Publications by authors named "Jianlong Xia"

34 Publications

Molecular Regulation on Carbonyl-Based Organic Cathodes: Toward High-Rate and Long-Lifespan Potassium-Organic Batteries.

ACS Appl Mater Interfaces 2021 Apr 1;13(14):16396-16406. Epub 2021 Apr 1.

School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, 122 Luoshi Road, Wuhan, Hubei 430070, People's Republic of China.

Organic redox-active molecules have been identified as promising cathodes for practical usage of potassium-ion batteries (PIBs) but still struggle with serious dissolution problems and sluggish kinetic properties. Herein, we propose a pseudocapacitance-dominated novel insoluble carbonyl-based cathode, [2,6-di[1-(perylene-3,4,9,10-tetracarboxydiimide)]anthraquinone, AQ-diPTCDI], which possesses high reversible capacities of 150 mAh g, excellent cycle stability with capacity retention of 88% over 2000 cycles, and fast kinetic properties. The strong intermolecular interactions of AQ-diPTCDI and formed cathode electrolyte interphase films support it against the dissolution problem. The high capacitive-like contribution in capacities and fast potassium-ion diffusion enhance its reaction kinetics. Moreover, a symmetric organic potassium-ion battery (OPIB) based on AQ-diPTCDI electrodes also exhibits outstanding K-storage capability. These results suggest that AQ-diPTCDI is a promising organic cathode for OPIBs and provide a practicable route to realize high-performance K storage.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsami.1c01745DOI Listing
April 2021

Charge transfer states impact the triplet pair dynamics of singlet fission polymers.

J Chem Phys 2020 Dec;153(24):244902

Department of Physics, Graduate Center, City University of New York, New York, New York 10016, USA.

Polymers are desirable optoelectronic materials, stemming from their solution processability, tunable electronic properties, and large absorption coefficients. An exciting development is the recent discovery that singlet fission (SF), the conversion of a singlet exciton to a pair of triplet states, can occur along the backbone of an individual conjugated polymer chain. Compared to other intramolecular SF compounds, the nature of the triplet pair state in SF polymers remains poorly understood, hampering the development of new materials with optimized excited state dynamics. Here, we investigate the effect of solvent polarity on the triplet pair dynamics in the SF polymer polybenzodithiophene-thiophene-1,1-dioxide. We use transient emission measurements to study isolated polymer chains in solution and use the change in the solvent polarity to investigate the role of charge transfer character in both the singlet exciton and the triplet pair multiexciton. We identify both singlet fluorescence and direct triplet pair emission, indicating significant symmetry breaking. Surprisingly, the singlet emission peak is relatively insensitive to solvent polarity despite its nominal "charge-transfer" nature. In contrast, the redshift of the triplet pair energy with increasing solvent polarity indicates significant charge transfer character. While the energy separation between singlet and triplet pair states increases with solvent polarity, the overall SF rate constant depends on both the energetic driving force and additional environmental factors. The triplet pair lifetime is directly determined by the solvent effect on its overall energy. The dominant recombination channel is a concerted, radiationless decay process that scales as predicted by a simple energy gap law.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1063/5.0029858DOI Listing
December 2020

Effect of the Energy Offset on the Charge Dynamics in Nonfullerene Organic Solar Cells.

ACS Appl Mater Interfaces 2020 Sep 21;12(39):43984-43991. Epub 2020 Sep 21.

School of Chemistry, Beihang University, Beijing 100191, P. R. China.

The energy offset, considered as the driving force for charge transfer between organic molecules, has significant effects on both charge separation and charge recombination in organic solar cells. Herein, we designed material systems with gradually shifting energy offsets, including both positive and negative values. Time-resolved spectroscopy was used to monitor the charge dynamics within the bulk heterojunction. It is striking to find that there is still charge transfer and charge generation when the energy offset reached -0.10 eV (ultraviolet photoelectron spectroscopy data). This work not only indicates the feasibility of the free carrier generation and the following charge separation under the condition of a negative offset but also elucidates the relationship between the charge transfer and the energy offset in the case of polymer chlorination.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsami.0c13085DOI Listing
September 2020

Triplet Acceptors with a D-A Structure and Twisted Conformation for Efficient Organic Solar Cells.

Angew Chem Int Ed Engl 2020 Aug 9;59(35):15043-15049. Epub 2020 Jun 9.

Center of Materials Science and Optoelectronics Engineering, College of Materials Science and Opto-Electronic Technology &, CAS Center for Excellence in Topological Quantum Computation &, CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China.

Triplet acceptors have been developed to construct high-performance organic solar cells (OSCs) as the long lifetime and diffusion range of triplet excitons may dissociate into free charges instead of net recombination when the energy levels of the lowest triplet state (T ) are close to those of charge-transfer states ( CT). The current triplet acceptors were designed by introducing heavy atoms to enhance the intersystem crossing, limiting their applications. Herein, two twisted acceptors without heavy atoms, analogues of Y6, constructed with large π-conjugated core and D-A structure, were confirmed to be triplet materials, leading to high-performance OSCs. The mechanism of triplet excitons were investigated to show that the twisted and D-A structures result in large spin-orbit coupling (SOC) and small energy gap between the singlet and triplet states, and thus efficient intersystem crossing. Moreover, the energy level of T is close to CT, facilitating the split of triplet exciton to free charges.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/anie.202006081DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7497160PMC
August 2020

Tuning Biradical Character to Enable High and Balanced Ambipolar Charge Transport in a Quinoidal π-System.

