Scaling of quantum interference from single molecules to molecular cages and their monolayers.

The discovery of quantum interference (QI) is widely considered as an important advance in molecular electronics since it provides unique opportunities for achieving single-molecule devices with unprecedented performance. Although some pioneering studies suggested the presence of spin qubit coherence and QI in collective systems such as thin films, it remains unclear whether the QI can be transferred step-by-step from single molecules to different length scales, which hinders the application of QI in fabricating active molecular devices. Here, we found that QI can be transferred from a single molecule to their assemblies. We synthesized and investigated the charge transport through the molecular cages using 1,3-dipyridylbenzene (DPB) as a ligand block with a destructive quantum interference (DQI) effect and 2,5-dipyridylfuran (DPF) as a control building block with a constructive quantum interference (CQI) effect using both single-molecule break junction and large area junction techniques. Combined experiments and calculations revealed that both DQI and CQI had been transferred from the ligand blocks to the molecular cages and the monolayer thin film of the cages. Our work introduced QI effects from a ligand to the molecular cage comprising 732 atoms and even their monolayers, suggesting that the quantum interference could be scaled up within the phase-coherent distance.

Melatonin promotes proliferation of Inner Mongolia cashmere goat hair follicle papilla cells through Wnt10b.

The study demonstrated that melatonin (MT) can induce the development of secondary hair follicles in Inner Mongolian cashmere goats through the Wnt10b gene, leading to secondary dehairing. However, the mechanisms underlying the expression and molecular function of Wnt10b in dermal papilla cells (DPC) remain unknown. This research aimed to investigate the impact of MT on DPC and the regulation of Wnt10b expression, function, and molecular mechanisms in DPC. The findings revealed that MT promotes DPC proliferation and enhances DPC activity. Co-culturing DPC with overexpressed Wnt10b and MT showed a significant growth promotion. Subsequent RNA sequencing (RNA-seq) of overexpressed Wnt10b and control groups unveiled the regulatory role of Wnt10b in DPC. Numerous genes and pathways, including developmental pathways such as Wnt and MAPK, as well as processes like hair follicle morphogenesis and hair cycle, were identified. These results suggest that Wnt10b promotes the growth of secondary hair follicles in Inner Mongolian cashmere goats by regulating crucial factors and pathways in DPC proliferation.

Highly Reversible Molecular Photoswitches with Transition Metal Dichalcogenides Electrodes.

The molecule-electrode coupling plays an essential role in photoresponsive devices with photochromic molecules, and the strong coupling between the molecule and the conventional electrodes leads to/ the quenching effect and limits the reversibility of molecular photoswitches. In this work, we developed a strategy of using transition metal dichalcogenides (TMDCs) electrodes to fabricate the thiol azobenzene (TAB) self-assembled monolayers (SAMs) junctions with the eutectic gallium-indium (EGaIn) technique. The current-voltage characteristics of the EGaIn/GaOx //TAB/TMDCs photoswitches showed an almost 100% reversible photoswitching behavior, which increased by ∼28% compared to EGaIn/GaOx //TAB/AuTS photoswitches. Density functional theory (DFT) calculations showed the coupling strength of the TAB-TMDCs electrode decreased by 42% compared to that of the TAB-AuTS electrode, giving rise to improved reversibility. our work demonstrated the feasibility of 2D TMDCs for fabricating SAMs-based photoswitches with unprecedentedly high reversibility.

Single-molecule photoelectron tunnelling spectroscopy.

Experimental mapping of transmission is essential for understanding and controlling charge transport through molecular devices and materials. Here we developed a single-molecule photoelectron tunnelling spectroscopy approach for mapping transmission beyond the HOMO-LUMO gap of the single diketopyrrolopyrrole molecule junction using an ultrafast-laser combined scanning tunnelling microscope-based break junction set-up at room temperature. Two resonant transport channels of ultrafast photocurrent are found by our photoelectron tunnelling spectroscopy, ranging from 1.31 eV to 1.77 eV, consistent with the LUMO + 1 and LUMO + 2 in the transmission spectrum obtained by density functional theory calculations. Moreover, we observed the modulation of resonant peaks by varying bias voltages, which demonstrates the ability to quantitatively characterize the effect of the electric field on frontier molecular orbitals. Our single-molecule photoelectron tunnelling spectroscopy offers an avenue that allows us to explore the nature of energy-dependent charge transport through single-molecule junctions.

