Synthesis Of ZnO Quantum Dots Research Articles

Templated synthesis of ZnO quantum dots via double solvents method inside MOF-801 as emerging photocatalyst for photodegradation of Acid Blue 25 under UV light

Templated synthesis of ZnO quantum dots (QDs) is one of the most important techniques for controlled synthesis of it without need of surfactants and advanced laboratory equipment. MOF-801 was used as a template for the synthesis of ZnO QDs with controlled shape and size. The “ship-in-a-bottle” approach was applied for templated synthesis of ZnO QDs into the MOF-801 porous matrix via double solvents method (DSM) combined with an in situ reduction route (ISRR). The formation of ZnO QDs inside MOF-801 template was monitored by PXRD, FT-IR, EDX, ICP-OES, XPS, BET, TEM, DRS, PL, EIS, and Mott − Schottky analyses. The ZnOQDs@MOF-801 nanocomposite as emerging photocatalyst exhibited better photocatalytic performance for degradation of Acid Blue 25 with a rate constant of 0.00179 min−1 which is 2.35 higher than MOF-801 (0.00076 min−1) under UV irradiation, due to ZnO QDs embedded inside MOF-801 template. The unique properties of ZnO QDs, including quantum confinement, multiple exciton generation, and efficient separation of charge carriers through decrease in electron-hole recombination at the quantum scale, contribute to the photocatalytic degradation of Acid Blue 25.

Organometallic one-pot synthesis of ZnO quantum dots coated by sulfoxides as L-type ligands

The introduction of low-molecular-weight L-type-protectors (i.e., sulfoxides) in non-surfactant-assisted one-pot organometallic procedure leads to brightly luminescent and solution-processable ZnO QDs.

Biomediated synthesis of ZnO quantum dots decorated attapulgite nanocomposites for improved antibacterial properties

Abstract Attapulgite (APT) is a natural one-dimensional clay mineral with good biocompatibility and has emerged as a promising nanomaterial for the construction of performance-enhanced nanocomposites. In this study, we developed a ZnO quantum dots-incorporated APT antibacterial nanocomposite by the Aloe vera extract-mediated green route. With the combined assistance of binding interactions of ZnO nuclei with APT and capping effect of active compounds in Aloe vera extract, the quantum-sized ZnO nanoparticles with hexagonal Wurtzite structure and sizes of <5 nm were uniformly decorated on the APT surface, resulting in a high-active antibacterial nanocomposite. The obtained ZnO/APT nanocomposites displayed favorable antibacterial activities, and the minimum inhibitory concentrations of the nanocomposite with ZnO loading of 20% against E. coli and S. aureus were 2.5 and 0.5 mg·mL−1, respectively. This antibacterial performance was far better than that of APT and could almost be comparable to that of pure ZnO. For the green process, the phenolic compounds, proteins, and amino acids in Aloe vera extract were involved in the reduction and capping of ZnO, which contributed to a facile green strategy for preparation of the ZnO-modified APT nanocomposites. The present work provides new insight into the potential applications of APT in the antibacterial fields.

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.

Epoxy siloxane/ZnO quantum dot nanocomposites: Model-fitting and model-free approaches to kinetic analysis of non-isothermal curing process

