Circularly Polarized Light
Photonic processes contributing to circularly polarized light emission (CPLE) from chiral nanostructures measured experimentally most commonly include both circularly ...polarized luminescence (CPL) and circularly polarized scattering (CPS). Engineering of materials with strong CPLE requires synergistic integration of both CPL and CPS effects. Such systems are reviewed by Shuang Jiang and Nicholas A. Kotov in article number 2108431.
Chiral Inorganic Nanostructures Ma, Wei; Xu, Liguang; de Moura, André F ...
Chemical reviews,
06/2017, Letnik:
117, Številka:
12
Journal Article
Recenzirano
The field of chiral inorganic nanostructures is rapidly expanding. It started from the observation of strong circular dichroism during the synthesis of individual nanoparticles (NPs) and their ...assemblies and expanded to sophisticated synthetic protocols involving nanostructures from metals, semiconductors, ceramics, and nanocarbons. Besides the well-established chirality transfer from bioorganic molecules, other methods to impart handedness to nanoscale matter specific to inorganic materials were discovered, including three-dimentional lithography, multiphoton chirality transfer, polarization effects in nanoscale assemblies, and others. Multiple chiral geometries were observed with characteristic scales from ångströms to microns. Uniquely high values of chiral anisotropy factors that spurred the development of the field and differentiate it from chiral structures studied before, are now well understood; they originate from strong resonances of incident electromagnetic waves with plasmonic and excitonic states typical for metals and semiconductors. At the same time, distinct similarities with chiral supramolecular and biological systems also emerged. They can be seen in the synthesis and separation methods, chemical properties of individual NPs, geometries of the nanoparticle assemblies, and interactions with biological membranes. Their analysis can help us understand in greater depth the role of chiral asymmetry in nature inclusive of both earth and space. Consideration of both differences and similarities between chiral inorganic, organic, and biological nanostructures will also accelerate the development of technologies based on chiroplasmonic and chiroexcitonic effects. This review will cover both experiment and theory of chiral nanostructures starting with the origin and multiple components of mirror asymmetry of individual NPs and their assemblies. We shall consider four different types of chirality in nanostructures and related physical, chemical, and biological effects. Synthetic methods for chiral inorganic nanostructures are systematized according to chirality types, materials, and scales. We also assess technological prospects of chiral inorganic materials with current front runners being biosensing, chiral catalysis, and chiral photonics. Prospective venues for future fundamental research are discussed in the conclusion of this review.
The intra- and extracellular positioning of plasmonic nanoparticles (NPs) can dramatically alter their curative/diagnostic abilities and medical outcomes. However, the inability of common ...spectroscopic identifiers to register the events of transmembrane transport denies their intracellular vs. extracellular localization even for cell cultures. Here we show that the chiroptical activity of DNA-bridged NP dimers allows one to follow the process of internalization of the particles by the mammalian cells and to distinguish their extra- vs intra-cellular localizations by real-time spectroscopy in ensemble. Circular dichroism peaks in the visible range change from negative to positive during transmembrane transport. The chirality reversal is associated with a spontaneous twisting motion around the DNA bridge caused by the large change in electrostatic repulsion between NPs when the dimers move from interstitial fluid to cytosol. This finding opens the door for spectroscopic targeting of plasmonic nanodrugs and quantitative assessment of nanoscale interactions. The efficacy of dichroic targeting of chiral nanostructures for biomedical applications is exemplified here as photodynamic therapy of malignancies. The efficacy of cervical cancer cell elimination was drastically increased when circular polarization of incident photons matched to the preferential absorption of dimers localized inside the cancer cells, which is associated with the increased generation of reactive oxygen species and their preferential intracellular localization.
Branched Aramid Nanofibers Zhu, Jian; Yang, Ming; Emre, Ahmet ...
