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Biomedical subjects

Kenneth S Suslick

Publications and source records attributed to Kenneth S Suslick.

At least 19 recordsLinked to original sources
PubMed2007

Colorimetric sensor array for soft drink analysis.

Fourteen commercial soft drinks have been analyzed using colorimetric sensor arrays made from a set of 25 chemically responsive dyes printed on a hydrophobic membrane. Digital imaging of the dye array before and after immersion provides a color change profile as a unique fingerprint for each specific analyte. The digital data library generated was analyzed with statistical and chemometric methods, including principal component analysis (PCA) and hierarchical clustering analysis (HCA). Facile identification of all of the soft drinks was readily achieved using comparison of the color change profiles or a PCA score plot. Using a HCA dendrogram, the misclassification rate was <2%, and even very similar sodas were easily differentiated. In addition, the monitoring of soft drinks as they degas or upon dilution also proved to be possible. This work demonstrates the potential of our colorimetric sensor array technology for quality assurance/control applications of sodas and perhaps other beverages as well.

Carbonated Beverages↗
PubMed2006

Mechanoluminescence: light from sonication of crystal slurries.

Mechanoluminescence, also known as triboluminescence or fractoluminescence, is light emission induced as a result of mechanical action on a solid--for example, Francis Bacon noted as long ago as 1605 that lumps of sugar emitted light when scraped. Here we elicit mechanoluminescence by a new means, acoustic cavitation, and find intense luminescence and emission lines that are not generated by other mechanisms such as grinding, cleaving, rubbing, scratching, biting or thermal shock.

Journal Article↗
PubMed2006

Porous carbon powders prepared by ultrasonic spray pyrolysis.

New, thermally robust meso- and macroporous carbon powders were prepared by ultrasonic spray pyrolysis (USP) of aqueous solutions using an inexpensive high-frequency ultrasound generator from a household humidifier. We choose our molecular precursors rationally, so that the expected decomposition pathways produce only remnant carbon atoms. Specifically, our rational design criterion led to halo-organic carboxylate salts, whose pyrolysis yields well-defined carbon solids with a temporary template being generated in situ, simply an inorganic salt, which is easily dissolved during aqueous workup. The materials have been characterized by SEM, TEM, XRD, 13C NMR MAS, XPS, FTIR spectroscopy, and BET surface area measurements. Changing the alkali metal alters the morphology and pore structure of the final material, which can be explained in terms of the observed differences in the DSC and TGA of the various precursors. This preparatory method provides an extremely facile and versatile method for the generation of meso- and macroporous carbons.

Journal Article↗
PubMed2006

Plasma quenching by air during single-bubble sonoluminescence.

We report the observation of sudden and dramatic changes in single-bubble sonoluminescence (SBSL) intensity (i.e., radiant power, phi(SL)) and spectral profiles at a critical acoustic pressure (P(c)) for solutions of sulfuric acid (H2SO4) containing mixtures of air and noble gas. Nitric oxide (NO), nitrogen (N2), and atomic oxygen emission lines are visible just below P(c). At P(c), very bright (factor of 7000 increase in phi(SL)) and featureless SBSL is observed when Ar is present. In addition, Ar lines are observed from a dimmed bubble that has been driven above P(c). These observations suggest that bright SBSL from H2SO4 is due to a plasma, and that molecular components of air suppress the onset of bright light emission through quenching mechanisms and endothermic processes. Determination of temperatures from simulations of the emission lines shows that air limits the heating during single-bubble cavitation. When He is present, phi(SL) increases by only a factor of 4 at P(c), and the SBSL spectrum is not featureless as for Ar, but instead arises from sulfur oxide (SO) and sulfur dioxide (SO2) bands. These differences are attributed to the high thermal conductivity and ionization potential of He compared to Ar.

Letter↗
PubMed2006

Colorimetric sensor arrays for the analysis of beers: a feasibility study.

Eighteen commercial beers have been analyzed in both liquid and gas phases using colorimetric sensor arrays made from selected chemically responsive dyes printed on a hydrophobic membrane. Digital imaging of the dye array before and after exposure to the complex analytes in either the liquid phase or the head-gas provides a color change profile as a unique fingerprint for the specific analyte. The digital data libraries generated were analyzed using statistical and chemometric methods, including principal component analysis (PCA) and hierarchical clustering analysis (HCA). In either liquid- or gas-phase experiments, facile identification of specific beers was achieved using comparison of the color change profiles; using HCA statistical analysis the error rate of identification was <3%. Differentiation between even very similar beers proved to be straightforward. In addition, differentiation of pristine beer from the effects of watering or decarbonation proved to be possible. These results suggest that colorimetric sensor arrays may prove to be useful for quality assurance/quality control applications of beers and perhaps other beverages.

Beer↗
PubMed2006

Colorimetric sensor arrays for volatile organic compounds.

