• 1 Jul 2020 Nature

    Observation of branched flow of light

    When waves propagate through a weak disordered potential with correlation length larger than the wavelength, they form channels (branches) of enhanced intensity that keep dividing as the waves propagate. This fundamental wave phenomenon is known as branched flow. It was first observed for electrons and for microwave cavities, and it is generally expected for waves with show more
  • 14 Aug 2019 Journal of the American Chemical Society

    Common Source of Cryoprotection and Osmoprotection by Osmolytes

    While recent studies clarify the effect of osmolytes on Coulomb interaction at elevated concentrations of salt, little is known about the way osmolytes affect the same interaction in cryoprotection. In this Communication we explore the effect of cold on the interaction between two charged surfaces immersed in ternary solution containing salt and osmolyte and find that show more
  • 9 Oct 2018 Journal of the American Chemical Society

    Zwitterionic Osmolytes Resurrect Electrostatic Interactions Screened by Salt

    Many cells synthesize significant quantities of zwitterionic osmolytes to cope with the osmotic stress induced by excess salt. In addition to their primary role in balancing osmotic pressure, these osmolytes also help stabilize protein structure and restore enzymatic activity compromised by high ionic strength. This osmoprotective effect has been studied extensively show more
  • 24 Jul 2018 Journal of the American Chemical Society

    Three-Dimensional Characterization of Layers of Condensed Gas Molecules Forming Universally on Hydrophobic Surfaces

    Understanding the solvation layer of hydrophobic surfaces is essential for elucidating the interaction between hydrophobic surfaces in aqueous solutions. Despite their importance, little is known on these layers due to the lack of lateral resolution in spectroscopic or scattering experiments and probe instability in the static scanning probe methods used in most show more
  • 22 Mar 2018 Nano Letters

    Hydration Structure of a Single DNA Molecule Revealed by Frequency-Modulation Atomic Force Microscopy

    Hydration interaction shapes biomolecules and is a dominant intermolecular force. Mapping the hydration patterns of biomolecules is therefore essential for understanding molecular processes in biology. Numerous studies have been devoted to this challenge, but current methods cannot map the hydration of single biomolecules, let alone do so under physiological conditions show more
  • 16 Oct 2017 Journal of the American Chemical Society

    Regulation of Surface Charge by Biological Osmolytes

    Osmolytes, small molecules synthesized by all organisms, play a crucial role in tuning protein stability and function under variable external conditions. Despite their electrical neutrality, osmolyte action is entwined with that of cellular salts and protons in a mechanism only partially understood. To elucidate this mechanism, we utilize an ultrahigh-resolution frequency show more
  • 28 Feb 2017 Langmuir

    New Information on the Hydrophobic Interaction Revealed by Frequency Modulation AFM

    Using ultrahigh resolution atomic force microscopy (AFM) operated in frequency modulation mode, we extend existing measurements of the force acting between hydrophobic surfaces immersed in water in three essential ways. (1) The measurement range, which was previously limited to distances longer than 2–3 nm, is extended to cover all distances, down to contact. The show more
  • 14 May 2016 Current Opinion in Colloid and Interface Science

    Reversed Hofmeister series-The rule rather than the exception

    Over recent years, the supposedly universal Hofmeister series has been replaced by a diverse spectrum of direct, partially altered and reversed series. This review aims to provide a detailed understanding of the full spectrum by combining results from molecular dynamics simulations, Poisson–Boltzmann theory and AFM experiments. Primary insight into the origin of the show more
  • 16 Feb 2016 Current Opinion in Colloid and Interface Science

    The inevitable accumulation of large ions and neutral molecules near hydrophobic surfaces and small ions near hydrophilic ones

    The present contribution offers a unified explanation to three central phenomena in physical chemistry of interfaces in contact with aqueous solution: (1) Accumulation of large anions at the air/water interface. (2) Accumulation of neutral gas molecules near hydrophobic surfaces and the resulting hydrophobic interaction between two such surfaces, and (3) The Hofmeister show more
  • 30 Apr 2013 Langmuir

    The governing role of surface hydration in ion specific adsorption to silica: an AFM-based account of the Hofmeister universality and its reversal

    AFM measurements of the force acting between silica surfaces in the presence of varied alkali chloride salts and pH’s elucidate the origin of the Hofmeister adsorption series and its reversal. At low pH, electrostatics is shown to be insignificant. The preferential adsorption of Cs+ to the silica surface is traced to the weak hydration of neutral silanols and the show more
  • 26 May 2012 ACS Nano

    Hollow Nanoneedle Array and Its Utilization for Repeated Administration of Biomolecules to the Same Cells