Angewandte Chemie (International ed.),
September 18, 2017, Letnik:
56, Številka:
39
Journal Article
Recenzirano
Odprti dostop
Interconnectivity of components in three‐dimensional networks (3DNs) is essential for stress transfer in hydrogels, aerogels, and composites. Entanglement of nanoscale components in the network ...relies on weak short‐range intermolecular interactions. The intrinsic stiffness and rod‐like geometry of nanoscale components limit the cohesive energy of the physical crosslinks in 3DN materials. Nature realizes networked gels differently using components with extensive branching. Branched aramid nanofibers (BANFs) mimicking polymeric components of biological gels were synthesized to produce 3DNs with high efficiency stress transfer. Individual BANFs are flexible, with the number of branches controlled by base strength in the hydrolysis process. The extensive connectivity of the BANFs allows them to form hydro‐ and aerogel monoliths with an order of magnitude less solid content than rod‐like nanocomponents. Branching of nanofibers also leads to improved mechanics of gels and nanocomposites.
Branching needed: The production of 3D networks with efficient stress transfer is enabled by branched aramid nanofibers (BANFs). The extensive connectivity of the BANFs leads to the formation of hydro‐ and aerogel monoliths with much less solid content than rod‐like nanocomponents. The branching also leads to improved gel mechanics, allowing the preparation of continuous microscale luminescent fibers and high‐performance nanocomposites.
The same properties that made carbon nanotube (CNT) composites interesting for electronics, sensing, and ultrastrong structural materials also make them an asset for biomedical engineering. The ...combination of electron conductivity, corrosion resistance, and strength are essential for neuroprosthetic devices. All of the studies in this area demonstrating cellular adhesion and signal transduction activity on CNT matrixes were conducted, so far, with terminally differentiated primary cells and cancerous cell lines. Neural stem cells are very plastic neural precursors capable of adapting to environmental conditions and recreating signal transduction pathways. Their intrinsic biological functionality not only makes the transition to stem cell cultures a difficult-to-avoid step but also implies several fundamentally important challenges. Here we demonstrate that mouse embryonic neural stem cells (NSCs) from the cortex can be successfully differentiated to neurons, astrocytes, and oligodendrocytes with clear formation of neurites on layer-by-layer (LBL) assembled single-walled carbon nanotube (SWNT)−polyelectrolyte multilayer thin films. Biocompatibility, neurite outgrowth, and expression of neural markers were similar to those differentiated on poly-l-ornithine (PLO), one of the most widely used growth substratums for neural stem cells.
Zinc oxide nanoparticles (ZnO-NPs) are attractive as broad-spectrum antibiotics, however, their further engineering as antimicrobial agents and clinical translation is impeded by controversial data ...about their mechanism of activity. It is commonly reported that ZnO-NP's antimicrobial activity is associated with the production of reactive oxygen species (ROS). Here we disprove this concept by comparing the antibacterial potency of ZnO-NPs and their capacity to generate ROS with hydrogen peroxide (H
O
). Then, using gene transcription microarray analysis, we provide evidence for a novel toxicity mechanism. Exposure to ZnO-NPs resulted in over three-log reduction in colonies of methicillin resistant S. aureus with minimal increase in ROS or lipid peroxidation. The amount of ROS required for the same amount of killing by H
O
was much greater than that generated by ZnO-NPs. In contrast to H
O
, ZnO-NP mediated killing was not mitigated by the antioxidant, N-acetylcysteine. ZnO-NPs caused significant up-regulation of pyrimidine biosynthesis and carbohydrate degradation. Simultaneously, amino acid synthesis in S. aureus was significantly down-regulated indicating a complex mechanism of antimicrobial action involving multiple metabolic pathways. The results of this study point to the importance of specific experimental controls in the interpretation of antimicrobial mechanistic studies and the need for targeted molecular mechanism studies. Continued investigation on the antibacterial mechanisms of biomimetic ZnO-NPs is essential for future clinical translation.
Control of the spin angular momentum (SAM) carried in a photon provides a technologically attractive element for next-generation quantum networks and spintronics
. However, the weak optical activity ...and inhomogeneity of thin films from chiral molecular crystals result in high noise and uncertainty in SAM detection. Brittleness of thin molecular crystals represents a further problem for device integration and practical realization of chiroptical quantum devices
. Despite considerable successes with highly dissymmetric optical materials based on chiral nanostructures
, the problem of integration of nanochiral materials with optical device platforms remains acute
. Here we report a simple yet powerful method to fabricate chiroptical flexible layers via supramolecular helical ordering of conjugated polymer chains. Their multiscale chirality and optical activity can be varied across the broad spectral range by chiral templating with volatile enantiomers. After template removal, chromophores remain stacked in one-dimensional helical nanofibrils producing a homogeneous chiroptical layer with drastically enhanced polarization-dependent absorbance, leading to well-resolved detection and visualization of SAM. This study provides a direct path to scalable realization of on-chip detection of the spin degree of freedom of photons necessary for encoded quantum information processing and high-resolution polarization imaging.
