Determination of the Aspect-ratio Distribution of Gold Nanorods in a Colloidal Solution using UV-visible absorption spectroscopy

Knowledge of the distribution of the aspect ratios (ARs) in a chemically-synthesized colloidal solution of Gold Nano Rods (GNRs) is an important measure in determining the quality of synthesis, and consequently the performance of the GNRs generated for various applications. In this work, an algorithm has been developed based on the Bellman Principle of Optimality to readily determine the AR distribution of synthesized GNRs in colloidal solutions. This is achieved by theoretically fitting the longitudinal plasmon resonance of GNRs obtained by UV-visible spectroscopy. The AR distribution obtained from the use of the algorithm developed have shown good agreement with those theoretically generated one as well as with the previously reported results. After bench-marking, the algorithm has been applied to determine the mean and standard deviation of the AR distribution of two GNRs solutions synthesized and examined in this work. The comparison with experimentally derived results from the use of expensive Transmission Electron Microscopic images and Dynamic Light Scattering technique shows that the algorithm developed offers a fast and thus potentially cost-effective solution to determine the quality of the synthesized GNRs specifically needed for many potential applications for the advanced sensor systems

Indium phosphide based membrane photodetector for optical interconnects on silicon

We have designed, fabricated and characterized an InP-based membrane photodetector on an SOI wafer containing a Si-wiring photonic circuit. New results on RF characterization up to 20 GHz are presented. The detector fabrication is compatible with wafer scale processing steps, guaranteeing compatibility towards future generation electronic IC processing

Effect of P‐induced gettering on extended defects in n‐type multicrystalline silicon

AbstractThe electrical properties and the minority charge carrier recombination behaviour of grain boundaries (GBs) and intragrain dislocations in different n‐type multicrystalline silicon (mc‐Si) ingots were systematically studied through microwave‐detected PhotoConductance Decay (µW‐PCD), Electron Beam Induced Current (EBIC) and PhotoLuminescence (PL) spectroscopy on as‐grown samples and on samples submitted to P‐diffusion step. It was confirmed that the overall quality of n‐type mc‐Si is high, indicating that n‐type‐Si is a valid source for photovoltaic applications. As expected, the average lifetime increases after the P‐diffusion process, which induces impurity gettering effects at the external surfaces, like in the case of p‐type samples, but an evident local increase of electrical activity of some GBs after that process was also observed using the EBIC mapping technique. Apparently, a redistribution of impurities occurs at the processing temperature and impurities are captured at the deepest sinks. In fact, while all GBs act as heterogeneous segregation/precipitation sites, some of them will compete with the external surfaces sinks, partly vanishing the effect of P‐gettering. Last but not least, it was experimentally demonstrated that the average lifetime values measured with the µW‐PCD technique well correlate with the recombination activity of GBs measured with the EBIC technique, showing the extreme importance of GBs on the effective lifetime of this material. Copyright © 2007 John Wiley & Sons, Ltd

Hybrid sputtering/evaporation deposition of Cu(In,Ga)Se2 thin film solar cells

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The geometrical nature of optical resonances : from a sphere to fused dimer nanoparticles

We study the electromagnetic response of smooth gold nanoparticles with shapes varying from a single sphere to two ellipsoids joined smoothly at their vertices. We show that the plasmonic resonance visible in the extinction and absorption cross sections shifts to longer wavelengths and eventually disappears as the mid-plane waist of the composite particle becomes narrower. This process corresponds to an increase of the numbers of internal and scattering modes that are mainly confined to the surface and coupled to the incident field. These modes strongly affect the near field, and therefore are of great importance in surface spectroscopy, but are almost undetectable in the far field

Plasma Small Extracellular Vesicles with Complement Alterations in GRN/C9orf72 and Sporadic Frontotemporal Lobar Degeneration

Cutting-edge research suggests endosomal/immune dysregulation in GRN/C9orf72-associated frontotemporal lobar degeneration (FTLD). In this retrospective study, we investigated plasma small extracellular vesicles (sEVs) and complement proteins in 172 subjects (40 Sporadic FTLD, 40 Intermediate/Pathological C9orf72 expansion carriers, and 49 Heterozygous/Homozygous GRN mutation carriers, 43 controls). Plasma sEVs (concentration, size) were analyzed by nanoparticle tracking analysis; plasma and sEVs C1q, C4, C3 proteins were quantified by multiplex assay. We demonstrated that genetic/sporadic FTLD share lower sEV concentrations and higher sEV sizes. The diagnostic performance of the two most predictive variables (sEV concentration/size ratio) was high (AUC = 0.91, sensitivity 85.3%, specificity 81.4%). C1q, C4, and C3 cargo per sEV is increased in genetic and sporadic FTLD. C4 (cargo per sEV, total sEV concentration) is increased in Sporadic FTLD and reduced in GRN+ Homozygous, suggesting its specific unbalance compared with Heterozygous cases. C3 plasma level was increased in genetic vs. sporadic FTLD. Looking at complement protein compartmentalization, in control subjects, the C3 and C4 sEV concentrations were roughly half that in respect to those measured in plasma; interestingly, this compartmentalization was altered in different ways in patients. These results suggest sEVs and complement proteins as potential therapeutic targets to mitigate neurodegeneration in FTLD

A Genome-Wide Screening and SNPs-to-Genes Approach to Identify Novel Genetic Risk Factors Associated with Frontotemporal Dementia

Frontotemporal dementia (FTD) is the second most prevalent form of early onset dementia after Alzheimer’s disease (AD). We performed a case-control association study in an Italian FTD cohort (n = 530) followed by the novel SNPs-to-genes approach and functional annotation analysis. We identified two novel potential loci for FTD. Suggestive SNPs reached p-values ~10-7 and OR > 2.5 (2p16.3) and 1.5 (17q25.3). Suggestive alleles at 17q25.3 identified a disease-associated haplotype causing decreased expression of -cis genes such as RFNG and AATK involved in neuronal genesis and differentiation, and axon outgrowth, respectively. We replicated this locus through the SNPs-to-genes approach. Our functional annotation analysis indicated significant enrichment for functions of the brain (neuronal genesis, differentiation and maturation), the synapse (neurotransmission and synapse plasticity), and elements of the immune system, the latter supporting our recent international FTD-GWAS. This is the largest genome-wide study in Italian FTD to date. Although our results are not conclusive, we set the basis for future replication studies and identification of susceptible molecular mechanisms involved in FTD pathogenesis