Following the biocatalytic activities of glucose oxidase by electrochemically cross-linked enzyme-Pt nanoparticles composite electrodes

An integrated platinum nanoparticles (NPs)/glucose oxidase (GOx) composite film associated with a Au electrode is used to follow the biocatalytic activities of the enzyme. The film is assembled on a Au electrode by the electropolymerization of thioaniline-functionalized Pt NPs and thioaniline-modified GOx. The resulting enzyme/Pt NPs-functionalized electrode stimulates the O 2 oxidation of glucose to gluconic acid and H 2O 2. The modified electrode is then implemented to follow the activity of the enzyme by the electrochemical monitoring of the generated H 2O 2. The effect of the composition of the Pt NPs/GOx cross-linked nanostructures and the optimal conditions for the preparation of the electrodes are discussed.     

Sensing and Biosensing with Semiconductor Quantum Dots

Due to an internal error, the following article was added after the original publication of the special issue on Nanochemistry (11-12/2012). Semiconductor quantum dots (QDs) exhibit unique photophysical properties, turning these nanomaterials into ideal components for the development of optical or optoelectronic sensors and biosensors. Various methods and mechanisms of using QDs for sensing have been implemented, including the probing of recognition events by the luminescence of the QDs, their application in fluorescence resonance energy transfer (FRET), electron transfer (ET), chemiluminescence resonance energy transfer (CRET), and photoelectrochemical generation of photocurrents. These different mechanisms are exemplified by discussing the QD-based sensing of low-molecular-weight substrates, chiroselective sensing of amino acids, probing of the catalytic activities of enzymes (casein kinase, tyrosinase, NAD⁺-dependent enzymes), and analysis of DNA and of aptamer-substrate complexes. Specifically, the amplified QD-based sensing of DNA using exonuclease III as target regeneration biocatalyst and the multiplexed detection of DNAs using differently sized QDs are discussed. Also, the implementation of the CRET process for the multiplexed analysis of DNA using differently sized QDs is addressed. Finally, the use of semiconductor QDs for the photoelectrochemical detection of DNA, aptamer-substrate complexes and enzyme activities are discussed. Specifically, the use of QDs for photoelectrochemical sensors, using the CRET process as internal excitation light source, is described. The future applications of the various QD-based sensors as analytical devices and as nanotools that probe intracellular processes are discussed.     

Amplified multiplexed analysis of DNA by the exonuclease III-catalyzed regeneration of the target DNA in the presence of functionalized semiconductor quantum dots

Quantum dots (QDs) functionalized with a black-hole quencher are used as optical tracer for the detection of DNA using exonuclease as a biocatalyst. The binding of the target DNA or of a target/open hairpin complex to the functionalized QDs leads to the exonuclease-stimulated recycling of the target DNA or the target/hairpin complex. This results in the triggering of the luminescence of the QDs that provides a readout signal for the amplified sensing process. By using different-sized QDs, the multiplexed detection of DNAs is demonstrated.     

A performance and implementation comparison of bidirectional anddual bus 2-D WDM multiple-plane optical interconnections with row-columnmultihop network structures

Bidirectional and dual bus wavelength division multiplexing (WDM) two-dimensional (2-D) multiple-plane optical interconnections with row-column multihop network structures using vertical-cavity surface-emitting lasers (VCSELs) and wavelength-selective detectors are analyzed and compared in terms of the expected number of hops (switching delay) and practical implementation considerations. The bidirectional WDM optical interconnection significantly reduces the necessary implementation hardware while maintaining the performance very closely compared to the dual bus architecture. Both WDM structures show significant performance improvements even when only three to five wavelengths are used. Also, the multihop efficiency is analyzed with the consideration of both electrical hops and optical hops     

All-fiber WDM optical crossconnect using ultrastrong widely tunableFBGs

We demonstrate an all-fiber wavelength-division-multiplexed optical crossconnect using ultrastrong fiber Bragg gratings (FBGs) with wide tunability. These FBGs have 0.2-nm bandwidths and can be tuned over ~52 nm due to a novel grating preparation technique to reduce mechanical strength degradation. There is negligible distortion in the transmission spectra while tuning the grating, and the crossconnect architecture uses cascades of these gratings for WDM operation. The ability to tune these >98% reflectivity gratings completely out of the entire WDM signal band minimizes the leakage of unwanted signal power and leads to the improvements of >10-dB crosstalk and >0.6-dB power penalty compared with conventional gratings     

40-nm-wide tunable fiber ring laser with single-mode operationusing a highly stretchable FBG

We demonstrate a 750-Hz linewidth single-mode erbium-doped fiber (EDF) ring laser with wide tunability using a widely tunable fiber Bragg grating (FBG). The stable single-mode operation is realized by using the FBG as a narrow wavelength-selective element and 4 m of unpumped EDF as a saturable absorber in the cavity. The 40-nm continuous tuning range of 1522-1562 nm is achieved using a highly stretchable FBG that exhibits a filter tuning range of over 52 nm. The grating is prepared with chemically stripped deuterium-loaded fiber to eliminate degrading factors for the grating strength, thereby achieving the wide tunability. The tuning range represents a 3.5-fold increase in wavelength tuning over previous use of FBGs     

Spectrally-efficient L-C band EDFA having a seamless interbandchannel region using sampled FBGs

We report a method and experimental demonstration for an L-C band silica-based erbium-doped fiber amplifier (EDFA) utilizing the entire wavelength range of both the L and C bands with no “dead zone” in between. Sampled fiber Bragg gratings (FBGs) are used to split the L and C bands, thereby providing amplification at many discrete wavelengths as well as a sharp transition between the two bands. Optical amplification with negligible power penalty is demonstrated within the interband zone using a 1.6-nm spacing between the highest C hand and lowest L band channels     

AFM characterization of the structure of Au-colloid monolayers and their chemical etching

Modification of a glass support with triethoxy propylaminosilane yields an active interface for the assembly of Au colloids. The colloids are imaged by AFM using a low applied load (0.5–0.7 nN). The lateral Au-colloid dimensions, 33±3 nm, deviate from the particle dimensions determined by TEM (19±2 nm) and absorption spectroscopy (15 nm). This deviation is attributed to the intrinsic curvature of the AFM tip. Application of higher loads on the tip (3 nN) results in the sweeping of Au colloids from the monolayer. The Au colloid monolayer is etched in the presence of CN⁻. The etching proceeds by the initial coincidental etching of Au particles followed by the kinetically favored etching of particles at the edges of the etched domains. This provides means for the micro machining and the chemical manipulation of Au colloids of controlled spatial arrangement.     

Optimal conditions for high-speed all-optical SOA-based wavelengthshifting

We analyze the system performance of gain-saturated semiconductor optical amplifier (SOA)-based all-optical wavelength shifting with respect to its dynamic characteristics. When considering the risetime, contrast ratio and intersymbol interference, we find that there exists an optimal probe power and wavelength for high-speed wavelength shifting which reduces the power penalty by 3 dB. The minimum power penalties for the data rates of 10 and 20 Gb/s are 25 and 5 dB, respectively