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1.
Asia Pac J Clin Oncol ; 20(1): 101-108, 2024 Feb.
Article in English | MEDLINE | ID: mdl-37898825

ABSTRACT

AIM: Cavitation of lesions is common in non-squamous non-small cell lung cancer (non-squamous-NSCLC) patients treated with vascular endothelial growth factor receptor tyrosine kinase inhibitors (VEGFRIs). However, traditional response evaluation criteria in solid tumors (RECIST) do not take cavitation into consideration and may no longer be accurate for potentially reflecting the real clinical efficacy of anti-vessel growth therapy. Here, we aimed to optimize the traditional RECIST version 1.1 by adding cavitation into the evaluation criteria. METHODS: We performed a post-hoc radiologic review of 517 patients in a phase III clinical trial of bevacizumab biosimilar (SIBP04) combined with chemotherapy for the treatment of non-squamous NSCLC. Tumor responses were assessed by RECIST1.1 and mRECIST criteria (modified RECIST, a novel alternate method where the longest diameter of the cavity was subtracted from the overall longest diameter of that lesion to measure target lesions), respectively, and correlated with clinical outcomes. RESULTS: Cavitations of pulmonary lesions were seen in nine (2%) patients at baseline, and 97 (19%) during treatment. The use of mRECIST resulted in an alteration of the response category. For patients with post-therapy cavitation, the objective response rate was 56% using RECIST1.1 and 67% by mRECIST. In addition, the survival rates between partial response, stable disease, and progressive disease when the mRECIST was applied were significantly different (p < 0.05), while RECIST1.1 failed to show survival differences (p = 0.218). CONCLUSION: For patients with post-therapy cavitation, mRECIST exhibited higher predictability of survival than RECIST1.1. Response assessment might be improved by incorporating cavitation into assessment, potentially altering outcomes of key clinical efficacy parameters.


Subject(s)
Carcinoma, Non-Small-Cell Lung , Lung Neoplasms , Humans , Carcinoma, Non-Small-Cell Lung/diagnostic imaging , Carcinoma, Non-Small-Cell Lung/drug therapy , Carcinoma, Non-Small-Cell Lung/pathology , Bevacizumab/adverse effects , Response Evaluation Criteria in Solid Tumors , Lung Neoplasms/diagnostic imaging , Lung Neoplasms/drug therapy , Lung Neoplasms/pathology , Vascular Endothelial Growth Factor A/therapeutic use
2.
Front Psychol ; 14: 1276812, 2023.
Article in English | MEDLINE | ID: mdl-37954178

ABSTRACT

Introduction: Drawing upon upper echelon theory and the resource-based view, this study employs a moderated mediation model to investigate the moderating role and underlying mechanisms of digital transformation in the influence of top management teams (TMT) on corporate green innovation. Methods: Our analysis of panel data from 19,155 Chinese A-share listed companies (2011-2020) demonstrates that TMT career experience heterogeneity has a positive effect on green innovation, a relationship that is further strengthened by digital transformation. Results: This study shows the role of digital transformation in amplifying the effects of TMT diversity on green innovation and the crucial role of industry-academia-research collaboration as a mediator. Heterogeneity analysis highlights that non-state-owned enterprises (non-SOEs) show more agility than state-owned enterprises (SOEs) in leveraging heterogeneous TMT to drive green innovation. Conversely, green innovation in SOEs benefits more from digital transformation, which includes both its direct and indirect effects of digital transformation. Enterprises located in non-Yangtze River Economic Belt regions benefit more from digital transformation, demonstrating the importance of a balanced distribution of digital resources. Discussion: This study provides novel insights into leveraging inclusive leadership and digital capabilities to enhance ecological sustainability. This study underscores the potential of diversified TMTs and digitalization technology integration to catalyze green innovation, which is critical for environmentally responsible transformation.

