Analytical Chemistry
DOI: 10.1021/acs.analchem.4c00324
[ASAP] Ultrasensitive Electrochemiluminescence Biosensor Based on Efficient Signal Amplification of Copper Nanoclusters Induced by CaMnO3 for CD44 Trace Detection
Analytical Chemistry
DOI: 10.1021/acs.analchem.4c00019
Elucidating the Structure of the Eu‐EDTA Complex in Solution at Various Protonation States
The structures of Eu-EDTA complexes at varying protonation state in aqueous solution are resolved with a combination of molecular dynamics simulations and extended X-ray absorption fine structure measurements.
Abstract
Ethylenediaminetetraacetic acid (EDTA), which has two amine and four carboxylate protonation sites, forms stable complexes with lanthanide ions. This work analyzes the coordination structure, in atomic resolution, of the Eu3+ ion complexed with EDTA in all its protonation states in aqueous solution. Eu-EDTA complexes were modeled using classical molecular dynamics (MD) simulations using force field parameters optimized with ab initio molecular dynamics (AIMD) simulations. Structures from the MD simulations were used to predict extended X-ray absorption fine structure (EXAFS) spectra and compared with EXAFS measurements of the Eu3+ aqua ion and Eu-EDTA complexes at pH 3 and 11. This work details how Eu-EDTA complex coordination structures change with increasing protonation of the EDTA ligand in the complex, from the tightly bound unprotonated complex to the unbinding of the fully protonated EDTA ligand from the Eu3+ ion as both become solvated by water. Agreement between predicted and measured EXAFS spectra supports the findings from simulation.
[ASAP] High-Fidelity Sensitive Tracing Circulating Tumor Cell Telomerase Activity
Analytical Chemistry
DOI: 10.1021/acs.analchem.3c05749
Structure Activity Relationships for Second‐Coordination Sphere Functional Group Dependent CO2 Reduction by Manganese Bipyridyl Electrocatalysts
A series of twelve [fac-Mn(R2bpy)(CO)3(CH3CN)]+ pre-catalysts with systematically varied second coordination sphere functionality for the proton-coupled electrocatalytic reduction of CO2 are reported, whereby a structure-determined shift in catalytic pathway is demonstrated and product selectivity is tuned from CO to competing HCO2H and H2 production.
Abstract
A series of twelve second coordination sphere (SCS) functionalized manganese tricarbonyl bipyridyl complexes are investigated for their electrocatalytic CO2 reduction properties in acetonitrile. A qualitative and quantitative assessment of the SCS functional groups is discussed with respect to the catalysts’ thermodynamic and kinetic efficiencies, and their product selectivities. In probing a broad scope of functional groups, it is clear that only the aprotic ortho-arylester SCS is capable of promoting the highly desired low-overpotential proton-transfer electron-transfer (PT-ET) pathway for selective CO production. The ortho-phenolic analogues cause an increase in overpotential with a product selectivity favoring H2 evolution, consistent with a high-overpotential pathway via the anionic [Mn−H]− intermediate. Alternative aprotic Lewis base functional groups such as trifluoromethyl, morpholine and acetamide are shown to also be capable of intermediate manganese hydride generation. The tertiary amine substituent, 2-morpholinophenyl, exhibits a desirable product distribution characteristic of syn-gas (CO : H2=30 : 48) with an impressive turnover frequency, while the secondary amine group, 2-acetamidophenyl, induces a notable shift in selectivity with a faradaic yield of 55 % for the formate (HCO2 −) product. In addition to their catalytic properties, cyclic voltammetry and infrared spectroelectrochemistry (IR-SEC) studies are presented to probe pre-catalyst electronic properties and the two-electron reduction activation pathway.
Molecular Driving Forces in the Self‐Association of Silaffin Peptide R5 from MD Simulations
The 19-residue silaffin-R5 peptide has been widely studied for its ability to precipitate uniform SiO2 particles through mild temperature and pH pathways, in the absence of any organic solvents. There is consensus that post-translational modification (PTM) of side chains has a large impact on the biomineralization process. Thus, it is imperative to understand the precise mechanisms that dictate the formation of SiO2 from R5 peptide, including the effects of PTM on peptide aggregation and peptide-surface adsorption. In this work, we use molecular dynamics (MD) simulations to study the aggregation of R5 dimer with multiple PTMs, with the presence of different ions in solution. Since this system has strong interactions with deep metastable states, we use parallel bias metadynamics with partitioned families to efficiently sample the different states of the system. We find that peptide aggregation is a prerequisite for biomineralization. We observe that the electrostatic interactions are essential in the R5 dimer aggregation; for wild type R5 that only has positively charged residues, phosphate ions HPO42- in the solution form a bridge between two peptides and are essential for peptide aggregation.
