Three dimensional printing technologies represent a revolution in the manufacturing sector because of their unique capabilities for increasing shape complexity while reducing waste material, capital cost and design for manufacturing. However, the application of 3D printing technologies for the fabrication of functional components or devices is still an almost unexplored field due to their elevated complexity from the materials and functional points of view. This paper focuses on reviewing previous studies devoted to developing 3D printing technologies for the fabrication of functional parts and devices for energy and environmental applications. The use of 3D printing technologies in these sectors is of special interest since the related devices usually involve expensive advanced materials such as ceramics or composites, which present strong limitations in shape and functionality when processed with classical manufacturing methods. Recent advances regarding the implementation of 3D printing for energy and environmental applications will bring competitive advantages in terms of performance, product flexibility and cost, which will drive a revolution in this sector. Broader contextIntensive research on additive manufacturing has been carried out during the last three decades to allow the fabrication of three dimensional objects by assembling materials without the use of tools or molds. Three dimensional printing technologies represent a potentially low-cost, new paradigm for the manufacture of energy conversion technologies offering unique capabilities in terms of shape/geometry complexity and enhancement of specific performance per unit of mass and volume of the 3D printed units. However, the fabrication of highly complex devices for the energy sector by using 3D printing is an almost unexplored field. In this work we review the state of the art of 3D printing technology to fabricate components or devices for energy and environmental applications, focusing on aspects related to the control of the microstructure, functionality and performance of the 3D printed structures.

Shining a light on spectrally converting lanthanide (Ln3+)-doped nanoparticles: progress, trends, and challenges in Ln3+-nanoprobes for near-infrared bioimaging, nanothermometry, and photodynamic therapy.

Glass ceramics of composition 95SiO2-5SnO2 doped with 0.4mol% Eu3+ have been prepared by thermal treatment of sol-gel glasses. The segregated SnO2 nanocrystals present a mean size comparable to the bulk exciton Bohr radius (about 2.4nm), corresponding to a wide band-gap quantum-dot system in an insulator SiO2 glass. A fraction of the Eu3+ ions is incorporated to the SnO2 nanocrystals in the process. In these strong confinement conditions, the energy gap presents a high dependence on the nanocrystal size. Taking advantage of this effect, it has been possible to excite selectively the Eu3+ ions located in the SnO2 nanocrystals, by energy transfer from the host, obtaining emission spectra that depend on the nanocrystal size. The Eu3+ ions environment in small nanocrystals (radius under 2nm) are very distorted, meanwhile they are like crystalline for nanocrystals with a radius of some nanometers.

The optically active dopant distribution in a Tm(3+)-Yb(3+) doped silica based glass ceramic sample has been investigated. A systematic analysis of the upconversion fluorescence of the Tm(3+)-Yb(3+) codoped glass and glass ceramic has been performed at room temperature. Tm(3+) and Yb(3+) single doped glass and glass ceramics have also been included in the study. Upon infrared excitation at 790 nm into the (3)H(4) level of the Tm(3+) ions a blue upconversion emission is observed, which is drastically increased in the Yb(3+) codoped samples. A rate equation model confirmed the energy transfer upconversion mechanism. Based on these results, the temporal dynamic curves of the levels involved in the upconversion process, (3)H(4), (2)F(5/2), and (1)G(4) were interpreted in the glass ceramic samples. The contribution of the optically active Tm(3+) and Yb(3+) ions in the crystalline and in the vitreous phase of the glass ceramic was distinguished and the ratio of Tm(3+) ions in the crystalline phase could be quantified for the 1 mol % Tm(3+)-2.5 mol % Yb(3+) glass ceramic. A surprising result was obtained for that concentration: the main contribution to the upconversion emission of the glass ceramic is due to Tm(3+)-Yb(3+) ions in the vitreous phase.

No abstract