Org Lett 2020 Apr 13;22(7):2553-2558. Epub 2020 Mar 13.

School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, Wuhan 430070, P. R. China.

Herein, two bis(dicyanomethylene)-substituted quinoidal molecules and were designed and synthesized to explore the open-shell effect on tuning the charge transport behavior of organic π-functional materials. The biradical character of was confirmed by DFT calculation, variable-temperature NMR, electron spin resonance (ESR), and superconducting quantum-interfering device (SQUID). The open-shell character enables an ambipolar characteristic under ambient conditions with highly balanced electron and hole mobilities of 0.32 and 0.16 cm V s, respectively.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.orglett.0c00453DOI Listing
April 2020

π-Extension, Selenium Incorporation, and Trimerization: "Three in One" for Efficient Perylene Diimide Oligomer-Based Organic Solar Cells.

ACS Appl Mater Interfaces 2020 Feb 14;12(8):9528-9536. Epub 2020 Feb 14.

School of Chemistry, Chemical Engineering and Life Science , Wuhan University of Technology , No. 122 Luoshi Road , Wuhan 430070 , China.

Perylene diimide (PDI) and the vinylene-bridged helical PDI oligomers are versatile building blocks for constructing nonfullerene acceptors (NFAs). In this contribution, a benzene-cored star-shaped NFA, namely, , was designed and synthesized for organic solar cells (OSCs). The NFA with smaller π-conjugated blades, namely, , was synthesized for comparison. Using the commercially available PTB7-Th as the electron donor, the best power conversion efficiency (PCE) of 3.62% was obtained for -based OSCs. However, a much higher PCE of 8.59% was achieved for -based devices owing to the π-extension in the peripheral panels. Moreover, the photovoltaic performance of -based OSCs is also superior to those of the parent NFA TPDI2 (PCE of 7.84%)- and the blade moiety PDI2-Se (PCE of 6.61%)- based ones. Additionally, a remarkable short-circuit current () value of 17.21 mA/cm was obtained for -based OSCs, which is among the highest values reported in PDI-based OSCs. These results argue that the so-called "three in one" molecule design strategy of π-extension, selenium incorporation, and trimerization offers a robust approach to constructing high-performance PDI-based NFAs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsami.9b21929DOI Listing
February 2020

Isomeric Effect on Optoelectronic Properties and Photovoltaic Performance of Anthraquinone-Core Perylene Diimide (PDI) and Helical PDI dimers.

Chemistry 2019 Sep 21;25(52):12137-12144. Epub 2019 Aug 21.

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Center of Smart Materials and Devices, Wuhan University of, Technology, No. 122 Luoshi Road, Wuhan, 430070, P.R. China.

Isomerism heavily influences the optoelectronic properties and self-assembly behavior of compounds and subsequently affects their device performance. Herein, two pairs of isomeric perylene diimide (PDI) dimers, PDI and PDI2, were designed and synthesized. The electron-deficient 9,10-anthraquinone group was employed as the bridge, and thus, the resultant dimers exhibited an acceptor-acceptor-acceptor (A-A-A) structure. To determine the isomeric effects on the optoelectronic properties and photovoltaic performance of these dimers, their absorptivity, luminescence, and redox behavior were studied. Bulk heterojunction organic solar cells based on these four dimers were fabricated and measured. The two PDI dimers exhibited clear differences in photovoltaic performance, whereas the two PDI2 analogues showed similar power conversion efficiencies (PCEs). The PCEs of the two PDI2 dimers are much higher than those of the PDI dimers. These results illustrate that the isomeric effect of PDI dimers is much larger than that of PDI2 dimers on the device performance, and proper expansion of conjugation could improve the device performance.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/chem.201902302DOI Listing
September 2019

Breaking Down Resonance: Nonlinear Transport and the Breakdown of Coherent Tunneling Models in Single Molecule Junctions.

Nano Lett 2019 04 5;19(4):2555-2561. Epub 2019 Mar 5.

Department of Applied Physics and Applied Mathematics , Columbia University , New York , New York 10027 , United States.

