332 research outputs found
Studies of photoinduced electron transfer and exciton dynamics in halide perovskite films and single particles [an abstract of dissertation and a summary of dissertation review]
No full text(主査) 教授 BIJU VASUDEVAN PILLAI, 教授 中村 貴義, 教授 八木 一三環境科学院（環境物質科学専攻
Crystal size, photoluminescence and electroluminescence optimization of MAPbBr3 perovskite microcrystals [an abstract of dissertation and a summary of dissertation review]
No full text(主査) 教授 Biju Vasudevan Pillai, 教授 小西 克明, 准教授 髙野 勇太環境科学院（環境物質科学専攻
Development of fluorescent molecules and nanobioconjugates for cell imaging and singlet oxygen sensing [an abstract of dissertation and a summary of dissertation review]
No full text(主査) 教授 BIJU VASUDEVAN PILLAI, 教授 小西 克明, 教授 野呂 真一郎環境科学院（環境物質科学専攻
Development of fluorescent molecules and nanobioconjugates for cell imaging and singlet oxygen sensing [an abstract of entire text]
No full textこの博士論文全文の閲覧方法については、以下のサイトをご参照ください。https://www.lib.hokudai.ac.jp/dissertations/copy-guides/(主査) 教授 BIJU VASUDEVAN PILLAI, 教授 小西 克明, 教授 野呂 真一郎環境科学院（環境物質科学専攻
Studies of photoinduced electron transfer and exciton dynamics in halide perovskite films and single particles [an abstract of entire text]
No full textこの博士論文全文の閲覧方法については、以下のサイトをご参照ください。https://www.lib.hokudai.ac.jp/dissertations/copy-guides/(主査) 教授 BIJU VASUDEVAN PILLAI, 教授 中村 貴義, 教授 八木 一三環境科学院（環境物質科学専攻
Rhacophorus pseudomalabaricus Vasudevan and Dutta 2000
No full textRhacophorus pseudomalabaricus Vasudevan and Dutta, 2000 Anaimalai Flying Frog (Daniels 2005) (Figures 1 C, 2 D, 3 H, 6 D, 9 A–G; Tables 1–3) Original name and description. Rhacophorus pseudomalabaricus Vasudevan and Dutta, 2000, A new species of Rhacophorus (Anura: Rhacophoridae) from the Western Ghats, India, Hamadryad, 25: 23. Name-bearing types. Holotype, BNHS (BNHM) 3095, by original designation, an adult female; Paratypes, ZSI/SRS VA/ 1078 – 79. Type locality. Andiparai Shola, (Valparai), Tamil Nadu, India. Current status of specific name. Valid name, as Rhacophorus pseudomalabaricus Vasudevan and Dutta, 2000. Other material studied/observed. KERALA: Idukki district, Kadalar, SDBDU 2011.1010 (adult male), collected by SDB on 22 September 2011; Palakkad district, Poopara, Parambikulam, SDBDU 2011.1422 (adult male), collected by SDB, RGK, AT, SG, RS & GS on 13 August 2011. TAMIL NADU: Coimbatore district, Valparai, SDBDU 1162–1165 (four adult males) and SDBDU 1160, SDBDU 1166 (two adult female), collected by SDB on 11 July 2002, ZSI/SRS VA 1078 (paratype, adult male), Andiparai Shola, BNHS 3095 (holotype, adult female), collected by K. Vasudevan on 23 January 1998, ZSI/SRS VA 1078 (paratype, adult male), collected by K. Vasudevan on 24 July 1998, WII 514 (paratype, adult male), collected by K. Vasudevan on 10 October 1998. Diagnosis. Rhacophorus pseudomalabaricus can be distinguished from known congeners by the following combination of characters: (1) large male adult size (SVL 47.2–53.6 mm); (2) green dorsal colour with light yellow webbing between fingers and toes in life; (3) finger webbing extensive, reaching beyond distal subarticular tubercle on inner side and base of disc in outer side of finger III; (4) thick dermal fringe from base of pad of toe V extends along lateral edge of tarsus to heel where it develops into broad flange with lateral projecting calcar on outer edge of heel; and (5) toe webbing extensive, reaching distal subarticular tubercle on either side of toe IV (Figure 9 F, G). Comparison. Rhacophorus pseudomalabaricus is unique by its uniform green colouration of dorsum with venation-like light grey lines in life. However, this species could be confused with Rhacophorus malabaricus due to comparable size in preservation. For differences with R. malabaricus, see ‘comparison’ of that species. Description of holotype. A detailed general description was published in Vasudevan and Dutta (2000). Variation. Measurements of three female, including holotype and six male specimens, are given in Table 2. No considerable variation in breeding and non breeding colour. Distribution and natural history. This species is currently reported from Kadalar, Poopara in Kerala and Andiparai Shola, Puduthottam in Tamil Nadu (Figure 6 D; Table 1). It is a high-altitude species found at ca. 955–1430 m asl. The Poopara specimen was located on a leaf at ca. 2 m above ground along a trek path in secondary forests on the fringe of abandoned cardamom plantations. The Kadalar specimen was located on a stem ca. 1.5 m above ground in a marshy area beside a perennial stream outside KFDC’s cardamom plantation. During breeding season the species is known to aggregate at artificial ponds (Vasudevan & Dutta 2000) and on vegetation overhanging marshy areas, ponds and streams. All collections in the present study were made between 18:00 to 20:00 hours. Species Voucher specimen Locality Accession number Source of sequences retrieved from GenBank. a. Bossuyt & Milinkovitch (2000), b. Hasan et al. (2012), NCBI, Genbank, unpublished, c. Delmore (2004), d. Meenakshi et al. (2009), NCBI, Genbank, unpublished.Published as part of Biju, S. D., Kamei, Rachunliu G., Mahony, Stephen, Thomas, Ashish, Garg, Sonali, Sircar, Gargi & Suyesh, Robin, 2013, Taxonomic review of the tree frog genus Rhacophorus from the Western Ghats, India (Anura: Rhacophoridae), with description of ontogenetic colour changes and reproductive behaviour, pp. 257-289 in Zootaxa 3636 (2) on pages 280-282, DOI: 10.11646/zootaxa.3636.2.3, http://zenodo.org/record/21852
