ChemSystemsChem最新文献

In the Research Article by Munenori Numata and co-workers a dissipative self-assembly system powered by flow and light is demonstrated. Supramolecular co-polymerization and rolling-up from the forward polymer's end led to the creation of discrete micrometer-sized supramolecular architecture featuring both molecular-level inner complexity and long-range order over molecular scale.

This work presents some ambitious perspectives on how Systems Chemistry can contribute to developing the quite new research line of Chemical Artificial Intelligence (CAI). CAI refers to the efforts of devising liquid chemical systems mimicking some performances of biological and human intelligence, which ultimately emerge from wetware. The CAI systems implemented so far assist humans in making decisions. However, such CAI systems lack autonomy and cannot substitute humans. The development of autonomous chemical systems will allow the colonization of the molecular world with remarkable repercussions on human well-being. As a beneficial side effect, this research line will help establish a deeper comprehension of the mesmerizing phenomenon of the origin of life on Earth and how cognitive capabilities emerge at a basic physico-chemical level.

The cover picture shows a scanning electron micrograph of self-organized chemical garden tubes. These calcium-based hollow structures are composed of porous walls separating an alkaline exterior liquid and acidic, metal salt interior solution. Natural analogs to this classic chemistry experiment are hydrothermal vents found at the base of the ocean. Their structures are composed of mineral walls which separate two disparate chemical environments maintaining a far-from-equilibrium setting. More in theResearch Article by Pamela Knoll and Corentin C. Loron.

Asymmetric chemical reactions on the surfaces of colloidal particles are known to propel them into directional motion. The dynamics of such chemical micromotors are sensitive to their local chemical environments, which also continually evolve with the reactions on motor surfaces. This two-way coupling between the motor dynamics and the local environment may result in complex nonlinear behaviors. As an example, we report that Janus Ag microspheres, which self-propel in hydrogen peroxide (H₂O₂), spontaneously reverse their direction of motion two or more times. We hypothesize that two distinct chemical reactions between Ag and H₂O₂ drive the micromotor in opposite directions, and which reaction dominates depends on the local pH. Interestingly, the local pH near a Ag micromotor oscillates spontaneously in H₂O₂, likely due to a complex interplay between the kinetics of the reaction between Ag and H₂O₂ and the diffusion of chemical species. Consequently, the pH-sensitive Ag micromotor reverses its direction of motion in response to these pH oscillations. This study introduces a new mechanism for regulating the speed and directionality of micromotors, highlights the potential of Ag micromotors in chemical sensing, and sheds new light on the interplay between chemical kinetics and micromotor dynamics.

The injection of rare-earth metal salt solutions into sodium silicate solution results in vertically growing tubular precipitate structures. At low input concentrations reaction kinetics is the rate-detemining process, leading to linear growth rates independent of injection rates. At higher concentrations, flow drives the precipitate growth, characterized by jetting mechanism. Among the studied rare-earth metal silicates, dysprosium silicate is found to have the most rigid structure with visible growth even at higher injection rates. The outer surface of the hollow tubes is smooth, on which rare-earth hydroxide – based on the result of the energy dispersive X-ray spectroscopy measurements – aggregates into globules.

The origin of life, being one of the most fascinating questions in science, is increasingly addressed by interdisciplinary research. In addition to developing plausible chemical models for synthesizing the first biomolecules from prebiotic building blocks, searching for suitable and plausible non-equilibrium boundary conditions that drive such reactions is thus a central task in this endeavor. This perspective highlights the remarkably simple yet versatile scenario of heat flows in geologically plausible crack-like compartments as a habitat for prebiotic chemistry. Based on our recent findings, it is discussed how thermophoretically driven systems offer insights into solving key milestones in the origin of life research, such as the template inhibition problem, prebiotic symmetry breaking, and the promotion of prebiotic chemistry by selective enrichment of biochemical precursors. Our results on molecular-selective thermogravitational accumulation, heat flow-induced pH gradients, and environmental cycles are put in the context of other approaches to non-equilibrium systems and prebiotic chemistry. The coupling of heat flows to chemical and physical boundary conditions thus opens up numerous future experimental research avenues, such as the extraction of phosphate from geomaterials or the integration of chemical reaction networks into thermal non-equilibrium systems, offering a promising framework for advancing the field of prebiotic chemistry.

Owing to their property to alter their surface-activity upon the irradiation with light, photoswitchable surfactants have gained tremendous interest in colloidal science. Their mere addition to a colloidal system allows, e. g., to obtain control over polyelectrolytes, micro- and nanoscale particles or emulsions. Most literature examples focus on azobenzene-based, or related, systems, which employ a photoisomerization reaction for switching. Other structures, such as spiropyrans, play a subordinate role, although they have gained increasing attention over the past few years. In this perspective article, we want to provide an overview about existing systems of photoswitchable surfactants. We address the issue that alternative photoswitches are given less attention, and what benefits surfactants could possess that are based on said switchable units. With our contribution, we want to broaden the view on stimuli-responsive surfactants – and to provide a guideline for the design of novel structures.

Biochemical communication is ubiquitous in life. Biology uses chemical reaction networks to regulate concentrations of myriad signaling molecules. Recent advances in supramolecular and systems chemistry demonstrate that feedback mechanisms of such networks can be rationally designed but strategies to transmit and process information encoded in molecules are still in their infancy. Here, we designed a polyelectrolyte reaction network maintained under out-of-equilibrium conditions using pH gradients in flow. The network comprises two weak polyelectrolytes (polyallylamine, PAH, and polyacrylic acid, PAA) in solution and one immobilized on the surface (poly-l-lysine, PLL). We chose PAH and PAA as their complexation process is known to be history-dependent (i. e., the preceding state of the system can determine the next state). Surprisingly, we found that the hysteresis diminished as the PLL-coated surface supported rather than perturbed the formation of the complex. PLL-coated surfaces are further exploited to establish that reversible switching between the assembled and disassembled state of polyelectrolytes can process signals encoded in the frequency and duration of pH pulses. We envision that the strategy employed to modulate information in this polyelectrolyte reaction network could open novel routes to transmit and process molecular information in biologically relevant processes.

The front cover illustrates cell-like functional molecular systems based on DNA nanotechnology and lipid vesicles. The base-specific interactions of DNA enable the construction of various functional components that can be integrated into lipid vesicles, aiming to create artificial molecular systems comparable to, or even surpassing, natural molecular systems, such as living cells. The Review by Y. Sato describes the latest achievements in functions realized through the combination of DNA nanotechnology and lipid vesicles.

Understanding the emergence of complex properties in dissipative non-equilibrium systems is crucial for unraveling the mysteries of life processes. The review focuses on the documented research on chemically fueled autonomous systems, self-sorting towards compartmentalization, self-replication via autocatalysis, and rhythmic chemical oscillators. In addition to that, the review also discusses newly introduced reactions and dynamic combinatorial libraries in dissipative systems.