Formation of Gold Nanoparticles in the Presence of Carbon Nanoparticles

Russian Journal of General Chemistry - The possibility to obtain gold nanoparticles due to the reduction of tetrachloroauric acid under the action of carbonaceous nanoparticles prepared by...     

Electrochemistry of Nanoparticles

Metal nanoparticles (NPs) find widespread application as a result of their unique physical and chemical properties. NPs have generated considerable interest in catalysis and electrocatalysis, where they provide a high surface area to mass ratio and can be tailored to promote particular reaction pathways. The activity of NPs can be analyzed especially well using electrochemistry, which probes interfacial chemistry directly. In this Review, we discuss key issues related to the electrochemistry of NPs. We highlight model studies that demonstrate exceptional control over the NP shape and size, or mass‐transport conditions, which can provide key insights into the behavior of ensembles of NPs. Particular focus is on the challenge of ultimately measuring reactions at individual NPs, and relating the response to their structure, which is leading to imaginative experiments that have an impact on electrochemistry in general as well as broader surface and colloid science.     

核壳结构纳米粒子

纳米粒子由于具有大量的潜在应用,近年来已引起人们极大的关注。通过表面改性(如制备核壳结构的纳米粒子)可以使其获得更多特殊的性质。本文就最近几年制备壳核结构纳米粒子的方法进行了总结,根据其核、壳的不同材料进行了分类,并对其中某些方法进行了比较。     

Polymersome-Embedded Nanoparticles

Summary: Polymersomes are self assembled vesicles composed of fully synthetic amphiphilic diblock copolymers. Many of their properties are similar to lipid vesicles, although with often higher thermal and mechanical stability within their curved membrane. Incorporation of nanosized objects into their hydrophilic interior or hydrophobic membrane represents an important method for functionalization of these biomimetic structures. We report on the embedding of hydrophobic gold nanoparticles (Au-NPs) into polymersomes. Nanoparticles were prepared and incorporated into polymersomes made by standard film rehydration techniques from commercially available diblock copolymers. Characterization of the resulting structures was achieved by dynamic light scattering (DLS) and by TEM. Results on the preparation method, its influence on the polymersome stability and the application of these new membrane-mimetics are reported.     

金纳米粒子的细胞毒性

金纳米粒子(AuNPs)是构建用于诊断和治疗的纳米药物/探针的理想纳米材料之一,因此研究AuNPs与细胞的相互作用具有重要意义。 本文详细分析了金纳米簇(AuNCs)、球形金纳米粒子A(AuNPss)、金纳米球壳(AuNSs)和金纳米棒(AuNRs)等不同形貌的Au NPs对不同细胞模型的细胞毒性;讨论了AuNPs的理化性质(大小、形状、化学功能和表面电荷)对其细胞毒性的影响。 总结了AuNP细胞毒性研究遇到的挑战并提出相应解决方法。     

无机纳米粒子的生物合成

无机纳米粒子的生物合成是指利用自然界中细菌、放线菌和真菌等微生物或一些高等植物在常温、常压下合成无机纳米粒子,不需使用有毒化学原料或不产生有毒副产品。该方法不仅是一种绿色的、环境友好的新型纳米材料合成策略,而且对深入了解生物矿化机理以及从理论上指导先进功能材料的设计和合成具有重要意义,因此近年来受到了化学、材料、生物科学等领域研究者的广泛关注。本文根据纳米粒子组成,分别综述了国内外利用生物体合成金属、硫化物和氧化物等无机纳米粒子的研究进展,重点讨论了生物合成的机理。结果表明:生物合成的无机纳米粒子具有尺寸分布窄、稳定性高、生物相容性好、产率高和成本低等优点; 为了适应高金属离子浓度的外界环境,生物体往往通过吸附、还原或沉淀、累积或排出等一系列生化过程改变金属离子的溶解性和毒性,从而导致无机纳米粒子的形成; 合成无机纳米粒子后,微生物通常仍具有繁殖能力,表明这些微生物可以被用于生产无机纳米粒子的生物工厂。然而,生物合成无机纳米粒子涉及到的生理过程非常复杂,微生物种类繁多,不同种类之间的差异也非常大。因此,在阐释生物合成机理、拓展纳米材料的种类和形貌、纳米粒子的后处理和应用等问题上仍需进一步深入研究。     

