Polarized X-ray scattering measures molecular orientation in polymer-grafted nanoparticles.

Polymer chains are attached to nanoparticle surfaces for many purposes, including altering solubility, influencing aggregation, dispersion, and even tailoring immune responses in drug delivery. The most unique structural motif of polymer-grafted nanoparticles (PGNs) is the high-density region in the corona where polymer chains are stretched under significant confinement, but orientation of these chains has never been measured because conventional nanoscale-resolved measurements lack sensitivity to polymer orientation in amorphous regions. Here, we directly measure local chain orientation in polystyrene grafted gold nanoparticles using polarized resonant soft X-ray scattering (P-RSoXS).

Tuning Hierarchical Order and Plasmonic Coupling of Large-Area, Polymer-Grafted Gold Nanorod Assemblies via Flow-Coating.

Solution-based printing of anisotropic nanostructures is foundational to many emerging technologies, such as energy storage devices, photonic elements, and sensors. Methods to rapidly (>mm/s) manufacture large area assemblies (≫cm) with simultaneous control of thickness (<10 nm), nanoparticle spacing (<5 nm), surface roughness (<5 nm), and global and local orientational order are still lacking. Herein, we demonstrate such capability using flow-coating to fabricate robust, self-supporting mono- and bilayer films of polystyrene-grafted gold nanorods (PS-AuNRs) onto solid substrates.

Projectile Impact Shock-Induced Deformation of One-Component Polymer Nanocomposite Thin Films.

Matrix-free assemblies of polymer-grafted nanoparticles (PGNs) enable mechanically robust materials for a variety of structural, electronic, and optical applications. Recent quasi-static mechanical studies have identified the key parameters that enhance canopy entanglement and promote plasticity of the PGNs below . Here we experimentally explore the high-strain-rate shock impact behavior of polystyrene grafted NPs and compare their energy absorption capabilities to that of homopolystyrene for film thicknesses ranging from 75 to 550 nm and for impact velocities from 350 to 800 m/s.

Autonomous materials discovery driven by Gaussian process regression with inhomogeneous measurement noise and anisotropic kernels.

A majority of experimental disciplines face the challenge of exploring large and high-dimensional parameter spaces in search of new scientific discoveries. Materials science is no exception; the wide variety of synthesis, processing, and environmental conditions that influence material properties gives rise to particularly vast parameter spaces. Recent advances have led to an increase in the efficiency of materials discovery by increasingly automating the exploration processes.

DNA-directed nanofabrication of high-performance carbon nanotube field-effect transistors.

Biofabricated semiconductor arrays exhibit smaller channel pitches than those created using existing lithographic methods. However, the metal ions within biolattices and the submicrometer dimensions of typical biotemplates result in both poor transport performance and a lack of large-area array uniformity. Using DNA-templated parallel carbon nanotube (CNT) arrays as model systems, we developed a rinsing-after-fixing approach to improve the key transport performance metrics by more than a factor of 10 compared with those of previous biotemplated field-effect transistors.

Precise pitch-scaling of carbon nanotube arrays within three-dimensional DNA nanotrenches.

Precise fabrication of semiconducting carbon nanotubes (CNTs) into densely aligned evenly spaced arrays is required for ultrascaled technology nodes. We report the precise scaling of inter-CNT pitch using a supramolecular assembly method called spatially hindered integration of nanotube electronics. Specifically, by using DNA brick crystal-based nanotrenches to align DNA-wrapped CNTs through DNA hybridization, we constructed parallel CNT arrays with a uniform pitch as small as 10.

A Low Energy Route to DNA-Wrapped Carbon Nanotubes via Replacement of Bile Salt Surfactants.

