Cobalt complexes as artificial hydrogenases for the reductive side of water splitting

The generation of H-2 from protons and electrons by complexes of cobalt has an extensive history. During the past decade, interest in this subject has increased as a result of developments in hydrogen generation that are driven electrochemically or photochemically. This article reviews the subject of hydrogen generation using Co complexes as catalysts and discusses the mechanistic implications of the systems studied for making H-2. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems. (C) 2013 Elsevier B.V. All rights reserved

Synthesis of a magnetic π-extended carbon nanosolenoid with Riemann surfaces

Riemann surfaces are deformed versions of the complex plane in mathematics. Locally they look like patches of the complex plane, but globally, the topology may deviate from a plane. Nanostructured graphitic carbon materials resembling a Riemann surface with helicoid topology are predicted to have interesting electronic and photonic properties. However, fabrication of such processable and large π-extended nanographene systems has remained a major challenge. Here, we report a bottom-up synthesis of a metal-free carbon nanosolenoid (CNS) material with a low optical bandgap of 1.97 eV. The synthesis procedure is rapid and possible on the gram scale. The helical molecular structure of CNS can be observed by direct low-dose high-resolution imaging, using integrated differential phase contrast scanning transmission electron microscopy. Magnetic susceptibility measurements show paramagnetism with a high spin density for CNS. Such a π-conjugated CNS allows for the detailed study of its physical properties and may form the base of the development of electronic and spintronic devices containing CNS species

A Highly Selective Turn-On Colorimetric, Red Fluorescent Sensor for Detecting Mobile Zinc in Living Cells

We describe ZRL1, a turn-on colorimetric and red fluorescent zinc ion sensor. The Zn2+-promoted ring opening of the rhodamine spirolactam ring in ZRL1 evokes a 220-fold fluorescence turn-on response. In aqueous media, ZRL1 turn-on luminescence is highly selective for Zn2+ ions, with no significant response to other competitive cations, including Na+, K+, Ca2+, Mg2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Cd2+, or Hg2+. In addition to these characteristics, preliminary results indicate that ZRL1 can be delivered to living cells and can be used to monitor changes in intracellular Zn2+ levels.National Institute of General Medical Sciences (U.S.) (GM065519

Platinum(II) polypyridyl complexes for visible light-driven hydrogen production from water

Thesis (Ph. D.)--University of Rochester. Dept. of Chemistry, 2009.This thesis employs Pt(II) terpyridyl and cyclometalated complexes as the chromophores to construct photoactive systems for hydrogen production from water. Several catalysts, including Pt nanoparticles, Pt(II) bi- and terpyridyl chloro complexes, and cobalt dimethylglyoximate complexes, were investigated to catalyze the hydrogen production reactions. Chapter 1, as an introduction part, describes the recent progress in photoinduced hydrogen production from water, including heterogeneous multiple-component systems, homogeneous multiple-component systems and an integrated approach to artificial photosynthesis for photoinduced hydrogen production. Chapter 2 studies a multiple-component system containing a platinum(II) terpyridyl acetylide chromophore, a sacrificial donor (TEOA), an electron relay (MV2+ and diquats) and colloidal platinum catalyst for photocatalytic generation of hydrogen from water. Hydrogen efficiency varies by using different Pt(II) photosensitizers and electron relays, as well as the different concentrations of each species. Chapter 3 discusses the real role of [Pt(ttpy)Cl]+ and Pt(dcbpy)Cl2 as the hydrogen production catalysts. TEM, EDAX and mecury tests show the Pt(II) chloro complexes are only the precursors to form colloidal platinum, which is the real catalyst for hydrogen generation. Chapter 4 and chapter 5 study a novel homogeneous system for photochemical hydrogen production using a cobalt(III) dimethylglyoximate complex as the hydrogen production catalyst and a Pt(II) terpyridyl acetylide complex as the photosensitizer. Cobalt(III) dimethylglyoximate has been used for hydrogen generation by electrochemical method. But very few examples have been reported in photochemical way. The variation of the photosensitizers and cobaloximes are also discussed, as well as the reaction mechanism. Chapter 6 discusses a novel terpyridyl cationic complex [Pt(TPPPB)Cl]Cl, containing a bulky terpyridyl ligand (1-terpyridyl-2,3,4,5,6-pentaphenyl-benzene (TPPPB)). The complex exhibits reversible vapochromic behavior upon exposure to methylene chloride vapors, changing color from red to green. The shift to higher energy in the emission maximum from 654 nm to 514 nm is the largest vapochromic shift (140 nm) yet reported. The [Pt(TPPPB)Cl]Cl complex exhibits high selectivity for certain volatile organic compounds (VOCs) including only methylene chloride, ethanol, ethyl acetate and acetonitrile. The crystal structures of both the green and red forms have been determined by single crystal X-ray diffraction. Chapter 7 describes the perspectives and future directions in this project. More potential efficient and stable cobalt complexes are designed and discussed. The platinum-cobalt supramolecular assemblies towards photochemical molecular devices show interesting properties for hydrogen production

An Unexpected Dual-Emissive Luminogen: Tunable Aggregation-Induced Emission with Cyan-White-Red Colors, Stable Inherent Chirality, and Enhanced Chiroptical Property

