Shape-controllable synthesis of hydrophilic NaLuF4:Yb,Er nanocrystals by a surfactant-assistant two-phase system

Water-soluble upconversion nanoparticles (UCNPs) were prepared by a one-pot procedure in a two-phase reacting system. Four kinds of surfactants were tested in the synthesis process as capping agent to tune size and morphology of nanocrystals. Nanoparticles (approximately 70 nm) and rods (400 nm and 2.5 μm) were synthesized, respectively. Then, Fourier transform infrared spectroscopy analysis confirmed the successful linking between UCNP surface and surfactant. Ionic liquids (ILs) and surfactants participated in synthesis process together, competing with each other to cap on UCNPs. ILs still led the competition of capping, while surfactants worked as cooperative assistants to develop functional surface. Further characterizations such as high-resolution transmission electron microscopy and X-ray diffraction indicated the changes in crystallization and phase transformation under the influence of surfactants. In addition, the growth mechanism of nanocrystals and upconversion fluorescence luminance was also investigated in detail. At last, the cytotoxicity of UCNPs was evaluated, which highly suggest that these surface-functionalized UCNPs are promising candidates for biomedical engineering.     

Facile preparation of gold nanoparticle with diarylethene polymers by disodium malate and its photoreversible optical properties

We have developed a synthetic procedure of gold nanoparticle covered with polystyrene (Au-poly(St)) using organic acid salts, followed by a ligand exchange reaction. First, various chain lengths of polystyrenes (poly(St)s) bearing thiol-end group were used as the covering agent of gold nanoparticle prepared by reduction using trisodium citrate. The resulting nanoparticles with ca. 13 nm diameter were dispersed in toluene when the molecular weight of the ligand poly(St) is larger than 1200. Larger sized Au-poly(St) could be obtained using disodium malate instead of the citrate. The colloidal gold nanoparticle with ca. 40 nm diameter was easily prepared only by changing the reducing agent. Finally, we have demonstrated to prepare larger sized gold nanoparticle covered with a photochromic diarylethene polymer (Au-poly(DE)) that shows large change in local surface plasmon resonance absorption according to the photochromic reaction even in a solution.     

Development of biocompatible NaGdF4: Er3+, Yb3+ upconversion nanoparticles used as contrast agents for bio‐imaging

Upconversion nanoparticles with special fluorescence and magnetic properties have been considered an alternative contrast agent for multiple bio‐imaging techniques. It is important to understand the effects of the surface properties and dosage of upconversion nanoparticles on both the magnetic resonance (MRI) image and the photoluminescence spectrum. Here, NaGdF₄: Er³⁺, Yb³⁺ upconversion nanoparticles (UCNPs) modified with amine functional group were produced through a one‐pot thermal decomposition. The average length of the cubic UCNPs is estimated at 53 ±13 nm. The effect of the dosage of amine modified UCNPs on the MRI image is investigated. The T₁ and T₂ relaxivities of the amine modified UCNPs in agarose gel at 3 T are r₁ = 6.79 ±0.14 and r₂ = 17.0 ±0.18 (mmol/L)^?1 s^?1, which are comparable to the relaxivities of commercially available MRI contrast agents. In addition, the photoluminescence of the amine modified UCNPs at low concentrations < 150 µg/mL are further investigated with the excitation wavelength (λ_ex) at 980 nm. The internalization of the amine modified UCNPs cultured with human umbilical vascular endothelial cells (HUVEC) is observed by the fluorescence imaging. Meanwhile, T₁‐weighted MRI imaging of HUVEC cells treated with amine modified UCNPs at 10 µg/mL can be obtained. No significant toxic effect on cells is found when the concentration of the amine modified UCNPs is < 300 µg/mL. This study indicates that a low concentration of amine‐modified NaGdF₄: Er³⁺, Yb³⁺ UCNPs can be used as the contrast agent for both fluorescence imaging and magnetic resonance imaging.     

