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Controlling the electrical conductance and in particular the occurrence of quantum interference in single-molecule junctions through gating effects has potential for the realization of high-performance functional molecular devices. In this work we used an electrochemically gated, mechanically controllable break junction technique to tune the electronic behaviour of thiophene-based molecular junctions that show destructive quantum interference features. By varying the voltage applied to the electrochemical gate at room temperature, we reached a conductance minimum that provides direct evidence of charge transport controlled by an anti-resonance arising from destructive quantum interference. Our molecular system enables conductance tuning close to two orders of magnitude within the non-faradaic potential region, which is significantly higher than that achieved with molecules not showing destructive quantum interference. Our experimental results, interpreted using quantum transport theory, demonstrate that electrochemical gating is a promising strategy for obtaining improved in situ control over the electrical performance of interference-based molecular devices.Electrochemical gating of single-molecule junctions shows signatures of anti-resonance typical of destructive quantum interference effects and conductance tuning by two orders of magnitude in thiophene molecules.

In-memory computing provides an opportunity to meet the growing demands of large data-driven applications such as machine learning, by colocating logic operations and data storage. Despite being regarded as the ultimate solution for high-density integration and low-power manipulation, the use of spin or electric dipole at the single-molecule level to realize in-memory logic functions has yet to be realized at room temperature, due to their random orientation. Here, we demonstrate logic-in-memory operations, based on single electric dipole flipping in a two-terminal single-metallofullerene (Sc 2 C 2 @ C s (hept)-C 88 ) device at room temperature. By applying a low voltage of ±0.8 V to the single-metallofullerene junction, we found that the digital information recorded among the different dipole states could be reversibly encoded in situ and stored. As a consequence, 14 types of Boolean logic operation were shown from a single-metallofullerene device. Density functional theory calculations reveal that the non-volatile memory behaviour comes from dipole reorientation of the [Sc 2 C 2 ] group in the fullerene cage. This proof-of-concept represents a major step towards room-temperature electrically manipulated, low-power, two-terminal in-memory logic devices and a direction for in-memory computing using nanoelectronic devices. Single-molecule electronics provide the potential solution for high-density integration and low-power consumption in massive data-driven applications, but have yet to be explored. Here, the authors report low-power logic-in-memory operations, based on single electric dipole flipping in the two-terminal single-metallofullerene device at room temperature.

Many natural products possess interesting medicinal properties that arise from their intriguing chemical structures. The highly-substituted carbocycle is one of the most common structural features in many structurally complicated natural products. However, the construction of highly-substituted, stereo-congested, five-membered carbocycles containing all-carbon quaternary center(s) is, at present, a distinct challenge in modern synthetic chemistry, which can be accessed through the all-carbon [3 + 2] cycloaddition. More importantly, the all-carbon [3 + 2] cycloaddition can forge vicinal all-carbon quaternary centers in a single step and has been demonstrated in the synthesis of complex natural products. In this review, we present the development of all-carbon [3 + 2] cycloadditions and illustrate their application in natural product synthesis reported in the last decade covering 2011–2020 (inclusive).

Keto-enol tautomerism, describing an equilibrium involving two tautomers with distinctive structures, provides a promising platform for modulating nanoscale charge transport. However, such equilibria are generally dominated by the keto form, while a high isomerization barrier limits the transformation to the enol form, suggesting a considerable challenge to control the tautomerism. Here, we achieve single-molecule control of a keto-enol equilibrium at room temperature by using a strategy that combines redox control and electric field modulation. Based on the control of charge injection in the single-molecule junction, we could access charged potential energy surfaces with opposite thermodynamic driving forces, i.e., exhibiting a preference for the conducting enol form, while the isomerization barrier is also significantly reduced. Thus, we could selectively obtain desired and stable tautomers, which leads to significant modulation of the single-molecule conductance. This work highlights the concept of single-molecule control of chemical reactions on more than one potential energy surface. Keto-enol tautomerism offers a promising platform for modulating charge transport at the nanoscale. Here, the authors show that the keto-enol equilibrium can be modulated on the single-molecule scale by controlling charge injection in a two-terminal junction system.

Full-carbon electronics at the scale of several angstroms is an expeimental challenge, which could be overcome by exploiting the versatility of carbon allotropes. Here, we investigate charge transport through graphene/single-fullerene/graphene hybrid junctions using a single-molecule manipulation technique. Such sub-nanoscale electronic junctions can be tuned by band gap engineering as exemplified by various pristine fullerenes such as C 60 , C 70 , C 76 and C 90 . In addition, we demonstrate further control of charge transport by breaking the conjugation of their π systems which lowers their conductance, and via heteroatom doping of fullerene, which introduces transport resonances and increase their conductance. Supported by our combined density functional theory (DFT) calculations, a promising future of tunable full-carbon electronics based on numerous sub-nanoscale fullerenes in the large family of carbon allotropes is anticipated. All-carbon electronics holds promise beyond the conventional silicon-based electronics, but it remains challenging to manufacture them with well-defined structures thus tunability. Tan et al. control charge transport in single-molecule junctions using different fullerenes between graphene electrodes.

The absolute stereochemical configurations of acremolides A and B were predicted by a biochemistry-based rule and unambiguously confirmed through their total syntheses. The features of the total syntheses include sequential Krische’s Ir-catalyzed crotylation, Brown’s borane-mediated crotylation, Mitsunobu esterification reaction, and cross-metathesis reaction. The efficient total synthesis enabled clear validation of the predicted stereochemistry for acremolides A and B.