纳米粒子的电容

纳米粒子的电容对由纳米点陈列所形成的单电子器件是一个十分重要的参数。基于少体理论,提出了计算纳米粒子量子点充电电容的理论模型,由此可以预测出室温下出现库仑台阶等单电子现象的最大纳米粒子粒径。采用简谐势模型计算模拟了CdS、PbS半导体纳米粒子的充电电容,发现CdS、PbS纳米粒子的尺寸上限为11与5 nm。理论计算结果与实验相吻合。     

Nanoparticles from Chitosan

Novel biodegradable nanoparticles were synthesized by chemical modification of the chitosan linear chain. A natural dicarboxylic acid (malic acid) was used as a crosslinking agent for intramolecular covalent condensation reaction to obtain hydrophilic nanoparticles based on chitosan. A variety of methods including, solubility studies, laser light scattering (DLS), transmission electron microscopy (TEM) and nuclear magnetic resonance (NMR) was used to characterize the crosslinked macromolecules. The prepared biodegradable chitosan nanoparticles, soluble in aqueous media, might be useful for various biomedical applications, like injectable drug- or gene-delivery systems.     

Visible-Light-Reactive Single-Chain Nanoparticles

We introduce a single-chain nanoparticle (SCNP) system capable of catalyzing the photooxidation of nonpolar alkenes up to three times more efficiently than an equivalent small-molecule photosensitizer at an identical concentration. Specifically, we construct a polymer chain constituted of poly(ethylene glycol) methyl ether methacrylate and glycidyl methacrylate which we compact via multifunctional thiol-epoxide ligation and functionalize with Rose Bengal ( RB ) in a one pot reaction, affording SCNPs with a hydrophilic shell and hydrophobic photocatalytic regions. Photooxidation of the internal alkene in oleic acid proceeds under green light. RB confined within the SCNP is three times more effective for nonpolar alkenes than free RB in solution, which we hypothesize is due to the spatial proximity of the photosensitizing units to the substrate in the hydrophobic region. Our approach demonstrates that SCNP based catalysts can afford enhanced photocatalysis via confinement effects in a homogeneous reaction environment.     

Nanoparticles as macromolecules

A review of recent trends in the dispersion, purification, and assembly of colloidal nanoparticles highlights a number of growing analogies with ideas borrowed from polymer science. Beyond the similar scales of size, several key concepts lying at the foundation of polymer physics—such as polydispersity, fractionation, phase ordering, and viscoelasticity—are taking on new and unique significance in the contemporary realm of nanotechnology. Leveraging “soft matter” at the nanoscale to simplify materials processing and improve material performance is becoming a reality, with potentially profound implications for a number of emerging technologies. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym. Phys. 2013 , 51, 1195–1208     

Chiral Gold Nanoparticles

Nanoparticle chirality has attracted much attention recently, and the application of chiral nanoparticles to chiral technologies (see figure) is also of interest. This Minireview deals with advances in the preparation and characterization of chiral gold nanoparticles. Origins of the chiroptical properties and potential applications are discussed.

     

Ultrafast Relaxation Processes of Conjugated Polymer Nanoparticles in the Presence of Au Nanoparticles

Considering the importance of conjugated polymer nanoparticles, major emphasis has been given for designing and understanding the energy transfer and charge transfer processes of organic‐inorganic hybrids for light harvesting applications. In the present study, we have designed an aqueous solution‐based light harvesting system using conjugated polymer nanoparticles (poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene], MEH‐PPV) and Au nanoparticles. The change in photo‐induced processes in the presence of metal nanoparticles are studied by steady‐state absorption, time‐resolved emission, time‐resolved fluorescence up‐conversion, ultrafast anisotropy and femtosecond transient absorption spectroscopy. Global and target analysis of transient absorption data validate the creation of a collective delocalized state in polymer nanoparticles, and the time scale for excitation energy funnelling from S₁ state to low lying collective delocalized state (CL_s) is 18 ps. Then, the electron transfer from the CL_s state to Au NP occurs with a time constant of 150 ps. The 815 ps long lived charge transfer (CT) state signifies the charge transfer from the CL_s state of polymer nanoparticles to Au NP. Such basic understanding of relaxation processes in hybrid systems is very important for designing inorganic‐organic hybrid light‐harvesting systems.     

