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  • 1.
    Ansari, Farhan
    et al.
    Stanford Univ, Dept Mat Sci & Engn, Stanford, CA 94305 USA..
    Ding, Yichuan
    Stanford Univ, Dept Mat Sci & Engn, Stanford, CA 94305 USA..
    Berglund, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Dauskardt, Reinhold H.
    Stanford Univ, Dept Mat Sci & Engn, Stanford, CA 94305 USA..
    Toward Sustainable Multifunctional Coatings Containing Nanocellulose in a Hybrid Glass Matrix2018In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, no 6, p. 5495-5503Article in journal (Refereed)
    Abstract [en]

    We report on a sustainable route to protective nanocomposite coatings, where one of the components, nanocellulose fibrils, is derived from trees and the glass matrix is an inexpensive sol-gel organic-inorganic hybrid of zirconium alkoxide and an epoxy-functionalized silane. The hydrophilic nature of the colloidal nanocellulose fibrils is exploited to obtain a homogeneous one-pot suspension of the nanocellulose in the aqueous sol-gel matrix precursors solution. The mixture is then sprayed to form nano composite coatings of a well-dispersed, random in-plane nano cellulose fibril network in a continuous organic inorganic glass matrix phase. The nanocellulose incorporation in the sol-gel matrix resulted in nanostructured composites with marked effects on salient coating properties including optical transmittance, hardness, fracture energy, and water contact angle. The particular role of the nanocellulose fibrils on coating fracture properties, important for coating reliability, was analyzed and discussed in terms of fibril morphology, molecular matrix, and nanocellulose/matrix interactions.

  • 2. Carville, N. Craig
    et al.
    Manzo, Michele
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Damm, Signe
    Castiella, Marion
    Collins, Liam
    Denning, Denise
    Weber, Stefan
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Rice, James
    Rodriguez, Brian
    Photoreduction of SERS-Active Metallic Nanostructures on Chemically Patterned Ferroelectric Crystals2012In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 6, no 8, p. 7373-7380Article in journal (Refereed)
    Abstract [en]

    Photodeposition of metallic nanostructures onto ferroelectric surfaces is typically based on patterning local surface reactivity via electric field poling. Here, we demonstrate metal deposition onto substrates which have been chemically patterned via proton exchange (i.e., without polarization reversal). The chemical patterning provides the ability to tailor the electrostatic fields near the surface of lithium niobate crystals, and these engineered fields are used to fabricate metallic nanostructures. The effect of the proton exchange process on the piezoelectric and electrostatic properties of the surface is characterized using voltage-modulated atomic force microscopy techniques, which, combined with modeling of the electric fields at the surface of the crystal, reveal that the deposition occurs preferentially along the boundary between ferroelectric and proton-exchanged regions. The metallic nanostructures have been further functionalized with a target probe molecule, 4-aminothiophenol, from which surface-enhanced Raman scattering (SERS) signal is detected, demonstrating the suitability of chemically patterned ferroelectrics as SERS-active templates.

  • 3.
    Chen, Guanying
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ohulchanskyy, T. Y.
    Liu, S.
    Law, W. -C
    Wu, F.
    Swihart, M. T.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Prasad, P. N.
    Core/shell NaGdF 4:Nd 3+/NaGdF 4 nanocrystals with efficient near-infrared to near-infrared downconversion photoluminescence for bioimaging applications2012In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 6, no 4, p. 2969-2977Article in journal (Refereed)
    Abstract [en]

    We have synthesized core/shell NaGdF 4:Nd 3+/NaGdF 4 nanocrystals with an average size of 15 nm and exceptionally high photoluminescence (PL) quantum yield. When excited at 740 nm, the nanocrystals manifest spectrally distinguished, near-infrared to near-infrared (NIR-to-NIR) downconversion PL peaked at ∌900, ∌1050, and ∌1300 nm. The absolute quantum yield of NIR-to-NIR PL reached 40% for core-shell nanoparticles dispersed in hexane. Time-resolved PL measurements revealed that this high quantum yield was achieved through suppression of nonradiative recombination originating from surface states and cross relaxations between dopants. NaGdF 4:Nd 3+/NaGdF 4 nanocrystals, synthesized in organic media, were further converted to be water-dispersible by eliminating the capping ligand of oleic acid. NIR-to-NIR PL bioimaging was demonstrated both in vitro and in vivo through visualization of the NIR-to-NIR PL at ∌900 nm under incoherent lamp light excitation. The fact that both excitation and the PL of these nanocrystals are in the biological window of optical transparency, combined with their high quantum efficiency, spectral sharpness, and photostability, makes these nanocrystals extremely promising as optical biomaging probes.

  • 4.
    Chen, Guanying
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Shen, Jie
    Ohulchanskyy, Tymish Y.
    Patel, Nayan J.
    Kutikov, Artem
    Li, Zhipeng
    Song, Jie
    Pandey, Ravindra K.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Prasad, Paras N.
    Han, Gang
    (alpha-NaYbF4:Tm3+)/CaF2 Core/Shell Nanoparticles with Efficient Near-Infrared to Near-Infrared Upconversion for High-Contrast Deep Tissue Bioimaging2012In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 6, no 9, p. 8280-8287Article in journal (Refereed)
    Abstract [en]

    We describe the development of novel and biocompatible core/shell (alpha-NaYbF4:Tm3+)/CaF2 nanoparticles that exhibit highly efficient NIRin-NIROut upconversion (UC) for high contrast and deep bioimaging. When excited at similar to 980 nm, these nanoparticles emit photoluminescence (PL) peaked at similar to 800 nm. The quantum yield of this UC PL under low power density excitation (similar to 0.3 W/cm(2)) is 0.6 +/- 0.1%. This high UC PL efficiency is realized by suppressing surface quenching effects via heteroepitaxial growth of a biocompatible CaF2 shell, which results in a 35-fold increase in the intensity of UC PL from the core. Small-animal whole-body UC PL imaging with exceptional contrast (signal-to-background ratio of 310) is shown using BALB/c mice intravenously injected with aqueously dispersed nanoparticles (700 pmol/kg). High-contrast UC PL imaging of deep tissues is also demonstrated, using a nanoparticle-loaded synthetic fibrous mesh wrapped around rat femoral bone and a cuvette with nanoparticle aqueous dispersion covered with a 3.2 cm thick animal tissue (pork).

