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Publications (10 of 31) Show all publications
Li, H., Duan, T., Haldar, S., Sanyal, B., Eriksson, O., Jafri, H., . . . Leifer, K. (2020). Direct Writing of Lateral Fluorographene Nanopatterns with Tunable Bandgaps and Its Application in New Generation of Moiré Superlattice. Applied Physics Reviews, 7, Article ID 011403.
Open this publication in new window or tab >>Direct Writing of Lateral Fluorographene Nanopatterns with Tunable Bandgaps and Its Application in New Generation of Moiré Superlattice
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2020 (English)In: Applied Physics Reviews, ISSN 1931-9401, Vol. 7, article id 011403Article in journal (Refereed) Published
Abstract [en]

One of the primary goals for monolayer device fabrications and an ideal model of graphene as an atomic thin “canvas” is one that permits semiconducting/insulating lateral nanopatterns to be freely and directly drawn on the semimetallic graphene surface. This work demonstrates a reversible electron-beam-activated technique that allows direct writing of semiconducting/insulating fluorographene lateral nanopatterns with tunable bandgaps on the graphene surface with a resolution down to 9–15 nm. This approach overcomes the conventional limit of semiconducting C4F in the single-sided fluorination of supported graphene and achieves insulating C2F. Moreover, applying this technique on bilayer graphene demonstrates for the first time a new type of rectangular moiré pattern arising from the generated C2F boat/graphene superlattice. This novel technique constitutes a new approach to fabricating graphene-based flexible and transparent electronic nanodevices with the CxF channels utilized as semiconducting or insulating counterparts, and also opens a route toward the tailoring and engineering of electronic properties of such materials in addition to the dominating triangular moiré patterns from a graphene/hBN system.

National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-401434 (URN)10.1063/1.5129948 (DOI)000515505800001 ()
Funder
Swedish Research Council, 621-2012-3679Swedish Research Council, 2016-05259Knut and Alice Wallenberg FoundationSwedish Research Council Formas, 2019-01538Swedish National Infrastructure for Computing (SNIC)
Available from: 2020-01-08 Created: 2020-01-08 Last updated: 2020-04-01Bibliographically approved
Han, Y., Li, H., Jafri, S. H., Ossipov, D. A., Hilborn, J. & Leifer, K. (2020). Optimization and analysis of pyrene-maltose functionalized graphene surfaces for Con A detection. Applied Surface Science, 510, Article ID 145409.
Open this publication in new window or tab >>Optimization and analysis of pyrene-maltose functionalized graphene surfaces for Con A detection
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2020 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 510, article id 145409Article in journal (Refereed) Published
Abstract [en]

Utilizing the non-covalent pi-pi stacking of pyrene functionalized molecules onto graphene surfaces has achieved great success in the detection of various bio-objects, while the fundamental investigations on surface modifications stills remain rarely exploited. Here, we report the nano and atomic scale analysis of the pi-pi stacking functionalized graphene surface regarding to its surface topography, molecular self-assembly as well as process optimizations. The 'amphipathic' molecule, pyrene-maltose, is used for the non-covalent functionalization of graphene and systematical analysis is performed to understand the influence of different solvents on the molecular surface arrangement. Atomic force microscopy (AFM) and spectroscopy analysis indicate the successful formation of pyrene-maltose layer on graphene surface and it is further confirmed by scanning tunneling microscopy, depicting the self-assembled and densely packed pyrene-maltose layer that give distinguished and ordered diamond-shape lattice as compared to triangular lattice in pristine graphene. We also demonstrated that the interfacial adhesion forces between the AFM probe and the functionalized surfaces allow the detection of the lectin protein Concavalin A through selective absorption. This work provides essential evidence of the pi-pi interactions between pyrene molecules and graphene, and the AFM based adhesion measurement also has the potential to be employed in a variety of bio-detection applications.

