Clear Colloidal Solutions Research Articles

Correction to "Potential Eye Drop Based on a Calix[4]arene Nanoassembly for Curcumin Delivery: Enhanced Drug Solubility, Stability, and Anti-Inflammatory Effect.

Curcumin is an Indian spice with a wide spectrum of biological and pharmacological activities but poor aqueous solubility, rapid degradation, and low bioavailability that affect medical benefits. To overcome these limits in ophthalmic application, curcumin was entrapped in a polycationic calix[4]arene-based nanoaggregate by a simple and reproducible method. The calix[4]arene–curcumin supramolecular assembly (Calix–Cur) appeared as a clear colloidal solution consisting in micellar nanoaggregates with size, polydispersity index, surface potential, and drug loading percentage meeting the requirements for an ocular drug delivery system. The encapsulation in the calix[4]arene nanoassembly markedly enhanced the solubility, reduced the degradation, and improved the anti-inflammatory effects of curcumin compared to free curcumin in both in vitro and in vivo experiments. Calix–Cur did not compromise the viability of J774A.1 macrophages and suppressed pro-inflammatory marker expression in J774A.1 macrophages subjec...

Potential Eye Drop Based on a Calix[4]arene Nanoassembly for Curcumin Delivery: Enhanced Drug Solubility, Stability, and Anti-Inflammatory Effect.

Curcumin is an Indian spice with a wide spectrum of biological and pharmacological activities but poor aqueous solubility, rapid degradation, and low bioavailability that affect medical benefits. To overcome these limits in ophthalmic application, curcumin was entrapped in a polycationic calix[4]arene-based nanoaggregate by a simple and reproducible method. The calix[4]arene-curcumin supramolecular assembly (Calix-Cur) appeared as a clear colloidal solution consisting in micellar nanoaggregates with size, polydispersity index, surface potential, and drug loading percentage meeting the requirements for an ocular drug delivery system. The encapsulation in the calix[4]arene nanoassembly markedly enhanced the solubility, reduced the degradation, and improved the anti-inflammatory effects of curcumin compared to free curcumin in both in vitro and in vivo experiments. Calix-Cur did not compromise the viability of J774A.1 macrophages and suppressed pro-inflammatory marker expression in J774A.1 macrophages subjected to LPS-induced oxidative stress. Histological and immunohistochemical analyses showed that Calix-Cur reduced signs of inflammation in a rat model of LPS-induced uveitis when topically administrated in the eyes. Overall, the results supported the calix[4]arene nanoassembly as a promising nanocarrier for delivering curcumin to anterior ocular tissues.

Influence of surface coating on structural, morphological and optical properties of upconversion-luminescent LaF3:Yb/Er nanoparticles

LaF3:Yb/Er (core), LaF3:Yb/Er@LaF3 (core/shell) and LaF3:Yb/Er@LaF3@SiO2 (core/shell/SiO2) nanoparticles were synthesized using citric-acid-based complexation process. X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray analysis, optical absorption, band-gap energy (E g), Fourier transform infrared and upconversion emission spectroscopy were employed to investigate the structural, morphological and optical properties of the synthesized core and core/shell/SiO2 nanoparticles. These core/shell/SiO2 nanoparticles can be well dispersed in aqueous solvents to form clear colloidal solution. The optical band-gap energy was decreased after shell formation due to increase in the crystalline size. The growth of an inactive and porous silica layers simultaneously on the surface of luminescent core-nanoparticles resulting an increase in average crystalline size of the nanoparticles. As-prepared inert shell-coated core/shell nanoparticles show intensive upconversion-luminescence as compared to the seed-core and silica-surface-modified core/shell/SiO2 nanoparticles because luminescent ions (Yb3+ and Er3+) ions located at the particle surface were protected from the non-radiative decay arising from surface dangling bonds and capping agent. However, our study revealed that there was only a slight reduction in upconversion efficiency for the silica-modified core/shell nanoparticles, indicating that upconversion properties of the upconversion nanoparticles are largely preserved in the core/shell/SiO2 nanoparticles. Absorption and upconversion-luminescence properties were examined for future application in the development of optical devices as well as optical bioprobes.

