Metal Oxide Nanocrystals Multi-Parametric Gas Sensors

Interest in nanowires of semiconducting oxides is exponentially grown in the last years,due to their attracting potential applications in electronic,optical and sensor field.We have focused our attention on the sensing properties of indium and zinc oxide nanostructures.We have studied the influence of the deposition conditions on the nanostructures morphology and sensing properties.We report on the growth of ZnO and In_2O_3 nanostructures on silicon and alumina substrates,using vapour phase technique.We have synthesized,depending on the growth conditions,different structures such as nano-wires, tetrapod,nano-comb,nano-necklace,nano-pencil ZnO/In_2O_3 without using any metal catalyst.

Light emitting devices based on Si nanoclusters:the integration with a photonic crystal and electroluminescence properties

We present the properties and potentialities of light emitting devices based on amorphous Si nanoclusters. Amorphousnanostructures may constitute an interesting alternative to Si nanocrystals for the monolithic integration of optical andelectrical functions in Si technology. In fact, they exhibit an intense room temperature electroluminescence (EL). The ELproperties of these devices have been studied as a function of current and of temperature. Moreover, to improve theextraction efficiency of the light, we have integrated the emitting system with a 2D photonic crystal structure opportunelyfabricated by using conventional optical lithography to reduce the total internal reflection of the emitted light. The extractionefficiency in such devices increases by a factor of 4 at a resonance wavelength.

Multiplication and division of the orbital angular momentum of light with diffractive transformation optics

We present a method to efficiently multiply or divide the orbital angular momentum(OAM)of light beams using a sequence of two optical elements.The key element is represented by an optical transformation mapping the azimuthal phase gradient of the input OAM beam onto a circular sector.By combining multiple circular-sector transformations into a single optical element,it is possible to multiply the value of the input OAM state by splitting and mapping the phase onto complementary circular sectors.Conversely,by combining multiple inverse transformations,the division of the initial OAM value is achievable by mapping distinct complementary circular sectors of the input beam into an equal number of circular phase gradients.Optical elements have been fabricated in the form of phase-only diffractive optics with high-resolution electron-beam lithography.Optical tests confirm the capability of the multiplier optics to perform integer multiplication of the input OAM,whereas the designed dividers are demonstrated to correctly split up the input beam into a complementary set of OAM beams.These elements can find applications for the multiplicative generation of higher-order OAM modes,optical information processing based on OAM beam transmission,and optical routing/switching in telecom.

Improved Peptidyl Linkers for Self-Assembly of Semiconductor Quantum Dot Bioconjugates

We demonstrate improved peptide linkers which allow both conjugation to biomolecules such as DNA and self-assembly with luminescent semiconductor quantum dots.A hexahistidine peptidyl sequence was generated by standard solid phase peptide synthesis and modified with the succinimidyl ester of iodoacetamide to yield a thiol-reactive iodoacetyl polyhistidine linker.The reactive peptide was conjugated to dye-labeled thiolated DNA which was utilized as a model target biomolecule.Agarose gel electrophoresis and fluorescence resonance energy transfer analysis confirmed that the linker allowed the DNA to self-assemble with quantum dots via metal-affinity driven coordination.In contrast to previous peptidyl linkers that were based on disulfide exchange and were thus labile to reduction,the reactive haloacetyl chemistry demonstrated here results in a more stable thioether bond linking the DNA to the peptide which can withstand strongly reducing environments such as the intracellular cytoplasm.As thiol groups occur naturally in proteins,can be engineered into cloned proteins,inserted into nascent peptides or added to DNA during synthesis,the chemistry demonstrated here can provide a simple method for self-assembling a variety of stable quantum dot bioconjugates.