Daniel E. Morse

University of California, Santa Barbara, Santa Barbara, California, United States

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Publications (212)1079.46 Total impact

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    ABSTRACT: Amorphous carbon is widely used as a support for Pt nanoparticle catalysts. We show here that catalytic performance can be greatly improved by functionalizing the carbon support with a nitrogen-containing molecule, in conjunction with a new method for the in situ synthesis of nanocrystalline Pt. Vulcan® carbon black is covalently functionalized with 4-aminomethylpyridine (4AMP) via formation of an acid chloride on the surface followed by amidation. The resulting 4AMP-functionalized Vulcan® (4AMP-VC) was thoroughly characterized and shown to contain N at the surface of the Vulcan® carbon support. Pt nanoparticles grown on the 4AMP-VC have a smaller average size and much narrower size distribution than Pt nanoparticles grown on bare Vulcan® (VC). In addition, the Pt/4AMP-VC catalysts show higher catalytic activity and are more durable than their Pt/VC counterparts. We infer through careful analysis of X-ray photoelectron spectra that the Pt nanoparticles bind preferentially to the pyridinic nitrogen of the 4AMP.
    Carbon. 01/2015; 81.
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    ABSTRACT: 'Giant' tridacnid clams have evolved a three-dimensional, spatially efficient, photodamage-preventing system for photosymbiosis. We discovered that the mantle tissue of giant clams, which harbours symbiotic nutrition-providing microalgae, contains a layer of iridescent cells called iridocytes that serve to distribute photosynthetically productive wavelengths by lateral and forward-scattering of light into the tissue while back-reflecting non-productive wavelengths with a Bragg mirror. The wavelength- and angle-dependent scattering from the iridocytes is geometrically coupled to the vertically pillared microalgae, resulting in an even re-distribution of the incoming light along the sides of the pillars, thus enabling photosynthesis deep in the tissue. There is a physical analogy between the evolved function of the clam system and an electric transformer, which changes energy flux per area in a system while conserving total energy. At incident light levels found on shallow coral reefs, this arrangement may allow algae within the clam system to both efficiently use all incident solar energy and avoid the photodamage and efficiency losses due to non-photochemical quenching that occur in the reef-building coral photosymbiosis. Both intra-tissue radiometry and multiscale optical modelling support our interpretation of the system's photophysics. This highly evolved 'three-dimensional' biophotonic system suggests a strategy for more efficient, damage-resistant photovoltaic materials and more spatially efficient solar production of algal biofuels, foods and chemicals.
    10/2014;
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    ABSTRACT: The synthesis and characterization of highly ordered three-dimensional photonic crystals have been the subjects of intense study over the past two decades due to the unique ability of these structures to control light at the nanoscale. Building on that work in recent years, increasing interest is now focused on the unique optical properties of disordered and quasi-ordered photonic structures. We present a study of the effects of shape anisotropy and disorder on the specular reflection properties of polymer-based colloidal films comprised of rod-shaped subunits of varying aspect ratio. We characterize the specular reflectance properties of these films as a function of their increasing levels of disorder, demonstrating progressive transition from resonant reflection to diffuse reflection. The onset of the diffuse reflection is governed by particle size. © 2014 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2014
    Journal of Polymer Science Part B Polymer Physics 04/2014; 52(9). · 2.22 Impact Factor
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    ABSTRACT: Organisms of the phylum Porifera, that is, sponges, utilize enzymatic hydrolysis to concatenate bioavailable inorganic silicon to produce lightweight, strong, and often flexible skeletal elements called spicules. In their optical transparency, these remarkable biomaterials resemble fused silica, despite having been formed under ambient marine biological conditions. Although previous studies have elucidated the chemical mechanisms of spicule formation and revealed the extensive hydration of these glasses, their precise composition and local and medium-range structures had not been determined. We have employed a combination of compositional analysis, 1H and 29Si solid-state nuclear magnetic resonance spectroscopy, and synchrotron X-ray total scattering to characterize spicule-derived silica produced by the demosponge Tethya aurantia. These studies indicate that the materials are highly hydrated, but in an inhomogeneous manner. The spicule-derived silica is, on average, perfectly dense for the given extent of hydration and regions of fully condensed and unstrained SiO networks persist throughout each monolithic spicule. To accommodate chemical strain and defects, the extensive hydration is concentrated in distinct regions that give rise to mesostructural features. The chemistry responsible for producing spicule silica resembles hydrolytic sol-gel processing, which offers exceptional control over the precise local atomic arrangement of materials. However, the specific processing involved in forming the sponge spicule silica further results in regions of fully condensed silica coexisting with regions of incomplete condensation. This mesostructure suggests a mechanism for atomistic defect tolerance and strain relief that may account for the unusual mechanical properties of the biogenic spicules.