The promise of the field of single-molecule electronics is to reveal a new class of quantum devices that leverages the strong electronic interactions inherent to subnanometer scale systems. Here, we form Au-molecule-Au junctions using a custom scanning tunneling microscope and explore charge transport through current-voltage measurements. We focus on the resonant tunneling regime of two molecules, one that is primarily an electron conductor and one that conducts primarily holes. We find that in the high bias regime, junctions that do not rupture demonstrate reproducible and pronounced negative differential resistance (NDR)-like features followed by hysteresis with peak-to-valley ratios exceeding 100 in some cases. Furthermore, we show that both junction rupture and NDR are induced by charging of the molecular orbital dominating transport and find that the charging is reversible at lower bias and with time with kinetic time scales on the order of hundreds of milliseconds. We argue that these results cannot be explained by existing models of charge transport and likely require theoretical advances describing the transition from coherent to sequential tunneling. Our work also suggests new rules for operating single-molecule devices at high bias to obtain highly nonlinear behavior.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.nanolett.9b00316DOI Listing
April 2019

New insights into the design of conjugated polymers for intramolecular singlet fission.

Nat Commun 2018 07 31;9(1):2999. Epub 2018 Jul 31.

School of Chemistry, Chemical Engineering and Life Science, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, 430070, Wuhan, China.

Singlet fission (SF), a multiple exciton generation process that generates two triplet excitons after the absorption of one photon, can potentially enable more efficient solar cell designs by harvesting energy normally lost as heat. While low-bandgap conjugated polymers are highly promising candidates for efficient SF-based solar cells, few polymer materials capable of SF have been reported because the SF process in polymer chains is poorly understood. Using transient spectroscopy, we demonstrate a new, highly efficient (triplet yield of 160-200%) isoindigo-based donor-acceptor polymer and show that the triplet pairs are directly emissive and exhibit a time-dependent energy evolution. Importantly, aggregation in poor solvents and in films significantly lowers the singlet energy, suppressing triplet formation because the energy conservation criterion is no longer met. These results suggest a new design rule for developing intramolecular SF capable low-bandgap conjugated polymers, whereby inter-chain interactions must be carefully engineered.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-018-05389-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6068183PMC
July 2018

Novel Star-Shaped Helical Perylene Diimide Electron Acceptors for Efficient Additive-Free Nonfullerene Organic Solar Cells.

ACS Appl Mater Interfaces 2018 Aug 13;10(33):27894-27901. Epub 2018 Aug 13.

School of Chemistry, Chemical Engineering and Life Science, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing , Wuhan University of Technology , Wuhan 430070 , China.

Two star-shaped helical perylene diimide (PDI) electron acceptors TPDI2 and FTPDI2 were designed and synthesized for nonfullerene organic solar cells (OSCs). The integration of helical PDIs into a three-dimensional structure provides a new strategy to tune the intermolecular interactions, and the as-cast blend films with PTB7-Th show favorable morphology as well as efficient charge transfer and separation, as evidenced by the morphology and femtosecond transient absorption (fs-TA) spectroscopy studies. A trade-off between suppressing the self-aggregation and maintaining the charge-transfer properties was achieved by FTPDI2. Using PTB7-Th as the electron donor, the FTPDI2-based nonfullerene OSCs show a high power conversion efficiency of 8.28%, without the assistance of any additives.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsami.8b06126DOI Listing
August 2018

A helical perylene diimide-based acceptor for non-fullerene organic solar cells: synthesis, morphology and exciton dynamics.

R Soc Open Sci 2018 May 2;5(5):172041. Epub 2018 May 2.

School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, No. 122 Luoshi Road, Wuhan 430070, People's Republic of China.

Helical perylene diimide-based (hPDI) acceptors have been established as one of the most promising candidates for non-fullerene organic solar cells (OSCs). In this work, we report a novel hPDI-based molecule, hPDI-CN, as an electron acceptor for OSCs. Combining the hPDI-CN with a low-bandgap polymeric donor (PTB7-Th), the blending film morphology exhibited high sensitivity to various treatments (such as thermal annealing and addition of solvent additives), as evidenced by atomic force microscope studies. The power conversion efficiency (PCE) was improved from 1.42% (as-cast device) to 2.76% after thermal annealing, and a PCE of 3.25% was achieved by further addition of 1,8-diiodooctane (DIO). Femtosecond transient absorption (TA) spectroscopy studies revealed that the improved thin-film morphology was highly beneficial for the charge carrier transport and collection. And a combination of fast exciton diffusion rate and the lowest recombination rate contributed to the best performance of the DIO-treated device. This result further suggests that the molecular conformation needs to be taken into account in the design of perylene diimide-based acceptors for OSCs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1098/rsos.172041DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5990788PMC
May 2018

A mobile precursor determines protein resistance on nanostructured surfaces.

Phys Chem Chem Phys 2018 May;20(18):12527-12534

School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, Wuhan 430070, China.

Biomaterials are often engineered with nanostructured surfaces to control interactions with proteins and thus regulate their biofunctions. However, the mechanism of how nanostructured surfaces resist or attract proteins together with the underlying design rules remains poorly understood at a molecular level, greatly limiting attempts to develop high-performance biomaterials and devices through the rational design of nanostructures. Here, we study the dynamics of nonspecific protein adsorption on block copolymer nanostructures of varying adhesive domain areas in a resistant matrix. Using surface plasmon resonance and single molecule tracking techniques, we show that weakly adsorbed proteins with two-dimensional diffusivity are critical precursors to protein resistance on nanostructured surfaces. The adhesive domain areas must be more than tens or hundreds of times those of the protein footprints to slow down the 2D-mobility of the precursor proteins for their irreversible adsorption. This precursor model can be used to quantitatively analyze the kinetics of nonspecific protein adsorption on nanostructured surfaces. Our method is applicable to precisely manipulate protein adsorption and resistance on various nanostructured surfaces, e.g., amphiphilic, low-surface-energy, and charged nanostructures, for the design of protein-compatible materials.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c8cp00887fDOI Listing
May 2018

Battery-Supercapacitor Hybrid Devices: Recent Progress and Future Prospects.

