Electrochemical Synthesis of Plasmonic Nanostructures

Thanks to their tunable and strong interaction with light, plasmonic nanostructures have been investigated for a wide range of applications. In most cases, controlling the electric field enhancement at the metal surface is crucial. This can be achieved by controlling the metal nanostructure size, shape, and location in three dimensions, which is synthetically challenging. Electrochemical methods can provide a reliable, simple, and cost-effective approach to nanostructure metals with a high degree of geometrical freedom. Herein, we review the use of electrochemistry to synthesize metal nanostructures in the context of plasmonics. Both template-free and templated electrochemical syntheses are presented, along with their strengths and limitations. While template-free techniques can be used for the mass production of low-cost but efficient plasmonic substrates, templated approaches offer an unprecedented synthetic control. Thus, a special emphasis is given to templated electrochemical lithographies, which can be used to synthesize complex metal architectures with defined dimensions and compositions in one, two and three dimensions. These techniques provide a spatial resolution down to the sub-10 nanometer range and are particularly successful at synthesizing well-defined metal nanoscale gaps that provide very large electric field enhancements, which are relevant for both fundamental and applied research in plasmonics.     

Surface Initiated Polymerization from Nanoparticle Surfaces

Abstract

The synthesis, characterization, and development of new nanoparticle materials have both scientific and technological significance. Surface initiated polymerization (SIP) from nanoparticle surfaces involves the growth of end‐tethered polymer brushes where the length or thickness can be more than twice the radius of gyration (Rg) compared to a free polymer in solution. Different mechanisms are possible on a variety of initiators, reaction conditions, monomers, and nanoparticles. Important differences to solution and bulk polymerization can be observed where the nanoparticles with grafted initiators behave as macroinitiators. In turn, the development of these materials will allow the preparation of thermodynamically and kinetically stable nanocomposites and colloids. Through the careful use of surface sensitive spectroscopic and microscopic techniques, much has been gained from the direct and in‐situ analysis of grafted polymers on the nanoparticles with regards to the kinetics and mechanism of the polymerization process. Parallels can be drawn to SIP on flat surfaces where surface sensitive spectroscopic and microscopic measurements are complementary to analysis methods for colloidal particles. Thus, this review surveys the different polymerization mechanisms and procedures towards forming core‐shell types of hybrid inorganic–organic polymer nanoscale materials.     

Nanoscale imaging of Li and B in nuclear waste glass,a comparison of ToF‐SIMS,NanoSIMS, and APT

It has been very difficult to use popular elemental imaging techniques to image Li and B distribution in glass samples with nanoscale resolution. In this study, time‐of‐flight secondary ion mass spectrometry, nanoscale secondary ion mass spectrometry, and atom probe tomography (APT) were used to image the distribution of Li and B in two representative glass samples, and their performance was comprehensively compared. APT can provide three‐dimensional Li and B imaging with very high spatial resolution (≤2 nm). In addition, absolute quantification of Li and B is possible, although there remains room for improving accuracy. However, the major drawbacks of APT include poor sample compatibility and limited field of view (normally ≤100 × 100 × 500 nm³). Comparatively, time‐of‐flight secondary ion mass spectrometry and nanoscale secondary ion mass spectrometry are sample‐friendly with flexible field of view (up to 500 × 500 µm² and image stitching is feasible); however, lateral resolution is limited to only about 100 nm. Therefore, secondary ion mass spectrometry and APT can be regarded as complementary techniques for nanoscale imaging of Li and B in glass and other novel materials. Copyright © 2016 John Wiley & Sons, Ltd.     

