New Dual Donor–Acceptor (2D‐π‐2A) Porphyrin Sensitizers for Stable and Cost‐Effective Dye‐Sensitized Solar Cells

A series of porphyrin sensitizers that featured two electron‐donating groups and dual anchoring groups that were connected through a porphine π‐bridging unit have been synthesized and successfully applied in dye‐sensitized solar cells (DSSCs). The presence of electron‐donating groups had a significant influence on their spectroscopic, electrochemical, and photovoltaic properties. Overall, the dual anchoring groups gave tunable electronic properties and stronger attachment to TiO₂. These new dyes were readily synthesized in a minimum number of steps in gram‐scale quantities. Optical and electrochemical data confirmed the advantages of these dyes for use as sensitizers in DSSCs. Porphyrins with electron‐donating amino moieties provided improved charge separation and better charge‐injection efficiencies for the studied dual‐push–pull dyes. Attenuated total reflectance–Fourier‐transform infrared (ATR‐FTIR) and X‐ray photoelectron spectroscopy of the porphyrin dyes on TiO₂ suggest that both p‐carboxyphenyl groups are attached onto TiO₂, thereby resulting in strong attachment. Among these dyes, cis-Zn2BC2A , with two electron‐donating 3,6‐ditertbutyl‐phenyl‐carbazole groups and dual‐anchoring p‐carboxyphenyl groups, showed the highest efficiency of 4.07 %, with J_SC=9.81 mA cm^?2, V_OC=0.63 V, and FF=66 %. Our results also indicated a better photostability of the studied dual‐anchored sensitizers compared to their mono‐anchored analogues under identical conditions. These results provide insight into the developments of a new generation of high‐efficiency and thermally stable porphyrin sensitizers.     

A Complex Pyrrolo-oxazinone and Its Iodo Derivative Isolated from a Tunicate

Two cytotoxic triphenylpyrrolo-oxazinones were isolated from a tunicate and their structures elucidated by spectral methods. Lukianol A ( = 3,7,8-tris(4-hydroxyphenyl)pyrrolo[2,1-c][1,4]oxazin-1 (1H)-one; 1 ) had MIC of 1 μg/ml in KB cytotoxicity tests; MIC value for 2 was 100 μg/ml.     

Development and validation of a multiplex real-time PCR method to simultaneously detect 47 targets for the identification of genetically modified organisms

Considering the increase of the total cultivated land area dedicated to genetically modified organisms (GMO), the consumers’ perception toward GMO and the need to comply with various local GMO legislations, efficient and accurate analytical methods are needed for their detection and identification. Considered as the gold standard for GMO analysis, the real-time polymerase chain reaction (RTi-PCR) technology was optimised to produce a high-throughput GMO screening method. Based on simultaneous 24 multiplex RTi-PCR running on a ready-to-use 384-well plate, this new procedure allows the detection and identification of 47 targets on seven samples in duplicate. To comply with GMO analytical quality requirements, a negative and a positive control were analysed in parallel. In addition, an internal positive control was also included in each reaction well for the detection of potential PCR inhibition. Tested on non-GM materials, on different GM events and on proficiency test samples, the method offered high specificity and sensitivity with an absolute limit of detection between 1 and 16 copies depending on the target. Easy to use, fast and cost efficient, this multiplex approach fits the purpose of GMO testing laboratories.

A two-step stimulus-response cell-SELEX method to generate a DNA aptamer to recognize inflamed human aortic endothelial cells as a potential in vivo molecular probe for atherosclerosis plaque detection

Aptamers are single-stranded oligonucleotides that are capable of binding wide classes of targets with high affinity and specificity. Their unique three-dimensional structures present numerous possibilities for recognizing virtually any class of target molecules, making them a promising alternative to antibodies used as molecular probes in biomedical analysis and clinical diagnosis. In recent years, cell-systematic evolution of ligands by exponential enrichment (SELEX) has been used extensively to select aptamers for various cell targets. However, aptamers that have evolved from cell-SELEX to distinguish the “stimulus-response cell” have not previously been reported. Moreover, a number of cumbersome and time-consuming steps involved in conventional cell-SELEX reduce the efficiency and efficacy of the aptamer selection. Here, we report a “two-step” methodology of cell-SELEX that successfully selected DNA aptamers specifically against “inflamed” endothelial cells. This has been termed as stimulus-response cell-SELEX (SRC-SELEX). The SRC-SELEX enables the selection of aptamers to distinguish the cells activated by stimulus of healthy cells or cells isolated from diseased tissue. We report a promising aptamer, N55, selected by SRC-SELEX, which can bind specifically to inflamed endothelial cells both in cell culture and atherosclerotic plaque tissue. This aptamer probe was demonstrated as a potential molecular probe for magnetic resonance imaging to target inflamed endothelial cells and atherosclerotic plaque detection.

