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Publications (10 of 249) Show all publications
Grigoriev, A., Jafri, S. H. & Leifer, K. (2020). Comment on "Quantum interference effects in biphenyl dithiol for gas detection" by J. Prasongkit and A. R. Rocha, RSC Adv., 2016, 64, 59299-59304 [Letter to the editor]. RSC Advances, 10(4), 2073-2074
Open this publication in new window or tab >>Comment on "Quantum interference effects in biphenyl dithiol for gas detection" by J. Prasongkit and A. R. Rocha, RSC Adv., 2016, 64, 59299-59304
2020 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 10, no 4, p. 2073-2074Article in journal, Letter (Other academic) Published
Abstract [en]

The paper [Prasongkit et al., RSC Adv., 2016, 64, 59299] by Prasongkit and Rocha calculates the binding energy of gas molecules attached to 1-8-biphenyl-dithiol (BPDT) molecules. We find from our calculations, that the binding energies calculated for the NO2 molecules are too low, most likely due to lacking optimization of the site at which the gas molecule binds to the BPDT. Though not shown explicitly here, the same statement might apply to the other gas molecules used in this paper.

National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-407162 (URN)10.1039/c9ra00451c (DOI)000507394900027 ()
Funder
Swedish Research Council
Available from: 2020-03-20 Created: 2020-03-20 Last updated: 2020-03-20Bibliographically approved
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
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
Henning, D. F., Merkl, P., Yun, C., Iovino, F., Xie, L., Mouzourakis, E., . . . Sotiriou, G. A. (2019). Luminescent CeO2:Eu3+ nanocrystals for robust in situ H2O2 real-time detection in bacterial cell cultures. Biosensors & bioelectronics, 132, 286-293
Open this publication in new window or tab >>Luminescent CeO2:Eu3+ nanocrystals for robust in situ H2O2 real-time detection in bacterial cell cultures
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2019 (English)In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 132, p. 286-293Article in journal (Refereed) Published
Abstract [en]

Hydrogen peroxide (H2O2) quantification in biomedicine is valuable as inflammation biomarker but also in assays employing enzymes that generate or consume H2O2 linked to a specific biomarker. Optical H2O2 detection is typically performed through peroxidase-coupled reactions utilizing organic dyes that suffer, however, from poor stability/reproducibility and also cannot be employed in situ in dynamic complex cell cultures to monitor H2O2 levels in real-time. Here, we utilize enzyme-mimetic CeO2 nanocrystals that are sensitive to H2O2 and study the effect of H2O2 presence on their electronic and luminescent properties. We produce and dope with Eu3+ these particles in a single-step by flame synthesis and directly deposit them on Si and glass substrates to fabricate nanoparticle layers to monitor in real-time and in situ the H2O2 concentrations generated by Streptococcus pneumoniae clinical isolates. Furthermore, the small CeO2:Eu3+ nanocrystals are combined in a single-step with larger, non-responsive Y2O3:Tb3+ nanoparticles during their double-nozzle flame synthesis to engineer hybrid luminescent nanoaggregates as ratiometric robust biosensors. We demonstrate the functionality of these biosensors by monitoring their response in the presence of a broad range of H2O2 concentrations in vitro from S. pneumoniae, highlighting their potential for facile real-time H2O2 detection in vitro in cell cultures.

Place, publisher, year, edition, pages
ELSEVIER ADVANCED TECHNOLOGY, 2019
Keywords
Nanozymes, Rare-earth doped nanoparticles, Hydrogen peroxide, Flame nanoparticle synthesis
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-382822 (URN)10.1016/j.bios.2019.03.012 (DOI)000464296300033 ()30884315 (PubMedID)
Funder
EU, European Research Council, 758705Swedish Research Council, 2016-03471Åke Wiberg Foundation
Available from: 2019-05-06 Created: 2019-05-06 Last updated: 2019-05-06Bibliographically approved
Han, Y., Qiu, Z., Nawale, G. N., Varghese, O. P., Hilborn, J., Tian, B. & Leifer, K. (2019). MicroRNA detection based on duplex-specific nuclease-assisted target recycling and gold nanoparticle/graphene oxide nanocomposite-mediated electrocatalytic amplification. Biosensors & bioelectronics, 127, 188-193
Open this publication in new window or tab >>MicroRNA detection based on duplex-specific nuclease-assisted target recycling and gold nanoparticle/graphene oxide nanocomposite-mediated electrocatalytic amplification
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2019 (English)In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 127, p. 188-193Article in journal (Refereed) Published
Abstract [en]

DNA technology based bio-responsive nanomaterials have been widely studied as promising tools for biomedical applications. Gold nanoparticles (AuNPs) and graphene oxide (GO) sheets are representative zero- and two-dimensional nanomaterials that have long been combined with DNA technology for point-of-care diagnostics. Herein, a cascade amplification system based on duplex-specific nuclease (DSN)-assisted target recycling and electrocatalytic water-splitting is demonstrated for the detection of microRNA. Target microRNAs can form DNA: RNA heteroduplexes with DNA probes on the surface of AuNPs, which can be hydrolyzed by DSN. MicroRNAs are preserved during the reaction and released into the suspension for the digestion of multiple DNA probes. After the DSN-based reaction, AuNPs are collected and mixed with GO to form AuNP/GO nanocomposite on an electrode for the following electrocatalytic amplification. The utilization of AuNP/GO nanocomposite offers large surface area, exceptional affinity to water molecules, and facilitated mass diffusion for the water-splitting reaction. For let-7b detection, the proposed biosensor achieved a limit detection of 1.5 fM in 80 min with a linear detection range of approximately four orders of magnitude. Moreover, it has the capability of discriminating non-target microRNAs containing even single-nucleotide mismatches, thus holding considerable potential for clinical diagnostics.

