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2021


Nanotecnología en Superficies y Plasma - Materiales Ópticos Multifuncionales

One-reactor vacuum and plasma synthesis of transparent conducting oxide nanotubes and nanotrees: from single wire conductivity to ultra-broadband perfect absorbers in the NIR

Castillo-Seoane, J; Gil-Rostra, J; Lopez-Flores, V; Lozano, G; Ferrer, FJ; Espinos, JP; Ostrikov, K; Yubero, F; Gonzalez-Elipe, AR; Barranco, A; Sanchez-Valencia, JR; Borras, A
Nanoscale, 13 (2021) 13882-13895

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The eventual exploitation of one-dimensional nanomaterials needs the development of scalable, high yield, homogeneous and environmentally friendly methods capable of meeting the requirements for fabrication of functional nanomaterials with properties on demand. In this article, we demonstrate a vacuum and plasma one-reactor approach for the synthesis of fundamental common elements in solar energy and optoelectronics, i.e. the transparent conducting electrode but in the form of nanotube and nanotree architectures. Although the process is generic and can be used for a variety of TCOs and wide-bandgap semiconductors, we focus herein on indium doped tin oxide (ITO) as the most previously researched in previous applications. This protocol combines widely applied deposition techniques such as thermal evaporation for the formation of organic nanowires serving as 1D and 3D soft templates, deposition of polycrystalline layers by magnetron sputtering, and removal of the templates by simply annealing under mild vacuum conditions. The process variables are tuned to control the stoichiometry, morphology, and alignment of the ITO nanotubes and nanotrees. Four-probe characterization reveals the improved lateral connectivity of the ITO nanotrees and applied on individual nanotubes shows resistivities as low as 3.5 +/- 0.9 x 10(-4) omega cm, a value comparable to that of single-crystalline counterparts. The assessment of diffuse reflectance and transmittance in the UV-Vis range confirms the viability of the supported ITO nanotubes as random optical media working as strong scattering layers. Their further ability to form ITO nanotrees opens a path for practical applications as ultra-broadband absorbers in the NIR. The demonstrated low resistivity and optical properties of these ITO nanostructures open a way for their use in LEDs, IR shields, energy harvesting, nanosensors, and photoelectrochemical applications.


Agosto, 2021 | DOI: 10.1039/d1nr01937f

Nanotecnología en Superficies y Plasma

Laser-induced scanning transfer deposition of silver electrodes on glass surfaces: A green and scalable technology

Molina, R; Ertugrul, M; Larrea, A; Navarro, R; Rico, V; Yubero, F; Gonzalez-Elipe, AR: De la Fuente, GF; Angurel, LA
Applied Surface Science, 556 (2021) 149673

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A pulsed laser ablation backwriting technique with high repetitive rates is implemented for the fabrication of silver coatings on glass surfaces. This method enables geometrical constraint-free deposition of metallic coatings. These exhibit sufficiently low electrical resistance to be used as electrodes in dielectric barrier discharge (DBD) plasma elements. Ambient air deposition of metallic silver electrodes on standard glass slides is explored using a sub-ns UV laser source, combined with hybrid beam scanning methods. The green nature of the overall deposition process includes a preliminary irradiation scan to homogenise the target surface before the subsequent backwriting step. Metal transfer is achieved by combining two phenomena within a simple beam scanning process: LIRT (laserinduced reverse transfer) of silver from the target to the glass, with a partial and secondary LIFT (Laser-Induced Forward Transfer) of silver from the glass to the target. Appropriate selection of pulse energy and pulse repetition rates, beam scanning velocities and target motion enable the growth of sufficiently thick Ag deposits on glass with the required low electrical resistivity and nearly 2D constraint-free geometry. This method avoids the use of vacuum and liquids, resulting in a cheap, facile and green methodology for the deposition of silver electrodes onto transparent substrate surfaces.