    Chemistry - A European Journal 03/2014; · 5.93 Impact Factor
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    ABSTRACT: A high-rate, continuous synthesis of functional nanomaterials using a home engineered reactor is reported. The reactor is able to produce low-cost, kilogram-scale BaTiO3 nanopowders with a nanocrystalline particle size less than 30 nm at mild temperatures (<100 °C) and ambient pressure. Nebulization and collision of warm microdroplets (60–80 °C) of Ba(OH)2 and Ti(O-nBu)4 very quickly result in total hydrolysis and subsequent conversion to BaTiO3, yielding 1.3 kg/day of high purity, highly crystalline nanoparticles (25–30 nm). This synthesis procedure also enables high-rate production of TiO2 anatase (2.9 kg/day). It therefore provides a general platform for processing and scaling up of functional inorganic nanomaterials under very mild conditions.
    Advanced Functional Materials 03/2014; 24(9). · 10.44 Impact Factor
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    ABSTRACT: Loliginid squid dynamically tune the structural iridescence of cells in their skin for active camouflage and communication. Bragg reflectors in these cells consist of membrane-bound lamellae periodically alternating with low refractive index extracellular spaces; neuronal signalling induces condensation of the reflectin proteins that fill the lamellae, consequently triggering the expulsion of water. This causes an increase in refractive index within the lamellae, activating reflectance, with the change in lamellar thickness and spacing progressively shifting the wavelength of reflected light. We used micro-spectrophotometry to measure the functionally relevant refractive index of the high-index lamellae of the Bragg reflectors containing the condensed reflectins in chemically fixed dermal iridocytes of the squid, Doryteuthis opalescens. Our high-magnification imaging spectrometer allowed us to obtain normalized spectra of optically distinct sections of the individual, subcellular, multi-layer Bragg stacks. Replacement of the extracellular fluid with liquids of increasing refractive index allowed us to measure the reflectivity of the Bragg stacks as it decreased progressively to 0 when the refractive index of the extracellular medium exactly matched that of the reflectin-filled lamellae, thus allowing us to directly measure the refractive index of the reflectin-filled lamellae as ncondensed lamellae ≈ 1.44. The measured value of the physiologically relevant ncondensed lamellae from these bright iridocytes falls within the range of values that we recently determined by an independent optical method and is significantly lower than values previously reported for dehydrated and air-dried reflectin films. We propose that this directly measured value for the refractive index of the squid's Bragg lamellae containing the condensed reflectins is most appropriate for calculations of reflectivity in similar reflectin-based high-index layers in other molluscs.
    Journal of The Royal Society Interface 01/2014; 11(95):20140106. · 4.91 Impact Factor
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    ABSTRACT: DNA-based information systems drive the combinatorial optimization processes of natural evolution, including the evolution of biominerals. Advances in high-throughput DNA sequencing expand the power of DNA as a potential information platform for combinatorial engineering, but many applications remain to be developed due in part to the challenge of handling large amounts of sequence data. Here we employ high-throughput sequencing and a recently developed clustering method (AutoSOME) to identify single-stranded DNA sequence families that bind specifically to ZnO semiconductor mineral surfaces. These sequences were enriched from a diverse DNA library after a single round of screening, whereas previous screening approaches typically require 5-15 rounds of enrichment for effective sequence identification. The consensus sequence of the largest cluster was poly-d(T)30. This consensus sequence exhibited clear aptamer behavior and was shown to promote the synthesis of crystalline ZnO from aqueous solution at near-neutral pH. This activity is significant, as the crystalline form of this wide-bandgap semiconductor is not typically amenable to solution synthesis in this pH range. High-resolution TEM revealed that this DNA synthesis route yields ZnO nanoparticles with an amorphous-crystalline core-shell structure, suggesting that the mechanism of mineralization involves nanoscale coacervation around the DNA template. We thus demonstrate that our new method, termed Single round Enrichment of Ligands by deep Sequencing (SEL-Seq), can facilitate biomimetic synthesis of technological nanomaterials by accelerating combinatorial selection of biomolecular-mineral interactions. Moreover, by enabling direct characterization of sequence family demographics, we anticipate that SEL-Seq will enhance aptamer discovery in applications employing additional rounds of screening.
