Biologically inspired band-edge laser action from semiconductor with dipole-forbidden band-gap transition (original) (raw)
A new approach is proposed to light up band-edge stimulated emission arising from a semiconductor with dipole-forbidden band-gap transition. To illustrate our working principle, here we demonstrate the feasibility on the composite of SnO2 nanowires (NWs) and chicken albumen. SnO2 NWs, which merely emit visible defect emission, are observed to generate a strong ultraviolet fluorescence centered at 387 nm assisted by chicken albumen at room temperature. In addition, a stunning laser action is further discovered in the albumen/SnO2 NWs composite system. The underlying mechanism is interpreted in terms of the fluorescence resonance energy transfer (FRET) from the chicken albumen protein to SnO2 NWs. More importantly, the giant oscillator strength of shallow defect states, which is served orders of magnitude larger than that of the free exciton, plays a decisive role. Our approach therefore shows that bio-materials exhibit a great potential in applications for novel light emitters, which...
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Photoluminescence in quantum-confined SnO[sub 2] nanocrystals: Evidence of free exciton decay
Applied Physics Letters, 2004
Nanocrystalline SnO 2 quantum dots were synthesized at room temperature by hydrolysis reaction of SnCl 2 . The addition of tetrabutyl ammonium hydroxide and the use of hydrothermal treatment enabled one to obtain tin dioxide colloidal suspensions with mean particle radii ranging from 1.5 to 4.3 nm. The photoluminescent properties of the suspensions were studied. The particle size distribution was estimated by transmission electron microscopy. Assuming that the maximum intensity photon energy of the photoluminescence spectra is related to the band gap energy of the system, the size dependence of the band gap energies of the quantum-confined SnO 2 particles was studied. This dependence was observed to agree very well with the weak confinement regime predicted by the effective mass model. This might be an indication that photoluminescence occurs as a result of a free exciton decay process.
Photoluminescence in quantum-confined SnO nanocrystals: Evidence of free exciton decay
Applied physics …, 2004
Nanocrystalline SnO 2 quantum dots were synthesized at room temperature by hydrolysis reaction of SnCl 2 . The addition of tetrabutyl ammonium hydroxide and the use of hydrothermal treatment enabled one to obtain tin dioxide colloidal suspensions with mean particle radii ranging from 1.5 to 4.3 nm. The photoluminescent properties of the suspensions were studied. The particle size distribution was estimated by transmission electron microscopy. Assuming that the maximum intensity photon energy of the photoluminescence spectra is related to the band gap energy of the system, the size dependence of the band gap energies of the quantum-confined SnO 2 particles was studied. This dependence was observed to agree very well with the weak confinement regime predicted by the effective mass model. This might be an indication that photoluminescence occurs as a result of a free exciton decay process.
Synthesis and time-resolved photoluminescence of SnO 2 nanorods
A solvo-thermal method is employed to synthesize SnO 2 nanorods and the Fourier transformed infrared spectroscopic analysis confirms the formation of SneO bond. The X-ray diffraction analysis suggests that SnO 2 nanorods exist in tetragonal rutile crystal structure phase. Transmission electron microscopy images show the formation of nanorods with an average diameter ~10e15 nm and length 35e50 nm. The deconvoluted photoluminescence spectrum suggests the existence of three distinct origins of photo-luminescence, which peaks at photon energies of ~423 nm (2.93 eV), ~470 nm (2.64 eV) and 480 nm (2.58 eV). The measured photoluminescence kinetics is best described by a tri-exponential decay model suggesting that the photoluminescence occurs from three distinct channels with time constants 1.31 ns, 4.89 ns and 13.24 ns. These studies suggest that SnO 2 nanorods synthesized by solvo-thermal method at mild conditions can be used for luminescent device applications. The long lived emission of SnO 2 nanorods in the visible region make them suitable candidate as an active materials for many opto-electronic devices such as light emitting diodes and solar cells.
Nature of Sub-Band Gap Luminescent Eigenmodes in a ZnO Nanowire
Nano Letters, 2008
The emission spectrum of individual high-quality ZnO nanowires consists of a series of Fabry−Pérot-like eigenmodes that extend far below the band gap of ZnO. Spatially resolved luminescence spectroscopy shows that light is emitted predominantly at both wire ends, with identical spectra reflecting standing wave polariton eigenmodes. The intensity of the modes increases supralinearly with the excitation intensity, indicating that the mode population is governed by scattering among polaritons. Due to strong light−matter interaction, light emission from a ZnO nanowire is not dictated by the electronic band diagram of ZnO but depends also on the wire geometry and the excitation intensity. Delocalized polaritons provide a natural explanation for the pronounced subwavelength guiding in ZnO wires that has been reported previously.
Advanced Functional Materials, 2017
Colloidal semiconductor nanocrystals (NCs), called quantum dots (QDs), have been intensively studied because of their excellent photoluminescence (PL) quantum yields. However, commercial QDs such as CdSe and InP contain toxic or expensive rare elements, limiting their sustainable use. This study focuses on nontoxic, stable, and cheap tin oxides, and synthesized luminescent SnO 2 NCs of ≈2 nm in size by a heating-up method. Tin precursors and diols in a high-boiling point solvent with oleylamine as the surfactant are heated at 240 °C. SnO 2 NCs show defect-related photoluminescence at 400-460 nm by excitation at 370 nm, achieving a high quantum yield of more than 60%. The PL intensity is stable even when the NCs are stored in atmospheric air at room temperature for over 1 year. The defect-related emissions of the SnO 2 NCs are studied using polyoxometalates (POMs) as the PL quencher. POMs efficiently quench the PL emissions by extracting excited electrons from the conduction band and shallow surface defects. The results reveal that PL emissions from SnO 2 NCs are associated with radiative charge recombination via shallow defect levels on the surface and in the bulk, demonstrating the effectiveness of the PL quenching technique using POMs in studying the PL emission mechanism in QDs.
Growth and photoluminescence properties of vertically aligned SnO2 nanowires
Journal of Crystal Growth, 2009
Vertically aligned SnO 2 nanowires (NWs) were grown for the first time by a vapor-liquid-solid method on c-sapphire with gold as a catalyst under Ar gas flow. Electron backscatter diffraction analysis indicated the NWs are single crystalline having the rutile structure, grow vertically along the [1 0 0] direction, and exhibit a consistent epitaxial relationship where lattice mismatch is estimated to be 0.3% along the SnO 2 [0 1 0] direction. The growth of these NWs is sensitive to many parameters, including growth duration, substrate type, source vapor concentration, and the thickness of the catalyst layer. Photoluminescence measurements at room temperature showed that the vertically aligned NWs exhibit an intense transition at 3.64 eV, a near band-edge transition which is rarely observed in SnO 2 .
Ultraviolet photodetectors made from SnO2 nanowires
Thin Solid Films, 2009
SnO 2 nanowires can be synthesized on alumina substrates and formed into an ultraviolet (UV) photodetector. The photoelectric current of the SnO 2 nanowires exhibited a rapid photo-response as a UV lamp was switched on and off. The ratio of UV-exposed current to dark current has been investigated. The SnO 2 nanowires were synthesized by a vapor-liquid-solid process at a temperature of 900°C. It was found that the nanowires were around 70-100 nm in diameter and several hundred microns in length. High-resolution transmission electron microscopy (HRTEM) image indicated that the nanowires grew along the [200] axis as a single crystallinity. Cathodoluminescence (CL), thin-film X-ray diffractometry, and X-ray photoelectron spectroscopy (XPS) were used to characterize the as-synthesized nanowires.
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