Benzene Oxidation with Ozone Over MnO(x)/MSU-H and MnO(x)/Mesoporous-SAPO-34 Catalysts.

Two mesoporous silica materials, MSU-H and mesoporous SAPO-34 (Meso-SAPO-34), were applied to the catalytic oxidation with ozone of benzene. The catalysts were characterized by X-ray diffraction, N2 adsorption-desorption, Brunauer-Emmett-Teller specific surface area, and H2-temperature programmed reduction. When MnO(x)/MSU-H was used at three different temperature, 50 degrees C, 80 degrees C, and 100 degrees C, the ozone conversion and CO(x) yield increased with increasing temperature. MnO(x)/MSU-H exhibited much higher catalytic activity than that of MnO(x)/Meso-SAPO-34. The high catalytic activity of MnO(x)/MSU-H seems to be due to the high oxygen ability and structural stability of MSU-H. The CO2 yield was somewhat enhanced by the addition of steam because steam facilitated desorption of the reaction intermediates adsorbed on the catalyst surface, enabling them to be oxidized further.

Fast and continuous microorganism detection using aptamer-conjugated fluorescent nanoparticles on an optofluidic platform.

Fast and accurate pathogen detection in aquatic environments is challenging in many biomedical studies and microbial diagnostic applications. In this study, we developed a real-time, continuous, and non-destructive single cell detection method using target specific aptamer-conjugated fluorescent nanoparticles (A-FNPs) and an optofluidic particle-sensor platform. A-FNPs selectively bound to the surfaces of target bacteria (Escherichia coli) and labeled them with high affinity and selectivity so that target bacteria can be countable particles in an optofluidic particle-sensor. A-FNP-labeled target bacterial complexes were detected by the optofluidic particle-sensing system, which provides rapid and continuous single-cell detection. A-FNPs selectively bound to E. coli with a dissociation constant of 0.83 nM, but did not bind Enterobacter aerogenes or Citrobacter freundii strains, which lacked affinity for the aptamer used. We demonstrated that our optofluidic device achieves a detection throughput of ~100 particles per second with high accuracy (~85%) in detecting single bacterial cells conjugated with A-FNPs. This approach can be immediately extended to the real-time, high-throughput detection of other microorganisms such as viruses that are selectively conjugated with A-FNPs. Collectively, these data suggest that optofluidic systems are widely applicable for the fast and continuous detection of microbial cells.

Electrospray-assisted ultraviolet aerodynamic particle sizer spectrometer for real-time characterization of bacterial particles.

The ultraviolet aerodynamic particle sizer (UVAPS) spectrometer is a novel, commercially available aerosol counter for real-time, continuous monitoring of viable bioaerosols based on the fluorescence induced from living microorganisms. For aerosolization of liquid-based microorganisms, general aerosolization methods such as atomization or nebulization may not be adequate for an accurate and quantitative characterization of the microorganisms because of the formation of agglomerated particles. In such cases, biological electrospray techniques have an advantage because they generate nonagglomerated particles, attributable to the repulsive electrical forces among particles with unipolar charges. Biological electrosprays are quickly gaining potential for the detection and control of living organisms in applications ranging from mass spectrometry to developmental microbiology. In this study, we investigated the size distribution, total concentration, and fluorescence percentage of bacterial particles in a real-time manner by electrospray-assisted UVAPS. A suspension containing Escherichia coli as a test microorganism was sprayed in a steady cone-jet mode using a specially designed electrospray system with a point-to-orifice-plate configuration based on charge-reduced electrospray size spectrometry. With the electrospray process, 98% of the total E. coli particle number concentration had a size of <1 mum and the geometric mean diameter was 0.779 mum, as compared with the respective values of 78% and 0.907 mum after nebulization. The fractions of fluorescence responsive particles and of particles that contained viable organisms in culture were 12% and 7%, respectively, from the electrospray process and 34% and 24% from nebulization. These results demonstrate that (1) the presence of agglomerated particles can lead to markedly overestimated fluorescence and culturability percentages compared with the values obtained from nonagglomerated particles, and (2) electrospray-assisted UVAPS can provide more accurate and quantitative real-time characterization of liquid-based microorganisms, owing to the generation of nonagglomerated particles.