DNA-wrapped carbon nanotubes are a class of bionano hybrid molecules that have enabled carbon nanotube sorting, controlled assembly, and biosensing and bioimaging applications. The current method of synthesizing these hybrids via direct sonication of DNA/nanotube mixtures is time-consuming and not suitable for high-throughput synthesis and combinatorial sequence screening. Additionally, the direct sonication method does not make use of nanotubes presorted by extensively developed surfactant-based methods, is not effective for large diameter (>1 nm) tubes, and cannot maintain secondary and tertiary structural and functional domains present in certain DNA sequences.

Differentiating Left- and Right-Handed Carbon Nanotubes by DNA.

New structural characteristics emerge when solid-state crystals are constructed in lower dimensions. This is exemplified by single-wall carbon nanotubes, which exhibit a degree of freedom in handedness and a multitude of helicities that give rise to three distinct types of electronic structures: metals, quasi-metals, and semiconductors. Here we report the use of intrinsically chiral single-stranded DNA to achieve simultaneous handedness and helicity control for all three types of nanotubes.

Intensity Ratio of Resonant Raman Modes for (n,m) Enriched Semiconducting Carbon Nanotubes.

Relative intensities of resonant Raman spectral features, specifically the radial breathing mode (RBM) and G modes, of 11, chirality-enriched, single-wall carbon nanotube (SWCNT) species were established under second-order optical transition excitation. The results demonstrate an under-recognized complexity in the evaluation of Raman spectra for the assignment of (n,m) population distributions. Strong chiral angle and mod dependencies affect the intensity ratio of the RBM to G modes and can result in misleading interpretations.

Variance Spectroscopy.

Spectroscopic analysis and study of nanoparticle samples is often hampered by structural diversity that presents a complex superposition of spectral signatures. By probing the spectra of small volumes within dilute samples, we can expose statistical variations in composition to obtain information unavailable from bulk spectroscopy. This new approach is demonstrated using fluorescence spectra of unsorted single-walled carbon nanotube samples to deduce structure-specific abundances and emissive efficiencies.

Redox sorting of carbon nanotubes.

This work expands the redox chemistry of single-wall carbon nanotubes (SWCNTs) by investigating its role in a number of SWCNT sorting processes. Using a polyethylene glycol (PEG)/dextran (DX) aqueous two-phase system, we show that electron-transfer between redox molecules and SWCNTs triggers reorganization of the surfactant coating layer, leading to strong modulation of nanotube partition in the two phases. While the DX phase is thermodynamically more favored by an oxidized SWCNT mixture, the mildly reducing PEG phase is able to recover SWCNTs from oxidation and extract them successively from the DX phase.

Directly measured optical absorption cross sections for structure-selected single-walled carbon nanotubes.

We have measured peak and spectrally integrated absolute absorption cross sections for the first (E11) and second (E22) optical transitions of seven semiconducting single-walled carbon nanotube (SWCNT) species in bulk suspensions. Species-specific concentrations were determined using short-wave IR fluorescence microscopy to directly count SWCNTs in a known sample volume. Measured cross sections per atom are inversely related to nanotube diameter.

Chromatic aberration short-wave infrared spectroscopy: nanoparticle spectra without a spectrometer.

A new method is described for measuring the short-wave infrared (SWIR) emission wavelengths of numerous individual nanoparticles without using a dedicated spectrometer. Microscope objectives designed for use at visible wavelengths often show severe axial chromatic aberration in the SWIR. This makes coplanar objects emitting at different SWIR wavelengths appear to focus at different depths.

Measuring single-walled carbon nanotube length distributions from diffusional trajectories.

A new method is demonstrated for measuring the length distributions of dispersed single-walled carbon nanotube (SWCNT) samples by analyzing diffusional motions of many individual nanotubes in parallel. In this method, termed "length analysis by nanotube diffusion" (LAND), video sequences of near-IR fluorescence microscope images showing many semiconducting SWCNTs are recorded and processed by custom image analysis software. This processing locates the individual nanotubes, tracks their translational trajectories, computes the corresponding diffusion coefficients, and converts those values to nanotube lengths.