Beyond n-dopants for organic semiconductors: use of bibenzo[d]imidazoles in UV-promoted dehalogenation reactions of organic halides.

2,2'-Bis(4-dimethylaminophenyl)- and 2,2'-dicyclohexyl-1,1',3,3'-tetramethyl-2,2',3,3'-tetrahydro-2,2'-bibenzo[d]imidazole ((N-DMBI)2 and (Cyc-DMBI)2) are quite strong reductants with effective potentials of ca. -2 V vs ferrocenium/ferrocene, yet are relatively stable to air due to the coupling of redox and bond-breaking processes. Here, we examine their use in accomplishing electron transfer-induced bond-cleavage reactions, specifically dehalogenations. The dimers reduce halides that have reduction potentials less cathodic than ca. -2 V vs ferrocenium/ferrocene, especially under UV photoexcitation (using a 365 nm LED). In the case of benzyl halides, the products are bibenzyl derivatives, whereas aryl halides are reduced to the corresponding arenes. The potentials of the halides that can be reduced in this way, quantum-chemical calculations, and steady-state and transient absorption spectroscopy suggest that UV irradiation accelerates the reactions via cleavage of the dimers to the corresponding radical monomers.

Spectral Signatures of a Negative Polaron in a Doped Polymer Semiconductor: Energy Levels and Hubbard U Interactions.

The modern picture of negative charge carriers on conjugated polymers invokes the formation of a singly occupied (spin-up/spin-down) level within the polymer gap and a corresponding unoccupied level above the polymer conduction band edge. The energy splitting between these sublevels is related to on-site Coulomb interactions between electrons, commonly termed Hubbard U. However, spectral evidence for both sublevels and experimental access to the U value is still missing. Here, we provide evidence by n-doping the polymer P(NDI2OD-T2) with [RhCp*Cp]2, [N-DMBI]2, and cesium. Changes in the electronic structure after doping are studied with ultraviolet photoelectron and low-energy inverse photoemission spectroscopies (UPS, LEIPES). UPS data show an additional density of states (DOS) in the former empty polymer gap while LEIPES data show an additional DOS above the conduction band edge. These DOS are assigned to the singly occupied and unoccupied sublevels, allowing determination of a U value of ∼1 eV.

Study on the removal of Pb(II) from water by coated sulfur-modified nanoscale zero-valent iron.

Being prepared by a liquid-phase reduction method, sulfur-modified nanoscale zero-valent iron (S-nZVI) was then coated with sodium alginate (SA) to form gel beads (SAS-nZVI) which are capable of removing Pb(II) from water. SAS-nZVI was characterized by SEM, EDS, FTIR, XRD, and BET, and its removal effect on Pb(II) in water, including the effects of pH, adsorbent dosage, shaking time, and initial concentration of lead, was also studied. The results demonstrated that the maximum removal efficiency of Pb(II) by SAS-nZVI was 97.89%, and the maximum uptake was 246.40 mg/g. In the Pb(II) removal behavior study, the pseudo-second-order kinetic model and the Langmuir isotherm model were found to fit the adsorption process well. SAS-nZVI was easier to recycle from the reaction system, and the removal efficiency of SAS-nZVI to Pb(II) in water was still able to reach 82.75% after five cycles. Therefore, this study suggests that SAS-nZVI has a high removal capacity for Pb(II) and great potential in water pollution treatment.

Utilization of sewage sludge ash in ultra-high performance concrete (UHPC): Microstructure and life-cycle assessment.

In this research, an economical and eco-friendly ultra-high performance concrete (UHPC) with compressive strength of more than 120 MPa was prepared with the dosage of sewage sludge ash (SSA) at 8 wt%. The results indicate that the addition of SSA has an adverse influence on the workability of UHPC samples due to its special morphology. Furthermore, the microstructure and phase assemblage of SSA-based UHPC were determined and the results show that SSA inhibits the early hydration of cement clinker, while promotes the precipitation of additional hydration products at later curing ages due to its pozzolanic reaction. The pore structure analysis of SSA-based UHPC determined by mercury intrusion porosimetry indicates that the addition of SSA increases the cumulative pore volume, while decreases the large pore volume of UHPC. Economic and environmental analysis indicates that using SSA-based UHPC greatly reduces the unit cost and the impacts on the environment.

Aggregation of P3HT as a preferred pathway for its chemical doping with F4-TCNQ.

The chemical doping reaction of P3HT with F4-TCNQ was studied by optical absorption spectroscopy, atomic force microscopy, and Kelvin probe force microscopy. We demonstrate that P3HT aggregation preferentially occurs before the actual charge transfer step takes place, emphasizing the impact of morphology on the chemical doping reaction of conjugated polymers at the molecular level.

Coupling Glucose Dehydrogenation with CO2 Hydrogenation by Hydrogen Transfer in Aqueous Media at Room Temperature.