Recent progress in the green synthesis of rare-earth doped upconversion nanophosphors for optical bioimaging from cells to animals

Rare-earth doped upconversion nanophosphors (UCNPs), which convert low energy near-infrared (NIR) photons into high energy photons such as ultraviolet, visible light and NIR light, have found various applications in optical bioimaging. In this review article, we summarize recent advances in the synthesis and applications of UCNPs achieved by us and other groups in the past few years. The approaches for the synthesis of UCNPs are presented, with an emphasis on the role of green chemistry in the advancement of this field, followed by a focused overview on their latest applications in optical bioimaging from subcellular structures through cells to living animals. Challenges and opportunities for the use of UCNPs in biomedical diagnosis and therapy are discussed.     

Functionalization of manganite nanoparticles and their interaction with biologically relevant small ligands: picosecond time-resolved FRET studies

We report molecular functionalization of the promising manganite nanoparticles La0.67Sr0.33MnO3 (LSMO) for their solubilization in aqueous environments. The functionalization of individual NPs with the biocompatible citrate ligand, as confirmed by Fourier transform infrared (FTIR) spectroscopy, reveals that citrates are covalently attached to the surface of the NPs. UV-VIS spectroscopic studies on the citrate functionalized NPs reveals an optical band in the visible region. Uniform size selectivity (2.6 nm) of the functionalization process is confirmed from high resolution transmission electron microscope (HRTEM). In the present study we have used the optical band of the functionalized NPs to monitor their interaction with other biologically important ligands. F?rster resonance energy transfer (FRET) of a covalently attached probe 4-nitrophenylanthranilate (NPA) with the capped NPs confirm the attachment of the NPA ligands to the surface functional group (-OH) of the citrate ligand. The FRET of a DNA base mimic, 2-aminopurine (2AP), with the NPs confirms the surface adsorption of 2AP. Our study may find relevance in the study of the interaction of individual manganite NPs with drug/ligand molecules.     

Surface passivation of CdSe-TOPO quantum dots by poly(acrylic acid): solvent sensitivity and photo-induced emission in water

The principal available methods for the preparation of high quality CdSe quantum dots (QDs) are based on organic ligands such as tri-n-octylphosphine oxide (TOPO) which lead to non-water soluble nanocrystal QDs. As most biological interactions take place in aqueous media, much effort has been made on preparation of water soluble QDs. In this report, the water soluble CdSe QDs were prepared via a ligand exchange process between organic soluble CdSe-TOPO quantum dots and poly(acrylic acid). The poly(acrylic acid) (PAA) can attach onto the surface of CdSe-TOPO quantum dots in a ligand exchange process to make water-soluble CdSe-PAA complexes. In spite of CdSe-TOPO QDs, the resultant CdSe-PAA QDs are soluble in polar solvents such as methanol or water. Optical properties of CdSe-PAA QDs in several solvents showed that the emission intensity of QDs was mainly decreased in protic solvents such as methanol or water. The TEM images of dots in different solvents were examined and some aggregation of dots was found in protic solvents. In comparison with PAA, the addition of PDMAEMA to the solution of CdSe-TOPO QDs in THF increased the emission intensity of QDs. Furthermore, we found that the entitled ligand exchange process was fast and conjugation process completed at short time intervals. The UV-irradiation of the CdSe-PAA conjugate in water showed that the emission was amplified by increasing the irradiation time.     

Cu2ZnSnSe4 nanocrystals capped with S2? by ligand exchange: utilizing energy level alignment for efficiently reducing carrier rec ombination

In this work, we employed a convenient one-step synthesis method for synthesizing Cu₂ZnSnSe₄ (CZTSe) nanocrystals (NCs) in an excess selenium environment. This excess selenium situation enhanced the reaction of metal acetylacetonates with selenium, resulting in the burst nucleation of NCs at relatively low temperatures. The phase morphology and surface and optoelectronic properties of NCs before and after ligand exchange were discussed in depth. It was found that pure tetragonal-phase structure CZTSe NCs with approximately 1.7-eV bandgap could be synthesized. The removal of large organic molecules on CZTSe NCs after ligand exchange by S²⁻ decreased the resistivity. The bandgap of the films after ligand exchange by 550°C selenization was also decreased due to better crystallinity. For potential application in CZTSe solar cells, we constructed an energy level diagram to explain the mutual effect between the absorption layer and CdS layer. Using cyclic voltammetry (CV) measurement, we found that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of CZTSe films shifted down after ligand exchange. After energy level alignment at the CdS/CZTSe interface, a type I band alignment structure was more conveniently formed after ligand exchange. This structure acted as the barrier against injection electrons from ZnO to the CZTSe layer, and recombination would subsequently be depressed.     