Chromium‐Catalyzed Reductive Cross‐Coupling to Construct C‐SS Bonds from Unactivated Alkyl Electrophiles
Low-valent chromium catalysts are cheap and less toxic compared to other transition metal catalysts. Here in, we reported a ligand-free chromium(III)-catalyzed manganese reductive cross-coupling of unactivated alkyl electrophiles, such as alkyl sulfonates and alkyl chlorides, with trisulfide dioxides as thiolation agents to form carbon-sulfur bonds. The powerful method featured ample substrate scope and wide functional group tolerance, constructing a large number of unsymmetrical disulfides under simple conditions.
Transparent Near‐IR Dye‐Sensitized Solar Cells: Ultrafast Spectroscopy Reveals the Effects of Driving Force and Dye Aggregation
Near-IR dyes for transparent dye-sensitized solar cells: The effects of small driving forces (−ΔG) and excited state quenching by energy transfer to aggregates studied by femtosecond differential absorption and fluorescence spectroscopy for two DPP cyanine dyes.
Abstract
In the context of developing transparent near-IR absorbing dye-sensitized solar cells, diketopyrrolopyrrole (DPP) cyanine dyes have recently emerged as an alternative to strongly aggregating linear cyanines. In our efforts to increase both the power conversion efficiency (PCE) and the average visible transmittance (AVT), a thienylated version, called TB202, that shows a red-shifted absorption with respect to our champion dye TB207 was designed. However, the lower energy LUMO level of TB202 brings along a lower driving force (−ΔG) for carrier injection, which we recently identified as the main parameter limiting the PCE to 1.5 % in the best device conditions. In the present paper, we publish a detailed account of the effect of the de-aggregating cheno-deoxycholic acid (CDCA) for both TB207 and TB202. Both transient absorption (TAS) and fluorescence up-conversion (FLUPS) data are presented, which allow to quantitively compare the effect of −ΔG and the CDCA concentration, in terms of the kinetic competition of ensemble averaged carrier injection and monomer-to-aggregate energy transfer (ET) rates. A comprehensive picture emerges on how ET is reduced by higher CDCA concentrations, leading in the best device conditions to injection efficiencies in the range of 65 % for TB207 and only 35 % for TB202.
CW or Pulsed laser – That is the Question: Comparative Steady‐state Photocrystallographic Analysis of Metal Nitrosyl Linkage Isomers
The investigation of photo-induced effects is profoundly influenced by the characteristics of photo-excitation sources. We present here a comprehensive analysis of the structures of two photoinduced linkage isomers (PLI) in a ruthenium nitrosyl complex trans-[Ru(py)4F(NO)](ClO4)2, following irradiation with both pulsed and continuous wave (CW) light sources under low temperature conditions.
Abstract
The investigation of photo-induced effects is profoundly influenced by the characteristics of photo-excitation sources. In this study, we present a comprehensive analysis of the structures of two photoinduced linkage isomers (PLI) in a ruthenium nitrosyl complex, trans-[Ru(py)4F(NO)](ClO4)2, following irradiation with both pulsed and continuous wave (CW) light sources under low temperature conditions. The X-ray (photo)diffraction analysis shows that the resulting PLI generated from the two types of irradiation sources, an isonitrosyl configuration of the nitrosyl ligand in the so-called metastable state MS1, and a side-on configuration of the nitrosyl ligand in the metastable state MS2, are identical. In-situ optical absorption spectroscopy was employed during CW and pulsed irradiation, enabling the monitoring of the population process of these PLI. The results obtained from the infrared spectroscopic analysis after pulsed irradiation give insight into the population mechanism illustrating that the generation of the isonitrosyl MS1 occurs through a two-step process, via the second PLI, the side-on configuration MS2.
Recent Advances in the Conversion of Methane to Syngas and Chemicals via Photocatalysis
This review provides an overview on the recent research progress in the photocatalytic methane conversion to syngas and chemicals including photocatalytic reforming, photocatalytic partial oxidation and photocatalytic coupling of methane.
Abstract
As a primary constituent of natural gas and shale gas, direct conversion of methane has attracted significant attention due to its potential to reduce energy consumption and CO2 emissions. Compared with thermal catalysis, photocatalysis has the capacity to transcend thermodynamic constraint and enable the conversion of sustainable solar energy into chemical energy under mild reaction condition, which contributes to optimize the utilization of methane. In this review, we undertake a comparative analysis of various strategies for photocatalytic methane conversion to syngas and chemicals, including photocatalytic reforming of methane, photocatalytic partial oxidation of methane and photocatalytic coupling of methane. The distinct reaction systems with corresponding catalysts and underlying mechanisms are expounded in detail to foster a profound comprehension of solar-driven methane conversion. Finally, the challenges and prospectives in photocatalytic methane conversion are discussed.