3.
J Cardiovasc Pharmacol ; 82(6): 496-503, 2023 12 01.
Article in English | MEDLINE | ID: mdl-37548460

ABSTRACT

ABSTRACT: This study aims to investigate whether venous injection of sedative agent or regional nerve block in alliance with major anesthesia could decrease the risk of postoperative delirium occurrence in patients receiving cardiothoracic surgery. Electronic academic databases were retrieved for related publications, and statistical software was used for data pooling and analysis. Forest plot was used to show the pooled sensitivity, specificity, and diagnostic odds ratio. Combined receiver operating characteristic curve was used to show the area under the curve of complex data. Seven studies were included for analysis. The risk of occurrence of delirium still showed no difference (risk rate = 0.93, 95% CI, 0.85-1.03) between the intervention group and placebo group. Postoperative pain feeling was more alleviated in patients with prophylactic application of regional nerve block. In addition, prophylactic application of regional nerve block could decrease the risk of postoperative in-hospital stay (risk rate = 0.28, 95% CI, 0.02-0.54). Our study demonstrated that, in elderly patients or pediatric patients undergoing cardiac surgery, prophylactic application of regional nerve block failed to decrease the incidence of postoperative delirium. However, the option of regional nerve block could decrease the duration of in-hospitalization stay and alleviate the acute pain during the postoperative period after open-heart surgery.


Subject(s)
Emergence Delirium , Nerve Block , Humans , Child , Aged , Emergence Delirium/etiology , Length of Stay , Pain, Postoperative/diagnosis , Pain, Postoperative/prevention & control , Pain, Postoperative/etiology , Nerve Block/adverse effects , Anesthesia, General
4.
Science ; 381(6658): 686-693, 2023 08 11.
Article in English | MEDLINE | ID: mdl-37561870

ABSTRACT

The use of bioelectronic devices relies on direct contact with soft biotissues. For transistor-type bioelectronic devices, the semiconductors that need to have direct interfacing with biotissues for effective signal transduction do not adhere well with wet tissues, thereby limiting the stability and conformability at the interface. We report a bioadhesive polymer semiconductor through a double-network structure formed by a bioadhesive brush polymer and a redox-active semiconducting polymer. The resulting semiconducting film can form rapid and strong adhesion with wet tissue surfaces together with high charge-carrier mobility of ~1 square centimeter per volt per second, high stretchability, and good biocompatibility. Further fabrication of a fully bioadhesive transistor sensor enabled us to produce high-quality and stable electrophysiological recordings on an isolated rat heart and in vivo rat muscles.


Subject(s)
Polymers , Semiconductors , Tissue Adhesives , Transistors, Electronic , Animals , Rats , Electrophysiological Phenomena , Polymers/chemistry , Heart/physiology , Muscle, Skeletal/physiology
5.
Sci Rep ; 13(1): 11077, 2023 Jul 08.
Article in English | MEDLINE | ID: mdl-37422570

ABSTRACT

Deep learning is currently being used to automate surface defect detection in aluminum. The common target detection models based on neural networks often have a large number of parameters and a slow detection speed, which is not conducive to real-time detection. Therefore, this paper proposes a lightweight aluminum surface defect detection model, M2-BL-YOLOv4, based on the YOLOv4 algorithm. First, in the YOLOv4 model, the complex CSPDarkNet53 backbone network was modified into an inverted residual structure, which greatly reduced the number of parameters in the model and increased the detection speed. Second, a new feature fusion network, BiFPN-Lite, is designed to improve the fusion ability of the network and further improve its detection accuracy. The final results show that the mean average precision of the improved lightweight YOLOv4 algorithm in the aluminum surface defect test set reaches 93.5%, the number of model parameters is reduced to 60% of the original, and the number of frames per second (FPS) detected is 52.99, which increases the detection speed by 30%. The efficient detection of aluminum surface defects is realized.


