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1.
In this paper we report the X-ray photoemission characteristics of CuO nanoparticles with surface modifications. We found the enhancement of interatomic resonant charge transfer and multi-electron relaxation processes in the coated CuO nanoparticles, which were in agree-ment with the conclusions of polaron-related structural transition appearing under quantum confinement and dielectric confinement effects, as observed in the optical absorption and infrared vibration spectra of this system. 相似文献
2.
Shahinur Acter Mark Louis P. Vidallon Simon Crawford Rico F. Tabor Boon Mian Teo 《Particle & Particle Systems Characterization》2020,37(9):2000166
In drug delivery applications, particle-based systems have been used widely due to their physicochemical properties such as size, shape, and surface charge to achieve desirable properties in intracellular environments. The way in which nanoparticles enter a biological cell is an important factor in determining their efficacy as drug carriers, their biodistribution, and toxicity. Most research thus far has focused on the comparison of spherical and rod-like particles on cellular internalization and transport. Here, the synthesis of bowl-shaped polydopamine (PDA) mesoporous nanoparticles with an average diameter of 200 nm and well-controlled radially oriented mesochannels are reported. By incubating bowl-shaped PDA nanoparticles and spherical nanoparticles with HeLa cells, their internalization behaviors are investigated using a suite of characterization techniques. Extensive experimental results demonstrate that bowl-shaped PDA nanoparticles adhere to the cell more efficiently and a faster rate of cellular uptake of bowl-shaped nanoparticles compared to their spherical counterparts. Overall, the cellular internalization behavior of particles is shape-dependent, and such information is crucial in designing nanoparticles for biomedical applications. 相似文献
3.
The presence of surfactants (Hexamine, tetraethylammonium bromide (TEAB), cetyltrimethylammonium bromide (CTAB), tetraoctylammonium bromide (TOAB) and PVP) on the surface of zinc oxide (ZnO) nanoparticles resulted variation in their optical properties. The optical properties of each surfactant-capped zinc oxide nanoparticles were investigated using UV-visible absorption and fluorescence techniques. The particle size of these nanoparticles were calculated from their absorption edge, and found to be in the quantum confinement range. The absorption spectra and fluorescent emission spectra showed a significant blue shift compared to that of the bulk zinc oxide. Large reduction in the intensity of visible emission of zinc oxide/surfactant was observed and these emissions were vanished more quickly, with the decrease in excitation energy, for the smaller nanoparticles. Out of the four surfactants (other than PVP), CTAB-capped zinc oxide has smallest particle size of 2.4 nm, as calculated from the absorption spectrum. Thus the presence of surfactant on the surface of zinc oxide plays a significant role in reducing defect emissions. Furthermore, ZnO/PVP nanoparticles showed no separate UV emission peak; however, the excitonic UV emission and the visible emission at 420 nm overlap to form a single broad band around 420 nm. 相似文献
4.
E. C. Niculescu N. Eseanu 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,79(3):313-319
The exciton effects on the interband absorption spectra in near-surface square and
semiparabolic quantum wells under intense laser field are studied taking into account the correct
dressing effect for the confinement potential and electrostatic self-energy due to the repulsive
interaction between carriers and their image charges. We found that for near-surface quantum wells with
different shapes the laser field induces significant effects on their electronic and optical properties.
The numerical results for the InGaAs/GaAs system show that the red-shift of the absorption peak induced
by the increasing cap layer can be effectively compensated using the blue-shift caused by the enhanced
laser parameter. In square quantum well without laser field our theoretical values for the absorption
peak position are in good agreement with the available experimental data. As a key result, we conclude
that the optical properties in near-surface quantum wells can be tuned by tailoring the heterostructure
parameters: well shape, capped layer thickness and/or dielectric mismatch as well as the external field
radiation strength. 相似文献
5.
Inorganic fullerene‐like closed‐cage nanoparticles of MoS2 and WS2 (IF‐MoS2; IF‐WS2), are synthesized in substantial amounts and their properties are widely studied. Their superior tribological properties led to large scale commercial applications as solid lubricants in numerous products and technologies. Doping of these nanoparticles can be used to tune their physical properties. In the current work, niobium (Nb) doping of the nanoparticles is accomplished to an unprecedented low level (≤0.1 at%), which allows controlling the work function and the band gap. The Nb contributes a positive charge, which partially compensates the negative surface charge induced by the intrinsic defects (sulfur vacancies). The energy diagram and position of the Fermi level on the nanoparticles surface is determined by Kelvin probe microscopy and optical measurements. Some potential applications of these nanoparticles are briefly discussed. 相似文献
6.
