Size Of QDs Research Articles

Hydrophobic, partially hydrophobic, and hydrophilic ZnO@SiO2 nanoparticles as fluorescent partitioning tracers for oil sensing applications

(a) Schematic representation of various functionalities on the surface of ZnO@SiO 2 nanoparticles. The partially hydrophobic (PH-NPs, S2), hydrophobic (HP-NPs, S3), and hydrophilic (H-NPs, S4) functionalities were developed on the surface of ZnO@SiO 2 NPs using various silanes having methyl, octyl, and amino groups, respectively. (b,c) The fluorescent NPs (S4) stayed entirely in the water phase due to the presence of –NH 2 group (hydrophilic nature), while the fluorescent NPs (S3) moved completely toward the oil phase due to the presence of octyl-group (hydrophobic nature) on their surface. However, the luminescent NPs (S2) were shifted toward the interface between two phases due to partially hydrophobic character ( CH 3 ) on their surface. • ZnO@SiO 2 NPs were synthesized via a modified sol–gel Stober protocol. • Surface functionalities were attained by co-condensation of various silanes. • Surface chemistry and partitioning behavior of ZnO@SiO 2 NPs were investigated. • ZnO@SiO 2 NPs have excellent fluorescence stability in aqueous environments. • Stability of ZnO@SiO 2 NPs was examined under harsh reservoir conditions. Fluorescent nano-tracers are being utilized for oil sensing applications in the reservoir. In this work, we developed various hydrophobic, partially hydrophobic, and hydrophilic zinc oxide encapsulated silica nanoparticles (ZnO@SiO 2 NPs) as smart nano-agents for oil sensing applications. The surface of ZnO@SiO 2 NPs was functionalized by co-condensation using various silanes in combination with tetraethyl orthosilicate (TEOS). Cryogenic TEM images display the average size of ZnO QDs (S0) and ZnO@SiO 2 nanoparticles (S1) around ∼5.3 nm and ∼50 nm, respectively. The surface chemistry and partitioning behavior of photoluminescent ZnO@SiO 2 NPs were investigated before and after mixing with the model oil under normal and UV light. The chemical and photoluminescence (PL) stability of ZnO@SiO 2 NPs was monitored in harsh reservoir conditions, such as variable temperature (30–100 °C) and high salinity (0–80 g L −1 ) environment. The results demonstrated that the surface modification and functionalization of these nano-agents with different functional groups (methyl, octyl) improved the nano-agents’ selectivity and stability after changing their hydrophilic-hydrophobic surface characters. This work is opening new research in the field of oil sensing, which promotes their potential utilization as cost-effective and efficient fluorescent tracer materials for the oil exploration industries.

New synthesis of quantum dots copper sulfide using the UV-irradiation technique

The article describes a new method for synthesizing quantum dots copper sulfide (CuS QDs) based on the UV-irradiation technique (photolysis method). Our process allows producing high-quality, small-size, very low cost and short time. The crystal structure of CuS QDs was characterized using X-ray diffraction (XRD) ,which confirmed the synthesized sample's hexagonal shape. The structure of the manufactured product was examined using energy-dispersive X-ray spectroscopy (EDX), and the result revealed just copper (Cu) and sulfide (S) elements, indicating that the synthetic material was pure. The morphology, optical properties, and particle size were investigated by photoluminescence spectroscopy (PL), scanning electron microscope (SEM), and transmission electron spectroscopy (TEM). The particles sizes of the CuS QDs were found to be range between 5.4 to 9.1 nm. Finally, this method successfully synthesized CuS QDs through the results.

Highly stable mixed halide perovskite quantum dots synthesized in the presence of fluorous ligands

AbstractThis work probes the potential of fluorous fatty acids as stabilizing ligands in the synthesis of mixed halide perovskite quantum dots (MHP QDs). Traditionally, MHP QDs are synthesized in the presence of oleic acid (OA) and oleyl amine (OAm). Here fluorous fatty acids have been used along with OA and OAm to yield MHP QDs with higher stability. Increased fractions of fluorous molecules in reaction mixture require the process to be carried out at a higher temperature due to the distinctive temperature‐dependent mixing behavior of perfluorinated ligands. Best of fluorous acid functionalized QDs in solution showed a 9% decrease in their photoluminescence quantum yield (PLQY) over 30 days compared to 27% in those without. The composition of fluorous fatty acids during synthesis influences the size, form and optical properties of MHP QDs. Further in situ addition of non‐carboxylic acid fluorous ligands (thiols) are also shown to the give similar improvements in stability and optical properties of MHP QDs. The in situ fluorous ligand functionalization studied in this work presents a new method to improve the stability of MHP‐QD while providing a thermally controlled handle to tune the structure of nanoparticle films.

