227 research outputs found
Efficient charge transfer in solution-processed PbS quantum dotâreduced graphene oxide hybrid materials
We developed a general approach to couple silane-functionalized rGO with colloidal semiconductor nanocrystals, which show efficient and tunable charge transfer
Photoinduced Temperature Gradients in Sub-wavelength Plasmonic Structures: The Thermoplasmonics of Nanocones
Plasmonic structures are renowned for their capability to efficiently convert
light into heat at the nanoscale. However, despite the possibility to generate
deep sub-wavelength electromagnetic hot spots, the formation of extremely
localized thermal hot spots is an open challenge of research, simply because of
the diffusive spread of heat along the whole metallic nanostructure. Here we
tackle this challenge by exploiting single gold nanocones. We theoretically
show how these structures can indeed realize extremely high temperature
gradients within the metal, leading to deep sub-wavelength thermal hot spots,
owing to their capability of concentrating light at the apex under resonant
conditions even under continuous wave illumination. A three-dimensional Finite
Element Method model is employed to study the electromagnetic field in the
structure and subsequent thermoplasmonic behaviour, in terms of the
three-dimensional temperature distribution. We show how the latter is affected
by nanocone size, shape, and composition of the surrounding environment.
Finally, we anticipate the use of photoinduced temperature gradients in
nanocones for applications in optofluidics and thermoelectrics or for thermally
induced nanofabrication
Scalable production of graphene inks via wet-jet milling exfoliation for screen-printed micro-supercapacitors
The miniaturization of energy storage units is pivotal for the development of
next-generation portable electronic devices. Micro-supercapacitors (MSCs) hold
a great potential to work as on-chip micro-power sources and energy storage
units complementing batteries and energy harvester systems. The scalable
production of supercapacitor materials with cost-effective and high-throughput
processing methods is crucial for the widespread application of MSCs. Here, we
report wet-jet milling exfoliation of graphite to scale-up the production of
graphene as supercapacitor material. The formulation of aqueous/alcohol-based
graphene inks allows metal-free, flexible MSCs to be screen-printed. These MSCs
exhibit areal capacitance (Careal) values up to 1.324 mF cm-2 (5.296 mF cm-2
for a single electrode), corresponding to an outstanding volumetric capacitance
(Cvol) of 0.490 F cm-3 (1.961 F cm-3 for a single electrode). The
screen-printed MSCs can operate up to power density above 20 mW cm-2 at energy
density of 0.064 uWh cm-2. The devices exhibit excellent cycling stability over
charge-discharge cycling (10000 cycles), bending cycling (100 cycles at bending
radius of 1 cm) and folding (up to angles of 180{\deg}). Moreover, ethylene
vinyl acetate-encapsulated MSCs retain their electrochemical properties after a
home-laundry cycle, providing waterproof and washable properties for
prospective application in wearable electronics
CeO2 Nanoparticles-Loaded pH-Responsive Microparticles with Antitumoral Properties as Therapeutic Modulators for Osteosarcoma
Osteosarcoma is an aggressive form of bone cancer mostly affecting young people. To date, the most effective strategy for the treatment of osteosarcoma is the surgical removal of the tumor with or without combinational chemotherapy. In this study, we present the development of a pH-sensitive drug-delivery system in the form of microparticles, with increased chemotherapeutic action against the osteosarcoma cell line SAOS-2, and with reduced toxicity against the heart myoblastic cell line H9C2. The delivery system is composed of calcium carbonate and collagen type I, and is loaded with cerium dioxide (CeO2) nanoparticles (<25 nm) and the anticancer drug doxorubicin. The fabricated microparticles were fully characterized morphologically and physicochemically, and their ability to induce or inhibit apoptosis/necrosis was assessed using in vitro functional assays and flow cytometry. The results presented in this study show that the highest concentration (250 ÎŒg/mL) of the therapeutic microparticles (CaCO3-based therapeutic modulators (C-TherMods)), which corresponds to 6.4 ÎŒg/mL of encapsulated doxorubicin, can protect the H9C2 cells even after 120 h, since the percentage of viable cells at this time point is 65%. On the contrary, when H9C2 cells are treated with 0.5 ÎŒg/mL of free doxorubicin, 75% of the cells are dead only after 24 h. When SAOS-2 cells are treated with the same concentration of C-TherMods (250 ÎŒg/mL), the viability of SAOS-2 cells is 80% after 24 h, while it reduces to 50% after 120 h. At pH 6.0, the synergic effect of the pro-oxidant CeO2nanoparticles and of the encapsulated doxorubicin leads to almost 100% of cell death, even at the lowest concentration of C-TherMods (50 ÎŒg/mL)
Reduction of moisture sensitivity of PbS quantum dot solar cells by incorporation of reduced graphene oxide
PbS nanocrystals are an important narrow-gap material for solar cells and photodetectors. Nevertheless, their application may be limited because device performance can be affected by atmospheric conditions. Indeed, the presence of oxygen and/or water can degrade the active layers, possibly leading to device failure. Strategies to address this issue are therefore actively explored. Here we report a solution-processed PbS quantum dot solar cell, consisting of a PbS-silane functionalized reduced graphene oxide (PbS-rGO) layer on top of the PbS absorber film, which enhances device stability, especially when the solar cells are exposed to moisture. Power conversion efficiency (PCE) measurements demonstrate a slower degradation under continuous illumination for solar cells with PbS-rGO. When storing the samples under saturated water vapor, differences are even more remarkable: with PbS-rGO the solar cells essentially maintain their initial PCE, while the PCE of the PbS reference devices is reduced by 50% after 5 days. Scanning electron microscopy, energy dispersive X-ray and X-ray photoelectron spectroscopy reveal the damage to the PbS films and the formation of PbSOX crystals in the PbS reference devices. Such crystals are not observed in the PbS-rGO devices, further supporting the importance of the PbSrGO barrier layer
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