Thermodynamic properties of diatomic CO, CN, C₂ and CO⁺ in CO₂-N₂ plasmas

The reliable data of plasma thermodynamic properties are of vital significance for aerodynamic modelling and plasma dynamics simulation. In this work, we have thoroughly evaluated the thermodynamic properties of diatomic CO, CN, C2 and CO+ by making use of a more rigorous approach. The internal energy levels were precisely determined by solving rotational dependence of the radial Schrödinger equation over a set of potential curves. The RKR method was used to generate the low-lying potential curves, while the ab initio results reported by the recent publications were selected for the potential curves of high-lying states. More electronic states were considered in this work than in previous publications, which helps to make the calculated results more accurate at high temperatures. The predicted results were verified by the available values in the recent studies and the relative deviations were systematically evaluated. The maximum relative difference of the equilibrium partition function is less than 7.7% for all species and not larger than 15.3% for equilibrium dimensionless specific heat.</p

Efficient Electrochemical Reduction of Carbon Dioxide to Acetate on Nitrogen-Doped Nanodiamond

Electrochemical reduction of CO₂ is an attractive technique for reducing CO₂ emission and converting it into useful chemicals, but it suffers from high overpotential, low efficiency or poor product selectivity. Here, N-doped nanodiamond/Si rod array (NDD/Si RA) was proposed as an efficient nonmetallic electrocatalyst for CO₂ reduction. It preferentially and rapidly converted CO₂ to acetate over formate with an onset potential of −0.36 V (vs RHE), overcoming the usual limitation of low selectivity for C2 products. Moreover, faradic efficiency of 91.2–91.8% has been achieved for CO₂ reduction at −0.8 to −1.0 V. Its superior performance for CO₂ reduction can be attributed to its high overpotential for hydrogen evolution and N doping, where N-sp³C species was highly active for CO₂ reduction. Electrokinetic data and <i>in situ</i> infrared spectrum revealed the main pathway for CO₂ reduction might be CO₂ → CO₂^•– → (COO)₂^• → CH₃COO^–

Halobenzoquinone-Induced Alteration of Gene Expression Associated with Oxidative Stress Signaling Pathways

Halobenzoquinones (HBQs) are emerging disinfection byproducts (DBPs) that effectively induce reactive oxygen species and oxidative damage in vitro. However, the impacts of HBQs on oxidative-stress-related gene expression have not been investigated. In this study, we examined alterations in the expression of 44 genes related to oxidative-stress-induced signaling pathways in human uroepithelial cells (SV-HUC-1) upon exposure to six HBQs. The results show the structure-dependent effects of HBQs on the studied gene expression. After 2 h of exposure, the expression levels of 9 to 28 genes were altered, while after 8 h of exposure, the expression levels of 29 to 31 genes were altered. Four genes (<i>HMOX1</i>, <i>NQO1</i>, <i>PTGS2</i>, and <i>TXNRD1</i>) were significantly upregulated by all six HBQs at both exposure time points. Ingenuity pathway analysis revealed that the Nrf2 pathway was significantly responsive to HBQ exposure. Other canonical pathways responsive to HBQ exposure included GSH redox reductions, superoxide radical degradation, and xenobiotic metabolism signaling. This study has demonstrated that HBQs significantly alter the gene expression of oxidative-stress-related signaling pathways and contributes to the understanding of HBQ-DBP-associated toxicity

Quantification of Viable but Nonculturable <i>Escherichia coli</i> O157:H7 by Targeting the <i>rpoS</i> mRNA

Escherichia coli O157:H7 easily becomes viable but nonculturable (VBNC) under environmental stresses and escapes detection by current methods. Here, we report a unique method enabling the quantification of VBNC E. coli O157:H7 using a selective marker within the rpoS gene. A nucleotide at position +543 within the rpoS gene open reading frame was identified to be unique to E. coli O157:H7. Specifically designed primers and probe combinations were able to differentiate E. coli O157:H7 from closely related bacteria and other common bacteria. The application of this strategy correctly identified 36 clinical and bovine isolates of E. coli O157:H7. A one-step quantification method combining reverse transcription (RT) and real-time quantitative polymerase chain reaction (qPCR) was developed to provide a linear relationship (R2 > 0.99) of copies of RNA with threshold cycles (Ct) and the capability of detecting a single copy of rpoS RNA standards. This technique was used to determine the copies of the rpoS mRNA in culturable cells at different growth phases (mid-log, late-log, and stationary phase) to be 1.57, 0.56, and 0.41 copies/CFU, respectively. VBNC E. coli O157:H7 was determined to have one copy of the rpoS mRNA for every 10 cells, and no rpoS mRNA was detected in 106 dead cells and negative controls. This technique had a linear dynamic range over 6 orders of magnitude and >90% amplification efficiency for tap and river water samples. It was able to selectively quantify as few as 7 E. coli O157:H7 cells in pure culture, 9 culturable cells in tap water and river water, and 23 VBNC cells in river water, demonstrating the best quantification limits for culturable and VBNC E. coli O157:H7 in environmental water

Cost-Effective Synthesis of Diamond Nano-/Microstructures from Amorphous and Graphitic Carbon Materials: Implications for Nanoelectronics

