Highly Ordered Superlattices from Self-assembly of Fe3O4 Nanocrystals

The nano materials often exhibit very interesting electrical, optical, magnetic, and chemical properties, which can not be achieved by their bulk counterparts. The development of uniform nanometer sized particles has been intensively pursued because of their technological and fundamental scientific importance. It is significant that nanostructured materials can be controllably assembled into the required geometry onto substrates, becoming the basis of the next generation of components and devices. The development of new methods and strategies for organizing the nanoparticle basic building blocks into the desired structures is required. Superlattices made from these building blocks give us the opportunity to study not only the properties of the individual building blocks, but also collective effects. The superparamagnetic iron oxide nanocrystals（NCs） have been used in the fields of bio-medicine, ferrofluids, refrigeration system, catalysis,     

纳米银的单颗粒-电感耦合等离子质谱法表征及其测定

建立单颗粒-电感耦合等离子体质谱法( SP-ICP-MS)测定稀溶液中纳米银颗粒粒度分布及纳米银颗粒数量浓度的方法。当停留时间为3 ms时,两个或多个纳米银颗粒同时进入检测器的可能性降至最低。采用5倍标准偏差迭代算法(5σ)区分纳米银颗粒信号和背景信号。采用SP-ICP-MS法测定3种商品级纳米银颗粒(30,50和100 nm)粒度分布和纳米颗粒浓度。结果表明：SP-ICP-MS法测定纳米银颗粒结果与纳米银的TEM值相近,可采用SP-ICP-MS法表征纳米银颗粒。本方法测定稀溶液中纳米银颗粒粒度检出限为25 nm,纳米银颗粒浓度检出限约为8×104个/L。将纳米银颗粒加入到自来水样品中并进行测定,获得相近的纳米银粒度分布及纳米颗粒浓度。本方法简单、快捷、灵敏度高,可为研究水环境中纳米银的风险评估提供可靠分析方法,并为饮用水中纳米银的监测提供分析技术。     

Silver nanoparticle decorated poly(2-aminodiphenylamine) modified carbon paste electrode as a simple and efficient electrocatalyst for oxidation of formaldehyde

This work describes the promising activity of silver nanoparticles on the surface of a poly(2-amino diphenylamine) modified carbon paste electrode (CPE) towards formaldehyde oxidation. Electrodeposition of the conducting polymer film on the CPE was carried out using consecutive cyclic voltammetry in an aqueous solution of 2-aminodiphenylamine and HCl. Nitrogen groups in the polymer backbone had a Ag ion accumulating effect, allowing Ag nanoparticles to be electrochemically deposited on the surface of the electrode. The electrochemical and morphological characteristics of the modified electrode were investigated. The electro-oxidation of formaldehyde on the surface of electrode was studied using cyclic voltammetry and chronoamperometry in aqueous solution of 0.1 mol/L NaOH. The electro-oxidation onset potential was found to be around -0.4 V, which is unique in the literature. The effect of different concentrations of formaldehyde on the electrocatalytic activity of the modified electrode was investigated. Finally, the diffusion coefficient of formaldehyde in alkaline media was calculated to be 0.47 × 10^-6 cm²/s using chronoamperometry.     

Synthesis of size tunable monodispersed silver nanoparticles and the effect of size on SERS enhancement

Spherical and monodispersed silver nanoparticles (AgNPs) are ideal for fundamental research as the contribution from size and shape can be accounted for in the experimental design. In this paper a seeded growth method is presented, whereby varying the concentration of sodium borohydride-reduced silver nanoparticle seeds, different sizes of stable spherical nanoparticles with a low polydispersity nanoparticles are produced using hydroquinone as a selective reducing agent. The surface-enhanced Raman scattering (SERS) enhancement factor for each nanoparticle size produced (17, 26, 50, and 65 nm) was then assessed using three different analytes, rhodamine 6G (R6G), malachite green oxalate (MGO) and thiophenol (TP). The enhancement factor gives an indication of the Raman enhancement effect by the nanoparticle. Using non-aggregated conditions and two different laser excitation wavelength (633 nm and 785 nm) it is shown that an increase in particle size results in an increased enhancement for each analyte used.     