  • 5. Chen, Si
    et al.
    Svedendahl, Mikael
    Antosiewicz, Tomasz J
    Käll, Mikael
    Plasmon-enhanced enzyme-linked immunosorbent assay on large arrays of individual particles made by electron beam lithography.2013In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 7, no 10Article in journal (Refereed)
    Abstract [en]

    Ultrasensitive biosensing is one of the main driving forces behind the dynamic research field of plasmonics. We have previously demonstrated that the sensitivity of single nanoparticle plasmon spectroscopy can be greatly enhanced by enzymatic amplification of the refractive index footprint of individual protein molecules, so-called plasmon-enhanced enzyme-linked immunosorbent assay (ELISA). The technique, which is based on generation of an optically dense precipitate catalyzed by horseradish peroxidase at the metal surface, allowed for colorimetric analysis of ultralow molecular surface coverages with a limit of detection approaching the single molecule limit. However, the plasmonic response induced by a single enzyme can be expected to vary for a number of reasons, including inhomogeneous broadening of the sensing properties of individual particles, variation in electric field enhancement over the surface of a single particle and variation in size and morphology of the enzymatic precipitate. In this report, we discuss how such inhomogeneities affect the possibility to quantify the number of molecules bound to a single nanoparticle. The discussion is based on simulations and measurements of large arrays of well-separated gold nanoparticles fabricated by electron beam lithography (EBL). The new data confirms the intrinsic single-molecule sensitivity of the technique but we were not able to clearly resolve the exact number of adsorbed molecules per single particle. The results indicate that the main sources of uncertainty come from variations in sensitivity across the surface of individual particles and between different particles. There is also a considerable uncertainty in the actual precipitate morphology produced by individual enzyme molecules. Possible routes toward further improvements of the methodology are discussed.

  • 6.
    Chen, Xi
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Chen, Yiting
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Nanosecond Photothermal Effects in Plasmonic Nanostructures2012In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 6, no 3, p. 2550-2557Article in journal (Refereed)
    Abstract [en]

    Photothermal effects in plasmonic nanostructures have great potentials in applications for photothermal cancer therapy, optical storage, thermo-photovoltaics, etc. However, the transient temperature behavior of a nanoscale material system during an ultrafast photothermal process has rarely been accurately investigated. Here a heat transfer model is constructed to investigate the temporal and spatial variation of temperature in plasmonic gold nanostructures. First, as a benchmark scenario, we study the light-induced heating of a gold nanosphere in water and calculate the relaxation time of the nanosphere excited by a modulated light. Second, we investigate heating and reshaping of gold nanoparticles in a more complex metamaterial absorber structure induced by a nanosecond pulsed light. The model shows that the temperature of the gold nanoparticles can be raised from room temperature to >795 K in just a few nanoseconds with a low light luminance, owing to enhanced light absorption through strong plasmonic resonance. Such quantitative predication of temperature change, which Is otherwise formidable to measure experimentally, can serve as an excellent guideline for designing devices for ultrafast photothermal applications.

  • 7. Ding, Fei
    et al.
    Wang, Zhuoxian
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    Shalaev, Vladimir M.
    Kildishev, Alexander V.
    Broadband High-Efficiency Half-Wave Plate: A Supercell-Based Plasmonic Metasurface Approach2015In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 9, no 4, p. 4111-4119Article in journal (Refereed)
    Abstract [en]

    We design, fabricate, and experimentally demonstrate an ultrathin, broadband half-wave plate in the near-infrared range using a plasmonic metasurface. The simulated results show that the linear polarization conversion efficiency is over 97% with over 90% reflectance across an 800 nm bandwidth. Moreover, simulated and experimental results indicate that such broadband and high-efficiency performance is also sustained over a wide range of incident angles. To further obtain a background-free half-wave plate, we arrange such a plate as a periodic array of integrated supercells made of several plasmonic antennas with high linear polarization conversion efficiency, consequently achieving a reflection-phase gradient for the cross-polarized beam. In this design, the anomalous (cross-polarized) and the normal (copolarized) reflected beams become spatially separated, hence enabling highly efficient and robust, background-free polarization conversion along with broadband operation. Our results provide strategies for creating compact, integrated, and high-performance plasmonic circuits and devices.

  • 8.
    Hamedi, Mahiar M.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hajian, Alireza
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Fall, Andreas B.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Håkansson, Karl
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Salajkova, Michaela
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lundell, Fredrik
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Highly Conducting, Strong Nanocomposites Based on Nanocellulose-Assisted Aqueous Dispersions of Single-Wall Carbon Nanotubes2014In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 8, no 3, p. 2467-2476Article in journal (Refereed)
    Abstract [en]

    It is challenging to obtain high-quality dispersions of single-wall nanotubes (SWNTs) in composite matrix materials, in order to reach the full potential of mechanical and electronic properties. The most widely used matrix materials are polymers, and the route to achieving high quality dispersions of SWNT is mainly chemical functionalization of the SWNT. This leads to increased cost, a loss of strength and lower conductivity. In addition full potential of colloidal self-assembly cannot be fully exploited in a polymer matrix. This may limit the possibilities for assembly of highly ordered structural nanocomposites. Here we show that nanofibrillated cellulose (NFC) can act as an excellent aqueous dispersion agent for as-prepared SWNTs, making possible low-cost exfoliation and purification of SWNTs with dispersion limits exceeding 40 wt %. The NFC:SWNT dispersion may also offer a cheap and sustainable alternative for molecular self-assembly of advanced composites. We demonstrate semitransparent conductive films, aerogels and anisotropic microscale fibers with nanoscale composite structure. The NFC:SWNT nanopaper shows increased strength at 3 wt % SWNT, reaching a modulus of 133 GPa, and a strength of 307 MPa. The anisotropic microfiber composites have maximum conductivities above 200 S cm(-1) and current densities reaching 1400 A cm(-2).