B. P. Gorshunov M. L. Shupegin V. Yu. Ivanov A. S. Prokhorov I. E. Spektor A. A. Volkov 《Technical Physics》2008,53(5):641-645
IR spectra of metal-containing diamondlike silicon-carbon films are taken for the first time. It is shown that the optical
response from the subsystem of free charge carriers in chromium-containing films can be described in terms of a simple model
that deals with carriers localized inside clusters several nanometers in size. The data obtained indicate that the electric
and dielectric properties of the films can be controlled by technological means during their synthesis and by varying the
size, concentration, and conductivity of metallic nanoclusters. 相似文献
7.
Nicoleta Eseanu 《Physics letters. A》2011,375(6):1036-1042
The 1S-exciton properties and interband absorption spectra in differently shaped near-surface quantum wells (NSQWs) with symmetrical/asymmetrical barriers, under intense laser field, are investigated taking into account the correct dressing effect for the confinement potential and electrostatic interaction between carriers and their image-charges. We found that: i) the 1S-exciton binding energy is significantly reduced by the laser intensity in InGaAs NSQWs of different asymmetrical shape; ii) the red-shift of the absorption peak induced by the asymmetry diminution or by increasing cap layer thickness can be effectively compensated using the blue-shift caused by enhancing laser parameter. Therefore, the optical properties of the differently shaped NSQWs could be tuned by proper tailoring of the heterostructure parameters (well shape, barrier asymmetry) and/or dielectric mismatch as well as by varying the laser field intensity. 相似文献
8.
采用量子限制效应模型对镶嵌有纳米非晶硅粒子的氢化氮化硅薄膜的光吸收进行了理论模拟,探讨了由吸收谱分析给出该结构薄膜光学参数的方法,并通过对不同氮含量样品的讨论给出了量子限制效应和纳米硅粒子表面的结构无序对薄膜光吸收特性的影响规律。分析结果表明,随氮含量的增加,薄膜有效光学带隙增大,该结果与薄膜中纳米硅粒子平均尺寸的减小引起的量子限制效应的增强相关,而小粒度纳米硅粒子比例增加所引入的较高微观结构无序度和较多缺陷将会导致薄膜低能吸收区吸收系数增加。 相似文献
9.
S. M.-M. Dubois Z. Zanolli X. Declerck J.-C. Charlier 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(1):1-24
Carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) represent
a novel class of low-dimensional materials.
All these graphene-based nanostructures are expected to display the
extraordinary electronic, thermal and mechanical properties of graphene
and are thus promising candidates for a wide range of nanoscience
and nanotechnology applications.
In this paper, the electronic and quantum transport properties
of these carbon nanomaterials are reviewed. Although these systems
share the similar graphene electronic structure, confinement effects are
playing a crucial role. Indeed, the lateral confinement of charge carriers
could create an energy gap near the charge neutrality point, depending
on the width of the ribbon, the nanotube diameter, the stacking of the
carbon layers regarding the different crystallographic orientations involved.
After reviewing the transport properties of defect-free systems, doping
and topological defects (including edge disorder) are also proposed as
tools to taylor the quantum conductance in these materials.
Their unusual electronic and transport properties promote these carbon
nanomaterials as promising candidates for new building blocks in a future
carbon-based nanoelectronics, thus opening alternatives to present
silicon-based electronics devices. 相似文献
10.
G.X. Chen M.H. Hong Q. He W.Z. Chen H.I. Elim W. Ji T.C. Chong 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1079-1082
Carbon nanoparticles were prepared by pulsed laser ablation in argon gas for studying their formation, properties and applications. The nanoparticles were produced at different background pressures and different substrate temperatures, respectively. Micro-Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the samples. Nonlinear optical limiting properties of the carbon nanoparticles were characterized using nanosecond laser pulses. Uniform carbon nanoparticles can be synthesized in a background gas for nonlinear optical applications. PACS 61.46.+w; 81.07.-b; 78.20.-e 相似文献
11.
