Water-dispersible Nanocrystals Research Articles

Sonication-Assisted Production of Fosetyl-Al Nanocrystals: Investigation of Human Toxicity and In Vitro Antibacterial Efficacy against Xylella Fastidiosa.

Recently, there is a growing demand in sustainable phytopathogens control research. Nanotechnology provides several tools such as new pesticides formulations, antibacterial nanomaterials and smart delivery systems. Metal nano-oxides and different biopolymers have been exploited in order to develop nanopesticides which can offer a targeted solution minimizing side effects on environment and human health. This work proposed a nanotechnological approach to obtain a new formulation of systemic fungicide fosetyl-Al employing ultrasonication assisted production of water dispersible nanocrystals. Moreover, chitosan was applicated as a coating agent aiming a synergistic antimicrobial effect between biopolymer and fungicide. Fosetyl-Al nanocrystals have been characterized by morphological and physical-chemical analysis. Nanotoxicological investigation was carried out on human keratinocytes cells through cells viability test and ultrastructural analysis. In vitro planktonic growth, biofilm production and agar dilution assays have been conducted on two Xylella fastidiosa subspecies. Fosetyl-Al nanocrystals resulted very stable over time and less toxic respect to conventional formulation. Finally, chitosan-based fosetyl-Al nanocrystals showed an interesting antibacterial activity against Xylella fastidiosa subsp. pauca and Xylella fastidiosa subsp. fastidiosa.

Monodisperse Gold Cuboctahedral Nanocrystals Directly Synthesized in Reverse Micelles: Preparation, Colloidal Dispersion in Organic Solvents and Water, Reversible Self-Assembly and Plasmonic Properties.

The synthesis of organic-solvent-dispersible gold nanoparticles in reverse micelles of didodecyldimethylammonium bromide (DDAB) is revisited in the present investigation. Some parameters of synthesis, specifically the reaction volume and the concentration of the reducing agent, were slightly modified obtaining directly monodisperse gold nanocrystals (AuNCs) without the need to use additional active surfactants or additional treatments such as digestive ripening. Interestingly, most of the obtained AuNCs display the same exposed crystalline faces composed of six bounding facets (four {111} faces and two {002} faces), corresponding to single-crystalline face-centered cubic nanoparticles with a cuboctahedron shape. When these AuNCs are subsequently functionalized with 1-decanethiol (C10H21SH) or 1-dodecanethiol (C12H25SH), they don't experience significant changes in their size or crystalline texture, however, they self-aggregate directly in the suspension at room temperature into faceted supramolecular structures and exhibit collective plasmonic excitations. Such self-organization is reversible under heating treatments allowing the observation of the influence of the AuNCs aggregation state on their plasmonic properties. Fourier transform infrared spectroscopy reveals that thiols only replace partially the DDAB molecules, and thus, DDAB molecules remain present in the thiol-capped AuNCs. To turn the thiol-capped nanocrystals into water-dispersible nanocrystals and extend their technological potential, they are stabilized with poloxamer 407 obtaining highly stable purple colloids in water.

Double bond terminated Ln3+-doped LiYF4 nanocrystals with strong single band NIR emission: simple click chemistry route to make water dispersible nanocrystals with various functional groups

A simple thiol–ene click chemistry strategy to develop upconverting nanocrystals with different functional groups.

Multifunctional Hydroxyapatite/Na(Y/Gd)F4:Yb3+,Er3+ Composite Fibers for Drug Delivery and Dual Modal Imaging

