Investigation of Factors Induced the Non-Intrinsic Optical Properties for Water-Soluble CdSe Semiconductor Quantum Dots

2010 ◽  
Vol 663-665 ◽  
pp. 437-440
Author(s):  
Heng Kang Qiu ◽  
Yue Shen ◽  
Lin Jun Wang ◽  
Jian Cheng Zhang ◽  
Kai Feng Qin
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Photoelectron Spectroscopy ◽  
Semiconductor Quantum Dots ◽  
Water Soluble ◽  
Nano Particles ◽  
Crystal Nucleation ◽  
Band Edge ◽  
Molar Ratio ◽  
X Ray

For the purpose of investigating the factors induced the non-band-edge excitation optical properties of water-soluble CdSe semiconductor quantum dots (QDs), the initial molar ratio of Cd and Se(or Cd/Se), the temperature of crystal nucleation and growing, the time of the growth etc. are systematically studied in the fabricated process. The properties of the as-prepared nano-particles (NPs) have been characterized by ultraviolet-visible absorption spectra (UV-Vis), photoluminescence (PL) spectroscopy, X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS). The measured results show that it is possible to exist surface trapping, impurities and other defect energy states in the products with the non-band-edge excitation PL properties, and all the characteristics are involved with the different synthetic routes and prepared techniques.

Synthesis and Optical Properties of L-Cysteine Hydrochloride-Stabilized CdSe Nanocrystals in a New Alkali System

2008 ◽  
Vol 8 (3) ◽  
pp. 1178-1182 ◽  
Author(s):  
Bin Feng ◽  
Feng Teng ◽  
Ai-Wei Tang ◽  
Yan Wang ◽  
Yan-Bing Hou ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Optical Properties ◽  
Photoelectron Spectroscopy ◽  
Water Soluble ◽  
Molar Ratio ◽  
Cdse Nanocrystals ◽  
X Ray ◽  
Transmission Electron ◽  
Cysteine Hydrochloride

Water-soluble CdSe nanocrystals were synthesized in a new alkali system at lower temperatures by using L-cysteine hydrochloride as a stabilizer and Na2SeSO3 as a selenium source to enable the synthesis of CdSe nanocrystals in a wider range of pHvalues. The CdSe nanocrystal powder was characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. We systematically investigated the effect of synthesis conditions on the optical properties of the L-cysteine hydrochloride-stabilized CdSe nanocrystals, and found that different sizes of CdSe nanocrystals can be obtained by changing the pHvalue, the molar ratio of L-cysteine hydrochloride to Cd2+, or the refluxing time. The emission maxima of the obtained CdSe nanocrystals can be tuned in a wider range from 477 to 575 nm by changing the pHvalue from 7 to 13. We observed an obvious blue-shift of the absorption and photoluminescence peak position by varying the molar ratio of L-Cys to Cd2+ from 3.5:1 to 2:1 at the same pHvalue. The size of the obtained nanocrystals increased and the full width at half maximum became narrower as reflux time increased. Transmission electron microscopy images indicate that the as-prepared CdSe nanocrystals have a good dispersion, which means that L-cysteine hydrochloride can control the grouping of CdSe nanocrystals excellently as a stabilizer in the new alkali system.

scholarly journals Studies of Effects of Calcination Temperature on the Crystallinity and Optical Properties of Ag-Doped ZnO Nanocomposites

2019 ◽  
Vol 3 (1) ◽  
pp. 18 ◽  
Author(s):  
Md. Molla ◽  
Mai Furukawa ◽  
Ikki Tateishi ◽  
Hideyuki Katsumata ◽  
Satoshi Kaneco
Keyword(s):  
Optical Properties ◽  
Calcination Temperature ◽  
Photoelectron Spectroscopy ◽  
Diffuse Reflectance Spectroscopy ◽  
Band Edge ◽  
High Yield ◽  
Band Edge Emission ◽  
X Ray ◽  
Calcination Temperatures ◽  
Doped Zno