Keywords
Gold nanoparticles, Graphene oxide, MicroRNA detection, Electrocatalytic amplification, Duplex-specific nuclease
National Category
Analytical Chemistry Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-377203 (URN)10.1016/j.bios.2018.12.027 (DOI)000457508800026 ()30611105 (PubMedID)
Funder
Swedish Research Council, 2016-05259Knut and Alice Wallenberg FoundationEU, Horizon 2020, 713683
Available from: 2019-02-25 Created: 2019-02-25 Last updated: 2019-04-24Bibliographically approved
Omanakuttan, G., Martinez Sacristan, O., Marcinkevicius, S., Uzdavinys, T. K., Jimenez, J., Ali, H., . . . Sun, Y.-T. (2019). Optical and interface properties of direct InP/Si heterojunction formed by corrugated epitaxial lateral overgrowth. Optical Materials Express, 9(3), 1488-1500
Open this publication in new window or tab >>Optical and interface properties of direct InP/Si heterojunction formed by corrugated epitaxial lateral overgrowth
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2019 (English)In: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 9, no 3, p. 1488-1500Article in journal (Refereed) Published
Abstract [en]

We fabricate and study direct InP/Si heterojunction by corrugated epitaxial lateral overgrowth (CELOG). The crystalline quality and depth-dependent charge carrier dynamics of InP/Si heterojunction are assessed by characterizing the cross-section of grown layer by low-temperature cathodoluminescence, time-resolved photoluminescence and transmission electron microscopy. Compared to the defective seed InP layer on Si, higher intensity band edge emission in cathodoluminescence spectra and enhanced carrier lifetime of InP are observed above the CELOG InP/Si interface despite large lattice mismatch, which are attributed to the reduced threading dislocation density realized by the CELOG method.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-379937 (URN)10.1364/OME.9.001488 (DOI)000460134500051 ()
Funder
Swedish Energy AgencySwedish Research Council
Available from: 2019-03-26 Created: 2019-03-26 Last updated: 2019-03-26Bibliographically approved
Ali, H., Warnatz, T., Xie, L., Hjörvarsson, B. & Leifer, K. (2019). Quantitative EMCD by use of a double aperture for simultaneous acquisition of EELS. Ultramicroscopy, 196, 192-196
Open this publication in new window or tab >>Quantitative EMCD by use of a double aperture for simultaneous acquisition of EELS
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2019 (English)In: Ultramicroscopy, ISSN 0304-3991, E-ISSN 1879-2723, Vol. 196, p. 192-196Article in journal (Refereed) Published
Abstract [en]

The weak signal strength in electron magnetic circular dichroism (EMCD) measurements remains one of the main challenges in the quantification of EMCD related EELS spectra. As a consequence, small variations in peak intensity caused by changes of background intervals, choice of method for extraction of signal intensity and equally differences in sample quality can cause strong changes in the EMCD signal. When aiming for high resolution quantitative EMCD, an additional difficulty consists in the fact that the two angular resolved EELS spectra needed to obtain the EMCD signal are taken at two different instances and it cannot be guaranteed that the acquisition conditions for these two spectra are identical.  Here, we present an experimental setup where we use a double hole aperture in the transmission electron microscope to obtain the EMCD signal in a single acquisition. This geometry allows for the parallel acquisition of the two electron energy loss spectra (EELS) under exactly the same conditions. We also compare the double aperture acquisition mode with the qE acquisition mode which has been previously used for parallel acquisition of EMCD. We show that the double aperture mode not only offers better signal to noise ratio as compared to qE mode but also allows for much higher acquisition times to significantly improve the signal quality which is crucial for quantitative analysis of the magnetic moments.

National Category
Other Materials Engineering
Research subject
Materials Science
Identifiers
urn:nbn:se:uu:diva-364715 (URN)10.1016/j.ultramic.2018.10.012 (DOI)000451180800026 ()30439606 (PubMedID)
Funder
Swedish Research Council, C0367901Swedish Research Council, 2016-05259Knut and Alice Wallenberg Foundation
Available from: 2018-10-31 Created: 2018-10-31 Last updated: 2019-12-06Bibliographically approved
Irkhina, A., Levcenko, S., Xie, L., Leifer, K. & Unold, T. (2019). Radiative emission from Cu2ZnSnS4/ZnSn core/shell nanocrystals. Journal of Materials Chemistry C, 7(20), 6129-6133
Open this publication in new window or tab >>Radiative emission from Cu2ZnSnS4/ZnSn core/shell nanocrystals
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2019 (English)In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 7, no 20, p. 6129-6133Article in journal (Refereed) Published
Abstract [en]

Kesterite Cu2ZnSnS4 (CZTS) nanocrystals so far have been found to luminesce neither at room temperature nor at low temperature. Here a core-shell architecture for kesterite CZTS nanocrystals is demonstrated by applying a ZnSn-alloy shell overcoating approach. These CZTS/ZnSn nanocrystals show luminescence emission at 1.05 eV, which is red-shifted by about 0.4 eV from the absorption onset and is attributed to a radiative transition involving a deep defect. Temperature-dependent photoluminescence measurements within a range of 20-200 K indicate the presence of a competing nonradiative channel with an activation energy of 50-60 meV.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2019
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-390604 (URN)10.1039/c9tc00904c (DOI)000472444800027 ()
Available from: 2019-08-13 Created: 2019-08-13 Last updated: 2019-08-13Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-8360-1877

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