Porous hydroxyapatite (HAp) composite fibers functionalized with up-conversion (UC) luminescent and magnetic Na(Y/Gd)F4:Yb(3+),Er(3+) nanocrystals (NCs) have been fabricated via electrospinning. After transferring hydrophobic oleic acid-capped Na(Y/Gd)F4:Yb(3+),Er(3+) NCs into aqueous solution, these water-dispersible NCs were dispersed into precursor electrospun solution containing CTAB. Na(Y/Gd)F4:Yb(3+),Er(3+)@HAp composite fibers were fabricated by the high temperature treatment of the electrospun Na(Y/Gd)F4:Yb(3+),Er(3+) NCs decorated precursor fibers. The biocompatibility test on MC 3T3-E1 cells using MTT assay shows that the HAp composite fibers have negligible cytotoxity, which reveals the HAp composite fibers could be a drug carrier for drug delivery. Because the contrast brightening is enhanced at increased concentrations of Gd(3+), the HAp composite fibers can serve as T1 magnetic resonance imaging contrast agents. In addition, the composites uptaken by MC 3T3-E1 cells present the UC luminescent emission of Er(3+) under the excitation of a 980 nm near-infrared laser. The above findings reveal Na(Y/Gd)F4:Yb(3+),Er(3+)@HAp composite fibers have potential applications in drug storage/release and magnetic resonance/UC luminescence imaging.

6-Aminohexanoic Acid를 이용하여 물에 분산되는 Maghemite 나노입자의 합성

This paper describes a simple route to synthesis of water-dispersible monodisperse maghemite () nanocrystals using 6-aminohexanoic acid (AHA) as a stabilizer. The water-dispersible nanocrystals with an average size of 5 nm were obtained simply by addition of into an octyl ether solution containing AHA at under argon condition. As-prepared AHA coated nanocrystals exhibited highly crystallinity and magnetic property while keeping a good dispersity in an aqueous phase. We also obtained water-dispersible AHA coated nanocrystals using ligand-exchange method, demonstrating that AHA can be a good candidate for preparing water-dispersible uniform metal oxide nanocrystals.

The use of polyethylenimine-modified graphene oxide as a nanocarrier for transferring hydrophobic nanocrystals into water to produce water-dispersible hybrids for use in drug delivery

In order to produce water-dispersible nanocrystals, including upconversion nanoparticles (UCNPs) which are the new generation fluorophores and magnetic nanoparticles (Fe3O4), a polyethylenimine-modified graphene oxide (PEI-GO) was used as a nanocarrier of nanocrystals, and PEI-GO-nanocrystal hybrids were prepared by transferring hydrophobic nanocrystals from an organic phase to water. Nanocrystals were anchored onto the hydrophobic plane of PEI-GO, which was confirmed by atomic force microscopy and electron microscopy. Molecular dynamics simulation further showed that hydrophobic interaction between PEI-GO and oleic acid molecules coated on the surface of the nanocrystals was the major driving force in the transfer process. The resulting hybrids had high stability in both water and physiological solutions, and combined the functionalities of the nanocrystals and PEI-GO, such as luminescence, superparamagnetism and drug delivery capability. Through π–π stacking interaction between PEI-GO-UCNP and an aromatic drug, PEI-GO-UCNP was able to load a water-insoluble anticancer drug, doxorubicin (DOX), with a superior loading capacity of 100wt.%. In addition, PEI-GO-UCNP did not exhibit toxicity on the human endothelial cells and PEI-GO-UCNP-DOX showed a high potency of killing cancer cells in vitro.

Spectroscopic characterization of ligands on the surface of water dispersible NaGdF4:Ln3+ nanocrystals

For electronic or biomedical applications it is desirable to have ligand-free water-dispersible nanocrystals (NCs). The commonly used FTIR spectroscopy often provides a direct evidence for molecules on the surface. In some cases, however, the strong bands of solvent molecules may obscure the peaks of surface bounded ligands. We show that in this regard the emission spectroscopy may be used as a more reliable probing tool. The relevant information can be obtained from emission and excitation spectra, emission decay times as well as from analysis of relative efficiency of excitation energy transfer from Gd3+ to Eu3+ ions. Using these methods we tested samples obtained by various synthetic routes and indicated that only nitrosonium tetrafluoroborate (NOBF4) removes successfully the organic ligands from the nanocrystals surface, yielding organic ligand-free NCs dispersible in aqueous solutions. The conclusions drawn from emission spectroscopy are useful for interpretation of results of FTIR, Raman and NMR studies. The detailed assignment of FTIR peaks for oleate-capped and oleate-free NCs is also provided. Finally, we point to the risk of drawing erroneous conclusions about colloidal stability of nanocrystals if refractive indexes of NCs and medium are similar.