Multivariable structural characterization of semicrystalline polymer blends by small‐angle light scattering

A new multi‐variable‐measurement approach for characterizing and correlating the nanoscale and microscale morphology of crystal‐amorphous polymer blends with melt‐phase behavior is described. A vertical small‐angle light scattering (SALS) instrument optimized for examining the scattering and light transmitted from structures ranging from 0.5 to 50 μm, thereby spanning the size range characteristic of the initial‐to‐late stages of thermal‐phase transitions (e.g., melt‐phase separation and crystallization) in crystal‐amorphous polymer blends, was constructed. The SALS instrument was interfaced with differential scanning calorimetry (DSC), and simultaneous SALS/DSC/transmission measurements were performed. We show that the measurement of transmitted light and SALS under H_V (cross‐polarized) optical alignments during melting can be used to reliably measure the thermodynamic (e.g., crystal melting and melt‐phase separation temperatures) and structural variables (e.g., crystalline fraction within the superstructures and volume fraction of superstructures) necessary for describing the multiphase behavior of crystal‐amorphous blends in one combined measurement. We also evaluate the orientation correlations of crystalline volume elements within the superstructures. Our results indicate that simultaneous measurement of transmitted light can provide a reliable estimate of the total scattering from density and orientation fluctuations and the melt‐phase separation temperature of polymer blends. For solution‐cast poly(?‐caprolactone)/poly(D,L‐lactic acid) blends, our multivariable measurements during melting provide the parameters necessary to generate a crystal–liquid and liquid–liquid phase diagram and characterize the solid‐state morphology. This opens up the challenge to explore use of our vertical SALS instrument as a rapid and convenient method for developing structure–property relationships for crystal‐amorphous polymer blends. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2714–2727, 2002     

Tuning nanoscopic self‐assembly of diblock copolymer blends on a two‐dimensional interface

Spreading amphiphilic diblock copolymers on a two‐dimensional liquid interface has been observed to produce nanoscale features via self‐assembly. Here, we develop a model that incorporates the effects of polymer entanglement and surface diffusion in polymer blends to quantitatively predict the size of experimentally observed structures. Simulations show that different polymers in the blend cooperate to self‐assemble into nanoscale features of varying sizes. Characteristic nanoscopic dimensions can be tuned by adjusting two easily controllable macroscopic quantities: the blend composition and the initial surface concentration. Theoretical predictions are in agreement with experimentally measured feature dimensions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Facile Assembly of Dispersed ZrMCM‐41 Nanoparticles Promoted in‐situ by Zirconium Salt

Mesoporous ZrMCM‐41 nanoparticles were synthesized by a usual way where tetraethyl‐orthosilicate (TEOS) and zirconium nitrate were used as the inorganic precursors. The obtained nanoscale ZrMCM‐41 was characterized by X‐ray diffraction, N₂ physis‐sorption, scanning electron microscopy and transmission electron microscopy. Characterization results revealed that zirconium salt added in the synthesis had a crucial effect on the assembly of nanoscale ZrMCM‐41 with relatively uniform particle size, which was rarely observed in reported studies for ZrMCM‐41 synthesized using the similar method. Meanwhile, the possible mechanism behind the synthesis was discussed based on the character of hydrolysis and condensation of TEOS and the mild acidic environment induced by the hydrolysable zirconium salt under aqueous conditions. Thus obtained nanoscale ZrMCM‐41 with developed pore structures may be advantageous to general applications in catalysis or adsorption host‐guest chemistry in terms of efficient mass transport of guest molecules.     

Flexible fabrication and applications of polymer nanochannels and nanoslits

Fluidic devices that employ nanoscale structures (<100 nm in one or two dimensions, slits or channels, respectively) are generating great interest due to the unique properties afforded by this size domain compared to their micro-scale counterparts. Examples of interesting nanoscale phenomena include the ability to preconcentrate ionic species at extremely high levels due to ion selective migration, unique molecular separation modalities, confined environments to allow biopolymer stretching and elongation and solid-phase bioreactions that are not constrained by mass transport artifacts. Indeed, many examples in the literature have demonstrated these unique opportunities, although predominately using glass, fused silica or silicon as the substrate material. Polymer microfluidics has established itself as an alternative to glass, fused silica, or silicon-based fluidic devices. The primary advantages arising from the use of polymers are the diverse fabrication protocols that can be used to produce the desired structures, the extensive array of physiochemical properties associated with different polymeric materials, and the simple and robust modification strategies that can be employed to alter the substrate's surface chemistry. However, while the strengths of polymer microfluidics is currently being realized, the evolution of polymer-based nanofluidics has only recently been reported. In this critical review, the opportunities afforded by polymer-based nanofluidics will be discussed using both elastomeric and thermoplastic materials. In particular, various fabrication modalities will be discussed along with the nanometre size domains that they can achieve for both elastomer and thermoplastic materials. Different polymer substrates that can be used for nanofluidics will be presented along with comparisons to inorganic nanodevices and the consequences of material differences on the fabrication and operation of nanofluidic devices (257 references).     