Rand Ismaeel Timothy Lee Ming Ding Mohammed Belal Gilberto Brambilla 《Laser \u0026amp; Photonics Reviews》2013,7(3):350-384
Optical microfiber waveguides with diameters close to the wavelength of light possess an intriguing combination of properties, such a tight modal confinement, tailorable dispersion, and high nonlinearity, which have been utilized in many passive applications. Here, the key fabrication techniques and optical properties of microfibers are introduced, followed by a discussion of the various passive microfiber devices and sensors. Applications exploiting their strong confinement are reviewed, including harmonic generation, supercontinuum sources, gratings, tips for optical trapping and intracellular sensing and subwavelength light sources, as well as devices based on large evanescent fields such as couplers, interferometers, optical manipulators, sensors, and resonators. Furthermore, the properties and practical intricacies of manufacturing various microfiber resonators are evaluated, with a focus on their applications in sensing ranging from temperature monitoring to current, pressure, refractive index and chemicals detection. 相似文献
12.
Xiong Wang Juanjuan Zhu Yan’ge Zhang Jinguo Jiang Subao Wei 《Applied Physics A: Materials Science & Processing》2010,99(3):651-656
Monodisperse ZnSe colloidal microspheres were fabricated by a green one-pot wet chemical strategy through aggregation of primary
nanoparticles without expensive organic additives or reductants involved. The as-prepared products were characterized by powder
X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectrum, X-ray photoelectron spectroscopy (XPS), UV–vis
absorption and room-temperature photoluminescence techniques. The size-dependent optical spectra of as-obtained microspheres
were blue-shifted in comparison with that of bulk ZnSe and exhibit near band edge luminescence, indicating the quantum confinement
effect. The strong and stable blue emission band from the ZnSe colloidal microspheres indicates their potential applications
as building blocks in photonic crystals. 相似文献
13.
M. M. Mezdrogina M. V. Eremenko S. M. Golubenko E. S. Moskalenko 《Physics of the Solid State》2012,54(1):194-201
The influence of nanoparticles and thin layers of Au, Eu phthalocyanine, and Er nanoparticles on the formation of luminescence
spectra of InGaN/GaN quantum-well structures has been investigated. It has been shown that the influence of localized plasmons
on the generation of charge carriers is determined by the size of Au nanoparticles under the assumption that the interaction
of plasmons with surface states of the structures plays a dominant role. The influence of Au nanoparticles on the formation
of luminescence spectra of multiple quantum-well structures based on InGaN/GaN, unlike the case of Au layers, is determined
by the indium concentration. The influence of Eu phthalocyanine films, which are deposited onto the surface of the studied
structures, on their photoluminescence spectra is similar to the influence of doping of these structures with europium. 相似文献
14.
Nanostructured semiconductor architectures have attractive optical properties mainly including bright photoluminescence (PL) resulting from the radiative recombination of charge carriers on surface states. Various approaches have been employed for the modification of surface states of these nanostructures to design new nanomaterials with enhanced PL primarily in aqueous medium to enable their applications in biological samples. Here, we report the varying efficiencies of three commercial surfactants viz. cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride (CTAC) and cetylpyridinium chloride (CPyC) on the dynamics of PL emission enhancement during initial growth and Ostwald ripening of ZnS nanoparticles (NPs). The counterion has been estimated to behave differently to govern the PL enhancement. The exceptionally high tendency of CPyC in PL enhancement has been assigned to participation of π-electrons of pyridinium ring. The impact of UV-light in photoactivation of surfactant stabilized ZnS NPs has been utilized in exploring significance of surfactants in improving the surface emitting states in water soluble semiconductor NPs. 相似文献
15.
We introduce an analysis model, an extended Drude–Lorentz model, and apply it to Fe-pnictide systems to extract their electron–boson spectral density functions (or correlation spectra). The extended Drude–Lorentz model consists of an extended Drude mode for describing correlated charge carriers and Lorentz modes for interband transitions. The extended Drude mode can be obtained by a reverse process starting from the electron–boson spectral density function and extending to the optical self-energy and, eventually, to the optical conductivity. Using the extended Drude–Lorentz model, we obtained the electron–boson spectral density functions of K-doped BaFe2As2 (Ba-122) at four different doping levels. We discuss the doping-dependent properties of the electron–boson spectral density function of K-doped Ba-122. We also can include pseudogap effects in the model using this approach. Therefore, this approach is very helpful for understanding and analyzing measured optical spectra of strongly correlated electron systems, including high-temperature superconductors (cuprates and Fe-pnictides). 相似文献
16.