Studies of photoinduced electron transfer and exciton dynamics in halide perovskite films and single particles
No full textLead halide perovskites have become the most promising semiconductor materials for light-harvesting and light-emitting applications. These materials in the nanocrystalline forms, obtained by reliable colloidal synthesis approaches, show high photoluminescence quantum yield, high charge carrier mobilities, long photoluminescence lifetimes, and high photostability. However, their exciton, charge carrier properties, and interfacial electron transfer dynamics need optimization for next-generation perovskite devices. This thesis mainly focuses on the electron donor-acceptor systems involving perovskite nanocrystal films or single-particles, including the exciton, charge carrier, and electron-transfer dynamics. It is summarized in five chapters. In chapter 1, I discuss the general properties and significance of lead halide perovskites. First, I introduce their structure, chemical compositions, and stability factors. Subsequently, I explain various perovskite nanocrystal synthesis methods to control the shape and dimensionality. The preparation methods for self-assembled perovskite nanocrystal thin films and different characterization techniques are discussed in the second section of this chapter. In the third section, I present the bandgap and fundamental optical properties of perovskite nanomaterials as functions of their halogen compositions, size, and shape. Also, I describe the charge carrier properties and quantum confinement in perovskite nanocrystals and films. In the final section, I explain the applications of halide perovskites to solar cells, photodetectors, and light-emitting diodes, summarizing my research motivation and objectives. In chapter 2, I provided complete details about the materials, synthesis methods, samples, and instrumentation techniques in this thesis. Perovskite nanocrystals are synthesized using hot injection, ligand-assisted reprecipitation, and a modified spray technique. Next, I explain the theoretical bases, working principles, and instrumental setups of various spectroscopic (UV-vis absorption, steady-state and time-resolved fluorescence spectroscopy, and transient absorption spectroscopy) and microscopic (single-particle fluorescence microscopy, transmission electron microscopy, and scanning electron microscopy) techniques. In chapter 3, I summarize the extent of carrier diffusion, the degree of radiative loss, and the rate of diffusion-controlled interfacial electron transfer in heterojunction films of cesium or formamidinium lead bromide nanocrystals and C60 or TiO2. Electron transfer and charge separation were confirmed by measuring the photoluminescence decays, intensities, and transient absorption spectra. By measuring the distance-dependent photoluminescence lifetimes and photocounts in samples containing halide perovskite-C60 or halide perovskite-TiO2 donor-acceptor junctions, I find long-range (>100 μm) carrier diffusion and distance-dependent (>800 μm) interfacial electron transfer. In chapter 4, I demonstrate the electron transfer dynamics at the single-particle level by analyzing the photoluminescence blinking of single perovskite nanocrystals with or without tetracyanoquinodimethane or tetracyanobenzene. The Gibbs free energy changes of electron transfer are estimated to be negative, using the donors and acceptors' redox potentials and the HOMO-LUMO gaps/bandgaps. The electron transfer rates are determined from time-resolved photoluminescence measurements. Further, the statistical analysis of >450 single perovskite nanocrystals and the ON-time and OFF-time probability distributions help understand the photoluminescence blinking to the electron transfer relationship. In chapter 5, I investigated exciton-plasmon interactions for perovskite nanocrystals on Au plasmonic nanogaps. I find a huge photoluminescence intensity enhancement for perovskite single nanoparticles directly synthesized in Au nanogaps. Here, the Au nanogaps are created by the controlled Au sputter-coating on glass substrates, followed by the spray-synthesis of perovskite nanocrystals on the Au-coated substrates. The radiative exciton recombination rate of perovskite nanocrystals in the Au substrate is dramatically increased by coupling with the localized surface plasmon, obvious from a drastic decrease in the photoluminescence lifetime and an increase in the photocounts. The increased radiative recombination rate is attributed to the chemical and electromagnetic coupling of the Au plasmon with perovskite nanocrystals. Finally, I summarize the thesis and provide the prospect of the work embodied in this thesis.(主査) 教授 BIJU VASUDEVAN PILLAI, 教授 中村 貴義, 教授 八木 一三環境科学院（環境物質科学専攻