Adv Sci (Weinh) 2017 07 21;4(7):1600539. Epub 2017 Feb 21.

School of Chemistry Chemical Engineering and Life Science and State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan Hubei 430070 P. R. China.

Design and fabrication of electrochemical energy storage systems with both high energy and power densities as well as long cycling life is of great importance. As one of these systems, Battery-supercapacitor hybrid device (BSH) is typically constructed with a high-capacity battery-type electrode and a high-rate capacitive electrode, which has attracted enormous attention due to its potential applications in future electric vehicles, smart electric grids, and even miniaturized electronic/optoelectronic devices, etc. With proper design, BSH will provide unique advantages such as high performance, cheapness, safety, and environmental friendliness. This review first addresses the fundamental scientific principle, structure, and possible classification of BSHs, and then reviews the recent advances on various existing and emerging BSHs such as Li-/Na-ion BSHs, acidic/alkaline BSHs, BSH with redox electrolytes, and BSH with pseudocapacitive electrode, with the focus on materials and electrochemical performances. Furthermore, recent progresses in BSH devices with specific functionalities of flexibility and transparency, etc. will be highlighted. Finally, the future developing trends and directions as well as the challenges will also be discussed; especially, two conceptual BSHs with aqueous high voltage window and integrated 3D electrode/electrolyte architecture will be proposed.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/advs.201600539DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5514976PMC
July 2017

The Role of Through-Space Interactions in Modulating Constructive and Destructive Interference Effects in Benzene.

Nano Lett 2017 07 28;17(7):4436-4442. Epub 2017 Jun 28.

Nano-Science Center and Department of Chemistry, University of Copenhagen , 1017 Copenhagen Ø, Denmark.

Quantum interference effects, whether constructive or destructive, are key to predicting and understanding the electrical conductance of single molecules. Here, through theory and experiment, we investigate a family of benzene-like molecules that exhibit both constructive and destructive interference effects arising due to more than one contact between the molecule and each electrode. In particular, we demonstrate that the π-system of meta-coupled benzene can exhibit constructive interference and its para-coupled analog can exhibit destructive interference, and vice versa, depending on the specific through-space interactions. As a peculiarity, this allows a meta-coupled benzene molecule to exhibit higher conductance than a para-coupled benzene. Our results provide design principles for molecular electronic components with high sensitivity to through-space interactions and demonstrate that increasing the number of contacts between the molecule and electrodes can both increase and decrease the conductance.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.nanolett.7b01592DOI Listing
July 2017

Influence of Nanostructure on the Exciton Dynamics of Multichromophore Donor-Acceptor Block Copolymers.

ACS Nano 2017 05 26;11(5):4593-4598. Epub 2017 Apr 26.

Department of Chemistry, Columbia University , New York, New York 10027, United States.

We explore the synthesis and photophysics of nanostructured block copolymers that mimic light-harvesting complexes. We find that the combination of a polar and electron-rich boron dipyrromethene (BODIPY) block with a nonpolar electron-poor perylene diimide (PDI) block yields a polymer that self-assembles into ordered "nanoworms". Numerical simulations are used to determine optimal compositions to achieve robust self-assembly. Photoluminescence spectroscopy is used to probe the rich exciton dynamics in these systems. Using controls, such as homopolymers and random copolymers, we analyze the mechanisms of the photoluminescence from these polymers. This understanding allows us to probe in detail the photophysics of the block copolymers, including the effects of their self-assembly into nanostructures on their excited-state properties. Similar to natural systems, ordered nanostructures result in properties that are starkly different than the properties of free polymers in solution, such as enhanced rates of electronic energy transfer and elimination of excitonic emission from disordered PDI trap states.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsnano.7b00056DOI Listing
May 2017

Role of miR-15a in intervertebral disc degeneration through targeting MAP3K9.

Biomed Pharmacother 2017 Mar 9;87:568-574. Epub 2017 Jan 9.

First Clinical College of Nanjing University of Chinese Medicine, Nanjing 210046, PR China. Electronic address:

Background: Accumulating evidence indicates that microRNAs are involved in various cellular processes, including cell proliferation, differentiation, apoptosis and metastasis. miR-15a is an important regulator of immune responses and angiogenesis, endogenous controls as well as potential targets and hallmarks of cancer. However, the role of miR-15a in intervertebral disc degeneration (IDD) has not been elucidated.

