RESUMEN
Graphitic carbon nitride (g-C3N4) is a promising conjugated polymer with visible light responsiveness and numerous intriguing characteristics that make it highly beneficial for a myriad of potential applications. A novel design and universal approach for the fabrication of unique plasmonic g-C3N4 nanoscale hybrids, with well-controlled morphology, is presented. A single gold nanoprism is encapsulated within dense or hollow g-C3N4 spheres for the formation of Au@g-C3N4 core-shell and Au@g-C3N4 yolk-shell nanohybrids. Au nanoprisms were chosen duo to the strong (visible range) plasmon resonances and electromagnetic field hotspots formed at their sharp corners. The incorporation of Au nanoprisms into the g-C3N4 nanospheres results in a dramatic â¼threefold rise in the emission of plasmonic g-C3N4 yolk-shell nanohybrids and â¼3.6-fold enhancement of the photocurrent density obtained from the plasmonic g-C3N4 core-shell nanohybrids, when compared with the g-C3N4 hollow nanospheres. Hence, these hybrids can potentially benefit applications in the areas spanning from solar energy harvesting to biomedical imaging and theranostics.
RESUMEN
SnO2 nanoparticles have been synthesized and used as electron transport material (ETM) in dye sensitized solar cells (DSSCs), featuring two peripherally substituted push-pull zinc phthalocyanines (ZnPcs) bearing electron donating diphenylamine substituents and carboxylic acid anchoring groups as light harvesters. These complexes were designed on the base of previous computational studies suggesting that the integration of secondary amines as donor groups in the structure of unsymmetrical ZnPcs might enhance photovoltaics performances of DSSCs. In the case of TiO2-based devices, this hypothesis has been recently questioned by experimental results. Herein we show that the same holds for SnO2, despite the optimal matching of the optoelectronic characteristics of the synthesized nanoparticles and diphenylamino-substituted ZnPcs, thus confirming that other parameters heavily affect the solar cells performances and should be carefully taken into account when designing materials for photovoltaic applications.
RESUMEN
Computational studies have suggested that the integration of secondary amine as donor groups in the structure of unsymmetrical zinc phthalocyanine (ZnPc) should have positive effects on photovoltaic performance, once the molecule is integrated as light harvester in dye sensitized solar cells (DSSCs). Aiming at obtaining experimental confirmation, we synthesized a peripherally substituted push-pull ZnPc bearing three electron donating diphenylamine substituents and a carboxylic acid anchoring group and integrated it as sensitizer in TiO2-based DSSCs. Detailed functional characterization of solar energy converting devices resulted in ruling out the original hypothesis. The causes of this discrepancy have been highlighted, leading to a better understanding of the conditions for an effective design of push-pull diarylamino substituted ZnPcs for DSSCs.
RESUMEN
The role played by the counter electrode (CE) in quantum dot sensitized solar cells (QDSSCs) is crucial: it is indeed responsible for catalyzing the regeneration of the redox electrolyte after its action to take back the oxidized light harvesters to the ground state, thus keeping the device active and stable. The activity of CE is moreover directly related to the fill factor and short circuit current through the resistance of the interface electrode-electrolyte that affects the series resistance of the cell. Despite that, too few efforts have been devoted to a comprehensive analysis of this important device component. In this work we combine an extensive electrochemical characterization of the most common materials exploited as CEs in QDSSCs (namely, Pt, Au, Cu2S obtained by brass treatment, and Cu2S deposited on conducting glass via spray) with a detailed characterization of their surface composition and morphology, aimed at systematically defining the relationship between their nature and electrocatalytic activity.
RESUMEN
The effect of a ZnO compact blocking layer (BL) in dye-sensitized solar cells (DSSCs) based on ZnO photoanodes is investigated. BL is generated through spray deposition onto fluorine-doped tin oxide (FTO) conducting glass before the deposition of a ZnO active layer. The functional properties of dye-sensitized solar cells (DSSCs) are then investigated as a function of the thickness of the BL for two different kinds of ZnO active layer, i.e., hierarchically self-assembled nanoparticles and microcubes composed of closely packed ZnO sheets. Presence of BL leads to the improvement of photoconversion efficiency (PCE), by physically insulating the electrolyte and the FTO. This effect increases at increasing BL thickness up to around 800 nm, while thicker BL results in reduced cell performance. Remarkable increase in Jsc is recorded, which doubles as compared to cells without blocking layer, leading to PCE as high as 5.6% in the best cell under one sun irradiation (AM 1.5 G, 100 mW cm(-2)). Electrochemical impedance spectroscopy (EIS) elucidates the mechanism boosting the functional features of the cells with BL, which relies with enhanced chemical capacitance together with an almost unchanged recombination resistance, which are reflected in an increased electron lifetime. The results foresee a straightforward way to significantly improve the performance of ZnO-based DSSCs.
RESUMEN
Beam deflection due to axial channeling in a silicon crystal bent along the 111 axis was observed with 400 GeV/c protons at the CERN Super Proton Synchrotron. The condition for doughnut scattering of protons by the atomic strings of the crystal was attained. Such a condition allowed one to observe a beam deflection of 50 murad with about 30% efficiency. The contribution of hyperchanneled states of protons to the observed beam deflection was less than 2% according to simulation results.
RESUMEN
A high performance apparatus has been designed and built by the H8-RD22 collaboration for the study of channeling and volume reflection phenomena in the interaction of 400 GeV/c protons with bent silicon crystals, during the 2006 data taking in the external beamline H8 of the CERN SPS. High-quality silicon short crystals were bent by either anticlastic or quasimosaic effects. Alignment with the highly parallel (8 murad divergence) proton beam was guaranteed through a submicroradian goniometric system equipped with both rotational and translational stages. Particle tracking was possible by a series of silicon microstrip detectors with high-resolution and a parallel plate gas chamber, triggered by various scintillating detectors located along the beamline. Experimental observation of volume reflection with 400 GeV/c protons proved true with a deflection angle of (10.4+/-0.5) murad with respect to the unperturbed beam, with a silicon crystal whose (111) planes were parallel to the beam.
RESUMEN
The volume reflection phenomenon was detected while investigating 400 GeV proton interactions with bent silicon crystals in the external beam H8 of the CERN Super Proton Synchrotron. Such a process was observed for a wide interval of crystal orientations relative to the beam axis, and its efficiency exceeds 95%, thereby surpassing any previously observed value. These observations suggest new perspectives for the manipulation of high-energy beams, e.g., for collimation and extraction in new-generation hadron colliders, such as the CERN Large Hadron Collider.