Structural and photoluminescence properties of Tb-doped CaMoO4 nanoparticles with sequential surface coatings

The crystal structure, surface chemistry and optical properties of Tb-doped CaMoO4 (CaMoO4:Tb) nanoparticles and the sequentially coated CaMoO4:Tb@CaMoO4 and CaMoO4:Tb@CaMoO4@SiO2 nanostructures have been characterized by X-ray diffraction (XRD), Thermo-gravimetric analysis (TGA), UV–vis absorption (UV–Vis), Fourier- transform infrared spectroscopy (FT-IR), Raman spectroscopy and Photoluminescence spectroscopy. The XRD results indicate that the obtained CaMoO4:Tb is sheelite tetragonal structure and well crystallized at 150 °C. The particle size increases from 21 to 48 nm by sequential coating of CaMoO4 and silica formation around the surface of core nanoparticles. These nanocrystals were well-dispersed in aqueous and non-aqueous solvents to form clear colloidal solutions. The colloidal solutions of three samples show well characteristic optical absorption band in UV/Visible region. The surface coating on core particles will significantly influence the structural and photoluminescence properties. The as-prepared core nanoparticles showed high photoluminescence as compared to surface coated core–shell nanoparticles because Tb3+ ion located at the particle surface. Absorption and luminescence spectroscopic studies have been examined for future application in the development of optical devices as well as optical bioprobes.

Influence of surface coating on structural and photoluminescent properties of CaMoO₄:Pr nanoparticles.

CaMoO4:Pr(core), CaMoO4:Pr@CaMoO4 (core/shell) and CaMoO4:Pr@CaMoO4@SiO2 (core/shell/shell) nanoparticles were synthesized using polyol method. X-ray diffraction (XRD), thermogravimatric analysis (TGA), UV-vis absorption, optical band gap energy analysis, Fourier transform infrared (FTIR), FT-Raman and photoluminescence (PL) spectroscopy were employed to investigate the structural and optical properties of the synthesized core and core/shell nanoparticles. The results of the XRD indicate that the obtained core, core/shell and core/shell/shell nanoparticles crystallized well at ~150 °C in ethylene glycol (EG) under urea hydrolysis. The growth of the CaMoO4 and SiO2 shell (~12 nm) around the CaMoO4:Pr core nanoparticles resulted in an increase of the average size of the nanopaticles as well as in a broadening of their size distribution. These nanoparticles can be well-dispersed in distilled water to form clear colloidal solutions. The photoluminescence spectra of core, core/shell and core/shell/shell nanoparticles show the characteristic charge transfer emission band of MoO4 (2-) (533 nm) and Pr(3+) 4f(2) → 4f(2), with multiple strong (3)H4 → (3)P2, (1)D2 → (3)H4 and (3)P0 → (3) F2 transitions located at ~490, 605 and 652 nm, respectively. The emission intensity of the CaMoO4:Pr@CaMoO4 core/shell and CaMoO4:Pr@CaMoO4@SiO2 core/shell/shell nanoparticles increased ~4.5 and 1.7 times,respectively, with respect to those of CaMoO4:Pr core nanoparticles. This indicates that a significant amount of nonradiative centers existing on the surface of CaMoO4:Pr@CaMoO4 core/shell nanoparticles can be eliminated by the shielding effect of CaMoO4 shells.

Synthesis of water-soluble luminescent LaVO4:Ln3+ porous nanoparticles

Water-soluble luminescent Eu3+ and Tb3+-doped LaVO4 porous nanoparticles were synthesized by co-precipitation method. X-ray diffraction (XRD), Field emission-transmission electron microscopy (FE-TEM), energy dispersive X-ray analysis, Fourier transform infrared spectroscopy, UV/Vis absorption, and photoluminescence spectroscopic techniques were employed to characterize the structure and morphology of as-prepared products. The results of the XRD confirm the formation of well-crystallized LaVO4 phase with a tetragonal zircon structure. The TEM images illustrate that the as-formed Eu3+ and Tb3+-doped LaVO4 nanoparticles have irregular spherical shape, hairy nanoporous structures with an average particle size 50–130 nm. These nanoparticles were well-dispersed in polar and non-polar organic solvents to form clear colloidal solutions. The colloidal solutions of Eu3+ and Tb3+-doped zircon-type LaVO4 nanoparticles show the most dominant characteristic emissions (hypersensitive transitions) of Eu3+ at 615 nm (5 D 0 → 7 F 2) and Tb3+ at 543 nm (5 D 4 → 7 F 5), respectively, as the result of an energy transfer from the VO4 3− to luminescent metal ions activators. Compared with other-shape nanocrystals, the luminescence intensity of the irregular hairy spherical porous-like nanoparticles are obviously enhanced. It therefore, suggests that we could obtain function-improved materials by tailoring the size and shape of the LaVO4:Ln3+ nanostructures that are very suitable for use in biological applications, such as protein-labeling, drug delivery, and fluorescent bioprobes.