Place, publisher, year, edition, pages
ELSEVIER, 2020
Keywords
pi-pi stacking, Non-covalent, Graphene, Self-assembled, Diamond-shape lattice
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-407511 (URN)10.1016/j.apsusc.2020.145409 (DOI)000514902000038 ()
Funder
Swedish Research Council, 2016-05259Knut and Alice Wallenberg FoundationSwedish Research Council Formas, 2019-01538
Available from: 2020-03-26 Created: 2020-03-26 Last updated: 2020-03-26Bibliographically approved
Wani, I. H., Jafri, S. H., Wärnå, J., Hayat, A., Li, H., Shukla, V. A., . . . Leifer, K. (2019). A sub 20 nm metal-conjugated molecule junction acting as a nitrogen dioxide sensor. Nanoscale, 11(14), 6571-6575
Open this publication in new window or tab >>A sub 20 nm metal-conjugated molecule junction acting as a nitrogen dioxide sensor
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2019 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 11, no 14, p. 6571-6575Article in journal (Refereed) Published
Abstract [en]

The interaction of a gas molecule with a sensing material causes the highest change in the electronic structure of the latter, when this material consists of only a few atoms. If the sensing material consists of a short, conductive molecule, the sensing action can be furthermore probed by connecting such molecules to nanoelectrodes. Here, we report that NO2 molecules that adhere to 4,4'-biphenyldithiol (BPDT) bound to Au surfaces lead to a change of the electrical transmission of the BPDT. The related device shows reproducible, stable measurements and is so far the smallest (<20 nm) gas sensor. It demonstrates modulation of charge transport through molecules upon exposure to nitrogen dioxide down to concentrations of 55 ppb. We have evaluated several devices and exposure conditions and obtained a close to linear dependence of the sensor response on the gas concentration.

National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-381056 (URN)10.1039/c8nr08417c (DOI)000464454400007 ()30916070 (PubMedID)
Funder
Swedish Research CouncilKnut and Alice Wallenberg FoundationGöran Gustafsson Foundation for Research in Natural Sciences and MedicineCarl Tryggers foundation Swedish Energy AgencySwedish Foundation for Strategic Research
Available from: 2019-04-03 Created: 2019-04-03 Last updated: 2019-05-03Bibliographically approved
Li, H., Liu, J. & Papadakis, R. (2019). Direct measurement of the surface energy of single-walled carbon nanotubes through atomic force microscopy. Journal of Applied Physics, 126(6), Article ID 065105.
Open this publication in new window or tab >>Direct measurement of the surface energy of single-walled carbon nanotubes through atomic force microscopy
2019 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 126, no 6, article id 065105Article in journal (Refereed) Published
Abstract [en]

Surface energy in nanomaterials is an essential parameter demonstrating a key role in their surface interactions and their functionalization aptitude. In this work, a new and facile methodology based on atomic force microscopy for the measurement of the surface energy of single-walled carbon nanotubes (SWCNTs) is reported. The proposed approach starts with the calibration based on a well-studied material, graphite, and the precision of the technique is confirmed by the measurement of the surface energy of multiwalled carbon nanotubes. Our measurements show that SWCNTs display a surface energy of 52.8mJ/m(2), which is in very good agreement with theoretical predictions of the measured property. Our experimental approach is essentially applicable to other nano-objects in contrast to conventional wet angle methods which are currently employed mainly in bulk materials.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-393735 (URN)10.1063/1.5108935 (DOI)000481451900031 ()
Available from: 2019-09-30 Created: 2019-09-30 Last updated: 2019-09-30Bibliographically approved
Han, Y., Li, H., Jafri, S. H., Ossipov, D. A., Hilborn, J. & LEIFER, K. (2019). Graphene Based Mechanical Biosensor by Employing Non-covalent Stacking Functionalization.
Open this publication in new window or tab >>Graphene Based Mechanical Biosensor by Employing Non-covalent Stacking Functionalization
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2019 (English)In: Article in journal, News item (Other academic) Submitted
Abstract [en]

Herein we demonstrate a novel methodology to achieve mechanical biosensor by employing the distinguished interaction forces between the atomic force microscope (AFM) probe and sensor surfaces as the response signal. This mechanical biosensor is fabricated by utilizing the non-covalent π-π stacking of pyrene-maltose onto graphene surfaces with Concanavalin A (Con A) as a target protein. The atomic resolution scanning tunneling microscopy (STM) images indicate the successful formation of the self-assembled and densely packed pyrene-maltose layer on the sensor surface, which gives distinct atomic lattice structure as compared to pristine graphene. This mechanical biosensor exhibits detection of Con A with the sensitivity down to nanomolar level. Therefore, this proposed mechanical biosensor has the potential to be employed in a variety of bio-sensing applications.