Solution structural characterization of an array of nanoscale aqueous inorganic Ga13–xInx (0 ≤ x ≤ 6) clusters by 1H-NMR and QM computations

NMR spectroscopy is the go-to technique for determining the solution structures of organic, organometallic, and even macromolecular species. However, structure determination of nanoscale aqueous inorganic clusters by NMR spectroscopy remains an unexplored territory. The few hydroxo-bridged inorganic species well characterized by ¹H Nuclear Magnetic Resonance spectroscopy (¹H-NMR) do not provide enough information for signal assignment and prediction of new samples. ¹H-NMR and quantum mechanical (QM) computations were used to characterize the NMR spectra of the entire array of inorganic flat-Ga_13–xIn_x (0 ≤ x ≤ 6) nanoscale clusters in solution. A brief review of the known signals for μ₂-OH and μ₃-OH bridges gives expected ranges for certain types of protons, but does not give enough information for exact peak assignment. Integration values and NOESY data were used to assign the peaks of several cluster species with simple ¹H-NMR spectra. Computations agree with these hydroxide signal assignments and allow for assignment of the complex spectra arising from the remaining cluster species. This work shows that ¹H-NMR spectroscopy provides a variety of information about the solution behavior of inorganic species previously thought to be inaccessible by NMR due to fast ligand and/or proton exchange in wet solvents.     

Chemical and Topographical Single‐Cell Imaging by Near‐Field Desorption Mass Spectrometry

Simultaneously acquiring chemical and topographical information within a single cell at nanoscale resolutions is vital to cellular biology, yet it remains a great challenge due to limited lateral resolutions and detection sensitivities. Herein, the development of near‐field desorption mass spectrometry for correlated chemical and topographical imaging is reported, thereby bridging the gap between laser‐based mass spectrometry (MS) methods and multimodal single‐cell imaging. Using this integrated platform, an imaging resolution of 250 nm and 3D topographically reconstructed chemical single‐cell imaging were achieved. This technique offers more in‐depth cellular information than micrometer‐range laser‐based MS imaging methods. Considering the simplicity and compact size of the near‐field device, this technique can be introduced to MALDI‐MS, expanding the multimodal abilities of MS at nanoscale resolutions.     

Multifunctional nanostructures based on inorganic nanoparticles and oligothiophenes and their exploitation for cellular studies

The combination of materials that possess different properties (such as, for instance, fluorescence and magnetism) into one single object of nanoscale size represents an attractive challenge for biotechnology, especially for their potential relevance in biomedical applications. We report here the preparation of novel bifunctional conjugates based on the linkage of inorganic nanoparticles to organic oligothiophene fluorophores (OTFs). In comparison to the organic dyes commonly used in bioimaging and more similarly to colloidal quantum dots, OTFs have broad optical absorption spectra, and therefore OTF fluorophores emitting at different colors can be excited with a single excitation source, allowing for easier multiplexing analysis. In this work we show the preparation of OTF-nanoparticle conjugates based on gold and iron oxide nanoparticles and their characterization using different techniques such as gel electrophoresis, photoluminescence spectroscopy, dynamic light scattering, and so on. In addition, by performing an in vitro study on human tumor cells we show that OTF-nanoparticle conjugates emitting at different colors can be used for multiplexing detection. Also, in the case of iron oxide-OTF conjugates, once uptaken by the cells, we show that they preserve both their fluorescent and their magnetic properties.     