Controllable Multicolor Upconversion Luminescence of Lanthanide Doped NaGdF4 Nanocrystals Through Single Laser Excitation at 980 nm

Room temperature multicolor Upconversion (UC) luminescence in Yb3+, Tm3+, Er3+ ions doped NaGdF4 nanocrystals have been successfully synthesized by a hydrothermal method. As-prepared nanocrystals are highly crystalline and well-dispersed in cyclohexane to form stable and clear colloidal solutions, which demonstrates strong emission properties with a single laser excitation at 980 nm. The multicolor light consists of blue, green, and red UC radiations that correspond to transitions 1G4 --> 3H6 of Tm3+, 2H(11/2)/4S(3/2) --> 4I(15/2), and 4F(9/2) --> 4I(15/2) of Er3+ ions, respectively. The UC mechanisms were proposed based on spectral, kinetic, and pump power dependence analyses.

Synthesis and characterization of Mn doped ZnS d-dots with controllable dual-color emissions

High-quality Mn doped ZnS d-dots were successfully synthesized via an alternative route based on the solvothermal method using oleic acid as stabilizing agent. X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as photoluminescence (PL) spectra were employed to characterize the obtained samples. The as-obtained d-dots are highly crystalline and uniform sized, and they can be well dispersed in hexane to form stable and clear colloidal solution. The optical properties of the d-dots with different Mn doped concentration are investigated in detail. The Mn doped ZnS d-dots have two emission bands, including surface state emission (blue) and Mn emission (orange), which are both sensitivity to the Mn doped concentration. By varying the Mn doped concentration, the relative PL intensities of dual-color emissions can be well manipulated, showing their application in tunable color output. Furthermore, a subsequent ligand exchange has been introduced to give the d-dots hydrophilic surfaces, which are favorable for biological applications.

Preparation of clear colloidal solutions of detonation nanodiamond in organic solvents

Highly transparent colloidal solutions of detonation nanodiamonds in organic solvents such as tetrahydrofuran (THF), methyl ethyl ketone (MEK) and acetone were attained in this investigation through an easy process, in which the detonation nanodiamond powder was oxidized at 420 °C for 1.5 h and then dispersed into solvents by beads-milling with the addition of the surfactant, oleylamine (OLA). The results of both Fourier transform infrared spectroscopy and zeta potential measurements confirm that a readily apparent number of Lewis acid sites composed of mainly carboxylic acid and cyclic acid anhydrides were derived on the surface of thermally oxidized nanodiamond (T-ND). This acid sites-derived T-ND is chemically active, favoring the formation of charge-transfer complexes with the amino-containing surfactants such as OLA and octadecylamine (ODA). After being dispersed with one of the surfactants, OLA or ODA, the T-ND shows good dispersion stability in organic solvents; however, the dispersion efficiency of the saturated ODA is not as good as that of the unsaturated OLA. By using the dispersant OLA, accompanied with de-agglomeration by beads-milling, a clear colloidal solution of T-ND in solvents of THF, MEK or acetone can be easily attained and stabilized for at least 3 months.

Shape and Phase-Controlled Synthesis of KMgF3 Colloidal Nanocrystals via Microwave Irradiation

In this paper, we present a facile one-step route to controlled synthesis of colloidal KMgF3 nanocrystals via the thermolysis of metal trifluoroacetate precursors in combined solvents (OA/OM) using microwave irradiation. X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric and differential thermal analysis (TG-DTA), Fourier transform infrared (FT-IR) spectra, and photoluminescence (PL) spectra were employed to characterize the samples. Only through the variation of the OA/OM ratio, can the phase and shape of nanocrystals be readily controlled, resulting in the formation of well-defined near-spherical nanoparticles, and nanoplates of cubic-phased KMgF3, as well as nanorods of tetragonal-phased MgF2, and a possible mechanism has been proposed to elucidate this effect. Furthermore, all these samples in this system can be well dispersed in nonpolar solvents such as cyclohexane to form stable and clear colloidal solutions, due to the successful coating of organic surfactants (OA/OM) on the nanocrystal surface. Additionally, we demonstrate the feasibility of incorporating Tb3+ ions into the KMgF3 host via this method, which shows strong green emission corresponding to the characteristic 5D4−7FJ (J = 3, 4, 5, 6) emission of Tb3+ ions, which can be potentially used as labels for biological molecules.