    ACS Nano 12/2013; · 12.03 Impact Factor
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    ABSTRACT: Loliginid squid use tunable multilayer reflectors to modulate the optical properties of their skin for camouflage and communication. Contained inside specialized cells called iridocytes, these photonic structures have been a model for investigations into bio-inspired adaptive optics. Here, we describe two distinct sexually dimorphic tunable biophotonic features in the commercially important species Doryteuthis opalescens: bright stripes of rainbow iridescence on the mantle just beneath each fin attachment and a bright white stripe centered on the dorsal surface of the mantle between the fins. Both of these cellular features are unique to the female; positioned in the same location as the conspicuously bright white testis in the male, they are completely switchable, transitioning between transparency and high reflectivity. The sexual dimorphism, location and tunability of these features suggest that they may function in mating or reproduction. These features provide advantageous new models for investigation of adaptive biophotonics. The intensely reflective cells of the iridescent stripes provide a greater signal-to-noise ratio than the adaptive iridocytes studied thus far, while the cells constituting the white stripe are adaptive leucophores - unique biological tunable broadband scatterers containing Mie-scattering organelles activated by acetylcholine, and a unique complement of reflectin proteins.
    Journal of Experimental Biology 10/2013; 216(Pt 19):3733-41. · 3.24 Impact Factor
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    ABSTRACT: A biologically inspired synthesis method is presented as a new tool for the design of novel electrochemically active materials, focusing on the advantages for fuel cell development. The need for cost-effective, high-performance materials is driving contemporary fuel cell research, with the expectation that advances in synthetic methods will be necessary for commercialization of this energy technology. Highly active electrocatalysts for proton-exchange-membrane (PEM) fuel cells are being developed, by combining a kinetically controlled synthesis method of the nanocrystalline metal catalyst with the mesoscale assembly of two morphologically different carbon building blocks of the supporting matrix. These methods provide access to new combinations of porosity, conductivity and electrochemical hydrogen oxidation. The relationships between the porous morphologies of the carbon matrices, the sizes of the platinum nanocrystals and their resulting electrochemical activities are discussed, correlating these with the relevant fuel cell principles.
    Advanced Functional Materials 09/2013; 23(36). · 10.44 Impact Factor
  • Christopher L. Kitting, Daniel E. Morse
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    ABSTRACT: Detailed examinations of an algal-microherbivore symbiosis have revealed mutualistic components of such herbivore-plant interactions. High-resolution photomicroscopy and experimental analyses in the field and laboratory were used to evaluate effects of foraging by Haliotis rufescens (red abalone) postlarvae ˜ 200 μm in length, on their encrusting red algal hosts, Lithothamnion (=Lithothamnium) californicum, Lithophyllum lichenare, and Hildenbrandia rubra (=H. prototypus). We have quantified the microscopic food availability, postlarval foraging behaviour, changes in stomach and faecal contents, growth, and mutualistic effects of grazing. Host algae were found to benefit both from a reduction in coverage by epiphytic algae, and from enhancement of vegetative growth.
