Projects | ISG

Silver nanoparticle synthesis by hemoglobin modified electrodes

Wed, 27 May 2020 00:00:00 +0000

We report a novel electrochemical approach for synthesising colloidal silver in aqueous phase by means of a haemoglobin-modified boron-doped diamond electrode. The resulting Ag nanoparticles are within 10 nm size and highly monodisperse with minimal electrode deposition. We also introduce a method for measuring the yield of synthesised nanoparticles using square-wave voltammetry as an alternative to UV-vis spectroscopy. More than 50% of transferred electrons contributed directly to the formation of silver nanoparticles. This high yield indicates that such electrochemical synthesis is an efficient one-pot method for producing colloidal silver free of toxic reagents and offers a path toward green metal nanoparticle synthesis in solution. A comparative study using alternative electrodes, modifiers and surfactants suggests a mechanism for the formation of silver nanoparticles mediated by haemoglobin-modified boron-doped diamond.

Nanocarbon and nanodiamond for high performance phenolics sensing

Thu, 27 Sep 2018 00:00:00 +0000

Phenolic compounds are pollutants of major concern, and effective monitoring is essential to reduce exposure. Electrochemical sensors offer rapid and accurate detection of phenols but suffer from two main shortcomings preventing their widespread use: electrode fouling and signal interference from co-existing isomers. Here we demonstrate a potential solution based on environmentally friendly and biocompatible carbon nanomaterials to detect monophenols (phenol and cresol) and biphenols (hydroquinone and catechol). Electrode fouling is tackled in two ways: by introducing electrochemically resistant nanodiamond electrodes and by developing single-use nanocarbon electrodes. We provide a comprehensive analysis of the electrochemical performance of three distinct carbon materials (graphene, nanodiamond and nanocarbon). Nanocarbon exhibits the lowest detection limit below 10−8 M, and one order of magnitude higher sensitivity than the other carbon nanomaterials. We detect co-existing phenol isomers with nanocarbon electrodes and apply it in river water and green tea samples, which may pave the way towards low-cost industrial scale monitoring of phenolic compounds.

Enzymatic nanomotors carrying a DNA cargo

Fri, 27 Jul 2018 00:00:00 +0000

A physical theory of the biological world requires that we quantitavely understand Active matter. These are systems that are maintained out-of-equilibrium and are capable of sustained motion, while they consume energy from their environment.

Molecular motors (kinesin, myosin, etc.) are examples of active matter at the nanoscale that convert ATP into mechanical energy in an environment dominated by thermal fluctuations and viscous forces. What are the physical constraints we have to overcome to manufacture devices of comparable complexity? . From first principles, we make use of simple building blocks, such as nanoparticles, enzymes and nucleic acids in order to self-assemble nanodevices capable of mimicking molecular motors, the workhorses of cells. With the tools of DNA nanotechnology we can self-assemble nanostructures from bottom-up (DNA Origami) and functionalise site-specifically these nanostructures with nanomotors. We use catalytic nanoparticles, as well as enzymes to help reach propulsion that goes beyond diffusion.

Bottom-up synthesis of catalytic nanomotors

Fri, 27 Apr 2018 00:00:00 +0000

Progress in nanotechnology has enabled the synthesis of active particles that can harness chemical energy and translate it into useful work. Catalytic self-propelled motors have implications for understanding out-of-equilibrium systems and have potential applications in active transport at the nanoscale, where they can be used as motors and pumps. Although much research has been done on micron-sized motors, progress in catalytic nanomotors of sub 100?nm is still in its infancy. These nanosized motors are of great importance for future molecular transport at the cellular level because they operate at length scales at which protein motors work. This opinion article focusses on recent advances in the synthesis of catalytic nanomotors and experimental strategies to measure their self-propulsion, which differ from that of micromotors. Enzymatic and metallic nanomotors are surveyed, together with various theoretical models for self-propulsion. Solutions to current challenges are proposed, which include a chemical synthesis approach, new characterisation of motor activity and potential uses of nanomotors in nanomedicine.

2D DNA self-assembled surfaces

Thu, 27 Apr 2017 00:00:00 +0000

Biomolecular self-assembly, using DNA as the building blocks of nanometre-scale structures, can be used to pattern surfaces with near-atomic precision. By combining this new technique with liquid crystal technology we have created DNA tiles that can be used as surfaces for testing liquid crystal (LC) alignment.

