Looking Back and Looking Ahead in Electrochemical Reduction of CO2

Electrochemical reduction of carbon dioxide (CO₂) to valuable organic compounds is promising as to recycling of carbon source of CO₂ and technical compatibility with systems using renewable energy resources. In recent years, considerable efforts have been devoted to the research field of CO₂ conversion using electrocatalysis. This personal account particularly focuses on the recent progress that has been achieved by the Ertl Center and a number of groups in South Korea that becomes one of the larger CO₂ emitters. The research trends of catalyst development divided into different categories according to the primary products are presented first. Afterwards, several studies on theoretical calculations and electrolytic reactors are reviewed taking into account the fundamental understanding and feasibility of the CO₂ electroreduction. Finally, a perspective on the challenges and needs in achieving the advanced level of research and development is presented.     

Looking for clear solutions

The familiar ways of reaching consensus about measurements are leading analytical chemists into troubled waters.     

Non-stationary forward flux sampling

We present a method, Non-Stationary Forward Flux Sampling, that allows efficient simulation of rare events in both stationary and non-stationary stochastic systems. The method uses stochastic branching and pruning to achieve uniform sampling of trajectories in phase space and time, leading to accurate estimates for time-dependent switching propensities and time-dependent phase space probability densities. It is suitable for equilibrium or non-equilibrium systems, in or out of stationary state, including non-Markovian or externally driven systems. We demonstrate the validity of the technique by applying it to a one-dimensional barrier crossing problem that can be solved exactly, and show its usefulness by applying it to the time-dependent switching of a genetic toggle switch.     

Suppressed forward scattering in photoelectron holography

The anisotropic nature of photoelectron source waves may be exploited to suppress forward scattering in photoelectron diffraction. Theoretical simulations show that this is the case for a geometry where the scattered electrons are measured close to a node of the electron source wave. As a consequence the quality of holographic reconstructions from such data improves considerably. The optimum geometry between the excitation source and the electron analyzer is evaluated quantitatively for the case of Mg K excited C1s electrons in CO molecules.     

Food safety measurement issues: way forward

Ensuring food safety (FS) is a persistent concern frequently faced by many countries. Safeguarding the quality of food that is fit for human consumption is the primary responsibility of the governmental regulatory agencies. For most part, agro-industries and food processors assume voluntary leadership for producing safe food. However, in the event of FS breach, the regulatory responsibility kicks into identify and rectify the situation. Notwithstanding whether it is the regulator or the industry that institutes the remedial action (e.g. improved hygiene and refined agricultural and manufacturing practices), the role of laboratory measurements is central in safeguarding the integrity of a functioning FS system. There are many analytical tools available to implement this task, such as validated analytical methods, natural matrix reference materials, field tested monitoring systems (proactive assessment) and effective surveillance systems (constant vigilance to prevent repeat safety violations). Way forward: existing FS tools are insufficient and should be strengthened with innovative approaches. Examples are: assembling swift intervention logistics to face FS breaches; rapid response systems including communication; robust metrology based measurement systems located at strategic locations in the country; and inter-disciplinary human resource to match the need for capacity development. These issues are discussed.     

Looking at atomic orbitals through fourier and wavelet transforms

Solutions of Hartree–Fock equations expressed as Gaussian functions are studied in various spaces: position, momentum, and position–momentum spaces. The use of the wavelet transform allows one to visualize position and momentum characteristics of atomic orbitals on the same drawing. A complementary viewpoint is then obtained on top of usual position and momentum representations. Applications to Gaussian “atomic” orbitals modeled as one-dimensional functions are performed. © 1993 John Wiley & Sons, Inc.     

Looking for the Origin of Allosteric Cooperativity in Metallopolymers

The basic concept of allosteric cooperativity used in biology, chemistry and physics states that any change in the intermolecular host–guest interactions operating in multisite receptors can be assigned to intersite interactions. Using lanthanide metals as guests and linear multi‐tridentate linear oligomers of variable lengths and geometries as hosts, this work shows that the quantitative modeling of metal loadings requires the consideration of a novel phenomenon originating from solvation processes. It stepwise modulates the intrinsic affinity of each isolated site in multisite receptors, and this without resorting to allosteric cooperativity. An easy‐to‐handle additive model predicts a negative power law dependence of the intrinsic affinity on the length of the linear metallopolymer. Applied to lanthanidopolymers, the latter common analysis overestimates cooperativity factors by more than two orders of magnitude.     

Investigating polymer blend miscibility with forward recoil spectrometry

We tested forward recoil spectrometry (FRES) as a method to determine miscibility by measuring coexistence compositions in binary polymer blends. In this study, equilibrium phase compositions were determined for a compositionally symmetric poly(styrene‐ran‐methyl methacrylate) random copolymer (S_0.49‐r‐MMA) and two homopolymers, deuterated polystyrene (dPS) and deuterated poly(methyl methacrylate) (dPMMA). Sample preparation, film dewetting, and beam damage were addressed, and the results for these polymer blends were in good agreement with those obtained through other experimental techniques. Deuteration had a strong effect on the miscibility of the dPS/S_0.49‐r‐MMA and dPMMA/S_0.49‐r‐MMA blends, to the extent that the asymmetric miscibility observed separately for the PS/S_0.49‐r‐MMA and PMMA/S_0.49‐r‐MMA blends was not found. Although this deuteration effect may limit the applicability of FRES for some polymer systems, the accuracy with which phase compositions can be determined with FRES makes it an attractive alternative to other less quantitative methods for investigating blend miscibility. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1547–1552, 2000     

Looking Back and Ahead: Gas-Phase Electron Diffraction at 75

At 75, gas-phase electron diffraction is still the method of choice for selected problems in molecular structure determination. It works best when being applied with other techniques in a concerted way.