Subject(s)
Algorithms , Aluminum , Neural Networks, Computer , Orientation, Spatial , Spine
6.
J Cancer Res Clin Oncol ; 149(14): 12713-12721, 2023 Nov.
Article in English | MEDLINE | ID: mdl-37452849

ABSTRACT

PURPOSE: SIBP04 is a bevacizumab biosimilar, and bevacizumab combined with carboplatin and paclitaxel in advanced non-squamous non-small-cell lung cancer (nsqNSCLC) has been recommended as the first-line treatment choice. However, the efforts of bevacizumab combined with carboplatin and paclitaxel for nsqNSCLC patients with EGFR mutation remained unclear. Here we report an EGFR mutation subgroup analysis of a prospective, randomized phase III clinical trial (NCT05318443). METHODS: In this randomized, double-blind, multi-center, parallel controlled, phase III clinical trial, locally advanced, metastatic NSCLC patients were enrolled, and EGFR expression was examined and considered as a stratification factor. All patients received 4 to 6 cycles of paclitaxel and carboplatin plus SIBP04 or bevacizumab 15 mg/kg intravenously followed by SIBP04 15 mg/kg maintenance until intolerable toxicity, disease progression or death. Patients with EGFR mutation and wild-type were assessed for progression-free survival (PFS) and overall survival (OS). RESULTS: EGFR expression was examined in 398 NSCLC patients (142 with EGFR mutation, 256 with EGFR wild type). PFS in EGFR mutation patients was significantly longer than EGFR wild-type patients (10.91 vs. 7.82 months; HR = 0.692, 95% CI 0.519-0.921, P = 0.011). The median OS in patients with EGFR mutation was not reached while that of EGFR wild-type group was 17.54 months (HR = 0.398, 95% CI 0.275-0.575, P < 0.001). However, there were no significant differences in objective response rate (61.97% vs. 55.86%, P = 0.237) or disease control rate (90.14% vs. 89.84%, P = 0.925). CONCLUSION: Bevacizumab combined with chemotherapy significantly prolonged the PFS and OS of advanced nsqNSCLC patients with EGFR mutation.

7.
Nano Lett ; 23(13): 5951-5958, 2023 Jul 12.
Article in English | MEDLINE | ID: mdl-37384632

ABSTRACT

Incorporating temperature- and air-stable organic radical species into molecular designs is a potentially advantageous means of controlling the properties of electronic materials. However, we still lack a complete understanding of the structure-property relationships of organic radical species at the molecular level. In this work, the charge transport properties of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) radical-containing nonconjugated molecules are studied using single-molecule charge transport experiments and molecular modeling. Importantly, the TEMPO pendant groups promote temperature-independent molecular charge transport in the tunneling region relative to the quenched and closed-shell phenyl pendant groups. Results from molecular modeling show that the TEMPO radicals interact with the gold metal electrodes near the interface to facilitate a high-conductance conformation. Overall, the large enhancement of charge transport by incorporation of open-shell species into a single nonconjugated molecular component opens exciting avenues for implementing molecular engineering in the development of next-generation electronic devices based on novel nonconjugated radical materials.

9.
Nat Mater ; 22(6): 737-745, 2023 Jun.
Article in English | MEDLINE | ID: mdl-37024592

ABSTRACT

Stretchable light-emitting materials are the key components for realizing skin-like displays and optical biostimulation. All the stretchable emitters reported to date, to the best of our knowledge, have been based on electroluminescent polymers that only harness singlet excitons, limiting their theoretical quantum yield to 25%. Here we present a design concept for imparting stretchability onto electroluminescent polymers that can harness all the excitons through thermally activated delayed fluorescence, thereby reaching a near-unity theoretical quantum yield. We show that our design strategy of inserting flexible, linear units into a polymer backbone can substantially increase the mechanical stretchability without affecting the underlying electroluminescent processes. As a result, our synthesized polymer achieves a stretchability of 125%, with an external quantum efficiency of 10%. Furthermore, we demonstrate a fully stretchable organic light-emitting diode, confirming that the proposed stretchable thermally activated delayed fluorescence polymers provide a path towards simultaneously achieving desirable electroluminescent and mechanical characteristics, including high efficiency, brightness, switching speed and stretchability as well as low driving voltage.