The synthesis of diamonds with different microstructures is important for various applications including nanoelectronic devices where diamonds can be implemented as heat spreaders. Here we report the synthesis of functional diamond microstructures and coatings, including diamond microfibers, microspheres, tubes, and large-area thin film, using amorphous and graphitic carbon precursors by hot filament chemical vapor deposition. The characteristics of microstructures depend upon initial carbon precursors and their laser annealing pretreatments. Low-cost and abundant carbon precursors act as diamond nucleation sites and accelerate diamond growth, while laser annealing can further promote the nucleation and growth of diamond. As a result, carbon microfibers are converted to diamond microfibers, while large diamond microspheres are formed from multipulse laser-annealed carbon microfibers. Both of the diamond structures consist of 5-fold twinned microcrystallites. Highly dense and phase-pure diamond films are observed using porous carbon seed, and individual diamond tubes with porous walls are obtained by using carbon nanotube hollow fibers. The electron backscatter diffraction analysis confirms the diamond cubic lattice structure, while sharp diamond peaks (1331–1333 cm–1) in Raman spectra demonstrate the excellent diamond quality of prepared diamond microstructures

Parasitism in Metal Nanoclusters: A Case Study of (AuAg)₂₅·(AuAg)₂₇

Studying the interactions of atomically precise metal nanoclusters in their assembly systems is of great significance in the nanomaterial research field, which has attracted increasing interest in the last few decades. Herein, we report the cocrystallization of two oppositely charged atomically precise metal nanoclusters in one unit cell: [Au1Ag24(SR)18]– ((AuAg)25 for short) and [AuxAg27–x(Dppf)4(SR)9]2+ (x = 10–12; (AuAg)27 for short) with a 1:1 ratio. (AuAg)27 could maintain its structure in the presence of (AuAg)25, whether in the crystalline and the solution state, while the metastable (AuAg)27 component underwent a spontaneous transformation to (AuAg)16(Dppf)2(SR)8 after dissociating the (AuAg)25 component from this cocrystal, demonstrating the “parasitism” relationship of the (AuAg)27 component over (AuAg)25 in this dual-cluster system. This work enriches the family of cluster-based assemblies and elucidates the delicate relationship between nanoparticles of cocrystals

Parasitism in Metal Nanoclusters: A Case Study of (AuAg)₂₅·(AuAg)₂₇

Studying the interactions of atomically precise metal nanoclusters in their assembly systems is of great significance in the nanomaterial research field, which has attracted increasing interest in the last few decades. Herein, we report the cocrystallization of two oppositely charged atomically precise metal nanoclusters in one unit cell: [Au1Ag24(SR)18]– ((AuAg)25 for short) and [AuxAg27–x(Dppf)4(SR)9]2+ (x = 10–12; (AuAg)27 for short) with a 1:1 ratio. (AuAg)27 could maintain its structure in the presence of (AuAg)25, whether in the crystalline and the solution state, while the metastable (AuAg)27 component underwent a spontaneous transformation to (AuAg)16(Dppf)2(SR)8 after dissociating the (AuAg)25 component from this cocrystal, demonstrating the “parasitism” relationship of the (AuAg)27 component over (AuAg)25 in this dual-cluster system. This work enriches the family of cluster-based assemblies and elucidates the delicate relationship between nanoparticles of cocrystals

Parasitism in Metal Nanoclusters: A Case Study of (AuAg)₂₅·(AuAg)₂₇

Studying the interactions of atomically precise metal nanoclusters in their assembly systems is of great significance in the nanomaterial research field, which has attracted increasing interest in the last few decades. Herein, we report the cocrystallization of two oppositely charged atomically precise metal nanoclusters in one unit cell: [Au1Ag24(SR)18]– ((AuAg)25 for short) and [AuxAg27–x(Dppf)4(SR)9]2+ (x = 10–12; (AuAg)27 for short) with a 1:1 ratio. (AuAg)27 could maintain its structure in the presence of (AuAg)25, whether in the crystalline and the solution state, while the metastable (AuAg)27 component underwent a spontaneous transformation to (AuAg)16(Dppf)2(SR)8 after dissociating the (AuAg)25 component from this cocrystal, demonstrating the “parasitism” relationship of the (AuAg)27 component over (AuAg)25 in this dual-cluster system. This work enriches the family of cluster-based assemblies and elucidates the delicate relationship between nanoparticles of cocrystals

CO₂ Electroreduction at Low Overpotential on Oxide-Derived Cu/Carbons Fabricated from Metal Organic Framework

Electrochemical reduction of CO₂ to chemical feedstocks is an attractive solution that prevents CO₂ accumulation in the atmosphere, but it remains a great challenge to develop the cost-effective catalysts. Herein, we synthesized oxide-derived Cu/carbon (OD Cu/C) catalysts by a facile carbonization of Cu-based MOF (HKUST-1). The resulting materials exhibited highly selective CO₂ reduction to alcohol compounds with total faradic efficiencies of 45.2–71.2% at −0.1 to −0.7 V versus reversible hydrogen electrode (RHE). High-yield methanol and ethanol has been achieved on OD Cu/C-1000 with the production rates of 5.1–12.4 and 3.7–13.4 mg L^–1 h^–1, respectively. Notably, the onset potential for C₂H₅OH formation is near −0.1 V (versus RHE), corresponding to ∼190 mV of overpotential, which is among the lowest overpotentials reported to date for the reduction of CO₂ to C₂H₅OH. The improvements in activity and selectivity of the oxide-derived Cu/carbon might be attributed to the synergistic effect between the highly dispersed copper and the matrix of porous carbon. These findings provide a new insight into design of practical catalysts for decreasing atmospheric CO₂ levels and synthesizing liquid fuels