White light wavefront control with a spatial light modulator.

Spatial light modulators are ubiquitous tools for wavefront control and laser beam shaping but have traditionally been used with monochromatic sources due to the inherent wavelength dependence of the calibration process and subsequent phase manipulation. In this work we show that such devices can also be used to shape broadband sources without any wavelength dependence on the output beam's phase. We outline the principle mathematically and then demonstrate it experimentally using a supercontinuum source to shape rotating white-light Bessel beams carrying orbital angular momentum.

Improved image contrast in nonlinear light-sheet fluorescence microscopy using i 2 PIE Pulse compression.

Nonlinear microscopy has become an invaluable tool for biological imaging, offering high-resolution visualization of biological specimens. In this manuscript, we present the application of a spectral phase measurement technique, i 2 PIE, to compress broad-bandwidth supercontinuum pulses for two-photon excitation fluorescence light-sheet fluorescence microscopy. The results demonstrated a significant improvement in the two-photon excitation response achieved. We also showed that the implementation of i 2 PIE allowed for enhanced image contrasts when compared to conventional compression techniques, with i 2 PIE producing an image contrast improvement over conventional methods by over 50%.

Temperature-Induced Effects on the Structure of Gramicidin S.

We report on the structure of Gramicidin S (GS) in a model membrane mimetic environment represented by the amphipathic solvent 1-octanol using one-dimensional (1D) and two-dimensional (2D) IR spectroscopy. To explore potential structural changes of GS, we also performed a series of spectroscopic measurements at differing temperatures. By analyzing the amide I band and using 2D-IR spectral changes, results could be associated to the disruption of aggregates/oligomers, as well as structural and conformational changes happening in the concentrated solution of GS. The ability of 2D-IR to enable differentiation in melting transitions of oligomerized GS structures is attributed to the sensitivity of the technique to vibrational coupling. Two melting transition temperatures were identified; at Tm1 in the range 41-47 °C where the GS aggregates/oligomers disassemble and at Tm2 = 57 ± 2 °C where there is significant change involving GS ß-sheet-type hydrogen bonds, whereby it is proposed that there is loss of interpeptide hydrogen bonds and we are left with mainly intrapeptide ß-sheet and ß-turn hydrogen bonds of the smaller oligomers. Further analysis with quantum mechanical/molecular mechanics (QM/MM) simulations and second derivative results highlighted the participation of active GS side chains. Ultimately, this work contributes toward understanding the GS structure and the formulation of GS analogues with improved bioactivity.

Embedding plasmonic gold nanoparticles in a ZnO layer enhanced the performance of inverted organic solar cells based on an indacenodithieno[3,2-b]thiophene-alt-5,5'-di(thiophen-2-yl)-2,2'-bithiazole-based push-pull polymer.

Recently, plasmonic nanoparticles (NPs) have attracted considerable attention as good candidates for enhancing the power conversion efficiency (PCE) of organic solar cells (OSCs) owing to their localized surface plasmon resonance (LSPR). In this study, the effect of embedding colloidal gold nanoparticles (cAu NPs) in the ZnO electron transport layer (ETL) on the PCEs of wide band gap polymer-based inverted OSCs was investigated. The active layer was composed of a bulk heterojunction of conjugated polymer based on indacenodithieno[3,2-b]thiophene and 5,5'-di(thiophen-2-yl)-2,2'-bithiazole PIDTT-DTBTz as a donor and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as an acceptor. The PCE of the reference device was improved by 22% when 10 wt% cAu NPs were embedded in the ZnO ETL. The short circuit current density (JSC) and fill factor (FF) were the main photovoltaic parameters contributing to the PCE enhancement. An improved absorption in the active layer due to the LSPR of cAu NPs as well as efficient exciton dissociation and charge collection were found to be the reasons for the enhanced JSC while the increase in FF was mainly due to the suppressed traps and improved conductivity of the ZnO layer by the NPs.

Templated polar order of a guest in a quasiracemic organic host.

A quasiracemic mixture of Dianin's compound and its thiol derivative enforces additional anisotropy of the guest-accessible space, thus facilitating a net polar arrangement of guest molecules; guest alignment is rationalized in terms of van der Waals volume considerations.