10.
Nat Commun ; 13(1): 2102, 2022 04 19.
Article in English | MEDLINE | ID: mdl-35440635

ABSTRACT

The development of next-generation organic electronic materials critically relies on understanding structure-function relationships in conjugated polymers. However, unlocking the full potential of organic materials requires access to their vast chemical space while efficiently managing the large synthetic workload to survey new materials. In this work, we use automated synthesis to prepare a library of conjugated oligomers with systematically varied side chain composition followed by single-molecule characterization of charge transport. Our results show that molecular junctions with long alkyl side chains exhibit a concentration-dependent bimodal conductance with an unexpectedly high conductance state that arises due to surface adsorption and backbone planarization, which is supported by a series of control experiments using asymmetric, planarized, and sterically hindered molecules. Density functional theory simulations and experiments using different anchors and alkoxy side chains highlight the role of side chain chemistry on charge transport. Overall, this work opens new avenues for using automated synthesis for the development and understanding of organic electronic materials.


Subject(s)
Polymers , Adsorption , Polymers/chemistry
11.
Adv Mater ; 34(23): e2201178, 2022 Jun.
Article in English | MEDLINE | ID: mdl-35448913

ABSTRACT

Organic electrochemical transistors (OECTs) represent an emerging device platform for next-generation bioelectronics owing to the uniquely high amplification and sensitivity to biological signals. For achieving seamless tissue-electronics interfaces for accurate signal acquisition, skin-like softness and stretchability are essential requirements, but they have not yet been imparted onto high-performance OECTs, largely due to the lack of stretchable redox-active semiconducting polymers. Here, a stretchable semiconductor is reported for OECT devices, namely poly(2-(3,3'-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-[2,2'-bithiophen]-5)yl thiophene) (p(g2T-T)), which gives exceptional stretchability over 200% strain and 5000 repeated stretching cycles, together with OECT performance on par with the state-of-the-art. Validated by systematic characterizations and comparisons of different polymers, the key design features of this polymer that enable the combination of high stretchability and high OECT performance are a nonlinear backbone architecture, a moderate side-chain density, and a sufficiently high molecular weight. Using this highly stretchable polymer semiconductor, an intrinsically stretchable OECT is fabricated with high normalized transconductance (≈223 S cm-1 ) and biaxial stretchability up to 100% strain. Furthermore, on-skin electrocardiogram (ECG) recording is demonstrated, which combines built-in amplification and unprecedented skin conformability.


Subject(s)
Polymers , Transistors, Electronic , Electronics , Oxidation-Reduction , Polymers/chemistry , Skin
12.
J Am Chem Soc ; 144(7): 3162-3173, 2022 02 23.
Article in English | MEDLINE | ID: mdl-35148096

ABSTRACT

Intermolecular charge transport through π-conjugated molecules plays an essential role in biochemical redox processes and energy storage applications. In this work, we observe highly efficient intermolecular charge transport upon dimerization of pyridinium molecules in the cavity of a synthetic host (cucurbit[8]uril, CB[8]). Stable, homoternary complexes are formed between pyridinium molecules and CB[8] with high binding affinity, resulting in an offset stacked geometry of two pyridiniums inside the host cavity. The charge transport properties of free and dimerized pyridiniums are characterized using a scanning tunneling microscope-break junction (STM-BJ) technique. Our results show that π-stacked pyridinium dimers exhibit comparable molecular conductance to isolated, single pyridinium molecules, despite a longer transport pathway and a switch from intra- to intermolecular charge transport. Control experiments using a CB[8] homologue (cucurbit[7]uril, CB[7]) show that the synthetic host primarily serves to facilitate dimer formation and plays a minimal role on molecular conductance. Molecular modeling using density functional theory (DFT) reveals that pyridinium molecules are planarized upon dimerization inside the host cavity, which facilitates charge transport. In addition, the π-stacked pyridinium dimers possess large intermolecular LUMO-LUMO couplings, leading to enhanced intermolecular charge transport. Overall, this work demonstrates that supramolecular assembly can be used to control intermolecular charge transport in π-stacked molecules.