Chirality at the nanometer scale represents one of the most rapidly developing areas of research. Self-assembly of DNA–nanoparticle (NP) hybrids enables geometrically precise assembly of chiral ...isomers. The concept of a discrete chiral nanostructure of tetrahedral shape and topology fabricated from four different NPs located in the corners of the pyramid is fundamental to the field. While the first observations of optical activity of mixed pyramidal assemblies were made in 2009 ( Chen W. ; Nano Lett. 2009, 9, 2153−2159 ), further studies are difficult without finely resolved optical data for precisely organized NP pyramidal enantiomers. Here we describe the preparation of a family of self-assembled chiral pyramids made from multiple metal and/or semiconductor NPs with a yield as high as 80%. Purposefully made R- and S-enantiomers of chiral pyramids with four different NPs from three different materials displayed strong chiroptical activity, with anisotropy g-factors as high as 1.9 × 10–2 in the visible spectral range. Importantly, all NP constituents contribute to the chiroptical activity of the R/S pyramids. We were able to observe three different circular dichroism signals in the range of 350–550 nm simultaneously. They correspond to the plasmonic oscillations of gold, silver, and bandgap transitions of quantum dots. Tunability of chiroptical bands related to these transitions is essential from fundamental and practical points of view. The predictability of optical properties of pyramids, the simplicity of their self-assembly in comparison with lithography, and the possibility for polymerase chain reaction-based automation of their synthesis are expected to facilitate their future applications.
DNA-bridged pairs of seemingly spherical metallic nanoparticles (NPs) have chiral geometry due to the nonideal oblong shape of the particles and scissor-like conformation. Here we demonstrate that ...deposition of gold and silver shells around the NP heterodimers enables spectral modulation of their chiroplasmonic bands in 400–600 nm region and results in significantly enhanced optical activity with g-factors reaching 1.21 × 10–2. The multimetal heterodimers optimized for coupling with the spin angular momentum of incident photons enable polymerase chain reaction (PCR)-based DNA detection at the zeptomolar level. This significant improvement in the sensitivity of detection is attributed to improvement of base pairing in the presence of NPs, low background for chiroplasmonic detection protocol, and enhancement of photon–plasmon coupling for light with helicity matching that of the twisted geometry of the heterodimers.
Multiple properties of plasmonic assemblies are determined by their geometrical organization. While high degree of complexity was achieved for plasmonic superstructures based on nanoparticles (NPs), ...little is known about the stable and structurally reproducible plasmonic assemblies made up from geometrically diverse plasmonic building blocks. Among other possibilities, they open the door for the preparation of regiospecific isomers of nanoscale assemblies significant both from a fundamental point of view and optical applications. Here, we present a synthetic method for complex assemblies from NPs and nanorods (NRs) based on selective modification of NRs with DNA oligomers. Three types of assemblies denoted as End, Side, and Satellite isomers that display distinct elements of regiospecificity were prepared with the yield exceeding 85%. Multiple experimental methods independently verify various structural features, uniformity, and stability of the prepared assemblies. The presence of interparticle gaps with finely controlled geometrical parameters and inherently small size comparable with those of cellular organelles fomented their study as intracellular probes. Against initial expectations, SERS intensity for End, Side, and Satellite isomers was found to be dependent primarily on the number of the NPs in the superstructures rationalized with the help of electrical field simulations. Incubation of the label-free NP–NR assemblies with HeLa cells indicated sufficient field enhancement to detect structural lipids of mitochondria and potentially small metabolites. This provided the first proof-of-concept data for the possibility of real-time probing of the local organelle environment in live cells. Further studies should include structural optimization of the assemblies for multitarget monitoring of metabolic activity and further increase in complexity for applications in transformative optics.
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