Nanoparticle assembly at fluid interfaces: structure and dynamics

The self-assembly of nanoparticles at fluid interfaces, driven by the reduction in interfacial energy, was investigated. With spherical, tri-n-octyl-phosphine-oxide covered cadmium selenide (CdSe) nanoparticles (1-8 nm), thermal fluctuations compete with the interfacial segregation giving rise to a size-dependent self-assembly of the particles. The structure of the nanoparticle assembly was studied using electron microscopy, atomic force microscopy, and X-ray scattering in situ, which indicate that the particles form a densely packed monolayer. The energetics of the adsorption of nanoparticles onto the interface was revealed by time-dependent fluorescence studies on a mixture of two different sized nanoparticles at the interface. The dynamics of the nanoparticles at the fluid interface, probed using fluorescence photobleaching methods, suggests a liquid-like behavior. The results have implications in the design of hierarchical self-assemblies of nanoparticles for the one-step fabrication of devices on multiple length scales.     

Platinum Nanoparticle Impacts at a Liquid|Liquid Interface

Single nanoparticle (NP) electrochemistry detection at a micro liquid|liquid interface (LLI) is exploited using the catalyzed oxygen reduction reaction (ORR). In this way, current spikes reminiscent of nanoimpacts were recorded, which corresponded to electrocatalytic enhancement of the ORR by Pt NPs. The nature of the LLI allows exploration of new phenomena in single NP electrochemistry. The recorded impacts result from a bipolar reaction occurring at the Pt NP straddling the LLI. O₂ reduction takes place in the aqueous phase, while ferrocene hydride (Fc‐H⁺; a complex generated upon facilitated interfacial proton transfer by Fc) is oxidized in the organic phase. Ultimately, the role of reactant partitioning, NP bouncing, or the ability of NPs to induce Marangoni effects, is demonstrated.     

Amidine-bearing lipoplex targeting to hepatocyte cells

A lipoplex （i.e., pDNA#1/lipid complex and transfection reagent for pDNA delivery） containing galactosylceramide （GalCer） and an amidine-bearing lipid （TRX） was examined whether the bound pDNA was specifically ingested by hepatocyte via asialoglycoprotein receptor （ASGPR） and then expressed protein. Gel electrophoresis and small-angle X-ray scattering （SAXS） confirmed that the TRX-GalCer liposome#2 complexed with pDNA and the resultant lipoplex took a hexagonally packed inverted cylinder structure when the GalCer composition was less than 20 wt.% of the total lipid. When the lipoplex carrying pGL3 （luciferase-cording pDNA） was administrated to HepG2, the luciferase activity was increased with increasing the GalCer composition until it reached 3 wt.% and then decreased upon further addition of GalCer. When we added galactose itself as a competitor, the luciferase activity was decreased, while glucose did not show such decrease, suggesting that HepG2 ingested the lipoplex via ASGPR-mediated endocytosis. This paper indicated that the hexagonally packed inverted cylinder structures of lipoplex may not always provide excellent transfection and presented a possibility that the TRX lipoplex#3 can obtain a cellulartargeting ability through the receptors for oligosaccharide.     

Arsenite Determination in Phosphate Media at Electroaggregated Gold Nanoparticle Deposits

Compared to bulk gold, highly reactive mesoporous gold film deposits are prepared on a boron‐doped diamond electrode surface. An electroaggregation process causing 5 nm diameter gold nanoparticles to deposit cathodically from aqueous solution is implemented to control the amount of mesoporous gold at the electrode surface. The resulting electrode surface is characterized by electron microscopy and by cyclic voltammetry.     

Nanoparticle deposition in granular filters at Reynolds numbers higher than unity

The influence of the inertia of a viscous incompressible liquid flow on the viscous drag and diffusion deposition of particles in model granular filters at Reynolds numbers higher than unity, Re > 1, has been considered. The granule drag forces and particle-collection efficiencies in isolated layers with square and hexagonal packings of granules have been calculated. The influence on each other of approaching monolayers of granules on pressure drop and nanoparticle deposition has been studied. It has been shown that, at Re > 1, the collection efficiency dramatically increases due to the effect of interception.     

