1,721,070 research outputs found
Study of benzophenone grafting on reduced graphene oxide by unconventional techniques
No full textUnderstanding the mechanisms acting behind the functionalization of graphene is of paramount importance for the application of functionalized graphene in polymeric nano-composite materials. This work reports the study of the influence of benzophenone in a UV-mediated grafting process on graphene oxide, carried out by unconventional spectroscopic techniques, such as electron spin resonance and thermogravimetric analysis coupled with in situ infra-red spectroscopy. Using these techniques, a direct investigation of the grafting process was achieved for the first time, while up to now only indirect evidence was provided, opening new perspectives for the study of small molecule grafting on graphene sheets. The presence of benzophenone grafted onto the reduced graphene oxide surface was demonstrated, and in particular an unstable radical species attributable to the semipinacol radical of benzophenone was revealed, which is a key step of the functionalization process. Moreover, X-ray photoelectron spectroscopy demonstrated that the grafting process effectively reduced graphene oxide recovering the properties of graphene, contemporarily leaving active sites for further polymer functionalization
Ti/Au Ultrathin Films for TES Application
No full textTransition-Edge Sensors (TESs) are versatile superconducting microcalorimeters used as single photon detectors in a large range of electromagnetic wavelength, from X-rays to near-infrared. Among the many materials investigated in literature, Ti/Au is one of the most widely used bilayer to fabricate TES thanks to simple deposition process, long term stability material and protection against oxidation of Ti film by Au over layer. Moreover, the criti-cal temperature of Ti/Au can be tuned by trimming the thickness of Ti and Au films. For low energy photon detection, the Ti/Au superconducting layer performs simultaneously as absorber and thermometer. This implies that a TES thickness reduction helps to significantly reduce the thermal capacitance, which has a direct impact on the detector energy resolution. In this paper we present a study of the superconducting prop-erties of Ti/Au films, grown in UHV by thermal evaporation as a function of Ti thickness. The chemical state of Ti and Ti/Au were analyzed by X-ray photoelectron spectroscopy, to evaluate the protective effect of Au film. The film morphology, structure and optical properties were investigated by ellipsometry. The critical temperature showed a marked trend on film thickness and was strongly affected by Au cover layer. Ti film of only 12 nm thick covered with 10 nm Au film showed a remarkable critical tem-perature of about 300 mK
Fabrication of Janus particles via a �photografting-from� method and gold photoreduction
No full textUltra-Thin Plasma-Polymerized Functional Coatings for Biosensing: Polyacrylic Acid, Polystyrene and Their Co-Polymer
Full text linkRecently, many efforts have been done to chemically functionalize sensors surface to achieve selectivity towards diagnostics targets, such as DNA, RNA fragments and protein tumoural biomarkers, through the surface immobilization of the related specific receptor. Especially, some kind of sensors such as microcantilevers (gravimetric sensors) and one-dimensional photonics crystals (optical sensors) able to couple Bloch surface waves are very sensitive. Thus, any kind of surface modifications devoted to functionalize them has to be finely controlled in terms of mass and optical characteristics, such as refractive index, to minimize the perturbation, on the transduced signal, that can affect the response sensitivity towards the detected target species. In this work, the study and optimization of ultra-thin plasma polymers and copolymers, compatible with these constrains and obtained from the vapours of acrylic acid containing a carboxylic (−COOH) group and styrene (an aromatic molecule with a vinyl as substituent at the ring), are reported. The obtained plasma polyacrylic acid (PPAA), plasma polystyrene (PPST) and their copolymer (PPAA-ST), characterized through optical contact angle analysis (OCA), Fourier transform infrared (FTIR) spectroscopy in attenuated total reflection (ATRFTIR), X-ray photoelectrons spectroscopy (XPS), and atomic force microscopy (AFM), are shown to match specific and critical requirements, such as low thickness (∼40 nm) and refractive index (∼1.5), high surface density of reactive groups (1015-1016 COOH/cm2), bioantifouling properties where required, reproducibility, and chemical resistance and stability
Role of electrochemical cell configuration on the selectivity of CuZnAl-oxide-based electrodes for the continuous CO2 conversion: aqueous electrolyte vs. catholyte-less configuration
Full text linkAbstract This research is a significant step forward in understanding how the electrochemical cell setup influences CO2 conversion. The performance of Cu–Zn–Al metal oxide-based catalysts was compared in two reactor configurations: a gas diffusion electrode (GDE) cell with an aqueous electrolyte and a Membrane Electrode Assembly (MEA) cell operating in the gas phase without catholyte. The different operations induced significant morphological and crystalline structural changes, profoundly impacting the catalytic behaviour. The MEA configuration, for instance, led to the formation of a higher Cu0/Cu1+ ratio in the catalysts, promoting C–C coupling for C2H4 production. Conversely, the GDE operation favoured alcohol (ethanol and methanol) production by balancing copper oxidation states formed in situ in the presence of the aqueous catholyte. Zn and Al oxides also played a role in stabilising the resulting Cu species, some of which remained oxidised on the electrode surface. These findings underscore the crucial influence of varying cell operation conditions on catalyst reconstruction, shaping the quantity of Cu0 + Cu1+ species formed in situ to tailor catalyst selectivity
Enhancing the performance and mechanical stability of 2D-based hybrid micro-supercapacitors using dendritic-gold as framework layer
Full text linkIn recent years scaling-down approaches on supercapacitors has led to the definition of Micro-Supercapacitors (μSC). The demand for these devices is increasing for many applications in microelectronics, such as wearable energy storage and self-powered sensors. Recently, many efforts have been made to achieve good results in terms of power and energy densities. However, the current research challenge is to develop a sustainable chain production, involving eco-friendly materials, such as water-based electrolytes, organic binders and low-impact active material. This work presents a hybrid μSC using low impact materials and a fully water-based solution. Different approaches were adopted for patterning the current collectors and for the deposition of the active materials. The material chosen as anode was MnO2 deposited by electroplating, which presents pseudocapacitive behavior. The active material used for the cathode was Activated Carbon (AC), deposited by drop-casting, which works through the electric double layer (EDL) capacitance effect. The electrolyte was 1 M Na2SO4 in water. We investigated the addition of an interlayer micro-structure made of Dendritic-Gold (D-Gold). The results show that such a layer seems to have positive effects in terms of wettability and mechanical stability, enhancing the adhesion of the active material. Electron microscopy measurement shows the characteristic tree-like shape of the layer. The device reports a capacitance of about 14 to 23 mF cm-2 and a large voltage window equal to 1.6 V. The present research explores, for the first time, the effects of dendritic gold in planar electrochemical capacitors. The findings should give an important contribution for boost energy storage densities in the field of 2D micro-supercapacitors
Investigation of Transport and Recombination Properties in Graphene/Titanium Dioxide Nanocomposite for Dye-Sensitized Solar Cell Photoanodes
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