Biosafe cerium oxide nanozymes protect human pluripotent stem cells and cardiomyocytes from oxidative stress.

BACKGROUND: Cardiovascular diseases (CVDs) have the highest mortality worldwide. Human pluripotent stem cells (hPSCs) and their cardiomyocyte derivatives (hPSC-CMs) offer a valuable resource for disease modeling, pharmacological screening, and regenerative therapy. While most CVDs are linked to significant over-production of reactive oxygen species (ROS), the effects of current antioxidants targeting excessive ROS are limited. Nanotechnology is a powerful tool to develop antioxidants with improved selectivity, solubility, and bioavailability to prevent or treat various diseases related to oxidative stress. Cerium oxide nanozymes (CeONZs) can effectively scavenge excessive ROS by mimicking the activity of endogenous antioxidant enzymes. This study aimed to assess the nanotoxicity of CeONZs and their potential antioxidant benefits in stressed human embryonic stem cells (hESCs) and their derived cardiomyocytes (hESC-CMs). RESULTS: CeONZs demonstrated reliable nanosafety and biocompatibility in hESCs and hESC-CMs within a broad range of concentrations. CeONZs exhibited protective effects on the cell viability of hESCs and hESC-CMs by alleviating excessive ROS-induced oxidative stress. Moreover, CeONZs protected hESC-CMs from doxorubicin (DOX)-induced cardiotoxicity and partially ameliorated the insults from DOX in neonatal rat cardiomyocytes (NRCMs). Furthermore, during hESCs culture, CeONZs were found to reduce ROS, decrease apoptosis, and enhance cell survival without affecting their self-renewal and differentiation potential. CONCLUSIONS: CeONZs displayed good safety and biocompatibility, as well as enhanced the cell viability of hESCs and hESC-CMs by shielding them from oxidative damage. These promising results suggest that CeONZs may be crucial, as a safe nanoantioxidant, to potentially improve the therapeutic efficacy of CVDs and be incorporated into regenerative medicine.

Supramolecular Radical Electronics.

Supramolecular radical chemistry is an emerging area bridging supramolecular chemistry and radical chemistry, and the integration of radicals into the supramolecular architecture offers a new dimension for tuning their structures and functions. Although various efforts have been devoted to the fabrication of supramolecular junctions, the charge transport characterization through the supramolecular radicals remained unexplored due to the challenges in creating supramolecular radicals at the single-molecule level. Here, we demonstrate the fabrication and charge transport investigation of a supramolecular radical junction using the electrochemical scanning tunneling microscope-based break junction (EC-STM-BJ) technique. We found that the conductance of a supramolecular radical junction was more than 1 order of magnitude higher than that of a supramolecular junction without a radical and even higher than that of a fully conjugated oligophenylenediamine molecule with a similar length. The combined experimental and theoretical investigations revealed that the radical increased the binding energy and decreased the energy gap in the supramolecular radical junction, which leads to the near-resonant transport through the supramolecular radical. Our work demonstrated that the supramolecular radical can provide not only strong binding but also efficient electrical coupling between building blocks, which provides new insights into supramolecular radical chemistry and new materials with supramolecular radicals.

Supramolecular Transistors with Quantum Interference Effect.

The charge transport through supramolecular junctions exhibits unique quantum interference (QI) effects, which provide an opportunity for the design of supramolecular transistors. Benefiting from the configuration dependence of QI, configuration control of the supramolecular assemblies to demonstrate the QI features is a key but challenging step. In this work, we fabricated the supramolecular transistors and investigated the charge transport through the conducting channel of the individual π-stacked thiophene/phenylene co-oligomers (TPCOs) using the electrochemically gated scanning tunneling microscope break junction technique. We controlled the configuration of the supramolecular channel and switched the QI features between the anti-resonance and resonance states of the supramolecular channels. We observed the supramolecular transistor with its on/off ratio above 103 (∼1300), a high gating efficiency of ∼165 mV/dec, a low off-state leakage current of ∼30 pA, and the channel length scaled down to <2.0 nm. Density functional theory calculations suggested that the QI features in π-stacked TPCOs vary depending on the supramolecular architecture and can be manipulated efficiently by fine-tuning the supramolecular configurations. This work reveals the potential of the supramolecular channels for molecular electronics and provides a fundamental understanding of intermolecular charge transport.