Электронный транспорт в одиночных коллоидных квантово-размерных частицах в межэлектродном нанозазоре

Based on the current-voltage characteristics of single colloidal QDs -InSb, -PbS, -HgSe, -CdSe quantum dots, on random samples statistically determined and investigated the mechanisms of barrier and ballistic tunneling, Coulomb confinement, quasi-periodic modulation of electron transport in the model of a deep extended potential well and depending on QDs size and de Broglie wavelength for the electron. The possibility of manifestation of Bloch oscillations has been experimentally confirmed. The parameters of all investigated processes were determined and tabulated

Electron transport in single colloidal quantum dots in an interelectrode nanogap

Based on the current-voltage characteristics of single colloidal QDs -InSb, -PbS, -HgSe, -CdSe quantum dots, on random samples statistically determined and investigated the mechanisms of barrier and ballistic tunneling, Coulomb confinement, quasi-periodic modulation of electron transport in the model of a deep extended potential well and depending on QDs size and de Broglie wavelength for the electron. The possibility of manifestation of Bloch oscillations has been experimentally confirmed. The parameters of all investigated processes were determined and tabulated. Keywords: Nanoparticle, quantum dot, dimensional quantization, quantum selection, barrier and ballistic tunneling, Coulomb confinement, Coulomb ladder, Bloch oscillations.

Nanoarchitectonics with NADPH Catalyst and Quantum Dots Copper Sulfide on Titanium Dioxide Nano-sheets Electrode for Electrochemical Biosensing of Sorbitol Detection.

Sorbitol accumulation in the tissue is known to cause diabetic complications. Nanotechnology-enabled biosensor methods have high sensitivity, selectivity, and more rapid detection of an analytic for sorbitol which is used as a biomarker of diabetic complications. The biosensor used aldose reductase from serum blood to oxidize the NADPH by the enzymatic reaction and reduce glucose to sorbitol. Biosensors can be developed for diagnostic testing. Developing a simple, sensitive, and rapid method for sorbitol detection is significant for efficient monitoring of diabetic complications like neuropathy at the initial stages. This project synthesized quantum dots of copper sulfide (CuS QDs) to fabricate an Electrochemical sensor for the detection of sorbitol by the UV-irradiation technique. The crystal structure of CuS QDs was characterized using X-ray diffraction (XRD), which confirmed the synthesized sample's hexagonal shape. The structure of the manufactured product was examined using energy-dispersive X-ray spectroscopy (EDX), and the result revealed just copper (Cu) and sulfide (S) elements, indicating that the synthetic material was pure. The morphology, optical properties, and particle size were investigated by scanning electron microscope (SEM), photoluminescence spectroscopy (PL), and transmission electron spectroscopy (TEM), respectively. The particle sizes of the CuS QDs were found to range between 5.4 to 9.1 nm. The CuS QDs will be dedicated to the conventional methods to synthesize the modified electrode functionalized with NADPH and covered with CuS QD (Ti-TiO2/CuS/NADPH) demonstrated switchable interfacial properties. The electrochemical process was characterized by cyclic voltammetry (CV). The developed sensor was successfully tested to detect sorbitol in human serum samples. The high catalytic activity and the redox behavior of CuS QD make it an efficient matrix for the realization of sorbitol. These results indicate that CuS QD is a suitable candidate material for developing enzyme-based sorbitol biosensors.

Tuning the Morphology and Size of Nimoo4 Qds Anchored on Reduced Graphene Oxide (Rgo) Nanosheets: The Optimized Hybrid Electrodes for High Energy Density Asymmetric Supercapacitors

Tuning the Morphology and Size of Nimoo4 Qds Anchored on Reduced Graphene Oxide (Rgo) Nanosheets: The Optimized Hybrid Electrodes for High Energy Density Asymmetric Supercapacitors

Tuning the Morphology and Size of Nimoo4 Qds Anchored on Reduced Graphene Oxide (Rgo) Nanosheets: The Optimized Hybrid Electrodes for High Energy Density Asymmetric Supercapacitors

Tuning the Morphology and Size of Nimoo4 Qds Anchored on Reduced Graphene Oxide (Rgo) Nanosheets: The Optimized Hybrid Electrodes for High Energy Density Asymmetric Supercapacitors

