Utility of far-field effects from tip-assisted Raman spectroscopy for the detection of a monolayer of diblock copolymer reverse micelles for nanolithography.

A modified set-up for Raman spectroscopy is proposed to utilize an AFM probe in a regime beyond the dependence on near field optics. Possible mechanisms for the observed enhancement have been explored through comparisons to spectra from other enhanced Raman techniques, including surface enhanced Raman, interference enhanced Raman and polarized Raman spectroscopies. The effects of polarization, focusing and interference are heightened when near field effects are diminished, giving rise to spectral enhancement. This technique allows for the characterization of a sub-20 nm monolayer of polystyrene-block-poly(2 vinyl pyridine) reverse micelles and paves the way for a promising method of non-destructive analysis of large self-assembled arrays of colloids.

Universal Transfer Printing of Micelle-Templated Nanoparticles Using Plasma-Functionalized Graphene.

Nanostructure incorporation into devices plays a key role in improving performance, yet processes for preparing two-dimensional (2D) arrays of colloidal nanoparticles tend not to be universally applicable, particularly for soft and oxygen-sensitive substrates for organic and perovskite-based electronics. Here, we show a method of transferring reverse micelle-deposited (RMD) nanoparticles (perovskite and metal oxide) on top of an organic layer, using a functionalized graphene carrier layer for transfer printing. As the technique can be applied universally to RMD nanoparticles, we used magnetic (γ-Fe2O3) and luminescent (methylammonium lead bromide (MAPbBr3)) nanoparticles to validate the transfer-printing methodology. The strong photoluminescence from the MAPbBr3 under UV illumination and high intrinsic field of the γ-Fe2O3 as measured by magnetic force microscopy (MFM), coupled with Raman measurements of the graphene layer, confirm that all components survive the transfer-printing process with little loss of properties. Such an approach to introducing uniform 2D arrays of nanoparticles onto sensitive substrates opens up new avenues to tune the device interfacial properties.

Mesoporous Ternary Nitrides of Earth-Abundant Metals as Oxygen Evolution Electrocatalyst.

As sustainable energy becomes a major concern for modern society, renewable and clean energy systems need highly active, stable, and low-cost catalysts for the oxygen evolution reaction (OER). Mesoporous materials offer an attractive route for generating efficient electrocatalysts with high mass transport capabilities. Herein, we report an efficient hard templating pathway to design and synthesize three-dimensional (3-D) mesoporous ternary nickel iron nitride (Ni3FeN). The as-synthesized electrocatalyst shows good OER performance in an alkaline solution with low overpotential (259 mV) and a small Tafel slope (54 mV dec-1), giving superior performance to IrO2 and RuO2 catalysts. The highly active contact area, the hierarchical porosity, and the synergistic effect of bimetal atoms contributed to the improved electrocatalytic performance toward OER. In a practical rechargeable Zn-air battery, mesoporous Ni3FeN is also shown to deliver a lower charging voltage and longer lifetime than RuO2. This work opens up a new promising approach to synthesize active OER electrocatalysts for energy-related devices.

Probing the multi-step crystallization dynamics of micelle templated nanoparticles: structural evolution of single crystalline γ-Fe2O3.

Iron oxide nanoparticles synthesized with narrow size distribution were characterized using Raman spectroscopy, transmission electron microscopy and a superconducting quantum interference device magnetometer to investigate their composition, crystal structure and magnetic properties. Raman allowed us to explore the polymorphous transition of the iron oxide from the beginning of the synthesis process, as Raman can be used to monitor the precursors, the diblock-copolymer micelles and the resultant particles simultaneously under various processing steps. As different polymorphs possess distinct Raman active phonon modes, it also allows the identification of the exact phases of the resultant nanoparticles. Consequently, we show that the reverse micelle process results in pure phase nanoparticles only under certain conditions. Using insights obtained from examining the entire synthesis process, we can adjust the structure of small nanoparticles (∼6 nm) to achieve coercivity and saturation magnetization values that are usually only obtainable from larger particles (25 nm or larger). In this way, we show a route to tunable magnetic response based on the purity of the crystal phase rather than the particle size. By understanding the evolution of the entire synthesis process, it is possible to adjust the processing conditions to yield monodisperse single crystal phase nanoparticles for widespread use in a variety of applications.

Improved hole injection for blue phosphorescent organic light-emitting diodes using solution deposited tin oxide nano-particles decorated ITO anodes.

Blue phosphorescent organic light-emitting diodes (PHOLEDs) were fabricated with tin oxide (SnOx) nano-particles (NPs) deposited at the ITO anode to improve their electrical and optical performances. SnOx NPs helped ITO to increase the work function enhancing hole injection capability. Charge balance of the device was achieved using p- and n-type mixed host materials in emissive layer and the devices' luminance and maximum external quantum efficiency (EQE) increased about nearly 30%. Tuning the work function using solution processed NPs allows rapid optimization of device efficiency.

Author Correction: disLocate: tools to rapidly quantify local intermolecular structure to assess two-dimensional order in self-assembled systems.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

disLocate: tools to rapidly quantify local intermolecular structure to assess two-dimensional order in self-assembled systems.

Order classification is particularly important in photonics, optoelectronics, nanotechnology, biology, and biomedicine, as self-assembled and living systems tend to be ordered well but not perfectly. Engineering sets of experimental protocols that can accurately reproduce specific desired patterns can be a challenge when (dis)ordered outcomes look visually similar. Robust comparisons between similar samples, especially with limited data sets, need a finely tuned ensemble of accurate analysis tools. Here we introduce our numerical Mathematica package disLocate, a suite of tools to rapidly quantify the spatial structure of a two-dimensional dispersion of objects. The full range of tools available in disLocate give different insights into the quality and type of order present in a given dispersion, accessing the translational, orientational and entropic order. The utility of this package allows for researchers to extract the variation and confidence range within finite sets of data (single images) using different structure metrics to quantify local variation in disorder. Containing all metrics within one package allows for researchers to easily and rapidly extract many different parameters simultaneously, allowing robust conclusions to be drawn on the order of a given system. Quantifying the experimental trends which produce desired morphologies enables engineering of novel methods to direct self-assembly.