13.
BMC Genom Data ; 23(1): 9, 2022 01 29.
Article in English | MEDLINE | ID: mdl-35093018

ABSTRACT

BACKGROUND: CesA and Csl gene families, which belong to the cellulose synthase gene superfamily, plays an important role in the biosynthesis of the plant cell wall. Although researchers have investigated this gene superfamily in several model plants, to date, no comprehensive analysis has been conducted in the common bean. RESULTS: In this study, we identified 39 putative cellulose synthase genes from the common bean genome sequence. Then, we performed a bioinformatics analysis of this gene family involving sequence alignment, phylogenetic analysis, gene structure, collinearity analysis and chromosome location. We found all members possess a cellulose_synt domain. Phylogenetic analysis revealed that these cellulose synthase genes may be classified into five subfamilies, and that members in the same subfamily share conserved exon-intron distribution and motif compositions. Abundant and distinct cis-acting elements in the 2 k basepairs upstream regulatory regions indicate that the cellulose synthase gene family may plays a vital role in the growth and development of common bean. Moreover, the 39 cellulose synthase genes are distributed on 10 of the 11 chromosomes. Additionally expression analysis shows that all CesA/Csl genes selected are constitutively expressed in the pod development. CONCLUSIONS: This research reveals both the putative biochemical and physiological functions of cellulose synthase genes in common bean and implies the importance of studying non-model plants to understand the breadth and diversity of cellulose synthase genes.


Subject(s)
Phaseolus , Computational Biology , Gene Expression Regulation, Plant/genetics , Glucosyltransferases , Multigene Family/genetics , Phaseolus/genetics , Phylogeny , Plant Proteins/genetics , Plants/genetics
14.
Theor Appl Genet ; 135(2): 439-447, 2022 Feb.
Article in English | MEDLINE | ID: mdl-34674010

ABSTRACT

KEY MESSAGE: An allene oxide cyclase 4, GmAOC4, was determined by GWAS and RT-PCR to be significantly associated with seed germination in soybean, and regulates seed germination by promoting more JA accumulation. The seed germination phase is a critical component of the plant lifecycle, and a better understanding of the mechanism behind seed germination in soybeans is needed. We used a genome-wide association study (GWAS) to detect a GWAS signal on chromosome 18. In this GWAS signal, SNP S18_56189166 was located within the 3'untranslated region of Glyma.18G280900, which encodes allene oxide cyclase 4 (named GmAOC4). Analysis of real-time PCR demonstrated that expression levels of GmAOC4 in the low-germination variety (KF, carrying SNP S18_56189166-T) were higher than in the high-germination variety (NN, carrying SNP S18_56189166-C). In these two varieties, KF showed a higher JA concentration than NN at 0 and 24 h after imbibition. Moreover, the overexpression of GmAOC4 led to an increase in the concentration of jasmonic acid (JA) in soybean hairy roots and Arabidopsis thaliana. Furthermore, it was found that GmAOC4-OE lines showed less seed germination than the wild type (WT) under normal conditions in Arabidopsis. After 7 days of ABA treatment, transgenic lines exhibited lower seed germination and higher expression levels of AtABI5 compared with WT, indicating that the overexpression of GmAOC4 resulted in hypersensitivity to ABA. Our findings demonstrate that GmAOC4, which promotes more JA accumulation, helps to regulate seed germination in soybeans.


