Supramolecular Control of Singlet Oxygen Generation

Singlet oxygen (¹O₂) is the excited state electronic isomer and a reactive form of molecular oxygen, which is most efficiently produced through the photosensitized excitation of ambient triplet oxygen. Photochemical singlet oxygen generation (SOG) has received tremendous attention historically, both for its practical application as well as for the fundamental aspects of its reactivity. Applications of singlet oxygen in medicine, wastewater treatment, microbial disinfection, and synthetic chemistry are the direct results of active past research into this reaction. Such advancements were achieved through design factors focused predominantly on the photosensitizer (PS), whose photoactivity is relegated to self-regulated structure and energetics in ground and excited states. However, the relatively new supramolecular approach of dictating molecular structure through non-bonding interactions has allowed photochemists to render otherwise inactive or less effective PSs as efficient ¹O₂ generators. This concise and first of its kind review aims to compile progress in SOG research achieved through supramolecular photochemistry in an effort to serve as a reference for future research in this direction. The aim of this review is to highlight the value in the supramolecular photochemistry approach to tapping the unexploited technological potential within this historic reaction.     

Shape optimization for a composite crack-length sensor

Conductive polymeric sensors can be used as crack-length gages. They have the advantages of being inexpensive, versatile in size and require inexpensive instrumentation. They also measure crack length continuously. The shape of these gages can be varied in several ways to improve their sensitivity. The gages with the 'optimized' or tapered shape overcome the principal disadvantages of rectangular gages, namely poor sensitivity at small crack lengths.     

Synthesis, characterization and application of cellulose/polyaniline nanocomposite for the treatment of simulated textile effluent

The aim of the study was to analyze the potential application of cellulose/polyaniline (Ce/Pn) nanocomposite for the treatment of synthetic reactive dye bath effluent. The Ce/Pn composite was synthesized by chemical oxidative polymerization of aniline. A central composite experimental design, a most popular design of response surface methodology, was applied to optimize the level of variables, namely, cellulose and polyaniline, to get the best response on dye removal. Biological transmission electron microscopy studies reveal that the cellulose particles were uniformly distributed on the nanocomposite. The results of the batch experiment studies indicate that Ce/Pn nanocomposite removed 95.9, 91.9, 92.7, and 95.7 % of RBBR, RO, RV, and RBK, respectively, and it decolorized 82 % of dye bath effluent. However, the presence of the salts reduced the adsorption rate of the dyes. The Langmuir model and pseudo first-order rate expression exhibited satisfactory fit to adsorption data of single component.     

Evolving trends in the dereplication of natural product extracts. 3: further lasiodiplodins from Lasiodiplodia theobromae, an endophyte from Mapania kurzii

Two further lasiodiplodins, (3R,4R)-4-hydroxy-de-O-methyl-lasiodiplodin and (E)-9-etheno-de-O-methyl-lasiodiplodin, together with three known lasiodiplodins from a cytotoxic extract obtained from a culture of Lasiodiplodia theobromae, an endophyte from the root tissues of Mapania kurzii (Cyperaceae) from the Malaysian rain forest, were characterized on microgram scale.     

Improvement in micro-structural and mechanical properties of zinc film by surface treatment with low temperature argon plasma

Nanocrystalline zinc films were deposited on gold coated borosilicate glass substrates by thermal evaporation method using zinc powders as the source material and then treated with argon plasma at various temperatures. From X-ray diffraction study, the as-deposited films are found to be metallic Zn and polycrystalline in nature. The crystalline nature improves with the increase of temperature up to 200 °C and decreases with the further increase of temperature to 300 °C. The binding energy observed for Zn 2p_3/2, and the binding energy separation between Zn 2p_3/2 and Zn 2p_1/2 in the X-ray photoelectron spectrum indicate that the films are metallic zinc films. Transmission electron microscopic study shows hexagonal shaped grains having size ∼58 nm upon treatment with Ar plasma. It is clearly shown the grain growth and distinct grain boundary with the increase in temperature. The average Young's modulus (E) and hardness (H) are measured to be 84 GPa and 4.0 GPa for as-deposited film, whereas 98 GPa and 5.8 GPa for plasma treated film at 200 °C. The enhancement in mechanical properties is attributed to improvement in crystalline nature of the film and better interlinking between grains and boundaries.     

Interaction of (G4)2 and (X4)2 DNA quadruplexes with Cu+, Ag+ and Au+ metal cations: a quantum chemical calculation on structural,energetic and electronic properties

Structural Chemistry - The present study is focused to cast light on the structural, electronic and energetic properties of isolated (G4)2 and (X4)2 DNA quadruplexes with transition metal cations...