Conversion of CO2 into value-added chemicals and fuels provides a direct solution to reduce excessive CO2 in the atmosphere. Herein, a novel catalytic reaction system is presented by coupling the dehydrogenation of glucose with the hydrogenation of a CO2 -derived salt, ammonium carbonate, in an ethanol-water mixture. For the first time, the hydrogenation of CO2 to formate by glucose has been achieved under ambient conditions. Under the optimal reaction conditions, the highest yield of formate reached approximately 46 %. We find that the apparent pH value in the ethanol-water mixture plays a central role in determining the performance of the hydrogen-transfer reaction. Based on the 13 C NMR and ESI-MS results, a possible pathway of the coupled glucose dehydrogenation and CO2 hydrogenation reactions was proposed.

NF-κB-dependent transcriptional upregulation of cyclin D1 exerts cytoprotection against hypoxic injury upon EGFR activation.

Apoptosis of neural cells is one of the main pathological features in hypoxic/ischemic brain injury. Nuclear factor-κB (NF-κB) might be a potential therapeutic target for hypoxic/ischemic brain injury since NF-κB has been found to be inactivated after hypoxia exposure, yet the underlying molecular mechanisms of NF-κB inactivation are largely unknown. Here we report that epidermal growth factor receptor (EGFR) activation prevents neuron-like PC12 cells apoptosis in response to hypoxia via restoring NF-κB-dependent transcriptional upregulation of cyclin D1. Functionally, EGFR activation by EGF stimulation mitigates hypoxia-induced PC12 cells apoptosis in both dose- and time-dependent manner. Of note, EGFR activation elevates IKKß phosphorylation, increases IκBα ubiquitination, promotes P65 nuclear translocation and recruitment at cyclin D1 gene promoter as well as upregulates cyclin D1 expression. EGFR activation also abrogates the decrease of IKKß phosphorylation, reduction of IκBα ubiquitination, blockade of P65 nuclear translocation and recruitment at cyclin D1 gene promoter as well as downregulation of cyclin D1 expression induced by hypoxia. Furthermore, NF-κB-dependent upregulation of cyclin D1 is instrumental for the EGFR-mediated cytoprotection against hypoxic apoptosis. In addition, the dephosphorylation of EGFR induced by either EGF siRNA transfection or anti-HB-EGF neutralization antibody treatment enhances hypoxic cytotoxicity, which are attenuated by EGF administration. Our results highlight the essential role of NF-κB-dependent transcriptional upregulation of cyclin D1 in EGFR-mediated cytoprotective effects under hypoxic preconditioning and support further investigation of EGF in clinical trials of patients with hypoxic/ischemic brain injury.

Formation of polyelectrolyte multilayers: ionic strengths and growth regimes.

This article presents a study of layer-by-layer (LbL) formation of poly-electrolyte multilayers (PEMs). Upon increasing ionic strength LbL growth patterns vary from linear for the lowest salt concentrations ([NaCl] = 0, 0.001, and 0.01 M) to exponential (for [NaCl] = 0.5 and 1 M). The slope of the linear growth at the lowest ionic strengths increases with increasing [NaCl]. During the LbL process at 0.5 M NaCl we observe a cross over from exponential to linear growth for which the slope is orders of magnitude larger than those observed at low salt concentrations. We provide a comprehensive interpretation of these growth behaviors, which are also reported for many other LbL PEM systems, based on the generic features of the phase diagram of aqueous solutions of mixtures of oppositely charged poly-electrolytes. Processes occurring in LbL formation of PEMs can be understood as moving in the direction of equilibrium, while never achieving it. The experimental model system in this study was: polydiallyldimethylammonium chloride/polystyrene sulfonate (PDADMAC/PSS). PEM formation was followed in situ by optical reflectometry in combination with well-controlled transport conditions (impinging jet stagnation point flow).

Genome-wide analysis of the auxin response factors (ARF) gene family in rice (Oryza sativa).

Auxin response factors (ARFs) are transcription factors that bind with specificity to TGTCTC-containing auxin response elements (AuxREs) found in promoters of primary/early auxin response genes and mediate responses to the plant hormone auxin. The ARF genes are represented by a large multigene family in plants. A comprehensive genome-wide analysis was carried out in this study to find all ARFs in Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa subsp. japonica), 23 and 25 ARF genes, named as AtARFs and OsARFs, were identified, respectively. Chromosomal locations of all OsARFs were presented and it was found that the duplication of OsARFs was associated with only the chromosomal block duplications but not local tandem duplications. A phylogenetic tree was generated from alignments of the full-length protein sequences of 25 OsARFs and 23 AtARFs to examine the phylogenetic relationships of rice and Arabidopsis ARF proteins. All 48 members of ARF gene families fell into three major classes, a total of 13 sister pairs, including 9 OsARF-OsARF, 2 AtARF-AtARF and 2 AtARF-OsARF sister pairs were formed, showing different orthologous relationships between AtARFs and OsARFs. EST analysis and RT-PCR assays demonstrated that 24 of all 25 OsARF genes were active and the transcript abundance of some OsARF genes was affected by auxin treatment or light- and dark-grown conditions. The outcome of the present study provides basic genomic information for the rice ARF gene family and will pave the way for elucidating the precise role of OsARFs in plant growth and development in the future.