Синтез и изучение некоторых свойств коллоидных квантовых точек антимонида индия

Colloidal quantum dots of indium antimonide have been synthesized by a known technique. The shape and average diameters of quantum dots have been investigated by transmission electron microscopy using a transmission microscope. Controlling the size and shape of colloidal QDs provides information on the formation of the crystal structure of nanoparticles and their possible physical and optical properties. It has been found that InSb quantum dots are characterized by a polygonal shape. The results obtained for QDs correspond to the crystal lattice system of a semiconductor with a cubic crystal lattice structure. Elemental analysis of nanoparticles has been monitored by X-ray microanalysis. The experimental determination error was no more than one percent. The percentages of indium and antimony in QDs according to X-ray microanalysis data corresponded to the theoretical stoichiometry In: Sb = 1:1. Impurities of other elements constituted the level of trace amounts, which confirmed the chemical purity of the synthesized InSb QDs. The fluorescent properties of indium antimonide nanoparticles have been studied. It has been found that the luminescence intensity of InSb nanoparticles at room temperature is insignificant, which is in agreement with the literature data. The quantum yield does not exceed 1%, and the luminescence maximum lies in the range of 1040 nm.

The effect of graphene on structure and optical properties of CdSe nanoparticles for optoelectronic application

CdSe-reduced Graphene Oxide (CdSe-rGO) nanocomposite was synthesized using a facile hot injection method with excellent control over the size and morphology. The superb distribution of the CdSe quantum dots (CdSe QDs) and the tightly anchoring to the graphene sheets enhance their optical properties. Therefore, the effect of reduced Graphene oxide (rGO) on the structure and optical properties of CdSe nanoparticles is studied by X-ray diffraction (XRD), UV–visible spectroscopy, and transmission electron microscopy (TEM). As well as Effective mass approximation model (EMA) and Polynomial Fitting Functions (PFF) were used to calculate the sizes of nanoparticles, yielding particle sizes ranging from 4.64 to 5.46 nm and 2.74–3.72 nm, respectively. These values were comparable to those obtained by TEM and XRD. Furthermore, the data revealed that the direct energy gap of the CdSe QDs was reduced from 2.33 eV for the smallest size to 2.17 eV for the largest size. The optical parameters of CdSe-rGO nanocomposite such as the refractive index and extinction coefficient were increased with the particle size growth. As well, optical dielectric constant and optical conductivity were improved due to the increase of the particle size of CdSe QDs in the CdSe-rGO nanocomposite. So, the capability of CdSe-rGO nanocomposite to tune the optical parameters makes it a suitable candidate for a wide range of applications, specifically optoelectronics.

Understanding the photovoltaic performances of ZnSe quantum dot-fullerene nanocomposites: A computational study

By using density-functional tight-binding method we herein explored the electronic structure of ZnSeQD-Fullerene nanocomposite system. Our objective is to understand the suitability of using this nanocomposite as building blocks for photovoltaic devices. We have shown that this composite has favorable band energy alignment for efficient charge separation and delayed electron-hole recombination. We have also calculated the photovoltaic efficiencies of ZnSeQD-Fullerene nanocomposite for ZnSe QDs of different sizes. The photovoltaic efficiency depends on the size of ZnSe QDs and can attain the maximum value of 18%.

Tailoring the crystalline phase and size of the MoO3 quantum dots via sonication induced modified top-down method

In this paper, a modified top-down method is adopted to synthesize highly stable and water-soluble Molybdenum trioxide quantum dots (MoO3 QDs) without any surfactants. In this sonication induced modified method, commercial Molybdenum Oxide powder and Hydrochloric acid were used as the precursor and etchant, respectively. The impact of sonication bath temperature on the morphological, microstructural, size, crystal-structural, and optical properties of MoO3 QDs have been systematically investigated. The controlled sonication bath temperature during the synthesis process results in the tunability of the QDs. The mechanism behind the controlled size of the QDs deeply rooted in the acoustic cavitation phenomenon. The synthesized QDs exhibit poly-crystallinity with mixed phases: orthorhombic (α-MoO3) and hexagonal (h-MoO3). Interestingly, the complete elimination of the hexagonal phase from the QDs has been observed as a function of sonication bath temperature.

The structure and optical properties of Cd1-xHoxS QDs prepared via ethylene glycol assisted solvothermal route for optoelectronic application

A series of Cd1-xHoxS semiconductor quantum dots were prepared via ethylene glycol assisted solvothermal approach, for the first time. The structure, elemental composition, and morphology of the Cd1-xHoxS QDs were characterized using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), selected area of electron diffraction (SAED), and transmission electron microscopy (TEM) measurements. The optical properties were studied using UV–Vis. Spectrophotometry and luminescence spectroscopy measurements. The substitution of the Cd-atoms by the Ho-atoms increases the crystallite size of the CdS QDs and decreases their optical bandgap. The inclusion of the Ho-atoms in the Cd-sites of the cubic CdS nanocrystals improves the luminescence intensity by 14 times. The Stokes shift revealed that the Ho-atoms decrease the surface defects of the CdS nanocrystals. The quantum yield of the Cd1-xHoxS nanocrystals reached 89%. These exceptional properties may open a new prospect for the Cd1-xHoxS QDs to be employed in the fields of the display panels and QLEDs.

