Optical enhancement by means of concentration tuning of gold precursors in polymer nanocomposite materials

In this work, we propose a new approach regarding the characterization and the enhancement of transmitted light travelling inside a chitosan polymeric film improved by implementation of gold precursors generating nanocomposite materials. Firstly, the experimental optical characterization indicates the influence of the presence of gold particles on the effective refractive index of the chitosan polymer films and, secondly, the influence of their thickness supported by the transmittivity enhancement at precise frequencies for each gold precursor concentration and each polymer film thickness. This developed analysis introduces a basic study for the light enhancement in future complex photonic devices suitable for sensing

Tuning Concept and Design Criteria of Efficient Planar Metallic Plasmon Waveguides Using Nanocomposite Materials for Electromagnetic Radiation Applications

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Real time optical pressure sensing for tactile detection using gold nanocomposite material

For the first time, we propose in this work a new concept of optical tactile pressure sensing. We develop a sensor integrating an optical tapered fiber force sensor based on electromagnetic (EM) coupling effect. The sensor consists of a tapered multimode Si fiber which couples the EM field coming from a broad band lamp source with the flexible gold/PDMS nanocomposite material (GNM). PDMS polymer film was used since it is suitable for the generation of gold nanoparticles starting from gold precursors and consecutively is suitable for light coupling: the formed gold nanoparticles increase the effective refractive index of the PDMS and support the EM coupling with the tapered region. By applying different weights that can be translated to pressure forces to the sensor, we experimentally observe in real time the intensity reduction of the transmittivity response at the output of the fiber sensor. This effect is most likely due to displacement of gold nanoparticles near the tapered region during the pressure application

In situ formation and size control of gold nanoparticles into chitosan for nanocomposite surfaces with tailored wettability.

The in situ formation of gold nanoparticles into the natural polymer chitosan is described upon pulsed laser irradiation. In particular, hydrogel-type films of chitosan get loaded with the gold precursor, chloroauric acid salt (HAuCl4), by immersion in its aqueous solution. After the irradiation of this system with increasing number of ultraviolet laser pulses, we observe the formation of gold nanoparticles with increasing density and decreasing size. Analytical studies using absorption measurements, atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy of the nanocomposite samples throughout the irradiation procedure reveal that under the specific irradiation conditions there are two competing mechanisms responsible for the nanoparticles production: the photoreduction of the precursor responsible for the rising growth of gold particles with increasing size and the subsequent photofragmentation of these particles into smaller ones. The described method allows the loca..

Conformation-based Molecular Memories for Nanoscale MemComputing

We investigate the use of endohedral fullerenes and 6-(Ferrocenyl)hexanethiol cation as molecular non-volatile memory devices. We demonstrate stable encoding of the information in the geometry and dipole moment of these molecules. The write operation can be performed with external programming electric fields that drive the switching of the molecule conformation. The read operation can be performed by reading the dipole moment through the generated electric fields. Moreover, the dipole moment encoding enables the integration of proposed memories with molecular Field-Coupled Nanocomputing logic. The capability to realize compatible and purely molecular memory and logic devices paves the way for molecular MemComputing, with new possibilities for nanoscale computing paradigms

Design of Pyrrole-Based Gate-Controlled Molecular Junctions Optimized for Single-Molecule Aflatoxin B1 Detection

Food contamination by aflatoxins is an urgent global issue due to its high level of toxicity and the difficulties in limiting the diffusion. Unfortunately, current detection techniques, which mainly use biosensing, prevent the pervasive monitoring of aflatoxins throughout the agri-food chain. In this work, we investigate, through ab initio atomistic calculations, a pyrrole-based Molecular Field Effect Transistor (MolFET) as a single-molecule sensor for the amperometric detection of aflatoxins. In particular, we theoretically explain the gate-tuned current modulation from a chemical–physical perspective, and we support our insights through simulations. In addition, this work demonstrates that, for the case under consideration, the use of a suitable gate voltage permits a considerable enhancement in the sensor performance. The gating effect raises the current modulation due to aflatoxin from 100% to more than 103÷104 %. In particular, the current is diminished by two orders of magnitude from the μA range to the nA range due to the presence of aflatoxin B1. Our work motivates future research efforts in miniaturized FET electrical detection for future pervasive electrical measurement of aflatoxins

NS-GAAFET Compact Modeling: Technological Challenges in Sub-3-nm Circuit Performance

NanoSheet-Gate-All-Around-FETs (NS-GAAFETs) are commonly recognized as the future technology to push the digital node scaling into the sub-3 nm range. NS-GAAFETs are expected to replace FinFETs in a few years, as they provide highly electrostatic gate control thanks to the GAA structure, with four sides of the NS channel entirely enveloped by the gate. At the same time, the NS rectangular cross-section is demonstrated to be effective in its driving strength thanks to its high saturation current, tunable through the NS width used as a design parameter. In this work, we develop a NS-GAAFET compact model and we use it to link peculiar single-device parameters to digital circuit performance. In particular, we use the well-known BSIM-CMG core solver for multigate transistors as a starting point and develop an ad hocresistive and capacitive network to model the NS-GAAFET geometrical and physical structure. Then, we employ the developed model to design and optimize a digital inverter and a five-stage ring oscillator, which we use as a performance benchmark for the NS-GAAFET technology. Through Cadence Virtuoso SPICE simulations, we investigate the digital NS-GAAFET performance for both high-performance and low-power nodes, according to the average future node present in the International Roadmap for Devices and Systems. We focus our analysis on the main different technological parameters with regard to FinFET, i.e., the inner and outer spacers. Our results highlight that in future technological nodes, the choice of alternative low-K dielectric materials for the NS spacers will assume increasing importance, being as relevant, or even more relevant, than photolithographic alignment and resolution at the sub-nm scale

Single-molecule Aflatoxin B1 Sensing via Pyrrole-based Molecular Quantum Dot

We investigate through ab-initio simulations the gold-8PyrroleDiThiol-gold (Au-8PyDT) molecular quantum dot as an amperometric single-molecule sensor for the aflatoxin B1 (AFB1) detection. We study the adsorption of AFB1 onto the Au-8PyDT and we analyze the transport characteristics for the most probable adsorption configuration. We find that a significant current modulation occurs, with around 80% of current decrease in presence of AFB1. Interestingly, the investigated sensor exhibits a voltage-dependent response, that we motivate through a transmission properties analysis. Our results, considering the synthesis simplicity of PolyPyrroles and their non-toxicity, motivate future research efforts in this direction

The monumental submerged Punic harbour of Malfatano and associated Piscinnì quarries: sea level changes and geoarchaeological approach

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Electronic Transport Study of Bistable Cr@C28 Single-Molecule Device for High-Density Data Storage Applications

We investigate through ab initio calculation the endohedral monometallofullerene Cr@C28 as a candidate for data storage applications. First, we study the encapsulation energy and the electronic properties of two stable states of the Cr@C28 - namely I-Cr@C28 and II-Cr@C28. Then, we address the adsorption of C28, I-Cr@C28, and II-Cr@C28 onto a gold substrate. Finally, by emulating a Scanning Tunneling Microscope (STM) break-junction experimental setup, we analyze the STM-mediated transport characteristics for the most probable adsorption configurations. We find and discuss a significant and measurable current difference between the two stable states. This outcome enables the binary encoding of the information, making the proposed device promising as a single-molecule data storage element for future high-density integrated circuits