Agosto, 2021 | DOI: 10.1016/j.apsusc.2021.149673

Fotocatálisis Heterogénea: Aplicaciones

ZnO/Ag3PO4 and ZnO–Malachite as Effective Photocatalysts for the Removal of Enteropathogenic Bacteria, Dyestuffs, and Heavy Metals from Municipal and Industrial Wastewater

Murcia, JJ; Hernández Miño, JS; Rojas, H; Brijaldo, MH; Martin-Gómez, AN; Sánchez-Cid, P; Navío, JA; Hidalgo, MC; Jaramillo-Pérez, C
Water, 13 (2021) 2264

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Different composites based on ZnO/Ag3PO4 and ZnO–malachite (Cu2(OH)2CO3) were synthesized in order to determine their effectiveness in the treatment of municipal and industrial wastewaters (mainly polluted by enteropathogenic bacteria, dyes, and heavy metals). The addition of Ag3PO4 and malachite did not significantly modify the physicochemical properties of ZnO; however, the optical properties of this oxide were modified as a result of its coupling with the modifiers. The modification of ZnO led to an improvement in its effectiveness in the treatment of municipal and industrial wastewater. In general, the amount of malachite or silver phosphate and the effluent to be treated were the determining factors in the effectiveness of the wastewater treatment. The highest degree of elimination of bacteria from municipal wastewater and discoloration of textile staining wastewater were achieved by using ZnO/Ag3PO4 (5%), but an increase in the phosphate content had a detrimental effect on the treatment. Likewise, the highest Fe and Cu photoreduction from coal mining wastewater was observed by using ZnO–malachite (2.5%) and ZnO/Ag3PO4 (10%), respectively. Some of the results of this work were presented at the fourth Congreso Colombiano de Procesos Avanzados de Oxidación (4CCPAOx).


Agosto, 2021 | DOI: 10.3390/w13162264

Materiales Ópticos Multifuncionales

Light-Harvesting Properties of a Subphthalocyanine Solar Absorber Coupled to an Optical Cavity

Esteso, V; Calio, L; Espinos, H; Lavarda, G; Torres, T; Feist, J; Garcia-Vidal, FJ; Bottari, G; Míguez, H
SOLAR RRL, (2021) 2100308

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Herein, both from the experimental and theoretical point of view, the optical absorption properties of a subphthalocyanine (SubPc), an organic macrocycle commonly used as a sunlight harvester, coupled to metallic optical cavities are analyzed. How different electronic transitions characteristic of this compound and specifically those that give rise to excitonic (Q band) and charge transfer (CT band) transitions couple to optical cavity modes is investigated. It is observed that whereas the CT band couples weakly to the cavity, the Q band transitions show evidence of hybridization with the photon eigenstates of the resonator, a distinctive trait of the strong coupling regime. As a result of the different coupling regimes of the two electronic transitions, very different spectral and directional light-harvesting features are observed, which for the weakly coupled CT transitions are mainly determined by the highly dispersive cavity modes and for the strongly coupled Q band by the less angle-dependent exciton-polariton bands. Modeling also allows discriminating parasitic from productive absorption in each case, enabling the estimation of the expected losses in a solar cell acting as an optical resonator.


Julio, 2021 | DOI: 10.1002/solr.202100308

Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Mechanistic Considerations on the H-2 Production by Methanol Thermal-assisted Photocatalytic Reforming over Cu/TiO2 Catalyst

Platero, F; Lopez-Martin, A; Caballero, A; Colon, G
CHEMCATCHEM, 13 (2021) 3878-3888

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We have studied the gas phase H-2 production by methanol thermo-photoreforming using Cu-modified TiO2. Metal co-catalyst has been deposited by means of photodeposition method. The concentration of methanol in the steam was also considered. It appears that H-2 production is notably higher as temperature increases. Moreover, the optimum H-2 yield is achieved using methanol concentration of 10 % v/v. CO and CO2 were monitored as side products of the overall reaction. It has been stated that CO evolution is significant at lower temperatures. As temperature increases, CO evolution is hindered and H-2 appeared boosted. We have demonstrated that other reactions such water-gas-shift or formate dehydration would participate in the overall process. On this basis, optimal operational condition for H-2 production is attained for thermo-photocatalytic reforming of methanol solution 10 % v/v at 200 degrees C.


Julio, 2021 | DOI: 10.1002/cctc.202100680

 

 

 

 

 

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