In this paper, we report on synthesis of ZnO quantum dots (QDs) nanoparticles with an epoxy siloxane composition as surface modifier, which facilitated the preparation of uniform epoxy siloxane based nanocomposite thanks to the compatibility of epoxy siloxane resin with surface modified ZnO QDs. The objective of this study was to evaluate the influence of zinc oxide quantum dots (ZnO QDs) on the reaction between poly (dimethyl siloxane), diglycidyl ether terminated (Epoxy-Siloxane), and 1,3-bis (amino methyl) cyclohexane (1,3BAC). Epoxy-Siloxane was filled with ZnO QDs at four treatment levels (0, 0.05, 0.1, and 0.15 wt.%) via direct dispersion method. After preparing the filled and unfilled samples, they were mixed with 1,3BAC after which their thermal behavior was studied using differential scanning calorimetry (DSC) under non-isothermal conditions. The reaction kinetics were derived using model-fitting methods as well as two different isoconversional approaches, i.e. the Friedman method and Ozawa-Flynn-Wall method. In the fitting procedure, the nth order coupled with autocatalysis model yielded relatively good results. The results indicated that the ZnO QDs incorporated into Epoxy-Siloxane slightly raised the activation energy of the reaction between epoxy siloxane and 1,3BAC, except for the sample containing 0.1 wt.% ZnO QDs. It also revealed a significant increase in the activation energy from ˜50 to ˜100 kJ/mol, which may be considered as the percolation threshold of the system. Atomic force microscopy and water contact angle measurements presented significant changes in the surface properties of the Epoxy-Siloxane films with respect to the content of ZnO quantum dots.

Cationic‐Polymer‐Functionalized Zinc Oxide Quantum Dots: Preparation and Application to Iron(II) Ion Detection

AbstractThis research focuses on the synthesis of ZnO quantum dots with a cationic polymer coating consisting of poly[2‐(methacryloyloxy)ethyl]‐ammonium chloride–co‐poly(poly‐ethyleneglycol methyl methacrylate (p(METAC‐PEOMEMA)) for Fe2+ detection. The copolymers of p(METAC‐PEOMEMA) at various molar ratios of METAC/PEOMEMA (100/0, 38/62, and 9/91) were synthesized by RAFT polymerization. The p(METAC‐PEOMEMA) capped trisodium citrate‐ZnO quantum dot (p(METAC‐PEOMEMA)‐ZnO QDs) were prepared via ionic interaction of trisodium citrate‐ZnO QDs and p(METAC‐PEOMEMA). The optical properties of the polymer‐capped ZnO QDs were studied by UV‐Vis and fluororescence spectrophotometry. The p(METAC‐PEOMEMA)‐ZnO QDs exhibited excellent properties such as high monodispersity in particle sizes, good stability, excellent water dispersibility, and good quantum yield of 27–32%. The p(METAC9‐PEOMEMA91)‐ZnO QDs is quenched by Fe2+ with a good selectivity over other metal ions such as Fe3+, Hg2+, Co2+, Pb2+, Cd2+, Ni2+, Ag+, Cu2+, and Na+. A good linear relationship between relative fluorescence intensity and the concentration of Fe2+ ion was observed over an Fe2+ concentration range from 0.47 μM to 5.6 μM, with a limit of detection and limit of quantitation at 0.34 μM and 0.51 μM, respectively. Its application for the detection of Fe2+ ion in drinking water samples was demonstrated.

Multifunctional Photostable Nanocomplex of ZnO Quantum Dots and Avobenzone via the Promotion of Enolate Tautomer.

Ideal multifunctional ultraviolet radiation (UVR) absorbents with excellent photostability, high molar absorptivity, broadband UVR screening, and desired skin sensorial properties remain a significant challenge for the sunscreen industry. The potential of the nanocomplex (NCx) formed by microwave synthesis of ZnO quantum dots (QDs) in the presence of Avobenzone (Av) for achieving these goals is reported. The NCx exhibits unique synergy between ZnO QD and Av components, which enhances the photostability and molar absorptivity, extends UVA filtering range, and provides a visible emission that matches the typical human in vivo skin emission color. Density functional theory (DFT) and time‐dependent DFT calculations of ZnO‐Av hybrid structures and comparison of their spectroscopic features with experiments suggest that ZnO QDs catalyze the formation of highly photostable surface enolate species via aldol condensation reaction. The combination of experiments and computations used in this study can advance the science and technology of photoprotection.

Water-free synthesis of ZnO quantum dots for application as an electron injection layer in light-emitting electrochemical cells

Large-area light emitters like organic (OLEDs) or quantum dot light-emitting devices (QLEDs) and light-emitting electrochemical cells (LECs) have gained increasing interest due to their cost-effective fabrication on various even flexible substrates.