Ag-doped ZnO nanocomposites are successfully synthesized at different calcination temperatures and times through a simple, effective, high-yield and low-cost mechanochemical combustion technique. Effects of calcination temperature on the crystallinity and optical properties of Ag/ZnO nanocomposites have been studied by X-ray diffraction (XRD), UV−visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence spectroscopy (PL) and X-ray photoelectron spectroscopy (XPS). The XRD patterns of the synthesized Ag/ZnO exhibit a well-crystalline wurtzite ZnO crystal structure. The grain size of Ag/ZnO nanocomposites is found to be 19 and 46 nm at calcination temperatures of 400 °C and 700 °C, respectively. The maximum absorption in the UV region is obtained for Ag/ZnO nanocomposites synthesized at a calcination temperature of 500 °C for 3 h. The peak position of blue emissions is almost the same for the nanocomposites obtained at 300–700 °C calcination temperatures. The usual band edge emission in the UV is not obtained at 330 nm excitation. Band edge and blue band emissions are observed for the use of low excitation energy at 335–345 nm.

Synthesis and Fluorescence Properties of Water-Soluble L-Cysteine-Modified ZnSe:Ag Quantum Dots

2014 ◽  
Vol 1033-1034 ◽  
pp. 1172-1175
Author(s):  
Li Ping Lin ◽  
Feng Hua Huang ◽  
Pei Feng Chen
Keyword(s):  
Crystal Structure ◽  
Quantum Dots ◽  
Optical Properties ◽  
Absorption Spectrum ◽  
Photoluminescence Spectrum ◽  
Water Soluble ◽  
Precipitation Method ◽  
X Ray ◽  
Surface Modifier ◽  
Co Precipitation

The water-soluble ZnSe:Ag quantum dots were synthesized in aqueous medium by chemical co-precipitation method with L-cysteine as surface modifier. The crystal structure and optical properties of the obtained ZnSe:Ag quantum dots have been characterized by X-ray power diffraction, infrared spectrum, UV-Vis absorption spectrum and photoluminescence spectrum. Results indicate that ZnSe:Ag quantum dots belong to the cubic blende structure and have good fluorescent characteristics. The L-cysteine modified on the surface of ZnSe:Ag quantum dots renders the quantum dots water-soluble, biocompatible.

scholarly journals One-Step Synthesis of High-Quality Water-Soluble CdSe Quantum Dots Capped byN-Acetyl-L-cysteineviaHydrothermal Method and Their Characterization

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Chunjin Wei ◽  
Jinyu Li ◽  
Fang Gao ◽  
Shuxia Guo ◽  
Yongcui Zhou ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Photoelectron Spectroscopy ◽  
Ph Value ◽  
Water Soluble ◽  
Molar Ratio ◽  
Cdse Quantum Dots ◽  
Cdse Qds ◽  
Hydrothermal Route ◽  
Experimental Conditions ◽  
One Step

Novel water-soluble CdSe quantum dots (QDs) have been prepared withN-acetyl-L-cysteine as new stabilizer through a one-step hydrothermal route. The influence of experimental conditions, including reaction time, molar ratio of reactants, and pH value, on the luminescent properties of the obtained CdSe QDs has been systematically investigated. The characterization of as-prepared QDs was carried out through different methods. In particular, we realized qualitative and semiquantitative studies on CdSe QDs through X-ray photoelectron spectroscopy and electron diffraction spectroscopy. The results show that the as-prepared CdSe QDs exhibit a high quantum yield (up to 26.7%), high stability, and monodispersity and might be widely used in biochemical detection and biochemical research.

scholarly journals Facile Synthesis of Ternary Alloy of CdSe1-xSx Quantum Dots with Tunable Absorption and Emission of Visible Light

Nanomaterials ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 979 ◽  
Author(s):  
Wageh Swelm ◽  
Ahmed Al-Ghamdi ◽  
Asim Jilani ◽  
Javed Iqbal
Keyword(s):  
Quantum Dots ◽  
Optical Absorption ◽  
Ternary Alloy ◽  
Photoelectron Spectroscopy ◽  
Synthesis Method ◽  
Semiconductor Quantum Dots ◽  
Visible Range ◽  
X Ray Diffraction ◽  
Color Analysis ◽  
X Ray

