One-Step Synthesis of Folic Acid Protected Gold Nanoparticles and Their Receptor-Mediated Intracellular Uptake

We report here a facile method to obtain folic acid (FA)-protected gold nanoparticles (Au NPs) by heating an aqueous solution of HAuCl4/FA in which FA acts as both the reducing and stabilizing agent. The successful formation of FA-protected Au NPs is demonstrated by UV/Vis spectroscopy, transmission electron microscopy (TEM), selected-area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). ne intracellular uptake of these nanoparticles is facilitated by HeLa cells overexpressing the folate reporter, which itself is significantly inhibited by free FA in a competitive assay as quantified by inductively coupled plasma mass spectroscopy (ICP-MS). This simple one-step approach affords a new perspective for creating functional nanomaterials, and the resulting biocompatible, functional Au NPs may find some prospective applications in various biomedical fields.

A novel urchinlike gold/platinum hybrid nanocatalyst with controlled size

In this paper, we have explored a simple and new strategy to obtain quasimonodisperse Au/Pt hybrid nanoparticles (NPS) with urchinlike morphology and controlled size and Pt shell thickness. Through changing the molar ratios of Au to Pt, the Pt shell thickness of urchinlike Au/Pt hybrid NPs could be easily controlled; through changing the size of Au NPs (the size was easily controlled from similar to 3 to similar to 70 nm via simple heating of HAuCl4-citrate aqueous solution), the size of urchinlike Au/Pt hybrid NPs could be facilely dominated. It should be noted that heating the solution (100 degrees C) was very necessary for obtaining three-dimensional (3D) urchinlike nanostructures while H2PtCl6 was added to gold NPs aqueous solution in the presence of reductant (ascorbic acid). The electrocatalytic oxygen reduction reaction (ORR, a reaction greatly pursued by scientists in view of its important application in fuel cells) and the electron-transfer reaction between hexacyanoferrate(III) ions and thiosulfate ions of urchinlike Au/Pt hybrid NPs were investigated. It is found that the as-prepared urchinlike Au/Pt hybrid NPs exhibited higher catalytic activities than that of similar to Pt NPs with similar size.

Different microstructures of ss-NaYF4 fabricated by hydrothermal process: Effects of pH values and fluoride sources

beta-NaYF4 microcrystals with a variety of morphologies, such as microrod, hexagonal microprism, and octadecahedron, have been synthesized via a facile hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra were used to characterize the samples. The intrinsic structural feature of beta-NaYF4 seeds and two important external factors, namely, the pH values in the initial reaction solution and fluoride sources, are responsible for shape determination of beta-NaYF4 microcrystals. It is found that the organic additive trisodium citrate (Cit(3-)) as a shape modifier has the dynamic effect by adjusting the growth rate of different facets under different experimental conditions, resulting in the formation of the anisotropic geometries of various beta-NaYF4 microcrystals. The possible formation mechanisms for products with various architectures have been presented. A systematic study on the photoluminescence of Tb3+-doped beta-NaYF4 samples with rod, prism, and octadecahedral shapes has shown that the optical properties of these phosphors are strongly dependent on their morphologies and sizes.

Highly uniform and monodisperse beta-NaYF4 : Ln(3+) (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprism crystals: Hydrothermal synthesis and luminescent properties

beta-NaYF4:Ln(3+) (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprisms with remarkably uniform morphology and size have been synthesized via a facile hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra as well as kinetic decays were used to characterize the samples. It is found that sodium citrate as a shape modifier introduced into the reaction system plays a critical role in the shape evolution of the final products. Furthermore, the shape and size of the products can be further manipulated by adjusting the molar ratio of citrate/RE3+ (RE represents the total amount of Y3+ and the doped rare earth elements such as Eu3+, Tb3+, Yb3+/Er3+, or Yb3+/Tm3+). Under the excitation of 397 nm ultraviolet light, NaYF4:xEu(3+) (x = 1.5, 5%) shows the emission lines of Eu3+ corresponding to D-5(0-3) -> F-7(J) (J = 0-4) transitions from 400 to 700 nm (whole visible spectral region) with different intensity, resulting in yellow and red down-conversion (DC) light emissions, respectively.

Comparative study of Ga2O3 : Dy3+ phosphors prepared by three methods

Trivalent dysprosium (Dy3+)-activated beta-gallium oxide (beta-Ga2O3) phosphors were synthesized by solid-state (SS), coprecipitation (CP), and citrate gel (CG) methods, respectively. The resulting beta-Ga2O3:Dy3+ phosphors were well characterized by X-ray diffraction, field-emission scanning electron microscopy (FESEM), and by photoluminescence and cathodoluminescence spectra. The phosphors prepared by different methods show different luminescence properties under the excitation of UV and low-voltage cathode rays. There exists an energy transfer from the beta-Ga2O3 host lattices to Dy3+, and the energy transfer efficiency was higher in the CG-derived phosphors than those of the SS- and CP-derived phosphors. Factors influencing the intensity of luminescence and the energy transfer efficiency from beta-Ga2O3 host to Dy3+ in beta-Ga2O3:Dy3+ phosphors were investigated in detail. It is shown that the CG method is the most respected process for the preparation of beta-Ga2O3:Dy3+ phosphors.