  • 9. Jana, Avijit
    et al.
    Nguyen, Kim Truc
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhu, Pengcheng
    Tan, Nguan Soon
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhao, Yanli
    Perylene-Derived Single-Component Organic Nanoparticles with Tunable Emission: Efficient Anticancer Drug Carriers with Real-Time Monitoring of Drug Release2014In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 8, no 6, p. 5939-5952Article in journal (Refereed)
    Abstract [en]

    An organic nanoparticle-based drug delivery system with high drug loading efficacy (similar to 79 wt %) was developed using a perylene-derived photoremovable protecting group, namely, perylene-3,4,9,10-tetrayltetramethanol (Pe(OH)(4)). The anticancer drug chlorambucil was protected by coupling with Pe(OH)(4) to form photocaged nanoparticles (Pe(OH)(4)). The photorelease mechanism of chlorambucil from the Pe(Cbl)(4) conjugate was investigated experimentally by high-resolution mass spectrometry and theoretically by density functional theory calculations. The Pe(Cbl)(4) nanoparticles perform four important roles: (i) a nanocarrier for drug delivery, (ii) a phototrigger for drug release, (iii) a fluorescent chromophore for cell imaging, and (iv) a photoswitchable fluorophore for real-time monitoring of drug release. Tunable emission of the perylene-derived nanoparticles was demonstrated by comparing the emission properties of the Pe(OH)(4) and Pe(Cbl)(4) nanoparticles with perylene-3-ylmethanol. These nanoparticles were subsequently employed in cell imaging for investigating their intracellular localization. Furthermore, the in vivo toxicity of the Pe(OH)(4) nanoparticles was investigated using the mouse model. Histological tissue analysis of five major organs, i.e., heart, kidney, spleen, liver, and lung, indicates that the nanoparticles did not show any obvious damage to these major organs under the experimental conditions. The current research presents a successful example of integrating multiple functions into single-component organic nanoparticles for drug delivery.

  • 10.
    Karabulut, Erdem
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Ankerfors, Mikael
    Material Processes, Innventia AB, Stockholm, Sweden.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Adhesive Layer-by-Layer Films of Carboxymethylated Cellulose Nanofibril Dopamine Covalent Bioconjugates Inspired by Marine Mussel Threads2012In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 6, no 6, p. 4731-4739Article in journal (Refereed)
    Abstract [en]

    The preparation of multifunctional films and coatings from sustainable, low-cost raw materials has attracted considerable interest during the past decade. In this respect, cellulose-based products possess great promise due not only to the availability of large amounts of cellulose in nature but also to the new classes of nanosized and well-characterized building blocks of cellulose being prepared from trees or annual plants. However, to fully utilize the inherent properties of these nanomaterials, facile and also sustainable preparation routes are needed. In this work, bioinspired hybrid conjugates of carboxymethylated cellulose nanofibrils (CNFC) and dopamine (DOPA) have been prepared and layer-by-layer (LbL) films of these modified nanofibrils have been built up in combination with a branched polyelectrolyte, polyethyleneimine (PEI), to obtain robust, adhesive, and wet-stable nanocoatings on solid surfaces. It is shown that the chemical functionalization of CNFCs with DOPA molecules alters their conventional properties both in liquid dispersion and at the interface and also influences the LbL. film formation by reducing the electrostatic interaction. Although the CNFC-DOPA conjugates show a lower colloidal stability in aqueous dispersions due to charge suppression, it was possible to prepare the LbL films through the consecutive deposition of the building blocks. Adhesive forces between muttilayer films prepared using chemically functionalized CNFCs and a silica probe are much stronger in the presence of Fe3+ than those between a multilayer film prepared from unmodified nanofibrils and a silica probe. The present work demonstrates a facile way to prepare chemically functionalized cellulose nanofibrils whereby more extended applications can produce novel cellulose-based materials with different functionalities.

  • 11. Lee, George P
    et al.
    Shi, Yichao
    Lavoie, Ellen
    Daeneke, Torben
    Reineck, Philipp
    Cappel, Ute B
    Huang, David M
    Bach, Udo
    Light-driven transformation processes of anisotropic silver nanoparticles.2013In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 7, no 7, p. 5911-21Article in journal (Refereed)
    Abstract [en]

    The photoinduced formation of silver nanoprisms from smaller silver seed particles in the presence of citrate anions is a classic example of a photomorphic reaction. In this case, light is used as a convenient tool to dynamically manipulate the shape of metal nanoparticles. To date, very little is known about the prevailing reaction mechanism of this type of photoreaction. Here we provide a detailed study of the shape transformation dynamics as a function of a range of different process parameters, such as photon energy and photon flux. For the first time, we provide direct evidence that the photochemical synthesis of silver nanoprisms from spherical seed nanoparticles proceeds via a light-activated two-dimensional coalescence mechanism. On the other hand, we could show that Ostwald ripening becomes the dominant reaction mechanism when larger silver nanoprisms are grown from photochemically synthesized smaller nanoprisms. This two-step reaction proceeds significantly faster and yields more uniform, sharper nanoprisms than the classical one-step photodevelopment process from seeds. The ability to dynamically control nanoparticle shapes and properties with light opens up novel synthesis avenues but also, more importantly, allows one to conceive new applications that exploit the nonstatic character of these nanoparticles and the ability to control and adjust their properties at will in a highly dynamic fashion.

  • 12.
    Lemme, Max C.
    et al.
    Harvard University, Department of Physics.
    Bell, David C.
    Williams, James R.
    Stern, Lewis A.
    Baugher, Britton W. H.
    Jarillo-Herrero, Pablo
    Marcus, Charles M.
    Etching of Graphene Devices with a Helium Ion Beam2009In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 3, no 9, p. 2674-2676Article in journal (Refereed)
    Abstract [en]

    We report on the etching of graphene devices with a helium ion beam, including in situ electrical measurement during lithography. The etching process can be used to nanostructure and electrically isolate different regions In a graphene device, as demonstrated by etching a channel in a suspended graphene device with etched gaps down to about 10 nm. Graphene devices on silicon dioxide (02) substrates etch with lower He ion doses and are found to have a residual conductivity after etching, which we attribute to contamination by hydrocarbons.

