imagem , Carcinoma Ductal de Mama/patologia , Carcinoma Ductal de Mama/cirurgia , Evolução Fatal , Feminino , Humanos , Mastectomia , Metástase Neoplásica/diagnóstico por imagem , Metástase Neoplásica/tratamento farmacológico , Recidiva , Fatores de Tempo , Tomografia Computadorizada por Raios X
12.
Gan To Kagaku Ryoho ; 37(2): 355-7, 2010 Feb.
Artigo em Japonês | MEDLINE | ID: mdl-20154502

RESUMO

The case was a 77-year-old male with swelling of his right leg. Physical examination revealed an ill-defined mass at RLQ. Computed tomography (CT) and 3 dimensional CT showed an 8-cm tumor on the IVC, partially replacing iliac vessels and invading the psoas muscle. A diagnosis of malignant fibrohistiocytoma was made by pathological examination of biopsied specimens at exploratory laparotomy. Five courses of combination chemotherapy of ifosfamide (IFM) and doxorubicin (DXR) resulted in PR. Edema of the lower leg and hydronephrosis were both alleviated. Another 5 courses of chemotherapy with epirubicin and IFM were added. PR lasted 2 years, though the patient succumbed to the disease in 2 years and 8 months.


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Doxorrubicina/uso terapêutico , Histiocitoma Fibroso Maligno/complicações , Histiocitoma Fibroso Maligno/tratamento farmacológico , Ifosfamida/uso terapêutico , Síndrome da Veia Cava Superior/etiologia , Veia Cava Inferior/patologia , Idoso , Biópsia , Doxorrubicina/administração & dosagem , Histiocitoma Fibroso Maligno/diagnóstico por imagem , Histiocitoma Fibroso Maligno/patologia , Humanos , Ifosfamida/administração & dosagem , Masculino , Estadiamento de Neoplasias , Síndrome da Veia Cava Superior/diagnóstico por imagem , Tomografia Computadorizada por Raios X
13.
Gan To Kagaku Ryoho ; 37(1): 123-6, 2010 Jan.
Artigo em Japonês | MEDLINE | ID: mdl-20087045

RESUMO

The patient was a 63-year-old male admitted for further evaluation of the bleeding esophageal tumor. Endoscopic biopsy revealed small cell carcinoma. CT scan of the abdomen demonstrated nodular enlargement at the celiac axis. Under diagnosis of small cell carcinoma of the esophagus at Stage IVa, neoadjuvant chemotherapy with FP (5-FU+CDDP) was given. Immediately after fluid load, levels of serum sodium decreased to 117 mEq/L and persisted during chemotherapy treatment despite aggressive corrections. Response and shrinkage of the distant nodal metastases were confirmed, and an esophagectomy was conducted. Pathological examination with IHC demonstrated positive staining for CD56, NSE and synaptophysin but negative for ADH. Lymph node and liver metastases recurred. Progression of the disease again triggered hyponatremia.


Assuntos
Carcinoma de Células Pequenas/complicações , Neoplasias Esofágicas/complicações , Síndrome de Secreção Inadequada de HAD/etiologia , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Carcinoma de Células Pequenas/terapia , Cisplatino/administração & dosagem , Neoplasias Esofágicas/terapia , Esofagectomia , Fluoruracila/administração & dosagem , Humanos , Masculino , Pessoa de Meia-Idade , Terapia Neoadjuvante
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