Suppressed Interfacial Charge Recombination of PbS Quantum Dot Photovoltaics by Graphene Incorporated into ZnO Nanoparticles

Single-layer graphene (SLG) was incorporated into ZnO nanoparticles (NPs), and use of this material in photovoltaic devices generated significant changes. The Fermi level of ZnO NPs underwent a downshift, whereas the conduction and valence bands were maintained with increasing SLG concentrations. Furthermore, the effective defect densities were reduced and carrier mobility was enhanced. Colloidal quantum dot photovoltaics (CQDPVs) with the SLG-incorporated ZnO NP layer as an electron transporting layer achieved significant performance enhancement. Poor performing CQDPVs were also observed with incorporation of an excess amount of SLG. This trend paralleled the interfacial charge recombination trends of CQDPVs. Effective suppression of interfacial recombination was achieved for CQDPVs with an appropriate SLG concentration, whereas dramatically increased interfacial recombination was observed for CQDPVs with an excess of SLG. For CQDPVs with appropriate SLG incorporation, efficient defect passivation and enhanced electron mobility of ZnO NPs facilitated loss-less electron transfer and efficient electron extraction without compromising the favorable energy level alignment. Excess SLG incorporation led to an increase in recombination within the PbS QD layer due to the presence of an energy barrier. This simple and powerful strategy provides an effective method for modulating the interfacial properties of CQDPVs

Epitaxial Phase Transition between Double Gyroid and Cylinder Phase in Diblock Copolymer Thin Film

The epitaxial relationship in the thermal phase transition between double gyroid (DG) and hexagonally packed cylinder (HEX) phases in polystyrene-<i>block</i>-polyisoprene thin films on Si wafer was investigated using transmission electron microtomography and grazing incidence small-angle X-ray scattering. Two different types of epitaxial transitions were observed, and they appeared to be selectively favored depending on the transition direction. One type of epitaxial relationship prevails in the phase transition from DG to HEX upon heating in which {121}_DG, {111}_DG, and {220}_DG are converted to {100}_HEX, {110}_HEX, and {001}_HEX, respectively. The interphase planes are {220}_DG and {001}_HEX, and the cylinders meet the {220}_DG plane perpendicularly (head-on, Type A) at the grain boundary between DG and HEX. Although there are small dimensional mismatch and distortion in the location of the cylinders in this epitaxial relationship, all cylinders are formed along the topologically equivalent DG skeletal path. On the other hand, in the transition from HEX to DG upon cooling, another epitaxial relationship as well as the head-on type epitaxy was observed, in which {100}_HEX, {110}_HEX, and {001}_HEX are converted to {121}_DG, {220}_DG, and {111}_DG, respectively. The interphase planes are {220}_DG and {110}_HEX, and the cylinders meet the {220}_DG plane in parallel (side-on, Type B) at the grain boundary between HEX and DG. The domain spacing and the symmetry of the two phases are matched near perfectly, but cylinders are converted to two different DG skeletal paths. The Type B epitaxy is hardly observed in the transition from DG to HEX

TRAF6ΔDC mice exhibit disruption of microbiotic homeostasis localized to the small intestine.

<p><b>(A)</b> Pie charts represent bacterial composition categorized by phylum in the small bowl of control (WT) or TRAF6ΔDC (ΔDC) mice. <b>(B)</b> Heatmap analysis shows relative abundance of taxa as a percentage of total 16S rRNA, organized according to genus or most specific assigned taxon. Color scales reflect proportion contributed by each taxon. Total bacterial genome was isolated from small intestinal contents of control (WT) or TRAF6ΔDC (ΔDC) mice (n = 4, 20 week old littermate and co-housed group). <b>(C)</b> The copy number of total bacterial 16S rRNA bacteria from fecal or small intestine contents of control (WT) and TRAF6ΔDC (ΔDC) was measured by comparing to reference E. coli 16S rRNA plasmids. Some groups were fed by broad-spectrum antibiotic water (Abx) for last 2 weeks before collecting samples. **p < 0.001; n.s., not significant. Data were analyzed by Anova on Prism software (n = 3).</p

Increased Tregs in GF TRAF6ΔDC lymphoid organs following antibiotic treatment.

<p><b>(A)</b> FACS plots gated on CD4⁺ T cells show intracellular staining Foxp3 from each indicated organ of germ-free (GF) TRAF6ΔDC bone marrow chimera (ΔDC-BMC) at 8 weeks post-reconstitution. Broad-spectrum antibiotic water was provided to a group of TRAF6ΔDC bone marrow chimeras (ΔDC) for the last 2 weeks. <b>(B)</b> Percentage of Foxp3⁺ CD4 T cells were determined from the indicated organs of TRAF6ΔDC bone marrow chimera (ΔDC-BMC) in germ-free (GF) or germ-free under antibiotics (GF-Abx). <b>(C)</b> Representative FACS plots show Foxp3⁺ CD4 T cells from each indicated organ of germ-free (GF) B6 mice. Some of the mice were provided with broad-spectrum antibiotic water (GF-Abx) for last 2 weeks. Percentage of Foxp3⁺ CD4 T cells were shown in each organs of germ-free B6 mice with (GF-Abx) or without antibiotics (GF). SP, spleen; MLN, mesenteric lymph node; SI, small intestine; COL, colon. **p < 0.01.</p

Germ-free conditions exacerbate inflammation of TRAF6ΔDC small intestine.

<p>(A) Representative gut images from control (WT) and TRAF6ΔDC (ΔDC) bone marrow chimera established in specific pathogen free (SPF) or germ-free (GF) condition at 8 weeks post-reconstitution. (B) Histological analyses were performed by H&E staining of duodenum from each mice. Scale bars represent 100 μm. (C) Lengths and masses of small intestines and colons were measured in control (WT) and TRAF6ΔDC (ΔDC) bone marrow chimera (n = 6). SPF, specific pathogen free; GF, germ-free. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001.</p

Broad-spectrum antibiotics ameliorate TRAF6ΔDC immune pathology exacerbated by GF conditions.

<p><b>(A)</b> FACS plots gated on CD4⁺ T cells show intracellular staining for interferon-γ (IFN-γ) and IL-13 from each indicated organ of TRAF6ΔDC bone marrow chimera (ΔDC-BMC) in germ-free (GF) condition at 8 weeks post-reconstitution. Some of TRAF6ΔDC bone marrow chimeras (ΔDC) were provided with broad-spectrum antibiotic water (Abx). The antibiotic water, containing 1 g/L Ampicillin, 1 g/L Neomycin, 0.5 g/L Vancomycin, and 1 g/L Metronidazole, was provided ad libitum in water to TRAF6ΔDC bone marrow chimera (ΔDC) for last 2 weeks. <b>(B)</b> Percentage of IL-13⁺ CD4 T cells were shown in each organs of TRAF6ΔDC bone marrow chimera (ΔDC-BMC) in germ-free (GF) or germ-free under antibiotics (GF-Abx). <b>(C)</b> Lengths and masses of small intestines were measured in GF and GF-Abx TRAF6ΔDC bone marrow chimera (ΔDC-BMC). <b>(D)</b> Fibrosis markers (Acta2 and Igf-1) and Th2 cell cytokines (IL-13, IL-5, and IL-4) mRNA expression levels in the ileum region of small intestines from GF and GF-Abx TRAF6ΔDC bone marrow chimera (ΔDC-BMC). Histograms (mean ± SD) are representative of four independent experiments. SP, spleen; MLN, mesenteric lymph node. *p < 0.05; **p < 0.01; ***p < 0.001.</p