National Category
Nano Technology Analytical Chemistry
Identifiers
urn:nbn:se:uu:diva-378559 (URN)
Available from: 2019-03-06 Created: 2019-03-06 Last updated: 2020-02-05Bibliographically approved
Li, H., Han, Y., Duan, T. & Leifer, K. (2019). Size-dependent elasticity of gold nanoparticle measured by atomic force microscope based nanoindentation. Applied Physics Letters, 115(5), Article ID 053104.
Open this publication in new window or tab >>Size-dependent elasticity of gold nanoparticle measured by atomic force microscope based nanoindentation
2019 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 115, no 5, article id 053104Article in journal (Refereed) Published
Abstract [en]

The elasticity is one of the key properties in gold nanoparticles (AuNPs) and plays an essential role in the process design and applications. In this work, we have proposed an Argon plasma based technique to obtain well dispersed and neat AuNPs without surface functional groups. Our investigation on the size-dependent elasticity focused on the AuNPs with the size ranging from 2 nm to 12 nm by using atomic force microscope based nanoindentation technique under the peakforce quantitative nanomechanical mapping mode. The results show clearly that when the AuNPs are smaller than 6 nm, there is a significant increase in the elasticity as the smallest nanoparticles displacing an elastic modulus of ~140 GPa.  Our result provides important experimental evidence that contributes to a better understanding of the size-property relations as well as process design in AuNPs, and it also can be applied to measure the mechanical properties in a wide range of nano-objects.

National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-378556 (URN)10.1063/1.5095182 (DOI)000478913700003 ()
Note

Hu Li and Yuanyuan Han contributed equally to this work.

Manuscript version in thesis list of papers did not include Tianbo Duan as author.

Available from: 2019-03-06 Created: 2019-03-06 Last updated: 2019-09-24Bibliographically approved
Tavares da Costa, M. V., Neagu, C., Fayet, P., Wiklund, U., Li, H., Leifer, K. & Gamstedt, E. K. (2018). Comparison of test methods estimating the stiffness of ultrathin coatings. Paper presented at 13th Coatings Science International Conference (COSI), JUN 26-30, 2017, Noordwijk, NETHERLANDS. Journal of Coatings Technology and Research, 15(4), 743-752
Open this publication in new window or tab >>Comparison of test methods estimating the stiffness of ultrathin coatings
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2018 (English)In: Journal of Coatings Technology and Research, ISSN 1935-3804, Vol. 15, no 4, p. 743-752Article in journal, Editorial material (Refereed) Published
Abstract [en]

A key engineering parameter of thin coatings is their stiffness. Stiffness characterization of ultrathin coatings with a nanometer scale thickness is experimentally challenging. In this work, three feasible methods have been used to estimate the Young’s modulus of metal coatings on polymer films. The methods are: (1) nanoindentation, (2) strain-induced elastic buckling and (3) peak-force measurements integrated in atomic force microscopy. The samples were prepared by atomic layer deposition of TiO2 (6 and 20 nm thick) and mixed oxides of TiO2 and Al2O3 (4 and 20 nm thick). The differences in estimated Young’s modulus are interpreted in terms of the underlying assumptions and test conditions. Their specific advantages and drawbacks are also compared and discussed. In particular, the nanoindentation necessitates a sufficiently sharp indenter tip to make localized measurements dominated by the coating. The strain-induced elastic buckling method is simple in practice, but showed a large scatter due to variation in local coating thickness and irregular deformation patterns. The stiffness characterization using atomic force microscopy gave the most consistent results, due to a sharp tip with a radius comparable to the thinnest coating thickness. All methods gave a higher Young’s modulus for the TiO2 coating than for the mixed oxide coating, with a variation within one order of magnitude between the methods.

National Category
Nano Technology Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:uu:diva-352043 (URN)10.1007/s11998-018-0085-0 (DOI)000439757000009 ()
Conference
13th Coatings Science International Conference (COSI), JUN 26-30, 2017, Noordwijk, NETHERLANDS
Available from: 2018-06-01 Created: 2018-06-01 Last updated: 2020-03-27Bibliographically approved
Sun, F., Li, H., Leifer, K. & Gamstedt, E. K. (2018). Effect of nanosectioning on surface features and stiffness of an amorphous glassy polymer. Polymer Engineering and Science, 58(10), 1849-1857
Open this publication in new window or tab >>Effect of nanosectioning on surface features and stiffness of an amorphous glassy polymer
2018 (English)In: Polymer Engineering and Science, ISSN 0032-3888, E-ISSN 1548-2634, Vol. 58, no 10, p. 1849-1857Article in journal (Refereed) Published
Abstract [en]