Subject(s)
Arabidopsis Proteins , Germination , Abscisic Acid/metabolism , Arabidopsis Proteins/genetics , Gene Expression Regulation, Plant , Genome-Wide Association Study , Germination/genetics , Seeds/genetics , Glycine max/genetics , Glycine max/metabolism
15.
Nano Lett ; 21(19): 8340-8347, 2021 10 13.
Article in English | MEDLINE | ID: mdl-34529446

ABSTRACT

Efficient long-range charge transport is required for high-performance molecular electronic devices. Resonant transport is thought to occur in single molecule junctions when molecular frontier orbital energy levels align with electrode Fermi levels, thereby enabling efficient transport without molecular or environmental relaxation. Despite recent progress, we lack a systematic understanding of the transition between nonresonant and resonant transport for molecular junctions with different chemical compositions. In this work, we show that molecular junctions undergo a reversible transition from nonresonant tunneling to resonant transport as a function of applied bias. Transient bias-switching experiments show that the nonresonant to resonant transition is reversible with the applied bias. We determine a general quantitative relationship that describes the transition voltage as a function of the molecular frontier orbital energies and electrode Fermi levels. Overall, this work highlights the importance of frontier orbital energy alignment in achieving efficient charge transport in molecular devices.


Subject(s)
Electronics , Nanotechnology , Electrodes
16.
Health Phys ; 121(2): 87-91, 2021 08 01.
Article in English | MEDLINE | ID: mdl-33867432

ABSTRACT

ABSTRACT: To realize a fast and reliable approach for continuous radon measurements, a CdZnTe (CZT) detector based on the electrostatic collection method was developed. The experimental results show that when the external temperature varies from 5 °C to 30 °C, the maximum drifts of the characteristic peak positions of 218Po and 214Po are only 8 and 6. Furthermore, the measurement error associated with the constant radon concentration is less than 5.5%. As the temperature increases or decreases, the measurement error becomes larger, with the maximum error being 43.1%. The response of the proposed instrument for constant radon concentration is better than that of the RAD7 radon measurement instrument. At 25 °C, the value measured using the NRL-II radon meter with the PIPS detector is in good agreement with the actual value. The new radon measurement instrument exhibits a good compliance from the third measurement cycle (measurement deviation 0.53-3.95%), while RAD7 has good compliance from the fourth measurement cycle (measurement deviation of 1.17-4.88%). The theoretical and practical values of the iterative correction factor (influence of the previous measurement on the current measurement) of the radon measurement instrument are in good agreement. The iterative correction factor can be used for performing continuous radon measurements independently, with the aim of achieving a rapid response to environmental radon concentrations.


Subject(s)
Air Pollutants, Radioactive , Radiation Monitoring , Radon , Air Pollutants, Radioactive/analysis , Cadmium , Radiation Monitoring/methods , Radon/analysis , Tellurium , Zinc
17.
Theor Appl Genet ; 134(5): 1329-1341, 2021 May.
Article in English | MEDLINE | ID: mdl-33507340

ABSTRACT

KEY MESSAGE: We detected a QTL qHSW-16 undergone strong selection associated with seed weight and identified a novel candidate gene controlling seed weight candidate gene for this major QTL by qRT-PCT. Soybean [Glycine max (L.) Merr.] provides more than half of the world's oilseed production. To expand its germplasm resources useful for breeding increased yield and oil quality cultivars, it is necessary to resolve the diversity and evolutionary history of this crop. In this work, we resequenced 283 soybean accessions from China and obtained a large number of high-quality SNPs for investigation of the population genetics that underpin variation in seed weight and other agronomic traits. Selective signature analysis detected 78 (~ 25.0 Mb) and 39 (~ 22.60 Mb) novel putative selective signals that were selected during soybean domestication and improvement, respectively. Genome-wide association study (GWAS) identified five loci associated with seed weight. Among these QTLs, qHSW-16, overlapped with the improvement-selective region on chromosome 16, suggesting that this QTL may be underwent strong selection during soybean improvement. Of the 18 candidate genes in qHSW-16, only SoyZH13_16G122400 showed higher expression levels in a large seed variety compared to a small seed variety during seed development. These results identify SoyZH13_16G122400 as a novel candidate gene controlling seed weight and provide foundational insights into the molecular targets for breeding improvement of seed weight and potential seed yield in soybean.