Crystal size, photoluminescence and electroluminescence optimization of MAPbBr3 perovskite microcrystals
No full textRecently, lead halide perovskites are the most attractive semiconductor materials for light-harvesting and light-emitting applications, which is attributed to their excellent properties, such as high photoluminescence quantum yield, large absorption coefficient, low formation energy, and tunable bandgap. However, there are still issues limiting its large-scale applications, like instability and efficiency roll-off. In this thesis, I mainly focus on the study of isotropic and high-quality perovskite microcrystal synthesis, light- induced ion migration and its effect on electroluminescence blinking, and time-resolved electroluminescence of MAPbBr3 microcrystals. The thesis is summarized in five chapters. In Chapter 1, I introduce the general information about halide perovskite. First, I introduce the structure of one unit cell, chemical compositions and stability factors. Following, I introduce different size halide perovskite synthesis methods, including micro-sized single crystal, nanocrystals and quantum dots. Then I introduce the characteristics of halide perovskite, including optical properties, bandgaps, charge carrier dynamics and blinking. Finally, I introduce applications of halide perovskites, especially to solar cells and light-emitting diodes. I also present my study motivation. In chapter 2, I introduce the materials, sample preparation methods and instruments I used throughout the studies. I show the synthesis the MAPbBr3 microcrystals by various methods, such as room temperature crystallization (RTC), anti-solvent vapor-assisted crystallization (AVC), inverse temperature crystallization (ITC), modified-ITC and blade-coating methods. I investigate the properties of the microcrystals using optical microscopy and fluorescence microscopy. I study the photoluminescence and electroluminescence blinking of perovskite microcrystals using single particle micro spectroscope, and the photoluminescence and electroluminescence decays by time-resolved photoluminescence and electroluminescence spectroscopy. In chapter 3, I demonstrated the synthesis of isotropic high quality MAPbBr3 microcrystals. I investigate the role of an additive N- Cyclohexyl-2-pyrrolidone and reaction temperature on the crystal size, shape, quality, and density. I also discuss the crystal nucleation mechanism and crystal growth kinetics. Finally, I expand the modified ITC method to various types of halide perovskites. In chapter 4, I investigate the light-soaking effect on the photoluminescence lifetime and electroluminescence blinking of MAPbBr3 microcrystals, the ON and OFF probability distribution of electroluminescence blinking statistics has been studied. The mechanism of light-induced halide ion migration and trap healing is correlated with the electroluminescence intensities and photoluminescence lifetime. In chapter 5, I investigate the time-resolved electroluminescence of MAPbBr3 microcrystals. First, I measure the optical spectra and electroluminescence decay of commercial blue, green and red LEDs, and confirm the instrument reliability for time-resolved electroluminescence measurements. Then, I study the photoluminescence spectra, electroluminescence, and photoluminescence decays of MAPbBr3 microcrystals. Finally, I investigate the influence of MABr treatment on electroluminescence and photoluminescence decays of MAPbBr3 microcrystals, where Br vacancies are filled. The mechanism of halide ion vacancy filling enhanced electroluminescence and photoluminescence decays increase are discussed.(主査) 教授 Biju Vasudevan Pillai, 教授 小西 克明, 准教授 髙野 勇太環境科学院（環境物質科学専攻
Leishmaniasis of the lip diagnosed by lymph node aspiration and treated with a combination of oral ketaconazole and intralesional sodium stibogluconate
No full textA 26-year-old male who presented to the dermatology OPD with complaints of a swelling on his lip of 6 months′ duration was on examination found to have a solitary ulcerated nodule over the lip and an enlarged submental lymph node. Skin smear and biopsy from the lesion did not yield the diagnosis. Needle aspiration from the draining lymph node revealed the diagnostic Leishman-Donovan bodies. The patient responded to treatment with a combination of oral ketoconazole and intralesional sodium stibogluconate. We report this case because of both the unusual location of the lesion and the unusual method of diagnosis and treatment
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