DNA wrapping around MWNTs and graphene: a SERS study

In recent years, carbon nanostructure as nanotubes (CNTs) and graphene are at the centre of a significant research effort due to the strong scientific and technological interest because of their unique physical and chemical properties: large surface area, excellent thermal and electric conductivity, high electron transfer kinetics and strong mechanical strength. Recently, a great attention has been paid to the interaction of DNA with carbon-based nanostructures such as C60, multiwalled-nanotubes (MWNTs), single-walled nanotubes (SWNTs) and graphene. The development of these studies is motivated by a wide spectrum of possible use of these materials e.g. as biosensors, drug delivery agents and diagnosis tools. In this work, we applied surface-enhanced Raman spectroscopy (SERS) to the study of DNA/MWNTs and DNA/graphene systems

Surface-Enhanced Raman Spectroscopy Characterization of Pristine and Functionalized Carbon Nanotubes and Graphene

Carbon nanotubes (CNTs) and graphene are at the center of a significant research effort due to their unique physical and chemical properties, which promise high technological impact. For the future development of all the foreseen applications, it is of particular interest the study of binding interactions between carbon nanostructures and functional groups. An appropriate method is the surface-enhanced Raman spectroscopy (SERS), which provides a large amplification of Raman signals when the probed molecule is adsorbed on a nanosized metallic surface. In this chapter, we present a review of principal results obtained applying SERS for the characterization of pristine and functionalized CNTs and graphene. The obtained results encourage us to consider SERS as a powerful method to obtain a rapid monitor of the procedures used to interface graphene and nanotubes

Validation of a Miniaturized Spectrometer for Trace Detection of Explosives by Surface-Enhanced Raman Spectroscopy

Surface-enhanced Raman spectroscopy (SERS) measurements of some common military explosives were performed with a table-top micro-Raman system integrated with a Serstech R785 miniaturized device, comprising a spectrometer and detector for near-infrared (NIR) laser excitation (785 nm). R785 was tested as the main component of a miniaturized SERS detector, designed for in situ and stand-alone sensing of molecules released at low concentrations, as could happen in the case of traces of explosives found in an illegal bomb factory, where solid microparticles of explosives could be released in the air and then collected on the sensor's surface, if placed near the factory, as a consequence of bomb preparation. SERS spectra were obtained, exciting samples in picogram quantities on specific substrates, starting from standard commercial solutions. The main vibrational features of each substance were clearly identified also in low quantities. The amount of the sampled substance was determined through the analysis of scanning electron microscope images, while the spectral resolution and the detector sensitivity were sufficiently high to clearly distinguish spectra belonging to different samples with an exposure time of 10 s. A principal component analysis procedure was applied to the experimental data to understand which are the main factors affecting spectra variation across different samples. The score plots for the first three principal components show that the examined explosive materials can be clearly classified on the basis of their SERS spectra

Confocal fluorescence microscopy and confocal raman microspectroscopy of X-ray irradiated LIF crystals

Radiation-induced color centers locally produced in lithium fluoride (LiF) are successfully used for radiation detectors. LiF detectors for extreme ultraviolet radiation, soft and hard X-rays, based on photoluminescence from aggregate electronic defects, are currently under development for imaging applications with laboratory radiation sources, as well as large-scale facilities. Among the peculiarities of LiF-based detectors, noteworthy ones are their very high intrinsic spatial resolution across a large field of view, wide dynamic range, and versatility. LiF crystals irradiated with a monochromatic 8 keV X-ray beam at KIT synchrotron light source (Karlsruhe, Germany) and with the broadband white beam spectrum of the synchrotron bending magnet have been investigated by optical spectroscopy, laser scanning confocal microscopy in fluorescence mode, and confocal Raman micro-spectroscopy. The 3D reconstruction of the distributions of the color centers induced by the X-rays has been performed with both confocal techniques. The combination of the LiF crystal capability to register volumetric X-ray mapping with the optical sectioning operations of the confocal techniques has allowed performing 3D reconstructions of the X-ray colored volumes and it could provide advanced tools for 3D X-ray detection

Persistent immune stimulation exacerbates genetically driven myeloproliferative disorders via stromal remodeling

Systemic immune stimulation has been associated with increased risk of myeloid malignancies, but the pathogenic link is unknown. We demonstrate in animal models that experimental systemic immune activation alters the bone marrow stromal microenvironment, disarranging extracellular matrix (ECM) microarchitecture, with downregulation of secreted protein acidic and rich in cysteine (SPARC) and collagen-I and induction of complement activation. These changes were accompanied by a decrease in Treg frequency and by an increase in activated effector T cells. Under these conditions, hematopoietic precursors harboring nucleophosmin-1 (NPM1) mutation generated myeloid cells unfit for normal hematopoiesis but prone to immunogenic death, leading to neutrophil extracellular trap (NET) formation. NET fostered the progression of the indolent NPM1-driven myeloproliferation toward an exacerbated and proliferative dysplastic phenotype. Enrichment in NET structures was found in the bone marrow of patients with autoimmune disorders and in NPM1-mutated acute myelogenous leukemia (AML) patients. Genes involved in NET formation in the animal model were used to design a NET-related inflammatory gene signature for human myeloid malignancies. This signature identified two AML subsets with different genetic complexity and different enrichment in NPM1 mutation and predicted the response to immunomodulatory drugs. Our results indicate that stromal/ECM changes and priming of bone marrow NETosis by systemic inflammatory conditions can complement genetic and epigenetic events towards the development and progression of myeloid malignancy