Pillar[5]arene-stabilized Plasmonic Nanoparticles as Selective SERS Sensors

We present here a simple procedure for the surface modification of plasmonic nanoparticles (NPs) with a cationic water-soluble ammonium pillar[5]arene (AP[5]A) in order to create selective surface-enhanced Raman scattering (SERS) spectroscopy based sensors. The strategy is based on a ligand exchange reaction between the AP[5]A and the stabilizing agent of the as-prepared plasmonic NPs. The approach could be applied to plasmonic nanoparticles either negatively charged, stabilized by citrate ions (Au spheres) or positively charged, stabilized by cetyltrimethylammonium bromide (Au and Au@Ag nanorods). The SERS performance of all systems was studied as a function of NP size and excitation laser line by using an analyte with no affinity towards the metal surface such as pyrene. The analytical enhancement factor (AEF) for the different systems was estimated between 0.55×10⁴ and 1.49×10⁵. Finally the synergistic effect of combining supramolecular chemistry and plasmonic NPs is demonstrated through SERS-based detection, in aqueous media, of molecules with no affinity towards a bare plasmonic substrate such as the contaminant pyrene or the biomolecule pyocyanin with nanomolar limit of detection.     

上转换发光材料在不同防伪领域的研究进展Q

稀土上转换纳米粒子（UCNPs）能够吸收低能量的红外光并转换为高能量的紫外或可见光,其具有自体发光背景低、发光颜色可调、荧光寿命长和光稳定性好等优异的光学性能,此外,其还具有可加工性高、表面功能化便捷等特点,因而如今已经成为了荧光防伪技术的研究前沿和研究热点,应用前景十分广泛。本文综述了UCNPs的发光机制和一系列制备方法并分析优缺点,阐述了近年来其在标签、图案、编码等荧光防伪领域应用的相关优秀研究成果。进一步地,还探讨了UCNPs在荧光防伪领域应用上所存在的问题和面临的挑战,提出了未来可能的发展方向。     

Phonon Raman spectra of colloidal CdTe nanocrystals: effect of size,non-stoichiometry and ligand exchange

Resonant Raman study reveals the noticeable effect of the ligand exchange on the nanocrystal (NC) surface onto the phonon spectra of colloidal CdTe NC of different size and composition. The oleic acid ligand exchange for pyridine ones was found to change noticeably the position and width of the longitudinal optical (LO) phonon mode, as well as its intensity ratio to overtones. The broad shoulder above the LO peak frequency was enhanced and sharpened after pyridine treatment, as well as with decreasing NC size. The low-frequency mode around 100 cm^-1 which is commonly related with the disorder-activated acoustical phonons appears in smaller NCs but is not enhanced after pyridine treatment. Surprisingly, the feature at low-frequency shoulder of the LO peak, commonly assigned to the surface optical phonon mode, was not sensitive to ligand exchange and concomitant close packing of the NCs. An increased structural disorder on the NC surface, strain and modified electron-phonon coupling is discussed as the possible reason of the observed changes in the phonon spectrum of ligand-exchanged CdTe NCs.     

上转换发光材料在不同防伪领域的研究进展Q

稀土上转换纳米粒子(UCNPs)能够吸收低能量的近红外光并转换为高能量的紫外或可见光,具有自体发光背景低、发光颜色可调、荧光寿命长和光稳定性好等优异的光学性能,还具有可加工性高、表面功能化便捷等特点,已成为荧光防伪技术的研究前沿和研究热点,应用前景广泛.该文综述了UCNPs的发光机制和制备方法,阐述了近年来其在标签、图案、编码等荧光防伪领域应用的相关研究成果.进一步地探讨了UCNPs在荧光防伪领域应用上所存在的问题和面临的挑战,提出了未来可能的发展方向.     