  • 13.
    Li, Jiantong
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Delekta, Szymon Sollami
    Zhang, Panpan
    Yang, Sheng
    Lohe, Martin R.
    Zhuang, Xiaodong
    Feng, Xinliang
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Electronics.
    Scalable Fabrication and Integration of Graphene Microsupercapacitors through Full Inkjet Printing2017In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 11, no 8, p. 8249-8256Article in journal (Refereed)
    Abstract [en]

    A simple full-inkjet-printing technique is developed for the scalable fabrication of graphene-based microsupercapacitors (MSCs) on various substrates. High-performance graphene inks are formulated by integrating the electrochemically exfoliated graphene with a solvent exchange technique to reliably print graphene interdigitated electrodes with tunable geometry and "thickness. Along with the printed polyelectrolyte, poly(4-styrenesulfonic acid), the fully printed graphene-based MSCs attain the highest areal capacitance of similar to 0.7 mF/cm(2), substantially advancing the state-of-art of all-solid-state MSCs with printed graphene electrodes. The full printing solution enables scalable fabrication of MSCs and effective connection of them in parallel and/or in series at various scales. Remarkably, more than 100 devices have been connected to form large-scale MSC arrays as power banks on both silicon wafers and Kapton. Without any extra protection or encapsulation, the MSC arrays can be reliably charged up to 12 V and retain the performance even 8 months after fabrication.

  • 14. Liu, Guofeng
    et al.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Sheng, Jianhui
    Li, Pei-Zhou
    Ong, Wee Kong
    Phua, Soo Zeng Fiona
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhu, Liangliang
    Zhao, Yanli
    Helicity Inversion of Supramolecular Hydrogels Induced by Achiral Substituents2017In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 11, no 12, p. 11880-11889Article in journal (Refereed)
    Abstract [en]

    Probing the supramolecular chirality of assemblies and controlling their handedness are closely related to the origin of chirality at the supramolecular level and the development of smart materials with desired handedness. However, it remains unclear how achiral residues covalently bonded to chiral amino acids can function in the chirality inversion of supramolecular assemblies. Herein, we report macroscopic chirality and dynamic manipulation of chiroptical activity of hydrogels self-assembled from phenylalanine derivatives, together with the inversion of their handedness achieved solely by exchanging achiral substituents between oligo(ethylene glycol) and carboxylic acid groups. This helicity inversion is mainly induced by distinct stacking mode of the self-assembled building blocks, as collectively confirmed by scanning electron microscopy, circular dichroism, crystallography, and molecular dynamics calculations. Through this straightforward approach, we were able to invert the handedness of helical assemblies by merely exchanging achiral substituents at the terminal of chiral gelators. This work not only presents a feasible strategy to achieve the handedness inversion of helical nanostructures for better understanding of chiral self-assembly process in supramolecular chemistry but also facilities the development of smart materials with controllable handedness in materials science.

  • 15. Lupina, Grzegorz
    et al.
    Kitzmann, Julia
    Costina, Ioan
    Lukosius, Mindaugas
    Wenger, Christian
    Wolff, Andre
    Vaziri, Sam
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Pasternak, Iwona
    Krajewska, Aleksandra
    Strupinski, Wlodek
    Kataria, Satender
    Gahoi, Amit
    Lemme, Max C.
    Ruhl, Guenther
    Zoth, Guenther
    Luxenhofer, Oliver
    Mehr, Wolfgang
    Residual Metallic Contamination of Transferred Chemical Vapor Deposited Graphene2015In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 9, no 5, p. 4776-4785Article in journal (Refereed)
    Abstract [en]

    Integration of graphene with Si microelectronics is very appealing by offering a potentially broad range of new functionalities. New materials to be integrated with the Si platform must conform to stringent purity standards. Here, we investigate graphene layers grown on copper foils by chemical vapor deposition and transferred to silicon wafers by wet etching and electrochemical delamination methods with respect to residual submonolayer metallic contaminations. Regardless of the transfer method and associated cleaning scheme, time-of-flight secondary ion mass spectrometry and total reflection X-ray fluorescence measurements indicate that the graphene sheets are contaminated with residual metals (copper, iron) with a concentration exceeding 10(13) atoms/cm(2). These metal impurities appear to be partially mobile upon thermal treatment, as shown by depth profiling and reduction of the minority charge carrier diffusion length in the silicon substrate. As residual metallic impurities can significantly alter electronic and electrochemical properties of graphene and can severely impede the process of integration with silicon microelectronics, these results reveal that further progress in synthesis, handling, and cleaning of graphene is required to advance electronic and optoelectronic applications.

  • 16.
    Mittal, Nitesh
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Ansari, Farhan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Department of Materials Science and Engineering, Stanford University, Stanford, CA, United States.
    Gowda, Krishne, V
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Brouzet, Christophe
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Chen, Pan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Larsson, Per Tomas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. RISE Bioeconomy, P.O. Box 5604, Stockholm, SwedenRISE Bioeconomy, P.O. Box 5604, Stockholm, Sweden.
    Roth, Stephan Volkher
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Lundell, Fredrik
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Kotov, Nicholas Alexander
    Söderberg, Daniel
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Multiscale Control of Nanocellulose Assembly: Transferring Remarkable Nanoscale Fibril Mechanics to Macroscale Fibers2018In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, no 7, p. 6378-6388Article in journal (Refereed)
    Abstract [en]

    Nanoscale building blocks of many materials exhibit extraordinary mechanical properties due to their defect-free molecular structure. Translation of these high mechanical properties to macroscopic materials represents a difficult materials engineering challenge due to the necessity to organize these building blocks into multiscale patterns and mitigate defects emerging at larger scales. Cellulose nanofibrils (CNFs), the most abundant structural element in living systems, has impressively high strength and stiffness, but natural or artificial cellulose composites are 3-15 times weaker than the CNFs. Here, we report the flow-assisted organization of CNFs into macroscale fibers with nearly perfect unidirectional alignment. Efficient stress transfer from macroscale to individual CNF due to cross-linking and high degree of order enables their Young's modulus to reach up to 86 GPa and a tensile strength of 1.57 GPa, exceeding the mechanical properties of known natural or synthetic biopolymeric materials. The specific strength of our CNF fibers engineered at multiscale also exceeds that of metals, alloys, and glass fibers, enhancing the potential of sustainable lightweight high-performance materials with multiscale self-organization.