Solvothermal synthesis of well-dispersed NaMgF 3 nanocrystals and their optical properties

Complex metal fluoride NaMgF 3 nanocrystals were successfully synthesized via a solvothermal method at a relatively low temperature with the presence of oleic acid, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectra, photoluminescence (PL) excitation and emission spectra, respectively. In the synthetic process, oleic acid as a surfactant played a crucial role in confining the growth and solubility of the NaMgF 3 nanocrystals. The as-prepared NaMgF 3 nanocrystals have quasi-spherical shape with a narrow distribution. A possible formation mechanism of the nanocrystals was proposed based on the effect of oleic acid. The as-prepared NaMgF 3 nanocrystals are highly crystalline and well-dispersed in cyclohexane to form stable and clear colloidal solutions, which demonstrate a strong emission band centered at 400 nm in photoluminescence (PL) spectra compared with the cyclohexane solvent. The PL properties of the colloidal solutions of the as-prepared nanocrystals can be ascribed to the trap states of surface defects.

Uniform Colloidal Alkaline Earth Metal Fluoride Nanocrystals: Nonhydrolytic Synthesis and Luminescence Properties

In this paper, we present a facile and general synthetic route to high-quality alkaline earth metal fluoride (AEF2, AE = Ca, Sr, Ba) nanocrystals and CaF2:Tb(3+) nanocrystals based on the thermal decomposition of corresponding trifluoroacetate precursors in hot oleylamine. X-ray diffraction, transmission electron microscopy, thermogravimetric and differential thermal analysis, Fourier transform infrared spectra, photoluminescence spectra, and kinetic decays were employed to characterize the samples. The use of single-source precursors plays an important role in the formation of high-quality AEF 2 nanocrystals, and the formation process is demonstrated in detail. The obtained AEF2 nanocrystals are nearly monodisperse in size and highly crystalline, and they can be well dispersed in nonpolar solvents to form stable and clear colloidal solutions, which all display purple emissions under ultraviolet excitation due to the numerous surface defects of nanocrystals with large surface/volume ratios. Furthermore, we demonstrate the feasibility of introducing Tb(3+) ions into the CaF2 host via this method, which shows strong green emission corresponding to the characteristic (5)D4-(7)F(J) (J = 3, 4, 5, 6) emission of Tb(3+) ions, which can be potentially used as labels for biological molecules.

Synthesis and characterization of highly luminescent CuInS 2 and CuInS 2/ZnS (core/shell) nanocrystals

High-quality CuInS 2/ZnS (core–shell) nanocrystals (NCs) were synthesized via a colloidal solvent process and characterized for their optical properties by UV–vis, room temperature solution photoluminescence (PL) spectroscopy, and further obtained powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and dynamic light scattering (DLS). The obtained CIS and CIS/ZnS core/shell NCs are quasimonodisperse with an average particle size of 2.4 and 4.6 nm, respectively. All of the as-synthesized NCs can be well dispersed in toluene or hexane to form stable and clear colloidal solutions, which show strong visible emission (blue for CIS/ZnS core/shell NCs) under UV excitation. The growth of a ZnS shell on CIS NCs, that is, the formation of CIS/ZnS core/shell NCs, resulted in an impact enhancement in the PL intensity compared to that of bare CIS NCs due to the eliminated surface defects and the reduced lattice mismatch between the core and shell materials. A dramatic increase of the PL intensity can be obtained from the ZnS-capped CIS with respect to that of the bare CIS NCs.

Solvothermal synthesis of well-dispersedMF2 (M = Ca,Sr,Ba) nanocrystals and their optical properties

MF2 (M = Ca,Sr,Ba) nanocrystals (NCs) were synthesized via a solvothermal process in the presence of oleic acidand characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM),Fourier transform infrared (FT-IR) spectra, UV/vis absorption spectra, photoluminescence(PL) excitation and emission spectra, and lifetimes, respectively. In the synthetic process,oleic acid as a surfactant played a crucial role in confining the growth and solubility of theMF2 NCs. Theas-prepared CaF2, SrF2 and BaF2 NCs present morphologies of truncated octahedron, cube and sheet in a narrowdistribution, respectively. Possible growth mechanisms were proposed to explain theseresults. The as-prepared NCs are highly crystalline and can be well dispersed incyclohexane to form stable and clear colloidal solutions, which demonstrate strong emissionbands centred at 400 nm in photoluminescence (PL) spectra compared with the cyclohexanesolvent. The PL properties of the colloidal solutions of the as-prepared NCs can be ascribedto the trap states of surface defects.