Hydrogen evolving activity on nickel–molybdenum deposits using experimental strategies

Hydrogen evolution on various Ni–Mo deposits was systematically compared using fractional factorial design (FFD) and response surface methodology (RSM). The electroplating variables such as pH, Ni/Mo atomic ratio and citrate concentration were found to be the key factors affecting the hydrogen evolution activity from the FFD study. The effects of Ni/Mo atomic ratio and citrate concentration in the plating bath on the apparent current density, the exchange current density, and the specific activity (based on i/q ^*) of hydrogen gas evolution, and on the Mo/(Ni + Mo) ratio of the deposits were examined using regression models. These models, represented as response surface contour plots, showed the maximum hydrogen evolving activity occurring on the Ni–Mo deposit electroplated from the bath with a pH of 8, a Ni/Mo ratio of 3.3 and a citrate concentration of 40 g l^–1, respectively.     

快速配体交换法制备水溶性磁性Fe3O4纳米粒子

为了获得水溶性Fe_3O_4纳米粒子,以聚乙二醇(PEG)磷酸酯为亲水性配体,在甲苯/四氢呋喃/水三元混合溶剂体系下通过快速配体交换法将油酸包覆的油溶性磁性Fe_3O_4纳米粒子转变成聚乙二醇磷酸酯包覆的水溶性Fe_3O_4纳米粒子。考察了四氢呋喃等溶剂在实现快速配体交换中所起到的作用。利用透射电子显微镜(TEM)、动态光散射(DLS)、X射线粉末衍射仪(XRD)、傅立叶红外光谱仪(FTIR)、振动样品磁强计(VSM)对磁性Fe_3O_4纳米粒子进行了分析表征。结果表明:四氢呋喃可以促进PEG磷酸酯与Fe_3O_4纳米粒子表面的有效接触并使得油酸分子从纳米粒子表面快速地脱附下来,此外,还消除了配体交换过程中出现的乳化效应。四氢呋喃的应用实现了快速配体交换法制备水溶性PEG磷酸酯包覆的磁性纳米粒子。     

Binding of Citrate-Fe3+ to Plastic Culture Dishes,an Artefact Useful as a Simple Technique to Screen for New Iron Chelators

NaCT mediates citrate uptake in the liver cell line HepG2. When these cells were exposed to iron (Fe³⁺), citrate uptake/binding as monitored by the association of [¹⁴C]-citrate with cells increased. However, there was no change in NaCT expression and function, indicating that NaCT was not responsible for this Fe³⁺-induced citrate uptake/binding. Interestingly however, the process exhibited substrate selectivity and saturability as if the process was mediated by a transporter. Notwithstanding these features, subsequent studies demonstrated that the iron-induced citrate uptake/binding did not involve citrate entry into cells; instead, the increase was due to the formation of citrate-Fe³⁺ chelate that adsorbed to the cell surface. Surprisingly, the same phenomenon was observed in culture wells without HepG2 cells, indicating the adsorption of the citrate-Fe³⁺ chelate to the plastic surface of culture wells. We used this interesting phenomenon as a simple screening technique for new iron chelators with the logic that if another iron chelator is present in the assay system, it would compete with citrate for binding to Fe³⁺ and prevent the formation and adsorption of citrate-Fe³⁺ to the culture well. This technique was validated with the known iron chelators deferiprone and deferoxamine, and with the bacterial siderophore 2,3-dihydroxybenzoic acid and the catechol carbidopa.     

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 100 wt.%. 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.     

