scholarly journals Effects of Temperature on the Morphology and Optical Properties of Spark Discharge Germanium Nanoparticles

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4431
Author(s):  
Anna Lizunova ◽  
Anastasia Mazharenko ◽  
Bulat Masnaviev ◽  
Egor Khramov ◽  
Alexey Efimov ◽  
...  
Keyword(s):  
Optical Properties ◽  
Primary Particle ◽  
Amorphous Matrix ◽  
Size Structure ◽  
Spark Discharge ◽  
Transmission Electron ◽  
Different Temperatures ◽  
The Mean ◽  
Effects Of Temperature ◽  
Germanium Nanoparticles

We report the spark discharge synthesis of aerosol germanium nanoparticles followed by sintering in a tube furnace at different temperatures varying from 25 to 800 °C. The size, structure, chemical composition and optical properties were studied. We have demonstrated a melting mechanism of nanoparticles agglomerates, the growth of the mean primary particle size from 7 to 51 nm and the reduction of the size of agglomerates with a temperature increase. According to transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) data, primary nanoparticles sintered at temperatures from 25 to 475 °C basically have a structure of Ge crystals embedded in a GeOx amorphous matrix, as well as visible photoluminescence (PL) with the maximum at 550 nm. Pure germanium nanoparticles are prepared at temperatures above 625 °C and distinguished by their absence of visible PL. The shape of the experimental UV-vis-NIR extinction spectra significantly depends on the size distribution of the germanium crystals. This fact was confirmed by simulations according to Mie theory for obtained ensembles of germanium nanoparticles.

Polyethyleneimine Modified Biocompatible Poly(N-isopropylacrylamide)-Based Nanogels for Drug Delivery

2008 ◽  
Vol 8 (5) ◽  
pp. 2377-2384 ◽  
Author(s):  
Chang-Yun Quan ◽  
Hua Wei ◽  
Yun-Xia Sun ◽  
Si-Xue Cheng ◽  
Kun Shen ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Drug Delivery ◽  
Transmission Electron Microscopy ◽  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Transmission Electron ◽  
Potential Applications ◽  
Different Temperatures ◽  
The Mean ◽  
Stimuli Sensitive

A series of biocompatible and stimuli-sensitive poly(N-isopropylacrylamide-co-propyl acrylic acid) (P(NIPAAm-co-PAAc)) nanogels were synthesized by emulsion polymerization. In addition, polyethyleneimine (PEI) was further grafted to modify the PNIPAAm-based nanogels. The P(NIPAAm-co-PAAc)-g-PEI nanogels exhibited good thermosensitivity as well as pH sensitivity. Transmission electron microscopy (TEM) showed that the P(NIPAAm-co-PAAc)-g-PEI and P(NIPAAm-co-PAAc) nanogels displayed well dispersed spherical morphology. The mean sizes of the nanogels measured by dynamic light scattering (DLS) were from 100 nm to 500 nm at different temperatures. The cytotoxicity study indicated P(NIPAAm-co-PAAc) nanogels exhibited a better biocompatibility than both PNIPAAm nanogel and P(NIPAAm-co-PAAc)-g-PEI nanogel although all the three kinds of nanogels did not exhibit apparent cytotoxicity. The drug-loaded nanogels, especially the PEI-grafted nanogels, showed temperature-trigged controlled release behaviors, indicating the potential applications as an intelligent drug delivery system.

Silver Nanocolloid: Synthesis, Optical and Thermo-Optical Properties

2013 ◽  
Vol 829 ◽  
pp. 670-674 ◽  
Author(s):  
Sakineh Hashemizadeh ◽  
Majid Rashidi Huyeh
Keyword(s):  
Silver Nanoparticles ◽  
Optical Properties ◽  
Extinction Spectrum ◽  
Noble Metal Nanoparticles ◽  
Shape Effect ◽  
Transmission Electron ◽  
Vis Spectroscopy ◽  
Different Temperatures ◽  
Two Peaks ◽  
Silver Nanocolloid