Herein we report a novel chiral bismacrocycle with unexpected dual emission and tunable aggregation-induced emission colors. A facile four-step synthesis strategy is developed to construct this rigid bismacrocycle, (1,4)[8]cycloparaphenylenophane (SCPP[8]), which possesses a 1,2,4,5-tetraphenylbenzene core locked by two intersecting polyphenylene-based macrocycles. The luminescent behavior of SCPP[8] shows the unique characteristics of both aggregation-caused quenching effect and aggrega-tion-induced emission (AIE) effect, inducing remarkable redshift emission including near white-light emission. SCPP[8] is configurationally stable and possesses a novel shape-persistent bismacrocycle scaffold with a high strain energy (up to 127.83 kcal/mol). In addition, SCPP[8] displays enhanced circularly polarized luminescence properties due to AIE effect

Noble Metal-Free Copper Hydroxide as an Active and Robust Electrocatalyst for Water Oxidation at Weakly Basic pH

Copper hydroxide (Cu­(OH)₂) is a quite inexpensive and abundant material, but the literature contains no reports of using it as a stable water oxidation catalyst (WOC). In this study, we report for the first time that Cu­(OH)₂ material synthesized from a simple copper salt can be used as a WOC with good activity and stability. Under optimal conditions using Cu­(OH)₂ as the electrocatalyst, a catalytic current density of 0.1 mA/cm² can be achieved under an applied potential of ∼1.05 V relative to Ag/AgCl at pH 9.2. The slope of the Tafel plot is 78 mV/dec. The Tafel plot indicates that a current density of ∼0.1 mA/cm² requires an overpotential of 550 mV. The Faradaic efficiency was measured to be ∼95%. The as-synthesized Cu­(OH)₂ material was characterized by X-ray powder diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy

Farm Environmental Enrichments Improve the Welfare of Layer Chicks and Pullets: A Comprehensive Review

Currently, cage housing is regarded as a global mainstream production system for laying hens. However, limited living space and confinement of birds in cages cause welfare and health problems, such as feather pecking, osteoporosis, obesity, and premature aging. Many studies have been conducted to alleviate layer welfare problems by providing farm environmental enrichments such as litter, sand, alfalfa bales, chick papers, pecking stones, pecking strings, perches, slopes, elevated platforms, aviaries and outdoor access with a trend towards complex enrichments. The provision of appropriate enrichments continuously attracts layers towards pecking, foraging, dust bathing, and locomotion, thereby giving lifelong benefits to laying hens. Hence, raising chicks and pullets under such conditions may reduce feather and skin damage, as well as accumulation of abdominal fat, and improve several biological features such as health, productivity, quality products, and docility of laying hens. Therefore, providing enrichment during the first few days of the layer’s life without any interruption is crucial. In addition, due to different farm conditions, environmental enrichment should be managed by well-trained farm staff. For example, in preventing feather pecking among the birds, litter materials for foraging are superior to dust bath materials or new items. However, a limited supply of litter creates competition and challenges among birds. Therefore, providing farm environmental enrichment for layers requires proper handling, especially in commercial layer farms. Hence, improving the welfare of chicks and pullets through optimizing on-farm environmental enrichments is essential for production systems practicing cage housing

Effects of Key Farm Management Practices on Pullets Welfare—A Review

Studies on animal behavior and welfare have reported that improving the management practices of pullets can enhance their growth, as well as their physical and mental condition, thus benefiting the productivity of laying hens. There is growing confidence in the international community to abandon the conventional practices of “cage-rearing and beak-trimming” to improve the welfare of chickens. Therefore, in this review, we summarized some of the effective poultry management practices that have provided welfare benefits for pullets. The results are as follows: 1. Maintaining similar housing conditions at different periods alleviates fear and discomfort among pullets; 2. Pullets reared under cage-free systems have better physical conditions and temperaments than those reared in cage systems, and they are more suitable to be transferred to similar housing to lay eggs; 3. Improving flock uniformity in appearance and body size has reduced the risk of pecking and injury; 4. Maintaining an appropriate population (40–500 birds) has reduced flock aggressiveness; 5. A combination of 8–10 h of darkness and 5–30 lux of light-intensity exposure via natural or warm white LED light has achieved a welfare–performance balance in pullets. (This varies by age, strain, and activities.); 6. Dark brooders (mimicking mother hens) have alleviated fear and pecking behaviors in pullets; 7. The air quality of the chicken house has been effectively improved by optimizing feed formulation and ventilation, and by reducing fecal accumulation and fermentation; 8. Complex environments (with litter, perches, straw bales, slopes, platforms, outdoor access, etc.) have stimulated the activities of chickens and have produced good welfare effects. In conclusion, the application of comprehensive management strategies has improved the physical and mental health of pullets, which has, in turn, improved the quantity and quality of poultry products

A Long π-Conjugated Poly-para-Phenylene-Based Polymeric Segment of Single-Walled Carbon Nanotubes

Conjugated polymers have attracted much attention for many years and have applications in various organic devices. Carbon nanotubes can be considered as all-carbon tube-shaped conjugated polymers containing only sp2-bonded atoms, which play an important role in nanotechnology and nanoelectronics. So far, no study has reported the realization of long π-conjugated polymers as diameter-specified carbon nanotube segments. Herein, we report the first synthesis of a π-conjugated polymeric segment (PS1) of armchair single-walled carbon nanotubes. PS1 is achieved by a rationally designed synthesis of a bifunctionalized cyclo-para-phenylene monomer, followed by inserting these ring-shaped units into the conjugated poly-para-phenylene backbone. Our PS1 was fully characterized by gel permeation chromatography (GPC) combined with NMR, FTIR, and Raman spectra. Its photophysical and unique electronic properties were also investigated. Possessing unique structural and physical properties, this long π-extended polymer PS1 can provide new insight for the development of bottom-up syntheses of uniform carbon nanotube segments and potential applications in electron-transport devices