Vittorio Scardaci

Bio: Vittorio Scardaci is an academic researcher from University of Catania. The author has contributed to research in topics: Saturable absorption & Carbon nanotube. The author has an hindex of 26, co-authored 57 publications receiving 20629 citations. Previous affiliations of Vittorio Scardaci include University College London & University of Cambridge.

Growth Kinetics and Sensing Features of Colloidal Silver Nanoplates

Abstract: This paper presents the growth mechanisms and the plasmon sensing features for a large class of silver nanoplates obtained in the colloidal form. The synthesis is conducted by seed-mediated growth and leads to plates with aspect ratios as large as 20, having localized surface plasmon resonances extending deeply into the infrared spectral region (1000 nm and above). We measure plasmon sensitivity by varying the colloidal local refractive index, and sensitivity values up to 500 nm/RIU are obtained. Theoretical considerations regarding the correlation between the refractive index sensitivity and the position of the main localized plasmon resonance band demonstrate that plasmon sensitivity does not depend directly on the nanoparticle shape and aspect ratio.

Nonlinear Optical Properties of Ag Nanoplates Plasmon Resonance and Applications in Ultrafast Photonics

Abstract: Metal nanomaterials have attracted increasing attention due to their outstanding nonlinear optical and photonic properties, making them as potential saturable absorber (SA) candidates for realizing ultrafast photonic devices. In this article, we demonstrate the generation of mode-locked dual-wavelength pulse trains in an Ag nanoplates (AgNPTs)-based Yb-doped all-fiber laser for the first time to the best of our knowledge. The AgNPTs are synthesized by seed-mediated growth and then integrated into a fiber ferrule by optical deposition, which serve as SA in the ring laser cavity. The plasmonic properties of such nanoplates are measured by absorption spectrophotometry and their nonlinear optical properties are characterized by Z-scan. The measured nonlinear saturable absorption of the AgNPTs-based SA is 6.4%. In our laser, the dual-wavelength synchronous mode-locking is achieved at the center wavelengths of 1031.92 and 1033.24 nm with 3-dB spectral bandwidth of 0.52 and 0.46 nm, respectively, where 293-ps pulse trains with a repetition rate of 11.43 MHz are obtained at the pump power of 350 mW. The results demonstrate that the solution-processed AgNPTs are promising SA candidates for achieving stable and low-cost pulsed laser sources which could be used for spectroscopy and ultrafast photonics.

Monochromatic light driven synthesis and growth of flat silver nanoparticles and their plasmon sensitivity

Abstract: The size and shape of metal nanoparticles play a key role in most of their technological applications because they determine their optical properties in the UV-vis-NIR range as well as their interaction with molecules in the surroundings. In this paper, we demonstrate the “in liquid” formation of flat silver nanoparticle colloids through the use of pulsed laser beams and monochromatic LEDs. The transformation of spherical to flat nanoparticles is driven and sustained by the addition of H2O2 and citrate under the irradiation of light. In this respect, it is demonstrated that high citrate concentrations limit the growth of some crystalline facets, yielding smaller plates with the plasmon resonance of the final colloid confined to the visible region, while the use of lower concentrations results in the formation of large plates with resonances in the near infrared region. Thus, the manipulation of citrate concentration in the solution and the choice of the irradiation wavelength give rise to the possibility to tune the position of the main plasmon resonance across the visible and near IR part of the spectrum. Plasmon sensitivity measurements show that nanoplates irradiated at the longest wavelength showed the highest response to a refractive index change.

Spray deposition of Silver Nanowire transparent conductive networks

Abstract: We investigate Silver Nanowire (AgNW) networks, deposited by spray coating, on a flexible plastic substrate, for application as transparent electrodes for Indium Tin Oxide (ITO) replacement. We demonstrate that the network performance is controlled by the size distribution of the droplets impinging the substrate. Droplet size distribution can be controlled by tuning the spray pressure. Under the most favorable conditions, we achieve networks with typical transmittance T∼90% and sheet resistance Rs∼50Ω/□, and Rs∼1kΩ/□ at T∼94%.

Surface Plasmon Resonance Dependent Third-Order Optical Nonlinearities of Silver Nanoplates

Abstract: A systematic study of the surface plasmon resonance (SPR)-dependent nonlinear optical response of Ag nanoplates is presented and discussed. The Ag nanoplates were synthesized using the well-known seed-mediated growth method. By performing the z-scan method with a nanosecond laser (532 nm, 5 ns), the optical nonlinearities of the Ag nanoplates, prepared tuning the SPR contribution in the 400–1000 nm range, were determined. The results showed a SPR-related competition between the saturable absorption and reverse saturable absorption mechanisms, while the nonlinear refraction changed from self-defocusing to self-focusing. Furthermore, the scattering effects contribute to determine the nature of the optical limiting response. The observed SPR-tunable third order optical nonlinearities make Ag nanoplates a suitable candidate to be used in different fields, i.e., laser pulse generation, optical limiting, or bio-imaging applications.

The rise of graphene

Abstract: Graphene is a rapidly rising star on the horizon of materials science and condensed-matter physics. This strictly two-dimensional material exhibits exceptionally high crystal and electronic quality, and, despite its short history, has already revealed a cornucopia of new physics and potential applications, which are briefly discussed here. Whereas one can be certain of the realness of applications only when commercial products appear, graphene no longer requires any further proof of its importance in terms of fundamental physics. Owing to its unusual electronic spectrum, graphene has led to the emergence of a new paradigm of 'relativistic' condensed-matter physics, where quantum relativistic phenomena, some of which are unobservable in high-energy physics, can now be mimicked and tested in table-top experiments. More generally, graphene represents a conceptually new class of materials that are only one atom thick, and, on this basis, offers new inroads into low-dimensional physics that has never ceased to surprise and continues to provide a fertile ground for applications.

The electronic properties of graphene

Abstract: This article reviews the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations. The Dirac electrons can be controlled by application of external electric and magnetic fields, or by altering sample geometry and/or topology. The Dirac electrons behave in unusual ways in tunneling, confinement, and the integer quantum Hall effect. The electronic properties of graphene stacks are discussed and vary with stacking order and number of layers. Edge (surface) states in graphene depend on the edge termination (zigzag or armchair) and affect the physical properties of nanoribbons. Different types of disorder modify the Dirac equation leading to unusual spectroscopic and transport properties. The effects of electron-electron and electron-phonon interactions in single layer and multilayer graphene are also presented.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene

Abstract: We measured the elastic properties and intrinsic breaking strength of free-standing monolayer graphene membranes by nanoindentation in an atomic force microscope. The force-displacement behavior is interpreted within a framework of nonlinear elastic stress-strain response, and yields second- and third-order elastic stiffnesses of 340 newtons per meter (N m(-1)) and -690 Nm(-1), respectively. The breaking strength is 42 N m(-1) and represents the intrinsic strength of a defect-free sheet. These quantities correspond to a Young's modulus of E = 1.0 terapascals, third-order elastic stiffness of D = -2.0 terapascals, and intrinsic strength of sigma(int) = 130 gigapascals for bulk graphite. These experiments establish graphene as the strongest material ever measured, and show that atomically perfect nanoscale materials can be mechanically tested to deformations well beyond the linear regime.

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.

Abstract: Single-layer metal dichalcogenides are two-dimensional semiconductors that present strong potential for electronic and sensing applications complementary to that of graphene.