  • 17.
    Mittal, Nitesh
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Biotechnology (BIO), Protein Technology. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Jansson, Ronnie
    KTH, School of Biotechnology (BIO), Protein Technology.
    Widhe, Mona
    KTH, School of Biotechnology (BIO), Protein Technology.
    Benselfelt, Tobias
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Innventia AB, Sweden.
    Håkansson, Karl M. O.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Lundell, Fredrik
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Biotechnology (BIO), Protein Technology. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Hedhammar, My
    KTH, School of Biotechnology (BIO), Protein Technology.
    Söderberg, Daniel
    KTH, School of Biotechnology (BIO), Protein Technology. KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Ultrastrong and Bioactive Nanostructured Bio-Based Composites2017In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 11, no 5, p. 5148-5159Article in journal (Refereed)
    Abstract [en]

    Nature’s design of functional materials relies on smart combinations of simple components to achieve desired properties. Silk and cellulose are two clever examples from nature–spider silk being tough due to high extensibility, whereas cellulose possesses unparalleled strength and stiffness among natural materials. Unfortunately, silk proteins cannot be obtained in large quantities from spiders, and recombinant production processes are so far rather expensive. We have therefore combined small amounts of functionalized recombinant spider silk proteins with the most abundant structural component on Earth (cellulose nanofibrils (CNFs)) to fabricate isotropic as well as anisotropic hierarchical structures. Our approach for the fabrication of bio-based anisotropic fibers results in previously unreached but highly desirable mechanical performance with a stiffness of ∼55 GPa, strength at break of ∼1015 MPa, and toughness of ∼55 MJ m–3. We also show that addition of small amounts of silk fusion proteins to CNF results in materials with advanced biofunctionalities, which cannot be anticipated for the wood-based CNF alone. These findings suggest that bio-based materials provide abundant opportunities to design composites with high strength and functionalities and bring down our dependence on fossil-based resources.

  • 18. Nowakowska, Sylwia
    et al.
    Mazzola, Federico
    Alberti, Mariza N.
    Song, Fei
    Voigt, Tobias
    Nowakowski, Jan
    Wackerlin, Aneliia
    Wackerlin, Christian
    Wiss, Jerome
    Schweizer, W. Bernd
    Broszio, Max
    Polley, Craig
    Leandersson, Mats
    Fatayer, Shadi
    Ivas, Toni
    Baljozovic, Milos
    Mousavi, S. Fatemeh
    Ahsan, Aisha
    Nijs, Thomas
    Popova, Olha
    Zhang, Jun
    Muntwiler, Matthias
    Thilgen, Carlo
    Stohr, Meike
    Pasti, Igor A.
    Skorodumova, Natalia V
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Diederich, Francois
    Wells, Justin
    Jung, Thomas A.
    Adsorbate-Induced Modification of the Confining Barriers in a Quantum Box Array2018In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, no 1, p. 768-778Article in journal (Refereed)
    Abstract [en]

    Quantum devices depend on addressable elements, which can be modified separately and in their mutual interaction. Self-assembly at surfaces, for example, formation of a porous (metal-) organic network, provides an ideal way to manufacture arrays of identical quantum boxes, arising in this case from the confinement of the electronic (Shockley) surface state within the pores. We show that the electronic quantum box state as well as the interbox coupling can be modified locally to a varying extent by a selective choice of adsorbates, here C-60, interacting with the barrier. In view of the wealth of differently acting adsorbates, this approach allows for engineering quantum states in on-surface network architectures.

  • 19. Pellarin, Michel
    et al.
    Ramade, Julien
    Rye, Jan Michael
    Bonnet, Christophe
    Broyer, Michel
    Lebeault, Marie-Ange
    Lerme, Jean
    Marguet, Sylvie
    Navarro, Julien R. G.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Cottancin, Emmanuel
    Fano Transparency in Rounded Nanocube Dimers Induced by Gap Plasmon Coupling2016In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 10, no 12, p. 11266-11279Article in journal (Refereed)
    Abstract [en]

    Homodimers of noble metal nanocubes form model plasmonic systems where the localized plasmon resonances sustained by each particle not only hybridize but also coexist with excitations of a different nature: surface plasmon polaritons confined within the Fabry-Perot cavity delimited by facing cube surfaces (i.e., gap plasmons). Destructive interference in the strong coupling between one of these highly localized modes and the highly radiating longitudinal dipolar plasmon of the dimer is responsible for the formation of a Fano resonance profile and the opening of a spectral window of anomalous transparency for the exciting light. We report on the clear experimental evidence of this effect in the case of 50 nm silver and 160 nm gold nanocube dimers studied by spatial modulation spectroscopy at the single particle level. A numerical study based on a plasmon mode analysis leads us to unambiguously identify the main cavity mode involved in this process and especially the major role played by its symmetry. The Fano depletion dip is red shifted when the gap size is decreasing. It is also blue-shifted and all the more pronounced that the cube edge rounding is large. Combining nanopatch antenna and plasmon hybridization descriptions, we quantify the key role of the face-to-face distance and the cube edge morphology on the spectral profile of the transparency dip.