The synthesis of alloyed semiconductor quantum dots has produced structures that have distinct properties in comparison with both their bulk counterparts and their parent binary semiconductor quantum dots. In this work, the quantum confined structures of a ternary alloy of CdSe1−xSx were synthesized by one-pot synthesis method in an aqueous medium at a low temperature and capped with 3-mercaptopropoionic acid. Structures of the synthesized quantum dots were investigated by energy dispersive X-ray, X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The obtained quantum dots had modified cubic structures as proven by X-ray diffraction and selected area electron diffraction. The optical properties of the synthesized quantum dots were characterized by optical absorption, photoluminescence, and color analysis. Optical absorption investigation revealed a widening of the band gap of CdSe1−xSx with increasing S content. This widening increased for the samples suspended in water relative to the samples measured in powder form due to the difference in the environment of the two cases. The size determined from the optical absorption measurements was found to be compatible with the sizes obtained from the X-ray diffraction with the value of bowing parameter around 1, which indicated a graded diffusion of sulfur. It was also ascertained that the emission of different compositions covered the most visible range with a small full width at half maximum. The x and y values of the chromaticity coordinates decreased with increasing sulfur content of up to 15%, while the z value increased.

scholarly journals Combining HR-TEM and XPS to elucidate the core–shell structure of ultrabright CdSe/CdS semiconductor quantum dots

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Florian Weigert ◽  
Anja Müller ◽  
Ines Häusler ◽  
Daniel Geißler ◽  
Dieter Skroblin ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Quantum Yield ◽  
Photoelectron Spectroscopy ◽  
Surface Passivation ◽  
Semiconductor Quantum Dots ◽  
Optical Measurements ◽  
Core Shell ◽  
Shell Nanoparticles ◽  
X Ray ◽  
The Core

AbstractControlling thickness and tightness of surface passivation shells is crucial for many applications of core–shell nanoparticles (NP). Usually, to determine shell thickness, core and core/shell particle are measured individually requiring the availability of both nanoobjects. This is often not fulfilled for functional nanomaterials such as many photoluminescent semiconductor quantum dots (QD) used for bioimaging, solid state lighting, and display technologies as the core does not show the application-relevant functionality like a high photoluminescence (PL) quantum yield, calling for a whole nanoobject approach. By combining high-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS), a novel whole nanoobject approach is developed representatively for an ultrabright oleic acid-stabilized, thick shell CdSe/CdS QD with a PL quantum yield close to unity. The size of this spectroscopically assessed QD, is in the range of the information depth of usual laboratory XPS. Information on particle size and monodispersity were validated with dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) and compared to data derived from optical measurements. In addition to demonstrating the potential of this novel whole nanoobject approach for determining architectures of small nanoparticles, the presented results also highlight challenges faced by different sizing and structural analysis methods and method-inherent uncertainties.

scholarly journals Phytosynthetic Fabrication of Lanthanum Ion-Doped Nickel Oxide Nanoparticles Using Sesbania grandiflora Leaf Extract and Their Anti-Microbial Properties

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 124
Author(s):  
Srihasam Saiganesh ◽  
Thyagarajan Krishnan ◽  
Golla Narasimha ◽  
Hesham S. Almoallim ◽  
Sulaiman Ali Alhari ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Optical Properties ◽  
Rare Earth ◽  
Nickel Oxide ◽  
Photoelectron Spectroscopy ◽  
Metal Oxide Nanoparticles ◽  
Oxide Nanoparticles ◽  
Nio Nanoparticles ◽  
X Ray ◽  
Sesbania Grandiflora