Ultrasound-responsive Homopolymer Nanoparticles

Nonin vasive ultraso und is a more effective strategy for on-demand drug delivery of polymeric nano particles than many other stimuli.However,the preparation of ultrasound-responsive homopolymer nanoparticles is still very challenging.In this study,we disclose the regulating factors of ultrasound responsiveness of homopolymer nanoparticles and the disaggregation behavior of homopolymer nanoparticle aggregates.Homopolymer nanoparticles such as vesicles and large compound micelles(LCMs)are self-assembled from poly(methoxyethyl methacrylate)(PMEMA)and poly(amic acid)(PAA),respectively.The ultrasound responsiveness of PAA vesicles at metastable state could be regulated by tuning the self-assembly temperature(7^),and was optimized when Ts is around the glass transition temperature(7g)of PAA.However,the PMEMA LCMs did not respond to ultrasound as they are at stable state.On the other hand,poly(2-(2-ethoxyethoxy)ethyl acrylate)(PEEA)could self-assemble into vesicle aggregates or complex micelle aggregates,which were dissociated upon sonication.Overall,the above findings provide us with a fresh in sight for designing ultrasound-responsive polymeric nanoparticles.     

Thermally-Polymerized Rylene Nanoparticles

Rylene dyes functionalized with varying numbers of phenyl trifluorovinylether (TFVE) moieties were subjected to a thermal emulsion polymerization to yield shape-persistent, water-soluble chromophore nanoparticles. Perylene and terrylene diimide derivatives containing either two or four phenyl TFVE functional groups were synthesized and subjected to thermal emulsion polymerization in tetraglyme. Dynamic light scattering measurements indicated that particles with sizes ranging from 70 - 100 nm were obtained in tetraglyme, depending on monomer concentration. The photophysical properties of individual monomers were preserved in the nanoemulsions and emission colors could be tuned between yellow, orange, red, and deep red. The nanoparticles were found to retain their shape upon dissolution into water and the resulting water suspensions displayed moderate to high fluorescence quantum yield.     

Physicochemical Properties of Nanoparticles: Interaction of Supported Platinum Nanoparticles with Gaseous Reactants

The shapes, sizes, and electronic structures of platinum nanoparticles supported onto highly oriented pyrolytic graphite and oxidized silicon by different methods and their adsorptive properties with respect to hydrogen, oxygen, water, and ammonia were established. The apparent activation energy of the reduction of single oxidized platinum nanoparticles with molecular hydrogen was determined. The possibility of controlling the rate of ammonia decomposition by a nanostructured platinum coating by the application of electric potentials of different values and polarities to it was demonstrated.     

Chemically Induced Sintering of Nanoparticles

We have observed solid‐state growth of pre‐existing silver nanoparticles (AgNPs) upon exposure to trace (ppb) concentrations of reactive gases at room temperature. The consequent change in localized surface plasmon resonances alters the visible absorbance of dried, printed sensor spots made from inks of 10 nm‐AgNPs and provides a novel mechanism for trace detection and dosimetry of reactive gases. Colorimetric sensor arrays based on these AgNP inks offer dosimetric identification of acidic and oxidizing gases and other reactive vapors with limits of detection below ppb levels for 1 h exposures. For an array of AgNP inks with various capping agents, a unique color response pattern is observed for each specific analyte. Excellent discrimination among 11 reactive gases was demonstrated using standard chemometric methods. The chemically induced sintering of NPs paves the way for novel solid‐state sensors for the ultrasensitive detection of reactive gases and their application to the monitoring of trace airborne pollutants.