The development of a low-cost, sensitive colorimetric sensor array for the detection and identification of volatile organic compounds (VOCs) is reported. Using an array composed of chemoresponsive dyes, enormous discriminatory power is possible in a simple device that can be imaged easily with an ordinary flatbed scanner. Excellent differentiation of closely related organic compounds can be achieved, and a library of 100 VOCs is presented. The array discriminates among VOCs by probing a wide range of intermolecular interactions, including Lewis acid/base, Brønsted acid/base, metal ion coordination, hydrogen bonding, and dipolar interactions. Importantly, by proper choice of dyes and substrate, the array is essentially nonresponsive to changes in humidity.

Biosensing Techniques↗
PubMed2006

Formation and characterization of polyglutamate core-shell microspheres.

The need for organ-targeted delivery of drugs and imaging agents creates an interest in biocompatible, biodegradable vesicles. We make protein microspheres using high-intensity ultrasound; these microspheres have a protein shell and a hydrophobic interior, making them ideal for delivering hydrophobic materials. We have previously shown that various proteins, e.g., bovine serum albumin (BSA), form a microsphere shell stabilized by interprotein cross-linking of cysteine residues. In this study, polyglutamate was used to form core-shell microspheres at slightly basic pH using sonication. These particles are smaller than our previous protein microspheres and are stable under conditions encountered in vivo. The stability of polyglutamate microspheres appears to be due to hydrogen bonding networks and not covalent cross-linking.

Biocompatible Materials↗
PubMed2006

Measurement of pressure and density inside a single sonoluminescing bubble.

The average pressure inside a sonoluminescing bubble in sulfuric acid has been determined by two independent techniques: (1) plasma diagnostics applied to Ar atom emission lines, and (2) light scattering measurements of bubble radius vs time. For dimly luminescing bubbles, both methods yield intracavity pressures approximately 1500 bar. Upon stronger acoustic driving of the bubble, the sonoluminescence intensity increases 10,000-fold, spectral lines are no longer resolved, and radius vs time measurements yield internal pressures > 3700 bar. Implications for a hot inner core are discussed.

Journal Article↗
PubMed2006

Tumor targeting by surface-modified protein microspheres.

Protein microspheres have been used in the fields of biomedical imaging and drug delivery, but surface modification for cell targeting has been problematic. We have for the first time used an electrostatic adhesion approach to adhere arginine-glutamic acid-aspartic acid (RGD) containing peptides to the surface of protein microspheres for the purpose of targeting these vesicles to tumor cells. RGD sequences are recognized by integrin membrane receptors, which are overexpressed in various tumors. We have succeeded in modifying the surface of serum albumin core-shell microspheres, which have a fluorescent nonaqueous core by using several polylysine peptides containing the RGD sequence. Fluorescence microscopy reveals that these modified microspheres are selectively bound and taken up by HT29 human colon cancer cells in vitro.

Antineoplastic Agents↗
PubMed2005

Dynamics of a sonoluminescing bubble in sulfuric acid.

The spectral shape and observed sonoluminescence emission from Xe bubbles in concentrated sulfuric acid is consistent only with blackbody emission from a spherical surface that fills the bubble. The interior of the observed 7000 K blackbody must be at least 4 times hotter than the emitting surface in order that the equilibrium light-matter interaction length be smaller than the radius. Bright emission is correlated with long emission times (approximately 10 ns), sharp thresholds, unstable translational motion, and implosions that are sufficiently weak that contributions from the van der Waals hard core are small.

Journal Article↗
PubMed2005

Chemical aerosol flow synthesis of semiconductor nanoparticles.

Nanometer-sized semiconductor particles (quantum dots) have been the subject of intense research during the past decade owing to their novel electronic, catalytic, and optical properties. Fundamental properties of these nanoparticles (1-20 nm diameter) can be systematically changed simply by controlling the size of the crystals while holding their chemical composition constant. We describe here a new methodology for the continuous production of fluorescent CdS, CdSe, and CdTe nanoparticles using ultrasonically generated aerosols of high boiling point solvents. Each submicron droplet serves as a separate nanoscale chemical reactor, with reactions proceeding as the liquid droplets (which hold both reactants and surface stabilizers) are heated in a gas stream. The method is inexpensive, scalable, and allows for the synthesis of high quality nanocrystals. This chemical aerosol flow synthesis (CAFS) can be extended to the synthesis of nanostructured metals, oxides, and other materials.

Aerosols↗
PubMed2005

Magnetic and porous nanospheres from ultrasonic spray pyrolysis.

We have used an inexpensive high-frequency ultrasound generator from a household humidifier to create a useful source for ultrasonic spray pyrolysis and produced submicrometer silica particles that are porous on the nanometer scale. By using two heated zones, we first initiate polymerization of organic monomers in the presence of silica colloid, which creates in situ a composite of silica with an organic polymer, followed by a second heating to pyrolyze and remove the polymer. The morphology and surface area of the final porous silica are controlled by varying the silica-to-organic monomer ratio. In a single flow process, ferromagnetic cobalt nanoparticles can be easily encapsulated in the porous silica, and the resulting nanospheres are extremely resistant to air oxidation. Products were characterized by SEM, (S)TEM, EDS, XPS, and SQUID.