Synthesis of two-dimensional gallium nitride via spin coating method: influences of nitridation temperatures

This paper reports the synthesis and characterization of gallium nitride (GaN) thin films deposited on p-type silicon (100) substrates by using low cost spin coating method under various nitridation temperatures. This work demonstrated that spin coating with the new prepared precursor solution can be used as a versatile method for the successfully growth of GaN thin films. Furthermore, the influence of varying nitridation temperatures on the structural, morphological, and optical properties of synthesized GaN thin films were studied in this work. The GaN thin films were characterized by X-ray diffraction, field-emission scanning electron microscopy, atomic force microscopy, photoluminescence and Raman spectroscopy. All the characteristics of the GaN thin films were effectively improved with the increasing of the nitridation temperatures from 750 to 950 °C and degraded at temperature of 1,050 °C. The measured results show that nitridation temperature plays an important role in improving the crystalline quality of the GaN thin films and the most efficient nitridation temperature was at 950 °C.     

Electron beam coater for reduction of charging in ice-embedded biological specimens using Ti(88)Si(12) alloy.

Biological macromolecules embedded in vitreous ice are known to suffer from charging while being imaged in an electron transmission cryomicroscope. We developed an electron beam coater that deposits conductive films onto the surface of frozen-hydrated specimens. The conductive films help to dissipate charge during electron irradiation of poorly conductive ice-embedded biological samples. We observed significant reduction in charging of ice-embedded catalase crystals suspended over holes in a holey carbon film after coating them with a 30-A-thick layer of an amorphous alloy, Ti(88)Si(12). Images of the crystals after coating showed diffraction spots of up to 3 A resolution.     

Infrared Spectroscopy of Size-Selected Hydrated Carbon Dioxide Radical Anions CO2.−(H2O)n (n=2–61) in the C−O Stretch Region

Understanding the intrinsic properties of the hydrated carbon dioxide radical anions CO₂^.−(H₂O)_n is relevant for electrochemical carbon dioxide functionalization. CO₂^.−(H₂O)_n (n=2–61) is investigated by using infrared action spectroscopy in the 1150–2220 cm⁻¹ region in an ICR (ion cyclotron resonance) cell cooled to T=80 K. The spectra show an absorption band around 1280 cm⁻¹, which is assigned to the symmetric C−O stretching vibration ν_s. It blueshifts with increasing cluster size, reaching the bulk value, within the experimental linewidth, for n=20. The antisymmetric C−O vibration ν_as is strongly coupled with the water bending mode ν₂, causing a broad feature at approximately 1650 cm⁻¹. For larger clusters, an additional broad and weak band appears above 1900 cm⁻¹ similar to bulk water, which is assigned to a combination band of water bending and libration modes. Quantum chemical calculations provide insight into the interaction of CO₂^.− with the hydrogen-bonding network.     

Spectroscopic Measurement of a Halogen Bond Energy

Halogen bonding (XB) has emerged as an important bonding motif in supramolecules and biological systems. Although regarded as a strong noncovalent interaction, benchmark measurements of the halogen bond energy are scarce. Here, a combined anion photoelectron spectroscopy and density functional theory (DFT) study of XB in solvated Br^? anions is reported. The XB strength between the positively‐charged σ‐hole on the Br atom of the bromotrichloromethane (CCl₃Br) molecule and the Br^? anion was found to be 0.63 eV (14.5 kcal mol^?1). In the neutral complexes, Br(CCl₃Br)_1,2, the attraction between the free Br atom and the negatively charged equatorial belt on the Br atom of CCl₃Br, which is a second type of halogen bonding, was estimated to have interaction strengths of 0.15 eV (3.5 kcal mol^?1) and 0.12 eV (2.8 kcal mol^?1).     

Dipole-bound anions of highly polar molecules: ethylene carbonate and vinylene carbonate

Results of experimental and theoretical studies of dipole-bound negative ions of the highly polar molecules ethylene carbonate (EC, C3H4O3, mu=5.35 D) and vinylene carbonate (VC, C3H2O3, mu=4.55 D) are presented. These negative ions are prepared in Rydberg electron transfer (RET) reactions in which rubidium (Rb) atoms, excited to ns or nd Rydberg states, collide with EC or VC molecules to produce EC- or VC- ions. In both cases ions are produced only when the Rb atoms are excited to states described by a relatively narrow range of effective principal quantum numbers, n*; the greatest yields of EC- and VC- are obtained for n*(max)=9.0+/-0.5 and 11.6+/-0.5, respectively. Charge transfer from low-lying Rydberg states of Rb is characteristic of a large excess electron binding energy (Eb) of the neutral parent; employing the previously derived empirical relationship Eb=23/n*(max)(2.8) eV, the electron binding energies are estimated to be 49+/-8 meV for EC and 24+/-3 meV for VC. Electron photodetachment studies of EC- show that the excess electron is bound by 49+/-5 meV, in excellent agreement with the RET results, lending credibility to the empirical relationship between Eb and n*(max). Vertical electron affinities for EC and VC are computed employing aug-cc-pVDZ atom-centered basis sets supplemented with a (5s5p) set of diffuse Gaussian primitives to support the dipole-bound electron; at the CCSD(T) level of theory the computed electron affinities are 40.9 and 20.1 meV for EC and VC, respectively.