Solochrome Dark Blue Azo Dye Removal by Sonophotocatalysis Using Mn2+ Doped ZnS Quantum Dots

This work investigates the degradation of the azo dye solochrome dark blue (SDB) by measurement of the photocatalytic, sonocatalytic and sonophotocatalytic activities, under low ultrasonic frequency (40 kHz) and UV-C (254 nm) light, using Mn-doped ZnS semiconductor quantum dots (Mn2+:ZnS Qds) as catalysts, prepared by a simple chemical precipitation procedure. In order to study the different morphological and optical crystal properties, various characterization techniques were used, such as high resolution transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, N2 adsorption-desorption at −196 °C and ultraviolet-visible spectroscopy. The average particle size of the semiconductor Qds was in the range of 3–4 nm. The optimal parameters affecting dye degradation, such as the catalyst loading, solution pH, time of irradiation, initial concentration of dye, dopant concentration, ultrasonic power and frequency effect were evaluated. The synthesized catalytic material exhibited a high activity for sonophotocatalytic degradation of SDB (89%), larger than that observed for sonocatalysis (69.7%) or photocatalysis (55.2%) alone, which was due to the improved electron-holes separation, formation of more reactive radicals and enhancement of the active surface area. Qds showed good stability and reusability after five repeated cycles. Finally, the degradation products were identified by liquid chromatography-mass spectrometry (LC-MS).

Preparation of AgInS2 quantum dots and their application for Pb2+ detection based on fluorescence quenching effect

Water soluble AgInS2 quantum dots (AIS QDs) were successfully prepared by an environmentally friendly one-pot water phase method using glutathione (GSH) as the stabilizing agent. The crystal structure, morphology, size, chemical states, and optical properties of as-prepared AIS QDs were characterized through X-ray diffraction (XRD), Scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometer (FTIR), Ultraviolet–visible spectrophotometer (UV–vis) and Photoluminescence spectrometer (PL). Factors affecting the fluorescence intensity of AIS QDs including reaction solution pH value, fluorescence test temperature and concentration of AIS QDs were investigated. The fluorescence stability of AIS QDs and the selectivity of AIS QDs toward Pb2+ detection was also evaluated. Under optimized test conditions, three excellent linear relationships ((F0−F)/F0=27.938CPb2+−0.002(R=0.998), (F0−F)/F0=10.362CPb2+−0.005(R=0.997), (F0−F)/F0=6.554CPb2+−0.240(R=0.9993) were achieved between the concentration of Pb2+ and the relative fluorescence quenching amount of AIS QDs in the range of 9–96 nM, 48–434 nM and 193–530 nM, respectively. The detection limit was 4 nM and the recovery was in the range of 92.2%–102.6%. Our method had wide detection range, excellent selectivity, high sensitivity and easy operability, and could be applied for the content determination of Pb2+ in water. The possible fluorescence quenching mechanism of AIS QDs by Pb2+ was discussed in detail and the dynamic quenching mechanism of light-induced electron transfer was put forward.

Enhanced Direct White Light Emission Efficiency in Quantum Dot Light‐Emitting Diodes via Embedded Ferroelectric Islands Structure

AbstractWhite light emission is of great importance in our daily life as it is the primary source of light indoor and outdoor as well as day and night. Among various materials and lighting technologies, intensive efforts have been made to quantum dots based‐light‐emitting diode (QD‐LEDs, or QLEDs) because of outstanding optical properties, facile synthesis, and bandgap tunability of QDs. Despite the fact that QLEDs are able to present various colors in a visible range, realizing efficient direct white light emission is a challenge as white light emission can only be achievable through stacking and patterning of QD films or mixing of different sizes of QDs. This inevitably involves energy band mismatch at interfaces, leading to degradation of device performance. Here, a new effective method to improve white QLED performances through embedding a ferroelectric islands structure is introduced, which induces an electric field to effectively modulate the energy band at the junction interface. The formation of a favorable energy landscape leads to efficient charge transport, improved radiative recombination, and consequently high external quantum efficiency in the white QLEDs. In addition, it is demonstrated that this new approach is proved to be effective in different color temperatures ranging from 3000 to over 120 000 K.