Near infrared luminescence behavior of organic–inorganic nanohybrid films containing Er 3+ doped YbPO 4 nanoparticles

Er 3+ doped YbPO 4 nanoparticles incorporated organic–inorganic nanohybrid material was prepared. Er 3+ doped YbPO 4 nanoparticles, which were synthesized in a high-boiling mixture solution of tributyl phosphate, trihexylamine, and diphenylether, had a good crystalline structure of tetragonal xenotime phase and an average particle size of about 3–4 nm. Clear colloidal solution containing the nanoparticles was dispersed homogeneously into the silica-based resin prepared by non-hydrolytic sol–gel process. Crack-free films with a thickness of 800 μm were fabricated by a single spin-coating action from the nanohybrid material. Highly transparent and uniform films without phase separation were obtained, even after incorporating 30 wt.% of Er 3+ doped YbPO 4 nanoparticles into the resin. The films showed a strong and broad emission at 1550 nm due to the 4I 13/2→ 4I 15/2 transition of Er 3+ ion.

Nonaqueous Synthesis of Colloidal ZnGa2O4Nanocrystals and Their Photoluminescence Properties

Colloidal ZnGa2O4 nanocrystals with a mean size of about 7 nm were successfully synthesized by using a non-aqueous sol–gel method.The nanocrystals can easily be dispersed in chloroform to form stable colloids without the use of any additional stabilizers. Strong blue fluorescence was observed from the clear colloidal solution of the nanocrystals under UV light.

Synthesis and Characterization of High-Quality ZnS, ZnS:Mn2+, and ZnS:Mn2+/ZnS (Core/Shell) Luminescent Nanocrystals

High-quality ZnS, ZnS:Mn2+, and ZnS:Mn2+/ZnS (core/shell) nanocrystals (NCs) were synthesized via a high-boiling solvent process and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra. The monodisperse ZnS NCs (size = 8 nm), which self-assembled into several micrometer-sized domains, were achieved by adopting poly(ethylene glycol) (PEG) in the reaction process (without using a size-selection process). The obtained ZnS:Mn2+ and ZnS:Mn2+/ZnS core/shell NCs are highly crystalline and quasimonodisperse with an average particle size of 6.1 and 8.4 nm, respectively. All of the as-formed NCs can be well dispersed in hexane to form stable and clear colloidal solutions, which show strong visible emission (blue for ZnS and red-orange for ZnS:Mn2+ and ZnS:Mn2+/ZnS) under UV excitation. The growth of a ZnS shell on ZnS:Mn2+ NCs, that is, the formation of ZnS:Mn2+/ZnS core/shell NCs, resulted in a 30% enhancement in the PL intensity with respect to that of bare ZnS:Mn2+ NCs due to the elimination of the surface defects.

A Facile Synthesis and Photoluminescent Properties of Redispersible CeF3, CeF3:Tb3+, and CeF3:Tb3+/LaF3 (Core/Shell) Nanoparticles.

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A Facile Synthesis and Photoluminescent Properties of Redispersible CeF3, CeF3:Tb3+, and CeF3:Tb3+/LaF3 (Core/Shell) Nanoparticles

CeF3, CeF3:Tb3+, and CeF3:Tb3+/LaF3 (core/shell) nanoparticles were prepared by the polyol method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), UV−vis absorption spectra, photoluminescence (PL) spectra, and lifetimes. The results of XRD indicate that the obtained CeF3, CeF3:Tb3+, and CeF3:Tb3+/LaF3 (core/shell) nanoparticles crystallized well at 200 °C in diethylene glycol (DEG) with a hexagonal structure. The TEM images illustrate that the CeF3 and CeF3:Tb3+ nanoparticles are spherical with a mean diameter of 7 nm. The growth of the LaF3 shell around the CeF3:Tb3+ core nanoparticles resulted in an increase of the average size (11 nm) of the nanopaticles as well as in a broadening of their size distribution. These nanocrystals can be well-dispersed in ethanol to form clear colloidal solutions. The colloidal solutions of CeF3 and CeF3:Tb3+ show the characteristic emission of Ce3+ 5d−4f (320 nm) and Tb3+ 5D4−7FJ (J = 6−3, with 5D4−7F...

Blue, green, and red upconversion emission from lanthanide-doped LuPO4 and YbPO4 nanocrystals in a transparent colloidal solution.

Light converter: The emission of visible light (Vis) upon excitation in the near-infrared (NIR) has been observed for the first time in a transparent solution. Excitation at 975 nm (marked red in the picture) of optically clear colloidal solutions of LuPO4:Yb3+, Tm3+, and YbPO4:Er3+ nanocrystals in chloroform leads to visible upconversion luminescence in the blue, green, or red spectral regions.