Structural biology studies inside cells and tissues require methods to thin vitrified specimens to electron transparency. Until now, focused ion beams based on gallium have been used. However, ion ...implantation, changes to surface chemistry and an inability to access high currents limit gallium application. Here, we show that plasma-coupled ion sources can produce cryogenic lamellae of vitrified human cells in a robust and automated manner, with quality sufficient for pseudo-atomic structure determination. Lamellae were produced in a prototype microscope equipped for long cryogenic run times (> 1 week) and with multi-specimen support fully compatible with modern-day transmission electron microscopes. We demonstrate that plasma ion sources can be used for structural biology within cells, determining a structure in situ to 4.9 Å, and characterise the resolution dependence on particle distance from the lamella edge. We describe a workflow upon which different plasmas can be examined to further streamline lamella fabrication.
Non-spherical nanostructures derived from soft matter and with uniform size-that is, monodisperse materials-are of particular utility and interest, but are very rare outside the biological domain. We ...report the controlled formation of highly monodisperse cylindrical block copolymer micelles (length dispersity < or = 1.03; length range, approximately 200 nm to 2 microm) by the use of very small (approximately 20 nm) uniform crystallite seeds that serve as initiators for the crystallization-driven living self-assembly of added block-copolymer unimers with a crystallizable, core-forming metalloblock. This process is analogous to the use of small initiator molecules in classical living polymerization reactions. The length of the nanocylinders could be precisely controlled by variation of the unimer-to-crystallite seed ratio. Samples of the highly monodisperse nanocylinders of different lengths that are accessible using this approach have been shown to exhibit distinct liquid-crystalline alignment behaviour.
Two metals are better than one: Main‐chain heterometallic block copolymers composed of iron‐ and cobalt‐rich blocks (see picture) were synthesized through consecutive photocontrolled ring‐opening ...polymerization (ROP) of sila1ferrocenophanes and dicarba2cobaltocenophanes followed by oxidation of the cobaltocene‐containing block. The redox properties and self‐assembly of the resulting block copolymers in solution were also studied.
Cotton-extracted cellulose nanocrystals are spin-coated from aqueous suspension (0.6 wt%) onto glass slides to give ca. 40 nm thick films. Impregnation with LiCl and redox active Fe(CN)63−/4− into ...this film gives extremely thin redox active layers (typically 170 nm at 60% relative humidity), which were investigated with a 4-point or 3-point probe electrochemical system based on 250 μm diameter platinum wire probes. Both voltammetry and impedance measurements were performed and effects from humidity, concentrations, and time domain on measurements are reported. Only a pico-litre volume under the working electrode was “active” to give a novel electroanalytical “spot test”.
Vacuum carbonization of organic precursors usually causes considerable structural damage and collapse of morphological features. However, for a polymer with intrinsic microporosity (PIM-EA-TB with a ...Brunauer–Emmet–Teller (BET) surface area of 1027 m2g–1), it is shown here that the rigidity of the molecular backbone is retained even during 500 °C vacuum carbonization, yielding a novel type of microporous heterocarbon (either as powder or as thin film membrane) with properties between those of a conducting polymer and those of a carbon. After carbonization, the scanning electron microscopy (SEM) morphology and the small-angle X-ray scattering (SAXS) Guinier radius remain largely unchanged as does the cumulative pore volume. However, the BET surface area is decreased to 242 m2g–1, but microporosity is considerably increased. The new material is shown to exhibit noticeable electrochemical features including two pH-dependent capacitance domains switching from ca. 33 Fg–1 (when oxidized) to ca. 147 Fg–1 (when reduced), a low electron transfer reactivity toward oxygen and hydrogen peroxide, and a four-point-probe resistivity (dry) of approximately 40 MΩ/square for a 1–2 μm thick film.
The surface modification of graphene oxide (GO) is carried out via the supramolecular functionalization route using a Zn(II)‐porphyrin which is soluble in common organic solvents on basis of long ...alkyl chains present at the exocyclic positions. This acts as a dispersing agent and decorates the surface of the graphene oxide uniformly, giving rise to a new nanohybrid denoted Zn(II)‐porphyrin@GO. The resulting Zn(II)‐porphyrin@GO nanohybrid forms a stable dispersion in ethanol (as characterized by several different spectroscopic techniques such as UV–vis, Fourier transform infrared, Raman). The morphology of Zn(II)‐porphyrin@GO nanohybrid is investigated by atomic force microscopy (AFM) and transmission electron microscope (TEM)/selected area electron diffraction. Both TEM and AFM measurements indicate that the Zn(II)‐porphyrin self‐assemble onto the surface of graphene oxide sheets. Steady‐state and time‐resolved fluorescence emission studies in the dispersed phase, and as a thin film, point toward the strongly quenched fluorescence emission and lifetime decay, suggesting that energy transfer occurs from the singlet excited state of Zn(II)‐porphyrin unit to GO sheets.
Design and synthesis of a novel porphyrin‐based nanohybrid whereby the entire surface of graphene oxide (GO) is modified via supramolecular assembly. The resulting Zn(II)‐porphyrin@GO nanohybrid forms stable dispersions in ethanol. The synthetic methodology presented here is of interest as it may open up new opportunities for the use of uniform dispersions of nanohybrid GO layered materials.
A novel two-photon-fluorescent N,O-heteroatom-rich carbon nanomaterial has been synthesized and characterized. The new carbon nanoparticles were produced by hydrothermal conversion from a ...one-photon-fluorescent poly(4-vinylpyridine) precursor (P4VP). The carbonized particles (cP4VP dots) with nonuniform particle diameter (ranging from sub-6 to 20 nm with some aggregates up to 200 nm) exhibit strong fluorescence properties in different solvents and have also been investigated for applications in cell culture media. The cP4VP dots retain their intrinsic fluorescence in a cellular environment and exhibit an average excited-state lifetime of 2.0 ± 0.9 ns in the cell. The cP4VP dots enter HeLa cells and do not cause significant damage to outer cell membranes. They provide one-photon or two-photon fluorescent synthetic scaffolds for imaging applications and/or drug delivery.
A one-step method of preparing photoelectrochemically active nanostructured BiVO
4
films is reported based on thermolysis (500 °C in air) of a polyethylene glycol (PEG300) “paint-on” precursor ...solution containing Bi
3+
(as nitrate) and VO
4
3−
(as the metavanadate ammonium salt). Films are formed directly on tin-doped indium oxide (ITO) substrates and characterised by electron microscopy (scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS)), X-ray diffraction, Raman spectroscopy, and photoelectrochemistry. The nanocrystalline film exhibited typically up to 52 % incident photon to current efficiency (IPCE) at 1.0 V vs. saturated calomel electrode (SCE) in aqueous 0.5 M Na
2
SO
4
with oxalate, strongly enhancing photocurrents.
Figure
Coloured FE-SEM image
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