Linked to Surface Plasmon Resonance (SPR) phenomena, optical and thermo-optical properties of metal-dielectric nanocomposite materials including noble metal nanoparticles dispersed in a dielectric host medium are worthily interested. Indeed these materials have been proposed for many applications such as photonics devices, bio sensors and even photo-thermal therapy. Colloidal silver nanoparticles were synthesized by reduction of silver nitrate using of ascorbic acid and citrate as stabilizer agent in a 30°C water bath. The transmission electron microscopy (TEM) micrograph image shows formation of spheroidal silver nanoparticles with an average of large and small diameters about 43 and 34 nm respectively. Extinction spectrum, measured using UV-Vis spectroscopy, represented two peaks located around 420 and 620 nm of wavelength. These peaks are attributed to SPR phenomena and confirm spheroidal and spherical silver nanoparticle formation in solution. Thermo-optical properties of synthesized silver nanocolloids are then evaluated by measuring of extinction spectrum at different temperatures. Results showed an enhancement in thermo-optical properties of silver nanocolloids around the SPR wavelengths. Theoretical analysis, done using Mie and Mie-Gans theories, showed that the different peaks observed in extinction spectrum are related directly to shape effect.

scholarly journals Microstructure and Optical Characterization of Mid-Wave HgCdTe grown by MBE under Different Conditions

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 296
Author(s):  
Xiao-fang Qiu ◽  
Sheng-xi Zhang ◽  
Jian Zhang ◽  
Yi-cheng Zhu ◽  
Cheng Dou ◽  
...  
Keyword(s):  
Optical Properties ◽  
Growth Temperature ◽  
Crystal Quality ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Different Temperatures ◽  
Higher Temperature ◽  
Lower Temperature

The mid-wave single-crystal HgCdTe (211) films were successfully grown on GaAs (211) B substrates by molecular beam epitaxy (MBE). Microstructure and optical properties of the MBE growth HgCdTe films grown at different temperatures were characterized by X-ray diffraction, scanning transmission electron microscopy, Raman and photoluminescence. The effects of growth temperature on the crystal quality of HgCdTe/CdTe have been studied in detail. The HgCdTe film grown at the lower temperature of 151 °C has high crystal quality, the interface is flat and there are no micro twins. While the crystal quality of the HgCdTe grown at higher temperature of 155 °C is poor, and there are defects and micro twins at the HgCdTe/CdTe interface. The research results demonstrate that the growth temperature significantly affects the crystal quality and optical properties of HgCdTe films.

EFFECT OF ANNEALING AT DIFFERENT TEMPERATURES ON THE STRUCTURE AND HARDNESS OF AL85Y8NI5CO2 ALLOY AMORPHOUS STRIPS

2018 ◽  
pp. 60-67
Author(s):  
A. G. Igrevskaya ◽  
A. I. Bazlov ◽  
N. Yu. Tabachkova ◽  
D. V. Louzguine ◽  
V. S. Zolotorevskiy
Keyword(s):  
Heat Treatment ◽  
Amorphous Alloys ◽  
Amorphous Matrix ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Maximum Value ◽  
Transmission Electron ◽  
Aluminum Solid Solution ◽  
Different Temperatures ◽  
Residual Amorphous Matrix

Aluminum-based metallic glasses are the new promising family of materials. However, the effect of heat treatment on the structure and properties of Al–Y–Ni–Co amorphous alloys has not been widely studied so far. In this paper, Al85Y8Ni5Co2 amorphous alloy strips were obtained by hardening on a rotary copper wheel. The effect of vacuum annealing at temperatures ranging from 100 to 500 °C for 30 minutes on the structure and hardness of these strips was investigated. Transmission electron microscopy, X-ray diffraction analysis, and differential scanning calorimetry were used to study changes in the structure of strips after heat treatment. Vickers microhardness was measured to investigate the effect of annealing on the mechanical properties of strips. The results obtained allowed for the conclusions made about changes in hardness depending on the Al85Y8Ni5Co2 alloy strip structure. It was found that as the temperature rises, strip microhardness increases reaching a maximum value of 575±7 HV after annealing at 350 °C, then it decreases with a further increase in the annealing temperature. It was shown that the Al85Y8Ni5Co2 alloy strips remain completely amorphous and no crystalline phases are detected in their structures after annealing at temperatures up to 250 °C for 30 minutes. A sharp increase in hardness after annealing at 350 °C is associated with 10–30 nm nanocrystals of an aluminum solid solution formed in the amorphous matrix and surrounded by a residual amorphous matrix, while further hardness decrease is associated with the increasing sizes of these crystals and Al3Y and Al19Ni5Y3 intermetallics formed in the structure.