Methods: Total RNA was extracted from degenerative nucleus pulposus (NP) tissues of 20 patients with IDD and NP cells, respectively. The expression levels of miR-15a were examined by quantitative real-time PCR. The stable overexpress or silence miR-15a expression cell lines and control cell lines were constructed by lentivirus infection. Subsequently, 3-(4,5-dimethylthia zol-2-yl)-2,5-diphenylte trazolium bromide (MTT) assay, flow cytometry test, TdT-mediated dUTP Nick-End Labeling (TUNEL) experiment, colony formation assay and western blot analysis were performed to detect the biological functions of miR-15a. Moreover, a luciferase reporter assay was conducted to confirm its target associations.

Results: Herein, the results found that miR-15a was dramatically up-regulated in degenerative NP tissues and NP cells compared with the controls. Overexpression of miR-15a promoted NP cells proliferation and induced apoptosis. Moreover, apoptosis-related protein caspase-3 was significantly up-regulated and bcl-2 was observably down-regulated when NP cells were transfected with miR-15a mimics, while bax and caspase-3 were significantly down-regulated as well as bcl-2 was observably up-regulated when NP cells were transfected with miR-15a inhibitors. Further, luciferase reporter assay showed that MAP3K9, an upstream activator of MAPK kinase, was putative target of miR-15a. There was a negatively relationship between miR-15a and MAP3K9 expression in NP cells. In addition, knockdown MAP3K9 inhibited NP cells proliferation and promoted apoptosis, which further inhibited the activation of p38 and ERK MAPK pathway.

Conclusion: This present study revealed that miR-15a might be considered as a novel therapeutic target for IDD treatment.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.biopha.2016.12.128DOI Listing
March 2017

Singlet Fission: Progress and Prospects in Solar Cells.

Adv Mater 2017 May 14;29(20). Epub 2016 Dec 14.

School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, No. 122 Luoshi Road, Wuhan, 430070, China.

The third generation of photovoltaic technology aims to reduce the fabrication cost and improve the power conversion efficiency (PCE) of solar cells. Singlet fission (SF), an efficient multiple exciton generation (MEG) process in organic semiconductors, is one promising way to surpass the Shockley-Queisser limit of conventional single-junction solar cells. Traditionally, this MEG process has been observed as an intermolecular process in organic materials. The implementation of intermolecular SF in photovoltaic devices has achieved an external quantum efficiency of over 100% and demonstrated significant promise for boosting the PCE of third generation solar cells. More recently, efficient intramolecular SF has been reported. Intramolecular SF materials are modular and have the potential to overcome certain design constraints that intermolecular SF materials possess, which may allow for more facile integration into devices.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/adma.201601652DOI Listing
May 2017

S100B suppresses the differentiation of C3H/10T1/2 murine embryonic mesenchymal cells into osteoblasts.

Mol Med Rep 2016 Oct 1;14(4):3878-86. Epub 2016 Sep 1.

Department of Orthopedics, Benq Hospital, Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210019, P.R. China.

S100 calcium-binding protein B (S100B) is expressed and released by adipocytes, and is positively correlated with body mass index, however, the direct effects of S100B on adipocytes remain unclear. Bone marrow‑derived mesenchymal stem cells have the capacity to differentiate into osteoblasts and adipocytes, which is important for bone metabolism. The current study aimed to determine the effect of S100B on adipogenesis and osteogenesis. The mouse embryo cell line C3H/10T1/2 was used to build cell models with varying levels of S100B protein expression. Western blot analysis was performed to assess the expression of various marker proteins. Oil red O staining and alizarin red S staining were used to detect adipogenesis and osteogenesis, respectively. S100B overexpression was associated with a significant increase in oil red O staining and a significant reduction in alizarin red S staining. Runt‑related transcription factor‑2 and bone morphogenetic protein 2 expression levels were significantly increased in the S100B underexpression group, however not in the S100B overexpression group. By contrast, the expression levels of the adipogenesis markers peroxisome proliferator‑activated receptor γ and CCAAT‑enhancer‑binding protein α was significantly increased in the S100B overexpression group, however not in the S100B underexpression group. Osteogenesis stimulation increased extracellular signal‑regulated kinase (ERK) phosphorylation, and adipogenesis stimulation increased c‑Jun N‑terminal kinase (JNK) phosphorylation. The results suggest that S100B inhibits osteogenesis, however stimulates adipogenesis. The ERK pathway is involved in the regulation of osteogenesis, whereas the JNK pathway is involved in the regulation of adipogenesis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3892/mmr.2016.5697DOI Listing
October 2016

Mapping the Transmission Functions of Single-Molecule Junctions.

Nano Lett 2016 06 19;16(6):3949-54. Epub 2016 May 19.

Molecular Foundry, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.