Here we explore two different approaches: on the one hand a two-layer Origami structure was used, on the other DNA brick/crystals of finite depth were assembled. TEM, AFM and fluorescence microscopy were used to assess the size and surface coverage of the tiles. DNA bricks grew to structures of the order of a micrometer and could be visualised by fluorescence microscopy. These were further developed by introducing a ridge pattern of 10 nm on the DNA surface. Liquid crystal molecules were deposited by inkjet printing and by spin-coating, achieving a LC thickness of few micrometers.

The experimental approach in this project consisted of finding the right DNA self-assembled surface, deposit it on the right substrate, visualise and characterise it. Finally, the liquid crystal was deposited on this surface to study any alignment induced by DNA.

Such structures provide a unique opportunity for studying complex intermolecular interactions at the nanometre scale and give access to a range of application spaces beyond next-generation liquid crystal displays.

Nanoimpact voltammetry of enzymatic nanomotors

Thu, 27 Apr 2017 00:00:00 +0000

DNA Nanoflowers

Wed, 27 Apr 2016 00:00:00 +0000

DNA-guided nanoparticle lattices are promising model systems for exploring the controlled assembly of matter. Ordered arrays of gold and silver nanoparticles, for example, are promising building blocks for plasmonic metamaterials.

In this work we created DNA Origami structures to allow flexible control of the effective valency and bond angles of encapsulated gold nanoparticles. These ‘nanoflower’ shaped hybrid nanostructures could be reprogrammed through a number of DNA linker strands to create lattices of different symmetries (hexagonal, square and linear chains).

DNA autocatalytic chemical waves

Mon, 27 Apr 2015 00:00:00 +0000

Bose-Fermi Mixture Immersed in a Fermi Sea

Wed, 27 Apr 2011 00:00:00 +0000

Mixtures of Ultracold Quantum Gases

In the experiment Fermi 1 at the Centre for Ultracold Atoms (CUA) of the Massachusetts Institute of Technology, we created a triply quantum degenerate mixture of bosonic 41K and two fermionic species, 40K and 6Li. In the group of Prof. Martin Zwierlein we built and used Fermi 1 to show that 41K is an efficient coolant for the two fermions, giving a versatile instrument for the observation of fermionic superfluids with imbalanced masses.

Experimental setup of Fermi 1. Two independent Zeeman slowers yield a high flux of $^{6}$Li and K allowing simultaneous loading and trapping in a UHV chamber of three atomic species: fermionic $^{6}$Li and $^{40}$K and bosonic $^{41}$K

More info: LiNaK : multi-species apparatus for the study of ultracold quantum degenerate mixtures by Ibon Santiago

Strongly Interacting Isotopic Bose-Fermi Mixture Immersed in a Fermi Sea

a)-c): Absorption images of triply degenerate quan- tum gases of 41 K, 40 K and 6 Li, imaged after 8.12 ms, 4.06 ms and 1 ms time of flight from the magnetic trap, respectively. The final rf-knife frequency was 500 kHz above the 254.0 MHz hyperfine transition of 41K. The white circles indicate the Fermi radius in time of flight t, RF = 2EF /m t. d)-f): Azimuthally averaged column density. Solid dots: gaussian fit to the wings of the column density. Solid black and blue lines are gaussian and Fermi-Dirac fits to the entire profile.

Bose-Fermi mixture of Na-K

Wed, 27 Apr 2011 00:00:00 +0000

We have created a quantum degenerate Bose-Fermi mixture of 23Na and 40K with widely tuneable interactions via broad interspecies Feshbach resonances. Over 30 Feshbach resonances between 23Na and 40K were identified, including p-wave multiplet resonances. The large and negative triplet background scattering length between 23Na and 40K causes a sharp enhancement of the fermion density in the presence of a Bose condensate. As explained via the asymptotic bound-state model, this strong background scattering leads to wide Feshbach resonances observed at low magnetic fields. Our work opens up the prospect to create chemically stable, fermionic ground-state molecules of 23Na-40K, where strong, long-range dipolar interactions would set the dominant energy scale.