  • 20. Polley, Craig M.
    et al.
    Buczko, Ryszard
    Forsman, Alexander
    Dziawa, Piotr
    Szczerbakow, Andrzej
    Rechcinski, Rafal
    Kowalski, Bogdan J.
    Story, Tomasz
    Trzyna, Malgorzata
    Bianchi, Marco
    Cabo, Antonija Grubisic
    Hofmann, Philip
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Tjernberg, Oscar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Balasubramanian, Thiagarajan
    Fragility of the Dirac Cone Splitting in Topological Crystalline Insulator Heterostructures2018In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, no 1, p. 617-626Article in journal (Refereed)
    Abstract [en]

    The "double Dirac cone" 2D topological interface states found on the (001) faces of topological crystalline insulators such as Pb1-xSnxSe feature degeneracies located away from time reversal invariant momenta and are a manifestation of both mirror symmetry protection and valley interactions. Similar shifted degeneracies in 1D interface states have been highlighted as a potential basis for a topological transistor, but realizing such a device will require a detailed understanding of the intervalley physics involved. In addition, the operation of this or similar devices outside of ultrahigh vacuum will require encapsulation, and the consequences of this for the topological interface state must be understood. Here we address both topics for the case of 2D surface states using angle-resolved photoemission spectroscopy. We examine bulk Pb1-xSnxSe(001) crystals overgrown with PbSe, realizing trivial/topological heterostructures. We demonstrate that the valley interaction that splits the two Dirac cones at each (X) over bar is extremely sensitive to atomic-scale details of the surface, exhibiting non-monotonic changes as PbSe deposition proceeds. This includes an apparent total collapse of the splitting for sub-monolayer coverage, eliminating the Lifshitz transition. For a large overlayer thickness we observe quantized PbSe states, possibly reflecting a symmetry confinement mechanism at the buried topological interface.

  • 21. Quignon, Benoit
    et al.
    Pilkington, Georgia A.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Ashfold, Michael N. R.
    Mattia, Davide
    Leese, Hannah
    Davis, Sean A.
    Briscoe, Wuge H.
    Sustained Frictional Instabilities on Nanodomed Surfaces: Stick Slip Amplitude Coefficient2013In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 7, no 12, p. 10850-10862Article in journal (Refereed)
    Abstract [en]

    Understanding the frictional properties of nanostructured surfaces is important because of their increasing application in modem minlaturized devices. In this work, lateral force microscopy was used to study the frictional properties between AFM nanotip and surfaces bearing well-defined ranging from tens to hundreds of nanometers. Our results show that the average lateral force varied linearly with applied load, as described by Amontons' first law of friction, although no direct correlation between the sample topographic properties and their measured friction coeffidents was identified. Furthermore, all the nanodomed textures exhibited pronounced osdllations in the shear traces, similar to the dassic stick slip behavior, under all the shear velocities and load regimes studied. That is, the nanotextured topography led to sustained frictional instabilities, effectively with no contact frictional sliding. The amplitude of the stick slip oscillations, ab was found to correlate with the topographic properties of the surfaces and scale linearly with the applied load. In line with the friction coefficient, we define the slope of this linear plot as the stick slip amplitude coeffident (SSAC). We suggest that such stick slip behaviors are characteristics of surfaces with nanotextures and that such local frictional instabilities have important implications to surface damage and wear. We thus propose that the shear characteristics of the nanodomed surfaces cannot be fully described by the framework of Amontons' laws of friction and that additional parameters (e.g., a, and SSAQ are required, when their friction, lubrication, and wear properties are important considerations in related nanodevices.

  • 22.
    Rönnlund, Daniel
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Xu, Lei
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Perols, Anna
    KTH, School of Biotechnology (BIO), Protein Technology.
    Eriksson Karlström, Amelie
    KTH, School of Biotechnology (BIO), Protein Technology.
    Auer, Gert
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Multicolor Fluorescence Nanoscopy by Photobleaching: Concept Verification and its Application to Resolve Selective Storage of Proteins in Platelets2014In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 8, no 5, p. 4358-4365Article in journal (Refereed)
    Abstract [en]

    Fluorescence nanoscopy provides means to discernthe finer details of protein localization and interaction in cells by offeringan order of magnitude higher resolution than conventional optical imagingtechniques. However, these super resolution techniques put higher demands onthe optical system as well as on the fluorescent probes, making multicolorfluorescence nanoscopy a challenging task. Here we present a new and simpleprocedure which exploits the photostability and excitation spectra of dyes toincrease the number of simultaneous recordable targets in STED nanoscopy. Weuse this procedure to demonstrate four color STED imaging of platelets with ≤40 nm resolution and low crosstalk. Platelets can selectively store, sequesterand release a multitude of different proteins, and in a manner specific fordifferent physiological and disease states. By applying multicolor nanoscopy tostudy platelets, we can achieve spatial mapping of the protein organizationwith a high resolution, for multiple proteins at the same time and in the samecell. This provides a means to identify specific platelet activation states fordiagnostic purposes and to understand the underlying protein storage andrelease mechanisms. We studied the organization of the pro- and anti-angiogenicproteins VEGF and PF-4 together with fibrinogen and filamentous actin, andfound distinct features in their respective protein localization. Further,colocalization analysis revealed only minor overlap between the proteins VEGFand PF-4 indicating that they have separate storage and release mechanisms,corresponding well with their opposite rules as pro- and anti-angiogenicproteins, respectively.

  • 23.
    Sangghaleh, Fatemeh
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Sychugov, Ilya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Yang, Zhenyu
    Veinot, Jonathan G C
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Near-Unity Internal Quantum Efficiency of Luminescent Silicon Nanocrystals with Ligand Passivation.2015In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 9, no 7, p. 7097-7104Article in journal (Refereed)
    Abstract [en]

    Spectrally resolved photoluminescence (PL) decays were measured for samples of colloidal, ligand-passivated silicon nanocrystals. These samples have PL emission energies with peak positions in the range 1.4-1.8 eV and quantum yields of 30-70%. Their ensemble PL decays are characterized by a stretched-exponential decay with a dispersion factor of 0.8, which changes to an almost monoexponential character at fixed detection energies. The dispersion factors and decay rates for various detection energies were extracted from spectrally resolved curves using a mathematical approach that excluded the effect of homogeneous line width broadening. Since nonradiative recombination would introduce a random lifetime variation, leading to a stretched-exponential decay for an ensemble, we conclude that the observed monoexponential decay in size-selected ensembles signifies negligible nonradiative transitions of a similar strength to the radiative one. This conjecture is further supported as extracted decay rates agree with radiative rates reported in the literature, suggesting 100% internal quantum efficiency over a broad range of emission wavelengths. The apparent differences in the quantum yields can then be explained by a varying fraction of "dark" or blinking nanocrystals.