Room-temperature logic-in-memory operations in single-metallofullerene devices.

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 (Sc2C2@Cs(hept)-C88) 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 [Sc2C2] 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.

Theoretical and DFT Study of Atypical Pentanuclear [(iPr3P)Ni]5Hn (n = 4, 6, 8) Clusters: What are the Rules?

The structure, bonding, and properties of a series of atypical pentanuclear nickel hydride clusters supported by electron-rich iPr3P of the type [(iPr3P)Ni]5Hn (n = 4, 6, 8; H4, H6, H8) and their anionic models where iPr3P are substituted by H- (H4', H6', H8') were investigated by density functional theory (DFT) calculations. All clusters were calculated to adopt a similar square pyramidal core geometry. Calculations indicate singlet ground states with small singlet-triplet gaps for H4 and H6, similar to previously reported experimental values. Molecular orbital theory description clusters were investigated using the simplified model complexes [HNi]5Hn5- (n = 4, 6, 8; H4', H6', H8'). The results show that there are three skeletal electron pairs (SEPs) in H4'. The addition of two molecules of H2 to form H6' and H8' results in the partial or full occupation of two degenerate MOs (e* set) that give two SEPs and one SEP, respectively. Indeed, the occupation of these low-lying weakly antibonding orbitals governs the multielectron chemistry available for these clusters and plays a role in their unique reactivity.

Design and Synthesis of Novel Helix Mimetics Based on the Covalent H-Bond Replacement and Amide Surrogate.

A novel hydrogen bond surrogate-based (HBS) α-helix mimetic was designed by the combination of covalent H-bond replacement and the use of an ether linkage to substitute an amide bond within a short peptide sequence. The new helix template could be placed in position other than the N-terminus of a short peptide, and the CD studies demonstrate that the template adopts stable conformations in aqueous buffer at exceptionally high temperatures.

Switching Quantum Interference in Single-Molecule Junctions by Mechanical Tuning.

The charge transport through single-molecule electronic devices can be controlled mechanically by changing the molecular geometrical configuration in situ, but the tunable conductance range is typically less than two orders of magnitude. Herein, we proposed a new mechanical tuning strategy to control the charge transport through the single-molecule junctions via switching quantum interference patterns. By designing molecules with multiple anchoring groups, we switched the electron transport between the constructive quantum interference (CQI) pathway and the destructive quantum interference (DQI) pathway, and more than four orders of magnitude conductance variation can be achieved by shifting the electrodes in a range of about 0.6 nm, which is the highest conductance range ever achieved using mechanical tuning.

Single-Molecule Tunneling Sensors for Nitrobenzene Explosives.

The tunneling current through the single-molecule junctions principally offers the ultimate solution for chemical and biochemical sensing via the interactions between probes and target analytes at the single-molecule level. However, it remains unexplored to achieve the sensitive and selective detection of targeted analytes using single-molecule junction techniques due to the challenge in quantitative evaluation of sensing sensitivity and selectivity. Herein, we demonstrate a single-molecule tunneling sensor for the highly sensitive and selective detection of nitrobenzene explosives using scanning tunneling microscope break junction (STM-BJ). Taking advantage of π-π stacking interactions between the molecular probes and nitrobenzene explosives, we use a spectral clustering algorithm to assign the signal of probes and π-stacked probes for sensitively detecting the targeted analytes and the distinguishable conductance change of probes when interacting with different nitroaromatic explosive compounds for selective detection. We find that pronounced conductance changes up to 0.8 orders of magnitude when the probes interact with TNT. Also, we obtain a sensitivity of up to ∼10 pM for TNT and high sensitivity for eight TNT analogues. Combined with theoretical calculations, we discover that the harness of the destructive quantum interference of the probe M1OH after interacting with TNT leads to high selectivity in sensing with TNT. Our work demonstrates the great potential of the single-molecule tunneling current for environmental sensing molecules with high selectivity and sensitivity.