Alternate assemblies of polyelectrolyte functionalized carbon nanotubes and platinum nanoparticles as tunable electrocatalysts for dioxygen reduction

A novel method based on electrostatic layer-by-layer self-assembly (LBL) technique for alternate assemblies of polyelectrolyte functionalized multi-walled carbon nanotubes (MWNTs) and platinum nanoparticles (PtNPs) is proposed. The shortened MWNTs can be functionalized with positively charged poly(diallyldimethylammonium chloride) (PDDA) based on electrostatic interaction. Through electrostatic layer-by-layer assembly, the positively charged PDDA functionalized MWNTs (PDWNTs) and negatively charged citrate-stabilized PtNPs were alternately assembled on a 3-mercaptopropanesulfonic sodium (NIPS) modified gold electrode and also on other negatively charged surface, e.g. quartz slide and indium-tin-oxide (ITO) plate, directly forming the three-dimensional (3D) nanostructured materials. This is a very general and powerful technique for the assembling three-dimensional nanostructured materials containing carbon nanotubes (CNTs) and nanoparticles. Thus prepared multilayer films were characterized by ultraviolet-visiblenear-infrared spectroscopy (UV-vis-NIR), scanning electron microscopy (SEM) and cyclic voltammetry (CV). Regular growth of the mutilayer films is monitored by UV-vis-NIR.

An approach for synthesizing nanometer- to micrometer-sized silver nanoplates

Silver nanoplates with controlled size are synthesized by seed-mediated growth approach in the presence of citrate. These nanoplates are single crystal with a mean size of 25-1073 nm and thickness of ca. 10-22 nm. The optical in-plane dipole plasmon resonance bands of these plates can be tuned from 458 to 2400 nm. Control experiments have been explored for a more thorough understanding of the growth mechanism. It was found that the additional citrate ions in the growth solution were the key to controlling the aspect ratio of silver nanoplates. Similar to the surfactants or polymers in the solution, citrate ions could be likewise dynamically adsorbed on the growing silver nanoparticles and promote the two-dimensional growth of silver nanoparticles under certain conditions. Small silver seeds were also found to play an important role in the formation of large thin silver nanoplates, although the structure of them was not clear yet and needed further investigations.

Rapid synthesis of hexagon-shaped gold nanoplates by microwave assistant method

The microwave (MW)-based thermal process was applied to the preparation of hexagon-shaped gold nanoplates. The fort-nation of gold nanoplates occurs rapidly in a single step, carried out by directly heating a reaction mixture of HAuCl4 with sodium citrate in an MW reactor. And the gold nanoplates were characterized by UV-visible spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The experimental results indicated that the sizes and morphologies of the gold nanomaterials strongly depend both on the heating methods and molar ratio of HAuCl4 to sodium citrate in the initial reaction mixture. At the molar ratio 5 : 4 (HAuCl4 to sodium citrate), hexagonal nanoplates with large Au (111) crystallographic facet were preferentially synthesized by the MW assistant method.

Controllable synthesis of pd nanocatalysts for direct formic acid fuel cell (DFAFC) application: From pd hollow nanospheres to pd nanoparticles

The controllable synthesis of nanosized carbon-supported Pd catalysts through a surface replacement reaction (SRR) method is reported in this paper. Depending on the synthesis conditions the Pd can be formed on Co nanoparticles surface in hollow nanospheres or nanoparticles structures. Citrate anion acts as a stabilizer for the nanostructures, and protonation of the third carboxyl anion and hence the nanostructure and size of the resulting catalysts are controlled via the pH of the synthesis solution. Pd hollow nanospheres, containing smaller Pd nanoparticles, supported on carbon are formed under the condition of pH 9 reaction solution. Meanwhile, highly dispersed carbon-supported Pd nanoparticles can be formed with higher pH (pH >= 10). All catalysts prepared through the SRR method show enhanced activities for the HCOOH electro-oxidation reaction compared to catalysts reduced by NaBH4.

Synthesis and structural characterization of new tungsten(VI) complexes with polycarboxylate ligands

The reactions of (NH4)(2)WS4 and three polycarboxylate ligands {including nitrilotriacetate (nta(3-)), citrate (Hcit(3-)) and ethylenediaminetetra acetate (EDTA(4-))} in H2O/EtOH at ambient temperature have resulted in three new trioxotungsten (VI) complexes, K-3[WO3(nta)]center dot H2O 1, (NH4)(4)[WO3(cit)]center dot 2 H2O 2 and K-2(NH4)(2)[W2O6(EDTA)]center dot 4H(2)O 3, respectively. These three complexes have been characterized by IR, XPS, TGA-DTA, H-1 and C-13 NMR spectroscopy. And their structures have been determined by X-ray crystallographic studies, which confirm that I and 2 are mononuclear compounds and 3 is a binuclear compound. Each tungsten atom in 1-3 is coordinated to three unshared oxygen atoms, which adopt fac stereochemistry, while the remaining fac positions are occupied by three atoms from the ligands. The electrochemical properties of 2 and 3 have been investigated.