Journal Article↗
PubMed2005

A colorimetric sensor array for organics in water.

Molecular recognition of organic compounds in aqueous solutions is inherently challenging due to the potential interference from the very high concentration of water. Here we present a simple colorimetric sensor array that probes a wide range of chemical properties. By printing hydrophobic dyes on a hydrophobic membrane, sensor arrays are easily prepared that provide substantial chemical selectivity for the identification and quantification of various organics (both single compounds and complex mixtures) dissolved in water. It is possible to differentiate easily even among closely related organic compounds. Upon immersion in aqueous solutions, digital imaging of the dye array before and after exposure to an analyte provide a color change profile that is a fingerprint for the organic components of the solution. Facile identification of a wide variety of aqueous organic solutions is possible over a concentration range of 0.1 M to 1 muM. Complex mixtures present no inherent difficulty; for example, a series of commercial soft drinks were easily distinguished using the colorimetric sensor array approach.

Colorimetry↗
PubMed2005

Plasma line emission during single-bubble cavitation.

Emission lines from transitions between high-energy states of noble-gas atoms (Ne, Ar, Kr, and Xe) and ions (Ar(+), Kr(+), and Xe(+)) formed and excited during single-bubble cavitation in sulfuric acid are reported. The excited states responsible for these emission lines range 8.3 eV (for Xe) to 37.1 eV (for Ar(+)) above the respective ground states. Observation of emission lines allows for identification of intracavity species responsible for light emission; the populated energy levels indicate the plasma generated during cavitation is comprised of highly energetic particles.

Journal Article↗
PubMed2005

Porous MoS2 synthesized by ultrasonic spray pyrolysis.

The hydrodesulfurization (HDS) activity of molybdenum sulfide-based catalysts is localized to the edges of this layered solid and is, therefore, highly dependent on the technique used to prepare the material. Here, ultrasonic spray pyrolysis (USP) was used to synthesize porous, nanostructured MoS2. Low surface area powders, not useful for catalysis, are generally produced by USP. This work shows that when combined with a dissolvable template, USP is capable of producing high surface area materials. An aqueous solution of ammonium tetrathiomolybdate and colloidal silica was nebulized and pyrolyzed to give a MoS2/SiO2 composite material. Leaching with HF removed the sacrificial SiO2, resulting in a highly porous MoS2 network with surface areas as high as 250 m2/g. Cobalt-promoted MoS2 networks were also synthesized. The thiophene HDS activities of these materials were substantially higher than those of unsupported MoS2 and RuS2 standards, illustrating the enhanced dispersion of the HDS active phase achieved by this synthetic technique.

Journal Article↗
PubMed2005

Plasma formation and temperature measurement during single-bubble cavitation.

Single-bubble sonoluminescence (SBSL) results from the extreme temperatures and pressures achieved during bubble compression; calculations have predicted the existence of a hot, optically opaque plasma core with consequent bremsstrahlung radiation. Recent controversial reports claim the observation of neutrons from deuterium-deuterium fusion during acoustic cavitation. However, there has been previously no strong experimental evidence for the existence of a plasma during single- or multi-bubble sonoluminescence. SBSL typically produces featureless emission spectra that reveal little about the intra-cavity physical conditions or chemical processes. Here we report observations of atomic (Ar) emission and extensive molecular (SO) and ionic (O2+) progressions in SBSL spectra from concentrated aqueous H2SO4 solutions. Both the Ar and SO emission permit spectroscopic temperature determinations, as accomplished for multi-bubble sonoluminescence with other emitters. The emissive excited states observed from both Ar and O2+ are inconsistent with any thermal process. The Ar excited states involved are extremely high in energy (>13 eV) and cannot be thermally populated at the measured Ar emission temperatures (4,000-15,000 K); the ionization energy of O2 is more than twice its bond dissociation energy, so O2+ likewise cannot be thermally produced. We therefore conclude that these emitting species must originate from collisions with high-energy electrons, ions or particles from a hot plasma core.

Journal Article↗
PubMed2005

Sonochemical preparation of hollow nanospheres and hollow nanocrystals.

Ceramic hollow spheres of MoS2 and MoO3 were obtained by sonochemical synthesis of MoS2 and MoO3 templated on silica nanoparticles (diameters 50-500 nm) followed by acid etching to remove the silica core. The resulting hollow materials have been characterized by elemental analysis, XPS, SEM, TEM, optical absorption, and hydrodesulfurization (HDS) studies. The TEM studies on the hollow ceramic materials indicate the formation of dispersed free spheres with a hollow core. The hollow materials obtained from thermally treated MoS2/SiO2 (450-700 degrees C) show the formation of layered MoS2 (lattice fringes approximately 6.2 A) with a wall thickness of 6-8 layers. The MoS2 hollow spheres are extremely active catalysts for the HDS of thiophene. Hollow spheres of MoO3 are prepared in a similar fashion. Surprisingly, upon heating, hollow crystals of MoO3 with sharp-edged truncated cubes containing inner voids are formed from the initial spheres.

Journal Article↗