Synthesis of ZnO quantum dots and their agglomeration mechanisms along with emission spectra based on ageing time and temperature**Project supported by the FRFCU (Grant No. 2016JBM066), 863 Program (Grant No. 2013AA032205), the National Natural Science Foundation of China (Grant Nos. 61575019, 51272022, and 11474018), and RFDP (Grant Nos. 20120009130005 and 20130009130001).

The ZnO quantum dots (QDs) were synthesized with improved chemical solution method. The size of the ZnO QDs is exceedingly uniform with a diameter of approximately 4.8 nm, which are homogeneously dispersed in ethanol. The optical absorption edge shifts from 370 nm of bulk material to 359 nm of QD materials due to the quantum size effect, while the photoluminescence peak shifts from 375 nm to 387 nm with the increase of the density of ZnO QDs. The stability of ZnO QDs was studied with different dispersion degrees at 0 °C and at room temperature of 25 °C. The agglomeration mechanisms and their relationship with the emission spectra were uncovered for the first time. With the ageing of ZnO QDs, the agglomeration is aggravated and the surface defects increase, which leads to the defect emission.

Synthesis of ZnO Quantum Dots with Enhanced Fluorescence Quantum Yield

Synthesis of ZnO Quantum Dots with Enhanced Fluorescence Quantum Yield

A facile one-step synthesis of ZnO quantum dots modified poly(triazine imide) nanosheets for enhanced hydrogen evolution under visible light

A heterojunction of crystalline poly(triazine imide) (PTI) nanosheets and ZnO quantum dots (QDs) (∼3 nm) was synthesized by a one-step ionothermal condensation of cyanamide. The resulting PTI/ZnO-QDs heterostructure exhibits a significantly enhanced H2 evolution to 63 times that of pure PTI and 3.4 times that of graphitic carbon nitride (g-C3N4) under visible light.

Effect of TEA on the blue emission of ZnO quantum dots with high quantum yield

This work reports the luminescence, morphology and synthesis of ZnO quantum dots using a simple wet chemical method and different concentrations of Triethanolamine (TEA) as surfactant. Those nanoparticles emitted a strong blue emission band centered at 429 nm when they are dispersed in hexane. Spherical quantum dots with sizes ranging from 3 to 7 nm were obtained for concentrations from 0 to 0.7 ml. of TEA, whereas a mixture with oval-like nanoparticles was observed from concentrations above of 1.1 ml of TEA. It was also possible to control the values of the band gap in ZnO quantum dots depending on the content of TEA. Based on the high quantum yield of 81% measured for those ZnO nanoparticles respect to quinine sulfate dye (QS), it is suggested that such nanoparticles could be used for biolabeling and ZnO based LEDs.

Low-temperature synthesis of ZnO quantum dots for photocatalytic degradation of methyl orange dye under UV irradiation

ZnO quantum dots were synthesized by a facile low-temperature solution process. The detailed structural characterizations revealed that the prepared nanoparticles were spherical in shape and possessed high crystallinity. The photocatalytic activity of ZnO quantum dots was examined for the use in the degradation of methyl orange dye, and exhibited high efficiency in decomposition of methyl orange (97% within 160min) under UV irradiation. This excellent photocatalytic property was attributed to high crystalline quality of ZnO quantum dots that produced reactive species to decompose the dye on the catalyst surface.

Size-controlled synthesis of ZnO quantum dots in microreactors

In this paper, we report on a continuous-flow microreactor process to prepare ZnO quantum dots (QDs) with widely tunable particle size and photoluminescence emission wavelengths. X-ray diffraction, electron diffraction, UV–vis, photoluminescence and transmission electron microscopy measurements were used to characterize the synthesized ZnO QDs. By varying operating conditions (temperature, flow rate) or the capping ligand, ZnO QDs with diameters ranging from 3.6 to 5.2 nm and fluorescence maxima from 500 to 560 nm were prepared. Results obtained show that low reaction temperatures (20 or 35 °C), high flow rates and the use of propionic acid as a stabilizing agent are favorable for the production of ZnO QDs with high photoluminescence quantum yields (up to 30%).