    Molluscan Research 06/2013; 18(2):183-196. · 0.62 Impact Factor
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    ABSTRACT: Squids have used their tunable iridescence for camouflage and communication for millions of years; materials scientists have more recently looked to them for inspiration to develop new "biologically inspired" adaptive optics. Iridocyte cells produce iridescence through constructive interference of light with intracellular Bragg reflectors. The cell's dynamic control over the apparent lattice constant and dielectric contrast of these multilayer stacks yields the corresponding optical control of brightness and color across the visible spectrum. Here, we resolve remaining uncertainties in iridocyte cell structure and determine how this unusual morphology enables the cell's tunable reflectance. We show that the plasma membrane periodically invaginates deep into the iridocyte to form a potential Bragg reflector consisting of an array of narrow, parallel channels that segregate the resulting high refractive index, cytoplasmic protein-containing lamellae from the low-index channels that are continuous with the extracellular space. In response to control by a neurotransmitter, the iridocytes reversibly imbibe or expel water commensurate with changes in reflection intensity and wavelength. These results allow us to propose a comprehensive mechanism of adaptive iridescence in these cells from stimulation to color production. Applications of these findings may contribute to the development of unique classes of tunable photonic materials.
    Proceedings of the National Academy of Sciences 01/2013; · 9.81 Impact Factor
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    ABSTRACT: Cephalopods (e.g. octopus, squid and cuttlefish) dynamically tune the colour and brightness of their skin for camouflage and communication using specialized skin cells called iridocytes. We use high-resolution microspectrophotometry to investigate individual tunable Bragg structures (consisting of alternating reflectin protein-containing, high-refractive index lamellae and low-refractive index inter-lamellar spaces) in live and chemically fixed iridocytes of the California market squid, Doryteuthis opalescens. This subcellular, single-stack microspectrophotometry allows for spectral normalization, permitting use of a transfer-matrix model of Bragg reflectance to calculate all the parameters of the Bragg stack-the refractive indices, dimensions and numbers of the lamellae and inter-lamellar spaces. Results of the fitting analyses show that eight or nine pairs of low- and high-index layers typically contribute to the observed reflectivity in live cells, whereas six or seven pairs of low- and high-index layers typically contribute to the reflectivity in chemically fixed cells. The reflectin-containing, high-index lamellae of live cells have a refractive index proportional to the peak reflectivity, with an average of 1.405 ± 0.012 and a maximum around 1.44, while the reflectin-containing lamellae in fixed tissue have a refractive index of 1.413 ± 0.015 suggesting a slight increase of refractive index in the process of fixation. As expected, incremental changes in refractive index contribute to the greatest incremental changes in reflectivity for those Bragg stacks with the most layers. The excursions in dimensions required to tune the measured reflected wavelength from 675 (red) to 425 nm (blue) are a decrease from ca 150 to 80 nm for the high-index lamellae and from ca 120 to 50 nm for the low-index inter-lamellar spaces. Fixation-induced dimensional changes also are quantified, leading us to suggest that further microspectrophotometric analyses of this iridocyte system can be used as a model system to quantify the effects of various methods of tissue fixation. The microspectrophotometry technique described can be expected to provide deeper insights into the molecular and physical mechanisms governing other biophotonically active cells and structures.
    Journal of The Royal Society Interface 01/2013; 10(85):20130386. · 4.91 Impact Factor
  • The Society for Integrative and Comparative Biology; 01/2013
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    The Society for Integrative and Comparative Biology; 01/2013
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    ABSTRACT: The way nature evolves and sculpts materials using proteins inspires new approaches to materials engineering but is still not completely understood. Here, we present a cell-free synthetic biological platform to advance studies of biologically synthesized solid-state materials. This platform is capable of simultaneously exerting many of the hierarchical levels of control found in natural biomineralization, including genetic, chemical, spatial, structural, and morphological control, while supporting the evolutionary selection of new mineralizing proteins and the corresponding genetically encoded materials that they produce. DNA-directed protein expression and enzymatic mineralization occur on polystyrene microbeads in water-in-oil emulsions, yielding synthetic surrogates of biomineralizing cells that are then screened by flow sorting, with light-scattering signals used to sort the resulting mineralized composites differentially. We demonstrate the utility of this platform by evolutionarily selecting newly identified silicateins, biomineralizing enzymes previously identified from the silica skeleton of a marine sponge, for enzyme variants capable of synthesizing silicon dioxide (silica) or titanium dioxide (titania) composites. Mineral composites of intermediate strength are preferentially selected to remain intact for identification during cell sorting, and then to collapse postsorting to expose the encoding genes for enzymatic DNA amplification. Some of the newly selected silicatein variants catalyze the formation of crystalline silicates, whereas the parent silicateins lack this ability. The demonstrated bioengineered route to previously undescribed materials introduces in vitro enzyme selection as a viable strategy for mimicking genetic evolution of materials as it occurs in nature.