利用飞秒泵浦探测技术研究了PbS半导体纳米颗粒复合的SiO2溶胶凝胶薄膜的瞬态动力学过程。通过改变激发探测波长和激发光强度,研究引起PbS半导体纳米颗粒的非线性吸收的两种机制。当激发探测波长选在激子吸收峰附近(620nm)时,由于激子的饱和吸收引起的光致漂白,当激发波长选在激子能态的低能侧(753,800nm),同时观察到激子的饱和吸收和双激子效应引起的光致吸收。研究了激子的饱和吸收和双激子效应引起的激发态吸收随激发态电子-空穴对浓度的变化关系,表明双激子效应与载流子浓度有很大关系。在高激发强度下,双激子效应引起的诱导吸收远远大于激子跃迁引起的光致漂白,双激子效应在非线性吸收中起着决定性作用。 相似文献
17.
Characterization,spectroscopic investigation of defects by positron annihilation,and possible application of synthesized PbO nanoparticles
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Sk Irsad Ali Anjan Das Apoorva Agrawal Shubharaj Mukherjee Maudud Ahmed P M G Nambissan Samiran Mandal Atis Chandra Mandal 《中国物理 B》2021,(2)
Nanocrystalline samples of highly pure lead oxide were prepared by the sol-gel route of synthesis.X-ray diffraction and transmission electron microscopic techniques confirmed the nanocrystallinity of the samples,and the average sizes of the crystallites were found within 20 nm to 35 nm.The nanocrystallites exhibited specific anomalous properties,among which a prominent one is the increased lattice parameters and unit cell volumes.The optical band gaps also increased when the nanocrystallites became smaller in size.The latter aspect is attributable to the onset of quantum confinement effects,as seen in a few other metal oxide nanoparticles.Positron annihilation was employed to study the vacancy type defects,which were abundant in the samples and played crucial roles in modulating their properties.The defect concentrations were significantly larger in the samples of smaller crystallite sizes.The results suggested the feasibility of tailoring the properties of lead oxide nanocrystallites for technological applications,such as using lead oxide nanoparticles in batteries for better performance in discharge rate and resistance.It also provided the physical insight into the structural build-up process when crystallites were formed with a finite number of atoms,whose distributions were governed by the site stabilization energy. 相似文献
18.
《Solid State Communications》2003,128(11):407-411
We report the optical and structural properties of PbS nanoparticles in zeolite A. The samples were obtained by sulfidation of the Pb2+ ion-exchanged zeolite in a thiourea solution at 50 °C. The optical properties of the samples were studied by diffuse reflectance spectroscopy. Their crystalline structure and morphology were studied by electron diffraction and by transmission and scanning electron microscopy. The results show that the nanoparticles are not inside the zeolite cages but outside, embedded in the zeolite matrix. Exciton absorption peaks at much higher energy than the fundamental absorption edge of bulk PbS indicate quantum confinement effects in the spherical shape nanoparticles as a consequence of their small size. 相似文献
19.
The electrical and the optical properties of InAs/GaAs quantum dots (QDs) grown by using atomic layer epitaxy (ALE) technique were investigated by using capacitance-voltage (C-V) and photoluminescence (PL) measurements. C-V curves showed that the plateaus related to the zero-dimensional carrier confinement effect existed and that the number of electrons occupying the InAs QD was approximately 7. The full width at half maxima of the interband transitions from the ground electronic subband to the ground heavy-hole subband and from the first excited electronic state to the first excited state heavy-hole subband were not significantly affected by the temperature variation, indicative of strong confinement of the carriers occupying the InAs QDs. These results can help improve understanding for applications of InAs/GaAs QDs grown by using ALE in high-efficiency electronic and optoelectronic devices. 相似文献
20.
Yu. A. Morozov I. S. Nefedov V. N. Gusyatnikov V. Ya. Aleshkin 《Technical Physics》2002,47(6):788-791
Anisotropy of the gain and loss associated with different TM-wave components in a long-wave intervalley-transfer laser is
analyzed numerically. The effect of field leakage into the substrate and of interference therein on the optical confinement
coefficient and loss coefficient due to absorption by free charge carriers is studied. 相似文献