MS-IDF: A Software Tool for Nontargeted Identification of Endogenous Metabolites after Chemical Isotope Labeling Based on a Narrow Mass Defect Filter.

Chemical isotope labeling liquid chromatography mass spectrometry (LC-MS) is an emerging metabolomic strategy for the quantification and characterization of small molecular compounds in biological samples. However, its subsequent data analysis is not straightforward due to a large amount of data produced and interference of biological matrices. In order to improve the efficiency of searching and identification of target endogenous metabolites, a new software tool for nontargeted metabolomics data processing called MS-IDF was developed based on the principle of a narrow mass defect filter. The developed tool provided two function modules, including IsoFinder and MDFinder. The IsoFinder function module applied a conventional peak extraction method by using a fixed mass differences between the heavy and light labels and by the alignment of chromatographic retention time (RT). On the other hand, MDFinder was designed to incorporate the accurate mass defect differences between or among stable isotopes in the peak extraction process. By setting an appropriate filter interval, the target metabolites can be efficiently screened out while eliminating interference. Notably, the present results showed that the efficiency in compound identification using the new MDFinder module was nearly doubled as compared to the conventional IsoFinder method (an increase from 259 to 423 compounds). The Matlab codes of the developed MS-IDF software are available from github at https://github.com/jydong2018/MS_IDF. Based on the MS-IDF software tool, a novel and effective approach from nontargeted to targeted metabolomics research was developed and applied to the exploration of potential primary amine biomarkers in patients with schizophrenia. With this approach, potential biomarkers, including N,N-dimethylglycine, S-adenosine-l-methionine, dl-homocysteine, and spermidine, were discovered.

Transport Modulation Through Electronegativity Gating in Multiple Nitrogenous Circuits.

Investigating the correlations of electron transport between multiple channels shows vital promises for the design of molecule-scale circuits with logic operations. To control the electron transport through multiple channels, the modulation of electronegativity shows an effective frontier orbit control method with high universality to explore the interactions between transport channels. Here, two series of compounds with a single nitrogenous conductive channel (Sg) and dual-channels (Db) are designed to explore the influence of electronegativity on electron tunneling transport. Single-molecule conductance measured via the scanning tunneling microscope break junction technique (STM-BJ) reveals that the conductance of Db series is significantly suppressed as the electronegativity of nitrogen becomes negative, while the suppression on Sg is less obvious. Theoretical calculations confirm that the effect of electronegativity extends to a dispersive range of molecular frameworks owing to the delocalized orbital distribution from the dual-channel structure, resulting in a more significant conductance suppression effect than that on the single-channel. This study provides the experimental and theoretical potentials of electronegativity gating for molecular circuits.

Strain of Supramolecular Interactions in Single-Stacking Junctions.

Supramolecular electronics provide opportunities to integrate molecular building blocks into electronic circuits, and investigations of the mechanical properties of the non-covalent interactions are necessary to understand the role of the assembly configuration in the electronic coupling among different assembly blocks. However, the mechanical characterization of supramolecular interactions remains experimentally challenging. We investigated the strain distribution of the supramolecular interactions through a series of single-stacking junctions. The alpha values exhibit a clear odd-even effect versus the numbers of thiophene rings. The theoretical calculations demonstrated that a larger rotational barrier of the single-stacking junctions with an even number of thiophene rings leads to limited torsional freedom and thus a smaller strain distribution. These results provide new insights into the control of supramolecular interactions by the design of the basic molecular building blocks.

Fano Resonance in Single-Molecule Junctions.

The Fano resonance in single-molecule junctions could be created by interaction with discrete and continuous molecular orbitals and enables effective electron transport modulation between constructive and destructive interference within a small energy range. However, direct observation of Fano resonance remains unexplored because of the disappearance of discrete orbitals by molecule-electrode coupling. We demonstrated the room-temperature observation of Fano resonance from electrochemical gated single-molecule conductance and current-voltage measurements of a para-carbazole anion junction. Theoretical calculations reveal that the negative charge on the nitrogen atom induces a localized HOMO on the molecular center, creating Fano resonance by interfering with the delocalized LUMO on the molecular backbone. Our findings demonstrate that the Fano resonance in electron transport through single-molecule junctions opens pathways for designs of interference-based electronic devices.