Two- and three-dimensional Au nanoparticle/CoTMPyP self-assembled nanotructured materials: Film structure, tunable electrocatalytic activity, and plasmonic properties

Two- and three-dimensional Au nanoparticle/[tetrakis(N-methylpyridyl)porphyrinato]cobalt (CoTMPyP) nanostructured materials were prepared by "bottom-up" self-assembly. The electrocatalytic and plasmonic properties of the Au nanoparticle/CoTMPyP self-assembled nanostructured materials (abbreviated as Au/CoTMPyP SANMs) are tunable by controlled self-assembly of the An nanoparticles and CoTMPyP on indium tin oxide (ITO) electrode. The electrocatalytic activity of the Au/CoTMPyP SANMs can be tuned in two ways. One way is that citrate-stabilized An nanoparticles are positioned first on ITO surface with tunable number density, and then positively charged CoTMPyP ions are planted selectively on these gold sites. The other way is that An nanoparticles and CoTMPyP are deposited by virtue of layer-by-layer assembly, which can also tune the amount of the as-deposited electrocatalysts. FE-SEM studies showed that three-dimensional SANMs grow in the lateral expansion mode, and thermal annealing resulted in both surface diffusion of nanoparticles and atomic rearrangement to generate larger gold nanostructures with predominant (I 11) facets.

Comparative study on the luminescent properties of Y3Al5O12 : RE3+ (RE : Eu, Dy) phosphors synthesized by three methods

By using metal nitrates and oxides as the starting materials, Y3Al5O12 (YAG) and YAG: RE3+ (RE: Eu, Dy) powder phosphors were prepared by solid state (SS), coprecipitation (CP) and citrate-gel (CG) methods, respectively. The resulting YAG based phosphors were characterized by XRD and photoluminescent excitation and emission spectra as well as lifetimes. The purified crystalline phases of YAG were obtained at 800degreesC (CG) and 900degreesC (CP and SS), respectively. Great differences were observed for the excitation and emission spectra of Eu3+ and Dy3+ between crystalline and amorphous states of YAG, and their emission intensities increased with increasing the annealing temperature. At an identical annealing temperature and doping concentration, the Eu3+ and Dy3+ showed the strongest and weakest emission intensity in CP- and CG-derived YAG phosphors, respectively. The poor emission intensity for CG-derived phosphors is mainly caused by the contamination organic impurities from citric acid in the starting materials. Furthermore, the lifetimes for the samples derived from CG and CP routes are shorter than those derived from the SS route.

Synthesis and characterization of Y0.9-xGdxEu0.1BO3 phosphors by spray drying process

Y0.9-xGdxEu0.1BO3 phosphors were synthesized by spray drying (SD) method, and the results were compared with those by conventional solid state (SS) and citrate gel (GC) methods. The PL intensity of phosphors increases with the increase of x value in Y0.9-xGdxEu0.1BO3 (prepared by SD) due to an energy migration process like Gd3+ - (Gd3+)(n) - Eu3+ occurred in the material. Compared with the latter two methods, the phosphor particles prepared by spray drying method have a better morphology, such as homogeneous size (about 1similar to3 mum) with spherical shape and smooth surface. Furthermore, the spray drying-derived phosphors have higher photoluminescence (PL) intensity than those by citrate gel method, but still a little lower than those by the solid state method.

Computer simulation of Gd(III) speciation in human interstitial fluid

The speciation and distribution of Gd(III) in human interstitial fluid was studied by computer simulation. The results show that at the background concentration, all the Gd(III) species are soluble and no precipitates appear. However as the total concentration of Gd(III) rises above 2.610 x 10(-9) mol/l the insoluble species become predominant. GdPO4 is formed first as a precipitate and then Gd-2(CO3)(3). Among soluble species, free Gd(III), [Gd(HSA)], [Gd(Ox)] and the ternary complexes of Gd(III) with citrate as the primary ligand are main species when the total concentration of Gd(III) is below 2.074 x 10(-2) mol/l. With the total concentration of Gd(III) further rising, [Gd-3(OH)(4)] begins to appear and gradually becomes a predominant species.

Surface-enhanced Raman scattering studies on aggregated silver nanoplates in aqueous solution

Four different sizes of citrate-protected silver nanoplates with the corresponding in-plane dipole resonance band at 530, 619, 778, and 858 nm, respectively, are synthesized for surface-enhanced Raman scattering (SERS) study. Their aggregation behaviors are monitored by use of UV-vis spectroscopy. During the aggregation process, a marked red shift of the in-plane dipole resonance of silver nanoplates is observed, whereas other resonance modes of them only have small alterations in the site or intensity. Aggregated silver nanoplates can serve as active SERS substrates with an enhancement factor of about 4.5 x 10(5) using 2-aminothiophenol as a probing molecule. The SERS performance of silver nanoplates is even superior to the commonly used Lee-Meisel silver colloid, making them very attractive for SERS applications.