TGA and magnetization measurements for determination of composition and polymer conversion of magnetic hybrid particles

Magnetic hybrid colloidal particles can be characterized using various techniques and numerous tools leading generally to particles size, size distribution, and electrokinetic properties. However, the chemical composition of these hybrid particles can be estimated using thermal gravimetric analysis (TGA). More interestingly, the combination of this quantitative technique with the magnetization measurement leads not only to chemical composition but also to the overall polymerization conversion and more precisely to the polymerization conversion on the seed particles. In fact, the TGA performed on dried magnetic particles leads to exact organic/inorganic chemical composition. Regarding the magnetization, the amount of magnetic material can be deduced, and consequently, the amount of non‐magnetic material can be also estimated. Thus, TGA and magnetization measurements are considered as complementary techniques for characterization of magnetic hybrid colloidal particles. Copyright © 2015 John Wiley & Sons, Ltd.     

Molecular Design of Bisphosphonates To Adjust Their Reactivity toward Metal Sources for the Surfactant‐Assisted Synthesis of Mesoporous Films

The precise control of primary reactions in solutions is one of the most significant steps for the nanoscale design of inorganic solids in multidisciplinary fields. However, further growth of the inorganic species to give bulkier species disturbs such designs. The surfactant‐assisted synthesis of mesoporous materials is a good strategy for addressing such concerns because pores formed by supramolecularly mediated processes are surrounded by nanometer‐sized continuous frameworks. Many experiments are generally conducted to optimize the reaction conditions for the synthesis of highly ordered mesostructures. Herein, to minimize such trial‐and‐error efforts, a new and practical concept is proposed for the precise design of porous materials. By adjusting the reactivity between bisphosphonates and metal sources through molecular design of the starting bisphosphonate compound, it was possible to synthesize mesoporous films with unique compositions by a surfactant‐assisted approach.     

Micro‐Lensed Fiber Laser Desorption Mass Spectrometry Imaging Reveals Subcellular Distribution of Drugs within Single Cells

The visualization of temporal and spatial changes in the intracellular environment has great significance for chemistry and bioscience research. Mass spectrometry imaging (MSI) plays an important role because of its unique advantages, such as being label‐free and high throughput, yet it is a challenge for laser‐based techniques due to limited lateral resolution. Here, we develop a simple, reliable, and economic nanoscale MSI approach by introducing desorption laser with a micro‐lensed fiber. Using this integrated platform, we achieved 300 nm resolution MSI and successfully visualized the distribution of various small‐molecule drugs in subcellular locations. Exhaustive dynamic processes of anticancer drugs, including releasing from nanoparticle carriers entering nucleus of cells, can be readily acquired on an organelle scale. Considering the simplicity and universality of this nanoscale desorption device, it could be easily adapted to most of laser‐based mass spectrometry applications.     

Multifunctional Porous Microspheres Based on Peptide–Porphyrin Hierarchical Co‐Assembly

Photocatalytically active, multi‐chambered, biomolecule‐based microspheres were prepared by hierarchical co‐assembly of simple dipeptides and porphyrins. The colloidal microspheres are highly hydrated and consist of a network of J‐aggregate nanoscale substructures that serve as light‐harvesting antennae with a relatively broad spectral cross‐section and considerable photostability. These optical properties can be exploited in photocatalytic reactions involving inorganic or organic species. Taken together, these structural and functional features suggest that soft porous biomolecule‐based colloids are a plausible photosynthetic model that could be developed towards demonstrating aspects of primitive abiotic cellularity.     

Self‐Templated Stepwise Synthesis of Monodispersed Nanoscale Metalated Covalent Organic Polymers for In Vivo Bioimaging and Photothermal Therapy

Size‐ and shape‐controlled growth of nanoscale microporous organic polymers (MOPs) is a big challenge scientists are confronted with; meanwhile, rendering these materials for in vivo biomedical applications is still scarce. In this study, a monodispersed nanometalated covalent organic polymer (MCOP, M=Fe, Gd) with sizes around 120 nm was prepared by a self‐templated two‐step solution‐phase synthesis method. The metal ions (Fe³⁺, Gd³⁺) played important roles in generating a small particle size and in the functionalization of the products during the reaction with p ‐phenylenediamine (Pa). The resultant Fe‐Pa complex was used as a template for the subsequent formation of MCOP following the Schiff base reaction with 1,3,5‐triformylphloroglucinol (Tp). A high tumor suppression efficiency for this Pa‐based COP is reported for the first time. This study demonstrates the potential use of MCOP as a photothermal agent for photothermal therapy (PTT) and also provides an alternative route to fabricate nano‐sized MCOPs.     

