Achieving high performance in molecular scale diode devices remains a formidable challenge due to the complexity of the charge transport process and the difficulty in device structure modulation.Herein,we demonstrated...Achieving high performance in molecular scale diode devices remains a formidable challenge due to the complexity of the charge transport process and the difficulty in device structure modulation.Herein,we demonstrated a low-cost and fast screening strategy to search for proper electroactive units and construct high performance self-assembled monolayer(SAM)-based molecular diodes.The strategy is based on off-the-shelf carboxylate-terminated alkane thiols and simple carboxylate-metal ion complexes,structures denoted as Au-S-(CH2)n-1COO−Mm+(Cn+Mm+),where n=11,12,13,14,16,18,and Mm+=Ca^(2+),Mn^(2+),Fe_(2)+,Fe3+,Co^(2+),Ni^(2+),Cu^(2+),and Zn^(2+),as the library of functional SAM layers on gold substrate.Combing the fast screening measurements using a eutectic indium-gallium alloy top contact(EGaIn),C18+Ca^(2+)and C18+Zn^(2+)structures were found to afford record high rectification ratio(RR)>700 at±1.5 V.Theoretical analysis based on a single level tunneling model shows that the C18+Ca^(2+)and C18+Zn^(2+)devices possessed an optimized combination of asymmetric voltage division,energy offset,and coupling of carboxylate-metal complexes with the electrode.This newly developed method represents a general strategy for fast,inexpensive,and effective exploration of the functional metal complex chemical space,and can largely accelerate the development of practical high performance molecular diode devices.展开更多
Series tunneling across peptides composed of various amino acids is one of the main charge transport mechanisms for realizing the function of protein. Histidine, more frequently found in redox active proteins, has bee...Series tunneling across peptides composed of various amino acids is one of the main charge transport mechanisms for realizing the function of protein. Histidine, more frequently found in redox active proteins, has been proved to be efficient tunneling mediator. While how it exactly modulates charge transport in a long peptide sequence remains poorly explored. In this work, we studied charge transport of a model peptide junction, where oligo-alanine peptide was doped by histidine at different position,and the series of peptides were self-assembled into a monolayer on gold electrode with soft EGa In as top electrode to form molecular junction. It was found that histidine increased the overall conductance of the peptide, meanwhile, its position modulated the conductance as well. Quantitative analysis by transport model and ultraviolet photoelectron spectroscopy(UPS) indicated a sequence dependent energy landscape of the tunneling barrier of the junction. Density-functional theory(DFT) calculation on the electronic structure of histidine doped oligo-alanine peptides revealed localized highest occupied molecular orbital(HOMO) on imidazole group of the histidine, which decreased charge transport barrier.展开更多
基金supported by the National Natural Science Foundation of China(grant nos.21973069 and 21773169)the National Key R&D Program(grant nos.2017YFA0204503 and 2016YFB0401100)+1 种基金the PEIYANG Young Scholars Program of Tianjin University(grant no.2018XRX-0007)the Industry-University-Research Cooperation Program of Tianjin University and Qinghai Nationalities University(grant no.2021XZC-0064).
文摘Achieving high performance in molecular scale diode devices remains a formidable challenge due to the complexity of the charge transport process and the difficulty in device structure modulation.Herein,we demonstrated a low-cost and fast screening strategy to search for proper electroactive units and construct high performance self-assembled monolayer(SAM)-based molecular diodes.The strategy is based on off-the-shelf carboxylate-terminated alkane thiols and simple carboxylate-metal ion complexes,structures denoted as Au-S-(CH2)n-1COO−Mm+(Cn+Mm+),where n=11,12,13,14,16,18,and Mm+=Ca^(2+),Mn^(2+),Fe_(2)+,Fe3+,Co^(2+),Ni^(2+),Cu^(2+),and Zn^(2+),as the library of functional SAM layers on gold substrate.Combing the fast screening measurements using a eutectic indium-gallium alloy top contact(EGaIn),C18+Ca^(2+)and C18+Zn^(2+)structures were found to afford record high rectification ratio(RR)>700 at±1.5 V.Theoretical analysis based on a single level tunneling model shows that the C18+Ca^(2+)and C18+Zn^(2+)devices possessed an optimized combination of asymmetric voltage division,energy offset,and coupling of carboxylate-metal complexes with the electrode.This newly developed method represents a general strategy for fast,inexpensive,and effective exploration of the functional metal complex chemical space,and can largely accelerate the development of practical high performance molecular diode devices.
基金supported by the National Natural Science Foundation of China (Nos. 21773169, 21973069, 21805144)Natural Science Foundation of Zhejiang Province (No. LY18B020016)the PEIYANG Young Scholars Program of Tianjin University (No. 2018XRX-0007)。
文摘Series tunneling across peptides composed of various amino acids is one of the main charge transport mechanisms for realizing the function of protein. Histidine, more frequently found in redox active proteins, has been proved to be efficient tunneling mediator. While how it exactly modulates charge transport in a long peptide sequence remains poorly explored. In this work, we studied charge transport of a model peptide junction, where oligo-alanine peptide was doped by histidine at different position,and the series of peptides were self-assembled into a monolayer on gold electrode with soft EGa In as top electrode to form molecular junction. It was found that histidine increased the overall conductance of the peptide, meanwhile, its position modulated the conductance as well. Quantitative analysis by transport model and ultraviolet photoelectron spectroscopy(UPS) indicated a sequence dependent energy landscape of the tunneling barrier of the junction. Density-functional theory(DFT) calculation on the electronic structure of histidine doped oligo-alanine peptides revealed localized highest occupied molecular orbital(HOMO) on imidazole group of the histidine, which decreased charge transport barrier.