    Proceedings of the National Academy of Sciences 06/2012; 109(26):E1705-14. · 9.81 Impact Factor
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    ABSTRACT: In the past, aligned arrays of carbon nanotubes (CNTs) have been observed to exhibit a foam-like dissipative response in compression, garnering attention for possible mechanical applications. Nanoparticles have previously been integrated with graphitic materials for electrochemical applications. Here, we synthesize nanoparticles of SnO2 and MnO2 in the interstices of aligned arrays of CNTs without altering the ordered structure of the arrays, and we characterize their mechanical response. We report that CNT arrays with embedded particles present superior energy dissipation relative to unmodified CNT arrays. In addition, energy dissipation, strain recovery, and structural failure (observed after repeated loading) depend on particle type (SnO2 versus MnO2).
    Carbon 05/2012; 50(12):4432. · 6.16 Impact Factor
  • Advanced Energy Materials 03/2012; 2(3). · 14.39 Impact Factor
  • Hong-Li Zhang, Daniel E. Morse
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    ABSTRACT: Large-scale industrial production of carbon nanotubes (CNTs) has recently become available, but there are relatively few reports of the investigation of these industrially produced bulk CNTs as potential electrode materials for electrochemical energy storage such as lithium-ion batteries (LIBs). Here, we report our evaluation of the electrochemical performance of the industrially produced CNTs from one manufacturer and our utilization of a kinetically controlled, vapor diffusion synthesis method combined with in-situ carbothermal reduction to homogeneously grow nanocrystalline tin (Sn) particles (∼200 nm) in the matrix of the CNTs, yielding a Sn@CNTs composite. After surface coating with a layer of carbon coating (3–4 nm), this composite was transformed to a surface-modified Sn@CNTs composite that exhibited much higher reversible capacity, initial Coulombic efficiency, and rate capacity than the pristine CNTs as anode materials for LIB.
    Journal of Materials Research. 01/2012; 27(02).
  • The Society for Integrative and Comparative Biology; 01/2012
  • The Society for Integrative and Comparative Biology; 01/2012

Publication Stats

6k Citations
1,079.46 Total Impact Points

Institutions

  • 1979–2014
    • University of California, Santa Barbara
      • • Department of Biomolecular Science and Engineering
      • • Institute for Collaborative Biotechnologies
      • • Materials Research Laboratory
      • • Department of Molecular, Cellular, and Developmental Biology
      • • Department of Physics
      • • Marine Science Institute
      Santa Barbara, California, United States
  • 2007–2013
    • CSU Mentor
      Long Beach, California, United States
  • 2011
    • University of Bologna
      • Interdepartmental Research Centre for Environmental Sciences
      Bologna, Emilia-Romagna, Italy
  • 2010
    • University of California, Santa Cruz
      • Department of Chemistry & Biochemistry
      Santa Cruz, CA, United States
  • 2008
    • University of Southern California
      • Department of Chemistry
      Los Angeles, CA, United States
  • 2002–2005
    • CUNY Graduate Center
      New York City, New York, United States
  • 2004
    • Vienna University of Technology
      Wien, Vienna, Austria
  • 1984–2003
    • Virginia Institute of Marine Science
      Gloucester Point, Virginia, United States
  • 1999
    • Luleå University of Technology
      Luleå, Norrbotten, Sweden
  • 1998
    • Beverly Hospital, Boston MA
      Beverly, Massachusetts, United States
  • 1997
    • Molecular and Cellular Biology Program
      Seattle, Washington, United States
  • 1992
    • University of Delaware
      Delaware, United States