Structure and Optical Properties of Si/InAs/Si Layers Grown by MBE on Si Substrate at Different Temperatures

2000 ◽  
Vol 618 ◽  
Author(s):  
N.D. Zakharov ◽  
P. Werner ◽  
U. Gösele ◽  
R. Heitz ◽  
D. Bimberg ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
Transmission Electron Microscopy ◽  
Optical Properties ◽  
High Resolution ◽  
Molecular Beam ◽  
Growth Direction ◽  
Si Substrate ◽  
Transmission Electron ◽  
Different Temperatures

ABSTRACTEpitaxial Si/InAs/Si heterostructure grown on (001) Si substrate by molecular beam epitaxy (MBE) and annealed at 800°C, and 880°C were investigated by High Resolution Transmission Electron Microscopy (HRTEM). Extensive interdiffusion at 800°C leads to the formation of an InAs solid solution as well as InAs-enriched regions with extensions of ∼6nm, which exhibit two kinds of ordering. The ordering of InAs molecules occurred, respectively, in {110} planes inclined and parallel to the [001] growth direction. It is attributed to the energy gain from the reduced number of mixed Si-As and Si-In bonds. The sample grown at 800°C shows photoluminescence in the 1.3.µm region, which is tentatively attributed to the recombination of excitons localised in the ordered regions

A transmission electron microscopic study of structural transitions in fast ionic conductors

1987 ◽  
Vol 45 ◽  
pp. 156-157
Author(s):  
R. B. Queenan ◽  
P. K. Davies
Keyword(s):  
Optical Properties ◽  
Ionic Conduction ◽  
Recent Observation ◽  
Ionic Conductivities ◽  
Sodium Aluminate ◽  
Two Dimensions ◽  
Ionic Conductors ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Trivalent Cations

Na ß“-alumina (Na1.67Mg67Al10.33O17) is a non-stoichiometric sodium aluminate which exhibits fast ionic conduction of the Na+ ions in two dimensions. The Na+ ions can be exchanged with a variety of mono-, di-, and trivalent cations. The resulting exchanged materials also show high ionic conductivities.Considerable interest in the Na+-Nd3+-ß“-aluminas has been generated as a result of the recent observation of lasing in the pulsed and cw modes. A recent TEM investigation on a 100% exchanged Nd ß“-alumina sample found evidence for the intergrowth of two different structure types. Microdiffraction revealed an ordered phase coexisting with an apparently disordered phase, in which the cations are completely randomized in two dimensions. If an order-disorder transition is present then the cooling rates would be expected to affect the microstructures of these materials which may in turn affect the optical properties. The purpose of this work was to investigate the affect of thermal treatments upon the micro-structural and optical properties of these materials.

scholarly journals Development of Quantum Dot (QD) Based Color Converters for Multicolor Display

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1089
Author(s):  
Muhammad T. Sajjad ◽  
Ashu K. Bansal ◽  
Francesco Antolini ◽  
Eduard Preis ◽  
Lenuta Stroea ◽  
...  
Keyword(s):  
Polymer Matrix ◽  
Cost Effective ◽  
Final Size ◽  
Force Microscopy ◽  
Morphological Studies ◽  
Color Displays ◽  
Transmission Electron ◽  
Different Temperatures ◽  
Color Conversion ◽  
Temperature Time

Many displays involve the use of color conversion layers. QDs are attractive candidates as color converters because of their easy processability, tuneable optical properties, high photoluminescence quantum yield, and good stability. Here, we show that emissive QDs with narrow emission range can be made in-situ in a polymer matrix, with properties useful for color conversion. This was achieved by blending the blue-emitting pyridine based polymer with a cadmium selenide precursor and baking their films at different temperatures. To achieve efficient color conversion, blend ratio and baking temperature/time were varied. We found that thermal decomposition of the precursor leads to highly emissive QDs whose final size and emission can be controlled using baking temperature/time. The formation of the QDs inside the polymer matrix was confirmed through morphological studies using atomic force microscopy (AFM) and transmission electron microscopy (TEM). Hence, our approach provides a cost-effective route to making highly emissive color converters for multi-color displays.

scholarly journals Temperature Dependence of Stress and Optical Properties in AlN Films Grown by MOCVD

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 698
Author(s):  
Wenwang Wei ◽  
Yi Peng ◽  
Jiabin Wang ◽  
Muhammad Farooq Saleem ◽  
Wen Wang ◽  
...  
Keyword(s):  
Optical Properties ◽  
Compressive Stress ◽  
Sapphire Substrate ◽  
Light Transmission ◽  
Chemical Vapor ◽  
Biaxial Stress ◽  
X Ray Diffraction ◽  
Patterned Sapphire Substrate ◽  
Transmission Electron ◽  
Nano Patterning