Microstructure-Controlled Aerosol–Gel Synthesis of ZnO Quantum Dots Dispersed in SiO2 Nanospheres

ZnO quantum dots dispersed in a silica matrix were synthesized from a TEOS:Zn(NO(3))(2) solution by a one-step aerosol-gel method. It was demonstrated that the molar concentration ratio of Zn to Si (Zn/Si) in the aqueous solution was an efficient parameter with which to control the size, the degree of agglomeration, and the microstructure of ZnO quantum dots (QDs) in the SiO(2) matrix. When Zn/Si ≤ 0.5, unaggregated quantum dots as small as 2 nm were distributed preferentially inside SiO(2) spheres. When Zn/Si ≥ 1.0, however, ZnO QDs of ∼7 nm were agglomerated and reached the SiO(2) surface. When decreasing the ratio of the Zn/Si, a blue shift in the band gap of ZnO was observed from the UV/Visible absorption spectra, representing the quantum size effect. The photoluminescence emission spectra at room temperature denoted two wide peaks of deep-level defect-related emissions at 2.2-2.8 eV. When decreasing Zn/Si, the first peak at ∼2.3 eV was blue-shifted in keeping with the decrease in the size of the QDs. Interestingly, the second visible peak at 2.8 eV disappeared in the surface-exposed ZnO QDs when Zn/Si ≥ 1.0.

Enhanced visible photoluminescence in ZnO quantum dots by promotion of oxygen vacancy formation

We report on the synthesis of ZnO quantum dots (QDs) rich in oxygen vacancies by inducing an oxygen deficient environment. The precise tunability of particle size is achieved by counter ion capping of the precursor used for synthesis. The prepared QDs show size tunable visible emission with high quantum yield.

Zinc oxide quantum dots synthesized by electrochemical etching of metallic zinc in organic electrolyte and their electrochemiluminescent properties

A universal and facile electrochemical etching method for synthesizing nanosized metal oxide semiconductors has been presented by taking the synthesis of ZnO quantum dots (QDs) from metallic zinc as an example. By applying an appropriate potential, metallic zinc was controllably oxidized to Zn 2+ ion, the latter (Zn 2+) was released into an organic electrolyte and hydrolyzed by trace dissolved water therein, giving rise to ZnO QDs. The electrochemically synthesized ZnO QDs were uniform particles with an average diameter of 5.0 nm, and exhibited good photoluminescent and electrochemiluminescent activities. The effects of applied potential window, amount of water and dissolved oxygen on the formation of ZnO QDs were investigated and discussed in detail. The presently proposed electrochemical etching method not only has provided a facile, low-cost and controllable way to obtain ZnO QDs, but also would be applicable as a universal method in synthesizing other kinds of nanosized metal oxide semiconductors from related metals.

Luminescence studies and formation mechanism of symmetrically dispersed ZnO quantum dots embedded in SiO 2 matrix

Surface effects significantly influence the functionality of semiconductor nanocrystals. In the current work we present synthesis of ZnO quantum dots (QD) vis-a-vis symmetrically dispersed ZnO quantum dots embedded in SiO 2 matrix and discussed their optical properties to understand the role of the surface effects. These nanomaterials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), fourier transform infrared (FTIR), absorption (UV–visible) and photoluminescence (PL) spectroscopy. TEM studies confirm the formation of ZnO nanophosphors inside the SiO 2 matrix in highly symmetrical manner. These symmetrically dispersed ZnO@SiO 2 nanophosphors exhibited enhanced stable emission over uncoated sample and would permit the conjugation of the nanocrystals to biological entities after functionalization. Furthermore, the mechanism behind the formation of symmetrically dispersed ZnO quantum dots embedded in SiO 2 matrix was discussed in detail.