    We present a novel hollow nanoneedle array (NNA) device capable of simultaneously delivering diverse cargo into a group of cells in a culture over prolonged periods. The silica needles are fed by a common reservoir whose content can be replenished and modified in real time while maintaining contact with the same cells. The NNA, albeit its submicrometer features, is show more
  • 6 Feb 2009 Langmuir

    From Repulsion to Attraction and Back to Repulsion: The Effect of NaCl, KCl, and CsCl on the Force between Silica Surfaces in Aqueous Solution

    The force between silica surfaces in NaCl, KCl and CsCl aqueous solutions is studied at pH 5.5 using an atomic force microscope (AFM). As ion concentration is increased, more cations adsorb to the negatively charged silica, gradually neutralizing the surface charge, hence, suppressing the electrostatic double layer repulsion and revealing van der Waals attraction. At show more
  • 13 Sep 2008 Nano Letters

    A two-state electronic antigen and an antibody selected to discriminate between these states

    Inspired by biology where pathways are triggered and suppressed by specific binding of two molecules, we realize a functional interface between electronics and biology by replacing one of the pair molecules with a two-state "electronic antigen" device comprising a hydroquinone monolayer assembled on gold, and choosing for the pair molecule an antibody that discriminates show more
  • 3 Aug 2006 Nano Letters

    Antibody Molecules Discriminate between Crystalline Facets of a Gallium Arsenide Semiconductor

    Seamless integration of biomolecules with manmade materials will most likely rely on molecular recognition and specific binding. In the following we show that combinatorial antibody libraries, based on the vast repertoire of the human immune system, can be harnessed to generate such binders. As a demonstration, we isolate antibody fragments that discriminate and bind show more
  • 3 May 2006 Physical Review Letters

    Short Range Attraction between Two Similarly Charged Silica Surfaces

    Using an atomic force microscope we measure the interaction between two identically charged silica surfaces in the presence of a saline solution. For pure NaCl the interaction is always repulsive. Upon addition of cobalt hexamine ions, Co(NH3)6+3, the repulsion is gradually suppressed and a pronounced attraction develops at distances show more
  • 21 Nov 2003 Science

    DNA-Templated Carbon Nanotube Field-Effect Transistor

    The combination of their electronic properties and dimensions makes carbon nanotubes ideal building blocks for molecular electronics. However, the advancement of carbon nanotube-based electronics requires assembly strategies that allow their precise localization and interconnection. Using a scheme based on recognition between molecular building blocks, we report the show more
  • 5 Jul 2002 Science

    Sequence-specific molecular lithography on single DNA molecules

    Recent advances in the realization of individual molecular-scale electronic devices emphasize the need for novel tools and concepts capable of assembling such devices into large-scale functional circuits. We demonstrated sequence-specific molecular lithography on substrate DNA molecules by harnessing homologous recombination by RecA protein. In a sequence-specific manner show more
  • 19 Feb 1998 Nature

    DNA-templated assembly and electrode attachment of a conducting silver wire

    Recent research in the field of nanometre-scale electronics has focused on two fundamental issues: the operating principles of small-scale devices, and schemes that lead to their realization and eventual integration into useful circuits. Experimental studies on molecular to submicrometre quantum dots and on the electrical transport in carbon nanotubes have confirmed show more
  • 5 Aug 1996 Physical Review Letters

    Mesoscopic Fluctuations in the Ground State Energy of Disordered Quantum Dots

    The ground state energy of disordered quantum dots is studied experimentally as a function of dot population. The fluctuations are found to be considerably larger than those predicted by random matrix theory and to display different statistics. Exact diagonalization of the Hamiltonian pertaining to small clusters shows, indeed, that the random matrix statistics holds show more
  • 24 Feb 1992 Physical Review Letters

    Coupled electron-hole transport

    We report on transport measurements in a novel system composed of two parallel 2D electron and hole gases separated by a barrier which is high enough to prevent tunneling and recombination while thin enough to allow for strong interlayer Coulomb interaction. Separate electrical contacts to each layer and independent control of both carrier densities facilitate a detailed show more
  • 8 Apr 1991 Physical Review Letters

    Interference and dephasing by electron-electron interaction on length scales shorter than the elastic mean free path

    A modified Young's double-slit experiment is realized for electrons in a high-mobility two-dimensional electron gas (2DEG). The observed quantum interference is employed to study dephasing by electron-electron interaction on length scales shorter than the elastic mean free path. It is found that the measured phase-breaking length agrees very well with theoretical show more
  • 1 Jan 1986 Physical Review B

    Multichannel Landauer formula for thermoelectric transport with application to thermopower near the mobility edge

    Various thermoelectric linear transport coefficients are defined and calculated for two reservoirs connected with ideal multichannel leads and a segment of an arbitrary disordered system. The reservoirs have different temperatures and chemical potentials. All of the inelastic scattering (and, thus, the dissipation) is assumed to occur only in the reservoirs. The show more