TiO_2/12-磷钨杂多酸/金复合纳米材料的制备及电化学性能

采用水热法制备TiO2纳米管(TNTs),然后以12-磷钨杂多酸(PTA)作为交联剂,运用光催化方法在TiO2纳米管表面负载金纳米颗粒(GNPs),从而得到新型复合纳米材料——TNTs-PTA-GNPs;借助傅立叶变换红外光谱仪,X射线衍射仪和透射电子显微镜分析了新型复合纳米材料的结构及形貌,并利用循环伏安法测试了其电化学性能.结果表明,GNPs均匀分布在TNTs表面,从而大幅度改善纳米材料的导电性;但复合纳米材料中无游离的金纳米颗粒.与此同时,TNTs-PTA-GNPs纳米材料具有良好的生物相容性,且可促进酶与电极之间的直接电子转移.     

Cationic Lipid-based Intracellular Delivery of Bacterial Effectors for Rewiring Malignant Cell Signaling

The abundance of bacterial effectors have inspired us to explore their potential in rewiring malignant cell signaling. Their incapability for entering cells, however, hinders such application. Herein we developed a cationic lipid-based high throughput library screening platform for effective intracellular delivery of bacterial effectors. As the misregulated MAPK signaling is a hallmark of many types of cancer, we turned to the Shigella effector OspF which irreversibly inactivates ERK, the terminal component of MAPK cascade. We created a function-based screening assay to obtain AMPA-O16B lipid nanoparticles for effective OspF intracellular delivery, which inhibited the malignant MAPK signaling and tumor growth in vitro and in vivo. Furthermore, the optimized lipid nanoparticle formulation can deliver OspF to modulate the immunosuppressive responses in macrophages. Our work is a general strategy to explore the therapeutic potentials of naturally evolved bacterial effectors.     

基于上转换纳米粒子的低损伤神经界面技术

Optogenetics is a neuromodulation technology that combines light control technology with genetic technology, thus allowing the selective activation and inhibition of the electrical activity in specific types of neurons with millisecond time resolution. Over the past several years, optogenetics has become a powerful tool for understanding the organization and functions of neural circuits, and it holds great promise to treat neurological disorders. To date, the excitation wavelengths of commonly employed opsins in optogenetics are located in the visible spectrum. This poses a serious limitation for neural activity regulation because the intense absorption and scattering of visible light by tissues lead to the loss of excitation light energy and also cause tissue heating. To regulate the activity of neurons in deep brain regions, it is necessary to implant optical fibers or optoelectronic devices into target brain areas, which however can induce severe tissue damage. Non- or minimally-invasive remote control technologies that can manipulate neural activity have been highly desirable in neuroscience research. Upconversion nanoparticles (UCNPs) can emit light with a short wavelength and high frequency upon excitation by light with a long wavelength and low frequency. Therefore, UCNPs can convert low-frequency near-infrared (NIR) light into high-frequency visible light for the activation of light-sensitive proteins, thus indirectly realizing the NIR optogenetic system. Because NIR light has a large tissue penetration depth, UCNP-mediated optogenetics has attracted significant interest for deep-tissue neuromodulation. However, in UCNP-mediated in vivo optogenetic experiments, as the up-conversion efficiency of UCNPs is low, it is generally necessary to apply high-power NIR light to obtain up-converted fluorescence with energy high enough to activate a photosensitive protein. High-power NIR light can cause thermal damage to tissues, which seriously restricts the applications of UCNPs in optogenetic technology. Therefore, the exploration of strategies to increase the up-conversion efficiency, fluorescence intensity, and biocompatibility of UCNPs is of great significance to their wide applications in optogenetic systems. This review summarizes recent developments and challenges in UCNP-mediated optogenetics for deep-brain neuromodulation. We firstly discuss the correspondence between the parameters of UCNPs and employed opsins in optogenetic experiments, which mainly include excitation wavelengths, emission wavelengths, and luminescent lifetimes. Thereafter, we introduce the methods to enhance the conversion efficiency of UCNPs, including optimizing the structure of UCNPs and modifying the organic dyes in UCNPs. In addition, we also discuss the future opportunities in combining UCNP-mediated optogenetics with flexible microelectrode technology for the long-term detection and regulation of neural activity in the case of minimal injury.     