ObjectiveRoots can effectively reduce soil detachment. However, the dynamics of different root effects on soil detachment with root growth time are not clearly understood. Therefore, our objectives were to characterize the dynamics of soil detachment with root growth time and compare the effectiveness of roots of different types and planting densities on soil detachment.Materials and methodsA laboratory experiment was conducted to quantify and elucidate the effect of fibrous ryegrass (Lolium perenne L.) roots and alfalfa (Medicago sativa L.) taproots on soil detachment, with two planting densities at 4 different growth stages. Root parameters, soil properties, and the soil detachment rate (with a flow discharge of 3 L min−1 for 15 min on a 15° slope) were measured at days 28, 56, 84, and 112.Results and discussionRoot parameters increased with root growth time, and the fibrous roots varied more significantly than taproots. Soil bulk density decreased with root growth time, while the contents of soil organic matter and water-stable aggregates increased with root growth time. The effect of fibrous roots on soil properties was significantly greater than that of taproots. The absolute soil detachment rate and relative soil detachment rate from fibrous roots decreased by 53.35% and 51.98% from days 28 to 112 respectively, but those from taproots did not change significantly. Soil detachment under high-density cultivation was lower than that under low-density cultivation at the early growth stage but inversely later. Soil detachment decreased exponentially with root parameters, and the equation of root parameters and soil detachment in RL (ryegrass with a low planting density) best explained the soil detachment variation (91.3–96.1%).ConclusionsPlants with fibrous roots had greater effect on soil detachment reduction than those with taproots. Treatments with high planting density had a more significant influence on soil detachment reduction than did those with low planting density at the early growth stage, but the opposite was true later. This experiment helped to explain the mechanism and process of root growth affecting soil detachment and provided a fundamental basis for erosion management practices.

ObjectiveThe plant canopy, plant roots, and biological soil crusts play important roles in soil detachment by overland flow. This study aims to quantify and analyze the effects of the plant canopy, plant roots, and soil crust on soil detachment via in situ experiments.Materials and methodsTwo typical dominant species, Bothriochloa ischaemum (Linn.) Keng (an herb) and Sophora davidii (Franch.) Skeel (a shrub) on the Loess Plateau, China, were selected. Four treatments were denoted T0 (bare land), T1 (canopy + root + crust), T2 (root + crust), and T3 (root) and subjected to flow scouring with a discharge of 5 L min−1 on a 20° slope.Results and discussionThe soil detachment rate (SDr) in all treatments decreased sharply in the first 3 min due to changes in the internal force of the soil particles. As the effects of the canopy, roots, and soil crust were subsequently superimposed, the SDr decreased by 87.42–93.42% compared with that of the bare land. The plant canopy, roots, and soil crust contributed 8.57–9.54%, 92.36–95.27%, and −1.90 to −3.84% of the soil detachment reduction (SDR), respectively. Additionally, the naturally restored herb roots decreased soil detachment by flowing water more significantly than shrub roots in the study area.ConclusionsThe effects of canopy, roots, and soil crust on SDr in grassland were similar to those in shrubland. Roots played a crucial role in strengthening soil resistance to detachment. Although shrubland had a greater effect on soil detachment reduction than grassland, herbs are strongly recommended for reducing soil erodibility due to the greater erosion-reducing potential of roots and their drought resistance on the Loess Plateau.

The dominant technical noise of a free-running laser practically limits bright squeezed light generation, particularly within the MHz band. To overcome this, we develop a comprehensive theoretical model for nonclassical power stabilization, and propose a novel bright squeezed light generation scheme incorporating hybrid power noise suppression. Our approach integrates broadband passive power stabilization with nonclassical active stabilization, extending the feedback bandwidth to MHz frequencies. This hybrid technique achieves an additional 9 dB technical noise suppression, establishing critical prerequisites for broadband bright squeezed light generation. Finally, a -5.5 dB bright squeezed light at 1 mW with kHz-MHz squeezing bandwidth was generated. The experimental results show excellent agreement with theoretical predictions, which represent we have comprehensively demonstrated a milliwatt-order bright squeezed light across kHz-MHz frequencies. Our work enables new quantum metrology applications and paves the way for next-generation quantum-enhanced technologies. Nonclassical hybrid passive–active power stabilization enables milliwatt-level bright squeezing across kHz–MHz band

The investigation of electronic excited states in single-molecule junctions not only provides platforms to reveal the photophysical and photochemical processes at the molecular level, but also brings opportunities for the development of single-molecule optoelectronic devices. Understanding the interaction mechanisms between molecules and nanocavities is essential to obtain on-demand properties in devices by artificial design, since molecules in junctions exhibit unique behaviors of excited states benefited from the structures of metallic nanocavities. Here, we review the excitation mechanisms involved in the interplay between molecules and plasmonic nanocavities, and reveal the influence of nanostructures on excited-state properties by demonstrating the differences in excited state decay processes. Furthermore, vibronic transitions of molecules between nanoelectrodes are also discussed, offering a new single-molecule characterization method. Finally, we provide the potential applications and challenges in single-molecule optoelectronic devices and the possible directions in exploring the underlying mechanisms of photophysical and photochemical processes.