The dynamics of PEG-coated nanoparticles in concentrated protein solutions up to the molecular crowding range

Polymer-coated nanoparticles are widely studied in the context of nanomedicine and it is therefore of utmost importance to understand not only how their struc-ture but also how their colloidal dynamics are affected by physiologically relevant conditions.A characteristic feature of the cytosol of cells is the very high concen-tration of proteins among other matrix components,often termed macromolecular crowding.Here,the structure and colloidal dynamics of poly(ethylene glycol)(PEG)-coated gold nanoparticles in the presence of bovine serum albumin(BSA)concentrations ranging from 0 to 265 mg/mL are studied with X-ray photon correla-tion spectroscopy.For protein–nanoparticle mixtures with high BSA concentrations,comparable to intracellular levels,a significant deviation of the apparent viscosity from expectations for pure BSA solutions is found.Thefindings strongly indicate that the nanoscopic viscous properties of the dense protein solutions are significantly affected by the nanoparticles.At these high concentrations,the colloidal stability of the samples depends on the molecular weight of the coating PEG–ligand,whereas at lower concentrations no differences are observed.

Multilayer black phosphorus as saturable absorber for an Er:Lu_(2)O_(3) laser at~3 μm

Multilayer black phosphorus(BP) nanoplatelets of different thicknesses were prepared by the liquid phase exfoliation method and deposited onto yttrium aluminum garnet substrates to form saturable absorbers(SAs). These were characterized with respect to their thickness-dependent saturable absorption properties at 3 μm. The BP-SAs were employed in a passively Q-switched Er:Lu_2O_3 laser at 2.84 μm. By using BP exfoliated in different solvents,stable pulses as short as 359 ns were generated at an average output power of up to 755 m W. The repetition rate in the experiment was 107 k Hz, corresponding to a pulse energy of 7.1 μJ. These results prove that BP-SAs have a great potential for optical modulation in the mid-infrared range.

THz-Enhanced DC Ultrafast Electron Diffractometer

Terahertz-(THz-)based electron manipulation has recently been shown to hold tremendous promise as a technology for manipulating and driving the next generation of compact ultrafast electron sources.Here,we demonstrate an ultrafast electron diffractometer with THz-driven pulse compression.The electron bunches from a conventional DC gun are compressed by a factor of 10 and reach a duration of~180 fs(FWHM)with 10,000 electrons/pulse at a 1 kHz repetition rate.The resulting ultrafast electron source is used in a proof-of-principle experiment to probe the photoinduced dynamics of single-crystal silicon.The THz-compressed electron beams produce high-quality diffraction patterns and enable the observation of the ultrafast structural dynamics with improved time resolution.These results validate the maturity of THz-driven ultrafast electron sources for use in precision applications.

Dose-efficient scanning Compton X-ray microscopy

The highest resolution of images of soft matter and biological materials is ultimately limited by modification of the structure,induced by the necessarily high energy of short-wavelength radiation.Imaging the inelastically scattered X-rays at a photon energy of 60 keV(0.02 nm wavelength)offers greater signal per energy transferred to the sample than coherent-scattering techniques such as phase-contrast microscopy and projection holography.We present images of dried,unstained,and unfixed biological objects obtained by scanning Compton X-ray microscopy,at a resolution of about 70 nm.This microscope was realised using novel wedged multilayer Laue lenses that were fabricated to sub-ångström precision,a new wavefront measurement scheme for hard X rays,and efficient pixel-array detectors.The doses required to form these images were as little as 0.02%of the tolerable dose and 0.05%of that needed for phase-contrast imaging at similar resolution using 17 keV photon energy.The images obtained provide a quantitative map of the projected mass density in the sample,as confirmed by imaging a silicon wedge.Based on these results,we find that it should be possible to obtain radiation damage-free images of biological samples at a resolution below 10 nm.

Coexisting charge density wave and ferromagnetic instabilities in monolayer InSe

Recently fabricated InSe monolayers exhibit remarkable characteristics that indicate the potential of this material to host a number of many-body phenomena.In this work,we systematically describe collective electronic effects in hole-doped InSe monolayers using advanced many-body techniques.To this end,we derive a realistic electronic-structure model from first principles that takes into account the most important characteristics of this material,including a flat band with prominent van Hove singularities in the electronic spectrum,strong electron–phonon coupling,and weakly screened long-ranged Coulomb interactions.We calculate the temperature-dependent phase diagram as a function of band filling and observe that this system is in a regime with coexisting charge density wave and ferromagnetic instabilities that are driven by strong electronic Coulomb correlations.This regime can be achieved at realistic doping levels and high enough temperatures,and can be verified experimentally.We find that the electron–phonon interaction does not play a crucial role in these effects,effectively suppressing the local Coulomb interaction without changing the qualitative physical picture.