Subject(s)
Chromosomes, Plant/genetics , Genome, Plant , Glycine max/genetics , Plant Proteins/genetics , Polymorphism, Single Nucleotide , Quantitative Trait Loci , Seeds/anatomy & histology , Chromosome Mapping/methods , Gene Expression Regulation, Plant , Genetic Linkage , Genetics, Population , Genome-Wide Association Study , Plant Breeding , Plant Proteins/metabolism , Seeds/genetics , Seeds/growth & development , Seeds/metabolism , Glycine max/growth & development , Glycine max/metabolism
18.
Front Pharmacol ; 11: 529553, 2020.
Article in English | MEDLINE | ID: mdl-33281601

ABSTRACT

MicroRNAs (miRNAs) have emerged as potential therapeutic targets for non-alcoholic fatty liver disease/non-alcoholic steatohepatitis (NAFLD/NASH). Traditional Chineses Medicine (TCM) plays an important role in the prevention or treatment of NAFLD/NASH. However, miRNA targets of TCM against NASH still remain largely unknown. Here, we showed that Yiqi-Bushen-Tiaozhi (YBT) recipe effectively attenuated diet-induced NASH in C57BL/6 mice. To identify the miRNA targets of YBT and understand the potential underlying mechanisms, we performed network pharmacology using miRNA and mRNA deep sequencing data combined with Ingenuity Pathway Analysis (IPA). Mmu-let-7a-5p, mmu-let-7b-5p, mmu-let-7g-3p and mmu-miR-106b-3p were screened as the main targets of YBT. Our results suggested that YBT might alleviate NASH by regulating the expression of these miRNAs that potentially modulate inflammation/immunity and oxidative stress. This study provides useful information for guiding future studies on the mechanism of YBT against NASH by regulating miRNAs.

19.
Nano Lett ; 20(7): 5490-5495, 2020 Jul 08.
Article in English | MEDLINE | ID: mdl-32511930

ABSTRACT

Robust molecule-metal linkages are essential for developing high-performance and air-stable devices for molecular and organic electronics. In this work, we report a facile method for forming robust and covalent bonding contacts between unprotected terminal acetylenes and metal (Ag) interfaces. Using this approach, we study the charge transport properties of conjugated oligophenylenes with covalent metal-carbon contacts to silver electrodes formed from unprotected terminal acetylene anchors. We performed single molecule charge transport experiments and molecular simulations on a series of arylacetylenes using gold and silver electrodes. Our results show that molecular junctions on silver electrodes spontaneously form silver-carbynyl carbon (Ag-C) contacts, resulting in a nearly 10-fold increase in conductance compared to the same molecules on gold electrodes. Overall, this work presents a simple, new electrode-anchor pair that reliably forms molecular junctions with stable and robust contacts for molecular electronics.

20.
J Am Chem Soc ; 142(10): 4852-4861, 2020 03 11.
Article in English | MEDLINE | ID: mdl-32069403

ABSTRACT

A major challenge in synthetic polymers lies in understanding how primary monomer sequence affects materials properties. In this work, we show that charge transport in single molecule junctions of conjugated oligomers critically depends on the primary sequence of monomers. A series of sequence-defined oligomers ranging from two to seven units was synthesized by an iterative approach based on the van Leusen reaction, providing conjugated oligomers with backbones consisting of para-linked phenylenes connected to oxazole, imidazole, or nitro-substituted pyrrole. The charge transport properties of these materials were characterized using a scanning tunneling microscope-break junction (STM-BJ) technique, thereby enabling direct measurement of molecular conductance for sequence-defined dimers, trimers, pentamers, and a heptamer. Our results show that oligomers with specific monomer sequences exhibit unexpected and distinct charge transport pathways that enhance molecular conductance more than 10-fold. A systematic analysis using monomer substitution patterns established that sequence-defined pentamers containing imidazole or pyrrole groups in specific locations provide molecular attachment points on the backbone to the gold electrodes, thereby giving rise to multiple conductance pathways. These findings reveal the subtle but important role of molecular structure including steric hindrance and directionality of heterocycles in determining charge transport in these molecular junctions. This work brings new understanding for designing molecular electronic components.

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