Sectioning of a glassy polymer, poly(methyl methacrylate), at nanoscale was carried out by means of an ultramicrotome. The effects of sectioning thickness and speed on the morphology and stiffness over the sectioned surface were then investigated by atomic force microscopy. A critical sectioning thickness and speed were identified, below which flat and smooth surfaces were created with homogeneous elasticity. Above the critical thickness or speed, periodic localized structures formed on the sectioned surfaces, leading to a nonhomogeneous distribution of the mapped elasticity. Finite element simulation reproduced the periodic structures observed in the experiments. The influence of sectioning speed on the surface stiffness was predicted by a phenomenological damage model and was found to correlate with the experimental results. The study lends confidence that critical sectioning conditions (e.g., the sectioning thickness and speed) can be identified to avoid undesirable local deformation and damage in the manufacture of small scale optical and photonic components and devices.

National Category
Mechanical Engineering Applied Mechanics
Identifiers
urn:nbn:se:uu:diva-328888 (URN)10.1002/pen.24793 (DOI)000448084000020 ()
Available from: 2017-09-04 Created: 2017-09-04 Last updated: 2019-01-22Bibliographically approved
Liu, J., Papadakis, R. & Li, H. (2018). Experimental observation of size-dependent behavior in surface energy of gold nanoparticles through atomic force microscope. Applied Physics Letters, 113(8), Article ID 083108.
Open this publication in new window or tab >>Experimental observation of size-dependent behavior in surface energy of gold nanoparticles through atomic force microscope
2018 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 113, no 8, article id 083108Article in journal (Refereed) Published
Abstract [en]

Surface energy plays a key role in the physicochemical interactions of material surfaces, and it is closely related to the unique properties and numerous surface functionalization possibilities of gold nanoparticles. Herein, we have reported an atomic force microscopy based technique to measure the surface energies of different materials in the peakforce quantitative nanomechanical mapping mode. Our study on gold nanoparticles focuses on the particles with diameters ranging from 2 to 14 nm. The experimental results indicate a clear size-dependent behavior in the surface energy of gold nanoparticles when the size is smaller than 5 nm, and the smallest gold nanoparticle displays a threefold higher surface energy compared to bulk gold. Therefore, our experimental results provide essential evidence that can lead to a better understanding of the size-property relationships allowing for process design in gold nanoparticles.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2018
National Category
Condensed Matter Physics Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-363935 (URN)10.1063/1.5046736 (DOI)000442615500039 ()
Available from: 2018-10-24 Created: 2018-10-24 Last updated: 2018-11-01Bibliographically approved
Mindemark, J., Tang, S., Li, H. & Edman, L. (2018). Ion Transport beyond the Polyether Paradigm: Introducing Oligocarbonate Ion Transporters for Efficient Light-Emitting Electrochemical Cells. Advanced Functional Materials, 28(32), Article ID 1801295.
Open this publication in new window or tab >>Ion Transport beyond the Polyether Paradigm: Introducing Oligocarbonate Ion Transporters for Efficient Light-Emitting Electrochemical Cells
2018 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 28, no 32, article id 1801295Article in journal (Refereed) Published
Abstract [en]

The light-emitting electrochemical cell (LEC) is fundamentally dependent on mobile ions for its operation. In polymer LECs, the mobile ions are commonly provided by dissolving a salt in an ion transporter, with the latter almost invariably being an ether-based compound. Here, the synthesis, characterization, and application of a new class of carbonate-based ion transporters are reported. A polymer LEC, comprising a star-branched oligocarbonate endowed with aliphatic side groups as the ion transporter, features a current efficacy of 13.8 cd A(-1) at a luminance of 1060 cd m(-2), which is a record-high efficiency/luminance combination for a singlet-emitting LEC. It is further established that the design principles of a high-performance carbonate ion transporter constitute the selection of an oligomeric structure over a corresponding polymeric structure and the endowment of the oligomer with functional side chains to render it compatible with the polymeric emitter.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2018
Keywords
light emission, organic electronics, phase separation, polycarbonates, polymer electrolytes
National Category
Polymer Chemistry Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-364983 (URN)10.1002/adfm.201801295 (DOI)000440810500004 ()
Funder
Swedish Foundation for Strategic Research Swedish Research CouncilSwedish Energy AgencyThe Kempe FoundationsKnut and Alice Wallenberg FoundationLars Hierta Memorial Foundation
Available from: 2018-11-07 Created: 2018-11-07 Last updated: 2018-11-16Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-1050-8441

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