Dissolved organic matter-mediated reduction of ionic Au(III) to elemental Au nanoparticles and their growth to visible granules

The biogeochemical transformation of gold (Au), i.e. its dissolution and re-precipitation, is critical in supergene transport of Au and formation of Au granules. Besides biogenic reduction, the formation Au granules can also be driven by chemical processes. Previous studies have showed the formation of Au nanoparticles (AuNPs) from ionic Au(III) can be mediated by dissolved organic matter under sunlight. In this letter, we further demonstrated that these AuNPs can further slowly (in years) grow into visible Au granules. Different sized nano-flower and fractal dendrite-like branched gold structures (from tens of nanometres to over 100 μm) were observed in the Au granule sample. This growth of AuNPs into visible Au granules may play a critical role in the supergene mineralization and enrichment of secondary Au and drive the biogeochemical cycle of Au.     

Deposition of Phosphate Nanoparticles onto Textile Fabrics via Sol-gel Method and Their Kinetics Desorption Studies

In this paper, phosphate nanoparticles were coated on cotton(CO) and polyester(PES) textile surfaces by sol-gel method using tetraethylorthosilicate(TEOS) and chloropropyltriethoxysilane(CPTS) as silica precursors. The deposited nanoparticles were observed with scanning electronic microscopy energy-dispersive X-ray spectroscopy (SEM-EDX). The release kinetics of phosphorus(P) from these textiles into the aqueous medium(Aq), acid(Ac), and basic(Ba) artificial sweats were then studied. The released amount of phosphorus was evaluated by the inductively coupled plasma(ICP) according to ISO NF EN 16711-2 procedure. The results revealed that the release of P into the aqueous medium is lower than in the artificial sweat. The kinetics data[the phosphorus desorption amount(mg/g) as a function of time] were modeled according to five models:the first order, the second order, the third order, simple Elovich and parabolic diffusion. The suitable model was chosen based on the coefficient of determination(R²) and the calculation of the sum of the absolute errors(EABS), which describes the error between the theoretical and experimental values. SEM observations were also carried out on the fabrics after desorption in order to show the impact of desorption on their morphology. Furthermore, the impact of P release on the tensile strength of CO and PES fabrics was investigated using a uniaxial tensile test. The thermal stability of all samples before and after desorption was assessed by thermogravimetric analysis(ATG).     

Reconfigurable Plasmonic Nanostructures Controlled by DNA Origami

Precise surface functionalization and reconfigurable capability of nanomaterials are essential to construct complex nanostructures with specific functions.Here we show tire assembly of a reconfigurable plasmonic nanostructure,which executes both conformational and plasmonic changes in response to DNA strands.In this work,different sized gold nanoparticles(AuNPs)were arranged site-specifically on the surface of a DNA origami clamp nanostructure.The opening and closing of the DNA origami clamp could be precisely controlled by a series of strand emplacement reactions.Therefore,the patterns of these AuNPs could be switched between two different configura-tions.The observed plasmon band shift indicates the change of the plasmonic interactions among the assembled AuNPs.Our study achieves the construction of reconfigurable nanomaterials with tunable plasmonic interactions,and will enrich the toolbox of DNA-based functional nanomachinery.