The electronic properties of colloidal quantum dots (QDs) are critically dependent on both QD size and surface chemistry. Modification of quantum confinement provides control of the QD bandgap, while ligand-induced surface dipoles present a hitherto underutilized means of control over the absolute energy levels of QDs within electronic devices. Here, we show that the energy levels of lead sulfide QDs, measured by ultraviolet photoelectron spectroscopy, shift by up to 0.9 eV between different chemical ligand treatments. The directions of these energy shifts match the results of atomistic density functional theory simulations and scale with the ligand dipole moment. Trends in the performance of photovoltaic devices employing ligand-modified QD films are consistent with the measured energy level shifts. These results identify surface-chemistry-mediated energy level shifts as a means of predictably controlling the electronic properties of colloidal QD films and as a versatile adjustable parameter in the performance optimization of QD optoelectronic devices.

Ticks transmit more pathogens to humans and animals than any other arthropod. We describe the 2.1 Gbp nuclear genome of the tick, Ixodes scapularis (Say), which vectors pathogens that cause Lyme disease, human granulocytic anaplasmosis, babesiosis and other diseases. The large genome reflects accumulation of repetitive DNA, new lineages of retro-transposons, and gene architecture patterns resembling ancient metazoans rather than pancrustaceans. Annotation of scaffolds representing ∼57% of the genome, reveals 20,486 protein-coding genes and expansions of gene families associated with tick–host interactions. We report insights from genome analyses into parasitic processes unique to ticks, including host ‘questing', prolonged feeding, cuticle synthesis, blood meal concentration, novel methods of haemoglobin digestion, haem detoxification, vitellogenesis and prolonged off-host survival. We identify proteins associated with the agent of human granulocytic anaplasmosis, an emerging disease, and the encephalitis-causing Langat virus, and a population structure correlated to life-history traits and transmission of the Lyme disease agent.

The development of a water oxidation catalyst has been a demanding challenge in realizing water splitting systems. The asymmetric geometry and flexible ligation of the biological Mn4CaO5 cluster are important properties for the function of photosystem II, and these properties can be applied to the design of new inorganic water oxidation catalysts. We identified a new crystal structure, Mn3(PO4)2·3H2O, that precipitates spontaneously in aqueous solution at room temperature and demonstrated its high catalytic performance under neutral conditions. The bulky phosphate polyhedron induces a less-ordered Mn geometry in Mn3(PO4)2·3H2O. Computational analysis indicated that the structural flexibility in Mn3(PO4)2·3H2O could stabilize the Jahn-Teller-distorted Mn(III) and thus facilitate Mn(II) oxidation. This study provides valuable insights into the interplay between atomic structure and catalytic activity.

Although the stoichiometry of bulk lead sulfide (PbS) is exactly 1:1, that of quantum dots (QDs) can be considerably different from this crystalline limit. Employing first-principles calculations, we show that the impact of PbS QD stoichiometry on the electronic structure can be enormous, suggesting that control over the overall stoichiometry in the QD will play a critical role for improving the efficiency of optoelectronic devices made with PbS QDs. In particular, for bare PbS QDs, we find that: (i) stoichiometric PbS QDs are free from midgap states even without ligand passivation and independent of shape, (ii) off stoichiometry in PbS QDs introduces new states in the gap that are highly localized on certain surface atoms, and (iii) further deviations in stoichiometry lead to QDs with "metallic" behavior, with a dense number of energy states near the Fermi level. We further demonstrate that this framework holds for the case of passivated QDs by considering the attachment of ligand molecules as stoichiometry variations. Our calculations show that an optimal number of ligands makes the QD stoichiometric and heals unfavorable electronic structure, whereas too few or too many ligands cause effective off stoichiometry, resulting in QDs with defect states in the gap.

Cas9-mediated gene editing is a powerful tool for addressing research questions in arthropods. Current approaches rely upon delivering Cas9 ribonucleoprotein (RNP) complex by embryonic microinjection, which is challenging, is limited to a small number of species, and is inefficient even in optimized taxa. Here we develop a technology termed Receptor-Mediated Ovary Transduction of Cargo (ReMOT Control) to deliver Cas9 RNP to the arthropod germline by injection into adult female mosquitoes. We identify a peptide (P2C) that mediates transduction of Cas9 RNP from the female hemolymph to the developing mosquito oocytes, resulting in heritable gene editing of the offspring with efficiency as high as 0.3 mutants per injected mosquito. We demonstrate that P2C functions in six mosquito species. Identification of taxa-specific ovary-specific ligand–receptor pairs may further extend the use of ReMOT Control for gene editing in novel species.

Chemically modified graphene sheets were dispersed in a high-performance polyimide (PI) matrix using polyamic acid (PAA)/graphene nanocomposite as a precursor. PI nanocomposite films with different loadings of graphene sheets were prepared by thermal imidization of the as-prepared PAA/graphene nanocomposites. Graphene oxide (GO) synthesized by Hummer's method was chemically reduced with various reducing agents to produce reduced GOs (rGOs). The incorporation of only 5 wt% GO resulted in an ~12-fold and ~18-fold increase in the tensile strength and tensile modulus of PI, respectively, while the PI/rGO nanocomposites were found to have relatively inferior tensile properties. The superior mechanical properties of the PI/GO nanocomposites were attributed to the good dispersion and effective stress transfer between the polymer and GO sheets, as evidenced by the results from X-ray diffraction (XRD) and morphological studies. Furthermore, the PI/GO nanocomposites exhibited higher loading capacity than PI/rGO. The thermo-oxidative stability of PI was also remarkably improved with the addition of both GO and rGOs, but rGOs had a more pronounced effect. The electrical conductivity of PI/rGO nanocomposites was higher than that of PI/GO, suggesting restoration of the graphene basal plane upon the reduction of GO. The highest electrical conductivity was achieved for the l-ascorbic acid reduced GO-reinforced PI nanocomposites.

The oxygen evolution reaction (OER) is considered a major bottleneck in the overall water electrolysis process. In this work, highly active manganese oxide nano-catalysts were synthesized via hot injection. Facile surface treatment generated Mn(III) species on monodisperse 10 nm MnO nanocrystals (NCs). Size dependency of MnO NCs on OER activity was also investigated. Surprisingly, the partially oxidized MnO NCs only required 530 mV @ 5 mA cm−2 under near neutral conditions.

Mn5O8 nanoparticles (NPs) were obtained via the controlled oxidation of MnO NPs. The oxygen evolution reaction (OER) properties of Mn5O8 NPs were evaluated using cyclic voltammetry (CV). A current density of 5 mA/cm2 was reached when 580 mV of overpotential was applied at pH 7.8. Electron paramagnetic resonance (EPR) analysis was conducted to investigate the origin of high OER activity of Mn5O8 NPs. From the EPR analysis, Mn3+ was found to be involved in the OER process of the Mn5O8 materials.