Photoacoustic Imaging of Nanoparticle Transport in the Kidneys at High Temporal Resolution

Noninvasive monitoring of kidney elimination of engineered nanoparticles at high temporal and spatial resolution will not only significantly advance our fundamental understandings of nephrology on the nanoscale, but also aid in the early detection of kidney disease, which affects more than 10 % of the worldwide population. Taking advantage of strong NIR absorption of the well‐defined Au₂₅(SG)₁₈ nanocluster, photoacoustic (PA) imaging was used to visualize its transport in situ through the aorta to the renal parenchyma and its subsequent filtration into the renal pelvis at a temporal resolution down to 1 s. High temporal and spatial resolution imaging of Au₂₅(SG)₁₈ kidney elimination allowed the accurate quantification of the glomerular filtration rate (GFR) of individual kidneys in normal and pathological conditions, broadening the biomedical applications of engineered nanoparticles in preclinical kidney research.     

Improving vaccines by targeting antigens to dendritic cells

A new approach to enhancing the effectiveness of vaccines is to deliver antigens selectively to dendritic cells (DC) in situ, via monoclonal antibodies specific for particular DC surface molecules. This can markedly enhance CTL responses and, via helper T cells, also enhance antibody responses. DC activation agents or adjuvants must also be administered for effective CTL responses, but in some cases good antibody responses can be obtained without adjuvants. Here we review the role of different DC subsets and different DC target molecules in obtaining enhanced immune responses.     

多肽修饰的纳米金加速油-水界面酶促反应

用固相合成法制备阳离子氨基酸组成的多肽,再将其连接到巯基化合物上,用于纳米金表面配体交换,制备阳离子多肽修饰的纳米金,并研究了这种纳米粒子对油-水(O/W)乳液界面酶促反应速度的影响.结果发现,将含有荧光底物的乳滴同酶直接混合时,45 min内溶液中未检测到荧光信号变化,但向该溶液中加入纳米粒子后溶液中荧光信号立即增强.出现该现象的主要原因是,当乳液界面酶促反应体系中含有纳米粒子时,纳米粒子表面的阳离子多肽同时吸附带负电荷的酶和乳液,迅速屏蔽酶与乳液之间的电荷排斥,使酶与乳液中的底物能有效接触,加速酶促反应进行;通过选用不同的油相制备乳液,调控纳米粒子与乳液之间的氢键作用,还可使酶促反应速度进一步提高.     

Crystallization-driven Nanoparticle Crystalsomes

Nanoparticle (NP) assembly has been extensively studied, and a library of NP superstructures has been synthesized. These intricate structures show unique collective optical, electronic, and magnetic properties. In this work, we report a bottom-up approach for fabricating spherical gold nanoparticle (AuNP) assemblies that mimic colloidosomes. Co-crystallization of lipoic acid-end-functionalized poly(ethylene oxide) (PEO) and AuNPs in solution via a self-seeding method led to the formation of hollow spherical NP assemblies named nanoparticle crystalsomes (NPCs). Due to the spherical shape, the translational symmetry of PEO crystals is broken in NPCs, which can be attributed to the competition between NP close packing and polymer crystallization. This was confirmed by tuning the NPC morphology via varying the self-seeding temperature, crystallization temperature, and PEO molecular weight. We envisage that this strategy paves the way to attaining exquisite morphological control of NP assemblies with broken translational symmetry.     

Cell-SELEX-based aptamer-conjugated nanomaterials for enhanced targeting of cancer cells

Early detection and treatment of cancer depends on developing highly sensitive and specific methods for targeting cancer cells. To do this, aptamers, which are generated by a novel technique called cell-SELEX (systematic evolution of ligands by exponential enrichment), have been widely applied in cancer cell targeting based on such merits as high target affinity and specificity, small size, minimal immunogenicity, and ease of chemical modification. Furthermore, aptamers can gain more flexibility as cancer c...     