AlN epilayers were grown on a 2-inch [0001] conventional flat sapphire substrate (CSS) and a nano-patterned sapphire substrate (NPSS) by metalorganic chemical vapor deposition. In this work, the effect of the substrate template and temperature on stress and optical properties of AlN films has been studied by using Raman spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible spectrophotometer and spectroscopic ellipsometry (SE). The AlN on NPSS exhibits lower compressive stress and strain values. The biaxial stress decreases from 1.59 to 0.60 GPa for AlN on CSS and from 0.90 to 0.38 GPa for AlN on NPSS sample in the temperature range 80–300 K, which shows compressive stress. According to the TEM data, the stress varies from tensile on the interface to compressive on the surface. It can be deduced that the nano-holes provide more channels for stress relaxation. Nano-patterning leads to a lower degree of disorder and stress/strain relaxes by the formation of the nano-hole structure between the interface of AlN epilayers and the substrate. The low crystal disorder and defects in the AlN on NPSS is confirmed by the small Urbach energy values. The variation in bandgap (Eg) and optical constants (n, k) with temperature are discussed in detail. Nano-patterning leads to poor light transmission due to light scattering, coupling, and trapping in nano-holes.

scholarly journals Using maize wastes, fermented by co-cultures of Trichoderma harzianum and Pseudomonas fluorescens, as grain dressing against m maize diseases under field conditions

2020 ◽  
Vol 30 (1) ◽  
Author(s):  
Sherien M. M. Atalla ◽  
Mokhtar M. Abdel-Kader ◽  
Nadia G. El-Gamal ◽  
Nehal S. El-Mougy
Keyword(s):  
Pseudomonas Fluorescens ◽  
Trichoderma Harzianum ◽  
Raw Materials ◽  
Chitosan Nanoparticles ◽  
Field Conditions ◽  
Optimum Ratio ◽  
Transmission Electron ◽  
Environmentally Safe ◽  
The Mean ◽  
Uv Visible

Abstract Maize (Zea mays L.) is one of the most economic crops in Egypt. Production of amylase from the waste of maize is the most economic and cheap renewable and most abundant raw materials present in environment. Biosynthesis of Cu-chitosan nanoparticles for amylase production by co-culturing between Trichoderma harzianum and Pseudomonas fluorescens at different ratios compared to free conditions was the main purpose of this study. The optimum ratio 8:2, recorded between P. fluorescens: T. harzianum, was the most promising for production of amylase produce 22.47 and 28.60 U/ml for free and nano, respectively. The UV visible spectral analysis Cu-chitosan NPs was 220 nm, while the mean diameter, using transmission electron microscopy was 0.5 μm. Application of fermented maize wastes by co-cultivation of P. fluorescence and T. harzianum, as a grain dressing before sowing declared the reduction in both root and foliar diseases during the maize growing season, starting from germination up to 70 days of its vegetative growth under field conditions. A promising approach is the creation and use of environmentally safe products, whose protective effect is based on the induction of hydrolase inhibitors in plants.

scholarly journals Role of Nanocrystallites of Al-Based Glasses and H2O2 in Degradation Azo Dyes

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 39
Author(s):  
Qi Chen ◽  
Zhicheng Yan ◽  
Hao Zhang ◽  
KiBuem Kim ◽  
Weimin Wang
Keyword(s):  
Metallic Glasses ◽  
Azo Dye ◽  
Amorphous Matrix ◽  
Nano Scale ◽  
Transmission Electron ◽  
Melt Spun ◽  
Degradation Ability ◽  
Tem Transmission Electron Microscopy ◽  
Dye Solutions

Al-based metallic glasses have a special atomic structure and should have a unique degradation ability in azo dye solutions. The Al88Ni9Y3 (Y3), Al85Ni9Y6 (Y6) and Al82Ni9Y9 (Y9) glassy ribbons are melt spun and used in degrading methyl orange (MO) azo dye solution with adding H2O2. With increasing cY, the as-spun ribbons have an increasing GFA (glass formability) and gradually decreased the degradation rate of MO solution. TEM (transmission electron microscopy) results show that the Y3 ribbon has nano-scale crystallites, which may form the channels to transport elements to the surface for degrading the MO solution. After adding H2O2, the degradation efficiency of Al-based glasses is improved and the Y6 ribbon has formed nano-scale crystallites embedded in the amorphous matrix and it has the largest improvement in MO solution degradation. These results indicate that forming nano-scale crystallites and adding H2O2 are effective methods to improve the degradation ability of Al-based glasses in azo dye solutions.

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