Single-Molecule Charge-Transport Modulation Induced by Steric Effects of Side Alkyl Chains.

The experimental investigation of side-chain effects on intramolecular charge transport in π-conjugated molecules is essential but remains challenging. Herein, the dependence of intra-molecular conductance on the nature of branching alkyl chains is investigated through a combination of the scanning tunneling microscope break junction (STM-BJ) technique and density functional theory. Three thiophene-flanked diketopyrrolopyrrole (DPP) derivatives with different branching alkyl chains (isopentane, 3-methylheptane, and 9-methylnonadecane) are used with phenylthiomethyl groups as the anchoring groups. The results of single-molecule conductance measurements show that as the alkyl chain becomes longer, the torsional angles between the aromatic rings increase due to steric crowding, and therefore, the molecular conductance of DPP decreases due to reduction in conjugation. Both theoretical simulations and 1 H NMR spectra demonstrate that the planarity of the DPPs is directly reduced after introducing longer branching alkyl chains, which leads to a reduced conductance. This work indicates that the effect of the insulating side chain on the single-molecule conductance cannot be neglected, which should be considered for the design of future organic semiconducting materials.

Enantioselective Total Synthesis of Cerorubenic Acid-III via Type II [5+2] Cycloaddition Reaction.

The first enantioselective total synthesis of cerorubenic acid-III is described in detail. Different strategies and attempts, based on a type II [5+2] cycloaddition reaction, leading to the bicyclo[4.4.1] ring system with a strained bridgehead double bond, are depicted. Furthermore, sodium naphthalenide was found to be efficient in the chemoselective reduction of 8-oxabicyclo[3.2.1]octene, with three transformations completed in one operation. An unusual SN1 transannular cyclization reaction was applied to construct the synthetically challenging vinylcyclopropane moiety. This strategy enabled the total synthesis of cerorubenic acid-III in 19 steps.

Evaluation of Sanders Type 2 Joint Depression Calcaneal Fractures in 197 Patients from a Single Center Using Three-Dimensional Mapping.

BACKGROUND This study aimed to evaluate Sanders type 2 calcaneal fractures in 197 patients from a single center using the 3D (three-dimensional) CT (computed tomography) mapping method. MATERIAL AND METHODS A consecutive series of 197 Sanders type 2 joint depression calcaneal fractures was used. The segment and split functions were used to create each calcaneal fragment using Mimics Research 20.0 software. The fracture fragments were reduced in 3-matic Research 12.0 software. In the E-3D Medical 18.01 software, after superimposing the fractured calcaneus entity with the calcaneus template, we drew the fracture line on the template. Finally, the heatmap was obtained by fracture statistical analysis function. Simultaneously, the distribution of the fracture lines in the anterior part of the calcaneus (APC) and middle talar joint was recorded. RESULTS There were 109 cases of Sanders type 2A, 46 cases of Sanders type 2B, and 42 cases of Sanders type 2C. Based on the data, we drew the characteristic fracture map of type 2A 2B and 2C. This study found that the most common types of Sanders type 2A in APC and middle talar articular surface are type AC and type AD. In Sanders type 2B, the most common type is type AC, and in Sanders type 2C it is type ACD. CONCLUSIONS The findings from this study showed that 3D CT imaging and reconstruction of the calcaneus was a useful diagnostic method to evaluate and classify joint depression calcaneal fractures. The calcaneal fracture map can be used to guide surgical planning and optimize the design of internal fixation.

Electric Field-Induced Assembly in Single-Stacking Terphenyl Junctions.

Molecular assembly is crucial in functional molecular materials and devices. Among the molecular interactions that can form assemblies, stacking among π-conjugated molecular backbones plays an essential role in charge transport through organic materials and devices. The single-molecule junction technique allows for the application of an electric field of approximately 108 V/m to the nanoscale junctions and to investigate the electric field-induced assembly at the single-stacking level. Here, we demonstrate an electric field-induced stacking effect between two molecules using the scanning tunneling microscope break junction (STM-BJ) technique and we found an increase in the stacking probability with increasing intensity of the electric field. The combined density functional theory (DFT) calculations suggest that the molecules become more planar under the electric field, leading to the energetically preferred stacking configuration. Our study provides a new strategy for tuning molecular assembly by employing a strong electric field.