Search results for "graphe"
showing 10 items of 563 documents
Microwave gas sensor based on graphene aerogel for breath analysis
2022
Exhaled breath can be used for early detection and diagnosis of diseases, monitoring metabolic activity, and precision medicine. In this work, we design and simulate a microwave sensor in which thin graphene aerogels are integrated into rectangular microwave waveguides. Graphene aerogels are ideal sensing platforms for gases and volatile compounds as they combine extremely high surface-to-volume ratio and good electrical conductivity at RF and microwave frequencies. The latter is modified by exposure to different gases, and -when integrated into a waveguide- these changes result in significant shifts in transmission and reflection scattering parameters. We model the aerogel as a graphene gr…
Auditiivisen ja kielellisen harjoittelun vaikutus kolmannella luokalla olevien heikkojen lukijoiden lukutaitoon
2012
Synthesis of a biocompatible aerogel based on graphene oxide and a modified polyethylene glycol
2016
The synthesis and self-assembly of a 3D aerogel built by graphene oxide (GO) and a modified polyethylene glycol (PEG) was achieved by a multi-step synthetic procedure, involving the preparation of an amino-terminated PEG (PEG-NH2) and the subsequent coupling with GO by carbodiimide in water, exploiting the carboxyl and epoxy moieties of GO and –NH2 terminations of the biopolymer. The resulting nanohybrid hydrogel was successively converted into an aerogel via dialysis plus freeze-drying [1] and fully characterized. FTIR, Raman, XPS, XRD and BET measurements were performed to confirm the successful modification for each reaction step, while morphological, mechanical and hemolytic tests were …
Graphene oxide and Fumed silica graphene oxide nanocomposites modification by thermal treatments
2014
In the present study we investigate post synthesis thermal treatments up to 400 °C of graphene oxide (GrO) prepared from commercial graphite and of GrO–silica nanocomposites prepared by a solution of commercial Fumed silica nanoparticles (average diameter 7 nm or 40 nm) and the GrO. The thermal treatments were carried out in air, vacuum or He atmosphere to highlight tunable changes. Two GrO batches with small differences in the D (~1350 cm–1) and G (~1580 cm–1) Raman bands have been employed to evaluate effects depending on preparation. Thermal effects have been monitored through the Raman spectroscopy focusing on D, G and 2D (2500–3500 cm–1) bands spectral ranges. The experiments evidenced…
IMPROVED STABILITY OF GRAPHENE OXIDE-SILICA NANOHYBRIDS AND RELATED POLYMER-BASED NANOCOMPOSITES
2014
Although its promising properties make the graphene oxide (GO) very interesting as filler for polymer matrices, some problems related to its thermal stability in the region which ranges from 80 to 200 °C, are crucial for the possibility to melt process GO together with practically all the polymers [1,2]. Moreover, above 100 °C GO lamellae were found to become stacked. In this work, two different ways to preserve the GO structure and ensure its dispersion within different polymer matrices have been investigated and schematized in Fig. 1. Exfoliation plays a key-role in the achievement of good mechanical properties since it preserves the GO from both stacking phenomena. The capability of sili…
Polyamide 6/Graphene Oxide Nanohybrids
2013
Facile and novel synthesis of Graphene oxide/Silica nanohybrids with tunable properties
2013
Gamma-Ray-Induced Structural Transformation of GQDs towards the Improvement of Their Optical Properties, Monitoring of Selected Toxic Compounds, and …
2022
Structural modification of different carbon-based nanomaterials is often necessary to improve their morphology and optical properties, particularly the incorporation of N-atoms in graphene quantum dots (GQDs). Here, a clean, simple, one-step, and eco-friendly method for N-doping of GQDs using gamma irradiation is reported. GQDs were irradiated in the presence of the different ethylenediamine (EDA) amounts (1 g, 5 g, and 10 g) and the highest % of N was detected in the presence of 10 g. N-doped GQDs emitted strong, blue photoluminescence (PL). Photoluminescence quantum yield was increased from 1.45, as obtained for non-irradiated dots, to 7.24% for those irradiated in the presence of 1 g of …
An Overview of Functionalized Graphene Nanomaterials for Advanced Applications
2021
Interest in the development of graphene-based materials for advanced applications is growing, because of the unique features of such nanomaterials and, above all, of their outstanding versatility, which enables several functionalization pathways that lead to materials with extremely tunable properties and architectures. This review is focused on the careful examination of relationships between synthetic approaches currently used to derivatize graphene, main properties achieved, and target applications proposed. Use of functionalized graphene nanomaterials in six engineering areas (materials with enhanced mechanical and thermal performance, energy, sensors, biomedical, water treatment, and c…
Suspended graphene device fabrication
2016
Tämän pro gradu -tutkielman aiheena oli tutkia itsekantavien grafeeninäytteiden valmistusta. Grafeeni syntetisoitiin kaasufaasikasvatuksella ilmakehän paineessa kupariohutkalvoille. Kupariohutkalvot valmistattiin käyttämällä elektronisuihkuhöyrystystä. Projektin aikana synteesiprosessia parannettiin optimoimalla synteesiparametreja. Syntetisoinnin jälkeen grafeeninäytteet siirrettiin piinitridikalvoille, joihin oli valmistettu reikiä. Viimeinen vaihe siirrossa on PMMA tukikerroksen poisto grafeenin päältä, jota tutkittiin käyttämällä kahta eri menetelmää. Näistä ensimmäinen menetelmä oli lämpökäsittely ja toinen kriittisen pisteen kuivaus PMMA:n asetoniin liuottamisen jälkeen. Näytteet kuva…