Over the past few years, the photogenic fabrication of metal oxide nanoparticles has attracted considerable attention, owing to the simple, eco-friendly, and non-toxic procedure. Herein, we fabricated NiO nanoparticles and altered their optical properties by doping with a rare earth element (lanthanum) using Sesbania grandiflora broth for antibacterial applications. The doping of lanthanum with NiO was systematically studied. The optical properties of the prepared nanomaterials were investigated through UV-Vis diffuse reflectance spectra (UV-DRS) analysis, and their structures were studied using X-ray diffraction analysis. The morphological features of the prepared nanomaterials were examined by scanning electron microscopy and transmission electron microscopy, their elemental structure was analyzed by energy-dispersive X-ray spectral analysis, and their oxidation states were analyzed by X-ray photoelectron spectroscopy. Furthermore, the antibacterial action of NiO and La-doped NiO nanoparticles was studied by the zone of inhibition method for Gram-negative and Gram-positive bacterial strains such as Escherichia coli and Bacillus sublitis. It was evident from the obtained results that the optimized compound NiOLa-04 performed better than the other prepared compounds. To the best of our knowledge, this is the first report on the phytosynthetic fabrication of rare-earth ion Lanthanum (La3+)-doped Nickel Oxide (NiO) nanoparticles and their anti-microbial studies.

scholarly journals Photocatalytic Reduction of CO2 to Methanol Using a Copper-Zirconia Imidazolate Framework

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 346
Author(s):  
Sonam Goyal ◽  
Maizatul Shima Shaharun ◽  
Ganaga Suriya Jayabal ◽  
Chong Fai Kait ◽  
Bawadi Abdullah ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Catalyst Support ◽  
Oxidation Potential ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Molar Ratios ◽  
Optimum Parameters ◽  
Reduction Of Co2 ◽  
Enhanced Yield

A set of novel photocatalysts, i.e., copper-zirconia imidazolate (CuZrIm) frameworks, were synthesized using different zirconia molar ratios (i.e., 0.5, 1, and 1.5 mmol). The photoreduction process of CO2 to methanol in a continuous-flow stirred photoreactor at pressure and temperature of 1 atm and 25 °C, respectively, was studied. The physicochemical properties of the synthesized catalysts were studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. The highest methanol activity of 818.59 µmol/L.g was recorded when the CuZrIm1 catalyst with Cu/Zr/Im/NH4OH molar ratio of 2:1:4:2 (mmol/mmol/mmol/M) was employed. The enhanced yield is attributed to the presence of Cu2+ oxidation state and the uniformly dispersed active metals. The response surface methodology (RSM) was used to optimize the reaction parameters. The predicted results agreed well with the experimental ones with the correlation coefficient (R2) of 0.99. The optimization results showed that the highest methanol activity of 1054 µmol/L.g was recorded when the optimum parameters were employed, i.e., stirring rate (540 rpm), intensity of light (275 W/m2) and photocatalyst loading (1.3 g/L). The redox potential value for the CuZrIm1 shows that the reduction potential is −1.70 V and the oxidation potential is +1.28 V for the photoreduction of CO2 to methanol. The current work has established the potential utilization of the imidazolate framework as catalyst support for the photoreduction of CO2 to methanol.

scholarly journals Study on the Electrical, Structural, Chemical and Optical Properties of PVD Ta(N) Films Deposited with Different N2 Flow Rates

Coatings ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 937
Author(s):  
Yingying Hu ◽  
Md Rasadujjaman ◽  
Yanrong Wang ◽  
Jing Zhang ◽  
Jiang Yan ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Optical Properties ◽  
Photoelectron Spectroscopy ◽  
Crystal Size ◽  
Silicon Substrates ◽  
X Ray Diffraction ◽  
Dc Magnetron Sputtering ◽  
Flow Rates ◽  
X Ray ◽  
N2 Flow Rate

By reactive DC magnetron sputtering from a pure Ta target onto silicon substrates, Ta(N) films were prepared with different N2 flow rates of 0, 12, 17, 25, 38, and 58 sccm. The effects of N2 flow rate on the electrical properties, crystal structure, elemental composition, and optical properties of Ta(N) were studied. These properties were characterized by the four-probe method, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). Results show that the deposition rate decreases with an increase of N2 flows. Furthermore, as resistivity increases, the crystal size decreases, the crystal structure transitions from β-Ta to TaN(111), and finally becomes the N-rich phase Ta3N5(130, 040). Studying the optical properties, it is found that there are differences in the refractive index (n) and extinction coefficient (k) of Ta(N) with different thicknesses and different N2 flow rates, depending on the crystal size and crystal phase structure.

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