Phytotoxic effects of CdTe quantum dots on root meristems of Allium cepa L.

The effect of solutions of cadmium telluride quantum dots (CdTe QD) as powerful cytotoxic effectors was investigated using a standard Allium cepa L. test system. The diameters of synthesized CdTe QD derived from the optical data varied within 3 – 4 nm. Toxicity of experimental solutions of CdTe QD at the organism level were evaluated by measuring biomass growth of onion roots and cytotoxic influence was estimated based on proliferative activity of root meristem cells. All of CdTe QD experimental solutions in concentration 10 µM significantly inhibited the growth of Allium cepa L. roots, proliferative activity, and total dehydrogenase activity. Relation between the QDs size and their phytotoxicity was not found. However, the highest inhibiting impact was for QDs solution with a nanocrystals size of 3.5 nm. Their ability to penetrate into cells and interact with their intracellular components may cause inhibiting mitosis without fixed clastogenic and aneugenic effects. Solutions of CdTe QD at a given concentration can be considered as potent cytostatic agents for plant cells with antimitotic properties.

0D, 1D, 2D molybdenum disulfide functionalized by 2D polymeric carbon nitride for photocatalytic water splitting

Photocatalytic activity of molybdenum disulfide structures with different dimensions (0D, 1D and 2D) functionalized with polymeric carbon nitride (PCN) is presented. MoS2 nanotubes (1D), nanoflakes (2D) and quantum dots (0D, QDs) were used, respectively, as co-catalysts of PCN in photocatalytic water splitting reaction to evolve hydrogen. Although, 2D-PCN showed the highest light absorption in visible range and the most enhanced photocurrent response after irradiation with light from 460 to 727 nm, QDs-PCN showed the highest photocatalytic efficiency. The detailed analysis revealed that the superior photocatalytic activity of QDs-PCN in comparison with other structures of MoS2 arose from (i) the most effective separation of photoexcited electron–hole pairs, (ii) the most enhanced up-converted photoluminescence (UCPL), (iii) the highest reactivity of electrons in conduction band. Moreover, a narrowed size of QDs affected shorter diffusion path of charge carriers to active reaction sites, higher number of the sites and higher interfacial area between molybdenum disulfide and PCN.

MXene-Derived Tin O2 n- 1 Quantum Dots Distributed on Porous Carbon Nanosheets for Stable and Long-Life Li-S Batteries: Enhanced Polysulfide Mediation via Defect Engineering.

The application of Li-S batteries has been hindered by the shuttling behavior and sluggish reaction kinetics of polysulfides. Here an effective polysulfide immobilizer and catalytic promoter is developed by proposing oxygen-vacancy-rich Tin O2 n -1 quantum dots (OV-Tn QDs) decorated on porous carbon nanosheets (PCN), which are modulated using Ti3 C2 Tx MXene as starting materials. The Tn QDs not only confine polysulfides through strong chemisorption but also promote polysulfide conversion via redox-active catalysis. The introduction of oxygen vacancies further boosts the immobilization and conversion of polysulfides by lowering the adsorption energy and shortening the bond lengths. The PCN provides a physical polysulfide confinement as well as a flexible substrate preventing OV-Tn QDs from aggregation. Moreover, the two building blocks are conductive, thereby effectively improving the electron/charge transfer. Finally, the ultrasmall size of QDs along with the porous structure endows OV-Tn QDs@PCN with large specific surface area and pore volume, affording adequate space for S loading and volume expansion. Therefore, the OV-Tn QDs@PCN/S delivers a high S loading (79.1 wt%), good rate capability (672 mA h g-1 at 2 C), and excellent long-term cyclability (88% capacity retention over 1000 cycles at 2 C). It also exhibits good Li+ storage under high S-mass loading and lean electrolyte.

Effect of alkali bases on the synthesis of ZnO quantum dots

Abstract The surface-modified zinc oxide quantum dots (ZnO QDs) have broad application prospects in the field of biomedicine because of their good water solubility, dispersibility, and high fluorescence stability. The alkali bases play important roles in controlling the morphology, size distribution, dispersity, and fluorescence intensity of the synthesized ZnO QDs. In this article, ZnO QDs were synthesized to induce hydrolysis–condensation reaction. The influences of alkali bases (LiOH, NaOH, and KOH) and the ratio of n(Zn2+):n(OH−) on the properties of synthesized ZnO QDs were investigated. The results show that the particle size of the ZnO QDs prepared using LiOH and NaOH as raw materials are smaller than that using KOH. ZnO QDs prepared at the ratio of n(Zn2+):n(LiOH) = 1:1 have the best fluorescence performance and dispersibility.