Antiferromagnetic Iron Nanocolloids: A New Generation in Vivo <i>T</i>₁ MRI Contrast Agent

A novel <i>T</i>₁ agent, antiferromagnetic α-iron oxide-hydroxide (α-FeOOH) nanocolloids with a diameter of 2–3 nm, has been successfully prepared. These nanocolloids, together with a post synthetic strategy performed in mesoporous silica, are a great improvement over the low <i>T</i>₁-weighted contrast common in traditional magnetic silica nanocomposites. The intrinsic antiferromagnetic goethite (α-FeOOH) shows very low magnetization (<i>M</i>_z) of 0.05 emu g^–1 at <i>H</i> = 2 T at 300 K (0.0006 emu g^–1 for FeOOH/WMSN-PEG), which is 2 orders of magnitude smaller than any current ultrasmall iron oxide NPs (>5 emu g^–1) reported to date, hence ensuring the low <i>r</i>₂ (∝ <i>M</i>_z) (7.64 mM^–1 s^–1) and <i>r</i>₂/<i>r</i>₁ ratio (2.03) at 4.7 T. These biodegradable α-FeOOH nanocolloids also demonstrate excellent in vitro cellular imaging and in vivo MR vascular and urinary trace imaging capability with outstanding biocompatibility, which is exceptionally well secreted by the kidney and not the liver as with most nanoparticles, opening up a new avenue for designing powerful antiferromagnetic iron <i>T</i>₁ contrast agents

Strategic Design of Three-Dimensional (3D) Urchin-Like Pt–Ni Nanoalloys: How This Unique Nanostructure Boosts the Bulk Heterojunction Polymer Solar Cells Efficiency to 8.48%

In this study, a simple and systematic shape-controlled synthetic protocol for tailoring nanoscale structures to generate large and monodispersed of three-dimensional (3D) urchin-like Pt–Ni multipods (MPs) and spherical nanoparticles (NPs) is reported, for which the mechanism of production is elaborated in detail. We then demonstrate, for the first time, that the 3D urchin-like Pt–Ni MPs possess good solution processability and substantially enhance both short-circuit current density (<i>J</i>_sc) and fill factor (FF) and consequently increase the overall power conversion efficiencies (PCEs), because of the combination of multiple scattering processes of incident light, improved conductivity, and facilitating the charge transport in the active layer. PSC fabricated using 5% Pt–Ni MPs embedded in a blend of poly­{[4,8-bis­(2-ethyl-hexyl-thiophene-5-yl)-benzo­[1,2-b:4,5-b′]­dithiophene-2,6-diyl]-<i>alt</i>-[2-(2′-ethyl-hexanoyl)-thieno­[3,4-<i>b</i>]­thiophen-4,6-diyl]} (PBDTTT-C-T) and [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM) leads to compelling device PCEs of 8.48%, in comparison to 7.38% of the reference device (PBDTTT-C-T:PC₇₁BM, fabricated and tested under the same conditions). This study thus demonstrates a novel approach to enhance the photovoltaic performance, in combination with 3D urchin-like nanoalloys

The Effects of Fluorine-Contained Molecules on Improving the Polymer Solar Cell by Curing the Anomalous S‑Shaped <i>I</i>–<i>V</i> Curve

In this study, we investigate the effects of fluorinated poly­(3,4-ethylene dioxythiophene):poly­(styrenesulfonate) buffer layer on the performance of polymer photovoltaic cells. We demonstrate for the first time, the deterioration of the device performance can be effectively mended by modifying the interface between the active layer and buffer layer with heptadecafluoro-1,1,2,2-tetra-hydro-decyl trimethoxysilane (PFDS) and perfluorononane. Device performance shows a substantial enhancement of short-circuit current from 7.90 to 9.39 mA/cm² and fill factor from 27% to 53%. The overall device efficiency was improved from 0.98% to 3.12% for PFDS modified device. The mechanism of S-shape curing is also discussed. In addition, the stability of modified devices shows significant improvement than those without modification. The efficiency of the modified devices retains about half (1.88%) of its initial efficiency (4.1%) after 30 d compared to the unmodified ones (0.61%), under air atmosphere

High-Efficiency Small-Molecule-Based Organic Light Emitting Devices with Solution Processes and Oxadiazole-Based Electron Transport Materials

We demonstrate high-efficiency small-molecule-based white phosphorescent organic light emitting diodes (PHOLEDs) by single-active-layer solution-based processes with the current efficiency of 17.3 cdA^‑1 and maximum luminous efficiency of 8.86 lmW^‑1 at a current density of 1 mA cm^‑2. The small-molecule based emitting layers are codoped with blue and orange phosphorescent dyes. We show that the presence of CsF/Al at cathodes not only improves electron transport in oxadiazole-containing electron transport layers (ETLs), but also facilitates electron injection through the reacted oxadiazole moiety to reduce interface resistance, which results in the enhancement of current efficiency. By selecting oxadiazole-based materials as ETLs with proper electron injection layer (EIL)/cathode structures, the brightness and efficiency of white PHOLEDs are significantly improved

Shape-Dependent Light Harvesting of 3D Gold Nanocrystals on Bulk Heterojunction Solar Cells: Plasmonic or Optical Scattering Effect?

In the work, mechanisms behind various 3D nanocrystals enhanced performance of bulk heterojunction solar cells were studied comprehensively. Four types of gold nanoparticles (NPs) with distinctly different shapes and great uniformity were designed and synthesized, including cubes, rhombic dodecahedra (RD), edge- and corner-truncated octahedra (ECTO), and triangular plates, to systematically probe their influences on photovoltaics. RD and triangular plates show a higher growth rate, while slower growth favors cubes and ECTO formation by controlling the reduction agent and capping ion amount. NPs with increasing corners and proper size of cross-section induce stronger near-field coupling and far-field scattering in P3HT:PC₆₁BM-based active layers. Both finite-difference time-domain simulation and UV–visible absorption spectra firmly support that RD exhibit the strongest localized surface plasmon resonance and optical scattering. With optimized conditions, a high power conversion efficiency exceeding 4% was reproducibly achieved