  • 24. Shi, Jingwen
    et al.
    Karlsson, Hanna L.
    Johansson, Katarina
    Gogvadze, Vladimir
    Xiao, Lisong
    Li, Jiangtian
    Burks, Terrance
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Garcia-Bennett, Alfonso
    Uheida, Abdusalam
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Mathur, Sanjay
    Morgenstern, Ralf
    Kagan, Valerian E.
    Fadeel, Bengt
    Microsomal Glutathione Transferase 1 Protects Against Toxicity Induced by Silica Nanoparticles but Not by Zinc Oxide Nanoparticles2012In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 6, no 3, p. 1925-1938Article in journal (Refereed)
    Abstract [en]

    Microsomal glutathione transferase 1 (MGST1) is an antioxidant enzyme located predominantly in the mitochondrial er membrane and endoplasmk reticulum and has been shown to protect cells from lipid peroxidation induced by a variety of cytostatic drugs and pro-oxidant stimuli. We hypothesized that MGST1 may also protect against nanomaterial-induced cytotoxicity through a specific effect on lipid peroxidation. We evaluated the induction of cytotoxicity and oxidative stress by TiO2, CeO2, SiO2, and ZnO in the human MCF-7 cell line with or without overexpression of MGST1. SiO2 and ZnO nanoparticles caused dose- and time-dependent toxicity, whereas no obvious cytotoxic effects were induced by nanoparticles of TiO2 and CeO2. We also noted pronounced cytotoxicity for three out of four additional SiO2 nanoparticles tested. Overexpression of MGST1 reversed the cytotoxicity of the main SiO2 nanoparticles tested and for one of the supplementary SiO2 nanoparticles but did not protect cells against ZnO-induced cytotoxic effects. The data point toward a role of lipid peroxidation In SiO2 nanoparticle-induced cell death. For ZnO nanoparticles, rapid dissolution was observed, and the subsequent interaction of Zn2+ with cellular targets is likely to contribute to the cytotoxic effects. A direct inhibition of MGST1 by Zn2+ could provide a possible explanation for the lack of protection against ZnO nanoparticles in this model. Our data also showed that SiO2 nanoparticle-induced cytotoxicity is mitigated in the presence of serum, potentially through masking of reactive surface groups by serum proteins, whereas ZnO nanoparticles were cytotoxic both In the presence and in the absence of serum.

  • 25.
    Smith, Anderson David
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Niklaus, Frank
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Paussa, Alan
    Schröder, Stephan
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Fischer, Andreas C.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Sterner, Mikael
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Wagner, Stefan
    Vaziri, Sam
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Forsberg, Fredrik
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Esseni, David
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Lemme, Max C.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Piezoresistive Properties of Suspended Graphene Membranes under Uniaxial and Biaxial Strain in Nanoelectromechanical Pressure Sensors2016In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 10, no 11, p. 9879-9886Article in journal (Refereed)
    Abstract [en]

    Graphene membranes act as highly sensitive transducers in nanoelectromechanical devices due to their ultimate thinness. Previously, the piezoresistive effect has been experimentally verified in graphene using uniaxial strain in graphene. Here, we report experimental and theoretical data on the uni- and biaxial piezoresistive properties of suspended graphene membranes applied to piezoresistive pressure sensors. A detailed model that utilizes a linearized Boltzman transport equation describes accurately the charge-carrier density and mobility in strained graphene and, hence, the gauge factor. The gauge factor is found to be practically independent of the doping concentration and crystallographic orientation of the graphene films. These investigations provide deeper insight into the piezoresistive behavior of graphene membranes.

  • 26.
    Svedendahl, Mikael
    et al.
    Chalmers University of Technology, Sweden.
    Käll, Mikael
    Fano interference between localized plasmons and interface reflections2012In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 6, no 8, p. 7533-7539Article in journal (Refereed)
    Abstract [en]

    Layers of subwavelength metal nanostructures that support localized surface plasmon resonances are of broad interest in applied nanotechnology, for example, in optical sensor development and solar energy harvesting devices. We measured specular reflection spectra as a function of incidence angle for two-dimensional layers of gold nanodisks on glass and found highly asymmetric line-shapes and a spectral red-shift of up to 0.2 eV, or 10% of the plasmon resonance energy, as the angle changed from normal toward grazing incidence. This dramatic angular dispersion is the result of a tunable Fano interference between the spectrally narrow plasmon emission and a "white" continuum caused by the interface reflection. The data are found to be in excellent agreement with predictions based on a theory for Fresnel reflection coefficients of an interface with subwavelength inclusions. The theory can also be used to derive analytical expressions for the Fano parameters.

  • 27.
    van der Wijngaart, Wouter
    KTH, Superseded Departments (pre-2005), Signals, Sensors and Systems. KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Shafagh, Reza Zandi
    Guo, Weijin
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Vastesson, Alexander
    E-Beam Nanostructuring and Direct Click Biofunctionalization of Thiol–Ene Resist2018In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086XArticle in journal (Refereed)
  • 28. Verre, Ruggero
    et al.
    Antosiewicz, Tomasz .
    Svedendahl, Mikael
    Chalmers University of Technology, Sweden.
    Lodewijks, Kristof
    Shegai, Timur
    Käll, Mikael
    Quasi-isotropic surface plasmon polariton generation through near-field coupling to a penrose pattern of silver nanoparticles2014In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 8, no 9, p. 9286-9294Article in journal (Refereed)
    Abstract [en]

    Quasicrystals are structures that possess long-range order without being periodic. We investigate the unique characteristics of a photonic quasicrystal that consists of plasmonic Ag nanodisks arranged in a Penrose pattern. The quasicrystal scatters light in a complex but spectacular diffraction pattern that can be directly imaged in the back focal plane of an optical microscope, allowing us to assess the excitation efficiency of the various diffraction modes. Furthermore, surface plasmon polaritons can be launched almost isotropically through near-field grating coupling when the quasicrystal is positioned close to a homogeneous silver surface. We characterize the dispersion relation of the different excited plasmon modes by reflection measurements and simulations. It is demonstrated that the quasicrystal in-coupling efficiency is strongly enhanced compared to a nanoparticle array with the same particle density but only short-range lateral order. We envision that the system can be useful for a number of advanced light harvesting and optoelectronic applications.