Raman microscopy analysis of graphene-based nanocomposite materials under UV-C exposure

In this work, we focused on the investigation of UV-C radiation effects on novel nanomaterials structured with graphene nanoplatelets (GNPs) and DNA. Multifunctional nanocomposites were realized by combining the good electrical conductivity of GNPs with the biocompatibility and UV sensitivity of double-stranded DNA. GNP/DNA nanostructures were prepared by sonication-driven self-assembly in aqueous solution, and then dispersed into a PEDOT:PSS (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)) matrix. The UV-sensitivity of the GNP/DNA/PEDOT:PSS samples was investigated by exposing them to the energetic UV-C band, and investigating their morphology, surface wettability, chemical and electrical properties before and after irradiation using several techniques (scanning electron microscopy, Raman spectroscopy, electrical impedance spectroscopy). In particular, Raman imaging was used as suitable technique to analyze the chemical arrangements and their modifications upon irradiation on selected surface areas. This technique allowed appreciating chemical changes caused by the UV-C interaction with the nanocomposite original structure. Results give information about the potential applications of GNP/DNA/PEDOT:PSS nanomaterials in all environments affected by UV radiations, for example for chemical reactions or sterilization purposes, or where they are naturally present, such as in space. In reference to space environment, the GNP/DNA/PEDOT:PSS nanocomposites were also tested under UV-C while reducing the amount of oxygen reaching the sample surface, in order to separate the effects due to the atmosphere from those of the irradiation

UV-induced modification of PEDOT:PSS-based nanocomposite films investigated by Raman microscopy mapping

Nanocomposite films with high electrical conductivity and UV sensitivity were prepared by integration of DNA-modified graphene nanoplatelets (GNPs) with a polymer matrix made of poly(3,4-ethylenedioxythio-phene):poly(styrenesulfonate) (PEDOT:PSS). The exceptional electrical properties and mechanical strength of graphene were used to enhance the PEDOT:PSS properties and stability, whereas DNA molecules are sensitive to UV and have an exfoliating effect on the GNPs in aqueous solution. GNP-DNA/PEDOT:PSS films were exposed to radiation in the energetic UV-C band (254 nm), and their properties investigated before and after irradiation. Several techniques, including scanning electron microscopy, optical contact angle, electrical impedance and Raman spectroscopies, were used to characterize the nanocomposites and to investigate their sensitivity to UV. In particular, Raman microscopy mapping was used to analyze the chemical structure of the films and its modification at molecular level upon exposure to UV-C radiation. Results of these investigations are useful for the application of the GNP-DNA/PEDOT:PSS films in ultra-small and lightweight UV sensor devices for use in space environment, for example during extravehicular activities (EVA), or for industrial settings on Earth that are characterized by high levels of UV-C radiation

Competitività e governance nel settore turistico: il caso della costiera amalfitana

Purpose. The success of tourist destinations is influenced by the structural aspect of the territory and its factors of attractiveness/competitiveness (Porter, 1998; Enright, Newton, 2004). The purpose of this paper is to study the factors of territorial competitiveness perceived by hotel managers and to analyze their propensity to develop collaborative relationships with other actors. The analysis is developed from the perspective attribute based (Enright, Newton, 2004; Crouch, Ritchie, 1999). Methodology. The study focuses on the hotels administering close-ended questions. Scope of the survey is the perception of the factors of regional competitiveness and the willingness to develop collaborative relationships with other tourism system actors. Descriptive statistics were used in order to analyze selected variables. Findings. The findings offer evidence of the factors of regional competitiveness as perceived by hotel managers. Some significant suggestions on the perception of the system of territorial governance are underlined. The paper finds in some cases readiness to cooperate with other actors. Limitations. The survey was conducted over a single territory: so no comparisons is possible between destinations. At the moment research is still ongoing and the questionnaire is being administered to a further sample of firms belonging to a different territory. Implications. The work provides guidance to policy makers to set a local policy to revitalize the area through a process of shared governance Originality/value. The paper presents the first results of a research in progress which are confirmed some interpretative models already present in the literatur

Mapping the residual strain of carbon nanotubes in DWCNT/epoxy nanocomposites after tensile load using Raman microscopy

The toughness mechanisms of epoxy-based nanocomposites reinforced by double-walled carbon nanotubes (DWCNT) are investigated using Raman microscopy mapping. Maps of the residual strain of the carbon nanotubes were generated for the fracture surfaces obtained after tensile loading. By imaging through different microscope objectives, Raman mapping allowed to determine the distribution of the nanotube residual strain, indicating tension or compression, in different sampling volumes near the fracture surface. The G′ band with its high sensitivity to nanotube diameter variations, and not overlapping with the characteristic epoxy Raman lines, was selected for the mapping. Results provide a quantitative analysis of the nanotube bridging and pull-out mechanisms identified by scanning electron microscopy (SEM) inspection of the fracture surfaces