Terpolymer Chelates: Synthesis,Characterization, and Biological Applications

Terpolymer ligand was synthesized from 8-hydroxyquinoline and anthranilic acid with formaldehyde (QAF) by solution condensation in an acid medium. Polychelates of Cu(II), Ni(II), Zn(II), and Pb(II) were prepared using the terpolymer as ligand. The ligand and chelates were characterized by elemental analysis, TGA, DSC, FTIR, electronic absorption, and NMR spectroscopy. The activation energy was calculated for the ligand and its polychelates formation by the Freeman-Carroll method. The ligand and its polychelates possess antimicrobial activity for certain bacteria such as Staphylococcus aureus, Escherichia coli, and fungi Aspergillus niger and Candida albicans. The surface morphology of the ligand and its polychelates was established by SEM.     

磁性纳米三苯基膦配体制备及其催化氢甲酰化反应研究

通过表面交换反应,以多巴胺为偶联剂,将三苯基膦担载到磁性纳米氧化铁表面制得磁性纳米三苯基膦配体,其结构通过红外光谱、元素分析以及热重分析进行了表征。初步考察了表面交换反应条件对三苯基膦在纳米粒子表面担载量的影响;提高多巴胺-三苯基膦衍生物与磁性纳米氧化铁粒子比例以及延长超声时间有助于提高三苯基膦的担载量。在优化后的反应条件下,即苯乙烯1.25 m L,30 mg磁性纳米三苯基膦,1.8 mg Rh(OAc)2,12 m L无水四氢呋喃,3 MPa合成气VCO∶VH2=1∶1,纳米三苯基膦配体中的三苯基膦含量为0.21μmol/mg,该配体能够与Rh(OAc)2一起催化苯乙烯的氢甲酰化反应并能重复使用4次,且仅有4.8%的三苯基膦配体从纳米粒子表面脱落。     

Redox polymer-based reagentless horseradish peroxidase biosensors: Influence of the molecular structure of the polymer

Reagentless amperometric biosensors were prepared using a variety of nitrogen donor groups containing co-polymers. The polymers were coordinated with Os-bis-N,N-(2,2′-bipyridil)-dichloride via a ligand exchange reaction thus assuring an efficient electron-transfer pathway between the polymer-entrapped horseradish peroxidase and the electrode surface by means of a sequence of electron-hopping steps. The impact of structural features of the polymer such as spacer length between the Os-complex and the polymer backbone or the ratio of 4-vinylpyridine and butylmethacrylate in a co-polymer on the activity of the horseradish peroxidase biosensors was investigated.     

The colloidal stability of fluorescent calcium phosphosilicate nanoparticles: the effects of evaporation and redispersion on particle size distribution

Understanding the colloidal stability of nanoparticles is important for biological applications, such as bio-imaging and drug delivery. This work combines theoretical calculations with experimental data to elucidate the mechanism of stabilization for calcium phosphosilicate nanoparticles containing Cy3 with both citrate and poly(ethylene glycol) (PEG) surface conjugation. The citrate surface is shown to provide electrosteric dispersion in water-ethanol mixtures as well as the ability to redisperse after evaporating the solvent. Improved colloidal stability is afforded with the addition of PEG with respect to redispersion after drying. Changes in average agglomeration number (AAN) are tracked and explained by DLVO and the Napper electrosteric and steric theories for dispersion, respectively.     

乙酰柠檬酸三丁酯的催化合成

目前常用的邻苯二甲酸酯类增塑剂可能诱发致癌,国内外都在寻找能够替代的无毒增塑剂,柠檬酸酯类增塑剂是安全的替代增塑剂之一.今以柠檬酸三丁酯和乙酸酐为原料,研究了硫酸氢钠、大孔强酸性阳离子交换树脂催化合成乙酰柠檬酸三丁酯的过程,考察了原料摩尔配比、催化剂用量、反应时间、反应温度对乙酰柠檬酸三丁酯收率的影响.在适宜条件下,两种催化剂催化合成乙酰柠檬酸三丁酯的收率可分别达到99.5%和99.8%.精制后,乙酰柠檬酸三丁酯的含量经气相色谱分析大于99%.催化剂重复使用情况的考察表明:硫酸氢钠有较好的重复使用性;使用后经无水乙醇洗涤并干燥过的大孔强酸性阳离子交换树脂也具有很好的重复使用性.