Electrogenerated Chemiluminescence Imaging of Electrocatalysis at a Single Au‐Pt Janus Nanoparticle

Noble metal nanoparticles are promising catalysts in electrochemical reactions, while understanding the relationship between the structure and reactivity of the particles is important to achieve higher efficiency of electrocatalysis, and promote the development of single‐molecule electrochemistry. Electrogenerated chemiluminescence (ECL) was employed to image the catalytic oxidation of luminophore at single Au, Pt, and Au‐Pt Janus nanoparticles. Compared to the monometal nanoparticles, the Janus particle structure exhibited enhanced ECL intensity and stability, indicating better catalytic efficiency. On the basis of the experimental results and digital simulation, it was concluded that a concentration difference arose at the asymmetric bimetallic interface according to different heterogeneous electron‐transfer rate constants at Au and Pt. The fluid slip around the Janus particle enhanced local redox reactions and protected the particle surface from passivation.     

铁纳米粒子共振光散射测定纳克级核酸

核酸作为生物遗传的物质基础,对其进行分析化学研究一直备受关注.当前,微流控分析技术的快速发展为核酸的高灵敏检测展示了新的前景.     

Bimetallic Dendrimer-encapsulated Nanoparticle Catalysts

Bimetallic dendrimer-encapsulated nanoparticles (DENs) have been receiving a significant amount of attention due to their promising properties, unique characteristics, and novel applications in catalysis and other advanced “nano-” science and technology areas. Bimetallic DENs catalysts, as reviewed here, have shown a higher catalytic activity than the monometallic DENs in various catalytic systems. In this review, a general background for the dendrimer is first presented, which is then followed by an introduction of two major routes that are most often adopted in the preparation of dendrimers: divergent method and convergent method. Then, recent research advances in the synthesis, characterization, and catalytic applications of bimetallic DENs are summarized and highlighted in this article. A conclusion is then provided.     

DNA步行器调控的纳米粒子超晶格

作为一种精巧的DNA纳米机器, DNA步行器因其优异的可设计性及可编程性在众多研究领域中展示出强大的应用价值. 本工作通过将基于催化发夹组装的双足DNA步行器与DNA功能化的金纳米粒子(即球形核酸)组装相结合, 开发了一种具有时间依赖性的DNA步行器驱动球形核酸恒温有序组装的策略. 以单组分球形核酸组装体系为例, DNA步行器通过发夹催化组装反应驱动在球形核酸表面上随机行走并逐渐产生带有活性粘性末端的DNA杂交结构, 促使球形核酸表面粘性末端间的“键合”速率与其组装速率在时间尺度上保持同步, 从而得到面心立方(FCC)晶型的超晶格结构. 基于类似原理, 作者还构建了一种DNA步行器驱动的双组分球形核酸组装体系并以此得到氯化铯(CsCl)晶型的超晶格结构.     

Repairing Nanoparticle Surface Defects

Solar devices based on semiconductor nanoparticles require the use of conductive ligands; however, replacing the native, insulating ligands with conductive metal chalcogenide complexes introduces structural defects within the crystalline nanostructure that act as traps for charge carriers. We utilized atomically thin semiconductor nanoplatelets as a convenient platform for studying, both microscopically and spectroscopically, the development of defects during ligand exchange with the conductive ligands Na₄SnS₄ and (NH₄)₄Sn₂S₆. These defects can be repaired via mild chemical or thermal routes, through the addition of L‐type ligands or wet annealing, respectively. This results in a higher‐quality, conductive, colloidally stable nanomaterial that may be used as the active film in optoelectronic devices.     

Nanoparticle photochemistry via nano-impacts

We report the use of nano-impacts as a novel method for the study of photochemical reactions of individual nanoparticles (NPs). The conversion of gelatine stabilised silver bromide (AgBr) NPs to silver (Ag) NPs through photochemical reduction by ascorbic acid is studied mechanistically. Two mechanisms are proposed and investigated by monitoring the amount of electrochemically accessible AgBr against the time scale of conversion, measured through the use of the nano-impacts technique.