EDTA Surface Capped Water-Dispersible ZnSe and ZnS:Mn Nanocrystals

ZnSe and ZnS:Mn nanocrystals were synthesized via the thermal decomposition of their corresponding organometallic precursors in a hot coordinating solvent (TOP/TOPO) mixture. The organic surface capping agents were substituted with EDTA molecules to impart hydrophilic surface properties to the resulting nanocrystals. The optical properties of the water-dispersible nanocrystals were analyzed by UV-visible and room temperature solution photoluminescence (PL) spectroscopy. The powders were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), and confocal laser scanning microscopy (CLSM). The solution PL spectra revealed emission peaks at 390 (ZnSe-EDTA) and 597 (ZnS:Mn-EDTA) nm with PL efficiencies of 4.0 (former) and 2.4% (latter), respectively. Two-photon spectra were obtained by fixing the excitation light source wavelengths at 616 nm (ZnSe-EDTA) and 560 nm (ZnS:Mn-EDTA). The emission peaks appeared at the same positions to that of the PL spectra but with lower peak intensity. In addition, the morphology and sizes of the nanocrystals were estimated from the corresponding HR-TEM images. The measured average particle sizes were 5.4 nm (ZnSe-EDTA) with a standard deviation of 1.2 nm, and 4.7 nm (ZnS:Mn-EDTA) with a standard deviation of 0.8 nm, respectively.

Microwave-Assisted Synthesis of Water-Dispersed CdTe Nanocrystals with High Luminescent Efficiency and Narrow Size Distribution

Water-dispersed nanocrystals with high photoluminescence quantum yield (PLQY) and narrow size distribution are desirable for a variety of bioapplications. In this report, we present a facile method assisted by microwave irradiation for rapidly synthesizing high-quality CdTe nanocrystals in aqueous phase. The PLQY of CdTe nanocrystals prepared in very short time (15 min) reaches as high as 82%, and the fwhm value is merely 27 nm meanwhile. Moreover, the PLQY is increased to a remarkable 98% after further amelioration through the illumination method. The key synthesis parameters (molar ratio of reagents, pH values, reaction temperature, and time) are fully discussed, and the optimum conditions are illuminated in this paper. In addition, the mechanism about microwave irradiation improving the quality of nanocrystals is discussed as well.

Magnetically superior and easy to handle L1-FePt nanocrystals

We report synthesis of monodisperse L10-FePt nanocrystals that are not only superior in magnetism but also easy to handle through being dispersible in solvents. Thanks to a thick SiO2 coating, the thermal treatment needed to form the L10 structure can be done even at 900°C without inducing coalescence and coarsening. The protecting shell was thereafter removed in a specific way that enabled us to recover the L10-FePt nanocrystals in a water dispersion. The SiO2-coated nanocrystals show a high coercivity of 18.5kOe at room temperature in spite of their core size of only 6.5nm in diameter, and the hysteresis loop of the water-dispersed nanocrystals, which were frozen under an external field, was almost rectangular indicating that their magnetic and structural orientation could be attained.

半導体ナノ粒子と蛍光体への応用

This article reviews the synthesis and the photoemission properties of semiconductor nanocrystals. The quantum size effects, the growth mechanism, the surface condition for high emission efficiency, and the single particle spectroscopy are described. The liquid-phase nanocrystallization is carried out either in water or organic solvent. Since the synthesis in water has an advantage over the sol-gel processing, we have intensively investigated the application. Glass phosphor with emission efficiencies higher than 50% were successfully prepared from the water dispersible nanocrystals by controlling the surface properties. The degree of photo-degradation is also estimated quantitatively.