  • 29. Yu, Longhai
    et al.
    Zheng, Jiajiu
    Xu, Yang
    Dai, Daoxin
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China .
    Local and Non local Optically Induced Transparency Effects in Graphene-Silicon Hybrid Nanophotonic Integrated Circuits2014In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 8, no 11, p. 11386-11393Article in journal (Refereed)
    Abstract [en]

    Graphene is well-known as a two-dimensional sheet of carbon atoms arrayed in a honeycomb structure. It has some unique and fascinating properties, which are useful for realizing many optoelectronic devices and applications, including transistors, photodetectors, solar cells, and modulators. To enhance lightgraphene interactions and take advantage of its properties, a promising approach is to combine a graphene sheet with optical waveguides, such as silicon nanophotonic wires considered in this paper. Here we report local and nonlocal optically induced transparency (OIT) effects in graphenesilicon hybrid nanophotonic integrated circuits. A low-power, continuous-wave laser is used as the pump light, and the power required for producing the OIT effect is as low as similar to 0.1 mW. The corresponding power density is several orders lower than that needed for the previously reported saturated absorption effect in graphene, which implies a mechanism involving light absorption by the silicon and photocarrier transport through the silicongraphene junction. The present OIT effect enables low power, all-optical, broadband control and sensing, modulation and switching locally and nonlocally.

  • 30.
    Zandi Shafagh, Reza
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    E-Beam Nanostructuring and Direct Click Biofunctionalization of Thiol-Ene Resist2018In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086XArticle in journal (Refereed)
    Abstract [en]

    Electron beam lithography (EBL) is of majorimportance for ultraminiaturized bio-hybrid sys-tem fabrication, as it allows combining biomolec-ular patterning and mechanical structure denitionon the nanoscale. Existing methods are limited bymulti-step biomolecule immobilization procedures,harsh processing conditions that are harmful to sen-sitive biomolecules, or the structural properties ofthe resulting protein monolayers or hydrogel-basedresists. This work introduces a thiol-ene EBL resistwith chemically reactive thiol groups on its nativesurface that allow the direct and selective "click"immobilization of biomolecules under benign pro-cessing conditions. We EBL structured features ofsize down to 20 nm, and direct functionalized the nanostructures with a sandwich of biotin and streptavidin.The facile combination of polymer nanostructuring with biomolecule immobilization enables mechanically ro-bust bio-hybrid components of interest for nanoscale biomedical, electronic, photonic and robotic applications.

  • 31. Zhang, Jinbao
    et al.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Johansson, Malin B.
    Vlachopoulos, Nick
    Boschloo, Gerrit
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Johansson, Erik M. J.
    Hagfeldt, Anders
    Strategy to Boost the Efficiency of Mixed-Ion Perovskite Solar Cells: Changing Geometry of the Hole Transporting Material2016In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 10, no 7, p. 6816-6825Article in journal (Refereed)
    Abstract [en]

    The hole transporting material (HTM) is an essential component in perovskite solar cells (PSCs) for efficient extraction and collection of the photoinduced charges. Triphenylamine- and carbazole-based derivatives have extensively been explored as alternative and economical HTMs for PSCs. However, the improvement of their power conversion efficiency (PCE), as well as further investigation of the relationship between the chemical structure of the HTMs and the photovoltaic performance, is imperatively needed. In this respect, a simple carbazole-based HTM X25 was designed on the basis of a reference HTM, triphenylamine-based X2, by simply linking two neighboring phenyl groups in a triphenylamine unit through a carbon-carbon single bond. It was found that a lowered highest occupied molecular orbital (HOMO) energy level was obtained for X25 compared to that of X2. Besides, the carbazole moiety in X25 improved the molecular planarity as well as conductivity property in comparison with the triphenylamine unit in X2. Utilizing the HTM X25 in a solar cell with mixed-ion perovskite [HC(NH2)(2)](0.85)(CH3NH3)(0.15)Pb(I0.85Br0.15)(3), a highest reported PCE of 17.4% at 1 sun (18.9% under 0.46 sun) for carbazole-based HTM in PSCs was achieved, in comparison of a PCE of 14.7% for triphenylamine-based HTM X2. From the steady-state photoluminescence and transient photocurrent/photovoltage measurements, we conclude that (1) the lowered HOMO level for X25 compared to X2 favored a higher open-circuit voltage (V-oc) in PSCs; (2) a more uniform formation of X25 capping layer than X2 on the surface of perovskite resulted in more efficient hole transport and charge extraction in the devices. In addition, the long-term stability of PSCs with X25 is significantly enhanced compared to X2 due to its good uniformity of HTM layer and thus complete coverage on the perovskite. The results provide important information to further develop simple and efficient small molecular HTMs applied in solar cells.

  • 32.
    Zhang, Miao
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics. KTH.
    Ngampeerapong, Chonmanart
    Redin, David
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Gene Technology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Ahmadian, Afshin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Gene Technology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Sychugov, Ilya
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Linnros, Jan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Thermophoresis-Controlled Size-Dependent DNA Translocation through an Array of Nanopores2018In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, no 5, p. 4574-4582Article in journal (Refereed)
    Abstract [en]

    Large arrays of nanopores can be used for high-throughput biomolecule translocation with applications toward size discrimination and sorting at the single-molecule level. In this paper, we propose to discriminate DNA length by the capture rate of the molecules to an array of relatively large nanopores (50–130 nm) by introducing a thermal gradient by laser illumination in front of the pores balancing the force from an external electric field. Nanopore arrays defined by photolithography were batch processed using standard silicon technology in combination with electrochemical etching. Parallel translocation of single, fluorophore-labeled dsDNA strands is recorded by imaging the array with a fast CMOS camera. The experimental data show that the capture rates of DNA molecules decrease with increasing DNA length due to the thermophoretic effect of the molecules. It is shown that the translocation can be completely turned off for the longer molecule using an appropriate bias, thus allowing a size discrimination of the DNA translocation through the nanopores. A derived analytical model correctly predicts the observed capture rate. Our results demonstrate that by combining a thermal and a potential gradient at the nanopores, such large nanopore arrays can potentially be used as a low-cost, high-throughput platform for molecule sensing and sorting.

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