Fabrication of flowerlike polymer superstructures using polymer/zeolite composites prepared with supercritical CO2

We report a route to the fabrication of unique flowerlike polymer superstructures with uniform petals at the nanoscale. In this method, polymer/zeolite composite is first prepared by loading corresponding monomer and initiator into the channels of the host zeolite with the aid of supercritical (SC) CO2, followed by thermal polymerization of monomers in the channels of the zeolite. The resultant polymer/zeolite composite is then treated with HF aqueous solution to allow the self-aggregation of the polymer and the inorganic components to form the polymeric layers and inorganic layers. Unique microscale flowerlike polymer superstructures are obtained after further treatment with HF aqueous solution. Different techniques, such as scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetry (TG), have been used to characterize the microflowers.     

Nanofabrication in Polymer Solutions

Nanostructured materials have drawn a great deal of attention in recent yearsbecause of their promising potentials in future applications.The fabrication of nano-materials has become a highly active research area involving scientists in many differentfields,e.g.,physics,chemistry,biology and materials science and engineering. Theinorganic synthesis including biomineralization by using intermolecular bonds to act in acooperative manner in order to construct organized supramolecular systems by s…     

Self‐Assembled Dipeptide Aerogels with Tunable Wettability

Constructing supramolecular materials with tunable properties and functions is a great challenge due to the complex competition between multiple assembly pathways. Herein, we report that dipeptides can self‐assemble into aerogels with entirely different surface wettability through precisely controlling the assembly pathways. Charged groups or aromatic residues are selectively exposed on the surface of their nanoscale building blocks which results either in a superhydrophilic or highly hydrophobic surface. With this special property, single component dipeptide aerogels can play diverse roles in medical care applications. This study suggests great promise in the synthesis of supramolecular materials with different targeted functions from the same molecular unit.     

Superior Ion‐exchange Property of Amorphous Aluminosilicates Prepared by a Co‐precipitation Method

The development of inexpensive inorganic ion‐exchangers for the purification of environmental pollutants is a social demand. Amorphous aluminosilicates with a relatively high homogeneous Al environment are prepared by a feasible co‐precipitation method, i. e., mixing an acidic aluminum sulfate solution and basic sodium silicate solution, which exhibit excellent ion‐exchange selectivity for Cs⁺ and Sr²⁺. The K_d value for Sr²⁺ was comparable with that of zeolite 4A. The local structures and ion‐exchange behavior of the amorphous aluminosilicates are systematically investigated. The ion‐exchange property of the amorphous aluminosilicates can be tuned by changing the interaction between the exchangeable cation and the amorphous aluminosilicates. Also, the amorphous aluminosilicates can adsorb bulky cations that zeolites hardly adsorb due to the limitation of the miropore size of zeolites.     

Chiral Supramolecular Nanoarchitectures from Macroscopic Mechanical Rotations: Effects on Enantioselective Aggregation Behavior of Phthalocyanines

Fluid dynamics, resulting from the macroscopic mechanical rotation of either a rotary evaporator or a magnetic stirrer, has been shown to selectively induce one of two enantiomers (mirror‐image structures) in certain nanoscale supramolecules. As an alternative to giving a chiral twist to synthesized supramolecules or polymers, it is a challenge to reproducibly prepare chiral species by only using macroscopic mechanical rotations. Demonstrated here is a highly reproducible method for rotary‐evaporation‐induced enantioselective H‐aggregation of achiral phthalocyanines. Chiral induction mechanisms are proposed by using the chiroptical‐sign‐based absolute structures. These results will provide insight to the origin of the homochirality of life, and serves as a pioneering study in a novel scientific field in terms of admixing nanoscale molecular chemistry and macroscopic fluid dynamics.