Charge transport phenomena in single-molecule junctions are often dominated by tunneling, with a transmission function dictating the probability that electrons or holes tunnel through the junction. Here, we present a new and simple technique for measuring the transmission functions of molecular junctions in the coherent tunneling limit, over an energy range of 1.5 eV around the Fermi energy. We create molecular junctions in an ionic environment with electrodes having different exposed areas, which results in the formation of electric double layers of dissimilar density on the two electrodes. This allows us to electrostatically shift the molecular resonance relative to the junction Fermi levels in a manner that depends on the sign of the applied bias, enabling us to map out the junction's transmission function and determine the dominant orbital for charge transport in the molecular junction. We demonstrate this technique using two groups of molecules: one group having molecular resonance energies relatively far from EF and one group having molecular resonance energies within the accessible bias window. Our results compare well with previous electrochemical gating data and with transmission functions computed from first principles. Furthermore, with the second group of molecules, we are able to examine the behavior of a molecular junction as a resonance shifts into the bias window. This work provides a new, experimentally simple route for exploring the fundamentals of charge transport at the nanoscale.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.nanolett.6b01592DOI Listing
June 2016

Quantitative Intramolecular Singlet Fission in Bipentacenes.

J Am Chem Soc 2015 Jul 14;137(28):8965-72. Epub 2015 Jul 14.

†Department of Chemistry, Columbia University, New York, New York 10027, United States.

Singlet fission (SF) has the potential to significantly enhance the photocurrent in single-junction solar cells and thus raise the power conversion efficiency from the Shockley-Queisser limit of 33% to 44%. Until now, quantitative SF yield at room temperature has been observed only in crystalline solids or aggregates of oligoacenes. Here, we employ transient absorption spectroscopy, ultrafast photoluminescence spectroscopy, and triplet photosensitization to demonstrate intramolecular singlet fission (iSF) with triplet yields approaching 200% per absorbed photon in a series of bipentacenes. Crucially, in dilute solution of these systems, SF does not depend on intermolecular interactions. Instead, SF is an intrinsic property of the molecules, with both the fission rate and resulting triplet lifetime determined by the degree of electronic coupling between covalently linked pentacene molecules. We found that the triplet pair lifetime can be as short as 0.5 ns but can be extended up to 270 ns.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jacs.5b04986DOI Listing
July 2015

Single-molecule diodes with high rectification ratios through environmental control.

Nat Nanotechnol 2015 Jun 25;10(6):522-7. Epub 2015 May 25.

1] Department of Applied Physics and Applied Mathematics, New York, New York 10027, USA [2] Department of Chemistry, Columbia University, New York, New York 10027, USA.

Molecular electronics aims to miniaturize electronic devices by using subnanometre-scale active components. A single-molecule diode, a circuit element that directs current flow, was first proposed more than 40 years ago and consisted of an asymmetric molecule comprising a donor-bridge-acceptor architecture to mimic a semiconductor p-n junction. Several single-molecule diodes have since been realized in junctions featuring asymmetric molecular backbones, molecule-electrode linkers or electrode materials. Despite these advances, molecular diodes have had limited potential for applications due to their low conductance, low rectification ratios, extreme sensitivity to the junction structure and high operating voltages. Here, we demonstrate a powerful approach to induce current rectification in symmetric single-molecule junctions using two electrodes of the same metal, but breaking symmetry by exposing considerably different electrode areas to an ionic solution. This allows us to control the junction's electrostatic environment in an asymmetric fashion by simply changing the bias polarity. With this method, we reliably and reproducibly achieve rectification ratios in excess of 200 at voltages as low as 370 mV using a symmetric oligomer of thiophene-1,1-dioxide. By taking advantage of the changes in the junction environment induced by the presence of an ionic solution, this method provides a general route for tuning nonlinear nanoscale device phenomena, which could potentially be applied in systems beyond single-molecule junctions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/nnano.2015.97DOI Listing
June 2015

Molecular length dictates the nature of charge carriers in single-molecule junctions of oxidized oligothiophenes.

Nat Chem 2015 Mar 2;7(3):209-14. Epub 2015 Feb 2.

Department of Chemistry, Columbia University, New York 10027, USA.

To develop advanced materials for electronic devices, it is of utmost importance to design organic building blocks with tunable functionality and to study their properties at the molecular level. For organic electronic and photovoltaic applications, the ability to vary the nature of charge carriers and so create either electron donors or acceptors is critical. Here we demonstrate that charge carriers in single-molecule junctions can be tuned within a family of molecules that contain electron-deficient thiophene-1,1-dioxide (TDO) building blocks. Oligomers of TDO were designed to increase electron affinity and maintain delocalized frontier orbitals while significantly decreasing the transport gap. Through thermopower measurements we show that the dominant charge carriers change from holes to electrons as the number of TDO units is increased. This results in a unique system in which the charge carrier depends on the backbone length, and provides a new means to tune p- and n-type transport in organic materials.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/nchem.2160DOI Listing
March 2015

Fast Singlet Exciton Decay in Push-Pull Molecules Containing Oxidized Thiophenes.

J Phys Chem B 2015 Jun 5;119(24):7644-50. Epub 2015 Feb 5.

‡Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States.

