50 research outputs found
Controlled photoluminescence in amorphous-silicon-nitride microcavities
Narrow-band and enhanced photoluminescence have been observed in hydrogenated amorphous-silicon-nitride microcavities. The distributed Bragg reflectors were fabricated using alternating layers of hydrogenated amorphous-silicon nitride and hydrogenated amorphous-silicon oxide. The microcavity resonance wavelength was designed to be at the maximum of the bulk hydrogenated amorphous-silicon-nitride luminescence spectrum. At the microcavity resonance, the phololuminescence amplitude is enhanced, while the photoluminescence linewidth is reduced with respect to the bulk hydrogenated amorphous-silicon nitride. © 2001 American Institute of Physics
Strong enhancement of spontaneous emission in amorphous-silicon-nitride photonic crystal based coupled-microcavity structures
We investigated photoluminescence (PL) from one-dimensional photonic band gap structures. The photonic crystals, a Fabry-Perot (FP) resonator and a coupled-microcavity (CMC) structure, were fabricated by using alternating hydrogenated amorphous-silicon-nitride and hydrogenated amorphous-silicon-oxide layers. It was observed that these structures strongly modify the PL spectra from optically active amorphous-silicon-nitride thin films. Narrow-band and wide-band PL spectra were achieved in the FP microcavity and the CMC structure, respectively. The angle dependence of PL peak of the FP resonator was also investigated. We also observed that the spontaneous emission increased drastically at the coupled-cavity band edge of the CMC structure due to extremely low group velocity and long photon lifetime. The measurements agree well with the transfer-matrix method results and the prediction of the tight-binding approximation
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Synthesis of prebiotic galactooligosaccharides from lactose using bifidobacterial β-galactosidase (BbgIV) immobilised on DEAE-Cellulose, Q-Sepharose and amino-ethyl agarose
The bifidobacterial β-galactosidase BbgIV was immobilised on DEAE-Cellulose and
Q-Sepharose via ionic binding and on amino-ethyl- and glyoxal-agarose via covalent
attachment, and was then used to catalyse the synthesis of galactooligosaccharides (GOS).
The immobilisation yield exceeded 90 % using ionic binding, while it was low using aminoethyl
agarose (25 – 28 %) and very low using glyoxal agarose (< 3 %). This was due to the
mild conditions and absence of chemical reagents in ionic binding, compared to covalent
attachment. The maximum GOS yield obtained using DEAE-Cellulose and Q-Sepharose was
similar to that obtained using free BbgIV (49 – 53 %), indicating the absence of diffusion
limitation and mass transfer issues. For amino-ethyl agarose, however, the GOS yield
obtained was lower (42 – 44 %) compared to that obtained using free BbgIV. All the supports
tried significantly (P < 0.05) increased the BbgIV operational stability and the GOS synthesis
productivity up to 55 °C. Besides, six successive GOS synthesis batches were performed
using BbgIV immobilised on Q-Sepharose; all resulted in similar GOS yields, indicating the
possibility of developing a robust synthesis process. Overall, the GOS synthesis operation
performance using BbgIV was improved by immobilising the enzyme onto solid supports, in
particular on Q-Sepharos
Influence of bloom number and plastifiers on gelatin matrices produced for enzyme immobilization
Production of glucose and fructose syrups from cassava (Manihot esculenta Crantz) starch using enzymes produced by microorganisms isolated from Brazilian Cerrado soil
Strong enhancement of spontaneous emission in hydrogenated amorphous silicon nitride coupled-microcavity structures
The modification of spontaneous emission from the hydrogenated amorphous silicon nitride layers in a coupled-microcavity (CMC) structure was investigated. The CMC structure was composed of alternating silicon-oxide and silicon-nitride multilayers. The results showed that the strong enhancement of spontaneous emisssion can be achieved throughout the cavity band