A common synthetic strategy used to design low-bandgap organic semiconductors employs the use of "push-pull" building blocks, where electron -rich and electron-deficient monomers are alternated along the π-conjugated backbone of a molecule or polymer. Incorporating strong "pull" units with high electron affinity is a means to further decrease the optical gap for infrared optoelectronics or to develop n-type semiconducting materials. Here we show that the use of thiophene-1,1-dioxide as a strong acceptor in "push-pull" oligomers affects the electronic structure and carrier dynamics in unexpected ways. Critically, the overall excited-state lifetime is reduced by several orders of magnitude relative to unoxidized analogs due to the introduction of low-energy optically dark states and low-energy triplet states that allow for fast internal conversion and intramolecular singlet fission. We found that the electronic structure and excited-state lifetime are strongly dependent on the number of sequential thiophene-1,1-dioxide units. These results suggest that both the static and dynamical optical properties are highly tunable via small changes in chemical structure that have drastic effects on the optoelectronic properties, which can impact the types of applications that involve these materials.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jp511704rDOI Listing
June 2015

A design strategy for intramolecular singlet fission mediated by charge-transfer states in donor-acceptor organic materials.

Nat Mater 2015 Apr 12;14(4):426-33. Epub 2015 Jan 12.

Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA.

The ability to advance our understanding of multiple exciton generation (MEG) in organic materials has been restricted by the limited number of materials capable of singlet fission. A particular challenge is the development of materials that undergo efficient intramolecular fission, such that local order and strong nearest-neighbour coupling is no longer a design constraint. Here we address these challenges by demonstrating that strong intrachain donor-acceptor interactions are a key design feature for organic materials capable of intramolecular singlet fission. By conjugating strong-acceptor and strong-donor building blocks, small molecules and polymers with charge-transfer states that mediate population transfer between singlet excitons and triplet excitons are synthesized. Using transient optical techniques, we show that triplet populations can be generated with yields up to 170%. These guidelines are widely applicable to similar families of polymers and small molecules, and can lead to the development of new fission-capable materials with tunable electronic structure, as well as a deeper fundamental understanding of MEG.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/nmat4175DOI Listing
April 2015

Quantum Dynamics Simulations Reveal Vibronic Effects on the Optical Properties of [n]Cycloparaphenylenes.

J Chem Theory Comput 2014 Sep;10(9):4025-36

Department of Chemistry, Boston University , Boston, Massachusetts 02215, United States.

The size-dependent ultraviolet/visible photophysical property trends of [n]cycloparaphenylenes ([n]CPPs, n = 6, 8, and 10) are theoretically investigated using quantum dynamics simulations. For geometry optimizations on the ground- and excited-state Born-Oppenheimer potential energy surfaces (PESs), we employ density functional theory (DFT) and time-dependent DFT calculations. Harmonic normal-mode analyses are carried out for the electronic ground state at Franck-Condon geometries. A diabatic Hamiltonian, comprising four low-lying singlet excited electronic states and 26 vibrational degrees of freedom of CPP, is constructed within the linear vibronic coupling (VC) model to elucidate the absorption spectral features in the range of 300-500 nm. Quantum nuclear dynamics is simulated within the multiconfiguration time-dependent Hartree approach to calculate the vibronic structure of the excited electronic states. The symmetry-forbidden S0 → S1 transition appears in the longer wavelength region of the spectrum with weak intensity due to VC. It is found that the Jahn-Teller and pseudo-Jahn-Teller effects in the doubly degenerate S2 and S3 electronic states are essential in the quantitative interpretation of the experimental observation of a broad absorption peak around 340 nm. The vibronic mixing of the S1 state with higher electronic states is responsible for the efficient photoluminescence from the S1 state. The fluorescence properties are characterized on the basis of the stationary points of the excited-state PESs. The findings reveal that vibronic effects become important in determining the photophysical properties of CPPs with increased ring size.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ct500524yDOI Listing
September 2014

Properties of sizeable [n]cycloparaphenylenes as molecular models of single-wall carbon nanotubes elucidated by Raman spectroscopy: structural and electron-transfer responses under mechanical stress.

Angew Chem Int Ed Engl 2014 Jul 18;53(27):7033-7. Epub 2014 May 18.

MALTA-Consolider Team, Department of Physical Chemistry, Chemistry Faculty, University Complutense of Madrid, 28040 Madrid (Spain).

[n]Cycloparaphenylenes behave as molecular templates of "perfectly chemically defined" single-wall carbon nanotubes. These [n]CPP molecules have electronic, mechanical, and chemical properties in size correspondence with their giant congeners. Under mechanical stress, they form charge-transfer salts, or complexes with fullerene, by one-electron concave-convex electron transfer.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/anie.201400719DOI Listing
July 2014

Breakdown of interference rules in azulene, a nonalternant hydrocarbon.

Nano Lett 2014 May 22;14(5):2941-5. Epub 2014 Apr 22.

Department of Chemistry and ‡Department of Applied Physics and Applied Mathematics, Columbia University , New York, New York 10027, United States.

We have designed and synthesized five azulene derivatives containing gold-binding groups at different points of connectivity within the azulene core to probe the effects of quantum interference through single-molecule conductance measurements. We compare conducting paths through the 5-membered ring, 7-membered ring, and across the long axis of azulene. We find that changing the points of connectivity in the azulene impacts the optical properties (as determined from UV-vis absorption spectra) and the conductivity. Importantly, we show here that simple models cannot be used to predict quantum interference characteristics of nonalternant hydrocarbons. As an exemplary case, we show that azulene derivatives that are predicted to exhibit destructive interference based on widely accepted atom-counting models show a significant conductance at low biases. Although simple models to predict the low-bias conductance do not hold with all azulene derivatives, we demonstrate that the measured conductance trend for all molecules studied actually agrees with predictions based on the more complete GW calculations for model systems.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/nl5010702DOI Listing
May 2014

Bandgap engineering through controlled oxidation of polythiophenes.

Angew Chem Int Ed Engl 2014 Feb 21;53(7):1832-6. Epub 2014 Jan 21.

Department of Chemistry, Columbia University, 3000 Broadway, MC3124, New York, NY 10027 (USA) http://camposgroup.chem.columbia.edu.

The use of Rozen's reagent (HOF⋅CH3 CN) to convert polythiophenes to polymers containing thiophene-1,1-dioxide (TDO) is described. The oxidation of polythiophenes can be controlled with this potent, yet orthogonal reagent under mild conditions. The oxidation of poly(3-alkylthiophenes) proceeds at room temperature in a matter of minutes, introducing up to 60 % TDO moieties in the polymer backbone. The resulting polymers have a markedly low-lying lowest unoccupied molecular orbital (LUMO), consequently exhibiting a small bandgap. This approach demonstrates that modulating the backbone electronic structure of well-defined polymers, rather than varying the monomers, is an efficient means of tuning the electronic properties of conjugated polymers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/anie.201309398DOI Listing
February 2014

Bridge-localized HOMO-binding character of divinylanthracene-bridged dinuclear ruthenium carbonyl complexes: spectroscopic, spectroelectrochemical, and computational studies.

Chem Asian J 2014 Apr 21;9(4):1152-60. Epub 2014 Jan 21.

Key Laboratory of Pesticide & Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, 152 Luoyu Road, Wuhan, Hubei 430079 (P.R. China), Fax: (+86) 27-67867725.

The electronic properties of four divinylanthracene-bridged diruthenium carbonyl complexes [{RuCl(CO)(PMe3)3}2(μ-CH=CHArCH=CH)] (Ar=9,10-anthracene (1), 1,5-anthracene (2), 2,6-anthracene (3), 1,8-anthracene (4)) obtained by molecular spectroscopic methods (IR, UV/Vis/near-IR, and EPR spectroscopy) and DFT calculations are reported. IR spectroelectrochemical studies have revealed that these complexes are first oxidized at the noninnocent bridging ligand, which is in line with the very small ν(C≡O) wavenumber shift that accompanies this process and also supported by DFT calculations. Because of poor conjugation in complex 1, except oxidized 1(+), the electronic absorption spectra of complexes 2(+), 3(+), and 4(+) all display the characteristic near-IR band envelopes that have been deconvoluted into three Gaussian sub-bands. Two of the sub-bands belong mainly to metal-to-ligand charge-transfer (MLCT) transitions according to results from time-dependent DFT calculations. EPR spectroscopy of chemically generated 1(+)-4(+) proves largely ligand-centered spin density, again in accordance with IR spectra and DFT calculations results.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/asia.201301544DOI Listing
April 2014

Dithia[3.3]paracyclophane-bridged bimetallic ruthenium acetylide complexes: synthesis, structures and influence of transannular π-π interactions on their electronic properties.

Dalton Trans 2013 Oct;42(39):14212-22

Key Laboratory of Pesticide & Chemical Biology, Ministry of Education College of Chemistry, Central China Normal University, 152 Luoyu Road, Wuhan, Hubei 430079, China.

Two dithia[3.3]paracyclophane-bridged bimetallic ruthenium acetylide complexes 2 and 3, in which the upper deck of the cyclophanes were assembled with naphthalenyl and anthracenyl rings, have been designed and synthesized. X-ray crystal structures of 2 and 3 show that there are effective transannular π–π interactions between the two rings in the cyclophane unit. Electrochemistry studies revealed that the successive introduction of naphthalenyl and anthracenyl rings reduced the thermodynamic stability of the corresponding mixed-valence states of 2 and 3. Radical cations and dications of complexes 2 and 3 were generated after the addition of 1.0 or 2.0 equivalents of ferrocenium hexafluorophosphate ([FcH][PF6]). The ν(C≡C) of radicals 2+ and 3+ shift 86 nm and 88 nm in contrast to 2 and 3, respectively. UV-Vis-NIR spectra of 2+ and 3+ exhibited three enveloped transitions in the NIR (10,000–4000 cm(−1)) range. DFT studies showed that the compositions of the FMOs of 2 and 3 are more naphthalenyl and anthracenyl in character than the upper deck of complex 1. Spectroscopy and DFT studies indicated that the influence of transannular π–π interactions on the electronic transitions is more pronounced than in complex 1.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c3dt51756jDOI Listing
October 2013
-->